Home About us Contact
|
Home About us Contact | ||
|
|
||
Energy Turnover (energy + turnover)
Selected AbstractsThe energetic cost of activation in mouse fast-twitch muscle is the same whether measured using reduced filament overlap or N -benzyl- p -toluenesulphonamideACTA PHYSIOLOGICA, Issue 4 2008C. J. Barclay Abstract Aim:, Force generation and transmembrane ion pumping account for the majority of energy expended by contracting skeletal muscles. Energy turnover for ion pumping, activation energy turnover (EA), can be determined by measuring the energy turnover when force generation has been inhibited. Most measurements show that activation accounts for 25,40% of isometric energy turnover. It was recently reported that when force generation in mouse fast-twitch muscle was inhibited using N -benzyl- p -toluenesulphonamide (BTS), activation accounted for as much as 80% of total energy turnover during submaximal contractions. The purpose of this study was to compare EA measured by inhibiting force generation by: (1) the conventional method of reducing contractile filament overlap; and (2) pharmacological inhibition using BTS. Methods:, Experiments were performed in vitro using bundles of fibres from mouse fast-twitch extensor digitorum longus (EDL) muscle. Energy turnover was quantified by measuring the heat produced during 1-s maximal and submaximal tetanic contractions at 20 and 30 °C. Results:,EA measured using reduced filament overlap was 0.36 ± 0.04 (n = 8) at 20 °C and 0.31 ± 0.05 (n = 6) at 30 °C. The corresponding values measured using BTS in maximal contractions were 0.46 ± 0.06 and 0.38 ± 0.06 (n = 6 in both cases). There were no significant differences among these values. EA was also no different when measured using BTS in submaximal contractions. Conclusion:, Activation energy turnover is the same whether measured using BTS or reduced filament overlap and accounts for slightly more than one-third of isometric energy turnover in mouse EDL muscle. [source] Association between fatigue and failure to preserve cerebral energy turnover during prolonged exerciseACTA PHYSIOLOGICA, Issue 1 2003L. Nybo Abstract Aim: This study evaluated if the fatigue and apathy arising during exercise with hypoglycaemia could relate to a lowering of the cerebral metabolic rates of glucose and oxygen. Methods and results: Six males completed 3 h of cycling with or without glucose supplementation in random order. Cerebral blood flow, metabolism and interleukin-6 (IL-6) release were evaluated with the Kety,Schmidt technique. Blood glucose was maintained during the glucose trial, while it decreased from 5.2 ± 0.1 to 2.9 ± 0.3 mmol L,1 (mean ± SE) after 180 min of exercise in the placebo trial with a concomitant increase in perceived exertion (P < 0.05). During hypoglycaemia, the cerebral glucose uptake was reduced from 0.34 ± 0.05 to 0.28 ± 0.04 ,mol g,1 min,1, while the cerebral uptake of , -hydroxybutyrate increased to 5 ± 1 pmol g,1 min,1 (P < 0.05). The reduced glucose uptake was accompanied by a lowering of the cerebral metabolic rate of oxygen from 1.84 ± 0.19 mmol g,1 min,1 during exercise with glucose supplementation to 1.60 ± 0.16 mmol g,1 min,1 during hypoglycaemia (P < 0.05). In addition, the cerebral IL-6 release was reduced from 0.4 ± 0.1 to 0.0 ± 0.1 pg g,1 min,1 (P < 0.05). Conclusions: Exercise-induced hypoglycaemia limits the cerebral uptake of glucose, exacerbates exercise, reduces the cerebral metabolic rate of oxygen and attenuates the release of IL-6 from the brain. [source] Cytomorphological alterations of the thymus, spleen, head-kidney, and liver in cardinal fish (Apogonidae, Teleostei) as bioindicators of stressJOURNAL OF MORPHOLOGY, Issue 1 2006Lev Fishelson Abstract Morphological and cytological alterations at the light microscope (LM) and transmission electron microscope (TEM) levels were observed in the thymus, spleen, head-kidney, and liver of cardinal fishes (Apogonidae, Teleostei) from the Gulf of Aqaba, Red Sea, sampled from a strongly polluted site at the northern end of the gulf, and compared to similar samples from a clean, reference site. At the polluted site, the most prominent change was the formation of numerous deposits of cells rich in phagosomes with lipofucin, melanin granules, and phagocytosed debris, including a high increase in number and dimensions of Hassall's corpuscles and melano-macrophage centers. The number of Hassall's corpuscles was 20 (±8.0)/mm2 and of melano-macrophage centers 18 (±4.0)/mm2 at the polluted site, and 7.0 (±4.0)/m2 vs. 5.0 (±2.0)/mm2 respectively at the reference site. In numerous instances the head kidney's melano-macrophage centers in fishes from the polluted site were encapsulated by reticulocytes, a phenomenon recognized as a marker of neoplasmosis and possible malignancy. In the spleens of fishes from the polluted site, numerous deposits of cell debris, peroxisomes, and enlarged lysosomes were also observed. The livers (hepatopancreas) of fishes from polluted waters demonstrated very strong hyperlipogeny. Many of their hepatocytes were laden with lipid vesicles, fragmented endoplasmic reticulula, and aberrant mitochondria. Although the observed alterations in the glands and liver do not indicate any immediate threat to the life of the fish, they can become crucial with respect to energy turnover and fecundity trajectories. This study strongly suggests the use of cytological alterations in vital organs, such as were observed, as pathological biomarkers to environmental stress. J. Morphol. © 2005 Wiley-Liss, Inc. [source] | ||||||||||