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Biomedical subjects

B D Nelson

Publications and source records attributed to B D Nelson.

At least 109 records · Page 6Linked to original sources
PubMed1977

Immunological studies on beef-heart ubiquinol--cytochrome c reductase (complex III)

Antibodies against isolated beef-heart ubiquinol--cytochrome c reductase (complex III) have been characterized. Antibodies to complex III react strongly with isolated beef heart complex III and intact beef heart mitochondria, as shown by immunodiffusion and rocket electrophoresis experiments. The complex III content of intact mitochondria can be quantitated with rocket electrophoresis using isolated complex III as a standard. Antibodies to complex III also react with beef liver mitochondria and with both heart and liver mitochondria from rats. The latter are very weak antigens compared to beef heart material. Antibodies to complex III do not react with respiratory chain complexes I and IV, or F1-ATPase from beef heart mitochondria, but gives a slight, but variable, reaction with complex II and the membrane fraction isolated from complex V (oligomycin-sensitive ATPase). Antigenic sites are located on at least five of the seven peptides of complex III. These peptides are presumably lacking in respiratory chain complexes which do not react with antibodies to complex III, and are assumed to be uniquely located in complex III. Antiserum against complex III inhibitis duroquinol--cytochrome c reductase activity in isolated complex III and in complex III incorporated into phospholipid vesicles. Oxidation of NADH and succinate is not affected in submitochondrial particles treated with 6-times more antibody than required for complete inhibition of enzyme activity in free complex III or in complex III-phospholipid vesicles.

Animals↗
PubMed1977

Funiculosin: an antibiotic with antimycin-like inhibitory properties.

The antibiotic funiculosin mimics the action of antimycin in several ways. It inhibits the oxidation of NADH and succinate, but not TMPD+ascorbate. The titer for maximal inhibition in Mg2+-ATP particles (0.4-0.6 nmol/mg protein) is close to the concentrations of cytochromes b and cc1. Funiculosin also induces the oxidation of cytochromes cc1 and an extra reduction of cytochrome b in the aerobic steady state, and it inhibits duroquinol-cytochrome c reductase activity in isolated Complex III. The location of the funiculosin binding site is clearly similar to that of antimycin. In addition, funiculosin, like antimycin, prevents electron transport from duroquinol to cytochrome b in isolated Complex III if the complex is pre-reduced with ascorbate. Funiculosin and antimycin differ, however, in the manner in which they modulate the reduction of cytochrome b by ascorbate+TMPD.

Aerobiosis↗
PubMed1976

Evidence for a function of core protein in complex III from beef-heart mitochondria.

Puried complex III ) ubiquinol-cytochrome c reductase) from beef heart mitochondria was alkylated with iodol [1-14C]acetamide. After 6-8 h of incubation with iodo[1-14C]acetamide, duroquinol and ubiquinol-2-cytochrome c reductase activites were inhibited approximately 50%. During this time 4.5 +/- 1.6 nmol of iodo[1-14C]acetamide reacted per mg of complex III protein. Experiments carried out over 24 h indicated that enzyme activity could be inhibited to 70% and the alkylation of complex III was proportional to inhibition. The rates of cytochrome b and c1 reduction by duroquinol are also decreased upon treatment of complex III with iodoacetamide. Separation of the peptides of complex III by electrophoresis in sodium dodecylsulfate shows that all of the radioactivity is located in a single peptide of 50 000 molecular weight, which has been identified as one of the two core proteins. The possible functions of core protein are discussed.

Animals↗
PubMed1976

Effects of fermentation time on in vivo/in vitro relationships.

The effects of six fermentation times, 24 through 84 h at 12 h intervals, were studied on in vivo/in vitro relationships and repeatability and variability of in vitro technique. Three stages of maturity each of bermudagrass, bahiagrass, rye-grass, sorghum-sudan, alfalfa, and orchardgrass were used. For one fermentation time for all types of forages, a 48-h fermentation demonstrated the smallest variation among runs and the least run X forage interaction. However, the optimum fermentation for perennials as a group was 60 h; and for annuals, legumes, and temperate grasses it was 36 h. Further studies in vitro compared a 48-h fermentation for all types of forage with 36 h for annuals and 60 h for perennials. Forty-eight forages, including 20 annuals and 28 perennials, were digested in vitro during three runs. With the 48-h fermentation, forages accounted for 86.43% of the total variation, runs 6.80%, and run X forage interaction 6.44%. Variation due to runs was reduced to .33%, and run X forage interaction to .90%, for a combined 36- and 60-h fermentation for annuals and perennials, respectively. Variation due to forage was increased to 98.53%.

Animal Feed↗
PubMed1975

Alkali-induced reduction of the beta-cytochromes in purified complex III from beef heart mitochondria.

Approx. 40-50% of the cytochrome b in purified Complex III is reduced by ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine or phenazine methosulfate at neutral pH. The remaining cytochrome b, including cytochrome b-565, is reduced by increasing the pH. The apparent pK for this reduction is between pH 10 and 11, and is more than two pH units higher than a similar alkali-induced transition in Mg-ATP particles. Alkali-induced reduction of cytochrome b occurs concomitantly with the exposure of hydrophobic tyrosine and tryptophan residues to a more hydrophilic environment. The relationship of these findings to the presence of a substrate accessibility barrier in Complex III is discussed.

Adenosine Triphosphate↗
PubMed1975

Analysis of the peptide composition of purified beef-heart complex III by dodecylsulfate electrophoresis.

The peptides of purified complex III from beef heart mitochondria have been studied by electrophoresis on dodecylsulfate gels. Of the 12 peptides consistently observed, only eight appear to be integral peptides of the functional complex. Attempts to identify these peptides have been made through co-electrophoresis of complex III and fractions in which the individual peptides were either purified or greatly enriched. Electrophoresis of complex III preparations which were not reduced by mercaptoethanol indicates that intermolecular disulfide bonds play no significant role in stabilizing the complex.

Animals↗