Browsing by Subject "Neurology"
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Item Anionic Ligand-Gated Ion Channels: The Convulsive Site and Mechanism of Action(2001-08-01) Dibas, Mohammed I.; Hriday Das; Thomas Yorio; Neeraj AgarwalDibas, Mohammed, Anionic Ligand-Gated Ion channels: The Convulsive Site And Mechanism of Action. Doctor of Philosophy (Biomedical Sciences), August 2001, pp153, 1 table, 24 illustrations, 76 titles. Picrotoxin, a CNS convulsant inhibits all anionic ligand gated ion channels. The mechanism and the binding site for picrotoxin and its related ligands are still undefined. The second transmembrane (TMII) domain of these ligand gated ion channels is found to play a key role in the mechanism of block by picrotoxin. It has been shown that the incorporation of a phenylalanine residue in place of threonine at position 6’ within the TMII domain of B2 subunit conferred high resistance toward picrotoxin in GABAA a3B2(T6’F)y2 receptors. Mediating their blocking effect through the PTX-site, PTZ, TBPS, and U-93631 lost their inhibitory effects due to the same mutation B2(T6’F). Interestingly, this mutation uncovered a low affinity, highly efficacious stimulatory site for PTZ. PTZ seems to mediate its stimulatory effect through a novel distinct site different from that for benzodiazepine. The effect of varying subunit configuration of GABAA receptors dramatically affected the ability of the mutation B2(T6’F) to abolish the inhibitory effect of picrotoxin. While picrotoxin failed to block the current induced by GABA in a3B2(T6’F)y2 receptors, picrotoxin partially blocked the current in a3B2(T6’F)y2 receptors. In B2(T6’F)y2 receptors, picrotoxin restores its full efficacy. When phenylalanine was incorporated at position 6’ in the a1 subunit, picrotoxin completely blocked the current induced by GABA in a1(T6’F)B2y2 receptors. The combined results showed that the ability of (T6’F) mutation to regulate the inhibitory mechanism of picrotoxin as dependent on the subunit configurations and at which subunit is mutated. In addition, picrotoxin is known to inhibit GABAA receptors in use-facilitated mechanism, while it inhibits the glycine receptor in a non-use facilitated fashion. The molecular determinant behind the use-facilitated mechanism was modulated by the nature of the amino acid at position 15’ within the second transmembrane domain. The mutation of serine 15’ to either glutamine or asparagine in the glycine a1 receptors converted picrotoxin from a non-use facilitated blocker to a use-facilitated one. The latter finding suggested that this residue might residue within the PTX binding site or play a key role in the transduction pathway for picrotoxin mechanism. The overall results further support the fact that TMII domain plays a key role in the picrotoxin mechanism.Item ANTI-NMDA RECEPTOR ANTIBODY ENCEPHALITIS: A CASE STUDY(2014-03) Mantilla, Emmanuel C. Jr.; Smith-Barbaro, Peggy; Brown, Allene; Khan, SaudWe present the case of a 25 year old Hispanic female, who presented to the ED with status epilepticus. She has had frequent hospital admissions since her seizures started six months ago, described as tonic clonic jerking. Her episodes have been associated with receptive and expressive aphasia, changes in personality, aggression, and flat affect. Work up revealed a normal MRI, intermittent slowing on EEG (Fig. 1), and lymphocytic pleocytosis with 4+ oligoclonal bands. NMDA receptor antibody encephalitis was highly suspected. Intravenous Solumedrol was given, with minimal improvement. Serology sent came back positive for NMDA receptor antibodies. Anti-N-methyl-D-asparate receptor (NMDAR) antibody encephalitis is a paraneoplastic syndrome affecting younger women, characterized by psychiatric symptoms, autonomic instability, neurologic abnormalities, and tonic-clonic type of seizures. CSF usually reveals lymphocytic pleocytosis, and MRI findings are non-specific. Diagnosis is confirmed with serology. 1 A large percentage of patients diagnosed also present with a detectable tumor, the most common of which is ovarian teratoma. 2 Anti-NMDA receptor antibody encephalitis is very responsive to treatment. The first line of management includes steroids, immunoglobulins, and plasma exchange. Rituximab and cyclophosphamide have shown to improve outcome in refractory cases. 3 Purpose (a): To describe a patient with anti-NMDA Receptor Antibody Encephalitis, discuss the clinical features based on this case study, and explore the management options for this condition. Methods (b): This is a case study on a 25 year old Hispanic female with no history of childhood seizures, who presented to the ED with status epilepticus. She has had frequent hospital admissions since her seizures started six months ago, described as tonic clonic jerking. Her episodes have been associated with intermittent receptive and expressive aphasia, changes in personality, aggression, and flat affect. During these admissions, all of her work-up, including MRI, CT scan, and CSF analysis have been negative for causing seizures. Her EEG has showed seizure focus and slowing of waves during these episodes. She has been followed by an outpatient neurologist, who has placed her on several anti-seizure medications, including Depakote, Tegretol, and Zonegran. On her latest admission, she presented to the ED with partial complex status epilepticus, exhibited generalized tonic-clonic movements, with associated tongue biting and urinary incontinence. Two days prior, she had bouts of nausea and vomiting. She was given Ativan and Cerebryx, which eventually resolved seizure activity. Further work up later revealed a normal MRI, intermittent slowing on repeat EEG, and lymphocytic pleocytosis with 4+ oligoclonal bands. Results (c): NMDA receptor antibody encephalitis was highly suspected. She was given Intravenous Solumedrol, minimal improvement was noted. Abdominal and pelvic CT were negative any neoplastic disease, including ovarian teratoma. Serology sent later came back positive for NMDA receptor antibodies. Conclusions (d): Anti-NMDA receptor antibody diagnosis should be high suspected in a young person presenting with seizures, psychiatric symptoms, speech disturbance, orofacial dyskinesias, and autonomic instability. Work-up should include serum and CSF titers for antibodies to NMDA receptors (NR1/NR2), as well as an extensive screen for any neoplasitic diseases, most especially ovarian teratomas in females.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 Effect of Progesterone on Calcium Signaling of Hippocampal Neurons(2006-05-01) Hwang, Ji-Yeon; Koulen; Singh, Meharvan; Yang, ShaohuaJi-yeon Hwang, Effects of Progesterone on Calcium Signaling of Hippocampal Neurons. Master of Science (Pharmacology and Neuroscience), May 2006, 74 pp., 18 Figures. Progesterone (P4) is one of the steroid hormones responsible for female sexual behavior. It has been recently show that P4 plays also multiple roles in the central nervous system (CNS) including neuroprotection. Calcium (Ca2+) is involved in numerous cellular processes in nerve cells such as neurotransmitter release and cell death. In the present studies, we present evidence that P4 increases the activity of IP3R-mediated Ca2+ release within nerve cells leading to cell survival and neuroprotection. The purpose of the present study is to identify the subcellular distribution of all IP3Rs and other signaling proteins including Akt and phosphor-Akt, in the primary hippocampal neuron and to test the hypothesis that P4 controls the gain of IP3R-mediated intracellular Ca2+ signaling in neurons. We observed that primary hippocampal neurons express predominantly IP3R type 1, 2, and 3. The cellular distribution of all IP3R isoforms as well as Akt and phospho-Akt was increased in primary hippocampal neurons by P4 treatment. In addition, phospho-Akt was translocated to nucleus in response to P4. P4-pretreated neurons showed potentiated IP3R-mediated intracellular Ca2+ responses. Acute application of P4 resulted in transient elevations of intracellular Ca2+ concentrations. Our results will contribute to establishing potential pharmacological approaches for the treatment of pathological conditions characterized by a dysregulation of cellular Ca2+ concentrations such as Alzheimer’s disease.Item Effects of Sex Steroids on Stroke(2004-02-01) Yang, Shaohua; Simpkins, James W.Yang, Shaohua, Effects of Sex Steroids on Stroke. Doctor of Philosophy (Biomedical Science), February 2004, pp210, 5 tables, 27 illustrations, 64 titles. Estrogens and androgens are recognized as major sex steroids for females and males, respectively. However, it is clear that estrogens as well as androgens are more than gender hormones. Our data indicated that female steroids, such as 17β-estradiol (E2), exert neuroprotective effects on stroke, while male steroids, like testosterone, exert deleterious effects on stroke. The neuroprotective effects of estrogens have been very well demonstrated both in vitro as well as in vivo. Our studies indicated that neuroprotective effects of E2 are exerted both ischemic and hemorrhagic stroke. In our subarachnoid hemorrhage (SAH) model, E2 reduced secondary ischemic damage and mortality consequent to SAH. These effects were not associated with the change of the clot volume in SAH. The neuroprotective effects of estrogens were not only seen in the pre-treatment paradigms. E2 exerted neuroprotective effects even when administered after ischemia, with a therapeutic window of about 3 hours in a permanent focal cerebral ischemia model. This effect of estradiol was associated with no immediate change on blood flow, but with a delayed increasing in cerebral blood flow (CBF). Further our studies indicated that a non-estrogen receptor (ER)-binding analogue possessed both neuroprotective and vasoactive effects, which suggests that both the neuroprotective and vasoactive effects of estrogens are receptor-independent. This molecule also offers the possibility of clinical application for stroke without the side effects of estrogens. We used immunochemistry, immunoblot and mass spectrometry to demonstrate that ERβ is localized to mitochondria. Our data established this ERβ localization in a variety of cell types, suggesting that ERβ is not a nuclear receptor, which was thought to mediate the genomic function of estrogens. In contrast to estrogens, testosterone increased neuronal toxicity and exacerbated cerebral ischemia-reperfusion injury. These results suggest that sex differences in outcome after stroke may result from both the protective effects of estrogens and the damaging effects of testosterone. Further, our study indicated that stress induced testosterone reduction contributes to cerebral ischemia tolerance against ischemia reperfusion injury, providing the first in vivo evidences for a neuroendocrine mechanism for the cerebral preconditioning in males.Item FKBP51 and Methylene Blue as Neuroprotective Targets(2011-05-01) Daudt, Donald R.; Thomas YorioPurpose: Neurodegenerative diseases and neurotraumas typically result in apoptosis of specific neurons leading to the pathology observed during the disease state. Existing treatments target the symptoms instead of preventing the death of these neurons. Although neuroprotective drugs should be useful as a treatment to prevent further loss of neurons, efficacious molecules are lacking. FK506 (tacrolimus), a widely used immunosuppressant drug, has significant neuroprotective and neuroregenerative properties throughout the central nervous system, including the eye. FK506 achieves these properties through interaction with FK506 binding proteins (FKBP), including FK506 binding protein 51 (FKBP51). In this study, we examine the effects of FKBP51 as a neuroprotective agent on a neuronal cell line. Methods: We cultured 661w cell cultures with or without FK506, or stably transfected them with an FKBP51 expression vector. These cells were then exposed to the apoptosis inducing agent staurosporine. Cell viability was determined using a calcein AM/propidium iodide assay. Protein levels and activation of nuclear factor kappa-light chain-enhancer of activated B cells (NF-κB) were determined by western immunoblot analysis. Results: FKBP51 overexpression significantly protected 661w cell cultures from staurosporineinduced apoptosis. FKBP51 overexpression also significantly increased NF-κB p65 protein 35 levels and activated NF-κB p65. FK506 treatment significantly protected 661w neuronal cultures from staurosporine-induced apoptosis. FK506 increased FKBP51, NF-κB p65, and levels of activated NF-κB p65 protein. Conclusions: These results suggest that FKBP51 protects 661w cell cultures from apoptosis induced by staurosporine. Additionally, FK506 protected 661w cell cultures from apoptosis and displayed a mechanism similar to that of FKBP51 overexpression. Both FK506 and FKBP51 appear to act through activation of NF-κB p65 protein, suggesting a common pathway for neuroprotection. These findings suggest that FKBP51 is a compound important to neuronal cell culture survival. FKBP51 may be a potential therapeutic drug target for preventing the neurodegeneration and neurotrauma that occur during neurodegenerative diseases.Item Identification of Oxidized Proteins in Alzheimer's Disease(2002-08-01) Choi, Joungil; Gracy, Robert R.; Harris, B.; Lacko, Andras G.Joungil Choi, Identification of Oxidized Proteins in Alzheimer’s Disease. Doctor of Philosophy (Molecular Biology and Immunology). August, 2002. Pages-110. Tables 8. Figures 24. Oxidative modification of specific proteins is central to the pathology of Alzheimer’s disease (AD). The purpose of this study was to identify the oxidation-sensitive proteins in neuronal cells, fibroblasts from AD subjects, and in the blood of AD patients. In all cases, age-matched non-Alzheimer’s samples were used as controls. Proteomic methods were used to isolate and characterize the oxidized proteins. These included two-dimensional gel electrophoresis, immunolocalization of oxidized proteins and identification by MALDI-TOF mass spectroscopic methods. It was hypothesized that knowledge of these critical oxidation-sensitive proteins would shed light on the underlying mechanism of the disease. In addition, it was postulated that these proteins might prove to be biomarkers for early detection and monitoring the progress of the disease. The results show that two different oxidative stressors (H2O2 generated enzymatically, or the amyloid beta peptide, AB25-35) induce apoptotic cell death and oxidation of specific proteins (heat shock protein 60 and vimentin) in skin fibroblasts from AD subjects and in neuronal cells. In addition, the results indicate that susceptibility of these two proteins to oxidative stress is increased in fibroblasts from AD patients, compared to non-AD controls. Pretreatment with antioxidants (e.g., vitamin E or flavonoids) protect these proteins from oxidative damage. Both heat shock protein 60 and vimentin, have been suggested to function as antiapoptotic proteins. Thus, their oxidative damage could lead to the apoptotic neuronal cell death in Alzheimer’s disease. In the blood plasma of AD subjects, isoforms of fibrinogen gamma chain and alpha-1 antitrypsin were found to be oxidized. These proteins exhibited to a two- to six-fold greater specific oxidation index in plasma from AD subjects when compared to controls. Both of these proteins have been suggested to be implicated in oxidation-mediated damage of inflammation in the AD brain.Item Identifying Unique Therapeutic Targets To Rescue Retinal Ganglion Cells From Degeneration After Optic Nerve Crush(2014-05-01) Sharma, Tasneem P.; Clark, Abbot F.Central nervous system (CNS) trauma and neurodegenerative disorders trigger a cascade of cellular and molecular events resulting in neuronal apoptosis and regenerative failure. The pathogenic mechanisms and gene expression changes associated with these detrimental events can be effectively studied using a rodent optic nerve crush (ONC) model. The purpose of this study was to use a mouse ONC model to: (a) evaluate changes in retina and ON gene expression, (b) identify neurodegenerative pathogenic pathways, (c) discover potential new therapeutic targets, and (d) evaluate the neuroprotective and axogenic properties of one selected therapeutic target on axotomized RGCs in vitro and the optic nerve crush (ONC) mouse model in vivo. Meta-analysis of altered gene expression (≥1.5 changes and ≤1.5 changes, p [less than] 0.05 demonstrated 29 up- and 20 downregulated retinal gene clusters and 82 up- and 42 down-regulated optic nerve clusters. Regulated gene clusters included regenerative change, synaptic plasticity, axonogenesis, neuron projection, and neuron differentiation related genes. Expression of selected genes (Vsnl1, Syt1, Synpr and Nrn1) from retinal and ON neuronal clusters was qualitatively and quantitatively examined for their relation to axonal neurodegeneration by immunohistochemistry and qRT-PCR. Axotomized RGCs treated with recombinant hNrn1 (selected target) significantly increased survival of RGCs by 29% (n=8, p [less than] 0.01) and neurite outgrowth of cultured neurons by 261% compared to controls in cultured neurons (n=5-7, p [less than] 0.05). RGC transduction with AAV2-CAG-hNRN1 prior to ONC promoted RGC survival (42%, n=5-8, p [less than] 0.05) and significantly preserved ERG RGC function by 41% until 28 dpc (n=6, p [less than] 0.05) compared to the control AAV2-CAG-GFP transduction group. These ONC induced neuronal loss and regenerative failure associated clusters can be extrapolated to changes occurring in other forms of CNS trauma or in clinical neurodegenerative pathological settings. In conclusion, this study identified potential therapeutic targets to address two key mechanisms of CNS trauma and neurodegeneration: neuronal loss and regenerative failure and presented Nrn1 as a potential therapeutic target for CNS neurodegenerative diseases.Item Interaction of Neural and Local Mechanisms in the Control of Skeletal Muscle Blood Flow(2003-12-01) Wray, David Walter; Michael L. SmithWray, David Walter, Interaction of Neural and Local Mechanisms in the Control of Skeletal Muscle Blood Flow. Doctor of Philosophy (Biomedical Science), December, 2003, 181 pp., 1 table, 19 illustrations, references, 139 titles. The current project sought to characterize the interaction of neural and local mechanisms of skeletal muscle blood flow control through exogenous and endogenous α-andrenoreceptor activation. We hypothesized that α1- and α2-adrenoreceptors in the human leg would exhibit differential distribution and responsiveness, and that unilateral knee-extensor exercise would attenuate α-adrenoreceptor-mediated vasoconstriction in an intensity-dependent manner. We also hypothesized that carotid baroreflex (CBR)-mediated sympathoexcitation would provoke less vasoconstriction during exercise than at rest. Intra-arterial infusion of phenylephrine (PE, α1-agonist) or BHT-933 (α2-agonist) reduced femoral blood flow (FBF) by approximately 60% at rest, but during exercise (27W) the degree of vasoconstriction evoked by PE and BHT was significantly reduced. During ramped (7W-37W) exercise, BHT did not reduce FBF at any intensity, while some degree of PE-induced vasoconstriction was evident at all but the highest exercise intensity. Using sinusoidal neck pressure, CBR-mediated changes in heart rate (HR), arterial blood pressure (ABP) muscle sympathetic nerve activity (MSNA), FBF, and tissue oxygenation (TOm) were seen at rest. During 7w exercise, CBR-mediated control of ABP, FBF, and Tom was attenuated. We conclude that exercise attenuates α-adrenergic responsiveness to exogenous and endogenous activation to ensure sufficient muscle blood flow while maintaining systemic ABP homeostasis.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 Neural Control of the Carotid Baroreflex During Exercise(2000-05-01) Gallagher, Kevin Matthew; Peter B. Raven; Stephen R. Grant; H. Fred DowneyGallagher, Kevin Matthew, Neural Control of the Carotid Baroreflex During Exercise. Doctor of Osteopathic Medicine/Doctor of Philosophy (Biomedical Sciences), May 2000; 151 pages; 13 tables; 19 figures; bibliography; 161 titles. Carotid baroreflex (CBR) function is reset upward and rightward to the prevailing blood pressure during dynamic and static exercise. Feedforward central neural inputs (central command) and negative feedback from skeletal muscle (exercise pressor reflex) both contribute to the resetting. The purpose of this investigation was to identify the individual roles of central command and the exercise pressor reflex in the resetting of the CBR during dynamic and static exercise. First, it was necessary to determine which receptor group that comprises the exercise pressor reflex, chemically-sensitive (chemoreceptors) or mechanically-sensitive (mechanoreceptors) receptors, was primarily involved in the regulation of the cardiovascular system. We observed the cardiovascular responses during exercise to individual action of the chemoreceptors and the mechanoreceptors. We demonstrated an increased mean arterial pressure (MAP) response to mechanoreceptor activation that was not identified during chemoreceptor stimulation. This finding suggested that the mechanoreflex was the primary exercise pressor mediated of arterial blood pressure during exercise. To identify the role of central command on CBR resetting, a second investigation increased central command by partial neuromuscular blockade during dynamic and static exercise. Resetting of CBR control of heart rate (carotid-cardiac; CSP-HR) and MAP (carodtid-vasomotor; CSP-MAP) during control exercise was further reset upward and rightward by increased central command without alterations in sensitivity. In conclusion, central command, a feedforward mechanism, was actively involved in the resetting of the CBR during exercise. To investigate the role of the exercise pressor reflex on CBR function, a third investigation activated by the exercise pressor reflex with the application of medical anti-shock trousers (MAS) during dynamic and static exercise. From control exercise, carotid-vasomotor function was further reset upward and rightward by the application of MAS trousers while CSP-HR function was only reset rightward. Sensitivity of the CSP-MAP and CSP-HR function curves were unaltered. The negative feedback mechanism of exercise pressor reflex, primarily mediated by mechanoreceptors, appeared to act as a modulator of CBR resetting during exercise.Item Neuroprotective properties of Phytoestrogens(2012-12-01) Brock, Courtney Anne; Singh, MeharvanWomen make up nearly two thirds of total Alzheimer’s cases in the United States. It has been speculated that the loss of endogenous estradiol during menopause is, at least in part, what renders the post-menopausal brain more vulnerable to the effects of aging and Alzheimer’s Disease. While hormone therapy can potentially thwart some of the undesirable consequences and increased risks associated with menopause, women are increasingly rejecting hormone therapy and seeking alternative therapy. There is a strong in interest in phytoestrogens as an alternative to traditional hormone therapy. Phytoestrogens are naturally occurring estrogen like compounds derived from plants which have been shown to have a variety of health benefits. Their effects in the brain however are not fully understood. It was my goal to evaluate the effect of phytoestrogens on brain cells as it relates to neuroprotection. We initially assessed the ability of genistein, the most abundant phytoestrogen found in soy, to protect brain cells against age-associated insults in vitro using the hippocampal cell line (HT22 cells), a cortical cell line (HCN-1A cells), and primary slice cultures of the cerebral cortex. The results of these experiments were such that genistein was protective in the explant model and HCN-1A cells, but not in the HT22 cells suggesting that certain key players must be present for genistein to elicit neuroprotective effects. Based on the known estrogen receptor (ER) profiles for the models used in our study, we hypothesized that ER profiles may dictate the effects of phytoestrogens on brain cells. As such, we evaluated male and female C57/Bl6 mice at 3 different ages for ER expression profile and the effects that a phytoestrogen diet had on BDNF, used in this study as a surrogate marker of neuroprotection. Results showed that phytoestrogens’ effects on the brain differ between the cortex and the hippocampus and are dependent upon the sex of the animal and age at which the diet was initiated. From our results we have proposed a mechanism by which phytoestrogens differentially elicit their effects in the brain. The data presented herein provides valuable insight into phytoestrogens’ effects on the brain.Item NEUROPROTECTIVE PROPERTIES OF SIGMA-1 RECEPTOR IN GLAUCOMA(2014-05-01) Mueller, Brett H.; Thomas YorioGlaucoma is an optic neuropathy commonly associated with elevated intraocular pressure (IOP) that affects over 70 million individuals worldwide. Glaucoma pathology is manifested as cupping of the optic disk, damage to the nerve fiber layer, and visual field deficits. The final pathological step of this disease contributing to visual field loss is the apoptosis of retinal ganglion cells (RGCs). Currently, the only therapeutic agents that are used to treat glaucoma are IOP lowering drugs. However, even when IOP is brought within normal range, a significant number of patients still have progression of visual deficits. Currently, there are no treatment options that have the ability to sustain the viability of RGCs during the disease process of glaucoma. Therefore, neuroprotective drugs that protect RGCs need to be developed as adjunct therapeutic agents to IOP lowering drugs. The sigma-1 receptor (σ-1r) is a non-opioid receptor that has been shown to have the ability to bind to benzomorphans, steroids, and psychotropic drugs. This receptor is ubiquitously expressed throughout the entire body; however, the endogenous ligand and function of σ-1r is not yet known. Several in vitro and in vivo studies have demonstrated the neuroprotective effects of σ-1r stimulation in several models of retinal neurodegenerative diseases including glaucoma and diabetic retinopathy. Numerous studies have linked the neuroprotective effects of σ-1r to its ability to block cytotoxic calcium ion influx through ligand gated and voltage gated ion channels, modulation of ER stress, maintenance of mitochondrial homeostasis, and stimulation of pro-survival intracellular signaling pathways. However in primary RGCs, there have been no studies demonstrating σ-1 receptor mechanism of action. The only proposed neuroprotective mechanism of action of σ-1r that has been performed in retinal flat mounts is blockage of calcium ion influx through activated NMDA receptors. This present research project investigated the mechanism of neuroprotective effects of σ-1rs in primary RGCs, particularly involving L-type voltage gated calcium channels (VGCCs) and activation of extracellular-signal-regulated kinases (ERK 1/2). We demonstrated that VGCCs were activated using KCl (20mM). Pre-treatment with a known L-type VGCC blocker produced a 57% decrease in calcium ion influx through activated VGCCs (following depolarization by KCl). In addition, calcium imaging showed that σ-1r agonists, (+)-N-allylnormetazocine hydrochloride [(+)-SKF10047] and (+)-Pentazocine, inhibited calcium ion influx through activated VGCCs. Treatment with a σ-1r antagonist, BD1047, produced a potentiation of calcium ion influx through activated VGCCs and abolished all inhibitory effects of the σ-1r agonists on VGCCs. This confirms that these ligands were acting through the σ-1r. An L-type VGCC blocker (Verapamil) also inhibited KCl activated VGCCs and when combined with the σ-1r agonists there was not a further decline in calcium entry suggesting similar mechanisms of action of both these agents. Lastly, co-localization studies demonstrated that σ-1rs and L-type VGCCs are co-localized in primary RGCs. Taken together, these results indicated that σ-1r agonists can inhibit KCl induced calcium ion influx through activated L-type VGCCs in primary RGCs. This is the first report of attenuation of L-type VGCC signaling through the activation of σ-1rs in primary RGCs. The ability of σ-1rs to co-localize with L-type VGCCs in primary RGCs implies that these two proteins are in close proximity to each other and that such interactions regulate L-type VGCCs Another signaling pathway that was studied as a potential target of σ-1r mediated neuroprotection was the MAP kinase pathway, in particular, ERK phosphorylation as an index of cell survival. RGCs subjected to oxygen and glucose deprivation (OGD) for 6 hours induced 50% cell death in primary RGCs and inhibited pERK1/2 expression by 65%. Cell death was attenuated when RGCs were treated with pentazocine under OGD and pERK1/2 expression was increased by 1.6 fold compared to OGD treated RGCs without pentazocine treatment. The co-treatment of with an ERK1/2 inhibitor PD098059 with pentazocine significantly abolished the protective effects of pentazocine on the RGCs during this OGD insult. These results established a link between σ-1 receptor stimulation and the neuroprotective effects of the ERK1/2 pathway in purified RGCs subjected to OGD. In conclusion, we have established two novel mechanisms underlying σ-1 receptor mediated neuroprotection in primary RGCs. These findings suggest that activation of the σ-1 receptor in RGCs has a role in calcium regulation and the activation of the ERK1/2 pathway. In addition, this study also demonstrates the robust neuroprotective effects of σ-1 receptor in RGCs when subjected to OGD. These data also provide evidence suggesting that σ-1 receptor may be a therapeutic target to protect RGCs during ocular neurodegenerative diseases like glaucoma.Item North Texas Health & Science - 2011, Issue 2(University of North Texas Health Science Center at Fort Worth, 2011-01-01)Item Obesity and Risk of Stroke in NHANES I Follow Up Study(2002-12-01) Soman, Ashwini; Umed Ajani; Antonio Rene; Karan SinghSoman, Ashwini, Obesity and risk of stroke in NHANES-I follow-up study, Masters of Public Health (Epidemiology), December 2002. 79pp., 20 tables, 3 illustrations, bibliography, 46 titles. Stroke is the third leading cause of death in the US. Role of obesity as an independent risk factor has been relatively well established for coronary heart diseases but not for stroke. Purpose of this study was to assess long-term risk of stroke due to obesity measured at baseline. The research was conducted using First National Nutritional Health and Examination Survey and its follow ups. Overall, increased risk of stroke was observed in obese individuals (BMI [greater than] 30 kg/m2). Similar association was observed in different subgroups of race, gender, those with or without diabetes and cardiovascular disease.Item Risk for Stroke Among Migraine Sufferers(2001-05-01) Hall, Rebecca G.; Antonio Rene; Manuel BayonaHall, Rebecca G., Risk for Stroke Among Migraine Sufferers. Master of Public Health (Epidemiology), May, 2000, 27 pp., 9 tables, references, 33 titles. The objective of this study was to investigate, using the National Health Interview Survey (NHIS), whether those who suffer from migraine or severe headache do. Odds ratios were calculated for stroke among migraine sufferers compared to those who do not suffer from migraine. Results were adjusted for age, gender, and race. Risk factors for stroke were also analyzed. The crude odds ratio for stroke among migraine sufferers compared to non-migraine sufferers is 2.17, increasing 3.77 with age-adjustment. These results suggest that vascular events that are associated with migraine may also be associated with an increased risk for stroke. Discovering the mechanism that generates this relationship has widespread implication to the population and may save taxpayers billions of dollars annually be leading to better treatments for and possible prevention of migraine.Item Role of catecholaminergic A2 neurons of nucleus of the solitary tract(NTS) in cardiovascular and respiratory adaptations to chronic intermittent hypoxia (CIH) in rats(2014-05-01) Bathina, Chandra Sekhar; Steve MifflinThis study examined the role played by the catecholaminergic A2 neurons of the nucleus of the solitary tract (NTS) of adult male Sprague- Dawley rats in the increased mean arterial pressure (MAP) noticed following exposure to chronic intermittent hypoxia (CIH), a rodent model to simulate arterial hypoxemic conditions occurring in humans suffering from sleep apnea. In one study, we tested the hypothesis that tyrosine hydroxylase (TH) knockdown in NTS reduces the sustained elevation in MAP noticed in the rats exposed to CIH. Adult male Sprague-Dawley rats were implanted with radiotelemetry transmitters and adeno-associated viral constructs with a GFP reporter having either short hairpin RNA for TH (shRNA) or scrambled virus (scrambled) were injected into caudal NTS. shRNA through formation of RNA-induced silencing complex reduced the amount of TH levels in the NTS. Virus injected rats were exposed to 7 days CIH (alternating 6 min periods of 10% O2 and 4 min of 21% O2 from 8am to 4pm; from 4pm to 8am rats were exposed to 21% O2). CIH increased MAP and HR during the day in both the scrambled (n= 14, p Experiments were also conducted to understand the molecular level changes occurring in the A2 neurons, following CIH exposure. mRNA expression changes occurring in the A2 neurons were analyzed by novel technique of laser capture microdissection (LCM) by labeling the A2 neurons using adeno-associated virus with TH promoter attached to green fluorescent protein (GFP). A2 neurons are found to express mRNA of angiotensin receptor subtypes AT1a and AT1b. Moreover, excitatory amino acids (EAAs) like glutamate released from chemoreceptor afferents during chronic intermittent hypoxia (CIH) are found to modulate the activity of the neurons in the region of NTS. The aim of this study was to assess the effect of CIH on the mRNA expression levels of AT1a, AT1b and EAAs receptor subunits in the A2 neurons. We utilized commercially available adeno associated virus (AAV) vector mediated delivery of green fluorescent protein (GFP) labeled tyrosine hydroxylase promoter (AAV-GFP-TH), which will incorporate into the TH genome and express GFP with the TH expression to label the A2 neurons. 7 virus injected rats were exposed to 7 days CIH (alternating 6 min periods of 10% O2 and 4 min of 21% O2 from 8am to 4pm; from 4pm to 8am rats were exposed to 21% O2). Laser capture microdissection was performed to capture the A2 neurons from caudal NTS. Total RNA from these neurons was extracted and the gene expression for different genes were assessed by quantitative real time reverse transcription polymerase chain reaction and compared between the control and CIH rats using 2-ΔΔct method. CIH is found to decrease AT1a (p=0.002; control - 1.08 ± 0.13, n=7; CIH – 0.48 ± 0.07, n= 6) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPA) receptor subunit GluR2 (p=0.03; control - 1.11 ± 0.24, n=7; CIH- 0.52 ± 0.12, n= 6) and increase transcription factor FosB (p=0.03; control - 1.14 ± 0.25, n=7; CIH- 1.97 ± 0.25, n= 5) mRNA expression levels in the A2 neurons. These results suggests that there is increase in activity of these neurons following CIH and a possibility of these neurons becoming more calcium permeable as GluR2 is found to resist calcium permeability. Western blot studies were also conducted from the whole NTS punches, to study the changes in protein levels of the genes studied using LCM. The changes in TH protein levels were not significant in both caudal and sub-postremal NTS (P [greater than] 0.05). GluR1 and GluR2 protein level changes were not significant in the caudal NTS, however, there was a significant decrease (P As the mRNA analysis of A2 neurons suggested, there might be changes occurring in the calcium permeability of A2 neurons following CIH, attempts were made to do calcium imaging studies on the A2 neurons. There was difficulty in the colocalization of GFP with the fura-2AM, the calcium imaging dye. So, calcium imaging was conducted on the NTS neurons of sham Sprague-Dawley rats and CIH exposed rats. 30 μM AMPA application caused a 340/380 ratio change of 0.17 ± 0.01 (n=5) in control rats and this change was significantly higher 0.55 ± 0.13 in CIH rats. The probability of neurons responding to AMPA application was considerably higher in CIH rats. CNQX treatment of the slices abolished the changes in intracellular calcium in neurons from both control and CIH rats, demonstrating that the responses noticed after AMPA application were AMPA receptor mediated. Increases in intracellular calcium levels following 500 μM potassium chloride applications validate the fact that the neurons were viable. Further studies on quantifying the phosphorylated GluR1 and GluR2, subunits of AMPA receptors are required to explain the driving force behind this uniform increase in intracellular calcium levels of NTS neurons after CIH. We conclude that the sustained hypertension observed during CIH can be prevented by TH knockdown and this mechanism might involve paraventricular nucleus (PVN) of forebrain, hypothalamo-pituitary adrenal axis (HPA axis) or intermediolateral cell column (IML) of spinal cord. A2 neurons also undergo molecular alterations that might increase their calcium influx in to the neuron and vise-versa.Item Synergy 2007: Annual Research Report(2007-01-01)Item Synergy 2008: Annual Research Report(2008-01-01)Item Synergy 2010: Annual Research Report(2010-01-01)