[Effect of a 22-day space flight on the lymphoid organs of rats]

The effect of a 22-day space flight on lymph organs of rats was studied. The exposure produced hypoplasia of lymph organs and reduced the weight of the spleen and the thymus to the greatest extent. It was shown histologically, morphometrically and cytologically that hypoplasia of the spleen was associated with the decreased number of lymphocytes and erythrocytes whereas hypoplasia of the thymus and lymph nodes was related to the diminished number of lymphocytes. Changes in the lymph organs of flight rats were reversible. The structure of lymph organs restored by the 27th postflight day. The paper discussed pathogenetic mechanisms of the changes in the lymph organs of rats due to space flight effects and compares the data with the postflight medical examination of cosmonauts.