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K Ohba

Publications and source records attributed to K Ohba.

At least 55 records · Page 3Linked to original sources
PubMed1998

African origin of GB virus C/hepatitis G virus.

Ninety-four GB virus C/hepatitis G virus (GBV-C/ HGV) RNA-positive serum samples were obtained from all over the world. We found that all 15 GBV-C/HGV isolates from the Pygmies and the Bantu in the Central African region had a 12-amino acid indel (i.e. insertion or deletion) in the non-structural protein (NS) 5A region. Phylogenetic analyses of the NS5A region, using GBV-A as an outgroup, showed that these 15 isolates had diverged from the common ancestor much earlier than the remaining isolates, indicating an African origin of GBV-C/HGV.

Africa↗
PubMed1998

Molecular characterization of the mouse mtprd gene, a homologue of human TPRD: unique gene expression suggesting its critical role in the pathophysiology of Down syndrome.

We and others recently isolated a human TPRD gene, possessing a motif of the tetratricopeptide repeat (TPR), from the Down syndrome-critical region (DCR) of chromosome 21q22.2. In this study, we isolated a mouse homologue of TPRD cDNA, mtprd, and examined its expression profile in mouse embryos. The gene was mapped to mouse chromosome 16C3.3-4, consistent with the location of DCR, and encodes 1,979 amino acid residues with 76% identity to TPRD. The mtprd protein has three units of the TPR motif with 91% homology to TPRD. The protein also has two regions homologous to several matrix proteins with 86 and 70% identities to those of TPRD. Several splicing variants of the 5' portion of the open reading frame of mtprd were identified by RT-PCR and sequencing of mRNAs. In situ hybridization showed that mtprd is ubiquitously expressed in mouse embryos but predominantly in the central nervous system, including the telencephalon, mesencephalon, and metencephalon. These results suggest that the TPRD gene is one of the genes responsible for not only the morphological anomalies but also the neurological abnormalities observed in Down syndrome. The presence of splicing variants indicates that the protein may also have several isoforms in mice.

Amino Acid Sequence↗
PubMed1998

Abscopal regression of hepatocellular carcinoma after radiotherapy for bone metastasis.

Spontaneous regression of hepatocellular carcinoma is a rare phenomenon. Abscopal regression of tumours resulting from the effect of irradiation of a tissue on a remote non-irradiated tissue is also rare. The case of a 76 year old Japanese man with hepatocellular carcinoma that regressed after radiotherapy for thoracic vertebral bone metastasis is described. Serum levels of tumour necrosis factor-alpha increased after radiotherapy. The findings suggests that such abscopal related regression may be associated with host immune response, involving cytokines such as tumour necrosis factor-alpha.

Aged↗
PubMed1998

The effect of acute cold exposure and norepinephrine on uncoupling protein gene expression in brown adipose tissue of monosodium glutamate-obese mice.

Abnormal regulation of mitochondrial uncoupling protein (UCP) gene expression was studied in brown adipose tissue (BAT) of monosodium glutamate (MSG)-induced obese mice. UCP mRNA levels in control mice increased markedly after acute cold exposure; however, MSG-obese mice showed an impaired response. In contrast, an injection of norepinephrine (NE) induced a comparable increase in UCP mRNA levels in control and MSG-obese mice. These results suggest that the impairment in the cold-induced increase in UCP mRNA is due to a deficient sympathetic input to BAT and/or to a diminished response of BAT to endogenous NE, which constitutes the mechanism of impaired thermoregulation in obese mice in a cold environment.

Adipose Tissue, Brown↗
PubMed1998

GB virus C/hepatitis G virus infection among Colombian native Indians.

To elucidate the prevalence of GB virus C/hepatitis G virus (GBV-C/HGV) infection in Colombian native Indians, serum GBV-C/HGV RNA was assayed in 163 native Indians and 67 members of the general population in Colombia. The native Indians (males:females = 40:123) and the members of the general population (males:females = 20:47) were tested by reverse transcription-semi-nested polymerase chain reaction. Of the 163 native Indians, 10 (6.1%) were positive for GBV-C/HGV RNA, compared with one (1.5%) of 67 from the general population. All Indians were negative for hepatitis B surface antigen and antibody to hepatitis C virus. Of 10 Indians with GBV-C/HGV RNA, the genotype of nine subjects was the Asian type. These data indicated that 1) the prevalence of GBV-C/HGV RNA in Colombian native Indians is high, and 2) GBV-C/HGV was probably brought from Asia and inherited for generations in some native Indian groups.

Adolescent↗
PubMed1998

Heterogeneity in E2 region of GBV-C/hepatitis G virus and hepatitis C virus.

GB virus C/hepatitis G virus (GBV-C/HGV) is related distantly to hepatitis C virus (HCV). HCV has a hypervariable region (HVR), and exists as quasispecies in vivo. Although GBV-C/HGV also has replaceable amino acids in the presumed antigenic region, the existence and fluctuation of population of heterogeneous virus have not been evaluated. In this study, the heterogeneity of GBV-C/HGV and HCV was investigated by the single-strand conformation polymorphism (SSCP) analysis in six concomitantly infected patients. Two patients were observed for 4 years without any treatment, and four were treated with interferon-alpha (IFN). By SSCP analysis, amplicons of GBV-C/HGV RNA were separated into 1-5 bands on gels for each patient. The amplicons had different nucleotide but the same amino acid sequences in the presumed antigenic region. The amplicons of HCV RNA, separated into 1-4 bands, had different nucleotide and amino acid sequences in the HVR. In the two patients without treatment, the predominant strain of GBV-C/HGV was unchanged for the 4 years. In the four patients administered IFN, some strains of GBV-C/HGV disappeared after IFN therapy, whereas other strains persisted. The mean genetic distance among GBV-C/HGV strains represented by SSCP analysis was significantly lower than that of HCV (P < 0.05). The data indicate that: 1) GBV-C/HGV can be devoid of antigenic drift unlike HCV; 2) GBV-C/HGV has no HVR as seen in HCV in the presumed antigenic region; and 3) the sensitivity to IFN differs among GBV-C/HGV strains in the same hosts, as with HCV.

Adult↗
PubMed1997

Expression of multiple alpha1-antitrypsin-like genes in hibernating species of the squirrel family.

In the chipmunk, a mammalian hibernator, a 140 kDa protein complex found in the blood, drastically decreases in concentration during hibernation. This complex contains four species of proteins, HP-20, -25, -27 and -55. In the present study, cDNA clones coding for the chipmunk HP-55 were isolated from a liver cDNA library. Sequence analysis revealed that HP-55 is produced as a precursor protein of 413 amino acids (aa), that it has a signal peptide of 24 aa, and that it contains four potential N-glycosylation sites. The deduced aa sequence shows 63% identity with that of rat alpha1-antitrypsin (alpha1-AT); however, the sequence corresponding to the reactive center P1-P1' residues was found to be Met-Leu, whereas it is Met-Ser in the rat alpha1-AT. During screening of the chipmunk liver cDNA library, four other related classes of cDNA clones were obtained, each also coding for an alpha1-AT-like protein. In spite of more than 86% overall aa sequence identity among the five chipmunk alpha1-AT-like proteins, they are highly divergent in the putative reactive center region; the putative P1-P1' sequences are Met-Leu (HP-55 or CM55-ML), Met-Met (CM55-MM), Met-Ser (CM55-MS), Ser-Ile (CM55-SI) and Ser-Thr (CM55-ST). Each of the alpha1-AT-like protein mRNAs was expressed in chipmunk liver, and the HP-55 mRNA level was greatly reduced during hibernation. Genomic Southern blot analysis and screening of a liver cDNA library from another hibernating squirrel species, the ground squirrel, also revealed expression of multiple members of the alpha1-AT gene family, whereas analysis of a cDNA library from a non-hibernating species, the tree squirrel, found only a single alpha1-AT gene.

Amino Acid Sequence↗
PubMed1997

Nitric oxide mediates down regulation of lipoprotein lipase activity induced by tumor necrosis factor-alpha in brown adipocytes.

We previously reported that tumor necrosis factor-alpha (TNF-alpha)/cachectin suppresses lipoprotein lipase activity and its gene expression in brown adipocytes differentiated in culture. Recent evidence suggests that the effect of TNF-alpha over various cells is related to the enhanced production of nitric oxide (NO). The present study examined whether the suppressive effect of TNF-alpha on lipoprotein lipase activity is mediated by production of NO in the brown adipocytes. A reverse transcription-polymerase chain reaction (RT-PCR) assay revealed that TNF-alpha caused a concentration- and time-dependent expression of inducible NO synthase in brown adipocytes. Increasing concentrations of TNF-alpha (0.5-50 ng/ml) for 24 h resulted in a concentration-dependent decrease in lipoprotein lipase activity with reciprocal increase in nitrite production in the medium. The suppressive effect of TNF-alpha on lipoprotein lipase activity was significantly prevented by NO synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine, but not by D-NAME, an inactive isomer. Furthermore, 8-bromoguanosine 3',5'-cyclic monophosphate, cell permeant cGMP, suppressed lipoprotein lipase activity and 1 H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one, a selective inhibitor for soluble guanylate cyclase, restored the TNF-alpha-suppressed lipoprotein lipase activity. These results suggest that TNF-alpha stimulates brown adipocytes to express inducible NO synthase, followed by production of NO, which in turn mediates the suppressive effect of TNF-alpha on lipoprotein lipase activity. The effect of NO is mediated, at least partly, through production of cGMP.

Adipocytes↗
PubMed1997

Three different GB virus C/hepatitis G virus genotypes. Phylogenetic analysis and a genotyping assay based on restriction fragment length polymorphism.

The 5'-untranslated region (5'-UTR) sequences of 33 GB virus C/hepatitis G virus (GBV-C/HGV) obtained from different geographic areas were determined through reverse-transcription polymerase chain reaction and dideoxy chain termination sequencing, the alignment of sequences, the estimation of the number of nucleotide substitution per site, and construction of phylogenetic trees. The 5'-UTR of GBV-HGV was found to be heterogeneous, with 70.9-99.5% homology. Three distinct phylogenetic branches were observed consistently in all phylogenetic trees. GBV-C is the prototype for one, HGV for another, and there is a new branch which consisted of GBV-C/HGV isolates from Asia. Genotype-specific restriction sites for the restriction enzymes, ScrFI and BsmFI, were identified, and a simple restriction fragment polymorphism analysis was developed for genotyping. These data provide evidence that GBV-C/HGV consists of three different genotypes. Our simple genotyping assay will also provide a tool for epidemiological studies of GBV-C/HGV infection.

Base Sequence↗
PubMed1997

Constrained evolution with respect to gene overlap of hepatitis B virus.

With the aim of elucidating the evolution of a hepadnavirus family, we constructed molecular phylogenetic trees for 27 strains of hepatitis B virus (HBV) using both the unweighted pair-grouping and neighbor-joining methods. All five gene regions, P, C, S, X, and preS, were used to construct the phylogenetic trees. Using the phylogenetic trees obtained, we classified these strains into five major groups in which the strains were closely related to each other. Our classification reinforced our previous view that genetic classification is not always compatible with conventional classification determined by serological subtypes. Moreover, constraints on the evolutionary process of HBV were analyzed for amino-acid-altering (nonsynonymous) and silent (synonymous) substitutions, because two-thirds of the open reading frame (ORF), P, contains alternating overlapping ORFs. In our unique analysis of this interesting gene structure of HBV, the most frequent synonymous substitutions were observed in the nonoverlapped parts of the P and C genes. On the other hand, the number of synonymous substitutions per nucleotide site for the S gene was quite low and appeared a strongly constrained evolution. Because the P gene overlaps the S gene in a different frame, the low rate of synonymous substitution for the S gene can be explained by the evolutionary constraints which are imposed on the overlapping gene region. In other words, synonymous substitutions in the S gene can cause amino acid changes in its overlapping region in a different frame. Thus, the evolution of HBV is constrained evolutionarily by the overlapping genes. We propose calling this mode of viral evolution "constrained evolution." The evolution of HBV represents a typical constrained evolution.

Amino Acid Sequence↗
PubMed1997

Role of nitric oxide, prostaglandins and tyrosine kinase in vascular endothelial growth factor-induced increase in vascular permeability in mouse skin.

We investigated role of nitric oxide (NO), prostaglandins (PG) and tyrosine kinase in vascular endothelial growth factor (VEGF)-induced increase in vascular permeability in mouse skin. Subcutaneous injection of VEGF (0.5-2.0 ng/site) induced dose- and time-dependent increase in vascular permeability at the injection site determined by a leakage of Pontamine sky blue. VEGF (1 ng/site)-induced dye leakage was partially inhibited by N(G)-nitro-L-arginine methyl ester (an inhibitor for both constitutive and inducible NO synthase) (5 and 10 mg/kg, i.v.) and by aminoguanidine (a selective inducible NO synthase inhibitor) (5-20 mg/kg, i.v.), but not by an inactive enantiomer, N(G)-nitro-D-arginine methyl ester (10 mg/kg, i.v.). Pretreatment with an intraperitoneal injection of indomethacin (a nonselective cyclooxygenase inhibitor) (5 mg/kg) or N-(2-cyclohexyloxy-4-nitrophenyl) methanesulphonamide (a cyclooxygenase-2 selective inhibitor) (1-100 microg/kg) almost completely inhibited the effect of VEGF (1 ng/site). Coadministration of PGE2 (3 and 30 nmol/site) with VEGF did not restore the inhibitory effect of indomethacin on VEGF (1 ng/site)-induced increase in vascular permeability. Lavendustin A (a selective tyrosine kinase inhibitor) (10 and 50 microg/kg, s.c.) dose-relatedly inhibited the VEGF (1 ng/site)-induced increase in dye leakage, whereas its negative control, lavendustin B (10 microg/kg, s.c.) had no effect. Another tyrosine kinase inhibitor, genistein (2.5 mg/kg, s.c.) also inhibited the response. Cycloheximide (a protein biosynthesis inhibitor) (35 mg/kg, s.c.) suppressed the response of VEGF (1 ng/site). Histologically, no cellular infiltration was observed in the area of VEGF injection. These results suggest that increased vascular permeability induced by VEGF is mediated by local production of NO and arachidonic acid metabolites other than PGE2, which are most probably produced by inducible NO synthase and cyclooxygenase-2, respectively. Protein tyrosine kinase-mediated phosphorylation and synthesis of any new proteins are likely to be required in this effect of VEGF in mouse skin.

Animals↗
PubMed1997

High prevalence of GB virus C/hepatitis G virus infection among the Jewish population in Uzbekistan.

Although a new virus, GB virus C/hepatitis G virus (GBV-C/HGV), has been isolated from patients with hepatitis by two different research groups, its prevalence in the world and pathogenesis are still unknown. In this study, 92 samples from the Jewish population of Uzbekistan were investigated for the prevalence of GBV-C/HGV. GBV-C/HGV RNA was detected by reverse transcription polymerase chain reaction (RT-PCR) using specific primers derived from the 5'-untranslated region (5'-UTR). Sequences were analyzed by a molecular evolutionary method. Of 92 samples, GBV-C/HGV RNA was detected in ten (10.9%), HCV RNA was present in two (2.2%), and HBsAg in eight (8.7%). HTLV-I and HIV infection was not detected. Single GBV-C/HGV infection was detected in eight (80%), and co-infection with HBV or HCV was detected in only two of the GBV-C/HGV infections. Alanine aminotransferase (ALT) levels were elevated in three (3.3%), but none with single GBV-C/HGV infection had an elevated ALT level. Nine people (90%) with GBV-C/HGV infection were distributed under the mean age of the population (P < 0.05). Molecular evolutionary analysis showed all GBV-C/HGV strains in this study were related to the HGV derived from the US. These results indicate that (1) GBV-C/HGV infection is highly prevalent among the Jewish population in Uzbekistan; (2) single GBV-C/HGV infections without persistent hepatitis are common; and (3) GBV-C/HGV infection is present among the younger generation.

Adolescent↗
PubMed1997

Genotype of GB virus C/hepatitis G virus by molecular evolutionary analysis.

GB virus C/hepatitis G virus is a newly described virus. Classification of GB virus C/hepatitis G virus into genotypes has not been established. We analyzed nucleotide sequences within the 5' untranslated region of GB virus C/hepatitis G virus isolates and segregated these isolates into genotypes. Twenty serum samples with GB virus C/hepatitis G virus RNA from Australia, Cameroon, the Congo, Japan, Mongolia, and Bangladesh were studied. Reverse transcription and polymerase chain reaction were used to obtain GB virus C/hepatitis G virus RNA. After nucleotide sequences from the 5' untranslated region were determined, 68 nucleotide sequences, including 48 previously reported sequences, were analyzed by molecular evolutionary methods. The phylogenetic tree of the 5' untranslated region showed that all strains could be divided into three major genotypes, GB type (type 1), HG type (type 2), and Asian type (type 3). Bootstrap analysis indicated that the strains could be divided into three major genotypes but could not be further subdivided. Moreover, frequency histograms of pairwise distances between nucleotide sequences demonstrated only one peak. These result indicated that GB virus C/hepatitis G virus can be classified into three major genotypes, GB type (type 1), HG type (type 2), and Asian type (type 3), and should not be divided into minor subtypes.

Base Sequence↗
PubMed1997

GB virus C (GBV-C)/hepatitis G virus (HGV) infection among intravenous drug users in Japan.

A sero-epidemiologic survey of 74 IVDUs and 86 age-matched controls was performed to investigate the prevalence, clinical significance, and genetic distribution of GB virus C (GBV-C)/hepatitis G virus (HGV) infection among intravenous drug users (IVDUs) in Japan. GBV-C/HGV RNA was detected by reverse transcriptase-hemi-nested polymerase chain reaction (RT-hemi-nested PCR) for the 5'-untranslated region (5'-UTR) in 43.2% (32/79) of the IVDUs compared with 1.2% (1/86) of the controls (P < 0.001). The duration of drug use did not correlate with the prevalence of GBV-C/HGV. Thirteen subjects positive for GBV-C/HGV RNA without HCV RNA had normal serum aminotransferase concentrations. Phylogenetic tree showed that the 32 GBV-C/HGV-positive isolates from IVDUs were classified within a new GBV-C/HGV group, which has been identified mainly in Asian subjects (type 3). The present study illustrated, (1) the high incidence of GBV-C/HGV infection among Japanese IVDUs, (2) GBV-C/HGV alone may not be an important pathogenic factor for hepatic injury, and (3) type 3 GBV-C/HGV was the most prevalent among IVDUs in Japan.

Adolescent↗
PubMed1997

Study of needlestick accidents and hepatitis C virus infection in healthcare workers by molecular evolutionary analysis.

In the five-year period between 1989 and 1993, 87 needlestick accidents occurred among healthcare workers at our hospital. Thirty-seven (43%) of these needlestick accidents involved blood contaminated with hepatitis C virus (HCV), and two of them (5.4%) led to the occurrence of hepatitis C infection. Case 1 was a 43-year-old nurse who was accidentally injured by a needle contaminated with blood from a patient who had cirrhosis and hepatocellular carcinoma due to hepatitis C. Acute hepatitis C occurred after five weeks and HCV RNA was positive after eight weeks. Case 2 was a 33-year-old nurse who was injured by a needle contaminated with blood from a patient who had chronic hepatitis C. Liver function was normal at 11 days after the accident. However, hepatitis C was diagnosed 21 months later after she had successfully given birth to her baby. The nucleotide sequence of the HCV E2/NS1 region was determined in the two patients and the needlestick victims, and phylogenetic trees were constructed by molecular evolutionary analysis. On the basis of these trees, transmission of HCV could be confirmed in both cases. This method of analysis may be useful for confirming the transmission of HCV even long after the event.

Adult↗
PubMed1997

Iodothyronine deiodinases in a mammalian hibernator, the chipmunk (Tamias asiaticus).

We examined the activities of iodothyronine deiodinase, a key enzyme for thyroid hormone metabolism, in selected tissues of the chipmunk (Tamias asiaticus), a mammalian hibernator, of both sexes in the summer season. Reverse T3 5'-deiodinase (5'-D) activity was the highest in the liver followed by the kidney; T4 5'-D activity was the highest in brown adipose tissue (BAT) and T3 5'-deiodinase (5-D) activity was the highest in the testes followed by the brain. Distributions of three types of deiodinase activities in liver kidney BAT, and brain were comparable to other mammals reported, except that the type III deiodinase was unique in testes. The 5'-D activity of liver and kidney of chipmunks was 52% and 24%, respectively, of male rats and the 5-D activity of brain and testes of chipmunks was 227% and 567%, respectively of male rats. In addition, the cold exposure increased BAT 5'-D activity in chipmunks as reported in the ground squirrels. Our results indicated that tissue distribution of deiodinases and response to cold exposure in BAT in hibernators are similar to nonhibernators. However, there was a quantitative difference of rT3 5'-D and T3 5-D activities in some tissues between chipmunks and rats, indicating different local thyroid hormone metabolisms in hibernators and nonhibernators.

Adipose Tissue, Brown↗
PubMed1997

Sequence variation and phylogenetic analysis of the 5' terminus of hepatitis G virus.

We determined the nucleotide and deduced amino acid sequence of the 5' terminus of the hepatitis G virus (HGV) genome from isolates of varied geographical origins. Our analysis showed that the putative 5' non-coding region (NCR) contains several blocks of highly conserved sequences that may be useful for the development of a reverse transcriptase-polymerase chain reaction (RT-PCR) assay for detection of HGV RNA. Overall, the degree of conservation within the 669-nucleotide (nt) 5'terminal sequence was found to range from 99.5% to 86% sequence identity. We also showed that the HGV NCR from some isolates contained conserved insertions or deletions that altered the translational reading frames at the 5'-end of the genome, resulting in different sizes of predicted polyproteins encoded by genomes of individual isolates. Specifically, the insertions/deletions affected the size of the peptide preceding the putative first envelope (E1) protein. Phylogenetic analysis of the nucleotide sequences suggested that the isolates examined can be classified into distinct groups that may be useful for studying the molecular evolution of HGV and possible relationships between isolate sequence characteristics and infection patterns.

Adenovirus E1 Proteins↗