Search PubMed⌕ Search

Biomedical subjects

T L Miller

Publications and source records attributed to T L Miller.

At least 109 records · Page 6Linked to original sources
PubMed1981

Hexachlorophene-induced changes in erythrocyte membrane ATPase activity.

Hexachlorophene (HCP) has been found to dramatically affect erythrocyte membrane ATPase activity. The Na+,K+,Mg2+-ATPase of erythrocyte membranes was strongly inhibited by HCP. The Mg2+-ATPase was stimulated at lower concentrations of HCP, while at higher concentrations of HCP the activity decreased toward control levels. Inclusion of bovine serum albumin in the incubation medium protected each enzyme from the effect of HCP. A possible mechanism for the alteration of erythrocyte membrane ATPase activity by HCP is presented.

Adenosine Triphosphatases↗
PubMed1980

Molybdate and sulfide inhibit H2 and increase formate production from glucose by Ruminococcus albus.

H2 production from glucose by Ruminococcus albus was almost completely inhibited by 10(-5) M molybdate only when sulfide was present in the growth medium. Inhibition was accompanied by a significant increase in the production of formate. Extracts of molybdate-sulfide-grown cells did not contain hydrogenase activity. Active enzyme in extracts of uninhibited cells was not inhibited by the molybdate-sulfide-containing growth medium. The results indicate that a complex formed from molybdate and sulfide prevents the formation of active hydrogenase and electrons otherwise used to form H2 are used to reduce CO2 to formate. Growth was significantly inhibited when molybdate was increased to 10(-4) M. Reversal of growth inhibition but not inhibition of H2 production occurred between 10(-4) and 10(-3) M molybdate. H2 production by R. bromei but not by R. flavefaciens, Butyrivibrio fibrisolvens, Veillonella alcalescens, Klebsiella pneumoniae and Escherichia coli was inhibited by molybdate and sulfide.

Bacteria↗
PubMed1979

Fermentations by saccharolytic intestinal bacteria.

Most nonsporing anaerobes of the intestinal tract use the Embden-Meyerhof-Parnas scheme to ferment carbohydrates. Almost all of them oxidize pyruvate, the key fermentation intermediate, to acetyl coenzyme A and CO2 with reduction of a low-potential electron acceptor. H2 is formed from the low potential acceptor or from NADH. Pyruvate is a precursor of lactate, and phosphoenolpyruvate is a precursor of succinate and propionate. Ethanol, acetate, and butyrate are formed from acetyl coenzyme A. Formate is produced by reduction of CO2 by Ruminococcus albus. Heme is required by human Bacteroides for the formation of succinate and, in the presence of vitamin B12, propionate. A fermentation equation derived from the concentration of volatile acids found in human feces suggests that the fermentation in the large intestine is similar to the rumen fermentation.

Actinomycetales↗
PubMed1979

Enzymology of butyrate formation by Butyrivibrio fibrisolvens.

Butyrivibrio fibrisolvens is a major butyrate-forming species in the bovine and ovine rumen. The enzymology of butyrate formation from pyruvate was investigated in cell-free extracts of B. fibrisolvens D1. Pyruvate owas oxidized to acetylcoenzyme A (CoA) in the presence of CoA.SH and benzyl viologen or flavin nucleotides. The bacterium uses thiolase, beta-hydroxybutyryl-CoA dehydrogenase, crotonase, and crotonyl-CoA reductase to form butyryl-CoA from acetyl-CoA. Reduction of acetoacetyl-CoA to beta-hydroxybutyryl-CoA was faster with NADH than with NADPH. Crotonyl-CoA was reduced to butyryl-CoA by NADH, but not by NADPH, only in the presence of flavin nucleotides. Reduction of flavin nucleotides by NADH was much slower than the flavin-dependent reduction of crotonyl-CoA. This indicates that flavoproteins rather than free flavin participated in the reduction of crotonyl-CoA. Butyryl-CoA was converted to butyrate by phosphate butyryl transferase and butyrate kinase.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1978

The pathway of formation of acetate and succinate from pyruvate by Bacteroides succinogenes.

Bacteroides succinogenes produces acetate and succinate as major products of carbohydrate fermentation. An investigation of the enzymes involved indicated that pyruvate is oxidized by a flavin-dependent pyruvate cleavage enzyme to acetyl-CoA and CO2. Active CO2 exchange is associated with the pyruvate oxidation system. Reduction of flavin nucleotides is CoASH-dependent and does not require ferredoxin. Acetyl-CoA is further metabolized via acetyl phosphate to acetate and ATP. Reduced flavin nucleotide is used to reduce fumarate to succinate by a particulate flavin-specific fumarate reductase reaction which may involve cytochrome b. Phosphoenolpyruvate (PEP) is carboxylated to oxalacetate by a GDP- specific PEP carboxykinase. Oxalacetate, in turn, is converted to malate by a pyridine nucleotide-dependent malate dehydrogenase. The organism has a NAD-dependent glyceraldehyde-3-phosphate dehydrogenase. The data suggest that reduced pyridine nucleotides generated during glycolysis are oxidized in malate formation and that the electrons generated during pyruvate oxidation are used to reduce fumarate to succinate.

Acetates↗
PubMed1978

Effects of halogenated antibacterials on the erythrocyte membrane.

The influence of halogenated antibacterials on membrane structure and function was investigated using the human erythrocyte membrane as a model. Measurements of hemolysis in isotonic solution, altered membrane permeability, and stabilization against hypotonic hemolysis resulting from exposure of erythrocytes to halogenated antibacterials served as criteria of membrane-related effects. The hemolytic potency of the compounds studied differed widely, decreasing in the order hexachlorophene (HCP) greater than 2,2'-methylenebis(3,5-dichlorophenol) (3,5-TCP) greater than 2,2'-methylenebis(3,4-dichlorophenol) (3,4-TCP) approximately equal to 2,2'-methylenebis(4,6-dichlorophenol) (4,6-TCP) greater than 2,2'-methylenebis(4-chlorophenol) (DCP) greater than 3,4'-tribromosalicylanilide (TBS) approximately equal to 3,3',4',5-tetrachlorosalicylanilide (TCSA). Each of the antibacterials tested stabilized the erythrocyte against hypotonic hemolysis, although there were marked differences in the concentrations required to afford maximum stabilization as well as in the extent of protection. The observed order of protective effectiveness was HCP greater than 3,4-TCP greater than 4,6-TCP greater than DCP approximately equal to TCS greater than TBS. As shown by measurements of the first-order rate constant for K+ efflux, the permeability of the erythrocyte membrane to K+ was increased upon exposure to the antibacterials, with the effect of HCP greater than 3,4-TCP greater than 4,6-TCP approximately equal to 3,4-TCP greater than DCP approximately equal to TCS greater than TBS. These results indicate that halogenated antibacterials are capable of perturbing mammalian membranes, a feature which may account in part for their mammalian toxicity.

Anti-Infective Agents↗
PubMed1977

Non-cooperative Ca(II) removal and terbium(III) substitution in carp muscle calcium binding parvalbumin.

Close coorelation of atomic absorption measurements for Ca(II) contents indicates that from pH 5.8-7.4 a twentyfold excess of EGTA1 removes but one of two Ca(II) from carp parvalbumin. Thus binding of the two Ca(II) appears to be noncooperative. The maximum in emission intensity observed at a nonintegral 1.4-1.7 equivs of added Tb(III) is shown to be due to quenching by excess Tb(III). The emission intensity at the maximum increased 40% upon dialysis to remove Tb(III) not bound in the CD or EF sites. Atomic absorption results show that both Ca(CD) and Ca(EF) of native parvalbumin are easily replaced by Tb(III). Emission of Tb(EF) is not quenched by Tb(CD), but by solution Tb(III) bound at a third site, perhaps the single water molecule bound to Tb(EF). Labeling of the single sulfhydryl group with a trifluoroacetonyl gorup yields a protein with ultraviolet circular dichroism, emission, and circularly polarized emission spectra closely similar to those of native parvalbumin.

Animals↗
PubMed1977

Influence of training in visual perceptual discrimination on drawings by children.

This study attempted to determine empirically the influence of visual perceptual remediation on drawing utilizing educationally handicapped children of elementary age as subjects. The 34 girls and 78 boys were of average intelligence, with one-half of the subjects evidencing measured visual perceptual dysfunction. In each experimental group, 14 visual perceptually impaired (learning disabled) and 14 non-perceptually impaired (learning disordered) children received instruction on one of three commercially available visual perceptual remedial materials, Controls (28 subjects) received no special training. Prior to the training, subjects' drawings were collected, as well as after the 12-wk. intevention period by five graduate students in art education. The analysis of variance used to determine the effects of the intervention program on seven specified descriptors of drawing behavior yielded only one statistically significant descriptor, "Non-awareness of Social Situations and Self vs Awareness of Social Situation and Self." There were no differences between the perceptually impaired and non-impaired subject groups on any of the drawing tasks.

Art↗
PubMed1976

Carbon-13 magnetic resonance spectra of nucleosides and their Pd(II) complexes.

Chemical shifts occurring in carbon-13 magnetic resonance spectroscopy are utilized to assess the site of complexation of nucleosides to enPdC12 in neutral aqueous solutions. Binding occurs at N3 in cytidine, thymidine, and uridien, at N7 in 1-methylguanosine, and at N1 in guanosine. For most carbon atoms adjacent to N3 in the pyrimidine nucleosides the complexation shifts of the basic ligand are about 30% of the corresponding upfield protonation shifts. All complexes are of the form enPdL2 indicating that the ligands are unidentate and that the tendency to chelation is weak. Carbon-13 magnetic resonance spectroscopy appears to be the best method for delineating these complexes in solution. Due to the high avidity of chloride ion for Pt(II), cis dichloro Pd(II) complexes may be better models for intracellular action of the corresponding Pt(II) complexes than the Pt(II) complexes themselves.

Binding Sites↗