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Biomedical subjects

W G Martin

Publications and source records attributed to W G Martin.

At least 37 records · Page 2Linked to original sources
PubMed1984

Application of hydrophobic chromatography to the large scale purification of Desulfovibrio desulfuricans cytochrome C3.

Hydrophobic chromatography on Phenyl-Sepharose was employed for large scale purification of cytochrome c3 from Desulfovibrio desulfuricans. This chromatographic procedure minimizes operational volumes and eliminates the lengthy dialysis ordinarily used to remove large amounts of salts. Pure cytochrome c3 was obtained after one additional purification by ion-exchange chromatography.

Amino Acids↗
PubMed1984

Combined trabeculectomy, intracapsular cataract extraction, and lens implantation: a clinical series.

Twenty-two eyes from 17 patients underwent a combined surgical approach for cataracts and glaucoma, involving an intracapsular cataract extraction, trabeculectomy, and anterior chamber intraocular lens implantation with an average follow-up of one year. The surgical technique is described. The average intraocular pressure fell from 24.9 mm Hg to 16.7 mm Hg. Seventy-three percent of the patients required no medication postoperatively for control of their glaucoma. Ninety-six percent of the patients showed an improvement in visual acuity improvement. Complications of flat peripheral anterior chambers and hyphema formation did not affect post-operative pressures or visual acuity results. The results encourage further investigation of this procedure.

Aged↗
PubMed1982

Changes in Mg+2-ATPase and taurine levels in Mg+2- deficient rats.

Tissue levels of Mg+2-ATPase and taurine were measured in rats fed Mg+2-deficient diets. Serum and urinary Mg+2 levels of rats fed the deficient diet were 50% below the control levels by day 10 on diet. The Mg+2-deficient rats showed a significant decrease in intestinal Mg+2-ATPase relative to the controls, despite having no significant decrease in intestinal Mg+2 levels. The effect of the Mg+2 deficiency on the distribution of subcutaneously injected 1,2-[14C]taurine in the skeletal muscle cytosol and organelles was measured. The cytosolic fraction contained 90% of the [14C]taurine, while the nuclear fraction contained 98% of the noncytosolic [14C]taurine. The skeletal muscle of Mg+2-deficient rats contained 14, 14, 81 and 53% more [14C]taurine than the control muscle at 1, 16, 24 and 48 hours after injection, respectively. There was 21, 60, 97 and 350% more [14C]taurine associated with the nuclear fraction of the muscle from Mg+2-deficient rats at the same sampling periods.

Adenosine Triphosphatases↗
PubMed1981

Kinetic and physical properties of the L-malate-NAD+ oxidoreductase from Methanospirillum hungatii and comparison with the enzyme from other sources.

The L-malate-NAD+ oxidoreductase of Methanospirillum hungatii was purified to homogeneity by using Blue Sepharose and ADP-Sepharose affinity chromatography. The molecular weight was estimated as 61 700 +/- 1900 by gel filtration and 64 200 +/- 1200 by ultracentrifugation. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis indicated that the protein is composed of two polypeptide chains, each corresponding to 31 350 +/- 2150 daltons. Inhibition patterns obtained for malate, alpha-oxoglutarate and ADP established that the sequential reaction mechanism was ordered, with NADH serving as the first substrate. Intracellular concentrations of oxaloacetate approximated the Km value of 27 microM, but NADH was present at less than Km values. Comparison of the amino-acid composition of the L-malate-NAD+ oxidoreductase of M. hungatii and 22 others from prokaryotic and eukaryotic cells revealed a significant direct relationship between average hydrophobicity and the frequency of non-polar side chains, as well as a significant indirect relationship between average hydrophobicity and the polarity ratio. Calculations based on amino-acid-composition data indicated significant composition similarity between pairs of mammalian-cytoplasmic or pairs of mitochondrial L-malate-NAD+ oxidoreductases from various sources, but no significant composition similarity between any of the pairs of bacterial species examined.

Amino Acids↗
PubMed1981

The identification and partial characterization of a plasmid containing the gene for the membrane-associated hydrogenase from E. coli.

Escherichia coli DNA was digested with restriction endonuclease PstI and ligated into the PstI site of plasmid pBR322. Recombinant plasmids that were constructed in this manner were used to transform E. coli H61, a mutant with a decreased level of hydrogenase activity. Complementation of this hydrogenase mutation identified a bacterial clone carrying the gene for the membrane-associated E. coli hydrogenase in plasmid pBL101. In E. coli minicells, the pBL101 DNA directed the synthesis of a protein of a size corresponding to that of the precursor of the E. coli membrane-associated hydrogenase, which appears to contain an uncleaved leader peptide. A restriction map of the cloned DNA was determined for 14 endonucleases.

Cell Membrane↗
PubMed1980

Ocular toxoplasmosis and visual field defects.

We studied 34 patients with peripapillary lesions secondary to toxoplasmosis. All patients had visual field defects corresponding to interruption of the nerve fiber layer of the retina. The extent of visual field loss increased with proximity to the disk.

Adult↗
PubMed1980

A biochemical and ultrastructural study of skeletal muscle from rats fed a magnesium-deficient diet.

In order to study changes in skeletal muscle during a magnesium deficiency, serum and muscle tissues were collected from male Sprague-Dawley rats fed either a control or magnesium-deficient diet. The rats were killed on days 7, 10, 14, 17, 19, 21 and 26 of the experiment. Ion concentrations in serum and muscle were determined by atomic absorption spectrophotometry, taurine concentrations of serum and muscle were determined by the Pentz method, and ultrastructural changes in skeletal muscle were detected with the use of the transmission electron microscope. The results indicated an increase in serum taurine which preceded an increase in muscle taurine concentration in rats fed a magnesium-deficient diet. The electron micrographs showed a swelling of mitochondria on day 14 of the deficiency and a total disorganization of the sarcoplasmic reticulum by day 26. In conclusion, in skeletal muscle from rats fed a magnesium-deficient diet, major ultrastructural changes apparently occur after the serum magnesium concentration is reduced and about the same time as muscle taurine concentration becomes elevated. The changes may be initiated by alterations in membrane permeability which may be influenced by taurine, since taurine has been shown to influence ion movement across membranes or membrane stability.

Animals↗
PubMed1980

Factors affecting the production of hydrogenase by Desulfovibrio desulfuricans.

An examination of conditions for the growth of Desulfovibrio desulfuricans, with the aim of optimizing hydrogenase production, is reported. An ammonium sulfate-lactate-yeast extract medium gave 5 to 10 times as much hydrogenase activity as a peptone-yeast extract medium. It made little if any difference whether the gas used for sparging was nitrogen, hydrogen, or a mixture thereof but increasing the rate of sparging and agitation did result in a slight decrease in activity. Control of pH during culture development was of little benefit to hydrogenase production. At least two hydrogenases were present in D. desulfuricans: one periplasmic, the other membrane bound.

Culture Media↗
PubMed1980

Purification and properties of the periplasmic hydrogenase from Desulfovibrio desulfuricans.

The periplasmic hydrogenase of Desulfovibrio desulfuricans was isolated and purified. Cells were washed with Tris-EDTA and the enzyme precipitated from the wash with ammonium sulfate. Absorption chromatography on DEAE and hydroxyapatite yielded the enzyme at better than 95% purity as judged by gel electrophoresis. The hydrogenase catalyzed the production of more than 9000 mumol H2/min mg protein(-1) from reduced methyl viologen at 37 degrees C. It is very stable and resists inactivation by heat (50% activity remained after 5 min in air at 65 degrees C) and by enzyme inhibitors (except N-ethylmaleimide and potassium ferricyanide). After storage in air at 4 degrees C for 1 month no activity was lost. The enzyme activity is sensitive to ionic environmental changes. With methyl viologen the optimum pH was 5.5 but with p-xylene polymeric viologen the optimum was about pH 7 but less sharp. The molecular weight was 47 X 10(3)(+/- 2 X 10(3), 52 X 10(3)(+/- X 10(3), and 56 X 19(3)(+/- 2 X 10(3) by SDS-gel electrophoresis, gel chromatography, and sedimentation equilibrium, respectively, and the isoelectric point was at pH 6.0. They enzyme might be useful in the production of hydrogen from water and solar energy.

Amino Acids↗
PubMed1980

Identification and partial characterization of an Escherichia coli mutant with altered hydrogenase activity.

An Escherichia coli mutant strain with altered hydrogenase activity was isolated using a filter paper assay. This assay depends on the ability of hydrogenase-containing microorganisms to reduce methyl viologen impregnated in filter paper, producing purple-colored colonies in the presence of hydrogen. Membrane-bound and cytoplasmic hydrogenase activities of wild-type and mutant strains were compared by amperometric measurement of hydrogen production. The cytoplasmic activities of mutant and wild type were comparable. The membrane-bound activity was lower in the mutant than in the wild type. Upon addition of detergent to the membrane fraction the specific activity of the enzyme from the mutant strain increased so that it equalled that of the wild type. The mutant requires an exogenous electron acceptor for anaerobic growth providing evidence for the function of the hydrogenase in anaerobic growth.

Escherichia coli↗
PubMed1979

A resonance Raman and electronic absorption probe of membrane energization. Quinaldine red in cells of Streptococcus faecalis.

Resonance Raman and electronic absorption spectra were used to show that the state of an amphiphilic cation, relative to dilute aqueous solution, changes when it is accumulated by cells of Streptococcus faecalis when they are energized. The general characteristics of the cation employed, quinaldine red, closely paralleled those of other amphiphilic cations which have been used to measure membrane potential. A major aspect of the change is that in sodium-loaded cells, essentially all of the quinaldine red accumulated as the result of energization forms a strong bond with an anionic group. This binding is similar to that which occurs for the basal level of quinaldine red taken up in nonenergized cells. Ionic binding was detected using resonance Raman spectroscopy through shifts associated with a N+ parallel C--C parallel C stretching vibration to lower frequency on uptake. Another aspect of the change in state is that the cell-localized probe cation can aggregate while ionically bonded in a card pack fashion, the transition dipoles being parallel. A combination of resonance Raman and electronic absorption spectroscopy was used to characterize this aggregation. The aggregates were estimated to contain at least five quinaldine red cations at or near van der Waals contact, and the presence of other molecules, such as phospholipids, could not be excluded. Aggregation effects are complex depending on the ratio of cells to probe cation, and on energization. The site of binding is suggested to be the lipid bilayer region of the plasma membrane on the basis of experiments with liposomes and other model systems. In addition, some quinaldine red may be present in the cytoplasm in an aggregated, ionically bound form. The change in state on uptake following energization seems to be associated with a membrane potential, similar spectral and uptake effects being produced by an artificially generated membrane potential in cells and liposomes. The results show that membrane potential cannot be computed in a simple manner from the distribution of quinaldine red between cells and medium, assuming that the thermodynamic activity coefficient of cell-localized material is identical with that in dilute aqueous solution. However, uptake as well as subsequent ionic binding of quinaldine red seems to be related to potential in an as yet undefined manner.

Cell Membrane↗
PubMed1979

The resonance Raman spectrum of carotenoids as an intrinsic probe for membrane potential. Oscillatory changes in the spectrum of neurosporene in the chromatophores of Rhodopseudomonas sphaeroides.

The resonance Raman spectrum of the carotenoid neurosporene is shown to be a sensitive monitor of absorption shifts, and thus changes in membrane potential, in chromatophores of the GlC mutant of Rhodopseudomonas sphaeroides. For a Raman excitation wavelength at 472.7 nm, the intensities of the two most prominent resonance Raman features (v1 and v2) respond very differently to small shifts in the absorption maxima. Thus, the ratio intensity v1/intensity v2 is a sensitive probe for absorption shifts. Changes in this ratio of approximately 20% were observed during a valinomycin induced diffusion potential. At 5 degrees C changes in the average intensity ratio of +6, -4 and -14% were brought about by oligomycin, FCCP and sodium deoxycholate, respectively. The changes in intensity ratio were temperature dependent and, in addition, effects due to the laser beam acting as an actinic light could be detected. Oscillatory changes were observed in absolute Raman and Rayleigh scattering intensities for chromatophores at 5 degrees C and for intact cells under growing conditions.

Bacterial Chromatophores↗
PubMed1979

Properties of malate dehydrogenase isolated from Methanospirillum hungatii.

A NADH-linked oxygen-tolerant malate dehydrogenase was purified 270-fold from cell extracts of Methanospirillum hungatii. Inhibitors of the enzyme included ADP, alpha-ketoglutarate, and excess NADH. Inhibition patterns for ADP were competitive with respect to NADH and non-competitive with respect to oxalacetate. Inhibition by alpha-ketoglutarate was non-competitive with oxalacetate as variable substrate and uncompetitive with respect to NADH. alpha-Ketoglutarate is surmised to function as an end-product inhibitor of the enzyme in reactions converting oxalacetate to alpha-ketoglutarate. No enzyme activity was detected in the direction of malate conversion to oxalacetate, in keeping with a strictly biosynthetic function of the enzyme. An analysis of variance of intial rate data fit to sequential and ping-pong equations showed that a sequential mechanism was perferred. The malate dehydrogenase of M. hungatii resembles those of many other bacteria and eucaryotic cells respect to molecular weight (61,700) and reaction mechanism, but may be regulated differently.

Enzyme Activation↗
PubMed1979

The interaction of polymeric viologens with hydrogenases from Desulfovibrio desulfuricans and Clostridium pasteurianum.

The interaction between hydrogenases from either Desulfovibrio desulfuricans or Clostridium pasteurianum and electron donors methyl viologen or polymeric viologens was examined. Extracts from each organism contained a single gel electophoretic band of active hydrogenase. The hydrogenase of D. desulfuricans was much more stable than that of Cl. pasteurianum. With methyl viologen apparent Km and Vm values were 0.5 mM and 0.62 mumole H2/min per milligram protein for the Cl. pasteurianum and 0.7 and 6.2 mumole H2/min per milligram protein, respectively, for the D. desulfuricans enzyme. The hydrogenases bound the polymeric viologens more tightly than methyl viologen, more so for the enzyme of D. desulfuricans than for Cl. pasteurianum. Maximal rate of hydrogen production was less with the polymeric than with methyl viologen. The results suggest that the D. desulfuricans enzyme in conjunction wiion than that from Cl. pasteurianum.

Clostridium↗