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Biomedical subjects

W G Martin

Publications and source records attributed to W G Martin.

At least 55 records · Page 3Linked to original sources
PubMed1978

Survival of microbial films in the microwave oven.

Air-dried films of Escherichia coli, Saccharomyces cerevisiae, and Bacillus subtilis spores on membrane filters, exposed to 10 min full power (650 W, 2450 MHz) irradiation in a Toshiba model ER776BT microwave oven, showed a 5-, 2-, and 0-log reduction of viable organisms respectively. Suspensions of cells or spores in phosphate buffer treated under similar conditions showed 8 logs of killing within 30 s (S. cerevisiae), 45 s(E. coli), and by 10 min (B. subtilis spores) of exposure.

Bacillus subtilis↗
PubMed1977

Energy requirements for the transport of methylthio-beta-D-galactoside by Escherichia coli: measurement by microcalorimetry and by rates of oxygen consumption and carbon dioxide production.

The energy cost for maintenance of gradients of methylthio-beta-d-galactoside in Escherichia coli was evaluated. Information was also obtained concerning the energy flow associated with gradient establishment under some circumstances. Energy flow was evaluated from transport-induced changes in the rate of heat evolution, oxygen consumption, and carbon dioxide production in metabolically active cells. Heats were measured with an isothermal calorimeter. Energy expenditure behavior was characterized by a transition that depended on the level of accumulation. The data for steady-state maintenance could be rationalized in terms of the Mitchell hypothesis, two models for influx and efflux, and a transition between them. At low levels of uptake, steady-state proton-methylthio-beta-d-galactoside (TMG) symport for influx and efflux occurred via a nonenergy-requiring exchange process. The only energy requirement was that necessary to pump back in any TMG exiting via a leakage pathway (model I). Above the transition, all influx occurred with proton symport, but all exit, leak and carrier mediated, occurred without proton symport (model II). The H(+)/TMG stoichiometric ratio computed for the region of model II applicability (carbon source present, high level of uptake) approached 1. This value agreed with that of other workers for downhill beta-galactoside flow, suggesting that the energy cost for both downhill and uphill flow was approximately the same. For low levels of uptake, initial establishment of the gradient was followed by a burst of metabolism that was much larger than that expected on the basis of the chemiosmotic hypothesis. In the absence of carbon source, the stimulation in respiration was sufficient to produce 13 times more protons than are apparently necessary to establish the gradient. The results indicate also that the nature of the biochemical process stimulated by TMG depends on its level of uptake. Insight into several aspects of the nature of these processes was provided through analysis of the heat, oxygen, and CO(2) data. The key factor controlling the transition in energy flow behavior is suggested to be rate of flux. The present data suggest that it occurs at a flux of approximately 120 nmol/min per mg of protein.

Biological Transport, Active↗
PubMed1975

Differences in coupling of energy to glycine and phenylalanine transport in aerobically grown Escherichia coli.

Differences exist in the coupling of energy to transport of glycine and phenylalanine in aerobically grown cells of Escherichia coli. Energy derived from respiration, although involved in both uptake systems, is not employed identically as shown by kinetic effects of cyanide and anoxia and by temperature dependencies. Additional evidence for aerobic differences was provided by the effects of azide which greatly decreased initial rates of uptake of glycine but not phenylalanine. The effect on glycine uptake was not due to uncoupling of oxidative phosphorylation or to a decrease in respiration rate. Evidence for anaerobic differences was provided by the addition of either glucose or ferricyanide to cell suspensions containing glycerol, thereby maintaining anoxic uptake of phenylalanine, but not glycine, at the aerobic level. Ferricyanide stimulation required a functional Ca, Mg-adenosine 5'-triphosphatase and involved cell metabolism. Ferricyanide was also found to produce differential stimulation of other amino acid transport systems; tyrosine, tryptophan and leucine uptakes were stimulated whereas those for alanine, proline, threonine, and glutamine were relatively unaffected.

Adenosine Triphosphate↗
PubMed1975

Coupling of glycine and alanine transport to respiration in cells of Escherichia coli.

Energy coupling for uptake of glycine and alanine in glycerol grown cells of Escherichia coli differs from that of the aromatic amino acids. Respiration and uptake of glycine and alanine show similar inactivations in cells exposed to high intensity violet light or to various concentrations of cyanide. In contrast,uptake of phenylalanine, tyrosine, and tryptophan is resistant to effects of light or cyanide. Anoxia largely inhibits uptake of glycine and alanine while that of the aromatic amino acids is only partially affected. Furthermore, ferricyanide (but not ferrocyanide) completely restores active uptake of aromatic amino acids under anoxic conditions but is without effect on glycine and alanine uptake. Adenosine 5'-triphosphate (ATP) concentration does not increase in anoxic cells exposed to ferricyanide, indicating that ATP cannot be responsible for this restoration. The data suggest that glycine and alanine represent amino acids whose transport shows a complete dependence on energy derived from respiration, while the energy for transport of the aromatic amino acids may be obtained from other sources

Adenosine Triphosphate↗
PubMed1975

Characterization and composition of the purple and red membrane from Halobacterium cutirubrum;.

The purple membrance (bacteriorhodopsin) isolated from cells of Halobacterium cutirubrum grown anaerobically in the light was shown to contain 77% protein and 20% lipils by weight. The protein component consisted of a single protein moeity, having a molecular weight of (19.6 plus or minus 0.8) times 10-3, complexed with retinal in mole ratio of 2:1, respectively. The protein moeity is not glycosylated but may be phosphorylated (ca. 2 mol of phosphate per mole of protein). The red membrance contains 56%protein and 38% lipids, including bacterioruberins. Several polypeptide components are present including some which may be glycosylated and/or phosphorylated. The lipids of both membranes contained phosphatidyl glycerophosphate (52%) and phosphatidyl glycerol (3-4%) but the sulfated lipid components, glycolipid sulfate and phosphatidyl glycerosulfate, were present exclusively in the purple membrane, the red membrane containing instead two unidentified glycolipids. Neutral lipids (squalenes, vitamin 75-8, etc.) were present in both membranes to the extent of 7-9%.

Amino Acids↗
PubMed1975

Comparison of the lipopretein profiles and the effect of N-phenylpropyl-N-benzyloxy acetamide in primates (38473).

Analytical ultracentrifugation showed Cebus and Rhesus monkeys had two low density components while only one was present in Squirrel monkeys. In untreated or W1372 treated monkeys, neither chylomicrons nor very low density lipoproteins were detected on analytical ultracentrifugation. Chylomicrons were not observed on agarose gel electrophoresis. Ultracentrifugal analysis showed W1372 treatment decreased the amount of LDL in all animals and also the HDL in Cebus monkeys on an atherogenic diet. Both untreated and W1372 treated Cebus monkeys on an atherogenic diet had abnormal amounts of LDL and HDL, while the LDL in treated animals occurred as multiple peaks. This was also evident on agarose gel electrophoresis. Accumulation of lipds in the liver and decrease of serum lipids indicated W1372 prevented release of lipoproteins from the liver.

Acetamides↗
PubMed1975

The synthesis of tautine from sulfate VIII. The effect of potassium (38580).

The in vitro and in vivo influence of K+ on the activity of rat heart and liver PAPS-sulfotransferase (P1) was tested. The P1 activity was optimal with 0.5 mumoles K+ per mug protein. The P1 activity was decreased by mild dialysis and lost by extended dialysis. The enzyme was stable when dialyzed with K+ and tests with other ions indicated K+ specificity. Rats fed purified diets with low, normal or high levels of K+ had significantly different heart taurine concentrations and P1 specific activities. These P1 specific activities became comparable to those from the rats receiving the normal K+ diet by the addition of KCl to the assay mixture.

Animals↗
PubMed1974

Some effects of visible light on Escherichia coli.

Light above 400 nm had selective effects on Escherichia coli ML-308: several processes or enzymes were strongly inhibited, whereas others were relatively unaffected. There was a correlation between the inhibition of respiration and the inhibition of active uptake of glycine. However, phenylalanine uptake did not show such a correlation. The decrease in adenosine 5'-triphosphate level during the first few minutes of illumination resembled the inactivation kinetics of phenylalanine uptake. The results suggest that phenylalanine uptake may not depend greatly on oxidative energy and may depend on the adenosine 5'-triphosphate level. The results for glycine suggest either that its active uptake and respiration involve a common photosensitive component or alternately, that only the respiratory chain contains the photosensitive component, and that glycine uptake is coupled almost exclusively to respiration. The critical photochemical lesion does not involve d-lactate dehydrogenase, succinate dehydrogenase, or l-alpha-glycerophosphate dehydrogenase since their inactivation rate is markedly lower than that for respiration.

Adenosine Triphosphatases↗