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Biomedical subjects

H Hayatsu

Publications and source records attributed to H Hayatsu.

At least 91 records · Page 5Linked to original sources
PubMed1992

Imbalance of deoxyribonucleoside triphosphates and DNA double-strand breaks in mouse mammary tumor FM3A cells treated in vitro with an antineoplastic tropolone derivative.

The mechanism by which alpha,alpha-bis(2-hydroxy-6-isopropyltropon-3-yl)-4-methoxytolu ene (JCI-3661) kills mouse mammary tumor FM3A (F28-7) cells was studied. When the cells were exposed to the drug at 3.7 microM, the intracellular dNTP pool became imbalanced because of decreases in dGTP and dATP and an increase in dTTP. The pattern of the dNTP imbalance was the same as that caused by hydroxyurea. When JCI-3661 was added to the culture medium, mature DNA strands broke, giving fragments of 100-200 kilobase pairs long as found by orthogonal-field-alternation gel electrophoresis. DNA strand breaks, detected by this technique, were observed in the cells at 12 h after the addition. The beginning of cell death was observed at about 14 h (trypan blue staining) or at about 12 h (colony-forming ability) after cultivation Breaks in the single and double strands of DNA, as measured by alkaline and neutral filter elution assay, became evident 24 h after treatment with 3.7 microM JCI-3661. Comparison of the ratio of single- and double-strand breaks caused by JCI-3661 to that following radiation suggested that JCI-3661 broke only double strands. Cycloheximide inhibited both the breakage of double strands and the cell death caused by JCI-3661. JCI-3661 decreased DNA synthesis more than RNA or protein synthesis. The breaks in double strands of DNA were probably important in the cell death caused by JCI-3661.

Animals↗
PubMed1992

Synthesis and properties of oligodeoxyribonucleotides containing a mutagenic base, N4-aminocytosine.

Oligodeoxyribonucleotides containing a mutagenic base analog, N4-aminocytosine, 5'-AATTGC(am)AATT-3' and 5'-AATTAC(am)AATT-3' (C(am); N4-aminocytosine) were prepared by chemical modification of 5'-AATTGCAATT-3' and 5'-AATTACAATT-3', respectively. The values of Tm were 29 degrees C for 5'-AATTGC(am)AATT-3' and 32 degrees C for 5'-AATTGCAATT-3'. In contrast, no melting was observed for 5'-AATTAC(am)AATT-3' and 5'-AATTACAATT-3'. These data show that the stability of C(am)-purine paris is C(am)-G > C(am)-A and that C(am)-G is less stable than C-G. This property is consistent with the incorporation specificity of N4-amino-dCTP during DNA synthesis in vitro.

Base Sequence↗
PubMed1991

Antitumor activity of FTC-092, a masked 5-trifluoromethyl-2'-deoxyuridine derivative.

1-(3-O-Benzyl-2-deoxy-beta-D-ribofuranosyl)-5-trifluoromethyl-2,4(1H,3)- pyrimidinedione (FTC-092), a fluorinated pyrimidine derivative, appeared to be effective against various transplantable tumors in mice following oral administration, and its activity was superior to that of several other antitumor fluorinated pyrimidines. The ED50 value for FTC-092 the dose effective in achieving 50% inhibition of tumor growth against the solid form of sarcoma 180 was 13.3 mg/kg daily, whereas those for 5-trifluoromethyl-2'-deoxyuridine (CF3dUrd), the parent compound of FTC-092, for 1-(2-tetrahydrofuryl)-5-fluorouracil (Tegafur, FT), the prodrug of 5-fluorouracil (FUra), and for FUra were 64.1, 122, and 28 mg/kg daily, respectively. The therapeutic indices (LD10/ED50) of FTC-092, CF3dUrd, FT, and FUra were 4.39, 1.7, 1.35, and 1.65, respectively. FTC-092 itself is not an active agent. After it has been absorbed from the gastrointestinal tract, FTC-092 undergoes a gradual biotransformation, mainly via the action of liver microsomes, releasing CF3dUrd over a long period. The levels of CF3dUrd in the stomach and small intestine of mice after the oral administration of FTC-092 were undetectable, whereas those following the administration of CF3dUrd at the same dose were high for a period of several hours. In contrast, the CF3dUrd level generated in plasma after the administration of FTC-092 remained at a high level for a longer period than did that observed on the administration of CF3dUrd. The low levels of CF3dUrd measured in stomach and small-intestine tissues and the maintenance of CF3dUrd in blood over long periods after the administration of FTC-092 are features that favor the possible clinical application of FTC-092.

Administration, Oral↗
PubMed1991

Mutagenicity and antimutagenicity of air-borne particulates.

A methanol extract of air-borne particulates collected in a suburban area of Okayama City showed not only mutagenicity but also antimutagenicity in the Ames test. Thus, when the mutagenicity of this preparation in Salmonella typhimurium TA98 (with metabolic activation) was measured, we observed that the dose response reached a plateau at 27 m3 air equivalent of the particulate, showing approximately equal numbers of revertants in the dose range 27-270 m3 equivalent. This plateau formation was not seen in the dose response of a blue-cotton extract of this preparation: the extract gave a linearly increasing dose response up to 270 m3 equivalent. This finding suggests that some factors that inhibit the mutagenicity were present in this methanol extract and that these inhibitors were not adsorbable to blue cotton, an adsorbent selective for compounds having 3 or more fused rings. From the portion unadsorbed to blue cotton, we isolated the antimutagenic factors and identified them as long-chain fatty acids: palmitic, stearic, oleic and linoleic acids. Analysis of several samples, including those from other parts of Japan, has suggested that these antimutagenic fatty acids are ubiquitous in air-borne particulates.

Air Pollutants↗
PubMed1991

The genotoxicities of N-nitrosamines in Drosophila melanogaster in vivo: the correlation of mutagenicity in the wing spot test with the DNA damages detected by the DNA-repair test.

The genotoxicities of a series of N-nitrosamines were assayed in the wing spot test and a new short-term test of Drosophila melanogaster. In the spot test, larval flies trans-heterozygous for the somatic cell markers mwh and flr3 were fed the test reagents and the wing hairs in adults were inspected for clones expressing the phenotypes of the markers. In the other test, larval stock consisting of meiotic recombination-deficient (Rec-) double mutant mei-9a and mei-41D5 males and repair-proficient Rec+ females were grown on feed containing the reagents and the DNA damages were detected with the preferential killing of the Rec- larvae as an endpoint. The carcinogenic nitrosamines tested, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-butylamine (NDBA), N-nitrosomorpholine (NMOR), N-nitro-sopiperidine (NPIP) and N-nitrosopyrrolidine (NPYR), all showed clearly positive activities in both tests. The activities in the wing spot test were ranked in a sequence of NDMA much greater than NMOR greater than NPIP greater than NDEA greater than NPYR greater than NDBA. A similar ranking was obtained in the repair assay. The genotoxicity of N-nitrosodiphenylamine (NDPhA), carcinogenicity studies of which are inconclusive, was marginal in the spot test. The non-carcinogenic N-nitrosoproline (NPRO) and the non-mutagenic N-nitrosothioproline (NTPRO) were negative in the spot test. NDPhA and NPRO were negative in the repair test as well. The DNA-repair test is thus a convenient technique for estimating the mutagenicity of compounds because of its simplicity compared with the wing spot test. These Drosophila tests may be useful in predicting carcinogenic potentials of compounds.

Animals↗
PubMed1991

Analysis of 2-amino-N6-hydroxyadenine-induced mutagenesis in phage M13mp2.

The mechanism of mutagenesis induced by 2-amino-N6-hydroxyadenine (AHA) and its deoxyriboside (AHAdR) was studied by determining the nucleotide sequences of phage M13mp2 mutant DNA samples. Mutations in the lac promoter-lacZ alpha region of the phage were induced by addition of this agent to culture media in which the phage was growing inside the host bacteria. The spectrum of spontaneous mutation was also investigated. The induced sequence changes were mostly base transitions (80% with AHA and 90% with AHAdR). A few single-base deletions and additions were detected, but they were ascribable to spontaneous mutations. These results are consistent with the incorporation type mechanism proposed by Janion (this issue). In the Ames Salmonella assay, both AHA and AHAdR showed strong mutagenicity in strain TA100 but no activity in TA98.

Adenine↗
PubMed1991

Mutagenicity of (p-nitrophenyl)adenines in Salmonella typhimurium.

Adenine derivatives having a p-nitrophenyl group at position 2, 8, or 9 were directly mutagenic towards Salmonella typhimurium strains TA98 and TA100, whereas N6-(p-nitrophenyl)adenine was not mutagenic. 2,9- And 8,9-bis-(p-nitrophenyl)adenines were also mutagenic, but N6,9-bis-(p-nitrophenyl)adenine was not. The study on 13 (p-nitrophenyl)adenine derivatives for their Salmonella mutagenicity indicates that only those having a p-nitrophenyl ring directly linked to the purine ring are mutagenic, implying the importance of the coplanar character of the nitrophenyl and the purine rings. The nitro group seems essential for the mutagenicity, as shown from the results of assays using nitroarene-sensitive and -insensitive Salmonella strains. The mutagenic potency of this class of compounds is high, comparable to that of 2-nitrofluorene.

Adenine↗
PubMed1991

Permanganate oxidation of nucleic acid components: a reinvestigation.

KMnO4 consumption in solution by nucleoside added at an excess was measured to explore any possible oxidative interactions between these molecules. Thymidine, 5-methyldeoxycytidine and deoxycytidine rapidly decomposed KMnO4 with the pseudo-first-order kinetics (thymidine greater than 5-methyl-deoxycytidine greater than deoxycytidine), while deoxyguanosine showed only a very slow consumption and deoxyadenosine did not decompose KMnO4 at all under the conditions employed (0.16 mM KMnO4, 0.80 mM nucleoside, at 27 degrees C and pH 4.3, 7.4 and 8.6, up to 60 min). UV absorption spectra of KMnO4-treated nucleosides also indicated modification of the pyrimidine nucleosides but not of the purine nucleosides. These results are consistent with the original report of Hayatsu and Ukita published in 1967 on the KMnO4 oxidation of nucleosides, and provide difficulty in understanding the mechanism of recently reported formation of 8-hydroxypurines on treatment of DNA with KMnO4.

Manganese↗
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

Probing salt-induced and supercoiling-induced B-Z junctions in DNA by bisulfitemethoxyamine.

Salt-induced and supercoiling-induced B-Z junctions in pWR756, a plasmid containing (GC)16, were probed with bisulfite-methoxyamine, a modification reagent specific for single-stranded nucleic acids. The modification sites were analyzed with S1 nuclease and the modified cytosines were determined from termination sites of DNA chain elongation by DNA polymerase. The results showed that most accessible cytosines are the same for both types of B-Z junctions.

DNA, Single-Stranded↗
PubMed1990

Heat production as a quantitative parameter for cell differentiation and cell function.

Heat production was measured in relation to cell differentiation and phagocytie function using cells of human monocyte-histiocyte cell line U937. U937 cells differentiated monocytic phagocytes when cultured with lymphokine. Heat production increased as result of differentiation and phagocytosis. An important finding was that the heat increase in differentiated cells and during phagocytosis was directly proportional to the concentration of lymphokine. This strongly suggested that heat production is a quantitative parameter not only for cell differentiation but also for phagocytic function. The measurement of heat produced by mammalian cells can therefore be used to quantitate the differentiation and function of cells.

Body Temperature Regulation↗
PubMed1990

Heat production due to intracellular killing activity.

Using Saccharomyces ceravisiae, Candida albicans and Stapylococcus aureus, heat production during phagocytosis was measured in U937 cells which are capable of differentiating to monocytic phagocytes. No increase in heat production of non-differentiated U937 was observed since they were not phagocytic cells. However after differentiation to monocytic phagocytes by lymphokine, U937 cells produced a remarkable amount of heat during phagocytosis. Although Ehrlich ascites tumor cells sensitized with antibody were capable of engulfing S. aureus, no increase in heat nor in superoxide anion production during phagocytosis was detected. It was also found that no heat increase occurred in neutrophils from a patient with chronic granulomatous disease (CGD). It can thus be concluded that the heat production during phagocytosis is due to the intercellular killing process of phagocytic cells.

Animals↗
PubMed1989

Formation of directly mutagenic alpha-hydroxy-N-nitrosopiperidine phosphate ester by near-ultraviolet irradiation of N-nitrosopiperidine in phosphate buffer.

Previously we found that direct-acting mutagens can be formed from N-nitrosodialkylamines on exposure to near-ultraviolet light in the presence of phosphates. We have now isolated the mutagenic photoproduct formed from N-nitrosopiperidine and inorganic phosphate and identified its structure as the phosphate ester of alpha-hydroxy-N-nitrosopiperidine. This reaction represents a new, non-enzymatic activation of promutagenic N-nitrosodialkylamines.

Buffers↗
PubMed1989

Spectrum of N4-aminocytidine mutagenesis.

N4-Aminocytidine, a nucleoside analog, is a potent mutagen towards phages, bacteria, Drosophila and mammalian cells in culture. In vitro, biochemical studies indicate that this reagent acts by being incorporated into DNA. To elucidate the mechanism of N4-aminocytidine mutagenesis, it is essential to identify the nature of DNA sequence alterations taking place during the mutagenesis. We have analyzed the nucleotide sequence changes in the lac promoter-lacZ alpha region of M13mp2 phage induced by treatment of phage-infected Escherichia coli with N4-aminocytidine. The sequence alterations of DNA samples from 89 mutants of the phage were determined. These mutants had single point mutations, except one mutant, in which a double point mutation was detected. Several hot spots were found: however, there are no apparent relations to particular DNA sequences regarding the locations of these spots. All the mutations are transitions; neither transversions nor deletions/insertions were found. A feature in these transitions is that the A/T to G/C and G/C to A/T changes occur at approximately equal rates. The overall picture of the mutagenesis is consistent with a scheme in which misincorporation and misreplication caused by the modified cytosine structure are the key steps in the DNA replication leading to transitions. Similar nucleotide alterations were found for the mutagenesis induced by an alkylated derivative, N'-methyl-N4-aminocytidine. N4-Aminocytidine also induced reversions of these mutants; both A/T to G/C and G/C to A/T transitions again took place.

Bacteriophages↗