Fig. 2.

Microscopic appearance of spermatogenesis in recipient seminiferous tubules following microinjection of donor testis cells preserved at −196 °C. a, Seminiferous tubule of donor testis from transgenic ZFlacZ mouse. Round spermatids and more mature stages stain blue following incubation with X-gal (Fig. 1a)^3,4,11. When staining is intense, immature stages also appear blue. b, Seminiferous tubule from recipient mouse treated with busulfan. No germ cell stages are present. Only Sertoli cells remain. c and d, Seminiferous tubules from busul-fan-treated recipient mice 891 and 771, respectively (Table 1). Blue staining of germ cells indicates their origin from transplanted donor cells that had been frozen 7 and 111 days, respectively. Background stain in all sections is neutral fast red. Scale bar, 50 μm.