Morphological study on the hypoplastic testis with aplasia of the epididymis, ductus deferens, and gland of the ductus deferens in the TW inbred rat

In the TW inbred rat, about 50% of the males show bilateral or unilateral testicular hypoplasia with aplasia of the ipsilateral epididymis, ductus deferens and gland of the ductus deferens. To investigate the pathogenesis of the testicular abnormality in the TW rats, the weight and morphology of the testes on the aplastic and normal side were studied between one week and one year of age. The weight of the testes on the affected side was greater than those on the normal side at four and five weeks. However, it rose to a plateau at six weeks and then remained at about one half to one third the weight of a normal testis. As for the testicular histology, there were no obvious changes from one day to three weeks of age. The diameter of the seminiferous tubules became larger and the number of germ cells decreased at four and five weeks. At six weeks, degeneration and loss of germ cells were observed and many multinucleated giant cells appeared. Thereafter, the loss of germ cells became more severe, and they eventually disappeared with increasing age, but Sertoli's cells continued to exist. In the interstitial area, edematous changes and proliferation of Leydig's cells were observed. The efferent duct of another strain, with normal testes, was ligated at three weeks of age, and changes of the testis after the operation were examined to investigate whether or not these anomalies of the TW strain were due to the absence of the accessories, which may block the excretion of the testicular fluid.(ABSTRACT TRUNCATED AT 250 WORDS)