ISSN:
1432-0878
Keywords:
Chicken pancreas
;
Pancreatic islet cells
;
Light and electron microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Light- and electron-microscopic observations were made on the alpha, beta and delta cells of the pancreatic islets of the domestic fowl and on their cytologic changes following the administration of glucose, glucagon, insulin, alloxan and carbutamide. 1. Under the light and electron microscope, two types of islets are recognized: (1) the “alpha” islet composed of alpha and delta cells and (2) the “beta” islet made up of beta and delta cells. 2. Alpha cells are large, round or columnar in shape, and contain less-developed cellular organelles and characteristic alpha granules. These dense, spherical granules are surrounded by a single smooth membrane and the matrix, with high magnification, exhibits a glomerular structure. 3. Beta cells are round, oval, or irregular in shape, and contain more or less developed cellular organelles and characteristic beta granules. These granules are polymorphic and consist of three main types; needle or bar-shaped, spherical, and ring-shaped; they are enclosed by a smooth membrane. 4. Delta cells are characterized by the presence of less dense spherical granules (diameter about 500 mμ) that are partially surrounded by an indistinct membrane. They are considered to be an independent type of cell of unknown function. 5. “Acinar-islet cells” with intermediate endocrine and exocrine morphology, are observed between the endocrine and exocrine cells along the periphery of the islets. The presence of occasional fragments of plasma membrane suggests that the cytoplasm of acinar and islet cells may intermingle. 6. The alpha cells exhibit margination of granules and release of granules by emiocytosis, in hypoglycemia induced by the administration of insulin or carbutamide. 7. After administration of glucose, glucagon or carbutamide, beta cells exhibit vacuolation and release of granules by intracytoplasmic dissolution of the specific needle- or bar-shaped granules followed by diacrine passage through the plasma membrane. On the other hand, after the administration of glucose, glucagon or carbutamide, Gomori-positive, dense, small-cored granules occur in the periphery of cytoplasm along the capillary with indications of release by emiocytosis. 8. Delta cells increase remarkably and extrude granules by emiocytosis, after the administration of glucagon, alloxan or carbutamide. 9. Administration of carbutamide stimulates the secretory activity of beta cells, as indicated by the diacrine feature of specific beta granules and the emiocytosis of small-cored granules. Carbutamide also causes an increase of immature non-granular cells in the alpha and beta islets.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00331262
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