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Biomedical subjects

M Omata

Publications and source records attributed to M Omata.

At least 469 records · Page 26Linked to original sources
PubMed1991

Detection and direct sequencing of hepatitis B virus genome by DNA amplification method.

Hepatitis B virus (HBV) DNA was detected with amplification by the polymerase chain reaction method. Cloned HBV DNA equivalent to one virus genome (3 x 10(-6) pg) was detectable by ethidium bromide staining after 50 cycles of polymerase chain reaction. By applying this method, presence of HBV DNA was studied in 23 hepatitis B surface antigen (HBsAg)-positive and 11 HBsAg-negative sera from patients with chronic liver disease. Hepatitis B virus DNA was positive in 8 of 8 hepatitis B e antigen (HBeAg)-positive, in 2 of 2 HBeAg- and anti-HBe-negative, and in 12 of 13 anti-HBe-positive sera. Hepatitis B virus DNA was undetectable in all HBsAg-negative sera even with amplification. To confirm specificity, the amplified product was directly sequenced. Sequences around 122nd and 160th codon of HBs gene, which determines subtypes d/y and w/r, respectively, were analyzed. The results were compatible with recent reports regarding the relation between HBV subtypes and HBV DNA sequence at those codons. Hepatitis B virus DNA could be detected at the level of one virion by gene amplification method, and its sequence could be determined by direct sequencing in a few days.

Base Sequence↗
PubMed1991

Clinical application of ras gene mutation for diagnosis of pancreatic adenocarcinoma.

Most pancreatic adenocarcinomas are known to have ras gene (oncogene) mutations. The site of the mutations is localized in codon 12 of K-ras gene. Such high incidence and localization of the ras gene mutations have not been observed in any other human malignancies. Polymerase chain reaction and direct sequencing method enabled us to analyze DNA sequence around codon 12 of K-ras gene in small quantities of specimens obtained from needle biopsies and aspirate samples for pathological diagnosis. All the materials obtained from 12 patients with pancreatic adenocarcinoma showed the mutations, whereas those obtained from 6 patients with chronic pancreatitis showed no mutations. In several cases using the mutations of K-ras gene as a marker, this analysis supplemented conventional pathology and cytology in making the diagnosis of pancreatic adenocarcinoma. The analysis of ras-gene mutations was useful for the clinical diagnosis of pancreatic adenocarcinoma.

Adenocarcinoma↗
PubMed1991

Detection of hepatitis C virus infection by enzyme-linked immunosorbent assay system using core protein expressed in Escherichia coli.

Enzyme-linked immunosorbent assay of the core protein of hepatitis C virus (HCV) expressed in E. coli led to detection of the antibody against this virus in patients with chronic hepatitis. Some of the negative results obtained using a different viral protein became positive with this E. coli-expressed viral protein, and were also positive for the viral RNA. Thus, use of the core protein of HCV facilitates accurate detection of HCV infection.

Base Sequence↗
PubMed1991

Stimulation of neutrophil adherence to vascular endothelial cells by histamine and thrombin and its inhibition by PAF antagonists and dexamethasone.

1. In order to clarify the roles of platelet-activating factor (PAF) in histamine- and thrombin-induced neutrophil adhesion to vascular endothelial cells, the effects of several PAF antagonists were examined. The effects of the glucocorticoid dexamethasone were also examined in order to gain further insight into the anti-inflammatory actions of glucocorticoids. 2. In culture, histamine and thrombin stimulated the adherence of rat peritoneal neutrophils to human endothelial cells from the umbilical vein. They did not stimulate neutrophil adherence in the absence of endothelial cells, suggesting that the target cells for the histamine- and thrombin-induced adherence of neutrophils were endothelial cells, not neutrophils. 3. Several PAF antagonists, such as CV-3988, L-652,731 and Y-24,180 inhibited the histamine- and thrombin-induced neutrophil adherence in a concentration-dependent manner. Indomethacin failed to inhibit it. 4. Dexamethasone, a steroidal anti-inflammatory drug, did not inhibit the histamine- and thrombin-induced adherence of neutrophils to endothelial cells when the drug was present only during the 20 min incubation period for the adherence assay. When the endothelial cells were preincubated for 3 h with dexamethasone, the adherence of neutrophils to endothelial cells induced by histamine or thrombin was not inhibited. 5. When the neutrophils were preincubated for 3 h with dexamethasone, the histamine- and thrombin-induced adherence of neutrophils to endothelial cells was inhibited. 6. Our studies indicate that: (a) adherence of neutrophils to endothelial cells induced by histamine and thrombin is mediated by PAF production since PAF antagonists inhibited the adherence of neutrophils; and (b) neutrophils, not endothelial cells, are the target cells through which dexamethasone acts to inhibit adherence.

Animals↗
PubMed1991

A role of peripheral leukocytes in vascular permeability and edema formation in air pouch type allergic inflammation in rats.

Using an air pouch type allergic inflammation model in rats, a role of circulating leukocytes in allergic inflammation responses was investigated by comparing normal rats with peripheral leukocytopenia rats induced by cyclophosphamide treatment. In the leukocytopenia rats, vascular permeability, edema formation, leukocyte infiltration into the pouch fluid, neutrophil chemotactic activity in the pouch fluid occurred both at the early phase (4 h) and the late phase (8 h) after the antigen challenge were decreased. However, edema formation induced by intradermal injection of arachidonate metabolites, serotonin, or platelet activating factor was not suppressed at all in the leukocytopenia rats. A possible role of peripheral leukocytes in allergic and non-allergic inflammation is discussed.

Animals↗
PubMed1990

Inhibition by dexamethasone of histamine production in allergic inflammation in rats.

In an allergic inflammation model of air pouch type in rats, histamine level in the pouch fluid and histidine decarboxylase activity of pouch wall tissues in the postanaphylaxis phase were increased. Although treatment with dexamethasone failed to inhibit histamine release from mast cells in the anaphylaxis phase, histamine production in the postanaphylaxis phase was inhibited dose dependently. Histamine production-increasing activity in the pouch fluid collected 8 h after the Ag challenge, which was estimated by an activity to stimulate histamine production by bone marrow cells, was decreased by the administration of dexamethasone at the time of the Ag challenge. The addition of steroidal antiinflammatory drugs, dexamethasone, prednisolone, or hydrocortisone, into the incubation medium inhibited the pouch fluid-induced histamine production by bone marrow cells. Hydrocortisone mesylate antagonized the inhibitory effect of dexamethasone on histamine production by bone marrow cells. However, hydrocortisone mesylate failed to recover the decrease in histamine production-increasing activity of the pouch fluid collected from dexamethasone-treated rats. In addition, the dialyzed sample of pouch fluid obtained from dexamethasone-treated nonsensitized rats did not reduce the stimulated histamine production by the pouch fluid sample obtained from the sensitized rats. However, increase in histamine production of bone marrow cells stimulated by the pouch fluid was not inhibited by cyclosporin A that inhibited histamine production induced by Con A. This observation indicates that the pouch fluid has no effect to induce production of the histamine production-increasing factor by bone marrow cells. Consequently, it is suggested that dexamethasone inhibits not only the production of histamine production-increasing factor but also the response of histamine-producing cells to this factor.

Animals↗
PubMed1990

Analysis of ras gene mutations in biliary and pancreatic tumors by polymerase chain reaction and direct sequencing.

Ras gene is one of the oncogenes most commonly detected in human cancers and consists of three families (H-ras, K-ras, N-ras) that are converted to active oncogenes by point mutations occurring in codon 12, 13, or 61. The authors analyzed mutations of these codons in 12 extrahepatic bile duct carcinomas, nine gallbladder carcinomas, and 20 pancreatic tumors (18 pancreatic adenocarcinomas and two islet cell tumors) by a method to directly sequence nucleotides, using polymerase chain reaction and a direct sequencing method. Point mutations at K-ras codon 12 were found in all of 18 pancreatic adenocarcinomas and in one bile duct carcinoma, but there were no mutations in the remaining 11 bile duct carcinomas, in all of 9 gallbladder carcinomas, or in two islet cell tumors. A very high incidence of ras gene mutations may be used clinically for the diagnosis of debatable cases of pancreatic adenocarcinoma.

Adenoma, Islet Cell↗
PubMed1990

Analysis of ras gene mutations in human hepatic malignant tumors by polymerase chain reaction and direct sequencing.

The ras gene is one of the oncogenes most commonly detected in human cancers, and it consists of three families (H-ras, K-ras, N-ras). These genes are converted to active oncogenes by point mutations occurring in either codon 12, 13, or 61. We analyzed mutations of these codons in 23 primary hepatic malignant tumors (12 hepatocellular carcinomas, nine cholangiocarcinomas, and two hepatoblastomas) by a method to directly sequence nucleotides, using polymerase chain reaction and a direct sequencing method. Of 23 hepatic malignant tumors, point mutations at K-ras codon 12 or K-ras codon 61 were found in six of nine cholangiocarcinomas. In contrast, there were no point mutations in any of 12 hepatocellular carcinomas or two hepatoblastomas around codon 12, 13, or 61 of the ras genes. These observations suggest that ras gene mutations are not related to pathogenesis of hepatocellular carcinoma, but play an important role in pathogenesis of cholangiocarcinoma.

Adenoma, Bile Duct↗
PubMed1990

Extrahepatic replication of duck hepatitis B virus: more than expected.

Replication of duck hepatitis B virus in extrahepatic tissue such as pancreas, kidney and spleen has been well documented. To assess whether there is more widespread extrahepatic virus replication, we assayed brain, heart, lung, thymus, pancreas, kidney, spleen and intestine of 1- to 16-wk-old ducklings for the presence of duck hepatitis B virus DNA and mRNA by blotting and in situ methods. Replicative intermediates and single-stranded duck hepatitis B virus DNA and RNA transcripts were detected in the brain, lung, heart, intestine, kidney, pancreas and spleen. In situ hybridization showed evidence of viral replication in the lung epithelium, germinal center of spleen, acinar cell of pancreas and tubular epithelium of kidney. These data suggest that extrahepatic duck hepatitis B virus replication is more widespread than previously thought. It is yet to be determined whether widespread extrahepatic replication is unique to duck hepatitis B virus infection or is a common feature of other mammalian hepatitis B-like viruses.

Animals↗
PubMed1990

Open reading frames on plus strand genome of duck hepatitis B virus.

Hepadnaviruses have open reading frames of surface, core, polymerase and X protein on the minus strand of the genome. We analyzed a plus strand of duck hepatitis B virus (DHBV) for the presence of open reading frame with a computer program. We found one frame on the area that is complement to 3' end of polymerase gene and 5' end of precore gene. That open reading frame is conserved in three strains of DHBV, and the predicted protein is about 80 amino acids.

Amino Acid Sequence↗
PubMed1990

Heterogeneity and evolution rates of delta virus RNA sequences.

To investigate the geographical divergence of delta virus RNA sequences, 868 nucleotides (nt), including the delta antigen-coding region, were determined in isolates from two Japanese patients, M and S, by polymerase chain reaction and direct sequencing and compared with three previously reported nucleotide sequences. The sequence obtained for hepatitis delta virus RNA from patient M was approximately 92% identical to sequences previously obtained for two other strains of hepatitis delta virus, whereas the sequence of hepatitis delta virus RNA obtained from patient S was approximately 81% identical to the previously sequenced strains. This suggests that 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. To study the evolution rate of delta virus RNA, viral isolates obtained 3 and 4 years apart from each of two patients were also sequenced. It was estimated that the substitution rate of viral RNA was 0.57 x 10(-3) nt per site per year in patient M and 0.64 x 10(-3) nt per site per year in patient S for the delta antigen gene.

Amino Acid Sequence↗
PubMed1990

Possible role for platelet-activating factor in neutrophil infiltration in allergic inflammation in rats.

Allergic inflammation was induced by injecting an antigen solution into an air pouch made on the dorsum of immunized rats with the antigen azobenzene-arsonate-conjugated acetyl bovine serum albumin. In this model, leukocyte infiltration into the pouch fluid was prominent 4-8 h after the antigen challenge. Most of the infiltrated leukocytes were neutrophils. Administration of the platelet-activating factor (PAF) antagonists such as CV-3988 and L-652,731 into the air pouch 15 min before and at the time of the antigen challenge failed to suppress leukocyte infiltration at 8 h. However, when the PAF antagonist was injected into an air pouch 4 h after the antigen challenge, neutrophil infiltration at 8 h was suppressed in a dose-dependent manner. Combined treatment with the 5-lipoxygenase inhibitor AA861 and the PAF antagonist did not potentiate the effect of the PAF antagonist, suggesting that participation of leukotriene B4 in neutrophil infiltration in this model is negligible. Eosinophil infiltration was very weak at 8 h, and the PAF antagonist showed no significant effect. At 8 h, the PAF level in the serum of the immunized rats was significantly higher than that of the nonimmunized rats. Intravenous administration of the PAF antagonist 15 min before the antigen challenge suppressed leukocyte infiltration more effectively than local administration into the pouch. These results indicate that PAF plays a significant role in neutrophil infiltration in allergic inflammation.

Animals↗
PubMed1990

Detection of hepatitis C virus ribonucleic acid in the serum by amplification with polymerase chain reaction.

Hepatitis C virus (HCV) RNA was detected in the sera of patients with non-A, non-B chronic liver disease by polymerase chain reaction (PCR). RNA was extracted from the serum, reverse transcribed to cDNA, and amplified by PCR. With this method, 30 patients with non-A, non-B chronic liver disease and 10 healthy subjects were tested. HCV RNA was detected in 13 of 16 (81%) anti-HCV-positive patients and also in 7 of 14 (50%) anti-HCV-negative patients, but in none of 10 anti-HCV-negative healthy subjects. Specificity of this method was confirmed by direct sequencing of amplified cDNA segment. The nucleotide sequences (37 nucleotides) obtained from 15 patients showed only 68-78% homology compared with the prototype HCV nucleotide sequence. In addition, of 15 nucleotide sequences, there were 12 different types. But the translated amino acid sequences (12 amino acids) showed 83-100% homology compared with the prototype HCV amino acid sequence. These data suggest the majority of anti-HCV-positive patients are carriers of HCV. But to detect all the viremic patients, the anti-HCV antibody testing may be insufficient. Direct detection of HCV RNA may be useful in the study of virus replication and its association with various liver diseases.

Adolescent↗
PubMed1990

Chemotactic activity for neutrophils in allergic inflammation in rats.

The number of neutrophils, eosinophils, and mononuclear cells that had migrated into pouch fluid were measured after injecting an antigen (azobenzenearsonate-conjugated acetyl bovine serum albumin) solution into air pouches made on the dorsum of immunized rats. The number of neutrophils began to increase 4 hr after the antigen challenge, reaching a maximum at 16-24 hr. Increases in the number of eosinophils and mononuclear cells were quite poor. The pouch fluid supernatant fraction was fractionated to hydrophilic and lipophilic fractions with the aid of an octadecylsilyl silica cartridge, and the chemotactic activity in each fraction was measured by the modified Boyden chamber method. The chemotactic activity in the pouch fluid supernatant fraction was the highest at 2-4 hr and decreased with time after the antigen challenge. At 16 and 24 hr, chemotactic activity was decreased to a very low level although there was a large number of neutrophils in the pouch fluid. At 4 hr, the chemotactic activity in the lipophilic fraction was significantly higher than that in the hydrophilic fraction. However, at 8 hr, the chemotactic activity in the lipophilic fraction was changed to a significantly lower level than that in the hydrophilic fraction. The chemotactic activity in the lipophilic fraction had decreased to a very low level at 8 hr. Heat treatment of the pouch fluid supernatant fraction at 92 degrees C for 5 min both at 4 and 8 hr significantly increased the chemotactic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Long-term treatment for non-A, non-B chronic hepatitis--effects on hepatitis C virus (HCV)].

We have treated 16 patients with chronic non-A, non-B hepatitis with short term (7-13 weeks) and long term (1 year) interferon. Sustained effect (normalization) of treatment was noted in all by long term treatment, where 7 of 8 with short term treatment showed flare-ups of transaminase after the therapy. In addition, negative turn of anti-HCV antibody was noted in 2 of 5 patients with long term treatment, whereas such change was noted in none of 6 anti-HCV antibody positive patients treated with short term treatment. These data suggest that long term interferon therapy may change natural course of chronic non-A, non-B hepatitis caused by HCV.

Adult↗