Biomedical subjects

T Mikami

Publications and source records attributed to T Mikami.

At least 199 records · Page 11Linked to original sources

PubMed1998

Molecular cloning of cDNAs and expression of mRNAs encoding alpha and beta subunits of soluble guanylyl cyclase from medaka fish Oryzias latipes.

Two cDNA clones encoding alpha and beta subunits of soluble guanylyl cyclase (GC) were isolated from medaka fish (Oryzias latipes) cDNA libraries and designated as OlGCS-alpha1 and OlGCS-beta1, respectively. The ORF of OlGCS-alpha1 encodes 678 amino acids and that of OlGCS-beta1 encodes 614 amino acids. Both subunits have a putative catalytic domain conserved with membrane GC and adenylyl cyclases. The amino acid sequences of OlGCS-beta1 and mammalian soluble GC subunits are highly conserved throughout the entire protein, suggesting that amino acid sequences outside the catalytic domain are important for the functioning of the beta subunit. On the contrary, amino acid sequences of alpha subunits outside the catalytic domain are fairly divergent between fish and mammals. Reverse transcription/PCR (RT/PCR) analysis showed that OlGCS-alpha1 and OlGCS-beta1 transcripts were abundant in the brain, eye, spleen and testis. RT/PCR analysis demonstrated that both transcripts were present in unfertilized eggs, were reduced immediately after fertilization, then increased again. In addition, our results suggest that expression patterns of OlGCS-alpha1 and OlGCS-beta1 genes are different from each other both during development and in adults.

Amino Acid Sequence↗

PubMed1998

Difference in dominant negative activities between mutant thyroid hormone receptors alpha1 and beta1 with an identical truncation in the extreme carboxyl-terminal tau4 domain.

Although different expression patterns of thyroid hormone receptor (TR) alpha1 and beta1 have been reported, no essential distinction has been established in their functions. Unlike the TR beta gene, a mutation in the TR alpha1 gene has never been found in patients with resistance to thyroid hormone (RTH). Previously we found a mutant TR beta with an 11-carboxyl (C)-terminal amino acid truncation (betaF451X) in a girl with severe RTH. BetaF451X is a natural mutant with disruption of the transactivation domain, tau4, and it had very strong dominant negative activities. Based on the fact that the 46 amino acid sequence in the extreme C-terminal region is identical in TR alpha1 and TR beta, except for a C-terminal three amino acid extension of TR alpha1, we constructed a mutant TR alpha1 (alphaF397X) with the identical C-terminal truncation to betaF451X, to study functional differences between TR alpha1 and beta1. Both betaF451X and alphaF397X had negligible T3 binding and transcriptional activities even with 1 microM T3. The dominant negative activities of the mutant TRs were remarkable and T3 response element (TRE)-dependent. Co-expression of betaF451X decreased the CAT activity of either wild-type TR alpha1 or beta1 at 100 nM T3 by approximately 90% on the TRE-pal2 and 70% on DR4. AlphaF397X inhibited the transcriptional activities of both wild-type TR alpha1 and beta1 by approximately 50% on TRE-pal2 and by 60% on DR4. The dominant negative potency of betaF451X was significantly stronger than that of alphaF397X on the TRE-pal2, -DR4 and chicken lysozyme silencer F2, but similar on TRE-myosin heavy chain alpha and malic enzyme. No partiality for the TR subtypes was found in the dominant negative effects of betaF451X and alphaF397X. Co-expression with RXR enhanced the dominant negative effects of alphaF397X, but not of betaF451X. The results indicate that there are different dominant negative properties between alphaF397X and betaF451X, which are TRE-dependent, despite their identical C-terminal truncation. Deletion in the tau4 domain might affect the receptor structures of TR alpha1 and beta1 differently.

Animals↗

PubMed1998

In vivo functions of the auxiliary genes and regulatory elements of feline immunodeficiency virus.

Feline immunodeficiency virus (FIV) is a widespread lentivirus of domestic cats that causes an acquired immunodeficiency syndrome (AIDS)-like disease similar to human AIDS caused by human immunodeficiency virus. FIV has a complex genome structure including structural, enzymatic and auxiliary genes and regulatory elements. In this article, we review the in vivo roles of some of these FIV auxiliary genes and regulatory elements, especially focusing on the dUTPase, vif, and ORF-A genes and AP-1 binding site in the enhancer region of the long terminal repeat, by comparison with those of other non-primate lentiviruses. These genes and elements are considered to be important for viral replication, immunological response and pathogenesis in cats.

Animals↗

PubMed1998

Comparison between in vivo mutagenicity and carcinogenicity in multiple organs by benzo[a]pyrene in the lacZ transgenic mouse (Muta Mouse).

To evaluate whether the in vivo mutagenicity test system using the lacZ transgenic mice (Muta Mouse) may be applied to carcinogenesis studies, both the in vivo mutagenicity and carcinogenicity of benzo[a]pyrene (BP) was tested in mice under the same administration conditions. The eleven organs of the mice on the 14th day after the final oral administration of BP at a dose of 125 mg kg(-1) day(-1) or corn oil for 5 consecutive days were tested for in vivo mutation by the positive-selection method. The data show that the colon had the highest lacZ mutant frequency (37-fold increase over the spontaneous frequency), followed by the ileum > forestomach > bone marrow, spleen > glandular stomach > liver, lung > kidney and heart. No significant mutations were found in the brain. These results may suggest that, in general, the organs with rapidly proliferative tissues have a marked increase in vivo mutant frequencies under the conditions of this experimental design. The forestomach and lymphatic organs including the spleen (malignant lymphoma) were the main target organs for BP carcinogenesis by 5 daily oral doses of 75 and 125 mg kg(-1) day(-1). These results suggest that the mutation results from the transgenic assay with BP reflect the carcinogenicity of BP in the mouse. They also indicate, however, that the magnitude of the in vivo lacZ mutant frequencies induced by BP in different organs did not fully correlate with the target organs for carcinogenicity.

Animals↗

PubMed1998

Characterization of anti-feline CD8 monoclonal antibodies.

We generated three monoclonal antibodies (mAbs) (2D7, 10C7 and 12A3) reactive to the alpha-chain of feline CD8 (fCD8) molecule. Further we showed that reference anti-fCD8 mAbs, FT2, 3.357 and vpg9 recognize the beta-chain, alpha-chain and alphabeta-complex epitope, respectively. Flow cytometric analysis using these mAbs suggested that fCD8alpha(+)beta(-) cells were present in lymphocytes of spleen, but not significantly in those of thymus, lymph nodes and peripheral blood of normal kittens.

Animals↗

PubMed1998

Structure and expression of a novel member, FGF-16, on the fibroblast growth factor family.

We have isolated cDNA encoding a novel member (207 amino acids) of the FGF family from the rat heart by homology-based polymerase chain reaction. As this protein is the 16th documented member of the FGF family, we tentatively term it FGF-16. Among FGF family members, FGF-16 is most similar (73% amino acid identity) to FGF-9. We have also determined the structure of human FGF-16 with high amino acid sequence identity (98.6%) to rat FGF-16. Although the predicted FGF-16 amino acid sequence lacks a typical signal sequence, recombinant rat FGF-16 was efficiently secreted by Sf9 insect cells infected with recombinant baculovirus containing the cDNA. FGF-16 mRNA was predominantly expressed in the rat heart among the adult major tissues examined. The expression profile of FGF-16 mRNA was quite different from those of other members of the FGF family. In rat embryos, FGF-16 mRNA was predominantly expressed in the brown adipose tissue. However, the expression decreased greatly after birth. These results indicate that FGF-16 in embryos might play a role in development of the brown adipose tissue.

Adipose Tissue, Brown↗

PubMed1998

Molecular analysis of the nucleocapsid protein of recent isolates of canine distemper virus in Japan.

We analyzed the molecular properties of the nucleocapsid protein (NP) of canine distemper viruses (CDV), isolated between 1992 and 1995 in Japan. Four CDV field isolates (Yanaka, Ueno, Hamamatsu, and Adachi strains) obtained were antigenically identical. Sequence analysis of entire region of the NP gene of a field isolate, the Yanaka strain, revealed that the NP gene contained 1683 nucleotides and was 93.2% homologous with a laboratory strain, the Onderstepoort strain. The deduced amino acid sequence contained 523 amino acids and was 95.2 and 99% homologous with those of the Onderstepoort and a virulent strain, A75/17 strain, respectively. Since most of the diversities in amino acid sequence occurred in two domains, at the N'- and the C'- termini, we further sequenced 3'-terminal regions of the remaining three field isolates. Based on the sequences, the new CDV isolates had one cluster that distinguished them from the laboratory strain.

Amino Acid Sequence↗

PubMed1998

p53 and p21(WAF1) expression in lymphocytic thyroiditis and thyroid tumors.

To clarify the roles of increased apoptosis and cell proliferation in chronic autoimmune lymphocytic thyroiditis and thyroid tumorigenesis, expression of p53 and p21(WAF1) proteins was immunohistochemically investigated in a series of 158 cases. Positive epithelial cells were quantified to give numbers per unit square and to score for distribution. They were found scattered in nontumorous thyroid tissue, their numbers increasing with the severity of thyroiditis and the correlation between expression of the two proteins, regardless of the presence or absence of thyroid neoplasms. Simultaneous expression of both proteins was occasionally found in the same cells by analysis of serial histologic sections. In thyroid tumors, increased expression was found to be diffuse, focal, or scattered for the distribution of p53- or p21(WAF1)-immunopositive cells in accordance with tumor cell dedifferentiation, showing significant correlation between expression of the two proteins. Correlated with these findings, enhanced apoptosis along with decreased Bcl-2 expression and increased Ki-67 labeling in lymphocytic thyroiditis and thyroid tumors was also confirmed in the same series, using in situ DNA nick-end labeling and immunohistochemical methods. Increased expression of p53 and/or p21(WAF1) proteins was thus suggestive of possible DNA damage and increased apoptosis in autoimmune thyroiditis. In addition, a significant correlation between protein overexpression and dedifferentiation of thyroid tumor cells was apparent.

Antibodies↗

PubMed1998

Toxicity profile of benzo[a]pyrene in the male LacZ transgenic mouse (MutaMouse) following oral administration for 5 consecutive days.

The toxicity profile of benzo[a]pyrene (BP) was examined in the MutaMouse. The transgenic mouse integrated with lambda gt10 lacZ vectors is used worldwide as an experimental animal in in vivo mutagenesis testing systems. There are few toxicity studies including carcinogenicity in the MutaMouse, and so far only a few carcinogenicity studies of BP accompanied with hematological and plasma biochemical examinations have been conducted even in generic mice. Accordingly, male mice were orally administered BP at doses of 75 and 125 mg/kg/day for 5 consecutive days, and complete autopsy was conducted together with pathological, hematological, and plasma biochemical examinations and measurement of organ weights 41 weeks after the last treatment. Squamous cell papilloma and hyperplasia in the forestomach were induced at incidences of 25 and 50%, respectively and were induced 26 weeks after the final treatment without any significant alterations in t he hematological and plasma biochemical parameters in mice of the 125 mg/kg/day BP-treated satellite group. Fourty-one weeks after the final treatments, 75 and 125 mg/kg/day BP induced squamous cell carcinoma, papilloma, and hyperplasia in the forestomach at incidences of 18 and 18%, 36 and 45%, and 91 and 91%, respectively, and anemia possibly due to continuous hemorrhage from tumors in the forestomach. BP (125 mg/kg/day) also produced malignant lymphoma with an incidence of 18%, accompanied by a marked increase in leukocyte count and decrease in erythrocyte count and by a remarkable decrease in body weights 26 and 39 weeks after the last treatment. Moreover, administration of 75 and 125 mg/kg/day BP induced bronchiolar-alveolar hyperplasia in the lung at incidences of 18 and 9%, respectively. Slight increases were also observed in the weight of the liver and in the levels of urea nitrogen, creatinine, and potassium ion in the plasma biochemical examinations, although no significant pathological alterations were found in the liver and kidney. This study provides new information about BP toxicity including carcinogenicity in the MutaMouse developed for in vivo mutational analysis.

Administration, Oral↗

PubMed1998

Small interspersed sequences that serve as recombination sites at the cox2 and atp6 loci in the mitochondrial genome of soybean are widely distributed in higher plants.

Mitochondrial DNA (mtDNA) fragments that contain cox2 and atp6 were cloned from a wild soybean (Glycine soja, accession 'B09002') and from a cultivated soybean (G. max, 'Harosoy'). Comparison of these DNAs revealed that two sets of repeated sequences, namely, 299 bp and 23 bp, were present in the 5' regions of cox2 and atp6. The 299-bp and 23-bp repeats were present close to each other on the 5' flanking region and the 5' part of the coding region of cox2 in both 'Harosoy' and 'B09002', as well as on the 5' flanking region of atp6 in 'Harosoy', while these two repeats were separated by a 706-bp nucleotide sequence that contained a truncated sequence of nad3 at the 5' flanking region of atp6 in 'B09002'. The mtDNA configurations upstream from atp6 and cox2 found in 'Harosoy' appeared to have been generated from configurations of cox2 and atp6 found in 'B09002' via recombination across the 299-bp or 23-bp repeated sequences, or vice versa, in the mitochondrial genome of the hypothetical progenitor of these plants. The 299-bp sequence was found to be interspersed in the mitochondrial genome. Eight loci were identified that include mtDNA configurations that are inter-convertible with each other via recombination across this sequence in 'B09002'. Various loci on the mitochondrial genomes of higher plants that harbor segments of the 299-bp repeats in Glycine were identified.

Base Sequence↗

PubMed1998

Evolutionary changes in the structures of the cox2 and atp6 loci in the mitochondrial genome of soybean involving recombination across small interspersed sequences.

Mitochondrial DNA (mtDNA) fragments that contained cox2 or atp6 loci were cloned from three accessions of wild soybean (Glycine soja) in order to understand the evolutionary changes of mitochondrial genomes in the genus Glycine subgenus Soja. Cox2 was cloned as a single configuration, while atp6 was cloned as either one or two configurations from each accession. Structural variations were detected in the 5' upstream region of cox2 and in both the 5' upstream and 3' downstream regions of atp6. These variations appeared to be the results of recombination events. A comparison of the mtDNA fragments previously cloned from a cultivated soybean (G. max) and a wild soybean revealed various sites of recombination, as well as various combinations of the 5' and 3' regions, at the cox2 and atp6 loci. Some of the cloned fragments were found to contain a set of repeated sequences, namely 299-bp and 23-bp repeats in the 5' region of cox2 or atp6, which were interspersed in the mitochondrial genome in the subgenus Soja. Recombination events involving the 299-bp or 23-bp repeated sequences were shown to account for the generation of structural variations in the 5' regions of these loci.

Base Sequence↗

PubMed1998

Telomerase activity significantly correlates with cell differentiation, proliferation and lymph node metastasis in colorectal carcinomas.

Telomerase activity was examined by the telomeric repeat amplification protocol assay, in a total of 37 colorectal adenocarcinomas, including stages A, B and C according to the Astler and Collier classification, and correlated with clinicopathological features. Of 17 stage C lesions, 13 were positive (76.5%; P<0.01), demonstrating a significant correlation with lymph node metastasis. In contrast, only 6 of 20 stage A and B carcinomas were positive (30.0%), this being significantly lower (P < 0.05). Moderately or poorly differentiated subtypes were more predominant in the telomerase-positive than in the telomerase-negative groups (P< 0.05) with greater elevation of mitotic and Ki-67 labeling indices (P < 0.0001). No significant relation was found between telomerase activity and p53 protein accumulation or Bcl-2 protein expression. The good correlation with tumor staging, lymph node metastasis, differentiation, and mitotic and Ki-67 labeling indices suggests that this parameter might have potential application in estimation of prognosis.

Adenocarcinoma↗

PubMed1998

Tam3 in Antirrhinum majus is exceptional transposon in resistant to alteration by abortive gap repair: identification of nested transposons.

Most transposon families consist of heterogeneous copies with varying sizes. In contrast, the Tam3 copies in Antirrhinum majus are known to have exceptionally conserved structures of uniform size. Gap repair has been reported to be involved in the structural alteration of copies from several transposon families. In this study, we have asked whether or not gap repair has affected Tam3 copies. Five Tam3 copies carrying aberrant sequences were selected from 40 independent Tam3 clones and their sequences were analyzed. Two of the five copies contain insertions in the Tam3 sequence. These two insertions, designated Tam356 and Tam661, are typical transposon-like sequences, which have terminal inverted repeats and cause target site duplication. These nested transposons were obviously associated with transpositional events, and did not originate from the gap-repair process. The remaining three copies had lost large parts of the Tam3 sequence. We could not find any relationship between the deletions of Tam3 sequence in the three copies and gap repair. PCR analysis of a Tam3 excision site in the nivea(recurrence:Tam3) mutant also showed that most of the repair events after the Tam3 excision involved end-joining. In addition to the results obtained here, among the other clones isolated, we could not find any of the internally deleted copies that comprise a major part of other transposon families. All of these data suggest that some feature of the Tam3 structure suppresses the structural alterations that are otherwise generated during the gap repair process.

Alleles↗

PubMed1998

Hemobilia caused by a giant benign hemangioma of the liver: report of a case.

We report herein the extremely unusual case of a 39-year-old woman in whom a giant cavernous hemangioma caused hemobilia. Cavernous hemangioma is the most common benign neoplasm of the liver and rarely causes any clinical symptoms or signs, while hemobilia usually occurs secondary to accidental operative or iatrogenic trauma, vascular disease, inflammatory disorders, gallstones, or tumors of the liver. Although invasive or malignant hepatic tumors often result in a communication between the biliary tract and the blood vessels, only one case of hemobilia caused by a benign cavernous hemangioma has ever been reported, but with no details about the patient. Our patient presented to a local hospital with severe melena as the initial main symptom, where ligation of the right hepatic artery was performed. This failed to relieve her symptoms, and she was subsequently referred to our department where a right hepatectomy was performed. Histopathological examination revealed no malignancy combined with the tumor; however, the hemangioma was exposed to the bile duct in segment VIII, which was presumably the cause of the hemobilia. This patient remains in good health almost 6 years after her operation. To the best of our knowledge this is the first case report of hemobilia caused by a cavernous hemangioma, and is accompanied by a detailed analysis.

Adult↗

PubMed1998

Characterization of an integrase mutant of feline immunodeficiency virus.

The role of the integrase region of feline immunodeficiency virus (FIV) in viral replication was examined using an integrase mutant clone of FIV which carries a frameshift mutation in the region. Upon transfection, although the integrase mutant was able to release virus-like particles into the supernatant from the transfected cells, the virions produced by the mutant contained unprocessed gag precursor protein and undetectable levels of reverse transcriptase activity. Furthermore, the mutant virions were unable to direct the synthesis of viral DNA after infection in target cells. To understand this phenotype of the integrase mutant in more detail, we constructed a gag-pol expression plasmid from an FIV molecular clone and assayed roles of the integrase region on virus particle formation following transfection. When an inframe deletion was introduced into the protease region of the expression plasmid, the mutant was able to efficiently release gag- and gag-pol precursor proteins into the supernatant from the transfected cells. An expression plasmid with mutations in both the protease and integrase regions, however, failed to release the gag-pol precursor protein from the cells. These results suggested an essential role for the integrase region for efficient incorporation of the gag-pol precursor into the virions.

Amino Acid Sequence↗

PubMed1998

In vitro recombination of feline herpesvirus type 1.

We investigated the possibility of in vitro recombination of three different strains of feline herpesvirus type 1 (FHV-1), a virulent strain (C7805), a vaccine strain (F2), and a candidate vaccine strain with a deletion in the thymidine kinase gene (C7301dlTK). The results showed that recombination within different genotypes of FHV-1 strains could occur at a relatively high frequency ranging from 10.1% to 21.5% in vitro. These results indicate the generation of multiple mutant viruses by in vitro recombination experiments. The possibility for generating a virulent virus or novel type of FHV-1 by recombination in vivo is discussed.

Animals↗

PubMed1998

Cross virus neutralizing antibodies against feline immunodeficiency virus genotypes A, B, C, D and E.

Feline immunodeficiency virus (FIV) is classified into five genotypes, A, B, C, D and E, based on the phylogenetic analysis of the env V3-V5 region. However, whether there is correlation between phylogenetic and antigenic diversities remains unknown. In this study, we examined the cross virus neutralization of FIV genotypes A through E by sera from cats infected with a single genotype. The results indicated some relationships between phylogenetic genotype and neutralization serotype, and that cross-clade virus neutralization is possible. For example, serum from a cat infected with genotype E virus neutralized all five FIV genotypes. Our results suggest that the FIV subtyping according to the sequence diversity is partially reflected by antigenic diversity and serum neutralization.

Animals↗

PubMed1998

Construction of a recombinant feline herpesvirus type 1 expressing Gag precursor protein of feline immunodeficiency virus.

We constructed a deletion mutant of feline herpesvirus type 1 (FHV-1) and a recombinant FHV-1. The deletion mutant is the virus with a region (367 bp) deleted from the start codon of thymidine kinase (TK) gene to the SmaI site within the TK gene, and the other is a recombinant FHV-1 expressing Gag protein of feline immunodeficiency virus (FIV), in which a cDNA encoding the Gag protein of FIV was inserted at the TK deletion site of the former deletion mutant. These viruses were designated as C7301ddlTK and C7301ddlTK-gag, respectively. Growth kinetics of these viruses in Crandell feline kidney cells was similar to that of the parent C7301 strain. By immunoblot analysis, C7301 ddlTK-gag was confirmed to express the FIV Gag precursor protein in the cells.

Alphaherpesvirinae↗