No description available.

No description available.

No description available.

No description available.

"Supermice" (TRrGH mice) contain multiple copies of rat growth hormone genes incorporated into a single chromosome. This results in double normal growth rates reaching adult body sizes twice that of normal mice. To determine how exposure to constant light (LL) affects various physiological processes, reproduction, feeding, and behaviour were examined in LL-reared TRrGH mice. Fertility, organ allometries, feeding rates, behavioural time budgets, and circadian feeding and sleep rhythms were compared for both LL and standard 12h dark: 12h light (LD). Both TRrGH and normal females exhibited a significant decrease in fertility in LL. On a mass-specific basis, TRrGH females showed increased combined ovary mass and a reduction in thymus and heart size in LL. TRrGH males demonstrated increased testes mass in LL. When adrenal size was compared between males and females, both TRrGH and normal females exhibited larger adrenals than their male counterparts in both light treatments. The fertility decrease observed in LL may have been associated with reduced food intake. LL-reared TRrGH females ate less than those in LD, although significantly more than TRrGH males in both LL and LD. When compared to normal mice, both sexes of TRrGH mice ate less in both photoperiods. The feeding rates of transgenic GLUT -4 mice were also examined. GLUT -4 mice contain double the amount of insulin responsive GLUT -4 glucose transporters which results in an increased blood glucose clearance rate. These mice, like TRrGH mice, ate less than normals, although a different age-related feeding pattern was observed. TRrGH mice in LL are behaviourally more lethargic than those reared in LD, and spend less time feeding and drinking. Circadian feeding and sleep patterns were shifted in LL by approximately 12 hours, and exhibited reduced peak amplitudes. Ultradian patterns appeared to survive the breakdown of circadian organization. TRrGH mice demonstrate a hormonal imbalance due to the excess allocation of energy into growth. It appears that, in LL, hormonal systems are further altered resulting in an increase in reproductive impairment associated with reduced feeding. One of these altered hormones may be estrogen. Hormones involved in hypothalamic-pituitary-adrenal axis (stress axis) are also implicated. It is concluded that photoperiod is important in regulating physiological processes, and TRrGH mice are more susceptible to environmental alterations due to their altered endocrinological state. / Thesis / Master of Science (MS)

The overall objective of this project was to investigate the role of locally derived growth factors and extracellular matrix proteins in regulating prepubertal heifer mammary development. In the first experiment, short-term treatment of heifers with GH or E increased proliferation of mammary epithelial cells. Coinciding with increased epithelial cell proliferation, IGF-I protein increased and IGFBP-3 protein decreased within mammary tissues. Thus, proliferation was associated with an apparent net increase in the biological availability of IGF-I within the mammary gland. In the second experiment, decreased mammary development and epithelial cell proliferation in response to ovariectomy coincided with decreased mammary expression of IGF-I mRNA and decreased binding of IGF-I to mammary microsomes. Taken together, these results imply an important role for locally derived IGF-I in regulating heifer mammary development. However, in contrast to our hypothesis, IGF-I mRNA did not differ between cleared or intact mammary fat pad, suggesting that expression of IGF-I mRNA is not regulated by epithelial:stromal interactions. Neither ovariectomy or epithelial:stromal interactions influenced the mRNA expression of IGFBP-3 or IGFBP-5 within mammary tissues. Ovariectomy increased the proportion of ERa positive mammary epithelial cells. In contrast, GH administration to prepubertal heifers did not influence the proportion of ERa-positive epithelial cells. Interestingly, mammary development was more severely affected in heifers ovariectomized before six weeks of age than heifers ovariectomized at three months of age, implying a critical period of ovarian stimulation during the first six weeks of age. Localization of laminin, fibronectin, and collagen in mammary parenchyma suggested specific roles for extracellular matrix proteins in regulating mammary development and ductal morphogenesis. Laminin was decreased and fibronectin was increased by ovariectomy, suggesting a possible role for interactions between the ovary and extracellular matrix proteins within the heifer mammary gland. Finally, the mitogenic capacities of mammary tissue extracts from control and ovariectomized heifers did not differ in their ability to stimulate in vitro proliferation of MAC-T cells. In conclusion, the overall results support the hypothesis that locally derived IGF-I regulates prepubertal heifer mammary development. However, ERa expression and extracellular matrix proteins also appear to be important regulators of heifer mammary development. / Ph. D.

Liver gene expression changes during development and is affected by growth hormone (GH). These changes in gene expression may be due to the differential expression of the liver-enriched transcription factors (LETFs). To study the potential involvement of LETFs in the regulation of gene expression in the bovine liver, we cloned the cDNA fragments of nine bovine LETFs, including hepatocyte nuclear factor (HNF)-1Æ Ã , 1Æ Ã , 3Æ Ã , 3Æ Ã , 3Æ Ã , 6, albumin D-element binding protein (DBP), and CCAAT/enhancer-binding proteins (C/EBP) -Æ Ã and Æ Ã , and compared the expression levels of them between adult and fetal bovine liver and between GH-treated and untreated adult bovine liver. The mRNA abundance of the LETFs was determined by ribonuclease protection assay (RPA). The cloned bovine LETF cDNA sequences showed high degrees of similarity (79 % to 99 %) to the LETF sequences of other species. The mRNA levels of HNF-1Æ Ã , HNF-3Æ Ã , and HNF-6 were significantly higher (P < 0.05) in the fetal liver (n=3) than in the adult liver (n=7). There were significant increases (P < 0.05) in the mRNA expression of HNF-3Æ Ã and HNF-6 in the liver of cows 24 h (n=6) and 1w (n=6) after GH administration. The results of this study suggest that HNF-1Æ Ã , HNF-3Æ Ã , and HNF-6 may play a role in differential regulation of gene expression between the fetal and adult bovine liver and that HNF-3Æ Ã and HNF-6 may be also involved in GH regulation of gene expression in the bovine liver. / Master of Science

The transcription factor, Pit-1, is involved in the transcriptional regulation of the mammalian prolactin (Prl), growth hormone (GH) and thyroid stimulating hormone b-subunit genes (TSHb) as well as its own gene. The role of Pit-1 in avian species is unknown. Three turkey (t) Pit-1 isoforms have been identified that arise from alternative transcription initiation and alternative splicing. Splicing of exon 1 to an alternative acceptor splice site in exon 2 results in a 28 amino acid insertion in tPit-1β* relative to tPit-1*. Both isoforms initiate transcription at exon 1. A tPit-1 transcript unique to the turkey has been identified and arises following transcription initiation upstream of the alternative acceptor splice site in exon 2. Western blot analysis of pituitary extracts has revealed two isoforms of 37 and 40 kDa. The ability of Pit-1 to transactivate the Prl, GH, and Pit-1 promoters was determined with cotransfection assays. The tPrl, tGH, tPit-1 and rat (r) Prl promoters were cloned upstream of the luciferase gene in a reporter construct. Turkey Pit-1 isoforms and rPit-1 were expressed under the control of the Avian Sarcoma Virus Long Terminal Repeat (ASVLTR) promoter. Cotransfection analyses in mouse L cells indicate that tPit-1* activates the tPrl, tGH, tPit-1 and rPrl promoters 4.6-, 3.8-, 1.7-, and 29.0-fold, respectively. Similar results were observed when cotransfection assays were performed in a turkey pituitary-derived cell line and in primary turkey pituitary cells. These results indicate that tPit-1 is not a strong activator of the tPrl, tGH, or tPit-1 genes, whereas Pit-1 does activate these genes in mammals. A point mutation at amino acid position 176 (ser ⟹ leu) in the POU-homeodomain results in a mutant tPit-1 that shows decreased activity on all promoters tested. Turkey Pit-1* (ser-176) activates the rPrl promoter 14-fold lower than the wild type tPit-1* (leu-176). / Master of Science

Yes / Objective: Many patients with acromegaly, a hormonal disorder with excessive growth hormone (GH) production, report pain in joints. We undertook this study to characterize the joint pathology of mice with overexpression of bovine GH (bGH) or a GH receptor antagonist (GHa) and to investigate the effect of GH on regulation of chondrocyte cellular metabolism. Methods: Knee joints from mice overexpressing bGH or GHa and wild-type (WT) control mice were examined using histology and micro–computed tomography for osteoarthritic (OA) pathologies. Additionally, cartilage from bGH mice was used for metabolomics analysis. Mouse primary chondrocytes from bGH and WT mice, with or without pegvisomant treatment, were used for quantitative polymerase chain reaction and Seahorse respirometry analyses. Results: Both male and female bGH mice at ~13 months of age had increased knee joint degeneration, which was characterized by loss of cartilage structure, expansion of hypertrophic chondrocytes, synovitis, and subchondral plate thinning. The joint pathologies were also demonstrated by significantly higher Osteoarthritis Research Society International and Mankin scores in bGH mice compared to WT control mice. Metabolomics analysis revealed changes in a wide range of metabolic pathways in bGH mice, including beta-alanine metabolism, tryptophan metabolism, lysine degradation, and ascorbate and aldarate metabolism. Also, bGH chondrocytes up-regulated fatty acid oxidation and increased expression of Col10a. Joints of GHa mice were remarkably protected from developing age-associated joint degeneration, with smooth articular joint surface. Conclusion: This study showed that an excessive amount of GH promotes joint degeneration in mice, which was associated with chondrocyte metabolic dysfunction and hypertrophic changes, whereas antagonizing GH action through a GHa protects mice from OA development. / Dr. Zhu's work was supported by Ohio University, the Arthritis National Research Foundation (grant 833836), a FIRST award from the American Society for Bone and Mineral Research, the NIH (grant R15-AR-080813), and a Hevolution Foundation AGE grant (AGE-008). Dr. Davis’ work was supported by a medical student seed grant from Ohio University. Dr. Lotz's work was supported by the NIH (grant R37-AG-059418). Dr. Berryman was supported by the NIH (grant R01-AG-059779). Dr. Kopchick was supported by the State of Ohio's Eminent Scholar Program that includes a gift from Milton and Lawrence Goll and the AMVETS, and by the NIH (grant R01-AG-059779).

Les travaux de cette thèse ont porté sur le contrôle des neurones à GHRH dans des conditions physiologiques et pathologiques. Le but étant de caractériser les mécanismes cellulaires et moléculaires impliqués dans le fonctionnement ou dérégulations du réseau de neurones à GHRH. Ces neurones sont les principaux stimulateurs de la libération de l’hormone de croissance (GH). Nous avons d’abord montré que l’axe de la croissance et de l’appétit peuvent être régulés indépendamment au niveau de l’hypothamus. En effet, la ghréline, seule hormone produite par le tractus gastro-intestinal et connue pour stimuler la libération de GH en agissant principalement sur les neurones GHRH, stimule ces derniers de manière uniquement directe. Ces effets sont indépendants de ceux qu’elle exerce sur les neurones voisins à NPY, orexigéniques. De plus, la ghréline et les GHS (agonistes sélectifs du récepteur de la ghréline) ne changent pas le mode de décharge électrique des neurones à GHRH ni ne les synchronise. Enfin, ces effets ne présentent pas de dimorphisme sexuel. Dans un second temps, la somatostatine, principal inhibiteur de l’axe GH, induit un rythme d’activité électrique des neurones à GHRH médié par les récepteurs de sous-type SST1 et SST2. Ces effets sont donc temps-dépendants, et aussi sexuellement dimorphiques. Ils sont probablement impliqués dans la modulation de la pulsatilité ultradienne de la libération de GH. Enfin, après un traumatisme crânien, nous observons un déficit de la libération de GH qui apparaît tôt et est soutenu, comme ceux observés chez l’humain. Aucune inflammation ni changement histologique n’a été observe dans l’hypophyse. Cependant, l’inflammation, impliquant une réaction tanycytaire, microgliale, astrocytaire, est présente dans le noyau arqué et l’éminence médiane (EM), ou sont respectivement présents les corps cellulaires et terminaisons des neurones à GHRH. Ceci est lié à des changements morpho-fonctionnels de l’EM (augmentation perméabilité, rupture des barrières tanycytaires). Aucun changement n’a été observé dans le noyau périventriculaire, où sont localisés les neurones à somatostatine. Enfin, les propriétés électriques passives des neurones à GHRH ne sont pas modifiées. En conclusion, une dérégulation de leur activité au niveau des terminaisons nerveuses doit expliquer les défauts posttraumatiques de libération de GH. / The works of this thesis were interested in the control of the hypothalamic GHRH neurons in physiological and pathological conditions. The goal was to clarify the molecular and cellular mechanisms involved in the control or impairments of GHR neuronal network functions. These neurons are the main stimulators of the GH release. We first showed that the hypothalamic growth axis could be regulated independently from the feeding network. Indeed, GHRH neurons are directly stimulated by ghrelin, which is the only hormone produced by the gastrointestinal tract known to stimulate the GH release through acting mainly on GHRH neurons. These effects are independent from its orexigenic effects exerted on the neighbourings NPY neurons. In addition, ghrelin and GHS (synthetic ghrelin receptor agonists) don’t change neither the firing rate of GHRH neurons, nor synchronize them. These effects are not gender-dependant; by contrast, Somatostatin, the major GH axis inhibitor, generates a sexual dimorphic and rhythmic inhibition of the GHRH neurons electrical activity mediated by its SST1 and SST2 receptors subtypes. These effects are so time-dependant direct and indirect effects and can probably be involved in the generation of the ultradian rhythm of the GH release. After a traumatic brain injury, we found an early and sustained deficiency of the GH release, like those observed in human. No pathological changes are visible in the pituitary gland. Inflammation occurs at the arcuate nucleus, and mainly at the median eminence levels; it involves a strong astrocyte reaction, tanycytes, and microglial and (or) infiltrated immune cells activations. These changes elicit morpho-functional impairments of the median eminence, permeability and leakage of the tanycyte barrier between the blood, CSF and Arc; at the opposite, nothing occur at the periventricular level, where are located SST neurons. Neither the number of GHRH neurons, neither their passive electrophysiological properties changed. Impairments of the activities of the GHRH nerve terminals, maybe associated to impairments of their regulated activity, must explain a GH deficiency.