Chemocytological observations on the parathyroid gland of the toad (Bufo vulgaris japonicus) in specimens taken throughout the year

The parathyroid gland of the toad (Bufo vulgaris japonicus) has been studied histochemically in specimens taken throughout the year. 1. The organ contains varying proportions of large peripheral and small central parenchymal cells and is covered with a vascular and connective tissue envelope. 2. The parathyroid cells contain 2,2′-dihydroxy-6,6′-dinaphthyl disulfide (DDD) diazo blue B reactive protein granules, 2-hydroxy-3-naphthoic acid hydrazide (HNAH) diazo blue B reactive protein granules, coupled tetrazonium proteins, glycogen, and ribonucleic acid (RNA). 3. Seasonal differences in the DDD diazo blue B reactive granules suggest that they reflect the secretory activity of the parathyroid cells. 4. The morphological feature of the HNAH diazo blue B reactive granules throughout the year is suggestive of their dual nature; the majority of the granules represent a mitochondrial pattern of the parathyroid cells, while their minority appearing to be of another cytophysiological significance such as the relation to the cellular activity of secretion. 5. The nuclear and cytoplasmic coupled tetrazonium reaction of the parathyroid cells is regarded as an indicator by which the extent of the cellular physiological activity is adequately reflected throughout the year. 6. The seasonal variation in the glycogen content of the parathyroid cells appears to indicate that this polysaccharide is present for the performance of the cellular activity; secretory and metabolic. 7. The cytoplasmic RNA of the parathyroid cells exhibits seasonal rise and fall in amount and its amount appears linked almost linearly to the cytoplasmic protein synthetic activity for either secretion or metabolism. 8. From the reactions of the peripheral and central parathyroid cells for proteins and amino acids, glycogen and RNA, the former cells are concluded to be more active in secretory function than the latter.