Estimation of capillary length density in skeletal muscle by unbiased stereological methods: II. Use of vertical slices of unknown thickness.

Abstract

The capillary network of the skeletal muscle was analyzed from a quantitative point of view with the purpose of determining the capillary length density--LV(cap/mus). A recent stereological method was applied to estimate this quantity using vertical slices of unknown thickness. First, the whole muscle was systematically sampled according to the fractionator method. The capillary length density was estimated on each chosen field of vision where the vertical axis was always identified as parallel to the major axis of the muscle fibers. Three measurements were performed: count of intersections between capillaries and cycloid test lines, count of intersections between capillaries and straight test lines, and count of capillary end points corresponding to the intersections of capillaries with the parallel planes of the vertical slices. The estimated capillary length density was 1,578 mm per mm3 of skeletal muscle tissue. The average thickness of the vertical slices was also estimated as 23.4 microns, which is roughly 6% less than the thickness measured using the microcator information on the microscope stage displacement. The advantages of this methodology were based on two main features: the method is assumption-free on the degree of capillary and muscle anisotropy, and the thickness of the vertical slices need not be known nor constant.