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D Y Chen

Publications and source records attributed to D Y Chen.

112 records · Page 7Linked to original sources
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Expression and phosphorylation of mitogen-activated protein kinases during spermatogenesis and epididymal sperm maturation in mice.

The expression and phosphorylation/dephosphorylation of mitogen-activated protein (MAP) kinases during mouse spermatogenesis and epididymal sperm maturation have been investigated by immunoblotting and immunohistochemical staining with commercially available anti-ERK2 and anti-Active MAPK antibodies. Two forms of MAP kinases, p42ERK2 and p44ERK1, were expressed in a similar amount in spermatogenic cells at different stages. ERK1 and ERK2 were phosphorylated (activated) in early spermatogenic cells from primitive spermatogonia to zygotene primary spermatocytes, while only a small quantity of phosphorylated MAP kinases could be detected in pachytene primary spermatocytes and spermatids. MAP kinase activity in primative spermatogonia and preleptotene primary spermatocytes was the highest among spermatogenic cells. ERK1 and ERK2 were also present in epididymal spermatozoa, and their phosphorylation was increased while spermatozoa pass through epididymis and vas deferens for maturation. It would appear that MAP kinase activation may contribute to the mitotic proliferation of primative spermatogonia, an early phase of spermatogenic meiosis, and, later, sperm motility acquirement.

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Mitogen-activated protein kinase and cell cycle progression during mouse egg activation induced by various stimuli.

A very sensitive method was established for detecting the activity of mitogen-activated protein (MAP) kinase in mouse eggs, and used to follow temporal changes of this kinase during fertilization and spontaneous or chemically-induced parthenogenic activation. MAP kinase activity increased between 1 and 2.5 h post-insemination, at which time the second polar body was emitted and sperm chromatin was dispersed; its activity decreased sharply at 8 h. when pronuclei were formed. Both calcium ionophore A23187 and ethanol simultaneously induced pronuclear formation and MAP kinase inactivation in aged eggs 8 h after incubation but less effectively in fresh eggs. The protein kinase inhibitor staurosporine induced pronuclear formation and MAP kinase inactivation more quickly than other treatments, with MAP kinase inactivation occurring slightly proceeding pronuclear formation. Okadaic acid, a specific inhibitor of protein phosphatase 1 and 2A, induced increase in MAP kinase activity, and overcame pronuclear formation induced by various stimuli. MAP kinase inactivation preceded pronuclear formation in eggs spontaneously activated by aging in vitro, perhaps due to cytoplasmic degeneration and thus delayed response of nuclear envelope precursors to MAP kinase inactivation. These data suggest that MAP kinase is a key protein kinase regulating the events of mouse egg activation. Increased MAP kinase activity is temporally correlated with the second polar body emission and sperm chromatin decondensation. Although different stimuli (including sperm) may initially act through different mechanisms, they finally inactivate MAP kinase, probably by allowing the action of protein phosphatase, and thus induces the transition to interphase.

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