TESTICULAR CELL CYTOSKELETON IN THE NEWT, TRITURUS-MARMORATUS MARMORATUS, DURING THE ANNUAL CYCLE

Light and electron microscopy immunohistochemical studies and Western blotting analysis of cytoskeletal proteins have been carried out in th e testis of the marbled newt (Triturus marmoratus marmoratus) during t he annual testicular cycle. The present findings revealed homologies a nd differences with regard to those reported in the testes of mammals and other vertebrates. Changes in immunohistochemical expression have also been detected in the course of the annual cycle. Actin and tubuli n, which were scanty and diffusely located in spermatogonia and sperma tocytes, increased their expression and reorganized during spermiogene sis. Vimentin and keratin, undetected in spermatogonia and spermatocyt es, were expressed in differentiating spermatids and spermatozoa. In t hese cells, actin might be related with the connection of the axial fi ber to the undulating membrane and the coordination of movement by bot h structures, while vimentin might be involved in the maintenance of t he spatial relationship between the axoneme and the marginal fiber. Du ring the first stages of spermatogenesis, the cytoplasm of Sertoli cel ls (follicular cells) showed a diffuse immunoreaction to actin, myosin , and tubulin and no vimentin immunolabeling. In advanced spermiogenes is, the follicular cells showed an intense immunoreaction to actin, my osin, tubulin, and vimentin in the apical projections that surrounded the spermatid heads. These apical cytoskeletal components might be inv olved in spermatid elongation, since the spermatids display no manchet te, and in spermatozoon positioning and grouping. The colocalization o f myosin and actin in the follicular cells suggests that actin filamen ts form contractile bundles and that contraction might be involved in changes in the Sertoli cell shape that accompany germ cell development during spermatogenesis. The interstitial cells immunostained to actin , myosin, tubulin, and vimentin. These cells, together with follicular cells, seemed to form the glandular tissue cells which showed a simil ar immunophenotype. The cells that surrounded the efferent duct epithe lium immunostained to desmin, and they are probably contractile cells involved in sperm evacuation. (C) 1996 Wiley-Liss, Inc.