PubMed Health⌕ Search

Biomedical subjects

E A Elfont

Publications and source records attributed to E A Elfont.

5 recordsLinked to original sources
PubMed1976

Studies on oxidative phosphorylation and steroidogenesis by ovarian mitochondria after gonadotropic stimulation.

No differences in oxidative phosphorylation or in the per cent of [4-14C]progesterone were found in ovarian mitochondria of immature rats after treatment with 20 IU of pregnant mare serum gonadotropin (PMSG) iv 30 min before killing. However, treatment of immature rats with 20 IU of PMSG sc 54 h prior to killing decreased the ADP:O ratio and increased the per cent of [4-14C]cholesterol conversion. Electron microscopic studies showed that mitochondria with lamellar cristae were prominent in ovaries of untreated rats, while large pleomorphic mitochondria and mitochondria with tubulovesicular cristae dominated in ovaries of PMSG-treated rats. Ovarian homogenates separated by zonal centrifugation showed three peaks od cytochrome oxidase activity which shifted to the heavier end of the gradient after PMSG treatment. These studies suggest that PMSG treatment influences ovarian mitochondria, possibly by stimulating the synthesis of additional functional components and/or the biogenesis of new mitochondria. Aminoglutethimide addition to bovine luteal mitochondria decreased steroidogenesis by 60% when succinate was used as substrate. However, there was a 16% increase in the ADP:O ratio, apparently due to a decrease in oxygen utilization. When oligomycin was added to luteal mitochondria, there was a 30% decrease in the ACP:O ratio but a 300% increase in [4-14C]cholesterol conversion. Dinitrophenol also decreased mitochondrial steroidogenesis. These results suggest that energy obtained from succinate oxidation can be diverted from phosphorylation to support steroidogenesis.

Age Factors↗
PubMedDate not supplied

Transmural mitochondrial differences in myocardium.

Two functional mitochondrial populations with different sedimentation rates (S) were obtained from homogenates of canine myocardium by rate zonal centrifugation using an iso-osmotic Ficoll gradient. To ascertain the origin of these populations, the left ventricular wall of normal myocardium was divided into subepicardial (outer one-third), intermediate (middle on-third), and subendocardial (inner one-third) layers. The slow S mitochondria comprised 75% of the mitochondrial population of the subepicardial layer. In contrast, the fast S mitochondria contributed 65% of the subendocardial population. Intermediate layer mitochondria resembled those of the subepicardium. Mitochondria isolated from the three layers had approximately the same density, as shown by isopycnic zonal centrifugation. These studies indicate that mitochondria from subepicardial and subendocardial layers of normal myocardium differ in size and shape but not in density. Electron micrographs (EM) of the subepicardium showed many mitochondria as long as 4 to 8 sarcomeres. Mitochondria from the outer and inner layers of normal myocardium had the same oxidative phosphorylation parameters. Acute myocardial infarction, lasting 1 or 2 hr, resulted in the selective loss of the fast S mitochondria. Because the fast S mitochondria are prevalent in the subendocardium, these results may explain the greater vulnerability of this layer to anoxia.

Animals↗