Interactions Between Osmotic and Oxidative Stress

Signal transduction events in spermatozoa are generally believed to be highly regulated by cross talk among intracellular pathways. ROS have been implicated in the promotion of tyrosine phosphorylation associated with sperm capacitation [36, 97]. In addition, recent evidence indicates that components of the extracellular signalregulated kinase (ERK) family of mitogen-activated protein kinases (MAPKs) are also present in spermatozoa and might be involved in motility and capacitation [98-100]. It was suggested that O- • could modulate the ERK pathway in human sperm [101] and that H2O2 could have a similar role in the modulation ofMAPK. In somatic cells, the involvement of ROS in cellular signaling is extensive, including activation of MAPK cascades [102] . As described above, osmotic shock can also activate p38 MAPK and Jak/STAT pathways in mammalian cells [103, 104]. Interestingly, Qin and coworkers reported that in B cells ROS were involved in mediating osmotic stress-induced activation of Syk, a protein-tyrosine kinase [105]. Further, the rise in intracellular calcium as seen during freezing [106] will drive ROS generation by the enzyme NOX 5 because the latter possesses EF-hand motifs (calcium-binding regions) that give this oxidase a sensitivity to calcium [66] . The increase in temperature-induced cell calcium is due to a sudden decline in Ca2+/ Mg2+-ATPase activity that occurs as sperm pass through their lipid-phase transition temperatures, thus resulting in elevated calcium.

3.3.5.1 Protection of Cryopreserved Sperm from Oxidative Damage

The addition of enzyme scavengers or antioxidants to sperm preparations in vitro has been successful at counteracting some of the effects of oxidative stress on sperm motility, viability, lipid peroxidation, sperm-oocyte fusion, and DNA fragmentation [36, 41, 49, 50, 52, 78, 95]. Accordingly, antioxidant addition to semen extenders has been implicated for cryopreservation of sperm to minimize the potential effects of oxidative stress during the freeze-thaw process. Not surprisingly, there is a wide variation in the outcome of these studies with considerable species differences. Nonetheless, researchers have demonstrated positive effects with the addition of enzyme scavengers and antioxidants to bull, boar, human, and rabbit spermatozoa [48, 53, 56, 86, 107-110].

Pregnancy Guide

Pregnancy Guide

A Beginner's Guide to Healthy Pregnancy. If you suspect, or know, that you are pregnant, we ho pe you have already visited your doctor. Presuming that you have confirmed your suspicions and that this is your first child, or that you wish to take better care of yourself d uring pregnancy than you did during your other pregnancies; you have come to the right place.

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