TABLE 1.

Rat spermatogonial stem cell transfer into mouse recipient testes

Experiment	Recipient mouse	Genotype	Per cent testis surface area covered* right, left	Time to analysis, days†	Number of testis tubules with donor cells‡ right, left	Rat sperm in epididymides§
1	761	SCID	50, 25	46	10, 10	ND
	763		50, 50	97	5, 4	0/852
2	766	Nude	80, 80	91	8, 3	0/399
	767		80, 90	110	≥12, ≥12	7/270
3	769	SCID	60, 25	42	4, 0	ND
	770		50, 30	104	≥12, ≥12	1/1832||
4	775	Nude	90, 50	127	≥12, ≥12	24/1273, 4/2041
	776		80, 50	77	3, 4	0/1284
	777		90, 90	121	8, ≥12	3/2370
	778		50, 50	96	8, 6	0/189

SCID mice, which lack B-cells and T-cells. Nude, Swiss nude mice, which lack T-cells. Recipient mice received 32 mg per kg busulphan, which destroys endogenous spermatogenesis but allows partial regeneration with time. This system provides carrier mouse spermatozoa and results in a mixed population of spermatozoa in the epididymis². Transgenic rat donor testis cells were collected and microinjected into the seminiferous tubules of recipient mice as previously described²: Experiment 1, 40 × 10⁶ cells per ml from 6 hemizygous transgenic 17-day-old rat testes; Experiment 2, 79 × 10⁶ cells per ml from 6 hemizygous transgenic and 6 control 12-day-old testes; Experiment 3, 65 × 10⁶ cells per ml from 4 hemizygous transgenic and 8 control 12-day-old testes; Experiment 4, 59 × 10⁶ cells per ml from 4 hemizygous transgenic and 4 control 13-day-old testes. Roughly 0.5 ml of cell suspension was used to inject each mouse.

^*Percentage of the surface seminiferous tubules in recipient testes filled by the injected rat cell suspension.

^†Number of days from injection of donor cells to analysis of the recipient testis for presence of spermatogenesis; the time available for spermatogenesis.

^‡Number of mouse seminiferous tubules with evidence of rat spermatogenesis as indicated by blue staining (Fig. 1). Tubules in testes with more than 12 stained could not be counted accurately because of convolution of the tubules².

^§ND, not determined. Numerator, number of rat spermatozoa; denominator, number of mouse spermatozoa. In all cases except 775, the spermatozoa from both epididymides were pooled. In 775 the first number is for right, the second for left. Spermatozoa were identified by characteristic morphology (see Fig. 3).

^||Rat spermatozoa had normal tail and small round head. Epididymides were fixed in neutral buffered formalin before dissection, which makes release of spermatozoa more difficult.