Browsing by Subject "Nervous System Diseases"
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Item 17 Beta-Estradiol, Integrins, and Synaptic Proteins(2009-05-01) Chandra, Manjari; Simpkins, James W.Item Antioxidants, Exercise, APOE Genotype and Brain Function(2014-12-01) Chaudhari, Kiran; Nathalie Sumien; Michael J. Forster; Eric B. GonzalesApolipoprotein E4 (APOE4) is a well-established and extensively prevalent genetic risk factor for the development of Alzheimer’s disease (AD). The presence of APOE4 allele accelerates the pathophysiology and symptomology of AD. A large set (36%) of the population suffering from AD expresses APOE4. Being a chronic progressive disease with very few pharmaco-therapeutic agents approved by FDA, non-drug lifestyle modifications have been an important part of management of AD. People often eat healthy diet rich in antioxidants and focus on healthy living habits such as exercise. Health care providers frequently suggest combining antioxidants with physical activity for higher benefits. Antioxidants have been beneficial in counteracting oxidative stress and improving learning and memory. Similarly, different regimens of exercise also improved cognition and delayed development of AD. However, the nature of the interaction between antioxidants and exercise remain elusive and complicated. While some studies reported additive effects, others have also shown a concerning antagonistic action of the antioxidants on the beneficial effects of exercise. In the context of APOE genotype, we set our study to determine the nature of such interaction between antioxidants and exercise. Using vitamins C and E and a treadmill-based forced exercise in a genetically modified mouse model expressing human APOE3 and APOE4 (GFAP-APOE3, GFAP-APOE4), we explored the nature of that interaction on functional and biochemical outcomes. We examined the mice for spatial learning and memory, working memory and executive function, coordinated running performance, muscular reflexes, spontaneous locomotor activity, anxiety and muscle strength. Interestingly, we observed that the young adult mice expressing E4 allele performed better on higher brain functions including spatial learning and memory and short term memory in contrast to middle age mice, which developed a cognitive deficit as expected. Motor functions, reflexes and coordination were poor among all the mice carrying E4 allele irrespective of age. Antioxidants and exercise interventions led to outcomes that were dependent on genotype, age and the brain function under consideration. There was additive beneficial effect of combination of antioxidants and exercise on cognitive outcomes but not on motor outcomes in middle age groups. However, in young adults, an antagonistic interaction was observed on motor outcomes but no such interaction was observed on cognitive outcomes. Hence we can conclude that, combination of antioxidants and exercise is not a “fit for all” approach and needs to be tailored base on individual’s age and genotype.Item Cellular and Molecular Mechanisms that Distinguish the Effects of Progestorone and Medroxyprogesterone Acetate on Neuroprotection(2006-07-28) Kaur, Paramjit; Goldfarb, Ronald; Singh, Meharvan; Agarwal, NeerajKaur, Paramjit. Cellular and Molecular Mechanisms That Distinguish the Effects of Progesterone and Medroxyprogesterone Acetate on Neuroprotection., Doctor of Philosophy, (Pharmacology and Neuroscience), July, 2006, 203 pp., 5 illustrations, 20 figures and bibliography. Women have a higher prevalence for Alzheimer’s disease (AD) than men, suggesting that the precipitous decline in gonadal hormone levels following the menopause may contribute to the risk of developing AD. However, principal results from the Women’s Health Initiative concluded that women taking conjugated equine estrogens combined with medroxyprogesterone acetate (MPA, tradename: Prempro) incurred more harmful than beneficial outcomes versus the placebo group (Rossouw et al., 2002). This dissertation was aimed at determining if the discrepancy between basic science reports and these clinical studies could have been due to the synthetic progestin, MPA. I hypothesized that P4 and MPA differed in their ability to protect against the excitotoxic/oxidative insult, glutamate. Further, I proposed that this difference in neuroprotective potential would be reflected in the difference in the ability of these hormones to elicit key effectors of two neuroprotection-associated signaling pathways, the ERK/MAPK and P13-Kinase pathways. Finally, studies were initiated to evaluate the potential importance of BDNF (brain-derived neurotrophic factor) in mediating the protective effects of P4. I used organotypic explants of the cerebral cortex, and found that both P4 and MPA elicit the phosphorylation of ERK and Akt, two signaling pathways implicated in neuroprotection, with maximal phosphorylation occurring at a concentration of 100 nM. Interestingly, P4 protected against glutamate- induced toxicity however, while an equimolar concentration of MPA (100nM) did not. Further, P4 resulted in an increase in BDNF, while MPA did not. Our data bring into question the relevance of using MPA as a component of hormone therapies in postmenopausal women, and instead, argue that the relevant progestin for use in treating brain-related disorders is progesterone. Collectively, the data presented here suggest that P4 is protective via multiple, and potentially related mechanism, and importantly, its neurobiology is different from the clinically used progestin, MPA.Item Clinical Internship with the Pediatric Clinic's Clinical Research at the Patient Care Center of the University of North Texas Health Science Center/Texas College of Osteopathic Medicine: Literature Review of Meningococcal Meningitis(2002-07-01) Puckett, Fredric Clark; Harold Sheedlo; Robin Newman; John FlingEpidemic meningococcal meningitis and meningococcemia disease is caused by the bacterial pathogen Neisseria meningitidis. Once infected with meningococci, onset of the disease is rapid with a high rate or morbidity and mortality. Without medical intervention the mortality rate is over 50%. Medical treatment is over 50%. Medical treatment of an outbreak of the disease with antibiotics can reduce the death rate to 10-15%. However, 10-20% of survivors will suffer from neurological damage that may include loss of hearing, paralysis or mental retardation. Recent concerns have been noted regarding the emergence of Neisseria meningitidis strains resistant to antibiotics. Vaccines have been developed in an effort to reduce epidemic outbreaks of meningococcal meningitis and meningococcemia. The first generation polysaccharide vaccines have shown to be safe and possess some degree of effectiveness but have shortcomings of limited length of immune protection and evidence of hyporesponsiveness to subsequent vaccinations. The second generation conjugated polysaccharide vaccines have been able to overcome these problems and show great promise in reducing the sale of epidemic meningococcal outbreaks with implementation of effective mass vaccination campaigns. In addition, reducing the number of infections will limit the exposure of Neisseria meningitidis to antibiotics and, in theory, slow the development of resistance to antibiotics.Item Endothelin receptor-mediated neurodegeneration in glaucoma(2017-08-01) McGrady, Nolan; Krishnamoorthy, Raghu R.; Yorio, Thomas; Clark, Abbot F.Primary open-angle glaucoma (POAG) is a complex set of optic neuropathies which are characterized by the degeneration of the optic nerve, cupping of the optic disk and loss of retinal ganglion cells (RGCs). There are approximately 3 million Americans who currently suffer from this disease although this is most likely an underestimation since many individuals with glaucoma are unaware that they have the disease. POAG is an age-related disease progressing slowly over the course of several decades and is most commonly associated with an elevation in intraocular pressure (IOP). Currently available treatments for glaucoma, both surgical and pharmacological, are solely focused on the regulation of IOP; nevertheless, some individuals continue to show progressive damage despite being on available therapies. In recent years, there has been increased momentum towards the development of neuroprotective strategies for POAG, particularly in preclinical models of glaucoma. Despite these efforts, there is still no neuroprotective treatment currently available for glaucoma patients. A potential target for the development of a neuroprotective approach is the endothelin system of peptides and their receptors. The endothelin (ET) system is composed of three vasoactive peptides (ET-1, ET-2 and ET-3) which are comprised of 21-amino acids. The peptides bind to two G-protein coupled receptors (ETA and ETB receptors) leading to activation of numerous signal transduction pathways. Although originally described for its role in the vasculature, all components of the ET system has been shown to be expressed in multiple tissues and cell types and are responsible for diverse cellular effects. Clinical studies have demonstrated an increase in ET-1 concentrations both in the aqueous humor and plasma of glaucoma patients. A previous study by our lab, using a rodent model of ocular hypertension, showed that endothelin B (ETB) receptor expression is increased when compared to control eyes and contributes to neurodegeneration (Minton et al., 2012). Preliminary data in the current study, using Brown Norway rats, demonstrated that ETA expression is also increased in the IOP elevated eyes, suggesting the possibility that the ETA receptor might also have a degenerative role during ocular hypertension. We hypothesize that the ETA expression increases following IOP elevation and contributes to the neurodegeneration of retinal ganglion cells and their axons. To test this hypothesis we employed a well-characterized in vivo model of glaucoma as well as multiple cellular and molecular approaches to understand the role of the ETA receptor in glaucomatous degeneration. Our data suggest that overexpression of the ETA receptor promotes cell death in cultured RGCs. Since both ETA and ETB receptors appear to contribute to neurodegeneration, we tested the ability of an FDA approved medication, macitentan, for neuroprotection in the Morrison model of glaucoma in rats and found it to promote RGC survival. Our studies raise the possibility of testing macitentan as a neuroprotective treatment for glaucoma patients.Item Evaluation of NK Cell – Astrocyte Interactions: Potential Role in HIV-Associated Neurocognitive Disorders and HIV- Associated Dementia(2015-05-01) Bowen, Kelly E.; Mathew, Porunelloor A.; Mathew, Stephen O.; Hodge, Lisa M.NK cells play important roles in immunity against pathogens and cancer. NK cell functions are regulated by inhibitory and activating receptors binding corresponding ligands on the surface of target cells. During pathological conditions, NK cells were shown to be recruited to the CNS and could impact CNS physiology by killing glial cells and by secreting IFN-g. Astrocytes are intimately involved in immunological and inflammatory events occurring in the CNS and reactive astrogliosis is a key feature in HIV-associated neurocognitive disorders (HAND). There is little data on NK cell-astrocyte interactions and ligands expressed on astrocytes that could impact NK cell function. This study aimed to identify NK-associated ligands expressed by human astrocytes that confer this NK-directed cytotoxicity of astrocytes and assay the cytotoxicity differences in presence and absence of HIV 3S peptide. Using a fusion protein consisting of the extracellular domain of NKp44 fused to Fc portion of human IgG, we determined the expression of a novel ligand for NKp44 (NKp44L) on astrocytes. Incubation of astrocytes with 3S peptide downregulated NKp44L expression on astrocytes implicating protection from NK mediated killing. Thus, our study demonstrated that NKp44 has a protective effect on astrocytes from NK cell mediated killing during HIV infection. Astrocytes could also secrete cytokines that affect the expression of NK receptors on NK cells. We evaluated the expression of receptors on NK cells after co-culture with astrocytes. CD38 expression was increased on primary NK cells after incubation with astrocytes. CD38 is expressed on both NK cells and astrocytes and has an important implication in HIV-1 infection. Blocking CD38 signaling in our studies decreased astrocyte lysis, suggesting CD38 signaling has important implications in NK-astrocyte interactions. Future studies providing novel insights into the role of NK cells in the pathogenesis of HAND and other brain disorders might result in the development of NK cell based therapies for brain pathologies.Item Genetic Modulation of β-Amyloid Neurotoxicity and Protection by Nicotinic Agents(2007-05-01) Martin, Shelley E.; Basu, Alakananda; Forster, Michael; Singh, MeharvanMartin, Shelley E., Genetic Modulation of β-Amyloid Neurotoxicity and Protection by Nicotinic Agents. Master of Science (Pharmacology and Neuroscience), May, 2007, 53 pp., 7 figures, 2 tables, bibliography, 95 titles. Β-amyloid1-42 (Aβ42) has been implicated in the pathogenesis of Alzheimer’s disease (AD); however, the amount of this peptide in the brain does not correlate well with the presence or severity of AD. This project tested the hypothesis that individual differences exist in susceptibility to Aβ42 neurotoxicity arising from the differences in the expression of α7 nicotinic acetylcholine receptors α7 nACHRs). This hypothesis was tested in primary neuronal cultures derived from inbred mouse strains which differ in expression of α7 nAChRs. Also, the ability of nicotinic agents to modulate Aβ42 toxicity was examined. Significant strain differences in susceptibility to Aβ42 toxicity were found; however, these were not related to levels of α7 nAChRs. Additionally, strain differences were found in the ability of α7-selective partial agonist, an α7-selective antagonist and a α4β2 nAChR-selective antagonist to protect against this toxicity. Inbred strains of mice may be useful in uncovering the pathophysiology of AD.Item Involvement of Caspase-7 in Photoreceptor and Retinal Ganglion Cell Death(2014-08-01) Choudhury, Shreyasi; Pang, Iok-Hou; Wordinger, Robert J.; Krishnamoorthy, Raghu R.Apoptosis has been implicated in retinal cell death during both retinal differentiation and degeneration. In diseases such as retinitis pigmentosa, glaucoma, age-related macular degeneration, diabetic retinopathy and traumatic optic neuropathy, retinal cell apoptosis plays an important role. Caspases, a family of cysteine proteases, are major players of apoptosis. Thus, one obvious target for modulating apoptosis is the caspase family of proteins. The role of initiator caspases (caspase-1, -2, -8, -9) and effector caspases (caspase-3, -6) in retinal neuronal apoptosis has been studied previously. But the role of a unique effector caspase, caspase-7, has never been studied before. The purpose of this study was to investigate the role of caspase-7 in retinal neuronal cell apoptosis, especially in photoreceptor and retinal ganglion cell (RGC) death. We used the T17M RHO mouse, an animal model for Autosomal Dominant Retinitis Pigmentosa, to study photoreceptor cell apoptosis, and evaluate the role of caspase-7 in a corresponding caspase-7 knockout mouse. Our results show that morphological (evaluated by spectral-domain optical coherence tomography (SD-OCT) and histology) and functional (by electroretinography (ERG)) degenerations in the photo-receptor cells of the T17M RHO mouse are significantly protected by knocking out caspase-7. We further discovered that caspase-7 inhibition reprograms the unfolded-protein response and reduces JNK-induced photoreceptor cell death. To assess the role of caspase-7 in RGC apoptosis, we used the mouse optic nerve crush-induced RGC death as a study model. We found that the insult activates caspase‐7 in RGCs in a time-dependent manner, concomitant with loss of the cells. We also observed the activation of calpain-1, an upstream activator of caspase-7 and the hydrolysis of caspase-7 specific substrates, confirming the involvement of caspase-7. Most importantly, in caspase--‐7 knockout mice, significantly more RGCs survive the optic nerve injury when compared to injured wild type mice as assessed morphologically (immunohistochemistry and SD-OCT) and functionally (ERG) throughout the 28-day post crush study period. Altogether, our findings indicate that caspase-7 appears to play a critical role in photoreceptor and RGC death and inhibition of caspase-7 activity may be a novel therapeutic strategy for retinal degenerative diseases.Item Measurement of Traumatic Brain Injury (TBI) Inpatient Activity Levels Through Accelerometry(2017-05-01) Ramsey, Jeffrey T.; Patricia A. Gwirtz; J. Cameron Millar; Stephen O. MathewPurpose: The purpose of this study was to use retrospective analysis of actigraphy data to describe activity levels for patients undergoing inpatient rehabilitation. This study also examined the differences between activity levels of the different areas of therapy. The final aim of this study was to examine the affect of demographic factors, and injury characteristics on activity levels. Method: Fifty individuals with Traumatic Brain Injury (TBI) undergoing inpatient rehabilitation wore accelerometers. Activity Counts (ACs) were summarized in one-minute intervals. ACs, demographic and outcome variables were analyzed using descriptive statistics and general linear regression analysis. Results: During active therapy patients averaged 241.3 +/- 97.8 AC, which decreased to 142.2 +/- 74.1 during non-active therapy. Recreational time had an average of 112.8 +/- 59.5 AC, and sleep time had an average of 26.7 +/- 14.8 AC. Using predetermined definitions of physical activity, patients were determined to be inactive during therapy and sedentary/inactive for large portions of their stay. Linear regression analysis showed that the main factor with a negative association with physical activity is age. Discussion: The findings of this study demonstrate that patients undergoing inpatient rehabilitation are largely inactive or sedentary. Although age was determined to have the largest impact on physical activity, the other demographic and outcome measures analyzed by this study along with other confounders’ impact on physical activity require further study to determine the best way to safely increase patient activity.Item Mechanisms of Chemoreflex Control of Muscle Sympathetic Nerve Activity and Blood Pressure in Humans(2004-05-01) Hardisty, Janelle M.; Smith, Michael; Shi, Xiangrong; Clark, MichaelHardisty, Janelle M., Mechanisms of Chemoreflex Control of Muscle Sympathetic Nerve Activity and Blood Pressure in Humans. Doctor of Philosophy (Integrative Physiology), May 2004. The mechanisms linking obstructive sleep apnea (OSA) and cardiovascular disease are not fully understood; however, studies report patients with OSA exhibit chronic elevations in muscle sympathetic nerve activity (MSNA). This appears to be due to altered chemoreflex control of MSNA, mediated primarily by hypoxia. Yet, a correlation between degree of hypoxia and chemoreflex control of MSNA is unknown. Therefore, it was evaluated whether degree of hypoxia occurring during apnea determines the sympathoexcitatory and blood pressure responses, and whether these responses are augmented in OSA patients. Additionally, it was studied whether altered chemoreflex function in OSA patients is predictive of blood pressure response to apnea. In a clinical setting, the blood pressure response to voluntary apnea was determined to evaluate whether this could be used as a non-invasive measure of chemoreflex gain in OSA. Finally, the effect of hyperoxia on MSNA was studied to determine whether 15 min of hyperoxia, following intermittent hypoxic apnea, reverses the elevation of MSNA and altered chemoreflex control of MSNA. Consistent with the hypotheses, a relationship between MSNA responses, blood pressure response and level of hypoxia were determined. MSNA and peak systolic pressure responses were augmented in OSA subjects (p≤0.05 and p≤0.05, respectively), as well as, chemoreflex gain (p≤0.05). Clinically, peak systolic pressure responses to apnea were augmented in OSA patients (p˂0.001). Finally, basal MSNA and chemoreflex control of MSNA, following hyperoxia, was not different from baseline through 180 min of recovery (p=0.940 and p=0.278, respectively). These data support the hypotheses that chemoreflex gain is predicative of the blood pressure response; and furthermore, the MSNA and blood pressure responses to hypoxic apnea are augmented in OSA. Additionally, peak systolic pressure responses to voluntary apnea are augmented in OSA. Additionally, peak systolic pressure responses to voluntary apnea are augmented in OSA patients and could possibly be used as a marker of chemoreflex gain. Moreover, these data support the hypothesis that hyperoxia can reverse basal sympathoexcitation and augmented chemoreflex control of MSNA, associated with hypoxic apnea, supporting that elevations in MSNA are hypoxia mediated.Item Mechanisms of Post-Apneic Symathoinhibition in Humans(2002-08-01) Swift, Nicolette Muenter; Michael Smith; David Barker; John R BurkMuenter Swift, Nicolette, Mechanisms of Post-Apneic Sympathoinhibition in Humans. Doctor of Philosophy (Biomedical Sciences), August, 2002, 110 pp., 14 figures, references. Apnea is accompanied by a concomitant rise in arterial pressure and muscle sympathetic nerve activity (MSNA), the latter primarily due to chemoreflex stimulation and possibly the lack of sympathoinhibitory input from pulmonary stretch receptors. The progressive sympathoexcitation during apnea suggests a possible overriding of arterial baroreflex sympathoinhibitory input to sympathoregulatory centers by apnea-induced sympathoexcitatory mechanisms. Nevertheless, it is unknown whether apnea attenuates baroreflex control of MSNA. Apnea termination is accompanied by a profound and immediate sympathoinhibition, the mechanisms of which are unclear; however, potential mediators include normalization of blood gases (i.e. chemoreflex unloading), the lung inflation reflex, and arterial baroreflex stimulation. Therefore, the purpose of the current studies was to: i) determine the contribution of chemoreflex unloading to post-apneic sympathoinhibition, ii) determine the contribution of the lung inflation reflex to post-apneic sympathoinhibition, and iii) determine whether carotid baroreflex control of MSNA is altered by apnea and its termination. The first study compared MSNA during post-apneic administration of room air versus a gas mixture designed to maintain the subjects’ end-apneic alveolar gas levels. Regardless of post-apneic gas administration, post-apneic MSNA was at or below baseline pre-apneic levels; thus; chemoreflex unloading does not contribute to post-apneic sympathoinhibition. Furthermore, quantification of post-apneic MSNA associated only with the low lung volume phase of respiration, when sympathoinhibitory input from the lung inflation reflex is minimal, demonstrated that post-apneic sympathoinhibition persists even during the low lung volume phase of respiration, when sympathoinhibitory input from the lung inflation reflex is minimal, demonstrated that post-apneic sympathoinhibition persists even during the low lung volume phase of respiration. Therefore, the lung inflation reflex does not appear to be the primary mediator of post-apneic sympathoinhibition. The second study utilized neck suction (NS) and neck pressure (NP) to assess carotid baroreflex function during and following sleep apnea. The sympathoinhibitory response to -60 Torr NS was maintained throughout apnea; conversely, the sympathoexcitatory response to +30 Torr NP was attenuated for nearly one minute post-apnea. Thus, carotid baroreflex control of MSNA is not altered by apnea but is transiently attenuated by apnea termination. We propose that the carotid baroreflex-MSNA function curve resets rightward and upward during apnea. Return of the function curve to baseline upon apnea termination may partly explain the reduced MSNA response to NP post-apnea.Item N-Acylethanolamine Signaling in Neurons(2008-12-01) Duncan, Raymond Scott; Koulen, Peter; Simpkins, James; Forster, MichaelDuncan, Raymond S., N-acylethanolamine signaling in neurons. Doctor of Philosophy (Biomedical Sciences), December 2008, 356 pp., 1 table, 70 illustrations, bibliography, 576 titles. Neurodegenerative diseases including Alzheimer’s disease are and will continue to be significant health problems as the aging population increases. The maintenance of neuronal calcium homeostasis has been a focus in degenerative disease research for many years. Within the last several years, lipids that activate cannabinoid receptors, and thus called cannabinoids, have gained recognition as neuroprotectants in models of neurodegenerative diseases. A subset of these cannabinoids, the N-acylethanolamines (NAEs), includes the well characterized neuroprotective lipid, arachidonylethanolamine. Other NAEs, such as palmitoylethanolamine (PEA), are more abundant in neurons and do not activate cannabinoid receptors, suggesting other targets for these lipids exist. Since non-cannabinoid NAEs rapidly accumulate after neuronal injury, it is likely they play a role in cellular responses to injury. Interestingly, some NAEs can alter intracellular Ca2+ signaling, but the underlying mechanism of action remains unclear. I hypothesized that the non-cannabinoid NAEs, such as PEA, protect the hippocampal cell line, HT22, from oxidative stress in part by reducing intracellular calcium release. I determined that HT22 cells and cultured mouse cortical neurons express proteins involved in NAE signaling, thus warranting the use of pharmacological inhibitors of these proteins in subsequent neuroprotection studies. Using HT22 cells, I determined that PEA exhibitis antiproliferative effects and neuroprotects against oxidative stress. In addition, I determined that PEA facilitates the nuclear translocation of putative protective proteins that can be regulated by Ca2+ through a mechanism not involving cannabinoid receptor activation. These findings led me to hypothesize that PEA alters release of Ca2+ from intracellular stores. To test this hypothesis, I determined that our cell models express inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) both of which are intracellular Ca2+ channels elevated in response to oxidative stress. I determined that treatment of HT22 cells with PEA reduced intracellular Ca2+ release elicited by chemical depolarization with KCI. My results suggest that non-cannabinoid NAEs, such as PEA, protect the hippocampal cell line, HT22, from oxidative stress in part by activating putative neuroprotective signaling proteins and by reducing intracellular calcium release.Item Neuroprotective Effects of Brn3b in PC12 Cells and Retinal Ganglion Cells under Glaucomatous Conditions(2015-08-01) Phatak, Nitasha R.; Raghu R. Krishnamoorthy; Weiming Mao; John V. PlanzGlaucoma is a group of chronic progressive optic neuropathies commonly characterized by elevated intraocular pressure (IOP) (a subset of glaucoma patients display neurodegenerative effects at ‘normal’ IOP) leading to axonal degeneration, optic nerve head cupping and apoptosis of retinal ganglion cell death (RGCs), which result in visual field defects and blindness. While there are medications available to lower IOP, there is an unmet need for neuroprotective treatments for glaucoma, since some neurodegenerative effects persist despite lowering IOP. The main focus of this study was on the class 4 POU domain transcription factor, Brn3b, which has been shown to play a key role in the development of RGCs. Two previous studies from other labs showed that a decrease in Brn3b expression occurs in animal model of glaucoma. A recent publication from our laboratory demonstrated neuroprotective effects of adeno-associated virus (AAV) mediated expression of Brn3b in a rat model of ocular hypertension. This research project identified some mechanisms of Brn3b-mediated neuroprotection in cultured PC12 cells (under the condition of hypoxia) and also in vivo in the Morrison’s model of ocular hypertension in rats. In the first part of the study, we demonstrated the effect of overexpression of Brn3b on various markers of synaptic plasticity in PC12 cells under conditions of normoxia as well as hypoxia. Immunoblot as well as immunocytochemical analyses revealed an increase in expression of neurite growth markers, GAP-43 and ac-TUBA, by Brn3b upregulation both under conditions of normoxia as well as hypoxia. . This suggests that transcription factor Brn3b has the ability to upregulate expression genes contributing to synaptic plasticity genes both under ‘normal’ conditions and during a glaucomatous insult (hypoxia). In the concluding part of this study, cell survival factors including, Bcl-2, Bcl-xL and p-AKT were studied as potential targets of Brn3b-mediated neuroprotection. Adeno-associated virus-mediated expression of Brn3b in rat eyes with elevated IOP promoted an upregulation of Bcl-2, Bcl-xL and p-AKT in RGCs, as determined by immunohistochemistry. Taken together, the evidence suggests that Brn3b has the potential to be developed as a therapeutic agent for neuroprotection during ocular neurodegenerative diseases like glaucoma.Item Novel androgen receptor splice variant in the substantia nigra(2017-08-01) Contreras, Jo Garza; Cunningham, Rebecca L.; Basha, Riyaz; Salvatore, MichaelTestosterone can increase calcium influx and cell death in dopamine neurons via a putative membrane androgen receptor (mAR). The mAR induced calcium increase may be due to activation of G-proteins involved in calcium mobilization. Previous studies using an N-terminal targeted androgen receptor (AR) antibody yielded low AR expression in dopamine neurons. Studies in our lab show high AR expression using a C-terminal targeted AR antibody. This difference in expression may be due to an AR variant. We hypothesize an AR variant is present in the membrane of dopaminergic neurons and associated with G proteins. To identify the presence of AR in dopaminergic neurons. We performed immunoblot, sucrose gradient, and immunohistochemistry studies. To determine the protein-protein interaction between mAR and G-proteins we performed co-immunoprecipitation studies. Our results show AR45 localizes in the membrane lipid rafts of dopaminergic neurons. Furthermore, AR45 interacts with Gαq and Gαo G-proteins, which can impact calcium signaling.Item Pharmacological Evaluation of the D2 and D3 Dopamine Receptor Selective Compounds on L-Dopa Dependent Abnormal Involuntary Movements in Rats(2008-05-01) Kumar, Rakesh; Robert Luedtke; Hriday K. Das; Nathalie SumienKumar Rakesh, Pharmacological Evaluation of the D2 and D3 Dopamine Receptor Selective Compounds on L-dopa Dependent Abnormal Involuntary Movements in Rats. Master of Science (Pharmacology & Neuroscience), May 2008, 106 pp, 21 illustrations, references, 31 titles. Parkinson’s Disease (PD) is a progressive, neurodegenerative disease of the dopamine neurons that innervate the striatum and is characterized by resting tremor, rigidity, bardykinesia and postural instability. L-dopa treatment is the most common and effective therapy for PD. However, both motor (wear-off phenomena, rigidity and dyskinesia) and non-motor (sweating, tachycardia, restless leg syndrome, anxiety, depression, confusion, reduced alertness, psychosis and/or dementia) side effects are associated with long term L-dopa therapy. Motor complications depend on the duration of L-dopa treatment and the abnormal involuntary movements are known as L-dopa-induced dyskinesia (LID). Several studies have suggested a possible role of the dopamine D3 receptor subtype in LID. Here I evaluated the effects of various D2 and D3 dopamine receptor selective compounds on LID in 6-hydroxydopamine-induced complete lesioned hemi-parkinsonian model of rat. D3 dopamine receptor selective compounds (agonists, partial agonists or antagonists) have antidyskinetic effects on LID. Co-administration of D3 dopamine receptor agonist and D3 dopamine receptor antagonist has additive effects in attenuating the LID instead of antagonizing the effects of each other in vivo. D3 dopamine receptor selective compounds attenuated apomorphine-induced dyskinesia.Item Regulation of intracellular calcium channels by their associated proteins homer 1 and presenilin 1(2006-05-01) Hwang, Sung-Yong; Koulen, Peter; Dillon, Glenn; Singh, MeharvanSung-Yong, Hwang, Regulation of intracellular calcium channels by their associated proteins homer 1 and presenilin 1. Doctor of Philosophy (Pharmacology and Neuroscience), May, 2006, 184 pp., 4 tables, 20 illustrations, 74 titles. In neurons, Calcium (CA2+) serves as a critical intracellular messenger that regulates a variety of cellular processes such as gene expression, neurotransmitter release, cell death, and synaptic plasticity. Therefore, it is essential for neurons to control their Ca2+ levels tightly. Ca2+ is released within the cell from intracellular stores such as the endoplasmic reticulum by activation of intracellular Ca2+ channels (ICCs) such as the inositol 1,4,5-triphosphate (IP3) receptors (IP3Rs) and ryanodine receptors (RyRs). Each of these two groups of ICC has three isoforms. A number of associated proteins of these two ICCs that were shown to modulate activity of the respective channel have been identified. Homer 1, a synaptic scaffolding protein not only physically associated with IP3R type1 (IP3R1), but also changes the activity of IP3R1, suggesting that Homer 1 is involved in intracellular Ca2+ signaling. Based on the similarity in amino acid sequence and molecular and physiological properties among IP3R isoforms and the fact that IP3R type 3 (IP3R3) contains the proline-rich motif (PPxxFr) that is required for the interaction with Homer, it was hypothesized that Homer 1 associates with IP3R3, leading to changes in the channel activity. Presenilin 1 (PS1) is a transmembrane protein, being expressed in cell body, dendrites, and axon in the neuron. Mutations in PS1 account for most cases of early-onset familial Alzheimer’s disease (AD). PS1 was shown to associate with RyRs and to modulate their channel activity. Therefore, it was hypothesized that specific regions of PS-1 bind to RyR type 2 (RyR2), a major isoform in the brain, resulting in changes in the channel activity. Homer 1c was shown to associate with IP3R3, leading to a decrease in channel activity. A specific region of PS1 that interacts with RyR2 was identified to increase the channel activity of RyR2. Results of the present study contributed to the understanding of the nature of intracellular Ca2+ signaling as well as the mechanisms of action by which ICCs are regulated by their associated proteins. These findings provide the rationale for novel strategies to study neurological disorders including AD and epilepsy that are mediated by Ca2+ dysregulation.Item Role of ΔFosB in nucleus of the solitary tract (NTS) in cardiovascular adaptations to chronic intermittent hypoxia (CIH) in rats(2015-08-01) Wu, Qiong; Mifflin, Steve W.; Cunningham, J. Thomas; Schreihofer, Ann M.Chronic intermittent hypoxia (CIH) rodent model is widely utilized to study obstructive sleep apnea (OSA) associated disease such as hypertension. Arterial chemoreceptor is activated by CIH, and leads to increased sympathetic nerve discharge, resulting in elevated arterial pressure. The central neuronal mechanisms of CIH induced hypertension are barely understood. The nucleus of the solitary tract (NTS) receives the first synaptic inputs from arterial chemoreceptor afferents. Transcription factor ΔFosB is increased in the NTS after a 7 day-CIH exposure. We hypothesize that NTS ΔFosB could mediate neuronal plasticity, contribute to CIH induced hypertension. Three specific aims were addressed. Aim 1: To determine the relationship between NTS ΔFosB and CIH hypertension. Viral constructs were delivered into NTS to functionally block ΔFosB (ΔJunD group). Mean arterial pressure (MAP) was measured in day time when rats were exposed to intermittent hypoxia and night time when they were in normoxia. The increase in MAP observed in ΔJunD and sham groups during day time was dampened in ΔJunD group during night time, indicating the contribution of ΔFosB to the sustained component of CIH associated hypertension. Aim 2: To determine the time-course of induction of ΔFosB immunoreactive NTS neurons during CIH exposure. Rats were separated into normoxia, 1 day, 3, 5, 7 days CIH, and 1 day, 3, 7 days recovery after 7 days CIH groups. ΔFosB immunoreactivity increased within 1 day CIH, and maintained this elevation throughout 7 days of CIH. 1 day recovery was sufficient to reduce ΔFosB immunoreactivity to normoxia level. Therefore, ΔFosB under CIH develops rapidly. Aim 3: To determine the function of ΔFosB in glutamatergic transmission after CIH. Miniature excitatory post-synaptic current (mEPSC) properties of NTS neurons of rats exposed to either different days of CIH or room air were compared. CIH increased mEPSC amplitude but not frequency, suggesting a post-synaptic site of effect. Additionally, functional blockade of NTS ΔFosB with ΔJunD decreased mEPSC amplitude back to normoxia level. Finally, overexpression of NTS ΔFosB increased mEPSC amplitude to similar levels as CIH. These results suggest that ΔFosB in NTS neurons mediates molecular adaptations which might play an important role in CIH associated hypertension.Item Sexually Dimorphic Anxiety-Like Interoceptive Discriminative Stimuli(1997-12-01) Jung, Marianna E.; Walls, Cleatus; Downey, H. Fred; Forster, MichaelJung, Marianna E., Sexually Dimorphic Anxiety-Like Interoceptive Discriminative Stimuli. Doctor of Philosophy (Biomedical Sciences), December 1997, 150 pp, introduction, 2 chapters, discussion, bibliography, 109 titles. This study compared gender differences in the anxiogenic stimuli induced by either a GABA-A antagonist, pentylenetetrazol (PTZ) or by a 5-HT1b/2 agonist, m-chlorophenylpiperazine (m-CPP) before and during ethanol withdrawal (EW). Rats were trained to discriminate either PTZ (16mg/kg, IP) or m-CPP (1.2 mg/kg, IP) from saline in a two lever choice task for food reward. Male and female rats were gonadectomized or sham-operated, and ovariectomized (OVX) female rats were tested during replacement treatment with 17β estradiol (2.5 mg, 21 day release, sc). The dose-response for the discrimination of the interoceptive stimulus (IDS) produced by PTZ (0-16 mg/kg) or m-CPP (0 to 1.2 mg/kg) was measured under all hormonal conditions. For m-CPP trained rats, latency to first lever-press response was also tested. Results: sham and estradiol-replaced female rats had higher ED50s for discrimination of the PTZ or m-CPP IDS than intact males or OVX rats. There is a dose-related impairment of operant responding after mCPP injection. Sham and estradiol replaced OVX rats showed an increased delay to the initiation of response after m-CPP injection as compared to sham or castrated male rats or OVX rats that showed no effect at the doses tested. Rats then received a chronic ethanol diet (6.5%) for 10 days. At twelve hours of ethanol withdrawl, they were tested for lever selection after saline injection. Fewer sham female and estradiol-replaced female rats responded on the drug lever during acute EW as compared to sham male, castrated or OVX rats. In general, the anxiogenic drug lever selection of OVX rats resembled that of male rats but was restored toward that of sham female rats by estradiol replacement. Castration did not alter the response of male rats to either PTZ or mCPP. Serum β –estradiol concentrations were determined by radioimmunoassay for sham, OVX, and estradiol-replaced female rats. The concentration was significantly higher in hormone-replaced female rats than in OVX. The estradiol concentration in sham female rats showed a cyclic pattern over 4 consecutive days, but this pattern did not correlate with any difference in IDS. Blood ethanol concentration (BEC) was determined using head space gas chromatography. BEC was higher in intact female rats than in intact male rats after ethanol injection (2 g/kg, ip), but did not differ during EW. Conclusions: females produce less anxiogenic IDS in response to either GABA inhibition or 5-HT1b/2 activation, but are more impaired by m-CPP in their ability to initiate operant responses than male rats. In addition, fewer intact females developed a spontaneous IDS during EW than males which is not the result of lower BEC. Estrogen appears to play a trophic role in altering responsiveness to anxiogenic stimuli.Item Synergy 2007: Annual Research Report(2007-01-01)Item Synergy 2008: Annual Research Report(2008-01-01)