The effects of training in hyperoxia vs. normoxia on skeletal muscle enzyme activities and exercise performance.
(9/21)
Inspiring a hyperoxic (H) gas permits subjects to exercise at higher power outputs while training, but there is controversy as to whether this improves skeletal muscle oxidative capacity, maximal O(2) consumption (Vo(2 max)), and endurance performance to a greater extent than training in normoxia (N). To determine whether the higher power output during H training leads to a greater increase in these parameters, nine recreationally active subjects were randomly assigned in a single-blind fashion to train in H (60% O(2)) or N for 6 wk (3 sessions/wk of 10 x 4 min at 90% Vo(2 max)). Training heart rate (HR) was maintained during the study by increasing power output. After at least 6 wk of detraining, a second 6-wk training protocol was completed with the other breathing condition. Vo(2 max) and cycle time to exhaustion at 90% of pretraining Vo(2 max) were tested in room air pre- and posttraining. Muscle biopsies were sampled pre- and posttraining for citrate synthase (CS), beta-hydroxyacyl-coenzyme A dehydrogenase (beta-HAD), and mitochondrial aspartate aminotransferase (m-AsAT) activity measurements. Training power outputs were 8% higher (17 W) in H vs. N. However, both conditions produced similar improvements in Vo(2 max) (11-12%); time to exhaustion (approximately 100%); and CS (H, 30%; N, 32%), beta-HAD (H, 23%; N, 21%), and m-AsAT (H, 21%; N, 26%) activities. We conclude that the additional training stimulus provided by training in H was not sufficient to produce greater increases in the aerobic capacity of skeletal muscle and whole body Vo(2 max) and exercise performance compared with training in N. (+info)
Fatty acid binding protein facilitates sarcolemmal fatty acid transport but not mitochondrial oxidation in rat and human skeletal muscle.
(10/21)
The transport of long-chain fatty acids (LCFAs) across mitochondrial membranes is regulated by carnitine palmitoyltransferase I (CPTI) activity. However, it appears that additional fatty acid transport proteins, such as fatty acid translocase (FAT)/CD36, influence not only LCFA transport across the plasma membrane, but also LCFA transport into mitochondria. Plasma membrane-associated fatty acid binding protein (FABPpm) is also known to be involved in sacrolemmal LCFA transport, and it is also present on the mitochondria. At this location, it has been identified as mitochondrial aspartate amino transferase (mAspAT), despite being structurally identical to FABPpm. Whether this protein is also involved in mitochondrial LCFA transport and oxidation remains unknown. Therefore, we have examined the ability of FABPpm/mAspAT to alter mitochondrial fatty acid oxidation. Muscle contraction increased (P < 0.05) the mitochondrial FAT/CD36 content in rat (+22%) and human skeletal muscle (+33%). By contrast, muscle contraction did not alter the content of mitochondrial FABPpm/mAspAT protein in either rat or human muscles. Electrotransfecting rat soleus muscles, in vivo, with FABPpm cDNA increased FABPpm protein in whole muscle (+150%; P < 0.05), at the plasma membrane (+117%; P < 0.05) and in mitochondria (+80%; P < 0.05). In these FABPpm-transfected muscles, palmitate transport into giant vesicles was increased by +73% (P < 0.05), and fatty acid oxidation in intact muscle was increased by +18% (P < 0.05). By contrast, despite the marked increase in mitochondrial FABPpm/mAspAT protein content (+80%), the rate of mitochondrial palmitate oxidation was not altered (P > 0.05). However, electrotransfection increased mAspAT activity by +70% (P < 0.05), and the mitochondrial FABPpm/mAspAT protein content was significantly correlated with mAspAT activity (r = 0.75). It is concluded that FABPpm has two distinct functions depending on its subcellular location: (a) it contributes to increasing sarcolemmal LCFA transport while not contributing directly to LCFA transport into mitochondria; and (b) its primary role at the mitochondria level is to transport reducing equivalents into the matrix. (+info)
Malate metabolism in Hoya carnosa mitochondria and its role in photosynthesis during CAM phase III.
(11/21)
Sida rhombifolia ssp. retusa seed extract inhibits DEN induced murine hepatic preneoplasia and carbon tetrachloride hepatotoxicity.
(15/21)
Sida rhombifolia ssp. retusa is a well established drug in the Ayurvedic system of medicine used for antirheumatism and antiasthmatism. Inhibitory effects of S. rhombifolia ssp. retusa seed extract on DEN induced hepatocellular preneoplastic foci and carbon tetrachloride (CCl4) induced hepatotoxicity was investigated in rats. Rats received DEN, 1ppm/g b.w. in drinking water for 6 weeks or CCl(4), 0.7 ml/kg i.p. once a week for 4 weeks and seed extract 50 mg, 100 mg/kg b.w. orally prior, during and after exposure to DEN/CCl4 for 20 or 5 weeks, respectively. Treatment with seed extract significantly inhibited the increase in DEN/CCl(4) induced activities of pre-cancerous marker enzymes; gamma-glutamyl transpeptidase, glutathione-S-transferase, hepatotoxicity marker enzymes; glutamate pyruvate transaminase, glutamate oxaloacetate transaminase and alkaline phosphatase as well as lipid peroxidase. Depleted glutathione, protein and albumin levels were restored. Also, histopathological and transmission electron microscopic studies showed prevention of cellular degenerative changes. The chemopreventive and hepatoprotective potentials of seed extract are due to free radical scavenging activity and restoration of cellular structural integrity. (+info)
Systemic activation of glutamate dehydrogenase increases renal ammoniagenesis: implications for the hyperinsulinism/hyperammonemia syndrome.
(16/21)