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Biomedical subjects

M Omata

Publications and source records attributed to M Omata.

At least 433 records · Page 24Linked to original sources
PubMed1993

Precore mutations and core clustering mutations in chronic hepatitis B virus infection.

BACKGROUND: Mutant hepatitis B virus is often associated with severe liver damage. The purpose of this study is to elucidate the relationship between mutations in hepatitis B precore/core gene and the severity of liver damage. METHODS: The hepatitis B precore/core gene from 20 patients with chronic hepatitis B virus infection was studied by polymerase chain reaction and direct sequencing. RESULTS: Missense mutations in the core gene were only found in patients with chronic active hepatitis. Three mutation clustering regions of core gene, codons 48-60, 84-101, and 147-155, had higher substitution rates than other regions. All patients with chronic active hepatitis had missense mutation(s) either in codons 84-101 or in codons 48-60. There was a trend of increasing substitutions in the precore/core gene from e antigen-positive asymptomatic carriers to e antibody-positive patients with chronic active hepatitis. CONCLUSIONS: These data suggest that (1) severe liver damage in chronic hepatitis B virus infection is related to the clustering missense mutations in codons 48-60 and 84-101 of core gene and that (2) the emergence of precore stop codon mutation and missense mutations around the carboxy-terminal processing site of precore/core protein (codons 147-155) may be the adaptive mechanisms of hepatitis B virus to decrease production and secretion of viral protein and retain the viral persistence.

Adult↗
PubMed1993

Quantification of sinusoidal cell function in vivo.

Although the clearance and distribution of ligand molecules in circulation represent the function of hepatic sinusoidal cells, these mechanisms revealed a network that is more intricate than would at first seem, since several receptors are common to not only one type of cell, but also to two or three types of cells in the liver. In the case of latex particles in which their uptake by a particular cell type seems to be determined by their size, sinusoidal endothelial cells are able to internalize particles up to 0.23 microns under physiologic conditions, in vivo, and larger particles are taken up by Kupffer cells. However, when the phagocytic function of Kupffer cells is impaired by frog virus 3 or alcohol, endothelial cells have been found to take up particles larger than 1 micron in diameter after the injection of an excess amount of latex particles. Endothelial cells would thus constitute a second line of defense in the liver in that they remove foreign materials from the blood when Kupffer cell phagocytic function is totally disturbed. This potential role may not, however, be fully expressed under physiologic conditions when Kupffer cells are active in clearing foreign substance from the circulation. The functions of liver sinusoidal cells are varied and complex and these cells can be regarded as "a sinusoidal cell unit." This cellular interaction must be taken into account for any quantitative analysis.

Animals↗
PubMed1993

Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line.

The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 G ohms, and 50 pF, respectively. Under the voltage-clamp condition, no voltage-dependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time- and voltage-independent K+ current. The ACh-induced hyperpolarization and K+ current persisted, while the His response desensitized quickly (< 1 min). These effects of ACh and His were mediated predominantly by m3-muscarinic and H1-His receptors, respectively. The K+ current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca(2+)-activated K+ channel current (IK.Ca). The measurement of intracellular Ca2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca. When EGTA in the pipette solution was increased from 0.15 to 10 mM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate IK.Ca by increasing [Ca2+]i in JR-1 cells. In the Ca(2+)-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca2+ (1.8 mM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca2+ release-related initial transient activation and the Ca2+ influx-related sustained activation of IK.Ca. Probably because of desensitization, the Ca2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without inositol 1,3,4,5-tetrakisphosphate (IP4), mimicked the ACh response. IP4 alone did not affect the membrane current. Under the steady effect of IP3 or IP3 plus IP4, neither ACh nor His further evoked IK.Ca. Intracellular application of heparin or of the monoclonal antibody against the IP3 receptor, mAb18A10, inhibited the ACh and His responses in a concentration-dependent fashion. Neomycin, a phospholipase C (PLC) inhibitor, also inhibited the agonist-induced response in a concentration-dependent fashion. Although neither pertussis toxin (PTX) nor N-ethylmaleimide affected the ACh or His activation of IK,Ca, GDP beta S attenuated and GTP gamma S enhanced the agonist response.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1993

Antiulcer drugs and gastric prostaglandin E2: an in vitro study.

Prostaglandin (PG) has been reported to be an important protective and acid-suppressive factor in the gastric mucosa. Although the mechanisms of some antiulcer drugs are attributed to their stimulatory effects on endogenous prostaglandins, an understanding of these actions has not been established. In the present study we investigated the effects of antiulcer drugs on PGE2 using cultured gastric mucosal cells. Rabbit gastric mucosal cells were cultured after isolation with collagenase and ethylenediaminetetraacetic acid. PGE2 was measured by enzyme-linked immunoassay. Histamine H2-blockers (cimetidine, ranitidine, famotidine), omeprazole, and sucralfate did not modulate the media content of PGE2, whereas sofalcone dose- and time-dependently increased it. Sofalcone-induced increase of PGE2 was dose-dependently prevented by indomethacin. Sofalcone did not affect intracellular Ca2+ as assessed by the calcium-sensitive probe indo-1. Deprivation of Ca2+ in the media did not modulate the action of sofalcone. Sofalcone significantly suppressed 15-OH-PG dehydrogenase. These results suggest that among the various antiulcer drugs only sofalcone increases PGE2, which may be a factor in its therapeutic effect against peptic ulcer diseases.

Animals↗
PubMed1993

Inhibition of protein synthesis and antiproliferative effect of the angiotensin converting enzyme inhibitor trandolaprilat in rat vascular smooth muscle cells.

OBJECTIVE: To investigate the effect of the angiotensin converting enzyme (ACE) inhibitor trandolaprilat on vascular smooth muscle cell growth, and to analyse its mechanism of action. DESIGN: Aortic vascular smooth muscle cells (VSMC) from Wistar-Kyoto rats were cultured, and cell proliferation was analysed using a cell synchrony technique. METHODS: Proliferative activity was assessed by [3H]-thymidine uptake and doubling time. Protein synthesis was assessed by [3H]-leucine incorporation. Actin formation was measured using sodium dodecylsulphate-polyacrylamide slab gel electrophoresis and a densitometric assay. The effect of trandolaprilat on translational protein synthesis was also examined using the cell-free protein synthesis system of reticulocyte lysate and messenger RNA from VSMC. RESULTS: Trandolaprilat decreased [3H]-thymidine uptake and increased the doubling time of randomly cycling VSMC. The cell synchrony study revealed that this antiproliferative effect was due to increased transition time from S to G2-M. Decreased cell cycle progression during G2-M was reflected by inhibition of cellular protein synthesis during this period. Cellular protein in randomly cycling VSMC was also decreased by trandolaprilat. This decreased protein synthesis was probably produced by inhibition of RNA translation. CONCLUSIONS: The ACE inhibitor trandolaprilat reduces VSMC proliferation by lengthening the G2-M phase of the cell cycle, and produces a decrease in cellular protein content. This effect is probably mediated by inhibition of protein synthesis at the translational level.

Actins↗
PubMed1993

Expression of HCV E2/NS1 protein as a fusion protein with maltose binding protein: detection of anti-E2/NS1 antibody in chronic liver disease.

The presence of anti-E2 antibody was investigated in the serum samples of 46 patients with liver disease, who were positive for hepatitis C virus-RNA, and in five subjects HCV-RNA-negative acting as controls. Antibody to E2/NS1 protein was found in seven of 46 (15%) of the patients with liver disease but in none of the control subjects. In one patient who was treated successfully with interferon, the levels of anti-E2 gradually decreased and then finally disappeared after treatment. This suggests that the E2/NS1 protein may play a role in active viral replication.

ATP-Binding Cassette Transporters↗
PubMed1993

Mutations in core nucleotide sequence of hepatitis B virus correlate with fulminant and severe hepatitis.

Infection with hepatitis B virus leads to a wide spectrum of liver injury, including self-limited acute hepatitis, fulminant hepatitis, and chronic hepatitis with progression to cirrhosis or acute exacerbation to liver failure, as well as an asymptomatic chronic carrier state. Several studies have suggested that the hepatitis B core antigen could be an immunological target of cytotoxic T lymphocytes. To investigate the reason why the extreme immunological attack occurred in fulminant hepatitis and severe exacerbation patients, the entire precore and core region of hepatitis B virus DNA was sequenced in 24 subjects (5 fulminant, 10 severe fatal exacerbation, and 9 self-limited acute hepatitis patients). No significant change in the nucleotide sequence and deduced amino acid residue was noted in the nine self-limited acute hepatitis patients. In contrast, clustering changes in a small segment of 16 amino acids (codon 84-99 from the start of the core gene) in all seven adr subtype infected fulminant and severe exacerbation patients was found. A different segment with clustering substitutions (codon 48-60) was also found in seven of eight adw subtype infected fulminant and severe exacerbation patients. Of the 15 patients, 2 lacked precore stop mutation which was previously reported to be associated with fulminant hepatitis. These data suggest that these core regions with mutations may play an important role in the pathogenesis of hepatitis B viral disease, and such mutations are related to severe liver damage.

Adult↗
PubMed1993

[Effect of carperitide (alpha-human atrial natriuretic polypeptide) on the cardiovascular system in experimental animals].

The cardiovascular and diuretic actions of carperitide were studied in experimental animals. Carperitide relaxed various canine arteries and veins that were contracted by high K+ or norepinephrine. Carperitide stimulated particulate guanylate cyclase from rat thoracic aortas. Carperitide had almost no effect on coronary perfusion pressure or heart rate, but caused a slight decrease in contractile force in isolated guinea pig hearts. Carperitide tended to decrease isoproterenol-induced renin release from isolated rat kidney slices and elicited decreases in angiotensin II-induced aldosterone release from bovine zona glomerulosa cells. Intravenous injection of carperitide elicited decreases in arterial blood pressure and total peripheral resistance in the anesthetized and conscious dogs. Carperitide also elicited transient increases in cardiac output and coronary blood flow followed by slight decreases in them. Intravenous infusion of carperitide elicited decreases in pulmonary capillary wedge pressure, pulmonary pressure and right atrial pressure in association with elevating plasma carperitide (ANP like immuno-reactivity) level in dogs with heart failure induced by coronary artery occlusion and saline loading. These results suggest that carperitide decreases both preload and afterload and can improve the untoward hemodynamic alterations in animals with acute experimental heart failure.

Animals↗
PubMed1993

Production of chemotactic factor, interleukin-8, from hepatocytes exposed to ethanol.

In a previous paper, we demonstrated proteinous chemotactic factors released from hepatocytes exposed to ethanol. In this study, we further characterized the chemotactic factors released from ethanol-treated hepatocytes. After fractionating the conditioned medium with gel chromatography, we demonstrated chemotactic activity at molecular weights of around 20 and 40 kD. When the conditioned medium was mixed with antiserum against interleukin-8, chemotactic activity was almost completely abolished. In addition, antiserum against interleukin-8 completely reduced chemotactic activity of the 20-kD chemotactic factor but did not influence the chemotactic activity of the 40-kD chemotactic factor. After gel electrophoresis of the conditioned medium, the protein reacted with antibody against interleukin-8 was demonstrated at a molecular weight of 20 kD but was not found at a molecular weight of 40 kD. These results suggest that a major part of the proteinous chemotactic factors released from hepatocytes exposed to ethanol could be a dimer form of interleukin-8, one of the proinflammatory cytokines, possibly contributing to the pathogenesis of alcoholic hepatitis.

Animals↗
PubMed1993

Quantification of hepatitis C virus by competitive reverse transcription-polymerase chain reaction: increase of the virus in advanced liver disease.

We developed a quantitative method of hepatitis C virus RNA by competitive reverse transcription-polymerase chain reaction. With this method, 36 patients with type C chronic liver disease were analyzed for the copy number of circulating hepatitis C virus in 50 microliters of serum. The amounts of hepatitis C virus RNA ranged from 10(1) to 10(7) copies in the 36 patients. The average amount of hepatitis C virus RNA was 10(3.3 +/- 2.2) copies in 12 patients with chronic persistent hepatitis, 10(5.7 +/- 1.6) copies in 12 patients with chronic active hepatitis and 10(6.0 +/- 1.6) copies in 12 patients with cirrhosis (including 4 patients with hepatocellular carcinoma). The amount of hepatitis C virus RNA in serum was significantly less in patients with chronic persistent hepatitis than in patients with chronic active hepatitis or cirrhosis (p < 0.01), and it tended to increase according to the progression of histopathological changes of the liver. Furthermore, it was revealed that the amount of hepatitis C virus RNA became exponentially larger as the term from infection became longer. Quantification of hepatitis C virus RNA by competitive reverse transcription-polymerase chain reaction may have many applications for the study of clinical features of hepatitis C virus infection.

Adult↗
PubMed1993

Prospective assessment of donor blood screening for antibody to hepatitis C virus and high-titer antibody to HBcAg as a means of preventing posttransfusion hepatitis.

Since December 1989, the Japan Red Cross Blood Bureau has screened blood donors for hepatitis C virus antibody on the basis of enzyme-linked immunosorbent assay and high titers of antibody to HBc antigen. To elucidate the effectiveness of the new screening tests in preventing posttransfusion hepatitis, the incidence of posttransfusion hepatitis after the introduction of the new tests (December 1989 to December 1990) was compared with the incidence before their introduction (January 1982 to December 1988). The incidence of posttransfusion hepatitis was 9.8% (219 of 2240), with a mean transfusion volume of 10.2 units, before the screening and 3.7% (12 of 326), with a mean transfusion volume of 14.7 units, after the introduction of the new tests. Statistical analysis revealed a significant decrease of incidence of posttransfusion non-A, non-B hepatitis after the introduction of the new tests (X2 = 10.9, p < 0.01). Posttransfusion hepatitis B occurred in 3 of 2,240 recipients (0.13%) before the introduction of HBc antibody testing. No cases of posttransfusion B viral hepatitis developed after the introduction of the new tests. Hepatitis C virus antibody status was investigated in 7 of 12 posttransfusion hepatitis patients who contracted the disease after the new screening tests were initiated. Hepatitis C virus antibody seroconversion occurred in three of the seven cases (43%), as detected on first- and second-generation hepatitis C virus antibody assays and reverse-transcription polymerase chain reaction.

Aged↗
PubMed1993

[Mutation in core and pre-core amino acid sequences of hepatitis B virus correlate with fulminant and severe hepatitis].

Infection with hepatitis B virus leads to a wide spectrum of liver injury, including self-limited acute hepatitis, fulminant hepatitis and chronic hepatitis with progression to cirrhosis or acute exacerbation to liver failure, as well as, an asymptomatic chronic carrier state. To investigate why an extreme immunological attack occurs in fulminant hepatitis and severe exacerbation, the entire precore and core region were sequenced in 13 subjects. No significant change was noted in the 6 self-limited acute hepatitis patients. In contrast, clustering changes in a small segment of core codons #84 to #99 were found in all 7 fulminant and severe exacerbation patients. These data suggest that this mutation clustering region may play an important role in the pathogenesis, and such mutations appear to be related to severe liver damage.

Adult↗
PubMed1993

[Heterogeneity of delta virus RNA sequences in Japan].

Hepatitis delta virus RNA sequences were determined in isolates from two Japanese patients, M and S, by polymerase chain reaction and direct nucleotide sequencing and compared with three isolates from Italy, USA and Taiwan. The sequence obtained for hepatitis delta virus RNA from patient M was 92-96% identical to the sequences obtained for three other strains of hepatitis delta virus, whereas the sequence of hepatitis delta virus RNA obtained from patient S was approximately 80% identical to the other sequenced strains. This suggests that the delta agent in Japan has a heterogeneous origin and the delta virus RNA sequence from Japanese patient S is the most divergent delta virus isolate yet analyzed.

Adult↗
PubMed1993

[ADH 2, 3 and ALDH 2 gene frequency in Japanese alcoholics].

To elucidate genetic susceptibility to alcoholic liver injury (ALD), polymerase chain reaction (PCR) method assay was developed to detect point mutations in each gene and gene frequency in various liver diseases was studied. It was shown previously that ALDH2(1) gene was more frequently found in patients with ALD (confirmed in this study), probably because they are able to consume too much alcohol (non-flushing type). This study revealed that, in addition to this ALDH heterogeneity, ADH heterogeneity may correlate with the severity of alcoholic liver injury, especially in those was low ADH activity and tend to have severe damage.

Alcohol Dehydrogenase↗
PubMed1992

Detection of antibody to hepatitis C E2/NS1 protein in patients with type C hepatitis.

Putative E2/NS1 sequence of hepatitis C virus was expressed in E. coli as a fusion protein with maltose binding protein. Approximately 80 kDa protein was obtained containing 38 kDa E2/NS1 protein. The antibody to this protein was detectable in the same serum from which the sequence was amplified. It was also detectable in none of 7 acute hepatitis, in 2 of 12 chronic persistent hepatitis, in 3 of 25 chronic active hepatitis, and in 2 of 4 cirrhosis. It was detectable in none of 10 normal subjects. In 3 cases who were positive for the antibody before the interferon treatment, it became undetectable after the treatment. Thus, it seems that the antibody is not a neutralizing antibody and is related to active viral replication.

Base Sequence↗
PubMed1992

Determination of nucleotide sequence of active site for catalytic properties of ADH3 genes.

Alcohol dehydrogenase genes show polymorphism. gamma subunits, which are encoded by ADH3 genes, have two subtypes according to the single base substitution of codon 271 and 349. This mutation of codon 271 directly determines subtypes with different catalytic properties. However, there has been no simple technique to detect nucleotide changes at codon 271. Specific amplification of nucleotides around codon 271 was difficult because of homologous nucleotide sequences around the region among 3 ADH genes (ADH1, 2 and 3). We have developed a method to amplify the ADH3 gene alone with a modification on 3'-end of primer by polymerase chain reaction. Approximately 200 nucleotides including codon 271 of ADH3 gene were sequenced, and genotypes of ADH3 gene were determined in 30 Japanese individuals. This method may facilitate the studies on racial differences of genotypes and involvement of ADH genes in patients with alcoholic liver disease.

Alcohol Dehydrogenase↗