Biomedical subjects

T L Miller

Publications and source records attributed to T L Miller.

3 recordsLinked to original sources

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↗

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↗

PubMedDate not supplied

Interaction of hydroxychlorobiphenyls--polychlorinated biphenyl metabolites--with the human erythrocyte membrane.

Effects of hydroxychlorobiphenyls (polychlorinated biphenyl metabolites) and chlorobiphenyls on membranes have been studied with the human erythrocyte membrane as a model. Many of the hydroxychlorobiphenyls are very effective hemolytic agents, whereas the parent chlorobiphenyls are generally quite ineffective at inducing hemolysis. The hemolytic potency of the hydroxychlorobiphenyls varies with the degree of chlorination and, more importantly, with the position of the chloro- and hydroxy- substituents. At lower concentrations, the hydroxychlorobiphenyls protect the erythrocyte against hypotonic hemolysis, while they induce hemolysis at higher concentrations. In the range of concentrations of each hydroxychlorobiphenyl required for maximum protection, the erythrocytes exist in altered morphological forms as opposed to normal discocytes. The chlorobiphenyls at lower concentrations also protect the erythrocytes from hypotonic hemolysis, but they do not induce hemolysis at higher concentrations. These studies suggest that products of the metabolism of chlorobiphenyls may be more biologically active than the parent compounds themselves. Effects on membranes may thus play a role in the mammalian toxicity of the hydroxychloro- and chlorobiphenyls.

Erythrocyte Membrane↗