Sizes of components in frog skeletal muscle measured by methods of stereology

Abstract

Stcreological techniques of point and intersection counting were used to measure morphological parameters from light and electron mlcrographs of frog skeletal muscle. Re.sults for sartoHus muscle arc as follows: myofibrils comprise 83 % of fiber volume; their surface to volume ratio is 3.8µm-1 Mitochondria comprise 1.6 % of fiber volume. Transverse tubules comprise 0.32 % of fiber volume, and their surface area per volume of fiber is 0.22µm-1 Terminal cistcrnac of the sarcoplasmic rcticuium comprise 4. 1% of fiber volume; their surface area per volume of fiber is 0.54/-m -I. Longitudinal sarcoplasmic rcticulum comprises 5.0 % of fiber volume, and its surface area per volume of fiber is 1.48µm-1 Longitudinal bridges between terminal cistcrnac on either side of a Z disk wcrc observed infrequently; they make up only 0.035 % of fiber volume and their surface area per volume of fiber is 0.009 µm-1. T-SR junction occurs over 67 % of the surface of transverse tubules and over 27 % of the surface of terminal cistcrnac. The surface to volume ratio of the cavcolac is 48µm-1 cavcolac may increase the sarcolcmmal surface area by 47 %. Essentially the same results wcrc obtained from scmitcndinosus fibers. © 1975, Rockefeller University Press., All rights reserved.