[The circahoral rhythm of the functional activity of rat adrenocorticocytes]

Functional manifestations of biological ultradian rhythms in the adrenal cortex were first confirmed on the cytologic level. The cycle of the ultradian rhythm in the cells of the adrenal cortex fascicular zone consisted was determined to involve three phases: accumulation of lipids, delipoidization, and the rest period. A definite volume of cells and their nuclei, certain nuclear-cytoplasmic relations, the number of liposomes and mitochondria on the square unit are characteristic of each phase. The activity of cells is especially high during the second phase which is characterized by the increase in nuclear sizes and nuclear-cytoplasmatic relations, by the decrease in cell volume and in the number of liposomes in their cytoplasm; this is indicative of the rised synthesis and secretion of hormones. It is underlined that the cell volume increases when liposomes are accumulated in the cytoplasm to decrease upon their disappearance.