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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.
271

Effets des facteurs biologiques hormonaux sur la performance langagière

Lamoureux, Charles January 2007 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
272

The Role of Testosterone and Estradiol in Women’s Preferences and Mating Strategies across the Menstrual Cycle: A Hormonal Perspective

Chen, Jennie Ying-Chen 2011 December 1900 (has links)
This dissertation project investigated fluctuations in estradiol and testosterone across the human menstrual cycle. During the part of the cycle when women are most fertile, women show stronger preferences for men with more masculine faces, and these preference changes may be related to changes in hormone levels during ovulation. The present study investigated preferences changes among women for higher testosterone men over the menstrual cycle as estradiol and testosterone in those women fluctuated. 32 women participated in this 5-week long study tracking their estradiol and testosterone levels and preferences for masculine men. Women with higher levels of estradiol preferred men who had higher levels of testosterone than women who had lower levels of estradiol. During ovulation, women were more like to find high testosterone men more attractive than other parts of the menstrual cycle. In addition to ratings of men, several other psychological tests were administered and examined for changes as a function of state and trait levels of hormones.
273

Ovarian steroids in rat and human brain : effects of different endocrine states

Bixo, Marie January 1987 (has links)
Ovarian steroid hormones are known to produce several different effects in the brain. In addition to their role in gonadotropin release, ovulation and sexual behaviour they also seem to affect mood and emotions, as shown in women with the premenstrual tension syndrome. Some steroids have the ability to affect brain excitability. Estradiol decreases the electroshock threshold while progesterone acts as an anti-convulsant and anaesthetic in both animals and humans. Several earlier studies have shown a specific uptake of several steroids in the animal brain but only a few recent studies have established the presence of steroids in the human brain. In the present studies, the dissections of rat and human brains were carried out macroscopically and areas that are considered to be related to steroid effects were chosen. Steroid concentrations were measured by radioimmunoassay after extraction and separation with celite chromatography. The accuracy and specificity of these methods were estimated. In the animal studies, immature female rats were treated with Pregnant Mare's Serum Gonadotropin (PMSG) to induce simultaneous ovulations. Concentrations of estradiol and progesterone were measured in seven brain areas pre- and postovulatory. The highest concentration of estradiol, pre- and postovulatory, was found in the hypothalamus and differences between the two cycle phases were detected in most brain areas. The preovulatory concentrations of progesterone were low and the highest postovulatory concentration was found in the cerebral cortex. In one study, the rats were injected with pharmacological doses of progesterone to induce "anaesthesia". High uptake of progesterone was found and a regional variation in the formation of 5&lt;*-pregnane-3,20-dione in the brain with the highest ratio in the medulla oblongata. Concentrations of progesterone, 5a-pregnane-3*20-dione, estradiol and testosterone were determined in 17 brain areas of fertile compared to postmenopausal women. All steroids displayed regional differences in brain concentrations. Higher concentrations of estradiol and progesterone were found in the fertile compared to the postmenopausal women. In summary, these studies show that the concentrations of ovarian steroids in the brain are different at different endocrine states in both rats and humans and that there are regional differences in brain steroid distribution. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1987, härtill 5 uppsastser</p> / digitalisering@umu
274

Leptin : a risk marker for cardiovascular disease

Söderberg, Stefan January 1999 (has links)
A major cause of morbidity and early death in the Western societies is cardiovascular disease (CVD) secondary to atherosclerotic disease. Metabolic aberrations have been linked to CVD. Particular combinations of these so-called risk markers are common and (central) obesity, Type 2 diabetes, impaired glucose tolerance, hypertension, dyslipidemia, dysfibrinolysis and hyperinsulinemia are often associated. This has been entitled the Insulin Resistance Syndrome (1RS), due to underlying insulin resistance. Moreover, aberrations in circulating levels of androgens and IGF-binding proteins are associated with 1RS. The main hypothesis in this thesis was that increased levels of leptin, the recently discovered adipocyte derived hormone in combination with obesity may be an important factor in the link between 1RS and the development of CVD. The association between leptin levels and variables associated with the Insulin Resistance Syndrome was studied in a healthy sample (n=163) of middle-aged men and women from the northern Sweden MONICA health survey. Central obesity was associated with high levels of leptin and insulin in men and women. In contrast, central obesity was linked to low testosterone levels in men, whereas in women, central obesity was associated with high testosterone but low SHBG levels. Furthermore, in males and postmenopausal women central obesity was a major determinant for circulating leptin. Leptin levels were associated with biochemical androgenicity in non-obese men and women. The direction of this association was dependent on gender and body fat distribution. Specifically, testosterone was inversely associated to leptin in non-obese men and in normal weight women whereas testosterone was positively associated to leptin in non-obese women. In contrast, adiposity and insulin levels, but not testosterone, were associated to leptin in obese men and women. Similarly, leptin was associated to IGFBP-1 and proinsulin in non-obese men and premenopausal women. Hyperleptinemia was significantly associated to high PAI-1 levels in men and in centrally obese women. In a multivariate model, high leptin levels predicted PAI-1 levels in men but not in women. Finally, leptin levels were related to blood pressure in obese men. The impact of hyperleptinemia on future risk for development of CVD was tested in a nested case-referent study based on the MONICA and the Västerbotten Intervention Program surveys. It was found that hyperleptinemia and high total cholesterol levels were associated with increased risk for development of myocardial infarction whereas high levels of apolipoprotein A-l were protective. Hyperleptinemia together with hypertension remained as significant risk markers for hemorrhagic stroke whereas hypertension alone predicted ischemic stroke. The combinations of hyperleptinemia on one hand and low apolipoprotein A- 1 and high blood pressure on the other were associated with a pronounced increased risk for myocardial infarction and hemorrhagic stroke, respectively. In conclusion, hyperleptinemia is independently associated with several risk markers for CVD included in the insulin resistance syndrome. Furthermore, high leptin levels predict the development of CVD. / <p>Härtill 5 uppsatser</p> / digitalisering@umu
275

Foundations of variation in male aggressiveness and tolerance between chacma baboons (Papio ursinus) in Botswana and Guinea baboons (P. papio) in Senegal / Foundations of variation in male aggressiveness and tolerance between chacma baboons (Papio ursinus) in Botswana and Guinea baboons (P. papio) in Senegal

Kalbitzer, Urs 16 July 2014 (has links)
Die Fitness-limitierende Ressource für die meisten männlichen Primaten ist die unteilbare Befruchtung von Weibchen. Daher herrscht in der Regel ein aggressives Konkurrenzverhalten unter Männchen, um sich den Zugang zu fertilen Weibchen zu sichern. Jedoch zeigen Männchen unterschiedlicher Arten eine erhebliche Variation in ihrer Aggressivität. In manchen Arten kann sogar ein kooperatives Verhalten zwischen Männchen beobachten werden, das meist mit weniger angespannten und toleranteren Sozialbeziehungen verbunden ist. Die proximaten und ultimaten Ursachen für diese interspezifische Variation werden durch verschiedene Aspekte des Sozialsystems einer Art bedingt, jedoch sind die zugrundeliegenden Ursachen noch nicht vollständig geklärt. Paviane (Papio spp.) stellen ein gut geeignetes Modell dar, um die Grundlage von männlicher Aggressivität und Toleranz zu untersuchen, da die unterschiedlichen Arten dieser Gattung eine erhebliche Variation in männlichem Konkurrenzverhalten und in anderen Aspekten ihrer Sozialsysteme zeigen. Männliche Bärenpaviane (P. ursinus) im südlichen und männliche Guineapaviane (P. papio) im westlichen Afrika scheinen dabei entgegengesetzte Extrema von Aggressivität und Toleranz darzustellen. Das Ziel meiner Promotion war daher, verschiedene Aspekte der männlichen Dominanzbeziehungen in den beiden Arten zu untersuchen und zu vergleichen. Bärenpaviane leben in stabilen Gruppen mit mehreren Männchen und mehreren Weibchen, in denen geschlechtsreife Männchen in benachbarte Gruppen abwandern. Dort versuchen sie mit Hilfe von aggressivem Verhalten einen hohen Rang zu erlangen, da ihnen dieser ein Vorrecht („Priority of access“) auf fertile Weibchen verschafft und über den reproduktiven Erfolg eines Männchens bestimmt. Im Gegensatz dazu leben Guineapaviane in einer mehrschichtigen (“multi-level“) Gesellschaft, in der nahverwandte Männchen häufig in der gleichen Gruppe verbleiben. Die Sozialbeziehungen zwischen Männchen scheinen dabei vor allem durch eine niedrige Frequenz agonistischer Interaktionen und eine hohe räumliche Toleranz sowie Kooperation gekennzeichnet zu sein. Daher stellen Aggressionen in dieser Art scheinbar nicht das primäre Mittel in der Konkurrenz um den Zugang zu Weibchen dar. Bisher gab es noch keine vergleichbaren Daten, um diese Vermutung über Verhaltensunterschiede zwischen den beiden Arten zu überprüfen. Daher war ein Ziel meiner Dissertation die Aggressivität und räumliche Toleranz zwischen männlichen Bärenpavianen im Moremi Game Reserve, Botsuana, und männlichen Guineapavianen im Parc National de Niokolo Koba, Senegal, zu vergleichen. Unterschiede in männlicher Konkurrenz spiegeln sich auch in unterschiedlichen altersabhängigen Verläufen des Reproduktionserfolgs wider. Bei Primaten ist dieser Verlauf wiederum mit Variation im Testosteronspiegel verbunden. Neben diesen Langzeitverläufen wurde gezeigt, dass zusätzliche, kurzfristige Anstiege in Testosteronspiegeln ein aggressives Verhalten während der Konkurrenz um Paarungspartner fördern (‚Challenge hypothesis‘). Das zweite Ziel meiner Dissertation war daher, den Zusammenhang zwischen Testosteron und dominanzbezogener Aggression zu untersuchen, indem ich die Variation in Testosteronspiegeln in Bezug auf Alter, Aggression, und Dominanzbeziehungen analysiert habe. Die Art und Weise, wie Individuen konkurrieren, beeinflusst auch, wie physiologische Kosten (oder ‚allostatic load‘) zwischen Individuen unterschiedlichen Dominanzstatus verteilt sind. Diese Kosten spiegeln sich in inter-individuellen Differenzen in Glucocorticoidspiegeln wider. Das dritte Ziel meiner Arbeit war daher die Effekte von männlichen Sozialbeziehungen auf physiologische Kosten zu untersuchen, indem ich die Variation in Glucocorticoidspiegeln in Relation zu Dominanzstatus zwischen Bären- und Guineapavianen analysiert habe. Inter-individuelle Unterschiede in Aggressivität sind stark erblich bedingt. Daher ist zu vermuten, dass auch Unterschiede zwischen Arten eine genetische Grundlage haben. Die beiden Längenpolymorphismen 5-HTTLPR - im Gen des Serotonintransporters - und MAOALPR - im Gen der monoaminen Oxidase A - beeinflussen die Aktivität des serotonergen Neurotransmittersystems und wurden mit Variation von Aggressivität in Verbindung gebracht. Verschiedene Allele dieser beiden Loci könnten daher auch mit Artunterschieden bei Pavianen gekoppelt sein. Das vierte Ziel meiner Dissertation war daher, Allele dieser beiden Loci zwischen fünf Pavianarten zu vergleichen. Durch die Erhebung der ersten unmittelbar vergleichbaren Verhaltensdaten für männliche Bären- und Guineapaviane konnte ich zeigen, dass männliche Bärenpaviane häufiger in agonistische Interaktionen verwickelt sind als Guineapaviane. Im Gegensatz dazu zeigen Guineapaviane eine höhere räumliche Toleranz gegenüber anderen Männchen und tauschen manchmal sogar affiliatives Verhalten aus. Des Weiteren zeigten männliche Bärenpaviane konsistente Dominanzbeziehungen und eine lineare Hierarchie, während die Linearität der Hierarchien von Guineapavianen allgemein niedriger war. Diese Beobachtungen stimmen mit vorherigen Beobachtungen über männliche Sozialbeziehungen in beiden Arten überein. Dies bedeutet, dass die beiden Arten sich tatsächlich in der Intensität von männlicher Wettbewerbskonkurrenz („contest competition“) unterscheiden. In keiner der beiden Arten konnte ein Zusammenhang zwischen Testosteronspiegel und Alter oder Dominanzrang gefunden werden. Es gab jedoch einen statistischen Trend, dass in Bärenpavianen der Testosteronspiegel mit Aggressivität korreliert. Dies wurde zuvor nur in Perioden beobachtet, in denen Männchen hoher Dominanzränge von anderen Männchen herausgefordert wurden (d.h. „unstabile Perioden“). Dies war in der vorliegenden Studie nicht der Fall. Jedoch könnten eine kurz zuvor beobachtete Teilung der Gruppe und darauf folgende regelmäßige Begegnungen der beiden neu entstandenen Gruppen eine ähnliche Situation verursacht haben. In Guineapavianen waren Testosteronspiegel nicht mit der Häufigkeit von agonistischen Verhalten korreliert. Dies könnte daran liegen, dass solche Verhalten in dieser Art keine bedeutende Rolle in der Konkurrenz um Paarungsmöglichkeiten spielen. Hochrangige männliche Bärenpaviane zeigten höhere Glucocorticoidspiegel als niedrigrangigere Männchen. Auch dies wurde bei Bärenpavianen bisher nur während „unstabiler Perioden“ beobachtet und weist wieder darauf hin, dass die unübliche Teilung der Gruppe eine ähnliche Situation hervorgerufen haben kann. In Guineapavianen korrelierten Glucocorticoidspiegel nicht mit Dominanzpositionen, was die Vermutung unterstütz, dass Dominanzränge in dieser Art wenig oder keine Bedeutung haben. Ein Vergleich von 5-HTTLPR und MAOALPR Allelen zwischen fünf Arten von Pavianen lässt vermuten, dass der 5-HTTLPR-Genotyp nicht mit interspezifischer Variation im Verhalten in Verbindung steht; dieser Locus war in fast allen Arten monomorph. Ein erweiterter Vergleich zwischen mehreren Arten von Pavianartigen (Papionini) deutete aber an, dass dieser Locus während der historischen Ausbreitung von Makaken nach Asien sehr wahrscheinlich unter Selektionsdrücken stand. Die Bedeutung dieser Variation muss noch untersucht werden, könnte aber eventuell mit Unterschieden in der Umwelt der jeweiligen Arten zusammenhängen. Im Gegensatz dazu war der Locus MAOALPR polymorph und das Muster verschiedener Allele passte überwiegend mit den vermuteten Verhaltensunterschieden zwischen Pavianarten zusammen. Die beobachtete Variation in diesem Locus bietet daher eine gute Möglichkeit, um genetisch bedingte Verhaltensunterschiede zwischen verschiedenen Pavianen genauer zu untersuchen und dadurch die genetischen Grundlagen der Variation in Aggressivität bei Primaten besser zu verstehen. Zusammengefasst hat meine Dissertation grundlegende Einblicke in die proximaten Ursachen und Kosten der Unterschiede in männlicher Dominanzbeziehungen zwischen Pavianarten geliefert. Erste Daten weisen darauf hin, dass Verhaltensunterschiede in Bezug auf Aggressivität zwischen Pavianen mit dem MAOALPR-Genotyp verbunden sind. Eine Untersuchung dieses Locus im Zusammenhang mit Neurotransmitter-Aktivität und Verhalten könnte daher weitere Aufschlüsse über die proximaten Mechanismen geben, die unterschiedlichen Aggressivitätsmustern in Primaten unterliegen. Verhaltensbeobachtungen und Glucocorticoid-Messungen lassen vermuten, dass die reproduktive Strategie von männlichen Guineapavianen mit weniger „offensichtlichen“ Kosten verbunden ist. Daher könnten eine Untersuchung der Mechanismen, die den Zugang zu Weibchen bei Guineapavianen regeln, und ein Vergleich des reproduktiven Erfolgs zwischen unterschiedlichen Männchen weitere Einblicke in die Evolution von reproduktiven Strategien und damit von Aggressivitäts- und Toleranzunterschiede zwischen männlichen Primaten liefern.
276

Kineziterapijos poveiki vyrams sergantiems hipogonadizmu, kuriems taikoma pakaitinė testosterono terapija / Effect of exercise therapy on males with hypogonadism treated with testosterone replacement therapy

Valonytė, Laura 28 June 2011 (has links)
Tikslas: įvertinti fizinių pratimų poveikį, vyrams sergantiems hipogonadizmu, kuriems taikoma pakaitinė testosterono terapija. Uždaviniai: 1. Nustatyti vyrų sergančių hipogonadizmu kūno masės komponentų pokyčius atsiradusius dėl 6 mėnesių trukmės kineziterapijos programos taikymo. 2. Palyginti kūno masės komponentus vyrų sergančių hipogonadizmu ir sveikų vyrų prieš ir po kinezirerapijos taikymo. 3. Nustatyti vyrų sergančių hipogonadizmu fizinių ypatybių (šuolio metu išvystomų rodiklių: jėgos, galingumo, greičio, aukščio, santykinio galingumo bei kūno slėgio centro svyravimų elipsės ploto) pokyčius atsiradusius dėl 6 mėnesių kineziterapijos programos taikymo 4. Palyginti fizinių ypatybių pokyčius (šuolio metu išvystomų rodiklių: jėgos, galingumo, greičio, aukščio, santykinio galingumo bei kūno slėgio centro svyravimų elipsės ploto) vyrų sergančių hipogonadizmu ir sveikų vyrų prieš ir po kineziterapijos taikymo. Tiriamieji: 38 vyrai: 18 – sergantys hipogonadizmu ir 20 sveikų vyrų. Tyrimo organizavimas: vyrai sergantys hipogonadizmu padalinti į du pogrupius: 8 vyrams 6 mėn. buvo taikyta pakaitinė testosterono terapija ir kineziterapija (2 k/sav. po 60 min), 10 vyrų taikyta tik pakaitinė testosterono terapija 3 k/6 mėn. kas 8 savaitės buvo švirkščiama Nebido 1000 mg/4 ml injekcinis tirpalas. Tyrimo metodai: 1. Tiriamųjų fizinis aktyvumas, naudojant Tarptautinį fizinio aktyvumo klausimyną (IPAQ). 2. Kūno sudėties analizė X – SCAN įranga – ūgį, kūno svorį, kūno masės indeksą... [toliau žr. visą tekstą] / The aim of the research is to assess the effect of exercise therapy on males with hypogonadism treated with testosterone replacement therapy. Objectives: 1. To determine changes in body weight components resulting from a six-month programme of exercise therapy. 2. To compare the body weight components in males with hypogonadism and healthy males before and after exercise therapy. 3. To determine changes in physical parameters (parameters achieved during jumping tasks: strength, power, speed, altitude, relative power, and the ellipse area of body centre pressure) in males with hypogonadism resulting from a six-month programme of exercise therapy programme. 4. To compare the changes in physical parameters (indicators achieved during jumping tasks: strength, power, speed, altitude, relative power, and the ellipse area of body centre pressure) in males with hypogonadism and healthy males before and after exercise therapy. Subjects: 38 males including 18 males with hypogonadism and 20 healthy males. Research design: males with hypogonadism were arranged into two subgroups: 8 men were treated with testosterone replacement therapy combined with exercise therapy for 6 months (2/60-minute sessions per week), 10 men were given testosterone replacement therapy only: 3 times per 6 months, i.e. every 8 weeks they received Nebido 1000 mg/4 ml injections. Research methods: 1. International Physical Activity Questionnaire to obtain estimates of physical activity. 2. X – SCAN for body... [to full text]
277

Jaunų ir vidutinio amžiaus vyrų reprodukcinės sveikatos ryšys su antropometrija, metaboline bei psichologine būkle / Association of reproductive health with anthropometry, metabolic and psychological parameters in young and middle-aged men

Čeponis, Jonas 14 July 2014 (has links)
Epidemiologiniais tyrimais nustatytos androgenų sąsajos su įvairiais metaboliniais veiksniais bei širdies ir kraujagyslių ligų rizika paskatino susidomėjimą naujais vyrų reprodukcinės sveikatos aspektais. Iki šiol Lietuvoje nebuvo nustatytos normalios vyrų androgenų koncen¬tracijos ribos, nebuvo atlikta reprodukcinės sveikatos, antropometrinių ir metabolinių rodiklių sąsajų analizės tyrimų. Pasaulyje iki šiol trūksta nuoseklios informacijos apie metabolinių ir antropometrinių rodiklių ryšius su lytiniais hormonais, ypač homogeniškose tiriamųjų imtyse. Trūksta informacijos apie androgenų sąsajas su pažintinėmis funkcijomis, emocine būkle ir gyvenimo kokybės vertinimu. Daugelis tyrimų, kuriais vertintas pakaitinio gydymo testosteronu efektyvumas – trumpalaikiai, juose dau¬giausiai dėmesio skirta struktūriniams, o ne funkciniams rodikliams. Šiuo tyrimu siekta aprašyti jaunų bei vidutinio amžiaus vyrų reprodukcinės sveikatos sąsajas su antro¬pometrijos, metabolinės bei psichologinės būklės rodikliais. Tai iki šiol didžiausia savo apimtimi Lietuvos vyrų androgenų sąsajų analizė. Šiuo darbu siekiama sistemingai atsakyti į iškeltus aktualius klau¬simus, nustatyti normalios ir optimalios androgenų koncentracijos ribas, homogeniškose amžiumi tiriamųjų grupėse įvertinti šių hormonų koncen¬tracijos grupių sąsajas su kūno sudėties ir medžiagų apykaitos rodikliais bei nustatyti, kokius sergančiųjų androgenų nepakankamumu funkcinius pokyčius sąlygoja ilgalaikis optimalus pakaitinis... [toliau žr. visą tekstą] / Associations between androgens and various metabolic factors, as well as cardiovascular morbidity shown in recent epidemiological studies sparked interest in new aspects of male reproductive health. Reference values for normal androgen levels in Lithuanian population have not yet been established and no relationship studies on reproductive health and anthropometric, as well as metabolic parameters have been performed. Unequivocal information on associations among the aforementioned factors is lacking globally, especially those performed in homogenous populations. More information on androgen associations with cognitive function, emotional state and evaluation of quality of life is required. Most of the studies on effectiveness of testosterone replacement therapy were of short duration and mostly focused on structural, rather than functional parameters. The purpose of the study was to describe associations between reproductive health and anthropometric, metabolic, as well as psychological parameters in young and middle-aged men. This is the largest androgen association analysis in Lithuanian population. This work seeks for systematic responses to questions of interest: to establish reference values for normal and optimal androgen levels, to evaluate their relationship with anthropometric and metabolic factors in populations that are homogenous by age, and to assess the functional changes that long-term optimal testosterone replacement therapy may induce in patients with... [to full text]
278

The Role of ALK3 in Urogenital Development

Di Giovanni, Valeria 15 February 2011 (has links)
The mammalian kidney and reproductive systems both derive from a common embryological origin, the intermediate mesoderm. Abnormal intermediate mesoderm development can result in congenital abnormalities of the urogenital system, yet the molecular mechanisms that govern intermediate mesoderm development are incompletely defined. The spatial and temporal expression of the proteins BMP2 and 4 and their receptor ALK3, in urogenital tissue, suggests a function for BMP-ALK3 signaling in the intermediate mesoderm. It was found that Alk3IM null kidneys display renal hypoplasia, associated with a decrease in kidney size and nephron number. The phenotype of renal hypoplasia in Alk3IM nulls was associated with early decreased number of developing nephron structures and secondary defects in branching morphogenesis. While neither apoptosis nor cell proliferation differed in metanephric mesenchyme cells in Alk3IM nulls, markers of renal progenitor cells were decreased in mutant animals. It was observed that Alk3 expression in the intermediate mesoderm also controls mesonephric tubule number. Alk3IM nulls had fewer mesonephric tubules and fewer derivative Leydig cells. The reduction in Leydig cells resulted in decreased levels in serum testosterone and defects in seminal vesicle formation and fertility. Alk3 expression was also required for normal development of the corpus epididymis. The morphological defects in nephrogenesis were associated with decreased phospho-p38 MAPK expression and in the testis with decreased Phospho-SMAD1/5/8. These results elucidated a requirement for Alk3 signaling in controlling progenitor cells derived from the intermediate mesoderm.
279

Rapid social regulation of 3β-HSD activity in the songbird brain

Pradhan, Devaleena S. 11 1900 (has links)
Rapid increases in plasma androgens are generally associated with short-term aggressive challenges in many breeding vertebrates. However, some animals such as song sparrows (Melospiza melodia) are aggressive year-round, even during the non-breeding season, when gonads are regressed and systemic testosterone (T) levels are non-detectable. In contrast, levels of the prohormone dehydroepiandrosterone (DHEA) are elevated year-round in the plasma and brain. The local conversion of brain DHEA to potent androgens may be critical in regulating non-breeding aggression. 3β-hydroxysteroid dehydrogenase/Δ4-Δ5 isomerase (3β-HSD) catalyzes DHEA conversion to androstenedione (AE) and the cofactor NAD⁺ assists in this transformation. In this thesis, I asked whether brain 3β-HSD activity is regulated by social encounters in seasonally breeding male songbirds. In Experiment 1, I looked at the long-term seasonal regulation of brain 3β-HSD activity. 3β-HSD activity was highest in the non-breeding season compared to the breeding season and molt. In Experiment 2, I hypothesized that brain 3β-HSD activity is rapidly regulated by short-term social encounters during the non-breeding season. A 30 min social challenge increased aggressive behavior. Without exogenous NAD⁺, there was ~355% increase in 3β-HSD activity in the caudal telencephalon and ~615% increase in the medial central telencephalon compared to controls (p<0.05). With exogenous NAD⁺, there was no effect of social challenge on 3β-HSD activity. These data suggest that endogenous cofactors play a critical role in the neuroendocrine response to social challenges. The increase in brain DHEA conversion to AE during social challenges may be a mechanism to rapidly increase local androgens in the non-breeding season, when there are many costs of systemic T.
280

Factors affecting the timing and success of sockeye salmon spawning migrations

Crossin, Glenn Terrence 11 1900 (has links)
Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye.

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