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Biomedical subjects

Isao Saito

Publications and source records attributed to Isao Saito.

At least 109 records · Page 6Linked to original sources
PubMed2003

Electrochemical detection of single-base mismatches in DNA by a redox-active intercalator conjugated oligonucleotide.

A simple and direct electrochemical detection of DNA single-base mismatches utilizing anthraquinone-modified oligonucleotides (AQ-ODNs) bound to gold electrodes has been described. By using the redox-active oligonucleotides, the redox-active center can be positioned at the desired base-pair pocket in double-helical DNA, enabling us to measure the charge transport between the redox-active center and the electrode that sandwich mismatched and full-matched base-pairs in double helix. AQ-ODNs immobilized on gold electrodes have been found to be useful in the electrochemical discrimination of hybrids containing a single-base mismatch from the one with fully matched bases.

Base Pair Mismatch↗
PubMed2003

Association of body mass index, body fat, and weight gain with inflammation markers among rural residents in Japan.

Because obesity is thought to play a key role in atherosclerosis through the low-grade chronic inflammation, the present study was designed to investigate associations of body mass index (BMI), body fat, and weight gain with optimized inflammation markers in 1,053 residents who were 40 years of age and older from a rural community (total population = 3,940 in 2000) in Japan. People reporting having a cold and those who did not undergo blood examinations were excluded. C-reactive protein (CRP), fibrinogen, serum albumin, and white blood cell (WBC) count were used as the markers for inflammation, body fat was calculated by a conventional method, and weight change since the age of 20 was assessed. The BMI and body fat significantly increased with CRP quartile, and its correlation coefficients to BMI or body fat were relatively high. Similar associations were found for fibrinogen, serum albumin and WBC. Multivariate-adjusted analysis found a high concentration of CRP was significantly associated with obesity, but attenuated the association in other markers. In an analysis restricted to people aged 40-69 years, body fat levels were more strongly associated with CRP and fibrinogen than with BMI only. Furthermore, only CRP concentrations were significantly elevated according to weight gain. Strong associations of CRP concentration with BMI, body fat, and weight gain were found among elderly Japanese, but not with fibrinogen, serum albumin or WBC.

Adipose Tissue↗
PubMed2003

Relative biological effectiveness and tolerance dose of fission neutrons in canine skin for a potential combination of neutron capture therapy and fast-neutron therapy.

To investigate the potential efficacy of fission neutrons from a fast-neutron reactor for the treatment of radioresistant tumors, the relative biological effectiveness (RBE) and tolerance dose of fission neutrons in canine skin were determined. The forelimbs of 34 healthy mongrel dogs received a single dose of fission neutrons (5.6, 6.8, 8.2, 9.6 or 11 Gy) or 137Cs gamma rays (10, 15, 20, 25 or 30 Gy). Based on observations of radiodermatitis for each radiation, the single-fraction RBE of fission neutrons in the sixth month was calculated as approximately 3. The tolerance doses of fission neutrons and gamma rays, defined as the highest doses giving no moist desquamation on the irradiated skin in the recovery phase, were estimated as 7.6 Gy and 20 Gy, respectively. The tolerance dose of 7.6 Gy of fission neutrons included 5.0 Gy of fast neutrons possessing high anti-tumor effects and 1.4 x 10(12) n/cm2 of thermal neutrons, which could be applicable to neutron capture therapy (NCT). The combination of fast-neutron therapy and NCT using a fast-neutron reactor might be useful for the treatment of radioresistant tumors.

Animals↗
PubMed2003

[Mortality among individuals diagnosed with glucose intolerance by the 75 g oral glucose tolerance test in rural Japanese communities].

OBJECTIVE: To examine mortality among individuals confirmed to have glucose intolerance by the 75 g oral glucose tolerance test (OGTT) in rural communities. METHODS: Subjects were 1,639 residents of seven rural communities in Japan (total population size = 54,000) who underwent an OGTT as a secondary screening test for diabetes during 1987-95 and had received no medication for diabetes at baseline. OGTT results were classified as diabetes (n = 471), impaired glucose tolerance (IGT) (n = 408), or normal glucose tolerance (NGT) (n = 760), according to the recommendations of the American Diabetes Association. Indirect age-adjusted mortality rates and standardized mortality ratios (SMRs) for diabetes and IGT groups were calculated using age-stratified mortality rates for people aged 40-89 in the communities as the standard population. Relative risks of death and 95% confidence intervals (CI) for diabetes and IGT were calculated using Cox's proportional models, adjusted for age and baseline factors such as body mass index (BMI), total cholesterol, hypertension, smoking, alcohol drinking, history of diabetes, and family history of diabetes. RESULTS: During 9.4 years of follow-up, we recorded 70 deaths for the NGT, 46 for the IGT, and 71 for the diabetes group. The SMRs for IGT and diabetic men and women were not significantly increased in comparison with the standard population values. However, when analyzed in our cohort, age-adjusted relative risks of death for IGT and diabetes versus NGT men were 1.10 (9.5% CI: 0.72-1.67) and 1.54 (95% CI: 1.05-2.24), respectively, whereas, the risks among women did not significantly vary. Finally, multivariate analysis, further adjusted for the baseline factors, indicated the relative risk of mortality with diabetes in men to be significantly increased (relative risk = 1.74, 95% CI: 1.11-2.75). CONCLUSION: During follow-up, mortality rates among screened IGT and diabetes were not significantly higher than those in general. Nonetheless, we found that diabetes elevated the risk of death in our cohort, primarily in men.

Adult↗
PubMed2002

Guanine of the third strand of C.G*G triplex serves as an effective hole trap.

We have examined the structural and electronic effects of the one-electron oxidation of the C.GG triplex, where G is located in a quite different environment from the G of duplex DNA. Upon photoirradiation of an external photosensitizer (riboflavin) with the C.GG triplex, oxidative DNA cleavage occurred exclusively at guanine repeat sequences in the third strand of triple helix DNA. Hole transport through the C.GG triplex also occurred, resulting in selective cleavage at G in the third strand. Thus, the hole generated in the duplex can migrate to GGG in the third strand and is trapped exclusively at Gs in the third strand. These experimental results, together with molecular orbital calculations, suggest that the origin of the selective strand cleavage can be explained as follows: (i) guanine repeat sequences in the third strand are more easily oxidized than in duplex DNA and (ii) in their radical cation states, G of the third strand rapidly deprotonates and reacts with oxygen and/or water, leading to strand cleavage. These results indicate that the oxidative damage preferentially occurred at Gs of the third strand owing to thermodynamic and kinetic features of the one-electron oxidation of the C.GG triplex.

Base Pairing↗
PubMed2002

Molecular design of a pyrrole-imidazole hairpin polyamides for effective DNA alkylation.

New hairpin polyamide-CPI (CPI = cyclopropylpyrroloindole) conjugates, compounds 12-14, were synthesized and their DNA-alkylating activities compared with the previously prepared hairpin polyamide, compound 1, by high-resolution denaturing gel electrophoresis with 450 base pair (bp) DNA fragments and by HPLC product analysis of the synthetic decanucleotide. In accord with our previous results, alkylation by compound 1 occurred predominantly at the G moiety of the sequence 5'-AGTCAG-3' (site 3). However, compound 12, in which the structure of the alkylating moiety of compound 1 is replaced with segment A of duocarmycin A DU-86 (CPI), did not show any DNA alkylating activity. In clear contrast, the hairpin CPI conjugate 13, which differs from compound 1 in that it lacks one Py unit and possesses a vinyl linker, alkylated the A of 5'-AGTCAG-3' (site 3) efficiently at nanomolar concentrations. Alkylation by compound 14, which has a vinyl linker, occurred at the A of 5'-AGTCCA-3' (site 6) and at several minor alkylation sites, including mismatch alkylation at A of 5'-TCACAA-3' (site 2). The significantly different reactivity of the alkylating hairpin polyamides 1, 12, 13, and 14 was further confirmed by HPLC product analysis by using a synthetic decanucleotide. The results suggest that hairpin polyamide--CPI conjugate 13 alkylates effectively according to Dervan's pairing rule, and with a new mode of recognition in which the Im-vinyl linker (L) pair targets G-C base pairs. These results demonstrate that incorporation of the vinyl-linker pairing with Im dramatically improves the reactivity of hairpin polyamide--CPI conjugates.

Alkylation↗
PubMed2002

Site-specific discrimination of Cytosine and 5-methylcytosine in duplex DNA by Peptide nucleic acids.

For site-specific discrimination of cytosine (C) and 5-methylcytosine (mC) in duplex DNA, we developed a new method using peptide nucleic acids (PNAs). The combination of a PNA-assisted DNA displacement complex and a fluorescein-labeled probe oligomer allowed the detection of mC at the defined sites in target DNA using a restriction enzyme. After treatment of the complex with a restriction enzyme, strong fluorescence emission was observed for the complex containing C at the target site, whereas the fluorescence intensity for the complex containing mC was extremely weak.

5-Methylcytosine↗
PubMed2002

N(2)-phenyldeoxyguanosine: modulation of the chemical properties of deoxyguanosine toward one-electron oxidation in DNA.

We have shown here that (1) substitution of an exocyclic amino group of dG is effective in modulating the chemical properties of dG toward one-electron oxidation and (2) decomposition of the guanine radical cation was effectively suppressed near dPhG. These results indicate that dPhG is a prototype of nucleosides functioning as an intrinsic antioxidant of duplex DNA toward one-electron oxidation.

Autoradiography↗
PubMed2002

Chemically induced hairpin formation in DNA monolayers.

A naphthyridine dimer that binds specifically to G-G mismatches has been used to induce hairpin formation in oligonucleotides immobilized onto chemically modified gold surfaces. Surface plasmon resonance (SPR) imaging measurements of DNA microarrays were used to demonstrate that binding of the naphthyridine dimer to G-G mismatches within the stem portion of an immobilized 42-mer oligonucleotide could be used to induce hairpin formation that prevented hybridization of DNA complementary to the loop sequence. In addition, the selectivity of the naphthyridine dimer for G-G mismatches was verified through SPR imaging measurements of the hybridization adsorption of an 11-mer oligonucleotide to a four-component DNA array of zero- and single-base mismatch sequences.

Base Sequence↗
PubMed2002

2-Amino-7-deazaadenine forms stable base pairs with cytosine and thymine.

2-Amino-7-deazaadenine ((AD)A) was incorporated into oligodeoxynucleotides (ODN) and their base-pairing properties with natural nucleobases were investigated. In melting temperature (T(m)) experiments, the duplex containing an (AD)A/C base pair showed a high stability comparable to that containing (AD)A/T base pair. Destabilization of the duplex usually observed for existing degenerate bases was not observed. However, the incorporation efficiency of dCTP was only 1.8% for TTP in single-nucleotide insertion reactions using polymerase.

Adenine↗
PubMed2002

Trends in fatal coronary heart disease among people aged 25-74 years in Oita City, Japan, from 1987-1998.

Serum cholesterol has been increasing in recent years in Japan. There is concern that risk of coronary heart disease (CHD) may be increasing too, but there is little information on validated fatal CHD trends in the Japanese population. We identified 1,056 deaths from heart disease and other deaths possibly hiding CHD from death certificates of residents aged 25-74 years in Oita City, Japan in 1987-1988, 1992-1993, and 1997-1998 (mean population, 273,000 in 1997-1998). We validated 994 of them by medical record review and physician interviews, classifying them into definite fatal acute myocardial infarction (AMI) and possible fatal AMI or CHD death based on Monitoring Trends and Determinants in Cardiovascular Disease project's criteria. Sudden death was defined to estimate the number of CHD sudden deaths. In men, age-adjusted mortality rates due to validated fatal CHD remained quite stable over 10 years (25.3 per 100,000 [95% CI, 15.0-35.5] in 1987-1988 to 24.2 per 100,000 [95% CI, 16.1-32.3] in 1997-1998). When 50% or all sudden deaths were included as fatal CHD, the rates for men tended to decline. This was due to decreasing out-of-hospital deaths in connection with a declining CHD death rate among men aged 65-74 years, whereas in-hospital CHD deaths were level. In women, the rate of validated fatal CHD was highest in 1992-1993, but the 1997-1998 rate was similar to the 1987-1988 rate. We did not find that fatal CHD rates increased in Oita men and women from 1987-1998. Rather, out-of-hospital fatal CHD tended to decline in Oita men.

Adult↗
PubMed2002

Modulation of remote DNA oxidation by hybridization with peptide nucleic acids (PNA).

We have examined the efficiency of DNA photooxidation in DNA/PNA duplex and DNA/(PNA)(2) triplex for the first time. DNA/PNA duplex was cleaved at GG steps by external riboflavin with high efficiency like specific GG cleavage in DNA/DNA duplex. However, the 5'G selectivity of the GG oxidation in DNA/PNA duplex was much lower than that observed in DNA/DNA duplex. Remote DNA oxidation of oxidant-tethered DNA/PNA duplex was considerably suppressed. In contrast, the formation of DNA/(PNA)(2) triplex by hybridization with two PNA strands completely inhibited the remote GG oxidation, indicating that PNA acts as an inhibition for remote oxidative DNA damage.

DNA↗
PubMed2002

Suppression of DNA-mediated charge transport by BamHI binding.

A guanine radical cation produced by one-electron DNA oxidation migrates over long distances through the DNA pi-stack. Fundamental questions regarding the likelihood of charge transport in genomic DNA, the effects of protein binding, and its biological consequences arise as the next issues of study. Electronic effects of protein binding on the efficiency of charge transport were investigated for the endonuclease BamHI-DNA complex. Direct contact of a positively charged guanidium group of BamHI to guanines in the recognition sequence 5'-GGATCC-3' completely suppressed one-electron oxidation of the guanine in the protein binding site and dramatically lowered the charge transport efficiency through the sequence. Electronically insulated guanines, by the hydrogen bonding contact of a guanidium group in BamHI, no longer function as a stepping stone in the charge transport through the DNA pi-stack.

Base Pairing↗
PubMed2002

Site-specific hydroxylation at polyguanosine in double-stranded DNA by nickel(II) in the presence of SH compounds: comparison with singlet oxygen-induced DNA damage.

We examined the mechanism of DNA damage induced by carcinogenic Ni(II) in the presence of SH compounds. In the presence of model endogenous SH compounds, dithiothreitol (DTT), 1,4-dithio-L-threitol, and dithioerythritol, Ni(II) induced damage to (32)P-5'-end-labeled DNA fragments obtained from the human c-Ha-ras-1 protooncogene and the p53 tumor suppressor gene. The intensity of Ni(II)-mediated DNA damage induced by DTT was stronger than that by other model endogenous SH compounds, 1,4-dithio-L-threitol and dithioerythritol. DNA damage induced by Ni(II) plus DTT was observed only when the DNA was treated with piperidine, suggesting that Ni(II) plus DTT caused only base damage. Formamidopyrimidine-DNA glycosylase, which is known to recognize 8-oxodG as well as Fapy residues, treatment induced cleavage sites, mainly guanine residues, particularly at the 5'-GG-3', 5'-GGG-3', and 5'-GGGG-3' sequences, in DNA incubated with Ni(II) in the presence of DTT. SOD and catalase inhibited the DNA damage, suggesting that DNA damage involved superoxide anion and hydrogen peroxide. Sodium azide, a potent and relatively specific scavenger of (1)O(2), inhibited DNA damage by Ni(II) in the presence of DTT, whereas the sequence specificity of DNA damage was different from that obtained by (1)O(2) generating agent. The formation of 8-oxodG in calf thymus DNA by Ni(II) was observed with the physiological thiols, dihydrolipoic acid and mercaptopyruvate, as well as with DTT. These results suggest that Ni(II) and DTT form a reactive species, which may be responsible for causing guanine-specific DNA damage. Endogenous SH compounds, which have similar chemical structures to DTT, would participate in nickel carcinogenesis through causing oxidative DNA damage.

Animals↗
PubMed2002

Recognition of DNA mismatch structures.

A dimeric form of 2-amino-1,8-naphthyridine strongly binds to a G-G mismatch by a zigzag intercalation. To gain insight into the mode of recognition for the G-G mismatch, we have synthesized a series of naphthyridine-heterocycle hybrids and evaluated the binding to G-G mismatches. Furthermore, assuming the G-G mismatch as a special variant of the G-X mismatch where X is G, A, and T, a general scheme for the zigzag binding of naphthyridine-heterocycle hybrids to a G-X mismatch was discussed. These structure activity relationships indicate that the zigzag binding of naphthyridine-heterocycle hybrids to a G-X mismatch could be deduced in a two-step sequence.

Base Pair Mismatch↗