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111.
The paper explores the capability of [(dppf)Pt(H-nbu2-DTO)]Cl (2) (dppf = 1,1′-diphenylphosphinoferrocene; H-nbu2-DTO = di-nbutyl-dithioxamidate) to act as a starting module for heterometallic linear chains. Actually, the reaction of 2 with [RuCl2(p-cymene)]2 affords the heterotrimetallic complex [Cl(p-cymene) Ru(μ-nbu2-DTO κ-N,N Ru κ-S,S Pt)Pt(dppf κ-P,P Pt) ]2 (4). However 2, allowed to stand, provides a blue compound of formula [(dppf)Pt(H-nbu2-DTO)]nCln (3), the most reliable value of n being 6. The oxidation behavior of the new species 2-4 has also been investigated. In particular, the oxidation behavior of cyclic compound 3 is quite unusual, and suggests a large delocalization of the HOMO over the whole multicomponent molecule. 相似文献
112.
Effects of elevated CO2 , temperature and N fertilization on nitrogen fluxes in a temperate grassland ecosystem 总被引:2,自引:0,他引:2
The soil nitrogen cycle was investigated in a pre‐established Lolium perenne sward on a loamy soil and exposed to ambient and elevated atmospheric CO2 concentrations (350 and 700 μL L?1) and, at elevated [CO2], to a 3 °C temperature increase. At two levels of mineral nitrogen supply, N– (150 kgN ha?1 y?1) and N+ (533 kgN ha?1 y?1), 15N‐labelled ammonium nitrate was supplied in split applications over a 2.5‐y period. The recovery of the labelled fertilizer N was measured in the harvests, in the stubble and roots, in the macro‐organic matter fractions above 200 μm in size (MOM) and in the aggregated organic matter below 200 μM (AOM). Elevated [CO2] reduced the total amount of N harvested in the clipped parts of the sward. The harvested N derived from soil was reduced to a greater extent than that derived from fertilizer. At both N supplies, elevated [CO2] modified the allocation of the fertilizer N in the sward, in favour of the stubble and roots and significantly increased the recovery of fertilizer N in the soil macro‐organic matter fractions. The increase of fertilizer N immobilization in the MOM was associated with a decline of fertilizer N uptake by the grass sward, which supported the hypothesis of a negative feedback of elevated [CO2] on the sward N yield and uptake. Similar and even more pronounced effects were observed for the native N mineralized in the soil. At N–, a greater part of the fertilizer N organized in the root phytomass resulted in an underestimation of N immobilized in dead roots and, in turn, an underestimation of N immobilization in the MOM. The 3 °C temperature increase alleviated the [CO2] effect throughout much of the N cycle, increasing soil N mineralization, N derived from soil in the harvests, and the partitioning of the assimilated fertilizer N to shoots. In conclusion, at ambient temperature, the N cycle was slowed down under elevated [CO2], which restricted the increase in the aboveground production of the grass sward, and apparently contributed to the sequestration of carbon belowground. In contrast, a temperature increase under elevated [CO2] stimulated the soil nitrogen cycle, improved the N nutrition of the sward and restricted the magnitude of the soil C sequestration. 相似文献
113.
Désiré L Bourdin J Loiseau N Peillon H Picard V De Oliveira C Bachelot F Leblond B Taverne T Beausoleil E Lacombe S Drouin D Schweighoffer F 《The Journal of biological chemistry》2005,280(45):37516-37525
beta-Amyloid peptides (Abeta) that form the senile plaques of Alzheimer disease consist mainly of 40- and 42-amino acid (Abeta 40 and Abeta 42) peptides generated from the cleavage of the amyloid precursor protein (APP). Generation of Abeta involves beta-secretase and gamma-secretase activities and is regulated by membrane trafficking of the proteins involved in Abeta production. Here we describe a new small molecule, EHT 1864, which blocks the Rac1 signaling pathways. In vitro, EHT 1864 blocks Abeta 40 and Abeta 42 production but does not impact sAPPalpha levels and does not inhibit beta-secretase. Rather, EHT 1864 modulates APP processing at the level of gamma-secretase to prevent Abeta 40 and Abeta 42 generation. This effect does not result from a direct inhibition of the gamma-secretase activity and is specific for APP cleavage, since EHT 1864 does not affect Notch cleavage. In vivo, EHT 1864 significantly reduces Abeta 40 and Abeta 42 levels in guinea pig brains at a threshold that is compatible with delaying plaque accumulation and/or clearing the existing plaque in brain. EHT 1864 is the first derivative of a new chemical series that consists of candidates for inhibiting Abeta formation in the brain of AD patients. Our findings represent the first pharmacological validation of Rac1 signaling as a target for developing novel therapies for Alzheimer disease. 相似文献
114.
115.
Rat hepatoma (HTC) cell 6-phosphofructo-2-kinase differs from that in liver and can be separated from fructose-2,6-bisphosphatase 总被引:4,自引:0,他引:4
A M Loiseau M H Rider D Foret G G Rousseau L Hue 《European journal of biochemistry》1988,175(1):27-32
6-Phosphofructo-2-kinase was purified from rat liver and hepatoma (HTC) cells. The HTC cell enzyme had kinetic properties different from those of the liver enzyme (more sensitive to inhibition by citrate and not inhibited by sn-glycerol 3-phosphate) and was not a substrate of the cyclic-AMP-dependent protein kinase. Unlike the liver enzyme, which is bifunctional and phosphorylated by fructose 2,6-[2-32P]bisphosphate, the HTC cell enzyme contained no detectable fructose-2,6-bisphosphatase activity and phosphorylation by fructose 2,6-[2-32P]-bisphosphate could not be detected. HTC cell fructose-2,6-bisphosphatase could be separated from 6-phosphofructo-2-kinase activity by purification. Antibodies raised against liver 6-phosphofructo-2-kinase did not precipitate HTC cell fructose-2,6-bisphosphatase whose kinetic properties were completely different from those of the liver enzyme. 相似文献
116.
J. Nafziger J. J. Guillosson Y. Adam C. Hecquet M. Payard M. Loiseau 《Cytotechnology》1991,6(3):227-232
New derivatives of imidazothiazole and imidazobenzothiazole were testedin vitro for their potential antiproliferative activity. Four imidazobenzothiazole derivatives exhibited a cytotoxic activity against two leukemic cell lines, compound I being the most effective. Cell cycle kinetics studies showed that this drug delays the progression of cells from G1 to S and G2 M phases. An inhibitory effect on DNA and RNA synthesis was also observed. The antiproliferative effect of this compound, analogue of immunosuppressive agents, suggested that it could be of interest for a therapeutic use and for the synthesis of new derivatives. 相似文献
117.
Jenny S. Carlson Juan E. Martínez‐Gómez Anthony Cornel Claire Loiseau Ravinder N. M. Sehgal 《Journal of vector ecology》2011,36(1):213-220
Avian malaria (Plasmodium spp.) has been implicated in the decline of avian populations in the Hawaiian Islands and it is generally agreed that geographically isolated and immunologically naïve bird populations are particularly vulnerable to the pathogenic effects of invasive malaria parasites. In order to assess the potential disease risk of malaria to the avifauna of Socorro Island, México, we surveyed for Plasmodium isolates from 1,300 resident field‐caught mosquitoes. Most of them were identified as Aedes (Ochlerotatus) taeniorhynchus (Wiedemann, 1821), which were abundant in the salt marshes. We also collected Culex quinquefasciatus Say, 1823 close to human dwellings. Mitochondrial ND5 and COII gene sequences of Ae. taeniorhynchus were analyzed and compared to corresponding sequences of mosquitoes of the Galápagos Islands, Latin America, and the North American mainland. Aedes lineages from Socorro Island clustered most closely with a lineage from the continental U.S. Plasmodium spp. DNA was isolated from both species of mosquitoes. From 38 positive pools, we isolated 11 distinct mitochondrial Cytb lineages of Plasmodium spp. Seven of the Plasmodium lineages represent previously documented avian infective strains while four were new lineages. Our results confirm a potential risk for the spread of avian malaria and underscore the need to monitor both the mosquito and avian populations as a necessary conservation measure to protect endangered bird species on Socorro Island. 相似文献
118.
Enantiomer separation of 1,4-sulfanylalcohols by conventional and low-temperature gas chromatography
Since 1990, the family of organosulfur molecules has assumed increasing importance in pheromone, flavour, and fragrance chemistry. Depending on the constitution of the functional groups, various volatile sulfur-containing compounds are chiral. However, hitherto it has been impossible to study the chirality of 1,4-sulfanylalcohols, since no adequate enantioselective analytical technique has been available. Here we report on the enantiomer separation of ten volatile 1,4-sulfanylalcohol homologues by applying an heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-beta-cyclodextrin phase, involving in some cases the use of a low-temperature gas chromatographic (ltGC) technique. The results are expected to open research potential on the asymmetry of volatile organosulfur molecules, particularly in the fields of pheromone, flavour, and fragrance research. 相似文献
119.
Chevrollier A Loiseau D Chabi B Renier G Douay O Malthièry Y Stepien G 《Journal of bioenergetics and biomembranes》2005,37(5):307-317
The three adenine nucleotide translocator ({ANT1} to {ANT3}) isoforms, differentially expressed in human cells, play a crucial
role in cell bioenergetics by catalyzing ADP and ATP exchange across the mitochondrial inner membrane. In contrast to differentiated
tissue cells, transformed cells, and their ρ0 derivatives, i.e. cells deprived of mitochondrial DNA, sustain a high rate of glycolysis. We compared the expression pattern
of {ANT} isoforms in several transformed human cell lines at different stages of the cell cycle. The level of {ANT2} expression
and glycolytic ATP production in these cell lines were in keeping with their metabolic background and their state of differentiation.
The sensitivity of the mitochondrial inner membrane potential (Δψ) to several inhibitors of glycolysis and oxidative phosphorylation
confirmed this relationship. We propose a new model for ATP uptake in cancer cells implicating the {ANT2} isoform, in conjunction
with hexokinase II and the β subunit of mitochondrial ATP synthase, in the Δψ maintenance and in the aggressiveness of cancer
cells. 相似文献
120.
Sehgal RN Buermann W Harrigan RJ Bonneaud C Loiseau C Chasar A Sepil I Valkiūnas G Iezhova T Saatchi S Smith TB 《Proceedings. Biological sciences / The Royal Society》2011,278(1708):1025-1033
Critical to the mitigation of parasitic vector-borne diseases is the development of accurate spatial predictions that integrate environmental conditions conducive to pathogen proliferation. Species of Plasmodium and Trypanosoma readily infect humans, and are also common in birds. Here, we develop predictive spatial models for the prevalence of these blood parasites in the olive sunbird (Cyanomitra olivacea). Since this species exhibits high natural parasite prevalence and occupies diverse habitats in tropical Africa, it represents a distinctive ecological model system for studying vector-borne pathogens. We used PCR and microscopy to screen for haematozoa from 28 sites in Central and West Africa. Species distribution models were constructed to associate ground-based and remotely sensed environmental variables with parasite presence. We then used machine-learning algorithm models to identify relationships between parasite prevalence and environmental predictors. Finally, predictive maps were generated by projecting model outputs to geographically unsampled areas. Results indicate that for Plasmodium spp., the maximum temperature of the warmest month was most important in predicting prevalence. For Trypanosoma spp., seasonal canopy moisture variability was the most important predictor. The models presented here visualize gradients of disease prevalence, identify pathogen hotspots and will be instrumental in studying the effects of ecological change on these and other pathogens. 相似文献