RELATIONSHIP BETWEEN OXIDATION OF MYOFIBRILLAR PROTEINS AND CONTRACTILE PROPERTIES IN SOLEUS MUSCLES FROM HYPERTHYROID RAT / 体力科学

We tested the hypothesis that a force reduction in soleus muscles from hyperthyroid rats would be associated with oxidative modification of myofibrillar proteins. Daily injection of thyroid hormone [3, 5, 3’-triiodo-_L-thyronine (T₃)] for 21 days depressed isometric forces in whole soleus muscle across a range of stimulus frequencies (1, 10, 20, 40, 75 and 100 Hz) (<i>P</i><0.05). In fiber bundles, hyperthyroidism also led to pronounced reductions (<i>P</i><0.05) in both K⁺- and 4-chloro-<i>m</i>-cresol-induced contracture forces. The degrees of the reductions were similar between these two contractures. These reductions in force production were accompanied by a remarkable increment (103% ; <i>P</i><0.05) in carbonyl groups comprised in myofibrillar proteins. In additional experiments, we have also tested the efficacy of carvedilol, a non-selective β₁-β₂-blocker that possesses anti-oxidative properties. Treatment with carvedilol prevented T₃-induced oxidation of myofibrillar proteins. However, carvedilol did not improve the hyperthyroid-induced reductions in force production. These data suggest that oxidative modification of myofibrillar proteins may not account for the reductions in force production of hyperthyroid rat soleus muscle.

CHANGES IN SARCOPLASMIC RETICULUM Ca²⁺-SEQUESTERING CAPACITY DURING RECOVERY FOLLOWING HIGH-INTENSITY EXERCISE / 体力科学

The purpose of this study was to investigate changes in sarcoplasmic reticulum (SR) Ca²⁺-sequestering capacity in rat fast-twitch plantaris (PL) and slow-twitch soleus (SOL) muscles during recovery after high-intensity exercise. The rats were subjected to treadmill runs to exhaustion at the intensity (10% incline at 50 m/min) estimated to require 100% of maximal O₂ consumption. The muscles were excised immediately after exercise, and 15, 30 and 60 min after exercise. Acute high-intensity exercise evoked a 27 % and 38 % depression (<i>P</i><0.05) in SR Ca²⁺-uptake rate in the PL and SOL, respectively. In the PL, uptake rate remained lower (<i>P</i><0.05) at 30 min of recovery but recovered 60 min after exercise. These alterations were paralleled by those of SR Ca²⁺-ATPase activity. On the other hand, SR Ca²⁺-uptake rate in the SOL recovered 15 min after exercise. Unlike the PL, discordant time-course changes between SR Ca²⁺-ATPase activity and uptake occurred in the SOL during recovery. SR Ca²⁺-ATPase activities were unaltered with exercise and elevated (<i>P</i><0.05) by 25, 30 and 30% at 15, 30 and 60 min of recovery, respectively. These results demonstrate that SR Ca²⁺-sequestering ability is restored faster in slow-twitch than in fast-twitch muscle during recovery periods following a single bout of high-intensity exercise and suggest that the rapid restoration of SR Ca²⁺-sequestering ability in slow-twitch muscle could contribute to inhibition of disturbances in contractile and structural properties that are known to occur with raised myoplasmic Ca²⁺ concentrations.

Annual reports : proceedings of reserch on chagas desaase and other infections diseases

Se ha dicho que producto final de una investigación es la publicación, es la compilación de trabajos de investigaciones donde están involucrados médicos, bioquimicos, veterinarios y bioligicos dedicados a enfermedades tropicales que son endemicas en enfermedad, tal como la medicina tradicional, epidemiologia, salud pública, atención primaria de comunidades rurales genetica, medicina nuclear, histopotologia, micro biologia y se tomo especialmente la enfermendad de chagas