Sperm Life Research Articles

Genetic evaluation for milk and semen variables on Egyptian buffaloes

2584 lactation records of Egyptian buffaloes calving between1992 to 2010 kept at Natafe El Gadded farm were studied. Several variables Animal model (SVAM) was used. Milk variables are milk production (MP), days in milk (DM), and calving interval (CI) and semen quality are ejaculate volume (EV) life of sperm (LS) and total Motility (TM). The overall means of MP, LL, CI, EV, LS, and TM were 2025 kg, 203 d, 447 d, 3.25 ml, 65.91% and 58.40%, respectively. Heritabilities were 0.23, 0.13, 0.02, 0.08, 0.27 and 0.24, for milk production, lactation length, current calving interval, ejaculate volume, live of sperm and total motility, respectively. Genetic association among MP and each of DM and CI were positive and were 0.80, 0.04, respectively, while among DM and CI was negative (-0.54). Genetic association among EV and each of LS and TM were .04 and -0.03, respectively, while among LS and TM was (1.0). In conclusion, our findings provide useful information on the heritability of milk production, life of sperm and mass motility traits in Egyptian buffaloes and relationships among them and should assist in selection for improvement of milk yield and semen traits in Egyptian buffaloes and bulls.

Effects of FSH on Sperm DNA Fragmentation: Review of Clinical Studies and Possible Mechanisms of Action.

Sperm DNA fragmentation (sDF) is an important reproductive problem, associated to an increased time-to-pregnancy and a reduced success rate in natural and in vitro fertilization. sDF may virtually originate at any time of sperm's life: in the testis, in the epididymis, during transit in the ejaculatory ducts and even following ejaculation. Studies demonstrate that an apoptotic pathway, mainly occurring in the testis, and oxidative stress, likely acting in the male genital tract, are responsible for provoking the DNA strand breaks present in ejaculated spermatozoa. Although several pharmacological anti-oxidants tools have been used to reduce sDF, the efficacy of this type of therapies is questioned. Clearly, anti-apoptotic agents cannot be used because of the ubiquitous role of the apoptotic process in the body. A notable exception is represented by Follicle-stimulating hormone (FSH), which regulates testis development and function and has been demonstrated to exert anti-apoptotic actions on germ cells. Here, we review the existing clinical studies evaluating the effect of FSH administration on sDF and discuss the possible mechanisms through which the hormone may reduce sDF levels in infertile subjects. Although there is evidence for a beneficial effect of the hormone on sDF, further studies with clear and univocal patient inclusion criteria, including sDF cut-off levels and considering the use of a pharmacogenetic approach for patients selection are warranted to draw firm conclusions.

No evidence of trade-offs in the evolution of sperm numbers and sperm size in mammals.

Post-copulatory sexual selection, in the form sperm competition, has influenced the evolution of several male reproductive traits. However, theory predicts that sperm competition would lead to trade-offs between numbers and size of spermatozoa because increased costs per cell would result in a reduction of sperm number if both traits share the same energetic budget. Theoretical models have proposed that, in large animals, increased sperm size would have minimal fitness advantage compared with increased sperm numbers. Thus, sperm numbers would evolve more rapidly than sperm size under sperm competition pressure. We tested in mammals whether sperm competition maximizes sperm numbers and size, and whether there is a trade-off between these traits. Our results showed that sperm competition maximizes sperm numbers in eutherian and metatherian mammals. There was no evidence of a trade-off between sperm numbers and sperm size in any of the two mammalian clades as we did not observe any significant relationship between sperm numbers and sperm size once the effect of sperm competition was taken into account. Maximization of both numbers and size in mammals may occur because each trait is crucial at different stages in sperm's life; for example size-determined sperm velocity is a key determinant of fertilization success. In addition, numbers and size may also be influenced by diverse energetic budgets required at different stages of sperm formation.

Proteins Involved in Motility and Sperm-Egg Interaction Evolve More Rapidly in Mouse Spermatozoa

Proteomic studies of spermatozoa have identified a large catalog of integral sperm proteins. Rapid evolution of these proteins may underlie adaptive changes of sperm traits involved in different events leading to fertilization, although the selective forces underlying such rapid evolution are not well understood. A variety of selective forces may differentially affect several steps ending in fertilization, thus resulting in a compartmentalized adaptation of sperm proteins. Here we analyzed the evolution of genes associated to various events in the sperm’s life, from sperm formation to sperm-egg interaction. Evolutionary analyses were performed on gene sequences from 17 mouse strains whose genomes have been sequenced. Four of these are derived from wild Mus musculus, M. domesticus, M. castaneus and M. spretus. We found a higher proportion of genes exhibiting a signature of positive selection among those related to sperm motility and sperm-egg interaction. Furthermore, sperm proteins involved in sperm-egg interaction exhibited accelerated evolution in comparison to those involved in other events. Thus, we identified a large set of candidate proteins for future comparative analyses of genotype-phenotype associations in spermatozoa of species subjected to different sexual selection pressures. Adaptive evolution of proteins involved in motility could be driven by sperm competition, since this selective force is known to increase the proportion of motile sperm and their swimming velocity. On the other hand, sperm proteins involved in gamete interaction could be coevolving with their egg partners through episodes of sexual selection or sexual conflict resulting in species-specific sperm-egg interactions and barriers preventing interspecies fertilization.

15 HEAT SHOCK COGNATE 70 PROTEIN IMPROVES THE LONG-TERM SURVIVAL OF RAM SPERMATOZOA DURING STORAGE AT 17°C IN A COMMERCIAL EXTENDER

Heat shock proteins (HSPs) are highly represented among oviductal epithelial cell (OEC) plasma membrane proteins (Sostaric et al. 2006 J. Proteome Res. 5, 3029–3027); their abundance increases in oviductal fluid in response to the presence of spermatozoa (Georgiou et al. 2005 Mol. Cell. Proteomics 4, 1785–1796), and they are capable of binding directly to spermatozoa (Boilard et al. 2004 Biol. Reprod. 71, 1879–1889). As a result of these observations, a role for HSPs in prolonging the functional life of spermatozoa in the oviduct prior to fertilization has been proposed. Poor fertility rates are often observed when fresh ram semen stored in conventional extenders is used for cervical AI (Salamon and Maxwell 2000 Anim. Reprod. Sci. 62, 77–111). This is due, in part, to extenders being unable to maintain the functional life of ram spermatozoa to the same extent as the oviduct. Therefore, in this study, we aimed to determine the effect of supplementing extenders with the HSPs, HSC70 and HSP70, on the maintenance of ram sperm function during storage. Eight freshly collected ram semen ejaculates were split and diluted in the extenders, INRA96 and RSD-1, to 25 � 106 spermatozoa mL–1, either alone (control) or supplemented with HSC70, HSP70, or α-tubulin (protein with a molecular weight similar to that of the two HSPs). The final concentration of protein in each case was 4 µg mL–1, and the samples were stored at 17�C for 48 h. At 1 h, 6 h, 24 h, and 48 h, the viability and DNA integrity of the stored spermatozoa was determined using the live and dead stains, SYBR�-14 and ethidium homodimer, and the Sperm-Ovis-Halomax kit, respectively. In each case, the mean percentage (%) of viable and DNA-fragmented (DF) spermatozoa was determined and log-transformed prior to analysis using factorial ANOVA. Statistical significance was defined as P < 0.05. In INRA96, but not RSD-1, the beneficial effect of protein supplementation on the % of viable spermatozoa observed during storage was significant (P < 0.001). Most noteworthy was INRA96 supplemented with HSC70, which maintained the % of viable spermatozoa observed during storage significantly (P < 0.001) better than INRA96 alone. Protein supplementation had no significant effect on the % of DF spermatozoa observed during storage. However, the % of DF spermatozoa observed increased significantly (P < 0.001) during storage, irrespective of the presence or absence of protein. On the basis of these findings, it is not implausible to suggest that supplementing the commercially available INRA96 extender with HSC70 would improve the fertility rates observed following cervical AI using stored ram semen. Furthermore, the increase in the incidence of DNA-fragmented spermatozoa observed during storage offers a potential explanation as to why poor fertility rates are often observed when ram semen stored in conventional extenders is used for cervical AI.

The potential impact of sperm encapsulation technology on the importance of timing of artificial insemination: a perspective in the light of published work.

To facilitate artificial insemination with encapsulated spermatozoa independently of oestrus, ways must be found to extend the life of spermatozoa at body temperature, and to devise encapsulation procedures which will allow progressive release of viable spermatozoa over several days. In the past, the most common approach to the preservation of semen has been the principle of reduced temperature. However, the research literature presents several promising clues to the resolution of these problems; these are reviewed, and new directions are identified and explored. The potential impact of a successful encapsulation technology is recognized as the driving force for implementing the novel research required.

Survival and aging of spermatozoa: A review

Both confirmatory and disputive evidence is presented on the hypothesis that spermatozoa aging in the female tract lose their ability to contribute to normal embryonic development before losing their capacity for fertilization. Studies of spermatozoa aging in female rats and guinea pigs have demonstrated no coincident increases in pre or postimplantation losses while other studies in rabbits have demonstrated such a relationship. One such study found that spermatozoa aging of 29 hours resulted in post implantation losses of 47% compared with 27% in controls. Another study observed an increase in chromosome anomalies at 30 hours aging. While the duration of fertilizing capacity of spermatozoa in the female tract varies widely within mammalian species spermatozoa generally maintain their motility much longer than their ability to fertilize ova. In mammals with estrus cycles and in induced ovulators the fertilizing life of spermatozoa is approximately equal to or greater than the maximum time between insemination and ovulation. Among mammals length of spermatozoan survival differs in different regions of the reproductive tract. In women the acidic vaginal milieu (pH 3 to 4) seems to limit spermatozoan life in the vagina. Hexosamines and carbohydrates in free or polysaccharide forms may contribute to the extended longevity of spermatozoa in the cervix. Estrogen (exogenous and endogenous) appears enhance spermatozoan survival in cervical secretions. Upon their deposition in the female reproductive tract spermatozoa are subjected to increased temperature changes in pH and great dilution and leukocyte invasion in the oviducts and uterus. Spermatozoa become highly motile. Capacitation and increased metabolism of spermatozoa may also limit survival. It is suggested that the ability of the spermatozoan aged in the male tract to contribute to a loss and a postimplantation loss. Aging in the male tract has been associated with an incidence of chromosomnomalies. Further study is required to determine wheter spermatozoan aging contributes significantly to reproductive failure in man.