Discipline: Veterinary Medicine
The pancreatic acini of the Philippine water buffalo were of variable size and shape. In both sexes each acinus was composed of 5-10 pyramidal-shaped secretory cells, centroacinar cell, and occasionally 1-2 "clear cells'. A characteristic feature of the secretory acinar cells was the presence of numerous supranuclearly located zymogen granules, which appeared larger and more numerous in the male than in the female animals. In male animals there were about 173-287 granules measuring 0.7µm-11µm while in female animals there were approximately 50-80 granules measuring 0.6µm-1µm. One or two centroacinar cells were identified in the lumen of each acinus. Their pale staining cytoplasm contained oval to round nucleus. Because of the low magnification used, cytoplasmic organelles were hardly identified in these cells. "Clear cells' had fewer zymogen granules and numerous dilated smooth endoplasmic reticulum. Pancreatic islets were very few in number. A, B, C and D cells were identified. B cells were the most predominant cell type. Their characteristic feature was the presence of many pleomorphic granules. Majority of the granules were round containing a homogenous mass surrounded by a halo of variable size. In some cells, there were numerous granules appearing like dilated vacuole-like bodies containing pleomorphic crystalloid bodies. The secretory granules of B cells measured from 0.22µm- 0.38µm. The secretory granules of A cells were more uniform in shape than B cells and consisted of dense homogenous core surrounded by a tight membrane. They appeared to be uniformly distributed around the nucleus. The granules measured about 0.13µm - 0.20µm. The secretory granules of D cells appeared almost identical to those of A cells except that they were fewer in number and less electron dense. They measured approximately 0.16µm-0.22µm. C cells had scanty and pale cytoplasm containing very few secretory granules. Some C cells completely lacked secretory granules. X, F and E cells demonstrated in other species were not observed in the Philippine water buffalo. The ultrastructural features of A,B,C and D cells of the pancreatic islets and the pancreatic acinus of the Philippine water buffalo generally conformed with those of other species of domestic animals.