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Biomedical subjects

K Hiramoto

Publications and source records attributed to K Hiramoto.

At least 55 records · Page 3Linked to original sources
PubMed1994

Mechanisms of the DNA breaking activity of mutagenic 5-diazouracil.

5-Diazouracil in monohydrated form showed mutagenicity and cytotoxicity on Salmonella typhimurium TA98 and TA100 strains without metabolic activation, and induced mouse micronucleated peripheral reticulocytes. Incubation of a plasmid supercoiled DNA with the compound caused DNA single-strand breaking: the supercoiled form was transformed into an open circular relaxed form and then into a linear form. The breaking was similarly caused in the absence of molecular oxygen. The breaking was not inhibited by superoxide dismutase and catalase, but inhibited by ethanol, butyl hydroxyanisole and 5,5-dimethyl-1-pyrroline N-oxide (DMPO), suggesting the involvement of radical species other than oxygen-derived radical species. Sequencing analysis of the singly 5'-end-labeled DNA fragment showed that the phosphodiester breaking was not site-specific. When Escherichia coli cells were incubated with the compound, the intracellular double-strand DNA was fragmented. The fragmentation was inhibited by ethanol, DMPO, N-tert.-butyl-alpha-phenylnitrone (PBN) and thiol compounds. Generation of the carbon-centered radical was confirmed by the electron spin resonance spin-trapping technique using DMPO and PBN. The mutagenicity and the DNA breaking activity of 5-diazouracil can be ascribed to the carbon-centered radical.

Animals↗
PubMed1994

Possible occurrence of new mutagens with the DNA breaking activity in coffee.

Brewed and instant coffee emitted strong chemiluminescence due to singlet oxygen and excited carbonyls, which may be originated by the Maillard reaction of sugars and amino acids but not by the reaction of polyphenolics. Instant coffee cleaved DNA giving single-strand breaks only after it was purified by high performance liquid chromatography (HPLC) or by gel filtration. Retention times of component(s) with strong DNA breaking activity in HPLC were different from those of chemiluminescence emitters, although they were coeluted on a gel filtration. The major DNA breaking component(s) must be different from chemiluminescence emitters. Active oxygen radicals participated little in DNA breaking because active oxygen radical scavengers had only a marginal effect on DNA breaking of the active gel fraction. DNA breaking by the active gel fraction was inhibited by high concentrations of inorganic salts probably because the salts stabilized the DNA double strands. The active gel fraction was mutagenic to Salmonella typhimurium TA98 without metabolic activation. The number of His+ revertant colonies/g of instant coffee powder was estimated to be 4000.

Animals↗
PubMed1994

Appearance of ESR signals by the reaction of 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS) and non-radical biological components.

The reaction of 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS) with non-radical biological components produced spin adducts with ESR signals. The reactions of DBNBS with Trp, Gly-Trp, Trp-Gly, Pro, Cys and glutathione at pH 7.5 and room temperature for more than 1 hour gave the nitroxyl free radicals with ESR signals, whereas the reactions with other amino acids and bovine serum albumin did not. Among the amino acids and the peptides, Trp and Trp-containing peptides gave the most intense signals. The reactions of DBNBS with unsaturated fatty acids, i.e., linoleic acid and oleic acid, gave weak ESR signals, whereas the reaction with stearic acid did not. While DBNBS gave no ESR signals by the reactions with DNA, nucleosides and nucleobases, it caused strand breaking in supercoiled DNA. DBNBS also gave ESR signals by the reaction with human plasma similar to those from the reaction with Trp. It was suggested that the nitroxyl free radicals were produced by the addition of DBNBS to the amino acids and unsaturated fatty acids followed by oxidation in the presence of DBNBS. Hence, the use of DBNBS spin trap to detect free radicals in systems containing these biological components after long incubation may give misleading results.

Benzenesulfonates↗
PubMed1993

Generation of DNA-breaking activity in the Maillard reaction of glucose-amino acid mixtures in a solid system.

Maillard products of 1:1 solid mixtures of glucose-amino acid heated at 200 degrees C for 5 min induced single-strand breaks of DNA after incubation at 37 degrees C and pH 7.4 overnight. The products of Gly, His, Trp, Tyr, Phe and CySH transformed a plasmid supercoiled DNA (form I) into an open circular relaxed form (form II) and a linear form (form III). The breaking activity of the product of CySH was the highest. The product of Tyr caused fragmentation of single-stranded DNA, but did not cleave double-stranded linear DNA. The breaking activity of the product of Tyr was little or not at all inhibited by scavengers of singlet oxygen, hydroxyl radical, superoxide and hydrogen peroxide. Aqueous solutions of the products of all amino acids except CySH emitted chemiluminescence, which was partly due to singlet oxygen. High-performance liquid chromatography of the product of Tyr showed that the substances responsible for the DNA-breaking activity were eluted in a broad range, whereas those for chemiluminescence were eluted in an overlapped sharp peak. The Maillard reaction of glucose-amino acid in a solid state produced substances having DNA-breaking activity together with those generating single oxygen and emitting chemiluminescence.

Amino Acids↗
PubMed1993

DNA breaking activity of the carbon-centered radical generated from 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH).

When supercoiled plasmid DNA was incubated with 2,2'-azobis (2-amidinopropane)hydrochloride (AAPH) at pH 7.4 in the presence and absence of oxygen, the DNA single strands were effectively cleaved. The breaking in the presence of oxygen was not inhibited by superoxide dismutase and catalase, but inhibited by mannitol, ethanol, butyl hydroxyanisole, thiol compounds, tertiary amines and spin trapping agents N-tert-butyl-alpha-phenylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The breaking in the absence of oxygen was inhibited by ethanol, a tertiary amine and PBN. By electron spin resonance spin-trapping with PBN, the carbon-centered radical was detected both in the presence and the absence of oxygen. Hydroxyl radical was detected by use of DMPO only in the presence of oxygen. The DNA breaking activity of AAPH was found to be due primarily to the aliphatic carbon-centered radical. While the reactivity of carbon-centered radicals have received little attention, the aliphatic carbon-centered radical generated from AAPH was found to be highly reactive to break the DNA strands.

Amidines↗
PubMed1992

Unique karyotypes in two patients with Prader-Willi syndrome.

A physical disruption of the Prader-Willi syndrome (PWS) chromosome region is thought to cause PWS. We describe 2 girls with PWS phenotype, who had unique chromosome 15 abnormalities. The first patient showed mosaicism: 45,XX,t(15;15)(qter----p11.1::q11.200----qter)/46,XX,t(15;15)(qter----p1 1.1::q 11.200----qter), +mar. The band 15q11.2 apparently remained intact in the t(15;15) chromosome, and the mar chromosome was considered as r(15) (p11.1q11.1). The second patient had a karyotype of 47,XX,del(15)(q11.200----q11.207), +idic (15)(pter----q11.1::q11.1----pter). The complex breakage and reunion involving the 15q11.2 regions of the father's homologous chromosomes 15 at meiosis appeared to have resulted in the idic(15) and the del(15) chromosomes. These cytogenetic findings suggest that the PWS chromosome region may be localized on the very proximal portion of band 15q11.2.

Child↗
PubMed1992

DNA strand breakage by hydroxyphenyl radicals generated from mutagenic diazoquinone compounds.

The mutagenic diazoquinone compounds p-diazoquinone (p-DQ), o-diazoquinone (o-DQ) and 3-diazo-N-nitrosobamethan (D-BM) cleaved the phosphodiester bond of lambda DNA, phi X174 RFI DNA and M13mp8ss DNA. p-DQ also cleaved the phosphodiester bond of bis(p-nitrophenyl)phosphate. The breakage of the phosphodiester bond was inhibited by the antioxidant butyl hydroxyanisole (BHA), ethanol, the spin trapping agent DMPO, cysteine and 2-mercaptoethanol. While incubation of p-DQ and o-DQ alone gave p-hydroquinone and catechol, respectively, incubation of these compounds in the presence of BHA and ethanol gave phenol in large yields. Incubation of p-DQ and o-DQ with the spin trapping agents DMPO and PBN gave spin adducts assignable as p- and o-hydroxyphenyl adducts, respectively. The breakage of the phosphodiester bond of DNA by the diazoquinone compounds is suggested to be due to the hydroxyphenyl radicals generated during incubation.

Bacteriophages↗
PubMed1991

Changes in ovalbumin and protein synthesis in vivo in the magnum of laying hens during the egg formation cycle.

1. The present study was carried out to investigate whether or not the rate of synthesis of total protein in various oviducal segments and ovalbumin, a major egg white protein, in the magnum fluctuated during the egg formation cycle in laying hens. 2. Synthesis of total protein and ovalbumin was measured in vivo by the incorporation of [15N]methionine after a primed continuous infusion of tracer for 3 hr. 3. Protein and ovalbumin contents in the magnum and the entire oviduct decreased sharply when an ovum moved down from the magnum to the isthmus, probably due to the secretion of egg white proteins. 4. In contrast, total protein and ovalbumin synthesis in the magnum was significantly higher when an ovum was in there than when it was in any other segments. Fluctuations of ovalbumin synthesis and total protein synthesis in the magnum were roughly parallel to those of total protein synthesis in the entire oviduct. 5. It was concluded, therefore, that the changes seen in total protein synthesis in the whole oviduct during the egg formation cycle were mainly attributable to those in magnum protein synthesis, of which a significant portion was accounted for by the synthesis of ovalbumin.

Animals↗
PubMed1990

Loss of the 3p25.3 band is critical in the manifestation of del(3p) syndrome: karyotype-phenotype correlation in cases with deficiency of the distal portion of the short arm of chromosome 3.

Two patients with monosomy for the distal portion of the short arm of chromosome 3 are described. Chromosome analysis on prometaphase cells demonstrated a karyotype of 46,XX,del(3) (p25.3) in one patient and 46,XX,r(3)(p26.1q29) in the other. The former patient showed characteristic clinical manifestations of the 3p- syndrome, including growth failure, mental retardation, microcephaly with a flat occiput, triangular face, synophrys, blepharoptosis, hypertelorism, broad and flat nose, long philtrum, down-turned mouth, micrognathia, apparently lowset and malformed ears, fingers abnormalities, and deafness. The latter patient had a nonspecific phenotype with mental retardation, growth failure and microcephaly. Karyotype-phenotype comparisons in the present cases and 16 previously reported cases with deficiency of the distal portion of 3p suggests that deficiency of the 3p25.3 band is critical to produce the main clinical manifestations of the del(3p) syndrome.

Chromosome Deletion↗
PubMed1990

Synchronization culture of amniotic fluid cells using excess thymidine block followed by deoxycytidine release and its application to high-resolution banding analysis of chromosomes.

We describe a simple synchronization culture technique of amniotic fluid (AF) cells to yield many earlier mitotic divisions with extended chromosomes. AF cell samples obtained by amniocentesis were cultured in the usual manner. Thirty hours after the first subculture, they were exposed to excess thymidine (0.5 mM). This cell cycle block was released by adding deoxycytidine (10 microM) 18 hr after synchronization. At exactly 7.5 hr after the release, the cultures were treated with Colcemid (0.02 microgram/ml) for 20 min then harvested. The mitotic index and the ratio of cells in the earlier mitotic stages were much higher in the synchronized cultures than in the control cultures. The same favorable effects were obtained also in AF cell cultures by combining this technique with ethidium bromide or actinomycin D treatment. The technique was less toxic to the cells, and was simple and reproducible. It was successfully applied to prenatal cytogenetic diagnosis of 2 families with a subtle inherited chromosome abnormality, so it is recommended for high-resolution banding analysis of AF cells and possibly chorionic villus samples.

Amniotic Fluid↗
PubMed1990

Strain differences in whole-body protein turnover in the chicken embryo.

1. Whether or not there is a strain difference in embryonic whole-body protein turnover rates was tested using the chicken embryos of Rhode Island Red carrying a sex-linked dwarf gene (dwarf), White Leghorn (layer), and White Cornish X White Plymouth Rock (broiler) strains on day 12 of incubation. 2. Whole-body protein synthesis was estimated by injecting L-[15N]-phenylalanine either intraperitoneally or intravenously on day 12 of incubation in order to investigate the effect of the route of isotope administration. The results showed that the values for fractional and absolute synthesis rates were approximately 13% higher by intravenous injection than by intraperitoneal injection. 3. Whole-body protein turnover, both in terms of fractional and absolute rates, was significantly faster in dwarf than in broiler embryos, with intermediate values in layer embryos, although no growth differences were observed on day 12. 4. Difference in egg weight, measured before incubation, did not affect protein turnover. 5. It was concluded that the strain difference manifested in whole-body protein turnover of the chicken embryo would probably be a reflection of differences in genetic background.

Animals↗
PubMed1990

Importance of albumen content in whole-body protein synthesis of the chicken embryo during incubation.

The importance of egg albumen content in whole-body protein synthesis was investigated in developing chicken embryos by using lines genetically selected for high and low albumen contents and by removing albumen from eggs before incubation. 2. Whole-body protein synthesis was estimated by injecting L-[15N]-phenylalanine intravenously on day 12 of incubation. 3. Embryos from high albumen eggs had higher whole-body protein synthesis rates than those from low albumen eggs. 4. Whole-body protein synthesis was reduced by the removal of albumen from eggs before incubation. 5. It was concluded that albumen content per se was of crucial importance in regulating whole-body protein synthesis in chicken embryos during incubation.

Animals↗
PubMed1990

Effect of methionine and lysine deficiencies on protein synthesis in the liver and oviduct and in the whole body of laying hens.

For laying hens, protein synthesis in the liver, in the oviduct (magnum and remaining portions), and in the whole body was measured in vivo in order to investigate the effect of a dietary deficiency of methionine or lysine. The rate of protein synthesis in tissues was calculated from the incorporation of L-[15N]phenylalanine into the protein fraction; whole-body protein synthesis was estimated from the plateau enrichment of free [15N]phenylalanine in plasma. The enrichment of labeled phenylalanine was analyzed by using a gas-chromatograph mass spectrometer, following a primed infusion of the isotope for 6 h. The whole-body protein synthesis of laying hens fed diets deficient in amino acids was significantly lower than that of control hens. Protein synthesis in the liver, magnum, and remainder of the oviduct was decreased by a dietary deficiency of the amino acids studied with larger rates of decrease than for the whole-body analysis. The proportion of reduction in protein synthesis resulting from the sum of the tissues studied, compared with that of the whole body, was 36 and 50%, respectively, for a deficiency of methionine and lysine.

Animals↗
PubMed1990

Protein synthesis in tissues and in the whole body of laying hens during egg formation.

The present study was conducted to investigate whether or not protein synthesis in tissues and in the whole body of laying hens would be affected by the position of an ovum passing along the oviduct during egg formation. Protein synthesis in tissues was measured in vivo by a primed-continuous infusion of [15N]methionine for 3 h, finishing at the time when an ovum would have stayed at one of the segments within the oviduct, i.e., infundibulum, magnum, isthmus, uterus, or vagina. The dissection of the entire oviduct immediately after the isotope infusion confirmed whether or not the ovum was in the expected position. Whole-body protein synthesis, estimated from plateau enrichment of free [15N]methionine in plasma at the end of the infusion, was not significantly affected by the position of an ovum along the various segments of the oviduct. The highest values were observed in the entire oviduct when an ovum was in the magnum portion, both for protein synthesis and protein synthesis per unit of RNA. Protein synthesis per unit of RNA in the sum of tissues other than the liver and oviduct was highest when an ovum was in the isthmus. The synthesis of liver protein was relatively constant and was not significantly affected by the position of the ovum passing along the oviduct.

Animals↗