Structural dissimilarities in different regions of the pineal gland of Pirbright white guinea-pigs.
In the present study, the proximal, intermediate and distal parts of dumbbell-shaped pineal glands of Pirbright White guinea-pigs were investigated with respect to structural dissimilarities. The most conspicuous difference was that while in the proximal part the pinealocytes were arranged in a random fashion, the intermediate and distal regions, except a small ventral area in the latter, exhibited a prominent follicular arrangement of the pinealocytes. Concretions were restricted to the subcapsular region of the intermediate part, whereas cells with hyperchromatic nuclei increased in number in an anterior-posterior direction. In males, pinealocyte nuclear size did not differ significantly in the regions investigated, whereas in females the karyometric results were much more heterogeneous. Exposure of male guinea-pigs to continuous illumination for 45 days resulted in (i) a 25% decrease of pineal volume, the intermediate area being relatively little affected, (ii) an increase in the number of follicles and (iii) a decrease in pinealocyte nuclear size, especially in a ventral zone of the proximal part of the pineal gland.
D000818:Animals; D005260:Female; D014644:Genetic Variation; D006168:Guinea Pigs; D006801:Humans; D007620:Karyometry; D008027:Light; D008297:Male; D009474:Neurons / Q000648:ultrastructure; D010870:Pineal Gland / Q000033:anatomy & histology*; D013045:Species Specificity