The influence of electrocardiogram (ECG) filters on the heights of R and T waves in children.

Anesthesiologists often compare intraoperative and preoperative electrocardiogram (ECG) waveforms in patients undergoing general anesthesia. In addition, many intraoperative ECG monitors have filters for removing electrocautery noise. In pediatric anesthesiology practice, we often note the appearance of elevated T waves-specifically, an increase in their height-with the use of such filters, even though no actual clinical change has occurred, which possibly leads to misdiagnosis. We investigated changes in R and T wave heights and in the T/R ratio according to the use of the strong (S) versus the diagnostic (D) filtering mode during pediatric anesthesiology. Primary outcomes were the dependence of the heights of the R and T waves on the filter mode and the correlation between rates of change in the R- and T-wave heights and heart rate (HR). In the S mode, the height of the R wave was lower (p = 0.013, η2 = 0.28) and the T/R ratio was higher than the corresponding values in the D mode (χ2 = 20.46, p < 0.001). The T/R ratios were also higher in the S mode than in the D mode, and when the D mode was changed to the S mode during tachycardia, there was a strong correlation between the rate of reduction in the R wave and HR (r = 0. 573, p = 0.041). Significant differences in the heights of the R wave and in the T/R ratio occur when using different intraoperative ECG filtering modes. Specifically, in S mode, a greater relative increase in T wave height may occur due to a significant decrease in R wave height. To avoid spurious diagnoses, anesthesiologists should be familiar with these potentially purely filter-driven changes whenever ECG is intraoperatively monitored.

Analytic and Integrative Framework for Understanding Human Sympathetic Arterial Baroreflex Function: Equilibrium Diagram of Arterial Pressure and Plasma Norepinephrine Level.

BACKGROUND: The sympathetic arterial baroreflex is a closed-loop feedback system for stabilizing arterial pressure (AP). Identification of unique functions of the closed system in humans is a challenge. Here we propose an analytic and integrative framework for identifying a static operating point and open-loop gain to characterize sympathetic arterial baroreflex in humans. METHODS AND RESULTS: An equilibrium diagram with two crossing functions of mechanoneural (MN) and neuromechanical (NM) arcs was analyzed during graded tilt maneuvers in seven healthy subjects. AP and plasma norepinephrine level (PNE), as a surrogate for sympathetic nerve activity, and were recorded after vagal modulation of heart function was blocked by atropine. The MN-arc curve was described as a locus of operating points during -7, 0, 15, and 60° head-up tilting (HUT) on a PNE-AP plane. The NM-arc curve was drawn as a line between operating points before and after ganglionic blockade (trimethaphan, 0.1 mg⋅ml-1⋅kg-1) during 0° or 15° HUT. Gain values were estimated from the slopes of these functional curves. Finally, an open-loop gain, which is a most important index for performance of arterial baroreflex, was given by a product of the gain values of MN (GMN) and NM arcs (GNM). Gain values of MN was 8.92 ± 3.07 pg⋅ml-1⋅mmHg-1; and GNM at 0° and 15° HUT were 0.61 ± 0.08 and 0.36 ± 0.05 mmHg⋅ml⋅pg-1, respectively. A postural change from supine to 15° HUT significantly reduced the open-loop gain from 5.62 ± 0.98 to 3.75 ± 0.62. The effects of HUT on the NM arc and open-loop gain seemed to be similar to those of blood loss observed in our previous animal studies. CONCLUSION: An equilibrium-diagram analysis contributes to a quantitative and integrative understanding of function of human sympathetic arterial baroreflex.

Relationship between the fall in blood pressure in the standing position and diaphragmatic muscle thickness: proof of concept study.

BACKGROUND: The diaphragm is an important muscle of respiration, and regulates the intrathoracic pressure. Blood pressure is regulated by the baroreceptor reflex system, and is also affected by intrathoracic pressure. We examined the relationship between the diaphragmatic muscle thickness and the degree of drop in blood pressure in the standing position. METHODS: We prospectively studied 15 healthy subjects. The diaphragmatic muscle thickness was measured using a B-mode ultrasonic imaging device. The blood pressure before and after standing was measured by a head-up tilt test. RESULTS: The diastolic blood pressure difference during expiration and inspiration showed a significant correlation with the diaphragmatic muscle thickness (r = 0.578, P = 0.024 and r = 0.518, P = 0.048, respectively). CONCLUSION: The diaphragmatic muscle thickness was related to the fall in diastolic blood pressure in the standing position. This indicates that adequate diaphragmatic muscle thickness helps to maintain intrathoracic pressure and prevents excessive drop in blood pressure in the standing position.

Effects of a preoperative immune-modulating diet in patients with esophageal cancer: a prospective parallel group randomized study.

PURPOSE: The aim of this pilot study was to investigate the effects of a preoperative immune-modulating diet (IMD) before thoracoscopic esophagectomy for patients with esophageal cancer. METHODS: Thirty patients who were diagnosed with resectable esophageal cancer were assigned to two groups: the IMD (n = 15) and the standard liquid diet (SLD; n = 15) groups. We evaluated postoperative parameters, such as the incidence of complications and the postoperative levels of cytokines as the primary endpoints. The secondary endpoint was the length of hospital stay. RESULTS: The peak levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α appeared on postoperative day (POD) 1 and POD 2 in the IMD and SLD group, respectively. The peak level of C-reactive protein (CRP) appeared on POD 3 in both groups (IMD 9.9 mg/dL, SLD 15.2 mg/dL). Overall, TNF-α levels in the IMD group were lower than those in the SLD group (P = 0.033). Furthermore, IL-6 (P = 0.182) and CRP (P = 0.191) levels, and the incidence of postoperative pneumonia (7.1 vs. 26.7%; P = 0.330) tended to be lower in the IMD group than in the SLD group. CONCLUSIONS: Preoperative IMD suppressed the elevation of the TNF-α levels after thoracoscopic esophagectomy in patients with esophageal cancer, although no different tendency was detected in terms of IL-6, CRP or postoperative complications.

Questionnaire survey on the use of a novel artificial pancreas by intensive care unit nurses.

The introduction of a color liquid-crystal display (LCD) on a novel artificial pancreas (STG-55, Nikkiso Co. Ltd. Tokyo, Japan) allowed nurses to more easily monitor changes in patients' blood glucose levels, compared to the previous model (STG-22). This study was conducted to examine the hypothesis that the STG-55 provided nurses with a feeling of security due to the introduction of the LCD screen. A questionnaire survey was conducted 6 months after the STG-55 was introduced (Survey 2012), among intensive care unit (ICU) nurses who had used both the STG-22 and the STG-55 for patient glycemic control. The results were then compared with the results from a questionnaire survey that was conducted after the STG-22 was introduced (Survey 2006). All ICU nurses (n = 19) responded to Survey 2012, and 95% of these nurses had responded to Survey 2006 (n = 19). After the introduction of the STG-22, 11 nurses (58%) reported becoming conscious of anxiety regarding hypoglycemia when they performed conventional glucose control with the sliding scale method. This anxiety awareness increased significantly (19 nurses, 100%; p < 0.01) after the STG-55 was introduced. However, there were no significant differences in the proportion of respondents who requested improvements in the blood withdrawal process. In conclusion, the results of our survey indicate that all ICU nurses became conscious of anxiety regarding the risk of hypoglycemia when using the conventional sliding scale method after the introduction of the STG-55. However, the respondents were not satisfied with the STG-55, due to difficulties encountered during blood withdrawal.

Metabolic effect of combined telmisartan and nifedipine CR therapy in patients with essential hypertension.

BACKGROUND: In addition to exerting a blood pressure (BP)-lowering effect, telmisartan produces favorable metabolic effects via peroxisome proliferator-activated receptor γ activation. While a combination of telmisartan and a calcium channel blocker is often used to achieve a target BP level, the metabolic effects of this drug combination remain unclear. Therefore, this study evaluated the metabolic effects of telmisartan plus nifedipine controlled release (CR) therapy, in hypertensive patients without metabolic disease. METHODS: Sixteen patients with essential hypertension, who had not undergone antihypertensive therapy in the previous 6 months, were studied. Patients were initiated on telmisartan (40 mg/day). If their office BP was not reduced to 140/90 mmHg after 6 weeks, nifedipine CR (20-40 mg per day) was added for 18 weeks. The other patients whose BP had achieved the target of 140/90 mmHg, continued only telmisartan. RESULTS: Telmisartan reduced BP (174 ± 13/92 ± 10 to 143 ± 22/78 ± 11 mmHg; P < 0.01) at 6 weeks in 16 patients, but eight patients did not achieve target BP levels and required addition of nifedipine. Telmisartan also resulted in a reduction in the homeostatic model assessment of insulin resistance (HOMA-IR) (1.30 ± 0.65 to 1.10 ± 0.42; P < 0.05) at 6 weeks, but did not affect adiponectin or leptin levels. Addition of nifedipine (n = 8) resulted in a reduction in BP (158 ± 18/80 ± 13 to 131 ± 8/73 ± 13 mmHg; P < 0.01) at 18 weeks, but did not affect the HOMA-IR (1.10 ± 0.40 to 1.02 ± 0.56; ns). In patients who did not require addition of nifedipine (n = 8), BP levels remained nearly identical at 18 weeks (127 ± 13/73 ± 9 to 128 ± 13/68 ± 8 mmHg; ns), and HOMA-IR also remained nearly identical. CONCLUSIONS: Telmisartan produced a favorable metabolic effect in hypertensive patients without preexisting metabolic disorders. Addition of nifedipine CR produced further BP-lowering effects, and resulted in maintenance of metabolic indices.

Influences of donepezil on cardiovascular system--possible therapeutic benefits for heart failure--donepezil cardiac test registry (DOCTER) study.

To study prospectively influences of donepezil, an acetylcholinesterase inhibitor against Alzheimer disease, on cardiovascular system, we evaluated cardiovascular changes occurring during new initialized treatment with donepezil in 49 dementia patients over 6 months. No patient suffered from cardiovascular events. In clinical changes between baseline and the first evaluation after donepezil treatment, heart rate and plasma brain natriuretic peptide (BNP) levels as a marker for heart failure did not change (BNP: 59.62 ± 62.71 pg/mL at baseline to 53.18 ± 42.34 pg/mL at first evaluation; P = 0.262). We further examined plasma BNP levels in 2 groups into which the patients were divided at baseline according to the cut-off plasma BNP level of 60 pg/mL. In patients with high level of BNP, the BNP levels decreased after administration of donepezil (116.39 ± 76.58 pg/mL at baseline to 82.24 ± 46.64 pg/mL at first evaluation; P = 0.011) with the tendency to be reduced in the follow-up period. BNP did not change in patients with low level of BNP. Donepezil seemed to be safe in patients with dementia without symptomatic heart disease and significantly decreased plasma BNP levels in patients with subclinical chronic heart failure.

Donepezil, anti-Alzheimer's disease drug, prevents cardiac rupture during acute phase of myocardial infarction in mice.

BACKGROUND: We have previously demonstrated that the chronic intervention in the cholinergic system by donepezil, an acetylcholinesterase inhibitor, plays a beneficial role in suppressing long-term cardiac remodeling after myocardial infarction (MI). In comparison with such a chronic effect, however, the acute effect of donepezil during an acute phase of MI remains unclear. Noticing recent findings of a cholinergic mechanism for anti-inflammatory actions, we tested the hypothesis that donepezil attenuates an acute inflammatory tissue injury following MI. METHODS AND RESULTS: In isolated and activated macrophages, donepezil significantly reduced intra- and extracellular matrix metalloproteinase-9 (MMP-9). In mice with MI, despite the comparable values of heart rate and blood pressure, the donepezil-treated group showed a significantly lower incidence of cardiac rupture than the untreated group during the acute phase of MI. Immunohistochemistry revealed that MMP-9 was localized at the infarct area where a large number of inflammatory cells including macrophages infiltrated, and the expression and the enzymatic activity of MMP-9 at the left ventricular infarct area was significantly reduced in the donepezil-treated group. CONCLUSION: The present study suggests that donepezil inhibits the MMP-9-related acute inflammatory tissue injury in the infarcted myocardium, thereby reduces the risk of left ventricular free wall rupture during the acute phase of MI.

Effects of various doses of aspirin on platelet activity and endothelial function.

Although aspirin has become an established medicine for cardiac and cerebrovascular diseases, the optimal dose remains unknown. We evaluated the optimal dose of aspirin on platelet activity and endothelial function by administering 11 healthy male volunteers (32 ± 6 years of age) doses of aspirin that were increased in a stepwise manner (0, 81, 162, 330 and 660 mg/day) every 3 days. Platelet activity was assessed as surface P-selectin expression (%) measured by flow cytometry and the platelet aggregation ratio. Endothelial function in the brachial artery was assessed by measuring flow-mediated dilation (FMD) before and after reactive hyperemia. Platelet aggregation and P-selectin expression were significantly and dose-dependently suppressed (81-660 mg), and the FMD ratio tended to increase from 0 to 162 mg, but decreased significantly at 660 mg. In conclusion, although aspirin suppressed platelet activity and even surface P-selectin expression, higher doses worsened endothelial-mediated arterial dilation.

Bolus oral or continuous intestinal amino acids reduce hypothermia during anesthesia in rats.

We hypothesized that, with oral or intestinal administration of amino acids (AA), we may reduce hypothermia during general anesthesia as effectively as with intravenous AA. We, therefore, examined the effect of bolus oral and continuous intestinal AA in preventing hypothermia in rats. Male Wistar rats were anesthetized with sevoflurane for induction and with propofol for maintenance. In the first experiment, 30 min before anesthesia, rats received one bolus 42 mL/kg of AA solution (100 g/L) or saline orally. Then for the next 3 h during anesthesia, they received 14 mL/kg/h of AA and/or saline intravenously. They were in 4 groups: I-A/A, both AA; I-A/S, oral AA and intravenous saline; I-S/A, oral saline and intravenous AA; I-S/S, both saline. In the second experiment, rats received 14 mL/kg/h duodenal AA and/or saline for 2 h. They were in 3 groups: II-A/S, duodenal AA and intravenous saline; II-S/A, duodenal saline and intravenous AA; II-S/S, both saline. Core body temperature was measured rectally. After the second experiment, serum electrolytes were examined. In both experiments, rectal temperature decreased in all groups during anesthesia. However, the decrease in rectal temperature was significantly less in groups receiving AA than in groups receiving only saline. In the second experiment, although there was no significant difference in the decrease in body temperature between II-A/S and II-S/A, Na(+) concentration was significantly lower in II-S/A. In conclusion, AA, administered orally or intestinally, tended to keep the body temperature stable during anesthesia without disturbing electrolyte balance. These results suggest that oral or enteral AA may be useful for prevention of hypothermia in patients.

Differential regulation of TNF receptors by vagal nerve stimulation protects heart against acute ischemic injury.

Vagal nerve stimulation (VS) has been reported to improve the survival after both acute and chronic myocardial infarction through the release of neurotransmitter ACh. However, the precise mechanism behind its beneficial effect is still unknown. In this study, we demonstrate the upregulation of tumor necrosis factor-alpha (TNF-alpha) and its cell survival TNF receptor-2 (TNFR2) as the mechanism behind VS induced myocardial protection. We investigated the effects of efferent VS on myocardial ischemic injury with in vivo and in vitro mouse models. In in vivo hearts VS significantly increased the expression of TNF-alpha both at the messenger and protein level after 3-hours of myocardial ischemia. In the in vitro studies ACh treatment before hypoxia, induced a significant upregulation of TNF-alpha compared to the untreated cardiomyocytes. Immunofluorescence analysis confirmed the synthesis of TNF-alpha by cardiomyocytes both in vivo and in vitro. VS also significantly reduced the myocardial infarct size (23.9+/-5.7% vs. 56+/-1.9%) and activated the cell survival Akt cascade system. Further, ACh upregulated the cell survival TNFR2 expression, while downregulating the cell destructive TNF receptor 1 (TNFR1) expression. These results were confirmed using the TNF receptors deficient mice, where the VS mediated protection was lost both in vivo and in vitro in TNFR2 (TNFR2(-/-)) and TNF receptors double knock out (TNFR1(-/-)2(-/-)) mice. VS and ACh protects the heart against acute ischemia or hypoxic injury by differentially regulating the TNF receptor subtypes.

Anti-Alzheimer's drug, donepezil, markedly improves long-term survival after chronic heart failure in mice.

BACKGROUND: We previously reported that chronic vagal nerve stimulation markedly improved long-term survival after chronic heart failure (CHF) in rats through cardioprotective effects of acetylcholine, independent of the heart rate-slowing mechanism. However, such an approach is invasive and its safety is unknown in clinical settings. To develop an alternative therapy with a clinically available drug, we examined the chronic effect of oral donepezil, an acetylcholinesterase inhibitor against Alzheimer's disease, on cardiac remodeling and survival with a murine model of volume-overloaded CHF. METHODS AND RESULTS: Four weeks after surgery of aortocaval shunt, CHF mice were randomized into untreated and donepezil-treated groups. Donepezil was orally given at a dosage of 5 mgxkg(-1)xday(-1). After 4 weeks of treatment, we evaluated in situ left ventricular (LV) pressure, ex vivo LV pressure-volume relationships, and LV expression of brain natriuretic peptides (BNP). We also observed survival for 50 days. When compared with the untreated group, the donepezil-treated group had significantly low LV end-diastolic pressure, high LV contractility, and low LV expression of BNP. Donepezil significantly reduced the heart weight and markedly improved the survival rate during the 50-day treatment period (54% versus 81%, P < .05). CONCLUSIONS: Oral donepezil improves survival of CHF mice through prevention of pumping failure and cardiac remodeling.

Vagal nerve stimulation prevents reperfusion injury through inhibition of opening of mitochondrial permeability transition pore independent of the bradycardiac effect.

BACKGROUND: In spite of recent advances in coronary interventional therapy, reperfusion injury is still considered to be a major problem in patients undergoing surgical procedures, such as bypass grafting. Here we demonstrate a novel therapeutic strategy against ischemia-reperfusion injury: vagally mediated prevention of reperfusion-induced opening of mitochondrial permeability transition pore. METHODS: We investigated the effects of efferent vagal stimulation on myocardial reperfusion injury with ex vivo and in vitro rat models. In the ex vivo model the hearts were perfused with intact vagal innervation, which allowed us to study the effects of the vagal nerve on the heart without other systemic effects. RESULTS: Compared with sham stimulation, vagal stimulation exerted a marked anti-infarct effect irrespective of the heart rate (34% +/- 6% vs 85% +/- 9% at a heart rate of 300 beats/min, 37% +/- 4% vs 43% +/- 5% at a heart rate of 250 beats/min, and 39% +/- 4% vs 88% +/- 7% at a heart rate of 350 beats/min) after a 30-minute period of global ischemia, activated cell-survival Akt cascade, prevented downregulation of the antiapoptotic protein Bcl-2, and suppressed cytochrome-c release and caspase-3 activation. Furthermore, vagal stimulation-treated hearts exhibited a significant improvement in left ventricular developed pressure (78 +/- 5 vs 45 +/- 8 mm Hg) and a significant attenuation in an incremental change in left ventricular end-diastolic pressure during reperfusion. These beneficial effects of vagal stimulation were abolished by a permeability transition pore opener, atractyloside. In the in vitro study with primary-cultured cardiomyocytes, acetylcholine prevented a reoxygenation-induced collapse in mitochondrial transmembrane potential through inhibition of permeability transition pore opening. CONCLUSION: Vagal stimulation would be a potential adjuvant therapy for the rescue of ischemic myocardium from reperfusion injury, and the protective effects are independent of its bradycardiac effects.

Chronic intermittent fasting improves the survival following large myocardial ischemia by activation of BDNF/VEGF/PI3K signaling pathway.

Chronic heart failure (CHF) is the major cause of death in the developed countries. Calorie restriction is known to improve the recovery in these patients; however, the exact mechanism behind this protective effect is unknown. Here we demonstrate the activation of cell survival PI3kinase/Akt and VEGF pathway as the mechanism behind the protection induced by intermittent fasting in a rat model of established chronic myocardial ischemia (MI). Chronic MI was induced in rats by occlusion of the left coronary artery. Two weeks later, the rats were randomly assigned to a normal feeding group (MI-NF) and an alternate-day feeding group (MI-IF). After 6 weeks of observation, we evaluated the effect of intermittent fasting on cellular and ventricular remodeling and long-term survival after CHF. Compared with the normally fed group, intermittent fasting markedly improved the survival of rats with CHF (88.5% versus 23% survival, P<0.05). The heart weight body weight ratio was significantly less in the MI-IF group compared to the MI-NF group (3.4+/-0.17 versus 3.9+/-0.18, P<0.05). Isolated heart perfusion studies exhibited well preserved cardiac functions in the MI-IF group compared to the MI-NF group (P<0.05). Molecular studies revealed the upregulation of angiogenic factors such asHIF-1-alpha (3010+/-350% versus 650+/-151%), BDNF (523+/-32% versus 110+/-12%), and VEGF (450+/-21% versus 170+/-30%) in the fasted hearts. Immunohistochemical studies confirmed increased capillary density (P<0.001) in the border area of the ischemic myocardium and synthesis VEGF by cardiomyocytes. Moreover fasting also upregulated the expression of other anti-apoptotic factors such as Akt and Bcl-2 and reduced the TUNEL positive apoptotic nuclei in the border zone. Chronic intermittent fasting markedly improves the long-term survival after CHF by activation through its pro-angiogenic, anti-apoptotic and anti-remodeling effects.

Intraoperative infusion of acetated Ringer solution containing glucose and ionized magnesium reduces ketogenesis and maintains serum magnesium.

The effect of glucose infusion during surgery on glucose metabolism has not been investigated sufficiently. We, therefore, examined the effect after the infusion of 1% glucose acetated Ringer solution containing Mg2+ during surgery on ketogenesis and serum Mg2+ concentrations. Patients, classified as ASA I-II, age 51-80 years, were randomly assigned to receive infusion of acetated Ringer solution. The G/Mg group received infusion with 1% glucose, Na+ 140mEq/L, Mg2+ 2 mEq/L, and the C group received infusion with glucose free solution containing Na+ 130 mEq/L without Mg2+. Both solutions were infused at a rate of 25 mL/kg for the first hour, and main-tained at 4 mL/kg/hr thereafter. Blood samples were collected three times: before infusion and at 1 hour and 4 hours after the start of infusion. Electrolytes and glucose metabolism were evaluated at each sampling. After rapid infusion, blood glucose level significantly increased to 170+/-19mg/dL in the G/Mg group, but it returned to close to baseline after 4 hours and serum ketone bodies did not increase during infusion. In the C group, however, blood glucose never increased beyond 110 mg/dL, but both acetoacetic and hydroxybutyric acids increased significantly at the third measurement.

A HIF-1alpha-related gene involved in cell protection from hypoxia by suppression of mitochondrial function.

Recently, we reported that acetylcholine-induced hypoxia-inducible factor-1alpha protects cardiomyocytes from hypoxia; however, the downstream factors reducing hypoxic stress are unknown. We identified apoptosis inhibitor (AI) gene as being differentially expressed between von Hippel Lindau (VHL) protein-positive cells with high levels of GRP78 expression and VHL-negative cells with lower GRP levels, using cDNA subtraction. AI decreased GRP78 level, suppressed mitochondrial function, reduced oxygen consumption and, ultimately, suppressed hypoxia-induced apoptosis. By contrast, knockdown of the AI gene increased mitochondrial function. Hypoxic cardiomyocytes and ischemic myocardium showed increased AI mRNA expression. These findings suggest that AI is involved in suppressing mitochondrial function, thereby leading to cellular stress eradication and consequently to protection during hypoxia.

Granulocyte colony-stimulating factor activates Wnt signal to sustain gap junction function through recruitment of beta-catenin and cadherin.

Our previous study reveals that connexin (Cx) 43 is targeted by ACh to prevent lethal arrhythmia. Granulocyte colony-stimulating factor (G-CSF), used against ischemic heart failure, may be another candidate, however, with unknown mechanisms. Therefore, we investigated the cellular effects of G-CSF. G-CSF activated the Wnt and Jak2 signals in cardiomyocytes, and up-regulated Cx43 protein and phosphorylation levels. In addition, G-CSF enhanced the localization of Cx43, beta-catenin and cadherin on the plasma membrane. G-CSF inhibited the reduction of Cx43 by enhancing Cx43 anchoring and sustained the cell-cell communication during hypoxia. Consequently, G-CSF suppressed ventricular arrhythmia induced by myocardial infarction. As a result, G-CSF could be used as a therapeutic tool for arrhythmia.

Acetylcholine inhibits the hypoxia-induced reduction of connexin43 protein in rat cardiomyocytes.

In a recent study, we demonstrated that vagal stimulation increases the survival of rats with myocardial infarction by inhibiting lethal arrhythmia through regulation of connexin43 (Cx43). However, the precise mechanisms for this effect remain to be elucidated. To investigate these mechanisms and the signal transduction for gap junction regulation, we investigated the effect of acetylcholine (ACh), a parasympathetic nerve system neurotransmitter, on the gap junction component Cx43 using H9c2 cells. When cells were subjected to hypoxia, the total Cx43 protein level was decreased. In contrast, pretreatment with ACh inhibited this effect. To investigate the signal transduction, cells were pretreated with L-NAME, a nitric oxide synthase inhibitor, followed by ACh and hypoxia. L-NAME was found to suppress the ACh effect. However, a NO donor, SNAP, partially inhibited the hypoxia-induced reduction in Cx43. To delineate the mechanisms of the decrease in Cx43 under hypoxia, cells were pretreated with MG132, a proteasome inhibitor. Proteasome inhibition produced a striking recovery of the decrease in the total Cx43 protein level under hypoxia. However, cotreatment with MG132 and ACh did not produce any further increase in the total Cx43 protein level. Functional studies using ACh or okadaic acid, a phosphatase inhibitor, revealed that both reagents inhibited the decrease in the dye transfer induced by hypoxia. These results suggest that ACh is responsible for restoring the decrease in the Cx43 protein level, resulting in functional activation of gap junctions.

Nitric oxide stimulates vascular endothelial growth factor production in cardiomyocytes involved in angiogenesis.

BACKGROUND: Hypoxia-inducible factor (HIF)-1alpha regulates the transcription of lines of genes, including vascular endothelial growth factor (VEGF), a major gene responsible for angiogenesis. Several recent studies have demonstrated that a nonhypoxic pathway via nitric oxide (NO) is involved in the activation of HIF-1alpha. However, there is no direct evidence demonstrating the release of angiogenic factors by cardiomyocytes through the nonhypoxic induction pathway of HIF-1alpha in the heart. Therefore we assessed the effects of an NO donor, S-Nitroso-N-acetylpenicillamine (SNAP) on the induction of VEGF via HIF-1alpha under normoxia, using primary cultured rat cardiomyocytes (PRCMs). METHODS AND RESULTS: PRCMs treated with acetylcholine (ACh) or SNAP exhibited a significant production of NO. SNAP activated the induction of HIF-1alpha protein expression in PRCMs during normoxia. Phosphatidylinositol 3-kinase (PI3K)-dependent Akt phosphorylation was induced by SNAP and was completely blocked by wortmannin, a PI3K inhibitor, and NG-nitro-L-arginine methyl ester (L-NAME), a NO synthase inhibitor. The SNAP treatment also increased VEGF protein expression in PRCMs. Furthermore, conditioned medium derived from SNAP-treated cardiomyocytes phosphorylated the VEGF type-2 receptor (Flk-1) of human umbilical vein endothelial cells (a fourfold increase compared to the control group, p < 0.001, n = 5) and accelerated angiogenesis. CONCLUSION: Our results suggest that cardiomyocytes produce VEGF through a nonhypoxic HIF-1alpha induction pathway activated by NO, resulting in angiogenesis.

Artificial baroreflex: clinical application of a bionic baroreflex system.

BACKGROUND: We proposed a novel therapeutic strategy against central baroreflex failure: implementation of an artificial baroreflex system to automatically regulate sympathetic vasomotor tone, ie, a bionic baroreflex system (BBS), and we tested its efficacy in a model of sudden hypotension during surgery. METHODS AND RESULTS: The BBS consisted of a computer-controlled negative-feedback circuit that sensed arterial pressure (AP) and automatically computed the frequency (STM) of a pulse train required to stimulate sympathetic nerves via an epidural catheter placed at the level of the lower thoracic spinal cord. An operation rule was subsequently designed for the BBS using a feedback correction with proportional and integral gain factors. The transfer function from STM to AP was identified by a white noise system identification method in 12 sevoflurane-anesthetized patients undergoing orthopedic surgery involving the cervical vertebrae, and the feedback correction factors were determined with a numerical simulation to enable the BBS to quickly and stably attenuate an external disturbance on AP. The performance of the designed BBS was then examined in a model of orthostatic hypotension during knee joint surgery (n=21). Without the implementation of the BBS, a sudden deflation of a thigh tourniquet resulted in a 17+/-3 mm Hg decrease in AP within 10 seconds and a 25+/-2 mm Hg decrease in AP within 50 seconds. By contrast, during real-time execution of the BBS, the decrease in AP was 9+/-2 mm Hg at 10 seconds and 1+/-2 mm Hg at 50 seconds after the deflation. CONCLUSIONS: These results suggest the feasibility of a BBS approach for central baroreflex failure.