Aron R. Johnson

A quality control system for the optimized sperm penetration assay

OBJECTIVE To develop a quality control system for the optimized sperm penetration assay (SPA) and to use this system to monitor interassay variability and stability over time. DESIGN Four semen donors were tested consecutively for a period of weeks (7 to 139 weeks) with the SPA. Their average semen analyses and SPA scores were evaluated to monitor natural biologic variation. Intra-assay variation was obtained by dividing 11 semen samples into three aliquots and testing each separately in the SPA. A single ejaculate from seven individuals was aliquoted and frozen to be used as a control. They were tested on different assay days in 1986 and subsequently in 1991 to evaluate the assay stability over time. MAIN OUTCOME MEASURES Results were expressed as a sperm capacitation index (mean number of sperm penetrations per ovum). RESULTS Consecutive weekly semen analyses and SPAs on donors exhibited coefficients of variation ranging from 20% to > 40%. In contrast, these variations were much greater than intra-assay variability. Analysis of frozen semen specimens tested in several SPAs also displayed a low coefficient of variation. When aliquots of these frozen samples were tested in the SPA 5 years later, there were no differences in the observed values, showing the remarkable stability of this assay over time. The lower limit of the normal fertile range did not change over a period of 2 years. CONCLUSIONS Results show that using fresh semen samples as a positive control in the SPA is inadequate. This deficiency has been overcome with the use of frozen semen controls. With frozen semen for quality control, the optimized SPA developed in this laboratory is a highly reproducible assay that meets the strict criteria required for clinical laboratory certification.

Effect of aging and cold temperature storage of hamster ova as assessed in the sperm penetration assay

The penetration of zona pellucida-free hamster ova by human spermatozoa has been used to quantitate sperm penetration potential. However, since mammalian eggs in vitro have limited viability, the effect of in vitro aging on the ability of hamster ova to be penetrated by human spermatozoa was examined. Zona-free ova maintained at room temperature (25 degrees C) lost their ability to be subsequently penetrated with a half-life of 50.1 +/- 8.8 minutes. This was partly the result of removing the zona pellucida by trypsin digestion, since zona-free oocytes in the presence of trypsin inhibitor or zona pellucida-intact oocytes had half-lives of 99.1 +/- 15.2 and 120.5 +/- 17.4 minutes, respectively. Reduction in penetration rates associated with ovum aging did not appear to be due to loss of viability and could be completely prevented by maintaining the ova on ice (4 degrees C). In the presence of TEST-yolk buffer at 4 degrees C, ova retained (100%) their ability to be penetrated for up to 24 hours and were morphologically indistinguishable from fresh ova. These observations show that ovum aging in vitro at 25 degrees C is much greater than previously anticipated. This may result in artifactually low and variable scores in the penetration bioassay.

The microsperm penetration assay: Development of a sperm penetration assay suitable for oligospermic males

OBJECTIVE To develop a specialized sperm penetration assay (SPA) for the evaluation of sperm from oligospermic patients. DESIGN The development of the assay is in four parts: determine optimal sperm number; demonstrate quality control; establish statistical limits for fertile population; compare results to in vitro fertilization (IVF) outcome. SETTING AND PATIENTS A group of 63 patients with oligospermia and/or poor motility and a group of 17 fertile donors were compared using the optimized SPA and the micro-SPA. Sperm from a third group of 35 patients were simultaneously incubated with human ova (IVF) and hamster ova (micro-SPA). MAIN OUTCOME MEASURES Both types of SPA scores are expressed as a sperm capacitation index (penetrations per ovum). Outcome of IVF is expressed as a percent of ova fertilized. RESULTS Using 25,000 sperm was found to be optimal. The normal fertile range was statistically determined to have a lower limit (-2 SD) of 2.0 penetrations per ovum. When scores from 63 male factor patients were compared using the optimized SPA, only 43% had sufficient swim-up sperm. However, the micro-SPA could accurately test 100% of the samples because it requires only one tenth the number of sperm. CONCLUSION The micro-SPA provides a valuable diagnostic test for the evaluation of the male factor patient.

Rapid method for quantitation of androgen binding protein in Sertoli cell cultures and its use for measurement of binding kinetics.

The accurate measurement of the kinetics of binding of 5 alpha-dihydrotestosterone to the Sertoli cell specific protein, androgen binding protein (ABP), has been frustrated by the extremely rapid rate of dissociation of the ABP-dihydrotestosterone complex. We describe a rapid and highly sensitive assay suitable for ABP quantitation which utilizes DEAE Bio-Gel and [3H]dihydrotestosterone. The assay has been used to accurately measure the rate of dissociation (8.25 X 10(-4) s-1, t1/2 14 min) and the rate of association (2.04 X 10(5) M s-1) of the binding of [3H]dihydrotestosterone to rat ABP. The ratio of these rate constants is in perfect agreement with the equilibrium dissociation constant determined by Scatchard analysis (4.0 nM). This multipoint assay is extremely rapid such that binding can be measured at equilibrium, it has high precision (coefficient of variation 3%), and is particularly useful at low protein concentrations (50 ng/ml); furthermore, the assay background of nonspecific 3H-binding is extremely low (0.2%). Since at such low protein concentrations a 10 point Scatchard analysis can be performed on 1 ml culture medium containing as little as 3 fmol ABP, the assay is suitable for monitoring changes in ABP secretion resulting from manipulations of cells in culture. The assay which utilizes DEAE Bio-Gel A is compared to five alternative methods: the standard method of steady state gel electrophoresis, Dextran-coated charcoal assay, hydroxylapatite assay, DEAE filter assay, and radioimmunoassay. The DEAE Bio-Gel assay has advantages over all of these alternative methods. In summary, this new assay is particularly useful for monitoring temporal changes in the secretion of ABP, and the method is equally effective in quantitating ABP in rat, rabbit and hamster Sertoli cell cultures.

A simple method for preparing modified TES and Tris yolk buffer that is optically clear and membrane filterable.

OBJECTIVES To determine whether modified TES and Tris (TEST) yolk buffer (TYB) made using a commercially available egg yolk extract would exhibit lab performance characteristics equal to the existing preparation made with whole egg yolk and to define the phospholipid content of the new modified TYB formulation. DESIGN Divided ejaculates from 21 normozoospermic and 7 oligozoospermic males presenting for pre-IVF evaluation were stored at 0 to 4 degrees C for 42 hours using commercially available or modified TYB before analysis in the optimized sperm penetration assay (SPA). SETTING A commercial tissue culture manufacturer and a clinical fertility reference laboratory. MAIN OUTCOME MEASURES Sperm swim-up recoveries and average penetrations per ovum, determined by the SPA, were used as measures of sperm function. High-pressure liquid chromatography (HPLC) was used to profile the egg yolk extract. RESULTS No significant differences in either sperm swim-up recovery rates or SPA results were found in normal or poor quality semen that was treated with modified or commercial TYB. The major constituent in commercial egg yolk extract is lecithin. CONCLUSIONS Commercially available egg yolk extract passes easily through a 0.2-microns filter, is a rich source of lecithin, and can be substituted effectively for whole egg yolk in preparing TYB.

Studies on human spermatozoa with round head syndrome**Supported in part by a grant from the Shell Companies Foundation, Incorporated.††Presented at the Fortieth Annual Meeting of The American Fertility Society, April 2 to 7, 1984, New Orleans, Louisiana.

The ability of spermatozoa with round head syndrome to penetrate zona pellucida-free hamster ova and to undergo nuclear decondensation was studied in three infertile patients. Whereas spermatozoa from pregnancy-proven donors bound to hamster ova and achieved a penetration rate of 100%, those with round heads did not bind to or penetrate any ova. While spermatozoa nuclear decondensation occurs after ovum penetration and indicates a positive result, it has now been demonstrated that this phenomenon can also be induced by incubating spermatozoa with crushed hamster ova. In addition, nuclei from normal and round-headed spermatozoa decondense in the presence of these ova to a similar degree. These observations suggest that infertility related to round head sperm morphology is associated with an inability to interact with and penetrate the oolemma, rathern than dysfunctional spermatozoan changes following penetration.