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61.
Laurent Beuf Sylvie Bédu Marie-Claire Durand Françoise Joset 《Plant molecular biology》1994,25(5):855-864
The involvement of a gene ofSynechocystis PCC6803,icfG, in the co-ordinated regulation of inorganic carbon and glucose metabolism, was established. TheicfG gene codes for a 72 kDa protein, which shows no homology with those registered in data libraries. Expression oficfG required glucose, the actual inducer probably being glucose-6-phosphate, and was independent of light and of the external inorganic carbon concentration. Mutants carrying an inactivated copy oficfG were constructed. Their growth characteristics were identical to those of the wild type under all regimes except in limiting inorganic carbon with glucose being present either before or after the transfer to the limiting conditions. These conditions completely prevented growth, both in the light and in the dark. The inhibition could be relieved by several intermediates of the tricarboxylic acid cycle. Assays of various enzymic activities related to inorganic carbon uptake and to its assimilationvia either the Calvin cycle or phosphoenolpyruvate carboxylase did not reveal the level of action of IcfG. Possible models include a blockage of the assimilation of both carbon sources in the absence of IcfG, or the inhibition of Ci incorporation route(s) essential under limiting inorganic carbon conditions, even when glucose is present, and even in the dark. 相似文献
62.
Frédérique Tihy Nicolas Vogt Dominique Recan Bernard Malfoy France Leturcq Michelle Coquet Françoise Serville Daniel Fontan Jean-Michel Guillard Jean-Claude Kaplan Bernard Dutrillaux Nicole Lemieux 《Human genetics》1994,93(5):563-567
A girl with severe Becker muscular dystrophy and apparently normal chromosomes had a heterozygous deletion for exons 51, 52, and 53 of the dystrophin gene. This deletion was transmitted by her mother, who was unaffected. To differentiate the normal and the deleted X chromosomes, fluorescence in situ hybridization (FISH) was applied to metaphase chromosomes, using probes for both exons 51 and 52, which are only 388 and 113 base pairs long, respectively. FISH signals were observed in one or both chromatids of one chromosome, but never on both chromosomes, suggesting the lack of hybridization on the deleted X chromosome. Using 5-bromodeoxyuridine incorporation to differentiate the late (inactive) and the early replicating (active) X chromosomes, 77% of the signals were observed on the active X chromosomes in the mother. This percentage was only 18% in the daughter, suggesting that skewed inactivation of the X chromosomes was responsible for the phenotypic differences. 相似文献
63.
Cobalt determinations in biological fluids are of great interest in biological or toxicological research programs. Cobalturia
is often chosen as an indicator for a biological monitoring program in occupational exposure to cobalt dusts. The method described
here derives from the IUPAC reference method for nickel determination. It enables cobaltemia and cobalturia to be measured
in small samples (1 mL). The mean usual values for cobalt in biological fluids are very low (2.7 nmol L−1 for serum and 6.7 nmol L−1 for urine), and therefore, thus require an analytical procedure with preconcentration and extraction. The sample is mineralized
by wet acid digestion. After digestion, inorganic cobalt is extracted in form of ammonium pyrrolidine dithiocarbamate complex
into isobutyl methyl ketone and measured in the organic layer by electrothermal atomic absorption spectrometry.
The analytical parameters are described in detail. The extraction output is about 99%. The detection limits are 1.93 and 1.89
nmol L−1 for serum and urine, respectively. Sensitivity (expressed as the concentration that gives a 0.044 absorbance) is 3.4 nmol
L−1 for serum and 3.3 nmol L−1 for urine.
Within-run precision ranged between 3.9 and 2.5% (coefficients of variation) for serum and 4.2 and 1.1% for urine, at 87 and
136 nmol L−1 levels, respectively. Between-run precision ranged between 4.3 and 3.3% (coefficients of variation) for serum and 4.2 and
2.3% for urine, at 87 and 136 nmol L−1 levels, respectively. At very low concentration, 5.7 nmol L−1 for serum and 2.5 nmol L−1 for urine, the between-run precision is, respectively, 19.5 and 28%.
Linearity is effective between 0 and 272 nmol L−1. Interferences and matrix effects are negligible for urine, serum, or plasma samples without hemoglobin. The method is easily
applicable for routine determinations. 相似文献
64.
Jean-Vincent Escalant Claude Teisson François Cote 《In vitro cellular & developmental biology. Plant》1994,30(4):181-186
Summary Somatic embryogenesis and plant regeneration of banana and plantain cultivars (Musa spp.) were obtained by culturing young male flowers. Multiplication and maintenance of embryogenic cultures were achieved
by culturing somatic embryos in a temporary immersion system (SIT). A multiplication rate of 40 allowed us to obtain more
than 6000 somatic embryos after 6 mo. of subculture. Plant recovery frequencies were 60 to 70%. This method was expanded to
different banana and plantain genomic groups. 相似文献
65.
The major intracellular protein tyrosine phosphatase (PTP1B) is a 50kDa protein, localized to the endoplasmic reticulum. This PTP is recovered in the particulate fraction of mamalian cells and can be solubilized as a complex of 150 kDa by extraction with non-ionic detergents. Previous work from this laboratory implicated phosphorylation of serine/threonine residues in the regulation of this PTP. Activity was several-fold higher in cells treated with activators of cAMP-dependent or Ca2+/phospholipid-dependent protein kinases or inhibitors of protein phosphatase 2A. Here we show that these treatments result in more than an 8-fold increase in the phosphorylation of the 50kDa PTP catalytic subunit within the 150kDa form of the phosphatase in HeLa cells. The phosphorylation occurred exclusively on serine residues, and the same tryptic and cyanogen bromide,32P-phosphopeptides were recovered in the PTP from control and stimulated cells. Either multiple kinases phosphorylate a common site in the PTP1B, or a single kinase is activated downstream of cAMP- and Ca2+/phospholipid-dependent kinases. The results indicate that phosphorylation of a serine residue in the segment 283–364, probably serine 352 in the sequence Lys-Gly-Ser-Pro-Leu, occurs in response to cell stimulation. Phosphorylation in this region of PTP1B, between the N-terminal catalytic domain and the C-terminal membrane localization segment, is proposed to regulate phosphatase activity. 相似文献
66.
Prospects for the genetics of human longevity 总被引:8,自引:0,他引:8
Longevity varies between and within species. The existence of species-specific limit to human life-span and its partial heritability indicate the existence of genetic factors that influence the ageing process. Insight into the nature of these genetic factors is provided by evolutionary studies, notably the disposable soma theory, which suggests a central role of energy metabolism in determining life-span. Energy is important in two ways. First, the disposable soma theory indicates that the optimum energy investment in cell maintenance and repair processes will be tuned through natural selection to provide adequate, but not excessive, protection against random molecular damages (e.g. to DNA, proteins). All that is required is that the organism remains in a sound condition through its natural expectation of life in the wild environment, where accidents are the predominant cause of mortality. Secondly, energy is implicated because of the intrinsic vulnerability of mitochondria to damage that may interfere with the normal supply of energy to the cell via the oxidative phosphorylation pathways. Oxidative phosphorylation produces ATP, and as a by-product also produces highly reactive oxygen radicals that can damage many cell structures, including the mitochondria themselves. Several lines of evidence link, on the one hand, oxidative damage to cell ageing, and on the other hand, energy-dependent antioxidant defences to the preservation of cellular homeostasis, and hence, longevity. Models of cellular ageing in vitro allow direct investigation of mechanisms, such as oxidative damage, that contribute to limiting human life-span. The genetic substratum of inter-individual differences in longevity may be unraveled by a two-pronged reverse genetics approach: sibling pair analysis applied to nonagenarian and centenarian siblings, combined with association studies of centenarians, may lead to the identification of genetic influences upon human longevity. These studies have become practicable thanks to recent progress in human genome mapping, especially to the development of microsatellite markers and the integration of genetic and physical maps. 相似文献
67.
Vincent Calcagno Patrice David Philippe Jarne François Massol 《Ecology letters》2023,26(Z1):S140-S151
How the complexity of food webs depends on environmental variables is a long-standing ecological question. It is unclear though how food-chain length should vary with adaptive evolution of the constitutive species. Here we model the evolution of species colonisation rates and its consequences on occupancies and food-chain length in metacommunities. When colonisation rates can evolve, longer food-chains can persist. Extinction, perturbation and habitat loss all affect evolutionarily stable colonisation rates, but the strength of the competition-colonisation trade-off has a major role: weaker trade-offs yield longer chains. Although such eco-evo dynamics partly alleviates the spatial constraint on food-chain length, it is no magic bullet: the highest, most vulnerable, trophic levels are also those that least benefit from evolution. We provide qualitative predictions regarding how trait evolution affects the response of communities to disturbance and habitat loss. This highlights the importance of eco-evolutionary dynamics at metacommunity level in determining food-chain length. 相似文献
68.
69.
Thelma Panaïotis Marcel Babin Tristan Biard François Carlotti Laurent Coppola Lionel Guidi Helena Hauss Lee Karp-Boss Rainer Kiko Fabien Lombard Andrew M. P. McDonnell Marc Picheral Andreas Rogge Anya M. Waite Lars Stemmann Jean-Olivier Irisson 《Global Ecology and Biogeography》2023,32(11):1991-2005
Aim
The distribution of mesoplankton communities has been poorly studied at global scale, especially from in situ instruments. This study aims to (1) describe the global distribution of mesoplankton communities in relation to their environment and (2) assess the ability of various environmental-based ocean regionalizations to explain the distribution of these communities.Location
Global ocean, 0–500 m depth.Time Period
2008–2019.Major Taxa Studied
Twenty-eight groups of large mesoplanktonic and macroplanktonic organisms, covering Metazoa, Rhizaria and Cyanobacteria.Methods
From a global data set of 2500 vertical profiles making use of the Underwater Vision Profiler 5 (UVP5), an in situ imaging instrument, we studied the global distribution of large (>600 μm) mesoplanktonic organisms. Among the 6.8 million imaged objects, 330,000 were large zooplanktonic organisms and phytoplankton colonies, the rest consisting of marine snow particles. Multivariate ordination (PCA) and clustering were used to describe patterns in community composition, while comparison with existing regionalizations was performed with regression methods (RDA).Results
Within the observed size range, epipelagic plankton communities were Trichodesmium-enriched in the intertropical Atlantic, Copepoda-enriched at high latitudes and in upwelling areas, and Rhizaria-enriched in oligotrophic areas. In the mesopelagic layer, Copepoda-enriched communities were also found at high latitudes and in the Atlantic Ocean, while Rhizaria-enriched communities prevailed in the Peruvian upwelling system and a few mixed communities were found elsewhere. The comparison between the distribution of these communities and a set of existing regionalizations of the ocean suggested that the structure of plankton communities described above is mostly driven by basin-level environmental conditions.Main Conclusions
In both layers, three types of plankton communities emerged and seemed to be mostly driven by regional environmental conditions. This work sheds light on the role not only of metazoans, but also of unexpected large protists and cyanobacteria in structuring large mesoplankton communities. 相似文献70.
Lucie Mahaut Philippe Choler Pierre Denelle Eric Garnier Wilfried Thuiller Jens Kattge Servane Lemauviel-Lavenant Sandra Lavorel François Munoz Delphine Renard Josep M. Serra-Diaz Nicolas Viovy Cyrille Violle 《Global Ecology and Biogeography》2023,32(4):561-572