Germinal epithelium degeneration is a nonspecific term that generally includes a number of degenerative features, such as tubular vacuolation, partial or segmental depletion of germ cells, degenerating (multinucleated or apoptotic) germ cells generally not restricted to a specific germ cell type or stage, and disordered arrangement of the germ cell layers (Figure 1, Figure 2, Figure 3, and Figure 4). Depending on severity, there may be a macroscopic reduction in size of the testis and a reduction in organ weight. The condition may progress to total loss of germ cells, leaving contracted tubules lined only by Sertoli cells (see ).
Frequently, there is a mixed effect on seminiferous tubules, with some showing degeneration and others having progressed to atrophy. Chemically induced germinal epithelium degeneration can be multifocal in distribution, but it is most often a bilateral lesion that affects most of the seminiferous tubules to varying degrees (Figure 1). It can also be an incidental background finding in rats and mice of any age, but the incidence increases with age. Depending upon the toxicant, in short-duration studies (~14-28 days) the earliest evidence of germinal epithelium degeneration may be preceded by specific degenerative features, such as vacuolation or cell- and stage -specific degeneration/depletion of germ cells.
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