ESTIMATION OF CAPILLARY LENGTH DENSITY IN SKELETAL-MUSCLE BY UNBIASEDSTEREOLOGICAL METHODS .1. USE OF VERTICAL SLICES OF KNOWN THICKNESS

Background: The unbiased estimation of the capillary length density in skeletal muscle tissue L(V)(cap/mus) has been performed in this study applying a new stereological methodology based on the use of vertical slices and the intersections of cycloid test curves with capillaries in a three-dimensional spa ce defined by systematically chosen fields of vision and the thickness of the sections. Methods: The following si mple requirements must be fulfilled: selection of a fixed vertical axi s in skeletal muscle, adequate systematic muscle sampling, obtention o f vertical slices of constant and known thickness but indifferent in m agnitude, superposition of a cycloid test system with the minor axis o f cycloid curves positioned perpendicularly to the vertical axis, and counting the intersections between cycloid curves and capillaries. In our study, the vertical axis was defined as that which is parallel to the natural, major axis of the muscle where fibres and capillaries are arranged parallel to this axis. The muscle sampling was performed usi ng the fractionator method, and 25 mu m thick sections were chosen. Re sults: The application of the equation for estimation of L(V)(cap/mus) permits determination of an average of 1,480 mm of capillaries per mm (3) of muscle tissue, knowing the number of intersections, section thi ckness, and the points hitting the muscle with a known ratio between c ycloid test curve length to a test point. Conclusions: The estimation of L(V)(cap/mus) is efficient, unbiasedly obtained, and no assumptions on the degree of capillary anisotropy are required. (C) 1995 Wiley-Li ss, Inc.