Browsing by Author "Oliva, C"

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    Cyclooxygenase-2/PGE(2) system mediates the effect of platelet activating factor in oviductal ciliated cells.
    (SOC STUDY REPRODUCTION, 1998) Villalon, M; Morales, B; Barrera, N; Oliva, C
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    Gonadotrophin-releasing hormone antagonists inhibit sperm binding to the human zona pellucida
    (1999) Morales, P; Kerr, B; Oliva, C; Pizarro, E; Kong, M
    Previous work from our laboratory indicated that gonadotrophin-releasing hormone (GnRH) increases human sperm-zona pellucida binding. Here we present evidence that GnRH antagonists inhibit sperm-zona pellucida binding in humans. Motile spermatozoa (10(7) cells/ml) were incubated in modified Tyrode's medium at 37 degrees C, in 5% CO2 in air. After 4.5 h, aliquots of spermatozoa were treated with saline (control) or with different concentrations of GnRH antagonists (test), Each sperm aliquot was then tested in the hemizona binding assay. In this assay, the control aliquot was incubated with half a human zona pellucida (hemizona) and the test aliquot was incubated with the matching half. After 20 min, the hemizonae were withdrawn and the number of zona-bound spermatozoa counted using phase-contrast microscopy, In addition, the effect of GnRH antagonists upon the pattern of sperm movement, frequency of sperm-zona pellucida collisions, and percentage of living and acrosome-reacted spermatozoa was determined. The results indicated that treatment with GnRH antagonists decreased the number of zona-bound spermatozoa and did not change the pattern of sperm movement, frequency of sperm-zona collisions, and percentage of acrosome-reacted spermatozoa, We suggest that this action of GnRH antagonists may be due to an effect on zona receptors on the sperm plasma membrane.
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    Syndecan-4 regulates non-canonical Wnt signalling and is essential for convergent and extension movements in Xenopus embryos
    (2006) Muñoz, R; Moreno, M; Oliva, C; Orbenes, C; Larraín, J
    Early shaping of Xenopus laevis embryos occurs through convergent and extension movements, a process that is driven by intercalation of polarized dorsal mesodermal cells and regulated by non-canonical Wnt signalling(1-3). Here, we have identified Xenopus syndecan-4 (xSyn4), a cell-surface transmembrane heparan sulphate proteoglycan. At the gastrula stage, xSyn4 is expressed in the involuting dorsal mesoderm and the anterior neuroectoderm. Later, it is found in the pronephros, branchial arches, brain and tailbud. Both gain- and loss-of-function of xSyn4 impaired convergent extension movements in Xenopus embryos and in activin-treated ectodermal explants. xSyn4 interacts functionally and biochemically with the Wnt receptor Frizzled7 (xFz7) and its signal transducer Dishevelled (xDsh). Furthermore, xSyn4 is necessary and sufficient for translocation of xDsh to the plasma membrane - a landmark in the activation of non-canonical Wnt signalling(1-3). Our results suggest that the ability of xSyn4 to translocate xDsh is regulated by fibronectin, a component of the extracellular matrix required for proper convergent extension movements(4-6). We propose a model where xSyn4 and fibronectin cooperate with xFz7 and Wnt in the specific activation of the non-canonical Wnt pathway.