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Yoshihiro Nishimura

Publications and source records attributed to Yoshihiro Nishimura.

42 records · Page 3Linked to original sources

Modulation of airway responsiveness by anionic and cationic polyelectrolyte substances.

To elucidate the effects of anionic and cationic polyelectrolyte substance on bronchoconstriction, we examined the serial changes in respiratory resistance (Rrs) in ovalbumin-sensitized guinea pigs after antigen exposure with or without pre-inhalation of low-molecular-weight heparin, poly-L-glutamic acid, poly-L-lysine and dextran, and with or without oral intake of dalteparin. Both immediate and late responses after antigen exposure were significantly decreased after pretreatment with inhaled low-molecular-weight heparin and poly-L-glutamic acid compared with saline alone. The late response was significantly decreased after pretreatment with oral dalteparin. Both low-molecular-weight heparin and poly-L-glutamic acid significantly decreased the airway response to methacholine in sensitized guinea pigs. In sensitized guinea pigs, the airway response to methacholine was significantly increased after pretreatment with inhaled poly-L-lysine. Pretreatment with inhaled low-molecular-weight heparin before poly-L-lysine exposure significantly suppressed the airway hyperresponsiveness after inhaled poly-L-lysine. These findings indicated that the "cationic-anionic interaction" plays an important role in airway responsiveness.

Airway Resistance↗

Properties of voltage dependent potassium currents in acutely isolated rat oculomotor neurons.

Voltage-dependent potassium currents in oculomotor neurons (OMNs) were studied with whole-cell patch clamp recordings. Fast inactivating outward currents (I(fast)) had half activation voltage (Vh) of -37.1 mV with slope factor (Vc) of 10.9 mV. I(fast) had half inactivation voltage (Vh) of -66.5 mV and Vc of 11.4 mV. I(fast) decayed with a time constant(tau) of 5.1 ms at +10 mV. I(fast) were sensitive to 4-aminopyridine, showing 50% inhibitory concentration (IC(50)) of 0.97 mM. Slowly inactivating outward currents (I(slow)) had two components. The low-concentration-TEA-sensitive currents had Vh of -3.7 mV with Vc of 9.7 mV in activation and had Vh of -54.7 mV with Vc of 23.8 mV in inactivation. The persistent currents had Vh of 7.4 mV and Vc of 11.8 mV in activation and Vh of -54.4 mV and Vc of 21.2 mV in inactivation. Decay of I(slow) (+10 mV) followed a double exponential time course (tau 215, 1165.6 ms). Low-concentration-TEA-sensitive currents were blocked completely by tetraethylammonium (TEA) of 3 mM with an IC(50) of 1.52 mM. Higher concentrations (3-20 mM) of TEA blocked the persistent currents, with an IC(50) of 6.9 mM.

Action Potentials↗

Bronchial hyperresponsiveness in patients with squamous cell lung cancer.

OBJECTIVE: The aim of this study was to examine the relationship between bronchial hyperresponsiveness, both in vivo and in vitro, and the type of lung cancer (squamous cell or adenocarcinoma). METHODOLOGY: We measured airway responsiveness by methacholine inhalation test in 33 patients with squamous cell lung cancer and 44 patients with lung adenocarcinoma. In addition, airway smooth muscle reactivity to acetylcholine was measured in vitro in specimens from some patients. RESULTS: Seventeen of 33 patients with squamous cell cancer and three of 44 patients with adenocarcinoma showed bronchial hyperresponsiveness (BHR). Multiple regression analysis as used to assess the log of the minimum cumulative dose to decrease respiratory conductance vs six variables: cancer phenotype, FEV1 (% predicted), FEV1/FVC (%), smoking pack years, gender and the location of tumour. The phenotype (squamous cell cancer) was the only factor associated with BHR. However, there was no significant difference in airway smooth muscle reactivity to acetylcholine in vitro in bronchial muscle samples from squamous cell cancer patients (n = 6) and adenocarcinoma patients (n = 6). CONCLUSION: The present findings suggest that bronchial hyperresponsiveness in patients with squamous cell lung cancer is not determined solely by bronchial smooth muscle hyperreactivity.

Adenocarcinoma↗

[Measurement of left ventricular chamber and myocardial volume in hypertrophic cardiomyopathy patients by ECG-gated myocardial perfusion SPECT: application of a newly developed edge-detection algorithm].

Quantitative gated SPECT (QGS) software has been reported to demonstrate inaccurate edge detection in the left ventricular chamber in hypertrophic cardiomyopathy patients. In this study we developed a method to calculate left ventricular volume (LVV) and left myocardial volume (LMV) from gated SPECT data using a newly developed edge-detection algorithm, and we compared it with the QGS method of calculating LVV and LMV in a phantom study. Our method gave more accurate measurements LVV and LMV whereas the QGS method underestimated LMV. Compared with QGS LVV and LMV, our method yielded better results in the phantom study.

Algorithms↗

Effects of haloperidol on K(+) currents in acutely isolated rat retinal ganglion cells.

PURPOSE: Effects of haloperidol on K(+) currents (IKs) of rat retinal ganglion cells (RGCs) were examined, with the hypothesis that its alteration of IKs explains alterations in the pattern electroretinogram (PERG). METHODS: Fast blue was injected into superior colliculi of rats (3-8 days old) to identify RGCs under epifluorescence illumination after retrograde transport to retinas. Retinas were dissected, treated enzymatically, and dissociated with trituration. Effects of haloperidol on membrane currents at -70 mV, voltage-dependent IK, and Ca(2+)-dependent K(+) currents (K(Ca)) were examined by whole-cell patch voltage clamp. Na(+) currents were abolished by tetrodotoxin (1 microM; TTX). Voltage-gated IKs were isolated by Ca(2+)-free perfusate. Persistent and transient components of the voltage-sensitive IKs were isolated by prepulses, and sensitivity of each component to tetraethylammonium (TEA, 20 mM) and 4-aminopyridine (5 mM) was tested. K(Ca) was identified by its response to TEA, charybdotoxin (CTX), and apamin. Haloperidol (0.01-100 microM) was instilled into the perfusate dissolved in dimethyl sulfoxide (DMSO). RESULTS: Currents recorded at -70 mV were not affected by haloperidol, whereas the persistent component of the voltage-dependent IK was reversibly reduced by haloperidol, with a dose dependence fitted with the Hill equation (median inhibitory concentration [IC(50)] = 4.2 microM). The transient component of the voltage-gated IK was less sensitive to haloperidol. Haloperidol (10 nM) blocked the apamin-sensitive K(Ca) but not the CTX-sensitive K(Ca). CONCLUSIONS: Haloperidol reduced voltage-dependent IKs in RGCs, but at a higher concentration than that needed to antagonize dopamine receptors. Haloperidol (10 nM) blocked the apamin-sensitive K(Ca) which modulates the firing rate of RGCs and may contribute to the alteration of PERG.

Animals↗