Spermatogonial intercellular bridges in whole-mounted seminiferous tubules from normal and irradiated rodent testes

Whole-mounted seminiferous tubules from normal and irradiated rodent testes were examined by light microscopy. These studies reveal the presence of intercellular bridges in all classes of spermatogonia except for the single A_s stem cells. It was demonstrated that A_s stem cells divide to produce new A_s spermatogonia or paired daughter cells that are united by a cytoplasmic bridge. Evidence was given that all subsequent progeny of these paired A's up to and including the production of type B spermatogonia remain linked by cytoplasmic bridges in increasingly larger and more complex syncytial networks. It is proposed that the intercellular bridges mediate both differentiation and degeneration of spermatogonia. The maintenance of synchronous development within cohorts of spermatogonia is attributed to the bridges. Moreover, the fact that spermatogonia in both normal and irradiated testes degenerate in clusters is determined by the presence of intercellular bridges. Lastly, the integrity of the bridges appears essential for normal germ cell development.