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1.
Abstract In Arabidopsis thaliana, cell fate in developing ovules is determined by the action of the homeodomain factor BELL1 (BEL1) and of the MADS-box factors SEEDSTICK (STK), SHATTERPROOF1 (SHP1) and SHP2. The analysis of the bel1 and the stk shp1 shp2 mutants revealed that the functional megaspore is formed, however, it does not proceed into megagametogenesis. In the bel1 stk shp1 shp2, quadruple mutant megasporogenesis does not take place. In this article we describe a detailed morphological analysis of the quadruple mutant, and we discuss the possibility that BELL1, STK, SHP1 and SHP2 not only control integument identity determination and development, but that they might also play a role during megasporogenesis. 相似文献
2.
Evelyne Decullier Véronique Lhéritier Fran?ois Chapuis 《BMJ (Clinical research ed.)》2005,331(7507):19
Objectives To describe the fate of protocols approved by the French research ethics committees, a national system created by the French 1988 Huriet-Sérusclat Act; to assess publication bias at a national level.Design Retrospective cohort study.Setting Representative sample of 25/48 French research ethics committees in 1994.Protocols 649 research protocols approved by committees, with follow-up information.Main outcome measures Protocols'' initial characteristics (design, study size, investigator) abstracted from committees'' archives; follow-up information (rates of initiation, completion, and publication) obtained from mailed questionnaire to principal investigators.Results Completed questionnaires were available for 649/976 (69%) protocols. Of these, 581 (90%) studies were initiated, 501/581 (86%) were completed, and 190/501 (38%) were published. Studies with confirmatory results were more likely to be published as scientific papers than were studies with inconclusive results (adjusted odds ratio 4.59, 95% confidence interval 2.21 to 9.54). Moreover, studies with confirmatory results were published more quickly than studies with inconclusive results (hazard ratio 2.48, 1.36 to 4.55).Conclusion At a national level, too many research studies are not completed, and among those completed too many are not published. We suggest capitalising on research ethics committees to register and follow all authorised research on human participants on a systematic and prospective basis. 相似文献
3.
Mutagenicity of 4-hydroxynonenal in V79 Chinese hamster cells 总被引:2,自引:0,他引:2
4-Hydroxynonenal (HNE), a major product of the peroxidation of liver microsomal lipids, was examined for mutagenic activity at the hypoxanthine-guanine phosphoribosyltransferase locus in V79 Chinese hamster lung cells. At concentrations ranging from 10 to 45 microM, HNE induced a dose-dependent increase in the number of mutations to 6-thioguanine resistance, which reached the level of 4.7X baseline at the highest concentration tested. 相似文献
4.
Two NADP-isocitrate dehydrogenase isoenzymes designated as NADP-IDH1 and NADP-IDH2 (EC 1.1.1.42) were identified in pea (Pisum sativum) leaf extracts by diethylaminoethylcellulose chromatography. The predominant form was found to be NADP-IDH1 while NADP-IDH2 represented only about 4% of the total leaf enzyme activity. These enzymes share few common epitopes as NADP-IDH2 was poorly recognized by the specific polyclonal antibodies raised against NADP-IDH1, and as a consequence NADP-IDH2 does not result from a post-translational modification of NADP-IDH1. Subcellular fractionation and isolation of chloroplasts through a Percoll gradient, followed by the identification of the associated enzymes, showed that NADP-IDH1 is restricted to the cytosol and NADP-IDH2 to the chloroplasts. Compared with the cytosolic isoenzyme, NADP-IDH2 was more thermolabile and exhibited a lower optimum pH. The data reported in this paper constitute the first report that the chloroplastic NADP-IDH and the cytosolic NADP-IDH are two distinct isoenzymes. The possible functions of the two isoenzymes are discussed.Abbreviations BSA
bovine serum albumin
- DEAE
diethylaminoethyl
- NADP-IDH
NADP-isocitrate dehydrogenase
- NADP-IDH1
cytosolic NADP-IDH
- NADP-IDH2
chloroplastic NADP-IDH 相似文献
5.
E Sturani R Brambilla L Morello M G Cattaneo R Zippel L Alberghina 《FEBS letters》1989,255(1):191-195
PDGF consists of two polypeptide chains, A and B, and all three possible dimers have been isolated from different sources. Human PDGF, essentially AB, porcine PDGF (BB) and recombinant PDGF-AA were tested on Swiss 3T3 fibroblasts for their ability to stimulate mitogenesis, phosphoinositide turnover and tyrosine phosphorylation of the PDGF receptor. When used in saturating amounts, the three isoforms were equally active in inducing mitogenesis. However, PDGF-AA was less active than AB and BB to induce the phosphorylation of the receptor and the turnover of phosphoinositides (30% and 50%, respectively). These findings suggest that, in Swiss 3T3 fibroblasts, PDGF receptors of the alpha-type are present in a slightly lower amount than beta-type. In addition, the two types of receptor appear to have similar physiological functions. 相似文献
6.
GABA-benzodiazepine receptor-chloride channel complexes have been detected by electrophysiological recording in Xenopus oocytes previously injected with messenger RNA extracted either from optic lobes of chick embryos or from adult rat hippocampi. The ability of the oocyte to correctly translate exogenous messengers was used to develop a routine method which could allow a quantitative evaluation of specific mRNA coding for GABA-benzodiazepine receptor proteins following an injection of a fixed amount of total poly(A+)-RNA. The conditions of the validation of this method have been determined. 相似文献
7.
Reggiani Remo; Cantu Carlo Alberto; Brambilla Ida; Bertani Alcide 《Plant & cell physiology》1988,29(6):981-987
In excised rice roots, anaerobic degradation of proteins gaverise to an increase of free-amino acids. Anoxic accumulationof alanine, -aminobutyric acid and proline was the consequenceof the interconversion of glutamate, aspartate and amides. Theshift in the composition of the amino acid pool appears to becaused by changes in keto acid levels. The role of reactionsinvolved in amino acid interconversion and the physiologicalsignificance of these interconversions are considered and discussed. (Received November 25, 1988; Accepted June 9, 1988) 相似文献
8.
A Martelli F Mattioli G Pastorino L Robbiano A Allavena G Brambilla 《Mutation research》1991,260(1):65-72
The results of this work, carried out to extend the limited information at present available on the genotoxic potential of chloramphenicol (CAP), indicate that in millimolar concentrations this antibacterial agent produced a minimal amount of DNA fragmentation in both V79 cells and metabolically competent rat hepatocytes. Moreover, a level of DNA-repair synthesis indicative of a weak but positive response was detected in primary cultures of liver cells obtained from 2 of 3 human donors, and a borderline degree of repair was present in those prepared from rats. The promutagenic character of CAP-induced DNA lesions was confirmed by a low but significant increase in the frequency of 6-thioguanine-resistant clones of V79 cells, which, however, was absent when the exposure was done in the presence of co-cultured rat hepatocytes. Finally, oral administration to rats of 1/2 LD50 CAP did not increase the incidence of either micronucleated polychromatic erythrocytes or micronucleated hepatocytes. Taken as a whole these findings suggest that CAP should be considered a compound intrinsically capable of producing a very weak genotoxic effect, but only at concentrations about 25 times higher than those occurring in patients treated with maximal therapeutic dosages. 相似文献
9.
B Ducommun P Brambilla M A Flix B R Franza Jr E Karsenti G Draetta 《The EMBO journal》1991,10(11):3311-3319
Activation of the cdc2 protein kinase at different stages of the cell cycle is regulated by post-translational modifications and interactions with cyclins. We show that in vitro translated human cdc2 binds very poorly to A and B cyclins, unless it has been preincubated with a Xenopus egg extract. This results in the phosphorylation of cdc2 which allows binding to cyclins. The replacement of Thr161, a residue conserved and phosphorylated in other protein kinases, with valine inhibits cdc2 association with A and B cyclins. In addition, mutations in the amino-terminus of cdc2 and within the conserved 'PSTAIR' region strongly inhibit binding. The Thr161Val mutation causes a lethal phenotype in the fission yeast Schizosaccharomyces pombe, while replacement of Thr161 with glutamic acid, potentially mimicking phosphorylation, causes uncoordination of mitosis and multiple cytokinesis. These results suggest that a threonine phosphorylation/dephosphorylation cycle is involved in regulating cdc2 function. 相似文献
10.
Delorme Evelyne; Gomez-Silva Benito; Stern Arthur I.; Schiff Jerome A. 《Plant & cell physiology》1986,27(1):177-182
Highly purified condensed mitochondria obtained from bleachedmutant. W10BSmL of Euglena gracilis Klebs var bacillaris Coriincorporate [35S]methionine into protein when fortified withmalate, ADP, Mg2+, phosphate and a sucrose osmoticum. Twentyto twenty-five polypeptide bands were found to be labeled inorganello when the labeled protein was subjected to sodium dodecylsulfatepolyacrylamide gel electrophoresis. Methionine incorporation,but not respiration or oxidative phosphorylation, was blockedby chloramphenicol and other 70S ribosomal translation inhibitorsbut cycloheximide and ribonuclease were without effect. Inhibitorsof electron transport and uncouplers of oxidative phosphorylationwere excellent inhibitors of protein synthesis. Thus, thesemitochondrial preparations carry out protein synthesis in organellothat is linked to respiration and oxidative phosphorylation.
1Present address: VA Hospital Outpatient Clinic, 17 Court St.,Boston, MA 02115, U.S.A.
2Present address: Laboratories de Microbiologia e Inmunologia,Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile.
3Present address: Botany Department, University of Massachusetts,Amherst, MA 01003, U.S.A. (Received June 17, 1985; Accepted October 28, 1985) 相似文献