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.
Shorey
C D
CD
Department of Histology and Embryology, University of Sydney, Australia.
Manning
L A
LA
Everitt
A V
AV
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