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61.
不同苗龄的尾穗苋黄化苗对10 min,15Wm~(-2)白光的反应能力不同。光诱导的苋红素合成始于播种后第 20h,至50h合成能力最大,82h以后幼苗对短时光照的反应能力趋于消失。苋红素合成的滞后期为3h,光处理后18h色素积累达到高峰。光调节苋红素合成符合红光—远红光可逆诱导反应等两个基本模式,确证光敏色素参与调控苋红素合成. 相似文献
62.
Linkage analysis of families with hereditary retinoblastoma: nonpenetrance of mutation, revealed by combined use of markers within and flanking the RB1 gene. 总被引:8,自引:4,他引:4
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H Scheffer G J te Meerman Y C Kruize A H van den Berg D P Penninga K E Tan D J der Kinderen C H Buys 《American journal of human genetics》1989,45(2):252-260
Nonpenetrance of the inherited mutation responsible for retinoblastoma has been reported. By DNA analysis in families with hereditary retinoblastoma, it is possible to identify healthy individuals in whom the mutation is nonpenetrant. This requires the use of DNA markers both within and flanking the retinoblastoma gene. We have analyzed the segregation of several markers in 19 families (69 meioses) with hereditary retinoblastoma. In two families a carrier was identified who showed nonpenetrance of the mutation predisposing to retinoblastoma. The intragenic markers were informative in 15 pedigrees. The use of flanking markers from the same chromosomal region caused an increase of the number of informative families to 18. No crossing-over within the gene was observed. In one family an inherited deletion involving one of the RB1 alleles was detected. Our findings emphasize the use of a combination of both intragenic and flanking markers to obtain both the highest reliability of carrier detection in families with hereditary retinoblastoma and an accurate estimate of the frequency of nonpenetrance. 相似文献
63.
Geok -Yong Tan Wai -Koon Tan 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,80(2):258-264
Summary Quantitative inheritance of resistance to Phytophthora pod rot (Ppr) was studied in cocoa hybrid progeny from 12 Trinitario x Amazonian crosses and their reciprocal crosses. The crossing scheme was similar to a factorial design. Disease was assessed by the number and percentage of infected pods on each tree. Highly significant differences due to general combining abilities (GCA) were obtained for all characters, except for the GCA of Trinitario on total pod production. Differences for specific combining ability (SCA) were not significant for all characters. There were no significant differences between reciprocal crosses. The Trinitario clone K82 provided the only source for the hybrid progenies of strong Ppr resistance to the hybrid progenies, while K20 provided moderate resistance. Other parental clones — KA2-101, KA5-201, KEE 2, KEE 5, and KEE 52 — produced progenies which were susceptible to Ppr. It is evident that resistance to Ppr in cocoa is inherited additively. Maternal and cytoplasmic effects were assumed to have no influence on inheritance of resistance. It is also concluded that resistance to Ppr of the kind shown by K82 is likely to be horizontal resistance. Breeding for high-yielding cultivars combined with Ppr resistance is the most effective way of controlling Ppr of cocoa on the crops of growers with small holdings in Papua New Guinea. 相似文献
64.
65.
A DNA helicase (delta helicase) which partially copurifies with DNA polymerase delta has been highly purified from fetal calf thymus. delta helicase differs in physical and enzymatic properties from other eukaryotic DNA helicases described thus far. The enzyme has an apparent mass of 57 kDa by gel filtration and is associated with polypeptides of 56 and 52 kDa by SDS-polyacrylamide gel electrophoresis. Photo-cross-linking of the purified enzyme with [alpha-32P]ATP resulted in labeling of a polypeptide of approximately 58 kDa, suggesting that the active site is present on the larger polypeptide. Unwinding of a partial duplex requires a nucleoside triphosphate which can be either ATP or dATP but not a nonhydrolyzable analogue of ATP. Other ribo- and deoxyribonucleoside triphosphates have little or no activity as cofactors. delta helicase also has DNA-dependent ATPase activity which has a relatively low Km for ATP (40 microM). delta helicase binds to single-stranded DNA but has little or no affinity for double-stranded DNA or single-stranded RNA. Similar to replicative DNA helicases from prokaryotes and the herpes simplex virus type 1 helicase-primase, delta helicase translocates in the 5'-3' direction along the strand to which it is bound and preferentially unwinds DNA substrates with a forklike structure. 相似文献
66.
The inhibition of xanthine oxidase by its reaction product, uric acid, was studied by steady state kinetic analysis. Uric acid behaved as an uncompetitive inhibitor of xanthine oxidase with respect to the reducing substrate, xanthine. Under 50 microM xanthine and 210 microM oxygen, the apparent K(i) for uric acid was 70 microM. Uric acid-mediated xanthine oxidase inhibition also caused an increase in the percentage of univalent reoxidation of the enzyme (superoxide radical production). Steady-state rate equations derived by the King-Altman method support the formation of an abortive-inhibitory enzyme-uric acid complex (dead-end product inhibition). Alternatively, inhibition could also depend on the reversibility of the classical ping-pong mechanism present in xanthine oxidase-catalyzed reactions. 相似文献
67.
Nagilactone E, a norditerpene dilactone isolated from a gymnosperm, Podocarpus nagi (Podocarpaceae), was able to stimulate the growth of cultured cells of Lactuca sativa cv. Grand Rapids at 0.1 g ml-1 but not at 0.01 or 1 g ml-1. Cell wet weight/unit time and cell number/unit wet weight were increased when they were recorded at the end of the 14-day incubation period. Also, the population of cells treated with that concentration of nagilactone E had a higher percentage of cells with shorter cell length compared to the control (untreated). 相似文献
68.
Zhuang G. S. Wang Y. S. Tan M. G. Zhi M. Pan W. Q. Cheng Y. D. 《Biological trace element research》1990,26(1):729-736
In order to study the relationships between trace element concentrations of hair and internal body burdens, a radiochemical NAA technique has been used for determination of the elements As, Cd, and Hg in autopsy samples of liver, kidney-cortex, lung, and hair from 24 male persons who died by accident. High significant positive correlations were observed between the As concentration in hair and in kidney-cortex, and between Cd and Zn concentrations in kidney-cortex. The contents of Cd, both for lung and kidney-cortex, were related to the smoking habits of the subjects.
相似文献69.
David M. Hwang Adam Dempsey Kiat-Tsong Tan Choong-Chin Liew 《Journal of molecular evolution》1996,43(5):536-540
HnifU, a gene exhibiting similarity tonifU genes of nitrogen fixation gene clusters, was identified in the course of expressed sequence tag (EST) generation from a
human fetal heart cDNA library. Northern blot of human tissues and polymerase chain reaction (PCR) using human genomic DNA
verified that the hnifU gene represented a human gene rather than a microbial contaminant of the cDNA library. Conceptual translation of the hnifU cDNA yielded a protein product bearing 77% and 70% amino acid identity to NifU-like hypothetical proteins fromHaemophilus influenzae andSaccharomyces cerevisiae, respectively, and 40–44% identity to the N-terminal regions of NifU proteins from several diazatrophs (i.e., nitrogen-fixing
organisms). Pairwise determination of amino acid identities between the NifU-like proteins of nondiazatrophs showed that these
NifU-like proteins exhibited higher sequence identity to each other (63–77%) than to the diazatrophic NifU proteins (40–48%).
Further, the NifU-like proteins of non-nitrogenfixing organisms were similar only to the N-terminal region of diazatrophic
NifU proteins and therefore identified a novel modular domain in these NifU proteins. These findings support the hypothesis
that NifU is indeed a modular protein. The high degree of sequence similarity between NifU-like proteins from species as divergent
as humans andH. influenzae suggests that these proteins perform some basic cellular function and may be among the most highly conserved proteins.
Correspondence to: C.-C. Liew 相似文献
70.
丝裂素活化蛋白激酶参与内皮素刺激的兔主动脉平滑肌细胞增生 总被引:11,自引:1,他引:10
内皮素(endothelin,ET)是已知的体内活性最强的缩血管物质,其缩血管作用由G蛋白偶联受体所介导。但ET强大的促血管平滑肌细胞(VSMC)增生效应的机理尚未完全阐明。本研究选用培养的兔胸主动脉VSMC,探讨丝裂素活化蛋白激酶(MAPK)在ET促细胞增生中的作用。结果表明:ET-1呈时间和浓度依赖性地促进细胞摄取 ̄3H-TdR和激活MAPK,此作用可被蛋白激酶C(proteinkinaseC,PKC)抑制剂Staurosporine(STP),H-7和ET_A受体拮抗剂BQ123所抑制,但不被酪氨酸激酶抑制剂HerbimycinA(Herb)所抑制,用PKC激动剂PMA(Phorbolmyristateacetate)预处理VSMC,使其PKC活性下调,可显著减弱ET-1对MAPK的激活能力。本结果提示:(1)MAPK参与ET-1所致的VSMC增生;(2)ET-1促细胞增生与激活MAPK的作用是由ET_A受体和PKC介导的。 相似文献