Co-existence of gametic and agametic seminiferous tubules in a chimeric mouse. A light- and electron-microscopic study.

Six chimeras, including 4 phenotypic males and 2 females, were produced by aggregation of F1 (C57BL x BALB/c) and Swiss white embryos. All were fertile, except 1 male, whose deviation in testicular structure prompted this light- and electron-microscopic study. This chimera had a well-developed sperm-conducting system, sperm in the epididymis and active accessory sex glands. The testes displayed typical parenchymal and stromal components with the important exception of co-existence of gametic and agametic seminiferous tubules. These tubules were organized in territories of quasi-lobular configurations which appeared to open separately into rete testis. The former corresponded to normally developed and active seminiferous tubules, while the latter were solid testicular cords devoid of any germ cells and embedded in solid masses of interstitial (Leydig) cells. Special mitochondrial transformations were identified in sustentacular (Sertoli) cells of both types of tubules, in maturing spermatids and sperm. These and other submicroscopic sperm defects might be the cause of infertility.