• Race and Income Association with Health Service Utilization for Veterans with Heart Failure

      Landrum, Laurie G.; Department of Nursing (2012-07)
      Disproportionate heart failure outcomes exist for Blacks in the Veterans Health Administration (VHA) despite equitable access and financial barrier minmization. No study has examined the association of race and income with health service utilization for veterans with heart failure. This observational study investigated race and income associations with readmissions, bed days of care, and emergency room (ER) visits for veterans with heart failure after controlling for predisposing, enabling, and illness severity factors. Medical record data were collected for 149 veterans telemonitored for heart failure during 2008-2011. Heart failure symptoms severity and comorbidities were measured using investigator-adapted scales based on the New York Heart Association IIV scale and the Charlson comorbidity index. Heart failure related outcomes (30 day, 90 day, 1 year, and total readmissions, ER visits, and total bed days of care) were modeled controlling for age, marital status, and heart failure and comorbidity severity. Of patients younger than 60 years of age, 18% were Black compared to 11% of Whites, Χ2 (2, N=149) = 5.15, p= .02. Blacks had a much higher comorbidity prevalence than Whites, p = .000. Ischemic heart disease and chronic kidney disease rates were double and triple national VHA rates, respectively, among Whites and Blacks. Race did not predict readmissions, bed days of care, or ER visits. The odds of a readmission or bed day of care ever decreased by 38% and 43%, respectively, for married men, p = .03. The odds of a readmission or bed day of care ever due to severe heart failure—compared to less severe heart failure—were four to five times higher, respectively, p ≤ .004. Income increased the odds of total bed days of care by 14%, p = .00, holding race constant. Overall, the sample experienced far fewer readmissions, bed days of care, or ER visits, compared to VHA national rates, but sample size may have limited accurate comparisons.
    • Rapamycin, an evolving role in up-regulation of autophagy to improve stroke outcome and increase neuronal survival to stroke type injuries

      Buckley, Kathleen; Department of Cellular Biology and Anatomy (2015-10)
      Rapamycin was shown to reduce infarct size in a non-reperfusion and a slow reperfusion model of murine stroke; it also improved neurological score and survival in the slow-reperfusion model. The rapamycin improvement was 50 percent greater than that observed with chloroquine. In HT22 mouse hippocampal neurons, rapamycin was shown to improve survival to an oxidative/reperfusion injury with H2O2 and a hypoxic/ischemic injury with oxygen and glucose deprivation to a larger degree than chloroquine. Rapamycin treatment increased punctate microtubule light chain associated protein 3, LC3, in the HT22 neurons in an uninjured and oxygen and glucose deprivation injured HT22 neurons compared to untreated neurons. Finally, genetic knockdown of autophagy with shRNA to autophagy protein 5, ATG5, abrogated the rapamycin’s positive effect on survival to injury.
    • Reactivation of latent herpes simplex virus and chemotherapy of herpes infection

      Se Kwon, Byoung; Department of Cell and Molecular Biology (1980-12)
    • Receptor-mediated endocytosis of vitellogenin in the oocyte of the frog, xenopus laevis

      Tucciarone, Linda M; Department of Cell and Molecular Biology (1983-05)
      The yolk protein, vitellogenin, is internalized by the developing oocyte by the process of receptor-mediated endocytosis. This process is initiated in Xenopus laevis by gonadotropic hormones. This study w~s designed to characterize the endocytot-ic pathway of vitellogenin in· the Xenopus oocyte and the influence-of gonadotropins on this pathway. One of the molecular-mechanisms of this pathway involves the enzyme transglutaminase which catalyzes E(-y-glutamyl) lysine crosslinks. These studies have demonstrated the presence of transglutaminase activity in Xenopus ovary. By the use of specific inhibitors of transglutaminase, dansylcadaverine and methylamine, the activity of this enzyme has been correlated with vitellogenin uptake by the oocytes. An increase in the activities of· the ovarian transglutaminase was also observed subsequent to in vitro exposure of ovarian fragments to hCG. The relationship of calmodulin, the calcium regulator protein, to transglutaminase activity in the ovary and uptake of vitellogenin was investigated because of the calcium requirement for both of these processes. In this study, the uptake of vitellogenin was shown to be sensitive to the calmodulin-directed drug, Stelazine. However, Stelazine failed to inhibit the transglutaminase activity of the ovary, suggesting that the functional role for calmodulin in endocytosis of vitellogenin must be at another site. The common endocytotic pathway of nutritional protein such as vitellogenin involves clathrin-coated pits and vesicles. Studies utilizing SDS-PAGE and immunolabelling techniques have shown that the 180,000 M r protein, clathrin, is present in both hCG treated and untreated ovaries.Extracts of Xenopus ovary containing coated vesicles have additional proteins in common with pig brain coated vesicles, including the two clathrin light chains of 33,000 M and 36,000 M • r · r An RIA for measuring gonadotropin induced alterations in the levels of clathrin in the ovary was developed. However, ·the sensitivity of the assay was very low and proved inadequate to measure small differences in cilathrin levels in the ovary •
    • Receptor-mediated endocytosis of vitellogenin in the oocyte of the frog, xenopus laevis

      Tuten, Susan Harris; School of Nursing (1988-07)
      The purpose of this study was two~fold: ( 1) to determine if the patency of the peripheral intermittent intravenous device could be maintained with sodium chloride as effectively as with dilute heparin, and (2) to determine if sodium chloride could be used effectively with fewer local co~plicatitins (i.e., infiltrati~n, phlebitis) than d i 1 u t e hepar in so 1 u t ion • The sample consisted of 77 I hospitalized medical surgical patients having a total of 1~4 peripheral intermittent intr~venous devices. During a 60 day period, the devices (N=43) of the 30 patients in the experimental group were maintained with sodium chloride (0.9%) while the devices (N=71) of the 47 patients in the control group were maintained with dilute heparin ClOOU/lml). Three hypotheses were tested utilizing the chi-square procedure with Yates correction for continuity statistical test. An alpha level of p < .OS was used to determine statistical significance. All three hypotheses. were rejected. No incidence of site loss due to coagulation was reported i~ either group, and no significant difference was demonstrated in the incidence of site loss associated with phlebitis cx2 = .140; p = • 708; df = 1) or infiltration C X 2 = • ·a 12 ; p = • 9 1 0 ; d f = 1 > between pat i en t s in the experimental and control groups. These findings indicate that sodium chloride may be used for peripheral intermittent intravenous device maintenance with similar rates of local complications (i.e., coagulation, infiltration, phlebitis) as seen with dilute heparin. It is r~commended that the study-'be replicated in a larger sample representing more diverse·clinical settings, and that the instrument utilized ·in this study be subjected to more rigorous validity and reliability testing.
    • Recombinant Bone Morphogenetic Protein-2 Induces Up-Regulation of Angiogenesis and Inflammatory Transcripts: Role of Reactive Oxygen Species

      Akeel, Sara K; Department of Oral Biology (2012-12)
      Large bone defects in the oral and maxillofacial region are mostly secondary to tumor resection, gunshot wounds or craniofacial anomalies. Reconstruction of large bone defects remains a clinical challenge despite the ability of bone to regenerate itself after fracture, mainly because bone regeneration requires recruitment of new cells as well as development of new bone tissue in order to restore anatomical and mechanical functions. Several biological and mechanical factors regulate bone formation. Early vascularization plays a critical role in skeletal bone development and bone fracture repair, and without a vascular supply, osteogenesis is impaired (Glowacki 1998; Akeno, Czyzyk-Krzeska et al. 2001; Carano and Filvaroff 2003). Furthermore, in the treatment of bone defects, vascularized bone grafts show less bone remodeling when compared to non-vascularized bone grafts (Cutting and McCarthy 1983; Wang, Yamazaki et al. 1996). This highlights the importance of angiogenesis in bone formation and remodeling. The close proximity of osteoblasts and osteoclasts to endothelial cells during bone formation suggests there is a cross-talk between these cells. Osteogenesis-inducing growth factors, such as bone morphogenetic proteins (BMPs), especially BMP-2 and -7, and vascular endothelial growth factor (VEGF) which is known to have a major role in angiogenesis, have been reported in many studies to play a major role in osteoblast-endothelial cell communication (Mayer, Bertram et al. 2005). The general goal of this study is to understand some of the molecular events that occur at the site of bone healing and the interaction of local growth factors produced by resident cells such as osteoprogenitor and endothelial cells. This will help us in developing techniques that enhance bone formation and provide better integration of bone grafts in the recipient site. Specifically, the aim of this study is to understand the mechanism by which recombinant bone morphogenetic protein-2 (rhBMP-2) induces bone formation and whether or not the effect of rhBMP-2 is through enhancing angiogenesis and inflammation.
    • Recombination and genetic polymorphism at the mouse alpha-globin locus

      Lewis, Jill B; Department of Cell and Molecular Biology (1988-12-08)
      Unusual genetic phenomena are often responsible for dramatic evolutionary changes at many mammalian loci. Among the possible genetic mechanisms involved in these changes are point mutation, gene-conversion, and homologous or nonhomologous recombination. Rarely can such evolutionarily significant events be studied as recent occurrences in mammalian systems. In most case.s it can only be postulated that such events occurred ·in the distant past. In the case analyzed in this research, however, the genetic rearrangement has occurred within the last fifteen years since the origination of a certa~n inbred mouse strain known as AKXL-7. The AKXL-7 recombinant inbred strain is the product of inbred parental strains AKR and C57L. AKR.has the Hba "f" genetic type which specifies only alpha-globin chain 5. C57L has the Hba "a" genetic type that specifies only alpha-globin chain 1. Chains 1 and 5 are identical except for a gly --> ala substitution at position 78. Although one would predict that any recombinant inbred strain resulting from thes,e parents would be homozygous for one of these two alpha-globin types, this is not the case for the AKXL-7 strain. These mice express both alpha-globin chains, with chain 1 present in greater amounts than chain 5. The type of genetic reassortment that has occurred has been ascertained through the use of DNA probes to flanking regions of the two non-allelic or "tandem" alpha-globin 1 genes. Southern blot analysis has revealed that the left and right AKXL-7 alphaglobin gene flanking regions are homologous to regions from different parents. This result indicates that the novel AKXL-7 genotype is the result of a reciprocal recombination event. Further analysis using an intergenic region probe narrowed the region of crossover to approximately 5.2 kb. Using the most distal flanking region probes, chromosome walking was performed to recover probes useful for characterization of three different induced mouse alphathalassemia mutations. Results indicate that in all three cases the deletion spans. at least 45 kb, including both alphaglobin genes and the-embryonic alpha-like x gene.
    • Regional Variability of Dentin Permeability

      Andringa, Hans-Jan; Department of Oral Biology (1987-08)
    • Regulation and Function of the Major Stress-Induced HSP70 Molecular Chaperone in vivo: Analysis of Mice with Targeted Gene Disruption of the HSP70.1 or HSP70A1

      Huang, Lei; Georgia Cancer Center (6/3/2002)
      (First Paragraph) The cellular response to stress, including exposure to environmental (UV radiation, heat shock, heavy metals), pathological (infection, fever, inflammation, malignancy, ischemia) or physiological (growth factor, hormonal stimulation, tissue development) stimuli is represented at the molecular level by synthesis of groups of protein named heat shock proteins [hsp(s)] (Benjamin 1998; Feder and others 1992; Jolly and Morimoto 2000; Li and Mivechi 1986; Lindquist 1986; Smith 1998). The presence of hsp(s) protect host cells from the damage caused by thermal stress, and after induction of hsp expression, cells are protected well from higher temperatures than they can normally tolerate. This phenomenon is defined as themiotoleranee (Gemer 1975; Li and Mivechi 1986). The protective role of hsp(s) is attributed to several functional properties, including active participation in maintaining proteins in their native correctly folded states, promoting degradation and refolding of misfolded proteins, and minimizing aggregation and incorrect interactions between proteins (Agashe and Hartl 2000; Gething and Sambrook 1992). In addition, hsp(s) can function in cellular protection by modulating the engagement and progression of apoptosis induced by a variety of stress stimuli (Beere and Green 2001). Besides the recognition of the cytoprotective function of hsp(s) under stress conditions, widespread clinical interests exist in their chaperone function during a range of human pathologies, including neurodegenerative conditions, such as amyloidosis, prion disease, and Alzheimer's disease, and cardiovascular diseases, such as myocardial ischemia, cardiac hypertrophy, stroke, and blood vessel injury (Benjamin 1998; Planas and others 1997; Smith 1998).
    • Regulation of Cytochrome Oxidase and F1Fo ATP Synthase by Protein Kinase C Isozymes: Implications for Cardiac Preconditioning and Ischemia / Reperfusion Injury

      Nguyen, Tiffany Tuyen M.; Department of Pharmacology and Toxicology (2010-03)
      Despite decades of intense research, heart disease associated with myocardial ischemia/reperfusion (IR) injury remains the most frequent cause of lethality worldwide. It has been known for over 2 decades that the mammalian heart can be protected from IR injury if exposed to a paradoxical response known as cardiac ischemic preconditioning (PC). Of interest, mitochondrial protein kinase C (PKC) isozymes have emerged as central players in both PC and IR mechanisms. Mitochondrial oxidative phosphorylation (OXPHOS) complexes are responsible for greater than 90% of myocardial ATP synthesis, and ATP levels decline substantially during myocardial IR injury. Therefore, we determined if direct protein-protein interactions occurred between individual PKC isozyme and specific subunits of each of these complexes during cardioprotective and cardiac IR responses. First, we have utilized an in situ rat coronary ligation model to establish an PKC-cytochrome oxidase subunit IV (COIV) coimmunoprecipitation (co- IP) in myocardium exposed to PC. This co-IP correlated with a 2.8-fold increase in mitochondrial PKC autophosphorylation (activation) and a 2-fold enhancement of cytochrome-c oxidase activity. In a second line of study, we demonstrated that following prolonged 4- phorbol 12-myristate-13-acetate (PMA) and hypoxia (Hx), PKC interacts with the “d” subunit of F1Fo ATP synthase (dF1Fo) to inhibit F1Fo activity in neonatal cardiac myocytes (NCMs). We next developed cell-permeable, mitochondrial-targeted peptide modulators (derived from the amino acid sequence of dF1Fo) based on the PKCdF1Fo interaction. In vitro binding assays and co-IP experiments using NCMs revealed a facilitator [NH2-YGRKKRRQRRMLATRALSLIGKRAISTSVCRVREYEKQLEKIKNMIDYKDDDK- COOH] and an inhibitor peptide [NH2-YGRKKRRQRRMLATRALSLIGKRAISTSVCAGRKLALKTIDWVSFDYKDDDDK- COOH] of the PKC-dF1Fo interaction. The inhibitor peptide reduced PMA/Hx-induced inhibition of F1Fo activity or PMA-Hx-induced PKC-dF1Fo co-IP in NCMs while the facilitator peptide has opposite effects. Administration of the inhibitor peptide to isolated rat hearts immediately after a 20 min global ischemia exposure, and just prior to a 90 min reperfusion, decreased infarct size and released of cardiac troponin I compared to rat hearts receiving a scrambled-sequence (inactive) peptide prior to IR exposures alone. Collectively our studies have revealed two key mitochondrial OXPHOS regulatory events involving PKC-enhancement and protection of cytochrome oxidase by ischemic PC and PKC suppression of F1Fo ATP synthase during IR injury. Further, our work suggests that the PKC-dF1Fo inhibitor peptide may have potential as a therapeutic compound targeting myocardial ischemia in humans.
    • Regulation of Embryonic Stem Cell Pluripotency and Differentiation by Notch Signaling

      Noggle, Scott A; Institute of Molecular Medicine and Genetics (2004-05)
      (First Paragraph) Mammalian development prior to implantation is primarily involved with establishing the support tissues needed for interaction with the mother’s uterine tissue and blood stream as the uterine tissue prepares to receive the embryo. Development of the embryo proceeds slowly while initiating differentiation of the first cell lineages, trophectoderm and the primitive endoderm, that are necessary for interactions with the mother’s uterine tissue. In mice, development from fertilization to the initiation of implantation of the blastocyst into the uterine wall takes about four and a half days (Fig. 1) whereas this period in human development requires about 7 days. This is in contrast to the much-accelerated development, for example, of amphibian species that produce embryos that develop in isolation of maternal support after fertilization.
    • Regulation of Endothelial Nitric Oxide Synthase by Subcellular Localization and

      Zhang, Qian; Department of Pharmacology and Toxicology (2007-04)
      Endothelial nitric oxide synthase (eNOS) is regulated by post-translational modifications that target eNOS to the plasma membrane (PM) and the perinuclear/Golgi region. It has been shown in COS-7 cells that targeting of eNOS to the Golgi or PM regulates the mechanism and degree of eNOS activation. However, little is known about the functional significance of eNOS targeting in endothelial cells (ECs). Our first goal was to isolate these two pools of enzyme in ECs and determine their functional significance in response to agonist stimulation and manipulation of membrane cholesterol levels. Using an RNAi strategy, we generated stable populations of EC that had greater than 90% inhibition of eNOS expression and lacked the ability to produce NO. Reconstitution of these eNOS “knockdown” EC with Golgi and PM targeted eNOS restored the ability of EC to produce NO. This approach can be broadly applied to endothelial cells from a number of different species and from different vascular beds and should have broad utility. Using these cells we found that the PM is the optimal location within the cell to produce NO, but it is also the most vulnerable to changes in cholesterol and oxidized LDL. Calcium-dependent agonists were the more efficient stimulus for the PM-restricted eNOS in EC. In contrast, Golgi eNOS was less responsive to both calcium and Akt-dependent agonists. The functional significance of the increased NO produced by the PM eNOS is reflected in the greater ability to elicit endothelium-dependent relaxation, greater suppression of vWF secretion, a key regulator of platelet aggregation, and inhibition of endothelial cell proliferation. Mechanistically, PM eNOS induces more nitrosylation of proteins such as NSF, but this is related to the amount of NO being produced, rather than its intracellular location. Increased superoxide formation in endothelial cells (ECs) has been identified as a causative factor in endothelial dysfunction by reducing nitric oxide (NO) bioavailability, uncoupling eNOS. A major source of intracellular superoxide is the NADPH oxidase (Nox) family of enzymes. In experiments to address the effect of superoxide on local eNOS activity, we found that Nox5 increased eNOS activity paradoxically in both cotransfected COS-7 cells and transduced bovine aortic ECs determined by chemiluminescence to measure the NO metabolite. Nox5 also activated eNOS in human aortic ECs as detected by a cGMP reporter assay that measured the release of biologically functional NO from cells in the presence of superoxide dismutase (SOD). To establish the functional significance of this observation in blood vessels, the endothelium of mouse aorta was tranduced with Nox5 or control adenoviruses. Nox5 potently inhibited Achinduced relaxation, potentiated contractile responses to phenylephrine. In precontracted blood vessels, acute exposure to SOD induced significant vascular relaxation in vessels exposed to Nox5 versus control and unmasked the ability of Nox5 to activate eNOS in blood vessel endothelium. These results are in contrast to a number of described mechanisms for eNOS inhibition and provide valuable clues that in complex diseases such as diabetes and hypertension that ROS production is not the sole cause of endothelial cell dysfunction.
    • Regulation of GluN2C-Containing N-methyl-D-aspartate (NMDA) Receptors

      Chung, Connie; Department of Neuroscience and Regenerative Medicine (6/3/2016)
      NMDA receptors (NMDARs) play a major role in the pathological events following excitotoxicity. Post-ischemic activation of NMDARs has been linked to opposing signaling that mediates pro-survival or pro-death activity. This dichotomy is largely due to distinct GluN2 subunit compositions governing important receptor functions including channel properties, receptor trafficking, and synaptic localization. Compared to GluN2A- and GluN2B-containing NMDARs, the trafficking of GluN2C in non-cerebellar granule neurons is less well understood. Moreover, the role of GluN2C following cerebral ischemia remains unknown. Here, we report 14-3-3 isoform-specific binding and regulation of GluN2C. Our findings highlight the isoform-specific structural and functional differences within the 14-3-3 family of proteins which determine GluN2C binding and its essential role in targeting the receptor to the cell surface to facilitate glutamatergic neurotransmission. Next, we sought to investigate the role of GluN2C following cerebral ischemia. We show that GluN2C expression promotes neuronal survival as a homeostatic mechanism by which intracellular Ca2+ levels are maintained by upregulation of GluN2C. Through such a mechanism, not only the intracellular Ca2+ level but also NMDAR signaling can be maintained at equilibrium.
    • Regulation of Granulosa Cell Proliferation in the Rat

      Cannon, Jennifer D.; Department of Biological Sciences (2006-08)
      The growth and maturation of the ovarian follicle is central to reproductive cyclicity in females and is under the endocrine control of the pituitary gonadotropins FSH and LH, as well as locally produced steroids and growth factors. A fundamental aspect of follicle development is proliferation and differentiation of granulosa cells, although the precise temporal dynamics and regulation remain largely unknown. FSH acts through its receptor to stimulate estradiol synthesis, which together with FSH induces proliferation of the granulosa cells in preantral and small antral follicles (95). In contrast, the LH surge initiates ovulation and formation of the corpus luteum (luteinization) in preovulatory follicles. Luteinization has been considered the terminal differentiation of granulosa to luteal cells and has been associated with a rapid reduction in granulosa cell proliferation (36, 114). However, more recent evidence suggests that (a) cell cycle control and luteinization are not functionally and/or mechanistically linked (113, 137), and (b) luteinization is associated with additional granulosa cell proliferation (100, 124, 126-128). The data presented herein challenge the dogma that granulosa cell proliferation is strictly associated with follicle growth and exit from the cell cycle is strictly associated with the LH surge and luteinization. The role of granulosa cell proliferation and differentiation in follicular development and luteinization is only just now beginning to be elucidated. Several ovarian pathologies are associated with defects in these processes, including luteinized unruptured follicle syndrome and polycystic ovarian syndrome (PCOS). PCOS, in particular, is a serious public health issue, affecting anywhere from 3.4% to 6.8% of women (138). Among females undergoing assisted reproductive technology (ART) cycles in the United States in 2003, 6% had been diagnosed with ovulatory dysfunction (139). Thus, pathologies associated with follicular development and luteinization have the potential to afflict large numbers of reproductive-age women. Further, the use of controlled ovarian stimulation (COS) cycles to generate large numbers of oocytes for use in ART procedures is fraught with problems, such as a shortened luteal phase as well as a heterogeneous population of antral follicles likely differing in size, health, and oocyte quality (140) all affecting the rate of pregnancy from these procedures. For example, of the 122,872 ART cycles performed in 2003, only 35, 785 (-30%) resulted in a live birth (139). Finally, a better understanding of the processes that govern granulosa cell proliferation has important ramifications for ovarian cancer, especially rare juvenile granulosa cell tumors that are nevertheless associated with a high mortality (141).
    • Regulation of Pharyngeal Region Patterning and Organogenesis by Sonic Hedgehog

      Moore-Scott, Billie A.; Department of Biochemistry and Molecular Biology (2005-03)
      Patterning of the pharyngeal region determines the proper development of multiple organs in addition to structures of the face, head and neck. The thymus and parathyroid originate from the third pharyngeal pouch and regulate the development of the immune system and calcium homeostasis, respectively. Although functionally these organs are in no way similar, they are derived from a common endodermal primordium, which develops around E l 1.0-El 1.5 in the mouse. At this stage it is apparent that the rudiment has regionalized into the parathyroid and thymus specific domains. Sonic hedgehog (Shh) is a secreted molecule that contributes to the patterning and regionalization of multiple tissues throughout embryonic development. As a morphogen, Shh initially specifies heterogeneous cell types within a field of cells, regionalizing the target tissue into functional domains. Shh activity can also regulate the proliferation and/or survival of those same cells continuing to contribute to the development of the tissue both morphologically and functionally. Since Shh expression is present in the pharyngeal endoderm, it was a promising candidate for patterning of the pharyngeal region as well as the regionalization of the common parathyroid/thymus primordium. Since die pharyngeal region is a specialized vertebrate structure from which several endocrine organs are derived, correct patterning of the pharyngeal region is important for these organs to initiate and develop properly. Our analysis of the Shh'A mutant has revealed multiple organ phenotypes which are die result of die necessity for Shh signaling at multiple stages of development in the pharyngeal region. These include loss of pharyngeal pouch identity, atrophy of the first pharyngeal arch, parathyroid agenesis, dysmorphic and ectopic growth of the thyroid; and thymic hypoplasia and improper differentiation of the thymic epithelial cell microenvironment. This dissertation is a description of our analysis of the early patterning and organogenesis phenotypes of the Shh'A mutant. Based on these data we propose a model describing the Shh-dependent mechanisms that regulate these events in the mid-gestation staged mouse embryo.
    • Regulation of Reduced-Folate Transporter-1 in Retinal Pigment Epithelium

      Naggar, Hany A.; Department of Cellular Biology and Anatomy (2003-04)
      (First Paragraph) The purpose of these studies was to analyze the regulation of the folate transport protein, reduced-folate transporter (RFT-1) in the retinal pigment epithelium (RPE) under conditions o f hyperglycemia, hyperhomocysteinemia and folate deficiency. A detailed description o f the retina, followed by information regarding folate and regulation o f RFT-1, is provided below.
    • Regulation of renal medullary endothelin B receptor function by angiotensin II: evidence of sex differences

      Kittikulsuth, Wararat; Department of Medicine (2012-08)
      The renin angiotensin system and endothelin (ET) systems play critical roles in regulating kidney function and blood pressure. Angiotensin (Ang) II exerts its prohypertensive effects through AT1 receptor activation. ET-1 has similar effects mediated by ETA receptor stimulation. In contrast, ET-1, via ETB receptors, mediates vasodilation, anti-inflammation, and natriuresis. In the clinical setting, hypertension is more common in men than in premenopausal women of the same age. Moreover, in a number of animal models of genetic or experimental hypertension, females are somewhat protected from high blood pressure compared to males. We previously found that hypertensive male rats, induced by chronic Ang II infusion, have impaired ETB receptor function. Because ETB receptors are highly expressed in the renal medulla, the overall aim of this dissertation is to determine the role of Ang II in mediating renal medullary ETB receptor function, and to determine if differences in renal medullary ETB receptor function contribute to the sex differences observed in Ang II hypertension. The first aim was to test the hypothesis that renal medullary ETB receptor function is impaired in male Ang II hypertensive rats. However, ET-mediated natriuresis is preserved in female rats in response to chronic Ang II infusion. We compared the diuretic and natriuretic responses to intramedullary infusion of the ETB receptor agonist, sarafotoxin 6c (S6c), in male and female rats treated with Ang II (260 ng/kg/min s.c.) or vehicle for 14 days. Male Ang II hypertensive rats had impaired ETB-dependent sodium and water excretion. In contrast, renal medullary ETB receptor function was preserved in female Ang II-treated rats. Moreover, ETA-mediated diuretic and natriuretic responses were maintained in female Ang II hypertensive rats. These data demonstrate that, in contrast to male Ang II hypertensive rats, ET receptor-induced diuretic and natriuretic responses are preserved in female rats during chronic Ang II infusion. The second aim was to determine if ETB receptors limit the hypertensive response and renal injury induced by chronic Ang II infusion in female rats compared to males. Male and female rats received Ang II infusion (150 ng/kg/min; sc.) along with a high salt diet (4% Na) for 4 weeks; blood pressure was measured by telemetry. After one week of Ang II infusion with a high salt diet, subsets of both male and female rats received the ETB antagonist, A-192621, at three doses on consecutive weeks (1, 3, and 10 mg/kg/d in food). Male rats had significantly higher blood pressure compared to females after 4 weeks of Ang II. A-192621 resulted in a dose-dependent increase in blood pressure in female Ang II hypertensive rat while there was no significant change in males. After 4 weeks of Ang II infusion, the levels of proteinuria and nephrinuria were higher in male rats compared to female. A-192621 did not further increase urinary excretion of protein or nephrin in either male or female Ang II hypertensive rats. In conclusion, ETB receptors provide more protection against hypertension during chronic Ang II infusion in female rats compared to male. The third aim was to determine the physiological role of Ang II in regulating renal ETB receptor function during salt deprivation, a model with high levels of endogenous Ang II. After 2 weeks of normal (0.4% Na) or low (0.01-0.02% Na) salt feeding, the activation of ETB receptors in the renal medulla increased urine flow and sodium excretion of rats on normal salt diet. While urinary ET-1 excretion was comparable between a normal and low salt diet, ETB-dependent diuresis and natriuresis in response to acute intramedullary infusion of S6c was reduced in the low salt treated rats. Chronic treatment with the AT1 receptor antagonist, candesartan, restored ETB-induced water and sodium excretion in rats fed low salt diet. These findings support the hypothesis that AT1 receptors regulate renal medullary ETB receptor function in a low salt diet model to conserve sodium. From these studies, we conclude that Ang II via the AT1 receptor attenuates renal medullary ETB receptor function resulting in sodium and water retention. During pathological situations, Ang II has a greater inhibitory effect on ETB receptor function in male rats compared to females, leading to a greater increase in blood pressure in response to chronic Ang II infusion.
    • REGULATION OF SYNAPSE DEVELOPMENT BY GABA ACTIVITY OF ERBB4-POSITIVE INTERNEURONS

      Lin, Thiri W.; Department of Neuroscience and Regenerative Medicine (11/2/2017)
      GABA activity has been implicated in neural development; however, in vivo genetic evidence is missing because mutant mice lacking GABA activity die prematurely. Here, we studied postnatal synapse development in ErbB4-Vgat-/- mice where Vgat was deleted in ErbB4+ interneurons. We show that the number of inhibitory axo-somatic synapses onto pyramidal neurons is layer-specific; however, inhibitory synapses on axon initial segments (AISs) were similar from layer to layer. On the other hand, PV+ErbB4+ interneurons and PV-only interneurons receive higher number of inhibitory synapses from PV+ErbB4+ interneurons, compared with ErbB4-only interneurons. Erbb4-Vgat-/- mice exhibited fewer inhibitory synapses from PV+ErbB4+ interneurons onto excitatory neurons (either axo-somatic or axo-axonic), compared with control mice. The Vgat mutation seemed to have little effect on inhibitory synapses onto PV+ and/or ErbB4+ interneurons. These morphological alterations were associated with concomitant changes in neurotransmission. Finally, perineuronal nets were increased in the cortex of ErbB4-Vgat-/- mice. These results demonstrate that GABA activity from ErbB4+ interneurons specifically regulates the development of inhibitory synapses onto excitatory neurons and provides in vivo evidence for a critical role of GABA activity in circuit assembly.