979 resultados para Estrous-cycle


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Pós-graduação em Cirurgia Veterinária - FCAV

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Pós-graduação em Medicina Veterinária - FCAV

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Several studies use only male rats in their experiments, even with all the evidence of differences between the sexes, not only in the reproductive behavior but also in the development of diseases. This absence of studies using female rats is due in part to the estrous cycle. It is known that one estrous cycle lasts four to 5 days and consists of four phases: proestrus, estrus, metestrus and diestrus. Ramos et al. (1999) identified and mapped a QTL in an F2 population derived from interbreeding of strains of SHR (spontaneously hypertensive rats) and Lewis (LEW) rats and found, on chromosome 4, the first QTL of the world related to anxiety in rats. After several backcrosses between SHR and LEW strains, it was developed a congenic strain called SLA16, to refine the study of this QTL. This QTL corresponds to a large genomic region, approximately 75 million basepairs (Mb), and was first called Ofil1 (inner open field locomotion 1). Currently it is called Anxrr16 (anxiety-related response region 16) according to the rat genome database (RGD). Izidio et al. (2011) suggested that the natural fluctuation of the hormones in the estrous cycle of female rats could influence the effects of this locus on behavior. That is, females in DP (diestrus-proestrus) present the QTL in the same genomic region that males, while females in EM (estrus-metestrus) do not present it. The effects of the estrous cycle in the SLA16 strain and its isogenic control SHR were analyzed on the elevated plus maze (EPM), black and white box and on the open field test (OF). In the open field test, the SLA16 strain had higher central locomotion (F=5.0, p <0.05) and peripheral locomotion (F=12.6, p <0.01) compared to the SHR strain. In the elevated plus maze test, the SLA16 strain had the higher number of entries (F=9.5, p <0.01) and time spent in the open arms (F=10.3, p <0.01) compared to the SHR strain. Finally, in the black and white box test, the SLA16 lineage spent more time ...

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The Brazilian federal government Agency for Health Surveillance detected pesticide residues in fresh food available for consumers all over the country. The current study investigated the effects of a mixture of some of those pesticides (dichlorvos, dicofol, dieldrin, endosulfan, and permethrin) on the reproductive system of Sprague-Dawley (SD), Wistar (WT), and Lewis (LEW) rats. Female rats from each strain were randomized into three experimental groups and were fed a control diet or diets added with pesticides mixture at their respective no-observed-effect level (NOEL)/no-observed-adverse-effect level (NOAEL) (low dose) (mg/kg/d): dichlorvos (0.23), dicofol (0.5), dieldrin (0.025), endosulfan (0.7), permethrin (5), or lowest-observed-effect level (LOEL)/lowest-effect level (LEL)/ lowest-observed-adverse-effect level (LOAEL) (toxically effective dose) (mg/kg/d): dichlorvos (2.3), dicofol (2.1), dieldrin (0.05), endosulfan (3.8), and permethrin (25) as reported in the literature. Euthanasia was performed between wk 10 and 12, during the estrous stage. Decreased body weights gain (SD and WT) and increased liver weights (SD, WT, and LEW) were observed in each strain fed the pesticides mixture at the higher levels. At that dose level, rat strains also varied in their responses regarding the estrous cycle, hormonal levels, and number of developing ovarian follicles. The studied mixture of pesticides was found to interfere with the female reproductive system when individual pesticides were mixed above a certain level, indicating a threshold exists for each of the strains studied.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Progesterone (P-4), 17 beta- estradiol (E2) and androstenedione (A4) plasma concentrations were correlated with palpated corpora lutea (CL), recovered embryos and viable embryos in 13 Nelore cows induced to superovulate with FSH, starting on Day 10 of the estrous cycle. Administration of FSH increased the number of ovulations and recovered embryos. Plasma P4, E2 and A4 levels on Day O and of P4 on Days 10 and 11 of the cycle were not correlated with the superovulatory response. Determination of CL by palpation per rectum was used to estimate the number of recovered embryos. Plasma P4 levels higher than 1 ng/ml on the induced estrus day (Day 14) had an adverse effect on the embryo viability rate. Plasma E2 concentrations on Day 14 were positively correlated with the number of viable embryos collected, a correlation that has not been previously reported. The present data indicate that plasma P4 and E2 concentrations in FSH-PGF2 alpha-treated Nelore cows are useful for the identification of 2 different populations of Nelore donors and are correlated with superovulatory response and, particularly, with the number of viable embryos.

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Alterations in the hypothalamic-pituitary-gonadal axis in females determine the transition from regular to irregular reproductive cycles, with loss of fertility. Stimulation of noradrenergic neurons of the anteroventral periventricular neurons (AVPV) is essential for regular reproductive cycles. Therefore, we examined the activity of neurons of the AVPV and measure the noradrenaline (NE) of acyclic rats, in constant estrus, and compared it with that of cyclic rats in estrus. Female cyclic (4-5months) and acyclic (17-18months) rats were euthanized at 10, 14, and 18h in estrus. Brains were processed for immunoreactivity to antigens related to Fos (FRA) in AVPV, and the NE was determined by HPLC-ED. Plasma concentrations of LH, FSH, E2 and P4 were determined. In the acyclic animals, plasma LH was higher but the FSH was lower. There was decreasing P4 at different times, while the E2 was constant and lower in acyclic rats. FRA-ir expression in AVPV neurons of acyclic rats as well as turnover of NE was higher when compared with cyclic group. The preliminary findings showed increased activity in AVPV neurons in aging contribute to changes in the temporal pattern of neuroendocrine signaling, compromising the accuracy of inhibitory and stimulatory effects, causing irregularity in the estrous cycle and determining reproductive senescence.

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Pós-graduação em Biologia Geral e Aplicada - IBB