Table 3. Response of mouse oocytes to the injection of a single or multiple human spermatozoa.

						No. of eggs developed (%)
Exp.	No. of human sperm injected into a single mouse oocyte	Status of acrosome	Total no. of oocytes injected (no. of reps.)	No. of oocytes survived ICSI and activated (%)	No. of oocytes with many vacuole-like structures 30 h after ICSI (%)	To 2-cell	Beyond 2-cell
A	1–3	Acrosome-intact	103 (6)	62 (60)	0 (0)	51 (82)a	0 (0)
B	4	Acrosome-intact	35 (5)	17 (49)	4 (24)b	10 (59)	0 (0)
C	5–6	Acrosome-intact	25 (6)	16 (64)	11 (69)c	5 (31)d	0 (0)
D	7–8	Acrosome-intact	11 (6)	7 (64)	7 (100)	0 (0)	0 (0)
E	7–8*	Acrosome-less	10 (2)	5 (50)	0 (0)	0 (0)	0 (0)
F	0†	–	40 (4)	–‡	0 (0)	0 (0)	0 (0)
G	1§	Acrosome-intact	50 (4)	34 (68)	0 (0)	27 (79)	0 (0)

Superscript letters: P < 0.05 for b vs. c; P < 0.001 for a vs. d.

^*Seven to eight acrosome-less sperm were injected into each oocyte

^†Sham operation. A total of 2 × 10^–5 μl of HEPES-CZB containing PVP (100 mg/ml) was injected into each oocyte. This volume of the medium corresponded roughly to that of the medium injected with two to eight spermatozoa

^‡Forty (100%) oocytes survived, but all surviving oocytes did not activate

^§A single spermatozoon in 2 × 10^–5 μl of HEPES-CZB containing PVP (100 mg/ml) was injected into each oocyte