The male partners of 68 couples exhibiting 5.1 +/- 0.3 (SEM) years of unexplained infertility were assessed using the conventional criteria of semen quality, the movement characteristics of the spermatozoa and the outcome of the zona-free hamster egg penetration test. After a follow-up period of 2.3 +/- 0.06 (SEM) years, 25 (37%) of these patients were found to have initiated a pregnancy, thereby permitting an analysis of those aspects of semen quality which most accurately predicted their subsequent fertility. A multivariate discriminant analysis revealed that the conventional semen profile, per se, was not of significant value in discriminating the incidence of pregnancy. However, significant discrimination (P = 0.0173) was obtained when the postcapacitation movement characteristics of the spermatozoa were incorporated into the analysis. The accuracy of this prognosis was further increased if either the duration of infertility or the outcome of the zona-free hamster egg penetration test was taken into consideration. Overall classifications of fertility were then 76.3% and 76.5% accurate, respectively. These results suggest that in vitro assessments of human sperm function are of significant value in evaluating male fertility.

Multivariate discriminant analysis has been used to determine the predictability of sub‐normal penetrating capacity in cases of unexplained infertility. The product of this analysis was the identification of 7 discriminating variables all of which described various aspects of the post‐capacitation movement characteristics exhibited by the spermatozoa, omitting all reference to the conventional parameters of semen quality. On the basis of these discriminating variables, 90.9% of samples exhibiting penetration rates within the normal range were correctly predicted to be functionally competent. The same variables correctly identified only 60% of samples with impaired penetrating capacity, indicating that in the remaining 40%, defects are present in the spermatozoa which are not reflected in their motility patterns.

The direct effects of gossypol and its acetic acid adduct, on the movement and functional competence of human spermatozoa were investigated employing exposure times of 1, 5 or 15 min and concentrations of 50 μM, 500 μM and 1000 μM. These compounds markedly reduced the motility, velocity, frequency of sperm head rotation and linearity of sperm progression, the most significant effects being observed with gossypol acetic acid on populations of ‘capacitated’ spermatozoa. Significant direct effects of gossypol on the ability of human spermatozoa to penetrate both cervical mucus and zona‐free hamster ova were also observed, which were independent of any effects on motility. These results reinforce the notion that gossypol may serve a contraceptive role in the female as a ‘spermicidal’ agent, and suggest that this compound may also be of scientific value as a probe for identifying and isolating functionally important components of the human spermatozoon.

An investigation has been carried out in normal fertile men on the correlates of fertilizing capacity as defined by the zona-free hamster egg penetration test. The results demonstrate that the apparent fertility of these men is compatible with a wide range of intrinsic sperm quality as reflected by penetration rates ranging from 14% to 90% and differences in the minimum concentration of motile spermatozoa required to initiate penetration. These differences in sperm function could not be correlated with any of the conventional parameters of semen analysis or any of a large number of sperm movement characteristics analyzed by time-exposure photomicrography, with two exceptions: (1) the percentage of progressively (greater than 25 micron/sec) motile spermatozoa exhibiting an amplitude of lateral head displacement (Ah) of less than 10 micron, which was positively correlated with penetrating capacity (P less than 0.01), and (2) the percentage of progressively (less than 25 micron/sec) motile spermatozoa exhibiting an Ah of greater than 10 micron, which was negatively correlated with penetration rate (P less than 0.05). The information obtained in this study should provide a useful basis against which to compare the properties of spermatozoa in cases of suspected infertility.

This study is based upon an analysis of 27 severely oligozoospermic men, in whom defects in sperm motility and morphologic defects were also evident, and 35 control subjects of proven fertility. Semen samples recovered from these men were assessed by conventional criteria, time-exposure photomicrography, and the zona-free hamster egg penetration test. Evidence of severely defective sperm function was obtained for the oligozoospermic group, which gave a mean +/- standard error (SE) fertilization rate of 2.8% +/- 1.5, compared with 44.0% +/- 3.4 for the normal fertile control subjects. Multivariate discriminant analysis was used for selection of those parameters of semen quality that could most accurately identify the 70% of oligozoospermic samples that failed to exhibit any fertilizing potential in the hamster egg assay. This analysis correctly identified 89% of such samples, on the basis of seven discriminating variables, of which the most significant were percentage of motile sperm, the log of sperm density, and a log transformation of the concentration of progressive spermatozoa.

A detailed analysis of semen quality was carried out in 85 couples with unexplained infertility by the use of conventional criteria of semen analysis, time-exposure photomicrography, and the zona-free hamster egg penetration test. According to the latter, 34.1% of the male partners exhibited evidence of defective sperm function, although only 4% of these patients were devoid of any demonstrable fertilizing capacity. Of the conventional parameters of semen analysis examined, the most revealing was the morphologic character of the sperm, which was significantly poorer (P less than 0.001) in the group with unexplained infertility than in the normal fertile control group and also showed a significant relationship (P less than 0.001) with the presence of subnormal fertilizing capacity in the hamster egg assay. A majority of movement characteristics measured by time-exposure photomicrography were significantly depressed in the group with unexplained infertility, compared with the normal fertile control group. In addition, certain of the movement characteristics investigated were significantly related to the fertilizing capacity of the spermatozoa; and, in this respect, a progressive swimming speed (greater than 25 micrometers/sec), a straight swimming mode of progression, and a small amplitude of lateral head displacement (Ah) all appeared to be important qualities.