The autonomic nervous system serves to maintain a constant inner environment, a process termed homeostasis. Thus, in response to the homeostatic challenge posed by infectious agents, the autonomic nervous system answers to signals from the immune system and elicits adaptive physiological and behavioral reactions. These so called sickness responses include fever, anorexia, hyperalgesia, social avoidance, and the release of stress hormones. Neuropeptides, used in the communication between neurons, are because of their release properties and sustained actions likely mediators of homeostatic responses. The enkephalinergic system constitutes one of the largest neuropeptidergic systems in the brain, but its involvement in inflammatory conditions has been little studied. We first examined the immune-induced activation of the parabrachial nucleus (paper I), an enkephalinergic autonomic relay center in the brain stem. We found that intravenous injection of bacterial endotoxin, lipopolysaccharide (LPS), activated the external lateral parabrachial subnucleus, as measured in terms of Fos expression, but that the enkephalinergic cell population in this subnucleus was largely separated from the LPS-activated neurons. Because Fos may not always be a reliable activity marker, we next examined by in situ hybridization the immune-induced expression of newly transcribed preproenkephalin (ppENK) heteronuclear RNA (hnRNA), which gives a direct indication of the utilization of enkephalin in a particular neuron (paper II). We detected induced expression of ppENK hnRNA in several autonomic structures in the brain, including the paraventricular hypothalamic nucleus (PVH) but not the parabrachial nucleus, indicating increased enkephalinergic signaling activity in the positively labeled structures during inflammatory condition. We then examined the projections of the immune-induced ppENK transcribing PVH neurons by injecting rats intraperitoneally with the retrograde tracer substance Fluoro-Gold, hence labeling neurons with axonal projections outside the blood-brain barrier, followed by systemic injection of LPS (paper III). Dual-labeling histochemical and hybridization techniques showed that the vast majority of the ppENK hnRNA expressing cells were hypophysiotropic cells, hence being involved in neuroendocrine regulation. These findings suggest that centrally produced enkephalin is involved in the coordination of the sickness responses during systemic immune challenge, including the modulation of the release of stress hormones or other hypothalamic hormones during inflammatory conditions. We next turned to the role of prostaglandins in the hypothalamic-pituitary-adrenal (HPA) axis response to inflammation. We injected mice deficient for the terminal prostaglandin (PG) E2 synthesizing enzyme mPGES-1 with LPS and studied their stress hormone release (paper IV). The genetically modified mice displayed attenuated plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone during the later phases of the HPA-axis response compared with wild type mice, and this impairment did not depend on a changed activation pattern in the brain, but instead correlated to an early decrease in corticotropin-releasing hormone mRNA expression in the PVH, hence being the likely cause of the blunted ACTH and corticosterone responses at later time-points. Based on these findings we suggest that a neural, mPGES-1-independent pathway, and a humoral, mPGES-1-dependent pathway act in concert but in distinct temporal patterns to initiate and maintain the HPA-axis response during immune challenge. In addition to activating the central limb of the HPA-axis, inflammatory mediators have been suggested to act directly on the adrenal gland to induce the release of corticosterone, but little is known about the underlying mechanisms. We examined adrenal tissue isolated from rats injected with LPS or interleukin-1β (IL-1β) (paper V), and found that immune stimulation resulted in dynamic changes in the adrenal immune cell population, implying a rapid depletion of dendritic cells in the inner cortical layer and the recruitment of immature cells to the outer layers. These changes were accompanied by an induced production of IL-1β and IL-1 receptor type 1, as well as of cyclo-oxygenase-2 and mPGES-1 in these cells, implying local cytokine-mediated PGE2 production in the adrenals, which also displayed EP1 and EP3 receptors in the cortex and medulla. Additional mechanistic studies using an IL-1 receptor antagonist showed that IL-1β acts locally to affect its own synthesis, as well as that of cyclooxygenase-2. Taken together these data demonstrate a mechanism by which systemic inflammatory agents activate an intrinsically regulated local signaling circuit that may influence the adrenals’ response to immune stress and may help explain the dissociation between plasma levels of ACTH and corticosteroids during chronic immune perturbations.

No description available.

Prenatal ethanol (E) exposure has marked effects on development of the hypothalamic-pituitary-adrenal (HPA) and -gonadal (HPG) axes. E rats show HPA hyperresponsiveness to stressors and altered reproductive function in adulthood. Importantly, prenatal ethanol differentially alters stress responsiveness in adult males and females, raising the possibility that gonadal hormones play a role in mediating ethanol effects on HPA function. To address this possibility, two studies were conducted to test the hypothesis that the differential alterations in HPA activity observed in E compared to control males are mediated, at least in part, by ethanol-induced changes in HPG effects on HPA regulation. The first study compared the effects of gonadectomy (GDX) on HPA and HPG activity in adult male offspring from prenatal E, pair-fed (PF) and ad libitum-fed control (C) dams. There were no differences among groups in basal testosterone levels under intact conditions. However, E males showed increased adrenocorticotropin but blunted testosterone and luteinizing hormone (LH) responses to restraint stress compared to PF and/or C rats, and no stress-induced elevation in arginine vasopressin (AVP) mRNA levels. GDX eliminated these differences among groups. The second study explored dose-related effects of testosterone on HPA regulation. Testosterone had less of an inhibitory effect on stress-induced CORT and LH increases in E than in PF and C males. Furthermore, testosterone had a reduced effect on central corticotropin-releasing hormone pathways, but an increased effect on central AVP pathways in E compared to PF and/or C males. Importantly, reduced androgen receptor (AR) mRNA levels, possibly reflecting downregulation of AR in key brain areas, may counteract the increased inhibitory AVP signals upstream from the paraventricular nucleus, and thus contribute to the HPA hyperresponsiveness seen in E males. Together these findings suggest that central regulation of both the HPA and HPG axes are altered by prenatal ethanol exposure. The capacity of testosterone to regulate HPA activity is altered in E males, with some effects mediated by the nutritional effects of ethanol. These changes would impair the ability to maintain homeostasis in E animals and have implications for the development of secondary disabilities in children with Fetal Alcohol Spectrum Disorder.

Background: Management of a transplant recipient involves the use of multiple immunosuppressant drugs. Currently there is no test that reflects the overall immune status of the patient. This results in under or over suppression of the immune system and consequently increases in morbidity and mortality rates. Evaluation of the proliferative response of PBMC's to a mitogen PHA by measurement of intracellular ATP was evaluated as a tool to assess the immune response in kidney transplant patients. Method: PBMC's were separated from the blood samples of healthy controls and kidney transplant patients on cyclosporine, sirolimus, and tacrolimus based regimens by density gradient centrifugation, cells were counted and incubated overnight with and without PHA. The luciferin-Iuciferase enzyme reaction which induces bioluminescence and the Turner Biosystem luminometer were used to measure intracellular ATP levels in relative light units (RLU). An A TP standard curve was generated for each test. Results: The ATP (nglml) levels measured in the transplant recipients were lower and statistically significantly different (p< 0.0001) than the healthy controls. No statistically significant difference was measured between the cycIosporine and sirolimus drug groups. Patients on tacrolimus gave a statistically significant (p<O.0001) stronger immune response than those receiving cyclosporine and sirolimus. Overall, the immune response results of kidney transplant patients were statistically significantly lower than the healthy control by 981 nglml. Linear regression analysis revealed no correlation between patient A TP (nglml) levels and therapeutic drug blood levels, immunosuppressant drug dosages, creatinine levels and white cell counts. The immune responses of patients who were diagnosed with infection or were clinically stable were characterised as low or moderate, of interest, one patient who was diagnosed with rejection was found to have a strong immune response (>501 nglml ATP). Conclusion: Future studies to determine the predictive value of the A TP assay in directing immunosuppressive therapy are required. The assay described in this study is simple, sensitive and rapid and has possible application in immunological monitoring in a variety of conditions that affects the immune system. Keywords: kidney transplantation, immunosuppression, bioluminescence, lymphocyte, Adenosine Triphosphate (A TP), Phytohemmagglutinin (PHA) / Thesis (M.Med.Sc.)-University of KwaZulu-Natal, Durban, 2008.

Prenatal ethanol (E) exposure has marked effects on development of the hypothalamic-pituitary-adrenal (HPA) and -gonadal (HPG) axes. E rats show HPA hyperresponsiveness to stressors and altered reproductive function in adulthood. Importantly, prenatal ethanol differentially alters stress responsiveness in adult males and females, raising the possibility that gonadal hormones play a role in mediating ethanol effects on HPA function. To address this possibility, two studies were conducted to test the hypothesis that the differential alterations in HPA activity observed in E compared to control males are mediated, at least in part, by ethanol-induced changes in HPG effects on HPA regulation. The first study compared the effects of gonadectomy (GDX) on HPA and HPG activity in adult male offspring from prenatal E, pair-fed (PF) and ad libitum-fed control (C) dams. There were no differences among groups in basal testosterone levels under intact conditions. However, E males showed increased adrenocorticotropin but blunted testosterone and luteinizing hormone (LH) responses to restraint stress compared to PF and/or C rats, and no stress-induced elevation in arginine vasopressin (AVP) mRNA levels. GDX eliminated these differences among groups. The second study explored dose-related effects of testosterone on HPA regulation. Testosterone had less of an inhibitory effect on stress-induced CORT and LH increases in E than in PF and C males. Furthermore, testosterone had a reduced effect on central corticotropin-releasing hormone pathways, but an increased effect on central AVP pathways in E compared to PF and/or C males. Importantly, reduced androgen receptor (AR) mRNA levels, possibly reflecting downregulation of AR in key brain areas, may counteract the increased inhibitory AVP signals upstream from the paraventricular nucleus, and thus contribute to the HPA hyperresponsiveness seen in E males. Together these findings suggest that central regulation of both the HPA and HPG axes are altered by prenatal ethanol exposure. The capacity of testosterone to regulate HPA activity is altered in E males, with some effects mediated by the nutritional effects of ethanol. These changes would impair the ability to maintain homeostasis in E animals and have implications for the development of secondary disabilities in children with Fetal Alcohol Spectrum Disorder.

Errata pasted onto back end-paper. / Bibliography: leaves 213-246. / xix, 246, [30] leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Describes the interactions among pituitary-derived peptides, intra-adrenal exposure to glucocorticoids and the local adrenal and endocrine IGF axes in the growth and functional activation of the ovine fetal adrenal gland before birth. Also considers the involvement of these systems in the fetal response to chronic stess and intra-uterine growth restriction. Proposes and develops several conceptual models of the control of adrenal growth and function in late-gestation. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 2000

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physiology, 2001. / Includes bibliographical references (leaves 228-257).

Tez (Tıpta Uzmanlık) - Süleyman Demirel Üniversitesi, Tıp Fakültesi, Radyodiagnostik Anabilim Dalı, 2003. / Bibliyografya var.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 5 uppsatser.