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排序方式: 共有266条查询结果,搜索用时 31 毫秒
21.
Metabolism of carcinogenic urethane to nitric oxide is involved in oxidative DNA damage 总被引:6,自引:0,他引:6
Carcinogenic urethane (ethyl carbamate) forms DNA adduct via epoxide, whereas carcinogenic methyl carbamate can not. To clarify a mechanism independent of DNA adduct formation, we examined DNA damage induced by N-hydroxyurethane, a urethane metabolite, using 32P-5'-end-labeled DNA fragments. N-hydroxyurethane induced Cu(II)-mediated DNA damage especially at thymine and cytosine residues. DNA damage was inhibited by both catalase and bathocuproine, suggesting a role for H(2)O(2) and Cu(I) in DNA damage. Free (*) OH scavengers did not inhibit the DNA damage, although methional did inhibit it. These results suggest that reactive species, such as the Cu(I)-hydroperoxo complex, cause DNA damage. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) was increased by N-hydroxyurethane in the presence of Cu(II). When treated with esterase, N-hydroxyurethane induced 8-oxodG formation to a similar extent as that induced by hydroxylamine. Enhancement of DNA cleavages by endonuclease IV suggests that hydroxylamine induced depurination. Furthermore, hydroxylamine induced a significant increase in 8-oxodG formation in HL-60 cells but not in its H(2)O(2)-resistant clone HP 100 cells. o-Phenanthroline significantly inhibited the 8-oxodG formation in HL-60 cells, confirming the involvement of metal ions in the 8-oxodG formation by hydroxylamine. Electron spin resonance spectroscopy, utilizing Fe[N-(dithiocarboxy)sarcosine](3), demonstrated that nitric oxide (NO) was generated from hydroxylamine and esterase-treated N-hydroxyurethane. It is concluded that urethane may induce carcinogenesis through oxidation and, to a lesser extent, depurination of DNA by its metabolites. 相似文献
22.
Fertilization by intracytoplasmic injection of mature sperm into mature eggs has previously been achieved in the sawfly, Athalia rosae (Insecta, Hymenoptera). In the present study, we examined the potential of spermatids, premature male gametes, for participating in development. When round spermatids and elongating spermatids from pupal testes were injected into the anterior end of mature eggs, about 5% of the total injected eggs developed into chimeric embryos (independent participation in development of the egg and spermatid nuclei). Some of them developed further, hatched, and pupated, with 1-2% of the total injected eggs becoming haploid chimeric male adults in which both the egg-derived and injected spermatid-derived nuclei contributed to the germline. No fertilized embryos were obtained by these injections. Elongated spermatids (immature sperm) from newly eclosed adult male testes upon injection did produce fertilized embryos that developed into normal diploid females (about 7% of the total injected). These results indicate that insect spermatids (round and elongating) have the potential to participate in development, but only independently of the egg nucleus. J. Exp. Zool. 286:181-192, 2000. 相似文献
23.
Nawa A Nishimori K Lin P Maki Y Moue K Sawada H Toh Y Fumitaka K Nicolson GL 《Journal of cellular biochemistry》2000,79(2):202-212
24.
Veridiano AM Garcia EA Pinheiro MC Nishimori FY Toledo OM Joazeiro PP 《Cell and tissue research》2007,330(1):161-167
Marked changes in mice pubic symphysis occur by the end of pregnancy. Tissue remodeling involves a dynamic balance between
cell proliferation and programmed cell death as well as changes in the extracellular matrix components. Therefore, it is important
to consider both of these cellular behaviors when investigating the mechanism that regulates interpubic tissue remodeling,
growth during late pregnancy and partus ensuring involution during the postpartum period. Proliferating and programmed death
cells were identified by immunohistochemistry (proliferating cell nuclear antigen and TUNEL detection, respectively) and the
rates at which these processes occurred were determined by morphometric analysis. The results demonstrated that cellular proliferation
was intense during the period of ligament formation, from D15 to D18, thereafter abruptly declining on D19. From parturition
(D19) onwards, an ever-increasing decline in the cellular proliferation levels could be observed. The quantitative analyses
of cellular death showed opposite results when compared to cellular proliferation. During early pregnancy the cycle of cellular
renovation was clearly proliferative and during late mouse pregnancy the cycle was directed by programmed cellular death.
Although the high levels of cellular death during postpartum involution could be shown by the TUNEL-positive cells, we were
unable to observed picnotic nucleus at the light microscopy. 相似文献
25.
Nishimori I Onishi S Vullo D Innocenti A Scozzafava A Supuran CT 《Bioorganic & medicinal chemistry》2007,15(15):5351-5357
The secretory isozyme of human carbonic anhydrase (hCA, EC 4.2.1.1), hCA VI, has been cloned, expressed, and purified in a bacterial expression system. The kinetic parameters for the CO(2) hydration reaction proved hCA VI to possess a k(cat) of 3.4 x 10(5)s(-1) and k(cat)/K(M) of 4.9 x 10(7)M(-1)s(-1) (at pH 7.5 and 20 degrees C). hCA VI has a significant catalytic activity for the physiological reaction, of the same order of magnitude as the ubiquitous isoform CA I or the transmembrane, tumor-associated isozyme CA IX. A series of amino acids and amines were shown to act as CA VI activators, with variable efficacies. l-His, l-Trp, and dopamine showed weak CA VI activating effects (K(A)s in the range of 21-42 microM), whereas d-His, d-Phe, l-DOPA, l-Trp, serotonin, and some pyridyl-alkylamines were better activators, with K(A)s in the range of 13-19 microM. The best CA VI activators were l-Phe, d-DOPA, l-Tyr, 4-amino-l-Phe, and histamine, with K(A)s in the range of 1.23-9.31 microM. All these activators enhance k(cat), having no effect on K(M), participating thus in the rate determining step in the catalytic cycle, the proton transfer reactions between the enzyme active site and the environment. 相似文献
26.
Increasing evidence reveals the carcinogenicity of UVA radiation. We demonstrated that UVA-irradiated NADH induced damage to (32)P-labeled DNA fragments obtained from the p53 gene in the presence of Cu(II). Formamidopyrimidine glycosylase (Fpg)-sensitive lesions were formed at guanine residues, whereas piperidine-labile lesions occurred frequently at thymine residues. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), upon UVA exposure in the presence of Cu(II), increased depending on NADH concentration. Catalase and bathocuproine, a Cu(I)-specific chelator, inhibited the DNA damage, suggesting the involvement of reactive species derived from H(2)O(2) and Cu(I). UVA-irradiated riboflavin induced DNA cleavage through electron transfer at 5' guanine of the 5'-GG-3' sequence with both Fpg and piperidine treatments; Fpg induced less cleavage at the guanine residues than piperidine. These results imply that NADH may participate as an endogenous photosensitizer in UVA carcinogenesis via H(2)O(2) generation, producing metal-mediated mutagenic lesions such as 8-oxodG. 相似文献
27.
Sasaki H Nonaka J Sasaki T Nakai Y 《Journal of industrial microbiology & biotechnology》2007,34(2):105-110
We isolated ammonia-assimilating microorganisms from the livestock manure treatment systems and evaluated their ammonia-assimilating
ability. Many isolates utilized ammonia at high rates when they were purely cultivated in a nitrogen-limited medium to which
sterilized lagoon extract had been added. Some isolates that were immobilized in polyvinyl alcohol (PVA) utilized ammonia
present in the media containing viable lagoon microorganisms. Staining with 4′,6′-diamidino-2-phenylindole (DAPI) indicated
that the immobilized high ammonia-assimilating isolates grew dominantly within the PVA beads. High ammonia-assimilating isolates
in the mixed culture containing viable lagoon microorganisms were identified as Pseudomonas spp. and member of Rhizobiaceae species by partial sequencing of the 16S ribosomal DNA. 相似文献
28.
Vullo D Nishimori I Minakuchi T Scozzafava A Supuran CT 《Bioorganic & medicinal chemistry letters》2011,21(12):3591-3595
Two new β-carbonic anhydrases (CAs, EC 4.2.1.1) from the bacterial pathogen Salmonella enterica serovar Typhimurium, stCA 1 and stCA 2, were characterized kinetically. The two enzymes possess appreciable activity as catalysts for the hydration of CO2 to bicarbonate, with kcat of 0.79 × 106 s−1 and 1.0 × 106 s−1, and kcat/Km of 5.2 × 107 M−1 s−1 and of 8.3 × 107 M−1 s−1, respectively. A large number of simple/complex inorganic anions as well as other small molecules (sulfamide, sulfamic acid, phenylboronic acid, phenylarsonic acid, dialkyldithiocarbamates) showed interesting inhibitory properties towards the two new enzymes, with several low micromolar inhibitors discovered. As many strains of S. enterica show extensive resistance to classical antibiotics, inhibition of the β-CAs investigated here may be useful for developing lead compounds for novel types of antibacterials. 相似文献
29.
Hiraku Sasaki Hiroki Ishikawa Toru Sato Satoshi Sekiguchi Hiromi Amao Eiichi Kawamoto Tetsuya Matsumoto Kazuhiko Shirama 《BMC microbiology》2011,11(1):55
Background
Pasteurella pneumotropica is a ubiquitous bacterium that is frequently isolated from laboratory rodents and causes various clinical symptoms in immunodeficient animals. Currently two RTX toxins, PnxIA and PnxIIA, which are similar to hemolysin-like high-molecular-weight exoproteins are known in this species. In this study, we identified and analyzed a further RTX toxin named PnxIIIA and the corresponding type I secretion system. 相似文献30.
Takeshi Kikko Yoshitaka Kataoka Katsuhiro Nishimori Yasuhiro Fujioka Yoshiaki Kai Kouji Nakayama Toshihide Kitakado 《Ichthyological Research》2011,58(4):370-376
Size at maturity of fluvial white-spotted charr, Salvelinus leucomaenis, was studied in small headwater tributaries of nine rivers around the Lake Biwa water system, Japan. Threshold size at maturity
in both sexes showed significant positive relationships with water discharge, indicating that smaller threshold sizes at maturity
of fluvial white-spotted charr occurred in smaller habitats. These results provide a link between size at maturity and habitat
size and have important implications for the management of both habitats and white-spotted charr populations. 相似文献