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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Effects of Androgens on Reproduction in Female Pigs

Jimenez, Esbal 24 June 2008 (has links)
No description available.
62

Preantral follicle population, spatial distribution, and ovarian tissue autotransplantation in mares

Hyde, Kendall A 01 August 2022 (has links)
Folliculogenesis is a complex and dynamic process by which follicles grow and develop with the goal of releasing a fertilizable oocyte upon ovulation. At birth, most females have a large pool of follicles; however, this pool is naturally depleted over time until ovarian senescence occurs and ovulation ceases. Thus, the population of preantral follicles is an appealing target for studies focused on female fertility, with the hopes of extending female reproductive lifespan. The studies within this thesis characterize, for the first time in mares, the population and spatial distribution of preantral follicles within the ovary and provide preliminary results documenting the success of a novel ovarian tissue transplantation site. The results from these studies showed that the population of preantral follicles in the mare ovary is similar to that of other species and that these follicles cluster in the ovary, comparable to mice and women. Furthermore, effects of age were observed, with young mares showing (i) a higher preantral follicle population, (ii) increased preantral follicle density in portions and regions, (iii) increased follicular clustering, specifically in the lateral and dorsal area of the ovary, and (iv) more numbers of neighbors per follicle than old mares. Additionally, interesting effects of spatial distribution in the ovary were also observed, with morphologically abnormal follicles in the intermediary portion being closest to the ovarian geometric center and with a tendency for increased follicular clustering in the ventral region. Furthermore, preantral follicles with neighbors were more likely to be morphologically normal. Moreover, despite having increased odds of lacking neighbors, it was observed that morphologically normal activated follicles had a higher number of neighbors than normal resting follicles. Lastly, the novel subvulvar mucosa was comparable to the established intramuscular location for heterotopic ovarian tissue transplantation, producing similar findings for macroscopic graft appearance, follicular density, and percentages of developing/growing follicles. The findings from these studies provide vital advancements in scientific understanding of preantral folliculogenesis in the mare and build important foundations for continuing to study folliculogenesis and treatments for infertility using the mare as an animal model.
63

The Role of Nucleotide Excision Repair Genes in the Repair of Methylene Blue Plus Visible Light-Induced DNA and Cellular Damage in Chinese Hamster Ovary Cells

Cowan, Robert 01 1900 (has links)
<p>Base excision repair (BER) is a DNA repair mechanism that involves the removal of single damaged bases from DNA and their excision as free bases. Another DNA repair mechanism known as nucleotide excision repair (NER) involves the removal of bulky lesions from DNA. Previous published reports have suggested a role for certain NER proteins in BER. Methylene blue (MB) is a type II photosensitizer, which upon excitation by visible light (VL) produces singlet oxygen that reacts with DNA to form 8hydroxyguanine (8-oxoG) lesions. The BER mechanism has been shown to preferentially remove 8-oxoG lesions from DNA. In the current work, the role of NER proteins in the BER of [MB+VL]-induced DNA damage was examined using a reporter gene assay. AdMCMVlacZ and AdHCMVlacZ are non-replicating adenoviruses that express the bacterial β-galactosidase ( β-gal) reporter gene under the control of the murine or human cytomegalovirus immediate early promoter, respectively. Host cell reactivation (HCR) of β-gal activity for a [MB+VL]-treated AdMCMVlacZ was examined in two repair-proficient normal Chinese hamster ovary (CHO) cell lines, NER-deficient mutants from rodent complementation groups (RCGs) 1 through 6, and the HER-deficient cell line EM9. Results show a decreased HCR capacity of [MB+VL]-induced DNA damage in the UV61 (RCG-6; CSB) cell line when compared to the repair-proficient normal AA8. This suggests an involvement of CSB in BER of [MB+VL]-induced damage. In contrast, the XRCCl-deficient EM9 showed an increased HCR capacity when compared to the parental AA8. This suggests a beneficial role for an XRCCl deficiency or for the specific gain-of-function gene mutation in the XRCCl gene for the repair of [MB+VL]induced damage. Similarly, the ERCCl-deficient UV20 (RCG-1) showed an increased HCR capacity when compared to the parental AA8. In contrast, another ERCCJdeficient cell line, 30PV, and the ERCCJ knock-out cell line, CH0-7-27, showed no significant increase in β-gal activity when compared to the parental CHO-Kl. The ability to induce BER of [MB+VL]-induced DNA damage was also examined. HCR of β-gal activity for [MB+VL]-treated AdHCMVlacZ or AdMCMVlacZ was examined in several CHO cell lines that were either untreated or treated with low levels of UVC or MB plus VL. Pre-treatment of NER-deficient UV61 and repair-proficient AA8 cells with UVC resulted in an enhanced HCR for [MB+VL]-treated AdHCMVlacZ, although the results were only significant for UV61. Similarly, an enhanced HCR of [MB+VL]-treated AdMCMVlacZ was observed in AA8 cells, suggesting that the repair of the [MB+VL]treated reporter gene is inducible by UVC. A significant enhancement in HCR of [MB+VL]-treated AdMCMV lacZ was not observed in AA8 cells following pre-treatment with MB, VL, or both, indicating that the detection of any induction in the repair of DNA damage from MB plus VL could not be made with the conditions of the HCR assay employed. As investigations into the effects of MB plus VL on whole cells have been limited, clonogenic survival of BER-and NER-deficient CHO cell lines was also observed following treatment with MB alone or MB plus VL. Results showed that the sensitivities of the NER-deficient CHO cell lines from RCGs 2, 4 and 5 and the BERdeficient EM9 cell line to MB alone were within the range obtained for the two repairproficient CHO normal cell lines, AA8 and K 1. In contrast, the UV20 cell line was more sensitive to MB alone compared to the normal cell lines. Additionally, both UV24 (RCG-3; XPB) and UV61 showed a decreased sensitivity toMB alone when compared to the normal AA8 cell line. The sensitivity of cells to MB plus VL was greater in the UV24, UV135 (RCG-5; XPG) and the XRCCl-deficient EM9 cell lines compared to that of the range obtained for the two repair-proficient normal cell lines, AA8 and Kl. Taken together with the results from the HCR assays, these results suggest that [MB+VL]induced DNA damage to cells and its repair do not play a major role in the survival of cells following treatment with MB plus VL. It appears likely that damage to cellular components other than DNA, such as protein, lipid and biological membranes, play a more important role in cell killing by MB plus VL.</p> / Thesis / Master of Science (MSc)
64

Reproductive Consequences of CRISPR/Cas9-Based avp Knock-Out in Zebrafish (Danio rerio)

Ramachandran, Divya 06 December 2022 (has links)
The nonapeptide family of hormones is deeply conserved in evolution. In teleost fishes, as in all vertebrates, two nonapeptide families exist. These are vasotocin (avp) and oxytocin (oxt). While vasotocin has been shown to regulate individual aspects of reproductive physiology in several teleost species, an integrative assessment of its role on male and female reproduction is currently lacking even in widely used fish models, such as the zebrafish (Danio rerio). Taking advantage of the genetic tractability of the zebrafish, and its emerging status as model to study reproductive physiology, I generated avp -/- mutants using a CRISPR/Cas9 based approach to determine reproductive consequences in female and male zebrafish. Following the identification of a female-specific reproductive phenotype which manifests as a reduction in oocyte release and decreased quivering behaviour, I investigated the potential mechanistic basis at the level of the gonad. In avp -/- ovaries, significantly fewer eggs were present compared to WT fishes. When comparing the distribution of oocyte maturation stages, a significantly lower percentage of stage I and higher percentage of stage V oocytes was present in avp-/- ovaries. The altered distribution in oocyte maturation stages coincided with significant decreases in ovarian transcript abundance of nanos2, a germ-cell specific marker suggesting a possible role for Avp in germ-cell maintenance. Additionally, I observed a decrease in the ovarian concentration of the prostaglandin PGF2, which coincided with a reduction in ovarian transcript abundance of pla2g4ab, a paralogue of the phospholipase A2 involved in mobilizing arachidonic acid, a precursor of PGF2,. Together, these finding suggests a role for Avp in PGF2 -mediated ovulation. Because Avp has pleiotropic effects and may thus affect female reproductive physiology indirectly, we assessed somatic growth, a key regulator of sexual maturation in zebrafish, as well as aspects of the endocrine stress axis known to affect oocyte growth in avp -/- mutants. While avp -/- mutants did not exhibit differences in somatic growth up to sexual maturation or GSI, mutants exhibited hypercortisolism. While other zebrafish knock-out mutants exhibiting persistent hypercortisolism do not share the observed reproductive phenotype, future studies investigating potential contributions of pleiotropic Avp effects are nevertheless warranted. Overall, I demonstrate that avp, while not essential, affects female reproductive success, at least iii in part by regulating oocyte maturation. This finding is in line with the recent findings from other vertebrate and invertebrate species, suggesting an evolutionarily ancient role in these processes. It is anticipated that such novel insights into the regulation of female oocyte maturation have in addition to increasing our understanding of female reproduction, translational potential for captive breeding (aquaculture, species conservation) and ecotoxicology (insight into mode of action of specific EDCs).
65

Reproductive and metabolic programming by exogenous steroids

Connolly, Fiona January 2014 (has links)
Polycystic ovary syndrome (PCOS) is a heterogeneous disorder encompassing reproductive and metabolic phenotypes. Genetic analysis, targeting candidate genes has to date proven unsuccessful in the search for a truly dominant genetic link. Another hypothesis to explain the etiology of PCOS is that of fetal programming in the context of developmental origins of health and disease. Extensive animal studies, validated by human data, support the fetal origins hypothesis of PCOS and highlight that PCOS may arise due to excess androgen exposure in fetal life. Previous reports from our laboratory found metabolic dysfunction in 11 month old prenatally androgenised females (d62-102 of fetal life), which included pancreatic and hepatic alterations. The pancreatic alterations seemed to result from gene expression changes induced in fetal life. Therefore, chapter 3 focuses on the gluconeogenic response in the day 90 fetus following maternal androgenisation from day 62 of gestation. Interestingly hepatic gluconeogenic enzymes, specifically phosphoenolpyruvate caboxykinase (PEPCK) and glucose 6 phosphatase (G6PC), were not altered. However they were decreased in the kidney, in a sex specific manner with PEPCK significantly decreased (P<0.01) and G6PC showing a strong trend toward reduction (P=0.056) in females only. This chapter progresses to explore regulatory pathways involved in gluconeogenic regulation. It seems probable that the female specific increase in circulating testosterone (P<0.001), with increased renal androgen reception (P<0.01), may be accountable for the altered expression of gluconeogenic enzymes in the kidney. Chapter 4 investigates why testosterone concentrations were not increased in the male fetus, after maternal androgenisation, by focusing on the site of testosterone production, the fetal testis. Results demonstrate that the day 90 fetus is capable of responding to prenatal androgenisation by decreasing luteinising hormone (P<0.01) and thus testicular testosterone production, such that there was a global down regulation in steroidogenic enzyme expression, in vivo testosterone production (P<0.001) and Leydig cell morphology was altered (P<0.001). As prenatal androgenisation is administered through the maternal route and placental aromatisation may occur, a novel method whereby the fetus was directly injected was utilised to assess the effects of control oil (C), testosterone (TP) or diethylstilboestrol (DES) on the fetal testis. Unlike DES, direct fetal injection with TP mimics the results found from maternal androgenisation. When the testis are examined at a later date, day 112, ten days after androgen treatment ceases, Leydig cell morphology and steroidogenic gene expression return to control values, although fascinatingly, an overshoot of in vivo testosterone production (P<0.01) was observed. When the maternal androgenisation window is extended to begin at day 30 of fetal life, further changes are noted including increased circulating testosterone (P<0.01), a strong trend toward decreased testis weight (P=0.0519) and altered expression of Sertoli and germ cell specific markers. These studies are followed up by assessing the legacy effect of testosterone on the peripubertal male testis in Chapter 5. At ten weeks of postnatal life, males, exposed to androgens from day 62-102 of fetal life had reduced testis weight (P<0.05). However, functional or cellular alterations were not observed and by 12 weeks of age, when LH had normalised, testicular weight and stimulated testosterone secretion of prenatally TP-treated males was comparable to controls. This highlights the remarkable plasticity of the testis and the unremarkable legacy of altered prenatal androgen exposure. The legacy effect of testosterone on the fetal ovary is examined in Chapter 6. Previous studies from our laboratory found minor functional alterations but no structural alterations in the fetal ovary at day 90 following androgenisation from day 62. However, as this was at a time of a highly androgenic environment we assessed the function and morphology of the ovary ten days after the removal of testosterone at day 112. In marked contrast to the normalisation of the male gonad, we observe structural changes with an increase in recruited follicles from the primordial to primary stage in the testosterone treated group (P<0.01). The chapter continues with an investigation of pathways involved in the altered follicular dynamics that may account for the change in follicular recruitment. Furthermore, the functional changes which were previously noted in the day 90 ovary were also examined in response to direct exogenous steroid treatment including, C, TP, DES and dexamethasone (DEX) and also when the window of maternal androgenisation was extended to begin at day 30. Interesting changes are observed such that the direct fetal injection treatments induce similar changes to each other, regardless of the steroid, whilst maternal androgenisation induces a different response. This highlights the complexity of the pathways involved in female gonadal development.
66

Platelet and endothelial function : Polycystic Ovary Syndrome and the renin-angiotensin system.

Rajendran, Sharmalar January 2009 (has links)
The phenomenon of platelet hyperaggregability and decreased platelet responsiveness to nitric oxide (also termed as nitric oxide resistance), documented in several cardiovascular disease states, is associated with adverse cardiovascular outcomes. The series of experiments described in this thesis address primarily some aspects of the pathophysiology, epidemiology and therapy of the phenomenon of end-organ resistance to nitric oxide (NO) in two important conditions, that are closely associated with cardiovascular risk factors and disease states:- Polycystic ovary syndrome, which is closely linked with the metabolic syndrome and premature subclinical atherosclerosis. The renin-angiotensin system, which is recognized as a significant mediator in the pathophysiology of a number of cardiovascular disease states. The first study examined the epidemiology/pathophysiology of putative platelet/endothelial dysfunction in young individuals with PCOS. The subsequent studies focused on the potential impact of the renin-angiotensin system on platelet and endothelial function. This mechanistic review is set in the context of a number of recent major clinical studies which have demonstrated surprising efficacy of certain angiotensin-converting enzyme (ACE) inhibitors (ramipril and perindopril) in the prevention of thrombotic processes. Thus we tested the hypothesis whether ACE inhibitor ramipril sensitizes platelets to NO (as a potential mechanism for improved cardiovascular outcomes) in a high risk patient cohort. In addition, particular attention will be given to the emerging role of the heptapeptide Angiotensin- (1-7), a possible physiological antagonist to Angiotensin II in the vasculature and the limitation of the current literature concerning potential effects of the renin-angiotensin system on thrombotic mechanisms. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1348615 / Thesis (Ph.D.) - University of Adelaide, School of Medicine, 2009
67

Expressão da Ciclo-oxigenase-2 e do Ki67 em tumores borderline serosos e mucinosos de ovario / Cyclooxygenase-2 (COX-22) and Ki67 expression in serous and mucinous ovarian borderline tumors

Borba, Patricia Patury 27 August 2008 (has links)
Orientador: Sophie Françoise Mauricette Derchain / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-11T15:16:33Z (GMT). No. of bitstreams: 1 Borba_PatriciaPatury_M.pdf: 2453144 bytes, checksum: b4164eabded853c9e2f9d0610b08c22a (MD5) Previous issue date: 2008 / Resumo: Introdução: os tumores borderline serosos e mucinosos de ovário formam um grupo especial de neoplasias, que difere dos tumores benignos e malignos das mesmas linhagens histológicas. Os marcadores moleculares estão atualmente provendo informações sobre as características biológicas e o comportamento clínico de vários tumores, entre eles, os tumores borderline. A ciclo-oxigenase-2 (COX-2), uma enzima ligada ao processo inflamatório, é sabidamente correlacionada com a carcinogênese. Por outro lado, o Ki67, marcador de proliferação celular, é capaz de identificar alterações do controle do ciclo celular e da apoptose. Objetivo: comparar a expressão da COX-2 em tumores borderline de ovário, serosos e mucinosos e verificar se essa expressão está relacionada à atividade proliferativa celular, avaliada através da expressão do Ki67, à presença de implantes peritoneais e ao estádio da doença. Sujeitos e métodos: para este estudo descritivo de corte transversal, foram selecionados os blocos de parafina das mulheres com tumores borderline de ovário, tratadas entre Janeiro de 1998 a Dezembro de 2004 na Universidade Estadual de Campinas (Unicamp), São Paulo, e no Instituto Nacional de Câncer (INCA), Rio de Janeiro, Brasil. Após revisão dos prontuários foram excluídas as mulheres grávidas no momento do diagnóstico, portadoras de outras neoplasias ou em uso registrado de antiinflamatórios não esteroidais. Todas as lâminas foram revisadas por dois patologistas e foram incluídos 86 casos de tumores borderline de ovário cujos blocos eram disponíveis para avaliação imunoistoquímica. Os tumores incluídos foram classificados como: serosos (36), mucinosos (46) e seromucinosos (4). Foram avaliadas a expressão citoplasmática da COX-2 e a expressão nuclear do Ki67, determinadas por imunoistoquímica realizada nestes cortes de tumores borderline de ovário conservados em parafina. Resultados: A idade média das mulheres estudadas foi de 42,4 anos (desvio padrão 16,5) não havendo diferença significativa entre aquelas com tumores serosos, mucinosos ou seromucinosos (p=0,62). Setenta e uma mulheres apresentaram a doença em estádio I e apenas três apresentaram doença em estádio II. Entre as treze mulheres com implantes peritoneais, sete eram portadoras de tumores borderline serosos, três apresentavam tumores mucinosos e três, tumores seromucinosos, sendo a proporção de mulheres com implantes peritoneais e estádio III significativamente maior, em mulheres com tumores seromucinosos (p=0,001). A expressão nuclear do Ki67 foi maior nos tumores mucinosos (65,8%), em comparação com os serosos (25%) e seromucinosos (25%) (p=0,001). Após análises multivariadas observou-se que a expressão citoplasmática da COX-2 foi significativamente maior nos tumores serosos em comparação com os tumores mucinosos (68.5% vs 52.5%; p<0.01). Não houve diferenças na expressão da COX-2 entre os tumores seromucinosos versus mucinosos, e tumores seromucinosos versus serosos. A maior expressão citoplasmática da COX-2 esteve significativamente associada com uma maior expressão do Ki67 em todos os tipos histológicos (p=0.03). Por outro lado, a expressão da COX-2 não se relacionou com o estádio da doença nem com a presença de implantes peritoneais. Conclusões: Esses resultados indicam que a expressão da COX-2 é maior nos tumores borderline serosos de ovário do que nos mucinosos. Também indicam que a COX-2 é uma boa preditora da proliferação celular pois, sua expressão aumenta com a expressão do Ki67. Entretanto, este estudo impede inferir se a COX-2 é uma moduladora do comportamento do tumor ou apenas um marcador de outros eventos biológicos já que não se associou com o estádio ou presença de implantes peritoneais / Abstract: Background: borderline serous and mucinous ovarian tumors form a special group of neoplasia, which differs from benign and malignant tumors of the same histological category. Molecular markers are currently providing information on the biological characteristics and clinical behavior of the ovarian tumors; among them, borderline tumors. Cyclooxygenase-2 (COX-2), an enzyme linked to the inflammation process, is known to correlate with carcinogenesis. On the other hand, the Ki67, a marker of cell proliferation, is capable of identifying abnormalities of the cell-cycle control system and apoptosis. Objective: to compare the expression of COX-2 in serous and mucinous borderline ovarian tumors and to evaluate whether this expression is related to cell proliferative activity, by its turn assessed with the expression of Ki67, to the presence of peritoneal implants and to the disease stage. Subjects and methods: for this cross-sectional descriptive study we selected paraffin blocks from women with borderline ovarian tumors, treated at the State University of Campinas, São Paulo, and at The National Institute of Cancer, Rio de Janeiro, Brazil, between January 1998 and December 2004. After revision of the medical records, women that were pregnant at the moment of diagnosis, that harbored other malignancies or that were using nonsteroidal antinflammatory drugs were excluded. All slides were reviewed by two pathologists and 86 blocks were selected to undergo immunohistochemical evaluation. The tumors that were included were categorized as: serous (36), mucinous (46) and seromucinous (4). The cytoplasmatic expression of COX-2 and the nuclear expression of Ki67 were determined with immunohistochemistry in slides obtained from these borderline tumor paraffin blocks. Results: the mean age of the women was 42.4 years (standard deviation 16.5), and there was no significant difference between the mean ages of women with serous, mucinous or seromucinous tumors (p=0.62). Seventy-one women had stage I disease and only three had stage II disease. Of the thirteen women with peritoneal implants, seven had serous borderline tumors, three had mucinous and three seromucinous tumors. The proportion of women with peritoneal implants and stage III disease was significantly higher among women with seromucinous tumors (p=0.0001). The nuclear expression of Ki67 was higher in mucinous tumors (65.8%) in comparison to serous (25%) and seromucinous (25%) (p=0.001). After multivariate analysis it was observed that the cytoplasmatic expression of COX- 2 was significantly higher in serous tumors compared to mucinous (68.5% vs 52.5%; p<0.01). There were no differences regarding the expression of COX-2 comparing seromucinous versus mucinous and mucinous versus seromucinous. The higher cytoplasmatic expression of COX-2 was significantly associated with an increased expression of Ki67 in all histological types (p=0.03). On the other hand, the expression of COX-2 was not related to disease stage and peritoneal implants. Conclusions: these results indicate that the expression of COX-2 is higher in serous borderline ovarian tumors compared to mucinous ones. They also indicate that COX-2 is a good predictor of cell proliferation because its expression increases in parallel to that of Ki67. However, this study does not allow concluding whether COX-2 is a modulator of the tumor's behavior or just a marker of other biological events, considering that it bore no relation to disease stage or peritoneal implants / Mestrado / Ciencias Biomedicas / Mestre em Tocoginecologia
68

THE DISRUPTION OF THE BLOOD FOLLICLE BARRIER IN OVARIAN FOLLICULAR CYST DEVELOPMENT: REGULATION BY NITRIC OXIDE

Nemade, Rashmi Vithal January 2000 (has links)
No description available.
69

Novel approaches to the development and assessment of an ovine model of polycystic ovary syndrome

Hogg, Kirsten January 2011 (has links)
Polycystic ovary syndrome (PCOS) is a common reproductive, endocrine and metabolic disorder present in women of reproductive age. Despite the widespread prevalence and heritability of PCOS, the heterogeneous and polygenic traits have made the successful identification of candidate genes difficult. Animal models have been developed on the premise that early exposure to sex steroids can programme epigenetic changes that predispose the fetus to the adult features of PCOS. Past research has modelled ovarian dysfunction, endocrine abnormalities and metabolic perturbances in rodent, non-human primate and sheep PCOS models, through the enhanced neonatal or prenatal exposure to the male sex hormone, testosterone. The modelling of PCOS in a large domestic species such as the sheep is advantageous due to similar biological reproductive function as the human. In this regard the sheep has been extensively used to model PCOS by the treatment of pregnant ewes from early to midgestation with androgens such as testosterone propionate (TP). These experiments have demonstrated the fetal programming effects of androgens on offspring that go on to develop PCOS-like characteristics in adulthood. One of the caveats of assessing steroid effects in this way is the effect of the placenta in mediating the transfer of these hormones. TP is an aromatisable androgen and thus some of its effects in the fetus may be attributable to placental by-products such as estrogens. This thesis describes the development and assessment of a novel model of prenatal androgenisation. Two models were compared: the indirect maternal exposure to TP (the current model) and the direct fetal injection of TP. In directly treating the fetus this allowed control over the dose of TP administered and avoidance of secondary effects that androgens may exert in the mother that could be transferred to the fetus. For the maternal model, pregnant Scottish Greyface ewes were administered TP twice weekly from day (d)62-102 of a 147 day gestation. For the fetal model, fetuses were injected twice while the ewe was anaesthetised with graded doses of TP during the same period of treatment as the maternal model. The effects of prenatal androgenisation were assessed in the female fetus shortly after treatment and also in young adult sheep. Fetal ovarian and adrenal steroidogenic gene expression was monitored and found to be altered in response to elevated levels of sex steroids. At d90 the morphology of the developing ovary was not changed by prenatal androgens. In the adult a detailed ovarian and endocrine assessment was undertaken, by examination of ovarian morphology, hormone levels, ovulatory cycles, hypothalamic pituitary ovarian function and follicle steroidogenesis, during the first breeding season. In addition, the metabolic effects of prenatal androgens were monitored by measuring body fat, insulin and glucose homeostasis and liver function. Neither maternal nor fetal prenatal androgenisation during mid-gestation resulted in a perturbed hormonal milieu or polycystic ovaries in young adults. These treatments did however programme a clear ovarian phenotype demonstrated by the increased capacity of follicles to secrete androgens, independently of an abnormal endocrine environment and disordered folliculogenesis. Furthermore, animals that were exposed maternally to TP developed fatty liver and had increased insulin secretion in response to glucose load. A major outcome of this study was the finding that the fetally injected control animals were phenotypically different than the maternal control animals. In fact, some of the reproductive and metabolic features of maternal TP exposure were found in the fetal control group. This unexpected finding has raised the possibility that it is the fetal exposure to stress, that is secondary to elevated maternal androgens, rather than androgens per se that is responsible for at least some of the multitude of anomalies encountered in PCOS.
70

Morphogenesis and Female Fate Determination in Vertebrates

Mork, Lindsey A. January 2011 (has links)
<p>A unique feature of the fetal gonad is its ability to form two distinct organs, the testis and the ovary, from a single bipotential primordium. The outcome of this decision, which is made by a population of somatic cells known as the bipotential supporting cell precursors, determines whether an embryo will develop as a phenotypic male or female. Though several molecular pathways have been shown to be required for female fate determination in vertebrates, the intricacies of ovarian morphogenesis are not well understood. A key event in ovarian development occurs around birth, when meiotic germ cells and somatic granulosa cells organize into primordial follicles, the structures that generate mature oocytes for ovulation in adult females. We investigated the embryonic origins and proliferative properties of granulosa cells in the fetal mouse ovary and found that the precursors emerge from the ovarian surface epithelium and then enter mitotic arrest in a specification process that extends from the bipotential stage to the end of the postnatal follicle assembly period. Maintenance of cell cycle arrest in granulosa cell precursors appears to be regulated by Wnt signaling. The first granulosa cells to be specified were exclusively incorporated into the subset of follicles that begin to grow immediately upon assembly. We show that this first group of granulosa progenitors derives from the supporting cell precursors present in the bipotential gonad. Interestingly, both XX and XY supporting cell precursors were mitotically arrested towards the end of the bipotential period, indicating that adoption of supporting cell fate might be regulated by the cell cycle. We also show that antagonism of Notch signaling may be required for these precursor cells to exit the cell cycle and differentiate.</p><p>In Witschi's classic model of vertebrate gonad development, the cortex and medulla of the undifferentiated gonad expand and differentiate in a mutually exclusive manner to yield the mature ovary and testis (Witschi 1951). Estrogen acts on both the cortex and medulla to promote female fate determination and ovary development in non-mammalian vertebrates. However, the downstream receptors and targets through which estrogen exerts its effects on the gonad have not yet been elucidated. We selected the red-eared slider turtle Trachemys scripta as a model with which to address this question. We first characterized the cellular composition of the turtle gonad before and after sex determination, identifying four populations of somatic cells distinguishable by their location within the gonad as well as the complement of transcription factors expressed. This information was then applied to an investigation of estrogen signaling pathways in the turtle ovary. We show that i) estrogen likely acts through its canonical receptors rather than a non-canonical pathway involving ERK signaling; ii) early exposure to estrogen resulted in the premature downregulation of a testis-specific gene, SOX9, in the medulla; iii) less estrogen is needed to promote ovarian differentiation in the cortex of the gonad than to repress testicular differentiation of the medulla, consistent with the localized production of estrogen in the medulla; and iv) estrogen's repressive effect on SOX9 expression may be mediated by Wnt signaling. </p><p>Our findings add complexity to the standard model of how the male and female supporting cell lineages are established in mice, reveal evolutionary conservation between mice and turtles in the timing of granulosa cell specification relative to sex determination., and refine our understanding of how estrogen acts to promote ovarian development in non-mammalian species.</p> / Dissertation

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