Browsing by Author "Villalón, M"

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    Effect of in vivo administration of epidermal growth factor on prostaglandin production and NOS activity in term rat placentae.: Possible participation of placental EGF receptors
    (2005) Ribeiro, ML; Farina, M; Billi, S; Martínez, SP; Brañes, MC; Villalón, M; Franchi, A
    Many authors hypothesize that the epidermal growth factor (EGF) is involved in the onset of labor. Previous reports from our laboratory showed that intrauterine administration of EGF delays the beginning of labor. The alms of this study were: 1) to analyze the effect of intrauterine administration of 500 ng EGF on placental prostaglandins and nitric oxide, and 2) to characterize the expression of EGF receptors (EGF-R) in pregnant rat placentae. Saline solution (sham group) and 500 ng EGF (EGF-treated group) were administered via intrauterine injection on day 21 of gestation, and both groups of animals were sacrificed on day 22 (sham rats delivered on day 22). Results showed that EGF treatment: 1) inhibited the production of prostaglandin E (p < 0.001) and F-2 alpha (P < 0.01), 2) increased the synthesis of nitric oxide (p < 0.001), and 3) reduced the expression of cyclooxygenase-II, the enzyme responsible for PG synthesis. Placentae were found to express EGF-R and its activated form, and the expressions of both forms were higher at mid and term pregnancy. Hence, EGF is a very interesting molecule for studying the regulation of placental prostaglandin and nitric oxide production related to the parturition process.
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    Plasma and intracellular membrane inositol 1,4,5-trisphosphate receptors mediate the Ca2+ increase associated with the ATP-induced increase in ciliary beat frequency
    (2004) Barrera, NP; Morales, B; Villalón, M
    An increase in intracellular free Ca2+ concentration ([Ca2+](i)) has been shown to be involved in the increase in ciliary beat frequency (CBF) in response to ATP; however, the signaling pathways associated with inositol 1,4,5-trisphosphate (IP3) receptor-dependent Ca2+ mobilization remain unresolved. Using radioimmunoassay techniques, we have demonstrated the appearance of two IP3 peaks occurring 10 and 60 s after ATP addition, which was strongly correlated with a release of intracellular Ca2+ from internal stores and an influx of extracellular Ca2+, respectively. In addition, ATP-dependent Ca2+ mobilization required protein kinase C (PKC) and Ca2+/ calmodulin-dependent protein kinase II activation. We found an increase in PKC activity in response to ATP, with a peak at 60 s after ATP addition. Xestospongin C, an IP3 receptor blocker, significantly diminished both the ATP-induced increase in CBF and the initial transient [Ca2+](i) component. ATP addition in the presence of xestospongin C or thapsigargin revealed that the Ca2+ influx is also dependent on IP3 receptor activation. Immunofluorescence and confocal microscopic studies showed the presence of IP3 receptor types 1 and 3 in cultured ciliated cells. Immunogold electron microscopy localized IP3 receptor type 3 to the nucleus, the endoplasmic reticulum, and, interestingly, the plasma membrane. In contrast, IP3 receptor type 1 was found exclusively in the nucleus and the endoplasmic reticulum. Our study demonstrates for the first time the presence of IP3 receptor type 3 in the plasma membrane in ciliated cells and leads us to postulate that the IP3 receptor can directly trigger Ca2+ influx in response to ATP.
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    Platelet activating factor increases ciliary activity in the hamster oviduct through epithelial production of prostaglandin E2
    (2001) Hermoso, M; Barrera, N; Morales, B; Pérez, S; Villalón, M
    We investigated the signal transduction mechanisms associated with an increase in ciliary beat frequency (CBF) produced by platelet activating factor (PAF) in oviductal ciliated cell cultures. In the range of concentrations similar to that produced by preimplantation embryos, PAF increased the CBF in a dose-dependent manner. The addition of PAF and prostaglandin E-2 (PGE,) to the cultures produced a synergic increase of ciliary beating, suggesting that PAF and PGE(2) signal transduction pathways may be associated. To demonstrate this hypothesis, cyclooxygenase-2 (COX-2) was selectively blocked by a specific inhibitor, NS-398, and the PAF-induced CBF increase was abolished. Moreover, a phospholipase A2 (PLA(2)) inhibitor, AACOCF3, blocks the PAF-induced CBF increase. PGE(2) production by oviductal epithelial cells is stimulated by PAF, and WEB-2086, a PAF-receptor blocker, specifically blocks the PAF-induced PGE(2) production. Using the fluorescent indicator fura-2, we measured the effect of PAF on intracellular Ca2+ concentration ([Ca2+](i)) in individual ciliated cells. PAF induced a transient increase of [Ca2+](i) that was blocked by WEB-2086 or by removal of extracellular Ca2+. We propose a mechanism for PAF-mediated signal transduction in the ciliated cells of the oviductal epithelium. Minimal doses of PAF trigger Ca2+ mobilization in tandem with increased PLA(2) activity and a COX-2-mediated increase in PGE(2). Local PGE(2) production by the oviductal mucosa suggests the presence of an autocrine loop controlling ciliary activity.
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    Social cues and hormone levels in male Octodon degus (Rodentia)
    (2005) Soto-Gamboa, M; Villalón, M; Bozinovic, F
    Social interactions are important factors determining and regulating individual behaviors. Testosterone has been related to agonistic interactions, while glucocorticoids have been related to social stress, especially during interactions of dominance. We compared testosterone and cortisol concentrations in male degus (Octodon degus, Rodentia) under laboratory conditions without male social interactions, with data from wild males in nature. Under natural conditions, males should present higher levels of testosterone during the breeding season due to social interactions (Challenge Hypothesis). Alternatively, intense social instability could act as a stressing environment, raising glucocorticoids, which inhibit testosterone concentrations. Our results show a significant increase in agonistic interactions between males during the breeding season, and disappearance of non-agonistic male interactions during this period. Hormone levels in breeding season show nonsignificant differences between laboratory groups, but testosterone concentrations in field males were significantly higher than in laboratory males. Testosterone levels were similar among pre-breeding and breeding periods, but in field animals the concentration was similar to30% higher than in laboratory degus. In field animals, we found two different mating strategies: resident males, with territorial behavior, and transient males, displayed an opportunistic approach to females. Finally, cortisol presents a similar pattern in both laboratory and field animals; pre-breeding values of cortisol are higher than during the breeding season. This suggests that social interactions in O.degus activate a rise in testosterone, supporting the Challenge Hypothesis, and could be considered as partial support of the Social Stress Hypothesis. (C) 2004 Elsevier Inc. All rights reserved.
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    TRPV4 channel is involved in the coupling of fluid viscosity changes to epithelial ciliary activity
    (2005) Andrade, YN; Fernandes, J; Vázquez, E; Fernández-Fernández, JM; Arniges, M; Sánchez, TM; Villalón, M; Valverde, MA
    Autoregulation of the ciliary beat frequency (CBF) has been proposed as the mechanism used by,A epithelial ciliated cells to maintain the CBF and prevent the collapse of mucociliary transport under conditions of varying mucus viscosity. Despite the relevance of this regulatory response to the pathophysiology of airways and reproductive tract, the underlying cellular and molecular aspects remain unknown. Hamster oviductal ciliated cells express the transient receptor potential vanilloid 4 (TRPV4) channel, which is activated by increased viscous load involving a phospholipase A(2)-dependent pathway. TRPV4-transfected HeLa cells also increased their cationic currents in response to high viscous load. This mechanical activation is prevented in native ciliated cells loaded with a TRPV4 antibody. Application of the TRPV4 synthetic ligand 4 alpha-phorbol 12,13-didecanoate increased cationic currents, intracellular Ca2+, and the CBF in the absence of a viscous load. Therefore, TRPV4 emerges as a candidate to participate in the coupling of fluid viscosity changes to the generation of the Ca2+ signal required for the autoregulation of CBF.