Features of Mesenteric Lymph Nodes Structure Exposured to a Gas Mixture in Space Flight Conditions
The objective is the study of mesenteric lymph nodes structural organization in mice after prolonged exposure to a mixture of acetaldehyde, acetone and ethanol. Material and methods. The research object is the mesenteric lymph nodes, obtained from 80 adult F1 (CBA×C57BL6) mice, subjected to the inhalation of acetone, acetaldehyde and ethanol mixture with a duration of 8, 22, 36 and 70 days. The recovery period was 14, 28, 64 and 90 days. Histological sections were stained by hematoxylin and eosin and by Van-Gizon method. Statistical processing included calculation of arithmetic mean values and their errors. The significance of differences was determined by the method of confidence intervals. Results. The number of lymphoid nodules in the lymph node cut by the 70<sup>th</sup> day was 2.06 times less than in the control. There was a gradual decrease in the length, width, area of the lymphoid nodules, both with the center, and without a germination center. Similar parameters decrease for the germination centers of lymphoid nodules. From the 22<sup>nd</sup> to the 70<sup>th</sup> day of the experiment the thickness of mesenteric lymph nodes capsule increases by 1.26 times, and the trabeculae by 1.53 times compared with the control, the thickness of the meat strands decreases. On the 60th day the size of lymphoid plaques, the number and size of lymphoid nodules, the proportion of lymphoid nodules with the center of reproduction, the absolute number of lymphoid cells in the lymphoid tissue of mesenteric lymph nodes corresponds to control. Conclusion. From the 22<sup>nd</sup> to the 70<sup>th</sup> day of the inhalation gas exposure, there is a depression immunocompetent function of the mesenteric lymph nodes by decreasing the proportion of lymphoid tissue and increasing the connective tissue component. After the end of the impact of damaging factors, the restoration processes of the lymph nodes are manifested only on the 60<sup>th</sup> day.