[Skeletal muscle mixed fiber tissue metabolism in rats after a flight on the Kosmos-690 biosatellite]. / Metabolizm tkani smeshannykh po tipu volokon skeletnykh myshts u krys posle poleta na biosputnike "Kosmos-690".

On the R+O day the quadriceps muscle of rats showed a decrease in the content of T protein and an inhibition of LDH activity of sacroplasmatic proteins. These changes resulted from the combined affect of space flight factors and gamma-irradiation, and may be considered as a decline of compensatory synthetic processes responsible for the recovery of muscle proteins in weightlessness. Inhibition of the age-associated shift of the M:H ratio of LDH found on the R+25 day can be attributed to the inhibitory effect of gamma-irradiation. No change in the content of glycogen in the gastrocnemius muscle of flight rats was noted.

[Changes in the soleus muscle tissue metabolism of rats after a flight on the Kosmos-690 biosatellite]. / Izmeneniia metabolizma tkani kambalovidnoi myshtsy u krys posle poleta na biosputnike "Kosmos-690".

The soleus muscle of flown rats did not show any effect of gamma-irradiation on the composition and enzymic activity of protein fractions. On the Ist postflight day a significant decrease in the content of myofibrillar and sarcoplasmatic proteins in the soleus muscle was found. Besides, a drastic increase in the activity of aspartate aminotransferase and lactate dehydrogenase of sarcoplasmatic proteins and an atrophic type change in the LDH pattern were demonstrated. Those changes were similar to the weighttlessness-induced processes of atrophy and dystrophy and proved reversible.

[Protein fractions and their enzymatic activity in the rat myocardium after a flight on the Cosmos-690 biosatellite]. / Belkovye fraktsii i ikh fermentativnaia akivnost' v miokarde krys posle poleta na biosputnike "Kosmos-690".

Gamma-irradiation of rats in the ground-based experiment decreased the activity of aspartate aminotransferase of sarcoplasmatic proteins of the myocardium and increased the activity of adenosine triphosphate of myosin of the myocardium 1 and 26 days post-test. Gamma-irradiation of flight rats also reduced the activity of aspartate aminotransferase of sarcoplasmatic proteins of the myocardium; however, the activity of ATPase of myosin of the myocardium was lowered both 1 and 26 days postflight. It is suggested that irradiation-induced inhibition of synthetic processes delayed the synthesis of myosin with a normal activity and diminished the protein content in the T fraction of myocardium on the 1st postflight day.

[Protein fractions and their enzyme activity in rat myocardium after a 22-hour space flight]. / Belkovye fraktsii i ikh fermentativnaia aktivnost' v miokarde krys posle 22-sutochnogo kosmicheskogo poleta

No significant changes in the content of sarcoplasmatic and myofibrillar proteins were found in the myocardium of rats that made a 22-day flight onboard the biosatellite. On the 2nd and 26th postflight days the activity of aspartate and alanine aminotransferases of sarcoplasmatic proteins was increased and the total activity of lactate dehydrogenase and its isoenzyme spectrum remained unchanged. On the 2nd postflight day the ATPase activity of myosin of the myocardium was substantially lowered and on the 26th postflight day it returned to the normal. This decline in the ATPase activity of myosin can be regarded as an adaptive reaction to weightlessness.

[Effect of a 22-day space flight on the metabolism of rat skeletal muscle tissue]. / Vliianie 22-sutochnogo kosmicheskogo poleta na metabolizm tkani skeletnykh myshts u krys

Skeletal muscles of flight rats showed no changes in the content of glycogen, adenosine triphosphatase activity of myosin and protein content in protein fractions (except the T fraction where the protein content increased on the 1st and returned to the normal on the 26th postflight day). On the 1st postflight day activities of aminotransferases and lactate dehydrogenase of sarcoplasmatic proteins were elevated and the isoenzyme spectrum of LDH was changed as if in muscular atrophy. The amount of free amino acids in muscles was lowered. On the 26 the postflight day the enzymic activity of sarcoplasmatic proteins remained increased whereas the isoenzyme spectrum of LDH returned to the normal and the amount of free amino acids grew significantly. In the microsomal fraction of muscles the phospholipid content decreased on the 1st and returned to the normal on the 26th postflight day.

[Overall activity and isoenzymatic spectrum of liver lactate dehydrogenase in hypobiotic rats]. / Obshchaia aktivnost' i izofermentnyi spektr laktatdegidrogenazy pecheni krys pri gipobioze

A total activity and isoenzyme spectrum of LDH from liver tissue were studied in rats, which were cooled down to the body temperature of 18-22 degrees and were kept in conditions of artificial hypobiosis for a long time (24 and 30 hrs). In cooled rats an increase in total LDH activity was observed. The increase might be a reflection of a stress-reaction to cooling since the method of developing of a hypobiosis involved an incomplete depression of thermoregulation. Subsequent extention of hypobiosis caused a gradual decrease in the total activity of LDH from liver tissue. The LDH activity reached values which were lower than the initial level. This phenomenon was probably due to attenuation of the stress-reaction and to a decrease in metabolic processes under effect of hypothermia. The alterations noted in the total LDH activity were determined by changes in the activity of a prevailing isoenzyme--LDH5. The increase in the LDH5 activity was assumed to be associated with activation of neoglucogenesis and determined by an orientation of the LDH-reaction in the direction of pyruvate.