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K Mamiya

Publications and source records attributed to K Mamiya.

At least 37 records · Page 2Linked to original sources
PubMed1998

Genetic polymorphism of cytochrome P450s, CYP2C19, and CYP2C9 in a Japanese population.

Genotypings of two mutations (*2 and *3) in CYP2C19 and the amino acid variants (Arg144/Cys, Tyr358/Cys, Ile359/Leu, and Gly417/Asp) in CYP2C9 were carried out in 140 unrelated Japanese subjects. Thirty-three subjects (23.6%) were genotypically identified as poor metabolizers of CYP2C19, and the allele frequencies of the CYP2C19*2 and CYP2C19*3 were 0.35 and 0.11, respectively. The authors' findings are in agreement with the 18% to 23% prevalence of poor metabolizers in the Japanese populations previously phenotyped. In CYP2C9, all subjects were homozygous (CYP2C9*1) for Arg144, Tyr358, Ile359, and Gly417, except for five subjects (3.6%) who were heterozygous for the Leu359 (CYP2C9*3). The frequencies of Arg144, Tyr358, Ile359, Leu359, and Gly417 variants were 1.0, 1.0, 0.982, 0.018, and 1.0, respectively. The low frequency of the Cys144 allele (CYP2C9*2) in the Japanese population is different from the frequency recently found in British subjects (allele frequency, 0.125 to 0.192). The results suggest that the known interindividual variations in the CYP2C9 sequence among Japanese subjects is small, and that Ile359/Leu is one possible site showing interracial polymorphism.

Adult↗
PubMed1998

The effects of genetic polymorphisms of CYP2C9 and CYP2C19 on phenytoin metabolism in Japanese adult patients with epilepsy: studies in stereoselective hydroxylation and population pharmacokinetics.

PURPOSE: The aim of this study was to clarify the effects of genetic polymorphisms of cytochrome P450 (CYP) 2C9 and 2C19 on the metabolism of phenytoin (PHT). In addition, a population pharmacokinetic analysis was performed. METHODS: The genotype of CYP2C9 (Arg144/Cys, Ile359/Leu) and CYP2C19(*1, *2 or *3) in 134 Japanese adult patients with epilepsy treated with PHT were determined, and their serum concentrations of 5-(4-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) enantiomers, being major metabolites of PHT, were measured. A population pharmacokinetic analysis (NONMEM analysis) was performed to evaluate whether genetic polymorphism of CYP2C9/19 affects the clinical use of PHT by using the 336 dose-serum concentration data. RESULTS: The mean maximal elimination rate (Vmax) was 42% lower in the heterozygote for Leu359 allele in CYP2C9, and the mean Michaelis-Menten constants (Km) in the heterozygous extensive metabolizers and the poor metabolizers of CYP2C19 were 22 and 54%, respectively, higher than those without the mutations in CYP2C9/19 genes. (R)- and (S)-p-HPPH/PHT ratios were lower in patients with mutations in CYP2C9 or CYP2C19 gene than those in patients without mutations. CONCLUSIONS: Although the hydroxylation capacity of PHT was impaired with mutations of CYP2C9/19, the impairment was greater for CYP2C9. In view of the clinical use of PHT, two important conclusions were derived from this population study. First, the serum PHT concentration in patients with the Leu359 allele in CYP2C9 would increase dramatically even at lower daily doses. Second, the patients with CYP2C19 mutations should be treated carefully at higher daily doses of PHT.

Aryl Hydrocarbon Hydroxylases↗
PubMed1998

Blood pressure control during eye surgery under local anesthesia using pulse oximetry.

We measured the arterial blood pressure and percutaneous O2 saturation (SpO2) in 39 elderly patients (age range, 70-89 years) who underwent cataract surgery under local anesthesia. Nineteen patients showed a 20% or greater increase in the systolic arterial pressure (SAP) measured every minute in the operating room compared to the basal value measured in the ward. We treated elevation of the SAP by intravenous bolus injection of 0.25 mg nitroglycerin (NTG), followed by continuous infusion at 0.1-0.3 microg/kg/min. NTG caused a statistically significant but clinically irrelevant decrease in SpO2 in the patients breathing room air. Two of these patients showed extremely decreased SpO2. Our results suggest that NTG does not typically cause a severe decrease in oxygenation. It might be advisable, however, for patients with severe lung dysfunction or ischemic heart disease to receive prophylactic O2 administration.

Aged↗
PubMed1998

[Two cases of mesial temporal lobe epilepsy associated with old intracerebral hemorrhage in the lateral temporal lobe without "dual pathology"].

Two cases of intractable temporal lobe epilepsy associated with old intracerebral hemorrhage in the lateral temporal lobe were reported. Although preoperative magnetic resonance imaging (MRI) failed to reveal hippocampal atrophy with T2 hyperintensity, electrocorticographic (ECoG) recording with chronic invasive subdural electrodes indicated the mesial temporal lobe to be an ictal onset zone. After anterior temporal lobectomy involving the lesion and hippocampectomy, the patients became seizure-free. Hippocampal sclerosis, namely "dual pathology", was not noted on histological examination. Careful ECoG recording with chronic subdural electrodes is mandatory even when the preoperative MRI does not demonstrate the radiological hippocampal sclerosis.

Adult↗
PubMed1997

Stereoselective 4'-hydroxylation of phenytoin: relationship to (S)-mephenytoin polymorphism in Japanese.

AIMS: The aim of this study was to clarify whether phenytoin (PHT) stereoselective hydroxylation cosegregates with (S)-mephenytoin phenotype. METHODS: A single dose of PHT (100 mg) was administered orally to six healthy Japanese subjects in whom the genotype and phenotype of CYP2C19 had been determined previously. The urinary excretion profiles of the metabolites of PHT, (R)- and (S)-p-HPPH [5-(4-hydroxyphenyl)-5-phenylhydantoin] up to 361 postdose were compared between the two groups of poor metabolizers (PMs, n = 3) and extensive metabolizers (EMs, n = 3) with respect to CYP2C19. CYP2C9 genotype was also determined. RESULTS: All the alleles were found to be wild type (Arg144 Tyr358Ile359Gly417) in each subject. The mean value for cumulative urinary excretion of unchanged PHT was not significantly different between the PMs and the EMs. However, recovery of (R)-p-HPPH at 36 h was 3.5-fold lower and that of (S)-p-HPPH 1.3-fold lower in PMs than in EMs. Although the mean urinary excretion values for both metabolites were significantly lower in the PMs than in the EMs, the difference between the two groups was larger for (R)-p-HPPH. A significant negative correlation was observed between the hydroxylation index of omeprazole (the ratio between the serum concentrations of omeprazole and hydroxyomeprazole in blood samples drawn 3 h after drug intake) and the log10 0-12 h urinary recovery of (R)-p-HPPH. CONCLUSIONS: In humans, the 4'-hydroxylation of PHT is highly stereoselective towards formation of the (S)-enantiomer. Thus, (S)-hydroxylation by CYP2C9 might be the major determinant of the disposition of PHT. However, these results support the hypothesis that the stereoselective hydroxylation pathway of PHT to form (R)-p-HPPH cosegregates with the CYP2C19 metabolic polymorphism.

Administration, Oral↗
PubMed1997

The efficacy of the "BURP" maneuver during a difficult laryngoscopy.

The displacement of the larynx in the three specific directions (a) posteriorly against the cervical vertebrae, (b) superiorly as possible, and (c) slightly laterally to the right have been reported and named the "BURP" maneuver. We evaluated the efficacy of the BURP maneuver in improving visualization of the larynx. Six hundred thirty patients without obvious malformation of the head and neck participated in this study. We divided the degree of visualization of the larynx using laryngoscopy into five grades and compared the visualization of the larynx using the BURP maneuver with that of laryngoscopy with and without simple laryngeal pressure ("Back"). The maneuver of Back and BURP significantly improved the laryngoscopic visualization from initial inspection. The BURP maneuver also significantly improved the visualization compared with the Back maneuver. We concluded that the BURP maneuver improved the visualization of the larynx more easily than simple back pressure on the larynx.

Female↗
PubMed1997

Greater incidence of delirium during recovery from sevoflurane anesthesia in preschool boys.

BACKGROUND: In the authors' clinical experience, preschool children are more likely to show delirium after sevoflurane than are older children. METHODS: Sixty-three preschool boys aged 3-5 yr (classified as American Society of Anesthesiologists [ASA] physical status I), and 53 school-age boys aged 6-10 yr (ASA physical status I) who underwent minor urologic surgery were randomly assigned to receive either halothane or sevoflurane, thus creating four groups: preschool-halothane (n = 32), preschool-sevoflurane (n = 31), school-halothane (n = 27), and school-sevoflurane (n = 26). Anesthesia was induced by inhalation of halothane or sevoflurane in oxygen and was maintained at 1 minimum alveolar concentration of each agent throughout surgery. For intra- and postoperative analgesia, caudal block with 0.5-1.0 ml/kg 0.25% plain bupivacaine and topical infiltration with 3-5 ml 1% lidocaine were provided for all patients. Recovery characteristics and incidence of delirium on emergence were compared among the four groups. RESULTS: Two patients in the preschool-halothane group, one in the preschool-sevoflurane group, and one in the school-halothane group were excluded from the comparison because of insufficient analgesia or agitation before induction. In both age groups, the time to emergence from sevoflurane was significantly faster (about 3 min) than from halothane. The incidence of delirium during recovery in the preschool-sevoflurane group (40%) was significantly greater than that in the other groups (preschool-halothane, 10%; school-halothane, 15.4%; school-sevoflurane, 11.5%). CONCLUSION: Sevoflurane provided quicker emergence and early recovery compared with halothane, but the incidence of delirium was greater in preschool boys after sevoflurane.

Age Factors↗
PubMed1996

Pharmacokinetics of omeprazole (a substrate of CYP2C19) and comparison with two mutant alleles, C gamma P2C19m1 in exon 5 and C gamma P2C19m2 in exon 4, in Japanese subjects.

The pharmacokinetic profile of omeprazole was examined in 27 healthy Japanese volunteers, and the results were analyzed in relation to genotype for the two mutations, CgammaP2C19m1 in exon 5 and CgammaP2C19m2 in exon 4, associated with the poor metabolizer phenotype. Of the 27 individuals analyzed, 10 were homozygous for the wild-type (wt) allele in both exon 5 and exon 4 (wt/wt; 37.0%, pattern GI), five were heterozygous for the CgammaP2C19m1 (wt/m1; 18.5%, G2), five were heterozygous for the CgammaP2C19m2 (wt/m2; 18.5%, G3), two were heterozygous for the two defects (m1/m2; 7.4%, G4), and five were homozygous for the CgammaP2C19m1 (m1/m1; 18.5%, G5). The allele frequencies of the m1 and m2 mutation were 0.31 and 0.13, respectively. A correlation between the rate of metabolism of omeprazole and genotype was observed. The mean clearance values of omeprazole in patterns G1, G2, G3, G4, and G5 were 1369.0, 332.7, 359.0, 70.8, and 89.5 ml/hr/kg, respectively. The relative area under the serum concentration-time curve (AUC) ratio of omeprazole to 5-hydroxyomeprazole in patterns G1, G2, G3, G4, and G5 was 1:2.8:3.4:16:17.2. A similar relation was observed in the omeprazole/5-hydroxyomeprazole serum concentration ratio, determined 3 hours after drug intake (1:3:4:18.8:20.3). There were significant (p < 0.05 to 0.01) differences in the disposition kinetics of omeprazole between the subjects with patterns G1, G2, and G3 and the subjects with patterns G4 and G5. The results indicate that the 5-hydroxylation pathway of omeprazole is clearly impaired in subjects with m1/m2 and m1/m1.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1995

Local anesthetics enhance nitric oxide production by human peripheral neutrophils.

Various neutrophil functions are suppressed by local anesthetics. We studied the effect of local anesthetics on nitric oxide (NO) generation in human peripheral neutrophils. Lidocaine and other local anesthetics stimulated NO generation in resting neutrophils. Canavanine, an NO synthase inhibitor, inhibited NO generation. Lidocaine and the other local anesthetics enhanced formylmethionyl-leucyl-phenylalanine (FMLP) or phorbol myristate acetate (PMA)-induced NO generation. These findings suggest that NO mediates various pharmacological effects of the local anesthetics on the host defense mechanism and the control of blood pressure.

Anesthetics, Local↗
PubMed1995

[Anesthetic management of two patients with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS)].

MELAS is a type of the mitochondrial myopathy characterized by elevation of pyruvate and lactate levels in both the blood and cerebrospinal fluid. This syndrome frequently accompanies cerebral infarction like symptoms. Recently, we experienced two patients for anesthesia with MELAS (both 11-year-old girls). V-P shunt construction and IVH reservoir implantation were conducted, respectively. Anesthesia was induced with fentanyl and midazolam, and vecuronium was used to facilitate tracheal intubation. Volatile anesthetic was avoided, and anesthesia was maintained with fentanyl, midazolam, and nitrous oxide. Arterial blood gases and pH were frequently checked, and acetated electrolyte solution was infused mainly during surgery. No complications occurred during anesthesia in both patients. In the anesthetic management for MELAS, measures to prevent malignant hyperthermia must also be considered.

Anesthesia↗
PubMed1994

[Effect of dopamine administration on ICG-disappearance rate during prone position anesthesia].

We evaluated the effect of dopamine administration (3 micrograms.kg-1.min-1) on ICG-disappearance rate during prone position in 10 patients undergoing elective spinal cord surgery. Anesthesia was maintained with isoflurane and 50% nitrous oxide in oxygen. ICG-disappearance rate was determined at 3 points, i.e., the day before surgery, during prone position and during the administration of dopamine. Systolic arterial pressure showed no significant difference before and during dopamine administration. ICG-disappearance rate during prone position was significantly lower than the preoperative value. However, ICG-disappearance rate showed no significant difference during dopamine administration and preoperative period. We conclude that dopamine administration may attenuate the depressant effect of the prone position on the hepatic blood flow.

Adult↗
PubMed1990

Pain-related somatosensory evoked potentials in cortical reflex myoclonus.

To elucidate the sensitivity to pain stimuli in patients with cortical reflex myoclonus, pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation and conventional electrically-stimulated SEPs (electric SEPs) were compared in four patients with cortical reflex myoclonus. The P25 peak of electric SEPs was considerably enhanced but the P320 potential of pain SEPs was of normal amplitude in all patients. After medication, myoclonus was reduced and the amplitude of P25 was decreased, but P320 showed no change. In our previous study of the scalp distribution in normal subjects, a subcortical site, probably the thalamus, was considered to be the generator source of P320. Because most pain stimuli do not reach the cortex, patients with cortical reflex myoclonus are not sensitive to pain stimuli and P320 in pain SEPs is not enhanced.

Adolescent↗