Current voltage curves of biomolecular lipid membranes.

The first part of this paper describes the current voltage curves of bimolecular membranes of oxidized cholesterol formed between two aqueous solutions of tetrabutylammonium chloride. These membranes are selectively permeable for cations and the membrane interfaces are electrically uncharged. The dependence of the membrane conductivity on the membrane potential can be described as the product of the conductivity at zero current ("zero conductivity") and a function called "overlinearity". The zero conductivity increases linearly with the concentration of tetrabutylammonium chloride. The overlinearity is independent of the concentration of tetrabutylammonium chloride. In the second part the Nernst-Planck and Poisson equations are integrated numerically for a three-phase system consisting of an aqueous electrolyte solution, a membrane and an aqueous electrolyte solution. Each phase is characterized by material constants. Appropriate boundary conditions cause the electric current to build up electrical double layers on both sides of the membrane. The opposing double layers with opposite electrical signs inject the soluble ions into the membrane. This ion injection accounts for the overlinearity of the current voltage curves, thus explaining the measured characteristics.


A model for the packing of lipids in bilayer membranes.

A number of known structural properties of mixed lipid bilayer membranes and monolayers are accounted for by a model in which lipids pack into bilayers and monolayers like building blocks, each characterized by a surface head group area and characteristic solid angle. In phospholipids above the melting transition the head group area (at a given temperature and degree of hydration) is fairly invariant while the hydrocarbon region may be liquid-like so long as the molecule is not compressed beyond its characteristic solid angle. Phosphatidylcholine and phosphatidylserine are tapered lipids, i.e. their surface head group areas are greater than their non-polar end areas; cholesterol is frayed, i.e. its polar end area is less than its non-polar end area; while phosphatidylethanolamine is almost cylindrical. The "condensing" effect of cholesterol in mixed phospholipid-cholesterol films is seen as a taper-fray accommodation. The lipid distribution in erythrocyte membrane is shown to be conducive to a stable strain-free membrane.


The relative rates of degradation of the plasma membrane glycoproteins from normal rat liver.

Rat liver plasma membranes, as fractionated by sodium dodecylsulfate/polyacrylamide gel electrophoresis, have been examined for the incorporation in their subunits of radioactive leucine, glucosamine and fucose. Specific spectra were obtained. In contrast to leucine, where the activity is distributed in many peaks all over the fractions, the glucosamine and fucose activities are found principally in the high molecular weight region. The relative rates of degradation of the glycoprotein components of the plasma membrane have been measured in normal liver using the double isotope technique. A marked heterogeneity of degradation was observed among the different subunits and a correlation between the rate of degradation and the size of the labelled subunits was found with glucosamine and fucose as well with leucine. This suggests a similar mode for the degradation of these membrane components.


Biogenesis of erythrocyte membrane proteins. In vivo studies in anemic rabbits.

To study the process of red cell membrane protein synthesis we have followed the time course of [3-H]leucine appearance in total protein and individual peptides of the erythrocyte membrane following injection of the amino acid into phenylhydrazine-anemic rabbits. Multiple peripheral blood samples were taken from single animals over a 5-week period. Erythrocyte membrane proteins were separated by polyacrylamide gel electrophoresis in sodium dodecylsulfate and dithiothreitol; incorporation of radioactivity was determined by gel slicing and liquid scintillation spectrometry. Appearance of [3-H]leucine in circulating erythrocytes reached a peak at 1-3 days, with a steady decline thereafter. The radioactive amino acid appeared first in the lowest molecular weight peptides and last in the largest peptides; at the earliest time point (8 h), little radioactivity was observed in any of the four largest peptides present in the membranes (bands A, 1, 2 and 3). Certain smaller peptides (bands 4, 5 and 9) were the predominant species labeled at this time. By 24 h all peptides showed significant incorporation. With maturation of the red cells, label largely disappeared from bands A, 9 and several smaller peptides; this was confirmed by finding that the peptides are virtually absent from mature circulating erythrocytes. These data are interpreted as showing that red cell membrane proteins are synthesized asynchronously during the life cycle of the erythrocyte; the largest peptides are made predominantly in the earlier marrow stages of development, while certain of the smaller peptides are still being synthesized in the reticulocyte stage. Several membrane proteins appear to be specific to the reticulocyte and are lost during the process of cell maturation in the circulation.


Biogenesis of erythrocyte membrane proteins. In vitro studies with rabbit reticulocytes.

The capability of rabbit reticulocytes to synthesize red cell membrane proteins has been tested in vitro. Reticulocyte-rich blood from phenylhydrazine-treated rabbits was incubated in vitro in a complete amino acid medium containing ferrous salts, glucose, rabbit plasma and [3-H]leucine. Red cell ghost membranes were prepared by hypotonic lysis and leucine incorporation into hemoglobin and total membrane proteins determined. The pattern of incorporation into individual peptides was determined by polyacrylamide gel electrophoresis of labeled membranes on large (19 mm) gels which were then sliced into 1 mm sections; radioactivity was compared with densitometric tracings of Coomassie blue stained analytical (6 mm) gels. Incorporation of [3-H]leucine into both hemoglobin and membrane protein was linear over 1 h. Gel analysis of labeled membranes revealed that the amino acid was primarily incorporated into peptides with molecular weights of 90 000 or less; three peptides of molecular weights 90 000, 60 000 and 33 000 showed the highest specific activity. Synthesis of the four largest peptide species was negligible. Removable of ferrous salts inhibited synthesis of both globin and membrane protein equally (approx. 50%). However, puromycin and cycloheximide preferentially inhibited the synthesis of globin as compared to membrane proteins. Reticulocytes remain capable of synthesizing a number of membrane proteins; these results are consistent with studies of red cell membrane synthesis in anemic rabbits in vivo.


Insulin and insulin inhibitor on amino acid transport in rat diaphragm in vivo.

Insulin stimulated the accumulation of alpha-aminoisobutyric acid by the rat diaphragm in vivo. This stimulation, but not the accumulation in the absence of insulin, was reduced by 30-40% by insulin inhibitor present in extracts of liver.


Proton NMR bandshape studies of lamellar liquid crystals and gel phases containing lecithins and cholesterol.

Proton NMR spectra for gel and liquid crystalline samples, composed of dimyristoyl and/or dipalmitoyl lecithin, cholesterol and water, can be consistently interpreted in terms of mesophase symmetry and molecular diffusion according to a model proposed by Wennerstrom (Wennerstrom, H. (1973) Chem. Phys. Lett. 18, 41-44). It is shown by computer simulation that the characteristic "super-lorentzian" bandshape of the lamellar mesophase can be described by the superposition of three gaussian curves. The NMR signal of the gel phase can be simulated by the superposition of two gaussian curves with widths at half height of 2.5 kHz and 19 kHz. An upper limit of the lateral diffusion coefficient of the lecithin molecules in the gel phase is calculated to be about 5-10(-15) m-2/s. It is therefore concluded that the static intermolecular dipolar couplings average to zero in the lamellar mesophase. An estimation of the order parameter of the liquid crystalline phase is made from experimental data and a calculated "rigid lattice" linewidth. A two phase system is shown to exist in the temperature range 28-34 degrees C for a mesophase of a mixture of dimyristoyl and dipalmitoyl lecithin. The presence of cholesterol results in enhanced lateral diffusion of the lecithin molecules at temperatures below the Chapman transition point.


Characteristics of rat jejunal transport of tryptophan.

The parameters of rat jejunal transport of tryptophan have been examined. The interactions between tryptophan and lysine or methionine have been reexamined, and some aspects of the trans effects of cellularly accumulates amino acids have been studied. It has been demonstrated that: (1) The influx of tryptophan across the jejunal brush border (Jmc-Trp) can be accounted for by the carrier of alpha-aminomonocarboxylic acids alone. (2) Tryptophan competes with lysine for the carrier of basic amino acids across the brush border membrane without itself being transported by this carrier. (3) Lysine has neither cis nor trans effects on Jmc-Trp, whereas intracellular tryptophan is highly inhibitory to Jmd-Lys. (4) The intracellular concentration of lysine and of tryptophan, [Lys]c and [Trp]c, are unaffected by tryptophan and lysine, respectively, although the transmural fluxes, from the mucosal side to the serosal side, Jms, of lysine, Jms-Lys, and of tryptophan, Jms-Trp, are inhibited by tryptophan and lysine, respectively. The latter effects thus represent inhibitory interactions at the basolateral membrane. (5) Methionine is a potent cis and transinhibitor of Jmc-Trp, but stimulated Jms-Trp and reduces [Trp]c. (6) Methionine causes trans acceleration of the influx of lysine across the brush border membrane, Jmc-Lys, but has no effect on the influx of galactose, Jmc-Gal. (7) Leucine causes trans inhibition of Jmc-Leu. (8) Tryptophan does not cause cis inhibition of Jmc-Gal, but is a strongtransinhibitor of Jmc-Gal. (9) Cellularly accumulated tryptophan appears to accelerate the eventual decline in transepithelial potential difference and short-circuit current. These results are consistent with the conclusions that: (1) Tryptophan is transported across the brush border membrane by the carrier of neutral amino acids alone, but leaves the cell across the basolateral membrane by a mechanism used by lysine also. (2) Leucine, methionine and probably tryptophan have a transeffect on the transport of neutral amino acids across the brush border membrane which may represent a phenomenon which can appropriately be termed decelerating exchange diffusion. (3) Cellularly accumulated tryptophan has a strong and indiscriminate depressive effect on all transport functions of rat jejunal epithelium.


The specificity of the synthetic reaction of two yeast alpha-glucosidases.

The specificity of the hydrolytic reaction has been compared to that of the synthetic reaction for maltase and isomaltase (alpha-methyl-D-glucosidase) from Saccharomyces oviformis. Maltase which hydrolyzes the alpha-1,4-disaccharide, maltose, and the alpha-1,6-disaccharide, isomaltose, catalyzes the formation of both maltose and isomaltose from free glucose. Isomaltase, which hydrolyzes isomaltose but not maltose, catalyzes the formation only of isomaltose from glucose. Both enzymes hydrolyze p-nitrophenyl-alpha-D-glucoside releasing the alpha-anomer of glucose. The enzymes utilize the alpha-anomer but not the beta-anomer for the synthesis of the disaccharides. These results are consistent with the double displacement mechanism for glycosidases and with the proposal that the glucosyl-enzyme complex is an intermediate in the reaction. The competitive inhibition by D-glucose is independent of its anomeric form for both enzymes.


Some properties of trehalase from Phycomyces blakesleeanus.

Trehalase (alpha, alpha-trehalase glucohydrolase EC 3.2.1.28) from Phycomyces spores occurs in two different forms which are convertible in vivo: a form with low activity found in dormant spores and an active form after breaking the dormancy. Between the two forms no difference in molecular weight and electrophoretic mobility can be detected. The molecular weight is estimated by gel filtration at about 210 000. The relation between substrate concentration and trehalase activity follows the Michaelis-Menten equation (K-m plus or minus 55 mM) in activated spores whereas in dormant spores trehalase shows a different substrate binding, indicating a negative cooperative effect. They differ further in thermostability and in sensitivity to inhibition by ATP. Other nucleosidephosphates have no inhibiting effect. Heating the spores at different temperatures between 38 and 44 degrees C results in a partial breaking of dormancy of the spore population and a corresponding partial activation of trehalase. This suggests a close connection between breaking dormancy and trehalase activation.


Inhibition of amylases from different origins by albumins from the wheat kernel.

The amylase activity of water extracts from 18 insect species, from 23 marine species and from 17 different species of birds and mammals was determined quantitatively. The inhibition of amylase in these extracts by three albumin fractions from the mature wheat kernel, which had been separated according to their molecular weights (60 000, 24 000 and 12 500 D), was determined as well. The inhibition activity of the three albumin fractions toward amylases extracted from a number of cereal species or from immature and germinating wheat kernel was also tested. The extracts from insects that are destructive of wheat grain and stored wheat products showed much higher amylase activities as compared to the other insect species that do not attack wheat and wheat products. On the basis of the effectiveness with which the three albumin fractions inhibit their activities, the amylase preparations tested were divided into susceptible, partially susceptible and resistent. Susceptible amylases, inhibited by any of the three albumin fractions, were found mainly in insects that attack wheat and in marine species. Partially susceptible amylases, inhibited by only one or two of the three albumin fractions, were present in a few avain and mammalian species including man. Resistent amylases were largely distributed in cereal, avian and mammalian species as well as in insect species that do not usually attack wheat grain or wheat flour products. At no stage of development, wheat alpha-amylase was inhibited by the albumin fractions from the mature kernel. The 12 500 dalton albumin fraction was the most effective in inhibiting insect amylases, but it was inactive toward avian and mammalian amylases. The 24 000 dalton albumin fraction was the most effective in inhibiting amylases from marine avian and mammalian species and inhibited as much as 33 amylases over 66 different amylases tested. It is suggested that protein inhibitors of amylase contributed to natural selection of polyploid wheats by giving some insect resistence to such wheats, even though some insect species were able to overcome this biochemical defense toa large degree by producing higher amylase activities.


The isolation and characterization of mouse liver glyoxalase I.

The purification of glyoxalase I (S-lactoyl-glutathione methylglyoxal-lyase (isomerizing) EC 4.4.1.5) from DBA/1J mouse liver employing ion exchange and affinity chromatography is described. The enzyme was purified 1140-fold and it exhibits a specific activity of 2200 units/mg of protein. The activity was determined to be homogeneous by sedimentation velocity and sedimentation equilibrium ultracentrifugation and by polyacrylamide electrophoresis. The molecular weight is approimately 43 000 and the sedimentation coefficient is 3.4 S. Kinetic data are consistent with a one-substrate (hemimercaptal) reaction mechanism but do not rule out alternate branches at low substrate and free glutathione concentrations.


Degree of dissociation of apohemoglobin studied by nano-second fluorescence-polarization technique.

A fluorescent dye 1-anilino-8-naphthalene sulfonate was complexed with human apohemoglobin and sperm whale apomyoglobin. Nanosecond fluorescence-polarization kinetics were measured for each of these complexes in KC1 solutions to obtain their fluorescence lifetimes and rotational correlation times. The rotational correlation time of apohemoglobin-dye complex was found to be 21 ns, which was about twice that of apomyoglobin-dye complex, 11 ns. These values were constant over an ionic strength range from 0 to 1.7. Circular dichroism spectra (215-300 nm) and fluorescence lifetimes of the complexes were also found to be independent of the ionic strength, indicating that no gross conformational change occurs with the change in the salt concentration, These results suggest that apohemoglobin remains dimeric over the ionic-strength range examined.


Isolation and partial characterization of a tubulin-like protein from human and swine synaptosomal membranes.

Synaptic membranes from human and swine brains were solubilized with 8 M urea and the proteins were reduced and alkylated. A protein was isolated from both sources and had identical amino acid compositions and molecular weights as determined by electrophoresis on polyacrylamide-sodium dodecylsulfate gels and by ion-exchange chromatography and gel filtration on Bioglas 1000. The apparent molecular weight of the protein was 53 000 on the acrylamide-sodium dodecylsulfate gels. Neither neutral sugars nor sialic acid was a significant component of the protein. When the proteins were digested with trypsin and the resultant peptides subjected to chromatography (n-butanol/acetic acid/water) and electrophoresis (pH 3.7) the peptide maps were identical. The protein comprises 1-2 percent of the total synaptosomal protein. With regard to amino acid composition, molecular weight, peptide map characteristics, behavior on DEAE-cellulose columns, electrophoretic mobility and sugar content, the synaptic protein is quite similar to the monomer of swine tubulin.


Agglutinin from Limulus polyphemus. Purification with formalinized horse erythrocytes as the affinity adsorbent.

We have purified an agglutinin from the hemolymph of Limulus polyphemus about 1500-3000-fold by adsorption to formalinized horse erythrocytes, elution with N-acetylneuraminic acid and subsequent fractionation on Sephadex G-200. Recovery was in the range of 50 percent. On ultracentrifugation the agglutinin behaves as an homogenous protein with a molecular weight of about 460 000. On polyacrylamide gel electrophoresis of the dissociated protein in sodium dodecylsulfate we found a single prominent diffuse band with an apparent molecular weight of 22 000 plus or minus 2000. This band contained carbohydrate as determined by periodic acid-Schiff staining. The intensity of staining compared with standards suggested a carbohydrate content of less than 4 percent. The protein contains a preponderance of acidic amino acids and has an isoelectric point of 4.83.5 residues per 1000 of glucosamine were detected on amino acid analysis. Agglutination of formalinized horse erythrocytes by the purified protein is inhibited not only by N-acetylneuraminic acid but also by D-glucuronic acid; but not by a number of other monosaccharides. D-Glucuronic acid may be used in place of N-acetylneuraminic acid as the eluting sugar in the purification procedure.


Isolation and partial characterization of intestinal calcium-binding proteins from the cow, pig, horse, guinea pig, and chick.

1. Intestinal calcium-binding proteins have been isolated in high purity from mucosal tissue of the cow, pig, horse, guinea pig, and chick. The proteins from all species exhibit rapid, although not identical, electrophoretic mobilities and possesses high affinities for calcium. 2. The intestinal calcium-binding proteins of mammalian origin exhibit a molecular size of approx. 11 000 by calibrated gel filtration and 9000 on the basis of amino acid composition. The analogous chick protein was found to be about 27 000-28 000 molecular weight by these methods. 3. The amino acid composition of each intestinal calcium-binding protein has been determined and indicates a considerable degree of similarity, especially among the mammalian species. 4. Immunoassay procedures have failed to show any species cross-reactivity when tested against antiserum prepared in response to either the bovine or chick intestinal calcium-binding protein.


The amino acid sequence of the cowpea strain of tobacco mosaic virus protein.

The amino acid sequence of the coat protein of the cowpea strain of tobacco mosaic virus (cowpea virus) has been determined. The tryptic peptide overlaps were obtained by digesting the protein with chymotrypsin and separating and analysing the lysine-and arginine-containing chymotryptic peptides. The primary structure of cowpea virus protein has been found to differ markedly from that of any other known strain of tobacco mosaic virus, and contains 3 amino acid residues more and 96 amino acid changes from the type strain. The significance of the distribution of those areas of the protein in which the amino acid residues are the same for all naturally occurring strains and chemically induced mutants of tobacco mosaic virus so far studied and the residues that form the important carboxyl-carboxylate pairs are discussed.


Studies on phytohemagglutinins. XXVI. A new type of a lentil hemagglutinin isolated from Lens esculenta Moench., subsp. microsperma (Baumg.) Barulina.

In seeds of the lentil Lens esculenta Moench., subsp. microsperma (Baumg.) Barulina, a nonspecific phytohemagglutinin was found, the properties of which differ from those of the previously described lentil hemagglutinins. The phytohemagglutinin is not adsorbed to the Sephadex matrix; its hemagglutinating activity is different towards erythrocytes of different human blood groups of the ABO system. The isolated phytohemagglutinin preparation is homogeneous by disc polyacrylamide and starch gel electrophoreses and by gel chromatography on Bio-Gel P-100. Ultracentrifugation of the phytohemagglutinin yields a single symmetrical peak with S20,W of 3.9 S. From the sedimentation data, a molecular weight of 53 300 was calculated. Phytohemagglutinins of similar properties were shown to be present also in other cultivars of Lens esculenta, subsp. microsperma.


Haemoglobin F Victoria Jubilee (alpha 2 A gamma 2 80 Asp-Try).

A new A gamma chain haemoglobin variant, haemoglobin F Victoria Jubilee, with an electrophoretic mobility slightly anodal to haemoglobin F Port Royal, was found in a Jamaican infant. The amino acid residue substitution of 80 Aspartic Acid leads to Tyrosine was associated with alanine in position 136. Haemoglobin F Victoria Jubilee constituted about 7.0 percent of the total haemoglobin F.


Haemoglobin Camperdown beta104(G6) arginine leads to serine.

Routine investigation of ante natal patients revealed a subtle change in the electrophoretic pattern on cellulose acetate of the proposita. Further investigations by isoelectric focussing in polyacrylamide gel suggested the presence of two major haemoglobin components. Using a modified cellulose acetate technique globin chain separation revealed an abnormal beta-chain. Chain separation on a carboxymethyl-cellulose column provided a pure sample of the abnormal beta-chain. After amino-ethylation, tryptic digestion and peptide mapping, amino acid analysis of relevant peptides showed the abnormality in the beta-chain to be a substitution of arginine by serine at the 104 position. The presence of a positively charged residue at this position would appear to be necessary for the stabilization of the haemoglobin central cavity. The replacement by serine in this haemoglobin leads to slightly decreased stability but does not appear to affect the oxygen affinity.


The effects of an electric field on soluble collagen.

Electric birefringence decay curves of collagen suspended in aqueous buffered media were plotted as functions of pulse width and amplitude. They were then resolved into two components by means of an analog simulator. When these data were combined with the results of repeated pulsing, it was shown that an electric field promotes aggregation of collagen, although the variety of aggregate sizes falls within a fixed range. Observations of electric birefringence of dissolved collagen preparations as a function of ionic strengths tend to indicate that the bonding that occurs in an electric field is electrostatic.


Circular dichroism and conformational transition of Dolichos biflorus and Robinia pseudoacacia lectins.

The conformation of the lectins from Dolichos biflorus and Robinia pseudoacacia was studied by means of circular dichroism (CD). It was found that N-acetyl-D-galactosamine induced significant changes in the near-ultraviolet CD spectrum of Dolichos lectin but was ineffective with the lectin from Robinia. Tyrosine and tryptophan chromophores were chiefly involved in this saccharide-lectin interaction. The far-ultraviolet CD spectra indicated that both lectins have a significant content of the pleated sheet conformation, but not much, if any, alpha-helix. The predominant conformation in these lectins is the aperiodic bend structure which is stabilized chiefly by hydrophobic interactions. This was ascertained by the effect of sodium dodecylsulfate on these proteins.


Interaction of myasthenic serum globulin with the acetylcholine receptor.

A serum factor from patients with myasthenia gravis which inhibited the binding of 125I-labeled alpha-bungarotoxin to acetylcholine receptor extracted with Triton X-100 from rat muscle has been studied in detail. The inhibitory activity was localized to the IgG fraction based upon the fractionations by sodium sulfate precipitation and DEAE chromatography as well as reaction with anti-IgG globulin. The myasthenic globulin inhibited toxin binding to receptors extracted from degenerated muscle but did not inhibit toxin binding to normal junctional receptors. At saturation levels of myasthenic globulin, the number of denervated acetylcholine receptors available for toxin binding was reduced approx. 50 percent. The myastehnic globulin was found to bind to denervated acetylcholine receptors but not to normal acetylcholine receptors by a radioimmunoassay technique in which myasthenic globulin incubated with 125I-labeled alpha bungarotoxin-receptor complexes was precipitated by anti-IgG serum. The globulin binding was saturable over the same range as inhibition of toxin binding. The data suggest that the myasthenic IgC binds to a site on the receptor complex juxtaposed to the acetylcholine receptor site. The myasthenic globulin appears to be a useful probe for investigation differences between acetylcholine receptors extracted from normal and denervated muscle and for investigating the pathogenesis of myasthenia gravis.


Collagen synthesis and secretion by isolated rat renal glomeruli.

Glomeruli were isolated from rat renal cortex and incubated with radioactive lysine to study in vitro collagen synthesis in these preparations. Glomerular basement membrane was obtained by sonication, and the appearance of [-14C]lysine and hydroxylysine in medium, membrane and intracellular proteins was determined. Total glomerular incorporation of [-14C]lysine into protein linearly increased for up to 2-h period, and membrane hydroxylysine content gradually rose during this time. Hydroxy[-14C]lysine was recovered in the 105 000 times g pellet, reaching a hydroxylysine content of 22 percent in this intracellular fraction after 90 min of incubation. 60 percent of the protein secreted into the medium, and about 75 percent of newly synthesized sonicated basement membrane was acetic acid soluble. Hydroxylysine content was 33 percent in the acetic acid-insoluble fraction of sonicated membrane, suggesting that basement-membrane collagen was a significant component of total collagen synthesized by these preparation, The ability of isolated glomeruli to synthesize and secrete basement-membrane protein will be useful for studies concerning control of glomerular collagen and basement-membrane synthesis.


Cholesterol sulfate. II. Studies on its metabolism and possible function in canine blood.

Previous in vitro studies to evaluate the possible role of cholesterol sulfate in the stabilization of the human erythrocyte membrane have been extended to the dog in vivo. Thus, following the injection of labelled cholesterol sulfate, a large fraction of the administered sterol conjugate is taken up by the membrane of the canine erythrocyte. Peak membrane levels were obtained within 30-60 min. Measurement of radioactivity associated with the plasma and red cell fractions in serial samples allowed the calculation of the half-life of cholesterol sulfate in each fraction. From the data obtained from the plasma of four dogs, the half-life was calculated to 5.8 plus or minus 0.9 h. The half-life of chlesterol sulfate associated with the erythrocyte membrane was calculated to be 6.7 plus or minus 1.2 h. In addition, following the intravenous administration of 0.2-0.7 mg of cholesterol sulfate/kg of body weight and withdrawal of serial blood samples, a significant diminution in the degree of hemolysis was observed when the red cells were exposed to hypotonic saline solutions. Maximal stabilization effects were observed at approx. 6-7 h after the administration of the sterol conjugate. Hemolytic properties returned to normal at approx. 24 h following the injection.


Physiological basis for preferential uptake of D-alpha-aminoadipate over the L-isomer by Alcaligenes denitrificans.

Alcaligenes denitrificans, pre-incubated with D-alpha-aminoadipate and assayed for L-isomer uptake without removal of extracellular D-isomer, exhibits a reduced rate of uptake and a reduced level at which steady state is achieved. During D- or L-isomer uptake, intracellular alpha-aminoadipate is exclusively the L-configuration. These data are consistent with an intracellular, mediated reduction in L-isomer uptake as the physiological basis for preferential D-alpha-aminoadipate uptake by A. denitrificans growing on racemic alpha-aminoadipate. Translocated D-alpha-aminoadipate is rapidly metabolized to form an L-isomer pool which subsequently reduces the rate of L-isomer uptake and the level at which steady state occurs resulting in a preferred D-isomer uptake. Competitive inhibition of L-alpha-aminoadipate uptake by the D-isomer or a difference in the maximum rates of uptate uptake is an inducible process expressed only in the presence of that compound and while uptake of L-alpha-animoadipate is also inducible there is a low rate of constitutive uptake. While L-alpha-aminoadipate uptake occurs against a concentration gradient, uptake of the D-isomer is not against a gradient. D- and L-isomer uptake are active processes since both are inhibited by azide, cyanide and 2,4-dinitrophenol.


Biphasic kinetic plots and specific analogs distinguishing and describing amino acid transport sites in S37 ascites tumor cells.

Curve-fitting procedures indicated that exo-2-amino-bicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) modified V and Km for one of two systems serving for histidine transport into the S37 ascites tumor cells. When this system was obliterated by leucine in the medium, BCH had no effect on histidine transport. Curve-fitting procedures similarly suggest N-methyl-alpha-aminoisobutyric acid affected the Km and V values for the other histidine-transporting system and that carboxymethylhistidine (His(Cm)) inhibited both transport systems. His(Cm) further inhibited histidine uptake into leucine-inhibited cells. Km and V values were altered simultaneously in the presence of several inhibitory analogs. Alanine methyl ester markedly inhibited high-concentration histidine uptake, whereas leucine methyl ester markedly inhibited low-concentration histidine uptake. The present results confirm earlier suggestions that our high c system is Christensen's A system and our low c system his L system. We also confirm a very high degree of specificity of N-methyl-alpha-aminoisobutyric acid for the A or high c system, and of BCH for the L or low c system. We suggest the utility of combining two approaches to the study of transport system properties; use of specific analogs and modification of biphasic plots. We demonstrate that the carboxyl group is not a prerequisite molecular feature for inhibitory interaction with the A or L system.


Independent blood-brain barrier transport systems for nucleic acid precursors.

The blood-brain barrier permeability to certain 14-C-labelled purine and pyrimidine compounds was studied by simultaneous injection in conjunction with two reference isotopes into the rat common carotid artery and decapitation 15s later. The amount of 14-C-labelled base or nucleoside remaining in brain was expressed in relation to 3-H2O (a highly diffusible internal standard) and 113m-In-labelled EDTA (an essentially non-diffusible internal standard). Of the 17 compounds tested, measurable, saturable uptakes were established for adenine, adenosine, guanosine, inosine and uridine. Two independent transport systems in the rat blood-brain barrier were defined. One transported adenine (Km equals 0.027 mM) and could be inhibited with hypoxanthine. Adenosine (Km equals 0.018 mM), guanosine, inosine and uridine all cross-inhibit, defining a second independent nucleoside carrier system. Adenosine inhibited [14-D]uridine uptake more effectively than did uridine, suggesting a weaker affinity of uridine for this nucleoside carrier.


Dipeptide transport in isolated intestinal brush border membrane.

Transport of glycyl-L-leucine into isolated brush border membrane vesicles was studied. On the basis of the following observations it was postulated that glycyl-L-leucine was transported intact by a specific dipeptide mechanism. (1) The differing time course and Na-+ stimulation of glycine, L-leucine and glycyl-L-leucine. (2) The failure of glycine and L-leucine to inhibit glycyl-L-leucine transport. (3) Initial presence of dipeptide within the vesicle. (4) Inhibition of glycyl-L-leucine uptake by other dipeptides. (5) The occurrence of accelerated amino acid uptake in the presence of the dipeptide.


Comparison between histones FV and F2a2 of chicken erythrocyte. II. Interaction with homologous DNA.

The conformation and stability of artificial complexes between chicken erythrocyte DNA and homologous histones FV and F2a2 was studied by circular dichroism (CD) and thermal denaturation followed by both absorbance and CD measurements. The complexes are made after a stepwise potassium fluoride gradient dialysis without urea and studied at low ionic strength (10-minus 3 M). 1) No structural changes of the DNA can be detected up to r equals 0.2 with FV and r equals 0.6 for F2a2. With FV at higher values of r the CD spectrum is altered, indicating the organization of DNA and histones in some kind of aggregate. 2) The conformation of histone molecules inside the complexes is not related to the ionic strength of the medium but to an effective ionic environment close to 0.1 M. This ionic strength would also correspond to the melting temperature of histone-covered DNA. 3) From the analysis of the absorbance melting profile the length of DNA covered with an histone molecule can be estimated. A good agreement is found between the negative charge of this piece of DNA and the net positive charge of the histone. 4) Since the CD transition at 227 nm occurs before the second absorbance transition at 280 nm, the DNA is stabilized no longer by native histone but partially or fully denatured histones. The helical regions of the histone molecule are not involved in the binding process, which appears to be almost purely coulombian and most likely related to some structural fit between the pattern of negative charges in the DNA helix and that of positive charges along the peptide chain.


Comparison between histones FV and F2a2 of chicken erythrocyte. I. Structure, stability and conformation of the free proteins.

Purified chicken erythrocyte histones FV and F2a2 were studied by means of circular dichroism as a function of ionic strength and temperature. The percentage of alpha-helical regions was calculated by comparison with reference spectra obtained with four standard proteins of known tertiary structure. Maximal alpha-helical organization, reached in high ionic strength, was estimated to 14% and 23% for FV and F2a2 respectively. We have compared our experimental determinations of the secondary structure of F2a2 with predictions made from amino-acid sequence according to Fasman's rules. When instability induced by the presence of charged residues close together is taken into account, a good agreement is found between predicted and observed values. The thermal denaturation of FV is cooperative and, unlike F2a2, seems to obey a two-state transition. The classical Arrhenius plot is linear, which indicates that the heat capacity is the same in both the native and the denatured state. Such a behaviour is typical of an expanded configuration of FV even in the "native" state.


An A + T-rich satelitte DNA in a monocotyledonous plant, Cymbidium.

The DNA of aseptically grown protocorms of a Cymbidium hybrid and in vitro developed leaves, as well as DNA of leaves and flower buds of Cymbidium ceres from the greenhouse, was analysed by analytical ultracentrifugation and thermal denaturation. Upon ultracentrifugation a satellite DNA with a buoyant density of 1.682 g/cm-3 appears as a shoulder on the main band (density 1.694 g/cm-3). Thermal denaturation reveals an inhomogeneous main peak with the major component melting at 84 degrees C and a separate peak melting at 75 degrees C. This is the first demonstration of a satellite DNA in a monocot, and one of the rare examples of a major A + T-rich DNA fraction in a plant.


Unusual properties of the DNA from Xanthomonas phage XP-12 in which 5-methylcytosine completely replaces cytosine.

Xanthomonas phage XP-12 contains 5-methylcytosine completely replacing cytosine. This substitution confers several unusual properties upon XP-12 DNA. The buoyant density of XP-12 DNA in CsCl gradients is 1.710 g/cm-3, 0.16 g/cm-3 lower than that expected for a normal DNA with the same percentage of adenine plus thymine. The melting temperature for XP-12 DNA in 0.012 M Na+ is the highest reported for any naturally occurring DNA, 83.2 degrees C, 6.1 degrees C higher than that of normal DNAs with the same percentage of adenine plus thymine. Unlike the minor amounts of 5-methylcytosine found in most plant and animal DNAs, the 5-methylcytosine residues of XP-12 derive their methyl group from the 3-carbon of serine instead of from the thiomethyl carbon of methionine.  .


Isolation of a DNA fraction highly enriched in transfer RNA genes from Xenopus laevis.

A DNA fraction highly enriched in tRNA genes can be isolated from the Xenopus laevis genome by the use of Ag+/Cs2SO4 density gradients. Ag+ shows a low affinity for some tRNA cistrons, allowing their separation from bulk DNA upon equilibrium centrifugation in a Cs2SO4 density gradient. Contaminating DNA in the resulting tDNA fraction is further removed by two additional CsCl density gradient centrifugations. The final DNA fraction is 60-fold enriched in tRNA genes, compared to the starting DNA material.


RNA synthesis in nuclei isolated from early embryos of Xenopus laevis.

1. Rates of RNA synthesis in isolated Xenopus embryo nuclei decrease from blastula through gastrula and neurula stages to hatching tadpoles. 2. In blastula and gastrula nuclei, net synthesis of RNA continues for over 30 min, both in the presence of KCl at 0.4 M and in its absence. In nuclei from later stages, net synthesis continues for only about 10 min in the absence of KCl. 3. At low ionic strength, RNA synthesis in all nuclei is greater with optimum Mg-2+ (6 mM) than with optimum Mn-2+ (1 mM). At high ionic strength the reverse is true. 4. An unusual feature, which gradually disappears as development proceeds, is that curves relating RNA synthesis to KCl concentration show a peak at 0.1 M KCl. In blastula nuclei, RNA synthesis is more rapid at 0.1 M KCl than at 0.4 M. 5. This peak at low ionic strength is not observed in the presence of the initiation inhibitor rifamycin AF/013. It is concluded that the peak arises from initiation of RNA synthesis by an excess of RNA polymerases bound non-specifically to the isolated nuclei. The residual synthesis, representing elongation of chains that were initiated in vivo, still declines as development progresses. 6. In blastula nuclei, over half of the RNA synthesis is effected by polymerase II (inhibited by alpha-amanitin), the proportion remaining roughly constant with increasing ionic strength. In neurula nuclei, the proportion rises from about one-half to three-quarters. The initiation-dependent peak in blastula and gastrula nuclei is contributed by both alpha-amanitin-sensitive and alpha-amanitin-resistant enzymes.


I. A study of the stages in the quantitative isolation of aminoacyl-tRNA synthetase activities from mouse liver.

The elution profiles of 17 aminoacyl-tRNA synthetases from chromatography of 149 000 x g supernatant on Sephadex G-200 were determined as well as the influence of different methods of homogenization and of chromatography on DEAE-cellulose on the elution profiles. With gentle homogenization all synthetases were eluted in the void volume in four different peaks, containing (a) leucyl- and phenylalanyl-, (b) lysyl-, prolyl-, isoleucyl-, methionyl-, glycl-, and valyl-, (c) arginyl-, alanyl-, and asparaginyl- and (d) aspartyl-, histidyl-, seryl-, threonyl-, glutaminyl-, and tyrosyl- tRNA synthetases. With less gentle homogenization, peaks of lower molecular weight appeared. More than two peaks for each aminoacyl-tRNA synthetases were never found. Of the aminoacyl-tRNA synthetases examined, alanyl-,arginyl-, aspartyl-, leucyl- and lysyl-tRNA synthetases were not inactivated by chromatography on DEAE-cellulose, whereas phenylalanyl- and seryl-tRNA synthetases lost 60% of their activity.


II. The influence of 17-beta-oestradiol on aminoacyl-tRNA synthetases from mouse uterus and mouse liver.

The activities of 17 aminoacyl-tRNA synthetases have been determined in liver and uterus preparations of mice. One group of mice were castrated and seven days later given 5 mug 17-beta-oestradiol in olive oil; a similar dose was given after 24 h. The animals were sacrificed one day later. A control group of mice which were also castrated, received olive oil without 17-beta-oestradiol. As the aminoacyl-tRNA synthetases may be found both in high molecular weight and low molecular weight forms, the forms present in the preparations are discussed. The activities of the aminoacyl-tRNA synthetases from uterus augmented under the influence of 17-beta-oestradiol, but to different degrees. The increase in the activities of isoleucyl- and prolyl-tRNA synthetases was not significant. In liver, only the activity of lysyl-tRNA synthetase augmented significantly.


Structure and transcription specificity of yeast RNA polymerase A.

DNA-dependent RNA polymerase A (Nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6) was isolated from whole yeast cells and purified to a nearly homogeneous state. The subunit structure as well as the transcription specificity of the purified enzyme were investigated. Polyacrylamide gel electrophoresis under denaturating conditions revealed that yeast polymerase A is made up of two large subunits having mol. wts of 190 000 and 135 000, and five smaller subunits with mol. wts of 54 000, 44 000, 35 000, 25 000 and 16 000, respectively. The molar ratios of all these polypeptides were found to be about unity. The transcription specificity of yeast polymerase A was tested using homologous nuclear DNA as a template. The in vitro synthesized RNA was characterized by determining its degree of self-complementarity and its ability to compete with purified ribosomal RNA in hybridization experiments. It was found that yeast polymerase A is capable of a highly selective transcription in vitro of the rRNA cistrons, provided DNA of high integrity is used as a template.


[Physico-chemical determination of the ploidy of the unicellular alga, Chlorella pyrenoidosa (strain 211/8b) (author's transl)].

The ploidy of the unicellular green alga Chlorella pyrenoidosa (strain 211/8b) has been determined by means of renaturation kinetics. The nuclear DNA is made up from fast, intermediate and slow renaturing sequences, which represent respectively about 5, 15 and 80% of the DNA. These observations are consistent with the findings in other eukaryotic nuclear DNAs. Nevertheless, the relative importance of the repeated sequences is much lower than that observed in Chlamydomonas reinhardi [16] and in higher plants [18-20], but slightly higher than that obtained in Chlorella vulgaris [17]. The kinetic complexity of the main fraction of the Cl. pyrenoidosa nuclear DNA is found to be 2.94 - 10-10 daltons (mean value of five independant experiments) assuming value of 2.1 - 10-8 daltons for Cl. pyrenoidosa chloroplastic DNA. When compared with the analytical complexity of this fraction (80% of the nuclear DNA analytical complexity, that is 2.02 - 10-10 daltons), one can assume that the slow renaturing fraction of the nuclear DNA is constituted by a unique nucleotide sequence. This result thus suggests that Cl. pyrenoidosa (strain 211/8b) is an haploid organism. The possible existence of an haploid genome in the nuclei of the algae from Chlorella genus and the apparent absence of sexuality might explain the high discrepancy observed in the G + C content of the Chlorella nuclear DNAs.


[Kinetic regularities of RNA synthesis. VI. Reverse problem of RNA accumulation in synchronous cell cultures].

An algorithm is presented for determining relative nucleotide composition and rates of synthesis of some RNA fractions according to the experimental data of the change with time of mean nucleotide composition of the mixture of RNA fractions of synchroneous cell culture. Piece-linear models with voluntary number of fractures are taken as the models of accumulation of separate RNA types.


[Dynamics of matrix synthesis in molecular biophysics].

The paper deals with connections of structural-functional and dynamic approaches in the problems of molecular biophysics with reversible problems of the dynamics of matrix synthesis of biopolymers. Operator equation of dynamics describing such connections is obtained.


[Possibility of modeling contractile structures with polyionic compounds].

Possibility was shown of modelling electro-mechanical transformer of biomechanical structures by polyionic combinations being in the contact with the solution of microions and with epsilon approximately 10(5). Oriented polyionic combinations are liable to model contractions if polyions work on stretching, and stretchings if they work on compression.


[Nuclear spin relaxation of absorbed water protons in biological matrices].

The theoretical calculation of the nuclear spin relaxation times of water protons absorbed on biological matrices in considered for the case of relaxation diffusive mechanism. The influence of the molecular elementary jump realization number and long-range order of the spin interaction on values T1 and T2 is shown.


[Quantum mechanical study of the antioxidative activity of a series of phenol compounds].

The highest filled and the lowest free electronic molecular orbital energy of 23 phenolic substances has been calculated with Hückel MO LKAO method. The obtained results have been compared with the data on antioxidizing activity. The majority of phenolic substances with marked antioxidizing activity possessed electrono-donor properties. The quantity of antioxidizing activity depends on the values of the highest filled electronic molecular orbital energy.


[Fluorescence quenching of chlorophyll and its analogs by oxidants].

The quenching of the fluorescence of chlorophyll, Zn- and Cd-pheophytinates, Mg-, Zn-, Cd-, Al-, Ga-, In-, Hf-tetraphenylporphine in different solvents with chlorinanyl, p-benzoquinone and m-dinitrobenzole has been studied. It is concluded from the dependence of quenching on medium viscosity that static and kinamatic mechanisms are in the basis of quenching. The first one dominates within the high values of viscosity, the latter within the law ones. In case of metals on one group the quenching constants are decreased with the growth of the ordinal number of the central atom. This fact supports the great role of the dynamic factor during the quenching of fluorescence of tetrapirrole pigments.


[Photochromism of visual pigments. III. Comparative study of photoconversions in bovine and frog rhodopsin].

Phototransformations of digitonin extracts of rhodopsin and suspensions of outer segments of frog rods at minus 22 degrees C under the effect of light with lambda 579 and 435  nm are studied. It is shown that the results are not dependent on the presence of digitonin and glycerine, but are characteristic of frog rhodopsin. Phototransformations of bovine rhodopsin under the same conditions differ from those of frog rhodopsin.


[Cell molecular computer. VII. Cell biophysics and realistic or information physics (1)].

Living organisms measure many parameters in order to have orientation in the outer medium. That is why biophysics cannot use the ordinary laws of physics and must take into account the influence on the phenomena to be studied not only of a measurement but also of a calculation process in the real physical and biophysical device predicting the future. Science taking into account the effects of the calculating process-realistical or informative (RI) physics-has different (laws) for different times, distances and numbers of measuring and predicting parameters. RI-physics deals with unreproducible events and considers only such time intervals and distances for which the prediction can be made on the basis of earlier measurements and calculations according to the laws with optimal difficulty. It is suggested that the living cell uses the laws which are close to these optimal (limiting) laws of RI-physics. Physics and quantum mechanics can be considered as a limiting case of RI-physics. In this case values of distances and times are large enough and the number of simultaneously measured independent parameters is such that the heat effect of the calculating device would become negligible. Molecular cell computer (MCC) [I] cannot calculate the interaction of a great quantity of different molecules, using the equations of quantum mechanics because the expense of the (price of action) would be very large and both MCC and the surrounding world could change.


[Possible role of phospholipid  molecule reorientation in ion transport through membranes].

A theory of ionic transport through membranes in which the phospholipid molecules play the role of ion-carriers is developed. The transport of ions is accompanied by a membrane asymmetry. Expressions for stationary-state ion-fluxes in the case of one sort of ions transport, and in the case of coupled transport of ions of two sorts, are obtained. In the latter case near equilibrium the cross-coefficients are equal in accordance with Onsager's law. The possible role of phospholipids as ioncarriers in native membranes is discussed.


[Photochromism of visual pigments. II. Kinetics of photoconversion of frog rhodopsin].

A kinetic scheme is suggested of reversible processes of rhodopsin phototransformation at --22 degrees C under light effect with lambda 579 and 435 mm. On the basis of this scheme quantum yields of certain stages are calculated from initial rates of transformations. Dependence of the quantum yield of photolysis of rhodopsin transformation on the wavelength of light and temperature is studied. The scheme of frog rhodopsin transformation is compared with the similar scheme of bovine rhodopsin phototransformation.


[Ultrastructure of frog muscle fiber thick filaments at rest and during potassium contracture].

Isolated slow and intermediate frog muscle fibres were fixed in the rest state and under potassium contracture (50-100 mM KC1). The longitudinal and cross sections of two types of fibres were investigated. It was shown that at the rest the thick filaments of different fibres had similar length (1.6-1.65 mum), diameter (160-165 A) and the amount of subunits (12-13). Under potassium contracture the length of the thick filaments of both fibre types was shortened by 25-30% of the rest-length, the diameter of the slow fibres increased to 180-185 A, the diameter of the intermediate fibres to 200-220 A. The amount of subunits increased to 14-15 in slow fibres and to 17-18 in intermediate fibres. We believe that the ultrastructural changes observed in the thick filaments are a result of molecular transformation in these filaments, which seems to be important for maintaining the contracture.


[Mechanism of trace hyperpolarization of the action potential of snail giant neurons].

Depolarization current decreases and hyperpolarization current increases the amplitude of tracing hyperpolarization of the neuron action potential. Calcium-defficient solution supresses the tracing depolarization, and turns the rhythmical activity of the neuron into the flashlike one. An increase of outer concentration of potassium ions decreases the tracing depolarization. The latter is suppressed completely when the membrane behaves as a potassium electrode. The suppressing effect of the increase of potassium outer concentration on tracing hyperpolarization decreases with a decrease of calcium ions content in the medium. When an active release of sodium ions from the cell is inhibited with DNP and substitution of sodium ions by lithium ions the tracing hyperpolarization of the action potential is suppressed. The tracing hyperpolarization is also suppressed during the shunting of the electrogenic effect of potassium pump with the outcoming current of chlorine ions. It is suggested that the tracing hyperpolarization of the single action potential is due to the calcium-dependent fraction of electrogenic release of sodium ions from the cell.


[Nature of the effect "rapid oxygen consumption" during the introduction of tissue homogenate or a mitochondrial suspension into the polarographic cell].

After introducing rat brain homogenate or mitochondria into polarographic cell without adding the substrate a quick shift of recording pen from the point of initial concentration of oxygen towards zero is observed. According to Kotova and coworkers (Biochemia, 38, 287, 1973) this shift is accompanied by a decrease of oxygen concentration (less than oxygen rapid consumption greater than). We established that the size of this shift was not proportional to the quantity of homogenate. Boiled homogenate of the rat brain, liver DNA solution, starch gel and casein glue caused less than oxygen rapid consumption greater than. It was proposed to locate the point of the initial oxygen concentration on the polragoramme in the position of the recording pen after the introduction of homogenate into the polragoraphic cell.


[Adsorptive and catalytic properties of cholinesterase on phospholipid monolyers in different oxidation states].

Adsorption isotherm and enzymatic activity of protein interacting with the surface of solid carrier formed by oriented fat lipid chains of differently oxidized phospholipids have been studied. It has been found that the appearance of peroxide groups in fat acid chains results in a twofold decrease of protein limiting adsorption on the lipid monolayer. The data on enzymatic activity of proteins at variously filled suface with protein molecules indicate that the peroxide groups produce an activating effect under the conditions when protein interactions can be neglected. Superoxidation of phospholipid fat acids is suggested to be one of the mechanisms involved in the control of the processes proceeding on the membranes.


[Measurement of thermogenesis and dissolved oxygen in the medium during cultivation of halophilic bacteria].

A technique is proposed for continuous measurements of heat production and solved oxygen during the cultivation of bacteria and production of (purple membranes). Interrelationship between heat production and pO2 during the cultivation of halophile is investigated.


[Energy parameters of Acetabularia cell membrane].

The energy parameters of the mechanism involved in the action of Acetabularia cell membrane were studied. The resistance of the membrane is found to be near 3 kohm per sq. cm when resting and at the peak of excitation it is much lower (100 ohm/cm(2). The power of the mechanism regulating the action of the membrane during the peak. The total power of the membrane system of Acetabularia is 8 microwatt per sp. cm. reaches 6.5 microwatt/cm(2). The energy consumed by the regulatory mechanism during the action potential is minus 290 plus or minus 20 erg/cm(2) and the total energy dissipation is 20 erg/cm(2). The values of the energy consumed by the cell during the action potential are compared with its energy resource.


[Protein-carbohydrate productivity of Chlorella and efficiency of use of light of varying spectral composition in photosynthesis].

Data are presented on the intensity of carbohydrates and protein biosynthesis during the cultivation of Chlorella asynchroneous culture illuminated with light different spectral regions. High photosynthetic activity of absorbed radiation of the spectrum green region is found.


[Measurement of the electric field of the heart in a homogeneous volume conductor].

The paper describes a technique and some results of experimental measurements of electrical potentials generated by an isolated dog heart in homogeneous conductor, drawing equipotential maps of the field, and calculating the characteristics of the dipole equivalent generator of the heart. The form of potential distribution on a spherical surface around the heart and its ideal orthogonal vectorcardiograms are discussed.


[Formation of impulses in an excitable medium].

The paper deals with the evolution of initial perturbation in an active distributed system, described by non-linear equations of a diffusion type. Division of all movements into the less than slow greater than and less than fast greater than ones in time and space makes it possible to give a simple analytical description of all the stages. The following cases are possible: a) Initial distribution limited in space falls into two diverging impulses, each of them consists of two sharp fronts connected by slow movements. While propagating each impulse acquires a stationary form; b) Meeting fronts are formed in the wave, the result is that the initial perturbation disappears in a finite time; c) A sharp front with zero rate of propagation is initiated; its slow evolution may lead to an autooscillation process. The solutions obtained are applicable to the description of concentration waves in oscillatory chemical reactions.


[Modeling calcium-45 metabolism in tissue, taking into account the structure and hemodynamics of the capillary system].

The accumulation of Ca-45 in the tissues and the degree of its desorption during the perfusion in the sufficiently extensive limits does not depend upon the rate of the perfused solution and is the function of the perfused solution volume. Taking into account strong dependence of the volume rate of filling the capillaries with the solution upon the capilliary radii (r-4) one may come to the conclusion that Ca-45 saturation of the paracapillary spaces in the wide capillaries occurs much sooner than in the narrow ones. As a result of developing these postulates, we have got the formulae which associates these two functions. It is shown that according to the theory the accumulation and desorption processes are interrelated and may be calculated.


[Frequency analysis of arterial pulse transmission in the cranial cavity].

The changes of intracranial and arterial pulse shape under functional loads (hypervolemia and intracranial hypertension) were compared. The logarithmic amplitude-frequency characteristics were found and used for the synthesis of equivalent electrical circuit of arterial pressure pulses transmission on cerebrospinal fluid (CSF) in the cranial cavity. The model obtained points to the necessity of taking into account the induction which was not performed in the earlier models of the CSF-system. It is found that the attenuation factor permitted to estimate the stability of the intracranial circulation system to input influences under different functional conditions.


[Active and passive properties of carotid arteries].

A mathematical model of carotid arteries is constructed from the known experimental data. Passive properties of the vascular wall are characterized by an alternating module of elasticity, the active ones by the specific power of muscle contraction. Its maximum value (0,023 n/m-3) is shown to be reached with intravascular pressure 190 mm Hg. The dependence of inner radius on the power of muscle contraction is studied at different values of intravascular pressure. It is shown that theactive properties of carotid arteries are essentially determined by their passive properties and depend on the stretching of the vessel wall.


[Kinematics of metachronous walking. I. Configurations].

?The notion of configuration of legs' spatial distribution is presented. The relationships between the legs' spatial distribution and the features of meachronal activity in the ipsilateral legs row of some less than abstract greater than animal's locomatory system were investigated on the basis of theoretical analysis of different configurations. Some hypotheses about the control of legs' metachronal activity are proposed.


[Application of the theory of oxygen transfer: determination of the Michaelis constant of glucose oxidase with respect to oxygen].

The oxidation of beta-D-glucose with glucose oxidase generally requires oxygen, which, under normal conditions is present at low concentrations in the reaction medium. Experiments show that glucose oxidase is no longer saturated by oxygen at enzyme concentrations greater than 0.4 mg.ml1. This is due to the decrease in the oxygen concentration of the solution. The value of the oxygen mass transfer coefficients and dissolved oxygen concentrations are determined. These dissolved oxygen concentrations are found to correlate with direct measurements with an oxygen electrode. From this, the Michaelis constant of glucose oxidase for oxygen is calculated. These experiments also show that oxygen is a limiting factor for this reaction.


[Noise resistance of the dolphin auditory analyzer as a function of the directional angle of the noise].

Masked tonal thresholds by noise in the bottlenose dolphin have been measured as a function of angle of noise direction. Sharp directional selectivity of hearing has been discovered resulting in an abrupt decrease of noise masking with the increase of the angle of noise coming. It has been shown that narrow directional characteristics of hearing is an angle 8 degrees plus or minus 2 degrees for the level of minus 3db. It is one of the main mechanisms supplying the echolocation system of the dolphin with the high level of resistance to noise.


[Role of information on the forces acting between feet and ground in the process of locomotion control].

For human locomotion along the hard ground it was shown that the power of bearing reaction was approximately ten times less than that of the mulscles. Therefore the control of locomotion on the hard surface may be accomplished practically without any information on forces acting between body and support.


Chicken fumarase. I. Purification and characterization.

Fumarase from chicken heart is purified 400 times from the crude muscle extract. The isolation procedure includes ammonium sulfate fractionations, Bio-Gel P-300 column chromatography and electrofocusings on pH-gradients from pH 3 to 10 and from pH 7 to 9. Chicken fumarase behaves as an homogeneous protein in sedimentation, diffusion and electrofocusing studies; the protein possesses a single amino-terminal residue: lysine. The analysis of the CD and ORD spectra suggests the presence of 60-65 p. cent of alpha-helix, 0 - 5 p. cent of beta-structure with the remaining portions of the protein in an unordered conformation. Chicken fumarase is found to be composed of 4 subunits of identical molecular weight (51.000) and devoid of disulfide bridges. Finally, the physicochemical properties of chicken fumarase are compared with those of the porcine enzyme.


Analytical and comparative chromatographic maps of oligosaccharides produced by acetolysis and partial acid hydrolysis of glycoprotids.

The authors describe a chromatographic mapping procedure of oligosaccharides present in acetolysates and partial acid hydrolysates of glycopeptides or glycoproteins. Oligosaccharides are first fractionated on charcoal-Celite columns and then identified by paper chromatography. This procedure is sensitive and reproducible and allows to compare the structure of N-glycans and of glycoproteins from various sources.


[Subatomic biology: electronic biology, biosemiconductivity].

The author gives a critical and hystorical review of the existing in biology theories which on the molecular and electronic levels explain a number of mechanisms of vital phenomena such as excitation, muscle contraction etc. The author discusses in the hystorical aspect the problem of formation of electronic and biological semi-conductivity (as the author names it) called to explain the vital mechanisms. He shows is which way this theory can explain the process of excitation.


The sugar part of kappa-caseins from cow milk and colostrum and its microheterogeneity.

Cow kappa-casein contains only three different sugars (Gal, GalNAc, NeuNAc). However detailed analyses achieved mainly by gas liquid chromatography suggested a microheterogeneity at the sugar level. After alkaline borohydride treatment, filtration on Bio-Gel P4 and paper chromatography, different carbohydrate parts were obtained. The two main compounds had the following molar compositions: GalNAc (1), Gal(1) and NeuNAc (1) and GalNAc (1), Gal(1) and NeuNAc (2). From these data and our previous sequence studies, some formulae of the polysaccharide part were proposed. One of them was closely related to the sugar sequence of a glycopeptide with MN activity which was in agreement with our observation concerning a cross antigenic reactivity between the N blood group substances and the caseinoglycopeptides. All the polysaccharide parts isolated from colostrum caseinoglycopeptide were much more complex than those obtained from the normal glycopeptide, confirming an evolution of the sugar part as a function of time after parturition.


[Resonance properties of protein solutions according to data from electrical conductance measurements in the frequency range 0.1-10 mHz, obtained by L.A. Lapaev].

Experimental and theoretical results of some studies by L. A Lapaeva are analysed which state that the dependence of electroconductance on the frequency of applied voltage in some globular protein solutions is of a resonance character in the frequency range of 0,1 minus 10 mHz. The evaluation shows that the theory suggested is not applicable for the results obtained at these frequencies. The measurement method of electroconductance applied by L. A. Lapaeva is critisized. The analysis of her results enables a conclusion that is is premature to speak about resonance properties of proteins as of the fact stated.


Eukaryotic ribosomal proteins. Molecular weights of proteins from rabbit liver subunits.

The molecular weights of the proteins from rabbit liver ribosomal 40 S and 60 S subunits were determined after preliminary separation of these proteins by two-dimensional electrophoresis: each spot present in the polyacrylamide slab was cut off, eluted and rerun in a SDS one-dimensional polyacrylamide gel. The molecular weights range from 9,000 to 35,000 with a number-average molecular weight of 19,600 for the 40 S proteins, and from 9,400 to 52,000 with a number-average molecular weight of 23,600 for 60 S proteins.


Nuclear and mitochondrial origin of rat liver double-stranded RNA.

We have studied the intracellular location of double-stranded RNA from rat liver. The majority of this dsRNA is associated with nuclear and mitochondrial fractions and the remaining portion is associated with microsomes. Mitochondrial dsRNA hybridizes specifically with purified strands of mitochondrial DNA and seems therefore to arise from transcription of the latter. A fraction of nuclear dsRNA hybridizes with repetitive sequences of nuclear DNA. Because of self-hybridization of dsRNA strands, it was not possible to determine whether another fraction of DSRNA is homologous to nonrepetitive sequences of DNA. Both mitochondrial and nuclear types of dsRNA are not retained on oligo(dT) cellulose columns and therefore seem to lack long poly A sequences. The mechanism of formation of dsRNA is discussed.


[Primary structure of the cytoplasmic aspartate aminotransferases from the swine myocardium. Isolation, purification and characteristics of the peptides from cyanogen bromide cleavage].

Cytoplasmic aspartate aminotransferase from pig heart muscle was cleaved with cyanogen bromide and 8 peptide fragments were isolated. The high tendency of the large peptides for aggregation was overcome only by the utilization of special procedures of the denaturation and acylation of the lysine residues of peptide with citraconic anhydride. Peptides were separated by gel chromatography on sephadex G-50 and G-75 and by ion exchange chromatography on cellulose DE-22 and DE-32 with use of concentrated urea solutions. Amino acid composition and N-terminal residues of isolated peptides were determined.


[Chromatography of nucleic acids, proteins and certain phages on granulated hydroxyapatite].

A modification of the classical method of hydroxyapatite synthesis is proposed. The essence of the modification is hydroxyapatite synthesis in the presence of an additional component silicic acid particles. The subsequent steps of the method are modified so, as to retain the intactness of crystals at all the stages of preparation and use of the adsorbent. The final product consists of large spherical agregates (200-250 mu in diameter) and contains about 1% of tightly bound silicic acid. It slightly differs from usual hydroxyapatite in its chromatographic properties. Granulated hydroxyapatite obtained has a high specific capacity and can be repeatedly used in experiments (up to 50 chromatographic cycles). Native high-polymeric T2 phage DNA was practically quantitatively eluated from the column. Conditions for chromatography of some proteins (lysozyme, RNase, DNase) are described. Fractionation and purification of T2 and T3 bacteriophages and TMV are carried out by means of chromatography on granulated hydroxyapatite.


[Interaction of trypsin with a trypsin inhibitor from bovine colostrum].

Kinetics of trypsin association with trypsin inhibitor from colostrum (IC) was studied. The association rate constant is 3-10-5 M- minus 1 sec- minus 1 at pH 7,8, 25 degrees C. The rate constant for the complex dissociation was determined from the kinetics of the IC displacement from the complex with trypsin by a specific substrate and was found to be 5-10- minus 6 sec- minus 1 (pH 7,8; 25 degrees C). The equilibrium constant (Ki) was measured in a special experiment and was equal to 4-10- minus 12 M (p H 7,8; 25 degrees C). The similarity of this reaction and the association of trypsin with other protein inhibitors was discussed.


[Mechanism of the enzymatic reaction catalyzed by uridine diphosphate glucose dehydrogenase. The chemical synthesis of uridine diphosphate glucose-6-H3 and its oxidation by uridine diphosphate glucose dehydrogenase].

The synthesis of UDP-glucose-6-s-H was performed through condensation of alpha-D-glucopyranosyl phosphate-6-3-H and uridine 5'-phosphomorpholidate. Enzymic oxidation of UDP-glucose-6-3-H with calf liver UDP-glucose dehydrogenase was found to proceed with direct transfer of the hydrogen from C-6 of UDP-glucose onto NAD.


[Hydrogenase activity in Thiocapsa roseopersicina according to the D2--H20 metabolic reaction].

Extracts of Thiocapsa roseopersicina cells show hydrogenase activity, measured by evolution of H2 from reduced methylviologene (MV) and by D2-H2O exchange reaction. According to these reactions the most part of hydrogenases is found to be in the soluble fraction. Hydrogenase activity measured in the exchange reaction is completely inhibited by p-chloromercurybenzoate (5-10- minus 3 M), iodacetate (1-10- minus 2 M) and 26% inhibited by KCN and o-phenanthroline (5-10- minus 3 M). Evolution of H2 from reduced MV was not inhibited by o-phenanthroline, KCN and iodacetate and was inhibited by 66% only with p-chloromercurybenzoate. Light and ATP stimulated hydrogenase activity of chromatophores did not affect on its activity in the soluble fraction. The results obtained show that there are certain differences in hydrogenase systems responsible for the exchange reaction and evolution of H2.


[Some characteristics of the kinetics of enzymatic reactions based on the example of catalase].

A method of kinetic analysis for quickly acting enzymes, which are characterized with substrate inhibition, on the catalase model is proposed. Catalase kinetics was shown to be full described, considering changes in the maximal reaction rate and Michaelis constant, by four parameters instead of two usual ones (Vmax, Km equals const.). The method described makes possible to calculate the change the Michaelis constant in time and to estimate real dependencies of the reaction rate on time and on the substrate concentration. Moreover, the enzyme concentration and its inactivation rate at any reaction moment can be calculated under saturation conditions. It is supposed that experimental dependencies of Km on t and of Vmax on t are the results of residual conformation changes accumulated by the enzyme in the reaction process.


[Amino acid makeup, structural characteristics and substrate specificity of rabbit plasma kininogen].

Highly purified kininogen preparation with the activity of 16-18 int. units per mg was isolated from rabbit blood serum. Its molecular weight was estimated to be 54 000 by gel filtration through Sephadex G-200. Leucine was identified as N-terminal amino acid by the dansylation method. Rabbit kininogen consists of 394 amino acid residues (except tryptophane). Amino acid composition of kininogen is characterized by a high content of dicarbonic amino acids, proline and by a low content of methionine. Kininogen molecule does not contain SH-groups. 13.1-13.5 SH-groups were found in kininogen after the reduction of S-S bonds with beta-mercaptoethanol in the presence of 8 M urea, thus indicating the presence of 6-7 S-S bonds in kininogen molecule. Kininogen group does not occupy C-terminal position in the molecule, because the treatment of the protein with carboxypeptidase B does not change the content of bradykinine in it. Purified kininogen preparation is a substrate for kallikrein from rabbit blood plasma, human saliva and trypsin. Unlike trypsin, kallikreines from human blood plasma and saliva release kinines from kininogen with reduced S-S bonds. Under spontaneous reoxidation of reduced S-S bonds up to 90%, substate properties of kininogen for tripsin recover only by 50%. Rabbit kininogen is similar to beef kininogen II in its molecular weight, amino acid composition and the number of S-S bonds.


[Creatine induction of creatine kinase synthesis in a developing monolayer culture of muscle cells].

Creatine action on the activity of creatine kinase (ATP: creatine-phosphotransferase; EC 2.7.3.2) and the content of water-soluble proteins in the developing monolayer culture of chick myoblasts are studied. Creatine at concentrations of 1.9-10- minus 3-3.8-10- minus 3 M is shown to increase reliably the creatine kinase activity by 1,1--2,9 times and to reduct considerably the content of water-soluble proteins. Lower concentrations of creatine (3.8-10- minus 5 M) also increased the creatine kinase activity but did not change the contents of water-soluble proteins. The creatine effect was maximal at the period preceding the termination of tissue cells differentiation. In the course of the combined effect of both actinomycin D (50 mcg/plate) and creatine (3.8-10- minus 3 M) the creatine kinase activity was much higher than that in the presence of actinomycin D alone which considerably reduced the enzyme activity as well as the contents of water-soluble proteins.


[Hydroxylation of aniline and aminoantipyrine derivatives (1-phenyl-2,3-dimethylaminopyrazolon-5) in liver endoplasmic reticulum].

The absence of correlation between the effect of aniline and aminoantipyrine derivatives on cytochrome P-450 reduction rate and its oxidation rate draw to the conclusion that the reductase reaction is not a limiting step of hydroxylation for all substrates. Km is found to be directly proportional to Vmax of hydroxylated substrates. Hence, in these reactions the Km value is determined not by the value Ks but by the kappa+2/kappa+1 ratio. Km is not a characteristic of the affinity of cytochrome P-450 to substrates. The calculations were made to show that cytochrome P-450 formed two types of the enzyme-substrate complexes containing one or two substrate molecules. The complex in which one molecule of cytochrome P-450 binds one substrate molecule is considered to be active.


[Isolation of oligonucleotides and aminoacylated nucleotides on a boron-arylated polymer].

2',3'-diol groups-containing oligonucleotides were shown to be adsorbed on N,N-diethyl-N-(p-methylphenylboryl) aminoethylsephadex A-25, forming the complex between boryl groups of the polymer and cys-diol part of oligonucleotides. This way the mixture of oligonucleotides pNn + (Np) n-1 Np can be fractionated. The procedure described is suitable also for the isolation of pure aminoacyl-nucleotides having free cys-diol groups in a carbohydrate part of the molecule.


[DNA-dependent RNA polymerase from the nuclei of the spleen of white rats].

DNA-dependent RNA polymerase was isolated from rat spleen cell nuclei and was identified as A and B RNA polymerases by data on DEAE- and P-cellulose ionic exchange chromatography and on concentration dependency on bivalent ions and (NH4)2SO4. Two forms of the enzyme differed from each other in the activity in RNA synthesizing system, and their activity was completely inhibited by actinomycin, DNase and RNase.


Indolethylamine-N-methyltransferase activity in psychiatric patients and controls.

The level of INMT activity was determined in the sera of 29 psychiatric patients and 11 healthy controls from St. Louis; and in 13 psychiatric patients and 15 healthy controls from Chicago. The level of enzyme activity in the serum of paranoid schizophrenics in the St. Louis group was significantly higher than in other types of schizophrenics. The mean level of enzyme activity in the serum in nonschizophrenic psychiatric patients in the Chicago group was significantly higher than that in the same group of patients from St. Louis. The serum level of INMT activity in all psychiatric patients and schizophrenic patients from St. Louis was positively correlated with severity of delusions. The only significant difference in the Chicago patients was that the occurrence of depressive features was greater in the group of patients with a low serum INMT level than in the group with a high enzyme level.


[Cholinesterase hydrolysis of acetylcholine derivatives with different structures of the ammonium grouping].

15 acetoxyethylenammonium compounds are studied as substrates for acetylcholinesterase (ACE) from bovine erythrocytes and for butyrylcholinesterase (BCE) from horse serum. Substitution of methyl groups of the ammonium grouping with other radicals and incorporation of onium nitrogen in the cycle resulted in the decrease of the hydrolysis rate under the action of BCE and ACE, the effect of BCE being more pronounced. The rate of the hydrolysis of N-acetoxyethylene-N-methylpiperidine iodide in the presence of ACE was 65 times as much as in the presence of BCE. This compound is a new specific substrate of ACE. Dipropylmethyl derivative turned not to be a good substrate for both enzymes. Dibutylmethyl and pyridinic derivatives were not attacked by ACE and BCE. Kinetic analysis of the compounds listed is performed, taking account of non-productive sorbtion. Possible role of hydrofobic regions in the orientation of substrates on the active surface of ACE and BCE is discussed.


[Use of chromatography on a poly U-cellulose column for isolating eukaryote messenger RNAs].

The methods are described for increasing the flow rate of the column. The data are aduced, permitting to determine the capacity of the column, and optimal conditions for specific sorbtion with individual rabbit globin mRNA as an example.


Human Pavlovian decelerative cardiac conditioning based on a respiratory-induced cardiac deceleration as an unconditional reflex.

This study was directed at examining the feasibility of using a respiratory-induced cardiac decelerative reflex as an unconditioned response (UCR) in a Pavlovian conditioning paradigm. Experiment I assessed the reflexive features of the cardiac response under a respiratory procedure which involved 3 sec of exhalation, 4 sec of inhalation, and then 30 sec of breath-holding (BH). The results indicated that the BH onset aspect of this respiratory cycle involved a phasic, large-magnitude cardiac deceleration (27 beats/min) with short latency, fast recruitment, and no indication of habituation over trials. Experiment II examined the feasibility of using BH onset as an unconditioned stimulus (UCS) in a Pavlovian paradigm by presenting an auditory conditional stimulus (CS) 1 sec prior to the instructed BH aspect of the respiratory cycle. A separate control condition involved presenting the CS 10 sec after BH onset which constituted a 'backward' conditioning control. The results indicated that the conditioning group displayed a significant cardiac deceleration on CS-alone test trials (under normal breathing) in contrast to the absence of such an effect for the control group. In brief, the study suggested that a decelerative conditioned response (CR) could be established by using a respiratory-induced cardiac deceleration as a Pavlovian UCS. Potential clinical applications of such a decelerative CR were noted.


Circadian rhythms of catecholamine excretion, shooting range performance and self-ratings of fatigue during sleep deprivation.

Circadian rhythms in urinary catecholamine excretion, performance and self-ratings were studied in two experiments with a total of 29 subjects who were deprived of sleep for 72 hr. Adrenaline excretion and fatigue ratings showed the most consistent circadian variations; noradrenaline and performance rhythms were more irregular. The average crest phase for adrenaline excretion was around 1400 hr, for noradrenaline about 0800 hr, for performance 1700 hr and for fatigue 0500 hr. Twenty-four hour levels of performance and 'subjective arousal' decreased over the three days of sleep deprivation, while adrenaline excretion levels increased.


Physiological responses during escape and non-escape from stress in field independent and field dependent subjects.

Psychophysiological responses (GSP, GSR, heart rate and respiration) were monitored while the subjects viewed stressful stimuli. In balanced order the subjects were exposed to a condition in which they viewed the stimuli for 15 sec and a condition in which they could escape the stimulus. The subjects were divided into four groups according to level of trait anxiety and rod and frame scores. The results suggested that escape from stress produced different patterns of physiological activity than non-escape conditions. The changes were most noticeable for tonic GSP, non-specific GSR and heart rate. Field independent subjects differentiated the conditions physiologically and behaviorally to a greater extent than field independent subjects. It was speculated that field independent subjects are more dependent upon physiological cues to evaluate their perceptions and emotions than field dependent subjects.


The impact of warning signal intensity on reaction time and components of the contingent negative variation.

Slow EEG potentials were recorded during performance of a simple reaction task in which warning signal intensity was varied from trial to trial under foreperiod durations of 1, 3 and 8 sec. As shown by speed of reaction, the warning signal had an activating effect which increased with its intensity and decreased with foreperiod duration. This effect was related to the amplitude of a slow potential which appears in the EEG shortly after presentation of the warning signal. This potential is interpreted as a component of the orienting response regulating sensitivity to subsequent stimulation, so that reaction time is affected through change in the effective intensity of the imperative signal.


The use of ischemic nerve block procedures in the investigation of the sensory control of movements.

In this study the ischemic nerve block (INB) technique is investigated as a procedure for blocking afferent information in the study of the sensory control of movements. A movement replication task is used. The results suggest that the elbow, wrist and metacarpal-phalangeal joints are at three different stages of sensory information loss or reduction. With the index finger, replications of joint position are not made in the correct direction significantly greater than chance. Error is also largest for the finger. The elbow joint appears to be least affected by the block. Motor impairment under the block is also investigated and the results show that there is a marked decrement in the force exerted in flexion and extension of the index finger, wrist and elbow joints after sensory drop-out. This finding indicates that there is substantial motor impairment of movements distal to the block. The limitations of the INB technique as a procedure for investigating the control of movement under conditions of sensory loss are discussed.


Scanning and transmission electron microscopy of calcified tissues.

Some recent innovations have been utilized to extend studies of the structure of calcified tissues on the ultra- and microstructural levels of organization. The introduction of hydrazine as a replacement for the conventionally used ethylene diamine to deproteinize calcified tissue samples has resulted in the acquisition of previously unobtainable information about the mineral phase as it exists in situ. This enables inference of mineral-organic interrelationships when coupled with the EDTA demineralization technique used to study collagen fiber frameworks. In addition, a method for obtaining whole single osteons and separating them into lamellar constituents permits observations of the collagen-apatite orientation within successive lamellae of compact Haversian bone. The use of the structural information derived to develop a fiber-reinforced model of compact bone as a composite material is outlined and discussed.


Design of experimentation with a platinum-magnesium bioelectric battery.

The utilization of metal electrodes in the fabrication of a bioelectric battery has been the subject of intensive study for several years. Up to this date, subcutaneous cathodes of black platinum or of silver-silver chloride have been used in conjunction with anodes of aluminum or zinc. The subcutaneous black platinum is not reliable as a function of time due to the growth of overlying heterogeneous tissues. The utilization of a smooth platinum cathode in the right endoauricular position allows good reliability with time, but does not allow using a large surface area. Furthermore we have a reduction of the H-+ ions and not of the oxygen. A pure Domal magnesium anode was utilized with this cathode, which seemed to be a good compromise between to battery's voltage, its lifetime, and its lack of toxicity to body tissues.


An approach to the numerical quantitation of acute tissue response to biomaterials.

The hydrolytic enzyme activity associated with the tissue reaction to implanted polyvinyl chloride rods containing graded concentrations of an organotin stabilizer was quantitated by microphotometry of tissue sections. The procedure was more sensitive to the effects of the additive than the usual histologic evaluation. It is considered that this type of approach offers a sensitive and objective index to supplement the more subjective morphologic observations in judging the acute histotoxicity of implants.


Some interactions of blood with tubular biomaterials.

Native human blood was exposed to polyethylene, poly(vinyl chloride), and Silastic tubing for varying time intervals, following which the relative degree of activation of the intrinsic coagulation system and alterations in cell counts were determined. The effects of pre-exposure of Silastic to purified albumin, high-density lipoprotein, or protein polysaccharide upon subsequent reactivity of blood with these surfaces was determined. In addition, the effects of aspirin, dextran, heparin, and Warfarin on reactivity of blood with Silastic were determined. In each case, changes in coagulation and cell counts were correlated with ultrastructural features of test surfaces following their exposure to blood. Pre-exposure of Silastic to purified proteins had relatively little effect upon subsequent reactivity with blood, while the presence of antithrombotic agents produced numerous changes.


Histologic evaluation of vitreous carbon endosteal implants in dogs.

A 6-month histologic study of vitreous carbon dental implants in dogs, without occlusion, has demonstrated that vitreous carbon is well tolerated by oral tissues in both permucosal and subgingival applications. Gingival tissues heal routinely and show the same degrees of irritation adjacent to the implant as tissues adjacent to natural teeth. Alveolar bone forms within grooves in the implant surface, providing mechanical retention, and both hard and soft tissues grow into the texture in the implant surface. The resulting interlocking between tissues and the implant appears to function effectively as a bacterial seal. The newly formed bone within the implant grooves appears to become more dense with time, resulting in a layer of dense bone surrounding the implant. No foreign body responses and no inflammation were observed in tissues adjacent to this implant material, and no degradation of the vitreous carbon implants was detected. A subsequent study of the implant under occlusion in dogs is also being conducted.


Future prospects for biomaterials.

Biomaterials have many uses in medicine and surgery but success in their use is often difficult to achieve. In this paper some of the deatures that contribute to the success or failure of biomaterials are discussed in relation to a hypothetical implant situation. The phenomena of biomaterial-tissue interfacial reactions, wear, prosthesis instability, infection, hypersensitivity and carcinogenesis are considered. Emphasis is given both to the causes and clinical significance of these phenomena and interpreted in terms of the furture prospects for the biomaterials.


Artificial liver support based on haemoperfusion of adsorbents.

The need for a device capable of performing the excretory functions of the liver during acute and chronic liver failure is described. Experience of artificial liver support systems is reviewed. The results of patients treatment with adsorbent haemoperfusion are discussed and problems of system design and biocompatibility are outlined.


Computer storage of pacemaker data.

An important factor in the choice of a pacemaker ought to be its reliability following implantation. Unfortunately, as the total number of patients increases, handling of basic data becomes a tedious and time consuming task. Analysis of data becomes an even more arduous task. Proposals are made for somputer storage of pacemaker data so that regulare up-dated "print-outs" can be made available. Analysis by computer then becomes a trivial task. The advantage of a single data handling centre for the whole of the United Kingdom is particularly attractive.


A ceiling module for a newborn intensive care unit.

In a traditional intensive care unit handling of neonates in incubators is usually obstructed by a surrounding clutter of electrical cables and gas tubings used for monitoring care. To solve these problems, an overhead module, provided with electrical and gas supplies and storage facilities for monitoring equipment and apparatus, was developed. The unit is suspended from the ceiling by two columns which serve as conduits for the gas tubing system and electrical wiring separately. The unit described allows for a maximum of flexibility and convenience for care.


Ultrasonic diagnostics: a look into the future.

The widespread introduction of ultrasonic diagnostics will depend upon the availability of simple-to-use, cost effective instruments producing results which are easily interpreted. There is scope for improvement in conventional two-dimensional scanning systems. Real-time display would allow the operator more effectively to interact with the machine. The identification of tissues may become possible. Blood flow volumes may be measured by the Doppler method, and hybrid Doppler/pulse-echo systems may have applications in the study of cardiovascular disease. Monitoring of foetal breathing may become routine. Time delay spectrometry holds some promise, but holography does not. Piezo-electric plastic transducers may be introduced.


A system for monitoring arterial oxygen tension in sick newborn babies.

The measurement of arterial oxygen tension (PaO2) has for some time now been regarded as an essential part of the management of newborn babies receiving oxygen therapy. A system for monitoring arterial oxygen tension by means of a catheter-tip transducer is described. Comparisons of the transducer output with PO2 obtained by blood sample analysis are discussed. Up to the present time the PaO2 of more than sixty sick newborn babies have been monitored using these transducers in the Neonatal Unit at University College Hospital. The results obtained with these transducers in the first eighteen babies are reported in detail and demonstrate the possibility of continuous, reliable measurement of PaO2 under routine clinical conditions.


Structural fluctuations in the steady state of muscular contraction.

Recent studies of the intensity fluctuation spectra of coherent light scattered from striated muscle have demonstrated the existence of large scale fluctuations in position and polarizability at the level of the myofibrillar sarcomere and its major structural subunits during the steady state of contraction. The existence of these fluctuations implies a fluctuating driving force. Various possible fluctuating motions of the thick and thin filaments, A and I bands, and entire sarcomeres are described. The magnitude of the fluctuating forces associated with the making and breaking of cross bridges is estimated. A mechanical model is proposed for coupling structural elements of a single sarcomere to one another and for coupling myofibrillar sarcomeres to one another. It is shown that the fluctuating force generated by the spontaneous making and breaking of cross bridges in conjunction with the model accounts for some of the features of the observed intensity fluctuation spectra.


Energetics of active transport processes.

Active sodium transport across epithelial membranes has been analyzed by means of linear nonequilibirium thermodynamics. In this formulation the rates of active sodium transport JNa and the associated metabolic reaction Jr are postulated to be linear functions of both the electrochemical potential difference of sodium--XNa and the affinity A (negative free energy) of the metabolic reaction of driving transport. Experimental studies in various epithelia demonstrate that both JNa and Jr (oxygen consumption) are indeed linear functions of XNa. Theoretical considerations and experimental studies in other systems suggest that likelihood of linearity in A as well. If so, A may be evaluated. Several observations indicate that the quantity A evaluated from the thermodynamic formalism does in fact reflect the substrate-product ratio of the metabolic reaction which supports transport. This is in contrast to measurements of mean cellular concentrations, which may not reflect conditions at the site of transport. Associated studies of isotope kinetics permit the distinction between effects on the permeability of the active and passive transport pathways. With these combined approaches, it may prove possible to characterize both the energetic and permeability factors which regulate transport. The formulation has been applied to an analysis of the mechanism of action of the hormone aldosterone.


Cross-bridge conformation as revealed by x-ray diffraction studies on insect flight muscles with ATP analogues.

The effects of three ATP analogues, alpha,beta-methylene-ATP [ATP(alpha,beta-CH1)], adenosine 5'-0-(3-thiotrophosphate) [ATP(gamma-S)], and beta,gamma-amino-ATP [ATP(beta,gamma-NH)] at various concentrations and temperatures on the X-ray fiber diagrams of glycerinated flight muscles from a water bug (Lethocerus maximus) have been investigated. It is shown that the "relaxed" state can be obtained with all three analogues at high concentrations, the result being particularly clear with ATP(gamma-S). It is inferred that the binding of an ATP-like molecule suffices to produce the relaxed state. At low concentrations ATP(beta,gamma-NH) produces state intermediate between rigor and relaxed which is not simply a mixture of the two. The possible nature of the intermediate is discussed.