Browsing by Author "Croxatto, Horacio B."

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    Early fitness consequences and hormonal correlates of parental behaviour in the social rodent, Octodon degus
    (2010) Ebensperger, Luis A.; Ramirez-Otarola, Natalia; Leon, Cecilia; Ortiz, Maria E.; Croxatto, Horacio B.
    Males are expected to assist their mates whenever this behaviour raises survival of offspring with little expense in terms of mating opportunities At a more proximate level cortisol and testosterone hormones seem involved in the expression of parental care in mammals We examined the consequences to postnatal offspring development and survival of the males presence in the social rodent Octodon degus Offspring quality and quantity and maternal condition of females were contrasted among females rearing their litters in the presence of the sire females breeding in the presence of a non-breeding female and females breeding solitarily We related these differences to variation in parental behaviour and plasma levels of testosterone and cortisol Twenty two females and their litters were studied under constant conditions of adult density nest availability food availability and breeding experience Males huddled over and groomed offspring However neither the number nor the mass of pups from dams that nested with the sire differed from those recorded to breeding females that nested with a non-breeding female and females that nested solitarily Body weight loss and associated levels of plasma cortisol in dams nesting with the sire were similar to those of solitary females but higher than mothers nesting with a non-breeding female Thus male care had no consequences to offspring and seemed detrimental to breeding females Circulating levels of cortisol and total testosterone were either poor (mothers) or no (fathers non-breeding females) predictors of parental care (C) 2010 Elsevier Inc All rights reserved
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    Effect of oestradiol and progesterone on the instant and directional velocity of microsphere movements in the rat oviduct
    (2007) Rios, Mariana; Hermoso, Marcela; Sanchez, Trinidad M.; Croxatto, Horacio B.; Villalon, Manuel J.
    The oviducal transport of eggs to the uterus normally takes 72 - 96 h in the rat, but this is reduced to less than 20 h after a single injection of oestradiol ( E2). This accelerated transport is associated with an increased frequency of pendular movements in the isthmic segment of the oviduct, with increased levels of the gap junction ( GJ) component Connexin ( Cx) 43, and is antagonised by progesterone ( P). In the present study, we investigated the effect of these hormones on the instant and directional velocity of pendular movements and the role of the GJ and its Cx43 component in the kinetic response of the oviduct to E2 and P. Using microspheres as egg surrogates, microsphere instant velocity ( MIV) was measured following treatment with E2, P or P+ E2, which accelerate or delay egg transport. Microspheres were delivered into the oviduct of rats on Day 1 of pregnancy and their movement within the isthmic segment was recorded. Oestrogen increased MIV with faster movement towards the uterus. After P or P+ E2, MIV was similar to that in the control group. Two GJ uncouplers, namely 18 alpha- and 18 beta- glycyrrhetinic acid, blocked the effect of E2 on MIV. Connexin 43 mRNA levels increased over that seen in control with all treatments. In conclusion, the effects of E2 on MIV resulted in faster movements that produced accelerated egg transport towards the uterus. Gap junctions are probably involved as smooth muscle synchronisers in this kinetic effect of E2, but the opposing effects of E2 and P are not exerted at the level of Cx43 transcription.