[Quantitative ultrastructure of the myocardium of Japanese quail after long-term hypodynamia]

Quantitative ultrastructural myocardial changes of myocardium of the japanese quail (Coturnix coturnix japonica) were studied during an immobilization stress (hypodynamia) lasting 9, 30, 60 and 90 days. Hypodynamic quails were fixed by waistcoats to the feeding place simulating conditions of long lasting space flight which the quails were determined for. The surveyed morphological parametres were: mitochondrial rate, mitochondrial volume in % of cytoplasm, volume of myofibres in % of cytoplasm, volume of single mitochondria, extent of cristolysis. Progressive mitochondrial hydratation and even local oedema were observed during the experiment. It led to a progressive increase of mitochondrial volume and simultaneous decrease of volume of myofilaments as a sign of intracellular atrophy of myofibres. The results correlated well with a decreased mass of myofibres observed in experimental quails from space flight on the orbital station MIR.