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T Kakutani

Publications and source records attributed to T Kakutani.

At least 37 records · Page 2Linked to original sources
PubMed1997

Genetic characterization of late-flowering traits induced by DNA hypomethylation mutation in Arabidopsis thaliana.

Arabidopsis DNA hypomethylation mutation, ddm1, results in a variety of developmental abnormalities by slowly inducing heritable lesions at unlinked loci. Here, late-flowering traits observed at high frequencies in independently-established ddm1 lines were genetically characterized. In all of the four late-flowering lines examined the traits were dominant and mapped to the same chromosomal region, which is close or possibly identical to the FWA locus. The ddm1-induced phenotypic onsets are apparently not random mutation events, but specific to a group of genes, suggesting the underlying epigenetic mechanism. The DNA methylation mutant provide useful system for identifying epigenetically-regulated genes important for plant development.

Arabidopsis↗
PubMed1997

The molecular mechanisms of 5-fluoro-2'-deoxyuridine induced cell death.

The molecular mechanism of cell death induced by 5-Fluoro-2'-deoxyuridine (FUdR) was investigated. FUdR caused cell death to induce dNTP pool imbalance and following DNA double strand breaks in mouse mammary tumor FM3A cells. We isolated a new endonuclease from FUdR-treated cells, named endonuclease S, that played an important role in FUdR-induced cell death. Cells treated with FUdR showed intracellular acidification before cell death formation. We observed that the endonuclease S in acidic cells may lead the DNA fragmentation. On the other hand, we observed that protease inhibitors (such as TLCK, TPCK, PMSF, p-APMSF, Pefabloc SC and Z-Asp-CH2-DCB) blocked intracellular acidification, DNA fragmentation and FUdR-induced cell death. But the inhibitors did not affect dNTP pool imbalance in the cells. These results suggest that proteases act at the point of downstream of dNTP pool imbalance and upstream of the intracellular acidification.

Animals↗
PubMed1996

Developmental abnormalities and epimutations associated with DNA hypomethylation mutations.

A number of aberrant morphological phenotypes were noted during propagation of the Arabidopsis thaliana DNA hypomethylation mutant, ddm1, by repeated self-pollination. Onset of a spectrum of morphological abnormalities, including defects in leaf structure, flowering time, and flower structure, was strictly associated with the ddm1 mutations. The morphological phenotypes arose at a high frequency in selfed ddm1 mutant lines and some phenotypes became progressively more severe in advancing generations. The transmission of two common morphological trait syndromes in genetic crosses demonstrated that the phenotypes are caused by heritable lesions that develop in ddm1 mutant backgrounds. Loss of cytosine methylation in specific genomic sequences during the selfing regime was noted in the ddm1 mutants. Potential mechanisms for formation of the lesions underlying the morphological abnormalities are discussed.

Arabidopsis↗
PubMed1995

Characterization of an Arabidopsis thaliana DNA hypomethylation mutant.

We have recently isolated two Arabidopsis thaliana DNA hypomethylation mutations, identifying the DDM1 locus, that cause a 70% reduction in genomic 5-methylcytosine levels [1]. Here we describe further phenotypic and biochemical characterization of the ddm1 mutants. ddm1/ddm1 homozygotes exhibited altered leaf shape, increased cauline leaf number, and a delay in the onset of flowering when compared to non-mutant siblings in a segregating population. Our biochemical characterization investigated two possible mechanisms for DNA hypomethylation. In order to see if ddm1 mutations affect DNA methyltransferase function, we compared DNA methyltransferase activities in extracts from wild-type and ddm1 mutant tissues. The ddm1 mutant extracts had as much DNA methyltransferase activity as that of the wild-type for both the CpI and CpNpG substrates suggesting that the DDM1 locus does not encode a DNA methyltransferase. Moreover, the ddm1 mutations did not affect the intracellular level of S-adenosylmethionine, the methyl group donor for DNA methylation. The possibility that the DDM1 gene product functions as a modifier of DNA methylation is discussed.

Arabidopsis↗
PubMed1994

Detection of Plasmodium falciparum in human blood by a nested polymerase chain reaction.

We have developed a simple method for direct detection of Plasmodium falciparum parasites in infected human blood using a nested polymerase chain reaction. Whole blood (10 microliters) was obtained by finger puncture and suspended in a microcentrifuge tube containing phosphate-buffered saline. For removal of components that might inhibit the PCR, blood samples were treated with saponin and washed by centrifugation. After three cycles of a two-step incubation (3 min at 94 degrees C and 3 min at 55 degrees C), the first amplification was done with oligonucleotide primers specific for the junction region of the gene coding for the dihydrofolate reductase-thymidylate synthase in P. falciparum. A 1-microliter portion of the first amplification was then amplified again with a second set of primers, and 226-basepair fragments were generated. The amplified products were analyzed by agarose gel electrophoresis with ethidium bromide staining. Experiments with cultured parasites showed that the method could detect as few as 13 parasites in 10 microliters of whole blood. In 1991, 101 samples from 98 donors were collected in Guadalcanal, Solomon Islands. Eight of these samples gave positive results by both examination of thin blood smears and by the nested PCR. There was a correlation between parasite densities and the intensity of the results by the nested PCR. The method is suitable for detection of asymptomatic parasite carriers and evaluation of medical treatment on clinical cases.

Adolescent↗
PubMed1993

Arabidopsis thaliana DNA methylation mutants.

Three DNA hypomethylation mutants of the flowering plant Arabidopsis thaliana were isolated by screening mutagenized populations for plants containing centromeric repetitive DNA arrays susceptible to digestion by a restriction endonuclease that was sensitive to methylated cytosines. The mutations are recessive, and at least two are alleles of a single locus, designated DDM1 (for decrease in DNA methylation). Amounts of 5-methylcytosine were reduced over 70 percent in ddm1 mutants. Despite this reduction in DNA methylation levels, ddm1 mutants developed normally and exhibited no striking morphological phenotypes. However, the ddm1 mutations are associated with a segregation distortion phenotype. The ddm1 mutations were used to demonstrate that de novo DNA methylation in vivo is slow.

5-Methylcytosine↗
PubMed1992

Suppression of genotoxicity of carcinogens by (-)-epigallocatechin gallate.

Epidemiological evidence shows that green tea may be a factor in lowering cancer risk. We have investigated the possibility that (-)-epigallocatechin gallate (EGCG), a major polyphenol in green tea, might be an antimutagenic substance. In the Ames Salmonella test, EGCG suppressed the direct-acting mutagenicity of 3-hydroxyamino-1-methyl-5H-pyrido-[4,3-b]indole (Trp-P-2(NHOH)) and 2-hydroxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1(NHOH)), the activated forms of food-derived carcinogens 3-amino-1-methyl-5H-pyrido[4,3-b]indole and 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole. EGCG was also effective in reducing the mutagenicity of Trp-P-2(NHOH) in mouse FM3A cells in culture. Furthermore, EGCG demonstrated a suppressive effect in the in vivo Drosophila mutation assays, i.e., the wing spot test, and the DNA repair test, on several carcinogens. EGCG was also effective in inhibiting DNA single-strand breaks in vitro caused by Glu-P-1(NHOH). We conclude that the mechanism of inhibition may not have resulted from direct interaction between EGCG and the mutagens, but rather from indirect interception of mutagen action by EGCG.

Animals↗
PubMed1992

Effect of chronic administration of phenobarbital on the hepatobiliary transport of phenol red: assessment by statistical moment analysis.

The effect of enzyme induction on the hepatobiliary transport of phenol red (PR) in rats was investigated by application of a new analytical system to determine local drug disposition based on statistical moment theory (T. Kakutani et al., J. Pharmacokin. Biopharm. 13:609-631, 1985). Employing the moment parameters obtained from the time courses of plasma and biliary concentrations of PR and its metabolite after intravenous injection, the hepatobiliary transport of PR was theoretically assessed by separating it into component subprocesses such as hepatic uptake, hepatobiliary transfer, and intrahepatic metabolism. The results demonstrated that the acceleration of plasma disappearance of PR caused by pretreatment with phenobarbital (PB), known to induce hepatic enzyme systems, could be attributed to elevation of both hepatic and extrahepatic clearances. While PB did cause bile flow elevation (choleresis) and increased metabolism, these effects were shown to make little contribution to accelerated plasma disappearance of PR, since it was shown that the hepatobiliary excretion of PR was rate-limited by the intrahepatic transfer process, which was unaffected by PB treatment. From the results of this study, this experimental/analysis methodology seems to be useful in obtaining detailed information about hepatobiliary transport of the drug from in vivo data.

Animals↗
PubMed1992

Nucleotide sequence analyses of peanut stunt cucumovirus RNAs 1 and 2.

The nucleotide sequences of the RNAs 1 and 2 of the peanut stunt virus strain J (PSV-J) were determined and compared with those of the cucumber mosaic virus strain Y (CMV-Y, subgroup I), strain Q (CMV-Q, subgroup II) and the tomato aspermy virus strain V (TAV-V) at both the nucleotide and protein levels. RNA 1 of PSV-J consists of 3355 nucleotides (nt) and has one large open reading frame (ORF) which can encode the putative 1a protein of Mr 112025. PSV-J RNA 1 and the 1a protein are 65 to 73% identical to those of CMV-Y and -Q, and 65 to 69% to those of TAV-V, RNA 2 of PSV-J contains 2946 nt and also has one large ORF which can encode the putative 2a protein of Mr 93575. For RNA 2 and the 2a protein, identities between PSV-J and two strains of CMV are calculated to be 53 to 61%. When compared with TAV-V, the same degree of similarity as seen with CMVs is observed. The 1a protein has the consensus sequences found in some helicases and methyltransferases and the 2a protein includes a sequence which exists in several RNA-dependent RNA polymerases.

Amino Acid Sequence↗
PubMed1991

Nucleotide sequence of RNA 3 of peanut stunt cucumovirus.

The nucleotide sequence of the RNA 3 of the peanut stunt virus strain J (PSV-J) was determined and compared with those of the cucumber mosaic virus strain Y (CMV-Y, subgroup I) and the tomato aspermy virus strain C (TAV-C) at both the nucleotide and protein levels. The RNA 3 of PSV-J consists of 2186 nucleotides and has two large open reading frames (ORFs). By analogy to other tripartite plant viruses, it is presumed that the first ORF (867 nucleotides) codes for the 3a protein and the second ORF (654 nucleotides) is the cistron of the coat protein which is expressed from subgenomic RNA 4 of 1010 nt residues. At the nucleotide level, PSV-J RNA 3 shows 60.6% homology to RNA 3 of CMV-Y and 66.3% to that of TAV-C, much lower than the value between the two CMV subgroups. For the 3a proteins there is 65.4% homology between PSV-J and CMV-Y and 70.2% homology between PSV-J and TAV-C. Although it has been known that PSV shows a distant serological relationship to CMV, the coat protein of PSV-J shows only 50% homology with that of CMV-Y.

Amino Acid Sequence↗
PubMed1991

Augmented anti-proliferative effect in combined use of human lymphotoxin with a nitrosourea derivative, ACNU, and the involvement of glutathione redox cycle.

The cytotoxic or cytostatic effect of the combined use of human lymphotoxin (LT) with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3- nitrosourea hydrochloride (ACNU) on L cells or Meth A tumor cells was studied. Simultaneous addition of LT derived from a human lymphoid cell line with ACNU (200 or 500 micrograms/ml) significantly augmented the cytotoxic effect. Similar augmented inhibition was obtained when LT was added to ACNU-treated L cells. The pre-treatment of Meth A tumor cells with ACNU (25 or 50 micrograms/ml) augmented recombinant human LT-mediated cytostasis. However, the addition of glutathione (1.0 mg/ml) to ACNU-treated Meth A tumor cells significantly nullified the augmented anti-proliferative effect of LT (10 U/ml). These results suggest that augmentation of the anti-proliferative effect on tumor cells could be induced through the combined use of LT with ACNU by lowering the intracellular level of glutathione.

Animals↗
PubMed1991

Usefulness of glycosylated recombinant human lymphotoxin for growth inhibition of human and murine solid tumors and experimental metastasis in mice.

We have examined the antitumor and antimetastatic effects of native-type, glycosylated recombinant lymphotoxin (LT) on human and murine tumors transplanted in mice. The results reported here are as follows: (a) The in vivo antitumor spectrum of LT is not coincident with the in vitro study, and it has a wide antitumor spectrum and substantially inhibits the growth of human solid tumors, (b) When both syngeneic and nude mice are transplanted with Meth A tumor, the significant growth-inhibitory effect of LT is obtained in syngeneic mice, but the effect is quite small in nude mice regardless of the routes; LT attains the same degree of effectiveness as that in syngeneic mice, but at an 8 to 16 times higher dose. Furthermore, the pretreatment with anti-asialo-GM1 antibody inhibits the antitumor effects of LT in syngeneic mice, (c) In the pulmonary metastasis model induced by i.v. injection of Meth A cells, a high preventive effect of LT is obtained by systemic administration in syngeneic mice, but not in nude mice. In addition, the pretreatment with anti-asialo-GM1 antibody completely prevents the antimetastatic effect of LT, but also blocks that effect of control mice without LT treatment. In conclusion, LT appears to be a potent cytokine against tumor growth and metastasis in vivo. The differences between nude and syngeneic mice suggest the involvement of host immunity in the expression of LT function.

Animals↗
PubMed1991

Ambisense segment 3 of rice stripe virus: the first instance of a virus containing two ambisense segments.

The complete nucleotide sequence of rice stripe virus (RSV) segment 3 shows that it has two open reading frames, one in the viral-complementary sequence, which codes for the nucleocapsid protein, and the other in the viral-sense sequence. The non-coding region between the ambisense genes in RSV segment 3 contains several U and A tracts, as do the ambisense S segments of phleboviruses and uukuviruses. As we have previously shown that RSV segment 4 has an ambisense nature, this is the first instance of a virus containing two ambisense segments.

Amino Acid Sequence↗
PubMed1991

The complete nucleotide sequence of cucumber green mottle mosaic virus (SH strain) genomic RNA.

The complete nucleotide sequence of the genomic RNA of cucumber green mottle mosaic virus watermelon strain SH (CGMMV-SH) was determined using cloned cDNA. This sequence is 6421 nucleotides long containing at least four open reading frames, which correspond to 186K, 129K, 29K and 17.3K proteins. The 17.3K protein is the coat protein. Sequence analysis shows that CGMMV-SH is very closely related to another watermelon strain. CGMMV-W, although three amino acid substitutions in the 29K protein were found between these strains. The sequence was also compared to those of other tobamoviruses, tobacco mosaic virus (TMV) vulgare, TMV-L (a tomato strain) and tobacco mild green mosaic virus reported by other groups. It shows 55 to 56% identity with these viruses. The size and location of the open reading frames are very similar to those of TMV but the 129K and 186K proteins are composed of 1142 and 1646 amino acids, being larger than those of TMV by 27 and 31 amino acids, respectively. The deduced amino acid sequences of these proteins are highly homologous to those of TMV, especially in the readthrough downstream region of the 186K protein.

Amino Acid Sequence↗
PubMed1991

Constitutive high-level production of human lymphotoxin by CHO-K1 cells transformed with the human lymphotoxin gene controlled by a human beta-actin promoter.

To achieve high-level production of human lymphotoxin (hLT), a plasmid (p beta LT-ldhfr) containing the hLT genomic DNA, a mouse dihydrofolate reductase (DHFR) cDNA, and a bacterial Ecogpt gene was cotransfected with a plasmid (p beta LTML) encoding only the hLT genomic DNA into Chinese hamster ovary (CHO-K1) cells at a 1:7 molar ratio. Subsequently one of the Ecogpt-positive clones (clone A31) was grown in stepwise increasing concentrations of methotrexate (MTX). A large amount of the hLT was secreted by cells resistant to increased levels of MTX as a result of coamplification of the DHFR cDNA and the hLT gene. A cell clone (clone M-1) resistant to up to 500 nM MTX constitutively expressed the hLT at a concentration of 80 micrograms per ml at an elevated level for about 2 months. The hLT was produced in glycosylated form the molecular mass of which was 23,000 daltons and the mRNA was normally spliced, so the protein molecules were probably homogeneous.

Actins↗
PubMed1990

2-(p-Nitrophenyl)-2'-deoxyadenosine, a new type of mutagenic nucleoside.

A crude preparation of 2-phenyladenosine was found to be mutagenic in the Ames Salmonella assay. In the purification of this preparation, it was revealed that 2-phenyladenosine itself was nonmutagenic but that 2-(m- and p-nitrophenyl)-adenosines (5m,p) contaminating the sample were the mutagenic principles. A structure-activity relationship study was carried out, and it was found that 5p, 2-(p-nitrophenyl)-adenine (7p), and 2-(p-nitrophenyl)-2'-deoxyadenosine (15p) were strongly mutagenic toward S. typhimurium TA98 and TA100 without metabolic activation, the potency being in the order 15p greater than 7p greater than 5p. The potency of 15p in TA98 was one order of magnitude greater than that of 4-nitroquinoline N-oxide. 15p also showed mutagenicity in the mouse cell line FM3A in culture.

Adenosine↗
PubMed1990

Statistical moments and disposition parameters in a local perfusion system under mammillary nonequilibrium condition.

Application of the statistical moment analysis to the local organ perfusion system leads moment parameters (moments) from the venous outflow concentration-time curve (dilution curve) of drug after its intra-arterial bolus injection. By introducing the chromatographic concept and the network theory, we had defined the disposition parameters such as steady state distribution volume, mean elimination time, and intrinsic clearance from moments based on the well-stirred model. In this paper, discussion was expanded to general two-compartment organ perfusion models and the meanings of these disposition parameters in them were investigated. The relationship between compartmentally defined microconstants and moments-oriented disposition parameters was examined and the effect of the nonequilibrium (mainly peripheral elimination) condition on the latter was discussed. The possible utility of the disposition parameters as noncompartmental indications of drug disposition characteristics was suggested.

Models, Biological↗