Histochemical and ultrastructural studies on the islets of langerhans of lean and obese hyperglycaemic mice with age

Abstract

A histochemical and ultrastructural study has been made on the islets of Langerhans of lean and obese mice with age.

Alpha (a, )s beta (8, and §,), delta (cy ) and F cells have been observed~ in both flea and mere mouse islets. Agranular cells were observed in the islets of old obese mice. These cells might represent atrophied $-cells.Many morphological changes develop in the islets of old obese mice. These changes include B-cell degranulation, ceroidbody accumulation, amyloid deposition, lymphocytic infiltration, platelet aggregation and islet vacuolation.

The formation of vacuoles in obese mouse islets has been examined with age. Early vacuolation is the consequence of 6-cell hyperactivity, degranulation and cytoplasmic rarefaction and vacuolation. Grossly vacuolated and disrupted B-cells were observed closely applied to fragile capillaries. The latter subsequently ruptured and formed a vacuole which increased in size at the expense of the disrupted B-cell. The vacuole eventually came to occupy most of the islet volume, and was subsequently invaded by fibrous connective tissue originating from the islet capsule. This pathological deterioration of the islet tissue was probably responsible for the depressed circulating level of insulin seen in elderly obese mice. Obesity, hyperglycaemia and raised circulating insulin levels induced in lean mice by GTG treatment suggest some mild form of insulin resistance. GTG induced obesity was not accompanied by islet vacuolation, although B-cell hyperplasia, ceroid body formation and enlargement of the Golgi apparatus and endoplasmic reticulum were observed. This would suggest that vacuolation is not a direct consequence of obesity per se, but the result of an interplay of hyperinsulinaemia, B-cell atrophy and some form of auto-immune phenomenon.

Date of Award	May 1978
Original language	English
Awarding Institution	Aston University