published_or_final_version / abstract / Zoology / Doctoral / Doctor of Philosophy

<p> Sexual receptivity in the female rat is dependent on dose and duration of estradiol exposure. A 2&micro;g dose of estradiol benzoate (EB) primes reproductive behavior circuits but without subsequent progesterone does not facilitate lordosis. However, 50&micro;g EB facilitates lordosis after 48 hours. Both EB doses activate membrane estrogen receptor-&alpha; complexed with metabotropic glutamate receptor-1a (mER&alpha;-mGluR1a), activating a multisynaptic circuit in the arcuate nucleus (ARH). I hypothesized that 50&micro;g EB downregulates ER&alpha; and mER&alpha;-mGluR1a complexes in the ARH. Total ARH ER&alpha; protein was reduced 48 hours after 50&micro;g EB, but the 2&micro;g dose was intermediate between oil and 50&micro;g EB. mER&alpha; that co-immunoprecipitated with mGluR1a were greater 48 hours after 2&micro;g EB treatment versus rats receiving 50&micro;g EB. Progesterone signals rapidly but not through progesterone receptor-dopamine D1 receptor complexes. These results indicate 2&micro;g EB maintains but 50&micro;g EB downregulates mER&alpha;-mGluR1a to regulate lordosis.</p>

<p>'Endocrine disrupting chemicals (EDCs) are compounds found in the environment that have the potential to disrupt normal endocrine function. Estrogenic EDCs (e-EDCs) is a subclass of EDCs and is defined as substances contaminating the environment that may mimic or inhibit the effect of endogenous estrogen and therefore may influence developmental and reproductive health in humans and animals. The aim of this study was to develop, validate and implement a battery of in vitro and in vivo screening assays for e-EDCs. The study was concluded by implementing this battery of assays to assess the Eerste River, South Africa at three sampling sites, namely Jonkershoek, Stellenbosch sewage treatment works (STW) effluent and Spier for e-EDCs. The control site, Jonkershoek contained very low levels of estrone. Water from this site showed no estrogenic activity when the E-screen and the ER_ induction in MCF-7 cells. Some of the water samples collected at this site tested positive for estrogenicity when analysed with the juvenile tilapia VTG assay, whereas the rest were negative. The estrone levels in the sewage effluent extracts as well as Spier were significantly higher. The assay using ER_ protein induction by the MCF-7 cell line, the MCF-7 proliferation assay and the tilapia in vivo screen for estrogenicity showed that these samples are estrogenic. Results obtained for estrogenicity at the three different sampling sites for each of the assays in the battery were comparable. In this study we developed, validated and also implemented a battery of assays encompassing both in vitro and in vivo assays, based on different biological mechanisms, to detect estrogenic EDCs. To our knowledge, this is the first study that has used a battery of bioassays to specifically assess a South Africa river for estrogenicity...'</p>

No description available.

The Corticotropin Releasing Factor (CRF) peptides are an evolutionarily conserved peptide family integral to the stress response. In 2002, an investigation was undertaken into possible homologues of CRF, which led to the discovery of the Teneurin C-terminal Associated Peptide (TCAP) family located on the C-terminal end of the teneurin proteins. This peptide family is involved in neuroprotection against stress. TCAP possesses a number of biological actions independent of teneurin, however, evidence of how TCAP is processed from its proprotein had not been determined. I hypothesize that TCAP is transcribed independently and has independent functionality in promoting filopodia elongation and outgrowth. Here, I show that TCAP-1 is independently expressed as an mRNA separate from the teneurin gene. Moreover, a key step in the TCAP-1 mediated molecular mechanism of filopodia outgrowth may require an interaction between Elongation Factor-1α (EF-1α) and the actin cytoskeleton, where this mechanism is not modulated by CRF.

The Corticotropin Releasing Factor (CRF) peptides are an evolutionarily conserved peptide family integral to the stress response. In 2002, an investigation was undertaken into possible homologues of CRF, which led to the discovery of the Teneurin C-terminal Associated Peptide (TCAP) family located on the C-terminal end of the teneurin proteins. This peptide family is involved in neuroprotection against stress. TCAP possesses a number of biological actions independent of teneurin, however, evidence of how TCAP is processed from its proprotein had not been determined. I hypothesize that TCAP is transcribed independently and has independent functionality in promoting filopodia elongation and outgrowth. Here, I show that TCAP-1 is independently expressed as an mRNA separate from the teneurin gene. Moreover, a key step in the TCAP-1 mediated molecular mechanism of filopodia outgrowth may require an interaction between Elongation Factor-1α (EF-1α) and the actin cytoskeleton, where this mechanism is not modulated by CRF.

The teneurin C-terminal associated peptides (TCAPs) are a newly-elucidated family of four bioactive peptides that were found during a screen for novel corticotropin-releasing factor (CRF)-like peptide families. The predicted peptide sequences have the characteristics of a bioactive peptide and are 40 or 41 amino acid residues long. One of the peptides in the family, TCAP-1, has numerous in vitro effects, where it modulates cAMP accumulation, neuronal proliferation, neurite outgrowth, brain-derived neurotrophic factor levels, and possesses neuroprotective effects under alkalotic or hypoxic conditions. However, little is known about TCAP-1’s in vivo effects. Given the structural similarity of TCAP-1 to the CRF family, it is expected that these peptide systems may interact in vivo. The aims of this research were to 1) investigate the role of TCAP-1 on CRF- and stress-induced behaviours in rats, and determine if intracerebral TCAP-1 could modulate stress-induced anxiety-like behaviours; 2) determine the areas of the brain where TCAP-1 is taken up and is active; and 3) investigate the role of TCAP-1’s cytoskeletal modulation on stress-sensitive areas of the brain so as to determine a mechanism for long-term behavioural changes in the brain. I have established that TCAP-1 modulates anxiety-like behaviour in exploratory tests of anxiety, and that TCAP-1 is particularly active in the limbic system, including the hippocampus, amygdala, septum, and medial prefrontal cortex, and that TCAP-1 increases the dendritic spine density in the hippocampus, a brain area important for anxiety, learning, and memory. These studies have confirmed that TCAP-1 indeed plays a role in stress-like behaviours and modulates stress-related processes in the brain.

The teneurin C-terminal associated peptides (TCAPs) are a newly-elucidated family of four bioactive peptides that were found during a screen for novel corticotropin-releasing factor (CRF)-like peptide families. The predicted peptide sequences have the characteristics of a bioactive peptide and are 40 or 41 amino acid residues long. One of the peptides in the family, TCAP-1, has numerous in vitro effects, where it modulates cAMP accumulation, neuronal proliferation, neurite outgrowth, brain-derived neurotrophic factor levels, and possesses neuroprotective effects under alkalotic or hypoxic conditions. However, little is known about TCAP-1’s in vivo effects. Given the structural similarity of TCAP-1 to the CRF family, it is expected that these peptide systems may interact in vivo. The aims of this research were to 1) investigate the role of TCAP-1 on CRF- and stress-induced behaviours in rats, and determine if intracerebral TCAP-1 could modulate stress-induced anxiety-like behaviours; 2) determine the areas of the brain where TCAP-1 is taken up and is active; and 3) investigate the role of TCAP-1’s cytoskeletal modulation on stress-sensitive areas of the brain so as to determine a mechanism for long-term behavioural changes in the brain. I have established that TCAP-1 modulates anxiety-like behaviour in exploratory tests of anxiety, and that TCAP-1 is particularly active in the limbic system, including the hippocampus, amygdala, septum, and medial prefrontal cortex, and that TCAP-1 increases the dendritic spine density in the hippocampus, a brain area important for anxiety, learning, and memory. These studies have confirmed that TCAP-1 indeed plays a role in stress-like behaviours and modulates stress-related processes in the brain.

xxiii, 171 leaves : ill. + appendix / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Physiology, 1973

Doctor of Philosophy / A large number of neuroendocrine studies indicate a possible relationship between the Hypothalamo-Pituitary-Gonadal (HPG) axis and major depressive illness in men. This observation is not surprising, considering the similarities between the symptom profiles of depression and hypogonadism. However, owing to the strong likelihood that a number of other demographic, clinical and treatment covariates may potentially obscure a possible relationship between HPG and depression, studies in this area have produced somewhat inconsistent results. The main objective of the present study was to investigate the relationship between depression and HPG hormone levels in a population of hospitalised men. Another objective was to examine the relationship of a number of demographic, behavioural, clinical and treatment variables with HPG hormone levels and depression. METHOD: Serum hormones of the HPG axis (Luteinizing Hormone (LH), Follicle Stimulating Hormone (FSH), Free Testosterone (free T), Total Testosterone (total T) and Sex Hormone Binding Globulin (SHBG)) were compared between fifty-two male patients with Major Depressive Disorder (mean age = 42.04; SD = 14.1) and twenty-five male patients with other psychiatric conditions (mean age = 40.72; SD = 13.8) on admission into hospital. In addition, to elucidate the possible relationship between clinical outcome of depression and gonadal function, HPG parameters were measured in patients with depression 3 to 6 months following discharge. Based on their HDRS (Hamilton Depression Rating Scale) score, patients were categorised as remitters and non-remitters. Demographic, behavioral, clinical and treatment variables were also examined as possible correlates of hormone levels. RESULTS: Comparison between patients with depression and patients with other diagnoses indicated a significantly lower free T and total T in patients with depression. There were no differences in other hormone parameters between the two diagnostic groups. Correlational analyses indicated significant negative relationships between free T and total T and severity as well as duration of depression. Age was inversely correlated to both free T and total T, whereas BMI was negatively correlated with Total T and SHBG. There was a positive relationship between Total T as well as Free T and measures of sexual dysfunction. While no difference in hormone parameters was observed as a function of psychotic features, patients with melancholic features exhibited significantly lower levels of free T and total T compared to patients with no melancholic features. In the multiple regression analyses, age, duration and severity of depression were the strongest predictors of both free and total T. In separate regression analyses somatic features, over and above other features of depression were found to account most in the variability in free T and total T. Longitudinal analysis revealed significantly higher free T and total T levels on follow-up compared to baseline in the patients who remitted. There was no significant change in any of the hormones studies in the non-remitting group. CONCLUSION: The main findings of the present study support previous results that both total and free testosterone levels are lower during depression and that concentrations of free T and total T parallel changes in severity of depressive symptomatology. Further investigations into the mechanism for this observation, and perhaps examinations of testosterone supplementation for treatment of depression are in order.