Biomedical subjects

T Rikihisa

Publications and source records attributed to T Rikihisa.

At least 19 recordsLinked to original sources

PubMed2001

Prevention of hepatitis C virus infection in a chimpanzee by vaccination and epitope mapping of antiserum directed against hypervariable region 1.

We previously reported on a chimpanzee immunized with both putative envelope glycoproteins (E1 and E2) of hepatitis C virus (HCV), strain HCV-N2, and synthetic peptides of hypervariable region 1 (HVR1) of a different isolate, HCV-#6. The chimpanzee showed complete protection against HCV-#6 infection only when the titer of anti-HVR1 increased, suggesting that an immune response to the HVR1 is more essential in protecting a chimpanzee from HCV infection than an immune response to E1 and E2. In this study, we immunized this chimpanzee with only synthetic HVR1 peptides after anti-E1 and anti-E2 antibody levels dropped and then rechallenged with 10 infectious chimpanzee doses of HCV. The immunized animal was protected, and neutralization of HCV with the antiserum from the protected animal was achieved by inoculating another chimpanzee with HCV preneutralized by this antiserum mixture. Epitope analysis of HVR1 by Pin-ELISA using this antiserum seemed to demonstrate that the antibody response was directed mainly against the C terminus of HVR1. Moreover, our results showed that, if a part of the sequences was conserved, a broad cross-reactivity of the antiserum could be observed, even if amino-acid sequences in this epitope were substituted for those of other HCV strains.

Journal Article↗

PubMed2001

[No relation between angiotensin-converting enzyme (ACE) inhibitor-induced cough and ACE gene polymorphism, plasma bradykinin, substance P and ACE inhibitor concentration in Japanese patients].

Persistent dry cough is well known as the most common side-effect of angiotensin-converting enzyme (ACE) inhibitors. We examined the relationship between a cough and ACE gene polymorphism, plasma bradykinin (BK), substance P (SP) and ACE inhibitor concentrations in patients with hypertension or chronic nephritis. First, ACE genotyping was carried out in 96 patients, 42 with coughs and 54 without coughs, which had been treated with various kinds of ACE inhibitors. However, no significant difference in the ACE genotypes was observed between the two groups. Second, the plasma concentrations of BK, SP and ACE inhibitor were measured in 12 patients, which were treated with trandolapril at a daily dose of 1 mg for 4-33 weeks. In 3 patients, the cough was induced during the trandolapril therapy, while it was induced not in 9 patients. The plasma levels of BK and SP did not significantly change after trandolapril administration in the patients with and without coughs. Between the two groups, there were no significant differences in the plasma levels of BK and SP either before or after the trandolapril therapy. Also the plasma concentrations of trandolapril and trandolaprilat, the active metabolite of trandolapril, did not significantly differ between the two groups. These results suggest that there is no significant relationship between the ACE inhibitor-induced cough and ACE gene polymorphism, plasma BK, SP and ACE inhibitor concentrations in patients with hypertension or chronic nephritis.

Aged↗

PubMed2000

Effect of cimetidine and probenecid on pilsicainide renal clearance in humans.

OBJECTIVE: To investigate the effect of cimetidine and probenecid on the renal clearance of pilsicainide in healthy subjects. METHODS: Nine healthy men (age range, 21 to 38 years) were given oral doses of 50 mg pilsicainide hydrochloride alone, with coadministration of 800 mg oral cimetidine, or with coadministration of 1,500 mg oral probenecid on three occasions in a Latin-square order. Urine and venous blood samples were collected on a timely basis. The concentration of pilsicainide in plasma and urine were determined by an HPLC method. RESULTS: Concomitant administration of cimetidine significantly increased the area under the plasma concentration-time curve of pilsicainide by a mean of 33%, prolonged elimination half-life by a mean of 24% (from 5 to 6.2 hours), reduced apparent oral clearance by a mean of 26% (from 14.7 +/- 0.1 to 10.8 +/- 0.8 L/h) and reduced renal clearance by a mean of 28% (from 196.8 +/- 53.9 to 141.8 +/- 25.9 mL/min). The net renal clearance by tubular secretion was significantly reduced by a mean value of 38%, from 151.4 +/- 62.9 to 93.0 +/- 31.1 mL/min. Coadministration of probenecid did not show any changes in plasma concentrations of pilsicainide, pharmacokinetics, or the net renal clearance by tubular secretion of pilsicainide. CONCLUSIONS: Pilsicainide appeared to be secreted by the active transport system for organic bases in the proximal tubule, and the excretion of pilsicainide was inhibited by cimetidine.

Adult↗

PubMed1999

Correlations between in vitro affinity of antipsychotics to various central neurotransmitter receptors and clinical incidence of their adverse drug reactions.

OBJECTIVE: This study was performed to determine whether in vitro affinities of currently available antipsychotics toward dopamine or other neuronal receptor systems are associated with their in vivo incidence of central and peripheral adverse drug reactions (ADRs). METHODS: For 17 antipsychotic drugs available in Japan, the clinical incidences of 7 different types of drug-induced ADRs (i.e., akathisia, dyskinesia, tremor, rigidity, drowsiness, hypotension and dry mouth) were obtained from both post-marketing ADR databases and the investigational clinical trials of eight pharmaceutical companies. Affinity constants (K(i)) of the respective drugs toward dopamine D(1) and D(2) receptors, alpha(1)-adrenoceptors, histamine H(1) receptors, serotonin 5-HT(2) receptors and muscarinic cholinoceptors, determined using rat brain synaptosomes, were obtained from the literature. Relationships between in vitro receptor-binding properties and in vivo incidences of the respective types of antipsychotic-related ADRs were analyzed using Spearman's rank correlation. RESULTS: Significant (P < 0.05) correlations were observed between the K(i) values for dopamine D(2) receptor and the clinical incidences of akathisia and dyskinesia (r(s) = -0.68 and -0. 66, respectively). Significant (P < 0.05) correlations were also observed between the K(i) values for alpha(1)-adrenoceptor and histamine H(1) receptor and the incidence of drowsiness (r(s)=-0.65 and -0.55, respectively), and between the K(i) values for three receptor systems (i.e., dopamine D(1) receptor, alpha(1)-adrenoceptor and histamine H(1) receptor) and the incidence of dry mouth (r(s) = -0.50, -0.81 and -0.62, respectively). CONCLUSION: Preclinical receptor-binding data of antipsychotic drugs toward central dopamine and other ancillary neurotransmitter systems may be useful for predicting not only in vivo antipsychotic potency but also clinical incidence of akathisia and dyskinesia for this class of agents. Newly developed antipsychotic drugs with more potent and selective antagonistic activity against the dopamine D(2) receptor may not necessarily be associated with a lower incidence of extrapyramidal ADRs.

Adverse Drug Reaction Reporting Systems↗

PubMed1999

Experimental vaccine activities of recombinant E1 and E2 glycoproteins and hypervariable region 1 peptides of hepatitis C virus in chimpanzees.

A chimpanzee was immunized with two recombinant envelope glycoproteins E1 and E2 of hepatitis C virus (HCV), strain HCV-N2, and the hypervariable region 1 (HVR1) peptides of a different isolate, HCV-#6, then received an intravenous inoculation of 10 chimpanzee infectious doses of HCV-#6. With high humoral immune response against E1 and E2 but a low response against HVR1, the vaccinee became infected with the HCV. However, after increasing the titer of anti-HVR1 against HCV-#6, the vaccinee showed protection. Neutralization of HCV-#6 with the antiserum from this protected vaccinee was achieved by inoculation of this mixture into another chimpanzee. These results suggest that vaccination with a peptide-vaccine of homologous HVR1 is effective in the chimpanzee.

Amino Acid Sequence↗

PubMed1999

Active oxygen species generation and cellular damage by additives of parenteral preparations: selenium and sulfhydryl compounds.

We investigated the relationship between active oxygen species (AOS) generation and cultured vascular endothelial cellular damage caused by simultaneous exposure to selenium compounds and sulfhydryl compounds such as cysteine (Cys) or reduced glutathione (GSH). Selenium compounds, selenite, selenate or selenomethionine (SeMet), are added to total parenteral nutrition (TPN) and intravenously administered. We confirmed by luminol dependent chemiluminescence, an indicator of AOS generation, that selenite generates AOS in the presence of clinical concentrations of sulfhydryl compounds, 0.5 mM Cys or 0.5 mM GSH, and that the amount of AOS generated reaches the maximum when their mole ratio is 1:50. However, AOS generation was not observed after simultaneous administration of various concentrations of selenate or SeMet with sulfhydryl compounds. Moreover, simultaneous exposure to 10 microM selenite and sulfhydryl compounds was found to result in significant increases in the [3H]-adenine and lactate dehydrogenase (LDH) release rates from cells, a significant decrease in the amount of cellular protein, and enhancement of cellular damage as compared with after exposure to selenite alone. However, simultaneous exposure to 10 microM selenate or 10 microM SeMet together with sulfhydryl compounds did not induce cellular damage. These findings revealed that selenite generates AOS and causes cellular damage in the presence of sulfhydryl compounds. Accordingly, it seems better to choose selenate or SeMet instead of selenite when a selenium compound is to be added to TPN.

Adenine↗

PubMed1995

Selective transmission of hepatitis C virus in vivo and in vitro.

A human plasma containing quasi-species of hepatitis C virus (HCV) was inoculated to a chimpanzee and to human lymphocytic cell lines, HPB-Ma clone 10-2, AD HPB, and Daudi, which support replication of HCV. Among six different hypervariable region (HVR) sequences detected in the inoculum, the same two were recovered both in vivo and in vitro.

Amino Acid Sequence↗

PubMed1995

Correlation of in vivo infectivity of hepatitis C virus to in vitro infectivity and to virion properties.

Serum from an individual who was chronically infected with hepatitis C virus (HCV) was inoculated into chimpanzees and a human T cell line. The serum contained a quasispecies population of HCV consisting of at least six genetic sequences. However, only two sequences (the same two sequences) were recovered both in chimpanzees and in cultured human T cell line, indicating that infection of the culture system reflects infection in vivo.

Amino Acid Sequence↗

PubMed1994

Possible occurrence of P450 related to P450 HFLb in extrahepatic tissues of human fetuses and its contribution to metabolic activation of promutagens.

P450 HFLb purified from human fetal livers has been shown to be constitutively expressed in fetal livers. In the present study, the occurrence of proteins immunochemically related to P450 HFLb in extrahepatic tissues of human fetuses and their contribution to mutagenic activation of promutagens were investigated. The mutagenic activation of aflatoxin B1 (AFB1), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and benzo[a]pyrene were observed in human fetal extrahepatic tissues, including adrenal glands, kidneys and lungs, at varying rates. Immunoblot analysis of homogenates of extrahepatic tissues with antibodies to P450 HFLb revealed the occurrence of proteins immunochemically related to P450 HFLb in adrenal glands, kidneys and lungs. Immuno-inhibition studies suggested that in fetal adrenal gland and kidney, the proteins cross-reactive with antibodies to P450 HFLb were capable of activating IQ and MeIQ to mutagens.

Adrenal Glands↗

PubMed1994

Immunochemical evidence for the occurrence of Mu class glutathione S-transferase in human fetal livers.

Immunoblot analysis showed that alpha-class glutathione S-transferase (GST), which is one of the major forms in adult human liver, was expressed in human fetal liver. Mu-class GST was also expressed in fetal liver. The majority of mu-class GST expressed in adult liver consisted of a subunit with a molecular weight of 27 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), whereas two subunits of 27 and 26 kDa were detected in fetal liver as proteins immunochemically related to mu-class GST. On reverse-phase HPLC, these two subunits cross-reactive with antibodies to rat GST 3-3 in fetal liver were indistinguishable from each other in their retention time; though, they could be separated by chromatofocusing analysis. The molecular weights of GSTs immunochemically related to rat GST 3-3, eluted at pH 7.1, 6.4, and 5.7, were 27, 27 and 26, and 26 kDa, respectively. In addition, the N-terminal amino acid sequence of these subunits suggested that GSTs related to rat GST 3-3 expressed in fetal liver may be homodimeric and heterodimeric proteins. As expected, pi-class GST was found to be a major form of GST in fetal liver but not in adult liver. In contrast, the GST immunochemically related to rat GST Yrs-Yrs, which is classified as theta-class GST, was detected in adult liver but not in fetal liver. These results indicate that several isoenzymes of GST are expressed in human fetal liver, but they are not the same as those in adult liver.

Amino Acid Sequence↗

PubMed1993

Sequence and gene structure of the hepatitis E virus isolated from Myanmar.

Hepatitis E virus (HEV) is a causative agent of enterically transmitted non-A, non-B hepatitis. Hepatitis E occurs not only in sporadic forms but also in epidemic outbreaks in the developing world. We have revealed the nucleotide and predicted amino acid sequences of full cDNA of HEV isolated from sporadic hepatitis E of Myanmar. The genome is 7194 nucleotides long, followed by a poly(A) tail, and has three open reading frames. The nonstructural gene is located in the 5' terminus, while the structural gene is situated in the 3' terminus. Our HEV strain has 98.5% nucleic acid identity with the HEV strain cloned by workers at Genelabs Incorporated from Myanmar. The difference is point nucleotide substitutions. There is a high degree of nucleotide relatedness among HEVs isolated from the same geographical location.

Amino Acid Sequence↗

PubMed1993

An epidemic outbreak of hepatitis E in Yangon of Myanmar: antibody assay and animal transmission of the virus.

An epidemic outbreak of hepatitis E occurred in an army recruit camp of Yangon, Myanmar, in October 1989. One hundred and eleven patients among 600 residents were hospitalized. As high as 83.7% of these patients were positive for the acute phase antibody against hepatitis E virus by an enzyme-linked immunosorbent assay developed in our laboratory. Also, 30.6% of 49 symptom-free residents examined were positive for the antibody. We prepared a stool extract from six patients and inoculated it into 10 rhesus monkeys for a series of three sub-passages. All of them developed acute biochemical hepatitis along with an elevation of antibody levels. A rechallenge with viruses of the present outbreak failed to provoke hepatitis in two monkeys that had previously recovered from acute hepatitis caused by an isolate of sporadic hepatitis E of the same area. Similarly, the rechallenge of the sporadic strain did not induce hepatitis in two monkeys that had been previously infected with the epidemic virus. These data suggested that the subjects would obtain neutralizing antibodies against the hepatitis E virus once infected, and many adult inhabitants of the endemic area had no protective antibodies and were still susceptible to hepatitis E infection.

Adult↗

PubMed1993

Studies on cytochrome P450 responsible for oxidative metabolism of imipramine in human liver microsomes.

The activity of imipramine 2-hydroxylase highly correlated with that of desipramine 2-hydroxylase but not with that of desipramine N-demethylase. The correlation was also found between N-demethylation and 2-hydroxylation when imipramine was used as a substrate, whereas no correlation was observed between them when desipramine was used in place of imipramine. Both activities of desipramine and imipramine 2-hydroxylase were markedly inhibited by quinidine but not by quinine. Although the activity of imipramine N-demethylase was slightly inhibited by both quinidine and quinine, the activity of desipramine N-demethylase was unaffected under the same conditions. The activity of imipramine N-demethylase was roughly correlated with the amounts of P450 3A4 immunochemically determined and the activities of testosterone 6 beta-hydroxylase in human liver microsomes. The P450 3A4 catalyzed imipramine N-demethylation much more efficiently than 2-hydroxylation in a reconstituted system, whereas neither N-demethylation nor 2-hydroxylation of desipramine was catalyzed by P450 3A4. The activity of imipramine N-demethylase was inhibited, to various extents, by anti-P450 3A4 antibodies in human liver microsomes. Taking together these and other results, it is suggested that P450 3A4, other than P450 2Cmp, also partly contributes to N-demethylation of imipramine, depending on human liver microsomes.

Cytochrome P-450 Enzyme Inhibitors↗

PubMed1993

Species differences of testosterone 16-hydroxylases in liver microsomes of guinea pig, rat and dog.

1. In hepatic microsomes, remarkable species differences in the activity of testosterone 16-hydroxylase was observed in guinea pig, dog, and rat. The activity of testosterone 16 beta-hydroxylase was higher than that of 16 alpha-hydroxylase in guinea pig, whereas 16 alpha-hydroxylated testosterone was predominant as the metabolite in dog and rat. 2. Since P4502B isoenzyme has been shown to be a catalyst for testosterone 16-hydroxylations, we compared the catalytic properties of the P4502B subfamily (P450GP-1, P450b and P450PBD-2) purified from liver microsomes of guinea pig, dog, and rat, respectively. P450GP-1, P450b and P450PBD-2 showed different stereoselectivities for hydroxylation of testosterone at the 16-position. 3. P450GP-1, P450b and P450PBD-2 together comprised 47, < 0.1 and 23% of total P450 in liver microsomes of untreated guinea pig, rat and dog, respectively, indicating that the amounts of the P4502B isoenzyme in untreated animals were clearly different in these three animal species. Both 16 alpha- and 16 beta-hydroxylations of testosterone in liver microsomes of phenobarbital-treated guinea pig, rat and dog were inhibited by anti-P450GP-1, anti-P450b and anti-P450PBD-2 antibodies, respectively. 4. These and other results indicate that the species difference observed in testosterone 16-hydroxylation may be, in part, due to differences in the amounts of P450 of the P4502B subfamily, and their stereoselectivities for 16-hydroxylation.

Animals↗

PubMed1993

Characterization of human liver microsomal cytochrome P450 involved in the reductive metabolism of zonisamide.

Zonisamide (1,2-benzisoxazole-3-methanesulfonamide) was metabolized to 2-sulfamoylacetylphenol (SMAP) in human liver microsomes under anaerobic conditions. The formation of SMAP was remarkably inhibited by cimetidine, n-octylamine, ketoconazole, and carbon monoxide, indicating that a cytochrome P450 is involved in the metabolism of zonisamide to SMAP in human liver microsomes. The SMAP-producing activity did not correlate with the spectrally determined amount of cytochrome P450. In contrast, the SMAP-producing activity from zonisamide correlated closely with the activity of testosterone 6 beta-hydroxylase (r2 = 0.96) and correlated slightly but significantly with the activity of imipramine 2-hydroxylase (r2 = 0.28), but not with those of aniline hydroxylase (r2 = 0.09) or benzphetamine N-demethylase (r2 = 0.20). In addition, immunoquantitation of cytochrome P450 enzymes in 21 human liver microsomal samples revealed that SMAP formation correlated closely with the amount of P450 3A enzyme and correlated moderately well with that of P450 2D6 but not with that of P450 2C enzyme in human liver microsomes. P450 3A4 exhibited SMAP-producing activity in a reconstituted monooxygenase system. The metabolism of zonisamide to SMAP was almost completely inhibited by anti-P450 3A4 antibody but not by anti-P450 2C9 or anti-P450 2D6 antibodies, suggesting that the amount of P450 3A enzyme may be a major factor influencing the level of metabolism of zonisamide to SMAP in human liver microsomes.

Anticonvulsants↗

PubMed1993

Purification from liver microsomes from untreated cynomolgus monkeys of cytochrome P450 closely related to human cytochrome P450 2B6.

A cytochrome P450 (P450) (referred to as P450CMLa) was purified and characterized from hepatic microsomes from untreated cynomolgus monkeys (Macaca irus). The final preparation was electrophoretically homogeneous and its estimated minimum molecular mass was 49.5 kDa. The amino-terminal amino acid sequence of the protein (first 34 residues) closely resembled that of the protein encoded by the 2B6 cDNA from humans (94%). This protein was cross-reactive with antibodies raised against P450 2B1 (P450 b), P450 2B11 (P450 PBD-2), and P450GP-1, which were purified from hepatic microsomes from phenobarbital-pretreated rats, beagle dogs, and guinea pigs, respectively. Also, the antibody raised against P450CMLa was able to cross-react with P450 2B1, P450 2B11, and P450GP-1. P450CMLa was capable of catalyzing benzphetamine N-demethylation and testosterone 16 beta-hydroxylation in a reconstituted system. Anti-P450CMLa antibody inhibited the activity of testosterone 16 beta-hydroxylase but not the activities of testosterone 2 beta- and 6 beta-hydroxylases in liver microsomes from cynomolgus monkeys. The content of P450CMLa, as estimated by immunoblot analysis, was 70 pmol/mg (about 5% of total P450). The protein immunoreactive with the anti-P450CMLa antibody was also present in liver microsomes from Japanese monkeys, baboons, common marmosets, and common squirrel monkeys. In liver microsomes from common squirrel monkeys, the content of protein immunoreactive with the anti-P450CMLa antibody and the activity of testosterone 16 beta-hydroxylase were effectively increased by pretreatment with phenobarbital. The antibody against P450CMLa strongly inhibited the activity of testosterone 16 beta-hydroxylase in liver microsomes not only from untreated cynomolgus monkeys but also from phenobarbital- and pregnenolone 16 alpha-carbonitrile-pretreated common squirrel monkeys. These results indicated that the P450CMLa purified here is very similar to the forms of P450 classified into the 2B subfamily, in its amino-terminal amino acid sequence, catalytic activities, and immunochemical properties.

Amino Acid Sequence↗

PubMed1992

Immunochemical characterization and toxicological significance of P-450HFLb purified from human fetal livers.

Immunochemical properties of P-450HFLb purified from human fetal livers were investigated. P-450HFLb cross-reacted with antibodies to rat P-4501A1 but not with antibodies to CYP2A6, CYP2C9, CYP3A7 (P-450HFLa) and rat CYP2B1. In addition, P-450HFLb also cross-reacted with both monospecific antibodies to rat CYP1A1 and CYP1A2. However, P-450HFLb was shown to be an immunochemically distinct form of cytochrome P-450 from P-450PA (human CYP1A2). Immunoblot analysis of human fetal livers with the antibodies to P-450HFLb showed that P-450HFLb was expressed in all fetal livers studied although there appeared to be individual differences in the amounts of P-450HFLb expressed in fetal livers. The formation of mutagens from IQ (but not from AFB1) in fetal liver homogenates was inhibited by the antibodies to P-450HFLb in a dose dependent manner. These results suggest that P-450HFLb may be a form of human cytochrome P-450 classified into CYP1 gene family, and that the cytochrome P-450 is, in part, responsible for the mutagenic activation of IQ in human fetal livers as well as CYP3A7 (P-450HFLa).

Aflatoxin B1↗

PubMed1992

Hepatitis E virus: cDNA cloning and expression.

Viral hepatitis E is endemic, frequently provoking epidemic outbreaks in many developing countries. We have attempted to clone the viral genome and to develop an antibody assay system. A lambda gt11 cDNA library was constructed from the bile juice containing putative causative viruses and was immunoscreened by the antisera obtained from patients and monkeys infected with hepatitis E. Three virus-specific clones were isolated and were revealed to overlap one another in sequence, with 1,459 nucleotides in total length. These clones direct the synthesis of polypeptides probably having common immunological epitope(s). Immunoplaque assay revealed the occurrence of antibodies against this epitope in the sera from experimental monkeys with the convalescent phase and from patients of Myanmar, Nepal and India. The data indicate that the cDNA fragments are useful for immunodiagnosis of hepatitis E.

Amino Acid Sequence↗