Abstract
The present work shows that a detailed description of the ultrastructure of the secretory cells of the South American catfish Rhamdia quelen pancreatic islets is presented. Evidence is offered to support the contention that the α-granules consist of a central and an outer portion of different electron densities and solubilities, that the δ-cells are most probably morphologically altered but viable α-cells, and that the β-granules possibly possess a repeating substructure and may therefore represent an intracellular crystalline storage form of insulin.
Highlights
The islets of Langerhans were discovered in the rabbit by Langerhans in 1869
Fish β-cells are readily distinguished from the α-cells by the morphology of the secretory granules
When secretory granules were visualized in the vicinity of the Golgi complex, crystalline subunits were not usually observed
Summary
The islets of Langerhans were discovered in the rabbit by Langerhans in 1869. They were reported by Stannius and Blockmann in teleosts about 20 years earlier and are less frequently, referred to as Stannius’s or Blockmann’s bodies. The islets of Langerhans are of endodermal origin and in most teleosts are found as small bodies scattered in the exocrine portion of the pancreas [1]. Exocrine pancreatic tissue can be found scattered along the intestinal tract. In mammals and humans most of the earlier electron microscopic descriptions of adult human pancreatic islets have been brief and minor portions of publications are primarily devoted to descriptions of βcell tumors or survey articles discussing the comparative morphology of the islets of several species [4]
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