Year

2002

Degree Name

Doctor of Philosophy

Department

University of Wollongong. Dept. of Biomedical Science

Abstract

This thesis describes the current obstacles that we are facing in the treatment of obesity. The aim of this study was to shed more light into the study of adipose tissue, which is hoped to provide more information about the difficulty of weight loss and more importantly, the difficulty of low weight maintenance.

The experiments performed are done on rats. Female rats were divided in two groups of sedentary and exercised animals. Exercised rats were placed under intensevoluntary exercise regimen in running wheels. Total body weight changes and fat cell size changes of retroperitoneal fat pads were then compared in exercised and sedentary rats. The results presented indicated a substantial reduction in body weight and fat cell sizes in subcutaneous fat pad of exercised rats compared to sedentary rats.

A new group of female rats were again divided in sedentary and exercised groups. These rats were subsequently used to study sympathetic innervation of adipose tissue. Three-dimensional whole mounts of omental fat pads were prepared and stained using avidin-biotin peroxidase. The subsequent staining of the sympathetic innervation in these slides revealed a complex meshwork of nerves both in sedentary and exercised rats. Some qualitative differences between the innervation of exercised and sedentary animals were also observed. The exercised rats displayed a denser level of innervation compared to sedentary rats. Stained whole mount slides were further used to compare the sizes of fat cells in contact with nerve fibres and those with no nerve contact. The cells in contact with nerves were significantly smaller than those cells with no nerve contact both in sedentary and exercised animals.

This study further revealed the presence of mast cells mainly in the exercised rats. A close examination of these results revealed a high density of mast cells near nerve fibres. The significance of this finding and its implications on the adipose tissue\ needs further research

The final part of this thesis explored the concept of apoptosis in mature isolated adipocytes. An apoptosis-inducing agent (DNA intercalator) was used to induce apoptosis in mature adipocytes. The isolated adipocytes incubated with this drug became apoptotic. The process of apoptosis was substantiated using qualitative analysis such as DNA gel electrophoresis, light and confocal microscopy.

Future study of the process of apoptosis in adipocytes is recommended using flow cytometry. This will provide valuable quantitative data looking at extent of apoptosis in these cells.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.