title: Immunohistochemical and ultrastructural studies on rat islet cell tumours induced by streptozotocin and nicotinamide.
abstract: Fourteen rat islet tumours induced by streptozotocin and nicotinamide were examined by light microscopy with indirect immunoperoxidase staining and by electron microscopy. Most tumours consisted predominantly of B cells, but over a half of the tumours examined showed mixed cellularity with considerable numbers of A cells and small numbers of D or PP cells. Only 4 tumours consisted exclusively of B cells. There was no positive reaction for any kind of specific islet hormone antibodies in 2 tumours. Ultrastructurally, most tumours were composed of cells containing numerous secretory granules with B cell properties, with great variation in size, shape and number. We often encountered enterochromaffin-like cells or atypical granular cells or cells containing non-beta secretory granules. We could not identify, however, the ultrastructural counterparts of A or D cells. The results suggested that the multiplicity of the endocrine cells of rat islet cell tumours might be an expression of the cellular dedifferentiation of tumour cells which could re-differentiate into the whole range of components of the endocrine pancreas.
mesh_terms: D007516:Adenoma, Islet Cell / Q000139:chemically induced / Q000276:immunology / Q000648:ultrastructure*; D000818:Animals; D000912:Antibodies, Neoplasm / Q000032:analysis; D002454:Cell Differentiation; D008297:Male; D009536:Niacinamide; D010190:Pancreatic Neoplasms / Q000139:chemically induced / Q000276:immunology / Q000648:ultrastructure*; D051381:Rats; D013311:Streptozocin
chemical_list: D000912:Antibodies, Neoplasm; D009536:Niacinamide; D013311:Streptozocin