Effect of short-term space flight on structure of liver, lungs, bone and bone marrow of Japanese quail hatched on orbital station mir

Abstract

The effect of hypergravity of launch, microgravity during short-term space flight, and hypergravity of landing on the structure of liver, lung, bone and bone marrow of 3 Japanese quail, that hatched on board the orbital station Mir was investigated. Chicks were 5 days old at landing. Eleven hours after landing 3 male chicks were killed and samples were collected for a wide variety of biochemical, histological, histochemical, electron microscopic and microbiological investigations. Results of the light microscopic, and transmission electron microscopic study are presented in this paper. Extensive deposits of fat droplets were revealed in almost all hepatocytes of all flight chicks versus ground and laboratory controls. Adipocytes, common in the bone marrow of control animals of the same age, were depleted or absent in bone marrow of flight chicks. There were no substantial effects on the structure/ultrastructure of the lungs, the structure of the bone and its development was not substantially affected. Morphometry of the liver revealed that hepatocytes contained significantly more lipid droplets (nearly 5-fold) than hepatocytes of ground control chicks of the same age hatched at the same time. Morphometric study of lungs revealed no significant difference in number, diameter and total surface of air capillaries between flight and control chicks of the same age. We propose that structural changes in the liver and bone marrow were not caused by direct effect of microgravity per se, but most probably resulted from an insufficient intake of feed due to stress of the microgravity environment and the resulting delay in uptake of lipids from liver. We suppose that these structural changes are the tissue and cellular response to microgravity and they are consistent with literature data known as "space adaptation syndrome".