Sexual selection and the maintenance of species diversity in Lake Malawi cichlid fishes are greatly dependent on optical communication, which is influenced by environmental, physiological and endocrinological factors. The diversity in spectral sensitivity of cichlids has been partially attributed to differences in opsin gene expression, with each species preferentially expressing a subset of seven possible genes. Hormones such as gonadotropin releasing hormone (GnRH) can mediate changes in gene expression and the presence of GnRH immunoreactive fibers and GnRH receptors throughout the retinal layers make it an excellent candidate for mediating changes in visual processes. Effects of exogenous GnRH administration on the visual system of zebra cichlids (Metriaclima zebra) via prolonged release cholesterol implants and intubation was investigated using electroretinogram (ERG) recordings, quantitative real-time RT-PCR and in situ hybridization. Three week and ten week sampling periods were used in the intubation study. No obvious differences in spectral sensitivity were evident when looking at a-wave, b-wave and d-wave components of the ERG waveform in any of the treatment groups. A multiple mechanism model was used to describe the cone mechanisms mediating spectral sensitivity and this analysis showed that the activity of cones was shaped by opponent and non opponent cone interactions based on subsets of five opsin genes previously described in cichlids (SWS1, SWS2b, RH2b, RH2aβ, and RH2aα). Although differences in the spectral sensitivity between control and GnRH-treated fish were not evident on a functional level, there were changes in the gonadosomatic index in the intubation group. Quantitative real-time RT-PCR (qRT-PCR) and in situ hybridization demonstrated that treatment with a synthetic GnRH3 analogue using the oral intubation delivery system resulted in statistically significant changes in opsin gene expression in both three week and ten week treatment groups, specifically the upregulation of RH2b and the downregulation of RH2a opsin genes. Moreover, in situ hybridization analysis showed that the pattern of labeling for the RH2a and RH2b riboprobes corroborated the changes in opsin gene expression found in the qRT-PCR data. In contrast, GnRH treatment using the cholesterol implant delivery system did not result in significant changes in spectral sensitivity or opsin gene expression. / Thesis (Master, Biology) -- Queen's University, 2011-01-05 22:57:11.308

Factors affecting bovine ovarian responsiveness to stimulation by pregnant mare's serum gonadotropin (PMSG) were studied. Initially, the effects of plasma progesterone concentration on the response were considered using a progesterone-releasing intravaginal device (PRID) to provide an artificial source of the hormone. Due to inherent biological variation in vivo, in vitro methods were developed in which cAMP and progesterone production by granulosa cells were measured. Regardless of the size of the follicles from which the cells originated, PMSG stimulated significant cAMP accumulation. Cyclic AMP production was similar between aspirated granulosa cells and those scraped from the follicle wall, between ovaries with and without a corpus luteum from the same animal, and between follicles from animals early ( 10 days) in their estrous cycles. The PMSG failed to stimulate bovine granulosa cells to synthesize significantly more progesterone than untreated cells. Unlike porcine granulosa cells, bovine cells from antral follicles of any size appeared to luteinize spontaneously in culture. / Hormonal changes in the preovulatory follicle were measured using the PMSG/hCG-treated prepubertal gilt as a model. After hCG administration, follicular fluid levels of cAMP peaked at 4 hr followed 24 hr later by a rise in prostaglandins F and E (PGF, PGE) concentrations which peaked near the expected time of ovulation. Indomethacin injection blocked ovulation and the prostaglandin rise, although the inhibition could be reversed by the administration of PGF(,2)(alpha). Temporal changes in estrone, estradiol-17(beta), progesterone, androstenedione, testosterone and 5 (alpha)-dihydrotestosterone were also measured. / In an effort to decrease endogenous levels of inhibin, thereby increasing endogenous FSH and thence follicular development, heifers, ewes and does were actively immunized against porcine follicular fluid or proteinaceous fractions of bovine seminal plasma. In some animals, plasma FSH concentrations were elevated although ovulation rates and estrous cycle lengths were not altered. / A culdoscopy technique was developed for repeated monitoring of ovarian morphological changes in cows.

viii, 117 leaves, 3 leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Obstetrics and Gynaecology, 1981

Thesis (PhD)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Polycystic ovary syndrome is a complex, heterogeneous disease that affects 5-10% of reproductive-aged women. It is characterized by clinical or biochemical hyperandrogenism, oligo-anovulation, and polycystic ovary morphology. Instigating endocrine findings include aberrantly rapid gonadotropin-releasing hormone pulsatile secretion, elevated luteinizing hormone, sub-optimal levels of follicle-stimulating hormone, and hyperandrogenism. Metabolic symptoms are also present including hyperinsulinemia, insulin resistance, and dyslipidemia. These endocrine and metabolic findings are also accompanied by ovarian dysfunction and improper folliculogenesis. Because aberrant functioning of the hypothalamic-pituitary-gonadal axis is central to the pathophysiology of polycystic ovary syndrome, it is beneficial to examine it for abnormalities. Polycystic ovary syndrome has been shown to have both genetic and environmental components. Its strong genetic component has been demonstrated in twin studies, family association studies, candidate gene studies, and genome-wide association studies. Previous genome-wide association studies have found many candidate genes including those for DENND1A (differentially expressed in normal and neoplastic cells domain containing 1A), THADA (thyroid adenoma-associated protein), FSHR (follicle-stimulating hormone receptor), and LHR (luteinizing hormone receptor). This, together with the central endocrine abnormalities, prompted this review on polymorphisms of receptors of the hypothalamic-pituitary-gonadal axis, including those for gonadotropin-releasing hormone, luteinzing hormone, follicle-stimulating hormone, estrogen, and progesterone, as well as anti-müllerian hormone. Studies on single-nucleotide polymorphisms of these receptors were found on PubMed, Web of Science, and Google Scholar and subsequently analyzed. Many different single-nucleotide polymorphisms were studied, but only a handful of them have been subjected to repeated studies. Only rs2293275 of the luteinizing hormone receptor and rs2349415 of the follicle-stimulating hormone receptor, both at 2p16.3, were found to have a possible role in the etiology of polycystic ovary syndrome, but all eight were found to have a possible phenotypic role: rs13405728, rs2293275, and rs4539842 of the luteinizing hormone receptor; rs6165, rs6166, rs2268361, and rs2349415 of the follicle-stimulating hormone receptor; and rs2002555 of the anti-müllerian hormone receptor. The limitations most affecting the results of these studies include small sample sizes, heterogeneous study populations, lack of generalizability due to ethnicity, and lack of control or adjustment for confounders. It is necessary to develop a standardized study protocol and separate polycystic ovary syndrome patients based on phenotype in order to obtain stronger results in the future.

Background: Hypothalamic kisspeptin and neurokinin B (NKB) are central regulators of GnRH and thus gonadotropin (LH and FSH) secretion. Men and women with loss-of-function mutations in NKB-kisspeptin pathway show hypogonadotropic pubertal delay with reduced GnRH/LH pulsatility. Studies in patients with defects in NKB signalling suggest that kisspeptin is functionally downstream of NKB, although there are very limited data on the relevance of the NKB pathway in normal men or women, and no hierarchical data on this. The studies described in this thesis have investigated the interaction between these neuropeptides in the control of human reproduction in conditions of varying sex-steroid environment, and in states of fast and slow LH secretion (men, menopause, various stages across the menstrual cycle). Overall hypothesis: Pharmacological blockade of NKB signalling will decrease LH secretion by modulating GnRH/LH pulsatility, indicating the involvement of the NKB pathway in normal human reproductive function. It is also hypothesised that this will not abrogate the stimulatory kisspeptin response, revealing a functional hierarchy whereby NKB signalling is upstream of kisspeptin. Research strategy: A specific neurokinin-3 receptor antagonist (NK3R antagonist, AZD4901) was administered 40 mg twice daily orally for 7 days with and without kisspeptin-10 (KP-10) challenge. Response of reproductive hormones (serum and urinary where applicable) was measured. LH was sampled every 10 minutes for 8 hours to assess LH pulsatility by blinded deconvolution. Results: Role of neurokinin B and kisspeptin in healthy men Six healthy men underwent LH pulsatility study pre-treatment and on day 7 of NK3R antagonist administration with iv KP-10 bolus (0.3 μg/kg) at 6 hours. NK3R antagonist reduced LH and testosterone secretion, whilst stimulatory LH response to KP-10 was unaffected. LH pulse frequency was unchanged by the NK3R antagonist but basal (nonpulsatile) and pulsatile LH secretion was markedly reduced. Role of neurokinin B and kisspeptin in postmenopausal women Eleven postmenopausal women underwent LH pulsatility study pre-treatment and on day 7 of NK3R antagonist administration with iv KP-10 bolus (0.3 μg/kg) at 6 hours. NK3R antagonist decreased LH secretion. Basal (nonpulsatile) LH secretion also fell and while LH pulse frequency did not change in a group as a whole, it did fall in the 8 of 11 postmenopausal womenwith hot flushes. These women reported a reduction in hot flush frequency (3.4±1.2 vs 1.0± 0.6 flushes/day with NK3Ra, p=0.008) and severity whilst on NK3R antagonist. LH response to KP-10 was minimal and unaffected by the NK3R antagonist. Role of neurokinin B across different phases of menstrual cycle The effect of NK3R antagonist on ovarian function was compared in early follicular (n=13), late follicular (n=6) and luteal phase (n=6) to no treatment control cycle. Early follicular: NK3R antagonist was commenced from cycle day 5-6. The diameter of the leading follicle was smaller than in controls at the end of treatment (9.3±0.4 vs 15.1±0.9 mm, p < 0.0001). Serum estradiol was also reduced and the endometrium was thinner. Although NK3R antagonist had no effect on LH pulse frequency, basal (nonpulsatile) LH secretion was decreased, suggesting that NKB modulates GnRH secretion. After stopping treatment, follicle development resumed and estradiol secretion increased thereby delaying the LH surge in 11/13 women (LH surge cycle day 22±1 vs 15±1, p=0.0006). The delayed LH surge and ovulation were confirmed by a similarly delayed rise in urinary progesterone and prolonged cycle length. NK3R antagonist did not affect luteal function. Late follicular: NK3R antagonist was administered from the emergence of a dominant follicle (≥12mm). Whilst there was an LH surge in all treated cycles, estrogen feedback was perturbed by the NK3R antagonist, as there was increased variation in the timing of LH surge compared to control cycle. NK3R antagonist had no effect on the growth of a dominant follicle and luteal function was unaffected. Luteal: NK3R antagonist was administered from day +2-3 of the disappearance of the dominant follicle. NK3R antagonist reduced the variation in the timing of peak estradiol secretion. Estradiol and progesterone concentrations remained unchanged, suggesting that luteal function was overall unaffected by this treatment. No difference in mean LH was observed, although LH pulsatility was not assessed. Role of neurokinin B and kisspeptin in the mid-cycle LH surge A model of follicular phase (cycle day 9-11) administration of estradiol (200μg/day) to induce LH secretion at 48 hours was used in twenty women, mimicking LH surge. In this model, KP-10 infusion (4μg/kg/hr for 7 hours) enhanced LH secretion, the response of which was directly correlated with estrogen concentration, indicating a role of kisspeptin in estrogen feedback. Pre-treatment with NK3R antagonist decreased LH pulse frequency and whilst the immediate LH response to KP-10 was unaffected, it blunted the duration of this response and abolished the relationship between estradiol and kisspeptin-induced LH secretion. Conclusions: These data indicate the role of NKB-KP pathway in regulating human reproductive function and that this is via the modulation of pulsatile GnRH secretion. Whilst NKB is predominantly proximal to kisspeptin, the hierarchy is more complex than simply linear in the control of human HPG axis. Manipulation of NKB-KP signalling has therapeutic potential in regulating GnRH/LH secretion in wide range of clinical settings, including contraception, sex-steroid dependent disorders and in the treatment of hot flushes.

Made available in DSpace on 2014-06-11T19:25:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-02Bitstream added on 2014-06-13T19:12:30Z : No. of bitstreams: 1 000742177.pdf: 1654502 bytes, checksum: 866898964213e96038c110158bf8a746 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação para o Desenvolvimento da UNESP (FUNDUNESP) / As alterações nos componentes reprodutivos do eixo hipotálamo-hipófise-gônadas em muitas fêmeas de mamíferos determinam a transição gradual de ciclos reprodutivos regulares para ciclos irregulares, com perda de fertilidade. A interação dos neurônios do hormônio liberador de gonadotrofinas (GnRH) e esteróides gonadais representa função chave na neurobiologia do envelhecimento, pois a sobreposição temporal da senescência endócrina e neural está mecanicamente interligada pelas alças de retroalimentação. Estímulos do locus coeruleus (LC) para a área pré-óptica (APO) e eminência mediana são essenciais para a liberação das gonadotrofinas e seus neurônios apresentam receptores para estrógeno e progesterona, sugerindo controle dos esteróides ovarianos. Neste estudo foi avaliado a atividade de células neuronais localizadas em áreas e núcleos envolvidos com o controle de ação dos neurônios GnRH de ratas Wistar no período de transição para a aciclicidade. Para este trabalho foram utilizadas fêmeas Wistar cíclicas (4 meses) e acíclicas (18-20 meses) submetidas à decapitação ou perfusão às 10, 14 e 18 h na fase do diestro. Após serem retirados, os cérebros dos animais decapitados foram congelados e armazenados para posterior determinação do conteúdo de GnRH hipotalâmico e do conteúdo de noradrenalina e dopamina na APO. Os cérebros perfundidos foram cortados seriadamente em secções coronais de 30 μm para a APO e o LC e... / Changes in reproductive components of the hypothalamic-pituitary-gonadal axis in many female mammals determine the gradual transition from regular reproductive cycles to irregular cycles, with loss of fertility. The interaction of neurons of gonadotropin-releasing hormone (GnRH) and gonadal steroids represents key role in the neurobiology of aging, because the temporal overlap of endocrine and neural senescence is mechanically interconnected by feedback loops. Stimulation of the locus coeruleus (LC) for the preoptic area (POA) and median eminence are essential for the release of gonadotropins and their neurons have receptors for estrogen and progesterone, suggesting control of ovarian steroids. Therefore, in this study we evaluated the activity of neuronal cells located in areas and nuclei involved in the control of action of GnRH neurons of female rats during the transition to acyclicity. For this study, we used cyclic female (4 months) and acyclic (18-20 months) rats underwent perfusion or decapitation at 10, 14 and 18 h of diestrus day. The brains from decapitated animals, after removed, were frozen and stored for subsequent determination of the hypothalamic GnRH content and the noradrenaline and dopamine content in the POA. The perfused brains were serially cut into coronal sections of 30 μm to POA and LC and subsequently submitted to immunohistochemical labeling for Fos (FRA) and FRA / TH, respectively. For quantitative analysis of the POA were considered plates containing AVPe being the counting of neurons FRA-ir performed from the insertion of the box with... / FAPESP: 12/14464-6

The recent decline and disappearance of many amphibians around the world is thought to be the sign of an impending sixth mass extinction that is driven by disease, habitat loss and pollution. Reproductive technologies are now required to establish captive colonies followed by reintroduction into suitable habitats. The AMPHIPLEX method is a hormone mixture that has successfully stimulated spawning in several amphibians. However, its extensive application requires further experimentation and knowledge regarding the basic neuroendocrine control of reproduction in amphibians. The role of the catecholamine neurotransmitter dopamine in the regulation of spawning and gonadotropin synthesis was investigated using multiple time- and dose-related approaches in the field and laboratory. These end points were explored in two distantly-related frog species: the Northern leopard frog (Lithobates pipiens) and the Western clawed frog (Silurana tropicalis). Northern leopard frogs were injected during the natural breeding season with three doses of a gonadotropin-releasing hormone agonist (GnRH-A) (0.1 μg/g , 0.2 μg/g and 0.4 μg/g) alone and in combination with two doses of the selective dopamine receptor D2 antagonist metoclopramide (MET) (5 μg/g and 10 μg/g). Injected animals were allowed to breed in mesocosms in an outdoor field. Time to amplexus and oviposition were assessed, and egg mass release, incidences of amplexus, egg mass weight, total egg numbers and fertilization rates were measured. The results revealed no statistically significant interaction between GnRH-A and MET on amplexus and oviposition. A series of GnRH-A dose-response spawning studies were conducted in the Western clawed frog. The current findings indicate that partial ovulation, male sexual behavior and fertilization can be induced by 4 μg/g of GnRH-A alone and in combination with 10 μg/g of MET. This represents a first step towards understanding basic neuroendocrine reproductive mechanisms in this species. These spawning results were paired with a second end point which explored the molecular mechanisms of gonadotropin synthesis in response to GnRH-A and MET alone and in combination. Pituitary gene expression results in the Northern leopard frog indicate a potentiating action of MET when combined with GnRH-A on the mRNA levels of gonadotropin subunits 36 hours following injection. The postulated mechanisms of action are through the upregulation of gonadotropin-releasing hormone receptor 1 and the downregulation of dopamine receptor D2. Such gene expression pathways were similarly explored in the Western clawed frog, however no significant changes in pituitary gonadotropin and receptor gene expression were present at 12 hours post-injection. The hypothesized inhibitory action of dopamine was supported by pituitary gene expression analysis, but not by spawning outcome. The results from this study provide a fundamental framework for future time- and dose-response investigations to improve current spawning methods in amphibians.

No description available.

Two studies were conducted to evaluate the effects of 5 or 7 d post-AI GnRH on first service PR, plasma P4, and CL volume in lactating dairy cows synchronized using 72 h Cosynch. All cows were synchronized and randomly assigned to one of three treatment groups: Control – no additional GnRH; 5 d – GnRH 5 d after TAI; 7 d – GnRH 7 d after TAI. In the first study, P4 concentrations were evaluated in samples collected at five separate times and CL volume and number were recorded at 30 d pregnancy examination for Holstein (n = 77) and Jersey (n = 33) cows. GnRH treatment did not affect PR (Control - 47.2%, 5 d GnRH - 40.5%, 7 d GnRH – 44.7%) or P4, but increased TCLV compared to controls (Control – 7.33 cm3, 5 and 7 d GnRH – 10.77 cm3). Incidence of accessory CL increased PR (94.7 vs. 60.6%), P4 (6.95 vs. 5.88 ng/mL), and TCLV (15.51 vs. 6.78 cm3) compared to cows with a spontaneous CL. Cows classified as cycling based on P4 evaluation had significantly higher PR than acyclic cows (54.4 vs. 16.1%). In the second study, Holstein cows (n = 1055) were submitted to the same experimental protocol and evaluated for first service PR. Post-AI GnRH treatment did not significantly affect PR. Primiparous cows (32.8%) tended to have higher PR than multiparous cows (27.6%), but GnRH treatment had no influence on this relationship. In conclusion, GnRH post-AI did not affect PR. Further evaluation of accessory CL incidence is warranted as it significantly affected PR. (Abbreviations: AI – artificial insemination, CL – corpus luteum, PR – conception rate, P4 – progesterone, TCLV – total corpus luteum volume) / Master of Science