Chiyohiko Shindoh

Effect of Nonuniform Muscle Contraction on Sustainability and Frequency of Triggered Arrhythmias in Rat Cardiac Muscle

Background— Arrhythmias are benign or lethal, depending on their sustainability and frequency. To determine why lethal arrhythmias are prone to occur in diseased hearts, usually characterized by nonuniform muscle contraction, we investigated the effect of nonuniformity on sustainability and frequency of triggered arrhythmias. Methods and Results— Force, membrane potential, and intracellular Ca2+ concentration ([Ca2+]i) were measured in 51 rat ventricular trabeculae. Nonuniform contraction was produced by exposing a restricted region of muscle to a jet of 20 mmol/L 2,3-butanedione monoxime (BDM) or 20 &mgr;mol/L blebbistatin. Sustained arrhythmias (>10 seconds) could be induced by stimulus trains for 7.5 seconds only with the BDM or blebbistatin jet (100 nmol/L isoproterenol, 1.0 mmol/L [Ca2+]o, 24°C). During sustained arrhythmias, Ca2+ surges preceded synchronous increases in [Ca2+]i, whereas the stoppage of the BDM jet made the Ca2+ surges unclear and arrested sustained arrhythmias (n=6). With 200 nmol/L isoproterenol, 2.5 mmol/L [Ca2+]o, and the BDM jet, lengthening or shortening of the muscle during sustained arrhythmias accelerated or decelerated their cycle in both the absence (n=10) and presence (n=10) of 100 &mgr;mol/L streptomycin, a stretch-activated channel blocker, respectively. The maximum rate of force relaxation correlated inversely with the change in cycle lengths (n=14; P<0.01). Sustained arrhythmias with the BDM jet were significantly accelerated by 30 &mgr;mol/L SCH00013, a Ca2+ sensitizer of myofilaments (n=10). Conclusion— These results suggest that nonuniformity of muscle contraction is an important determinant of the sustainability and frequency of triggered arrhythmias caused by the surge of Ca2+ dissociated from myofilaments in cardiac muscle.

Effects of l-NAME and l-Arginine on Diaphragm Contraction in a Septic Animal Model

The effects of nitric oxide on diaphragm contraction after endotoxin administration were studied in Wistar rats. The animals were divided into seven treatments: a saline-injected group as control, three groups injected with L-NAME (0.01, 0.1, 1 mg/kg) and three groups injected with L-arginine (1, 10, 100 mg/kg). Escherichia coli endotoxin was injected into the peritoneal cavity 15 min later. Twitch kinetics and force-frequency curves were measured 0, 2, and 4 hr after endotoxin injection. In the control group, the force-frequency curves significantly decreased from 0 hr to 4 hr. In the L-NAME group, the force-frequency curves at 4 hr showed significant increases in a dose-dependent manner. In the L-arginine group, the force-frequency curve with 100 mg/kg at 4 hr showed a significant increase. There was no consistent change in the contraction time, half relaxation time, or fatiguability. NADPH diaphorase histochemistry performed on diaphragm muscle samples 4 hr after endotoxin injection showed positive in the control and L-arginine group, but was only weakly observed in L-NAME group. These data suggest that nitric oxide contributes to the endotoxin induced diaphragm contractile deterioration.

Effect of clenbuterol on peripheral airway obstruction in bronchial asthma

A study was carried out in 6 patients with bronchial asthma to investigate the effects of clenbuterol, a beta 2-sympathomimetic bronchodilator, on peripheral airway obstruction. The basal lung functions of the patients were almost within normal range in both vital capacity (VC) and forced expiratory volume in 1 second (FEV1), but their maximal flow rates were lower in effort-independent phase of both maximal expiratory flow volume (MEFV) curve and partial expiratory flow volume (PEFV) curve. Furthermore, they demonstrated marked basal frequency dependence of dynamic compliance [CL,dyn]. Oral administration of clenbuterol (40 micrograms) produced a significant increase in the maximal flow in effort-independent phase of both MEFV and PEFV curves, and markedly decreased frequency dependence of CL,dyn in comparison with the baseline values, while it improved both VC and FEV1 to a lesser extent. These results suggest that clenbuterol preferentially reduced the peripheral airway obstruction in bronchial asthma.

The total urine protein-to-creatinine ratio can predict the presence of microalbuminuria.

Background The Kidney Disease: Improving Global Outcomes chronic kidney disease (CKD) guidelines recommend that CKD be classified based on the etiology, glomerular filtration rate (GFR) and degree of albuminuria. The present study aimed to establish a method that predicts the presence of microalbuminuria by measuring the total urine protein-to-creatinine ratio (TPCR) in patients with cardiovascular disease (CVD) risk factors. Methods and Results We obtained urine samples from 1,033 patients who visited the cardiovascular clinic at St. Lukes International Hospital from February 2012 to August 2012. We measured the TPCR and the urine albumin-to-creatinine ratio (ACR) from random spot urine samples. We performed correlation, receiver operating characteristic (ROC) curve, sensitivity, and subgroup analyses. There was a strong positive correlation between the TPCR and ACR (R2 = 0.861, p<0.001). A ROC curve analysis for the TPCR revealed a sensitivity of 94.4%, a specificity of 86.1%, and an area under the curve of 0.903 for detecting microalbuminuria for a TPCR cut-off value of 84 mg/g of creatinine. The subgroup analysis indicated that the cut-off value could be used for patients with CVD risk factors. Conclusions These results suggest that the TPCR with an appropriate cut-off value could be used to screen for the presence of microalbuminuria in patients with CVD risk factors. This simple, inexpensive measurement has broader applications, leading to earlier intervention and public benefit.

Inhalation of Budesonide/Formoterol Increases Diaphragm Muscle Contractility

BACKGROUND Although budesonide/formoterol (BUD/FORM) is used clinically as a steroid/β(2)-agonist single inhaler, it has not yet been clarified whether BUD/FORM has inotropic effects on diaphragm muscles after inhalation. METHODS We examined the effects of BUD/FORM inhalation, endotoxin injection, and BUD/FORM inhalation plus endotoxin injection on diaphragm contractile properties and nitric oxide (NO) production. After these three treatments, the diaphragm muscle was dissected, and its contractile properties were measured. Histochemistry for the reduced form of nicotinamide adenine dinucleotide phosphate diaphorase was performed for each muscle to assess NO production. RESULTS The force-frequency curves showed an upward shift 1 h after inhalation (p < 0.05) in the BUD/FORM inhalation only group. The force-frequency curves showed a downward shift 4 h after injection (p < 0.001) in the endotoxin injection groups. In the BUD/FORM inhalation plus endotoxin injection groups, a downward shift in the force-frequency curves at 4 h after endotoxin injection was prevented. NO production was inhibited in the BUD/FORM inhalation plus endotoxin injection group compared with that of the endotoxin injection only groups. CONCLUSIONS BUD/FORM inhalation has an inotropic effect on diaphragm muscle, protects diaphragm muscle deterioration after endotoxin injection, and inhibits NO production. Increments in muscle contractility with BUD/FORM inhalation are induced through a synergistic effect of an anti-inflammatory agent and β(2)-agonist.

Effects of Changes in Breathing Pattern on the Sensation of Dyspnea during Inspiratory Loaded Breathing

The ventilatory responses to external resistive and elastic loadings of the respiratory system have been extensively studied in a variety of experimental animals as well as also humans. It has been known that there are marked differences in the pattern of breathing during sustained inspiratory loadings between awake and anesthetized subjects (Margaria et al., 1973; Cherniack and Altose,1981; Milic-Emili and Zin,1986). In awake subjects sustained external elastic loading generally leads to increased breathing frequency and decreased tidal volume, whereas inspiratory resistive loading causes decreased frequency and increased tidal volume. By contrast in anesthetized subjects the changes in respiratory frequency are small or absent and independent of the type of external loading (Milic-Emili and Zin, 1986). Because the different responses between the awake and anesthetized subjects cannot be explained as a simple reflex (Cherniack and Altose,1981; Milic-Emili and Zin, 1986), it is assumed that conscious awareness of breathing or behavioral response may be responsible for the different breathing pattern observed during inspiratory resistive and elastic loadings. However, the nature of the behavioral control has not yet been evaluated. Thus, the aim of the present study was to examine the hypothesis that the breathing pattern during inspiratory loading might be optimized through cortical response so that the sensation of dyspnea would be minimized.

Diaphragm Muscle Contraction Decrease in a Mouse Model of Ovalbumin-Induced Allergic Airway Inflammation

Objective: We investigated diaphragm contractile and inflammatory properties of mice with OVA sensitization and challenge. Methods: BALB/c mice were sensitized to OVA by intraperitoneal (i.p.) injection at 0 and 7 days, and challenged with aerosolized OVA on 21, 22, and 23 days (O/O group). Budesonide/Formoterol combination was inhaled on days 21, 22, and 23 before OVA challenge on those same days (O/OC group). Control mice were sensitized and challenged with an aerosolized saline (O-group). The diaphragm contractile and inflammatory properties were measured on day 24. NOS activity in the diaphragm muscle was evaluated by NADPH diaphorase staining. IL-4 and IL-13 levels of BALF, as well as lung tissue and diaphragm muscle homogenates were measured by ELISA. Results: Force-frequency (F/f) curves of O/O and O/OC shifted downward in comparison with O- (p<0.05). NADPH diaphorase staining results of O/O and O/OC showed a significantly higher density compared with O-. The IL-4 level of diaphragm muscle homogenates increased significantly in the O/O compared with the O- and O/OC. Conclusions: OVA sensitization and challenge decreased diaphragm muscle contraction, increased NOS activity, IL-4 levels of diaphragm in a mouse model. Budesonide/Formoterol combination could protect diaphragm muscle weakness and inflammation. According to the traditional concept of the contemporary Immunology, neither autoimmune diseases nor allergic diseases can be cured completely. Nevertheless, a fortunate coincidence led me to discovery of a novel concept that eliminations of the causes of these diseases are possible. In other words, combinations of pathogenic antibodies with responsible cells, namely, cytolytic T lymphocytes in cases of autoimmune diseases and mast cells in cases of allergic diseases, can be decomposed by replacing the pathogenic antibodies with non-specific antibodies. In more detail, intradermal injections with a non-specific antigen preparation induce production of non-specific antibodies in the body of the patient. Repetitions of the injections bring about an accumulation of them. Accumulated non-specific antibodies will occupy most of the receptors on the surface of responsible cells. When the accumulation reaches the sufficient level, virtually no pathogenic antibodies would remain on the receptors. That is, no causes of the diseases remain. Naturally, where there is no cause, there is no disease. Details are demonstrated elsewhere.

Effect of Carbenoxolone on Arrhythmogenesis in Rat Ventricular Muscle.

BACKGROUND Connexin43 (Cx43) is a major connexin that forms gap junction (GJ) channels in the heart and is also present in the cell membrane as unopposed/non-junctional hemichannels and in the inner mitochondrial membrane. By using carbenoxolone (CBX), a blocker of Cx43, the effect of the blockade of Cx43 on Ca(2+)waves and triggered arrhythmias in the myocardium with non-uniform contraction was examined. METHODS AND RESULTS Trabeculae were obtained from rat hearts. Force, [Ca(2+)]i, and the diffusion coefficient were measured. Non-uniform contraction was produced with a 2,3-butanedione monoxime jet. Ca(2+)waves were induced by electrical stimulation. Inducibility of arrhythmias was estimated based on the minimal [Ca(2+)]oat which arrhythmias were induced. The Ca(2+)spark rate was measured in isolated single rat ventricular myocytes. CBX reduced the GJ permeability, whereas it did not change force and [Ca(2+)]itransients. CBX increased the Ca(2+)leak from the sarcoplasmic reticulum in trabeculae and increased the Ca(2+)spark rate in isolated single myocytes. CBX increased the velocity of Ca(2+)waves and further increased the inducibility of arrhythmias. Modulation of mitochondrial KATPchannels by diazoxide, cromakalim and 5-hydroxydecanoic acid affected the inducibility of arrhythmias increased by CBX. CONCLUSIONS These results suggest that in diseased hearts, Cx43 plays an important role in the occurrence of triggered arrhythmias, probably under the modulation of mitochondrial KATPchannels.

Modified cut-off value of the urine protein-to-creatinine ratio is helpful for identifying patients at high risk for chronic kidney disease: Validation of the revised Japanese guideline

Chronic kidney disease (CKD) is a global public health issue, and strategies for its early detection and intervention are imperative. The latest Japanese CKD guideline recommends that patients without diabetes should be classified using the urine protein-to-creatinine ratio (PCR) instead of the urine albumin-to-creatinine ratio (ACR); however, no validation studies are available. This study aimed to validate the PCR-based CKD risk classification compared with the ACR-based classification and to explore more accurate classification methods. We analyzed two previously reported datasets that included diabetic and/or cardiovascular patients who were classified into early CKD stages. In total, 860 patients (131 diabetic patients and 729 cardiovascular patients, including 193 diabetic patients) were enrolled. We assessed the CKD risk classification of each patient according to the estimated glomerular filtration rate and the ACR-based or PCR-based classification. The use of the cut-off value recommended in the current guideline (PCR 0.15 g/g creatinine) resulted in risk misclassification rates of 26.0% and 16.6% for the two datasets. The misclassification was primarily caused by underestimation. Moderate to substantial agreement between each classification was achieved: Cohens kappa, 0.56 (95% confidence interval, 0.45-0.69) and 0.72 (0.67-0.76) in each dataset, respectively. To improve the accuracy, we tested various candidate PCR cut-off values, showing that a PCR cut-off value of 0.08-0.10 g/g creatinine resulted in improvement in the misclassification rates and kappa values. Modification of the PCR cut-off value would improve its efficacy to identify high-risk populations who will benefit from early intervention.

Effects of Inhalation or Incubation of Oxitropium Bromide on Diaphragm Muscle Contractility in Mice

BACKGROUND Although oxitropium bromide is used clinically as an anticholinergic drug (i.e., parasympathetic antagonist) to relax airway smooth muscle, we examined whether it has or does not have any effects on diaphragm muscle. METHODS Three treatment sets, an oxitropium bromide inhalation only group, an oxitropium bromide inhalation plus endotoxin injection group (in vivo) and an oxitropium bromide incubation group (in vitro) were studied as to diaphragm muscle contractile properties. RESULTS Oxitropium bromide inhalation shifted force-frequency curves upward at 2 h after inhalation (p < 0.05) and inhibited the decrease of force-frequency curves due to endotoxin injection in vivo. Incubation with oxitropium bromide of untreated diaphragm muscle and diaphragm muscle injected with endotoxin did not increase the force-frequency curves dose-dependently in vitro; however, it caused both types of muscle to be fatigue resistant. CONCLUSIONS We speculate that the increment of muscle contractility with the inhalation of oxitropium bromide was induced by the antagonization of musucarinic acetylcholine receptors (mAChR). In addition, the changes of fatigue resistance provoked by oxitropium bromide, which also is speculated to antagonize mAChR, may be beneficial in the treatment of patients with COPD.