[Effect of repeated sublethal overheating on the cytogenetic processes in the corneal epithelium and bone marrow cells of white rats].

A study was made of the effect of five-fold 1 1/2-hour sublethal hyperthermia on cytogenetic processes in the corneal epithelium and bone marrow cells in rats. Hyperthermia exerted a powerful stressful effect on the animals. Immediately after hyperthermia was terminated the mitotic activity (MA) was inhibited almost 10-fold. After 2 hours the MA returned to normal and tended to increase, and after 6 hours it increased almost 5-fold. The level of pathological mitoses (PM) increased 10-fold after overheating and exceeded 2-4-fold the control values at varying times of the observation period. After 2 and 6 hours five-fold sublethal hyperthermia was accompanied by the decrease in the number of DNA-synthesizing cells and in the label intensity. At the same time hyperthermia in adrenalectomized animals brought about the reduction of the colchicine mitotic index after 2 hours. The content of aneuploidy cells in adrenalectomized animals exposed to five-fold hyperthermia increased 6-fold, whereas in the animals with the adrenals it remained unchanged.