S Bina

Uniformed Services University of the Health Sciences, Maryland, United States

Are you S Bina?

Claim your profile

Publications (32)102.61 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND:Mutations in the ryanodine receptor type 1 gene (RYR1) that encodes the skeletal muscle-specific intracellular calcium (Ca(2+)) release channel are a cause of malignant hyperthermia (MH). In this study, we examined RYR1 mutations in a large number of North American MH-susceptible (MHS) subjects without prior genetic diagnosis.METHODS:RYR1 was examined in 120 unrelated MHS subjects from the United States in a tiered manner. The α-1 subunit of the dihydropyridine receptor gene (CACNA1S) was screened for 4 variants in subjects in whom no abnormality was found in ≥100 exons of RYR1.RESULTS:Ten known causative MH mutations were found in 26 subjects. Variants of uncertain significance in RYR1 were found in 36 subjects, 16 of which are novel. Novel variants in both RYR1 and CACNA1S were found in the 1 subject who died of MH. Two RYR1 variants were found in 4 subjects. Variants of uncertain significance were found outside and inside the hotspots of RYR1. Maximal contractures in the caffeine-halothane contracture test were greater in those who had a known MH mutation or variant of uncertain significance in RYR1 than in those who did not.CONCLUSIONS:The identification of novel RYR1 variants and previously observed RYR1 variants of uncertain significance in independent MHS families is necessary for demonstrating the significance of these variants for MH susceptibility and supports the need for functional studies of these variants. Continued reporting of the clinical phenotypes of MH is necessary for interpretation of genetic findings, especially because the pathogenicity of most of these genetic variants associated with MHS remains to be elucidated.
    Anesthesia and analgesia 04/2013; · 3.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A healthy 6-year-old boy developed lower extremity rigidity, trismus, and fever after playing in a splash pool. On arrival in the emergency department, he appeared to be seizing. An endotracheal tube was emergently placed using succinylcholine. Cardiac arrest followed. He could not be resuscitated. Postmortem genetic analysis found a novel RYR1 variant. Family testing revealed the same variant in his father who also had muscle contracture testing diagnostic for susceptibility to malignant hyperthermia and central core disease diagnosed histologically. Because there was no exposure to volatile anesthetics before the onset of symptoms, this is a case of "awake" malignant hyperthermia worsened by succinylcholine.
    Anesthesia and analgesia 12/2012; · 3.08 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mutations in the type 1 ryanodine receptor gene (RYR1) result in malignant hyperthermia, a pharmacogenetic disorder typically triggered by administration of anesthetics. However, cases of sudden death during exertion, heat challenge, and febrile illness in the absence of triggering drugs have been reported. The underlying causes of such drug-free fatal "awake" episodes are unknown. De novo R3983C variant in RYR1 was identified in two unrelated children who experienced fatal, nonanesthetic awake episodes associated with febrile illness and heat stress. One of the children also had a second novel, maternally inherited D4505H variant located on a separate haplotype. Effects of all possible heterotypic expression conditions on RYR1 sensitivity to caffeine-induced Ca release were determined in expressing RYR1-null myotubes. Compared with wild-type RYR1 alone (EC50 = 2.85 ± 0.49 mM), average (± SEM) caffeine sensitivity of Ca release was modestly increased after coexpression with either R3983C (EC50 = 2.00 ± 0.39 mM) or D4505H (EC50 = 1.64 ± 0.24 mM). Remarkably, coexpression of wild-type RYR1 with the double mutant in cis (R3983C-D4505H) produced a significantly stronger sensitization of caffeine-induced Ca release (EC50 = 0.64 ± 0.17 mM) compared with that observed after coexpression of the two variants on separate subunits (EC50 = 1.53 ± 0.18 mM). The R3983C mutation potentiates D4505H-mediated sensitization of caffeine-induced RYR1 Ca release when the mutations are in cis (on the same subunit) but not when present on separate subunits. Nevertheless, coexpression of the two variants on separate subunits still resulted in a ∼2-fold increase in caffeine sensitivity, consistent with the observed awake episodes and heat sensitivity.
    Anesthesiology 09/2011; 115(5):938-45. · 5.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lipid emulsion (20%) is advocated as a rescue drug for local anesthetic toxicity. No study has measured the impact of lipid emulsion therapy on postmortem local anesthetic serum levels. We anesthetized Yorkshire swine (n = 11) and standard monitors were placed. The swine received 1.5 mg/kg/min IV ropivacaine until death (asystole). Blood samples were drawn before infusion (baseline) and at 5-minute intervals during the infusion for measurement of blood gases and free, bound, and total serum ropivacaine concentrations via high-performance liquid chromatography. Five swine received ropivacaine only, and 6 swine received ropivacaine plus a single bolus dose of 20% lipid emulsion (1 mg/kg) when the mean arterial blood pressure reached 50 mm Hg. Ropivacaine infusions were terminated at asystole and no resuscitation was initiated. Total ropivacaine dose and time to death were recorded. The swine were cooled (mean temperature, 25.5°C ± 0.8°C at 6 hours postmortem) to reflect morgue conditions. Serum samples were drawn at asystole, 1, 3, and 6 hours postmortem for analysis. Additionally, a craniotomy and laparotomy were performed at those times to remove 1.5 to 3 g each of brain, lung, liver, kidney, and muscle for analysis. Analysis of the postmortem serum ropivacaine concentrations in the control and the lipid-treated animals indicated that both the total (bound and not bound to proteins) and free (not bound to proteins) ropivacaine concentrations were significantly higher in the lipid-treated animals (P = 0.0094 and P = 0.0063, respectively). Furthermore, time had a significant effect on increasing the postmortem free ropivacaine concentrations (P = 0.0095). The lipid group had a statistically significant earlier onset of death (asystole) compared with the control group (P = 0.0274). Tissue analysis indicated that the ropivacaine concentration significantly decreased postmortem in the lung, kidney, and brain tissues of the lipid-treated animals (P = 0.0168, P = 0.0073, and P = 0.0018, respectively). Tissue drug concentrations in the control animals remained unchanged after death. Our data show that postmortem blood samples in swine that experience local anesthetic cardiovascular collapse and are treated with lipid emulsions will result in measurements that cannot be directly extrapolated to premortem drug concentrations.
    Anesthesia and analgesia 08/2011; 114(4):894-900. · 3.08 Impact Factor
  • Biophysical Journal 01/2011; 100(3). · 3.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Malignant hyperthermia susceptibility (MHS) is diagnosed by an invasive in vitro caffeine-halothane contracture test (CHCT) carried out on biopsied skeletal muscle tissue. We are presenting a novel blood test approach for malignant hyperthermia testing in a swine model. Our main aim was to determine whether adenosine production from lymphocytes after 4-chloro-m-cresol (4CmC) stimulation distinguishes homozygous swine carrying the Arg615Cys mutation in the ryanodine receptor type 1 (RyR1) gene (MHS swine) from normal swine. Lymphocytes were isolated from arterial blood (40 ml) obtained from MHS (n = 7) and normal (n = 7) swine. Cells were suspended in Hank's balanced salt solution and treated with 4CmC (0-10 mm) at 37°C in the presence of adenosine deaminase inhibitor. After termination and purification of samples, aliquots (50 μl) were assayed for adenosine content using high performance liquid chromatography. Baseline adenosine levels before stimulating lymphocytes with 4CmC were 0.025 ± 0.004 and 0.041 ± 0.006 μm (mean ± SEM) in lymphocytes from normal and MHS swine, respectively (P = 0.125). Maximum responses were achieved at 1 mm 4CmC for both cell-line groups. Adenosine levels after stimulation with 4CmC (1 mm) were 0.185 ± 0.009 and 0.397 ± 0.038 μm in lymphocytes from normal and MHS swine, respectively (P = 0.0035). There was no overlap between adenosine levels in stimulated lymphocytes from MHS and normal swine. 4CmC stimulation of porcine lymphocytes induces increased adenosine formation in MHS cells relative to those from normal swine; evaluation of adenosine formation in response to RyR1 agonists in human lymphocytes is needed.
    Anesthesiology 10/2010; 113(4):917-24. · 5.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ropivacaine is a long-acting local anesthetic used frequently for peripheral nerve blocks and continuous peripheral nerve block catheters. Combat trauma patients at Walter Reed Army Medical Center often receive continuous peripheral nerve block catheters as part of their pain regimen. These catheters remain in situ for several days to weeks. In this study, we evaluated the free ropivacaine drug levels over time in trauma patients by measuring the serum concentration of bound and unbound local anesthetic. The corresponding alpha(1)-acid glycoprotein concentration in patients with prolonged ropivacaine infusions was also measured. Fifteen patients were enrolled in the study; 2 patients were excluded because only a single ropivacaine level was obtained. Of the remaining 13 patients in the study, 2 had peripheral nerve catheters placed at the time of enrollment; the remaining 11 patients had catheters placed before enrollment. These patients were already receiving 0.2% ropivacaine infusions for a period of 18-126 h before the first assessment of local anesthetic level. Catheters infused 0.2% ropivacaine at a rate of 6-14 mL/h; catheter boluses were administered with 0.5% ropivacaine. Local anesthetic blood concentrations were scheduled to be measured on Days 1, 3, 5, 7, and 10 and every 3 days thereafter until all catheters were removed, although not all patients underwent each assessment. Specimens were assayed using high-performance liquid chromatography for total and free serum ropivacaine concentrations. Alpha(1)-acid glycoprotein was also measured. Thirteen patients remained in the study, for a total of 59 blood samples. The median number of days catheters remained in situ for the duration of acute pain therapy was 7 days (range: 6-27 days). The median number of days catheters remained in situ after enrollment into the study was 7 days (range: 4-25 days). The median number of blood samples collected per patient was 4 (range: 2-10 samples). Two patients had isolated increased concentrations of free ropivacaine into a previously identified toxic range with no obvious mitigating factors; both patients had received a 300-mg bolus of 0.5% ropivacaine approximately 24 h before that blood collection. The median ropivacaine concentration over the length of the study was 0.11 mg/L (range: undetectable to 0.63 mg/L). During the first week of the study, the median change in ropivacaine concentration per patient was 0.00 mg/L (range: -0.35 to 0.47 mg/L). Although 2 patients demonstrated isolated serum ropivacaine concentration spikes into a previously identified toxic range, continuous peripheral nerve block catheter management and local anesthetic doses as practiced at Walter Reed Army Medical Center did not result in clinically evident systemic ropivacaine toxicity. There was no correlation between free ropivacaine concentration and alpha(1)-acid glycoprotein concentration except in patients who had already been receiving ropivacaine infusions before entering the study. Despite this lack of correlation, the total duration of local anesthetic infusion did not seem to influence the free concentration of the drug.
    Anesthesia and analgesia 12/2009; 110(2):630-4. · 3.08 Impact Factor
  • Anesthesiology 12/2009; 112(1):239-44. · 5.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: It has been suggested that exertional rhabdomyolysis (ER) and malignant hyperthermia (MH) are related syndromes. We hypothesize that patients with unexplained ER harbor mutations in the ryanodine receptor gene type 1 (RYR1), a primary gene implicated in MH, and therefore ER patients are at increased risk for MH. Although there are reported cases of MH in individuals of African descent, there are no data available on molecular characterization of these patients. We analyzed RYR1 in six, unrelated African American men with unexplained ER, who were subsequently diagnosed as MH susceptible (MHS) by the Caffeine Halothane Contracture Test. Three novel and two variants, previously reported in Caucasian MHS subjects, were found in five studied patients. The novel variants were highly conserved amino acids and were absent among 230 control subjects of various ethnic backgrounds. These results emphasize the importance of performing muscle contracture testing and RYR1 mutation screening in patients with unexplained ER. The MHS-associated variant Ala1352Gly was identified as a polymorphism predominant in individuals of African descent. Our data underscore the need for investigating RYR1 across different ethnic groups and will contribute to interpretation of genetic screening results of individuals at risk for MH.
    Clinical Genetics 10/2009; 76(6):564-8. · 4.25 Impact Factor
  • S Bina, S Muldoon, R Bünger
    [Show abstract] [Hide abstract]
    ABSTRACT: The caffeine/halothane contracture test in North America and the in vitro contracture test in Europe are currently the only validated bioassays for diagnosing malignant hyperthermia susceptibility and phenotyping families. Both tests are invasive requiring surgical muscle biopsy. Here, we report first use of the selective ryanodine receptor type I agonist ryanodine in a percutaneous microdialysis protocol designed to test whether microdialysis-induced local metabolic responses of skeletal muscle due to ryanodine receptor activation can differentiate between malignant hyperthermia-sensitive and normal pigs. Six microdialysis catheters were implanted percutaneously into the adductor muscles of the right and left thighs of malignant hyperthermia-susceptible (n = 9) and normal (n = 8) anaesthetized (ketamine/propofol) and mechanically ventilated swine. Systemic blood gases, haemodynamic parameters and creatine kinase levels were measured before, during and after microdialysis perfusion of ryanodine. After a post-implantation equilibration period of 30 min, one catheter perfused (2 micro min-1) with 0.9% NaCl (control) and was compared with the remaining five catheters perfused with increasing concentrations of ryanodine (0.2-100 micromol). Lactate and pyruvate levels were measured enzymatically. Continuous perfusion with ryanodine revealed dose-dependent sigmoidal increases in the dialysate lactate and lactate-pyruvate ratio parameters; these effects were greatly augmented in malignant hyperthermia-susceptible pigs compared to normal pigs (two- to threefold): estimated EC50 greatly decreased (>19-fold) while the maximum effect increased (>twofold) in the malignant hyperthermia-susceptible group. The in vivo percutaneous microdialysis protocol for skeletal muscle, using ryanodine as the ryanodine receptor type I agonist and dialysed lactate-pyruvate parameters as metabolic index, can reproducibly differentiate between malignant hyperthermia-susceptible and normal swine.
    European Journal of Anaesthesiology 01/2008; 25(1):48-57. · 2.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Skeletal muscle fibers from malignant hyperthermia (MH)-susceptible humans and swine are markedly more sensitive to ryanodine receptor (RyR1) agonists than those from normal individuals. Reproducible shifts in the dose-response of skeletal muscle to caffeine and halothane are the basis of the current in vitro diagnostic caffeine-halothane contracture test. In an attempt to develop a less invasive MH diagnostic test, the authors determined the effects of RyR1 agonists (caffeine, 4-chloro-m-cresol [4CmC], and halothane) on the adductor muscle with respect to the lactate-pyruvate (L/P) system that was percutaneously dialyzed using a microdialysis technique in homozygous MH-susceptible compared with normal swine. Animals were anesthetized (ketamine-propofol) and artificially ventilated. Sets of six CMA/20 microdialysis catheters were implanted; each catheter was perfused with different RyR1 agonist concentrations. After a 30-min equilibration after implantation, one of the catheters was perfused (2 microl/min) with vehicle (0.9% saline or lipid emulsion), and the other five were perfused with caffeine (1-64 mM), 4CmC (0.1-8 mM), or halothane (prepared in lipid emulsion; 10-500 mM). Outflow dialysate fractions collected at 10-min intervals and L/P parameters were measured enzymatically. Only in the MH-susceptible group did all RyR1 agonists increase dialysate L/P in a dose-dependent manner. The dose-effect relations were most prominent with 4CmC. With the halothane lipid emulsion, data scatter was high compared with that of the caffeine group and especially the 4CmC group. There were no signs of global muscle rigidity, systemic hypermetabolism, or a clinical MH episode during microdialysis RyR1 perfusion. The authors data demonstrate that the in vivo muscle microdialysis of the porcine L/P system reveals distinct differences between MH-susceptible and MH-normal muscle, especially in response to highly specific RyR1 agonists such as 4CmC. The microdialysis L/P technique seems to have an MH diagnostic potential in the clinical setting.
    Anesthesiology 02/2006; 104(1):90-100. · 5.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The caffeine halothane contracture test (CHCT) is the only validated test for diagnosing malignant hyperthermia (MH) susceptibility (MHS) and phenotyping MHS families. Although most diagnostic laboratory tests can check intra- and interlaboratory consistency through the use of standard control samples, there has been no practical way to achieve this goal for the CHCT. The distances between diagnostic centers and time constraints of the CHCT protocol (5 h) prohibit centers from sharing tissue samples. In this study, we investigated varying storage conditions to extend the standard viability period of skeletal muscle to 24 h. Twenty MHS patients were tested according to the North America protocol. After standard CHCT, the surplus muscle samples were placed in one of the following four treatment groups. In Groups 1 and 2, muscles remained under tension and were stored in Krebs buffer (pH 7.4) at 23 degrees C-25 degrees C (clamped-warm) and 4 degrees C (clamped-cold), respectively. In Groups 3 and 4, muscle strips were dissected, and the ends were tied with silk sutures, cut from the clamp, and placed in Krebs buffer at 23 degrees C-25 degrees C (free-warm) and 4 degrees C (free-cold), respectively. The responses of the treatment groups to halothane (3%) and caffeine (0.5-32 mM) were tested at 22-26 h after excision. The clamped-warm storage group correctly diagnosed MHS in all patients. IMPLICATIONS: Varying conditions for storage of muscle were investigated to extend the viability period of muscle in the malignant hyperthermia (MH) test from 5 to 24 h. Muscles stored for 24 h under tension at room temperature remained viable and correctly diagnosed MH susceptibility in all patients.
    Anesthesia & Analgesia 02/2003; 96(1):153-8, table of contents. · 3.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Altered Ca2+ homeostasis in skeletal muscle is a key molecular event triggering malignant hyperthermia (MH) in malignant hyperthermia-susceptible (MHS) individuals. Genetic studies have shown that mutations in the type 1 ryanodine receptor (RYR1) are associated with MH susceptibility. Because human B lymphocytes express the RYR1, it is hypothesized that Ca2+ homeostasis in B lymphocytes is altered in MHS individuals. This study investigated the Ca2+ response of B cells to caffeine and 4-chloro-m-cresol in 13 MHS and 21 MH-negative (MHN) individuals who had been diagnosed by caffeine halothane contracture test (CHCT) and 18 healthy volunteers. Changes in [Ca2+]i in B cells were measured directly in fluo-3 loaded cells using a dual-color flow cytometric technique. Further, B cell phenotype was correlated with CHCT results in a family with the Val2168Met (G6502A) mutation. Caffeine-induced (50 mm) increases in [Ca2+]i in B cells were significantly greater in MHS than in MHN (P = 0.0004), control (P = 0.0001) or non-MHS (MHN and control) individuals (P < 0.0001). The 4-chloro-m-cresol-induced (400 microm) increases in [Ca2+]i were also significantly different between MHS and controls (P = 0.003) or between MHS and non-MHS (MHN and control) individuals (P = 0.0078). A study of a family with the Val2168Met mutation demonstrated expression of the RYR1 mRNA mutant in B cells from the family members with MHS phenotype and a clear segregation of genotype with B-cell phenotype. The Ca2+ responses to caffeine or 4-chloro-m-cresol in B lymphocytes showed significant differences between MHS and MHN (or control) individuals. Although the molecular mechanisms of these alterations are currently undetermined, the results suggest that the enhanced Ca2+ responses are associated with mutations in the RYR1 gene in some MHS individuals.
    Anesthesiology 11/2002; 97(5):1052-8. · 5.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In North America, the caffeine halothane contracture test (CHCT) is the standard test for the diagnosis of malignant hyperthermia (MH). Current CHCT protocol recommends that the test be completed within 5 h of muscle excision. The purpose of this study was to investigate whether the period of skeletal muscle viability could be extended to 24 h. We tested the gracilis muscle from normal (n = 8) and MH-susceptible swine (n = 8). After baseline (1-2 h after excision) CHCT, the remaining muscles were placed into one of the following four treatment groups. In Groups 1 and 2, the muscles remained under tension and were stored in Krebs buffer (pH 7.4) at 23 degrees C-25 degrees C (clamped-warm) and 4 degrees C (clamped-cold), respectively. In Groups 3 and 4, the muscle strips were dissected, and the ends were tied with silk sutures, cut from the clamp, and placed in Krebs buffer at 23 degrees C-25 degrees C (free-warm) and 4 degrees C (free-cold), respectively. The responses of the treatment groups to halothane (3%) and caffeine (0.5-32 mM) were tested 22-26 h after excision. The clamped-warm storage was the only storage method to correctly diagnose MH susceptibility in all muscle strips tested. This finding was also confirmed in muscle stored under clamped-warm conditions and shipped overnight to another testing center for a parallel CHCT.
    Anesthesia & Analgesia 10/2001; 93(3):781-6. · 3.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The current studies were undertaken to investigate the role of endothelin-1 (ET-1) and its receptors in contractions of isolated pulmonary vessels of the pig induced by diaspirin cross-linked hemoglobin (DCLHb). Second-order pulmonary arteries (PAs) and veins (PVs) were isolated from pigs, cut into rings (4 to 5 mm), and mounted at optimal passive tension in 37 degrees C Krebs-filled tissue baths bubbled with 95% O2/5% CO2. Isometric tension was recorded continuously. In paired rings, concentration responses to ET-1 (10(-10) to 10(-7) mol/L), DCLHb (10(-9) to 3x10(-6) mol/L), and N-nitro-L-arginine (LNA) (10(-6) to 5x10(-5) mol/L) in the presence and absence of the ET(A) receptor antagonist BQ123 (3x10(-5) mol/L) were determined. PVs and PAs with intact endothelium and rings from which the endothelium was removed (denuded) were pretreated with the ET(B) receptor antagonist BQ788 to determine the contribution of ET(B) receptors to ET-1, DCLHb, and LNA responses. ET-1, DCLHb, and LNA caused concentration-dependent increases in tension in all vessels. In the presence of BQ123, the 50% effective concentration (EC50) of ET-1 was significantly increased (by 5-fold to 10-fold) in all vessels. DCLHb concentration responses were significantly attenuated-in the PVs by 45% and in the PAs by 79%-during treatment with BQ123. BQ123 attenuated LNA responses in PVs by 35% and in PAs by 87%. Treatment with BQ788 had no effect on endothelium-intact PVs or PAs but significantly increased ET-1 EC50 (log of the molar concentration) from -9.0+/-0.22 to -7.8+/-0.05 in denuded PAs. The ET-1 EC50 was significantly decreased in denuded PAs (-9.0+/-0.22) as compared with responses in endothelium-intact PAs (-8.1+/-0.18). DCLHb concentration responses were attenuated by 71% and LNA responses by 80% during antagonism with BQ788 in the intact PAs only. These data demonstrate that ET-1 plays a role in DCLHb-induced contractions in the PA and PV. The contributions of ET are mediated by both ET(A) and ET(B) receptors in the PA but only by ET(A) receptors in the PV. These results suggest that the vasoconstrictor actions of DCLHb, which have previously been shown to depend on its interference with endothelium-generated NO, may also involve ET. This may reflect the importance of the interaction of these two endothelium-generated physiologic antagonists in the pulmonary circulation.
    Journal of Laboratory and Clinical Medicine 06/1999; 133(5):478-87. · 2.62 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Intravenous administration of diaspirin crosslinked hemoglobin (DCLHb) can result in elevated pulmonary and systemic arterial pressures in some mammalian species. This study was designed to evaluate the ability of inhaled nitric oxide (INO) to attenuate elevations in pulmonary artery pressure in a closed-chested swine model. Yorkshire pigs received escalating doses of INO followed by escalating doses of DCLHb or a single dose of DCLHb followed by escalating doses of INO. Systemic and pulmonary arterial pressures were monitored continuously. Significant elevations occurred in systemic and pulmonary arterial pressure following a cumulative dose of 0.1 gm/kg DCLHb. A single dose of 0.3 gm/kg also resulted in elevations of pulmonary and systemic arterial pressure. Inhaled nitric oxide partially reversed the changes in pulmonary but not systemic pressure. These results indicate that INO might be a therapeutic option for humans who may experience increased pulmonary artery pressure following administration of DCLHb.
    Artificial Cells Blood Substitutes and Biotechnology 06/1999; 27(3):203-13. · 0.85 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Guanosine 3',5'-cyclic monophosphate (cGMP) is an important second messenger in many biological systems including vascular smooth muscle where it mediates relaxation. Cellular levels of cGMP are regulated primarily by three enzymes; nitric oxide (NO) synthase, soluble guanylate cyclase, and cGMP-phosphodiesterase. Basal cGMP levels of isolated endothelium intact porcine pulmonary vein are five fold higher than in pulmonary artery. The objective of this study was to investigate possible reasons for this difference. Therefore, we compared NO synthase activity of pulmonary vein with artery and used pharmacologic approaches to compare soluble guanylate cyclase and phosphodiesterase activities in these vessels. NO synthase activities of pulmonary vein and artery were measured by monitoring the conversion of exogenous L-[14C]arginine to L-[14C]citrulline and by quantifying NO formation from endogenous L-arginine. Rates (pM/min per mg protein) of basal L-citrulline and NO formation from endothelium intact pulmonary vein (29.0 +/- 4.8 and 44 +/- 7.1, respectively) were significantly higher than from artery (8.3 +/- 2.2 and 17.1 +/- 3.3). Western blot analysis indicated higher constitutive NO synthase protein in the vein than in artery. N-nitro-L-arginine (0-100 microM), a potent inhibitor of NO synthase, induced contractions of the pulmonary vein which were significantly higher than those of the artery. N-nitro-L-arginine (5 and 20 microM) in the presence of phosphodiesterase inhibitors, decreased basal cGMP levels of endothelium intact blood vessels. In endothelium denuded pulmonary vein and artery, basal cGMP levels were not different from each other, but increased significantly following stimulation of soluble guanylate cyclase with exogenous NO. In the presence of both non-specific and specific cGMP phosphodiesterase inhibitors, exogenous NO-induced cGMP levels of endothelium denuded tissues were not significantly different from each other. However, in the absence of the phosphodiesterase inhibitors, exogenous NO-induced cGMP was significantly less in the artery than in the vein. These results suggest that (I) the intact porcine pulmonary vein contains higher levels of NO synthase activity than pulmonary artery, and that (II) the soluble guanylate cyclase activities in pulmonary vein and artery are equally responsive to NO, and finally (III) pulmonary artery expresses greater phosphodiesterase activity than vein. Higher NO synthase and lower phosphodiesterase activity may explain the greater accumulation of cGMP in the pulmonary vein compared to the artery.
    European Journal of Pharmacology 07/1998; 351(2):253-60. · 2.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Endothelial cells play an important role in the regulation of vascular activity through the release of endothelium derived relaxing factor (EDRF) now believed to be nitric oxide (NO). NO and the NO donor drug nitroglycerin relax vascular smooth muscle by stimulating soluble guanylyl cyclase leading to elevation of intracellular levels of cyclic guanosine 3',5'-monophosphate (cGMP). Halothane has been shown to inhibit the action of NO on blood vessels. This study was designed to further investigate the mechanisms by which halothane attenuates NO-induced vascular relaxations. This was done by examining the effects of halothane on nitroglycerin and NO-induced relaxations in the presence and absence of the inhibitors of soluble guanylyl cyclase, methylene blue and 6-anilino-5,8-quinolinedione (LY 83583). Thoracic aortas from anesthetized male Sprague-Dawley rats were excised and cut into rings and the endothelium was removed. The aortic rings were suspended in organ baths containing Krebs solution and equilibrated at their optimal passive tension. When a stable plateau of contraction was produced by EC60 concentrations of norepinephrine, increasing concentrations of nitroglycerin or NO were added to the baths to relax the rings. This contraction-relaxation procedure was repeated three or four times. In some baths halothane was administered by a calibrated vaporizer 10 min before beginning the second procedure. Either methylene blue or LY 83583 was added to the baths 20 min before the third procedure. The combination of halothane, methylene blue or LY 83583 was added before the fourth procedure. Halothane, methylene blue or LY 83583 significantly inhibited nitroglycerin-induced relaxation individually. Halothane and LY 83583 also significantly inhibited NO-induced relaxations (5 x 10(-9)-3 x 10(-8) M and 5 x 10(-9)-3 x 10(-5) M, respectively) individually. The combination of halothane and methylene blue or halothane and LY 83583 significantly inhibited nitroglycerin-induced relaxation, also, the combination of halothane and LY 83583 significantly inhibited NO-induced relaxations. Halothane, methylene blue and LY 83583 treatment led to rightward shift in the concentration-effect curves. Halothane, in combination with methylene blue or LY 83583, produced inhibition equivalent to the sum of their individual effects. The present study demonstrates that the halothane, methylene blue and LY 83583 attenuate nitroglycerin and NO-induced relaxations of endothelium-denuded rat aortic rings. This suggests that halothane, methylene blue and LY 83583 may act through competitive antagonism at a common site of action on soluble guanylyl cyclase in the EDRF/NO relaxation pathway.
    European Journal of Pharmacology 01/1998; 342(2-3):217-24. · 2.59 Impact Factor
  • Anesthesiology 01/1998; 89. · 5.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two studies, each utilizing short-term treadmill exercise of a different intensity, assessed the metabolic and hormonal responses of women to exercise in the morning (AM) and late afternoon (PM). In study 1, plasma concentrations of growth hormone, arginine vasopressin, catecholamines, adrenocorticotropic hormone, cortisol, lactate, and glucose were measured before, during, and after high-intensity exercise (90% maximal O2 uptake) in the AM and PM. In study 2, plasma concentrations of adrenocorticotropic hormone, cortisol, lactate, and glucose were measured before, during, and after moderate-intensity exercise (70% maximal O2 uptake) in the AM and PM in the follicular (days 3-9), midcycle (days 10-16), and luteal (days 18-26) phases of the menstrual cycle. The results of studies 1 and 2 revealed no significant diurnal differences in the magnitude of responses for any measured variable. In addition, study 2 revealed a significant time-by-phase interaction for glucose (P = 0. 014). However, net integrated responses were similar across cycle phases. These data suggest that metabolic and hormonal responses to short-term, high-intensity exercise can be assessed with equal reliability in the AM and PM and that there are subtle differences in blood glucose responses to moderate-intensity exercise across menstrual cycle phase.
    Journal of Applied Physiology 01/1998; 83(6):1822-31. · 3.48 Impact Factor

Publication Stats

404 Citations
102.61 Total Impact Points

Institutions

  • 1994–2011
    • Uniformed Services University of the Health Sciences
      • Department of Anesthesiology
      Maryland, United States
  • 2001
    • Georgetown University
      Washington, Washington, D.C., United States
  • 1998
    • Adventist University of Health Sciences
      Orlando, Florida, United States
  • 1996
    • Wilford Hall Ambulatory Surgery Center
      Lackland Air Force Base, Texas, United States
  • 1993
    • George Mason University
      Fairfax, Virginia, United States