Now showing items 1-20 of 35


      Hassan, Nazeera; Zarzour, Abdalrahman; Department of Biological Sciences; Department of Medicine; College of Allied Health Sciences; Kim, Ha Won; Weintraub, Neal; Augusta University (2019-02-13)
      Our group has previously identified histone deacetylase 9 (HDAC9) as a regulator of adipocyte differentiation, and its expression levels were elevated in diet induced obese (DIO) mice.� We also reported that global HDAC9 deletion protected mice against DIO through promoting beige adipogenesis. Here, we hypothesized that adipose HDAC9 correlate with human obesity similar to murine models, and its deletion is sufficient to protect against DIO. To test this hypothesis we crossed HDAC9 floxed mice with adiponectin-cre mice to generate adipose-specific HDAC9 knockout mice (AdipCre-HDAC9), which exhibited 30% less weight gain when fed high fat diet compared to control despite increased food intake, in association with increased energy combustion & O2 consumption, improved insulin sensitivity and glucose tolerance. However, unlike global HDAC9 deletion, this was not associated with increased beige adipogenesis nor increase in brown adipose tissue function. Interestingly, AdipoCre-HDAC9 mice fed normal chow diet didn�t exhibit altered energy expenditure nor weight differences when compared to littermate controls. These finding suggest that adipose HDAC9 regulate energy expenditure in response to high fat diet and can be a promising therapeutic target to combat obesity.
    • Questionnaire Design and Responsiveness in a Data Capture Tool for Student Sharing of Experiences of Statewide Clerkship Sites

      Zheng, Stephanie; Behrman, David; Agrawal, Parth; Basco, Brian; Ball, Charlotte; Rose, Jennifer; Miller, Samel; Wood, Elena (2017-03)
      Positive clerkship experiences and student performance in the clinical years has been correlated to perceived quality of education and specialty choice amongst medical students [1-3]. The Medical College of Georgia uses a distributed campus model with more than 250 clerkship rotation sites across the state and beyond, making student clerkship choices imperative to their development as physicians. We developed a survey to collect both quantitative and qualitative data from students during their clerkship years and a system to distribute that information to students. The data allowed us to evaluate the effectiveness of various question formats through responsiveness, the length of responses, and time spent on the survey. In addition to this, we looked at the number of responses per clerkship in order to see whether or not our survey was getting information about all of the 3rd year rotations. We aspire to take these findings and utilize them to expand t he program and improve the questionnaire in order to yield more responsiveness from students.
    • An Investigation of the Chronic Disease Self-Management Program - Assessing CDSMP Facilitators' Perceptions of the Program's Effect

      Hillman, L. M.; Anderson, C.; Stoodt, G.; Department of Medicine; Augusta University (2017-03)
      Chronic conditions are public health threats. The Chronic Disease Self-Management Program (CDSMP) is an evidence-based disease management program that addresses personal self-management of chronic conditions. The CDSMP involves peer trainers who instruct and assist with chronic disease preventive measures. Although disease management demonstrates promise to improving patient self-maintenance, previous researchers have not evaluated how the program affects program leaders. The purpose of this study was to discover how self-help leaders feel about the CDSM program. The overarching research question asked about perspectives that self-help leaders had toward the program. Through a narrative qualitative approach, the perceptions of peer leaders were examined to determine if the program was personally beneficial. Guided by the social cognitive theory, a purposeful convenience sample of 20 participants completed the study. The participants were practicing peer trainers in the CDSMP prog ram. Data analysis included hand coding using open and axial coding and content analysis. Study findings included themes surrounding how the CDSMP program benefits health in general as well as the management of facilitators’ own chronic diseases, health behaviors, and increased quality of life. The ability for chronic disease management leaders to experience positive effects of the program they administer may result in positive social change. This awareness can positively affect social change by enhancing an already established evidence-based community health program with stronger and better-equipped leaders.
    • 96 plays a role in the virulence of C. jejuni

      Rathbun, Kimberly M; Department of Medicine (2009-05)
      Campylobacter jejuni is a gastrointestinal pathogen of humans but part of the normal flora of poultry. C. jejuni therefore grows well at both 37°C and 42°C. Proteomic studies on temperature regulation in C. jejuni strain 81-176 revealed the upregulation at 37°C of CJ0596, a predicted periplasmic chaperone that is similar to proteins found to be involved in outer membrane protein (OMP) folding and virulence in other bacteria. The cj0596 gene was highly conserved in multiple strains and species of Campylobacter (24 in total), implying the importance of this gene. To study the role CJ0596 plays in Campylobacter pathogenesis, a mutant derivative of strain 81-176 was constructed in which the cj0596 gene was precisely deleted. This mutant was complemented by restoring the gene to its original chromosomal location. The mutant strain demonstrated a decreased growth rate and lower final growth yield, yet was more motile than wild-type. The cj0596 mutant also showed altered levels of several outer membrane proteins (OMPs), and changes in membrane-associated characteristics (antimicrobial sensitivity, autoagglutination, and biofilm formation). In either single or mixed infections, the mutant was less able to colonize mice than wild-type. Purified, recombinant CJ0596 had peptidyl-prolyl cistrans isomerase (PPIase) activitty, but did not functionally complement an E. coli surA mutant. These results suggest that C. jejuni CJ0596 is a PPIase and loss of CJ0596 alters phenotypes that have been shown to be related to the pathogenesis of the bacterium.
    • Mechanisms of ET-1-mediated 02~ production in the rat aorta

      Loomis, E. D.; Department of Medicine (2004-06)
      The objectives of this project were to test the hj^othesis that in the rat aorta endothelin-I (ET-I) binds to the ETa receptor stimulating superoxide (O2’ ) production. Furthermore, we wanted to identify the mechanism through which ET-1-mediates O2' production. Chemiluminescent detection of O2” production using probes such as lucigenin has been widely used with enzyme systems, leukocytes, and vascular tissues. Our first goal was to develop a microplate high-throughput protocol for lucigeninamplified chemiluminesence detection of 0 2 'L We have developed a novel adaptation to lucigenin-based assays that allows up to 36 samples to be counted at virtually the same time. Recent studies have shown that NOS 3 can become uncoupled and produce O2* when deprived of its cofactor BH4 . In addition several authors have shown that ONOOoxidizes BH4 in vitro. Using the high-throughput lucigenin assay and dihydroethidine (DHE) staining we have shown that (1) ET-1 is able to stimulate 0 2 "^ production in both endothelium-intact and -denuded vessels through the ETA-receptor, (2) ET-1 stimulates O2’ production through both NAD(P)H oxidase and an endothelial source of NOS, and (3) addition of exogenous tetrahydrobiopterin (BH4 ) and inhibition of peroxynitrite (ONOO-) inhibit ET-I-mediated 0 2 *^ production. Therefore our data have led us to hypothesize that ET-I stimulates O2* production by activating NAD(P)H oxidase through the ETa receptor. O2' production by NAD(P)H oxidase leads to the formation of ONOO- and the degradation of BH4. The loss of BH4 leads to uncoupled NOS which then contributes to ET-1-mediated production. In addition, we have found that (1) ET-1 increases the production of interleukin- 6 (IL-6 ) and (2) ET-1-mediated O2' production adversely affects vascular contractility. Although these consequences do not appear to be due to NOS uncoupling, they help support the role of ET-1 in vascular dysfunction.
    • Role of GCN2-dependent metabolic stress in regulating myeloid cell activation and differentiation.

      Liu, Haiyun; Department of Medicine (2014-12)
      Amino acid metabolism is a pivotal regulator of innate and adaptive immunity. During inflammation, myeloid cells expressing enzymes such as indoleamine 2, 3-dioxygenase (IDO) and arginase 1 (ARG1) that degrade the amino acids L-tryptophan (L-Trp) and L-arginine (L-Arg), respectively. This serves a critical role in controlling cellular survival, development, and function. Therefore, it is important to understand the metabolic stress sensing pathways that regulate immune cell behavior, which further control the overall inflammatory environment. General Control Non-depressible 2 (GCN2) is an integrated stress response (ISR) kinase activated by intracellular amino acid limitation. Activated GCN2 phosphorylates eukaryotic initiation factor 2 α (eIF2α), which leads to global translation repression while up-regulating various stress-associated transcription factors. We found that in a murine LPS-induced endotoxemia model, IDO expression in macrophages depleted L-Trp that activated the GCN2. GCN2 signaling promoted macrophage cytokine production (IL-6, IL-12), increased CHOP expression and NF-κB activation. GCN2 knockout (GCN2KO) mice showed significantly lower serum and splenic cytokine levels compared to wild-type (WT) mice, and were protected from septicemia induced mortality. In the murine EG7 tumor model, GCN2 signaling was also activated in myeloid-derived suppressor cells (MDSCs) mediated by ARG1 depletion of L-Arg. We found that GCN2 was required for transcription factor C/EBPβ induction and monocytic bone marrow MDSC (BM-MDSC) development. GCN2KO BM-MDSCs showed significantly reduced ARG1 activity and failed to suppress antigen-specific cytotoxic T lymphocytes (CTLs) in vitro and in vivo. GCN2KO mice also exhibited increased efficacy in eliminating tumor cells after adoptive CTL transfer therapy. These data suggest that myeloid cells actively deplete intracellular amino acids to regulate their own cellular behavior. Different amino acid metabolic stress signals converge on the GCN2 pathway which serves as a secondary messenger to modulate downstream transcription factors. Depending on the type of inflammation, GCN2 can either promote pro-inflammatory responses or the immunosuppressive function of myeloid cells. Thus, targeting the GCN2 pathway in myeloid cells may have great potential in clinical therapy.
    • Regulation of Virulence in the Human Pathogen Campylobacter jejuni by the RNA Binding Protein CsrA

      Fields, Joshua A; Department of Medicine (2011-10)
      Campylobacter jejuni is a leading bacterial cause of gastroenteritis in both the industrialized and developing world and has been associated with the onset of long term, debilitating sequelae such as Guillain-Barre Syndrome and reactive arthritis. The RNA binding protein CsrA (carbon storage regulator A), one of the relatively few regulatory elements in the C. jejuni genome, has been shown to regulate a number of processes in several other bacterial species including metabolism and virulence characteristics. We proposed the hypothesis that CsrA globally regulates C. jejuni pathogenesis via post-transcriptional repression or activation of virulence associated proteins. We created a csrA mutant in the C. jejuni strain 81-176 to investigate the role of CsrA in the virulence and physiology of the organism. In the absence of CsrA, we found that C. jejuni was no longer able to resist oxidative stresses, form biofilms, or adhere to intestinal epithelial cells in vitro in comparison to the wild type. We also found that C. jejuni was less motile than its parent strain and was defective in autoagglutination and fibronectin binding in vitro and mouse colonization in vivo. When we compared the proteome of the mutant strain to that of the wild type, we found that CsrA acted mostly upon the expression of proteins in stationary phase. In the absence of CsrA proteins responsible for various steps in C. jejuni metabolism, motility, oxidative stress responses, and epithelial cell adherence were differentially expressed. Finally, to further understand the molecular mechanisms of C. jejuni CsrA, we expressed it in a csrA mutant strain of E. coli. By heterologously expressing the C. jejuni protein in strain in which CsrA had been thoroughly characterized, we were able to show by complementation that C. jejuni CsrA was capable of both activating and repressing known targets of E. coli CsrA indicating that the molecular mechanisms of the two proteins are inherently the same.
    • Role of Oxidative Stress in High Endothelin Models of Hypertension

      Elmarakby, Ahmed A.; Department of Medicine (2004-07)
      Recent studies have shown that the potent vasoconstrictor peptide endothelin-1 (ET-1) stimulates superoxide production in vivo and in vitro. We hypothesized that ET-1 induced hypertension, at least in part, is due to an increase in oxidative stress. In the initial experiments, we hypothesized that ETA receptor stimulation contributes to the elevated blood pressure and superoxide production in ETB receptor deficient rats as an example of a high endothelin model of hypertension. Experiments were conducted on homozygous {si/si) ETB deficient and wild type {wt) rats fed a high salt diet for three weeks. Separate groups of rats were given normal drinking water or water containing the ETA receptor antagonist, ABT 627. On a normal salt diet, sl/sl rats had a significantly elevated systolic blood pressure (SBP) compared to wt. High salt caused a significant increase in SBP in sl/sl compared with wt rats. ETA receptor blockade decreased SBP in sl/sl rats on high salt without affecting the blood pressure in wt rats. Plasma 8-isoprostane levels, an indirect measure of oxidative stress, were significantly higher in sl/sl rats compared with the wt. ETa receptor blockade significantly attenuated the elevation in plasma 8- isoprostane levels in sl/sl rats'. These findings suggest that ET-1, through the ETA receptor, contributes to salt-induced hypertension and superoxide production in ETB deficient rats. We hypothesized that ET-1 increases superoxide production via the stimulation of the NADPH oxidase system. Chronic ET-1 infused rats were fed a high salt diet and either allowed to drink tap water, water containing the SOD mimetic, tempol, or the NADPH oxidase inhibitor, apocynin, for two weeks. Infusion of ET-1 increased mean arterial pressure (MAP) when compared to baseline values. Neither tempol nor apocynin treatment had any effect on the increase in MAP produced by ET 1. Plasma 8-isoprostane was increased significantly in ET-1 infused rats compared to rats on a high salt diet alone. Both tempol and apocynin treatment significantly attenuated the ET-1 induced increase in plasma 8-isoprostane. These data provide evidence that chronic ET-1 infusion increases vascular NADPH oxidase dependent superoxide production, but does not account for chronic ET-1-induced hypertension. Finally, experiments were performed to determine if increased kinins and/or decreased superoxide attenuates the elevation in blood pressure in chronic Ang II hypertensive rats. Four groups of rats, all given Ang II, were studied and allowed to drink tap water, water containing enalapril, tempol, or both for two weeks. Ang II infusion significantly increased SBP when compared with the baseline. Neither enalapril nor tempol treatment alone was able to attenuate the elevation in SBP. Combined administration of tempol and enalapril prevented the increase in SBP. Plasma 8-isoprostane was elevated significantly in Ang II infused rats when compared with control untreated rats. Tempol treatment alone or tempol plus enalapril significantly attenuated the increase in plasma 8-isoprostane. These studies support the hypothesis that an antioxidant alone is not effective in preventing Ang II hypertension. However, administration of an ACE inhibitor with an antioxidant enhances antioxidant efficiency in preventing Ang II hypertension. Overall, these studies showed that ETA receptor stimulation participates in superoxide production via the stimulation of NADPH oxidase and that antioxidant treatment alone is not sufficient to lower blood pressure in high endothelin models of hypertension.
    • Mechanisms of Diet-Induced Hypertension and Vascular Disease Risk in Dahl Rats

      Spradley, Frank T.; Department of Medicine (2011)
      Dahl salt-sensitive (SS) rats are genetically predisposed to cardiovascular-renal disease. These studies examined cardiovascular-renal outcomes in response to a high-fat diet/normal-salt diet in SS rats. In a separate study, we examined cardiovascular-renal disease risk in SS rats on different standard chow diet/normal-salt diets. We tested the hypotheses that: (1) a high-fat diet induces hypertension and renal injury in SS rats; (2) a high-fat diet enhances aortic vasoconstriction in SS rats; (3) a high-fat diet induces aortic perivascular adipose tissue (PVAT) dysfunction in SS rats; and (4) two standard chow diets, namely AIN-76A and Teklad diet, induce differential vasoconstriction or vasorelaxation phenotypes in aorta and small mesenteric arteries from SS rats. In the high-fat diet studies, rats were provided high-fat diet starting at 12 weeks old. At 16 weeks old, SS rats on the high-fat diet had hypertension and greater renal glomerular and tubular injury than SS-13BN rats. SS rats supplemented with the immunosuppressive drug mycophenolate mofetil (MMF; 30 mg/kg/day, oral) for the duration of the high-fat diet did not develop hypertension. High-fat diet was associated with reduced vasoconstrictive response to angiotensin II and increased acetylcholine-mediated vasorelaxation in SS rats via increased nitric oxide synthase (NOS) function in comparison to SS rats maintained on a normal-fat/normal-salt diet. In regards to PVAT function, high-fat diet increased thoracic aorta PVAT deposition and induced PVAT-mediated blunting of aortic vasoconstriction. In the standard chow diet studies, 16-week old SS rats placed on the AIN or Teklad diet at weaning had similar NOS functional regulation of vasoconstriction and vasorelaxation in large and small arteries. However, by using a diet-switch protocol, we demonstrated that SS rats placed on AIN diet at weaning and changed to Teklad diet at 12 weeks old had reduced NOS-mediated vasorelaxation and reduced NOS buffering of vasoconstriction in small arteries from SS rats, which was not observed in the corresponding diet-switch group. In conclusion, these studies highlight differential renal and vascular responses to a short-term high-fat diet, and even changes in standard chow diet, when genetically predisposed to hypertension.
    • Role of Endothelin-1 (ET-1) in Glomerular Inflammation and Glomerular Permeability in Normal and Diabetic Kidneys

      Saleh, Mohamed Ahmed; Department of Medicine (2010-11)
      Endothelin-1 (ET-1) is a potent vasoactive peptide implicated in the pathogenesis of hypertension and renal disease. The overall specific aim of this dissertation is to investigate the role of ET-1 in mediating glomerular inflammation and permeability, especially in diseases characterized by high activity of the ET-1 system, such as diabetic nephropathy. The first study was designed to test the hypotheses that ET-1 increases albumin permeability of glomeruli isolated from normal rats and that chronic ET-1 infusion will increase glomerular permeability and inflammation independent of blood pressure. Glomerular permeability to albumin (Palb) was determined from the change in glomerular volume induced by exposing isolated glomeruli to oncotic gradients. Incubation of glomeruli taken from normal rats with ET-1 at a concentration that did not produce direct glomerular contraction (1 nM) significantly increased Palb, reaching a maximum after 4 hrs. Chronic ET-1 infusion for 2 weeks in Sprague-Dawley (SD) rats significantly increased Palb and nephrin excretion rate, effects that were attenuated in rats given an ETA receptor antagonist, ABT-627. Urinary protein and albumin excretion and mean arterial pressure (telemetry) were not changed by ET-1 infusion. Acute incubation of glomeruli isolated from ET-1-infused rats with the selective ETA antagonist significantly reduced Palb, an effect not observed with acute treatment with a selective ETB antagonist. Chronic ET-1 infusion increased glomerular and plasma sICAM-1 and MCP-1 and elevated the number of macrophages and lymphocytes in renal cortices (CD68- and CD3-positive staining, respectively). These effects were all attenuated in rats given an ETA selective antagonist. These data support the hypothesis that ET-1 directly increases glomerular permeability to albumin and renal inflammation via ETA receptor activation independent of changes in arterial pressure. The second study was designed to test the hypothesis that ETA receptor activation increases Palb and elevates pro-inflammatory markers in hyperglycemic rats. Male SD rats were given streptozotocin (STZ) or saline (sham). Half of the animals in each group received ABT- 627 beginning immediately after hyperglycemia had been confirmed. Glomeruli were isolated by sieving and Palb determined from the change in glomerular volume induced by exposing glomeruli to oncotic gradients of albumin. Glomerular nephrin expression was assessed by immunofluorescence, whereas urinary nephrin was measured by enzymelinked immunosorbent assay. Three and 6 weeks after STZ injection, proteinuria was significantly increased compared to sham controls and was significantly reduced by ABT-627 treatment. Palb was also increased at 3 and 6 wk post-STZ; ABT-627 had no effect on Palb or protein excretion in sham rats. Glomerular and plasma content of sICAM-1 and MCP-1 were significantly increased 6 wk after STZ. ABT-627 attenuated these increases. After 6 weeks of hyperglycemia, glomerular nephrin expression was decreased with a concurrent increase in urinary nephrin excretion; ABT-627 prevented glomerular nephrin loss in the hyperglycemic rats. These observations support the hypothesis that ET-1, via the ETA receptor, mediates the increase in proteinuria and Palb, possibly via nephrin loss, as well as early inflammation in the hyperglycemic rat. In the third study, we determined the actions of ETA and ETB receptors on measures of glomerular function and renal inflammation in the early stages of diabetic renal injury in rats. Six weeks after STZ-induced hyperglycemia, rats were given ABT-627 (5 mg/kg/d) a selective ETA antagonist; A-182086 (10 mg/kg/d), a combined ETA/B antagonist; or vehicle for 1 week. Sham controls received STZ vehicle (saline). Hyperglycemia led to significant proteinuria, increased Palb, nephrinuria, and an increase in total matrix metalloprotease (MMPs) and transforming growth factor-beta 1 (TGF-β1) activities in glomeruli. Plasma and glomerular sICAM-1 and MCP-1 were elevated after 7 weeks of hyperglycemia. Daily administration of both ABT-627 and A-182086 for 1 week significantly attenuated proteinuria, the increase in Palb, nephrinuria, and total MMPs and TGF-β1 activity. However, glomerular sICAM-1 and MCP-1 expression was attenuated with ABT-627, but not A-182086 treatment. In summary, both selective ETA and combined ETA/B antagonists reduced proteinuria, glomerular permeability and restored glomerular filtration barrier components integrity, but only ETA selective blockade had anti-inflammatory and anti-fibrotic effects. We conclude that selective ETA antagonists are more likely to be preferred for treatment of diabetic kidney disease.
    • The Role of Myostatin (GDF-8) in Chondrogenesis and Fracture Healing

      Elkasrawy, Moataz N.; Department of Medicine (2010-11)
      Traumatic musculoskeletal injuries frequently include damage to both muscle and bone where muscle injury itself can delay bone healing. Myostatin (GDF-8) is a member of the transforming growth factor-β (TGF-β) superfamily, and a negative regulator of skeletal muscle growth. Loss of myostatin function leads to a doubling of skeletal muscle mass, a general increase in bone density, and an increase in fracture callus bone volume. Myostatin is highly expressed during the first twenty-four hours after fracture, yet nothing is known about its role in fracture repair. We hypothesize that myostatin is a key regulator in the process of bone regeneration, and is a major therapeutic target for enhancement of fracture healing. Pharmacological inhibition of myostatin may therefore improve the regenerative capacity of both muscle and bone.
    • 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.
    • Novel Nitric Oxide Synthase-Dependent Mechanism of Vasorelaxation in Small Arteries from Hypertensive Rats

      Kang, Kyu-Tae; Department of Medicine (2007-10)
      Endothelial dysfunction in hypertension is associated with impaired endothelium-dependent vasorelaxation, which is consistently observed in conduit vessels. However, the controversial observation of either impaired or intact vasorelaxation of small resistance arteries from hypertensive animals suggests that the mechanism(s) of endothelium-dependent vasorelaxation in small resistance arteries may be different from that observed in conduit vessels under hypertensive condition. Vasorelaxation in small resistance arteries is mediated via multiple pathways including nitric oxide synthase (NOS)-, cyclooxygenase (COX)-, and endothelium-derived hyperpolarizing factor (EDHF)-mediated pathway. Therefore, the overall goal of these studies was to determine the mechanism(s) involving vasorelaxation of small arteries from hypertensive rats. For these studies, normotensive (NORM), angiotensin II-infused (ANG), high salt (HS), ANG high salt (ANG/HS), placebo, and deoxycorticosterone acetate-salt (DOCA) rats were studied. The studies with pharmacological blockade of each pathway demonstrated that the NOS-dependent component was increased to maintain acetylcholine (ACh)-induced vasorelaxation in small mesenteric arteries from hypertensive rats. Furthermore, increased NOS-dependent pathway appears to compensate for the dysfunctional Ca2+-activated K+ channel-sensitive EDHF pathway in small mesenteric arteries from ANG compared to NORM. These results led us to design further experiments to test the hypothesis that both NO and H2O2 serve as NOS-dependent mediators to maintain vasorelaxation in small mesenteric arteries from hypertensive rats. In small arteries from ANG, ACh increased NOS-dependent cGMP production. ACh also increased NOS3 phosphorylation at Ser 633 and decreased phosphorylation at Thr 495. While, NOS3 phosphorylation at Ser 1177 was impaired in response to ACh in ANG, which was accompanied by reduced basal and a less extended ACh-stimulated cGMP production in ANG compared to NORM. To investigate the alteration of signal transduction pathways related to impaired NOS3 phosphorylation at Ser 1177 in response to ACh, Akt phosphorylation at Ser 473 and VASP phosphorylation at Ser 239 were tested. These pathways were not changed by ACh in the small mesenteric arteries from ANG. Our results indicate that the NO/cGMP signaling is present in response to ACh in small mesenteric arteries from ANG, however this signaling pathway-mediating vasorelaxation may be facilitated via neither Akt nor PKG. On the other hand, ACh stimulated L-NAME-sensitive H2O2 production in small mesenteric arteries from ANG, but not NORM. H2O2 induced vasorelaxation and catalase blunted ACh-mediated vasorelaxation in small mesenteric arteries from ANG. Reduced BH4/BH2 ratio was observed in small mesenteric arteries from ANG compared to NORM, which might be one of the mechanisms of NOS-mediated H2O2 production. Antioxidant enzyme capacity was also determined in small mesenteric arteries from ANG and NORM. Total superoxide dismutase (SOD) activity and protein expression of CuZn SOD and ecSOD were reduced in ANG compared to NORM, while Mn SOD expression was comparable between groups. Interestingly, both activity and expression of catalase were reduced in ANG compared to NORM, whereas GPx activity and expression were not changed. These results indicate that reduced catalase activity and expression may contribute to the augmentation of H2O2 in small mesenteric arteries from ANG, whereas reduced SOD does not greatly influence the H2O2 production in both basal and ACh-stimulated condition. In conclusion, the NOS pathway appears to be the primary endothelium-derived relaxing factor (EDRF) pathway in small mesenteric arteries from experimental animal models of hypertension. The increased dependence on the NOS pathway in ACh-induced vasorelaxation is mediated by both NOS-derived NO/cGMP signaling and NOS-mediated H2O2.
    • Salmonella newport bacteremia in a 12-day-old infant.

      Singh, Abhijit; Wilkins, Thad; Schade, Robert R.; Department of Family Medicine (2011-03)
      In the United States, Salmonella infections (salmonellosis) cause multiple medical problems. Although the most common presenting symptom is diarrhea, bacteremia can also occur. An estimated 1.4 million cases of salmonellosis occur annually in the United States. We present a case of Salmonella bacteremia in a 12-day old infant. We discuss the presenting signs, symptoms, and management strategies for a patient younger than 28 days old (neonate) presenting with fever and diarrhea.
    • Diagnosis and management of upper gastrointestinal bleeding.

      Wilkins, Thad; Khan, Naiman; Nabh, Akash; Schade, Robert R.; Department of Family Medicine; Department of Medicine (2012-03-01)
      Upper gastrointestinal bleeding causes significant morbidity and mortality in the United States, and has been associated with increasing nonsteroidal anti-inflammatory drug use and the high prevalence of Helicobacter pylori infection in patients with peptic ulcer bleeding. Rapid assessment and resuscitation should precede the diagnostic evaluation in unstable patients with severe bleeding. Risk stratification is based on clinical assessment and endoscopic findings. Early upper endoscopy (within 24 hours of presentation) is recommended in most patients because it confirms the diagnosis and allows for targeted endoscopic treatment, including epinephrine injection, thermocoagulation, application of clips, and banding. Endoscopic therapy results in reduced morbidity, hospital stays, risk of recurrent bleeding, and need for surgery. Although administration of proton pump inhibitors does not decrease mortality, risk of rebleeding, or need for surgery, it reduces stigmata of recent hemorrhage and the need for endoscopic therapy. Despite successful endoscopic therapy, rebleeding can occur in 10 to 20 percent of patients; a second attempt at endoscopic therapy is recommended in these patients. Arteriography with embolization or surgery may be needed if there is persistent and severe bleeding.
    • Anomalous coronary artery found in the syncopal workup of an elderly man

      Oommen, Ronnie; Wilkins, Thad; Chen, Stephen Y; Arora, Vishal; Department of Family Medicine; Department of Medicine; Department of Cardiology (2012-07)
      Syncope, defined as a transient loss of consciousness, is seen in 1% of all visits to emergency departments and urgent care clinics in the United States. Syncope is categorized as cardiogenic, neurologic, or psychogenic. Anomalies of the coronary arteries are rare, and anomalous coronary arteries present as syncope more often in the young than in the elderly; syncope rarely occurs in patients 65 years of age and older. There are 2 major variants of coronary anomalies. In the first variant, the left main coronary artery arises from the right aortic sinus. In the second variant, the right coronary artery arises from the left aortic sinus. The risk of sudden death is higher in patients with the left coronary artery arising from the right aortic sinus. We present a case of an anomalous coronary artery discovered during the syncopal workup in a 66-year-old man because no such cases have been published in the United States. We will discuss the management of anomalous coronary arteries as well as a systematic approach to the diagnosis and management of syncope.
    • Accelerated Growth Plate Mineralization and Foreshortened Proximal Limb Bones in Fetuin-A Knockout Mice

      Seto, Jong; Busse, Bjorn; Gupta, Himadri S.; Schafer, Cora; Krauss, Stefanie; Dunlop, John W. C.; Masic, Admir; Kerschnitzki, Michael; Zaslansky, Paul; Boesecke, Peter; et al. (2012-10-16)
      The plasma protein fetuin-A/alpha2-HS-glycoprotein (genetic symbol Ahsg) is a systemic inhibitor of extraskeletal mineralization, which is best underscored by the excessive mineral deposition found in various tissues of fetuin-A deficient mice on the calcification-prone genetic background DBA/2. Fetuin-A is known to accumulate in the bone matrix thus an effect of fetuin-A on skeletal mineralization is expected. We examined the bones of fetuin-A deficient mice maintained on a C57BL/6 genetic background to avoid bone disease secondary to renal calcification. Here, we show that fetuin-A deficient mice display normal trabecular bone mass in the spine, but increased cortical thickness in the femur. Bone material properties, as well as mineral and collagen characteristics of cortical bone were unaffected by the absence of fetuin-A. In contrast, the long bones especially proximal limb bones were severely stunted in fetuin-A deficient mice compared to wildtype littermates, resulting in increased biomechanical stability of fetuin-A deficient femora in three-point-bending tests. Elevated backscattered electron signal intensities reflected an increased mineral content in the growth plates of fetuin-A deficient long bones, corroborating its physiological role as an inhibitor of excessive mineralization in the growth plate cartilage matrix - a site of vigorous physiological mineralization. We show that in the case of fetuin-A deficiency, active mineralization inhibition is a necessity for proper long bone growth.
    • Asymptomatic Severe Hypocalcemia Secondary to Vitamin D Deficiency in an Elderly Patient

      Aldasouqi, Saleh; Glassy, Crystal M.; Glassy, Matthew S.; Treska, Anxhela; Caldwell-McMillan, Molly; Gossain, Ved; Department of Medicine (2011-11-2)
    • Rac1 Activation Driven by 14-3-3f Dimerization Promotes Prostate Cancer Cell-Matrix Interactions, Motility and Transendothelial Migration

      Goc, Anna; Abdalla, Maha; Al-Azayzih, Ahmad; Somanath, Payaningal R.; Department of Medicine (2012-07-13)
      14-3-3 proteins are ubiquitously expressed dimeric adaptor proteins that have emerged as key mediators of many cell signaling pathways in multiple cell types. Its effects are mainly mediated by binding to selective phosphoserine/threonine proteins. The importance of 14-3-3 proteins in cancer have only started to become apparent and its exact role in cancer progression as well as the mechanisms by which 14-3-3 proteins mediate cancer cell function remain unknown. While protein 14-3-3s is widely accepted as a tumor suppressor, 14-3-3f, b and c isoforms have been shown to have tumor promoting effects. Despite the importance of 14-3-3 family in mediating various cell processes, the exact role and mechanism of 14-3-3f remain unexplored. In the current study, we investigated the role of protein 14-3-3f in prostate cancer cell motility and transendothelial migration using biochemical, molecular biology and electric cell-substrate impedance sensing approaches as well as cell based functional assays. Our study indicated that expression with wild-type protein 14-3-3f significantly enhanced Rac activity in PC3 cells. In contrast, expression of dimer-resistant mutant of protein 14-3-3f (DM-14-3-3) inhibited Rac activity and associated phosphorylation of p21 activated kinase-1 and 2. Expression with wild-type 14-3-3f or constitutively active Rac1 enhanced extracellular matrix recognition, lamellipodia formation, cell migration and trans-endothelial migration by PC3 cells. In contrast, expression with DM 14-3-3f or DN-Rac1 in PC3 cells significantly inhibited these cell functions. Our results demonstrate for the first time that 14-3-3f enhances prostate cancer cell-matrix interactions, motility and transendothelial migration in vitro via activation of Rac1-GTPase and is an important target for therapeutic interventions for prostate cancer.
    • Association between Genetic Variants in DNA and Histone Methylation and Telomere Length

      Kim, Sangmi; Parks, Christine G.; Xu, Zongli; Carswell, Gleta; DeRoo, Lisa A.; Sandler, Dale P.; Taylor, Jack A.; Department of Medicine (2012-07-11)
      Telomere length, a biomarker of aging and age-related diseases, exhibits wide variation between individuals. Common genetic variation may explain some of the individual differences in telomere length. To date, however, only a few genetic variants have been identified in the previous genome-wide association studies. As emerging data suggest epigenetic regulation of telomere length, we investigated 72 single nucleotide polymorphisms (SNPs) in 46 genes that involve DNA and histone methylation as well as telomerase and telomere-binding proteins and DNA damage response. Genotyping and quantification of telomere length were performed in blood samples from 989 non-Hispanic white participants of the Sister Study, a prospective cohort of women aged 35–74 years. The association of each SNP with logarithmically-transformed relative telomere length was estimated using multivariate linear regression. Six SNPs were associated with relative telomere length in blood cells with p-values<0.05 (uncorrected for multiple comparisons). The minor alleles of BHMT rs3733890 G>A (p = 0.041), MTRR rs2966952 C>T (p = 0.002) and EHMT2 rs558702 G>A (p = 0.008) were associated with shorter telomeres, while minor alleles of ATM rs1801516 G>A (p = 0.031), MTR rs1805087 A>G (p = 0.038) and PRMT8 rs12299470 G>A (p = 0.019) were associated with longer telomeres. Five of these SNPs are located in genes coding for proteins involved in DNA and histone methylation. Our results are consistent with recent findings that chromatin structure is epigenetically regulated and may influence the genomic integrity of telomeric region and telomere length maintenance. Larger studies with greater coverage of the genes implicated in DNA methylation and histone modifications are warranted to replicate these findings.