Mast cells in the mammalian area postrema.

Abstract

Mast cells, identified by metachromasia of perikarya in material fixed by two-step perfusion with Bouin's solution, were studied in the area postrema of 25 mammalian species. (A) The appearance of mast cells varied greatly, and when the population of these cells was high, they were predominantly of the pale type with pyknotic nuclei. (B) The mast cells tended to accumulate near the ventricular surface in primates and carnivores, while in other species the distribution was diffuse. (C) They were found in large numbers, up to 16 000, in such adult animals as the chimpanzee, stumptailed and cynomolgus monkeys, dog and cat, and in smaller numbers in the capuchin monkey, opossum, agouti and acuchi, but more rarely or not at all in most rodents and the lagomorph. No mast cells occurred in the mulatta monkey, with the exception of a 28-year-old female. (D) In the stumptailed and cynomolgus monkeys, the number increased with weight of the animal and, in both the cynomolgus monkey (already present at birth) and the cat, with age; even then, in individual instances, mast cells were absent. Infection was considered as a factor contributing to an increase in number, but study of pathogen-free cynomolgus monkeys was inconclusive. Appearance and content of mast cells in monkeys and/or cats were not affected by dietary regimen, treatment with reserpine, L-histidine, cortisone or thyrotropic hormone, or castration. —At this stage of experience, the role of mast cells in the area postrema remains enigmatic.