Infundibular (arcuate) neurokinin B (NKB) neurons play a critical role in neuroendocrine control of reproduction. Specifically, a local network of arcuate neurons that co-express kisspeptin, neurokinin B, and dynorphin (so-called, KNDy neurons), has emerged as a potential pacemaker driving the pulsatile secretion of gonadotropin-releasing hormone (GnRH) that is required for normal reproduction. These neurons are the target of estrogen and may be an important link in estrogen negative feedback on GnRH functioning. KNDy neurons respond to estrogen withdrawal with dramatic changes in gene expression and somatic hypertrophy, an effect that is reversible by estradiol replacement. Studies addressing the effects of estrogen withdrawal and replacement on morphological and electrophysiological features of KNDy neurons have been hindered by the inability to target this subpopulation of neurons in the live tissue. This dissertation examines estrogen-induced changes in arcuate NKB circuitry and excitability and discusses its implications in reproductive axis. First, the novel Tac2-EGFP transgenic mouse model was characterized. The reproductive function, EGFP-ir distribution in the brain, and co-localization of EGFP with proNKB in the arcuate nucleus were examined and compared to littermate controls. Indices of reproductive function (puberty onset, estrous cyclicity, and LH pulsatility) were comparable between Tac2 and wildtype mice, suggesting that the transgenic animals have preserved estrogen negative feedback. The long-term estrogen withdrawal via ovariectomy and estradiol replacement model was used to examine electrophysiological and morphological changes in arcuate NKB neurons. We found that low-dose chronic estradiol replacement results in decreased excitability of arcuate NKB neurons, a finding that is consistent with the proposed role of this neuronal population in estrogen negative feedback on reproductive axis. Changes in excitability were seen despite the overall similarity in intrinsic properties of estradiol-treated and untreated ovariectomized mice. We also demonstrated for the first time that single arcuate NKB neurons form a local network by way of recurrent collaterals. Axonal targets of single NKB neurons included the internal zone of the median eminence, ependymal layer of the 3rd ventricle, and sites lateral and dorsal to the borders of the arcuate nucleus. Long-term treatment with estradiol resulted in decreased somatic volume and decreased dendritic spine density. Together, these data demonstrate that low-dose chronic estradiol replacement in ovariectomized mice resulted in morphological plasticity of arcuate NKB neurons that was accompanied by changes in excitability of this neuronal population, supporting the role of these neurons in estrogen negative feedback on GnRH secretion.

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Despite the success of modern medicine in treating infections, infectious diseases remain a major source of morbidity and mortality worldwide. The evolution of antibiotic resistant strains of bacteria means that new innovations in therapeutics must be pursued to combat this emerging threat. A novel approach is to utilize the anti-infective properties of endogenous host defense peptides by creating smaller synthetic peptides with enhanced protective activities. Some of these peptides directly kill bacteria and many display varied immunomodulatory activities, enhancing the host innate immune response to more effectively clear an infection. Here I examined the efficacy of several synthetic peptides in a murine model of invasive bacterial infection, induced by the Gram positive bacterium Staphylococcus aureus. Several peptides were able to significantly reduce peritoneal bacterial load in vivo by up to 4-logs relative to the controls, either through direct antibacterial killing or immunomodulatory activity. The latter class was studied in more detail; in particular, the peptides IDR-1 and 1002 displayed significant immunomodulatory effects in vivo. Both peptides were able to significantly induce the proinflammatory chemokines MCP-1, RANTES and KC, as well as increased recruitment of neutrophils and monocytes to the site of infection. These effects were not dependent on live bacteria, as heat inactivated S. aureus was also able to induce chemokines and cell migration. Mice that had been depleted of macrophages did not respond to peptide treatment, indicating that macrophages are an important effector cells through which immunomodulatory peptides counter infections. These results suggest that synthetic peptides have the potential to become a viable treatment option for bacterial infections.

Spontaneous subarachnoid hemorrhage (SAH) is a form of hemorrhagic stroke that accounts for approximately 7% of all strokes worldwide. Recently, researchers have gained insight into some possible genetic influences involved in the response to SAH. The goal of this study was to investigate the potential contribution of different mouse genetic backgrounds to brain injury after SAH. SAH was induced in 7 inbred strains of mice, and the degree of large artery vasospasm and brain injury was assessed. After 48 hours, SAH mice showed a significant reduction in middle cerebral artery diameter and increased neuronal injury in the cerebral cortex compared to sham controls. The degree of vasospasm and brain injury varied across strains. This data suggests that vasospasm and neuronal injury may not correlate, and that different genetic factors may influence each one. Future investigations may provide invaluable insight into the causes of these inter-strain differences and potential genetic contributors.

No description available.

Spontaneous subarachnoid hemorrhage (SAH) is a form of hemorrhagic stroke that accounts for approximately 7% of all strokes worldwide. Recently, researchers have gained insight into some possible genetic influences involved in the response to SAH. The goal of this study was to investigate the potential contribution of different mouse genetic backgrounds to brain injury after SAH. SAH was induced in 7 inbred strains of mice, and the degree of large artery vasospasm and brain injury was assessed. After 48 hours, SAH mice showed a significant reduction in middle cerebral artery diameter and increased neuronal injury in the cerebral cortex compared to sham controls. The degree of vasospasm and brain injury varied across strains. This data suggests that vasospasm and neuronal injury may not correlate, and that different genetic factors may influence each one. Future investigations may provide invaluable insight into the causes of these inter-strain differences and potential genetic contributors.

No description available.

Vitamin A and its derivatives, collectively termed retinoids, are essential for proper growth and development as well as maintenance of homeostasis in the adult. Retinoic acid (RA), the major biologically active vitamin A metabolite, is well characterized for its crucial roles in gene activation during embryogenesis. Our lab had previously performed a microarray analysis to identify genes induced by exogenous RA in the tailbud of early mouse embryos. Three genes were chosen from the microarray results for further investigation; Germ Cell Nuclear Factor (GCNF/NR6A1), Prickle1 (Pk1) and Ror2, the latter of which are known members of the planar cell polarity (PCP) pathway. These genes were further examined for RA regulation by embryo culture and RT-PCR, which strongly supported a direct regulatory mechanism of NR6A1 by RA. Further analysis aiming to identify a functional response element in the promoter of the targets was attempted, including chromatin immunoprecipitation (ChIP), made possible by the generation and characterization of a highly specific antibody against RARγ. This antibody was used in a ChIP promoter walk, which identified regions on target gene promoters that are occupied by RARγ in vivo, and therefore likely harbor RA response elements.

The ecology of small mammal communities found in set-aside and adjacent farm land was investigated to determine the ecological consequences of set-aside land to small mammals. Field work was carried out for two years at three study sites in NE Scotland. First Aldroughty farm, a mosaic of set-aside, crop and semi-natural land. The two remaining study sites; Ythan Lodge at Newburgh, and Fraser's farm near Aldroughty, were whole fields of set-aside. Wood mice <i>Apodemus sylvaticus</i>, bank voles <i>Clethrionomys glareolus</i> and field voles <i>Microtus agrestis</i> were trapped in the habitat mosaic at Aldroughty, and wood mice and field voles in the set-aside at Newburgh. Wood mice had higher densities, greater survival, heavier weights, longer breeding seasons and more juveniles at Aldroughty than Newburgh. These differences were thought to be due to a difference in habitat productivity between the two sites. Field voles showed less of a difference in population dynamics between Aldroughty and Newburgh, and both species of vole maintained populations at low density. The home range size of 33 wood mice was measured using radiotelemetry. At both study sites home range size was smaller than in other habitats revealed by other studies. The apparently anomalous results obtained, of low population densities and small home range sizes of wood mice in the set-aside at Newburgh, may have been due to predation from cats <i>Felis catus</i>. Wood mice showed no clear habitat preference, nesting and foraging in all habitat types, while both vole species showed almost exclusive preference for rough grassland. An assessment of the habitat characteristics of the study sites showed that there was heterogeneity in the vegetation communities found in set-aside.