Transcriptome and gene expression profile of ovarian follicle tissue of the triatomine bug Rhodnius prolixus

Insect oocytes grow in close association with the ovarian follicular epithelium (OFE), which escorts the oocyte during oogenesis and is responsible for synthesis and secretion of the eggshell. We describe a transcriptome of OFE of the triatomine bug Rhodnius prolixus, a vector of Chagas disease, to increase our knowledge of the role of FE in egg development. Random clones were sequenced from a cDNA library of different stages of follicle development. The transcriptome showed high commitment to transcription, protein synthesis, and secretion. The most abundant cDNA was a secreted (S) small, proline-rich protein with maximal expression in the vitellogenic follicle, suggesting a role in oocyte maturation. We also found Rp45, a chorion protein already described, and a putative chitin-associated cuticle protein that was an eggshell component candidate. Six transcripts coding for proteins related to the unfolded-protein response (UPR) by were chosen and their expression analyzed. Surprisingly, transcripts related to UPR showed higher expression during early stages of development and downregulation during late stages, when transcripts coding for S proteins participating in chorion formation were highly expressed. Several transcripts with potential roles in oogenesis and embryo development are also discussed. We propose that intense protein synthesis at the FE results in reticulum stress (RS) and that lowering expression of a set of genes related to cell survival should lead to degeneration of follicular cells at oocyte maturation. This paradoxical suppression of UPR suggests that ovarian follicles may represent an interesting model for studying control of RS and cell survival in professional S cell types. (C) 2011 Elsevier Ltd. All rights reserved.

Sex difference in the suppressive effect of cortisol on pulsatile secretion of luteinizing hormone in sheep

We tested the hypothesis that there are sex differences in the inhibitory effect of cortisol on pulsatile LH secretion and pituitary responsiveness to GnRH in gonadectomized sheep. In experiment 1, pulsatile LH secretion was examined in gonadectomized ewes and rams infused with either saline, a low (250 µg/kg·h) or a high (500 µg/kg·h) dose of cortisol for 30 h. In experiment 2, direct pituitary actions of cortisol were assessed by monitoring LH pulse amplitude in response to exogenous GnRH in hypothalamo-pituitary disconnected ewes and rams infused with the low dose of cortisol. In experiment 1, the mean (±SEM) plasma LH concentration was (P < 0.05) reduced significantly during cortisol infusion in both sexes, but the effect was greater in rams. In ewes, LH pulse amplitude and frequency were reduced (P < 0.05) at the high, but not the low, cortisol dose, whereas total LH output (LH pulse amplitude multiplied by frequency) was reduced (P < 0.05) at both doses. In rams, LH pulse frequency and amplitude and total LH output were (P < 0.05) reduced significantly at both cortisol doses. In experiment 2, plasma LH concentration and pulse amplitude in response to exogenous GnRH were not affected by infusion of cortisol in either sex. We conclude that gonadectomized rams are more sensitive than gonadectomized ewes to the effects of cortisol to inhibit LH secretion and that sex differences exist in the specific actions of cortisol on LH pulses. The results of experiment 2 suggest that intact hypothalamic input to the pituitary is necessary for cortisol to inhibit pituitary responsiveness to GnRH.

Sustained but not repeated acute elevation of cortisol impaired the luteinizing hormone surge, estrus, and ovulation in gilts

We tested the hypothesis that sustained and repeated acute elevation of cortisol would impair the LH surge, estrus, and ovulation in gilts. Cortisol was injected intramuscularly, to achieve a sustained elevation of plasma concentrations of cortisol, or intravenously, to achieve an acute elevation of plasma concentrations of cortisol. Control gilts received i.m. injections of oil and i.v. injections of saline. These treatments were administered to gilts (n = 6 per treatment) at 12-h intervals from Days 7 to 11 of the estrous cycle until after estrus ceased or until Day 27 or 28 of the estrous cycle, whichever came first. The repeated acute elevation of cortisol had no effect on the LH surge, estrus, or ovulation. In contrast, when the elevation of cortisol was sustained, the LH surge, estrus, and ovulation were inhibited. We conclude that cortisol is capable of direct actions to impair reproductive processes in female pigs but that plasma concentrations of cortisol need to be elevated for a substantial period for this to occur.

Insuficiência de vitamina D em pacientes infectados pelo HIV tratados com terapia antirretroviral contendo tenofovir

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Insuficiência de vitamina D em pacientes infectados pelo HIV tratados com terapia antirretroviral contendo tenofovir

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Hypothyroidism in adult male rats alters posttranscriptional mechanisms of luteinizing hormone biosynthesis

BACKGROUND: Studies in men are not consistent regarding the effects of thyroid hormone on the production of gonadotropins. In hypothyroidism consequent to diverse causes, an increase or no change in serum luteinizing hormone (LH) have been reported. The attempt to explain the mechanisms involved in this pathology using rats as an experimental model also seems to repeat this divergence, since hypothyroidism has been shown to induce hypogonadotropic hypogonadism, a hypergonadotropic state, or not to affect the basal levels of LH. Notably, the promoter region of the gene encoding the Lh beta subunit and GnRH (gonadotropin-releasing factor) does not contain a thyroid responsive element. Therefore, we investigated the hypothesis that, in male rats, posttranscriptional mechanisms of LH synthesis are altered in hypothyroidism. We also attempted to determine if hypothyroidism directly affects testicular function in male rats. METHODS: Male Wistar rats, 60 days old, were thyroidectomized or sham-operated. After 20 days, they were decapitated, and the pituitaries were collected and analyzed for Lh mRNA, LH content, poly(A) tail length, and polysome profile. The testes were collected and analyzed for Lh receptor mRNA, LH receptor content, and histology using morphometric analyses. The testis, epididymis, seminal vesicle, and ventral prostate were weighed, and serum concentrations of LH, testosterone, thyrotropin (TSH), and triiodothyronine (T3) were measured. RESULTS: Hypothyroidism was associated, in the pituitary, with an increase in Lh mRNA expression, a reduction in Lh mRNA poly(A) tail length, a reduction in the number of LH transcripts associated with polysomes. Pituitary LH was decreased but serum LH was increased from 102 to 543 pg/mL. Despite this, serum testosterone concentrations were decreased from 1.8 to 0.25 ng/mL. A decreased germinative epithelium height of the testes and a reduced weight of androgen-responsive tissues were observed (ventral prostrate: 74 vs. 23 mg/100 g body weight [BW]; seminal vesicle undrained: 280 vs. 70 mg/100 g BW; and seminal vesicle drained: 190 vs. 60 mg/100 g BW). CONCLUSIONS: Hypothyroidism in adult male rats has dual effects on the pituitary testicular axis. It alters posttranscriptional mechanisms of LH synthesis and probably has a direct effect on testicular function. However, these data suggest the possibility that reduced LH bioactivity may account in part for impaired testicular function.

Studies on Estradiol, growth hormone, and suppressors of cytokine signalling-2, and the influence in liver metabolism

Programa de doctorado: Clínica Veterinaria e Investigación Terapéutica