[Morphological study of gastrocnemius muscle in Japanese quail chicks hatched out in space flight]

Slovak experiment Quail SK-6 aboard orbital station Mir in the period of February 20-27, 1999 resulted in hatching out of viable chicks of the Japanese quail. The paper presents morphologic results of investigation of m. gastrocnemius of the chicks after 4-5-d life in space microgravity. On the whole, histologically the gastrocnemius of the space chicks was very much similar to that of the control group. Muscular fibers were, which is typical, striated; bundles of myofibrills and numerous nuclei were on the periphery of the fiber under the sarcolemma. However, despite the similarity of the muscular histology, the chicks borne and exposed in microgravity displayed some deviations in the gastrocnemius as compared to their controls. Thus, Z-lines in some of the muscular fibers had a zigzag form or were doubled. In places, mitochondria were increased in size and lined up in chains longer than a sarcomere; internal membranes of the mitochondria were thickened and vacuolized, there were expanded tubules in the sarcotubular apparatus, and muscular fibers with multiple fatty vacuoles.