bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of G proteins involved in activation of nonselective cation channels and arachidonic acid release by norepinephrine/α1A-adrenergic receptors
Authors: Kawanabe Yoshifumi , Hashimoto Nobuo , Masaki Tomoh
Published: February 2004

We demonstrated recently that norepinephrine activates Ca2+-permeable nonselective cation channels (NSCCs) in Chinese hamster ovary cells stably expressing α1A-adrenergic receptors (CHO-α1A). Moreover, extracellular Ca2+ through NSCCs plays essential roles in norepinephrine-induced arachidonic acid release. The purpose of the present study was to identify the G proteins involved in the activation of NSCCs and arachidonic acid release by norepinephrine. For these purposes, we used U73122, an inhibitor of phospholipase C (PLC), and dominant negative mutants of G12 and G13 (G12G228A and G13G225A, respectively). U73122 failed to inhibit NSCCs activation by norepinephrine. The magnitudes of norepinephrine-induced extracellular Ca2+ influx in CHO-α1A microinjected with G13G225A were smaller than those in CHO-α1A. In contrast, the magnitudes of norepinephrine-induced extracellular Ca2+ influx in CHO-α1A microinjected with G12G228A were similar to those in CHO-α1A. In addition, neither a Rho-associated kinase (ROCK) inhibitor nor a phosphoinositide 3-kinase inhibitor affected norepinephrine-induced extracellular Ca2+ influx. G13G225A, but not G12G228A, also inhibited arachidonic acid release partially. These results demonstrate that 1) the Gq/PLC-pathway is not involved in NSCCs activation by norepinephrine, 2) G13 couples with CHO-α1A and plays important roles for norepinephrine-induced NSCCs activation, 3) neither ROCK- nor PI3K-dependent cascade is involved in NSCCs activation, and 4) G13 is involved in norepinephrine-induced arachidonic acid release in CHO-α1A.
Combined growth hormone/insulin-like growth factor I in addition to glutamine-supplemented TPN results in net protein anabolism in critical illness
Authors: Carroll Paul V. , Jackson Nicola C. , Russell-Jones David L. , Treacher David F. , Sönksen Peter H. , Umpleby A. Margot
Published: January 2004

Protein loss leading to reduced lean body mass is recognized to contribute to the high levels of morbidity and mortality seen in critical illness. This prospective, randomized, controlled study compared the effects of conventional parenteral nutrition (TPN), glutamine-supplemented (0.4 g·kg-1·day-1) TPN (TPNGLN), and TPNGLN with combined growth hormone (GH, 0.2 IU·kg-1·day-1) and IGF-I (160 μg·kg-1·day-1) on protein metabolism in critical illness. Nineteen mechanically ventilated subjects [64 ± 3 yr, body mass index (BMI) 23.8 ± 1.3, kg/m2] were initially studied in the fasting state ( study 1) and subsequently after 3 days of nutritional with/without hormonal support ( study 2). All had recently been admitted to the ICU and the majority were postemergency abdominal surgery (APACHE II 17.5 ± 1.0). Protein metabolism was assessed using a primed constant infusion of [1-13C]leucine. Conventional TPN contained mixed amino acids, Intralipid, and 50% dextrose. TPNGLN, unlike TPN alone, resulted in an increase in plasma glutamine concentration (∼50%, P < 0.05). Both TPN and TPNGLN decreased the rate of protein breakdown (TPN 15%, P < 0.002; TPNGLN 16%, P < 0.05), but during these treatments the patients remained in a net negative protein balance. Combined treatment with TPNGLN + GH/IGF-I increased plasma IGF-I levels (10.3 ± 0.8 vs. 48.1 ± 9.1 nmol/l, study 1 vs. study 2, P < 0.05), and in contrast to therapy with nutrition alone, resulted in net protein gain (-0.75 ± 0.14 vs. 0.33 ± 0.12 g protein·kg-1·day-1, study 1 vs. study 2, P < 0.05). Therapy with GH/IGF-I + TPNGLN, unlike nutrition alone, resulted in net positive protein balance in a group of critically ill patients.
C-peptide improves adenosine-induced myocardial vasodilation in type 1 diabetes patients
Authors: Johansson Bo-Lennart , Sundell Jan , Ekberg Karin , Jonsson Cathrine , Seppänen Marko , Raitakari Olli , Luotolahti Matti , Nuutila Pirjo , Wahren John , Knuuti Juhani
Published: January 2004

Patients with type 1 (insulin-dependent) diabetes show reduced skeletal muscle blood flow and coronary vasodilatory function despite intensive insulin therapy and good metabolic control. Administration of proinsulin C-peptide increases skeletal muscle blood flow in these patients, but a possible influence of C-peptide on myocardial vasodilatory function in type 1 diabetes has not been investigated. Ten otherwise healthy young male type 1 diabetic patients (Hb A1c 6.6%, range 5.7-7.9%) were studied on two consecutive days during normoinsulinemia and euglycemia in a double-blind, randomized, crossover design, receiving intravenous infusion of C-peptide (5 pmol·kg-1·min-1) for 120 min on one day and saline infusion on the other day. Myocardial blood flow (MBF) was measured at rest and during adenosine administration (140 μg·kg-1·min-1) both before and during the C-peptide or saline infusions by use of positron emission tomography and [15O]H2O administration. Basal MBF was not significantly different in the patients compared with an age-matched control group, but adenosine-induced myocardial vasodilation was 30% lower ( P < 0.05) in the patients. During C-peptide administration, adenosine-stimulated MBF increased on average 35% more than during saline infusion ( P < 0.02) and reached values similar to those for the healthy controls. Moreover, as evaluated from transthoracal echocardiographic measurements, C-peptide infusion resulted in significant increases in both left ventricular ejection fraction (+5%, P < 0.05) and stroke volume (+7%, P < 0.05). It is concluded that short-term C-peptide infusion in physiological amounts increases the hyperemic MBF and left-ventricular function in type 1 diabetic patients.
Higher production of IL-8 in visceral vs. subcutaneous adipose tissue. Implication of nonadipose cells in adipose tissue
Authors: Bruun Jens M. , Lihn Aina S. , Madan Atul K. , Pedersen Steen B. , Schiøtt Kirsten M. , Fain John N. , Richelsen Bjørn
Published: January 2004

IL-8 is released from human adipose tissue. Circulating IL-8 is increased in obese compared with lean subjects and is associated with measures of insulin resistance, development of atherosclerosis, and cardiovascular disease. We studied 1) the production and release of IL-8 in vitro from paired samples of subcutaneous (SAT) and visceral (VAT) adipose tissue and 2) the production of IL-8 from whole adipose tissue, isolated adipocytes, and nonfat cells of adipose tissue. IL-8 release from VAT was fourfold higher than from SAT ( P < 0.05), and IL-8 mRNA was twofold higher in VAT compared with SAT ( P < 0.01). Dexamethasone (50 nM) attenuated IL-8 production by 50% ( P < 0.05), and IL-1β (2 μg/l) increased IL-8 production up to 15-fold ( P < 0.001). IL-8 release from whole SAT explants correlated with body mass index (BMI; r = 0.78; P < 0.001), as did IL-8 release from nonfat cells ( r = 0.79; P < 0.001). However, no correlation was found between IL-8 release from the fraction of isolated adipocytes and BMI ( r = 0.01). In conclusion, we demonstrated an increased release of IL-8 from VAT compared with SAT. Furthermore, our data suggest that the observed elevation in circulating levels of IL-8 in obese subjects is due primarily to the release of IL-8 from nonfat cells from adipose tissue. The high levels of IL-8 release from human adipose tissue and accumulation of this tissue in obese subjects may account for some of the increase in circulating IL-8 observed in obesity.
Insulin stimulates interleukin-6 and tumor necrosis factor-α gene expression in human subcutaneous adipose tissue
Authors: Krogh-Madsen Rikke , Plomgaard Peter , Keller Pernille , Keller Charlotte , Pedersen Bente Klarlund
Published: January 2004

High circulating levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) are found in patients with hyperinsulinemia. Insulin stimulates release of IL-6 from adipocyte cultures, and it stimulates IL-6 gene expression in insulin-resistant, but not control, rat skeletal muscle. In addition, TNF-α may be involved in the pathogenesis of insulin resistance. Therefore, we studied the effect of insulin on IL-6 and TNF-α gene expression in human skeletal muscle and adipose tissue. Nine healthy young volunteers participated in the study. They underwent a 6-h hyperinsulinemic euglycemic clamp at a fixed insulin infusion rate, with blood glucose clamped at fasting level. Blood samples drawn at 0, 1, 2, 3, 4, 5, and 6 h were analyzed for IL-6 and TNF-α. Muscle and fat biopsies, obtained at 0, 2, 4, and 6 h, were analyzed for IL-6 and TNF-α mRNA with real-time PCR. IL-6 mRNA increased 11-, 3-, and 5-fold at 2, 4, and 6 h, respectively, in adipose tissue (ANOVA P = 0.027), whereas there was no significant effect of insulin on skeletal muscles. Plasma IL-6 increased during insulin stimulation. TNF-α mRNA increased 2.4-, 1.4-, and 2.2-fold in adipose tissue (ANOVA P = 0.001) and decreased 0.74-, 0.64-, and 0.68-fold in muscle tissue (ANOVA P = 0.04). Plasma levels of TNF-α were constant. In conclusion, the finding that insulin stimulates IL-6 and TNF-α gene expression in adipose tissue only and inhibits the TNF-α production in skeletal muscles suggests a differential regulation of muscle- and adipose tissue-derived IL-6 and TNF-α.
Metabolic regulation of growth hormone by free fatty acids, somatostatin, and ghrelin in HIV-lipodystrophy
Authors: Koutkia Polyxeni , Meininger Gary , Canavan Bridget , Breu Jeff , Grinspoon Steven
Published: January 2004

Human immunodeficiency virus (HIV)-lipodystrophy is a syndrome characterized by changes in fat distribution and insulin resistance. Prior studies suggest markedly reduced growth hormone (GH) levels in association with excess visceral adiposity among patients with HIV-lipodystrophy. We investigated mechanisms of altered GH secretion in a population of 13 male HIV-infected patients with evidence of fat redistribution, compared with 10 HIV-nonlipodystrophic patients and 11 male healthy controls similar in age and body mass index (BMI). Although similar in BMI, the lipodystrophic group was characterized by increased visceral adiposity, free fatty acids (FFA), and insulin and reduced extremity fat. We investigated ghrelin and the effects of acute lowering of FFA by acipimox on GH responses to growth hormone-releasing hormone (GHRH). We also investigated somatostatin tone, comparing GH response to combined GHRH and arginine vs. GHRH alone with a subtraction algorithm. Our data demonstrate an equivalent number of GH pulses (4.1 ± 0.6, 4.7 ± 0.8, and 4.5 ± 0.3 pulses/12 h in the HIV-lipodystrophic, HIV-nonlipodystrophic, and healthy control groups, respectively, P > 0.05) but markedly reduced GH secretion pulse area (1.14 ± 0.27 vs. 4.67 ± 1.24 ng·ml–1·min, P < 0.05, HIV-lipodystrophic vs. HIV-nonlipodystrophic; 1.14 ± 0.27 vs. 3.18 ± 0.92 ng·ml–1·min, P < 0.05 HIV-lipodystrophic vs. control), GH pulse area, and GH pulse width in the HIV-lipodystrophy patients compared with the control groups. Reduced ghrelin (418 ± 46 vs. 514 ± 37 pg/ml, P < 0.05, HIV-lipodystrophic vs. HIV-nonlipodystrophic; 418 ± 46 vs. 546 ± 45 pg/ml, P < 0.05, HIV-lipodystrophic vs. control), impaired GH response to GHRH by excess FFA, and increased somatostatin tone contribute to reduced GH secretion in patients with HIV-lipodystrophy. These data provide novel insight into the metabolic regulation of GH secretion in subjects with HIV-lipodystrophy.
The ubiquitin-proteasome system is responsible for cysteine-responsive regulation of cysteine dioxygenase concentration in liver
Authors: Stipanuk Martha H. , Hirschberger Lawrence L. , Londono Monica P. , Cresenzi Carrie L. , Yu Anthony F.
Published: February 2004

Hepatic cysteine dioxygenase (CDO) activity is a critical regulator of cellular cysteine concentration and availability of cysteine for anabolic processes and is markedly higher in animals fed diets containing excess sulfur amino acids compared with those fed levels at or below the requirement. Rat hepatocytes responded to a deficiency or excess of cysteine in the culture medium with a decrease or increase in CDO level but no change in CDO mRNA level. The cysteine analog, cysteamine, but not cysteine metabolites or thiol reagents, was also effective in increasing CDO. Inhibitors of the 26S proteasome blocked CDO degradation in cysteine-deficient cells but had little or no effect on CDO concentration in hepatocytes cultured with excess cysteine. High-molecular-mass CDO-ubiquitin conjugates were observed in cells cultured in cysteine-deficient medium, whether or not proteasome inhibitor was present, but these CDO-ubiquitin conjugates were not observed in cells cultured in cysteine-supplemented medium with or without proteasome inhibitor. Similar results were observed for degradation of recombinant CDO expressed in human heptocarcinoma cells cultured in cysteine-deficient or cysteine-supplemented medium. CDO is an example of a mammalian enzyme that is robustly regulated via its substrate, with the presence of substrate blocking the ubiquitination of CDO and, hence, the targeting of CDO for proteasomal degradation. This regulation occurs in primary hepatocytes in a manner that corresponds with changes observed in intact animals.
High-resolution visualization of oxygen distribution in the liver in vivo
Authors: Paxian Markus , Keller Steve A. , Cross Brian , Huynh Toan T. , Clemens Mark G.
Published: January 2004

Microcirculatory failure after stress events results in mismatch in oxygen supply and demand. Determination of tissue oxygen distribution in vivo may help elucidate mechanisms of injury, but present methods have limited resolution. Male Sprague-Dawley rats were anesthetized, prepared for intravital microscopy, and received intravenously the oxygen-sensitive fluorescent dye Tris(1,10-phenanthroline)ruthenium(II) chloride hydrate [[Formula: see text]]. An impaired hepatic oxygen distribution was induced by either phenylephrine or hemorrhage. Intensity of [Formula: see text] fluorescence was compared with NADH autofluorescence indicating changes in the mitochondrial redox potential. Ethanol was injected to affect the NADH-to-NAD+ ratio without altering the Po2. Infusion of [Formula: see text] resulted in a heterogeneous fluorescence under baseline conditions reflecting the physiological acinar Po2 distribution. A decrease in oxygen supply due to phenylephrine or hemorrhage was paralleled by an increase in [Formula: see text] and NADH fluorescence reflecting an impaired mitochondrial redox state. Ethanol did not alter [Formula: see text] fluorescence but increased NADH fluorescence indicating independence of Po2 and redox state imaging. Intravenous administration of [Formula: see text] for intravital videomicroscopy represents a new method to visualize the hepatic tissue Po2. Combined with NADH autofluorescence, it provides additional information regarding the tissue redox state.
Changes in pharyngeal corticobulbar excitability and swallowing behavior after oral stimulation
Authors: Power M. , Fraser C. , Hobson A. , Rothwell J. C. , Mistry S. , Nicholson D. A. , Thompson D. G. , Hamdy S.
Published: January 2004

Faucial pillar (FP) stimulation is commonly used in swallowing rehabilitation, yet its physiological basis remains uncertain. We investigated the effects of intraoral FP stimulation on human corticobulbar excitability and swallowing behavior, to explore the possibility of a central mechanism for functional change. In 10 healthy subjects, corticobulbar projections to pharynx were investigated with transcranial magnetic stimulation, via intraluminal electrodes, before and up to 1 h after 10 min of electrical FP stimulation with three frequencies (0.2, 1, and 5 Hz) or sham and peripheral (median nerve) stimulation. In a second study, swallowing behavior was assessed with videofluoroscopy before and after FP stimulation. FP stimulation at 5 Hz inhibited the corticobulbar projection (-14 ± 6%, P < 0.02) and lengthened swallow response time (+114 ± 24%, P = 0.02). By comparison, FP stimulation at 0.2 Hz facilitated this projection (+60 ± 28%, P < 0.04), without enhancing swallowing behavior. Neither 1-Hz, sham, nor median nerve stimulation altered excitability. Thus changes in corticobulbar excitability to FP stimulation are frequency dependent with implications for the treatment for neurogenic swallowing dysfunction.
Cannabinoid receptor type 1 modulates excitatory and inhibitory neurotransmission in mouse colon
Authors: Storr M. , Sibaev A. , Marsicano G. , Lutz B. , Schusdziarra V. , Timmermans J.-P. , Allescher H. D.
Published: January 2004

The effects of cannabinoid receptor agonists and antagonists on smooth muscle resting membrane potentials and on membrane potentials following electrical neuronal stimulation in a myenteric neuron/smooth muscle preparation of wild-type and cannabinoid receptor type 1 (CB1)-deficient mice were investigated in vitro. Double staining for CB1 and nitric oxide synthase (neuronal) was performed to identify the myenteric CB1-expressing neurons. Focal electrical stimulation of the myenteric plexus induced a fast (f) excitatory junction potential (EJP) followed by a fast and a slow (s) inhibitory junction potential (IJP). Treatment of wild-type mice with the endogenous CB1 receptor agonist anandamide reduced EJP while not affecting fIJP and sIJP. EJP was significantly higher in CB1-deficient mice than in wild-type littermate controls, and anandamide induced no effects in CB1-deficient mice. N-arachidonoyl ethanolamide (anandamide), R-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3,-de]- 1,4-benzoxazin-6-yl]-1-naphtalenylmethanone, a synthetic CB1 receptor agonist, nearly abolished EJP and significantly reduced the fIJP in wild-type mice. N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-caroxamide (SR141716A), a CB1-specific receptor antagonist, was able to reverse the agonist effects induced in wild-type mice. SR141716A, when given alone, significantly increased EJP in wild-type mice without affecting IJP in wild-type and EJP in CB1-deficient mice. Interestingly, SR141716A reduced fIJP in CB1-deficient mice. In the mouse colon, nitrergic myenteric neurons do not express CB1, implying that CB1 is expressed in cholinergic neurons, which is in line with the functional data. Finally, excitatory and inhibitory neurotransmission in the mouse colon is modulated by activation of CB1 receptors. The significant increase in EJP in CB1-deficient mice strongly suggests a physiological involvement of CB1 in excitatory cholinergic neurotransmission.
Study of intestinal flow by combined videofluoroscopy, manometry, and multiple intraluminal impedance
Authors: Imam Hala , Sanmiguel Claudia , Larive Brett , Bhat Yasser , Soffer Edy
Published: January 2004

Assessment of patterns of flow in the small bowel is difficult. Multiple intraluminal impedance has been recently used for study of flow dynamics in the esophagus. Our aims were 1) to validate multiple intraluminal impedance by correlating impedance events with intestinal flow as detected by fluoroscopy and 2) to determine intestinal flow patterns in the fasting and postprandial period and their correspondence with manometry. First, six healthy subjects underwent simultaneous video-fluoroscopic, manometric, and impedance recording from the duodenum. Videofluoroscopy was used to validate impedance patterns corresponding with barium flow in the fasting and postprandial periods. Next, 16 healthy subjects underwent prolonged simultaneous recording of impedance and manometry in both periods. Most flow events were short (10 cm or less), with antegrade flow being the most common. Correspondence between impedance and videofluoroscopy increased with increasing length of barium flow. Impedance corresponded better with flow, at any distance, than manometry. However, impedance and manometric events, when analyzed separately as index events, always corresponded with fluoroscopic flow. The fasting and postprandial periods showed comparable patterns of flow, with frequent, highly propulsive manometric and impedance sequences. Motility index was positively and significantly associated with length of impedance events. Phase 3 of the migrating motor complex could be easily recognized by impedance. Multiple intraluminal impedance can detect intestinal flow events and corresponds better with fluoroscopic flow than manometry.
Gastrointestinal satiety signals II. Cholecystokinin
Authors: Moran Timothy H. , Kinzig Kimberly P.
Published: January 2004

During a meal, ingested nutrients accumulate in the stomach, with a significant portion passing on to the small intestine. The gastrointestinal presence of ingested nutrients initiates a range of physiological responses that serve to facilitate the overall digestive process. Thus peptides and transmitters are released, and various neural elements are activated that coordinate gastrointestinal secretion and motility and can eventually lead to meal termination or satiety. Among the range of gastrointestinal peptides released by ingested nutrients is the brain/gut peptide CCK. CCK plays a variety of roles in coordinating gastrointestinal activity and has been demonstrated to be an important mediator for the control of meal size.
Gastrointestinal Satiety Signals I. An overview of gastrointestinal signals that influence food intake
Authors: Woods Stephen C.
Published: January 2004

An overview is presented of those signals generated by the gastrointestinal (GI) tract during meals that interact with the central nervous system to create a sensation of fullness and satiety. Although dozens of enzymes, hormones, and other factors are secreted by the GI tract in response to food in the lumen, only a handful are able to influence food intake directly. Most of these cause meals to terminate and hence are called satiety signals, with CCK being the most investigated. Only one GI signal, ghrelin, that increases meal size has been identified. The administration of exogenous CCK or other satiety signals causes smaller meals to be consumed, whereas blocking the action of endogenous CCK or other satiety signals causes larger meals to be consumed. Satiety signals are relayed to the hindbrain, either indirectly via nerves such as the vagus from the GI tract or else directly via the blood. Most factors that influence how much food is eaten during individual meals act by changing the sensitivity to satiety signals. This includes adiposity signals as well as habits and learning, the social situation, and stressors.
In vivo adenoviral transfer of sorcin reverses cardiac contractile abnormalities of diabetic cardiomyopathy
Authors: Suarez Jorge , Belke Darrell D. , Gloss Bernd , Dieterle Thomas , McDonough Patrick M. , Kim Yun-Kyung , Brunton Laurence L. , Dillmann Wolfgang H.
Published: January 2004

In many types of heart failure cardiac myocyte Ca2+ handling is abnormal because of downregulation of key Ca2+-handling proteins like sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)2a and ryanodine receptor (RyR)2. The alteration in SERCA2a and RyR2 expression results in altered cytosolic Ca2+ transients, leading to abnormal contraction. Sorcin is an EF-hand protein that confers the property of caffeine-activated intracellular Ca2+ release in nonmuscle cells by interacting with RyR2. To determine whether sorcin could improve the contractile function of the heart, we overexpressed sorcin in the heart of either normal or diabetic mice and in adult rat cardiomyocytes with an adenoviral gene transfer approach. Sorcin overexpression was associated with an increase in cardiac contractility of the normal heart and dramatically rescued the abnormal contractile function of the diabetic heart. These effects could be attributed to an improvement of the Ca2+ transients found in the cardiomyocyte after sorcin overexpression. Viral vector-mediated delivery of sorcin to cardiac myocytes is beneficial, resulting in improved contractile function in diabetic cardiomyopathy.
Attenuation of IK,slow1 and IK,slow2 in Kv1/Kv2DN mice prolongs APD and QT intervals but does not suppress spontaneous or inducible arrhythmias
Authors: Kodirov Sodikdjon A. , Brunner Michael , Nerbonne Jeanne M. , Buckett Peter , Mitchell Gary F. , Koren Gideon
Published: January 2004

Overexpression of a truncated Kv1.1 or Kv2.1 channel polypeptide in the heart (Kv1DN or Kv2DN) resulted in mice with a prolonged action potential duration (APD) due to marked attenuation of rapidly activating, slowly inactivating K+ current ( IK,slow1) or slowly inactivating outward K+ current ( IK,slow2) in ventricular myocytes. ECG monitoring, optical mapping, and programmed electrical stimulation of Kv1DN mice revealed spontaneous and inducible reentrant ventricular tachycardia due to spatial dispersion of repolarization and refractoriness. Recently, we demonstrated upregulation of IK,slow2 in apical cardiomyocytes derived from Kv1DN mice. We therefore hypothesized that the selective upregulation of Kv2.1-encoded currents underlies the apex-to-base dispersion of repolarization and the reentrant arrhythmias. To test this hypothesis, the Kv1DN line was crossbred with the Kv2DN line to produce Kv1/Kv2DN lines. Whole cell voltage-clamp recordings from left ventricular cells of Kv1/Kv2DN confirmed that the 4-aminopyridine- and tetraethylammonium-sensitive components of IK,slow were eliminated, resulting in marked APD prolongation compared with wild-type, Kv1DN, and Kv2DN cells. Telemetric ECG recordings revealed prolongation of the corrected QT in Kv1/Kv2DN compared with Kv1DN and Kv2DN mice. However, attenuation of Kv2.1-encoded currents in Kv1DN mice did not suppress the arrhythmias. Thus, the elimination of IK,slow2 prolongs APD and the QT intervals, but does not have an antiarrhythmic effect.
Flow-mediated dilation in human brachial artery after different circulatory occlusion conditions
Authors: Betik Andrew C. , Luckham Victoria B. , Hughson Richard L.
Published: January 2004

Different magnitudes and durations of postocclusion reactive hyperemia were achieved by occluding different volumes of tissue with and without ischemic exercise to test the hypotheses that flow-mediated dilation (FMD) of the brachial artery would depend on the increase in peak flow rate or shear stress and that the position of the occlusion cuff would affect the response. The brachial artery FMD response was observed by high-frequency ultrasound imaging with curve fitting to minimize the effects of random measurement error in eight healthy, young, nonsmoking men. Reactive hyperemia was graded by 5-min occlusion distal to the measurement site at the wrist and the forearm and proximal to the site in the upper arm. Flow was further increased by exercise during occlusion at the wrist and forearm positions. For the two wrist occlusion conditions, flow increased eightfold and FMD was only 1 to 2% ( P > 0.05). After the forearm and upper arm occlusions, blood flow was almost identical but FMD after forearm occlusions was 3.4% ( P < 0.05), whereas it was significantly greater (6.6%, P < 0.05) and more prolonged after proximal occlusion. Forearm occlusion plus exercise caused a greater and more prolonged increase in blood flow, yet FMD (7.0%) was qualitatively and quantitatively similar to that after proximal occlusion. Overall, the magnitude of FMD was significantly correlated with peak forearm blood flow ( r = 0.59, P < 0.001), peak shear rate ( r = 0.49, P < 0.002), and total 5-min reactive hyperemia ( r = 0.52, P < 0.001). The prolonged FMD after upper arm occlusion suggests that the mechanism for FMD differs with occlusion cuff position.
P2 receptor-mediated Ca2+ transients in rat cerebral artery smooth muscle cells
Authors: Kamishima Tomoko , Quayle John M.
Published: January 2004

Significant Ca2+ release was previously noted with the activation of L-type Ca2+ current in rat superior cerebral artery smooth muscle cells. Here we examined whether the P2X current that is partly carried by Ca2+ also triggers Ca2+ release in this preparation. Application of P2X agonists evoked membrane currents and concomitant Ca2+ transients in whole cell voltage-clamped single cells. The expected increase in intracellular Ca2+ concentration ([Ca2+]i) was calculated from the time-integrated P2X current by assuming Ca2+ is the only charge carrier. The measured increase in [Ca2+]i was plotted as a function of the expected increase in [Ca2+]i, and Ca2+-buffering power was obtained as a reciprocal of the linear fit to this relationship. Both ryanodine, a Ca2+-induced Ca2+-release inhibitor, and cADP ribose, a putative activator of Ca2+-induced Ca2+ release, had no significant effects on Ca2+-buffering power. These results suggest that Ca2+ influx through P2X receptors does not trigger significant Ca2+ release. We then examined whether P2X responses influence the subsequent P2Y response. P2Y responses were characterized by measuring the rate of [Ca2+]i increase obtained as the slope of the linear regression to the rising phase of the Ca2+ transient. During simultaneous application of the P2X and P2Y agonist, the rate of [Ca2+]i increase was facilitated or suppressed depending on the size of the P2X receptor-mediated [Ca2+]i increase. Membrane depolarization close to the Ca2+ equilibrium potential significantly promoted the rate of [Ca2+]i increase. Our results suggest that the [Ca2+]i increase and membrane depolarization caused by the P2X current may regulate the subsequent P2Y response.
Role of AIF in human coronary artery endothelial cell apoptosis
Authors: Zhang Wenguang , Li Dayuan , Mehta Jawahar L.
Published: January 2004

Apoptosis-inducing factor (AIF), which exerts its effect via a caspase-independent pathway, has been suggested to be a mediator of cell injury. We have recently identified the expression of AIF in human coronary artery endothelial cells (HCAECs). The present study was designed to determine the pathophysiological role of AIF in oxidized low-density lipoprotein (ox-LDL)-induced apoptosis of HCAECs. The cells were cultured and treated with ox-LDL (40 μg/ml) for 24 h. Ox-LDL increased AIF expression, caused apoptosis of HCAECs (determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining and large-scale DNA fragmentation), and induced translocation of AIF from the cytoplasm to the nucleus (fluorescence immunocytochemistry). Pretreatment of HCAECs with a caspase inhibitor (ZVAD-fmk) did not influence AIF-mediated apoptosis in response to ox-LDL. We developed a specific antisense oligonucleotide targeted to the 5′-TCG CCG AAA TGT TCC GGT GTG GA-3′ portion of the human AIF mRNA sequence (AIF-AS) to bind a complementary sequence overlapping the translational start site. Pretreatment of cells with the AIF-AS for 24 h resulted in suppression of ox-LDL-upregulated AIF protein, as measured by immunoblot analysis. AIF-AS also reduced apoptosis and AIF translocation ( P < 0.01 vs. ox-LDL alone). Next, we constructed a recombinant AIF plasmid by inserting whole-length AIF cDNA into the expression vector pcDNA3.1 with a cytomegalovirus promoter. HCAECs transfected with plasmid showed a two- to fourfold increase in AIF expression, extensive apoptosis, and translocation of AIF from the cytoplasm to the nucleus. These results from two approaches indicate that AIF plays an important role in ox-LDL-induced endothelial injury.
Strain softening is not present during axial extensions of rat intact right ventricular trabeculae in the presence or absence of 2,3-butanedione monoxime
Authors: Kirton R. S. , Taberner A. J. , Young A. A. , Nielsen P. M. F. , Loiselle D. S.
Published: January 2004

Recent studies of passive myocardial mechanics have shown that strain softening behavior is present during both inflation of isolated whole rat hearts and shearing of tissue blocks taken from the left ventricular free wall in pigs. Strain softening is typically manifested by a stiffer forceextension relation in the first deformation cycle relative to subsequent cycles and is distinguished from viscoelasticity by a lack of recovery of stiffness, even after several hours of rest. The causes of this behaviour are unknown. We investigated whether strain softening is observed in uniaxial extensions of intact, viable, rat right ventricular (RV) cardiac trabeculae. Stretch and release cycles of 5%, 10%, and 15% muscle length were applied at a constant velocity at 26°C. Muscles were tested in random order in the presence and absence of 50 mM 2,3-butanedione monoxime (BDM). Whereas strain softening was displayed by nonviable trabeculae, it was not observed in viable preparations undergoing physiologically relevant extensions whether in the presence or absence of BDM. BDM also had no effect on passive compliance. There was a reversible increase of muscle compliance between the first and subsequent cycles, with recovery after 30 s of rest, independent of the presence of BDM. We conclude that strain softening is neither intrinsic to viable rat RV trabeculae nor influenced by BDM and that passive trabeculae compliance is not altered by the addition of BDM.
Cerebral autoregulation and gas exchange studied using a human cardiopulmonary model
Authors: Lu K. , Clark J. W. , Ghorbel F. H. , Robertson C. S. , Ware D. L. , Zwischenberger J. B. , Bidani A.
Published: January 2004

The goal of this work is to study the cerebral autoregulation, brain gas exchange, and their interaction by means of a mathematical model. We have previously developed a model of the human cardiopulmonary (CP) system, which included the whole body circulatory system, lung and peripheral tissue gas exchange, and the central nervous system control of arterial pressure and ventilation. In this study, we added a more detailed description of cerebral circulation, cerebrospinal fluid (CSF) dynamics, brain gas exchange, and cerebral blood flow (CBF) autoregulation. Two CBF regulatory mechanisms are included: autoregulation and CO2 reactivity. Central chemoreceptor control of ventilation is also included. We first established nominal operating conditions for the cerebral model in an open-loop configuration using data generated by the CP model as inputs. The cerebral model was then integrated into the larger CP model to form a new integrated CP model, which was subsequently used to study cerebral hemodynamic and gas exchange responses to test protocols commonly used in the assessment of CBF autoregulation (e.g., carotid artery compression and the thigh-cuff deflation test). The model can closely mimic the experimental findings and provide biophysically based insights into the dynamics of cerebral autoregulation and brain tissue gas exchange as well as the mechanisms of their interaction during test protocols, which are aimed at assessing the degree of autoregulation. With further refinement, our CP model may be used on measured data associated with the clinical evaluation of the cerebral autoregulation and brain oxygenation in patients.
Nitric oxide decreases the biological activity of norepinephrine resulting in altered vascular tone in the rat mesenteric arterial bed
Authors: Kolo Lacy L. , Westfall Thomas C. , Macarthur Heather
Published: January 2004

Nitric oxide (NO) reacts with catecholamines resulting in their deactivation. In this study, we demonstrated that coincubation of NO donors with sympathetic neurotransmitters decreased the amount of norepinephrine detected but not ATP or neuropeptide Y (NPY). Furthermore, we found that the ability of norepinephrine to increase perfusion pressure in the isolated perfused mesenteric arterial bed of the rat was attenuated by the incubation of norepinephrine with the NO donor diethylamine NONOate. Conversely, the vasoconstrictive ability of NPY and ATP was unaffected by incubation with NONOate. Periarterial nerve stimulation in the presence of the NO synthase (NOS) inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) resulted in an increase in both perfusion pressure response and norepinephrine levels. This was prevented by l-arginine, demonstrating that the effects of l-NAME were indeed specific to the inhibition of NOS. To confirm that NO was not altering the release of norepinephrine from the sympathetic nerve via presynaptic activation of guanylate cyclase, we repeated the experiments in the presence of the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]-quinoxaloine-one (ODQ). Unlike l-NAME, ODQ infusion did not increase norepinephrine overflow, demonstrating that modulation of norepinephrine by NO at the vascular neuroeffector junction of the rat mesenteric vascular bed is not the result of presynaptic guanylate cyclase activation. These results demonstrate that, in addition to being a direct vasodilatator, NO can also alter vascular reactivity at the sympathetic neuroeffector junction in the rat mesenteric bed by deactivating the vasoconstrictor norepinephrine.
Chronic intermittent hypoxia impairs endothelium-dependent dilation in rat cerebral and skeletal muscle resistance arteries
Authors: Phillips Shane A. , Olson E. B. , Morgan Barbara J. , Lombard Julian H.
Published: January 2004

The goal of the present study was to evaluate the effects of relatively short-term chronic intermittent hypoxia (CIH) on endothelial function of resistance vessels in the skeletal muscle and cerebral circulations. Sprague-Dawley rats were exposed to 14 days of CIH (10% fraction of inspired oxygen for 1 min at 4-min intervals, 12 h/day, n = 6). Control rats ( n = 6) were housed under normoxic conditions. After 14 days, resistance arteries of the gracilis muscle (GA) and middle cerebral arteries (MCA) were isolated and cannulated with micropipettes, perfused and superfused with physiological salt solution, and equilibrated with 21% O2-5% CO2 in a heated chamber. The arteries were pressurized to 90 mmHg, and vessel diameters were measured via a video micrometer before and after exposure to ACh (10–7–10–4 M), sodium nitroprusside (10–6 M), and acute reduction of Po2 in the perfusate/superfusate (from 140 to 40 mmHg). ACh-induced dilations of GA and MCA from animals exposed to CIH were greatly attenuated, whereas responses to nitroprusside were similar to controls. Dilations of both GA and MCA in response to acute reductions in Po2 were virtually abolished in animals exposed to CIH compared with controls. These findings suggest that exposure to CIH reduces the bioavailability of nitric oxide in the cerebral and skeletal muscle circulations and severely blunts vasodilator responsiveness to acute hypoxia.
Effects of electroporation on optically recorded transmembrane potential responses to high-intensity electrical shocks
Authors: Nikolski V. P. , Sambelashvili A. T. , Krinsky V. I. , Efimov I. R.
Published: January 2004

The outcome of defibrillation shocks is determined by the nonlinear transmembrane potential (Δ Vm) response induced by a strong external electrical field in cardiac cells. We investigated the contribution of electroporation to Δ Vm transients during high-intensity shocks using optical mapping. Rectangular and ramp stimuli (10–20 ms) of different polarities and intensities were applied to the rabbit heart epicardium during the plateau phase of the action potential (AP). Δ Vm were optically recorded under a custom 6-mm-diameter electrode using a voltage-sensitive dye. A gradual increase of cathodal and well as anodal stimulus strength was associated with 1) saturation and subsequent reduction of Δ Vm; 2) postshock diastolic resting potential (RP) elevation; and 3) postshock AP amplitude (APA) reduction. Weak stimuli induced a monotonic Δ Vm response and did not affect the RP level. Strong shocks produced a nonmonotonic Δ Vm response and caused RP elevation and a reduction of postshock APA. The maximum positive and maximum negative Δ Vm were recorded at 170 ± 20 mA/cm2 for cathodal stimuli and at 240 ± 30 mA/cm2 for anodal stimuli, respectively (means ± SE, n = 8, P = 0.003). RP elevation reached 10% of APA at a stimulus strength of 320 ± 40 mA/cm2 for both polarities. Strong ramp stimuli (20 ms, 600 mA/cm2) induced a nonmonotonic Δ Vm response, reaching the same largest positive and negative values as for rectangular shocks. The transition from monotonic to nonmonotonic morphology correlates with RP elevation and APA reduction, which is consistent with cell membrane electroporation. Strong shocks resulted in propidium iodide uptake, suggesting sarcolemma electroporation. In conclusion, electroporation is a likely explanation of the saturation and nonmonotonic nature of cellular responses reported for strong electric stimuli.
Gender-related differences in myocardial inflammatory and contractile responses to major burn trauma
Authors: Horton Jureta W. , White D. Jean , Maass David L.
Published: January 2004

Gender-related differences in immune responses to hemorrhage and sepsis have been described. However, most trauma studies continue to limit experimental models to males to avoid the variable responses associated with hormonal fluctuation in proestrus/estrus females. In the present study, male and female (either diestrus or proestrus/estrus) Sprague-Dawley rats (250–325 g) were given a third-degree scald burn over 40% total body surface area and fluid resuscitated (4 ml/kg per %burn of lactated Ringer solution); sham burn males and diestrus as well as sham burn proestrus/estrus female rats were included to provide controls. Twenty-four hours postburn, hearts were either perfused to examine mechanical function (Langendorff, n = 8 to 9 hearts/group) or to prepare cardiomyocytes (collagenase digestion, n = 4 to 5 hearts/group). Left ventricular developed pressure and the positive and negative first derivative of left ventricular pressure responses to increases in preload were significantly lower in burned males compared with responses measured in either burned proestrus/estrus or burned diestrus females; burn trauma increased cardiomyocyte secretion of tumor necrosis factor-α, interleukin-1β, and nitric oxide to a lesser extent in proestrus/estrus females than levels secreted by either diestrus females or males. Similarly, myocytes from proestrus/estrus females accumulated significantly less sodium/calcium compared with values measured in males ( P < 0.05). Our data confirm gender-related differences in myocardial function and myocardial inflammatory responses to burn injury.
Hemodynamics of orthostatic intolerance: implications for gender differences
Authors: Fu Qi , Arbab-Zadeh Armin , Perhonen Merja A. , Zhang Rong , Zuckerman Julie H. , Levine Benjamin D.
Published: January 2004

Women have a greater incidence of orthostatic intolerance than men. We hypothesized that this difference is related to hemodynamic effects on regulation of cardiac filling rather than to reduced responsiveness of vascular resistance during orthostatic stress. We constructed Frank-Starling curves from pulmonary capillary wedge pressure (PCWP), stroke volume (SV), and stroke index (SI) during lower body negative pressure (LBNP) and saline infusion in 10 healthy young women and 13 men. Orthostatic tolerance was determined by progressive LBNP to presyncope. LBNP tolerance was significantly lower in women than in men (626.8 ± 55.0 vs. 927.7 ± 53.0 mmHg × min, P < 0.01). Women had steeper maximal slopes of Starling curves than men whether expressed as SV (12.5 ± 2.0 vs. 7.1 ± 1.5 ml/mmHg, P < 0.05) or normalized as SI (6.31 ± 0.8 vs. 4.29 ± 0.6 ml·m–2·mmHg–1, P < 0.05). During progressive LBNP, PCWP dropped quickly at low levels, and reached a plateau at high levels of LBNP near presyncope in all subjects. SV was 35% and SI was 29% lower in women at presyncope (both P < 0.05). Coincident with the smaller SV, women had higher heart rates but similar mean arterial pressures compared with men at presyncope. Vascular resistance and plasma norepinephrine concentration were similar between genders. We conclude that lower orthostatic tolerance in women is associated with decreased cardiac filling rather than reduced responsiveness of vascular resistance during orthostatic challenges. Thus cardiac mechanics and Frank-Starling relationship may be important mechanisms underlying the gender difference in orthostatic tolerance.
Protein kinase βII in Zucker obese rats compromises oxygen and flow-mediated regulation of nitric oxide formation
Authors: Bohlen H. Glenn
Published: January 2004

In severe obesity, microvascular endothelial regulation of nitric oxide (NO) formation is compromised in response to muscarinic stimulation, and major arteries have suppressed flow-mediated dilation. Because normal microvessels are highly dependent on flow-mediated stimulation of NO generation and are responsive to intra- and extravascular oxygen availability, they are likely a major site of impaired endothelial regulation. This study evaluated the blood flow and oxygen-dependent aspects of intestinal microvascular regulation and NO production in Zucker obese rats just before the onset of hyperglycemia. Ruboxistaurin (LY-333531) was used to inhibit PKC-βII to determine whether flow or oxygen-related NO regulation was improved. Blood flow velocity was increased by forcing arterioles to perfuse ∼50% larger tissue areas by occlusion of nearby arterioles, and oxygen tension in the bath was lowered to create a modest oxygen depletion. When compared with lean Zucker rats, the periarteriolar NO concentration ([NO]) for obese rats was ∼30% below normal. At elevated shear rates, the [NO] for arterioles of obese animals was 20–30% below those in the arterioles of lean rats, and the NO response to decreased oxygen was about half normal in obese rats. All of these regulatory problems were essentially corrected in obese rats by PKC blockade with only minor changes in the microvascular behavior in lean rats. Therefore, activation of PKC-βII in endothelial cells during obesity suppressed NO regulation both at rest and in response to increased flow velocity and decreased oxygen availability.
Novel anti-inflammatory actions of amlodipine in a rat model of arteriosclerosis induced by long-term inhibition of nitric oxide synthesis
Authors: Kataoka Chu , Egashira Kensuke , Ishibashi Minako , Inoue Shujiro , Ni Weihua , Hiasa Ken-ichi , Kitamoto Shiro , Usui Makoto , Takeshita Akira
Published: January 2004

Amlodipine (a new class of calcium channel antagonist) has been shown to limit the progression of arteriosclerosis and decrease the incidence of cardiovascular events. The mechanisms underlying the beneficial effects of amlodipine, however, remain unclear. Therefore, we hypothesized that amlodipine attenuates the development of arteriosclerosis through the inhibition of inflammation in vivo. Long-term inhibition of nitric oxide (NO) by administration of a NO synthase inhibitor, Nω-nitro-l-arginine methyl ester (l-NAME), to rats induces coronary vascular inflammation [monocyte infiltration, monocyte chemoattractant protein-1 (MCP-1) expression, increased activity of angiotensin-converting enzyme (ACE)], and arteriosclerosis. Here, we used the rat model to investigate the anti-inflammatory effects of amlodipine in vivo. Treatment with amlodipine markedly inhibited the l-NAME-induced increase in vascular inflammation, oxidative stress, and local ACE and Rho activity and prevented arteriosclerosis. Interestingly, amlodipine prevented the l-NAME-induced increase in MCP-1 receptor CCR2 expression in circulating monocytes. Amlodipine markedly attenuated the high mortality rate at 8 wk of treatment. These data suggest that amlodipine attenuated arteriosclerosis through inhibiting inflammatory disorders in the rat model of long-term inhibition of NO synthesis. The anti-inflammatory effects of amlodipine seem to be mediated not only by the inhibition of local factors such as MCP-1 but also by the decrease in CCR2 in circulating monocytes. Inhibition of the MCP-1 to CCR2 pathway may represent novel anti-inflammatory actions of amlodipine beyond blood pressure lowering.