Biomedical subjects

H Kasai

Publications and source records attributed to H Kasai.

At least 109 records · Page 6Linked to original sources

PubMed1998

Nucleotide excision repair proteins may be involved in the fixation of glyoxal-induced mutagenesis in Escherichia coli.

To investigate the influence of nucleotide excision repair (NER) on glyoxal-induced mutations, we treated wild-type and NER-deficient (uvrC) Escherichia coli strains with glyoxal, and analyzed mutations in the chromosomal lacI gene. In both strains, the cell death and the mutation frequency increased according to the dose of glyoxal added to the culture medium, and cell death was induced to a similar level in both strains. Interestingly, the frequency of glyoxal-induced mutations in the wild-type strain was higher than that in the uvrC strain. Particularly, the frequency of base-pair substitutions was 4.7-fold higher in the wild-type strain. In the wild-type strain, G:C-->T:A transversions were predominant, followed by G:C-->A:T and A:T-->T:A mutations. In the uvrC strain, G:C-->A:T transitions were predominant, followed by G:C-->T:A transversions. All the base-pair substitutions except for G:C-->A:T transitions were >4-fold higher in the wild-type strain than in the uvrC strain. These results suggest that NER may be involved in the fixation of glyoxal-induced base-pair substitutions.

Bacterial Proteins↗

PubMed1998

Genotoxicity of ribo- and deoxyribonucleosides of 8-hydroxyguanine, 5-hydroxycytosine, and 2-hydroxyadenine: induction of SCE in human lymphocytes and mutagenicity in Salmonella typhimurium TA 100.

The induction of SCE by ribo- and deoxyribonucleosides of 8-hydroxyguanine, 5-hydroxycytosine, and 2-hydroxyadenine was tested using human peripheral blood lymphocytes. All of these compounds caused an increase in SCE frequency. The potency of SCE induction was as follows: 5-OH-C, 5-OH-dC > 8.OH-G > 8-OH-dG > 2-OH-A, 2-OH-dA. These results suggest that the oxidized nucleosides are incorporated into DNA with different efficiencies (or are repaired with different efficiencies) and exhibit genotoxicity in human blood cells. Ribo- and deoxyribo-derivatives of 5-OH-Cyt and 2-OH-Ade also showed mutagenic activity in Salmonella typhimurium TA 100.

Cytosine↗

PubMed1998

Genetic polymorphisms and alternative splicing of the hOGG1 gene, that is involved in the repair of 8-hydroxyguanine in damaged DNA.

The hOGG1 gene encodes a DNA glycosylase that excises 8-hydroxyguanine (oh8Gua) from damaged DNA. Structural analyses of the hOGG1 gene and its transcripts were performed in normal and lung cancer cells. Due to a genetic polymorphism at codon 326, hOGG1-Ser326 and hOGG1-Cys326 proteins were produced in human cells. Activity in the repair of oh8Gua was greater in hOGG1-Ser326 protein than in hOGG1-Cys326 protein in the complementation assay of an E. coli mutant defective in the repair of oh8Gua. Two isoforms of hOGG1 transcripts produced by alternative splicing encoded distinct hOGG1 proteins: one with and the other without a putative nuclear localization signal. Loss of heterozygosity at the hOGG1 locus was frequently (15/ 23, 62.2%) detected in lung cancer cells, and a cell line NCI-H526 had a mutation leading to the formation of the transcripts encoding a truncated hOGG1 protein. However, the oh8Gua levels in nuclear DNA were similar among lung cancer cells and leukocytes irrespective of the type of hOGG1 proteins expressed. These results suggest that the oh8Gua levels are maintained at a steady level, even though multiple hOGG1 proteins are produced due to genetic polymorphisms, mutations and alternative splicing of the hOGG1 gene.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1998

Anticancer efficacy in vivo and in vitro, synergy with 5-fluorouracil, and safety of recombinant methioninase.

The elevated exogenous-methionine dependency of tumors for growth has been observed in all major cancer cell types. We have previously cloned a methioninase (rMETase) from Pseudomonas putida to deplete methionine. Growth inhibition followed by apoptotic cell death was induced by treatment of tumor cells with rMETase in vitro. A single i.p. injection of 300 units of rMETase can lower the serum methionine level in the mice from 70 microM to less than 1 microM within 2 h and maintain this depleted level for 8 h. Repeated dosing of rMETase of tumor-bearing mice could be administered without acute immune-hypersensitivity. rMETase treatment demonstrated growth inhibitory activity against human tumors in nude mice, including those which were multiple drug-resistant. No body weight loss or hematotoxicity, except a slight anemia, was found throughout the therapy. The combined treatment of the Lewis lung carcinoma with a fixed rMETase dose and increasing doses of 5-fluorouracil (5-FU) resulted in a dose-dependent enhanced antitumor efficacy for survival as well as tumor growth inhibition. Thus, methionine depletion by rMETase potentiates the antitumor efficacy of 5-FU. The data presented in this report thus indicate that rMETase is active alone, is synergistic in combination with 5-FU, and has negligible toxicity suggesting a novel clinical approach for effective cancer therapy.

Animals↗

PubMed1998

The (6-4) photoproduct of thymine-thymine induces targeted substitution mutations in mammalian cells.

Two major ultraviolet-induced photolesions of TpT, a (6-4) photoproduct [T(6-4)T] and a cis-syn cyclobutane TT dimer (T=T), were incorporated into a predetermined site of one of the leading and lagging template strands of a double-stranded vector, and the modified DNAs were transfected into simian COS-7 cells. The DNAs replicated in the cells were recovered and were transfected again into Escherichia coli. The DNA replication efficiencies of plasmids containing T(6-4)T and T=T in the template strand for lagging strand synthesis were 93 and 79%, respectively, as compared with the unmodified DNA. Similar inhibitory effects were observed in the cases of the photoproducts in the template strand for leading strand synthesis (71 and 58%, respectively). These results indicated that T(6-4)T blocked DNA replication more weakly than T=T during leading and lagging strand syntheses in mammalian cells. The mutation frequencies of T(6-4)T were 2.3 and 4.7% in the leading and lagging template strands, respectively. The T=T lesion was less mutagenic and induced mutations with 0.2-0.7% frequencies. The T(6-4)T lesion primarily elicited 3'-T-->C substitutions, and T=T induced various types of mutations. These results indicate that T(6-4)T is more mutagenic than T=T during leading and lagging strand syntheses in simian cells. Moreover, this is the first evidence that shows T(6-4)T mainly elicits targeted substitutions at its 3'-T site in mammalian cells.

Animals↗

PubMed1998

Induction of chromosomal gene mutations in Escherichia coli by direct incorporation of oxidatively damaged nucleotides. New evaluation method for mutagenesis by damaged DNA precursors in vivo.

We have developed a new strategy for the evaluation of the mutagenicity of a damaged DNA precursor (deoxyribonucleoside 5'-triphosphate) in Escherichia coli. 8-Hydroxydeoxyguanosine triphosphate (8-OH-dGTP) and 2-hydroxydeoxyadenosine triphosphate (2-OH-dATP) were chosen for this study because they appear to be formed abundantly by reactive oxygen species in cells. We introduced the oxidatively damaged nucleotides into competent E. coli and selected mutants of the chromosomal lacI gene. Both damaged nucleotides induced lacI gene mutations in a dose-dependent manner, whereas unmodified dATP and dGTP did not appear to elicit the mutations. The addition of 50 nmol of 8-OH-dGTP and 2-OH-dATP into an E. coli suspension induced 12- and 9-fold more substitution mutations than the spontaneous event, respectively. The 8-OH-dGTP induced A.T --> C.G transversions, and the 2-OH-dATP elicited G.C --> T.A transversions. These results indicate that the two oxidatively damaged nucleotides are mutagenic in vivo and suggest that 8-OH-dGTP and 2-OH-dATP were incorporated opposite A and G residues, respectively, in the E. coli DNA. This new method enables the evaluation and comparison of the mutagenic potentials of damaged DNA precursors in vivo.

Bacterial Proteins↗

PubMed1998

Effects of forced and spontaneous exercise on 8-hydroxydeoxyguanosine levels in rat organs.

We investigated the effects of forced and spontaneous exercise on the levels of 8-hydroxydeoxyguanosine (8-OH-dG), a form of oxidative DNA damage, in rat organs (heart, lung, and liver). Rats were randomly assigned to one of three groups: forced exercise group (F), spontaneous exercise group (S), and sedentary control group (C). The mean levels of 8-OH-dG in the F group were 1.9-, 2.1-, and 2.4-fold higher in the heart, lung, and liver DNA, respectively, than in the S group. In the S group of rats, the distance run was not significantly correlated to the 8-OH-dG levels in the heart, lung, and liver DNA. These results demonstrate that the intensity of exercise is an important determinant in DNA damage, and suggest that spontaneous physical exercise is beneficial for maintaining a low level of oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1998

Genomic structure and chromosomal localization of the mouse Ogg1 gene that is involved in the repair of 8-hydroxyguanine in DNA damage.

8-Hydroxyguanine (7,8-dihydro-8-oxoguanine: oh8Gua) is a damaged form of guanine induced by oxygen-free radicals and causes GC to TA transversions. Previously we isolated the hOGG1 gene, a human homolog of the yeast OGG1 gene, which encodes a DNA glycosylase and lyase to excise oh8Gua in DNA. In this study, we isolated a mouse homolog (Ogg1) of the OGG1 gene, characterized oh8Gua-specific DNA glycosylase/AP lyase activities of its product, and determined chromosomal localization and exon-intron organization of this gene. A predicted protein possessed five domains homologous to human and yeast OGG1 proteins. Helix-hairpin-helix and C2H2 zinc finger-like DNA-binding motifs found in human and yeast OGG1 proteins were also retained in mouse Ogg1 protein. The properties of a GST fusion protein were identical to human and yeast OGG1 proteins in glycosylase/lyase activities, their substrate specificities, and suppressive activities against the spontaneous mutagenesis of an Escherichia coli mutM mutY double mutant. The mouse Ogg1 gene was mapped to Chromosome (Chr) 6, and consisted of 7 exons approximately 6 kb long. Two DNA-binding motifs were encoded in exons 4 through 5. These data will facilitate the investigation of the OGG1 gene to elucidate the relationship between oxidative DNA damage and carcinogenesis.

Amino Acid Sequence↗

PubMed1998

Haemagglutinin-esterase protein (HE) of murine corona virus: DVIM (diarrhea virus of infant mice).

The acetylesterase (AE) activity of DVIM (diarrhea virus of infant mice) was assigned to the haemagglutinin-esterase (HE) protein. The substrate specificity was examined using the natural substrate bovine submaxillary mucin (BSM) and/or synthetic substrates p-nitrophenylacetate (p-NiA) and alpha-naphthylacetate (alpha-NA) and compared with several strains of MHV and influenza viruses. The AE of DVIM hydrolyzed the O-acetylester bond of BSM, and the two synthetic substrates p-NiA and alpha-NA in vitro. MHV-S reacted efficiently with both p-NiA and alpha-NA but less with BSM. Influenza virus (C/Miyagi/77) reacted with BSM efficiently, however reacted with p-NiA weakly, but not with alpha-NA at all. Thus, the AE-reactivity of DVIM was distinctly different from that of MHV-S and influenza C virus, suggesting that the AE of HE may have a modified function. Isolation of HE by the treatment with non ionic detergent NP40, resulted in globules approximately 5 nm in diameter. DVIM-binding proteins were demonstrated in the plasma membrane of mouse intestinal brush-border cells and hepatocytes. The same protein was recognized by MHV-S and MHV-4. The cell membranes obtained from these target tissues were substrates for the AE of DVIM. The biological importance of the HE protein for DVIM is discussed.

Acetylesterase↗

PubMed1998

Characterization of haemagglutinin-esterase protein (HE) of murine corona virus DVIM by monoclonal antibodies.

We analyzed the characteristics of seven monoclonal antibodies (mAbs) raised against purified HE (hemagglutinin-esterase) glycoprotein of the murine coronavirus DVIM (diarrhea virus of infant mice). Immunocrossreaction of these mAbs with JHM and/or MHV-S suggest that antigenic epitopes of HE of DVIM are similar to those of JHM and/or MHV-S. Four mAbs (1b4, 3a28, 4c19, 10b7), designated as group A mAbs, strongly inhibited both HA and AE activities. On the other hand, three mAbs (5a3, 6a6, 13a4), referred to as group B, had a comparatively weak HA inhibition activity. These results indicate that the antigenic epitopes of this glycoprotein can be classified into at least two groups and that the functional sites of HA and AE activities are similar but not identical. Neutralizing activity was shown in group A mAbs exclusively, suggesting that the ratio of HA and/or AE activities may play important roles in the cell fusion activity of DVIM-infected cells.

Animals↗

PubMed1998

Reduction of 8-hydroxyguanine in human leukocyte DNA by physical exercise.

We investigated the effect of physical exercise on the level of 8-hydroxyguanine (8-OH-Gua), a form of oxidative DNA damage, and its repair activity in human peripheral leukocytes. Whole blood samples were collected by venipuncture from 21 healthy male volunteers (10 trained athletes and 13 untrained men), aged 19-50 years, both before and after physical exercise. Trained athletes showed a lower level of 8-OH-Gua (2.4+/-0.5/10(6) Gua, p = 0.0032) before exercise when compared to that of untrained men (6.2+/-3.5). The mean levels of 8-OH-Gua of untrained subjects decreased significantly (p = 0.0057) from 6.2+/-3.5/10(6) Gua (mean+/-SD/10(6) Gua) to 3.3+/-1.4/10(6) Gua after physical exercise. On the other hand, the mean levels of repair activity of untrained subjects significantly increased after exercise (p = 0.0093) from 0.037+/-0.024 (mean DNA cleavage ratio+/-SD) to 0.056+/-0.036. In the trained athletes 8-OH-Gua level and its repair activity were not changed before and after the exercise. We also observed inter-individual differences in 8-OH-Gua levels and its repair activities. These results suggest that physical exercise causes both rapid and long-range reduction of oxidative DNA damage in human leukocytes, with individually different efficiencies.

Adult↗

PubMed1998

DNA modifications by the mutagen glyoxal: adduction to G and C, deamination of C and GC and GA cross-linking.

The mutagen glyoxal was reacted with DNA or deoxynucleosides under physiological conditions (pH 7.4, 37 degrees C) in vitro and the products were analyzed by HPLC coupled with a photodiode array UV detector. The efficient formation of a cyclic glyoxal-dG adduct (dG+) was observed in DNA, as well as with dG. The monomeric dG + was gradually decomposed to dG at pH 7.4 and 37 degrees C (t1/2 14.8 h). However, the dG+ formed in single- and double-stranded DNA was rather stable under physiological conditions and the half-lives were 19 and 40 times longer respectively than that of the monomer (t1/2 285 and 595 h respectively). By reaction of glyoxal with deoxycytidine (dC), the deamination products deoxyuridine and 5-hydroxyacetyl-dC (dC+) were formed. Under the same conditions, 5-methyl-dC was deaminated to dT at a higher rate. Deoxyuridine was also formed in DNA by glyoxal treatment. When glyoxal was reacted with various combinations of deoxynucleosides for a prolonged period, dG-glyoxal-dC (GgC), dG-glyoxal-dA (GgA), dG-glyoxal-dG (GgG) and dC-glyoxal-dC (CgC) cross-links were detected, although structures were not assigned unequivocally. Among these, the former two, the GC and GA cross-links, were detected in glyoxal-treated DNA. The yields of these products in DNA were in the following order; dG+ > dU > GgA > GgC > dC+. These DNA modifications may be relevant to glyoxal-induced mutations at GC pairs.

Cytosine↗

PubMed1998

Infrequent mutations of the hOGG1 gene, that is involved in the excision of 8-hydroxyguanine in damaged DNA, in human gastric cancer.

DNA glycosylase, encoded by the hOGG1 gene, repairs 8-hydroxyguanine (oh8Gua), which is an oxidatively damaged mutagenic base. To clarify whether the DNA repair activity of hOGG1 protein is involved in gastric carcinogenesis, we examined 9 gastric cancer cell lines and 35 primary gastric cancers for mutations and genetic polymorphisms of the hOGG1 gene by polymerase chain reaction-single strand conformation polymorphism analysis. A G-to-A transition was detected in a gastric cancer cell line, MKN1. This nucleotide change caused the conversion of the amino acid from Arg to His at codon 154, which is located in a domain highly conserved among human, mouse, and yeast OGG1 proteins. No mutation was detected in primary gastric cancers. We compared the distribution of the polymorphic alleles associated with enzymatic activity (hOGG1-Ser326 vs. hOGG1-Cys326) between 35 gastric cancer patients and 42 healthy individuals. Although the frequency of the Cys326 allele, associated with low enzymatic activity, in gastric cancer patients was a little higher than that in healthy individuals, the difference did not reach statistical significance. These results suggest that low hOGG1 activity due to mutations and genetic polymorphisms is involved in the development of only a small subset of gastric cancers.

DNA Damage↗

PubMed1998

Lung cancer patients have increased 8-hydroxydeoxyguanosine levels in peripheral lung tissue DNA.

The 8-hydroxydeoxyguanosine (8-OH-dG) levels in the peripheral parts of human lung tissues were compared between lung cancer patients (n=70) and non-cancer patient controls (n=15). An increased level of 8-OH-dG was observed in the lung cancer group, in both the adenocarcinoma and non-adenocarcinoma (mainly squamous cell carcinoma) groups, as compared to the non-cancer control group. This result suggests that reactive oxygen species are partly involved in the induction of lung carcinomas (both adenocarcinoma and non-adenocarcinoma).

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1998

Shortening of the intraventricular conduction time in premature ventricular beats during ventricular extrastimulation: possible role of dimensional shortening of the conducting distance during ventricular systole.

INTRODUCTION: Conduction time (CT) is given by the formula: conducting distance divided by conduction velocity. Based on this formula, we hypothesized that CT shortening (i.e., supernormal conduction) may result from dimensional shortening of the distance of impulse propagation, which naturally occurs during ventricular systole. METHODS AND RESULTS: To test the above, two separate groups of patients were studied, group A (14 patients) for electrophysiologic study and group B (12 patients) for echocardiographic study. In group A patients, CT from the stimulus artifact to the basal lateral wall of the left ventricle (LV) (S-LV interval) was measured using right ventricular (RV) apical extrastimulus testing. S-LV interval shortening in premature RV beats was demonstrated in all 14 patients. The maximum shortening was 20 +/- 9 msec (range 10 to 40), and the maximum % shortening was 16% +/- 6% (7% to 27%). In group B patients with implanted pacemakers, the major (long) and minor (short) axis dimensions of the LV were measured with echocardiography. The major axis dimension was used as an approximate measure of the linear length from the RV apex to the basal lateral wall of LV. The maximum % shortening of the major axis dimensions was 15% +/- 4%, 16% +/- 2%, and 11% +/- 4% during VVI pacing, respectively, at paced cycle lengths of 1,000 (11 patients), 800 (5 patients), and 600 msec (12 patients). The maximum % shortening of the S-LV intervals was comparable in magnitude with that of the major axis dimensions: 20% versus 15% +/- 4%, 15% +/- 7% versus 16% +/- 2% and 16% +/- 6% versus 11% +/- 4%, respectively, at paced cycle lengths of 1,000, 800, and 600 msec. There was also a good temporal correlation between the electrophysiologic (CT shortening) versus echocardiographic (dimensional shortening) parameters. Thus, the intraventricular CT and the major axis dimension of the LV were shortened in a similar magnitude and also at a similar timing in the cardiac cycle. CONCLUSION: These findings suggest the possibility that supernormal conduction may result, at least in part, from dimensional shortening of the pathway length of impulse propagation from the stimulating to recording electrodes, which naturally occurs during ventricular systole.

Adult↗

PubMed1998

Saphenous vein graft shrinkage as a mechanism of stenosis soon after bypass surgery.

A 63-year-old man with left main coronary artery disease underwent aortocoronary bypass surgery using saphenous vein grafts. Less than 1 month later, severe narrowing occurred in the mid-portion of the vein graft to the left anterior descending coronary artery. Preintervention intravascular ultrasonography revealed prominent vein graft shrinkage. Percutaneous transluminal angioplasty failed because the stenotic lesion could not be dilated, even by high-pressure balloon inflation. Saphenous vein graft shrinkage appears to be one of the mechanisms of early saphenous vein graft stenosis, and balloon angioplasty to the vein graft stenosis with prominent shrinkage may be of only limited value.

Coronary Artery Bypass↗

PubMed1998

Asymptomatic hyponatremia due to inappropriate secretion of antidiuretic hormone as the first sign of a small cell lung cancer in an elderly man.

A 72-year-old man was hospitalized with asymptomatic hyponatremia. Despite hyponatremia, urinary sodium excretion with urine osmolality exceeding plasma osmolality persisted. Plasma vasopressin levels were high and independent of plasma osmolality during hypertonic saline infusion. Computed tomography of the chest showed enlarged mediastinal and right hilar lymph nodes. Microscopically, a specimen of lymph nodes obtained by biopsy represented vasopressin-producing small cell lung carcinoma. Chemotherapy plus irradiation improved the hyponatremia. Thus, careful evaluation is necessary to determine the cause of hyponatremia disorders in elderly patients.

Aged↗

PubMed1998

Construction of the gyrB Database for the Identification and Classification of Bacteria.

Nucleotide sequences of small-subunit rRNA (16S rRNA) are most commonly used for the identification and characterization of bacteria and their complex communities. However, 16S rRNA evolves slowly and is often not very convenient to resolve bacterial strains at the species level. We have therefore attempted to develop a rapid and more convenient system for bacterial identification using the gyrB gene sequences. We chose the gyrB gene, because (i) it is rarely transmitted horizontally, (ii) its molecular evolution rate is higher than that of 16S rRNA, and (iii) the gene is distributed ubiquitously among bacterial species. We PCR-amplified the 1.2 kb-long gyrB segments from about 1,000 bacterial species by using degenerate primers and determined their nucleotide sequences. The resultant data have been assembled into the gyrB database accessible via WWW.

Journal Article↗