In a "blind" study, skeletal muscle biopsies were obtained from the trunk of 13 nondiabetics, eight chemical diabetics, and four overt diabetics of comparable age. On electron micrographs of 20 capillaries from each case, the areas of various components of the capillary structure were measured with a planimeter. The area of the basal lamina was expressed as a percentage of the total vessel area. This method for measuring objectively the relative thickness of capillary basal lamina considered the vessel size, plane of sectioning, and the function state of the vessel. The theoretical validity of the method is discussed. The widths of the basal lamina of the capillaries of the trunk skeletal muscles of both diabetics and nondiabetics were identical. Morphological differences between the two groups were not present. The discrepancies in results of investigations concerned with the quantity of basal lamina in capillaries of skeletal muscle may be due to naturally occurring regional differences, or because capillary beds of different organs or tissues may be affected differently in diabetes mellitus.
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