Self-repair of thymine dimer in duplex DNA.
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Base Composition↗
Biomedical subjects
Takeo Ito
Publications and source records attributed to Takeo Ito.
Photoinduced reductive repair of thymine glycol: implications for excess electron transfer through DNA containing modified bases.
Photoinduced reduction of thymine glycol in oligodeoxynucleotides was investigated using either a reduced form of flavin adenine dinucleotide (FADH(-)) as an intermolecular electron donor or covalently linked phenothiazine (PTZ) as an intramolecular electron donor. Intermolecular electron donation from photoexcited flavin (FADH(-)) to free thymidine glycol generated thymidine in high yield, along with a small amount of 6-hydroxy-5,6-dihydrothymidine. In the case of photoreduction of 4-mer long single-stranded oligodeoxynucleotides containing thymine glycol by *FADH(-), the restoration yield of thymine was varied depending on the sequence of oligodeoxynucleotides. Time-resolved spectroscopic study on the photoreduction by laser-excited N,N-dimethylaniline (DMA) suggested elimination of a hydroxyl ion from the radical anion of thymidine glycol with a rate constant of approximately 10(4) s(-1) generates 6-hydroxy-5,6-dihydrothymidine (6-HOT(*)) as a key intermediate, followed by further reduction of 6-HOT(*) to thymidine or 6-hydroxy-5,6-dihydrothymdine (6-HOT). On the other hand, an excess electron injected into double-stranded DNA containing thymine glycol was not trapped at the lesion but was further transported along the duplex. Considering redox properties of the nucleobases and PTZ, competitive excess electron trapping at pyrimidine bases (thymine, T and cytosine, C) which leads to protonation of the radical anion (T(-)(*), C(-)(*)) or rapid back electron transfer to the radical cation of PTZ (PTZ(+)(*)), is presumably faster than elimination of the hydroxyl ion from the radical anion of thymine glycol in DNA.
DNA↗
Product and pulse radiolysis studies on radical-ion splitting of N(1)-C(5')-linked dimer hydrates of 5-substituted uracils by one-electron reduction in anoxic aqueous solution.
Steady-state gamma-radiolysis, pulse radiolysis, and cyclic voltammetry have been performed to identify the mechanism by which N(1)-C(5')-linked homodimer hydrates [1-(6'-hydroxy-5',6'-dihydrothymin-5'-yl)thymine (2a) and [1-(5'-fluoro-6'-hydroxy-5',6'-dihydrouracil-5'-yl)-5-fluorouracil (2b)], N(1)-C(6')-linked dimer hydrate [1-(5'-hydroxy-5',6'-dihydrothymin-6'-yl)thymine (3a)], and N(1)-C(5')-linked heterodimer hydrate [1-(6'-hydroxy-5',6'-dihydrothymin-5'-yl)-5-fluorouracil (2ba)] undergo radiolytic reductive splitting to regenerate the parent monomers in anoxic aqueous solution. Radiolytic reductions of the thymine homodimer hydrates 2a and 3a by hydrated electrons (e(aq)-) regenerated the parent thymine (1a) almost quantitatively, while the 5-fluorouracil homodimer hydrates cis-2b and trans-2b afforded 1-(uracil-5'-yl)-5-fluorouracil efficiently along with a small amount of the parent 5-fluorouracil (1b). In contrast to 2b, the heterodimer hydrate analogue 2ba with noneliminating 5'-methyl substituent releases 5-fluorouracil 1b almost quantitatively in the radiolytic reduction. The pulse radiolysis studies suggested that the electron adducts are produced primarily at the thymine and 5-fluorouracil structural unit in the dimer hydrates 2a,b, respectively, in which the resulting dimer hydrate radical anion of 2b (2b*-) was more stable than that of 2a (2a*-). As characterized by pulse radiolysis and cyclic voltammetry, the 5-fluorouracil homodimer hydrate 2b bearing F-substituent at C(5') undergoes one-electron reduction to eliminate exclusively fluoride ion along with the formation of dimer hydrate C(5') radical (2b(-F)*) with oxidizing property. The formation of a possible dimer hydrate radical intermediate 2b(-F)* was also supported by the effect of amines as the reducing additives on the yields of 1b and 4b in the radiolytic reduction of 2b.
Journal Article↗
Links between bronchial asthma and allergic rhinitis in the Oita Prefecture, Japan.
Recent studies have strengthened the concept that bronchial asthma and allergic rhinitis are manifestations of an inflammatory process within a continuous airway. This study was performed to compare clinical findings in asthma with or without rhinitis in Japan. Nasal symptoms were present in 99.6% of asthma patients. The prevalence of allergic rhinitis in patients with asthma was 52.4%. Bronchial asthma attacks in one third of patients with rhinitis were coincident with worsening of nasal symptoms. In adults (> 16 years of age), rhinitis frequently preceded asthma, whereas asthma preceded rhinitis in children (< 16 years of age). The frequency of rhinitis in asthma decreases with increasing age. This study demonstrated a clear link between upper and lower airway disorders in Japan.
Asthma↗
[A case of drug-induced pneumonitis due to bepridil].
A 66-year-old man had been given bepridil for the treatment of atrial fibrillation since April 28, 2002. The patient developed exertional dyspnea with hypoxemia in the middle of June 2002 and was admitted to our hospital. The chest X-ray and chest CT scans showed diffuse reticulonodular infiltrates in the lower lung fields. Pulmonary function tests revealed depletion of diffusion capacity for carbon monoxide. Bronchoalveolar lavage fluid contained increased percentages of lymphocytes, neutrophils and eosinophils, and a CD4/8 ratio was low. The transbronchial lung biopsy specimens demonstrated alveolar septal thickening with infiltration of mononuclear cells and intraalveolar organization. As drug-induced pneumonitis was suspected, bepridil was discontinued, resulting in improvement of dyspnea and hypoxemia. The patient was then treated with corticosteroid, which led to complete resolution of infiltration on chest X-ray. According to the clinical data consistent with drug-induced pneumonia, the prompt improvement after cessation of bepridil and the absence of other possible causes, we diagnosed this case as bepridil-induce pnemonitis.
Aged↗
Recognition of guanines at a double helix-coil junction in DNA by a trinuclear copper complex.
Coordination between guanine N7 and a trinuclear copper complex appears critical for selective and efficient strand scission of DNA at a helix-coil junction as indicated by the lack of reactivity of comparable DNA containing 7-deazaguanine in place of guanine; both the base pair at the junction and coil flexibility also modulate the specificity of DNA oxidation.
Copper↗
Synthesis and photochemical properties of photoactivated antitumor prodrugs releasing 5-fluorouracil.
A new family of antitumor prodrugs (1-3) of 5-fluorouracil (5-FU) possessing photolabile 2-nitrobenzyl chromophores have been designed and synthesized to investigate the efficiency and mechanism of photoactivated 5-FU release upon UV-irradiation at lambda(ex)= 365 nm. The photoactivated prodrug 3 derived from conjugation of 2 with a tumor-homing cyclic peptide Cys-Asn-Gly-Arg-Cys (CNGRC) was so designed as to manifest a tumor-targeting function.
Anisoles↗
[A case of sarcoidosis manifesting as acute febrile polyarthritis following bronchoalveolar lavage].
A 32-year-old man was incidentally found to have abnormal shadows on a chest X-ray film and was admitted on May 2004. His chest images showed mediastinal and bilateral hilar lymphadenopathy. The serum level of angiotensin-converting enzyme was elevated. We also found non-caseating epithelioid cell granulomas in transbronchial lung biopsy specimens, and confirmed the diagnosis of sarcoidosis. We carried out bronchoalveolar lavage (BAL) for evaluation of disease activity of sarcoidosis. After BAL, he suffered high fever and polyarthralgia. Both ankles were extremely inflamed. We suspected infectious arthropathy caused by atypical pathogens and thus administered antibiotics, but they had no effect at all. Also, no findings suggesting collagen-vascular disorders, including rheumatoid arthritis, were detected. His symptoms improved after three-weeks of treatment with non-steroidal anti-inflammatory drugs. Thus, this case was diagnosed as having acute sarcoid polyarthritis. BAL may have influenced the onset of febrile arthritis in this patient This case indicates that sarcoidosis should be considered as a possible cause of acute febrile polyarthritis.
Acute Disease↗
Reductive electron injection into duplex DNA by aromatic amines.
An assay based on photoinduced reaction and subsequent cleavage of duplex DNA containing a bromodeoxyuridine ((Br)U) residue and an abasic site was developed to screen aromatic amines for their ability to initiate charge transfer by reductive electron donation. Two candidates, N,N,N',N'-tetramethyl-1,5-diaminonaphthalene (TMDN) and 1,5-diaminonaphthalene (DAN), expressed the desired activity, and an oligodeoxynucleotide-TMDN conjugate was subsequently prepared to identify additional variables affecting the efficiency of electron injection and transfer into DNA. This system demonstrated only mild sensitivity to molecular oxygen but was strongly inhibited by high concentrations of 2-mercaptoethanol. The nucleobase counter to the attached TMDN strongly modulated charge transfer as evident by a 60-fold decrease in reduction of the distal (Br)U when the counterbase A was substituted for C. An inverse relationship between this reduction and quenching of TMDN fluorescence by the counterbase was also discovered and is consistent with a competition between radical recombination and electron migration away from the initial site of its injection into DNA.
2-Naphthylamine↗
Criteria for efficient transport of excess electrons in DNA.
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Base Sequence↗
Excess electron transfer from an internally conjugated aromatic amine to 5-bromo-2'-deoxyuridine in DNA.
DNA duplexes containing an N,N,N',N'-tetramethyl-1,5-diaminonaphthalene analogue and 5-bromo-2'-deoxyuridine (BrdU) provide a readily accessible system for investigating excess electron transfer in DNA. Photoexcitation of the aromatic amine (lambda > 335 nm) induces reductive electron transfer as observed by strand cleavage adjacent to the BrdU residue. The weak exponential distance dependence (0.3 A-1) of electron transfer determined for this system of mixed dA-T and dG-dC base pairs suggests that thermally activated electron hopping is competitive with proton transfer within the dG.dC radical anion. The UV-dependent transfer of excess electrons and subsequent strand cleavage proceeds equivalently under anaerobic and aerobic conditions and is not sensitive to e-(aq) or hydroxyl radical trapping agents.
Amines↗
Use of an infrared sensor system to take long-term bedside measurements of rest-activity patterns in the elderly with dementia.
In order to study long-term rest-activity patterns of elderly residents in care facilities, an infrared sensor system was developed. This sensor system detects a resident's presence or absence from their bed and their activity with little inconvenience. Using this system, the rest-activity patterns of two elderly people with dementia was assessed over a period of 3 months. For both subjects, frequent activity peaks and absences from their beds were often observed during the night. Such a sensor system will be useful for evaluating the sleep-wake rhythms of people with sleep disorders.
Activity Cycles↗