Ultrastructure and enzyme histochemistry of the pancreatic islets in the horse |
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Authors: | Nils Björkman Claes Hellerström Bo Hellman Ulf Rothman |
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Institution: | (1) Department of Anatomy and Histology and the Laboratory for Electron microscopy, Royal Veterinary College, Stockholm 50;(2) Department of Histology, University of Uppsala, Uppsala, Sweden |
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Abstract: | Summary The characteristic localization of the silver-negative A2 cells in the central part of the pancreatic islets in the horse offers a good opportunity to study the ultrastructure and histochemistry of this type of islet cell. Electron microscopical analyses revealed that the A2 cells contained dense spherical granules varying considerably in size. Light and dark A2 cells were identified. The presence of numerous secretory granules of very low density was the most conspicous feature of the B cells. These cells also showed considerable differences in density. A second type of peripheral islet cell was characterized by a very high content of mitochondria and ribosomes. These small islet cells contained tiny granules and are probably identical with the A1 cells.Negative reactions for alkaline and acid phosphatases were obtained throughout the islet tissue, while a strong glucose-6-phosphatase activity was displayed by the peripheral cells. The diphosphopyridine and triphosphopyridine nucleotide diaphorase activities were high in the peripheral cells, considerably weaker reactions being noted in the A2 cells. On the whole there was a low succinic dehydrogenase activity in the islet tissue with a somewhat weaker enzyme staining in the A2 than in the peripheral cells. The reactions for glucose-6-phosphate dehydrogenase and lactic dehydrogenase were also less pronounced in the A2 cells than in the intensely reacting peripheral cells.The following abbreviations are used DPN
Diphosphopyridine nucleotide
- DPND
Diphosphopyridine nucleotide diaphorase
- DPNH
Diphosphopyridine nucleotide, reduced form
- G-6-PD
Glucose-6-phosphate dehydrogenase
- LD
Lactic dehydrogenase
- MTT
3,5-diphenyl-2-(4,5-dimethylthiazol-2-yl)-tetrazolium bromide
- Nitro-BT
2,2-di-p-nitrophenyl-5,5-diphenyl-3,3-(3,3-dimethoxy-4,4-biphenylene)-ditetrazolium chloride
- SD
Succinic dehydrogenase
- TPN
Triphosphopyridine nucleotide
- TPND
Triphosphopyridine nucleotide diaphorase
- TPNH
Triphosphopyridine nucleotide, reduced form
Supported by the Swedish Medical Research Council and the research grant A-5759 from the National Institute of Arthritis and Metabolic Diseases, United States Public Health Service. |
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