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41.
Abstract Rheocricotopus (Psilocricotopus) taiwanensis sp. n. from Taiwan, China, is described as male imagines. The species is allied to R. (P.) chalybeatus (Edwards) but it is easily separated from the latter in lacking setae in all reins, much lower AR and more pronounced crista dorsalis in gonostylus. The genus is new to Taiwan Province, China. The specimen is deposited at the Department of Biology, Nankai University, Tianjin. 相似文献
42.
43.
A rapid extraction method for screening aflatoxin producing potential ofAspergillus flavus group isolates is described. The method is performed using a moist wheat medium with ca. five infected grains extracted with 2 mL of chloroform, and using thin layer chromatography. This method was proved with 95A. flavus isolates from animal feeds. 相似文献
44.
Yan Yongshan Fen Shang Liu Lianrui 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(1):147-153
Summary A 8.3 /ml 6-thioguanine (6TG)-resistant strain was isolated from a rat tetraploid cell line by step-by-step selection in 6TG-medium. In the 6TG-resistant cell population 51% of the cells were tetraploid and 35% of the cells were hypertetraploid, i.e., one chromosome more than a tetraploid. The 6TG-resistant strain grew very well in RPMI 1640 medium with intervals of three days between subcultures. The 6TG-resistant cells all have a homogeneously staining region (HSRs) in one of the X chromosomes which do not stain after chromosome C-banding. They also possess a higher NORs activity and much lower frequency of sister chromatid exchanges (SCE). When the 6TG-resistant RCT cells were subcultured in 6TG-free medium for three days, their SCE frequency did not change. 5-bromodeoxyuridine (BrdU) significantly suppressed the NORs activity for both 6TG-resistant cells and 6TG-sensitive cells (P<0.001).Abbreviations 6TG
6-thioguanine
- HSRs
homogeneously staining region
- NORs
nucleolar organizer region
- SCE
sister chromatid exchange
- BrdU
5-bromodeoxyuridine
- HPRT
Hypoxanthine phosphoribosyl transferase 相似文献
45.
Purification and Characterization of a Substrate-Size-Recognizing Metalloendopeptidase from Streptococcus cremoris H61 总被引:6,自引:5,他引:1
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Tsong-Rong Yan Norihiro Azuma Shuichi Kaminogawa Kunio Yamauchi 《Applied microbiology》1987,53(10):2296-2302
During the ripening of Gouda-type cheese, two kinds of endopeptidases were found to participate in the degradation of αs1-CN(f1-23), a specific product from αs1-casein hydrolyzed by chymosin. One of the endopeptidases, lactic acid bacteria endopeptidase (LEP-II), which can recognize the size of its substrates, has already been purified and characterized (T. R. Yan, N. Azuma, S. Kaminogawa, and K. Yamauchi, Eur. J. Biochem. 163:259-265, 1987). The other endopeptidase, LEP-I, was purified to homogeneity by conventional chromatographic techniques from Streptococcus cremoris H61. The enzyme appeared to be monomeric, with an apparent molecular weight of 98,000, and its isoelectric point was 5.1. For the hydrolysis of αs1-CN(f1-23), the enzyme had an optimum pH and temperature of 7.0 to 7.5 and 40°C, respectively. Its activity was inhibited by such chelating agents as EDTA and 1,10-phenanthrolin, and it could be fully reactivated by Mn2+. Inhibitors specific for serine and thiol proteases had no effect on the protease activity. The enzyme showed a high affinity toward the Glu-Asn peptide bond of αs1-CN(f1-23) and αs1-CN(f91-100) but showed no hydrolysis activity toward αs1-CN(f1-52), αs1-CN(61-122), αs1-CN(136-196), αs1-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin. The Km and Vmax of LEP-I for αs1-CN(f1-23) were 14.2 pM and 139 U, respectively. 相似文献
46.
Association of viral and plasmid DNA with the nuclear matrix during productive infection 总被引:1,自引:0,他引:1
The association of simian virus 40 (SV40) DNA or plasmid DNA in subcellular fractions from either infected or transfected cells was examined. In lytically infected cells, approx. 25% of viral specific DNA during the infection cycle was retained in nuclei after washing with low ionic strength buffer and 1% Triton X-100. Viral replicating DNA found in the nuclear matrix was capable of performing limited DNA synthesis by the endogenous DNA polymerase in vitro. Viral DNA synthesized in vitro hybridized preferentially to SV40 Hind-III B and C fragments which are in proximity to the origin of replication. In plasmid-transfected COS-7 cells (SV40-transformed cells), the amount of plasmid DNA found in the nuclear matrix was related to its replication efficiency in cells. More than 80% of the plasmid DNA was tightly associated with subnuclear structures. Little or no plasmid DNA was found in the cytoplasmic fraction. The results suggest that, in extrachromosomal model systems, the association of DNA with nuclear matrix is important for the regulation of DNA replication. 相似文献
47.
An endopeptidase (LEP-II), which has a unique substrate specificity, was purified to homogeneity by conventional chromatographic techniques from Streptococcus cremoris H61. The enzyme was a metalloendopeptidase since it was inhibited by EDTA and 1,10-phenanthroline; the metal-depleted enzyme could be fully reactivated by micromolar levels of Zn2+ and was not inhibited by specific inhibitors for serine or thiol protease. The molecular mass of the enzyme was estimated to be 80 kDa by Sephacryl S-300 gel filtration and high-performance liquid chromatography with a TSK-G3000SW column. The enzyme consisted of two identical subunits and the N-terminal sequence of LEP-II was determined up to the 19th residue. Although the enzyme had a broad substrate specificity it specifically hydrolyzed the peptide bonds involving the amino groups of hydrophobic amino acid residues. Various small polypeptides, such as alpha s1-CN(f1-23), alpha s1-CN(f91-100), oxidized insulin B chain, glucagon and some biologically active peptides were hydrolyzed. However, a variety of larger polypeptides or proteins, such as alpha s1-CN(f1-54), alpha s1-CN(f61-123), alpha s1-CN(f136-196), alpha s1-casein, beta-casein, and kappa-casein were not hydrolyzed. LEP-II recognized the size of its substrates, which were limited below a molecular mass of about 3.5 kDa. 相似文献
48.
Production of enterotoxin A by supposedly nonenterotoxigenic Staphylococcus aureus strains 总被引:2,自引:0,他引:2
E Gomez-Lucía J Goyache J A Orden J L Blanco J A Ruiz-Santa-Quiteria L Domínguez G Suárez 《Applied and environmental microbiology》1989,55(6):1447-1451
The production of staphylococcal enterotoxins A (SEA) and B (SEB) was studied by inoculating six well-defined staphylococcal collection strains into cow's, goat's, or sheep's milk (individually or as a 50% mixture of cow's + goat's or cow's + sheep's), into brain heart infusion, and into a medium generally used to enhance the synthesis of enterotoxins (3+3 medium). Four of the strains used are considered to be SEB producers, another is considered an SEA producer, and the remaining strain is nonenterotoxigenic but produces large quantities of staphylococcal protein A. Staphylococcal protein A masked the results in most cases. Only one strain secreted exclusively SEB, while the other three SEB producers synthesized SEA in different amounts. We conclude that enterotoxin production depends on the natural substrate and may differ from the results obtained when the strain is grown on cellophane over agar to determine its toxigenicity. 相似文献
49.
Suárez-Cortez R Alvarez-Gallegos J González-Mora E 《Biotechnology and bioengineering》1989,33(4):377-385
The design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface. 相似文献
50.
Lidija Simova Carolyn Williams Georgi D. Efremov Aleksandra Gordova-Muratovska Stojka Suštić Eila K. Watson Robert Williamson 《Human genetics》1990,85(4):432-433
Summary Chromosomes from 19 unrelated Southern Yugoslav families in which cystic fibrosis (CF) occurs were analysed for the presence
of the ΔF508 mutation, using polymerase chain reaction amplification followed by dot blot and polyacrylamide gel analysis.
Of the 38 CF chromosomes, 15 (39.5%) carry the ΔF508 deletion. Restriction fragment length polymorphism haplotypes for KM19/PstI, XV2c/TaqI and J3.11/PstI marker loci were determined and are compared for a total of 34 N and 37 CF chromosomes. 相似文献