NADH-dependent formation of superoxide anions (O-2) by rabbit cardiac submitochondrial particles (SMP) was stimulated after exposure of the isolated heart to 90 min of ischemic perfusion. This effect was more evident in the rotenone-inhibited region of the respiratory electron chain in comparison to the antimycin-inhibited region. The kinetic study of the NADH-dependent reaction showed that at the level of the rotenone-inhibited region, ischemia reduced Km value for NADH, differently from the antimycin-inhibited region where the kinetic constants remain unchanged. No significant changes of the Vmax values were observed in both SMP-producing O-2 sites.
The ischemic perfusions also produced a reduction of mitochondrial function, particularly evident when glutamate as substrate was studied. 相似文献
Summary The uptake and binding of the lipophilic cations ethidium+, tetraphenylphosphonium+ (TPP+), triphenylmethylphosphonium+ (TPMP+), and tetraphenylarsonium+ (TPA+) in rat liver mitochondria and submitochondrial particles were investigated. The effects of membrane potential, surface potentials and cation concentration on the uptake and binding were elucidated. The accumulation of these cations by mitochondria is described by an uptake and binding to the matrix face of the inner membrane in addition to the binding to the cytosolic face of the inner membrane. The apparent partition coefficients between the external medium and the cytosolic surface of the inner membrane (K'o) and the internal matrix volume and matrix face of the inner membrane (K'i) were determined and were utilized to estimate the membrane potential from the cation accumulation factorRc according to the relation =RT/ZF ln [(RcVo–K'o)/(Vi+K'i)] whereVo andVi are the volume of the external medium and the mitochondrial matrix, respectively, andRc is the ratio of the cation content of the mitochondria and the medium. The values of estimated from this equation are in remarkably good agreement with those estimated from the distribution of86Rb in the presence of valinomycin. The results are discussed in relation to studies in which the membrane potential in mitochondria and bacterial cells was estimated from the distribution of lipophilic cations. 相似文献
The effects of fasting and refeeding on the concentration of uncoupling protein in brown adipose tissue mitochondria have been investigated in mice. Fasting mice for 48 h led to a large decrease in the total cytochrome oxidase activity of the interscapular brown fat pad. Mitochondrial GDP binding and the specific mitochondrial concentration of uncoupling protein also fell on fasting. After 24 h refeeding both GDP binding and the mitochondrial concentration of uncoupling protein were normalized, but there was no alteration in the total tissue cytochrome oxidase activity. Fasting appears to induce a selective loss of uncoupling protein from brown adipose tissue mitochondria, which is rapidly reversible on refeeding. 相似文献
X-ray fluorescence spectrometry and atomic absorption spectrometry were used in a quantitative study of zinc, copper, and
magnesium in 71 postmortal human hearts. Samples were obtained from individuals who had demonstrated no previous clinical
or subsequent pathological findings of myocardial infarction and from victims of a recent or an old infarction. A significant
difference (p<0.001) in the elemental levels was observed between the noninfarct and the recent infarct groups. The noninfarct group had
higher cardiac levels of all three elements. However, the difference in elemental concentrations between the noninfarct and
the old-infarct groups was not significant. Cardiac levels of zinc (p<0.001) and copper (p<0.01) were significantly greater in the old-infarct group than in the recent-infarct group. Magnesium levels were higher
in the recent-and-old-infarct group than in the recent infarct group (p<0.01). It is possible that the elements are redistributed during myocardial infarction, and that uptake of these elements
(from the serum pool) by the heart may be important in maintaining myocardial integrity and function. 相似文献
Chlorotetracycline inhibits the uncoupled oxidation of exogenous NADH by Jerusalem artichoke (Helianthus tuberosus L.) mitochondria extensively (over 80%) and rapidly (inhibition complete in 10 s) in the presence of added Ca2+. Half-maximal inhibition is observed at 15 μM chlorotetracycline in the presence of 2 mM Ca2+. The oxidation of succinate is only affected marginally by chlorotetracycline plus Ca2+. The inhibition of NADH oxidation and the fluorescence of CTC are well correlated. Mn2+ is the only other cation which shows an (increased) inhibition in the presence of chlorotetracycline. The inhibition by Ca2+ and chlorotetracycline disappears at acid pH, and the pH optimum in their presence is 6.4. The inhibition caused by other lipid-soluble Ca2+-chelators is not reversible or is enhanced by the addition of excess Ca2+. In contrast, inhibition caused by relatively water-soluble chelators is completely reversed by added Ca2+. It is suggested that a neutral 1:2 complex is formed between Ca2+ and chlorotetracycline which can substitute for Ca2+ bound at sites in the lipophilic phase of the inner mitochondrial membrane, which are essential for the activity of the external NADH dehydrogenase. 相似文献
Fragments derived from human plasma fibronectin by enzymatic degradation were tested in the Boyden chamber for chemotactic activity towards various fibroblast strains. The results provide clear evidence that the chemotactic activity is restricted to a defined region of the fibronectin molecule which is the same for various fibroblast strains. The active domain is localized between the collagen binding site and the major heparin binding site, about 170 kDa apart from the N-terminal and about 70 kDa from the C-terminal ends of the two subunit peptide chains. 相似文献
Summary Post-fertilization changes in the periphery of the egg of Spirorbis borealis are described. The nuclear envelope and cell membrane are formed by the coalescence of short strands of membrane perhaps produced by the Golgi complex. Annulate lamellae are abundant in the forming cells giving rise to endoplasmic reticulum and apparently contributing to genesis of mitochondria. This possibility is discussed.We are grateful to Professor E. W. Knight-Jones in whose department the work was carried out. 相似文献
1. 1.|The mitochondrial population in hypothalamic and hypophysial brain tissue from warm (30°C) and cold (5°C) acclimated goldfish (Carassius auralus L.) was analyzed using sterological techniques.
2. 2.|It was revealed that there is a significantly larger volume density (Vv) in the cold acclimated tissue, with no significant difference in either of the surface densities (Svext and Svint) from either of the brain areas.
3. 3.|The hypothalamic brain tissue has a significantly lower specific surface (S/V) in the cold acclimated tissue but there is not a significant difference in this parameter for the hypophysial brain tissue.
4. 4.|The values for these three parameters (Vv, Svext and SVint, and S/V) indicate that mitochondria from acclimated brain tissue undergo shape changes in response to thermal stress.
5. 5.|We suggest that the shape changes may be related to the change in the phospholipid composition of the inner mitochondrial membrane with acclimation temperature.
The interrelation of palmitate oxidation with amino acid formation in rat brain mitochondria has been investigated in purified mitochondria of nonsynaptic origin by measuring the formation of aspartate, -ketoglutarate, and glutamate during palmitate oxidation, and also by assaying14C-products of [1-14C]palmitate oxidation. Oxidation of palmitate (or [1-14C]palmitate) resulted in the formation of aspartate (or14C-aspartate), and the oxidation was inhibited by aminooxyacetate (an inhibitor of transaminase), Palmitate oxidation also resulted in -ketoglutarate formation, which was sensitive to the effect of aminooxyacetate. Addition of NH4Cl was found to increase14C-products and formation of -ketoglutarate, whereas glutamate formation was not increased unless the rate of palmitate oxidation was reduced by 50% by aminooxyacetate or -ketoglutarate was added exogenously. Exogenous -ketoglutarate was found to decrease14C-products, but not aspartate formation. These results indicated that palmitate oxidation was closely related to aspartate formation via aspartate aminotransferase. During palmitate oxidation without aminooxyacetate or added -ketoglutarate, however, -ketoglutarate was not available for glutamate formation via glutamate dehydrogenase. We discuss the possibility that this was because (a) oxidative decarboxylation of -ketoglutarate to form succinyl-CoA was favored over glutamate formation for the competition for -ketoglutarate in the same pool, and (b) the pool of -ketoglutarate produced in the aspartate aminotransferase reaction did not serve as substrate for glutamate formation. 相似文献