Ultrastructural studies of the hyperplastic islets of Langerhans of spiny mice (Acomys cahirinus) before and during the development of hyperglycemia.

Abstract

Acomys Cahirinus, the spiny mouse, is a small rodent living in the semi-desertic areas of the Eastern Mediterranean. The observation that diabetes may occur spontaneously in this species, at least under laboratory conditions, has led to its breeding at the Institut de Biochimie Clinique, where a colony has been maintained over the last 3 years. Diabetes occurs in approximately 15% of the animals reaching one year of age; some of these are obese, but not all. Diabetes occurs in the presence of, and despite a striking hyperplasia of the endocrine pancreas, which may make up as much as 15% of the total organ in adult mice. This hyperplasia is present in all animals, whether hyperglycemic or not. — The islets of Langerhans of 22 spiny mice have been examined with the electron microscope and form the basis for an analysis of the different cell types observed, at different times relative to the onset of diabetes. Findings in the B cells of this species have included the generally high degree of development of the Golgi complex, the great variability of glycogen accumulation in diabetic animals, the frequent fusion of the granular sacs, and the occurrence of grossly hyper-granulated cells. — The hyperplasia of the islets of Langerhans in spiny mice is associated with a remarkable cellular polymorphism. However, the authors do not feel that this is the result of the presence in these islets of many distinct cell types. It would seem much more likely, that they represent different functional states of a small number of distinct types of cells, among which only A, B and perhaps D cells have been securely identified. Another feature of this cellular polymorphism is thefrequent presence of mixed or intermediate cells (exocrine-endocrine, or endocrine A-B), which suggests that the stimulation leading to hyperplasia of the endocrine cells in this species might result in the removal of some part of the nuclear inhibition usually associated with fully differentiated cells.