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排序方式: 共有148条查询结果,搜索用时 15 毫秒
1.
10 "false negative" chemical carcinogens, i.e. ineffective in bacterial mutagenicity assays, were thoroughly investigated for their genotoxic activity in the mould Aspergillus nidulans. Forward mutations (methionine suppressors), mitotic crossing-over and chromosome malsegregation were the end-points scored. Positive results were obtained in tests for the induction of mitotic segregation with benzene, ethylenethiourea and urethane, which increased the frequency of abnormal presumptive aneuploid colonies with euploid sectors showing whole chromosome segregation (i.e. non-disjunctional diploids and haploids). The same compounds were ineffective in increasing the frequency of mitotic crossing-over or forward mutations. The other chemical carcinogens investigated, namely acetamide, amitrole, dieldrin, heptachlor epoxide, nitrilotriacetic acid, p,p'-DDT and thiourea were ineffective both as inducers of forward mutations and mitotic segregation. 相似文献
2.
Thirteen pesticides, aminotriazole, benomyl, captafol, captan, dalapon-Na, dichlorvos, dinobuton, dodine, ioxynil, mecoprop, neburon, picloram and tordon were tested for ability to induce (1) point mutations to 8-azaguanine resistance, (2) mitotic crossing-over, and (3) mitotic non-disjunction and haploidization in Aspergillus nidulans. Tests were performed at three different pHs, i.e. 4.5, 7, 8.2. Three of the pesticides, captan , captafol and dichlorvos induced point mutations; dichlorvos also induced a high frequency of mitotic crossing-over and non-disjunction; benomyl induced a very high frequency of non-disjunction whereas aminotriazole induced weakly both types of somatic segregation. 相似文献
3.
4.
The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30?kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected. 相似文献
5.
Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation. 相似文献
6.
Lucaccioni A Morpurgo G Achilli A Barberio C Casalone E Babudri N 《Folia microbiologica》2007,52(1):35-38
The effect of colony density on the dimorphic switch was determined in natural strains of Saccharomyces cerevisiae. In some strains invasiveness and pseudohyphal (PH) growth were highly sensitive to colony density; moreover, strains constitutively able to invade the substrate with PH formation positively influenced the invasiveness but not the PH growth of a different strain less prone to the dimorphic switch. 相似文献
7.
L Morpurgo I Savini G Gatti M Bolognesi L Avigliano 《Biochemical and biophysical research communications》1988,152(2):623-628
A very pure ascorbate oxidase solution was obtained by dissolving a crystalline sample of the enzyme. The ratio between 280 and 610 nm absorbancies was 22.5. It contained 8.0 +/- 0.2 Cu ions, 50% EPR detectable, per dimeric molecule (140,000 M.W.) with a molar extinction coefficient of 10,000 cm-1 at 610 nm. Two Cu ions were removed by treatment with N,N-diethyldithiocarbamate. The optical blue absorption band was unaffected, while two EPR detectable Cu ions were lost, with disappearance of the type 2 Cu signal. It is concluded that native ascorbate oxidase contains two type 1, two type 2, and four type 3 Cu ions. 相似文献
8.
Giovanna De Matteis Enzo Agostinelli Bruno Mondovì L. Morpurgo 《Journal of biological inorganic chemistry》1999,4(3):348-353
Bovine serum amine oxidase (BSAO) reacts with 2-hydrazinopyridine, which binds the organic cofactor 2,4,5-trihydroxyphenylalanine
quinone, forming a band at 435 nm. The band shifts to 526 nm around 60 °C, to 415 nm upon denaturation, but only shifts to
429 nm upon Cu2+ depletion. Its wavelength and intensity suggest that the adduct has the azo conformation, whilst the same adduct of crystallineEscherichia coli amine oxidase (ECAO) shows the hydrazone conformation in the X-ray structure. The steady state kinetics of aminomethyl- and
aminoethylpyridines confirm that the formation of the product Schiff base, analogous to the azo form of the 2-hydrazinopyridine
adduct, is not hindered in solution. The structural stability of the adduct in the absence of Cu2+ is taken to imply hydrogen bonding of the pyridyl nitrogen to a conserved aspartate, as in the ECAO adduct. Thus the ECAO
adduct provides a good model for a transient intermediate leading to formation of the BSAO azo adduct. On the basis of this
model and of the catalytic competence of Co2+-substituted BSAO, confirmed by the present data, a catalytic reaction scheme is proposed.
Received: 2 December 1998 / Accepted: 22 March 1999 相似文献
9.
Morpurgo M Monfardini C Hofland LJ Sergi M Orsolini P Dumont JM Veronese FM 《Bioconjugate chemistry》2002,13(6):1238-1243
The effects of the type and location of polymer grafting on the biological activity of different mono-PEG derivatives of the somatostatin analogue RC160 were evaluated. A chemical strategy to obtain mono-PEG alkylation or acylation of the peptide's alpha-terminal or lysil-epsilon primary amines was devised. Selective BOC protection of the two available primary amines, followed by reaction with two different PEG reagents and removal of the protecting group, was carried out. Chemical characterization, structural studies, and the evaluation of the biological activity of the bioconjugates synthesized allowed the identification of the one having characteristics more suitable for therapeutic application. This corresponds to the mono-epsilon-lysil-pegylated form, obtained by reductive alkylation, where the amine's positive charge is preserved. The results obtained suggest the importance of preliminary studies in the development of new polymer-peptide conjugates with improved pharmacological properties. 相似文献
10.