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Biomedical subjects

S Higuchi

Publications and source records attributed to S Higuchi.

At least 37 records · Page 2Linked to original sources
PubMed2000

Catalytic activity of three variants (Ile, Leu, and Thr) at amino acid residue 359 in human CYP2C9 gene and simultaneous detection using single-strand conformation polymorphism analysis.

This study evaluated the catalytic activity of three variants (Ile, Leu, and Thr) at codon 359 of CYP2C9 enzymes expressed in a yeast cDNA expression system, and then established single-strand conformation polymorphism (PCR-SSCP) analysis for simultaneous detection as a screening method. Diclofenac was used for the in vitro experiment, and its hydroxy metabolite (4'-hydroxydiclofenac) was measured by HPLC. To discuss the in vivo effect of the Thr359 variant on the pharmacokinetics of phenytoin, a case report is presented. The efficiency of the SSCP method was evaluated by analyzing DNA samples from a homozygote for Ile359 and a heterozygote for Leu359 or Thr359. To evaluate the interaction between the P450 level and reductase activity, two batches of the Thr359 variant with a different P450:reductase activity ratio (1:4.0 and 1:1.4) were used. The in vitro study revealed that recombinant Ile359, Leu359, and Thr359 (2 batches) possessed a mean Km of 2.0, 16.5 and (3.8 and 2.9) micromol and Vmax of 12.4, 17.9 and (4.4 and 5.1) nmol/min/nmol P450, respectively. Although the magnitude of the change in catalytic efficiency for the Thr359 variant was close to that of the Leu359 variant, the effect of the two variants on diclofenac 4'-hydroxylation appears to be different because Leu359 variant was associated with a high Km, and Thr359 with a low Vmax. No significant differences in the kinetic data were observed between the two Thr359 enzymes, suggesting that low reductase activity in the Thr359 enzyme was not a major determinant in the present in vitro experiment. Estimated pharmacokinetic parameters of phenytoin obtained by the Bayesian method in an epileptic patient who was a heterozygote carrier for Thr359 variant were: Km = 6.45 microg/mL, Vmax = 5.77 mg/kg/d, and Vmax/Km = 0.89 L/kg/day. The Vmax/Km value in this patient was similar to the population mean value (0.90 L/kg/day) in Japanese heterozygotes for the Leu359 variant. Results for PCR-SSCP were in complete agreement with those obtained using established methods. Thus, the PCR-SSCP approach is useful for identifying these three variants of the CYP2C9 gene.

Adult↗
PubMed2000

Characterization of microsomal alcohol oxygenase catalyzing the oxidation of 7-hydroxy-delta 8-tetrahydrocannabinol to 7-oxo-delta 8-tetrahydrocannabinol in rat liver.

The formation of 7-oxo-delta8-tetrahydrocannabinol (7-oxo-delta8-THC) from 7beta-hydroxy-delta8-THC was found in hepatic microsomes of rats. The activity was stereoselective and about 3-fold higher than that from 7alpha-hydroxy-delta8-THC. The oxidative activity of 7alpha- and 7beta-hydroxy-delta8-THC to 7-oxo-delta8-THC was significantly higher in male than in female, and significantly enhanced by both dexamethasone and phenobarbital, and then inhibited up to about 20% of the control value by antibody against P450GPF-B, presumably a member of the 3A subfamily, a major enzyme responsible for the formation of 7-oxo-delta8-THC in guinea pigs. This antibody also inhibited the formation of 7alpha- and 7beta-hydroxy-delta8-THC, and 7-oxo-delta8-THC from delta8-THC by hepatic microsomes of rats. These results indicate that there is a sex-related difference in the oxidation of 7-hydroxy-delta8-THC to 7-oxo-delta8-THC and the reaction is mainly catalyzed by P450 enzyme(s) belonging to the 3A subfamily as major enzyme(s) of microsomal alcohol oxygenase in rats.

Animals↗
PubMed2000

Evaluation of intracranial pressure by transcranial Doppler ultrasonography in dogs with intracranial hypertension.

Transcranial Doppler ultrasonography (TCD) has been used to confirm changes in cerebral hemodynamics. In this study, we investigated whether the parameters for the basilar artery measured by TCD were correlated with the intracranial and cerebral perfusion pressures in extreme intracranial hypertension. An intracranial hypertension model was produced in seven dogs by inflating a balloon inserted into the epidural space. The resistance index was compared with the corresponding intracranial pressure and cerebral perfusion pressure values during intracranial hypertension. A significant correlation was recognized between the resistance index and cerebral perfusion pressure. Therefore, measurement of the basilar artery by TCD in the dog with intracranial hypertension is useful in estimating the intracranial circulation in cases where the measurement of intracranial pressure is not available or not indicated.

Animals↗
PubMed2000

Purification of bovine urinary beta2-microglobulin and its biochemical characteristics.

In this study, bovine beta2-m was purified from urine by ion-exchange chromatography and gel chromatography, and the characteristics were compared with those of colostral beta2-m by the immunological reactivity, isoelectric points, peptide map, and amino acid sequence. The characteristics of purified urinary beta2-m were consistent with those of the colostral beta2-m. The urinary and colostral beta2-m possessed the same polypeptide chain consisting of 98 amino acids, and its molecular weight is 11.8 kDa. Furthermore, four isoforms of beta2-m were found. The isoelectric points were different from each other.

Amino Acid Sequence↗
PubMed2000

Alcohol and aldehyde dehydrogenase genotypes in Korsakoff syndrome.

BACKGROUND: Previous studies have suggested a genetic predisposition to the development of Wernicke-Korsakoff syndrome (WKS), a neuropsychiatric syndrome commonly associated with alcoholism; however, little is known about this genetic risk factor. METHODS: To test the hypothesis that altered alcohol or aldehyde regulation is related to the development of WKS, the genetic polymorphisms of aldehyde dehydrogenase-2 (ALDH2) and alcohol dehydrogenase-2 (ADH2) were examined in 47 alcoholic subjects with WKS and compared with those of 342 alcoholic subjects without any WKS symptoms and 175 nonalcoholic controls. RESULTS: Although the frequencies of the ALDH2 genotypes and alleles did not differ significantly between alcoholic subjects with WKS and alcoholics without WKS, the ADH2*1/2*1 genotype and ADH2*1 allele were significantly increased in WKS. CONCLUSIONS: These findings suggest that the ADH2*1/2*1 genotype is a risk factor for the development of WKS in alcoholic patients.

Aged↗
PubMed2000

Is heavy alcohol consumption an attributable risk factor for cancer-related deaths among Japanese men?

BACKGROUND: Over the past four decades, per capita alcohol consumption in Japan has increased 4-fold. Age-adjusted cirrhosis mortality rates for men have also increased, whereas the rates for women have declined gradually. This widening difference in mortality could be due to a decreasing prevalence of viral hepatitis infection for both sexes and to differences in alcohol consumption between the sexes. Difficulties in estimating the impact of increased alcohol consumption on mortality rates in Japan also arise from changes in the prevalence of non-alcohol-related risk factors. METHODS: To measure the relative contribution of alcohol to death from cirrhosis, liver cancer, esophageal cancer, and head and neck cancer among Japanese men, we used the mortality rate for Japanese women as the standard because alcohol consumption for women has been low. We used published vital statistics data from 1992 to 1996 to calculate the attributable risk percent (ARP) in 5-year cohorts of Japanese men age 20 and older. RESULTS: Among Japanese men, heavy alcohol consumption accounted for 70.7% of deaths due to cirrhosis, 76.8% of liver cancer deaths, 88.5% of esophageal cancer deaths, and 87.4% of head and neck cancer deaths. When we examined ARPs by age group, ARPs for these four diseases were approximately 80% in the middle age groups. However, for older groups, the ARPs for cirrhosis and liver cancer were much lower than those for esophageal cancer and head and neck cancer. The prevalence of previous hepatitis C virus infection, considered to be the major cause of cirrhosis and liver cancer, increased with age. CONCLUSIONS: The results support previous epidemiologic studies conducted in Japan. Heavy alcohol consumption is a major public health problem among younger Japanese men, accounting for approximately 80% of the deaths for the four diseases examined.

Adult↗
PubMed2000

Genetic polymorphism of the CCK gene in patients with alcohol withdrawal symptoms.

BACKGROUND: Cholecystokinin (CCK) is considered to play an important role in the central nervous system via its interaction with other neurotransmitters such as dopamine, serotonin, gamma-aminobutyric acid, substance P, and enkephalins. We investigated the relationship between the C to T substitution in the Sp1 binding cis-element of the CCK gene promoter region (at position -45 numbered from initiation codon) and alcohol withdrawal symptoms. METHODS: We examined 214 Japanese men with alcoholism (93 with delirium tremens, 49 with hallucination, 38 with seizure, and 93 with none of these symptoms) and 98 age-matched Japanese male controls by using a polymerase chain reaction-based single strand conformational polymorphism analysis. RESULTS: Patients who displayed hallucination were significantly more likely to possess the C allele than control subjects (chi2 = 8.17, p = 0.017, Bonferroni correction: p = 0.064). In addition, we investigated the influence of CCK gene polymorphism on alcohol consumption among the control subjects but found no significant relationship. CONCLUSIONS: Our data suggested that the C allele at -45 locus of the CCK gene was higher in patients with hallucination than the control group at a rate that was not quite significant after Bonferroni correction for multiple testing.

Adult↗
PubMed2000

Population pharmacokinetics and pharmacodynamics of TS-943 for selective nonpeptide platelet glycoprotein IIb/IIIa receptor antagonist in normal healthy subjects.

The pharmacokinetics and pharmacodynamics of TS-943 were evaluated with use of NONMEM in 36 healthy male subjects after constant infusion of five different single-dose regimens. Population analysis showed the plasma concentration-time profiles of TS-943 to be best-fit characterized by a two-compartment open model with constant infusion and first-order elimination. The pharmacodynamic model that best fitted the platelet aggregation was a sigmoid Emax model. The final estimates for baseline effect, 50% inhibitory concentration (IC50), and the Hill coefficient were 79.4%, 23.4 ng/mL and 1.63, respectively. The maximum effect (Emax) was fixed at 80% (submaximal aggregation response). In addition, correlations between TS-943 plasma concentration and extension of template bleeding time were examined by fitting with an exponential model. The model estimates that the TS-943 plasma concentration necessary to double template bleeding time is approximately 63 ng/mL (ie, 2.7-fold greater than the IC50). The population approaches for pharmacokinetic-pharmacodynamic investigation can be useful for the analysis of concentration-effect relationships and concentration-adverse event relationships for a platelet glycoprotein IIb/IIIa receptor antagonist.

Adult↗
PubMed2000

Basis for dosing time-dependent changes in the antiviral activity of interferon-alpha in mice.

The influence of dosing time on the pharmacological effect (antiviral activity) of interferon-alpha (IFN-alpha), and the pharmacological and pharmacokinetic mechanisms, were investigated in ICR male mice under a 12-h light/dark cycle (lights on from 7:00 AM to 7:00 PM). 2'-5'Oligoadenylate synthetase activity in plasma at 24 h after IFN-alpha (10 MI.U./kg, i.v.) injection, as an index of antiviral activity, was significantly higher for injections given at 9:00 AM than for injections given at 9:00 PM (P <.05). The uptake of [(3)H]thymidine by lymphocytes after 24-h incubation with IFN-alpha, as an index of lymphocyte-stimulating effect, was significantly higher in cells obtained at 9:00 AM than in the cells obtained at 9:00 PM (P <.01). The number of receptors per cell and the expression of interferon-stimulated gene factor in lymphocytes after 24-h incubation with IFN-alpha were significantly higher in the cells obtained at 9:00 AM than at 9:00 PM (P <.05). A significant dosing time-dependent difference was demonstrated for the pharmacokinetic parameters of IFN-alpha, which showed higher clearance for injections given at 9:00 PM than for those at 9:00 AM (P <.05). The metabolism of IFN-alpha was significantly higher in kidney obtained at 9:00 PM than at 9:00 AM (P <.05). These findings support that choosing the most appropriate time of day for administration of IFN-alpha, associated with the rhythmicity of IFN-alpha receptor function and IFN-alpha pharmacokinetics, may increase the antiviral activity in experimental and clinical situations.

2',5'-Oligoadenylate Synthetase↗
PubMed2000

Chronopharmacology of antitumor effect induced by interferon-beta in tumor-bearing mice.

The mechanisms underlying the dosing time-dependent change in the antitumor effect of interferon-beta (IFN-beta) were investigated based on the sensitivity of tumor cells and the pharmacokinetics of the drug. Tumor-bearing mice were housed under standardized light-dark cycle conditions (lights on at 7:00 AM, off at 7:00 PM) with food and water available ad libitum. The antitumor effect of IFN-beta (0.5 MI.U./kg, intratumoral) was more efficient in early light phase than in early dark phase. The higher antitumor effect of IFN-beta was observed when specific binding of IFN receptor and DNA synthesis in tumor cells increased, and the lower effect was observed when these levels decreased. The dosing time-dependent effect of IFN-beta was supported by the time-dependent expression of transcription factor (signal transducers and activators of transcription 1) and cell proliferation inhibitor (p21 wild-type p53-activated fragment 1) protein induced by IFN-beta. There was a significant dosing time-dependent change in IFN-beta concentration in tumor, with a higher level in early light phase and a lower level in early dark phase. The dosing time-dependent change of IFN-beta concentration in tumor was associated with that of IFN-beta-induced antitumor effect. These results suggest that by choosing the most suitable dosing time for IFN-beta, the efficacy of the drug can be increased in certain experimental and clinical situations.

Animals↗
PubMed2000

Comparison of drug disposition between wild-type and novel tissue-type plasminogen activator pamiteplase in rats.

The pharmacokinetics of pamiteplase in rats was compared with the pharmacokinetics of recombinant wild-type tissue-type plasminogen activator (rwt-PA). The half-life in the beta-phase and total clearance after administration of (125)I-labeled pamiteplase ((125)I-pamiteplase) to rats were 480 and 22% of those of (125)I-labeled rwt-PA ((125)I-rwt-PA), respectively. The amount of radioactivity distributed in the liver after administration of (125)I-pamiteplase was lower than that of (125)I-rwt-PA; consequently, a possible difference in metabolism between the drugs was assessed by an integration plot and a tissue-sampling single-injection technique. Use of these two methods revealed that the hepatic clearances of both compounds accounted for almost all of the total clearance and also revealed that the hepatic clearance of (125)I-pamiteplase was markedly lower than that of (125)I-rwt-PA. Therefore, the lower distribution of pamiteplase in the liver compared with rwt-PA is thought to contribute greatly to the higher plasma concentration of pamiteplase. Additionally, the uptake of (125)I-pamiteplase in the liver was inhibited by rwt-PA, suggesting that there is a common uptake mechanism for both compounds.

Animals↗
PubMed2000

CYP3A4 is a major isoform responsible for oxidation of 7-hydroxy-Delta(8)-tetrahydrocannabinol to 7-oxo-delta(8)-tetrahydrocannabinol in human liver microsomes.

The human liver enzyme microsomal alcohol oxygenase was able to oxidize both 7alpha- and 7beta-hydroxy-Delta(8)-tetrahydrocannabinol (7alpha- and 7beta-hydroxy-Delta(8)-THC) to 7-oxo-Delta(8)-THC. The oxidative activity was determined by using a panel of 12 individual cDNA-expressed human cytochrome P450s (CYPs) (1A1, 1A2, 2A6, 2B6, 2C8, 2C9-Arg, 2C9-Cys, 2C19, 2D6-Met, 2D6-Val, 2E1 and 3A4). Among the CYP isoforms examined, CYP3A4 showed the highest activity for both of substrates. The metabolism of 7alpha- and 7beta-hydroxy-Delta(8)-THC to 7-oxo-Delta(8)-THC was also detected for CYPs 1A1 (4.8% of CYP3A4), 1A2 (4.7%), 2A6 (2.3%), 2C8 (16.6%), and 2C9-Cys (5.4%), and CYPs 1A1 (0.4%), 2C8 (1.3%), 2C9-Arg (4.3%), and 2C9-Cys (0.9%), respectively. The 7alpha- and 7beta-hydroxy-Delta(8)-THC microsomal alcohol oxygenase activities in human liver were significantly inhibited by addition of 100 microM troleandomycin, 1 microM ketoconazole, and anti-CYP3A antibody, although these activities were not inhibited by 1 microM 7, 8-benzoflavone and 50 microM sulfaphenazole. When the substrates were incubated with the CYP3A4-expressed microsomes under oxygen-18 gas phase, atmospheric oxygen was incorporated into 35% of 7-oxo-Delta(8)-THC formed from 7alpha-OH-Delta(8)-THC, but only 12% of 7-oxo-Delta(8)-THC formed from 7beta-OH-Delta(8)-THC. These results indicate that CYP3A4 is a major isoform responsible for the oxidation of 7alpha- and 7beta-hydroxy-Delta(8)-THC to 7-oxo-Delta(8)-THC in liver microsomes of humans, although the oxidation mechanisms for 7alpha- and 7beta-hydroxy-Delta(8)-THC might be different.

Adolescent↗
PubMed1999

Mutational analysis of the anion exchanger 3 gene in familial paroxysmal dystonic choreoathetosis linked to chromosome 2q.

Familial paroxysmal dystonic choreoathetosis (PDC) is an autosomal dominant neurological disorder characterized by episodes of involuntary movement precipitated by caffeine, alcohol, or emotional stress. The locus for PDC has recently been mapped to chromosome 2q32-36, but its causative gene has not yet been identified. PDC is most likely a kind of channelopathy, as suggested by the fact that other paroxysmal neurological disorders are caused by various ion channel mutations. Although no ion channel is located in this candidate region, anion exchanger 3 (AE3) has been mapped to 2q36 and has also been reported to be the most promising candidate gene of PDC. In this study we performed sequencing of the coding region of the AE3 gene in patients with familial PDC linked to chromosome 2q and excluded the AE3 gene as the causative gene for PDC. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:733-737, 1999.

Amino Acid Sequence↗
PubMed1999

Utility of postcolumn addition of 2-(2-methoxyethoxy)ethanol, a signal-enhancing modifier, for metabolite screening with liquid chromatography and negative ion electrospray ionization mass spectrometry.

A strategy for highly sensitive metabolite screening by liquid chromatography-electrospray ionization (ESI) mass spectrometry with the negative-ion mode that involves the use of a reversed-phase column in gradient-elution mode and postcolumn addition of 2-(2-methoxyethoxy)ethanol (2-MEE), a novel signal-enhancing modifier, has been described. When a mobile phase of 50 mM ammonium acetate/acetic acid buffer (pH 4.4) at a flow rate of 100 microL/min was employed, poor ESI response of ibuprofen as a model drug, probably due to both the high surface tension of the mobile phase and the ion-suppression effect of acetate anion in the mobile phase, was observed. On the other hand, the postcolumn addition of 2-MEE (50 microL/min) into the mobile phase counteracted the ion suppression as well as the surface tension problem, resulting in approximately 100-fold signal enhancement of the analyte. The metabolite screening of ibuprofen in human urine was subsequently carried out comparing the results with and without postcolumn addition of 2-MEE. The results indicated that the postcolumn addition of 2-MEE dramatically improved the ESI responses of all urinary metabolites detected without affecting the chromatographic separation.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Molecular cloning and sequence analysis of cDNAs coding for 3-methylcholanthrene-inducible cytochromes P450 in Xenopus laevis liver.

Liver microsomes of Xenopus laevis were investigated for specific cytochrome P450s (CYPs) that would be inducible in response to the administration of either 3-methylcholanthrene (3MC) or beta-naphthoflavone (BNF), potent inducers for mammalian CYP1A. When probed with antibodies raised against rat CYP1A1, a 54-kDa protein was detected after administration of polycyclic aromatic hydrocarbons. However, there was no immunoreactive protein in microsomes from untreated frogs. In order to obtain structural information about this CYP1A-like protein, a liver cDNA library of 3MC-treated frog was constructed and screened using a fragment of rat CYP1A2 cDNA under low stringency conditions. We have isolated two cDNA clones (MC1 and MC2) with inherent features of the CYP1A subfamily. The sequence determination revealed that both of them coded for polypeptides composed of 526 amino acid residues, which differed from each other by 30 amino acids. A comparison with other mammalian CYP enzymes demonstrated that both of the sequences share 55 to 63% identity with the sequences of CYP1A family members. Northern blot analysis and RT-PCR results further demonstrated that two discrete transcripts corresponding to clones MC1 and MC2 are indeed inducible in the frog liver by treatment with 3MC or BNF. The names CYP1A6 and CYP1A7 were given to clones MC1 and MC2, respectively.

Animals↗
PubMed1999

Bradykinin-potentiating peptides and C-type natriuretic peptides from snake venom.

Cloning of cDNAs encoding bradykinin-potentiating peptides (BPPs)-C-type natriuretic peptide (CNP) precursor or its homologue was performed for cDNA libraries of Bothrops jararaca (South American snake), Trimeresurus flavoviridis, Trimeresurus gramineus and Agkistrodon halys blomhoffi (Asian snakes), all belonging to Crotalinae subfamily. Each cDNA library was constructed from the venom glands of a single snake to preclude ambiguity by intraspecies variation in venom components. Thirteen positive clones derived from B. jararaca were divided into two types depending on restriction sites. Differences in the nucleotide sequence arise at three locations and two of them accompanied amino acid conversions. Despite the differences, both types of cDNA clones encode the BPP-CNP precursor of 256 amino acid residues. Sequence analysis demonstrated that cDNA clones from three Asian snakes encode homologues of the BPP-CNP precursor from B. jararaca. In a precursor polypeptide, a signal sequence (approximately 25 aa) at the N-terminus is followed by sequences of BPP or the analogue (5-13 aa) with flanking spacer sequences (indefinite number of aa), an intervening linker sequence (approximately 144 aa) with unidentified function, and a CNP sequence (22 aa) with a preceding processing signal sequence (10 aa). cDNA clones from A. halys blomhoffi encode two distinct peptides in place of BPP, and T. flavoviridis and T. gramineus were shown to have considerably different sequences in the BPP domain from those known as BPP sequences. The present results provide evidence for a wide distribution of the orthologous gene expressing a series of bioactive peptides among Crotalinae subfamily.

3' Untranslated Regions↗