Maturational changes of effective elastance in the first 10 days of life.

The effective elastance of the respiratory system (E'rs) is a measure of its ability to resist a change in tidal volume under conditions of changing elastic loads. E'rs was measured while subjects breathed air and 2% CO2 and 4% CO2 in air in two groups of premature infants of different gestational ages at 1 day 3-4 days, and 7-10 days of age. E'rs was shown to decrease with increasing maturation and was independent of changes in control tidal volume. The decrease of E'rs with increased gestational age could be accounted for by differences in calculated thoracic gas volumes in all but one instance, where E'rs was lower in one group on the 3rd day of life. The activity of the Hering-Breuer reflex, as measured by the degree of slowing of inspiratory time after occlusion at FRC, has been previously reported to be normal to increased in similar infants. This suggests that differences related to size account for most of the maturational changes of E'rs in newborns.


Canine hyperthermia with cerebral protection.

Extreme whole-body hyperthermia was achieved without lasting side effects in canines by elevating body core temperature to 42 degrees C, using a warm water bath. Cold water irrigation of the nasal alar fold permitted an additional core temperature elevation of 0.5-1.0 degrees C above brain temperature for periods up to 1.5 h. The brain-core temperature differential was maintained by a physiological arteriovenous heat exchanger located at the base of the brain. The maximum tolerable core temperature for the 21 nonirrigated dogs was 42 degrees C for 60-90 min, whereas that for the 28 irrigated dogs was 42.5-43 degrees C for similar time intervals. A mathematical model of the total heat transfer system described the observed dynamic temperature responses. It was the solution of a differential equation which fit the normalized experimental data points and predicted reasonable values for known and unknown experimental parameters.


Energy cost of speec skating and efficiency of work against air resistance.

The energy expenditure during speed ice skating (PB=650 mmHg; T=-5 degrees C) was measured on 13 athletes (speed range: 4-12 m/s) from VO2 and (for speeds greater than 10 m/s) from blood lactic acid concentration. The energy spent (O2 equivalents) per unit body wt and unit distance (Etot/V, ml/kg-min) increases with the speed (v, m/s): Etot/v=0.049 + 0.44 X 10(-3) V2. At 10 m/s, Vtot/v amounts then to 0.093 ml/kg-m: about half the value of running. The constant 0.049 ml/kg-m is interpreted as the energy spent against gravitational and inertial forces. The term 0.44 X 10(-3) v2 indicates the energy spent against the wind, the constant 0.44 X 10(-3) ml-s2-kg-1-m-3 being a measure of k/e, where k is the coefficient relating drag to v2, and e the efficiency of work against the wind. From a direct estimate of k in a wind tunnel, e was calculated as 0.11. In running, skating, and cycling k/e is similar (approximately 0.020 ml-s2-m-3 per m2 body area), hence at a given speed the energy spent against the wind is equal. On the contrary, the energy spent against other forces decreases in the above order: 0.19, 0.05, 0.018 ml-m-1 per kg body wt. This explains the different speeds attained in these exercises with the same power output.


Posthyperventilation isocapnic hyperpnea.

Subjects voluntarily hyperventilated for 10 breaths. A dynamic end-tidal forcing technique manipulated inspired gases to hold end-tidal CO2-O2 tensions at normal values during the voluntary ventilation period and the postvoluntary ventilation recovery period when the subjects returned to spontaneous breathing. Six of the seven subjects studied exhibited a hyperpnea during the recovery period. Although intersubject and intrasubject variations were evident, the average response for 30 experiments in the six subjects was characterized by an initial drop to 32% of the hyperventilation magnitude followed by an exponential-like decrease with a time constant of 22 s. This recovery period response is consistent with theoretical properties of neural network and physical oscillators where there is a persistence in the amplitude response after the removal of the stimulus. Thus, such oscillator properties may govern the respiratory center behavior in man. Furthermore, since isocapnic voluntary ventilation increases cardiac output, the recovery period response may be a consequence of cardiodynamic hyperpnea.


Effects of external pressure loading on human skin blood flow measured by 133Xe clearance.

Forearm skin blood flow was measured during external pressure loading in normal human subjects using 133Xe washout from intracutaneous injection sites. Pressures ranging between 5 and 150 mmHg were applied through a 3-cm-diameter disc placed over the site of flow determination. The pressure was maintained constant by a servo-controlled loading mechanism. Flow decreased with pressures from 5 to 10 and 30 to 150 mmHg, but remained constant with pressures from 10 to 30 mmHg. Reactive hyperemia occurred following removal of pressures of 90 mmHg or greater, but did not occur following removal of lower pressures. The pressure-flow curve for parasacral skin of paraplegic subjects closely paralleled the pressure-flow curve of normal skin at pressures tested: 5-15 mmHg. These data are interpreted to demonstrate autoregulation of skin blood flow. Autoregulation in parasacral skin of paraplegic subjects suggests a peripheral mechanism. The occurrence of hyperemia at pressures which exceed the ability of skin to autoregulate suggests that both autoregulation and post occlusion hyperemia may have the same mechanism.


High salt intake and blood pressure in lower primates (Papio hamadryas).

One year of increased salt intake in monkeys elevates mean blood pressure significantly. This effect is more marked in animals exposed just after birth. In animals exposed as adults, the response in males is more pronounced than in females, mainly due to a marked increase of pulse pressure. Th hypertensive response was potentiated by reduction of renal mass, which caused GFR values (in terms of body weight) to decrease compared with intact salt-fed animals, in which GFR values were elevated above the control level. It is concluded that the mechanisms involved in the hypertensive response are similar to those in the rat and dog.


Physiological responses of men working in 25.5 degrees C water, breathing air or helium tri-mix.

Fourteen scuba divers in swim trunks did ergometer work while breathing air at 3 m in 25.5 degrees C water. They were stressed by work and cold. Exercise produced increases in heart rate, minute ventilation (VE), oxygen consumption (VO2), and catecholamine excretion. Cold lowered rectal temperature (Tre) despite exercise, and contributed to the increase in VO2 and catecholamine excretion. Immersion, cutaneous vasoconstriction, work, and scuba breathing contributed to a brisk diuresis, probably by centralizing blood volume and thus stimulating central vascular volume receptors. Similar exercise in 25.5 degrees C water, breathing helium tri-mix (gas density less than air), produced higher VE but lower VO2 when compared to air breathing. Tri-mix scuba breathing resulted in a smaller diuresis, perhaps because its lower density leads to lesser atrial distension during work. The fall in Tre during work in 25.5 degrees C water was identical whether air or helium tri-mix was respired, since helium does not accentuate respiratory convective heat transfer.


Maximum exercise tests on "postcoronary" patients.

The maximum oxygen intake has been measured directly (uphill treadmill walking) in 36 patients following recovery from myocardial infarction. These were selected as follows: 15 consecutive new entrants to an exercise program that is currently accepting about one-sixth of the total reported myocardial infarction hospital admissions in metropolitan Toronto (group A), 12 patients not responding well to training (group B), and 9 patients now running substantial distances (group C). The only clinical complications were two episodes of ventricular tachycardia. Twenty patients reached an oxygen plateau, and in group C, the maximum heart rate (170/min) reached Scandinavian norms, with a maximum oxygen intake (2.63 +/- 0.35 1/min STPD, 36.9 +/- 4.8 ml/kg-min STPD) as in healthy men of the same age. The rate of adaptation to a progressive submaximum test was such that comparable Astrand nomogram predictions of VO2max were obtained from data in the 3rd and 5th min at the third load. Predictions generally agreed closely with directly measured values. It may be concluded that in patients who have recovered sufficiently to enter an exercise rehabilitation program 1) predictions of VO2max have about the same accuracy (+/-10) as in healthy subjects, and 2) direct measurements can often be pursued to an "oxygen plateau" without due risk.


An automated system for assessing metabolic and respiratory function during exercise.

This paper provides a brief description of a new, totally automated system for assessing metabolic and respiratory function during exercise. This system was evaluated simultaneously against two established systems, one a computer-based system and the other a semiautomated system, to determine its validity over a wide range of metabolic levels, i.e., less than 2 to greater than 16 mets. A total of 112 males and females, 12-65 yr of age, performed either arm or leg exercises on a bicycle ergometer or treadmill, starting at approximately 2 mets and progressing by approximately 1 met/min to the point of volitional fatigue. Respiratory and metabolic assessments were made each minute during the entire exercise bout. Comparisons across the three systems demonstrated remarkable agreement, particularly when all potential sources of error for each system are considered. Although several statistically significant differences between two of the systems were noted at the lowest work levels, the difference in VO2 between any two systems never exceeded 1.1 ml/kg-min.


A noncontact method for three-dimensional analysis of vascular elasticity in vivo and in vitro.

A new method is described to measure the deformation of the blood vessel wall simultaneously in longitudinal and circumferential directions. This information is of paramount importance for further characterization of the elastic properties of the arterial wall. The new method consists of a closed-circuit TV system in conjunction with a video dimension analyzer (VDA). The VDA utilizes the video signal from the TV camera and forms a DC voltage proportional to the distance between two selected points in the scene. The resulting analog voltage, calibrated in dimensional units, is recorded. Dimensional changes in two directions, due to intraluminal pressure oscillations, are tracked continuously. The measurement can be performed in vivo on exposed vessels as well as in vitro on excised specimens. Distortion caused by the end effects is completely eliminated. For further data analysis, the wall thickness of the artery is determined microscopically. Stress and strain relationship in longitudinal and circumferential directions is calculated for every intraluminal pressure change. This approach yields data on mechanical properties of the vessel wall in a far more physiological way than the hitherto used direct-contact techniques.


Measurement of brain oxygen utilization with radioactive oxygen-15: experimental verification.

This study was designed to provide direct experimental evidence in support of the method employing radioactive 15O-tagged hemoglobin for the in vivo and regional measurement of the cerebral oxygen utilization rate (CMRO2). This was accomplished by simultaneously measuring in vivo the mean CMRO2 in monkeys and human beings by the 15O method and a direct appeal to the Fick principle using measured arteriovenous oxygen differences of brain. The correlation between the 2 methods was excellent, with a correlation coefficient of 0.90 (P less than 0.001) in monkeys and 0.88 (P less than 0.001) in human beings.


A shower spray facility for accurate control and rapid changes of skin temperature.

A shower spray facility (SSF) was built to closely clamp the skin temperature of human subjects, while retaining capability for controlled rapid changes. The subject is enclosed from the neck down in a small chamber containing three water spray manifolds which terminate in 64 small shower heads; the manifolds provide independent temperature control of left leg, right leg, and arm/torso. A dual, solenoid-switched plumbing system for each manifold allows rapid, preset temperature changes. Preliminary tests showed that single thermocouples can accurately indicate average skin temperature for each of the three controlled body areas. Initial experiments with spikes, step functions, and periodic wave forms have proven the SSF as a potentially powerful tool for studying mechanisms of human thermoregulation.


Oral administration of radioactive sulfate to measure extracellular fluid space in man.

Radioactive sulfate-35 (35S) was administered to eight human subjects intravenously and orally, to compare respective kinetics of distribution. Intravenously administered 35S attained equilibration within 60-90 min. Orally administered 35S attained equilibration within 60-105 min and thereafter achieved plasma activity equivalent to the intravenously administered tracer. Eighty percent or greater of the 35S dose was recovered in the 24-h urine, following either intravenous or oral administration. The mean extracellular fluid space demonstrated less than 9% mean difference between routes of administration. It is concluded that 35S is completely absorbed at tracer doses, and may be administered orally as a reliable substitute for intravenously administered 35S for measuring extracellular fluid space.


Limiting factors to oxygen transport on Mount Everest.

The effect of a sudden increase of the inspired oxygen tension on the maximal aerobic performance was studied on 23 subjects acclimated to high altitude (5,350-8,848 m above sea level) in the course of a 4-mo expedition to Mt. Everest. Inhalation of 100% O2 at 390 mmHg or a rapid descent (20 min) by helicopter to 2,850 m (Pio2 = 117 mmHg) raised maximal oxygen consumption (Vo2 max) from an average 0.7 of the control sea-level value, respectively, to 0.92 and 0.97. The failure of acclimated subjects to increase markedly or even to resume the preexisting sea-level Vo2mxa while breathing O2 in the presence of a 40% increase of blood Hb concentration and of a limited reduction of maximal cardiac output (Qmax), is attributed to changes in the peripheral circulation. These may consist of a) a hindrance of O2 diffusion due to erythrocytes packing secondary to increased hematocrit (Hct up to 70%); b) a bypass of arterial blood from the high-resistance working areas of the body aimed at reducing the load on the heart caused by increased blood viscosity. A 11.6% increase above normal controls of Hb concentration still found in 13 subjects 25 days after leaving altitude does not increase significantly maximum O2 consumption.


Effect of neck versus chest cooling on responses to work in heat.

Six young men performed bench-stepping at a load of 40 W, once at room temperature of 23 degrees C and 3 times in heat (39.5 degrees C db, 30.3 degrees C wb). Two of the heat exposures included cooling of either the neck or chest by circulating cool water having an inlet temperature of 8.3 degrees C. The heat exchanges for the neck and chest were of equal size and they consisted of PVC tubes, having a total length of 3m each, which covered 2.2% of the body surface area. Heat exchange between the tubing assemblies and the environment was prevented by proper insulation. As compared with no cooling in heat, each method of cooling resulted in no change in heart rate, a decrease of 0.5 degrees C in rectal temperature, small and insignificant decreases in skin temperature and 16-22% decreases in sweat rates. Heat removed from the neck and chest equalled 63.1 and61.9 W-m-2, respectively. This large heat removal and the substantial decreases in rectal temperature and sweat rate as a result of cooling 2.2% of the body surface area were explained in terms of the powerful effect of conductive cooling and the particular regions which were cooled.


Alveolar-capillary CO2 and O2 gradients due to uneven hematocrits.

The effect of uneven hematocrit of the blood perfusing the different pulmonary capillaries on gas exchange in the lung was studied in vitro. Venous blood was separated anaerobically into plasma and red cell fractions, arterialized in separate tonometers, and finally reconstituted anaerobically. This simulated the effect of complete separation of plasma and red cells on pulmonary gas exchange. The reconstituted blood had a significantly higher carbon dioxide tension and a lower oxygen tension compared with whole blood similarly arterialized. Experiments in which plasma and red cells were incompletely separated yielded qualitatively similar results; the changes in gas tensions were smaller but still significant. While the degree and extent of separation of plasma and red cells in the pulmonary capillary in vivo is uncertain, direct observation and hemodynamic consideration suggest it must occur to some extent. Thus unevenness in the hematocrit of the perfusing pulmonary capillary blood is a mechanism in the genesis of the alevolar-arterial gradients which should be considered in addition to the known mechanisms of uneven ventilation-perfusion ratios and diffusion defects.


Autonomic origin of heart rate fluctuations at the onset of muscular exercise.

The time courses of the heart rate (HR) changes were studied in six healthy male subjects who performed step changes from rest to light dynamic leg exercise (50 W) in the sitting position during a) control, b) parasympathetic blockade (atropine, 2-2.5 mg iv), c) beta-adrenergic blockade (propranolol, 10 mg iv), and d) during combined blockade with both drugs. During the control and beta-blockade experiments all subjects showed an immediate, rapid increase in HR, reaching a peak value after about 10 s, whereafter an equally rapid transient drop by 10-20 beats/min took place reaching the lowest values about 17 s after the onset of work. HR then again increased to reach a  steady-state level within 60-90 s. In the atropine experiments this response pattern was not evident at all, whereas in the experiments with combined blockade it could be distinguished to a small, but significant degree. It is concluded that the observed fluctuations of HR  at the onset of light dynamic exercise can be explained by a rapid vagal withdrawal, followed by a transient increase in vagal tone.


Critical thermal maximum in mice.

The critical thermal maximum (the colonic temperature of heat-induced convulsion and righting reflex loss) and thermoregulatory response of male mice were examined following I, exposure to colonic temperature (Tco) 42 degrees C; II, a single exposure to the critical thermal maximum (Tco  44 degrees C); AND III, acclimation at ambient temperatures of 15 or 30 degrees C for 14 days. The critical thermal maximum (CTM) was greater in 30 degrees C acclimated mice than 15 degrees C acclimated mice  but was unchanged in mice surviving exposure to Tco 42 degrees C or the CTM. The heating time to apparent breakdown of thermoregulation coincident with an explosive rise in the Tco during exposure to ambient temperature 40.8 degrees C was increased (100%) during the 48-h period following exposure to Tco 42 degrees. It appeared that mice exposed to severe, short-term heat stress (Tco 42 degrees) undergo a compensatory increase in their thermoregulatory cooling capacity with little or no change in the upper temperature tolerated. The animals did, however, exhibit the capability for adaptive adjustments of the upper thermal limit during extended exposure to the more prolonged and less severe environmental heat stress of acclimation at 30 degrees C.


Regulation of respiration in sleeping dogs.

We have examined the respiratory changes that occur during physiological sleep in three dogs with exteriorized cervical vagal loops. Sleep stage was determined by behavioral and EEG criteria. During non-REM (NREM) sleep breathing was slower (mean change, 23%),deeper (mean change, 18%), and less variable (coefficients of variation, 0.05-0.10) than during wakefulness (W); minute volume of ventilation (Ve) decreased (mean change, 14%) and alveolar CO2 pressure (PAco2) increased slightly (mean change, 1.3 mmHg). In addition, the rate of O2 consumption and ventilatory response to hypercapnia were decreased. In contrast, REM sleep was characterized by rapid, shallow, and considerably more irregular (coefficients of variation, 0.18-0.30) breathing; Ve increased markedly and PAco2 decreased (mean change, 5.2 mmHg). Blockade of both cervical vagus nerves produced comparable changes in each stage of sleep (W, NREM, REM): breathing became slower and deeper, but the differences between stages and the marked irregularity in REM sleep persisted. In contrast, the Hering-Breuer inflation reflex (HBIR) was strong in W and NREM sleep, but weak in REM sleep. The results indicate that changes in respiratory control and stability during sleep are not due to fluctuations in vagal influence despite the fact that one vagal reflex (HBIR) was sleep-state dependent.


Sweating responses to central and peripheral heating in spinal man.

Studies of central and peripheral heating of a resting spinal man (T6) were performed under various ambient temperatures (20-34 degrees C). It was found that at a constant core temperature, sweating could not be initiated by sentient skin heating alone, but skin cooling alone did produce a rapid decrease in sweating response. Central heating alone induced sweating responses and the central temperature thresholds of sweating were inversely related to the ambient (sentient skin) temperatures. The local and mean sweating rates were found to be linearly related to the core temperature. The slopes of local sweating rates versus the core temperature vary increasingly with the following locations: chest, forearm, and forehead; but the slopes of mean sweating rates versus core temperature were essentially constant.


Rate of bicarbonate-chloride exchange in human red cells at 37 degrees C.

The rate of exchange of bicarbonate and chloride ions across the red cell membrane was studied in a continuous flow rapid reaction apparatus at 37 degrees C. A transmembrane gradient both ions was produced by mixture of cells suspended in a solution of one ion with an isosmotic solution of the other ion. Carbonic anhydrase activity was inhibited by acetazolamide to prevent changes in CO2 concentration during the experiments. Chloride and bicarbonate efflux from cells were studied in separate experiments at each experimental pH. Using a least squares technique, values of chloride and bicarbonate permeabilities were fitted to each pair of independent experiments. Chloride permeability averaged 1.1 (+/- 0.2 SD) X 10-4 cm/s and was not affected by change in pH. Recovered bicarbonate permeabilities varied widely, always remaining at least fivefold greater than chloride permeability. While bicarbonate permeability could not be accurately characterized, it appears to be greater than chloride permeability. Analysis of CO2 transfer with the estimated permeabilities indicates that the bicarbonate-chloride exchange by itself probably does not limit CO2 transfer.


Factors affecting a single-breath N2 washout phase IV.

A lung model was constructed to examine the effects of the following factors on the phase IV of a single-breath N2 washout: the lung's elasticity change with age, closing pressure (CP), regional volume (Volr) distribution, pleural pressure, and gradient (Grad). The analysis revealed 1) when the CP was assumed to be + 1.0 cmH2O, predicted changes in closing capacity (CC) due to alterations in elasticity agreed with previous experimental results for individuals above 40 yr; for younger age groups, the predicted values were apparently larger, suggesting the CP may be near zero; 2) difference in Volr distribution alone caused alterations in CC and the slope of phase IV; 3) for 1 cmH2O elevation of CP, closing capacity /total lung capacity (CC/TLC) was predicted to increase about 8%; 4) for 0.1 cmHiO/cm Grad increase, CC/TLC was predicted to rise approximately 7%. In conclusion, multiple factors affect phase IV.


Relationship of AaDO2 TO AIRWAY PCO2 in dog lungs.

We measured the arterial Po2 and AaDo2 in open-chest dogs respired with air and with 5% CO2 in air at various lung volumes using a constant hyperventilatory pattern. The AaDo2 was an inverse function of lung volume with both air and 5% CO2 and was also an inverse function of both alveolar and arterial Pco2 values except at quite high lung volumes. There were two series of closed-chest experiments. In the first series, ventilation was varied to produce alveolar Pco2 and Po2 changes. In the second series, the dogs were hyperventilated at a constant rate and Pco2 was varied by adding CO2 with alveolar Po2 levels kept relatively constant. In both series the AaDo2 was inversely related to Pco2. We conclude that, in dogs, the AaDo2 is independent upon the Pco2 and speculate that this may be related to the effect of CO2 on collateral ventilation, although the Bohr effect may account for some of the dependence.


Effect of exercise on cardiac output and distribution of uterine blood flow in pregnant ewes.

This study was designed to determine what effect physical training has on heart rate and stroke volume responses to exercise stress and to determine if exercise altered the distribution of uterine blood flow. Measurements were made in ten pregnant ewes at rest and immediately following exercise on a treadmill. Five ewes underwent physical training for 3 wk prior to measurement. An increase in heart rate with no change in stroke volume was observed following exercise in both trained and untrained ewes. Total uterine blood flow was not changed following exercise, but distribution was altered in favor of the placenta. Blood flow was evenly distributed within the placenta before and after exercise. The redistribution of flow to the placenta that occurs after exercise. tphe redistribution of flow to the placenta that occurs after exercise might represent a compensatory  mechanism for the fetus.


Frequency response analysis of the diaphragm in vivo.

Frequency response analysis was used to determine the dynamic response characteristics of cat diaphragm under isovolumetric conditions at functional residual capacity (FRC) and at lung volumes above and below FRC. In apneic cats, sinusoidally modulated pulse rate patterns were applied to both phrenic nerves. Modulation frequencies over the range of 0.05-4 Hz were used. Amplitude ratio vs. frequency plots obtained at FRC for intratracheal, intraesophageal, and intragastric pressures were essentially flat at low frequencies but decreased at higher frequencies. Intratracheal and intraesophageal pressure responses were altered by changes in resting lung volume while intragastric pressure was not. The amplitude ratio was decreased at lung volumes above FRC but increased at volumes below FRC. Thus, lung volume significantly affected the input-output relations between phrenic nerve input and diaphragm muscle output. In all preparations studied, significant phase lags were present throughout the entire modulation frequency range. However, in contrast to the effect of lung volume on amplitude ratio, phase lag was not dependent on changes in lung volume.


Closing volumes in man immersed to the neck in water.

Closing volumes (CV), along with residual volume (RV), vital capacity (VC), along with residual volume (RV), vital capacity (VC), and expiratory reserve volume (ERV) were determined in 10 subjects in the dry and while immersed to the neck in water. Closing volumes during immersion increased 41.3% (P less than 0.001) over dry values while RV decreased 9.35% (P less than 0.001) and VC decreased 9.94% (P less than 0.001). The large decrease of 71.3% (P less than 0.001) in ERV resulted in the impingement of closing capacity (CV + RV) on the tidal volume in 9 out of 10 subjects. We interpret this to mean that airway closure occurs during tidal ventilation in immersed subjects and may result in impaired gas exchange. When tourniquets were applied to all four limbs during immersion closing volumes increased only 32.1%, but increased to 64.3% when they were removed. If engorgement of peribronchial vessels predisposes airways to collapse, a reduction of plasma volume during an extended period of immersion might lessen this possibility. In a series of long term (2.5-h) immersion experiments where moderate reductions (-10 to -7%y in plasma volume were observed, we found, however, no correlative changes in closing volume.


Maximum exercise heart rate reduction with maturation in the rat.

Maximum exercise heart rate decreases with maturation in the rat as well as in man. The present study was undertaken to investigate the mechanism(s) which might be responsible for this reduction in max exercise heart rate in the rat. Maximum exercise heart rates were 618 +/- 7 vs. 580 +/- 9 beats/min for the young (5 wk) and mature (19 wk) rats, respectively. Atropine had no effect on max exercise heart rate. Propranolol reduced max heart rate in both groups with the older rats having the lowest value. Resting heart rates were recorded following injections of atropine propranolol, and propranolol plus atropine. Under all conditions, including control, heart rates were lower in the mature rats. Electrical stimulation in situ showed a significant difference in the threshold voltage for stimulation at 600 beats/min: 1.1 +/- 0.2 vs. 1.6 +/- 0.1 V for the young and mature rats, respectively. These data suggest that intrinsic changes occur in the myocardium with maturation and the reduction in max exercise heart rate is due to these intrinsic changes as opposed to changes in neural influences.


Gas embolism due to intravenous FC 80 liquid fluorocarbon.

Lethal gas embolism always occurs after FC 80 liquid fluorocarbon is injected intravenously (0.1 ml/kg body mass) in dogs breathing room air but not in dogs breathing oxygenated FC 80 liquid fluorocarbon. Gas embolism is not prevented in dogs that have been injected intravenously with FC 80 when they are exposed to 2 ATA (atmospheres absolute) 20% 02-80% N2, 9 ATA 5% O2-95% He, or 1 ATA 100%, O2. In dogs that die of FC 80-induced gas embolism, free gas in the right atrium contains approximately 0.5 g FC 80/liter, and Po2 and Pco2 in the gas are in equilibrium with their corresponding tensions in right atrial blood. These observations are consistent with the hypothesis that PFC 80 in alveolar gas does not equilibrate with PFC 80 (55 mmHg) in blood. The total gas tension in pulmonary capillary blood containing FC 80 and its vapor thus exceeds the total tension of alveolar gases (atmospheric pressure). Bubbles of O2, CO2, N2, FC 80, and water vapor form in the regions of the pulmonary capillary bed where the total tension of gases dissolved in blood exceeds the absolute blood pressure.


Acclimatization in a hot, humid environment: energy exchange, body temperature, and sweating.

Four trained young men, worked for 4 h/day at 43-50% of their maximum aerobic capacity for 3 days at 25 degrees C db, 18 degrees C wb and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. Their thermal status was assessed using direct calorimetry. As a group, the men showed classical acclimization responses, but there were marked individual differences. The calorimetric analysis revealed that reductions in strain were associated with minor changes in heat balance confined to the first and last hours of exposure. Events occurring within the first 4 days appeared to have little effect on body temperatures. Significant decreases in body temperature took place only when sweat and evaporation rate increased. A 10% increase in evaporation rate was accompanied by a 30% increase in sweat rate and a 200% increase in unevaporated sweat; thus, there is a wasteful overproduction of sweat. By the 10th day skin temperature was confined to the level necessary to evaporate sufficient sweat to achieve thermal balance with a fully wet body surface. The efficiency of heat transport within the body did not change with acclimatization.


Acclimization in a hot, humid environment: cardiovascular adjustments.

Four trained young men worked for 4 h/day at 40-50% of their maximum aerobic capacity first  for 3 days at 25 degrees C db, 18 degrees C wb, and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. This portion of the study was mainly concerned with central circulatory changes during acclimatization. The central circulatory adaptation to work in heat could be divided into four distinct phases: phase I (day 1) was characterized by a progressive fall in stroke volume (SV) during heat exposure but cardiac output (CO) was maintained above control values by high heart rates. Phase II (days 2 and 3) was marked by increases in SV ande decreases in heart rate but with little change in CO from phase I. During phase III (days 4-8 of acclimatization), CO increased due to increases in SV. Phase IV (days 6-8) was associated with decreases in rectal and skin temperature towards control levels. SV and HR both decline in this phase so that CO was not elevated greatly above  control levels. The results indicated that central circulatory and temperature regulating events are not casually associated in acclimatization.


Acclimatization in a hot, humid environment: body fluid adjustments.

Four trained men worked 4 h/day at 40-50% of their maximum aerobic capacity first for 3 days at 25 degrees C db, 18 degrees C wb and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. Between days 1 and 2 of heat exposure mean total circulating protein (TCP) and plasma volume (PV) increased 11.6% and 9%, respectively. Preexposure TCP and PV increased until day 6 of heat exposure. Of the protein fractions beta-globulins underwent the largest relative increase. During work movement of protein into and out of the vascular compartment was similar in control and acclimatizing subjects but the latter generally maintained a greater amount of protein and fluid within the vascular volume. There was no evidence of salt and water retention. The increase in vascualr volume was ascribed to transfer of interstitial protein and water to the vascular volume. Regression coefficients indicated significant correlations for changes in plasma volume versus heart rate, stroke volume, and cardiac output during acclimatization. It was concluded that the most critical event in heat acclimatization is the expansion of the plasma volume.


Adrenergic receptors and vascular resistance in cerebral circulation of the cat.

Infusion of catecholamines and pharmacologic blockade were used to demonstrate the presence of an adrenergic receptor system with both alpha and beta components inthe feline cerebral vasculature. For this purpose, the anatomically isolated brain preparation was perfused under controlled constant-pressure conditions to eliminate active autoregulatory changes and passive fluctuations in calculated cerebral vascular resistance (CVR) secondary to alterations of perfusion pressure. Alpha adrenergic activity was demonstrated as substantial cerebral vasoconstriction in response to infusions of l-norepinephrine and epinephrine; cerebral blood flow (CBF) was decreased by mean values of 25% and 29%, respectively, with calculated increases in CVR of 82% and 62%, respectively. Marked reductions in the vasoconstriction produced by these two catecholamines followed the use of the alpha receptor blocking drug, phenoxybenzamine. Isoproterenol consistently produced cerebral vasodilation (mean CVR decrease of 22%), and this vasodilation was blocked during infusion of a specific beta adrenergic blocking agent, propranolol. Histamine vasodilation (mean CBF increase 49%) appeared to be independent of the classic adrenergic mechanisma. The observed responses are explained on the basis of a functionally significant cerebrovascular adrenergic system having high specificity and demonstrating considerable potency. The data also indicate a predominance of alpha over beta adrenergic cerebrovascular reception.


Occlusion pressures in men rebreathing CO2 under methoxyflurane anesthesia.

The effect of general anesthesia on control of breathing was studied by CO2 rebreathing and occlusion pressure measurements in six normal human subjects under methoxyflurane anesthesia. CO2 was found to increase the amplitude of the occlusion pressure wave without changing its shape, so that CO2 responses in terms of the occlusion pressure developed 100 ms after the onset of inspiration  (Po/0.1) gave results equivalent to the responses in terms of Po/1.o or any other parameter of the pressure wave. Methoxyflurane depressed the ventilatory response to CO2 but not the occlusion pressure response, implying that the most important action of the anesthetic was to increase the effective elastance of the respiratory system rather than to depress the respiratory centers. The elastance was further increased by CO2, and this mechanical change had the effect of shifting the "apneic threshold" extrapolated from the ventilatory response curve to a lower PAco2. Frequency of breathing, inspiratory and expiratory times were not altered by CO2 in anesthetized subjects.


Solubility of 92 in blood with different hemoglobin concentrations at low temperatures.

The Brunsen solubility coefficients for O2 in blood obtained from healthy nonsmoking subjects have been determined at 0, 6, and 12 degrees C for bloods of hemoglobin concentrations 5.6, 10.2, 15.7, and 22.5 g/100 ml. Direct gasometric measurements show that blood has a relative solubility (alphabeta/alphah2o) different for each hemoglobin concentration but constant for any given hemoglobin concentration at the temperatures studied (0.6, and 12 degrees C). For hemoglobin concentrations 5.6, 10.2, 15.7, and 22.5 g/100 ml alphabetao degrees C/alphabeta 12 degrees C rations were 1.36, 1.35, 1.35, and 1.35, respectively. The alpha H20(0 degrees C)/alpha H20(12 degrees C) ratio is 1.34. Consequently, it was possible to construct a table for the Brunsen solubility coefficients for O2 in blood from O to 15 degrees C of different hemoglobulin concentrations. Values from 10 to 15 degrees C published in the Biologal Hanbook, Respiration and Circulation, based on extrapolations from previous direct measurements of temperatures from 18 to 37 degrees C differ only 1% from our present results.


Local regulation of collateral ventilation  by oxygen and carbon dioxide.

The effects of changes in CO2 and O2 on the mechanics of collateral ventilation were studied in anesthetized paralyzed dogs. A doublelumen catheter was wedged into a peripheral airway obstructing a segment of lung distal to the catheter. Through one lumen of the catheter, air, 5% CO2 in air, 10% CO2 in air, 5% O2 in N2, or 5% CO2 in N2 was infused at a constant flow (V). Pressure (Ps) was monitored through the other lumen. At functional residual capacity the resistance  to collateral flor Rcoll = Ps/V. When V was interrrupted , the time for Ps to fall 63% was defined as the time constant for collateral ventilation, Tcoll. The effective compliance (Cs') = Tcoll/Rcoll. When air was replaced by 5% CO2, Rcoll fell 46.3% (+/- SE 2.8) and Tcoll fell 41.5% (+/- SE 3.0). When the CO2 concentration was increased from 5% to 10%, Rcoll fell an additional 9.2% (+/- SE 2.2) and Tcoll fell an additional 5.1% (+/- SE 4.4). When air was replaced by 5% O2 in N2, Rcoll rose 36.6% (+/- SE 6.0) and Tcoll rose 13.6% (+/- SE 10.5). No significant changes in Cs' were noted. We conclude that varying concentrations of CO2 and O2 provide potent mechanisms for the control of collateral ventillation which may be of importance in the regulation of ventillation perfusion relationships at the local level.


Electromechanical stimulator for presenting moving cutaneous stimuli.

Recent interest in the neural processing of complex cutaneous stimuli such as moving stimuli has necessitated more versatile stimulating devices. This article describes the construction  and application of a relatively inexpensive instrument, utilizing equipment readily available in most neurophysiological laboratories, which provides a variety of moving cutaneous stimuli of selected velocities, excursions, and directions. The electronic portion of the instrument consists of a logically controlled varable rate integrator wired to conform to the electrical and mechanical characteristics of a Grass P5 plug-in. This circuitry operates the remainder of the instrument which consists of a P5 driver amplifier used to drive the pen motor mechanism that provides the moving cutaneous stimulus.


Analytical refinements in animal calorimetry.

An analysis is presented of a system for indirect calorimetric measurement. Emphasis has been placed upon problems associated with the use of large climate-controlled chambers. The dynamics of gas exchange and the influence of ambient conditions on various parameters have been subjected to physical analysis which has led to the following conclusions: 1) Fast-response measurement of heat production can be achieved even if the size and hence washout time of the chamber is large. 2) Accurate continuous measurement of heat production over long periods, without correction for changes in barometric pressure, is possible if suitable instrumentation is chosen. 3) A method for calibration of a paramagnetic oxygen analyzer achieved high accuracy at low cost. 4) The entire system has been checked by simulation of gas exchange in the chamber, by injection of nitrogen at a known rate.


Technique for serial right and left ventricular endocardial biopsy in dogs.

A method is described for obtaining left and right ventricular endocardial biopsies repeatedly over a period of 3-6 mo in the dog. The left ventricular endocardial biopsy technique consists of the placement of a catheter via the venous route across the atrial septum and into the left ventricle. The biopsy catheter is in turn placed within this transseptal catheter. Tissues obtained by this method were satisfactory for both light and electron microscopic examination. At postmortem examination, only minimal and insignificant damage existed at the biopsy site. Consequently, we recommend this technique for the study of progressive pathologic changes in the endocardium that occur during the course of an experiment which can be identified and quantified in comparison to the control state.


Oxygen uptake measurements during competitive marathon running.

Oxygen uptakes and running speeds of two marathon runners as well as average slopes of the running terrain were measured approximately every 3 miles of a competitive marathon. The runners had energy expenditures requiring from 68 to 100% of their Vo2 max, confirming previous estimates. As the race progressed, both runners exhibited decreases in V92 while running at similar rates and slopes. At 23.4 miles, one runner was found to be utilizing 4.54 l/min, a value equivalent to his Vo2 max.


Fluid-filled blood pressure measurement systems.

The performance of catheter-manometer systems for the measurement of pulsatile pressure has been evaluated by both experimental techniques and theoretical considerations. The former approach has shown, on occasion, multiple maxima in the amplitude response. The latter has been approached in a variety of ways, ranging from extreme lumping to application of transmission line theory while employing different configurations in the system's representation. Multiple maxima have also been seen, The present paper identifies the sources of the differences found and compares the relative merits of various theoretical approaches. It introduces the compliance of the system as a figure of merit and provides a simple first-order approximation formula for evaluation of the quality of a system. Damping and impedance matching to improve the system's frequency response were studied. It was found that they were not needed in a very stiff or a very compliant system, nor should one worry about the  representation of such a system.


Determing the pulmonary excretion rate of carbon monoxide in newborn infants.

A simplified technique was devised for measurement carbon monoxide excretion rates in newborn infants. Determinations can be performed quickly and repetitively in a noninvasive manner, with a sensitivity sufficient for use even on small preterm infants. Resolution of the method is +/- 4.3 mul/h (SD); however, variations in infant respiration rate may cause much greater changes in actual excretion rate. Preliminary results with five full-term newborn agree to within 15% of previously reported data. The system will be used extensively in ongoing studies involving total bilirubin production as a function of gestational age.


A model of graded ischemia in the isolated perfused rat heart.

Insertion of a flow pump into the Langendorff retrograde perfusion apparatus has permitted the production of stable, graded ischemia in hearts whose hemodynamic and metabolic response may be evaluated. Ventricular pressures were monitored with a modified balloon and catheter-tip manometer system, and oxygen consumption , lactate and glucose metabolism, and tissue high-energy phosphate stores measured. A 15-min stabilization period in 56 paced hearts was followed by 15 min of either full, 40, 30, 20, or 10% coronary flow, after which the ventricular tissue was freeze-clamped for tissue assay. Tissue creatine phosphate fell progressively from 23.7 in full flow hearts to 9.9 mumol/g dry wt after 90% reduction in flow. This was accompanied by a graded reduction in ATP from 20.3 to 14.0 mumol/g dry wt and a rise in AMP from 1.1 to 2.6 mumol/g dry wt. Tissue lactate rose progressively from 22.3 to 60.1 mumol/g dry wt. Hemodynamic function correlated with coronary flow. This preparation offers an opportunity to study pharmacological and metabolic interventions in ischemic heart disease.


Comparison of proximal tubule fluid-to-plasma ultrafiltrate chloride ratio in rats and dogs.

Previous studies in rats have demonstrated that the concentration of chloride in proximal tubule fluid is greater than that in plasma. The gradient reaches a free-flow steady-state level in the early proximal tubule and is maintained throughout the accessible proximal tubule. On the other hand, studies in dogs are in conflict regarding either the existence of a gradient or the development of a free-flow steady-state level. Since a species difference of tubule fluid to plasma chloride (TF/PC1) may exist, the present study was done to systematically compare the tubule fluid to ultrafiltrate chloride ratio (TF/UFC1) in hydropenic rats and dogs during normal acid-base balance. Chloride was analyzed by microelectrometric titration. In the rat the TFC1 and UFC1 concentrations were 139 +/- 1.4 and 120 +/- 1.2 meq/1, respectively. In the dog the TFC1 and UFC1 concentrations were 138 +/- 1.3 and 121 +/- 1.5 meq/1, respectively. Thus, there was no significant difference in the TF/UFC1 ratio between the rat (1.17 +/- 0.02) and the dog (1.14 +/- 0.01). Furthermore, regression analysis indicates that there is no correlation between TF/UFC1 and TF/PIn in either the rat or dog, which suggests that the gradient originates early in the proximal tubule and is maintained throughout the accessible proximal tubule in both species.


Glucagon and plasma catecholamines during beta-receptor blockade in exercising man.

Seven men ran at 60% of individual maximal oxygen uptake to exhaustion during beta-adrenergic blockade with propranolol (P), during lipolytic blockade with nicotinic acid (N), or without drugs (C). The total work times (83 +/- 9 (P), 122 +/- 8 (N), 166 +/- 10 (C) min, mean and SE) differed significantly. Epinephrine rose progressively above preexercise levels (0.06 +/- 0.01 ng/ml); at exhaustion concentrations in P experiments (2.15 +/- 0.41) were larger than in N (1.08 +/- 0.31) and C (0.72 +/- 0.28) experiments. Norepinephrine increased consistently while insulin decreased. After an initial decrease glucagon concentrations increased progressively in parallel with declining plasma glucose and were at exhaustion always three times preexercise values. Thus beta-adrenergic blockade did not diminish the glucagon response. Nor was this response increased when alpha-receptor stimulation in P experiments was intensified. Carbohydrate combustion was smaller and NEFA and glycerol concentrations in serum larger during C experiments. Alanine concentrations were never raised at exhaustion. Accordingly, neither stimulation of adrenergic receptors nor NEFA and alanine concentrations are major determinants for the exercise-induced glucagon secretion in man. It is suggested that decreased glucose availability enhances the secretion of glucagon and epinephrine during prolonged exercise.


Ventilatory responses to the metabolic acidosis of treadmill and cycle ergometry.

Ventilation and acid-base responses were studied at comparable levels of O2 uptake during cycle ergometer and treadmill exercise, to determine the extent to which the type of exercise affects these responses. Twenty male subjects performed 50-, 100-, and 150-W cycle ergometer exercise and three work rates of similar O2 uptake on a treadmill. At comparable oxygen uptakes, arterial lactate and VE were higher and arterial pH and bicarbonate were lower for cycle ergometer than treadmill exercise. These differences could be accounted for by the greater degree of metabolic acidosis during cycle ergometer work. The increment in VE over that predicted (from an extrapolation of the linear relationship of the VE-VO2 relationship for low work rates) was linearly related to the decrease in arterial bicarbonate; VE was increased by approximately 4 1/min for each meq/1 of bicarbonate decrease for both treadmill and cycle ergometry.


Oxygen consumption in relation to work load in students with cerebral palsy.

Eighteen adolescents with various forms of cerebral palsy performed tests on a mechanically braked ergometer bicycle. VO2 was measured at different loads and net mechanical efficiency calculated. It was found that efficiency was poor at light loads for most of the students but that there were significant intergroup differences in mechanical efficiency at higher loads. The leveling-off plateau demonstrated by healthy adolescents was only attained by a few of the disabled students. It was concluded that the muscle hypertonia and involuntary movements were responsible for the high level of energy expended in the mechanical work performed.


Skeletal muscle enzyme alterations after sprint and endurance training.

Specifically designed programs of sprint and endurance running were used to determine how different types of training affect enzyme activities in selected energy metabolism pathways. Three types of rat skeletal muscle were studied. After 8 wk of training, small but significant decreases in lactate dehydrogenase activity (15%) were found in the soleus and white vastus lateralis muscles of the sprint animals. Decreased levels of phosphoglucomutase and lactate dehydrogenase (approx. 20%) of the white vastus lateralis muscles of the endurance group were observed at the same time. By 16 wk of training, fumarase activity increased approximately twofold in the white vastus muscles and 45% in the soleus and plantaris muscles of the endurance group. Similarly, increased fumarase activity (42%) was seen in the soleus muscles of the sprint group. In all muscles, phosphoglucomutase and lactate dehydrogenase activities generally were lower in the endurance animals than in the control animals. No significant differences were found between the sprint and endurance groups at either or sixteen weeks of training. These results suggest that similar enzyme adaptations occur over time with both types of training.


Changes in distribution of cardiac output by surface-induced deep hypothermia in dogs.

The effects of surface-induced deep hypothermia on organ blood flow and on the distribution of cardiac output were investigated in the anesthetized dog. Organ flows were determined by the radioactive microsphere technique. Phenoxybenzamine (POB) was administered prior to hypothermia to minimize vasoconstriction and hence facilitate cooling. Measurements were made before POB, on stabilization after POB, and during hypothermia. Cardiac output was reduced by POB as was blood flow to the pancreas, small intestine, and skeletal muscle. Hypothermia, following POB, produced a further fall in Q and during this maneuver blood flow fell in all organs and vascular beds studied. The relative distribution of Q during hypothermia was essentially the same as in the control except the brain, kidneys, and pancreas received a smaller fraction of the total output. The relatively normal distribution of a reduced cardiac output during hypothermia was in marked contrast to distribution of comparable low cardiac output induced by hemorrhage. In the latter condition, the fraction of the cardiac output perfusing the brain, kidneys, adrenals, and hepatic artery was increased.


Phasic reflux of pulmonary blood flow in atelectasis: influence of systemic PO2.

In 16 dogs ventilated with 100% O2, control blood flow to the left lung was 35 +/- 2% of aortic flow. When left lung atelectasis was induced, left pulmonary artery flow fell to 19 +/- 2% of aortic flow. A large retrograde component of flow developed in this pulmonary artery, suggesting that blood flows into the pulmonary arteries of both lungs during systole, but flows back out of the collapsed lung and into the uncollapsed lung during diastole. Systemic PaO2 remained above 78 mmHg. Subsequently, when the ventilation of the right lung was changed from oxygen to room air, systemic PaO2 fell to 64 +/- 3 mmHg and atelectatic left lung flow rose from 19 +/- 2% to 28 +/- 2% f aortic flow. This was associated with a reduction in reflux from the atelectatic lung. These results suggest that the attenuation of flow to an atelectatic lung is more pronounced if systemic normoxemia is maintained by adequate oxygenation of the normal lung.


Effect of indomethacin and atropine in experimental asthma in conscious guinea pigs.

Pulmonary mechanics were measured in unanesthetized guinea pigs sensitized to horseradish peroxidase (HRP) before and during two aerosolized challenges of this antigen. During the first challenge the pulmonary resistance increased in all animals. Prior to second challenge the animals received either atropine (0.2 mg/kg) or indomethacin (10 mg/kg) intraperitoneally. We found that during the second challenge the indomethacin group had an increase in pulmonary resistance slightly greater or similar to that during the first exposure to the antigen, while the animals treated with atropine had a significantly diminished response (P less than 0.05). In five guinea pigs sensitized to HRP but challenged with a nonspecific aerosal made up of rabbit albumin, we found that pulmonary resistance increased in some animals and that this increase could be partially blocked by atropine. These results show that indomethacin has no effect on this model of allergic airways disease. They also confirm the importance of the vagus nerves in allergic bronchoconstriction and in addition show that nonspecific hyperirritability can be induced in some animals by immunization.


Respiratory load compensation in awake and sleeping dogs.

We have investigated immediate and progressive ventilatory responses to external elastic loads in five dogs with cervical vagal loops. Three dogs were studied while awake (W) and during non-REM sleep (S); the other two during barbiturate anesthesia (A). Elastic loads were applied at the end expiration for 1-6 breaths by having the dogs breathe from a rigid container (partial load) or against an occluded airway (infinite load). "Effective" elastance (EE) was determined from the tidal volume (VT)-tracheal pressure relationships of the unloaded, partially loaded, and infinitely loaded breaths. Passive thoracic elastance during W and S averaged 16.7 cmH2O/1. EE averaged 55.8 cmH2O/1 during W, 54.7 during S, and 59.5 during A. Vagal blockade (VB) induced large changes in VT but no change in EE in W or S; during A, EE decreased 37.5%. With sustained loading (partial) there was a progressive increase in VT but a corresponding increase in chemical (primarily hypoxic) respiratory drive, so that EE remained constant during five loaded breaths. VB augmented the progressive increase in VT during W or S but virtually abolished the increase in A. Thus the responses to elastic loads in W and S are similar and independent of conscious reactions or vagal influence; responses during A differ considerably. "Progressive load compensation" is a reflection of increasing of increasing chemical drive and not of progressive changes in EE.


Respiratory and other responses in subjects immersed in cold water.

Subjects have been immersed in water at 27 degrees C and 10 degrees C and while immersed their respiratory rates, minute volumes, and end-tidal PCO2 levels were measured. Measurements were made with the subjects at rest, exercising at approximately 0.8 liter oxygen-min-1, and very vigorously at 1.8-2.0 liters oxygen-min-1. Immersion in the cold water caused an increase in respiratory rate and a fall in end-tidal PCO2. At the moderate rate of exercise the hyperventilation persisted in relation to the oxygen demand and there was still a significant reduction in end-tidal PCO2. At the greatest rates of exercise, the end-tidal PCO2 did not differ from that obtained in similar rates of exercise in warm water. Preheating the subject in a sauna so as to increase skin temperature, with minimal change in body temperature, greatly attenuated the ventilatory and end-tidal PCO2 responses to cold water immersion. The significance of these findings is discussed.


Plasma vasopressin and renin activity in women exposed to bed rest and +Gz acceleration.

To study the effect of prolonged recumbency on plasma vasopressin and renin activity, eight women (23-34 yr) were subjected to 17 days of absolute bed rest. The +3 Gz tolerance of the subjects was tested before and after 14 days of bed rest. From day 2 and through day 17 of bed rest, plasma arginine vasopressin (AVP) levels were reduced 33%. Plasma renin activity (PRA) increased 91% (P less than 0.05) above ambulatory control values from days 10 through 15 of bed rest. When compared to precentrifuge values, exposure to +3 Gz prior to bed rest provoked a 20-fold rise (P less than 0.05) in mean plasma AVP but resulted in only a slight increase in PRA. After bed rest, acceleration increased plasma AVP 7-fold (P less than 0.02); however, the magnitude of this increase was less than the post +3Gz value obtained prior to bed rest. After bed rest, no significant rise was noted in PRA following +3 Gz. This study demonstrates that prolonged bed rest leads to a significant rise in the PRA of female subjects, while exposure to +Gz acceleration provokes a marked rise in plasma AVP.


Trapped air in ventilated excised rat lungs.

Degassed excised rat lungs were ventilated in a water-filled plethysmograph with the carina as the zero pressure reference. Pressure-volume curves were recorded from a minimum transpulmonary pressure (Pmin) of -5 cmH2O to a maximum pressure (Pmin) of 30 cmH2O. An index of the minimun volume for the lung (Vm) divided by the maximum lung volume for the same cycle (Vmax) was used as an index of the amount of air trapped within the lung. As the flow rate was decreased from 38.2 to 1.9 ml/min, there were significant increases in the amount of air trapped in the lung. As the maximum pressure was decreased to 25 and 20 cmH2O, or the minimum pressure was increased to 6 and 11 cmH2O, the amount of trapped air in the lung significantly decreased. The rate of lung inflation had a much greater influence on the amount of trapped air than either the deflation rate or stress relaxation. The results are consistent with the theory that bubbles are formed during inflation and are the main cause of air trapped in the excised lung.


Visceral blood flow distribution during exercise to exhaustion in conscious dogs.

We measured changes in organ blood flow (OBF) distribution and systemic hemodynamics in 9 dogs running 5-13 km/h during steady-state (SS) and exhaustive (EE) exercise on a treadmill at 8-15% grade for an average of 35 min. SS was defined when a heart rate (HR) of 80% maximum was attained and when HR was constant for 5-8 min. EE was defined as when the dog collapsed, unable to run longer. We measured heart rate, mean aortic pressure, cardiac output, and stroke volume via implanted probes and catheters. All hemodynamic parameters rose significantly (P less than 0.05) with exercise. Stroke volume and aortic pressure did not rise above SS levels during EE. OBF, determined with microspheres, to the liver, stomach, and intestines declined during SS and returned to control levels during EE. OBF to the kidneys and pancreas was not significantly changed by either SS or EE. OBF to the spleen declined progressively with SS and EE. We concluded that 1) the effect of exercise on OBF depends on the severity of exercise, emphasizing the need to quantify work loads in exercise studies, and 2) the splanchnic organs do not respond homogeneously to exercise and that this response is not adequately described by % of CO assessments.


Renal and intrarenal blood flow distribution in swine during severe exercise.

It is known that a compensatory reduction and diversion of renal flow occurs in severe exercise in humans but not in dogs. We investigated this in miniature swine by measuring changes in total renal blood flow (TRF) and intra-renal blood flow (IRBF) distribution with tracer microspheres (15 +/- 5 mum) at rest and during steady-state exercise at 4.8-7.2 kph and 0% grade, and during severe exercise at 4.8-7.2 kph and 10% grade. We measured heart rate and cardiac output (Q) via implanted probes. TRF was determined as a percent of Q and as ml/100 g per min. IRBF was determined for the outer cortex, inner cortex, outer medulla, and inner medulla. Our results show that renal blood flow is significantly (P less than 0.05) reduced in pigs with exercise. Steady-state exercise reduced flow to about 66% of control and severe exercise reduced renal flow to 30% of control. IRBF was unchanged throughout. These results show that the exercising pig augments blood flow to skeletal muscle by reducing blood flow to kidneys, a response known to occur in man.


Respiratory mechanics in normal hamsters.

Lung volumes and quasi-static deflation volume-pressure relationships were measured in male golden hamsters anesthetized with pentobarbital. Volume was measured with a pressure plethysmograph, and pleural pressure was estimated by the use of a water-filled esophageal catheter. Mean body weight +/- SE was 122.3 +/-3.0 g, mean lung weight was 0.74 +/- 0.2 g or about 0.6% of body weight. Mean lung volume at 25 cmH2O transpulmonary pressure (TLC25) was 7.2 +/- 0.14 ml, 9.78 +/- 0.17 ml/g lung weight or 5.92 +/- 0.06 ml/100 g body weight. Mean functional residual capacity was 2.4 +/- 0.06 ml or 33.3% of TLC25. Mean vital capacity was 5.2 +/- 0.13 ml. Mean quasi-static compliance of lung was 0.63 +/- 0.03 ml/cmH2O. Chord compliance of chest wall between lung volumes of 1 and 4 ml above RV was 3.39 +/- 0.53 ml/cmH2O. At FRC, the chest wall recoiled inward, so that pleural pressure was positive (1.4 +/- 0.13 cmH2O) and the lung was resisting further collapse. The slope of the lung's deflation volume-pressure curve changed at FRC, ERV was small (0.36 +/- 0.03 ml), and RV was determined by complete airway closure. Thus the mechanisms determining FRC are unusual and include an influence of airway closure.


Delineation of flow-limiting segment and predicted airway resistance by movable catheter.

Using intrabronchial lateral pressure catheters, we determined the precise location and movement of the flow-limiting segment (FLS) in excised dog and human lungs; under maximal flow conditions, profiles of resistance and transmural pressure from the "mouth" to segmental bronchi were also obtained. In the same lungs, using the interrupter technique, IVFP curves were constructed; with these curves and lung compliance, the relationship between Vmax and Pel was studied using the analysis of Pride et al. The FLS consisted of well-demarcated short lengths (2-3 cm) of the trachea at large lung volumes which moved to lobar or semental bronchi at small volumes (10-20% TLC). These relationships, coupled with observations of the movement of the equal pressure point (EPP), support the idea that in the excised lung the location of the FLS is determined by both the location of the EPP and the compliance of the downstream airway wall; thus FLS MAY NOT FOLLOW UPSTREAM MOVEMENTS OF EPP until EPP reaches a more compliant segment of the bronchial tree (lobar and proximal segmental bronchi). Upstream resistance (Rs) and transmural pressure of collapse (Ptm') calculated indirectly from the slope and intercept of the Vmax vs. Pel relationship accurately predicted values of resistance and transmural pressure measured directly in the same lungs at a point just upstream to FLS.


Pulmonary elasticity in children and adolescents.

Static (Cst(L)), dynamic (Cdyn(L)), and "specific lung compliance (CL/TLC, CL/FRC) and the elastic recoil pressure of the lungs (Pst/(L)) were measured in 131 healthy children and the adolescents (age 6 to 17 years) from simultaneous recordings of esophageal pressure and lung volume. Esophageal elastance and vertical esophageal pressure gradients were also studied. Pst(L), measured at different lung volumes (fractional) from the expiratory quasi-static pressure-volume (PV) curves of the lungs, increased significantly with increasing body height, age, and body surface. Cst(L), determined from the midportion of PV curves, and Cdyn(L) measured during normal breathing at frequencies around 20/min also increased significantly with somatic growth. "Specific" Cst(L) decreased with increasing body height, age, and body surface. "Specific" Cdyn(L), esophageal elastance, and the vertical esophageal pressure gradient were independent of body height, age, and body surface, Cdyn(L) was less than Cst(L) mainly in smaller and younger children, and was not considered a valid index of pulmonary elasticity. Values of Pst(L), "specific" Cst(L), and the change of slope of the midportion of PV curves in children and adolescents suggested developmental changes of pulmonary elasticity in man over the age range studied.


Influence of lung volume and electrode position on electromyography of the diaphragm.

In cats anesthetized with Nembutal, electromyograms of the diaphragm (Edi) were recorded from an anchored esophageal electrode, a pair of silver hooks inserted in the paratendinous region, and a pair of silver hooks and a pair of clips of small surface inserted in the costal region of the diaphragm facing the rib cage at FRC but covered with lung tissue at FRC + 80 ml. When single supramaximal electrical stimuli were applied to an isolated phrenic nerve, changes in lung volume from RV to near TLC had a negligible effect on muscle potentials from esophageal or paratendinous hooks, but increased the amplitude of potentials recorded from peripheral hooks and clips. In addition, it was found that small displacements of the esophageal electrode caused substantial changes in the amplitude of the recorded muscle potentials. The integration of the Edi spontaneously generated during occluded inspirations, recorded from paratendinous hooks and the esophageal electrode was linearly related to transdiaphragmatic pressure up to 50 cmH2O at all lung volumes. Above that level, esophageal electrode recordings showed a curvilinear Edi/Pdi relationship, while hook recordings showed a rectilinear relationship.


Design improvement for the Scholander gas analyzer.

A simple design improvement is presented which eliminates stopper leakage and improves the reliability and convenience of the Scholander gas analyzer.


Blood pressure responses as an indicator of the anesthetic level in ground squirrels.

In many experiments in visual physiology which employ halothane anesthesia, it is difficult to judge accurately an animal's anesthetic state, particularly so because of the necessity for paralysis and artificial respiration. For the ground squirrel (Citellus tridecemlineatus and C. mexicanus), we find that measures of arterial pressure response to a noxious stimulus combined with mean arterial pressure allow for an accurate division of halothane anesthetic state into five stages. All five stages are identified and are the same regardless of whether the animal is unparalyzed or is paralyzed and artificially respired. Use of these measures in long-term experiments allows for recognition of and adjustment for small perturbations of anesthetic state that may occur even though inhaled halothane concentration remains constant.


VO2max during horizontal and inclined treadmill running.

The VO2max response of 12 well-trained and highly motivated college males was measured using two treadmill protocols: horizontal (H) and inclined (I). The duration of each test averaged 10 min. In the H test the treadmill bed was horizontal with the running rate held constant for the first 6 min, after which time it was increased at 1-min intervals to near maximal subject running speed, according to the HR response, until exhaustion. The I method simulated the protocol of Costill and Fox, with the treadmill speed at about 80-90% of mean maximal running rate established from 12- and 15-min track runs. The treadmill bed was held horizontal during the first 4 min, after which time it was elevated to 4% and elevated 2% each 2 min thereafter until exhaustion. No significant differences were found in VO2max, 4.267 1/min (I), and 4.192 1/min (H), average max HR, 190.4/MIN (I), and 188.9/min (H); respiratory rate, 56.4/min (I), and 62.0/min (H); and VEBTPS, 145.2 1/min (I), and 143.3 1/min (H). It was concluded that the intensities of both treadmill methods, H and I, were sufficient to produce a nonsignificant difference in maximal VO2 values with the type subjects employed.


Microcannulation--a new micropuncture technique application in cat pancreas secretion.

A new micropuncture technique of microcannulation has been developed and applied in cats to study exocrine secretion in the pancreatic ducts. Two micropipets of different diameters are assembled with the smaller pipet (10-20 mum) mounted inside the larger (25-50 mum). Using the combination, a larger pancreatic duct (less than 300 mum) is directly punctured and the inner pipet is advanced into the lumen of a small (20-50 mum) duct, which would otherwise be inaccessible. In anesthetized cats, during maximal stimulation with secretin (GIH 4-6 units/kg per h iv) the average chloride concentration of juice obtained from small ducts (25-50 mum) was 106 +/- 3 meq/1 and from large ducts (50-150 mum) was 75 +/- 5 meq/1. The results were confirmed by conventional micropuncture techniques which were technically more difficult. This method to collect fluid from small ducts is more physiological than direct micropuncture and thus the technique is a useful addition to micropuncture methodology.


Digital stimulator control system for introducing premature stimuli.

A control system to convert a general-purpose stimulator into one which will generate premature stimuli at variable but controlled intervals is described. The control system was developed to sense spontaneous cardiac depolarizations and inject premature stimuli at preset elapsed times after every 10th or every spontaneous depolarization. The delay may be set by an analog circuit or by digital thumb-wheel switches. The output of the stimulator also may be coupled to the input, permitting the use of the system as a standard asynchronous stimulator with digital control of the pulse interval. A block diagram is presented to permit duplication of the system using standard digital and analog integrated circuits.


A mechanical-reflex oscillator hypothesis for parkinsonian hand tremor.

Spectral analysis was performed on postural hand tremor records obtained from 22 parkinsonian subjects. Of these 22 subjects, 18 had postural hand tremor that occurred primarily at a single frequency during any one 16-s period. In general, this tremor occurred at different steady-state frequencies (each calculated over 16 s) between about 4 Hz and 8-9 Hz. This frequency decreased approximately 1 Hz for each 10-fold increase in displacement amplitude (root-mean-square, rms, amplitude determined at 16 cm from the wrist), decreasing from 8-9 Hz at about 30 mum to 3.75-4.0 Hz at about 30,000 mum. The major finding was that the frequency of parkinsonian hand tremor was nearly the same as that for hand tremor from normal subjects when these frequenceis were compared at similar rms displacement levels. This comparison, plus a comparison between other aspects of these two kinds of tremor, indicate that the mechanism for parkinsonian hand tremor is similar to that for large-displacement (greater than 100 mum) hand tremor of normal subjects, i.e., a mechanical-reflex oscillator mechanism.


Transport of glucose and glycine in Schizosaccharomyces pombe during the cell cycle.

Cell growth and uptake of glucose and glycine during the cell cycle were studied in synchronous cultures of Schizosaccharomyces pombe. Rates of accumulation of glucose and glycine were constant during most of the cell cycle, implying a constant rate of cell mass increase. Rates of uptake of glycine appeared to double at an average cell age of 0.9 generations.


Oxygen requirement for acetylene reduction by pure cultures of rhizobia.

The oxygen and nutritional requirements for acetylene reduction by Rhizobium japonicum and Rhizobium sp. in liquid culture are described. The optimal oxygen concentration was about 0.1% in the gas phase, which is lower than that of any other known aerobic nitrogen-fixing microorganism. these organisms are also unique in that nitrogenase synthesis is not repressed in the presence of ammonium chloride under certain cultural conditions, in contrast to other wild-type bacteria.


Natural paucity of anaplerotic enzymes: basis for dependence of Arthrobacter pyridinolis on L-malate for growth.

Previous work has shown that in Arthrobacter pyridinolis the transport systems for glucose and several amino acids are respiration coupled, with malate oxidation occurring concomitantly with transport. The requisite malate has to be supplied exogenously, so that growth on glucose or certain amino acids only occurs if malate is also present in the medium. These and other data suggested that A. pyridinolis might be deficient in anaplerotic enzymes, which maintain intracellular levels of dicarboxylic acids. A comparative study was undertaken of anaplerotic enzymes in A. pyridinolis and in a closely related species, A. crystallopoietes, which has respiration-coupled transport of glucose but can grow on glucose without added malate. The paucity of anaplerotic enzymes in A. pyridinolis and its probable relationship to the malate requirement for growth on glucose were documented as follows: (i) A. crystallopoietes, but not A. pyridinolis,  possesses phosphoenolpyruvate carboxylase activity, and neither species contains pyruvate carboxylase; (ii) both A. pyridinolis and A. crystallopoietes possess glyoxylate pathways that are induced by acetate but not by hexoses; (iii) isocitrate lyase-deficient mutants of A. pyridinolis fail to grow on rhamnose and fructose as well as acetate; and (iv) mutants of A. crystallopoietes that require malate for growth on glucose are deficient in phosphoenolpyruvate carboxylase.


Pathways of 4-hydroxybenzoate degradation among species of Bacillus.

The pathways used by three bacterial strains of the genus Bacillus to degrade 4-hydroxybenzoate are delineated. When B. brevis strain PHB-2 is grown on 4-hydroxybenzoate, enzymes of the protocatechuate branch of the beta-ketoadipate pathway are induced. In contrast, B. circulans strain 3 contains high levels of the enzymes of the protocatechuate 2,3-dioxygenase pathway after growth on 4-hydroxybenzoate. B. laterosporus strain PHB-7a degrades 4-hydroxybenzoate by a novel reaction sequence. After growth on 4-hydroxybenzoate, strain PHB-7a contains high levels of gentisate oxygenase (EC 1.13.11.4) and maleylpyruvate hydrolase. Whole cells of strain PHB-7a (grown on 4-hydroxylbenzoate) accumulate 2,5-dihydroxybenzoate (gentisate) from 4-hydroxybenzoate when incubated in the presence of 1mM alpha,alpha'-dipyridyl. Thus, strain PHB-7a appears to convert 4-hydroxybenzoate to gentisate, which is further degraded by the glutathione-independent gentisic acid pathway. These pathway delineations provide evidence that Bacillus species are derived from a diverse evolutionary background.


Amidase activity involved in peptidoglycan biosynthesis in membranes of Micrococcus luteus (sodonensis).

Membrane suspensions prepared from Micrococcus luteus (sodonensis) in both the exponential and stationary phases of growth contained a transglycosidase activity capable of synthesizing linear peptidoglycan. Exponential-phase membranes also contained an N-acetylmuramyl-L-alanine amidase activity which degraded the peptidoglycan as it was formed. The product of this amidase was purified and found to be free pentapeptide. The amidase was specific for peptidoglycan and could not attack lower-molecular-weight substrates even though the susceptible bond was present. Crude cell wall preparations isolated from exponential-phase cells also contained high levels of amidase. This cell wall-bound amidase would preferentially degrade in vitro-synthesized peptidoglycan over its own cell wall. Amidase activity could be solubilized from both cell walls and membranes by Triton X-100 treatment, butanol extraction, or LiCl extraction. Both membrane- and cell wall-derived amidases, solubilized by LiCl extraction, appeared to be of high molecular weight (greater than 150,000). Once solubilized, these wall- and membrane-derived amidases could attack the cross-bridged peptidoglycan of purified native cell walls, whereas bound amidases could not.


Catabolism of L-tyrosine by the homoprotocatechuate pathway in gram-positive bacteria.

A metabolic pathway for L-tyrosine catabolism involves 3,4-dihydroxyphenylacetic acid (homoprotocatechuic acid) as substrate for fission of the benzene nucleus. Cell extracts of an organism tentatively identified as a Micrococcus possessed the enzymes required for degrading homoprotocatechuate to succinate and pyruvate, and stoichiometry was established for several of these reactions. When the required coenzymes were added, cell extracts degraded L-tyrosine to the ring-fission product of homoprotocatechuate 2,3-dioxygenase and also converted 4-hydroxyphenylpyruvic acid into 4-hydroxyphenylacetic acid. This compound, in turn, gave stoichiometric amounts of the ring-fission product of homoprotocatechuate by the action of a nicotinamide adenine dinucleotide phosphate-dependent 3-hydroxylase coupled with homoprotocatechuate 2,3-dioxygenase. Evidence is presented that this route for L-tyrosine catabolism is taken by five other gram-positive strains, including Micrococcus lysodeikticus and a species of Bacillus. Five other gram-positive bacteria from other genera employed the alternative homogentisate pathway.


Regulation of enzyme synthesis in the tryptophan pathway of Acinetobacter calcoaceticus.

In Acinetobacter calcoaceticus the seven genes coding for the enzymes responsible for tryptophan synthesis map at three chromosomal locations. Two three-gene clusters, one (trpGDC) specifying the small subunit of anthranilate synthase, phosphoribosyl transferase, and indoleglycerol phosphate synthase and the other (trpFBA) specifying phosphoribosyl anthranilate isomerase and both tryptophan synthase subunits, are not linked to each other or to the trpE gene specifying the large anthranilate synthase subunit. When regulation of trp gene expression is studied in the wild type, only the level of the trpF gene product decreases upon addition of tryptophan to the medium. Tryptophan starvation of tryptophan auxotrophs, however, results in increased levels of all the tryptophan enzymes; this and additional evidence suggests that the expression of all the trp genes is subject to repression. The trpGDC genes are coordinately controlled, and the trpE gene is regulated in parallel with them. The trpFBA genes are controlled neither coordinately nor in parallel with the other trp genes, but respond proportionally when compared with each other. So far, two types of constitutive mutants have been found. The first class of mutants apparently occurs in the structural gene for a repressor protein; this repressor locus is unlinked to any of the biosynthetic trp genes and affects only the expression of trpE and the trpGDC cluster. The second class contains mutants closely linked to the trpGDC region; they overproduce only the gene products of this cluster.


Synthesis and turnover of the regularly arranged surface protein of Acinetobacter sp. relative to the other components of the cell envelope.

The formation of the components of the cell envelope of Acinetobacter sp. 199A was investigated by measuring the incorporation of [3H]leucine into protein, [14C]galactose into lipopolysaccharide, 32P into phospholipid, and [3H]diaminopimelic acid into peptidoglycan. Whereas the lipopolysaccharide and intrinsic protein of the outer membrane were stable, some of the regularly arranged surface protein, the alpha-protein, was lost into the growth medium. Only newly synthesized alpha-protein was lost. The peptidoglycan of the murein layer was also labile. Selective inhibition of the formation of individual components of the cell envelope with penicillin, chloramphenicol, and bacitracin showed that incorporation of protein into the outer membrane required the simultaneous formation of complete lipopolysaccharide. The converse was not true: protein synthesis was not required for lipopolysaccharide incorporation. Formation of the outer membrane and the murein layer proceeded independently.


Evidence for a complex life cycle and endospore formation in the attached, filamentous, segmented bacterium from murine ileum.

Light and electron microscope observations showed that the filamentous, segmented bacterium commonly found attached to the ileal epithelium of rats and mice undergoes a complex life cycle. Filaments comprising up to 90 segments were attached to the microvillous border of absorptive epithelial cells by a specialized terminal holdfast segment. Starting at the free end of the filament and progressing toward the attached end, undifferentiated segments were converted into reproductive or mother segments. Within each mother cell two new holdfast segments developed. As the holdfasts matured, their mother cells degenerated and released them into the intervillar space where they attached, grew, and divided to produce new segmented filaments. Alternately, in some filaments, newly formed but not yet released holdfasts were converted into endospores, which were released in the same manner as holdfasts, presumably to spread the bacterial colony to other members of the rodent population.


Inactivation of the phosphoenolpyruvate-dependent phosphotransferase system in various species of bacteria by vinylglycolic acid.

The alkenoic hydroxyacid 2-hydroxy-3-butenoic acid (vinylglycolate) specifically inhibited the phosphotransferase system in a variety of bacteria while not affecting respiration-coupled transport systems.


Mutants of Salmonella anatum that block bacteriophage epsilon infection at early stages.

A total of six mutants, to which phage epsilon could adsorb but failed to lyse, were isolated from Salmonella anatum and characterized. A significant portion of active phage particles could be recovered from the phage-bacterium complexes before they became irreversibly absorbed, and adsorbed phage did not kill these mutants at all. These reversibly adsorbed phage had become sensitive to chloroform, at least in some cases. The results indicate that the steps that may be blocked are deoxyribonucleic acid ejection or penetration. The mutants were tentatively classified into three groups by their susceptibility to phages c341 and Felix O. The inhibition of phage infection was overcome by host range mutants of phages epsilon and c341. The isolated lipopolysaccharide from the parent strain inactivated phages epsilon, c341, and a host range mutant of epsilon in vitro. However, neither phage epsilon nor c341, or the host range mutant of phage epsilon, was inactivated by incubation with the mutant lipopolysaccharides, even when they were derived from the mutants susceptible to c341 or the host range mutant of epsilon. These results may suggest that more than the receptor lipopolysaccharide of the bacterial surface is involved in the early stages of phage infection.


Some new views of the cell surface.

In recent years, it has become possible to investigate the cell surface of normal and tumor cells in new ways, and a number of lines of evidence obtained by various investigators have provided important new views of the surface of mammalian cells. Recent work has, for example, revealed the structure of the histocompatibility antigens, which appear to be ubiquitous on mammalian cells of different types. The dependency on these antigens of lymphocyte interactions with viruses suggests a new hypothesis: histocompatibility molecules may serve as cell surface adaptors for the recognition of foreign antigens such as viruses by T cell receptors. Contrary to older notions, the molecules that make up the cell surface, including the histocompatibility antigens, are not fixed but move freely in the cell membrane, which is a bilayer of lipid. It has been shown in several laboratories that cross-linking of cell surface proteins or "receptors" such as antibodies leads to clustering of these mobile receptor molecules into patches which are subsequently collected as a cap at one pole of the cell. The interactions among different cells and signaling from the surface of each cell to the interior depend upon the structure and physico-chemical interactions of such receptors and on their linkage to structures underlying the cell membrane. Work in our laboratory has produced consistent evidence that the motion and distribution of cell surface molecules are under control of an intracellular system consisting of a network of special proteins. We have found, for example, that mitogenic lectins such as concanavalin A bind to the carbohydrate portions of surface receptors and cross-link them. This binding to some receptors leads to inhibition of motion of all other receptors on the cell surface, suggesting that the original cross-linkage affects a general network responsible for anchoring cell surface receptors. Explorations of the nature of this network suggest that it consists in part of assemblies below the surface membrane containing microfilaments and microtubules.


Properties and function of indoleamine 2,3-dioxygenase.

Available evidence indicates that indoleamine 2,3-dioxygenase, which is particularly abundant in the lung, colon, and intestine, catalyzes the oxidative ring cleavage of the pyrrole moiety of not only tryptophan and 5-hydroxytryptophan but also serotonin, melatonin, and other indoleamine derivatives. Our recent experiments with slices of intestine, together with those with organ culture of pineal glands, perfusion of heart and lung preparations and intact animals, which I did not have time to mention today, indicate that the oxygenative ring cleavages of various indoleamines do occur in vivo to a significant extent. Secondly, this enzyme appears to utilize superoxide anion rather than molecular oxygen. If superoxide anion is demonstrated, unequivocally, to be the true substrate of this enzyme, not only in vitro but also in vivo, then indoleamine 2,3-dioxygenase may be the first example of a new class of enzymes which utilize superoxide anion as an oxidizing agent just as peroxidases utilize hydrogen peroxide. Lastly, this novel enzyme produced a new class of biogenic amines, which may be referred to, generically, as "anthraniloylamines." Although their natural occurrence has not yet been established, they may have hitherto unknown biological or pharmacological activities and are currently under investigation in our laboratory.


Functional differentiation of mouse fetal liver in circumfusion system cultures.

The authors investigated the in vitro functional differentiation of fetal mouse liver cultured in Rose's circumfusion system with the use of two biochemical markers: The analysis of the inductive response of key enzymes in carbohydrate metabolism to insulin, and the analysis of the liver-specific isozyme of pyruvate kinase [EC 2.7.1.40]. The glucokinase [EC 2.7.1.2] activity, which is only found in mammalian adult liver, emerged on cultivation of 2-3 days and reached a maximum level equivalent to one-half of the adult level. Two- or 3-fold increases in the glucokinase, pyruvate kinase, and glucose-6-phosphate dehydrogenase [EC 1.1.1.49] were induced by a single dose of insulin in fetal liver after 12 days of cultivaton. Hexokinase [EC 2.7.1.1] activity was barely influenced by insulin. These results suggested that fetal mouse liver cultured in this system for 2 weeks maintained the same response to insulin as in vivo adult mouse liver. The pyruvate kinase isozyme patterns of mouse livers in various developmental stages and of cultured fetal mouse liver in the present system were investigated by isoelectric fractionation. The pyruvate kinase isozymes having the highest relative activity were the pI-5.5 isozyme for the adult liver and the pI-6.5 isozyme for 13- to 14-day-old fetal liver. As development in vivo proceeded, a gradual change in isozyme pattern occurred; this consisted of a progressive decrease of the pI-6.5 pyruvate kinase isozyme, "fetal type," in favor of the pI-5.5 isozyme, "adult type." The pyruvate kinase isozyme pattern in 13- to 14-day fetal liver cultured in the system for 2 weeks was similar to that found in adult liver. Thus, it was shown that "fetal type" pyruvate kinase was also replaced by "adult type" pyruvate kinase in vitro. It can be concluded from these findings that fetal mouseliver cultured in the circumfusion system for 2 weeks maintains its functional and morphological identitites as it differentiates toward the adult liver.


Isolation and some properties of a subtilisin inhibitor from barley.

An inhibitor affecting subtilisin [EC 3.4.21.14] was isolated from barley (Hordeum vulgare L cv. Kikaihadaka) by extraction with 1% sodium chloride, fractionation with ammonium sulfate, chromatography on CM- and DEAE-cellulose columns, and gel filtration on Sephadex G-100. The final preparation appeared to be homogeneous on the basis of polyacrylamide gel electrophoresis; the inhibitory activity against subtilisin was increased about 140-fold during purification. This inhibitor was protein having a molecular weight of about 20,000, and containing 177 amino acid residues. Both the amino- and carboxyl-terminal residues were alaine. The inhibitor inactivated subtilisin, probably for formation of an enzyme-inhibitor complex in a molar ratio of 1: 1, but had little or no effect on the activities of other enzymes tested. The dissociation constant of the subtilisin-inhibitor complex was 1.5 X 10(-10) M. The inhibitor appears to be distinct from the barley microbial proteinase isoinhibitors reported by Mikola and Suolinna, in respect of most of its physiochemical and inhibitory properties.


Effects of estrogen on the turnover rates of ornithine amino transferase in rat liver and kidney.

The turnover rates of ornithine aminotransferase in the liver and kidney of control rats and those treated with estrogen were determined by injecting L-[14C]leucine (U) and following the decay of specific radioactivity incorporated into immunoprecipitates from the partially purified enzymes. The half-life of the ornithine aminotransferase [EC 2.6.1.13] in the liver (t1/2=0.95 days) was significantly different from that of the kidney enzyme (t1/2=4.0 days). Studies on the incorporation of radioactive leucine into ornithine aminotransferase in the kidney under steady-state conditions showed that the rate of synthesis of this enzyme after treatment with estrogen was 5 to 6 times higher than that in untreated animals. The rate constant of degradation of kidney ornithine aminotransferase under steady-state conditions induced by estrogen treatment was not significantly different from that under control conditions. The results showed that the increase in the rate of biosynthesis, not to a decrease in the rate of degradation. No significant changes in the rates of biosynthesis and degradation of liver ornithine aminotransferase were observed after administration of estrogen.


Effect of ionic sites of surfactants on leukocyte metabolism.

The effect of ionic and nonionic surfactants on the metabolism of leukocytes was studied. Among anionic surfactants, sodium laurylsulfate, sodium laurate, and sodium lauroyllactate stimulated oxygen uptake and glucose oxidation through the hexose monophosphate pathway. The magnitude of the effect of anionic surfactants seemed to be related to the electrostatic strength of the ionic site of each compound. Cationic, amphoteric, and nonionic surfactants were inhibitory to leukocyte metabolism.


The state of lysosomes and protein turnover in rat liver. Effect of excess vitamin A.

Administration of excess vitamin A to rats induces labilization of liver lysosomal membranes, as shown by the release of lysosomal cathepsins upon tissue homogenization. The effect of lysosomal labilization on liver protein turnover was investigated. The apparent turnover rate of liver proteins in the hypervitaminotic animals, as measured by a double isotope-labeling technique (Glass and Doyle (1972) J, Biol. Chem, 247, 5234-5242), was found to be the same as that in control animals. Neutral and alkaline fructose-1, 6-biphosphatase [EC 3.3.3.11] activities in the liver were also found to be unchanged in hypervitaminosis A. These data indicate that the rate of intracellular protein degradation is not determined by the level of "free cathepsins. Protein synthesis in the livers of the hypervitaminotic animals was partially  imparied, as shown by the shift of polysomal profiles toward lighter aggregates.


Studies on the composition of phospholipids in rat small intestinal smooth muscle.

The phospholipid composition of rat small intestinal smooth muscle was investigated in comparison with those of the mucosa and liver. Phospholipid content per g of the wet smooth muscle was almost identical with that of the mucosa and was about 1/4 of that in the liver. The phospholipid/protein ratio of the smooth muscle was about 1/2 of the value in the liver. Sphingomyelin content was significantly high and amounted to 18% of total phospholipids. This value was about twice that in the mucosa and 4 times higher than that in the liver. On the other hand, the percent distribution of phosphatidylcholine was lowest in the smooth muscle. Distribution patterns of phosphatidylserine and phosphatidylinositol in the smooth muscle as well as in the mucosa were different from those in the liver. The occurrence of vinyl-ether and ether phospholipids was clearly demonstrated in the smooth muscle as well as in the mucosa. A major part of the ether lipids was detected in the phosphatidylethanolamine fraction, in which they amounted to about 50%; 40% as alkenyl-acyl type and 12% as alkyl-acyl type. A high content of ether lipids was also observed in the phosphatidylethanolamine fraction from mucosa, but the distribution was reversed, that is, 14% alkenyl-acyl type and 28% alkyl-acyl type. Fatty aldehydes, fatty alcohols, and fatty acids were also determined by gas-liquid chromatography. The compositions of fatty aldehydes in the phosphatidylethanolamine fraction from smooth muscle and from mucosa were similar, whereas the compositions of long chain fatty alcohol and fatty acids were clearly different. The compositions of fatty alcohols and fatty acids of the phosphatidylcholine fraction from smooth muscle showed significantly different patterns from those of the phosphatidylethanolamine fraction and from those of the same phospholipid fraction in the mucosa.


Effect of guanidine hydrochloride on the holo- and apo-enzymes of pig heart lipoamide dehydrogenase.

1. The effect of guanidine hydrochloride (GuHCl) on pig heart lipoamide dehydrogenase [NADH: lipoamide oxidoreductase, EC 1.6.4.3.] was investigated by means of enzymatic activity and optical measurements (CD, absorption, and fluorescence spectra). The activity of the enzyme decreased on increasing the concentration of GuHCl and the enzyme was completely inactivated in 2.0 M GuHCl. 2. The contents of alpha-helix, beta, and unordered forms in lipoamide dehydrogenase were estimated to be 34, 14, and 52%, respectively. On increasing the concentration of GuHCl, the content of alpha-helix in lipoamide dehydrogenase decreased, whereas the content of the beta form hardly changed. 3. The native lipoamide dehydrogenase showed absorption, CD, and fluorescence spectra characteristic of bound FAD in the visible region, suggesting hydrophobic interaction between the protein moiety and FAD chromophore. The absorption, CD, and fluorescence spectra of the enzyme in 2.0 M GuHCl were similar to those of free FAD in the buffer, suggesting the release of FAD from the protein moiety. 4. The protein fluorescence spectrum of lipoamide dehydrogenase had a maximum at 350 nm blue-shifted by 8 nm from that of tryptophan in aqueous solution. The maximum of the enzyme in 2.0 M GuHCl was red-shifted to 357 nm. This suggests exposure of tryptophan residues to a polar environment. The maximum, 352nm, of the apoenzyme shifted to 350 nm on addition of FAD. These results show that the conformation in the microenvironment of some tryptophan residues in lipoamide dehydrogenase is affected by the dissociation-association of FAD. 5. The contents of alpha-helix, beta, and unordered forms in the apoenzyme were estimated to be 35, 8, and 57%, respectively. These values are similar to those of the native holoenzyme. The alpha-helical structure in the apoenzyme molecule was more sensitive to GuHCl than that in the holoenzyme. FAD and two hydrophobic probes, 8-anilinonaphthalene-1-sulfonate (ANS) and 4 benzolamido-4'-aminostilbene-2,2'-disulfonate (MBAS), which can bind to the apoenzyme, stabilized the alpha-helical structure in the apoenzyme molecule.