Browsing by Subject "Systems and Integrative Physiology"
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Item A Clinical Research Study Involving the Use of Erythropoietin in Perioperative Patients Undergoing Surgery for Gynecologic Cancer(2002-07-01) Larson, Sharon Beth; Richardson, Barbara; Martin, MichaelThe purpose of this internship practicum report is to analyze the pathophysiology and impact of anemia in low-income gynecologic cancer patients. The report also assesses the impact of erythropoietin on hemoglobin levels prior to gynecologic cancer surgery. This report is based on a clinical research study to determine whether or not erythropoietin will mitigate the suppression of bone marrow inherent to the gynecologic cancer population and alleviate some of the symptoms and side effects of the anemia.Item Adenosine Receptor Blockade Increases Lactate and Purine Release But Does Not Affect Functional Recovery in Isolated Rabbit Myocardium(1995-12-01) Wang, Sheng; Downey, H. Fred; He, Miao-Xiang; Mallet, Robert T.Wang, Sheng, Adenosine Receptor Blockade Increases Lactate and Purine Release but does not Affect Functional Recovery in Isolated Rabbit Myocardium Master of Science (Biomedical Sciences), December 1995; 67 pp; 3 tables; 8 figures; bibliography, 121 titles. This study tests the hypothesis that endogenous adenosine mediates recovery of cardiac function in ischemia/reperfused rabbit hearts. Isolated isovolumic rabbit hearts perfused at constant pressure was subjected to mild ischemia (perfusion pressure 50 cm H2) or moderate ischemia (perfusion pressure 30 cm H2O) for 90 min followed by 60 min of reperfusion. In treated hearts, infusion of 100 μM 8-p-sulfophenyl theophylline (SPT) was initiated 20 min before ischemia and maintained throughout the experiment. Adenosine receptor blockade did not affect left ventricular function assessed from pressure-heart rate product (PRP). Lactate release increased to 152 ± 24% of baseline during mild ischemia and 259 ± 26% of baseline during moderate ischemia in untreated hearts. Lactate release was markedly elevated at baseline, ischemia and reperfusion by SPT treatment (p [less than] 0.05 compared to untreated). Purine nucleoside release was 4.1 ±0.7 nmol · min-1 · g-1 in SPT treated group and 1.8 ± 0.24 nmol · min-1 · g-1 in untreated group during moderate ischemia (P [less than] 0.05). Myocardial efficiency was significantly lower in the SPT treated hearts (240 ± 11 mmHg · g=1 · μl-1 O2) compared to untreated hearts (300 ± 22 mmHg · g-1 · μl-1 O2) during reperfusion after moderate ischemia. In conclusion, adenosine receptor blockade stimulates glycolysis in normoxic and ischemic myocardium, but does not affect post-ischemic functional recovery.Item Baroreflex Mediated Autonomic Modulation by Acute Pain and Orthostatic Stress(2008-10-01) Raven, Joseph Simon; James Caffrey; Joan Carroll; Robert MalletRaven, Joseph Simon, Baroreflex Mediated Autonomic Modulation by Acute Pain and Orthostatic Stress. Doctor of Philosophy (Integrative Physiology), October 2008, 147 pp.; 23 figures; bibliography; 123 titles. Nociceptive and baroreceptor afferent neurons are implicated as the components responsible for carotid baroreceptor reflex (CBR) resetting. The purpose of this dissertation was to identify the effect of cold induced pain, and cardiopulmonary baroreceptor (CPBR) unloading accompanied by pain, on CBR resetting. First, the relationships between cold induced pain to cardiovascular responses, pain perception, and muscle sympathetic nerve activity (MSNA) were investigated. Questions were addressed through use of the cold pressor test (CPT), finger plethysmography, and microneurography. This study demonstrated perceived pain, MSNA, and blood pressure responses to a cold stimulus were reproducible. Furthermore, graded responses observed in mean arterial pressure (MAP) and MSNA directly correlated to the intensity of the pain stimulus. The next study examined cold induced pain on CBR gain and operational point resetting in healthy normotensive subjects. Using similar experimental methodologies to the previous study, the data demonstrated acute pain shifted the CBR operational point toward the lower limiting value of MSNA. These data also confirmed an upward-rightward shift and increased gain of the CBR function curve during pain. Finally, CBR gain and operational point resetting during simultaneous CPBR unloading and cold induced pain in healthy normotensive subjects was addressed. Using the previous experimental paradigm, this investigation revealed CPBR unloading during acute pain did not abolish the shift of the CBR operational point. Thus, the capacity for hypotensive buffering remained enhanced. This study also determined CPBR unloading during acute pain produced higher prevailing blood pressures compared to periods of CPBR unloading alone. In summary: 1)MSNA and cardiovascular responses were tightly coupled to pain. 2) The CPT was a reliable technique for producing repeated sympathoexcitation within a subject. 3) Acute pain increased CBR gain and induced a shift of the CBR operational point. 4) The CBR operational point shift remained in the presence of CPBR unloading, which precipitated increased MAP during hypotensive stimuli. These findings suggested pain improves blood pressure maintenance during central hypovolemic stress.Item Cardiac Autonomic Response to Hypovolemia --- Effect of Age(1997-08-01) Wang, Hong-Wei; Raven, Peter B.; Shi, Xiangrong; Caffrey, James L.Objective: The beat-to-beat variation in heart rate reflects the dynamic response of the cardiovascular control systems to physiological perturbations such as respiration and postural change. The heart rate variation (HRV) is a part of the rapidly reacting component of cardiovascular homeostasis largely influenced by parasympathetic and sympathetic input. Thus, beat-to-beat variation in heart rate can be used as a measure of cardiac autonomic responses. The standard deviation of R-R interval is a measure of the overall variability in heart rate and has been shown to decrease with aging (9,23). This measure, however, can not identify individual sources of the variation. Spectral analysis reduces a signal to its constituent frequency components and the relative power of these components has been indicated related to parasympathetic mediation, combined sympathetic and parasympathetic mediation, and sympathetic mediation (1, 14, 17). Limited data are available regarding power spectral analysis of heart rate variation to study aging changes under orthostatic stress. An attenuated cardiac sympathetic nerve activity was found in older group vs younger individuals (7, 11, 19) during posture change. However, these studies were carried out using either posture change from to upright or passive head-up tilt. During these posture changes, both cardiopulmonary baroreceptors (i.e., intrathoracic hypovolemia) and arterial baroreceptors (postural hypotension) were unloaded. Therefore, it is unclear whether there is any difference in the HR variability between the young and the elderly during unloading of cardiopulmonary baroreceptors (or low-pressure baroreceptors) alone. In this study, we investigated the age difference in cardiac autonomic modulation of heart rate during unloading of cardiopulmonary baroreceptors with or without systemic arterial hypotension. For the purpose, we examined beat-to-beat heart rate variability in both the time and frequency domain using power spectral analyses in healthy individuals from ages 18 to 68 under basal conditions and in response to graded lower body negative pressure induced central hypovolemia. Not only individual low and high frequency spectral content were analyzed and those parameters were compared in order to find a quantitative evaluation of sympathetic and parasympathetic modulation and under the graded lower body negative pressure.Item Clinical Internship in the Surgery Department at the University of North Texas Health Science Center: Assessment of Human Antibody Response to Urokinase Part A: Specimin Acquisition Trial for the Assessment of Human Antibody Response to Urokinase in Subjects Treated for Acute Lower-Extremity Ischemia(2003-12-01) Hughes, Telicia A.; Rustin E. ReevesSignificance and Specific Aim of the Study. Significance. FDA has informed Abbott Laboratories of additional concerns related to manufacturing deficiencies for urokinase (Abbokinase). Until these problems are corrected, further distribution of Abbokinase would violate federal laws designed to assure the safety of drugs for patient use. FDA’s concerns about the product relate to serious deficiencies in the manufacturing processes, the testing of the product, and the screening and testing of the donors of the kidney cells used to make Abbokinase. Abbokinase is derived from cultures of human kidney cells from newborns who have died of natural causes, and is approved in the United States to dissolve blood clots in the lungs and heart arteries. It is also approved to help clear intravenous catheters. During inspections of Abbott Laboratories and of BioWittaker, Inc. Abbott’s supplier of human kidney cells, FDA identified numerous significant deviations from current good manufacturing practice (CGMP) regulations designed to assure product safety. Compliance with CGMP is important because products manufactured from human sources have the potential to transmit infectious agents. CGMP for products such as Abbokinase requires important, overlapping safeguards in the production process, including adequate –screening of donors and testing of cells, -controls for proper harvesting, storage, and handling of materials used in all stages of manufacturing, and –processes to remove or inactivate infectious agents from the product. Over the past several months, the firm has reported to FDA that a number of in-process lots of Abbokinase was contained with microorganisms. Six such lots were found to contain various strains of reovirus, a virus that usually results in no symptoms or causes minor respiratory or gastrointestinal symptoms. Association of reovirus infection with other human diseases have been reported, although a causal link has not been established. Another in-process lot was contaminated with mycoplasma, a microorganism that can cause respiratory infections, and, on rare occasions, other infections that may be serious. Abbott has assured FDA that none of these in-process lots were manufactured into final product or distributed. These recent findings of contamination and Abbott’s inability to locate the source of the problem have raised further concerns at FDA about Abbott’s entire manufacturing process for Abbokinase. Abbot’s deviations from CGMP could significantly impact the safety of the product. One FDA concern is that deficiencies in manufacturing practices could also lead to the product being contaminated with microorganisms that have not yet been detected. FDA also obtained additional information regarding the inadequacy of the screening and testing of the mothers and donors of the human kidney cells used to produce Abbokinase. Information was also obtained regarding the seven instances of in-process lots of product being contaminated with reovirus and mycoplasma. In the letter to Abbott, the agency has detailed the steps Abbott needs to take to correct the serious and significant manufacturing deviations. These include: -completing a thorough and adequate investigation of the reovirus and mycoplasma contamination, including the source of the contamination, -manufacturing Abbokinase using human kidney cells that have been obtained, processed, and tested through adequate methods, and –assuring that fully validated methods are used in the manufacturing process to test for infectious agents and remove them. Abbott submitted a supplemental new drug application providing for changes in procurement and processing of neonatal kidney cells, improvements in the manufacture and testing of the drug substance and drug product, revised release specifications for the drug substance and drug product, revised release specifications for the drug substance and drug product, a revised CBER lot release protocol, withdrawal of the “Open-Cath” dosage strengths, and revised labeling. Labeling revisions include updated information regarding product source and adverse reactions, as well as withdrawal of the coronary artery thrombosis and catheter clearance indication. The Department of Health and Human Services completed the review of that supplemental application, as amended, and it was approved based on Abbott’s written commitments, one of which is –To conduct a study to assess the immunogenicity of Urokinase after primary dosing. Urokinase is indicated in adults for the lysis of acute massive pulmonary emboli, defined as obstruction of blood flow to a lobe or multiple segments for the lysis of pulmonary emboli accompanied by unstable hemodynamics, i.e., failure to maintain blood pressure without supportive measures. Therefore, it is important to complete this study, to meet federal requirements, so that Urokinase could be fully marketed and help to improve the quality of life. Specific Aim. 1. To access the human antibody response to Urokinase, a thrombolytic agent in subjects treated for lower extremity ischemia. A.) Technique: All subjects will receive an intra-arterial infusion of a minimum of 240,000 IU of Urokinase (UK). In part A of this study we will obtain serum specimens from subjects receiving UK. These blood specimens will be used in part B of this study for the qualitative/quantitative assessment of antibody response to Urokinase, specifically IgM, IgE, IgG. Antibody directed against the UK drug substance, API, and the inactive peptides/protein in the formulation.Item Deltoid Opioid Receptor Phenotype Modulation of Hindlimb Vascular Conduction(2008-10-06) Barlow, Matthew A.; Raven, Peter B.; Gwirtz, Patricia A.; Dillon, Glenn H.Barlow, Matthew A. Deltoid Opioid Receptor Phenotype Modulation of Hindlimb Vascular Conduction. Doctor of Philosophy (Integrative Physiology), Oct 6th, 2008, 136 pp, 1 table 26 figures. Hypertension, diabetes mellitus and their presumed precursor the metabolic syndrome are part of a complex disease process associated with insulin resistance. Neurovascular complications in diabetics commonly involve the lower limbs resulting in a vicious cycle of autonomic neuropathy, painful occlusive claudication and resulting immobility that precipitates inactivity and progressive disability. The fixed neural and vascular diseases evolve slowly and the early events in this progressive decline in function are poorly understood. Sympathetic vasoconstriction is a major component of blood flow regulation in muscle. Active vasoconstriction in the lower limbs depends on continued transmission of efferent vasomotor signals through the lumbar sympathetic chain ganglia. Opioid receptors actively reduce normal ganglionic transmission presumably by lowering acetylcholine release. In the heart, the subtypes of delta-opioid receptors (DORs) facilitate (DOR-1, vagotonic) and inhibit (DOR-2, vagolytic) cholinergic transmission in the heart. The DOR-2 mediated inhibitory effects in heart are alterable and can change rapidly. Diabetes impairs vascular control. Ganglionic transmission is metabolically vulnerable during high fat feeding and insulin resistance. We hypothesized that the DOR-2 stimulation significantly facilitates vasodilation by reducing cholinergic transmission within the sympathetic chain ganglion. The ability to activate DOR-1 stimulation facilitates to cause further vasoconstriction in the anesthetized and surgically instrumented state of the dog did not show dose dependent activation. The DOR-1 activity in the insulin resistant dogs appears to be decreased as the DOR-1 blockade had no effect on the dose responses in the heart or the hindlimb. Enhanced sympathetic tone through BCO by increasing and reducing cholinergic transmission in the lumbar sympathetic ganglion shows an enhanced pro-constrictor phenotype under stresses of severe hypotension possibly through a DOR-1 mediated activation.Item Effects of Endurance Training on Aortic and Carotid Baroreflex Function(1999-06-01) Smith, Scott Alan; Peter B. Raven; Michael Smith; Patricia A. GwirtzSmith, Scott Alan, Effects of Endurance Training on Aortic and Carotid Baroreflex Function. Doctor of Philosophy (Biomedical Sciences), June 1999; 122 pp; 8 tables; 10 figures; bibliography, 148 titles. Arterial bareflex control of cardiac function is dependent upon afferent input from both the aortic arch and carotid sinus bareceptors. Extensive research in animals has generated conflicting results as to the range of arterial pressures over which each baroreflex operates. Further, the complex integration of afferent signals within the medullary cardiovascular center, in reference to aortic and carotid baroreceptor input, has been characterized as additive, inhibitory, and facilitatory in nature. Such reports make it difficult to draw definitive conclusions about the behavior or central neural processing within the brainstem. In addition, these relationships have yet to be examined in humans. Therefore, the purpose of the investigations described herein, was to quantify the range of pressures over which the arterial aortic and carotid baroreflexes operate as well as to describe the interactive relationship between the aortic and carotid baroreceptors. In order to investigate these questions, we isolated the arterial, aortic, and carotid-cardiac baroreflexes in volunteer subjects generating sigmoidal stimulus-response curves for each reflex arc. Arterial and aortic baroreflex (ABR) control of heart rate (HR) was assessed by inducing graded increases and decreases in mean arterial pressure (MAP) by bolus infusion of the vasoactive agents phenylephrine (PE) and sodium nitroprusside (SN), respectively. Carotid baroreflex (CBR) function was determined utilizing ramped five second pulses of both pressure and suction applied to the carotid sinus via a neck chamber collar, independent of drug administration. The MAP at which the threshold and saturation were elicited did not differ among the reflexes examined indicating each reflex operated over a similar range of arterial pressures. Further, the simple sum of the independently driven HR response ranges of the CBR and ABR was significantly greater than that produced when both baroreceptor populations were concomitantly stimulated (i.e. arterial baroreflex) suggesting an inhibitory interaction. To investigate differential baroreflex control of HR in response to chronic endurance exercise training, a second investigation was designed implementing the reflex isolation techniques described previously. Stimulus-response relationships were compared between high fit (maximal oxygen uptake, VO2max [greater than] 60ml˖kg-1˖min-1) and average fit (VO2maxml˖kg-1˖min-1) individuals. Interestingly, neither the range of operating pressures for each reflex nor the integrative relationship between the ABR and CBR were altered as a result of aerobic training. However, the HR response range elicited from the aortic baroreceptors as a result of hypotensive and hypertensive insult was markedly attenuated in the aerobically trained population compared to their sedentary counterparts, exclusively causing a requisite reduction in arterial baroreflex sensitivity.Item Effects of Testosterone on Obesity-Related Cardiac Hypertrophy and Fibrosis(2009-08-01) Wilson, Ana Kaye; Joan F. Carroll; James L. Caffrey; Robert T. MalletWilson, Ana Kaye. Effects of testosterone on obesity-related cardiac hypertrophy and fibrosis. Master of Science (Integrative Physiology), August 2009, 71 pp, 3 tables, 6 figures. Both testosterone and obesity are known to increase renin-angiotensin system activity, leading to cardiovascular dysfunction. This study determined the interactive effects of obesity and testosterone on left ventricular hypertrophy and cardiac fibrotic factors. Male New Zealand White rabbits were fed a lean or 10% added fat diet. After 12 weeks, fat-fed rabbits exhibited increased left ventricular weight (6.05±0.16 vs. 4.75±0.10 g, respectively, p≤0.05) and cardiomyocyte cross-sectional area compared to lean rabbits (372.3±19.0 vs. 305.0±13.4μm2, respectively; p≤0.01). These effects were attenuated by both castration and treatment with the angiotensin type 1 receptor blocker, losartan. Obese rabbits did not exhibit increased myocardial collagen as expected. However, castration and losartan treatment increased matrix metalloproteinase-2 (MMP-2) activity in obese rabbits. Despite the effects of castration hypertrophy and MMP-2 activity, castration did not attenuate plasma renin activity of aldosterone. These data suggest that testosterone contributes to obesity-related left ventricular hypertrophy and decreases collagen degradation, independent of renin activity.Item Endothelin-1-Induced Signaling Involved in Extracellular Matrix Remodeling(2006-12-01) He, Shaoqing; Thomas Yorio; Neeraj Agarwal; Peter KoulenET-1-Induced Signaling in ECM Remodeling in Astrocytes. Shaoqing He, Department of Pharmacology & Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107. ET-1 levels are elevated under pathophysiological conditions, including glaucoma, however, ET-1’s ocular functions are not fully documented. Therefore, ET-1-induced signaling and ECM remodeling in astrocytes and at the optic nerve head were determined in this study. Three signaling pathways, including ERK1/2, PKC, and P13 kinase, were involved in ET-1-medicated cell proliferation of U373MG astrocytoma cells. Blocking one of these pathways completely abolished cell proliferation. It appeared that ERK1/2 activation was involved, but was independent of PKC and P13 kinase activation by ET-1. It was also determined that the ETB receptor was the dominant receptor involved in ERK1/2 phosphorylation and cell proliferation. In addition, ERK1/2 phosphorylation was not transactivated by the EGF receptor by ET-1. The studies also indicated that there was no activation of c/nPKC, although PKC was involved in cell proliferation. In U373MG astrocytoma cells, MAPK-ERK, PKC and P13K pathways appear to exert their roles in parallel without a direct, apparent “cross-talk”. Based on the signaling pathways obtained from U373MG astrocytoma cells, the regulation of MMPs/TIMPs and fibronectin in ET-1-activated human optic nerve head astroctyes (hONAs) was also determined. ET-1 not only induced rapid phosphorylation of ERK1/2 and PKC βI/ βII/δ but also increased the activity of MMP-2 and the expression of TIMP=1 and 2. The activity of MMP-2 was enhanced in the presence of inhibitors of MAPK or PKC in hONAs, whereas the expression of TIMP-1 and 2 was abolished. ET-1 increased the soluble fibronectin (FN) expression as well as FN matrix formation, however, the expression and deposition of FN were MAPK- and PKC-independent, whereas expression and activity of MMps and TIMPs were MAPK- and PKC-dependent. Therefore, ET-1 shifted the balance of MMPs/TIMPs and substrates that altered the ECM composition and subsequently let to ECM remodeling in activated hONA cells. ET-1’s effects on ECM remodeling at the optic nerve head were also examined following intravitreal administration of ET-1 in rats. The increased expression of MMP-9 and collagen VI was detected in both ETB deficient rats and wildtype Wistar rats post ET-1 intravitreal injection for 2 and 14 days, whereas the deposition of FN and collagen IV was unchanged. There was no significant difference in staining of MMP-9 and collagen VI between ETB deficient rats and wildtype Wistar rats. In this study, ECM remodeling was demonstrated in rats injected with ET-1 into the vitreous. Such changes in the ECM seen in the current study provide additional insight into the mechanisms that might explain the glaucomatous changes observed in ET-1-injection or perfusion models. In summary, ET-1 not only activated several signaling pathways in cell proliferation of astrocytes, but also modulated the expression of ECM molecules in vitro and in vivo, indicating that ET-1 plays a regulatory role in ECM remodeling. These effects coupled with observations that ET-1 levels are elevated in glaucoma patients, suggests that ET-1 may be involved in glaucomatous optic neuropathy.Item Endurox R4® & Gatorade®: Effects of Recovery Drinks After Prolonged Glycogen-Depleting Exercise(1999-06-01) Williams, Michael Brandon; Raven, Peter B.; Smith, Michael; Shi, XiangrongWilliams, Michael B., Endurox R4® & Gatorade®: Effects of Recovery Drinks After Prolonged Glycogen-Depletion Exercise. Master of Science (Biomedical Sciences, Integrative Physiology), June, 1999, 73 pp., 2 tables, 18 figures, references. Purpose: Eight high-fit (bicycle Vo2max=62.4 ± 1.10 ml·kg-1·min-1) male cyclists, aged 28.4±1.65 yrs, performed a two-hour endurance bicycle exercise to achieve depletion of skeletal muscle and liver glycogen. During recovery, Endurox R4 Recovery Drink®, or Gatorade®, was ingested to investigate their relative restorative capacities to enable further exercise. Methods: Each subject performed two days of testing: one for each drink presented in random order. On each testing day, the twelve-hour fasted subject performed a two-hour cycling exercise bout at 75% VO2max followed by one to three five-minute sprints at 85% VO2max. At the end of the exercise blood glucose concentrations were 3.98±0.138 mmol/L. A four hour recovery period ensued in which the subject was given 24-ounces of the recovery drink. A performance test at 85% VO2max to exhaustion was then conducted. Ventilatory responses were collected breath-to-breath, while venous blood samples were measured for oxidation products, glucose and insulin concentrations. Results: The recovery phase showed significant increases in both plasma glucose and serum insulin following Endurox R4 Recovery Drink® ingestion as compared to Gatorade®. There was a significant increase in time to exhaustion (+55%) following Endurox R4 Recovery Drink® during the performance ride compared to Gatorade®. Final oxidation products following Endurox R4 Recovery Drink® ingestion were significantly decreased as compared to Gatorade® ingestion, in that Thiobarbituric Acid Reactive Substrates (T-BARS) were significantly decreased. Conclusions: These data indicate that the Endurox R4 Recovery Drink®, when compared to Gatorade®, significantly enhanced recovery from glycogen-depleting exercise. In addition, Endurox R4 Recovery® Drink decreased the formation of final oxidation products, when compared to Gatorade®.Item Hypoxic Conditioning Suppresses Cytotoxic Nitric Oxide Production Upon Myocardial Reperfusion(2007-05-01) Ryou, Myoung-Gwi; H. Fred Downey; Rong Ma; Raghu KrishnamoortyRyou, Myoung-gwi. Hypoxia conditioning suppresses nitric oxide production upon myocardial reperfusion. Master of Science (Integrative Physiology), May 2007, 61pp, 2 tables, 9 figures. This study was conducted in mongrel dogs to test the hypothesis that 20 d normobaric intermittent hypoxic conditioning (IHC) evokes cardioprotective adaptations of the myocardial nitric oxide synthase (NOS) system. Specifically, the proposal that IHC suppresses myocardial NOS activity sufficiently to dampen the cytotoxic burst of NO formation upon reperfusion of ischemic myocardium was tested. Mongrel dogs were conditioned by a 20 d program of IHC (FIO2 9.5-10%; 5-10 min hypoxia/cycle, 5-8 cycles/d with intervening 4 min normoxia). On day 21, ventricular myocardium was sampled for measuring NOS activity (colorimetric assay) and endothelial NOS (eNOS) content (immunoblot). In separate experiments, myocardial nitrite (NO2) release, an stable product of NO oxidation, was measured at baseline and during reperfusion following 1 h occlusion of the left anterior descending coronary artery (LAD). Values in IHC dogs were compared with respective values in non-conditioned, control dogs. IHC lowered left and right ventricular NOS activity by 60%, from 100-115 to 40-45 mU/g protein (P [less than] 0.01), and decreased eNOS content by 30%. IHC dampened cumulative NO2 release during the first 5 min reperfusion from 32 ± 7 to 14 ± 2 μmol/g (P [less than] 0.05), but did not alter hyperemic LAD flow (15 ± 2 vs. 13 ± 2 ml/g). Attenuation of the NOS/NO system may contribute to IHC-induced protection of myocardium from ischemia-reperfusion injury.Item Influence of the Carotid Baroreflex on Cerebral Blood Flow During Seated Upright Rest(2007-07-01) Eubank, Wendy L.; Peter B. Raven; Robert Mallet; James CaffreyEubank, Wendy L., Influence of Carotid Baroreflex on Cerebral Blood Flow During Seated Upright Rest. Master of Science (Integrative Physiology), July, 2007, 25 pp., 1 table, 4 illustrations, 34 references. This study tested the hypothesis that sympathetic activation via the carotid baroreflex directly influences cerebral vasomotion during seated upright test. This study also examined the effects of pulsatile neck pressure (NP) and neck suction (NS) during seated upright rest in healthy human subjects. Changes in mean arterial pressure (MAP) and mean middle cerebral arterial velocity (MCA V mean), were measured. The power spectral density (PSD) of MAP of 0.1Hz increased during pulsatile NP and NS. The PSD of MCA V mean at 0.1Hz was much greater during NP than that of NS. There were no significant differences between end-tidal CO2 between each condition. These findings suggest that cerebral vasoconstriction during NP was a result of the autoregulatory response to the NP mediated pulsatile changes in arterial pressure and the NP induced sympathetically mediated vasoconstriction.Item Influence of Thermoregulatory and Nonthermoregulatory Control Mechanisms of Arterial Blood Pressure During Recivert from Exercise in Humans(2001-05-10) Carter, Robert; Michael L. Smith; Robert L. Kaman; Thomas YorioCarter, III Robert, Thermoregulatory and nonthermoregulatory control of arterial pressure during recovery from exercise in humans. Doctor of Philosophy (Biomedical Sciences). May 2001; 153p; 4 tables, 17 figures; 100 titles. The mechanisms of arterial blood pressure control during exercise is well established; however, much less is known about the regulation of arterial blood pressure immediately after intense or prolonged dynamic exercise. Inactive recovery from dynamic exercise is associated with cessation of the primary exercise stimuli from the brain (central command), Skeletal muscle pumping, which contributes to increases in venous return during exercise is also stopped during inactive recovery from exercise. Thus, the skeletal muscle pump and central command each contribute importantly to elevation and maintenance of arterial blood pressure regulation and cerebral blood flow during exercise. When exercise is intense and/or prolonged, the resulting thermal load exacerbates the challenge to maintain arterial blood pressure and cerebral blood flow both during exercise and particularly during recovery from exercise and thereby increases the risk of syncope. Recently, we found that the skeletal muscle pump plays a major role in arterial blood pressure control during recovery from brief (3 min), mild (60% of maximal HR) exercise in which there was no thermal load. However, how the mechanisms of arterial pressure regulation operate during recovery from intense or prolonged exercise when a thermal load occurs is unknown. Therefore, the purpose of the investigations described herein, was to quantify the mechanisms of the carotid baroreflex function, central command, and the skeletal muscle pump when a thermal stress occurs on arterial blood pressure regulation during recovery from exercise in humans. In addition, differences in arterial blood pressure regulation in women and men during recovery from exercise were addressed in women and men. To investigate these mechanisms, we investigated the carotid-cardiac baroreflex function, cardiovascular, and thermoregulatory responses in volunteer subjects during inactive and active recovery from prolonged exercise improved the function of the baroreflex by increasing the functional reserve of the reflex to buffer against hypotensive stimuli. Our data also suggest that thermoregulatory factors contribute to decreases in MAP after inactive recovery from exercise. In addition, the metabolic state of skeletal muscle during longer duration exercise (15 min) may contribute to these responses during inactive recovery from exercise. These results support the hypothesis that thermal stress contributes to the rapid decreases in arterial blood pressure during inactive recovery following dynamic exercise. To investigate gender differences in arterial pressure regulation during recovery from exercise, we compared 11 women and 8 men during 3 min of exercise and 5 min of inactive and active recovery from exercise. Interestingly, at 1 minute after exercise, MAP decreased less during inactive recovery in men when compared to women. This difference was due to greater decreases in SV and less increase in TPR during inactive recovery from exercise in women compared to men. MAP decreased less during active recovery in men when compared to women. These findings suggest that women may have increased risk of post-exercise orthostatic hypotension and that active recovery from exercise may reduce this risk.Item Intermittent hypoxia induced opioidergic protection of the heart(2015-08-01) Estrada, Juan A.; Robert T. Mallet; Steve W. Mifflin; J. Thomas CunninghamNormobaric intermittent hypoxia conditioning (IHC) induces a robust cardioprotected phenotype in dogs that is remarkably resistant to ischemia and reperfusion induced myocardial infarction and lethal arrhythmias. Previous studies demonstrated that IHC induced cardioprotection requires β1-adrenergic receptor activity. Cardiac opioid systems are stimulated by, and counteract the harmful effects of, excessive stressors such as sympathetic activity. Additional modes of hypoxic conditioning have been shown to induce synthesis of cardiac enkephalins and delta opioid receptors (DOR). The hypothesis that DOR mediates IHC cardioprotection was examined in two studies conducted in intermittent hypoxia conditioned and non-hypoxic sham dogs. For the first study dogs were assigned to groups subjected to non-hypoxic sham conditioning, IHC, IHC plus the aminothiol antioxidant N-acetylcysteine (NAC), and IHC plus the DOR antagonist naltrindole. After IHC or sham conditioning, the dogs were subjected to an left anterior descending coronary artery occlusion/reperfusion protocol and incidence of reperfusion arrhythmias and myocardial infarct size were measured and adjusted for coronary collateral flow. Naltrindole and NAC abolished the anti-infarct and anti-arrhythmia effects of IHC, in a manner independent of collateral blood flow. Intermittent hypoxia conditioning is thus dependent on DOR activity as well as formation of reactive oxygen species (ROS) during cylic hypoxia-reoxygenation. Whether ROS are generated upstream, downstream, or in parallel to DOR activation remains to be determined. DORs are abundant on dog parasympathetic nerves and therefore are ideally positioned to stimulate cardioprotective cholinergic activity. However it is unknown in what direction IHC modulates bimodal DORs, i.e. modulation of synaptic inhibitory or excitatory activity. In the second study dogs were assigned to sham conditioned, IHC, and IHC plus naltrindole groups. IHC resulted in a profound enhancement of vagal bradycardia, in the absence and presence of increasingly vagolytic doses of the DOR agonist MEAP. This result demonstrated that IHC shifts DOR signaling in favor of the vagotonic DOR-1 receptor subtype. However, the fate of the vagolytic DOR-2 receptors was unknown. Immunolabeling of atrial tissue revealed that IHC increased content of the monosialoganglioside GM1 in autonomic nerve fibers associated with parasympathetic fibers, an effect which may shift DOR signaling in favor of the DOR-1 subtype. In addition, IHC increased the number of fibers containing the vesicular acetylcholine transporter within the sinoatrial node. However, DOR positive fibers in both the atria and SAN were decreased after IHC, perhaps reflecting redistribution or intracellular trafficking of DOR1 and/or DOR2 receptors. Immunoblotting revealed decreased content of adrenergic protein tyrosine hydroxylase in the left ventricle following IHC. Collectively, these results indicate IHC is dependent on opioidergic activity to induce cardioprotection by enhancing cholinergic signaling components at the expense of adrenergic proteins, suggesting IHC-induced shifting of autonomic balance in favor of parasympathetic control of the heart.Item Local Enkephalins Modulate Vagal Control of Heart Rate(2001-05-01) Jackson, Keith E.; James L. Caffrey; H. Fred Downey; Michael W. MartinJackson, Keith E., Local Enkephalins Modulate Vagal Control of Heart Rate. Doctor of Philosophy (Biomedical Sciences), May 2001; 112pp; 7 tables; 22 figures; bibliography, 99 titles. Endogenous opioids, such as enkephalins, were first investigated for their ability to modulate pain. A body of evidence now supports opioid actions in many facets of regulation, including the cardiovascular system. Our laboratory is particularly interested in the ability of opioids to modulate autonomic function. Specifically, the role of the endogenous encephalin, methionine-enkephalin-arginine-phenylalanine (MEAP) was investigated to determine its ability to modulate parasympathetic function in the canine. To investigate MEAP’s response in the sinoatrial (SA) node a novel application of microdialysis was employed, whereby microdialysis was employed, whereby microdialysis probes were fabricated as described by Dr. David Van Wylen (38), and implanted in the SA node. After implantation of the probe, there was a significant attenuation of vagal function during the nodal application of MEAP. Specifically, vagally mediated bradcardia was reduced as compared to control, during the nodal application of MEAP. This inhibition of the vagus by MEAP was blocked by naltrindole, a selective delta antagonist. These data suggested that the vagolytic effects of MEAP were elicited via a delta opioid receptor. To test the hypothesis that MEAP’s effects were elicited through a delta opioid receptor mechanism, selective agonists and antagonists for the opioid receptors were utilized. An attenuation of vagal bradycardia was only observed during the infusion of a very selective delta opioid receptor agonist, deltorphin. A mu and kappa agonist showed no significant differences from control. Deltorphin was observed to elicit vagolytic effects in a similar concentration range as MEAP. However, deltorphin was more efficacious that MEAP. There was a significant attenuation of the deltorphin and MEAP’s vagolytic effects, during the co-infusion of the selective delta antagonist, naltrindole. The mu and kappa antagonists were both ineffective. These data further demonstrate that the observed vagolytic effect is linked to a delta opioid receptor. Endogenous MEAP. A series of experiments were undertaken to determine if endogenous MEAP could be demonstrated in the SA node and is so, was it similarly vagolytic. A preconditioning-like protocol was performed to produce intermittent local nodal ischemia to increase the local concentration of endogenous MEAP. The resulting MEAP was measured and was observed to be elevated during the periods of local nodal ischemia and return to control during reperfusion. Contrary to expectations an augmentation of vagal function was observed, during vagal stimulation. The augmented vagal bradycardia was only observed during ischemia, when MEAP was elevated and returned to control during each subsequent reperfusion. Therefore, there was a correlation between elevated MEAP concentrations and augmented vagal bradycardia. The delta antagonist, naltrindole, prevented the augmented vagal response, during nodal ischemia Glibenclamide, a selective KATP channel blocker, partially reversed the augmented vagal response. These data confirm that delta opiate receptors are involved in the augmented vagal bradycardia and that the mechanism may involve the activation of a KATP channel.Item Mechanisms of Chemoreflex Control of Muscle Sympathetic Nerve Activity and Blood Pressure in Humans(2004-05-01) Hardisty, Janelle M.; Smith, Michael; Shi, Xiangrong; Clark, MichaelHardisty, Janelle M., Mechanisms of Chemoreflex Control of Muscle Sympathetic Nerve Activity and Blood Pressure in Humans. Doctor of Philosophy (Integrative Physiology), May 2004. The mechanisms linking obstructive sleep apnea (OSA) and cardiovascular disease are not fully understood; however, studies report patients with OSA exhibit chronic elevations in muscle sympathetic nerve activity (MSNA). This appears to be due to altered chemoreflex control of MSNA, mediated primarily by hypoxia. Yet, a correlation between degree of hypoxia and chemoreflex control of MSNA is unknown. Therefore, it was evaluated whether degree of hypoxia occurring during apnea determines the sympathoexcitatory and blood pressure responses, and whether these responses are augmented in OSA patients. Additionally, it was studied whether altered chemoreflex function in OSA patients is predictive of blood pressure response to apnea. In a clinical setting, the blood pressure response to voluntary apnea was determined to evaluate whether this could be used as a non-invasive measure of chemoreflex gain in OSA. Finally, the effect of hyperoxia on MSNA was studied to determine whether 15 min of hyperoxia, following intermittent hypoxic apnea, reverses the elevation of MSNA and altered chemoreflex control of MSNA. Consistent with the hypotheses, a relationship between MSNA responses, blood pressure response and level of hypoxia were determined. MSNA and peak systolic pressure responses were augmented in OSA subjects (p≤0.05 and p≤0.05, respectively), as well as, chemoreflex gain (p≤0.05). Clinically, peak systolic pressure responses to apnea were augmented in OSA patients (p˂0.001). Finally, basal MSNA and chemoreflex control of MSNA, following hyperoxia, was not different from baseline through 180 min of recovery (p=0.940 and p=0.278, respectively). These data support the hypotheses that chemoreflex gain is predicative of the blood pressure response; and furthermore, the MSNA and blood pressure responses to hypoxic apnea are augmented in OSA. Additionally, peak systolic pressure responses to voluntary apnea are augmented in OSA. Additionally, peak systolic pressure responses to voluntary apnea are augmented in OSA patients and could possibly be used as a marker of chemoreflex gain. Moreover, these data support the hypothesis that hyperoxia can reverse basal sympathoexcitation and augmented chemoreflex control of MSNA, associated with hypoxic apnea, supporting that elevations in MSNA are hypoxia mediated.Item Molecular Regulation of Wound Contraction and Scar Formation Using a Three-Dimensional Connective Tissue Model(2002-12-01) Kern, Jami RaDel; Thomas Yorio; Robert W. Gracy; Peter B. RavenKern, Jami RaDel, Molecular Regulation of Wound Contraction and Scar Formation Using a Three-Dimensional Connective Tissue Model. Doctor of Philosophy (Biomedical Sciences, Biochemistry and Molecular Biology), December 2002, 156 pp., 1 table, 27 illustrations, references, 112 titles. The focus of these studies was to characterize a novel connective tissue model for use in experiments examining possible contraction initiators in the wound healing process, i.e. endothelin-1 (ET-1). Through these studies, it has been shown that use of a telomerized dermal fibroblast cell line addresses the concerns relating to variations due to heterogeneity of normal human cells cultured in vitro, without creating a cancerous cell line or interfering with normal phenotypic changes. In addition, the incorporation of telomerized cells into our TE, which does not spontaneously contract (US Patent #6471958), provides a unique model to study the contraction and scar formation process. Using the TE populated with hTERT fibroblasts, an innovative technique was developed to identify the initiation of tissue contraction using an optical fiber interferometry system. The process allows observation of contraction within five minutes of stimulus addition and also enables continuous data capture over a period of several hours. The greatest strength of this system is its sensitivity, since optic interferometer allows measurement of displacement (contraction) to the tens of nanometers. Along those lines, the current studies have identified ET-1 as a potential early initiator in wound healing and suggest a novel pathway through which it functions. This proposed mechanism includes both direct effects of ET-1 through the Rho-associated kinase pathway and indirect effects potentiated by TGF-β. Future studies addressing whether TGF-β converges on the Rho-associated kinase pathway or acts independently through other signaling mechanisms should be initiated. The discovery of early initiators of tissue contraction is essential in the identification of potential therapeutic targets in the quest to reduce prolonged and severe tissue contracture and scaring.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 Nitric Oxide Contributes to Right Coronary Vasodilation During Systemic Hypoxia(2003-08-01) Martinez, Rodolfo B.; Downey, H. Fred; Mallet, Robert T. ; Singh, MeharvanMartinez, Rodolfo Randy. Nitric Oxide Contributes to Right Coronary Vasodilation During Systemic Hypoxia. Master of Science (Biomedical Sciences), August, 2003, 85 pp., 1 table, 5 figures, references, 121 titles. Background: Hypoxia increases right ventricular (RV) work, as arterial O2 is reduced. Mechanisms responsible for RV O2 supply/demand balance during hypoxia have not been delineated. To address this problem, right coronary blood flow (RCF) was directly measured, for the first time, in conscious, instrumented dogs exposed to acute hypoxia. Since we have found that nitric oxide (NO) contributes to RV O2 supply/demand balance during acute pulmonary hypertension, we investigated the role of NO in hypoxia-induced coronary hyperemia. Methods: Nine mongrel dogs were chronically instrumented. Briefly, catheters were placed in the RV for measuring pressure, in the ascending aorta for measuring arterial pressure and for sampling arterial blood and in a right coronary vein in order to obtain right coronary venous blood. A flow transducer was placed around the right coronary artery. After recovery from surgery, the dogs were exposed to normobaric hypoxia in a Plexiglas chamber ventilated with N2. O2 in the chamber was monitored, and blood samples and hemodynamic data were collected as chamber O2 was reduced progressively to 8-10%. Following control measurements, the chamber was opened and the dog allowed to recover. LNA was then administered (35mg/kg, via RV catheter) to inhibit nitric oxide production, and the hypoxic protocol was repeated. Results: RCF increased exponentially as PaO2 decreased. To normalize changes in arterial pressure, RC conductance was computed from the ration of RCF and arterial pressure. LNA blunted the hypoxia-induced increase in conductance. RV O2 extraction remained constant as PaO2 was decreased but extraction increased when after LNA. Hypoxia increased RV myocardial oxygen consumption (MVO2), but LNA decreased RV MVO2 any respective PaO2. Analysis of RC conductance as a function of RV MVO2 confirmed that LNA depressed the slope of the conductance/MVO2 relationship (P-0.03). Conclusion: Increases in RV MVO2 during hypoxia are met by increasing right coronary blood flow. In the absence of NO, myocardial supply/demand balance during hypoxia was maintained by increasing flow and extraction. Nitric oxide contributes to RC vasodilation and thus helps to maintain RV oxygen supply/demand balance during systemic hypoxia.Item Pyruvate-Enriched Ringer's Solution Protects Hindlimb and Myocardial Tissue During Hemorrhagic Shock and Hindlimb Ischemia(2011-07-22) Gurji, Hunaid Adam; Mallet, Robert T.; Olivencia-Yurvati, Albert; Raven, Peter B.Gurji, HA. Pyruvate-Enriched Ringer’s Solution Protects Hindlimb and Myocardial Tissue During Hemorrhagic Shock and Hindlimb Ischemia. Doctor of Philosophy (Integrative Physiology), July 22, 2011, 111 pp, 1 table, 23 figures, 209 references, 142 titles. Copious blood loss is the leading cause of death in military combat. Extreme exsanguination following traumatic injury causes hypotension which may culminate in hemorrhagic shock, multiple open organ failure, and death. Currently, the only available strategy to treat hemorrhage is to apply tourniquets and administer resuscitative fluids. Although necessary to limit blood loss, protracted tourniquet application imposes ischemia on distal tissues. Revascularization of the injured limb reintroduces oxygenated blood into the ischemic zone, forming toxic reactive oxygen species. These highly reactive compounds can inactivate key metabolic enzymes, hamper ATP production, and cause end organ dysfunction. Fluid resuscitation provides crucial hemodynamic support, and affords an opportunity to treat the deleterious effects of hemorrhagic shock and ischemia-reperfusion. In order to mitigate the harmful effects of hemorrhagic shock and ischemia-reperfusion of tourniqueted extremities, a fluid resuscitant should contain agents capable of suppressing the formation of reactive oxygen and nitrogen species, thus protecting cellular metabolic function; stabilizing tissue energetics; and safeguarding end organic function. Pyruvate, an endogenous energy substrate, possesses strong antioxidative properties. This study tested whether substituting pyruvate for lactate in a Ringer’s solution would be effective at mitigating reactive oxygen species formation, protect key ATP-generating and ATP-shuttling enzymes from inactivation, bolster skeletal and cardiac muscle phosphorylation potentials, and stabilize cardiac electrical function in goats subjected to hemorrhagic shock and hindlimb ischemia-reperfusion. Isoflurane-anesthetize goats were subjected to a controlled hemorrhaged to reduce the mean arterial pressure to c. 50 mmHg. After reaching this target pressure, hindlimb ischemia (HLI) was imposed for a total of 90 min by femoral artery crossclamp and tourniquet application around the hindlimb. After 30 min of hindlimb ischemia, pyruvate- (PR) or lactate- enriched (LR) Ringer’s solution was infused intravenously (10mL/min) for 90 min. Time control (TC) goats were neither hemorrhaged nor subjected to hindlimb ischemia. At the conclusion of- and 3.5 h after- fluid resuscitation, the left ventricle and the right gastrocnemius were biopsied and flash-frozen for biochemical analysis of metabolites, enzymes, and markers of oxidative stress. In addition, custom-written software was developed to analyze QT interval variability- a marker of electrical instability- from the lead II electrocardiogram. The first phase of this project tested the hypothesis that resuscitation with PR vs. LR effectively protects cardiac metabolism and preserves cardiac electrical performance during hemorrhagic shock and hindlimb ischemia. Resuscitation with PR effectively suppressed the formation of myocardial tissue 8-isoprostane vs. goats resuscitated with LR during the acute and subacute phases of the protocol. In addition, myocardial creatine kinase (CK) activity fell after LR administration vs. TC; however, PR preserved CK activity better than LR during fluid resuscitation and 4 h after hindlimb ischemia reperfusion. PR administration augmented myocardial phosphocreatine phosphorylation potential during fluid administration and 3.5 h later to values significantly higher than those in LR-resuscitated goats. Pro-arrhythmic QTc variability was markedly increased in LR vs. PR and TC during both phases of the protocol. The second phase of this project tested the hypothesis that resuscitation with PR preserves tissue energetics in the reperfused gastrocnemius during hemorrhagic shock and hindlimb ischemia. Resuscitation with PR vs. LR effectively protected the gastrocnemius from oxidative stress in both protocols, as evidenced by the suppression of 8-isoprostane formation. PR prevented CK and aconitase inactivation vs. LR during the acute phase of reperfusion, and this enzyme protection persisted at least 3.5 h after completing fluid resuscitation. Additionally, PR augmented muscle phosphocreatine phosphorylation potential vs. TC and LR during the acute phase of reperfusion, and, like CK and aconitase activities, this augmented energy state persisted 3.5 h after the end of fluid resuscitation. We conclude that 1) Pyruvate Ringer’s resuscitation during hemorrhagic shock and hindlimb ischemia provides antioxidative protection in skeletal and cardiac muscle during fluid resuscitation; 2) Pyruvate-fortified fluid resuscitation prevents inactivation of enzymes involved in production and shuttling of ATP; 3) PR augments cardiac and muscle phosphorylation potentials during fluid resuscitation; and 4) Resuscitation with PR effectively protects cardiac electrical rhythm in the face of hemorrhagic shock and hindlimb ischemia. These investigations demonstrate the powerful antioxidative protection imposed by pyruvate, its positive effects on muscle and cardiac metabolism and energy state and its role in stabilizing cardiac electrical function during hemorrhagic shock and hindlimb ischemia.