No abstract

The notion of a gamete recognition system that alerts females to the presence of gametes in their reproductive tract profoundly influences our understanding of the physiology of events leading to conception and the bearing of offspring. Here, we show that the female responds to gametes within her tract by modulating the environment in which pregnancy is initially established. We found distinct alterations in oviductal gene expression as a result of sperm and oocyte arrival in the oviduct, which led directly to distinct alterations to the composition of oviductal fluid in vivo. This suggests that either gamete activates a cell-type-specific signal transduction pathway within the oviduct. This gamete recognition system presents a mechanism for immediate and local control of the oviductal microenvironment in which sperm transport, sperm binding and release, capacitation, transport of oocytes, fertilization, and early cleavage-stage embryonic development occur. This may explain the mechanisms involved in postcopulatory sexual selection, where there is evidence suggesting that the female reproductive tract can bias spermatozoa from different males in the favour of the more biologically attractive male. In addition, the presence of a gamete recognition system explains the oviduct's ability to tolerate spermatozoa while remaining intolerant to pathogens.

Current protocols for boar sperm cryopreservation require the centrifugation of semen in order to separate sperm cells from the seminal plasma. This study evaluated the influence of different centrifugation regimes on both sperm recovery and yield (percentage of viable sperm with an intact acrosome relative to the initial sperm population) after centrifugation (experiment 1) as well as the influence of different centrifugation regimes on boar sperm cryosurvival (experiment 2). In both experiments, sperm-rich fractions from 3 boars were diluted, pooled, and cooled to 17ЊC before centrifugation. In experiment 1, the g-forces tested were 400, 800, 1600, and 2400 ϫ g for 3 or 5 minutes, using the standard regime (800 ϫ g for 10 minutes) as a reference. Sperm recovery (Bü rker Chamber) and yield (triple fluorescent stain of PI/R123/FITC-PNA [DNA-specific fluorochrome propidium iodide/mitochondria-specific fluorochrome rhodamine-123/acrosome-specific fluorochrome fluorescein isothiocyanate-labeled peanut (Arachis hypogaea) agglutinin]) were calculated. The highest recovery and yield (P Ͻ .05) values were achieved using 2400 ϫ g for 5 or 3 minutes and 1600 ϫ g for 5 minutes, which showed no differences (P Ͼ .05) from the reference in terms of sperm yield. In experiment 2, cooled semen was centrifuged using 3 different regimes: C1 (2400 ϫ g for 3 minutes), C2 (1600 ϫ g for 5 minutes), and C3 (800 ϫ g for 10 minutes). Pellets were diluted in lactose-egg yolk (LEY)-glycerol-Equex STM (1 ϫ 10 9 cells/mL) and frozen in 0.5-mL straws. After thawing, sperm quality was assessed after 30 and 150 minutes of incubation (37ЊC). Centrifugation regimes C1 and C2 showed significantly (P Ͻ .05) higher postthaw sperm motility (assessed with a computer-assisted semen analysis system), viability (evaluated as for experiment 1), and percentage of uncapacitated sperm (assessed with a chlortetracycline assay) than did C3. In addition, C1 had the highest (P Ͻ .05) oocyte penetrating ability (assessed with the homologous in vitro penetration test performed with immature oocytes). Malondialdehyde production, assessed with the thiobarbituric acid reactive species test, was unaffected (P Ͼ .05) by the centrifugation regime used. We conclude that high g-force (2400 ϫ g) and short centrifugation time (3 minutes) do not affect sperm recovery and yield and that, moreover, they have a positive effect on the cryosurvival of boar sperm. Therefore, we recommend the use of short-term centrifugation with a relatively high g-force (2400 ϫ g for 3 minutes) in boar sperm cryopreservation protocol.

The study evaluated the protective effect of seminal plasma (SP) added to freezing extender against cryopreservation injuries to boar spermatozoa. Pooled sperm-rich fractions collected from 9 fertile boars were frozen in 0.5-mL straws after being extended in a conventional freezing extender either alone or supplemented with 5% of SPs (SP1-SP4) collected from the sperm-rich fractions (diluted 1:1, vol/vol, in Beltsville Thawing Solution extender) from 4 boars (1-4) with known sperm cryosurvival (poor, moderate, and good sperm freezers). Cryopreservation injuries were assessed in terms of postthaw sperm motility (assessed by computer-assisted sperm analysis), viability (plasma membrane and acrosome integrity assessed simultaneously by flow cytometry), membrane lipid peroxidation (malondialdehyde [MDA] production), and the ability of thawed spermatozoa to fertilize in vitro-matured homologous oocytes. The addition of SP from good sperm freezers (SP3 and SP4) improved (P , .01) the motility and viability of thawed spermatozoa without any influence on MDA production. Moreover, SP from good sperm freezers also increased (P , .05) the percentage of penetrated (SP3) and polyspermic oocytes (SP4) with respect to the control. Neither the total amount of SP proteins, protein profiles, nor antioxidant capacity of the different SPs were related to the various cryosurvival/fertilizing capacities of the processed spermatozoa.