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排序方式: 共有106条查询结果,搜索用时 31 毫秒
1.
The pyrogallol related compounds reduce UV-induced mutations in Escherichia coli B/r WP2 总被引:1,自引:0,他引:1
Plant components with bio-antimutagenic activity were screened on UVC (254 nm)-induced mutagenesis using E. coli B/r WP2. The components with a pyrogallol moiety including gallic acid, (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) reduced the mutation induction, but other components such as caffeic acid, chlorogenic acid and quercetin did not. The above compounds with a pyrogallol moiety were also effective on UVAB (295-400 nm)-induced mutagenesis, while they showed little effect on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced mutagenesis. As this bio-antimutagenic effect was not seen in the DNA excision-repair-deficient strains WP2s and ZA159, the activity by the above plant components might be based on the promotion of the excision-repair system in E. coli B/r WP2. 相似文献
2.
UV-induced mutagenesis in Escherichia coli B/r WP2 was enhanced by certain derivatives of methyl cinnamate which themselves were not mutagenic. Methyl ferulate, methyl isoferulate and methyl sinapate showed this effect markedly. Such an enhancement effect was absent with the derivatives of cinnamic acid and ethyl cinnamate and was not observed in Escherichia coli WP2s uvrA. Methyl sinapate also enhanced 4NQO-induced mutation and suppressed liquid-holding recovery in the above repair-proficient strain. The presence of methyl sinapate in plating agar medium decreased the survival of UV-irradiated cells of a recombination-repair-deficient strain, CM571 recA. However, the effect was not observed with those of WP2s uvrA. In an in vitro experiment in which the removal rate of thymine dimers was measured, methyl sinapate clearly inhibited this repair event. From these results, we conclude that methyl sinapate inhibits DNA excision repair, thus enhancing UV mutagenicity. 相似文献
3.
A series of isogenic transformable strains of Bacillus subtilis carrying the uvr-19 or rec-43 mutation or both were constructed. Both mutations made competent cells defective in repairing UV-irradiated cellular or transforming DNA, and their effects were additive in a doubly deficient strain, suggesting that two repair processes, requiring uvr-19+ and rec-43+ gene products, are independently functional in competent cells of B. subtilis. 相似文献
4.
Summary Sporulation and competent cell formation have been studied in four Bacillus subtilis strains, carrying septum-initiation mutations of different loci, div-31, div-341, div-12 and div-355 which exhibit filamentous growth at 45° C. The div-31 mutant was found to be defective in competence development at 30°–40°C whereas the div-12 mutant was affected only slightly. The div-341 and div-355 mutants showed lower competence, particularly at the higher temperatures. The four div mutant strains all showed poor sporulation at higher temperatures compared to the wild-type strain. We propose that some of the initial steps of septation are involved both in sporulation (possibly in forespore septum formation) and in competent cell formation and that these two processes share certain common features distinct from those in vegetative cell division. 相似文献
5.
Antimutagenic effects of cinnamaldehyde on mutagenesis by chemical agents were investigated in Escherichia coli WP2 uvrA- trpE-. Cinnamaldehyde, when added to agar medium, greatly reduced the number of Trp+ revertants induced by 4-nitroquinoline 1-oxide (4-NQO) without any decrease of cell viability. This antimutagenic effect could not be explained by inactivation of 4-NQO caused by direct interaction with cinnamaldehyde. Mutagenesis by furylfuramide (AF-2) was also suppressed significantly. Mutations induced by methyl methanesulfonate (MMS) and ethyl methanesulfonate (EMS) were slightly inhibited. However, cinnamaldehyde was not at all effective on the mutagenesis of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Two derivatives of cinnamaldehyde, cinnamyl alcohol and trans-cinnamic acid, did not have as strong antimutagenic effects on 4-NQO mutagenesis as cinnamaldehyde had. Because cinnamaldehyde showed marked antimutagenic effects against mutations induced by UV-mimic mutagens but not those induced by MNNG or EMS, it seems that cinnamaldehyde might act by interfering with an inducible error-prone DNA repair pathway. 相似文献
6.
Kunie Yoshikawa Takehiko Nohmi Rumiko Miyata Motoi Ishidate Jr. Naoki Ozawa Masakazu Isobe Tadashi Watabe Tuneo Kada Takashi Kawachi 《Mutation research》1982,96(2-3)
Comparison studies for detecting differences between liver microsome and S9 preparations from 4 strains (Donryu, Fischer, Sprague-Dawley, Wistar) of young male rats were carried out with pretreatment of the animals by inducers such as PCBs and PB plus 5,6-BF. Each microsome fraction was assayed for the enzymic activity of metabolism of model substrates such as aniline, benzophetamine, BP, DMN and 7-ethoxycoumarin. The hepatic S9 sample was also compared, as regards its metabolizing ability to activate 9 pre-mutagens (2AA, AAF, o-AAT, BP, DAB, DMBA, DMN, m-PDA, quinoline) to directly acting mutagens in the Salmonella/hepatic S9 activation test by using TA98, TA100 and TA1537 strains with or without cytochrome P450 inhibitors (SKF-525A, metyrapone, 7,8-benzoflavone).In the enzymic assay with PCBs-induced microsomes, BP hydroxylation revealed a strain-specific difference: the microsomes from Fischer and Wistar rats were more effective for metabolizing BP than those from the other strains of rat. The effect of induction by PB plus 5,6-BF for Fischer rats showed relatively higher enzymic activity in the same induction group. Other microsomes prepared from rats with and without induction by PB plus 5,6-BF did not show a clear-cut strain dependency in the enzymic activities assayed.In the mutation experiments with hepatic S9 samples, the examination of DAB and quinoline revealed a marked strain difference when S9 samples prepared from PCBs-pretreated and PB-plus-5,6-BF-induced rats were used: the S9 sample from Fischer rats was available for activating the two pre-mutagens to directly acting mutagens. No marked difference in the metabolic activation of the remaining 7-pre-mutagens was observed on other S9 preparations.In examinations of mutagenicity activities with the use of three inhibitors, the two S9 preparations made with the two induction methods showed inhibition profiles closely similar to each other. However, there were minor differences in the profiles by these inhibitors.From these findings it was concluded that Fischer rat-liver S9 is useful for detecting mutagens in the metabolic activation test, when induction by PB plus 5,6-BF was used in the Ames Salmonella test. 相似文献
7.
The detection of DNA-damaging agents by repair-deficient bacterial assays is based on the differential inhibition of growth of repair-proficient and repair-deficient bacterial pairs. The various methodologies used are described and recommendations are made for their improved use. In a survey of the literature through April 1979, 91 of 276 papers evaluated contained usable data, resulting in an analysis of 611 compounds that had been assayed in 1 or more of 55 pairs of repair-proficient and repair-deficient strains. The results indicate that (1) a liquid suspension assay is more sensitive than a spot (diffusion) test. In a review of the Escherichia coli polA assay, 45 compounds that gave "No Test" in the spot test were clearly positive or negative in the liquid suspension assay. (2) Of the 21 compounds analyzed by the E. coli polA assay and by other E. coli repair-deficient strains (e.g., rec, uvr, hcr, and exr derivatives of WP2 and AB1157), 10 were in complete agreement in all strains except uvrA strains. This indicates that strains other than polA+/polA- are useful for detecting DNA-damaging agents. However, in selecting strains for use in these assays, care should be taken to consider repair pathway specificity for particular compounds. (3) There was a 78% correspondence between results obtained with E. coli polA and Bacillus subtilis (H17/M45, 17A/45T) rec assay and between E. coli polA and Proteus mirabilis. (4) In a comparison of test results with carcinogenicity data, 44 of 71 (62%) carcinogenic compounds assayed by the polA system were positive, 10 (14%) were negative, and 17 (24%) gave No Test or doubtful results. 7 carcinogens were assayed by other E. coli strains and all were positive. 56 carcinogens were assayed in B. subtilis: 24 (43%) were positive, 9 (16%) were negative, and 23 (41%) gave No Test or doubtful results. Of the 7 carcinogens assayed in P. mirabilis, 6 (86%) were positive and 1 (14%) was negative. (5) The results were analyzed with respect to chemical classes. E. coli polA detected the highest percentage of hydroxylamines and alkyl epoxides. The B. subtilis rec assay detected the highest percentage of nitrosamines and sulfur and nitrogen oxides. It is concluded that some of these test systems are effective tools for the detection of DNA-damaging and potentially carcinogenic compounds, especially if the assay is done in liquid suspension and if more than 1 pair of tester strains is used. Advantages and disadvantages of the assay are discussed and suggestions are made for improvements in the system. 相似文献
8.
Gruber HJ Hahn CD Kada G Riener CK Harms GS Ahrer W Dax TG Knaus HG 《Bioconjugate chemistry》2000,11(5):696-704
This study provides a critical examination of protein labeling with Cy3, Cy5, and other Cy dyes. Two alternate situations were tested. (i) Antibodies were covalently labeled with Cy dye succinimidyl ester at various fluorophore/protein ratios and the fluorescence of the labeled antibodies was compared to that of free Cy dye. (ii) Fluorescent biotin derivatives were synthesized by derivatizing ethylenediamine with one biotin and one Cy3 (or Cy5) residue. The fluorescence properties of these biotin-Cy dye conjugates were examined at all ligand/(strept)avidin ratios (0 = n = 4). The results showed an astounding discrepancy between Cy3 and Cy5: Cy3-labeled antibodies fluoresced very well, even at high Cy3/protein ratios, and the same applied to (strept)avidin with up to four bound biotin-Cy3 conjugates. In contrast, antibodies with six covalently bound Cy5 labels (obtained with the recommended procedure) were almost nonfluorescent, only at 2-3 Cy5 labels/IgG some moderate fluorescence was obtained. By analogy, the biotin-Cy3 conjugate fluoresced intensely, even at high ligand/avidin ratio, in contrast to the weakly fluorescing biotin-Cy5 conjugate. Three mechanisms are responsible for the discrepancy between Cy3 and Cy5. (i) Attachment of Cy3 to a protein's surface causes an anomalous enhancement in fluorescence (by 2-3-fold) while no enhancement occurs with Cy5. (ii) Mutual quenching of IgG-bound Cy dyes by resonance energy transfer is much more pronounced for Cy5 labels than for Cy3. (iii) In IgG with six bound Cy5 labels, about one-third of the labels adopt a nonfluorescent state which is characterized by a large UV-vis absorption maximum at 600 nm instead of at 650 nm. Cy3.5 was found to mimick the properties of Cy3, while Cy7, and to some extent also Cy5.5, were similar to Cy5. In conclusion the Cy dye series is divided into two groups: Antibodies with multiple Cy3 or Cy3.5 labels yield bright fluorescence while extensive quenching occurs in antibodies labeled with Cy5 and Cy7. 相似文献
9.
Genetic evidence for posterior specification by convergent extension in the Xenopus embryo 总被引:2,自引:2,他引:0
Genetic studies substantiate that mesodermal convergent extension expressed behind the anteroposterior borderline, in the form of a gradient with the posterior apex after gastrulation, regulates morphogenesis of the posterior zone at the dorsal and dorso-lateral levels which is in full agreement with the model of dorsalization–caudalization. In contrast, how anteroposterior specification of mesodermal tissues occurs at the ventral and latero-ventral levels is not yet understood. 相似文献
10.