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121.
Kinds and spectrum of mutations induced by 1-nitrosopyrene adducts during plasmid replication in human cells. 总被引:5,自引:2,他引:3 下载免费PDF全文
1-Nitropyrene has been shown in bacterial assays to be the principal mutagenic agent in diesel emission particulates. It has also been shown to be mutagenic in human fibroblasts and carcinogenic in animals. To investigate the kinds of mutations induced by this carcinogen and compare them with those induced by a structurally related carcinogen, (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetra-hydrobenzo [a]pyrene (BPDE) (J.-L. Yang, V. M. Maher, and J. J. McCormick, Proc. Natl. Acad. Sci. USA 84:3787-3791, 1987), we treated a shuttle vector with tritiated 1-nitrosopyrene (1-NOP), a carcinogenic mutagenic intermediate metabolite of 1-nitropyrene which forms the same DNA adduct as the parent compound, and introduced the plasmids into a human embryonic kidney cell line, 293, for DNA replication to take place. The treated plasmid, pZ189, carrying a bacterial suppressor tRNA target gene, supF, was allowed 48 h to replicate in the human cells. Progeny plasmids were then rescued, purified, and introduced into bacteria carrying an amber mutation in the beta-galactosidase gene in order to detect those carrying mutations in the supF gene. The frequency of mutants increased in direct proportion to the number of DNA-1-NOP adducts formed per plasmid. At the highest level of adduct formation tested, the frequency of supF mutants was 26 times higher than the background frequency of 1.4 X 10(-4). DNA sequencing of 60 unequivocally independent mutant derived from 1-NOP-treated plasmids indicated that 80% contained a single base substitution, 5% had two base substitutions, 4% had small insertions or deletions (1 or 2 base pairs), and 11% showed a deletion or insertion of 4 or more base pairs. Sequence data from 25 supF mutants derived from untreated plasmids showed that 64% contained deletions of 4 or more base pairs. The majority (83%) of the base substitution in mutants from 1-NOP-treated plasmids were transversions, with 73% of these being G . C --> T . A. This is very similar to what we found previously in this system, using BPDE, but each carcinogen produced its own spectrum of mutations. Of the five hot spots for base substitution mutations produced in the supF gene with 1-NOP, two were the same as seen with BPDE-treated plasmids. However, the three other hot spots were cold spots for BPDE-treated plasmids. Conversely, four of the other five hot spots seen with BPDE-treated plasmids were cold spots for 1-NOP-treated plasmids. Comparison of the two carcinogens for the frequency of supF mutants induced per DNA adduct showed that 1-NOP-induced adducts were 3.8 times less than BPDE adducts. However, the 293 cell excised 1-NOP-induced adducts faster than BPDE adducts. 相似文献
122.
The N-terminal -amino groups of 1-bungarotoxin (1-Bgt) fromBungarus multicinctus venom were modified with trinitrobenzene sulfonic acid and the modified derivative was separated by high performance liquid chromatography. The trinitrophenylated (TNP) derivative contained two TNP groups at the -amino groups of A chain and B chain and showed a marked decrease in enzymatic activity. Methionine residues at positions 6 and 8 of the A chain were oxidized with chloramine T or cleaved with cyanogen bromide to remove the N-terminal octapeptide. Oxidation of methionine residues and removal of the N-terminal octapeptide caused a precipitous decrease in enzymatic activity, whereas antigenicity remained unchanged. The presence of dihexanoyllecithin influenced the interaction between 1-Bgt and 8-antilinonaphthalene sulfonate (ANS) and revealed that 1-Bgt consists of two types of ANS-binding sites, one at the substrate binding site of the A chain and the other might be at the B chain. The modified derivatives still retained their affinity for Ca2+ and ANS, indicating that the N-terminal region is not involved in Ca2+ and substrate binding. A fluorescence study revealed that the -amino group of the A chain was in the vicinity of substrate binding site and that the TNP -amino groups were in proximity to Trp-19 of the A chain. In addition, the study showed that the N-terminal region is important for stabilizing the architectural environment of Trp-19. The results, together with the proposal that Trp-19 of the A chain is involved in substrate binding, suggest that the N-terminal region of the A chain plays a crucial role in maintaining a functional active site for 1-Bgt. 相似文献
123.
Regional localization of polymorphic DNA loci on the proximal long arm of the X chromosome using deletions associated with choroideremia 总被引:13,自引:7,他引:6
Summary In two unrelated families, males have been identified who suffer from choroideremia and at the same time have an interstitial deletion on the proximal long arm of the X chromosome. By high-resolution banding we have characterized the deletion chromosomes as del(X)(q21.1-q21.33) and del(X)(q21.2-q21.31) respectively. By Southern blot analysis we have mapped ten different polymorphic DNA loci relative to the position of the deletion and the choroideremia locus TCD. One probe, p31, was shown to cover one of the breakpoints of the smallest deletion. The following order of the loci was suggested by deletion mapping: cen-DXS106-DXS72-TCD-(DXYS1/DXYS23/DXYS5)-DXYS2-(DXYS12/DXS3)-(DXS17/DXS101)-Xqter. 相似文献
124.
125.
M. A. Alexander V. W. Yang T. W. Jeffries 《Applied microbiology and biotechnology》1988,29(2-3):282-288
Summary
Candida shehatae exhibits different fermentative capacities when grown under different aeration conditions. These studies investigated the titers of xylose reductase, xylitol dehydrogenase, glucose-6-phosphate dehydrogenase and alcohol dehydrogenase in crude extracts ofCandida shehatae grown in continuous culture with various specific aeration rates. Carbon source, aeration rate, dilution rate and temperature were examined as variables. Xylose reductase and xylitol dehydrogenase were induced by xylose and were largely absent in glucose-grown cells. Alcohol dehydrogenae levels were higher in glucose-grown cells than in xylose-grown cells. The levels of this enzyme also correlated with the fermentative character of metabolism, having a low value under fully aerobic conditions, a high value under anaerobic conditions, and intermediate levels under various semi-aerobic conditions. Temperature had no effect on any enzyme level over the range of 20–30°C.Maintained in cooperation with the University of Wisconsin-Madison 相似文献
126.
I-Ching Tang Shang-Tian Yang Martin R. Okos 《Applied microbiology and biotechnology》1988,28(2):138-143
Summary Acetic acid was produced from anaerobic fermentation of lactose by the co-culture ofStreptococcus lactis andClostridium formicoaceticum at 35° C and pHs between 7.0 and 7.6. Lactose was converted to lactic acid, and then to acetic acid in this mixed culture fermentation. The overall acetic acid yield from lactose was about 95% at pH 7.6 and 90% at pH 7.0. The fermentation rate was also higher at pH 7.6 than at pH 7.0. In batch fermentation of whey permeate containing about 5% lactose at pH 7.6, the concentration of acetic acid reached 20 g/l within 20 h. The production rate then became very slow due to end-product inhibition and high Na+ concentration. About 30 g/l acetate and 20 g/l lactate were obtained at a fermentation time of 80 h. However, when diluted whey permeate containing 2.5% lactose was used, all the whey lactose was converted to acetic acid within 30 h by this mixed culture. 相似文献
127.
128.
天麻球茎中一种抗真菌蛋白的分离和部分特性 总被引:18,自引:1,他引:17
白天麻(Gastrodia elata)顶生球茎中分离并纯化了一种抗真菌蛋白(Gastrodia Antifungal Protein),简称GAFP。在马铃薯葡糖琼脂培养基上,4μg GAFP滴加在直径0.6 cm圆纸片上可明显抑制木霉(Trichoderma reesei)菌丝生长。从每千克鲜球茎中可分离得GAFP约20 mg。用SDS-PAGE和凝胶过滤层析测得该蛋白为单多肽链,分子量14.0kD;用离子交换结合法测得电点为8.1;富含Asn,Ala,Gly和Leu,但无Met,Cys和Pro。未经热变性或SDS处理的GAFP与考马氏亮蓝试剂不发生显色反应。GAFP不具有几丁质酶和β-1,3-葡聚糖酶活性。球茎外层组织富含这种蛋白,内层薄壁组织无此蛋白。认为GAFP在阻止真菌侵染当年生顶生和侧生球茎的防卫机制中起重要作用。 相似文献
129.
130.
水稻原生质体产生细胞团的冰冻保存和冻后再生植株形成 总被引:4,自引:0,他引:4
水稻(Oryza sativa L.)原生质体产生的细胞团加上10-20%的二甲亚枫(DMSO)和10-20%的蔗糖,置于液氮中保存。冻后细胞生存率达到对照的40-50%。存活的细胞在附加2×10~(-5)mol/l 2,4-D 的Linsmier-Skoog(Ls)固体培养基上再生长,然后将形成的愈伤组织块转到附加10~(-6)mol/l NAA,4×10~(-6)mol/l 激动素和10~(-6)mol/l 2 IP 及8%的蔗糖的 LS培养基上分化出芽并形成植株。 相似文献