Morphometrical analysis of skeletal muscle fibre ageing and the effect of hypophysectomy and food restriction in the rat.
Morphometrical analyses were carried out on muscle fibres from cross-sectional areas of the medial head of gastrocnemius muscles from 5 groups each of 4 male Wistar rats representing young (aged approximately 100 days), medium-aged (400 days), old (1,000 days), old hypophysectomized (1,000 days) and old food-restricted (1,000 days) rats. Approximately 18,000 muscle fibres were measured in each group. Rats were hypophysectomized when young at 60-70 days and food restriction began at the same age. The results show that there is a reduction in type 2 fibre size (measured as the mean equivalent circle diameter) from 59.7 micron in medium-aged controls to 50.3 micron in old controls, but there is no significant difference between the sizes of type 2 fibres in controls, hypophysectomized or food-restricted rats in old age. Analysis of type 1 fibres demonstrated no differences between young, medium-aged and old controls and the old food-restricted group, but type 1 fibres in the old hypophysectomized group (45.5 micron) were significantly smaller than in the old controls (54.6 micron) and old food-restricted rats (58.5 micron). In old controls there is a 4-fold increase in the range of fibre sizes (coefficient of variation) for type 1 fibres and a 2-fold increase for type 2 fibres, indicating fibre atrophy and hypertrophy. Long-term hypophysectomy is more effective than food restriction in preserving the smaller range of the coefficient of variation of fibre size seen in young controls.
Department of Histology and Embryology, University of Sydney, Australia.
C D
CD
Shorey
L A
LA
Manning
A V
AV
Everitt
D000375:Aging; D000818:Animals; D005508:Food Deprivation / Q000502:physiology*; D007016:Hypophysectomy; D008297:Male; D009132:Muscles / Q000473:pathology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains