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T Koda

Publications and source records attributed to T Koda.

At least 73 records · Page 4Linked to original sources
PubMed1993

Influence of carbonate on sintering of apatites.

Sintering of carbonate apatite, prepared at 100 degrees C and pH 9.0 for 3 days, was studied by thermal analysis, x-ray diffraction, and infrared spectroscopy. The sintering temperature, at which the linear thermal shrinkage of isostatically compacted specimens increased sharply, decreased in proportion to the amount of carbonate initially present in the apatite. For example, specimens with over 8 wt% carbonate could be sintered at a temperature (650 degrees C) which was nearly 400 degrees C lower than that needed for sintering a specimen with no carbonate. Amounts of carbonate lost at the end of sintering, estimated chemically and by infra-red spectroscopy, were approximately equal to sample weight losses estimated thermogravimetrically.

Carbonates↗
PubMed1992

Cell cycle dependent gene expressions and activities of protein phosphatases PP1 and PP2A in mouse NIH3T3 fibroblasts.

We determined the mRNA levels and the activities in nuclear and non-nuclear fractions of protein phosphatase type 1 (PP1) and type 2A (PP2A) through the cell cycle in synchronized mouse NIH3T3 fibroblasts. The mRNA level for PP1 alpha was gradually elevated in late G1 phase, began to decrease in M phase, and reached the control level with entering into the next G1 phase. The mRNA level for PP2A was rapidly increased in early G1 phase, kept at the high level, and decreased after S phase. In nuclear fractions of cells, spontaneous activities of both PP1 and PP2A were gradually increased until M phase and rapidly decreased with entering the next G1 phase, while in non-nuclear fraction such dramatic alterations were not observed. Potential activities of PP1 in both fractions revealed by Co(2+)-trypsin treatment showed an oscillaion patterns similar to those of the spontaneous activities. These results strongly suggest that cell cycle dependent gene expressions and activities of PP1 and PP2A play roles in DNA synthesis and mitosis during the cell cycle.

Animals↗
PubMed1992

Dtrk, a Drosophila gene related to the trk family of neurotrophin receptors, encodes a novel class of neural cell adhesion molecule.

We report the identification and molecular characterization of Dtrk, a Drosophila gene encoding a receptor tyrosine kinase highly related to the trk family of mammalian neurotrophin receptors. The product of the Dtrk gene, gp160Dtrk, is dynamically expressed during Drosophila embryogenesis in several areas of the developing nervous system, including neurons and fasciculating axons. gp160Dtrk has structural homology with neural cell adhesion molecules of the immunoglobulin superfamily and promotes cell adhesion in a homophilic, Ca2+ independent manner. More importantly, this adhesion process specifically activates its tyrosine protein kinase activity. These findings suggest that gp160Dtrk represents a new class of neural cell adhesion molecules that may regulate neuronal recognition and axonal guidance during the development of the Drosophila nervous system.

Amino Acid Sequence↗
PubMed1992

Prevalence of four blood-borne viruses (HBV, HCV, HTLV-I, HIV-1) among haemodialysis patients in Japan.

To investigate the prevalence of four blood-borne viruses among a cohort of haemodialysis (HD) patients in Japan, hepatitis B surface antigen (HBsAg), antibody to hepatitis C virus (anti-HCV), antibody to human T-cell lymphotropic virus type-I (anti-HTLV-I), and antibody to human immunodeficiency virus type-1 (anti-HIV-1) were studied in the sera from 393 consecutive HD patients and in the sera from 786 age- and sex-matched healthy individuals from the general population (controls). The prevalence of anti-HCV and anti-HTLV-I was significantly higher in HD patients than in the controls (17.8% vs. 1.1% and 3.8% vs. 0.5%), but the prevalence of HBsAg showed no significant difference. No patients or controls were positive for anti-HIV-1. In HD patients with no history of blood transfusion, anti-HCV was detected in only one (2.1%) of 48 patients undergoing HD treatment for less than 3 years, and there was no significant difference between the prevalence of anti-HCV in these patients and in the controls. In HD patients who had received blood transfusion, anti-HTLV-I was detected in only one (1.0%) of 103 patients undergoing HD treatment for less than 3 years, and there was no significant difference between the prevalence of anti-HTLV-I in these patients and in the controls. These findings suggest that in recent years, the risk of HCV transmission by routes other than blood transfusion in HD patients is low, and that of HTLV-I transmission by transfusion is very low or non-existent.

Adolescent↗
PubMed1992

Hepatitis C virus RNA and hepatitis C virus antibody in the serum of patients with abnormal liver function.

In order to elucidate the relation between hepatitis C virus (HCV) RNA and antibody to HCV (anti-HCV) in serum, we examined samples of serum collected from 228 HBsAg-negative patients, with abnormal alanine aminotransferase (ALT) values, for HCV-RNA by nested polymerase chain reaction (PCR) assay and for anti-HCV using C100 protein as the antigen. HCV-RNA was detected in 99 (92.5%) of 107 anti-HCV-IgG-positive samples, regardless of ELISA optical density cut-off value (ELISA ratio), and in 34 (28.1%) of 121 anti-HCV-IgG-negative samples in which the frequency of the presence of HCV-RNA became higher in proportion to the ELISA ratio. Among 42 discordant cases (34 anti-HCV-IgG-negative, RNA-positive cases and eight anti-HCV-IgG-positive, RNA-negative cases), 10 were positive for anti-HCV-IgM (8/34 and 2/8, respectively) irrespective of clinical status. These findings suggest that in patients with abnormal ALT values, even if they are anti-HCV-IgG negative, HCV infection cannot be excluded. Furthermore, PCR assay for detecting HCV-RNA may be more suitable for identifying patients with infectious virus than is detection of anti-HCV-IgG. Detection of anti-HCV-IgM may also be useful.

Alanine Transaminase↗
PubMed1992

[Detection of hepatitis delta virus (HDV) markers in HBV carriers].

To investigate the prevalence and clinical features of hepatitis delta virus (HDV) superinfection in hepatitis B virus (HBV) carriers, antibody to hepatitis delta antigen (anti-HD) was determined in the sera of 328 HBV carriers in Japan. 1) Of the 328 HBV carriers, six (1.8%) were seropositive for anti-HD by enzyme linked immunosorbent assay. IgM-antibody to hepatitis delta antigen was detected in 2/6 patients with a high anti-HDV titer. None of the patients was positive for hepatitis dealt antigen. 2) HBV carriers with chronic liver disease had a greater frequency of seropositivity of anti-HD than asymptomatic HBV carriers. These data indicate that HDV superinfection may be an etiologic agent of chronic liver disease in HBV carriers.

Aged↗
PubMed1992

[Studies on hepatitis C virus infection in haemodialysis patients].

To examine the prevalence of hepatitis C virus (HCV) in haemodialysis patients without blood transfusion in Hiroshima Prefecture, antibody to HCV (anti-HCV) was studied by the Ortho ELISA Kit in sera from 393 consecutive haemodialysis patients and in sera from 510 age and sex matched healthy members of the general population (control). An additional confirmatory test was done by a recombinant immunoblot assay. 1) Anti-HCV was detected in 70 of the 393 dialysis patients and 3 of the 510 healthy controls (17.8% vs 0.6%, p less than 0.01). Prevalence of anti-HCV in haemodialysis patients sera was increased by the volume of blood transfusion, and even in dialysis patients who had no blood transfusion, the frequency of anti-HCV positivity (9.2%) was greater than the healthy controls (p less than 0.01). Thus, the major route of HCV transmission in haemodialysis patients without blood transfusion may be via the haemodialysis treatment. 2) The prevalence of anti-HCV increased significantly with the ALT level and abnormal ALT activity of the anti-HCV positive group were significantly greater than that of the negative group. Thus, it is suggested that HCV infection may be an etiologic factor of liver dysfunction in haemodialysis patients.

Adult↗
PubMed1991

Mechanism of activation of the vav protooncogene.

vav is a human locus that appears to be specifically expressed in cells of hematopoietic origin regardless of their differentiation lineage. This gene was first identified as a result of its malignant activation during the course of gene transfer assays (Katzav, S., Martin-Zanca, D., and Barbacid, M. EMBO J., 8: 2283-2290, 1989). In this study, we report the isolation of complementary DNA clones containing the entire coding sequence of the mouse vav protooncogene. Antisera raised against a peptide corresponding to a predicted hydrophilic domain have allowed us to identify the product of the vav gene as a 95,000 Da protein. Analysis of the deduced amino acid sequence of p95vav revealed an amino-terminal leucine-rich region not present in the activated vav oncogene. This region consists of an amphipathic helix-loop-helix followed by a leucine zipper, a structure reminiscent of the carboxy-terminal region of myc proteins and the steroid binding domain of nuclear receptors. In vitro mutagenicity studies have indicated that removal of the amphipathic helix-loop-helix is sufficient to activate the transforming potential of human and mouse vav protooncogenes. vav proteins also possess a cysteine-rich domain whose sequence predicts the formation of two putative metal binding-like domains, Cys-X2-Cys-X13-Cys-X2-Cys and His-X2-Cys-X6-Cys-X2-His. Replacement of some of these cysteine and histidine residues completely abolished the transforming activity of vav genes. Further examination of the alignment of cysteine residues in this region revealed an alternative structure, Cys-X2-Cys-X13-Cys-X2-Cys-X7-Cys-X6-Cys, which is reminiscent of the phorbol ester binding domain of protein kinase C. A similar domain has been recently identified in a second enzyme, diacylglycerol kinase. These structural similarities, along with its expression pattern, suggest that the vav protooncogene codes for a new type of signal-transducing molecule that may play an important role in controlling hematopoiesis.

Amino Acid Sequence↗
PubMed1990

Leachability of denture-base acrylic resins in artificial saliva.

We studied the influence of salivary acidity on leachability of denture-base acrylic resins with etiological interest in denture stomatitis because denture surfaces are frequently exposed to acidic conditions in the oral cavities. Auto-, heat-, and microwave-polymerized resins were immersed in artificial saliva with pH ranging from 4.0 to 6.8 at 37 degrees C, and leachables were pursued quantitatively with time. Methyl methacrylate, methacrylic acid, and benzoic acid leached from all resins. Their concentrations in the saliva were markedly high for auto-polymerized resins, while leachability of heat- and microwave-polymerized resins was so low that quantitative analysis of leachables was impossible. Lower pH showed higher concentrations of methyl methacrylate, although no apparent association was confirmed between salivary acidity and its own leachability. The concentrations of methacrylic acid increased remarkably with an increase in pH, which was probably due to hydrolysis of methyl methacrylate. These results suggest that chemotoxic actions of auto-polymerized resins are potentially ascribable to methyl methacrylate under more acidic conditions and to methacrylic acid under less acidic conditions.

Acrylic Resins↗