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931.
Anne Schoendorf Roberte Bronner Jean Broadhvest François Bernier 《Sexual plant reproduction》1998,11(3):140-147
In the tobacco (Nicotiana tabacum) Appendix mutant, anthers are tipped by a miniature style and stigma. The outgrowth appears on the anther when it is already
differentiating and follows the developmental timing of the central carpel. The Appendix mutation thus represents a late homeotic
transformation suggesting that the APPENDIX (APX) gene either could be a misregulated organ identity gene or could be involved in regulating the expression of such genes.
RFLP analysis with two class B (TM6 and NTGLO) and a class C (NAG) probes revealed that the Appendix phenotype is not caused by a mutation in one of these genes. However, in situ hybridization
showed important changes in the expression of NTGLO and NAG in the mutant when compared with wild-type tobacco. Surprisingly, although no phenotypic alteration other than the style
and stigma outgrowth is observed in the Appendix mutant, changes in class B and class C gene expession were not restricted
to the anther tip cells from which the outgrowth originates. As expected, NAG was expressed in the Appendix outgrowth but it was also overexpressed in the normal third and fourth whorl organs at the
time the outgrowth, as well as the central styles and stigmas, differentiated. Overexpression of a class C gene is probably
responsible for the Appendix phenotype. In normal and mutant flowers, NTGLO was expressed in the second, third and fourth whorls up to the time of carpel fusion. Expression of this class B gene then
ceased in the fourth whorl organs but was reactivated at later stages only in the styles and stigmas as well as in the outgrowths
of the mutant. It thus seems that the function of the APX gene is either to regulate the late expression of organ identity genes or to control cell proliferation in such a way that,
in the mutant, some cells are in a state where they respond in an unusual way to developmental signals.
Received: 17 October 1997 / Revision accepted: 24 March 1998 相似文献
932.
Cadmium uptake by Spirulina maxima: toxicity and mechanism 总被引:4,自引:0,他引:4
Augusto da Costa A.C. de França F.P. 《World journal of microbiology & biotechnology》1998,14(4):579-581
Cadmium uptake by Spirulina maxima cells was more pronounced in living than in dead cells, with a maximum recovery of 47.63mg Cd/g cells for living cells and 37.00mg Cd/g cells for inactivated cells. When in the medium at 1.2mg/l, cadmium affected cell growth and diminished cell productivity. Cadmium was detected in the outer and inner faces of the external membrane, essentially in the lipid layer. 相似文献
933.
934.
Parameters of VERO cell growth and metabolism were studied in cultures performed on microcarriers (MCs) using a bioreactor with a working capacity of 3.7?l. Kinetic studies of VERO cell growth in batch, semi-batch and perfusion cultures using concentrations of 2 and 10?mg/ml of MCs showed that a high concentration of MCs (10?mg/ml) and the use of medium perfusion allowed the attainment of higher final yields of VERO cells (6?×?106 cells/ml after 10 days of culture). Perfusion also allowed better use of MCs as indicated by the observation of about 100% of MCs totally covered by cells and the appearance of multilayered cells on 64% of MCs after 13 days of VERO cell culture with 2?mg/ml of MCs. Concerning the concentration of nutrients in the cultures, the medium perfusion was able to sustain suitable levels of galactose and glutamine, which quickly decreased after 4 days in batch cultures. The air inlet in the batch cultures was capable of eliminating the NH4 + which accumulated in the medium culture. Lactate accumulated during the first days of culture but then was utilized by the cells and decreased along the culture time. The optimization of VERO cell cultures on microcarriers as indicated by the concentration of MCs, medium perfusion and air inlet is discussed. 相似文献
935.
936.
937.
Stéphanie Finet Françoise Bonneté Jean Frouin Karine Provost Annette Tardieu 《European biophysics journal : EBJ》1998,27(3):263-271
A combination of small angle X-ray scattering and gel techniques was used to follow the kinetics of protein crystal growth
as a function of time. Hen egg white lysozyme, at different protein concentrations, was used as a model system. A new sample
holder was designed, in which supersaturation is induced in the presence of salt by decreasing the temperature. It had been
shown previously that a decrease in temperature and/or an increase in crystallizing agent induces an increase in the attractive
interactions present in the lysozyme solutions, the lysozyme remaining monomeric. In the present paper we show that similar
behaviour is observed in NaCl when agarose gels are used. During crystal growth, special attention was paid to determine whether
oligomers were formed as the protein in solution was incorporated in the newly formed crystals. From these first series of
experiments, we did not find any indication of oligomer formation between monomer in solution and crystal. The results obtained
are in agreement with the hypothesis that lysozyme crystals in NaCl grow by addition of monomeric particles.
Received: 28 July 1997 / Revised version: 4 December 1997 / Accepted: 5 December 1997 相似文献
938.
Joẽl Simeray Jean-Pierre Chaumont Françoise Bevalot Jacqueline Vaquette 《Phytochemistry》1985,24(11):2720-2721
From the stem bark of Zanthoxylum thomense a new amide, zanthomamide has been isolated and characterized as N-methyl, N-cinnamyl-(3′,4′-methylenedioxy)-phenylethylamine. Other constituents identified are the known benzophenanthridines, decarine, norchelerythrine and angoline. 相似文献
939.
André Luís Branco de Barros Valbert Nascimento Cardoso Luciene das Graças Mota Ricardo José Alves 《Bioorganic & medicinal chemistry letters》2010,20(1):315-317
Three carbohydrate derivatives, MAG3-Gl, MAG3-Ga, MAG3-NG, were synthesized and radiolabeled in high yields. These substances were injected in health Swiss mice and their biodistribution were evaluated. Among them, 99mTc-MAG3-Ga displayed higher accumulation in hepatic tissue, due to the presence of specific receptors in the liver for this carbohydrate. Thus, the use of 99mTc-MAG3-Ga to assess hepatic function can be considered. 相似文献
940.
Frédéric Le Gac Philippe Guionneau Jean-François Létard Patrick Rosa 《Inorganica chimica acta》2008,361(12-13):3519-3524
We have studied the peculiarities of complex [Zn(PM–PEA)2(NCS)2], which presents large void cavities. As powder it does not show solvent inclusion, while as single crystals we have evidenced the existence of various polymorphs, with and without solvent inclusion. These results are preliminary results for the comprehension of the behaviour of mixed [FexZn1?x(PM–PEA)2(NCS)2], where Zn has been used to decrease the cooperative interactions between Fe atoms and check the effects on the wide hysteresis reported for this compound. 相似文献