Table 2. In vitro fertilization (IVF) assays using sperm from wild type and SP hyh mice.
| sperm (sperm/ml) | Fertilized (n) | Total (n) | Fertilization (%) | |
| Experiment A | wt (2×105) | 15 | 29 | 52 |
| hyh (2×105) | 5 | 50 | 10 ** | |
| Experiment B | wt (2×105) | 27 | 39 | 69 |
| hyh (4×105) | 31 | 67 | 46 * |
Metaphase II eggs from wild type (Napa (+/+)) female mice were incubated with sperm from wild type (Napa (+/+), wt) or mutant homozygous with the slow progressive phenotype (Napa(hyh/hyh), hyh) mice. Following capacitation, sperm from wild type and hyh mice were diluted to 2 or 4×105 sperm/ml and coincubated with eggs from wild type female mice. In experiment “A”, the same number of sperm cells from wt and hyh mice was used (2×105 sperm/ml). In experiment “B” the number of sperm from hyh mice was duplicated (4×105 sperm/ml). (*, p<0.02 or **, p<0.001 for hyh versus wt; Fisher's exact probability test).