Extramedullary plasmacytoma of the head and neck, parotid and submandibular salivary glands.

Twenty-two cases of extramedullary plasmacytomas (EMP) were diagnosed in the Birmingham region during 1962-1973. Five cases of EMP of the head and neck are discussed, including cases involving the parotid and submandibular salivary glands. Comparative data on incidence, age, sex, and survival is presented. A multidisciplinary approach is important for diagnosis, treatment and follow-up. It is mandatory to carry out investigations to exclude multiple myeloma. Radiotherapy is the treatment of choice; clinical, radiological and pathological evidence are cited. However, a residuum may be left after an initial response to radiotherapy which may require surgical removal. Chemotherapy has a place in multiple site lesions. A proportion of cases proceed to multiple myeloma after a variable period of time and thus follow-up should be life-long.


An unusual foreign body (tooth) in the tongue.

This unusual foreign body in the tongue of a 45-year-old lady must be unique. The most interesting feature of the present case was that the patient had sustained a gun-shot injury about five months earlier leading to traumatic extraction of the first left lower molar tooth and its impaction into the tongue. The patient herself was not aware of it and she attended the hospital complaining only of a simple swelling of tongue.


Oesophageal involvement in epidermolysis bullosa.

Epidermolysis bullosa dystrophica causing oesophageal stricture in two males of a family of 4 siblings--2 females and 2 males, and whose parents are not related, is reported. The stricture was treated with repeated dilatations and oral prednisolone on and off with complete success. A brief comment is also made with regards to the pathology and management of this condition.


Urea transport in the dogfish kidney.

There is increasing evidence that urea movement across many epithelia involves more than passive diffusion. Of particular interest is the observation that urea transport across the erythrocyte membrane and across the vasopressin-stimulated urinary bladder of the toad occurs by facilitated diffusion, and can be selectively inhibited by phloretin and chromate. These inhibitory agents have been employed in studies of renal urea reabsorption by the spiny dogfish Squalus acanthias. Both agents inhibit urea reabsorption; the effect of chromate is of particular interest, since it blocks urea reabsorption to a proportionately greater extent than sodium reabsorption, and does so irreversibly.


Microtubules in the "chloride cell" of the gill and disruptive effects of colchicine on the salt balance of the sea water adapted Mugil capito.

Electron-microscopic examination of the gill of the grey mullet, Mugil capito adapted to sea water, reveals the presence of numerous microtubules in the apical region of the mitochondria-rich cells. No microtubules are found in other types of epithelial cell. Exposure of the fish to colchicine  (10(-4)M) for four hours induces a 20% increase of plasma Na and Cl. Colchicine leaves the water permeability of the gill unchanged but Cl and Na exchange fluxes are inhibited by 30-50% and the gill potential pattern is altered. Salt gain replaces salt excretion across the gill. The K dependent Na and Cl efflux components, independent of the gill potential shift produced by K, are totally inhibited by colchicine. Exposure to lumicolchicine is not followed by a significant change of these Na and Cl efflux-components and potential pattern. The possibility that microtubules intervene in the salt excretion process across the chloride cells is discussed.


Volume regulation by flounder red blood cells: the role of the membrane potential.

The nucleated red blood cells of the Winter Flounder Pseudopleuronectes americanus demonstrate a volume regulatory response subsequent to osmotic perturbation. The net water movements associated with response are secondary to net inorganic cation flux. The increased net cation fluxes occur in response to increased cation permeability (Pcation). While ionic strength and cell volume do not appear to be the stimulus for the volume regulatory response i.e. increased Pcation, changes in the cell membrane potential (Vm), as calculated from the chloride distribution ratio, do appear to result in increased Pcation. These studies demonstrate that manipulations leading to membrane hyperpolarization result in net loss of cellular K and water. In contrast treatments which depolarize Vm lead to cellular uptake of Na, K, Cl and water.


Killifish opercular skin: a flat epithelium with a high density of chloride cells.

In teleosts the head region, particularly the gills, plays the key role in osmoregulatory NaCl transport, presumably by mechanisms located in the chloride cell. As interest has focused on specific mechanisms of chloride cell function, two classical preparations, the intact fish and the isolated, perfused gill, have continued to serve as the only available model systems. However, both of these preparations have severe limitations, e.g., as they are not flat sheets, they cannot be studied readily under the ideal thermodynamic conditions achieved with the short-circuit current technique. The present sutdy describes the histology and ultrastructure of a particular area of skin in the head region of both killifish (Fundulus heteroclitus) and sea raven (Hemitripterus americanus). This skin lies on the inside of the operculum and possesses a flat epithelium containing chloride cells. In the present study the identity of the chloride cell in this epithelium was definitively established with the electron microscope. Although the opercular epithelium from the marine sea raven contains few chloride cells, that from the euryhaline killifish adapted to pond water, 100%-, and 200% artificial seawater is predominately chloride cells. Significantly, the teleost gill has never been reported to contain more than 10% chloride cells. Thus the opercular skin of the killifish can serve as a model to study the adaptive role of chloride cells in euryhaline teleosts. A separate electrophysiological study has deminstrated that the short-circuit current technique can be applied to this skin.


Interdependence of Active Na+ and Cl- transport by the isolated urinary bladder of the teleost, Pseudopleuronectes americanus.

The relationship between transepithelial Na+ and Cl- active transport from the mucosal toward the serosal surface was studied by ion substitution experiments in the isolated, perfused urinary bladder of the winter flounder, Pseudopleuronectes americanus. The tissue behaves as a simple ohmic resistance of about 1000 ohm-cm2 which was not significantly changed by perfusion of the lumen (mucosal surface) with Na-free or Cl-free solutions. Trans-epithelial electrical potential difference and short-circuit current were reversed (mucosa positive to negative) by Cl-free perfusion but unaltered by Na-free medium. Short-circuit current did not agree with isotopically measured net Na+ and Cl- flux in either control or ion-substituted medium. Cl-free perfusion depressed net Na+ flux more than 50% and a similar effect was seen on net Cl- flux upon Na-free perfusion. A kinetic analysis of the relationship of Na+ or Cl- flux to the concentration of Na+ or Cl- in the perfusate in the presence and absence of Cl- or Na+, respectively, indicated that Cl-free medium acted as a non-competitive inhibitor of Na+ transport, and the effect of Na-free medium on Cl- transport could be interpreted similarly. This inter-dependence of Na+ and Cl- transport was taken as an indication of co-transport of these two ions. Amiloride (10(-4) M) seemed to inhibit a component of Na flux distinct from the Cl-dependent flux. It had no effect on Cl- transport.


The phlorizin effect on the transport of sugars at the antiluminal face of teased flounder tubules.

The effect of phlorizin on the uptake of sugars by teased renal tubules of the flounder (Pseudopleuronectes americanus) and slices of rabbit kidney cortex was investigated: 1. Increasing concentrations (0.05-0.5 mM) of phlorizin inhibited the uptake of D-glucose at the antiluminal face of the tubular cells by affecting primarily the cellular levels of glucose phosphates, whereas the levels of free glucose remained constant. This result suggests the possibility that the actual transport step is associated with sugar phosphorylation. 2. As opposed to the high affinity of phlorizin for the Na+-dependent active transport system for methyl-alpha-D-glucoside in flounder and rabbit kidney, the carrier shared by glucose, 2-deoxyglucose and mannose at the antiluminal face of tubular cells displays a low affinity for the inhibitor. It is suggested that glucose and its C2-analogs enter the renal tubular cells at the antiluminal face by a phosphorylating pathway which has a low affinity for phlorizin, and mix readily with the metabolic pool. This transport pathway serves the nutritional requirements of the cells.


Molecular aspects of chloride cell formation in Oncorhynchus. II. Isolation and characterization of gill transfer RNA's during active salt secretion.

The transfer ribonucleic acids (tRNAs) from gill filaments of coho salmon, Oncorynchus kisutch, have been isolated and were separated into individual species of acceptor tRNAs by reversed-phase column chromotography. Crude tRNAs isolated from gill filaments undergoing active salt excretion were acrylated with 14C-amino acids and combined with tRNAs acylated with 3H-amino acids, but obtained from non-secreting filaments. The radioactively labeled tRNA mixture was cochromatographed and the results showed significant differences in the elution profiles of tRNAasp and tRNAtyr. These elution profiles may reflect the differentiation of the chloride cell population that is found within the gill epithelium.


Renal tubule ion transport and collecting duct function in the elasmobranch little skate, Raja erinacea.

Renal micropuncture and microdissection techniques with ultramicro fluid analysis have been applied to evaluate single nephron function in the skate, Raja erinacea. We have divided the skate nephron into three proximal tubular segments (PTS I-III), three distal coilings (DC I-III), and a countercurrent loop system located between the proximal segments and the distal coilings. The collecting duct is the principal site of urinary dilution. Following exposure of the fish to 75% seawater for about 24 hours, the sodium concentration difference between the end collecting duct lumen and plasma is decreased sufficiently to account for the urinary dilution. The principal site for magnesium, phosphate and sulphate secretion appears to be PTS II. This segment is located on the ventral surface of the kidney. PTS II is also the main nephron site for reabsorption of sodium and chloride in excess of water.


Volume regulation of muscle fibres in the killifish, Fundulus heteroclitus.

Cell volume regulation has been observed in vitro in many tissues. In the killifish it was studied in vivo during transfer from SW to FW and from FW to SW. It was found that the cell water content in acclimated fish varies inversely with the osmolality of the medium. During transfer from SW to FW the plasma osmolality decreased. Cell swelling was prevented through net loss of solutes from the cells. The solutes lost were not potassium or sodium and are presumed to be organic solutes. Dund no significant increase in cell solute content could be found during eight hours. During prolonged acclimation cell water content returns to a higher value.


Cytological changes in chloride cells following altered ionic media.

The rock-eel, Pholis, and guppy, Lebistes, adapted to fresh or saltwater were exposed to low concentrations of unnatural ions or transport inhibitors including thiocyanate, potassium and ouabain, which caused cytological alterations in the chloride cells of the gills. Some of the other substances used caused generalized damage to intracellular membranes. Highly ordered geometric arrays of the tubular reticulum were produced under certain conditions. The conditions of the experiments suggest that the tubular reticulum plays a role in ionic segragation and that the normal configuration of the reticulum is dependent on the ionic composition of the intracellular milieu.


Free amino acids in tissues of the skate Raja erinacea and the stingray Dasyatis sabina: effects of environmental dilution.

Concentrations of individual free amino acids were determined in various tissues of the skate (Raja erinacea) and the stingray (Dasyatis sabina), and the relationship of cellular free amino acid concentrations to intracellular osmoregulation was investigated by adapting these elasmobranchs to half-strength seawater. Each tissue characteristically had high levels of certain specific amino acids. Skate sing muscle contained high concentrations of sarcosine and beta-alanine, skate heart had high concentrations of taurine, and skate erythrocytes had high levels of taurine and beta-alanine. Amino acid levels in skate plasma were very low. High concentrations of aturine and glutamate were found in stingray brain. Adaptation of skates and stingrays to half-strength seawater was accompanied by significant decreases in concentrations of the major free amino acids in skate wing muscle and erythrocytes and in stingray brain, but not in skate heart. The data suggest that in these elasmobranchs certain specific free amino acids are selectively involved in intracellular osmoregulatory mechanisms.


Interaction of azathioprine and glutathione in the liver of the rat.

Azathioprine was administered to rats in order to study its interaction with glutathione in vivo. Glutathione levels were measured sequentially in liver, red blood cells, kidney and small intestine after i.p. injections of azathioprine (6.25-100 micronmol/100 g b.wt.). Five minutes after drug administration, dose-related selective depletion of hepatic glutathione up to 50% of control was observed. By 60 minutes 80% depletion of hepatic glutathione was observed. Red cell glutathione depletion was also observed but lagged behind hepatic changes. Five minutes after azathioprine administrations, no change in red cell glutathione was seen with all doses of azathioprine, but a dose-related increase in plasma 6-mercaptopurine and azathioprine was observed. At all azathioprine doses and at all time intervals after drug administration, the hepatic contribution to total glutathione consumption predominated. No change in glutathione levels in kidney or small intestine was observed after azathioprine. Thus, the liver plays a major role in the metabolism of azathioprine through the interaction of the drug with glutathione.


The metabolism of d-, l- and dl-methadone in the isolated perfused rat liver.

Five-milligram doses of d-, l- and dl-methadone were added to the perfusate of the isolated perfused rat liver and the disposition of each compound was monitored over a period of 120 minutes. There was an initial rapid decline in concentration of each drug in the perfusate, with approximately 70% disappearing in the first 10 minutes of the perfusion. Thereafter, the rate of decline of each compound slowed and the apparent half-life was about 100 minutes. In experiments with d- l- and dl-methadone the mean hepatic extraction from the perfusate at 10 minutes was 72, 66 and 69%, respectively. A comparison of the rate of disappearance of the d- and the l-isomers from the perfusate showed that the concentration of the d-isomer at each sampling time was lower than the concentration of the l-isomer and this concentration ratio ranged between 68 and 79%. A study of the disposition of dl-methadone in the isolated perfused liver indicated that the initial rapid decline of the drug in the perfusate in the first 10 minutes was caused primarily by the uptake of the unchanged drug into the liver. Thereafter, the concentration of methadone in the perfusate and liver declined slowly with time and was paralleled by an increase in the concentration of the primary mono-N-demethylated metabolite, which appeared in the liver, perfusate and bile. Smaller quantities of more polar metabolites, including hydroxylated compounds and conjugates, were also present in the liver and bile. Addition of SKF 525-A retarded the rate of decline of methadone from the perfusate and pretreatment of the rat with phenobarbital increased the rate of biotransformation of methadone in the isolated perfused liver.


Flunixin meglumine: a non-narcotic analgesic.

The N-methyl-d-glucamine salt of flunixin (flunixin meglumine) is a potent non-narcotic analgesic agent after parenteral administration in mice, rats and monkeys. It is significantly more potent than pentazocine, meperidine and codeine in the rat yeast paw test after subcutaneous administration in saline. Activity on intramuscular administration is comparable to that after subcutaneous administration and is enhanced when dissolved in buffered saline as compared to nonbuffered saline. In addition, flunixin meglumine also had oral activity and differs from indomethacin in having more analgesic activity per unit of anti-inflammatory activity. In mice, flunixin meglumine is equipotent to pentazocine and more potent than meperidine and codeine in the abdominal constriction test. In primates, flunixin meglumine at 10 mg/kg i.m., produced a degree of analgesic efficacy comparable to that of a clinically effective dose of morphine (0.3 mg/kg). In contrast to codeine, tolerance to the analgesic action of flunixin meglumine was not observed. Furthermore, flunixin meglumine retained its activity in rats made tolerant to codeine. Unlike narcotics, the analgesic effect of flunixin meglumine is not antagonized by naloxone after acute administration in rats. These results indicate that flunixin meglumine is a parenterally and orally effective analgesic in animals and is unlikely to have narcotic or drug dependence liability.


Is 2-dimethylaminoethanol (deanol) indeed a precursor of brain acetylcholine? A gas chromatographic evaluation.

Acute administration of deanol-p-acetamidobenzoate (Deaner; deanol) has been reported to elevate brain choline (CH) and acetylcholine (ACh) levels. We have developed a specific and sensitive gas chromatographic assay to measure deanol levels in tissue and have applied this assay to our studies of the effect of acute deanol administration on deanol, ACh and Ch levels in rodent brains. Details of the method are described in this text. This procedure is quantitative and yields reproducible results over a wide range of deanol concentrations (0.30-200 nmol). Seven endogenous and pharmacological parameters have been studied using this procedure. In control rodent brain, liver, heart, lung and plasma, we detected no free endogenous deanol (less than 1 nmol/g). After deanol administration, we were able to detect deanol in tissue and have attempted to determine a relationship between these levels and values of ACh in the same tissue. Regardless of deanol pretreatment time (1-30 minutes) or doses (33.3-3000 mg/kg i.p.) used, we detected no increase in mouse whole brain ACh levels. Likewise, there was no detectable elevation in ACh levels in rat whole brain, cortex, striatum or hippocampus after a 15-minute pretreatment with 550 mg/kg of deanol (i.p.). The only elevation in ACh levels which we detected occurred selectively in the striatum of mice pretreated with a massive dose (900 mg/kg i.p.) of deanol for 30 minutes. This selective increase in striatal ACh levels oculd not, however, be related to levels of deanol in the striatum because there was no greater accumulation of deanol in the striatum than in other brain areas tested or in whole brain. These data do not confirm the results of other investigators who reported elevations in whole brain or striatal ACh levels after acute administration of lower doses of deanol. The data emphasize the need for further investigation into the mode of action of deanol and question its suggested role as an immediate precursor of ACh synthesis in the central nervous system.


Involvement of cholinergic presynaptic receptors of nicotinic and muscarinic types in the control of the spontaneous release of dopamine from striatal dopaminergic terminals in the rat.

Rat striatal slices (two) were superfused continuously with L-3,5-3H tyrosine and 3H-dopamine (3H-DA) release was estimated in serial fractions of superfusates. The spontaneous release of 3H-DA was reduced by about 50% when slices were superfused with a calcium-free medium containing ethylene glycol bis (beta-aminoethyl ether)- N,N'-tetraacetic acid (EGTA) (10(-4) M) or with a medium containg tetrodotoxin (5 x 10(-7) M). These effects were not related to a change in 3H-DA synthesis since the rate of L-3,5-3H tyrosine hydroxylation, as measured by 3H-H2O formation was not significantly reduced. Acetylcholine (ACh) (10(-5) M) stimulated the release of 3H-DA (about 100%). This effect was abolished in the absence of calcium; it was partially blocked by pempidine (10(-5) M), atropine (10(-6) M) or scopolamine (10(-5), 10(-6) M). Oxotremorine (10(-5) M) enhanced 3H-DA release but to a lesser extent (60%) than ACh (10(-5) M); its action was completely blocked by atropine (10(-6) M) and unaffected by pempidine (10(-5) M). The ACh- (10(-5) M) and oxotremorine- (10(-5) M) stimulatine effects on 3H-DA spontaneous release were still detected in slices superfused in the presence of tetrodotoxin (5 x 10(-7) M). In the presence of the neurotoxin, the effect of ACh (10(-5) M) was significantly reduced by pempidine (10(-5) M) and the effect of oxotremorine (10(-5) M) was blocked by atropine (10(-6) M). These results suggest the presence of cholinergic presynaptic receptors of the nicotinic and muscarinic types on striatal dopaminergic terminals.


Anticonvulsant activity of phenobarbital and phenytoin in combination.

The anticonvulsant properties of phenobarbital and phenytoin given individually or in various combinations were determined by the maximal electroshock seizure test in rats 2 hours after subcutaneous administration. Drug concentrations in brain and plasma obtained immediately after maximal electroshock seizure were measured by gas-liquid chromatography. Total brain anticonvulsant drug concentrations required to abolish the hindlimb extensor component of maximal electroshock seizure were similar when these drugs were employed singly or in combinations. The median effective brain concentrations (EC50) were: phenobarbital, 12.2 micronmol/kg; phenytoin 12.3 micronmol/kg; and phenobarbital plus phenytoin, 14.8 micronmol/kg. Brain/plasma concentration ratios of these drugs were not affected by concomitant administration of the other agent: phenobarbital alone, 0.73; phenobarbital in the presence of phenytoin 0.77; phenytoin, 1.21; and phenytoin in the presence of phenobarbital, 1.22. Brain and plasma concentrations of phenytoin relative to the dose employed were significantly higher (P less than .001) when phenobarbital was administered concurrently than when phenytoin was given alone. This resulted in an apparent potentiation of anticonvulsant activity at 2 hours when these drugs were administered simultaneously. The anticonvulsant activity of the two combinations could be accounted for by the sum of the concentrations of the individual drugs in brain.


Influence of prostaglandin precursors and synthesis inhibitors in vascular bed perfused without a pump.

The present investigation was coducted to examine the role of endogenous prostaglandin (PG) on blood flow and arenergic responses in the paw vasculature perfused without a pump. The PG precursors, arachidonic acid and dihomo-gamma-linolenic acid, given i.a. caused only small increments in paw blood flow which were much less than that caused by PGE2 and PGE1. The i.a. administration of the PG synthesis inhibitors, indomethacin, meclofenamate and naproxen, caused a decrease in paw blood flow and increase in vascular resistance, whereas eicosa-5,8,11,14-tetraynoic acid had no significant effect. Vasoconstrictor responses evoked by norepinerphrine were unaffected after administration of indomethacin or eicosa-5,8,11,14-tetraynoic acid, whereas slight potentiation of the response to sympathetic nerve stimulation was obtained after indomethacin. These results suggest that in the cutaneous vascular bed of the paw, endogenous PG decreases the vascular resitance, but plays only a minor adrenergic modulating role, and then only on the response to adrenergic nerve stimulation.


Prostaglandins and the renin-angiotensin system in canine endotoxemia.

Adminstration of endotoxin to dogs caused a rapid initial decline in blood pressure followed by a transient recovery preceding death. Plasma renin activity was elevated 5 minutes after endotoxin administration and continued to rise throughout the course of shock. Indomethacin given 60 minutes after endotoxin caused an elevation of blood pressure and a 50% decrease in plasma renin activity. Pretreatment with indomethacin markedly attenuated both the hemodynamic changes and the rise in plasma renin activity caused by endotoxin administration. Prostaglandin (PG) E-like material was observed in renal venous blood 30 minutes after endotoxin administration and was abolished by indomethacin. In addtion, a non-PG substance was found in dialysate from both arterial and renal venous blood within 5 minutes of endotoxin administration, Renal and mesenteric angiograms were taken at various stages of shock. Endotoxin administration caused a substantial increase in the diameter of intrarenal arterial branches which was temporally associated with the appearance of PGE-like material in the renal venous effluent. The mesenteric arteries were initially and transiently constricted by endotoxin and then were markedly and chronically dilated. Indomethacin simultaneously abolished renal PG and decreased renal and mesenteric arterial diameter.


Modulation of phagocytosis by and lysosomal enzyme secretion from guinea-pig neutrophils: effect of nonsteroid anti-inflammatory agents and prostaglindins.

Guinea-pig neutrophils released lysosome granule-associated beta-glucuronidase, but not cytoplasmic lactate dehydrogenase during cell contact with and phagocytosis of serum-treated zymosan particles. Naproxen, chloroquine and indomethacin inhibited particle uptake by and lysosomal enzyme secretion from neutrophils incubated with zymosan in Krebs-Ringer phosphate medium, pH 7.4, at 37 degrees C. Acetylsalicyclic acid, fenoprofen and ibuprofen were inactive. Prostaglandins (PG) E1, E2, A1, A2, B1 and B2 reduced particle ingestion by and discharge of lysosomal enzymes from neutrophils. PGF2alpha accelerated lysosomal enzyme release, had no effect on phagocytosis at high concentrations and inhibited both processes at low concentrations.. PGF1alpha was inactive. In the presence of cytochalasin B, an agent which inhibits phagocytosis while havine no effect on selective lysosomal enzyme secretion, naproxen, chloroquine and indomethacin, continued to inhibit the discharge of beta-glucuronidase from neutrophils. PGE1, PGE2, PGA1, PGA2, PGB1 and PGB2 reduced lysosomal enzyme release from cytochalasin B-treated neutrophils. PGF2alpha accelerated at high and inhibited at low concentrations the selective secretion of beta-glucuronidase from cytochalasin B-treated neutrophils. PGF1alpha was again inactive. These studies indicated that guinea-pig neutrophils are capable of a selective release of lysosomal enzymes (beta-glucuronidase) during ingestion of serum-treated zymosan particles and that certain anti-inflammatory drugs and prostaglansins may function as modulators of the phagocytic release of lysosomal enzymes from neutrophils.


Adjuvant polyarthritis I: incorporation of quantitative measurements of humoral and cellular immune response.

A modified model of adjuvant arthritis is described that permits simultaneous quantitative measurement of the humoral and the cellular immune response to a secondary immunogen (el4 cells) in the arthritic rat. Application of the new model system to mechanism studies is illustrated with cyclophosphamide. The drug is shown to suppress adjuvant arthritis by a combined anti-inflammatory and immunosuppressive action.


Modulation of brain tryptophan hydroxylase activity by brain tryptophan content.

Although hydroxylation of tryptophan (TP) is considered to be the rate-limiting step in serotonin synthesis, the mechanism whereby tryptophan hydroxylase (TPH) participates in the regulation of serotonin synthesis is still in question. Since the brain TP concentration is probably near the Km for tryptophan hydroxylase, changes in brain TP content could affect the rate of its hydroxylation. However, it has not been established whether in vivo the activity of TPH and TP in several brain nuclei and other regions of rat brain after treatments known to lower brain TP levels. Chlorimipramine, loading with neutral amino acids and a TP-deficient diet decreased the TP content of some, but not all, brain regions studied. Whenever TP decrease withe TP  injections. Several brain nuclei accumulate TP at different rates after a TP load. These data suggest possible mechanisms for regulation of serotonin synthesis in the face of fluctuating plasma levels of TP.


Pharmacological evaluation of new calcium antagonists: 2-substituted 3-dimethylamino-5,6-methylenedioxyindenes.

Calcium antagonists are valuable pharmacological tools for the study of stimulussecretion and excitation-contraction coupling mechanisms. Two 2-substituted 3-dimethylamino-5,6-methylenedioxyindene hydrochlorides were tested for antagonism of the spasmogenic action of various agonists on isolated smooth muscle preparations. The 2-n-propyl and 2-n-butyl aminoindenes (5 X 10(-5) to 10(-4) M) blocked the spasmogenic action on the estrogen-treated rat uterus of prostaglandin E2 (10(-7) M), prostaglandin F2alpha tromethamine salt (10(-7) M), oxytocin (10(-3) U/ml), barium chloride (BaCl2-2H2O; 2.2 X 10(-4) M), acetylcholine chloride (10(-6) M) and ergonovine maleate (7.5 X 10(-4) M); they also blocked the contractile effect on the ileum of acetylcholine chloride (10(-6) M; rat) and histamine hydrochloride (10(-6) M; guinea pig). In further experiments on rat uterus using the agonists acetylcholine chloride (10(-6) M; which presumably acts by increasing influx of extracellular calcium into cells) and barium chloride (2.2 X 10(-4) M; which presumably contracts smooth muscle by releasing intracellular calcium), a progressive increase in extracellular calcium concentration (from 9 X 10(-4) to 7.2 X 10(-3) M CaCl2-2H2O) was paralleled by progressive reversal of the blockade produced by both 2-substituted aminoindene antagonists. In studies on the perfused bovine adrenal medulla, the 2-n-propyl aminoindene (10(-4) M) completely blocked the calcium-dependent catecholamine secretion evoked by 0.1 and 3.3 mM carbachol, without affecting the calcium-independent catecholamine secretion evoked by 33 mM acetaldehyde. These findings suggest that the aminoindene antagonists interfere with the action of calcium and that in smooth muscle the antagonism is at an intracellular site involved in excitation-contraction coupling.


Effects of diazepam on the biliary excretion of diphenylhydantoin in the rat.

Studies were performed to examine the effects of diazepam (DZP) on the biliary excretion of diphenylhydantoin (DPH, phenytoin) in the rat. One-hour pretreatment with DZP (150 mg/kg i.p. or 10 mg/kg i.v.) markedly suppressed the rates as well as the cumulative amounts of radioactivity excreted in bile after administration of 14C-DPH (70, 35 or 10 mg/kg i.v.). No changes in bile flow were apparent and the decreases in biliary excretion were not accompanied by increases in the urinary elimination of the drug or its metabolites. Disappearance of DPH from plasma and tissue were also reduced, and at 4 and 6 hours after DPH administration higher plasma and tissue concentrations were encountered in the DZP-treated group. The possible mechanisms by which DZP pretreatment altered the biliary excretion and the tissue distribution of DPH were examined; studies in vitro were correlated with the in vivo findings. DPH hepatic uptake and storage were apparently unaffected by DZP treatment, but liver/bile concentration ratios were suppressed. However, a direct competition between the two drugs for biliary transport was not evident. Further studies showed that liver microsomes from rats treated with DZP metabolized DPH in vitro less effectively than those from control rats. The metabolism of DPH was more markedly inhibited by the direct addition of DZP to the incubation mixtures in concentrations greater than 0.05 mM. Therefore, it appears that the effect of DZP on the metabolism of DPH is responsible for most of the observed effect although other mechanisms, including a direct effect on hepatocyte function, cannot be completely ruled out.


Mechanism of ketamine block of nerve conduction.

The node of action of ketamine on the nerve membrane has been studied in intact and internally perfused squid giant axons at 10-12 degrees C. Voltage clamp techniques have been employed to measure the maximal values of peak transient and steady-state conductances as an index of activity and to measure the apparent reversal potential for peak transient current. When applied externally to intact axons, kketamine decreased the resting membrane potential, suppressed steady-state conductances and slightly decreased theleakage conductance, although the last effect was not statistically significant. Peak transient conductance was not appreciably affected. However, when the drug was applied internally, both peak transient and steady-state conductances were suppressed. Ketamine applied externally either to intact axons or to internally perfused axons with internal flow temporarily suspended shifted the apparent reversalpotential for peak transient current towards hyperpolarization. The shift was estimated to be 28.5 mV for 200 micronM ketamine. Wahing the intact axons with drug-free sea water shifted the reversal potential further towards membrane hyperploarization. However, internal washing quickly returned the reversal potential to near control value. The change in resting sodium influx caused by external exposure to ketamine was also measured by using radioactive sodium in external sea water at 10 degrees C. Ketamine (200 micronM) changed the resting sodium influx from (28.9 +/- 5.6) x 10(-12 mol/cm2-sec to (41.8 +/- 5.6) x 10(-12 mol/cm2-sec (mean +/- S.E.M.). The data presented in this paper strongly suggest that the shift in the reversal potential for peak current caused by ketamine is due partly to sodium ion accumulation inside the nerve and partly to the increase in the PR/PNa ratio during peak current. These changes would have a profound narcotic effect on the electrical activity of nerve fibers and nerve endings in the brain during ketamine anesthesia.


Effect of lidocaine and methyl lidocaine on cardiac conduction.

The effects of lidocaine and methyl lidocaine on cardiac conduction were studied using His bundle recordings from isolated blood perfused dog hearts. The input and output characteristic of the atrioventricular (AV) node can be described as consisting of three components, namely, minimal conduction time, fatigue, and the effect of prematurity (deltaCT). Lidocaine (2.5-10.0 mg/kg) increased minimal conduction time but not fatigue.  Methyl lidocaine (1.25-5.0 mg/kg) increased both. A dose of 5 mg/kg or less of either drug caused a nonparallel shift of the deltaCT curve to the right. High doses of lidocaine (10 mg/kg) cause deltaCT to become rate-dependent. Lidocaine slowed atrial conduction only slightly. Atrial block prevented the observation of the effect of methyl lidocaine in doses higher than 5.0 mg/kg. Both drugs showed greater effect on atrial conduction at fast heart rate. Lidocaine did not affect ventricular conduction time at slow heart rates and had only minimal effects at fast heart rates. Methyl lidocaine increased ventricular conduction time at all heart rates. The results of this study indicate that lidocaine and methyl lidocaine have entirely different spectra of activity on cardiac conduction, in that their effect on AV nodal conduction do not differ greatly whereas the quaternary analog has a much stronger depressant effect on atrial and ventricular conduction.


Inhibition of norepinephrine uptake by phenoxybenzamine and desmethylimipramine in the isolated guinea-pig atrium.

The effects of phenoxybenzamine (PBZ) and desmethylimipramine (DMI) on 3H-norepinephrine uptake by sympathetic nerve terminals of isolated guinea-pig left atrium has been investigated in the absence and in the presence of norepinephrine, tyramine, cocaine and isoproterenol, used as protecting agents. PBZ blocked the uptake of 3H-norepinephrine by 50% at a concentration of 3 micronM. For DMI the ID50 was approximately 0.33 micronM. These doses were used for all subsequent protection experiments. When incubation with PBZ was carried out in the presence of tyramine (574 micronM) the blocking effects of PBZ were completely reversed. In contrast, tyramine was unable to protect against 3H-norepinephrine uptake blockade elicited by DMI. Norepinephrine (20 micronM) or cocaine (29 micronM) afforded no protection against DMI-induced 3H-norepinephrine uptake blockade, but both agents significantly protected against blockade of PBZ. Isoproterenol (40 micronM) was unable to protect against 3H-norepinephrine uptake blockade evoked either by PBZ or DMI. The results provide strong evidence for a different site and/or mechanism of action of PBZ and DMI on the norepinephrine uptake system at adrenergic nerve terminals.


Role of depolarization in acetylcholine-induced contractions of dog trachealis muscle.

The effects of acetylcholine (ACh) and K+ on tension and membrane potential were studied in order to determine the role of electromechanical and pharmacomechanical coupling in ACh-induced contractions of dog trachealis muscle. Potassium causes sustained contractions of the muscle via membrane depolarization, which appears to be related in a linear manner to the log of the external K+ concentration. From the K+ experiments a curve relating membrane potential and tension was obtained. The resting membrane potential of the trachealis is -30 +/- 1 mV. At a dose of 10(-7) M ACh the membrane is depolarized to about -55 mV and then at 10(-6) M ACh there is more depolarization to about -40 mV. At higher doses of drug there is no further change in membrane potential. The relationship between the dose of ACh and tension is much different. Contraction begins at 10(-7) M ACh but does not saturate until a dose of 10(-3) M is reached. The data were interpreted by using the relationship between EM and tension from the K+ experiments and the ACh dose-response curves as follows. At 10(-7) M ACh only pharmacomechanical coupling is involved in the contraction. At higher drug doses both pharmaco- and electromechanical coupling are involved, but pharmacomechanical coupling appears to play a much greater role. The maximal contribution of electromechanical coupling is approximately 30% of the contraction and this occurs at 10(-6) M ACh.


Uptake of uric acid by separated renal tubules of the rabbit. II. Effects of drugs.

The effect of various drugs on the rate of uptake of uric acid by separated renal tubules of the rabbit was investigated. Determinations were made of 150 values and slopes of the inhibition curves. The most potent inhibitor of uric acid uptake was sulfinpyrazone, with an 150 of 0.02 mM. Calcium ipodate and benzbromarone were also potent inhibitors. Uricosuric drugs, with the exception of benzbromarone, had shallow inhibition slopes. Diuretic drugs had steep inhibition slopes. More than one mechanism of action is probably involved in the inhibition of uric acid uptake in separated renal tubules by drugs.


Potassium release from the rat submaxillary gland in vitro. III. Effects of pretreatment with reserpine.

The release of K+ from submaxillary gland slices of rats pretreated with reserpine was compared in vitro with that from control slices in paired experiments involving stimulation with catecholamines and with cholinergic secretagogues. The slices were incubated at 37 degrees C in enriched Krebs-Ringer bicarbonate medium gassed with a 95% O2-5% CO2 mixture, in the presence and in the absence of ouabain, Ca++, substrates and specific antagonists. The results indicate that: 1) slices from the treated animals had a similar extent of basal (unstimulated) net K+ release but a significantly higher extent of stimulated net K+ release than control slices; 2) in the presence of ouabain, slices from control and treated animals had similar extents of K+ efflux during basal and stimulated conditions; 3) removal of glucose from the medium resulted in an increased net K+ release from both types of slices, but removal of both glucose and the purines further increased net K+ release from control slices but not from those of treated animals; 4) blockade of receptors 2 minutes after stimulation resulted in a slower rate of K+ reuptake in the slices from treated animals when alpha receptors were blocked with phenolamine but not when cholinergic receptors were blocked with atropine; 5) removal of Ca++ from the medium inhibited the response to norepinephrine and to carbachol, but subsequent addition of Ca++ resulted in a higher extent of net K+ release form the slices of treated animals after norepinephrine, but not carbachol stimulation; 6) there was a 2.57-fold shift to the left and a 3.47-fold shift to the left in the dose-response curve to norepinephrine and carbachol, respectively, after pretreatment with reserpine. It is concluded that reserpine pretreatment: 1) alters the ability of the salivary cells to recover the extruded K+ and 2) induces supersensitivity to secretagogues which is most likely related to changes in the physiological state of the salivary cells.


Effect of acetazolamide and parathyroid hormone on HCO3 and PO4 excretion.

It has been recently demonstrated that parathyroid hormone (PTH) inhibits renal cortical carbonic anhydrase. Based on this in vitro study, it was suggested that PTH depresses proximal reabsorption of phosphate and bicarbonate reabsorption in vivo by inhibiting carbonic anhydrase. To test this hypothesis, we measured bicarbonate and phosphate excretion in four groups of dogs. Group I received PTH for 2 hours; group II received acetazolamide for 2 hours; group III received PTH for 2 hours and acetazolamide in the 2nd hour; and in group IV, acetazolamide was given for 2 hours with PTH ADDED IN THE 2ND HOUR. Acetazolamide administration resulted in maximal bicarbonate excretion in the 1st hour and maximal phosphate excretion in the 2nd hour. Addition of acetazolamide to animals receiving PTH or addition of PTH to animals receiving acetazolamide resulted in additional increases in bicarbonate and phosphate excretion. These data demonstrate that PTH induces bicarbonate and phosphate excretion regardless of whether carbonic anhydrase is intact or nearly 100% inhibited by acetazolamide. These data do not support the hypothesis that PTH inhibits bicarbonate and phosphate reabsorption by inhibiting carbonic anhydrase.


Study of the sites and mechanisms of action of bumetanide in man.

Acute clearance studies were performed in normal subjects to establish the site(s) and mechanism of action of the new diuretic agent, bumetanide (3-n-butylamino-4-phenoxy-5-sulfamylbenzoic acid), in the human kidney. When the drug was administered during water diuresis, solute-free water formation was unchanged associated with a peak increment in fractional sodium excretion of approximately 15% of filtered load. However, studies performed in hydropenic subjects demonstrated a virtual abolition of free water reabsorption. The diuretic caused a mild phosphaturia which did not appear to be related to alterations in parathyroid hormone. Furthermore, whereas net hydrogen ion excretion and urinary pH were unchanged, the excretion of ammonium ion, titratable acidity and bicarbonate all increased mildly. Taken together, the data suggest that the primary site of action of bumetanide is the medullary portion of the ascending limb of the loop of Henle, but that in addition, bumetanide inhibits the transport of sodium in the proximal nephron. Despite the fact that the drug is a sulfonamide derivative, its proximal activity seems unrelated to a carbonic anhydrase inhibitory effect. More likely the agent interferes with proximal reabsorption by impairing sodium-phosphate linked transport.


Cannabidiol--antiepileptic drug comparisons and interactions in experimentally induced seizures in rats.

A comparison of the anticonvulsant and neurotoxic effects of cannabidiol (CBD), delta 9tetrahydrocannabinol, cannabinol and antiepileptic drugs (phenytoin, phenobarbital, carbamazepine, chlordiazepoxide, clonazepam, ethosuximide and trimethadione) was made in rats. Median effective potencies (ED 50 values) for maximal electroshock, audiogenic seizures and TD50 values for a rotor rod neurotoxicity test were calculated. Additionally, the interactive effects of CBD and the antiepileptic drugs against maximal electroshock and audiogenic seizures were studied. Each drug was given orally at peak effect time. CBD was an effective and relatively potent anticonvulsant in both maximal electroshock and audiogenic seizure tests. The anticonvulsant potency of phenytoin was significantly increased when combined with phenobarbital, CBD and phenobarbital plus CBD. Additionally, CBD reliably reduced the anticonvulsant potencies of chlordiazepoxide, clonazepam, trimethadione and ethosuximide. These data indicate that CBD is an effective anticonvulsant with a specificity more comparable to drugs clinically effective in major than minor seizures. Furthermore, it appears that CBD enhances the anticonvulsant effects of the former and reduces the effects of the latter types of antiepileptic drugs.


Narcotics and the hypothalamic-pituitary-gonadal axix: acute effects on luteinizing hormone, testosterone and androgen-dependent systems.

The effects of narcotics on several aspects of the hypothalamic-pituitary-gonadal axis were examined in the male rat. Our results indicate that a large number of narcotics acutely depress serum luteinizing hormone levels and that these reduced gonadotropin levels lead to a subsequent fall (1-2 hours later) in serum testosterone levels. The luteinizing hormone-depleting effect of the narcotics appears to represent a specific narcotic action since the (-)-isomers of the narcotics were much more effective than the ()-isomers, naloxone antagonized their effects and tolerance rapidly developed. Further, our studies indicate that the impairment of the functional and structural integrity of the secondary sex organs produced by chronic narcotic administration is not due to a direct effect of these drugs since they have no effect on the uptake of subcellular distribution of testosterone in the secondary sex organs or on the androgen-dependent accumulation of myo-inositol. Consequently, it appears that the testosterone depletion produced by the narcotics is solely responsible for their adverse effect on the secondary sex organs. The results of these studies suggest that the effects of the narcotics on the hypothalamic-pituitary-gonadal axis are confined to either the hypthalamus or the pituitary gland.


Identification of the biologically active form of sulindac.

In five animal species, the only quantitatively significant biotransformations undergone by cis-5-fluoro-2-methyl-1-[p-(methylsulfinyl) benzylidene]indene-3-acetic acid (sulindac) are oxidation of its sulfinyl substituent to sulfone, and reduction to sulfide. The former metabolite is eliminated unchanged and elicits no pharmacological response. The sulfide, on the other hand, is readily reoxidized in vivo to sulindac. In each of seven in vivo models of inflammation, sulfide administered as such is more active than sulindac. The inference that the activity of sulindac might be attributed in whole or in part to the sulfide was tested directly by comparison of responses with concentrations of each reduction oxidation species in appropriate biological fluids. Regression analyses of circulation levels of sunlindac and sulfide vs. inhibition of rat paw edema, and of their levels in synovial fluid vs. response in the dog knee joint assay, show highly significant correlations only for sulfide. Sulindac thus appears to be a "latentiated" or "pro-drug," oral dosage with chich may circumvent the gastrointestinal side effects commonly associated with nonsteriod anti-inflammatory agents.


Responsiveness to various dipsogenic stimuli in rats treated chronically with norethynodrel, ethinyl estradiol and both combined.

Administration of the estrogen, ethinyl estradiol (36 microng/kg/day), alone, and in combination with the progestogen, norethynodrel (165 microng/kg/day), significantly attenuated the dipsogenic response characteristically induced by acute s.c. administration of the beta adrenergic agonist, dl-iosproterenol (50 microng/kg). Attenuation was apparent within 1 week of steroid treatment, and remained during the 4 weeks of testing. After 16 weeks of steroid treatment, the drinking response to acute i.p. administration of renin (2 and 4 Goldblatt units/rat) was tested. The groups receiving ethinyl estradiol alone, and in combination with norethynodrel, but not norethynodrel alone, showed a reduced water intake compared with untreated controls. Drinking induced by administration of hypertonic saline (1% of body weight of 1 M NaCl solution, i.p.) was also reduced in rats treated with the estrogenic, but not the progestational, agent. However, estrogen treatment did not affect drinking after a 24-hour period of dehydration. Although the reduced dipsogenic response to isoproterenol observed in estrogen-treated rats may reflect a reduced renin secretion, drinking could not be induced in these animals by administration of renin. In addition, the reduced dipsogenic response to hypertonic NaCl loading suggests that estrogens may inhibit thirst mechanisms centrally. Dehydration, which combines hypovolemic and osmotic thirst situmul was, however, sufficient to overcome the reduced dipsogenic responsiveness of estrogen-treated rats.


Lithium: modification of behavioral activity and brain biogenic amines in developing hyperthyroid rats.

Daily treatment of neonatal rats with 1-triiodothyronine for 30 days increased locomotor activity as well as the synthesis and presumably, release of brain norepinephrine, dopamine and 5-hydroxytryptamine. Whereas administration of lithium carbonate (60 mg/kg) to normal rats for 10 days, beginning from the 20th day of age, produced no significant effect, this antimanic drug significantly decreased the observed increase in spontaneous locomotor activity in l-triiodothyronine-treated rats. Lithium treatment in normal rats increased the activity of striatal tyrosine hydroxylase, but produced no significant effect on the endogenous levels of norepinephrine and dopamine in several discrete brain regions examined. Lithium, enhanced deamination of catecholamines as evidenced by increased level of 3,4-dihydroxyphenylacetic acid and monoamine oxidase activity in normal rats. The activity of catechol o-methyltransferase was decreased to 82 and 59% in midbrain and crebral cortex of normal rats, respectively. Furthermore, chronic treatment with lithium increased endogenous levels of tryptophan, tryptophan hydroxylase, 5-hydroxytryptamine and its metabolite, 5-hydroxyindoleacetic acid, in normal animals. In contrast to the effects seen in normal rats, admininstration of lithium in l-triiodothyronine-treated animals significantly decreased tyrosine hydroxylase as well as dopamine and its metabolite, 3,4-dihydroxyphenylacetic acid, suggesting that this antimanic drug reduced the synthesis and turnover of dopamine. However, the steady-state levels of norepinephrine were raised in hypothalamus, pons-medulla, midbrain and striatum of lithium-treated hyperthyroid rats. As seen in normal animals, lithium in l-triidothyronine-treated rats increased trytophan, tryptophan hydroxylase and 5-hydroxytryptamine levels, but decreased the concentration of 5-hydroxyindoleacetic acid. The results show that the suppressed behavioral activity seen in lithium-treated hyperthyroid rats may be associated with decreased synthesis of norepinephrine and dopamine in the brain. Finally, the effects exerted by lithium on the brain catecholamine metabolizing system of young hyperthyroid rats were not similar to those seen in normal rats of the corresponding age group.


Tension in mechanically disrupted mammalian cardiac cells: effects of magnesium adenosine triphosphate.

1. Maximum and submaximum Ca-activated tension in mechanically disrupted rat ventricular fibres was examined in solutions containing 30 micron, 100 micron and 4 mM-MgATP and either 50 micron or 1 mM ionized Mg. 2. In the absence of added Ca, significant amounts of base-line tension (up to 50% of maximum) develop in solutions containing less than 30 micron-MgATP. This effect is Mg-dependent; more tension is produced with 50 micron-Mg than with 1 mM. 3. Increasing the MgATP concentration shifts the pCa-% maximum tension relationship in the direction of increasing Ca required for activation. At 50 micron-Mg the pCa which produces 50% maximum tension is 5-8, 5-3 and 5-5 for the 30 micron, 100 micron and 4 mM-MgATP solutions. The effect of MgATP on position is relatively independent of the Mg concentration. 4. The steepness of the pCa-% maximum tension curve increases as MgATP is elevated to the millimolar range. The Hill coefficients for the different MgATP curves at 50 micron-Mg are 1-1, 1-3 and 3-0. This change in steepness accounts for the slightly lower Ca concentration needed for half-maximum tension as the MgATP concentration is increased to millimolar levels. Raising the Mg concentration to 1 mM greatly diminishes the effect of MgATP on the slope of the pCa-tension relationship. 5. The maximum tnesion a fibre bundle can produce decreases as the amount of MgATP is raised from micromolar to millimolar levels. For 50 muM-Mg, maximum tension drops about 35% as MgATP is raised from 30 micronM to 4 mM. For any concentraiton of MgATP, maximum tension is higher at 1 mM-Mg than at 50 micron-Mg. 6. Existing theories of interaction between myosin heads and the thin filament are sufficient to account for the effects of MgATP on the position of the pCa-tension curves and on maximum tension. The effects on slope are less satisfactorily explained.


Effects of cytochalasin B and dimethylsulphoxide on isosmotic fluid transport by rabbit gall-bladder in vitro.

1. Net fluid transport rate, transepithelial ohmic resistance and potential difference (p.d.), and unidirectional fluxes of Na+ were measured in rabbit gall-bladder preparations in vitro exposed on both sides to Ringer solutions of identical electrolyte composition. 2. Bilateral application of 1% dimethylsulphoxide (DMSO), the solvent for cytochalasin B, rapidly and reversibly depressed net fluid transport rate by 15% and increased the lumen positive p.d. by 1-5-2-0 mV. Resistance did not change significantly. These effects of DMSO were shown to be non-specific osmotic effects. 3. Cytochalasin B (10(-5)M) applied bilaterally caused: (a) a progressive inhibition of net fluid transfer rate to 40-50% of its control value within 60 min; the effect was partly reversible within 60 min and independent of the substrates glucose, glutamate and pyruvate; (b) a progressive depression of the mucosal-to-serosal Na+ flux within the first 30 min with no further change in the flux during the following 30 min of exposure to cytochalasin B; the effect was partly reversible within 70 min; (c) a rapid but moderate increase in the passive serosal-to-mucosal Na+ flux, which continued to increase gradually during the entire 60 min period of exposure to cytochalasin B; the effect was completely reversible within 70 min; (d) a prompt drop in ohmic resistance (30%) and p.d. (40%) with no further changes in these parameters during the following 60 min of exposure to cytochalasin B. The effect on resistance was partly reversible within 90 min; the effect on p.d. was completely reversible within 30 min. 4. The results are interpreted to indicate an early inhibitory action of cytochalasin B on the active transcellular pump mechanism and to suggest a cytochalasin B-mediated progressive increase in cell membrane permeability to sodium resulting ultimately in a highly leaky epithelium. The results are compatible with the concept that a mechanochemical process is involved in isosmotic transcellular transport of fluid across low-resistance epithelia.


The orderly recruitment of motor units of the masseter and temporal muscles during voluntary isometric contraction in man.

1. The contractile properties of the motor units of the masseter and temporal muscles of human subjects were studied during voluntary isometric contractions, using a method previously employed to examine units of a small hand muscle. 2. Over the range of forces studied (0-6 kg), the units of both muscles were recruited in an orderly fashion, with a nearly linear relationship between the voluntary force at which units were recruited and their measured twitch tensions. 3. The range of contraction times (25-90 msec) was similar to that observed for the hand muscle. In some subjects it seemed that small units, recruited at low forces, exhibited shorter contraction times.


Reaction of intact spinal motoneurones to partial denervation of the muscle.

1. The properties of soleus motoneurones of the cat were examined with intracellular electrodes about 3 weeks after partial denervation of the soleus muscle. Soleus motoneurones whose axons had been left intact were distinguished from those whose axons had been sectioned by the presence or absence of muscle contraction in response to intracellular stimulation of each motoneurone. 2. The average twitch tension of motor units evoked by intracellular stimulation of intact soleus motoneurones after partial denervation of the muscle was not significantly different from that observed in control, unoperated cats. Therefore, it was assumed that the majority of intact motoneurones had not been subject to injuries in their axons upon partial denervation. 3. Soleus motoneurones whose axons had been sectioned showed a significant increase in overshoot of action potentials and a significant decrease in resting membrane potential, in axonal conduction velocity and in the duration of after-hyperpolarization. 4. Soleus motoneurones whose axons had been left intact also showed a significantly shorter after-hyperpolarization than that seen in control, unoperated cats. Other electrophysiological properties of the intact soleus motoneurones were indistinguishable from those observed in unoperated animals. 5. The decrease of the duration of after-hyperpolarization in intact soleus motoneurones was greater in highly denervated preparations than in moderately denervated preparations. 6. The decrease of the duration of after-hyperpolarization in intact soleus motoneurones was associated with a decrease in contraction times of the innervated muscle fibres, the former preceding the latter by one to two weeks. 7. It is concluded that motoneurone properties can be modified without injury to their axons and that alterations in the properties of intact motoneurones depend upon the degree of partial denervation of the muscle. The possible signal for alterations of motoneurone properties is discussed. 8. It is also concluded that the contractile properties of muscle fibres can be modified without cross-union of the nerves. It is suggested that the contractile properties of muscle fibres may be linked to the duration of after-hyperpolarization or to some mechanism related to this factor in the innervating motoneurones.


Reduction of potassium permeability by chloride substitution in cardiac cells.

1. The efflux of radioactive K and Cl ions was measured in cow Purkinje fibres and ventricular preparations of cow, cat and frog. The effect of K and Cl was studied by changing the extracellular K concentration between zero and 54 mM, and by substituting Cl ions by acetylglycinate, isethionate, benzenesulphonate, propionate and nitrate. 2. In the absence of Cl the rate coefficient for 42K efflux showed a pronounced fall, which was more pronounced the higher the K concentration. This effect was not related to the change in membrane potential. The rate coefficient for 42K efflux increased in the presence of higher extracellular K concentrations. 3. 36Cl efflux increased in the presence of reduced as well as increased extracellular K concentrations. 4. The calculated permeability coefficient for K (PK) was maximal at 5-4 mM-K, decreased slightly at higher K concentrations, but fell markedly in K-free solutions, (to about 1/5 of the value in 5-4 mM-K). In Cl-free medium PK reduced to 0-67 of the value in the Cl medium, irrespective of the K concentration. 5. The calculated PCl was greater in K-free and 16-2 mM-K than in 5-4 mM-K. 6. The ratio PK/PCl showed important changes as a function of extracellular K concentration: the value was 5 in 5-4 mM-K and fell to 2 and 0-5 respectively in 16-2 and K-free solutions. 7. The results suggest that part of the changes in membrane resistance measured by electrical methods in Cl-free media is due to a simultaneous decrease in K conductance.


The effect of insulin on the transport of sodium and potassium in rat soleus muscle.

1. The action of insulin on the transport and the distribution of Na and K has been studied in rat soleus muscles incubated at 30 degrees C in glucose-free Krebs-Ringer bicarbonate buffer. 2. Measurements of the uptake and the wash-out of 22Na indicate that the muscles contain an intracellular pool of Na available for transport which is confined to the water space not available to sucrose. Ouabain (10(-4)-10(-3)M) inhibited 22Na efflux by 69% (0-287 micronmole/g tissue wet weight per minute) and 42K-influx by 40% (0-196 micronmole/g tissue wet weight per minute). When all extracellular Na was replaced by Li, both 22Na-efflux adn 42K-influx were inhibited to about the same extent and ouabain produced very little further inhibition. 2,4-dinitrophenol decreased the ouabain-resistant component of 22Na-efflux by 39%. 3. Insulin (from 0-1 to 100 mu./ml.) increased the rate coefficient of 22Na-efflux by from 11 to 46% within 15 min. In the presence of ouabain (10(-3)M), the same relative increase was obtained, indicating that the hormone stimulates the glycoside-sensitive and the glycoside-insensitive Na transport to a similar extent. The effect of insulin on 22Na-efflux was not abolished by tetracaine (0-5 X 10(-3)M), phlorizin (0-5 X 10(-2)M) or by the substitution of Na, K, Mg or Ca. In the presence of 2,4-dinitrophenol (0-5 X 10(-4)M) or at temperatures below 15 degrees C, the hormone produced no detectable change in 22Na-efflux. 4. Insulin increased 42K-influx from 0-525 to 0-664 mumole/g tissue wet weight per minute. This effect was entirely blocked by ouabain but not by tetracaine. Insulin produced a 14% transient decrease in 42K-efflux. 5. The continued exposure to insulin led to a new steady state, in which the intracellular Na pool was decreased from around 10 to around 5 mumole/g tissue wet weight and the K content increased by an equivalent amount. In the presence of ouabain or at low extracellular concentrations of K, insulin increased the rate of 22Na-influx by around 35%. This effect was blocked by 2,4-dinitrophenol but not be tetracaine. 6. It is concluded that insulin stimulates the active coupled transport of Na and K, possibly by increasing the relative Na-affinity of the system mediating this process.


The electrical properties and active ion transport across the urinary bladder of the urodele, Amphiuma means.

1. The electrical properties and the active transport processes of the isolated urinary bladder of the urodele, Amphiuma means, were studied by mounting this tissue as a flat sheet between two halves of a lucite chamber. The mean transepithelial potential difference was 70-2 +/- 2-3 mV (serosa positive), the mean short-circuit current was 10-9 +/- 0-5 micrionA/mg of dry weight and the mean transepithelial d.c. resistance was 6540 +/- 374 omega mg of dry weight. 2. The short-circuit current (Isc) accounted for 92% of the net 22Na+ flux from the mucosa to the serosa. The difference resulted from a transport of 36Cl- in the same direction as sodium. 3. The active sodium transport exhibited typical saturation kinetics, having a Km of 15-4 m-equiv/l. and approaching zero order at 60-70 m-equiv/l. The transepithelial potential difference increased linearly with the log of the mucosal sodium concentration at a rate of 50-3 mV per tenfold concentration change. 4. In the absence of the major anions (HCO3- and Cl-) from the bathing solutions, the electrical properties and the sodium influx decreased to less than 40% of their control values. The presence of only one of these two anions in the serosal bathing solution was sufficient to maintain these parameters. 5. Amiloride (10(-5)M) and ouabain (10(-6)M) inhibited the sodium transport 97% and 85% respectively. Amphotericin B (10(-6)M) stimulated the sodium transport 47%. Furosemide (10(-3)M) inhibited the chloride transport 43%. The sodium transport was insensitive to the action of two enurohypophyseal peptides tested, lysine-vasotocin and pitocin.


Metabolic energy dependence of glucose, water and sodium absorption in the presence and absence of 'downhill' sodium gradients across isolated rat small intestine.

1. Absorption of glucose and water was studied in isolated perfused rat small intestine with arterial infusion under normal conditions and with a 'downhill' sodium gradient across the mucosa. 2. The effects of metabolic inhibitors, iodoacetate phenformin and dinitrophenol, on absorption were determined in the presence of normal and 'downhill' sodium gradients. 3. Glucose absorption was inhibited by each inhibitor, and the inhibition was independent of the direction of the sodium gradient. 4. Net sodium flux across the mucosa was also inhibited under 'downhill' sodium gradient conditions. 5. The simultaneous and parallel inhibition of both glucose and sodium transport is consistent with, but does not prove, the sodium gradient theory.


Comparison of the critical periods for monocular and directional deprivation in cats.

1. Earlier experiments rearing kittens with one eye closed and reversing the closure after a certain age, or rearing kittens in a rotating drum and reversing the direction after a certain age, suggest that the critical periods for ocular dominance and directional sensitivity may differ. Since these results were obtained by different investigators in different laboratories, we have made a direct comparison of the two types of visual deprivation. 2. Four pairs of litter-mate kittens (matched in weight) were reared. One animal in each pair was monocularly deprived with subsequent eye reversal; the other animal was directionally deprived with reversal of drum direction. All reversals took place at age 5 weeks. Both kittens in a given pair were either 'left first' (left eye open first or left direction first) or both were right first. One died prematurely. 3. Recordings were made from the visual cortex at some age after 4 months. Some recordings were made in the left cortex and some in the right. In all cases of monocular deprivation, the majority of cells were driven by the eye that was open last (i.e. open after 5 weeks of age). In all cases of directional deprivation, the majority of the cells preferred movement in the first direction of exposure (i.e. the direction before 5 weeks of age). 4. We conclude that the critical period for directional deprivation terminates earlier than the critical period for monocular deprivation.


Microcalorimetric determination of energy expenditure due to active sodium-potassium transport in the soleus muscle and brown adipose tissue of the rat.

1. The resting heat production rate (E) of soleus muscles from young rats and brown adipose tissue from adult rats was measured by means of a perfusable heat flux microcalorimeter in the absence and presence of ouabain. In the soleus muscle, the acute response of E to ouabain was compared with the ouabain-suppressible components of 22Na-efflux and 42K-influx. 2. In standard Krebs-Ringer bicarbonate buffer, ouabain (10(-3)M) induced an immediate but transient decrease in E of around 5%. Both in muscle and adipose tissue this was followed by a progressive rise in heat production rate. 3. When the medium was enriched with Mg (10 mM), ouabain produced a sustained decrease in E of the same magnitude as in the standard medium and the secondary rise was less marked or abolished. Under these conditions, in the soleus muscle, ouabain inhibited E by 5% (i.e. by 1-76 +/- 0-22 mcal.g wet wt.-1.min-1), 22Na-efflux by 58% (0-187 +/- 0-013 micronmole. g wet wt.-1.min-1) and 42K-influx by 34% (0-132 +/- 0-028 micronmole. g wet wt.-1.min-1). 4. When the muscles were loaded with Na by pre-incubation in K-free Mg-enriched medium, the addition of K (3mM) induced an immediate ouabain-suppressible increase in E of 2-98 +/- 0-33 mcal. g wet wt.-1.min-1 and a concomitant stimulation of 22Na-efflux of 0-388 +/- 0-136 micronmole. g wet wt.-1.min-1. 5. Maximum Na/ATP ratios for the active Na-K transport process were computed, with no assumption as to the in vivo free energy of ATP hydrolysis. These were 2-1, 1-9 and 2-3 under the conditions described in paragraphs (2), (3) and (4) respectively. 6. The calculated reversible thermodynamic work associated with active Na-K transport corresponded to 34% of the measured ouabain-induced decrease in E. On the premise that the maximum efficiency of the cellular energy conservation processes is 65%, this estimate indicates that the minimum energetic efficiency of ATP utilization by the active Na-K transport process in mammalian muscle is 52%.


Effects of applied currents on turtle cones in darkness and during the photoresponse.

1. The voltage changes, produced by pulses of current of various intensities and polarities into turtle cones, were examined both in darkness and during the photoresponse. 2. Depolarizing pulses of current produced voltage deflexions which, during the photoresponse, were increased to a greater extent than those produced by pulses of current of the same intensity and opposite polarity. 3. Voltage-current relationships were measured both in darkness and during illumination. During illumination they display a non-linear behaviour, the curve being steeper for positive than for negative currents. 4. These non-linearities are greatly attenuated following exposure of the retina to a solution containing 5 mM-CoCl2 which is known to block synaptic transmission. The effects of CoCl2 are readily reversible when the retina is returned to normal conditions. 5. By comparing the effects produced by pulses of current injected into individual cones with those observed in horizontal cells following stimulation with a radial current, it is observed that the non-linear behaviour of the cone membrane during the photoresponse can be, at least in part, accounted for by events occurring in post-synaptic elements (i.e. horizontal cells).


The release of vasopressin by nicotine: further studies on its site of action.

1. In cats anaesthetized with chloralose the release of vasopressin in response to nicotine injections was examined. This release was measured by assaying the hormone in samples of venous blood. 2. Nicotine injections were given by three different routes, namely intravertebral, intracarotid and intravenous. The first two represent close arterial routes to the medulla and to the hypothalamus, respectively, the effects of which could be compared to those following intravenous, i.e. systemic, administration. 3. Nicotine was found to increase vasopressin secretion by all three routes of administration. The potency of intracarotid injections was found to be no greater than that of intravenous injections, in sharp contrast to intravertebral injections, which were 4-5 times more potent. 4. In terms of vascular effects, intracarotid and intravenous injections of nicotine were found to increase blood pressure, whereas intravertebral injections of low doses of nicotine were always followed by a fall in blood pressure. Higher doses of intravertebral nicotine produce mixed results, pressor or depressor, in different animals. 5. The vasodepressor effect of intravertebral nicotine was part of a cardiovascular response which included a lowering of total peripheral resistance and of stroke work, whereas the cardiac output, the heart rate and the stroke volume remained essentially unchanged. 6. These results clearly indicate that a medullary area, which has been previously described, is the most sensitive site for the vasopressin releasing action of nicotine and that systemic administration of the drug induces vasopressin secretion by virtue of its action on the medulla, rather than directly on the supraoptic nucleus. 7. The results also indicate that the vasodepressor effect which follows the application of nicotine on the medulla is chiefly due to vasodilator effects on systemic blood vessels, with practically no action on cardiac function. The significance of these results is discussed.


Excitatory responses of neurones in rat bulbar reticular formation to bulbar raphe stimulation and to iontophoretically applied 5-hydroxytryptamine, and their blockade by LSD 25.

1. The micro-iontophoretic technique has been used to study the responses of single neurones in the bulbar reticular formation to 5-hydroxytryptamine and to noradrenaline, ACh or glutamate, and to compare these with the responses to electrical stimulation in or near the bulbar raphe nuclei. 2. In the bulbar reticular formation, most neurones were excited by 5-hydroxytryptamine; forty-three of fifty-one neurones excited by 5-hydroxytryptamine were also excited by stimulation in nucleus raphe magnus, nucleus raphe pallidus or nucleus raphe obscurus. Most of these stimulation-induced excitations were of long latency: LSD reduced six of seven of these excitations tested, while 5-hydroxytryptamine excitations were blocked on all seven. 3. In contrast, stimulation of areas adjacent to the raphe nuclei excited only fifteen of forty-six neurones excited by 5-hydroxytryptamine. Most of these stimulation effects were of short latency and none of the three tested were reduced by LSD, although 5-hydroxytryptamine excitations were blocked. 4. The relationship of the long-latency excitatory effects of stimulation with the position of the stimulating electrode in the raphe nuclei indicates that these effects are probably mediated via the raphe neurones and this is supported by the correlation of the effects of raphe stimulation with the effects of 5-hydroxytryptamine applied iontophoretically and by the ability of LSD to block both effects. 5. The results provide a physiological basis for the excitatory effects of iontophoretically applied 5-hydroxytryptamine in the bulbar reticular formation.


Axon-collateral activation by dorsal spinocerebellar tract fibres of group I relay cells of nucleus Z in the cat medulla oblongata.

1. The problem whether the group I hind limb cerebral tract and the dorsal spinocerebellar tract (DSCT) have common spinal axons has been investigated in the present study. 2. Thirty-two cells located in the nucleus Z of the cat medulla oblongata and activated by spinal fibres in the dorsolateral fascicle were selected for the study. 3. Extracellular recording from these neurones demonstrated that most of them were monosynaptically linked to spinal fibres excited by ipsilateral hind limb group I muscle afferents. The cells exhibited a restricted spatial convergence and had a limited excitatory convergence from group II muscle and from skin afferents. 4. Antidromic activation from the contralateral thalamus showed that they were bulbothalamic relay cells. 5. Cerebellar surface or depth stimulation activated 88% of the twenty-six cells tested at a short latency. With a collision technique it was demonstrated that twelve out of twenty-three (52%) of these group I relay neurones were activated by axon-collaterals of the DSCT. 6. 43% of the cells activated from the cerebellum, but not proven to be linked to the DSCT, could, nevertheless, have been excited by DSCT axon-collaterals, if it is assumed that different fibres converging with excitation on the group I relay cells were activated in the collision test.


Input from ipsilateral proprio- and exteroceptive hind limb afferents to nucleus Z of the cat medulla oblongata.

1. Extracellular recordings have been made from proprio- and exteroceptive neurones in nucleus Z of the cat medulla oblongata. 2. Seventeen non-relay cells were excited by ipsilateral hind limb group I muscle afferents. Their functional were similar to those of the corresponding relay cells (Johansson & Silfvenius, 1977), i.e. activation by axon-collaterals of dorsolateral fascicle (DLF) fibres was observed, indicative of an input from the dorsal spinocerebellar tract (DSCT) to these neurones. The non-relay cells differed, however, from the relay cells in that a larger proportion of them were disynaptically connected to the spinal fibres. It is suggested that the non-relay cells by inhibition modulate the group I relay transmission in nucleus Z. 3. Fifteen cells were excited by ipsilateral hind limb low threshold skin afferents with their spinal fibres at the first cervical segment located either in the DLF or in the dorsal column (DC). Evidence for a cutaneous hind limb bulbothalamic path independent of that of the DC and of the spinocervicolemniscal path is presented. 4. Six cells were activated by ipsilateral hind limb joint afferents at low threshold. At the C1 level the spinal fibres were located either in the DLF or in the DC. No joint activated relay-cells were encountered. Axon-collateral activation of DLF-linked joint cells was observed during cerebellar stimulation, indicating that segmental DSCT cells mediated the joint input to nucleus Z. 5. The topographical organization within nucleus Z and its input relation to the DSCT is discussed.


Fractionation studies on the absorption of labelled immunoglobulin G by the gut of young rats.

1. Centrifugation in density gradients was used to study the fragments produced during intraluminal and intracellular digestion, after the injection of 125I-labelled immunoglobulin G (IgG) into different regions of the small intestine of 14 to 15-day-old (pre-closure) and 24-day-old (post-closure/ rats. 2. After injection into the proximal small intestine and into the ileum of pre-closure animals, the bulk of the radioactivity recorded for gut washes and gut homogenates was located at 4S-7S. The serum from animals which had received injections into the proximal small intestine had high radioactivity and one peak at 7S; the serum from animals which had received injections into the ileum had low radioactivity and no activity in the 7S region. 3. After injection into the proximal small intestine of post-closure animals, the bulk of the radioactivity recorded for gut wash samples was located at 3-5S--5S. Gut homogenates had peak activity at 2-5S--4S. Thus large molecular weight products can be absorbed by the proximal enterocytes of post-closure rats and degraded. The sera of these animals had low radioactivity. 4. After injection into the distal small intestine of post-closure animals, the bulk of the radioactivity recorded for gut wash and gut homogenate samples was located at 4S-7S and in this respect the radioactivity plots resembled those for (2) above. Serum radioactivity was low. 5. The effect of precipitation with trichloroacetic acid and incubation with specific antiserum upon the radioactivity of gut washes, gut homogenates and serum samples was recorded. 6. The relevance of these findings to studies on the transmission of protein by the rat small intestine is discussed.


Connexions from large, ipsilateral hind limb muscle and skin afferents to the rostral main cuneate nucleus and to the nucleus X region in the cat.

1. Evidence is presented for an input from ipsilateral hind limb group I muscle afferents and low threshold cutaneous afferents, to cells in the rostral division of the main cuneate nucleus (rMCN) and in the region of the descending vestibular nucleus and the nucleus X of Brodal & Pompeiano (1957a), the (DV-X). 2. Thirteen group I-rMCN cells were recorded from. The functional properties of these cells were similar to those of nueleus Z (Landgren & Silfvenius, 1971; Johansson & Silfvenius, 1977a, b). The cells were monosynaptically linked to spinal dorsolateral fascicle (DLF) fibres. Nine cells projected to the contralateral thalamus, i.e. a second group I hind limb bulbothalamic tract is described. Ten cells were synaptically activated from the ipsilateral cerebellum from the anterior projection zone of the dorsal spinocerebellar tract (DSCT). Axon-collateral activation by DSCT fibres was established for two of these cells. They were both bulbothalamic relay cells. For the remaining eight cells, activated from the cerebellum, this was not proven. These cells could, however, either be linked to DSCT fibres or to short axon-collaterals of a cell body of unknown location. A projection from the rMCN to the cerebellum is described and agrees with recent anatomical findings. Two cells were not excited from the cerebellum. 3. Four rMCN cells were activated by cutaneous afferents with their secondary axons in the DLF. Suggestive evidence for a bulbothalamic cutaneous hind limb path via the rMCN is presented. Two cells were activated from the cerebellum, presumably via axon-collaterals of nonsegmental cells. 4. Eight group I-DV-X cells were recorded from. They were monosynaptically linked to spinal DLF fibres and resembled functionally the nucleus Z and rMCN cells when stimulated from the periphery. Two cells projected to the contralateral thalamus, and two others were synaptically excited. Seven cells were activated from the ipsilateral cerebellum. Two of them projected to the cerebellum, and three were synapitcally activated by axon-collaterals of an undefined non-segmental cell. 5. Two DV-X cells which were activated by cutaneous afferents possibly had their spinal fibres deep in the dorsal column. Both were activated from the cerebellum, one by collaterals of a spinal axon. The functional organization of the three juxtaposed medullary nuclei, Z, rMCN and DV-X is discussed.


Cellular and extracellular dehydration, and angiotensin as stimuli to drinking in the common iguana Iguana iguana.

1. After water deprivation, the iguana promptly drank slightly more than enough water to restore the body fluids to isotonicity even under conditions of hypervolaemia. 2. In response to systemic injections of hypertonic solutions of NaCl and sucrose, the iguana drank and retained enough water to dilute the injected load to isotonicity irrespective of whether water was offered immediately or after 3 hr, and irrespective of whether the solute was administered I.V. or I.P. 3. Hypertonic solutions to glucose, urea, sorbitol and KCl caused little drinking. 4. The long latencies to drinking after hypertonic loads, which were not dependent on the nature of the solute, the route of administration or the dosage, were shown not to be a result of slow distribution of the solute throughout the body fluids. 5. Clearance of injected solutes via renal and extra-renal (nasal salt gland) routes was negligible during the 6 hr experimental period. 6. Measurements of plasma [Na], haematocrit, osmotic pressure and inulin space showed that the iguana drank, in response to cellular dehydration, enough water to restore the intracellular fluid volume to normal. 7. We conclude that, in response to substances which dehydrate cells, the iguana regulates its body osmolality precisely and efficiently provided it is able to do so by drinking. In this respect the responses of the iguana are similar to those of the nephrectomized rat since, in the short term, both rely exclusively on drinking to restore cellular water to normal. 8. The iguana also drinks in response to extracellular dehydration produced by hyperoncotic peritoneal dialysis, and in response to I.P. angiotensin II.


Three pharmacologically distinct potassium channels in molluscan neurones.

1. Potassium currents were studied under voltage-clamp conditions in nerve cell bodies of the nudibranch Tritonia diomedia. 2. Potassium currents could be separated into three distinct components on the basis of their sensitivity to 4-aminopyridine (4-AP), tetraethyl-ammonium (TEA) and to Co2+ and Mn2+ ions. 3. A transient potassium current, similar to the fast outward current described by Connor & Stevens (1971b) and Neher (1971), was blocked by externally applied 4-AP but was much less sensitive to TEA or to Co2+ or Mn2+. A single 4-AP ion binds each receptor with an apparent dissociation constant of 1-5 X 10(-3) M. 4-AP decreases the rates of activation and inactivation and reduces the maximum conductance of transient current channels. 4. Delayed outward current was not effected by 4-AP at concentrations which blocked the transient current, but it could be divided into two components by external application of TEA and Co2+ or Mn2+. 5. A voltage-dependent component of delayed current, termed K-current, was blocked by TEA. Each K-current receptor binds a single TEA ion with an apparent dissociation constant of 8 X 10(-3) M. Co2+ and Mn2+ have little or no effect on K-current. 6. A second component of delayed outward current, termed C-current, depends on Ca2+ entry for its activation. It is similar to the Ca2+ dependent potassium current reported by Meech & Stranden (1975) in Helix cells. C-current is essentially blocked by 30 mM external Co2+ or Mn2+. It is little affected by TEA, however, being reduced by about 20% at a TEA concentration of 100 mM. 7. It is concluded that three sets of potassium selective channels contribute to the outward current and that these channels can be separated pharmacologically.


Utilization of blood-borne and intramuscular substrates during continuous and intermittent exercise in man.

1. Substrate utilization in the legs during bicycle exercise was studied in five subjects when performing intermittent intense exercise (15 sec work--15 sec rest) as well as continuous exercise during 60 min, with an almost identical average power output and oxygen uptake in both situations. 2. Muscle biopsies were obtained from vastus lateralis at rest, during, and after exercise in order to determine intramuscular lipid and carbohydrate utilization. The contribution from blood-borne substrates to total oxidative metabolism was determined by arterial-femoral venous (a-fv) differences for oxygen, FFA, glucose, and lactate and leg blood flow. 3. Intermittent and continuous exercise revealed a similar glycogen depletion and the intramuscular lactate accumulation was rather small. A similar uptake of blood-borne substrate (FFA, glucose) was found in both situations whereas a release of lactate only was observed in intermittent exercise. 4. ATP and CP levels oscillated between work and rest periods in intermittent exercise but were not resynthesized to resting levels at the end of the rest periods. The mainly aerobic energy release during each work period in intermittent exercise is partly caused by myoglobin functioning as an oxygen store; this factor was calculated to be more important than ATP and CP or lactate level oscillations. 5. The metabolic response to intermittent exercise was found to be similar to that found in continuous exercise with approximately the same average power output and oxygen uptake. This indicates that some factor in the intermediary metabolism, for instance citrate, functions as a regulator retarding glycolysis and favouring lipid utilization and an aerobic energy release in intermittent exercise.


The sensory mechanism of servo action in human muscle.

1. Anaesthesia of the thumb suppresses servo action in the long flexor of the thumb during movements of the terminal phalanx. 2. It needs a greater subjective effort to flex an anaesthetized thumb than a normal one. 3. Anaesthesia of other digits is without effect on the thumb flexor. 4. In an anaesthetic thumb without servo responses the changes in force exerted when a mechanical perturbation is applied which are due purely to the passive mechanical properties of the muscle can be measured. Subtraction of these gives the active components of servo action in the normal thumb and thus an estimate of the mechanical gain of the servo. 5. Giving the subject a visual tracking task can partially restore servo action when the thumb is anaesthetic. 6. After some years subjects become resistant to the effect of peripheral anaesthesia. 7. Peripheral anaesthesia has no detectable effect on servo responses in the long flexor of the great toe, in infraspinatus or in pectoralis major. Servo action in these muscles is presumably based predominantly on muscle receptors. 8. Tendon jerks are not apparently influenced by peripheral anaesthesia. 9. The Discussion considers the possibility that, for the thumb, muscle afferents co-operate with a somatic and a visual input in a servo loop via the cerebral cortex.


The sensitization of high threshold mechanoreceptors with myelinated axons by repeated heating.

1. Seventy high threshold mechanoreceptor units (HTMs) with myelinated axons were isolated from the sural nerves of cats and rabbits. Thirteen cat and forty-two rabbit HTMs were testec by controlled, repeated heating of the skin of the foot or lower leg to noxious levels. 2. Many of the units (77% in the cat and 40% in the rabbit) fired to heating. Only six (11%) of these fired to the first brief heating to 50-55 degrees C. The rest required 2-6 heat trials before responding. 3. Heat responding units always became more sensitive with repeated heat stimulation but their mechanical sensitivity showed no comparable changes when heat sensitization occurred. 4. If these results are applicable to man, they suggest that HTMs play little role in generating the first pain that follows skin heating but that they may be involved in the increased sensitivity to heat pain (hyperalgesia) shown by skin previously injured by heating.


The permeability of the skin of a neotenous urodele amphibian, the mudpuppy Necturus maculosus.

1. The permeability of the isolated skin of a neotenous urodele amphibian, the mudpuppy Necturus maculosus, to Na, Cl, urea and water was measured. 2. Unidirectional transcutaneous flux measurements and the action of ouabain and amiloride, showed that there was normally no active Cl or Na transport, nor a Cl/Cl exchange diffusion process. 3. Amphotericin B initiated a transcutaneous potential difference and short-circuit current, which could be inhibited by ouabain. 4. The short-circuit current was nearly equivalent to the net Na Transport and this was also inhibited by ouabain. 5. A transcutaneous active Na transport mechanism thus appears to be incipient in the mudpuppy but is limited by a low permeability of the outer barrier of the cells. 6. Vasotocin increased the skin's diffusion permeability for water but had no effect on the influx of Na or urea. 7. The function of Necturus skin is in several respects unique compared to that of other amphibians.


Inhibition of the intracellular release of calcium by Dantrolene in barnacle giant muscle fibres.

1. Ca movements in resting and in activated single giant muscle fibres of the barnacle were analysed before and after exposure to Dantrolene Na, a synthetic hydantoin derivative. 2. In fibres micro-injected with the photoprotein aequorin, the resting rate of light emission (resting glow) reversibly decreased upon exposure to Dantrolene. Similar results were obtained if the fibre had first been equilibrated in a O Ca-1 mM-EGTA medium. 3. The influx of 45Ca into resting muscle fibres was not modified by 35 micronM Dantrolene which also failed to significantly reduce the influx of 45Ca into muscle fibres which had been depolarized by exposure to external solutions in which K+ had been increased to 60 or 200 mM. 4. In fibres micro-injected with 45Ca, the calcium efflux was reversibly decreased by Dantrolene. This effect was still observed in O Ca medium and in O Ca-ONa medium. A possible effect of Dantrolene on the Na-Ca exchange process at the outer membrane was excluded by showing that when the direction of the Ca2+ movement was inverted in aequorin-loaded fibres by the sudden removal of Na+ from the external medium, a marked increase in the resting glow was recorded which was not affected by exposure to Dantrolene. 5. It is argued that the reduction of Ca2+ efflux by Dantrolene does not result from any direct inhibitory effect on the metabolically driven Ca pump at the outer membrane, but that it is rather related to the reduction of the concentration of myoplasmic Ca2+ which is indeed demonstrated by the reduced resting glow. This in turn is thought to result from a shift in the balance between Ca2+ movements into and out of the intracellular storage sites, and namely the sarcoplasmic reticulum (SR). 6. The Ca2+ transient in aequorin-loaded fibres and the force of the isometric contraction elicited by imposed membrane depolarizations were markedly reduced by Dantrolene. The electrochemical threshold for eliciting intracellular Ca2+ release was not significantly modified. The linear relation between membrane depolarization and Ca2+ transient became less steep. The process of sequestration of myoplasmic Ca2+ back into SR was not significantly affected by Dantrolene which appeared to inhibit rather selectively the Ca2+ release from SR into the cytosol.


Plasma concentrations of ethynyl oestradiol and norethindrone after oral administration to women.

Plasma concentrations of ethynyl oestradiol and norethindrone in women were measured by radioimmunoassays after oral administration of 50 microng and 1000 microng respectively. The maximum values were obtained 1 h after administration. The calculated half-life was 6 1/2 h for ethynyl oestradiol and 7 h for norethindrone. At most 2-3% of the administered dose was present in the plasma at 1 h and had decreased to about 0-5% by 24 h.


Adrenergic activity of the oviduct of the domestic fowl.

The adrenergic activity of the domestic hen was investigated. Administration of noradrenaline to laying hens at dose levels of 3-5, 7-0, and 14-0 microng/kg produced an increase in the magnal pressure, and a simultaneous decrease in the uterine pressure. Similar doses given to ovariectomized hens caused an inhibition of activity in both segments. Strips of tissues from the vagina and the uterovaginal junction of laying hens were exposed in vitro to noradrenaline at concentrations of 1-5 x 10(-6) and 2.9 x 10(-6) M. The vaginal strips reacted with a sharp increase in tension, while the uterovaginal preparations showed a more gradual and prolonged response. It is suggested that the beta inhibitory activity of the uterus and the alpha excitatory activity of the rest of the oviduct are involved in the regulation of ovum transport.


Serum corticosterone concentrations in reproductively mature and inhibited deermice (Peromyscus maniculatus bairdii).

Serum corticosterone concentrations were measured to see if there was any correlation between adrenal activity and reproductive inhibition. Males and females from two growing and one stable (asymptotic) population had significantly smaller reproductive organs (seminal vesicles, testes, uteri, ovaries) than controls. The weights of the adrenal glands of population mice were smaller, often significantly so, than those of controls, but the mean serum corticosterone concentrations were higher than those of control mice for the two growing populations and significantly higher for the asymptotic population. These data suggest that adrenal function may be associated with the reproductively inhibited condition, but not in a direct or dose-response fashion and that adrenal hyperfunction in this species may not be reflected by adrenal hypertrophy.


Accumulation of steroids in rabbit preimplantation blastocysts.

The concentrations of progesterone, androstenedione, testosterone, oestrone and oestradiol were measured by radioimmunoassay in blastocysts and uterine fluid flushings collected from rabbits 110 to 159 h post coitum (p.c.). None of the blastocysts or uterine flushings contained detectable levels of androstenedione, testosterone or oestrone. All uterine flushings contained large amounts of progesterone and some of the flushings also contained oestradiol. A small amount of progesterone (approximately 7-5 pg/blastocyst) was first detectable in some blastocysts at 135 h p.c.; progesterone levels/blastocyst then increased progressively, reaching levels of about 122-158 pg/blastocyst at 159 h p.c. Micropuncture of blastocysts at 159 h p.c. indicated that greater than or equal to 90% of the progesterone in the embryo was in the blastocoelic fluid. Blastocysts from rabbit uterine horns containing oestradiol also contained oestradiol but those in which oestradiol was detected were never observed in uteri lacking the hormone. It is inferred that rabbit blastocysts accumulate both progesterone and oestradiol from uterine fluid.


The effect of RMI 12, 936 synthetic antiprogestional steroid, on ovarian steroidogenesis in the rat.

A series of physiochemical investigations confirmed that the product of chemical and enzymatic isomerization of RMI 12,936 was 7alpha-methyltestosterone. The total activity per pair of ovaries of delta5 3-ketosteroid isomerase in vitro was unchanges by RMI 12,936 pretreatment or by advancing pregnancy, significant changes in ovarian weight being accompanied by reciprocal changes in enzyme activity/mg tissue. The initial rate of isomerization of RMI 12,936 was approximately five times greater than the corresponding rate of delta5-progesterone isomerization at equal substrate concentrations. It is concluded that RMI 12,936 does not inhibit progesterone biosynthesis by alteration of delta5 3-ketosteroid isomerase activity, but that it may do so by acting as an alternative substrate for this enzyme.