PubMed Health⌕ Search

Biomedical subjects

F Nakata

Publications and source records attributed to F Nakata.

At least 19 recordsLinked to original sources
PubMed2004

Search for electron neutrino appearance in a 250 km long-baseline experiment.

We present a search for electron neutrino appearance from accelerator-produced muon neutrinos in the K2K long-baseline neutrino experiment. One candidate event is found in the data corresponding to an exposure of 4.8 x 10(19) protons on target. The expected background in the absence of neutrino oscillations is estimated to be 2.4+/-0.6 events and is dominated by misidentification of events from neutral current pi(0) production. We exclude the nu(micro) to nu(e) oscillations at 90% C.L. for the effective mixing angle in the 2-flavor approximation of sin((2)2theta(microe)( approximately 1/2sin((2)2theta(13))>0.15 at Deltam(2)(microe)=2.8 x 10(-3) eV(2), the best-fit value of the nu(micro) disappearance analysis in K2K. The most stringent limit of sin((2)2theta(microe)<0.09 is obtained at Deltam(2)(microe)=6 x 10(-3) eV(2).

Journal Article↗
PubMed2003

Indications of neutrino oscillation in a 250 km long-baseline experiment.

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

Journal Article↗
PubMed1999

Tannins and related polyphenols of melastomataceous plants. VIII. Nobotanins L, M and N, trimeric hydrolyzable tannins from Tibouchina semidecandra.

Three hydrolyzable tannins, nobotannins L, M and N, were isolated from the water-soluble portion of the leaf extract of Tibouchina semidecandra, and their trimeric structures were elucidated from spectral and chemical evidence. Nobotanins L and N exist as equilibrium mixtures of four anomers due to the presence of two unacylated anomeric centers.

Carbohydrate Sequence↗
PubMed1995

[Hemodynamic effects of amrinone during emergence from cardiopulmonary bypass].

Amrinone, a phosphodiesterase III inhibitor, is known to exert inotropic and vasodilating effects. This study was undertaken to investigate the hemodynamic effects and optimal dose of amrinone in patients undergoing coronary artery bypass surgery. Seventeen patients with ejection fraction > 0.45 were included. In both group B and C, amrinone 0.5 mg.kg-1 was administered in the venous reservoir near the end of cardiopulmonary bypass (CPB), and doses of 1 and 5 micrograms.kg-1.min-1 by an intravenous infusion. Additional group of A did not receive amrinone. In group B, amrinone increased cardiac index by 79% and stroke index by 81% while decreased mean arterial pressure by 19% and systemic vascular resistance by 59% in comparison with group A. Heart rate did not increase. In group C, changes of hemodynamic variables were almost the same compared with group B. These data suggests that amrinone improves left ventricular performance without increasing myocardial oxygen demand while recovering from CPB. However, a high dose of amrinone should be used in combination with catecholamines because its vasodilating action is potentiated by hyperdynamic state after CPB.

Aged↗
PubMed1993

[Septic attack during percutaneous nephrolithotripsy under epidural anesthesia].

A 59-year-old man was scheduled for percutaneous nephrolithotripsy (PNL) for renal calculus. Anesthesia was maintained by epidurally administered mepivacaine 1.5% under prone position. During surgical manipulation, the patient complained of shivering and chill accompanied with fever and tachycardia. His temperature peaked at 40.7 degrees C and decreased gradually by cooling. Serratia was detected from arterial blood obtained in the operating room. It was thought that fever attack was due to excessive increase of intrarenal pressure by irrigation fluid which might have led to septicemia. Therefore, careful attention for septic attack must be paid during PNL procedure as well as postoperatively.

Anesthesia, Epidural↗
PubMed1992

Hemodynamic effects of nicardipine-induced hypotension during enflurane/nitrous oxide anesthesia in man.

Hemodynamic effects of nicardipine-induced hypotension during enflurane/nitrous oxide were evaluated in 10 surgical patients. An infusion of nicardipine was titrated to maintain mean arterial pressure at 60 to 70 mmHg under enflurane 1.5 to 2.0 vol% and nitrous oxide 60 vol%. Mean arterial pressure was well controlled with the nicardipine infusion, whereas cardiac index increased with decreased systemic vascular resistance. Heart rate increased concomitantly with decreased blood pressure, which indicated that enflurane 1.5 to 2.0 vol% did not suppress baroreceptor reflex during nicardipine administration. However, rate-pressure-product was not increased by the nicardipine. Right and left ventricular systolic work indices were not increased by the nicardipine. Right ventricular ejection fraction was not also changed by the nicardipine. Although serum norepinephrine level increased during the nicardipine infusion, the values remained within physiological ranges. Our results suggest that nicardipine-induced hypotension may be safely performed during enflurane/nitrous oxide anesthesia because neither ventricular work nor myocardial oxygen demand was increased by nicardipine.

Journal Article↗
PubMed1991

Combined negative inotropic effects of calcium entry blockers and isoflurane on canine isolated heart muscles.

The combined negative inotropic effects of isoflurane and calcium entry blockers (verapamil, diltiazem, nifedipine, nicardipine) were studied utilizing isolated heart preparations of ventricular muscles from dogs. All of these calcium entry blockers exerted dose-dependent decreases in maximal velocity of shortening (Vmax), maximal developed isometric force (Fm), and the maximal first derivative of Fm (maximal dF/dt). Dose-dependent decreases of these variables of muscle mechanics were augmented in isoflurane-depressed myocardium. At equimolar concentrations, direct myocardial depression was demonstrated in the following order of severity: nifedipine > diltiazem = verapamil > nicardipine. Percent depressions of Vmax, Fm and maximal dF/dt were significantly greater in muscles when calcium entry blockers were combined with 1MAC isoflurane than in muscles of calcium entry blockers alone. These data suggest that the negative inotropic effects of verapamil, diltiazem, nifedipine, and nicardipine were potentiated by isoflurane.

Journal Article↗
PubMed1991

[An autopsy case of chronic germanium intoxication presenting peripheral neuropathy, spinal ataxia, and chronic renal failure].

We report here an autopsy case of chronic germanium intoxication with major pathological changes in the central and peripheral sensory nervous systems. The patient was a 4-year-old girl who had suffered from gait disturbance and generalized muscle weakness for 22 months. She had been given orally germanium compounds (containing germanium dioxide, 225-450 mg/day) for the previous 28 months. In addition to the findings of chronic renal failure and anemia, she presented characteristic neurological symptoms exemplified by diffuse muscle atrophy, tongue fasciculation, sensory impairment and truncal ataxia as well as areflexia. Median and ulnar sensory nerve conduction velocities were also reduced. On the 17th hospital day, she died of renal failure. In addition to conspicuous degeneration of renal tubular cells, pathological studies revealed marked nerve fiber loss, degeneration and gliosis in the dorsal column of the spinal cord, which were most conspicuous in the thoracic and cervical cord. Axonal degenerative changes were also conspicuous in the sural and sciatic nerves. High concentration of germanium was detected in the brain, cerebellum, spinal cord, sciatic nerve, liver and kidney. It was suggested that the neural involvement in the current case was caused by chronic toxicity of germanium.

Ataxia↗
PubMed1990

Comparative inotropic effects of local anesthetics in isolated cat papillary muscles.

The direct inotropic action of seven local anesthetics: procaine, mapivacaine, lidocaine, tetracaine, chloroprocaine, bupivacaine and etidocaine were compared in isolated cat papillary muscles. All of the local anesthetics produced a dose-related depression of maximal velocity of shortening (Vmax), maximal developed force (Fm) and maximal dF/dt. The more potent local anesthetics such as bupivacaine and etidocaine depressed myocardial contractility at significantly lower concentrations than the less potent local anesthetics such as lidocaine and mepivacaine. Depression of Vmax by bupivacaine or etidocaine was three times greater than that by lidocaine and ten times greater than that by procaine. At the same concentration (10(-4) M), direct myocardial depression was demonstrated in the following order of severity: etidocaine >/= bupivacaine >> tetracaine >> chloroprocaine >/= lidocaine >> mepivacaine >> procaine.

Journal Article↗
PubMed1990

Noninvasive assessment of cardiac performance of intravenous benzodiazepines by systolic time intervals.

The effects of anesthetic induction by diazepam, flunitrazepam and midazolam on cardiac performance were evaluated in 33 ASA class I surgical patients (average age was 36 years). The patients were divided according to the 3 drug groups, and the effects of each drug assessed utilizing measurements of systolic time intervals. An increase in heart rate and decrease in blood pressure was observed following flunitrazepam and midazolam induction. There was no changes in PEPI (pre-ejection period index) and LVETI (left ventricular ejection time index) by benzodiazepines induction. The PEP/LVET ratio was increased by diazepam while the DPTI (diastolic pressure time index)/TTI (tension time index) was reduced by flunitrazepam and midazolam. However, these changes in PEP/LVET and DPTI/TTI were within normal limits. These data indicate that in healthy humans the induction dose of either diazepam, flunitrazepam or midazolam does not extremely influence either PEP/LVET for cardiac performance or DPTI/TTI for cardiac oxygen balance. The results also suggest that the simultaneous use of PEP/LVET and DPTI/TTI is more informative than any single variable for the evaluation of cardiac effects of anesthetics.

Journal Article↗
PubMed1989

Clinical evaluation of esophageal doppler cardiac output measurement during general anesthesia.

We evaluate the accuracy of cardiac output measurement with esophageal Doppler ultrasonography (ECO). A total of 71 simultaneous measurement of esophageal Doppler and thermodilution cardiac output were compared in 16 patients undergoing general anesthesia in the supine position. ECO was determined easily with minimal experience, and significantly correlated with thermodilution cardiac output (TDCO) measurement ( P < 0.001). The regression equation obtained was Y = 0.983X + 0.019, and the correlation coefficient was 0.935. Furthermore, ECO was more reproducible than TDCO. However, ECO is not able to assess CO accurately in either lateral or prone position and after cardiopulmonary bypass in open heart surgery. Our results suggest that the esophageal Doppler technique allows a noninvasive and continuous cardiac output monitoring in patients during general anesthesia, and that it is more useful in patients for whom invasive monitoring is considered inappropriate. However, further improvement in this technique will be necessary for its routine use in clinical anesthesia.

Journal Article↗
PubMed1989

Continuous mixed venous oxygen saturation monitoring during general anesthesia.

Clinical evaluation of continuous SvO2 monitoring during general anesthesia was made in 21 surgical patients utilizing a fiberoptic reflectometry system combined with a pulmonary artery flow-directed balloon catheter. On-line in vivo values for SvO2 by the system were closely related to those obtained in vitro from a Radiometer ABL-300. There was a good correlation between changes of in vivo SvO2 and corresponding changes in cardiac index. We also observed that there were significant correlations between SvO2 and oxygen extraction ratio, and SvO2 and oxygen delivery. These data indicate that continuous monitoring of SvO2 during general anesthesia can provide on-line information not only about hemodynamic state but also on oxygen transport, which will be especially helpful in managing hemodynamically unstable patients during anesthesia.

Journal Article↗