To explore in detail the relationships between basal lamina (BL) and regenerating cells, we have studied the reconstruction of skeletal muscle fibers and their associated capillaries in portions of rat and rabbit skeletal muscles after injury with either freezing, ischemia, Where an old layer of BL is present overlying a newly formed layer, the old layer may be retained or it may be removed . Removal of redundant BL is probably mediated by interstitial cells which embrace the outside surfaces of BL of regenerated skeletal muscle fibers and capillaries .
SUMMARYCapillary sizes, the amounts of endothelium, pericytes, basal lamina (BL), and lumina were measured with planimeter on electron micrographs of 20 capillary cross sections from each of 40 skeletal muscle specimens obtained from any of eight specific body sites of 20 diabetics. While the capillaries in the distal abdomen and the proximal thigh do not have thickened BL, those in the muscles of mid-abdomen, chest wall, hand, mid-thigh, mid-lower leg, and foot have significantly increased amounts of BL. The remaining parameters differ among body sites, generally following a pattern established earlier for the skeletal muscle capillaries of nondiabetics. Because of the focal and regional distribution of BL thickening and because it occurs also in nondiabetics, it is concluded that BL thickening is a common but not characteristic feature of diabetes mellitus. A possible mechanism which may lead to BL thickening is proposed and discussed.Additional Indexing Words:
Basement membrane Basal lamina Dilatation EndotheliumSize of capillaries D EGENERATIVE CHANGES of vessels account for the common and serious complications of diabetes mellitus.13 Arteriosclerosis, indistinguishable from that occurring in nondiabetics, is the principal lesion of arteries and arterioles, while excessive accumulation of basal lamina (BL*) characterizes in part the structural changes in the capillaries. In the capillaries of the retina4 and in the glomeruli58 BL thickening occurs characteristically and commonly in the presence of diabetes mellitus while in capillaries of skinr"0 and skeletal muscles"-"6 of diabetics it From the
Excessive deposition of basal lamina in capillaries and othei structures of individuals with diabetes mellitus is characterized by formation of multiple layers of basal lamina and accumulation of cell debris between the layers. In capillaries with multiple BL layers, between pericytes and endothelial cells, only a single layer is generally present These and other features suggest that basal lamina formation is a quantified event and that excessive accumulation could be the result of (1) cell death and cell replacement, (2) discrete turning on and off of basal lamina production or (3) defective resorption of old basal lamina layers. Evidence indicating that the major component in the pathogenesis of basal lamina accumulation is cell death and cell regeneration is presented. Whether interrupted production or impaired resorption also contribute to this process is unknown. The common presence of BL layering in patients with diabetes mellitus indicates that diabetics' cells are different from nondiabetics', the difference manifesting itself by increased rate of cell death. The focal nature of this process suggests further that injurious events in the cells' environment contribute to the pathogenesis of this lesion.Whatever the cause, the BL characteristics discussed, like rings on cross-sections of tree trunks, give some indication of the number of cell generations which have occurred at that particular site. DIABETES 23:94-104, February, 1974.In patients with diabetes mellitus several related lesions are caused by excessive accumulation of basal lamina (BL).* The lesions are encountered not only in capillaries, where they give rise to diabetic microangiopathy and glomerulosclerosis, but also in many other sites where BL is normally present. Accumula-*Basal lamina (BL) is used synonymously with basement membrane and basement lamina.
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