Histochemical and ultrastructural aspects of m. vastus lateralis in sedentary old people (age 65--89 years).

Biopsies for histochemical and ultrastructural studies were taken from the M. vastus lateralis of 45 healthy sedentary men and women aged 65--89 years. With increasing age the histochemical reactions reveal changes inthe fibre type distribution characterized by a decrease in the percentage and predominant atrophy of type II fibres. The most frequent changes in the oldest subjects are: targetoid fibres, type I fibre predominance, and type grouping phenomena; expressions of denervation. Myopathic alterations are observed unusually. Electron microscopic findings are characterized by myofibrillar disorder, streaming of Z line and rod formation, and dilatation and increase of sarcoplasmic reticulum. As the age increases, the fibres become richer in intracellular lipid droplets and lysosomes. Intramuscular microcirculatory alterations, consisting of arteriolosclerotic changes and increase in width of the capillary basement membrane, are also observed and discussed.