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191.
By combining small colloidal gold probes with video-enhanced quantitative microscopy, the intracellular dynamics of specific proteins in living cells can now be studied. 相似文献
192.
N de Wind M Dekker N Claij L Jansen Y van Klink M Radman G Riggins M van der Valk K van't Wout H te Riele 《Nature genetics》1999,23(3):359-362
Cancer predisposition in hereditary non-polyposis colon cancer (HNPCC) is caused by defects in DNA mismatch repair (MMR). Mismatch recognition is attributed to two heterodimeric protein complexes: MutSalpha (refs 2, 3, 4, 5), a dimer of MutS homologues MSH2 and MSH6; and MutSbeta (refs 2,7), a dimer of MSH2 and MSH3. These complexes have specific and redundant mismatch recognition capacity. Whereas MSH2 deficiency ablates the activity of both dimers, causing strong cancer predisposition in mice and men, loss of MSH3 or MSH6 (also known as GTBP) function causes a partial MMR defect. This may explain the rarity of MSH6 and absence of MSH3 germline mutations in HNPCC families. To test this, we have inactivated the mouse genes Msh3 (formerly Rep3 ) and Msh6 (formerly Gtmbp). Msh6-deficient mice were prone to cancer; most animals developed lymphomas or epithelial tumours originating from the skin and uterus but only rarely from the intestine. Msh3 deficiency did not cause cancer predisposition, but in an Msh6 -deficient background, loss of Msh3 accelerated intestinal tumorigenesis. Lymphomagenesis was not affected. Furthermore, mismatch-directed anti-recombination and sensitivity to methylating agents required Msh2 and Msh6, but not Msh3. Thus, loss of MMR functions specific to Msh2/Msh6 is sufficient for lymphoma development in mice, whereas predisposition to intestinal cancer requires loss of function of both Msh2/Msh6 and Msh2/Msh3. 相似文献
193.
M. R. Kernan D. J. Faulkner L. Parkanyi J. Clardy M. S. de Carvalho R. S. Jacobs 《Cellular and molecular life sciences : CMLS》1989,45(4):388-390
Summary Luffolide (4) is a minor metabolite of the spongeLuffariella sp. from Palau. The structure of luffolide was determined by single crystal X-ray analysis. Luffolide is relatively unstable and undergoes a complex cyclization reaction to give the hexacyclic products5 and6. Luffolide (4) has some of the anti-inflammatory properties of manoalide (1): this may help to define the chemical reaction between manoalide (1) and phospholipase A2.All crystallographic calculations were done on a PRIME 9950 computer operated by the Cornell Chemistry Computing Facility. Principal programs employed were: FOBS, a data reduction program by G.D. Van Duyne, Cornell University, 1987; MULTAN 80, and RANTAN 80, systems of computer programs for the automatic solution of crystal structures from X-ray diffraction data (locally modified to perform all Fourier calculations including Patterson syntheses) written by P. Main, S. E. Hull, L. Lessinger, G. Germain, J. P. Declercq and M. M. Woolfson, University of York, England, 1980 BDLS, an, anisotropic block diagonal least squares refinement written by K. Hirotsu, E. Arnold, and G. D. Van Duyne, Cornell University, 1987; PLUTO 78, a locally modified crystallographic illustration program by W. D. S. Motherwell, Cambridge Crystallographic Data Centre, 1978; and BOND, a program to calculate molecular parameters and prepare tables written by K. Hirotsu and G. Van Duyne, Cornell University, 1985.Acknowledgment. We thank the Government of the Republic of Palau for a scientific research permit. We thank Dr Klaus Rützler, Smithsonian Institution, Washington, D.C. for identifying the sponge and Mary Kay Harper for performing additional bioassays. This research was supported by grants from the Sea Grant College Programs of California [Projects R/MP-30 to DJF) and R/MP-31 (to RSJ)] and New York (to JC) and the National Institutes of Health (CA 24487 to JC). 相似文献
194.
介绍了清洁发展机制(CDM)的概念及中日在山西实施CDM的可行性。探讨了由此带来的环境、经济和社会效应,以及可能存在的一些问题。 相似文献
195.
Stable expression of the bacterial neor gene in Leishmania enriettii 总被引:28,自引:0,他引:28
Molecular genetic studies in parasitic protozoa have been hindered by the lack of methods for the introduction and expression of modified or foreign genes in these organisms. Two recent reports described the transient expression of the bacterial chloramphenicol acetyl transferase (CAT) gene under the control of parasite-specific sequences. We now describe the stable expression of a selectable marker, the gene for neomycin resistance (neor) in Leishmania enriettii. A chimaeric gene containing the neor gene inserted between two alpha-tubulin intergenic sequences was introduced into the cells and drug-resistant L. enriettii were observed which stably expressed the neor gene. One goal of this work was to analyse the sequences necessary for trans-splicing of messenger RNA, as trypanosomatids have a novel process of RNA trans-splicing, described initially in Trypanosome brucei and subsequently in several other trypanosomatids, including L. enriettii. Many trypanosomatid genes are arranged in tandem arrays and the intergenic sequences contain both the splice acceptor site for the addition of the spliced leader sequence and a putative polyadenylation site. Messenger RNA isolated from several different neor L. enrietti lines contained the spliced leader sequence joined to the neor gene at the position of the splice acceptor site in the alpha-tubulin intergenic sequence. The neor mRNA was also polyadenylated. Plasmid DNA is present within the drug-resistant organisms and appears to be extrachromosomal. The development of these methods allows the functional analysis of sequences necessary for trans-splicing. 相似文献
196.
197.
198.
199.
H de Barjac 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(15):1175-1178
The comparative study of the larvicidal action of B. thuringiensis var. israelensis on A. aegypti and A. stephensi shows the greater sensitivity of A. aegypti, with 100% of mortality in 30 to 40 min. at high doses. But, for both species of Mosquito, the toxicity of these bacteria is very high, as shown by the mortality regression curves and by the LC50. This toxicity is associated with the crystals and can be extracted from them by dilute alkali solution, like the general case of the other serotypes of B. thuringiensis. In contrast with these serotypes, B. thuringiensis var. israelensis is not pathogenic to the tested larvae of Lepidoptera. 相似文献
200.
F. Foresti C. Oliveira L. Foresti de Almeida-Toledo 《Cellular and molecular life sciences : CMLS》1993,49(9):810-813
This paper describes a new technique for preparing mitotic fish chromosomes using short-term in vitro treatment with colchicine. The results show that a large number of good quality metaphases (many suitable for chromosome banding) can be obtained by this technique, which requires an average of 1 h and 30 min for all steps. The procedure considerably reduces the time normally required for chromosome preparations in fish.This work was supported by grants FUNCUNESP, FAPESP and CNPq.The authors are grateful to Mr Renato Devidé for technical assistance. 相似文献