Isolation of plasma membrane from porcine spermatozoa.
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Animals↗
Biomedical subjects
E D Clegg
Publications and source records attributed to E D Clegg.
An electron-dense stain for isolated fragments of plasma and acrosome membranes from porcine sperm.
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Animals↗
Phospholipid composition of bovine sperm fractions, seminal plasma and cytoplasmic droplets.
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Animals↗
Methods for assessing sperm motility, morphology, and counts in the rat, rabbit, and dog: a consensus report. ILSI Risk Science Institute Expert Working Group on Sperm Evaluation.
Reproductive toxicity studies are increasingly including assessments of sperm parameters including motility, morphology, and counts. While these assessments can provide valuable information for the determination of potential reproductive toxicity, the methods for conducting the assessments have not been well developed in all laboratories and are continually evolving. The use of different methods in different laboratories makes comparison of data among laboratories difficult. To address the differences in methods, a working group was convened to discuss methods currently in use, share data, and try to reach consensus about optimal methods for assessing sperm parameters in rats, rabbits, and dogs. This article presents the consensus report, as well as future research needs, with the hope that optimized common methods will aid in the detection of reproductive effects and enhance interlaboratory comparisons.
Animals↗
Leydig cell hyperplasia and adenoma formation: mechanisms and relevance to humans.
Leydig cell adenomas are observed frequently in studies evaluating the chronic toxicity of chemical agents in laboratory animals. Doubts have been raised about the relevance of such responses for human risk assessment, but the question of relevance has not been evaluated and presented in a comprehensive manner by a broad group of experts. This article reports the consensus conclusions from a workshop on rodent Leydig cell adenomas and human relevance. Five aspects of Leydig cell biology and toxicology were discussed: 1) control of Leydig cell proliferation; 2) mechanisms of toxicant-induced Leydig cell hyperplasia and tumorigenesis; 3) pathology of Leydig cell adenomas; 4) epidemiology of Leydig cell adenomas; and 5) risk assessment for Leydig cell tumorigens. Important research needs also were identified. Uncertainty exists about the true incidence of Leydig cell adenomas in men, although apparent incidence is rare and restricted primarily to white males. Also, surveillance databases for specific therapeutic agents as well as nicotine and lactose that have induced Leydig cell hyperplasia or adenoma in test species have detected no increased incidence in humans. Because uncertainties exist about the true incidence in humans, induction of Leydig cell adenomas in test species may be of concern under some conditions. Occurrence of Leydig cell hyperplasia alone in test species after lifetime exposure to a chemical does not constitute a cause for concern in a risk assessment for carcinogenic potential, but early occurrence may indicate a need for additional testing. Occurrence of Leydig cell adenomas in test species is of potential concern as both a carcinogenic and reproductive effect if the mode of induction and potential exposures cannot be ruled out as relevant for humans. The workgroup focused on seven hormonal modes of induction of which two, GnRH agonism and dopamine agonism, were considered not relevant to humans. Androgen receptor antagonism, 5 alpha-reductase inhibition, testosterone biosynthesis inhibition, aromatase inhibition, and estrogen agonism were considered to be relevant or potentially relevant, but quantitative differences may exist across species, with rodents being more sensitive. A margin of exposure (MOE; the ratio of the lowest exposure associated with toxicity to the human exposure level) approach should be used for compounds causing Leydig cell adenoma by a hormonal mode that is relevant to humans. For agents that are positive for mutagenicity, the decision regarding a MOE or linear extrapolation approach should be made on a case-by-case basis. In the absence of information about mode of induction, it is necessary to utilize default assumptions, including linear behavior below the observable range. All of the evidence should be weighed in the decision-making process.
Adenoma↗
Semen quality and human fertility: a prospective study with healthy couples.
Measures of semen quality are used as surrogate measures of male fertility in clinical andrology, reproductive toxicology, epidemiology, and risk assessment. However, only limited data are available to relate those measures to fertility. This prospective study with 210 reproductive-age couples was conducted to provide information on the value of semen quality measures for predicting human male fertility potential and for development of models to estimate the effects of changes in semen quality on fertility in a given population for risk assessment. Couples without known risk factors for infertility and who had discontinued contraception to have a child were accepted. The study followed each couple for up to 12 menstrual cycles while they attempted to conceive and evaluated semen quality measures from multiple ejaculates per man with known abstinence intervals. For each cycle, the day of ovulation was predicted, and the couple was advised to have intercourse multiple times on that day and on the days around it. Among the demographic variables assessed, parity, contraception status prior to entering the study, male education level, and male smoking were associated significantly with 12-cycle pregnancy rate. Several semen quality measures also were associated significantly with pregnancy rate, with percentage morphologically normal sperm by strict criteria and measures involving total number of sperm showing particularly strong associations. Localized regression-smoothing plots of semen quality data against proportion of couples pregnant suggested levels below which fertility declines for several semen quality measures. These results have applications in both clinical andrology and in assessment of risk to male fecundity from environmental or pharmaceutical exposures. In particular, they contribute information on behavior of fertility with varying semen quality and can allow development of models to predict effects on fertility in populations from decrements in semen quality.
Adult↗
Relationship of semen quality, number of sperm inseminated, and fertility in rabbits.
The relationship between the total number of sperm inseminated, semen quality, and fertility in rabbits was investigated, using fractionated or unfractionated semen and different diluting fluids. Semen was from Dutch-belted males collected twice weekly with an artificial vagina. All does were superovulated except in Experiment 3. In Experiment 1, sperm were fractionated on discontinuous 4% and 10% bovine serum albumin columns. Sperm from each portion of the gradient, along with unfractionated controls, were diluted to give 0.25 x 10(6), 0.5 x 10(6), 1.0 x 10(6), and 2.0 x 10(6) total sperm per insemination. In Experiment 2, sperm were diluted with Dulbecco's phosphate-buffered saline to provide 0.10 x 10(6), 0.50 x 10(6), and 1.0 x 10(6) total sperm per insemination, with minimal processing time. In Experiment 3, does were allowed to kindle after inseminating 0.1 x 10(6) or 1.0 x 10(6) sperm. In Experiment 4, sperm were diluted with TALP buffer: seminal plasma 1:1 to 0.025 x 10(6), 0.05 x 10(6), and 0.10 x 10(6) total sperm per insemination. Over 2,800 embryos or unfertilized oocytes were obtained either 24 or 48 hours after insemination to measure fertility. Sperm numbers required for normal fertility were 0.50 x 10(6) in Experiment 1 and only 0.05 x 10(6) in Experiment 4. This reduction presumably was due primarily to reduced processing time and diluent change. Litter size was normal with 0.1 x 10(6) sperm (Experiment 3). In Experiment 4, computer-assisted sperm analysis (HTM 2030 system; Beverly, Massachusetts) was adapted to successfully screen out some of the "interfering" granules in rabbit semen.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Evaluation of computer-assisted semen analysis (CASA) with IDENT stain to determine sperm concentration.
This study was undertaken to compare a new fluorescent stain-based computer-assisted semen analysis (CASA) system (IDENT) for determining human sperm concentration to the manual hemacytometric method and to conventional CASA (CASA-CONV). Normal healthy semen donors as well as patients provided samples that were evaluated for sperm concentration with the CASA-IDENT method, the hemacytometer method, and CASA-CONV. Each field was examined visually to determine the sources of overcounting and undercounting for the two CASA methods. Four ranges of sperm concentration were examined: 0-10, > 10-30, > 30-100, and > 100 x 10(6)/ml. The main outcome measures were sperm concentration, debris counted as sperm, and missed sperm. Our results showed that significantly more debris was counted as sperm and more sperm were missed with CASA-CONV than CASA-IDENT. As the sperm density increased, so did the number of counting errors for the CASA-CONV system. The error rate was much greater using CASA-CONV (12.1 +/- 42.2%) than with CASA-IDENT (0.4 +/- 0.7%) when compared to hemacytometer counts (P = 0.068). We conclude that the CASA-IDENT method of sperm counting is highly accurate and less time-consuming when compared to the hemacytometer method. There are significant differences in the amount of debris counted as sperm and number of missed sperm between CASA-CONV and CASA-IDENT with varying sperm density. With both parameters, the counts are more accurate using the CASA-IDENT method.
Benzimidazoles↗
The relationship of the postcoital test and semen characteristics to pregnancy rates in 200 presumed fertile couples.
OBJECTIVE: To evaluate the postcoital test (PCT) and semen analysis (SA) in the prediction of pregnancy in 200 potentially fertile couples. METHODS: 200 couples without risk for infertility were prospectively followed for 1 year. Couples were attempting pregnancy for 12 menstrual cycles. In the first three cycles, the women underwent monthly PCTs and collected daily urines while the men provided bimonthly semen analyses. For the next nine cycles, the couples were monitored for pregnancy. The PCT included hours post-coitus, amount of mucus, spinnbarkeit, number of motile sperm, and percent of motile sperm. Since multiple PCTs and SAs were available for each couple, values were averaged to provide one mean value per couple. The Wilcoxon ranked sum test was used to detect differences in PCT and SA. RESULTS: Pregnancy occurred in 163/200 couples (82%) in 12 cycles. Mean sperm count per high-power field (p = 0.01) and mean number of highly motile sperm (p = 0.03) were higher among women in whom pregnancy occurred. Amount of mucus and spinnbarkeit were similar between women who became pregnant and those who did not. Semen concentration, motile sperm count, and percent motile sperm were significantly higher among men whose partner conceived (P < .02). Only 93 couples (47%) had PCTs that were correctly timed. CONCLUSIONS: Measures predictive of pregnancy included vigorously moving sperm per high-power field, sperm concentration, motile sperm count, and percent motility. Mucus characteristics were not predictive of pregnancy. Additionally, a high number of sperm seen in the PCT correlated with a high number of motile sperm in the SA. These results support the use of the PCT for initial evaluation of the infertile couple.
Adult↗