A silver impregnation utilizing only reagent-grade chemicals for visualization of peripheral axons and fibroblasts

A silver impregnation procedure is described that enables the representation of numerous tissue components. It especially visualizes nerves and fibroblasts, which may be clearly distinguished from other tissue elements. Since it can be performed on thick sections, three-dimensional analysis of nerve terminations and fibroblasts in the tissues can be performed. The results are illustrated with the innervation of the rat snout and human labial sweat glands for nerves, and with bovine and pathological human material for fibroblasts. Axons are visualized as thin, sinuous black structures, sometimes, as in the case of autonomic efferents, with varicosities. Fibroblasts are revealed in their total extent by the darker staining of their nuclei and cytoplasm compared with that of the surrounding collagen. Cell processes can thus be followed for long distances, and may be seen to approach other cells. Previously published methods for the visualization of nerves and fibroblasts depended upon the use of commercial formalin, which is subject to the manufacturers' modifications. The method presented here uses exclusively analytical-grade reagents and distilled water. It is also less dependent than other methods on the fixation protocol.