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Ferasyi, Teuku Reza. "Mathematical model of the reproductive endocrine system in male sheep." University of Western Australia. School of Animal Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0080.
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[Truncated abstract] The activity of the reproductive endocrine axis is the result of interactions among many organs and tissues, particularly the hypothalamus, pituitary gland and gonad. However, it depends on more than the communication between anatomical structures because it is also affected by genotype, internal factors (e.g., metabolic inputs) and external factors (e.g., photoperiod, socio-sexual cues, stress, nutrition). This multifactorial complexity makes it difficult to use animal experimentation to investigate the pathways and mechanisms involved. Therefore, in this study, I have turned to mathematical modelling. The general hypothesis was that, by modelling the hormonal feedback loop that links the hypothalamus, pituitary gland and gonad, I would be able to discover the critical control points in this homeostatic system. This would allow me to inform and direct research into the processes that control reproduction, including inputs from environmental factors. My studies began with the development of a model of the negative feedback loop through which testosterone controls the secretion of pulses of gonadotrophin-releasing hormone (GnRH) by the hypothalamus. The model incorporated two critical factors: testosterone concentration and a time delay in the inhibition of the activity of the GnRH 'pulse generator' by testosterone. The general assumptions were: i) there are two positive feedforward processes (GnRH pulses stimulate LH pulses, and, in turn, LH pulses stimulate testosterone secretion); ii) testosterone exerts negative feedback that reduces the frequency of GnRH pulses. The model incorporated a group of equations that represent the GnRH pulse generator, through which the inhibitory effect of testosterone acted to reduce GnRH pulse frequency. Simulations were run with various values for the time delay in feedback and, as model development progressed, the simulations were extended to include combinations of time delays and levels of sensitivity of the GnRH pulse generator to inhibition by testosterone. The output of the simulations showed clearly that a time delay in negative feedback, as well as the concentration of testosterone, can greatly affect the frequency of GnRH pulses and the shape of the GnRH secretory profile. Importantly, the effect of the time delay depends on the sensitivity of the pulse generator to testosterone. In addition, the simulations suggested two additional components that might be involved in the control of the GnRH pulse generator: i) a delay in the rate of adaptation to a change in steroid feedback; and ii) a minimum pulse interval (maximum frequency). These studies iii therefore suggest that the regulation of the activity of the GnRH pulse generator, and thus the frequency and profile of GnRH and LH pulses, requires interactions among these four components. These interactions should be tested in animal experimentation. In the next stage, I extended the model so I could test whether the feedback delay might involve the process of aromatization in which testosterone is converted to oestradiol at brain level. ... This information can be used to direct future experimental studies that will help us to understand the factors that underlie the dynamic behaviour of the hypothalamic and pituitary systems that control reproduction.
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Melnyk, Peter M. (Peter Michael). "Estrogen regulation of testicular function in the adult ram." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59414.
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During the nonbreeding season (July), three groups of five Dorset x Leicester x Suffolk rams were assessed over a period of 5 days. One group of rams (control) was implanted (sc) with five 5cm empty Silastic capsules (i.d. 3.4mm, o.d. 4.6mm); two other groups, designated as Low-E$ sb2$ and High-E$ sb2$, received five estradiol filled capsules of either 5cm or 10cm, respectively for 4 days. Estradiol treatment elevated serum estradiol concentration about 150% in the Low-E$ sb2$ groups (15.7 $ pm$ 1.3 pg/ml) and 300% in the High-E$ sb2$ groups (26.6 $ pm$ 2.4 pg/ml) compared with controls (6.3 $ pm$ 0.8 pg/ml). In the absence of LH pulsing, mean LH, FSH and testosterone concentrations were all decreased significantly (P $<$.05) with increasing estradiol concentration, while PRL concentration was increased (P $<$.05) by as much as 105%. In the LH-pulsed groups, LH-peak height on day 4 was comparable for all three groups of rams and peak frequency was, as expected, consistently increased to 4 peaks per 6 hours. The increase in mean testosterone concentration (P $<$.05) in all three groups was due to an increase in testosterone baseline concentration and testosterone peak frequency.
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Zhang, Song. "Peripheral and central pathways linking metabolic status and reproduction in male sheep." University of Western Australia. School of Animal Biology, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0037.
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[Truncated abstract] Reproductive activity is affected by external factors such as photoperiod, social cues, stress and nutrition, all of which can alter the pulsatile activity of the GnRH neurons, which is the major neuroendocrine system used by the brain to control gonadal function. In the male Merino sheep, nutrition is one of the most powerful factors that affect pulsatile LH secretion, used commonly to bioassay GnRH neuronal activity. More accurately, the reproductive system responds to “metabolic status”, rather than “nutrition”, and the three factors that contribute to metabolic status are food intake, the amount of body reserves and the rate of energy expenditure ... In this thesis, I tested the general hypothesis that the metabolic hormones and hypothalamic neuropeptides that are known to control food intake also mediate the effect of metabolic status on the activity of the GnRH neurons ... In conclusion, the results from my experiments provide some insight into the mechanisms by which metabolic status affects reproductive activity in male sheep. Plasma insulin, which changes with alterations in metabolic status, appears to play a critical role in the regulation of GnRH neuronal activity. The level of leptin seems to have a permissive role only in lean animals. Orexins acting via OX2 receptors could be involved in the activation of reproductive function following an acute increase in nutrition. However, the neuropeptidergic systems can not be ruled out because they might be involved in very early steps of responses to nutrition.
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Earl, Colin R. "The regulation of the timing of melatonin secretion in the sheep." Title page, summary and table of contents only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phe12.pdf.
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Includes bibliographical references (leaves 166-195) Addresses the nature of the central mechanisms involved in the regulation of the circadian pattern of secretion of the pineal hormone melatonin in the highly seasonal Suffolk breed of sheep. Provides new information on the behaviour of the onset and offset of melatonin secretion under different photoperiodic conditions.
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Archer, Zoe Anne. "Neuroendocrine control of appetite and reproduction in sheep." Thesis, University of Aberdeen, 2001. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602029.
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Reproductive neuroendocrine activity and appetite are modulated at the hypothalamus by both nutritional status and photoperiod in the seasonal animal. The objectives of this work were (1) to measure circulating hormones and/or metabolites that relay information about peripheral nutritional status to the hypothalamus, (2) to identify which hypothalamic neuropeptides and receptors that are responsive to photoperiodic and nutritional feedback and (3) to establish which changes in peripheral signals and/or hypothalamic neuropeptides are associated with alterations in the activity of the reproductive neuroendocrine axis. Three main experiments were carried out. The first experiment (Chapter 1) utilised a 2 x 2 design to examine the separate and interactive effects of photoperiod and food restriction on hypothalamic neuropeptide and receptor mRNA expression and on GnRH/LH secretion. In the second experiment (Chapter 2), two components of nutritional status, BC and increased food intake were investigated since both are positively related to reproductive performance in sheep. In the final experiment (Chapter 3) the approach was to use an exogenous treatment to artificially raise plasma insulin in an attempt to "drive" some of the foregoing effects. Collectively these studies have lead to the first localisation AgRp, MCH, orexin, Mc3R, Mc4R gene expression in the ovine hypothalamus. They indicate that circulating insulin and leptin are major factors relaying information about nutritional status to the hypothalamus. In addition, they have dissociated BC and food intake as signals to the hypothalamus. Moreover these studies have provided no evidence that NPY, AgRp, POMC, MCH and ObRb play a role in driving seasonal changes in appetite and gonadotrophin secretion. However they do suggest NPY-ergic and melanocortin pathways are important in maintaining appetite/bodyweight/energy homeostasis or restoring energy balance following perturbation. Furthermore the results show that changes in nutrient-sensitive hypothalamic neuropeptide and receptor gene expression may not necessarily lead to alterations in the activity of the reproductive neuroendocrine axis. However, they do indicate that increased NPY biosynthesis during food restriction may be involved in the inhibition of pulsatile GnRH/LH release.
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Nassiri, Mohammad Taghi Beigi. "Aspects of prolificacy in Cambridge sheep." Thesis, Bangor University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321435.
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Pryor, Andrew William. "Reproduction and Endocrine Aspects of Early and Mid Lactation Holstein Cows." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32486.
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This study was designed to determine the effects of stage of lactation and subsequent energy status on metabolic and endocrine measures, follicular development, and the quality of oocytes obtained from Holstein cows. Holstein cows were selected prior to calving and assigned to the early lactation (EL) group (n=8) while, cows at d 90 postpartum were selected for the mid-lactation (ML) group (n=7). Blood samples were taken twice weekly from 4 wk prior to the start of follicular aspirations and then on through the aspiration periods for metabolite and hormone determination. Ultrasound-guided transvaginal follicular aspiration (TVFA) was conducted twice weekly for a 10-wk period on all cows. Follicular fluid samples were obtained from the largest follicle, > 10 mm in diameter, for hormone determination. All data were analyzed by ANOVA, using the general linear model procedures. Mean energy balance was positive for (2.43 ± 0.32 Mcal/kg) for ML cows and negative (-1.55 ± 0.33 Mcal/kg) for EL cows. In ML cows serum progesterone (P4) decreased rapidly from 2.7 ± 0.1 ng/ml at the first aspiration session to a nadir of 0.33 ± 0.1 ng/ml at wk 8, while follicular fluid P4 increased from 0.9 ± 0.5 to 5.6 ± 0.5 ng/ml. In the EL cows serum and follicular fluid P4 remained relatively constant over the course of aspirations. There was a linear increase in follicular fluid insulin-like growth factor I (IGF-I) for EL and ML cows, however the increase was more rapid for ML cows (159 ± 36 to 200 ± 36 ng/ml) than for EL cows (145 ± 36 to 164 ± 36 ng/ml). Over the aspiration period nonesterified fatty acids (NEFA) declined rapidly for the EL cows (0.32 ± 0.2 to 0.22 ± 0.2 mEq/L), while serum NEFA for the ML cows were relatively stable (0.19 ± 0.2 to 0.22 ± 0.2 mEq/L). The number of follicles observed during the aspiration sessions increased linearly for both EL and ML cows (P < 0.05) over the 10-wk period. However, the increase was larger for the ML cows than for the EL cows, going from 14.2 ± 0.5 to 18.1 ± 0.5 and 14.9 ± 0.3 to 15.7 ± 0.5, respectively. These results show that cows in early lactation are physiologically under more production stress than cows in mid lactation. Furthermore, increasing levels of serum and follicular fluid IGF-I in mid lactation may reflect differences in follicle and oocyte measures.<br>Master of Science
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Hamudikuwanda, Humphrey. "Endocrine and metabolic mediators of dietary energy status and reproduction in dairy cows." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28770.
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Five experiments were undertaken to identify metabolites and hormones that could mediate the effect of dietary energy status on reproduction, particularly pulsatile secretion of luteinizing hormone (LH) postpartum dairy cows.<br>In the first two experiments, the concentration of progesterone (P4) in tailhead adipose tissue and plasma in 12 cows at different stages of pregnancy and lactation was determined as was P4 produced in vitro by explants of tailhead adipose tissue. Concentration of P4 in adipose tissue was correlated with that of plasma P4 near estrus and during the luteal phase of the estrous cycle, and P4 was released in vitro by fat mobilization.<br>In the third and fourth experiments, blood was collected continuously for 16 h from four ovariectomized cows offered maintenance or restricted energy diets after priming with P4 or estradiol (E2) using a crossover experimental design. The results indicated that P4 released during body fat mobilization is minor and is not related to LH secretion. Dietary energy restriction influenced plasma LH concentration and pulse amplitude but the effect was modulated by P4 and E2 priming. Dietary energy restriction decreased glucose concentration but did not influence plasma non-esterified fatty acids (NEFA), cortisol, P4 and insulin levels. Cortisol was negatively related to LH pulse frequency. Glucose and insulin were positively and negatively correlated with LH pulse amplitude, respectively. Cortisol, NEFA and glucose jointly had a negative correlation with LH concentration.<br>In the fifth experiment, blood samples were collected daily for 60 d and every 10 min for 8 h on 18, 36 and 54 d postpartum from 24 cows (12 ovariectomized) fed low (1.4 Mcal/kg DM) (L) or high (1.7 Mcal/kg DM) (H) energy in a 2 x 2 factorial treatment design. LH pulse frequency was reduced at 18 d postpartum in ovariectomized cows, but not in intact cows, fed L. First postpartum ovulation occurred later in intact cows fed L compared to those fed H. Energy balance and plasma glucose concentration were lower, but plasma NEFA, $ beta$-hydroxybutyrate (BHB) and E2 concentrations higher, in cows fed L compared to those fed H. E2 concentration in intact cows fed L was elevated for a prolonged period prior to first ovulation. Diet had no influence on plasma P4 and insulin concentrations. Plasma E2 and BHB concentrations were positively correlated with LH pulse frequency in intact cows across diets and ovariectomized cows fed L, respectively. NEFA were negatively correlated with LH pulse amplitude in ovariectomized cows fed L. Glucose, NEFA and P4 were negatively, but BHB, E2 and insulin positively correlated, individually or in association, with LH concentration.<br>Overall, the results suggest that the effect of dietary energy status on LH patterns and timing of onset of postpartum ovulation is modulated by priming with or presence of ovarian steroids. The relationships of metabolites and hormones with LH patterns appear to change with dietary energy level, ovarian status and mutual associations among the metabolites and hormones. These parameters, especially glucose and BHB, may be potential mediators of the effect of dietary energy status on LH patterns. (Abstract shortened by UMI.)
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Cassidy, Carrie. "Further evidence that prostaglandin F2-alpha is the obligatory eicosanoid in porcine ovulation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/MQ44139.pdf.
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Cote, Fabienne. "Induction of prostaglandin endoperoxide synthase 2 in the follicles of equine chorionic gonadotropinhuman chorionic gonadotropin treated prepubertal gilts." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33741.
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Prostaglandin G/H synthase-2 (PGHS-2) is a key rate limiting enzyme in the prostaglandin (PG) biosynthetic pathway, and PG synthesis is required for ovulation in pigs. The objective of this study was to characterize the expression and regulation of PGHS-2 in porcine follicles prior to ovulation. The combination of equine chorionic gonadotropin (eCG; 750 IU) followed by human chorionic gonadotropin (hCG; 500 IU) 72 h later was used to induce ovulation in prepubertal gilts. Previous studies have shown that ovulation is generally induced between 40 and 44 h post-hCG in this model. Ovariectomies were performed at 0, 24, 30, 34 and 38 h post-hCG (n = 4 or 5 animals per time-point), and all follicles larger than 4 mm in diameter were isolated. The regulation of PGHS-1 and PGHS-2 proteins was studied by immunohistochemistry and Western blot analyses, whereas the regulation of PGHS-2 mRNA was studied by Northern blot. PG production was assessed by radioimmunoassay (RIA). (Abstract shortened by UMI.)
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Algire, James Edgar. "Prostaglandins in follicular development and ovulation in cattle." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61849.
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Mootoo, Judy E. (Judy Elizabeth). "Lipoxygenase metabolites of arachidonic acid in the porcine ovulatory process." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22779.
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It is widely accepted that prostaglandins (PGs), produced via the cyclooxygenase pathway from arachidonic acid, are essential to the ovulatory process in the pig. In support of this, ovulation is preceded by an increase in follicular fluid (FF) PG concentration, indomethacin (INDO) suppresses both the PG increase and ovulation, and ovulation can be restored by administration of exogenous PGs (Downey and Ainsworth, 1980; Prostaglandins 19: 17-22). Recent studies in the rat have shown that ovulation is also preceded by a rise in ovarian concentrations of 15-hydroxyeicosatetraenoic acid (15-HETE), a product of the lipoxygenase pathway (Tanaka et al., 1989; Endocrinology 15: 1373-1377) and inhibition of this pathway suppresses ovulation (Reich et al., 1983; Prostaglandins 26: 1011-1020). Furthermore, INDO, a cyclooxygenase inhibitor, inhibits 15-lipoxygenase as well as PG synthesis (Tanaka et al., 1989 Endocrinology 15: 1373-1377). The PMSG/hCG prepuberal gilt model was used to investigate the involvement of 15-HETE in the procine ovulatory process, and the effect of INDO on the 15-lipoxygenase pathway. Follicular fluid concentrations of 15-HETE were elevated 40 h post hCG (p $<$ 0.01). The effects of INDO and nordihydroguaiaretic acid (NDGA), an inhibitor of lipoxygenase activity, on ovulation rate, FF 15-HETE and FF PGF$ rm sb{2a}$ were investigated by intraovarian administration of INDO or NDGA. INDO inhibited ovulation rate (p $<$ 0.01) and PGF$ rm sb{2a}$ (p $<$ 0.01) as well as 15-HETE (p $<$ 0.01). NDGA also suppressed ovulation rate (p $<$ 0.01) but did not inhibit 15-HETE or PGF$ rm sb{2a}$ production. In in vitro experiments, 15-HETE production by both granulosa cell (GC) and theca interna cell (TIC) cultures 40 h post hCG was greater (p $<$ 0.01) than at 0 h post hCG. INDO inhibited 15-HETE production in 40 h post hCG TIC cultures (p $<$ 0.01) but not GC cultures, while NDGA inhibited 15-HETE production by both cell types (p $<$ 0.01). These results sugges
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Grant, Gerald F. "The association between prostaglandins and the plasminogen activator/plasmin system in the porcine ovulatory process /." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69759.
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The objectives were: (1) to determine the pre-ovulatory changes in plasminogen activator (PA) and (PA) inhibitor (PAI) activities in the porcine follicle, and, (2) to determine if changes in the PA/plasmin system associated with ovulation were prostaglandin (PG)-dependent. PA activity (change in absorbance/h/mg wet tissue weight, three gilts per treatment group) was elevated in both granulosa cells (GC) and theca interna cells (TIC) prior to human chorionic gonadotropin (hCG) administration (0.582 $ pm$ 0.171 and 0.718 $ pm$ 0.221, respectively) but returned to basal levels in these two compartments (0.023 $ pm$ 0.013 and 0.052 $ pm$ 0.024, respectively) at 29 h post-hCG. PA activity remained basal thereafter in GC but increased approximately ten-fold in the TIC (0.549 $ pm$ 0.239) at the time of ovulation (three gilts at 41 h and one of three gilts at 38 h). PAI activity did not change in TIC over the pre-ovulatory period but increased in GC as ovulation approached. PAI activity in GC peaked at 38 h (being significantly different (p $<$ 0.05) to all other times except 41 h). Although indomethacin (INDO) effectively inhibited both PG synthesis (1.1 $ pm$ 0.2 vs. 9.2 $ pm$ 0.9 ng/ml in controls) and ovulation (0 vs. 27-61% in controls), elevated PA activity (0.801 and 0.349) was detected in the TIC of two out of nine INDO-treated gilts. Levels were basal (0.074 $ pm$ 0.028) in the other gilts. These inconclusive results are believed to reflect the occurrence of ovulation earlier than predicted, in as many as 40% of control gilts, and the short duration of increased PA activity at this time. In conclusion, elevated PA activity, in GC and TIC prior to ovulation induction, may play a role in follicular development. Elevated TIC PA activity may play an important role in the ovulatory process, but is probably PG-independent.
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Kwan, Ivy. "The effect of ACTH and steroidal antiinflammatory agents on prostaglandin F2a levels in vivo and in vitro using a spontaneously established porcine granulosa cell line /." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61233.
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In vivo experiments were conducted to determine if elevated plasma glucocorticoid concentrations would suppress intrafollicular prostaglandin F2$ alpha$ (PGF2$ alpha$) synthesis and, thereby, inhibit ovulation in the pig. Following ACTH administration, PGF2$ alpha$ concentrations in FF tended to be lower than in controls. Injections of betamethasone partially suppressed the preovulatory rise of PGF2$ alpha$ in FF at 40h, although the effect was less marked than that produced by indomethacin. While no ovulations occurred in the indomethacin-treated group at any time, betamethasone resulted in a lower number of ovulated follicles at 44h than in the control animals. Progesterone concentrations were unaffected by the treatments.<br>In vitro studies were conducted with a spontaneously established cell line developed through continuous culturing of primary granulosa cells collected from prepuberal gilts six hours after they had received PMSG. Characterization of these cells revealed that aromatase and steroidogenesis were functional but gonadotropin receptors were not present. When extracellular PGF2$ alpha$ levels were measured, dexamethasone was able to significantly suppress PGF$ sb{2 alpha}$ concentrations, but not as effectively as with indomethacin. (Abstract shortened by UMI.)
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Krown, Kevin Alan. "Pituitary changes in force-molted hens." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185205.
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The effect of forced molt on pituitary function and other endocrine parameters was investigated in three year old hens subjected to a dietary forced molting procedure. In addition to molting, fasting caused cessation of egg production, body and organ weight loss, alterations in hormone secretion and morphological changes in some endocrine glands. Body and ovary weights decreased but returned to normal with ad libitum feeding. Pituitary, thyroid and adrenal weights were not affected but serum hormone levels measured by RIA revealed a decrease in LH, FSH and PRL and increases in TSH, T₃ and GH all of which returned to higher levels with ad libitum feeding. Serum P₄ levels remained low (and egg-laying stopped) until ad libitum feeding was resumed and then increased and egg-laying returned to a typically productive level. Serum ACTH and T₄ increased with fasting and remained elevated. Gonadotrophs and corticotrophs increased in numbers with fasting and/or food restriction but thyrotrophs, somatotrophs and lactotrophs decreased. Correlations between cell populations and serum hormone levels was quite common. Colloid-filled follicles resembling a hypertrophic thyroid gland occurred throughout the pituitary pars distalis. Granules appear to be discharged into the follicular lumen through exocytotic pores in the apical plasmalemma of follicular cells. Lactotrophs, corticotrophs and somatotrophs are commonly arranged in follicles or clusters. PRL-containing granules are in the center of some follicles and are concentrated near pituitary cysts. Pituitary cysts, lined with ciliated epithelium and sparse mucous cells, are more prevalent in fasted hens and decline with the resumption of feeding. Reduced lactotroph populations and presumptively degenerated lactotrophs in cyst lumens are correlated with reduced serum PRL levels. Necrotic cells occurred in the pituitary parenchyma of fasted birds but dilated RER in the thyrotrophs of fasted hens indicate enhanced activity of these cells. Ultrastructural evidence presented here indicates that pituitary secretion by lactotrophs occurs both intraluminally and perivascularly.
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Spaulding, Benjamin W. "Endocrine Disruption in Atlantic Salmon (Salmo salar) Exposed to Pesticides." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/SpauldingBW2005.pdf.
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Fernandes, Herman A. "Vitellogenesis in the teleost Brachydanio rerio (Zebra fish) /." Title page, abstract and table of contents only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phF363.pdf.
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Stackpole, Catherine Amelia. "The effects of isolation and restraint stress, and cortisol, on the responsiveness of the anterior pituitary to gonadotrophin-releasing hormone in rams and ewes." Monash University, Dept. of Physiology, 2004. http://arrow.monash.edu.au/hdl/1959.1/9585.
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Abdo, Michael A. "Tumour necrosis factor : alpha signal transduction in rat corpus luteum apoptosis." University of Western Australia. School of Anatomy and Human Biology, 2002. http://theses.library.uwa.edu.au/adt-WU2003.0024.
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[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] Apoptosis is a morphologically distinct form of cell death that is involved in the regulation of normal and aberrant cell systems. The complexities of the apoptotic cell death pathway arise from variation in both the cellular specialisation and initial stimulus. The corpus luteum (CL) is an endocrine gland that whilst critical to the maintenance of pregnancy in the rat, regresses at the completion of each oestrous cycle and pregnancy. This regression is facilitated through apoptosis; though, the stimulus and factors involved in the apoptotic pathway are poorly understood. Previous studies suggest that CL regression is not initiated through failure of luteotrophic support, but rather the active production of a luteolytic factor, of which tumour necrosis factor -alpha (TNFα) is one possible candidate. Several publications have reported the participation of the immune system in ovarian events. There is evidence that TNFα expression within the ovary is coordinated between cells of the immune system and the hormonal regulation of the CL. This study has focussed on the role of TNFα in CL apoptosis and the factors involved in this apoptotic pathway. TNFα-induced cell death is governed by the presence of the two TNFα receptors (TNFR) and several second messenger systems that include; the sphingolipids, mitogen-activated protein (MAP) kinases, nitric oxide (NO), nuclear factor-kappaB (NF-κB) and the caspases. These factors and their interactions were assessed in the rat CL during pregnancy and post-partum, and in vitro. Apoptosis was measured through the analysis of DNA fragmentation using DNA 3’ end labelling and single cell electrophoresis (COMET assay). Assessment of mRNA and protein expression was through Real-time RT-PCR and Western blot analysis; proteins were localised within the CL by immunocytochemistry. In addition, specific measurement of sphingolipid expression and nitric oxide (NO) production was by high performance liquid chromatography (HPLC) and NO assay respectively. Following parturition, TNFα mRNA and protein expression increased corresponding to the onset of CL apoptosis and increased expression of the chemotactic factor monocyte chemoattractant protein -1 (MCP-1). Furthermore, CL apoptosis was induced by treatment with recombinant TNFα in a time- and dose-dependent manner. A similar effect was observed in isolated luteal cells. Simultaneously, the functional regression of the CL was assessed by measurement of both progesterone synthesis and steroidogenic acute regulatory (StAR) protein expression. StAR mRNA and protein expression declined toward parturition in vivo. Immunocytochemical studies revealed the presence of TNFα receptors 1 (TNFR1) and 2 (TNFR2) in luteal cells. Furthermore, TNFR mRNA was isolated from CL throughout pregnancy and post-partum. Subsequently, the role of the sphingolipids ceramide and sphingosine was examined during CL apoptosis in vitro. Ceramide and sphingosine were found to be potent apoptotic agents when administered in vitro (50µM). The downstream signal transduction of TNFα and ceramide was assessed through MAP kinase expression. Both TNFα and ceramide increased expression of the pro-apoptotic p38 MAP kinase with no change to the non-apoptotic extracellular signal-related kinase (ERK1&2). Despite previous reports of c-Jun NH2 terminal kinase (JNK) involvement in the cell death pathway, JNK expression was not evident in the rat CL. The caspases are a family of cysteine proteases central to the regulation and execution of apoptosis. General inhibition of the caspase cascade in vitro was effective in preventing apoptosis regardless of the apoptotic stimulus (TNFα, ceramide and sphingosine), suggesting that this pathway is central to CL apoptosis. Specific inhibition of several caspases produced a varying effect; inhibition of caspases 3, 6 and 8 significantly reduced the level of TNFα-induced apoptosis, thus supporting their classification as either regulatory or effector caspases. NO is endowed with the unique ability to initiate and to block apoptosis and this dichotomy extends to the cytotoxic actions of TNFα. Inhibition of NO production by treating CL with L-NAME prevented the onset of apoptosis, whilst NO production increased in response to increasing levels of apoptosis following trophic withdrawal. However, this effect was not seen during TNFα-induced apoptosis, suggesting that the actions of NO are independent of TNFα. The data presented within this study examine multiple elements of the TNFα cell death pathway in a single system. The results suggest that these elements are involved in TNFα signal transduction and furthermore, in rat CL apoptosis. It can be said that TNFα plays an active role in CL regression through the activation of the caspases, the sphingolipids and the MAP kinases.
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Kahwa, David. "Gametogenesis, gonadal recrudescence, restraint and spawning patterns in Nile perch, Lates niloticus (Linnaeus, 1758)." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001834.
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The Nile perch, Lates niloticus (Linnaeus, 1758), is a predacious freshwater fish widely distributed throughout the Afro-tropic eco-zone. The species was introduced to Lake Victoria in the early 1950s and by 1980 it had dominated the fisheries of Lake Victoria. This was followed by a dramatic decrease in the Nile perch fisheries production due to uncontrolled exploitation. The purpose of this thesis is to provide fundamental knowledge that can be applied in aquaculture and fisheries management through the study of the reproductive biology of L. niloticus. The research was aimed at the studying of the diverse aspects of the reproductive biology of L. niloticus in the Lake Victoria, Ugandan populations. This included reproductive patterns in relation to proximate environmental conditions, size at sexual maturity, gonad and gamete structure, gametogenesis and induced ovulation. The size at 50% sexual maturity for female Nile perch was 59.4 cm, which is lower than the earlier reported size of greater than 90 cm total length. Male L. niloticus matured at 57.8 cm total length in Lake Victoria. Microscopy revealed that L. niloticus from Lake Victoria had one spawning period that started in November and ended in March. Type I atresia occurred at high frequency from March to June, and type III atresia was present from July to September and between November and December. Spermatogenesis in L. niloticus is cystic and sperm development is the result of asynchronous activation of the germ cells. Type II spermatozoa are simple, uni-flagellate aquasperm with no acrosome. Oogenesis in L. niloticus differed from that of other fishes in that no cortical alveoli were present in any stage of oogenesis. Numerous oil globules were present in the primary yolk vesicle stage. This formed one centrally positioned, large oil globule in the tertiary yolk vesicle oocytes during final oocyte maturation. Clove oil was an effective sedative and an anaesthetic for the handling of L. niloticus. Induction time was more rapid at clove oil concentrations of 50 - 100 μl L⁻¹ than in fish exposed to clove oil concentrations less than 50 μl L⁻¹. Fish exposed to high concentrations exhibited significantly short induction times of less than 240 seconds. On average, fish recovered within 673 ± 58 seconds for all the concentrations used. Prolonged exposure of L. niloticus to low clove oil concentrations of 2.5 - 10 μl L⁻¹ did not change the blood plasma cortisol, glucose, and the lactate and chloride ion concentration, relative to the control treatment. Captive breeding was attempted by conducting induced spawning experiments. Only final oocyte maturation was achieved using a decapeptide Gonadotropin Releasing Hormone (Dargin, sGnRH-MET), combined with a water-soluble dopamine receptor antagonist metoclopramide. This thesis suggests a research approach that provides a basis for aquaculture of the new species by first studying reproductive biology patterns and then linking the information to gonad and gamete structure so that spawning times can be estimated. It further provides insights into aspects of the reproductive biology of the species and the effects of hormonal intervention on oocytes by showing at which stage of oocyte development hormones should be applied in L. niloticus. Clove oil can be used to sedate and anaesthetise L. niloticus broodfish to reduce the stress related to the handling of large specimens.
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Kromrey, Natalie A., and University of Lethbridge Faculty of Arts and Science. "The effects of wastewater treatment plant effluent and agricultural runoff on the reproductive systems of fathead minnow, Pimephales promelas." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, c2009, 2009. http://hdl.handle.net/10133/2519.
Full textAbstract:
Endocrine disrupting compounds and pesticides have been detected in rivers and
irrigation canals of Southern Alberta, a semiarid region with irrigation-dependent crop
production, intensive livestock operations, and a growing human population. However,
little is known about the effects of agricultural runoff or wastewater treatment plant
(WWTP) effluent in Southern Alberta on fish. Reproductive effects of WWTP effluents
from the cities of Lethbridge and Medicine Hat, as well as agricultural runoff in the
Lethbridge Northern Irrigation District canals, were investigated in a field study with
wild fathead minnows (FHMN) in the Oldman and the South Saskatchewan rivers, in
Alberta, Canada, and in a laboratory study with laboratory reared FHMN exposed in vivo
to the city of Lethbridge WWTP effluent for 21 days. Biochemical and morphological
endpoints were measured to characterize reproductive status. Liver vitellogenin, a
biomarker of exposure to estrogen mimics, was analyzed using quantitative RT-PCR, and
gonadal histology was used to determine sex, gonadal maturity, and intersex. Adverse
reproductive effects were detected in FHMN exposed for 21 days to 10 and 25% of
Lethbridge WWTP effluent. In the field, effluents from both Lethbridge and Medicine
Hat had an effect on the reproductive systems of FHMN. In canals, reproductive effects
were detected in wild fathead minnows in years when water quality in irrigation drain
canals decreased. Exposure to pesticides was estimated using acetylcholinesterase
(AChE) inhibition. Exposure to Lethbridge WWTP effluent did not inhibit AChE,
whereas results from the field study were inconclusive. In conclusion, reproductive
systems of fathead minnows in Southern Alberta were impacted by anthropogenic
chemicals.<br>xi, 104 leaves : ill. (some col.), maps ; 29 cm
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Corbel, Tanguy. "Mécanismes toxicocinétiques impliqués dans l'exposition foetale au Bisphénol A." Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0034/document.
Full textAbstract:
Le Bisphénol A (BPA) est un perturbateur endocrinien dont les effets développementaux observés chez les rongeurs soulèvent la question du risque pour la santé humaine relatif à une exposition fœtale au BPA. L’objectif de cette thèse est de déterminer les mécanismes toxicocinétiques impliqués dans l’exposition fœtale au BPA. La caractérisation in vivo dans un modèle intégratif ovin des expositions maternelles et fœtales au BPA et à ses métabolites ont permis d’identifier le transfert placentaire et le métabolisme fœto-placentaire comme les déterminants majeurs de l’exposition fœtale au BPA. Le transfert bidirectionnel du BPA à travers le placenta humain se fait par diffusion passive conduisant à un rapport maximal des concentrations plasmatiques de BPA libre entre le fœtus et sa mère de 1. En revanche, la perméabilité placentaire du BPA-G est très limitée, en particulier dans le sens materno-fœtal. Les activités de conjugaison hépatique du BPA ont été faibles chez le fœtus ovin à un stade précoce de gestation et ont augmenté au cours du développement. Par ailleurs la réactivation des conjugués du BPA mise en évidence ex vivo dans les gonades fœtales ovines pourrait conduire à une exposition locale au BPA actif. L’ensemble de ces données suggère que le début de la gestation pourrait représenter une fenêtre critique d’exposition au BPA<br>Bisphenol A (BPA) an endocrine disruptor interfering with developmental processes in rodents, raises the question of risk for human health related to fetal exposure to BPA. The goal of this work was to determine the toxicokinetic mechanisms involved in fetal exposure to BPA. The disposition of BPA and its metabolites in the maternal-placental-fetal unit in an in vivo ovine model enabled us to identify the placental transfer and the fetal-placental metabolism as the major determining factors of fetal exposure to BPA. Bidirectional placental transfer of BPA occurs by passive diffusion leading to a ratio of free BPA between the fetal and maternal plasma concentrations of about 1. By contrast, the permeability of BPA-G is very limited, particularly in materno-to-fetal direction. The hepatic conjugation activities were very low in ovine fetus at an early stage of development and increased throughout pregnancy. Hydrolysis of BPA conjugates observed ex vivo into fetal ovine gonads could lead to local exposure to native BPA. Altogether, these results suggest that the early stage of pregnancy is a critical window of exposure for the developing fetus
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Dunlap, Kathrin Anson. "Nongenomic inhibition of oxytocin binding by progesterone in ovine uteri." Thesis, 2002. http://hdl.handle.net/1957/31586.
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Earl, Colin R. "The regulation of the timing of melatonin secretion in the sheep." Thesis, 1989. http://hdl.handle.net/2440/19577.
Full textAbstract:
Includes bibliographical references (leaves 166-195)<br>xxi, 195 leaves : ill. ; 30 cm.<br>Addresses the nature of the central mechanisms involved in the regulation of the circadian pattern of secretion of the pineal hormone melatonin in the highly seasonal Suffolk breed of sheep. Provides new information on the behaviour of the onset and offset of melatonin secretion under different photoperiodic conditions.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Sciences, 1989
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Papachristoforou, Christakis. "Androgenic and oestrogenic effects on the endrocrinology of reproductive development in male and female sheep (Ovis aries L.) / by Christakis Papachristoforou." 1988. http://hdl.handle.net/2440/18634.
Full textAbstract:
Typescript.<br>"April 1987."<br>Includes bibliograpical references (leaves 160-194).<br>xii, 194 leaves : ill. ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>Presents direct comparative information on growth and endocrinological aspects of reproductive development in intact and gonadectomized male and female Merino lambs born in autumn and treated prepubertally with either a non-aromatizable androgen (trenbolone acetate) with higher androgenic potency than testosterone, oestradiol -17beta(oestradiol), or a combination of these two steroid hormones.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Sciences, 1988
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Papachristoforou, Christakis. "Androgenic and oestrogenic effects on the endrocrinology of reproductive development in male and female sheep (Ovis aries L.) / by Christakis Papachristoforou." Thesis, 1988. http://hdl.handle.net/2440/18634.
Full textAbstract:
Typescript.<br>"April 1987."<br>Includes bibliograpical references (leaves 160-194).<br>xii, 194 leaves : ill. ; 30 cm.<br>Presents direct comparative information on growth and endocrinological aspects of reproductive development in intact and gonadectomized male and female Merino lambs born in autumn and treated prepubertally with either a non-aromatizable androgen (trenbolone acetate) with higher androgenic potency than testosterone, oestradiol -17beta(oestradiol), or a combination of these two steroid hormones.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Sciences, 1988
27
Slayden, Ov Daniel. "Endocrine regulation of uterine physiology in mink." Thesis, 1990. http://hdl.handle.net/1957/37449.
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Fitzpatrick, Martin S. "Endocrine regulation of final oocyte maturation and sex differentiation in salmonids." Thesis, 1990. http://hdl.handle.net/1957/37097.
Full textAbstract:
Sexual maturation and sex differentiation comprise facets of a
common theme: reproduction. The endocrine system regulates many
of the critical physiological processes necessary for reproduction and
offers a framework within which technologies can be developed for
controlling sexual maturation and sex differentiation. The studies
described in this thesis were undertaken to improve the
understanding of the endocrine control of these critical stages of
development in salmonids.
Final ovarian maturation in salmon is accompanied by dynamic
changes in plasma hormone levels. Ovulation can be accelerated
through the use of hormones such as gonadotropin releasing hormone
or its analogs (GnRHa). The effectiveness of GnRHa often depends on
the timing of treatment. To determine if plasma concentrations of
steroids can be used to predict the sensitivity of adult female coho
salmon (Oncorhynchus kisutch) to GnRHa, circulating levels of
testosterone, 17α,20β-dihydroxyprogesterone (DHP), and estradiol
were measured before and after injection with GnRHa to accelerate
ovulation. We found that high levels of testosterone were predictive of
early response of coho salmon to GnRHa treatment.
The correlation between testosterone and ovulatory response to
GnRHa suggested a possible functional relation. However.
implantation or injection of testosterone. 17α-methyltestosterone
(MT), or the antiandrogen, cyproterone acetate (CA), before or with
GnRHa treatment did not affect the ovulatory response of coho or
chinook salmon ( 0. tshawytscha) to GnRHa. Chinook salmon treated
with MT alone had accelerated ovulation in comparison to controls.
If steroids are involved in sex differentiation. steroids must be
produced early in development. In vitro production of steroids in both
coho salmon and rainbow trout (0. mykiss) was assessed from hatch
through sex differentiation. Cortisol, androstenedione, testosterone,
and estradiol were produced just after hatching by tissue explants that
contained anterior kidneys and gonads of coho salmon. To circumvent
the problem of not knowing the sex of individuals until after sex
differentiation, single-sex populations of rainbow trout were produced
by gynogenesis or androgenesis. Tissue explants produced more
androstenedione than testosterone or estradiol. More androgens were
produced by testes and more estradiol was produced by ovaries within
6 to 10 weeks of hatching. Dietary treatment with estradiol or MT
inhibited gonadal steroid secretion.
Electrophoresis of gonadal homogenates from salmonids
revealed several sex-specific bands. In particular, a prominent band of
about 50,000 daltons was apparent in ovaries but not testes.
Production of sex-specific proteins may be affected by dietary steroid
treatment.<br>Graduation date: 1991
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Fouché, Chris Henri. "Endokrinologie en histomorfologie van die gonades van Cyprinus carpio L." Thesis, 2014. http://hdl.handle.net/10210/10618.
Full textAbstract:
M.Sc. (Zoology)<br>The histomorphology of the ovaries of Cyprinus carpio L., as well as the histomorphological changes that occur in these ovaries during the breeding cycle, were investigated. Concurrently, the blood plasma and ovarian cytosol were analized for the presence of gonadotropin (GtH), FSH, LH, Oestriol, Cortisol and Progesterone, with the aid of Test Kits which are commonly used for determining the levels of these hormones in human blood plasma. C. carpio possesses cystovaria which are continuous with the oviducts which unite before opening to the exterior via a gonopore. The results clearly show that C. carpio has a four season breeding cycle and that egg laying occurs during Spring and Summer. Furthermore morphological changes of the ovary (which occurred during the breeding cycle) as well as the oocyte developmental stages, closely resemble those respectively described for teleosts in general by Kesteven (1960) and Malhotra et al., (1978). The endocrinological tests clearly indicated the presence of GtH, FSH, LH, Oestriol and Cortisol, while all the tests for Progesterone were negative. A comparison between the presence of the abovementioned hormones and the histomorphological development of the ovaries during the breeding cycle indicate that the endocrinological control mechanisms are similar to those which have been described for other teleosts. However, a clear distinction was found between FSH and LH which is a possible indication that C. carpio does not possess a single gonadotropin, but rather that FSH and LH have evolved in this species.
30
Von, Deneen Karen M. "Plasma and fecal progestins during placentation in the mare." Thesis, 2002. http://hdl.handle.net/1957/32378.
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Putluru, Ravi K. "Differential expression of superoxide dismutases (SODS) in bovine corpus luteum during estrous cycle and pregnancy." Thesis, 2006. http://hdl.handle.net/10125/20395.
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Reed, Pamela J. "Studies on luteinizing hormone and gonadal steroids in male and female llamas (Lama glama)." Thesis, 1996. http://hdl.handle.net/1957/34576.
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Cortell, Anna Katherine. "Cyclopropenoid fatty acid-induced suppression of ovine corpus luteum function." Thesis, 1990. http://hdl.handle.net/1957/38222.
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Lynch, Kathleen Sheila. "Hormonal mechanisms for variation in female mate choice." Thesis, 2005. http://hdl.handle.net/2152/1619.
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Abu, Hasan Abu Dalya. "Human sperm diagnostic tests : a sequential approach during assisted reproduction management." 2011. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000160.
Full textAbstract:
D. Tech. Biomedical Sciences.<br>Discusses despite significant advances in andrological techniques, the execution of semen analysis is currently not performed in a sequential manner. As such, it is important that reproductive biology laboratories establish an optimal diagnostic scheme that will assist reproductive health workers to direct patients to a specific therapeutic intervention and procedure.
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Luna, Gonzalo. "Endocrine changes associated with the effect of nutrition on the timing of reconception and puberty in dairy cattle." Diss., 2000. http://hdl.handle.net/2263/22854.
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Sucheta, Susan Leers. "Secretion of luteinizing hormone in response to exogenous melatonin in postpartum beef cows and ovariectomized beef heifers." Thesis, 1993. http://hdl.handle.net/1957/35696.
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Widmann, Andrea A. "Development of an enzyme immunoassay using whole plasma to determine progesterone concentrations during early pregnancy in the mare." Thesis, 1991. http://hdl.handle.net/1957/37384.
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Ramsey, Mary Elizabeth 1965. "Molecular mechanisms underlying steroid hormone action during sex determination in the red-eared slider turtle, Trachemys scripta elegans." Thesis, 2007. http://hdl.handle.net/2152/3148.
Full textAbstract:
Many reptiles, including the red-eared slider turtle (Trachemys scripta elegans), exhibit temperature-dependent sex determination (TSD). Temperature determines sex during a temperature sensitive period (TSP), when gonadal sex is labile to both temperature and hormones -- particularly estrogen. Estrogen production is a key step in ovarian differentiation for many vertebrates, including TSD reptiles, and temperaturebased differences in aromatase expression during the TSP may be a critical step in ovarian determination. Steroidogenic factor-1 (Sf1) is a key gene in vertebrate sex determination and regulates steroidogenic enzymes, including aromatase. The biological actions of steroid hormones are mediated by their receptors, defined here as the classic transcriptional regulation of target genes. To elucidate the mechanism of estrogen action estrogen during sex determination, I examined aromatase, Sf1, ER[alpha], ER[beta], and AR expression in slider turtle gonads before, during and after the TSP, as well as following sex reversal via temperature or steroid hormone manipulation by administering exogenous estradiol (E2) or aromatase inhibitor (AI) to the eggshell. Sf1 is expressed at higher levels during testis development and following maleproducing temperature shift and AI treatment, while aromatase increases during ovary determination and feminizing temperature shift and E2 treatment. My results do not lend support to a role for Sf1 in the regulation of aromatase expression during slider turtle sex determination, but do support a critical role for estrogen in ovarian development. Estrogen receptor [alpha] and AR levels spike at the female-producing temperature just as aromatase levels are increasing during ovarian sex determination, while ER[beta] remains constant and only increases late in ovarian differentiation -- well after estrogen levels have increased, indicating that ER[alpha] and ER[beta] may have distinct roles in slider turtle ovarian development. Estrogen receptor [alpha] and ER[beta] are expressed along developing sex cords in the absence of estrogen (AI treatment). When shifted to female-producing temperatures, embryos maintain medullary ER[alpha] and AR expression while ER[beta] is reduced. By contrast, ER[alpha] and ER[beta] redirect to the cortex in E2-created ovaries. Warmer temperature and E2 result in the same endpoint (ovarian development), but may entail different steroid signaling patterns between temperature- and estrogen-induced feminization.<br>text
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Wilson, Colleen Gay. "Metabolism of progestins in the pregnant equine." Thesis, 1992. http://hdl.handle.net/1957/37058.
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Riad, Mohamed Tarek. "Urinary estrogens and progestins in pregnant pony mares." Thesis, 1993. http://hdl.handle.net/1957/36880.
Full textAbstract:
Urinary steroids have been studied during early and late pregnancy in
domestic horses or sporadic samples at various stages of pregnancy in wild
equidae. In our studies, urinary estrone sulfate (E1S) and pregnanediol
glucuronide (PdG) were monitored throughout pregnancy in six pony mares by
enzyme immunoassay (EIA). Both hormones were corrected by creatinine (Cr)
index to compensate for the variation in specific gravity. The mean
concentration for ElS, (μg/mg Cr), was .38 ± .03 at d 0, decreased to .17 ±
.04 at d 1, and maintained at less than .5 μg/mg Cr until d 30. Although, there
was an apparent increase to .80 ± .34 at d 34 (NS, P = .122), the first
significant increase was .69 ± .15 at d 46 (P = .0275). Mean concentrations
remained relatively stable at this approximate level until d 60. This level was
followed by a sustained significant increase observed from d 60 onwards.
Mean concentrations of El S increased to 1.11 ± .25, 2.01 ± .45, and 5.48
± 1.47 at d 64, d 76, and d 86, respectively. Levels of EIS further increased
reaching a peak of 143.3 ± 9.51 at d 142 (P = .0006), with maximum for
individual mares ranging from d 114 to 170, and also ranging from 115.4 to
286.1 pg/mg. In all cases, maximum concentrations were followed by a
gradual decline toward parturition with a more rapid decrease 1 to 3 days
before parturition. The first significant decrease following the maximum
concentration was 91.40 ± 13.11 (P = .0024) at d 184. Estrone sulfate was
12.1 ± 3.8 one day prepartum and decreased to .4 ± .1 and .1 ± .01 at d 1
and 4 postpartum, respectively. The mean concentrations of PdG (ng/mg Cr)
increased from 147 ± 4.3 at d 0 to 50.87 ± .17 (NS, P> .05), 36.8 ± 8.1
(P = .016), and 27.6 ± 7.3 (P = .049) at d 6, 8 and 10, respectively. This
increase was followed by a decline and generally the levels fluctuated ranging
from 20 to 30 ng/mg Cr until d 80. At d 86, the PdG levels increased to 54.7
± 11.7 (P = .033). This was followed by a further increase to 141.8 ± 21.4
(P = .0139, compared to d 93) at d 135, then continued to increase to 213.0
± 25.2 at d 198, and remained at this approximate level until d 303. During
the last month of gestation, the mean concentrations of PdG increased from
171.8 ± 9.8 at d 29 prepartum to reach a peak of 388.4 ± 108.6 at d 7
prepartum. Maximum concentrations were followed by a slight decrease to
354.5 ± 84.0 at d 1 prepartum and then decreased to 150.6 ± 23.4 and 39.6
± 9.3 ng/mg Cr at d 1 and 4 postpartum.
In comparing the two hormones, E1S remained baseline followed by a
slight increase at d 35, whereas PdG was relatively stable until both hormones
increased after d 70 of gestation. This might be related to secretion of both
hormones by the fetus and their rapid metabolism by placenta. Estrone sulfate
reached a peak at approximately d 142 followed by a decline toward parturition
while PdG showed a rapid increase from d 70 to 150, followed by a slow
sustained increase to d 300 then increased dramatically again before
parturition, while El S continued to decline. The profile of these urinary
hormones throughout pregnancy appeared to parallel previously published
concentrations in blood. Since the patterns of urinary EIS and PdG are
different, their sites and mechanism of metabolism are likely different. The
results indicate that the presence of the feto-placental unit is important for the
secretion of both estrogens and progestins throughout pregnancy and thus
could be utilized as a reliable method for pregnancy determination after three
months of pregnancy.<br>Graduation date: 1993
42
Orchinik, Miles. "Biochemical and behavioral characterization of steroid receptors in neuronal membranes." Thesis, 1992. http://hdl.handle.net/1957/36531.
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Fernandes, Herman A. "Vitellogenesis in the teleost Brachydanio rerio (Zebra fish) / Herman A. Fernandes." Thesis, 1994. http://hdl.handle.net/2440/22503.
Full textAbstract:
Bibliography: leaves 129-158.<br>xvii, 159, [11] leaves, [24] leaves of plates : ill. (some col.) ; 35 cm.<br>The major estrogen inducible protein in zebra fish liver has been purified to homogeneity by FPLC using anion exchange chromatography (Mono-Q Pharmacia) with purification being monitored by SDS-PAGE electrophoresis.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Obstetrics and Gynaecology, 1995?
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Maffucci, Jacqueline Ann. "The role of the N-methyl-D-aspartate receptor (NMDAR)--NR2b subunit in female reproductive aging." 2008. http://hdl.handle.net/2152/18180.
Full textAbstract:
Reproductive senescence in females is a natural part of the aging process. However, the process by which it occurs, and the relative role of each level of the hypothalamic-pituitary-gonadal axis, remains largely unknown. The neural circuitry regulating the hypothalamic axis, including glutamate acting through N-Methyl-D-Aspartate receptors (NMDARs) on GnRH neurons, appears to be key to this process. The NMDAR is tetrameric and composed of an obligatory NR1 subunit together with NR2 subunits. The subunit composition determines the channel kinetics of the receptor and changes through the life span. This dissertation examines the physiological role of the NR2b subunit on LH pulsatile release and LH surge, both important for reproductive function. The expression of NR2b subunits in the anteroventral periventricular (AVPV) nucleus of the hypothalamus was also examined in aging rats. Experiment 1 showed that the NR2b-antagonist, ifenprodil, enhanced pulsatile LH release in estradioltreated females (both age groups). Experiment 2 showed that the LH surge in middle-aged animals was slightly accelerated and that results were dependent upon prior reproductive status of the animals. In Experiment 3, examination of the NR2b-immunoreactive cell population in young, middle-aged, and aged ovariectomized females given vehicle, estradiol, or estradiol with progesterone showed an age-associated decline in NR2b density. However, the immunofluorescent fraction volume of NR1 colocalized with NR2b increased with aging, and that of immunofluorescent fraction volume of NR2b increased with estradiol treatment. This is indicative of the amount of protein expressed in the AVPV. In total, NR2b cell density in the AVPV declines with age, but the amount of NR2b expressed in NR1-positive cells increases, suggesting a larger population of NR2b containing channels. This may translate to age-associated inhibition of GnRH/LH activity, which is relieved with blockade of NR2bcontaining NMDARs. Thus, this dissertation describes a novel way to examine the mechanism by which age-associated changes to neuromodulators of the HPG axis may affect the onset of reproductive senescence.<br>text
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Al-Matubsi, Hisham Y. "Regulation of ovarian oxytocin and prostaglandin F2[alpha] release in the ovine oestrous cycle." Thesis, 1998. https://vuir.vu.edu.au/15557/.
Full textAbstract:
This thesis addresses the regulation of ovarian oxytocin and prostaglandin F2a (PGF2a) release in the ovine oestrous cycle, their role in luteolysis and a possible mechanism by which the oxytocin secretory pathway is controlled in ovarian tissue.
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Deshpande, Shayu. "Insights Into The Hormonal Regualtion Of Epididymal Function : A Role For Estrogen." Thesis, 2005. http://etd.iisc.ernet.in/handle/2005/1374.
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Maswanganye, Kgaogelo Amanda. "The effect of temperature and photoperiod on selected male reproductive characteristics in two seanonally breeding ( Cryptomys hottentotus hottentotus and Cryptomys hottentotus pretoriae ) and one aseasonally breeding mole-rat species ( Cryptomys damarensis )." Diss., 2003. http://hdl.handle.net/2263/27822.
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