Semen

About: Semen is a research topic. Over the lifetime, 14571 publications have been published within this topic receiving 407739 citations. The topic is also known as: come & ejaculate.

Reliability of the comet assay in cryopreserved human sperm

Abstract: BACKGROUND: Although the comet assay has potential value for measuring DNA damage in large epidemiological human sperm studies, it is impractical to perform the assay daily on fresh semen samples. Therefore, before its use in epidemiological studies, the reliability of the comet assay in measuring DNA damage in cryopreserved sperm should be compared with that in fresh human sperm. METHODS: Semen samples from 16 men were cryopreserved in liquid nitrogen (LN) using four methods: flash freezing with and without cryopreservative, and programmable freezing with and without cryopreservative. Neutral microgel electrophoresis was performed and comets were stained with YOYO-1. Comet length was measured using an eyepiece micrometer at 400 magnification. RESULTS: The highest correlation was between comet assay results obtained from fresh human semen compared with semen flash frozen without cryopreservative (R 0.88). However, the method of cryopreservation, as compared with other sources of variability, accounted for only 6% of the variability. Inter-individual variability accounted for 20%, and individual sperm-to-sperm variability within an ejaculate accounted for 65%. CONCLUSIONS: Flashfreezing in LN without cryopreservative most closely reproduced the results obtained using fresh human semen samples, and thereby represents the most appropriate cryopreservation method for human semen in epidemiological studies utilizing the neutral comet assay.

Sperm competition and the evolution of nonfertilizing sperm in mammals.

Abstract: Nonfertilizing sperm with special morphologies have long been known to exist in invertebrates. Until recently, abnormal sperm in mammals were considered errors in production. Now, however, Baker and Bellis (1988, 1989) have proposed that mammalian sperm, like some invertebrate sperm, are polymorphic and adapted to a variety of nonfertilizing roles in sperm competition, including prevention of passage of sperm inseminated by another male. More specifically, their "kamikaze" sperm hypothesis proposes that deformed mammalian sperm are adapted to facilitate the formation and functioning of copulatory plugs (Baker and Bellis, 1988). Here I argue that most, maybe all, mammals are unlikely to produce nonfertilizing sperm. First, mammals might not be able to afford to evolve nonfertilizing sperm, given that a) fertilization is often unlikely despite the huge numbers of sperm produced; b) production of larger numbers of sperm is constrained, presumably because of metabolic costs, evidence for which includes the fact that in species in which sperm morphology and anatomy of the female reproductive tract increase the probability of fertilization, the numbers of sperm produced is lower than in others; and c) selection appears to act against the production of deformed sperm. Second, some of the evidence advanced for the existence of nonfertilizing sperm does not in fact support the idea. Third, accessory gland secretions are sufficient on their own to coagulate semen and produce fully functioning plugs; thus the male that used accessory gland secretions would be at a clear advantage over the male that diluted his fertilizing sperm with "kamikaze" sperm; and indeed, current evidence indicates selection on accessory glands, not sperm morphology, to enhance coagulation of semen. Fourth, predictions made on the basis of the "kamikaze" sperm hypothesis are not supported by quantitative comparisons of data from polyandrous and monandrous primates (i.e., those in which several males mate with a fertile female, and therefore in which sperm competition should be operating, and those in which only one male mates). Although sperm competition is almost certainly more intense in polyandrous genera than in monandrous genera (as indicated by, e.g., more frequent copulations and the production of more sperm per ejaculate from larger spermatogenic organs), polyandrous genera do not produce a greater proportion of deformed (i.e., nonfertilizing) sperm than do monandrous genera, or even necessarily a greater number of deformed sperm; nor a greater variety of sperm sizes-indeed they might produce fewer; nor fewer motile sperm (as might be expected if sperm are selected to stay behind and compete with sperm from subsequent males); and nor larger sperm (as might be expected if sperm are produced for functions other than to reach the egg). In sum, currently available evidence suggests that the function of all mammalian sperm is to fertilize, and that sperm competition in mammals occurs through scramble competition, not contest competition.

Characterizing semen parameters and their association with reactive oxygen species in infertile men.

Abstract: A routine semen analysis is a first step in the laboratory evaluation of the infertile male. In addition, other tests such as measurement of reactive oxygen species can provide additional information regarding the etiology of male infertility. The objective of this study was to investigate the association of semen parameters with reactive oxygen species (ROS) in two groups: healthy donors of unproven and proven fertility and infertile men. In addition, we sought to establish an ROS cutoff value in seminal plasma at which a patient may be predicted to be infertile. Seminal ejaculates from 318 infertile patients and 56 donors, including those with proven fertility were examined for semen parameters and ROS levels. Correlations were determined between traditional semen parameters and levels of ROS among the study participants. ROS levels were measured using chemiluminescence assay. Receiver operating characteristic curves were obtained to calculate a cutoff value for these tests. Proven Donors (n = 28) and Proven Donors within the past 2 years (n = 16) showed significantly better semen parameters than All Patients group (n = 318). Significantly lower ROS levels were seen in the two Proven Donor groups compared with All Patients. The cutoff value of ROS in Proven Donors was determined to be 91.9 RLU/s with a specificity of 68.8% and a sensitivity of 93.8%. Infertile men, irrespective of their clinical diagnoses, have reduced semen parameters and elevated ROS levels compared to proven fertile men who have established a pregnancy recently or in the past. Reactive oxygen species are negatively correlated with traditional semen parameters such as concentration, motility and morphology. Measuring ROS levels in the seminal ejaculates provides clinically-relevant information to clinicians.