[Quantitative analysis of the changes in the nuclear apparatus of thyrocytes in experimental thyroid hyperfunction].

Quantitative ultrastructural characteristics (volume, surface area, volume fraction and surface density) of the nucleus, nucleolus and cell were studied in albino rats after long-term (5, 10, 15, 20 days) melanotropin (MSH) administration. The experiments showed that enhanced functional activity of thyroid cells induced by MSH administration was accompanied by an increase in the volume, surface area of the nucleus, nucleolus and the cell proper, as well as by an increased nuclear pore diameter. Consequently, the nucleus-cytoplasm ratio in thyroid cells rises.