An electron microscopical morphometrical study on pinealocytes of pregnant rats.

A morphometrical study was made on the cut-surface of the pinealocytes in electron micrographs of the pineals from pregnant, puerperal and non-pregnant female rats. No significant differences in the cross-sectional area of the pinealocytes and the nuclei or in the nucleo-cytoplasmic ratio were found among the three groups of pregnant, puerperal and non-pregnant rats. The cross-sectional area of the nucleoli was, however, larger in the pinealocytes of the rats in pregnancy and early puerperium. This has been statistically confirmed by the ranking method (the U-test) of Wilcoxon, Mann and Whitney. The enlargement of nucleoli suggests the enhanced function of the pineal in pregnancy and early puerperium.