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991.
Although temporary cyst stages are common in dinoflagellates,their role remains unclear. Every year Alexandrium taylori (Dinophyceae)forms dense patches (106 cells l-1) along La Fosca beach (Spain,northwest Mediterranean), which last for 2 months (July, August).One of the characteristics of the life history of A. tayloriis the shift from a vegetative motile stage to non-motile temporarycysts. Here we present the temporal changes in the abundanceof temporary cysts in sediments and their in situ encystmentand excystment rates. The in situ encystment rate of temporarycysts from the water column to the sediment ranged from 1.8x 106 to 4.4 x 106 cysts m-2 day-1, whereas the excystment ratewas between 0.9 x 106 to 2.7 x 106 cysts m-2 day-1 during thebloom period. Some of the temporary cysts in the sediment tookmore than 1 day to produce vegetative cells and remained viablefor at least 4 days. We propose that temporary cyst formationin this species is a tool for reducing population losses. Theproduction of temporary cysts can be an advantage since partof the population is stored in the sediments. 相似文献
992.
Mutations in torsinA cause dominantly inherited early-onset torsion dystonia in humans. In this issue of Neuron, Goodchild et al. show that torsinA knockout and knockin mice have similar phenotypes, which suggests that the mutant torsinA allele causes disease because it has decreased function. The experiments also highlight the possible role of nuclear envelope dynamics in maintaining normal neuronal function. 相似文献
993.
McCarthy TR Torrelles JB MacFarlane AS Katawczik M Kutzbach B Desjardin LE Clegg S Goldberg JB Schlesinger LS 《Molecular microbiology》2005,58(3):774-790
Mycobacterium tuberculosis (M. tb) pathogenesis involves the interaction between the mycobacterial cell envelope and host macrophage, a process mediated, in part, by binding of the mannose caps of M. tb lipoarabinomannan (ManLAM) to the macrophage mannose receptor (MR). A presumed critical step in the biosynthesis of ManLAM, and other mannose-containing glycoconjugates, is the conversion of mannose-6-phosphate to mannose-1-phosphate, by a phosphomannomutase (PMM), to produce GDP-mannose, the primary mannose-donor in mycobacteria. We have identified four M. tb H37Rv genes with similarity to known PMMs. Using in vivo complementation of PMM and phosphoglucomutase (PGM) deficient strains of Pseudomonas aeruginosa, and an in vitro enzyme assay, we have identified both PMM and PGM activity from one of these genes, Rv3257c (MtmanB). MtmanB overexpression in M. smegmatis produced increased levels of LAM, lipomannan, and phosphatidylinositol mannosides (PIMs) compared with control strains and led to a 13.3 +/- 3.9-fold greater association of mycobacteria with human macrophages, in a mannan-inhibitable fashion. This increased association was mediated by the overproduction of higher order PIMs that possess mannose cap structures. We conclude that MtmanB encodes a functional PMM involved in the biosynthesis of mannosylated lipoglycans that participate in the association of mycobacteria with macrophage phagocytic receptors. 相似文献
994.
The present study was aimed (1) to investigate the effect of cholesterol and fat enriched diets on the development of steatohepatitis in apolipoprotein E-knockout mice, and (2) to study the chronological relationships between the development of hepatic alterations, hypercholesterolemia and atherosclerotic lesions in this experimental model. The study consisted of two protocols. Protocol 1 was used in 90 mice subdivided in groups of 18. For 10 weeks, each group was given a diet with different fat and cholesterol contents. Protocol 2 was used in 42 mice, subdivided in four groups. Each group was given a diet enriched with cholesterol and palm oil and they were sacrificed at 8, 13, 18 and 24 weeks of age. Results were as following. (1) Mice given high fat/high cholesterol diets developed an impairment of liver histology consisting of fat accumulation, macrophage proliferation, and inflammation. (2) These effects were modulated by the type of fat: olive oil was mainly associated with macrovesicular steatosis and cholesterol plus palm oil with severe steatohepatitis. (3) There was a chronological and quantitative relationship between liver impairment and the formation of atheromatous lesions. We conclude that apolipoprotein E-knockout mice may be a useful model for investigating the mechanisms of diet-induced steatohepatitis. (Mol Cell Biochem 268: 53–58, 2008) 相似文献
995.
Jordi Clarimon Georgia Xiromerisiou Johanna Eerola Vanesa Gourbali Olli Hellström Euthimios Dardiotis Terhi Peuralinna Alexandros Papadimitriou George M Hadjigeorgiou Pentti J Tienari Andrew B Singleton 《BMC neurology》2005,5(1):1-5
Background
Fibroblast growth factor 20 (FGF20) is a neurotrophic factor preferentially expressed in the substantia nigra of rat brain and could be involved in dopaminergic neurons survival. Recently, a strong genetic association has been found between FGF20 gene and the risk of suffering from Parkinson's disease (PD). Our aim was to replicate this association in two independent populations.Methods
Allelic, genotypic, and haplotype frequencies of four biallelic polymorphisms were assessed in 151 sporadic PD cases and 186 controls from Greece, and 144 sporadic PD patients and 135 controls from Finland.Results
No association was found in any of the populations studied.Conclusion
Taken together, these findings suggest that common genetic variants in FGF20 are not a risk factor for PD in, at least, some European populations. 相似文献996.
The aim of this study was to characterize the reactivity of monoclonal antibodies (mAbs) that had been submitted to the HLDA8 Workshop. The lineage specificity of target molecules was tested by analyzing their expression patterns on blood cells, leukocytes, and lymphocyte subsets. The expression of target molecules during B cell development, ranging from early precursors to plasma cells, was analyzed using a large panel of B cell lines. Our results have permitted us to characterize the expression of 10 new CD molecules: CD316 (HM1.24, BST2), CD268 (BAFF-R, TNFRSF13C), CD269 (BCMA, TNFRF17), CD267 (TACI, TNFRSF13B), CD275 (ICOSL, B7H2), CD254 (TRANCE, TNFSF11), CD252 (OX40L TNFSF4), CD315 (CD9-P), CD316 (EWI-2, PGRL), and CD307 (IRTA-2 or FcRH5). Three of these new CDs, CD267, CD269, and CD307 presented a B cell-restricted expression pattern. MAbs against these novel cell-surface molecules may offer new tools for research, diagnosis, and therapy. 相似文献
997.
The F7 gene and clotting factor VII levels: dissection of a human quantitative trait locus 总被引:3,自引:0,他引:3
Soria JM Almasy L Souto JC Sabater-Lleal M Fontcuberta J Blangero J 《Human biology; an international record of research》2005,77(5):561-575
Localization of human quantitative trait loci (QTLs) is now routine. However, identifying their functional DNA variants is still a formidable challenge. We present a complete dissection of a human QTL using novel statistical techniques to infer the most likely functional polymorphisms of a QTL that influence plasma levels of clotting factor VII (FVII), a risk factor for cardiovascular disease. Resequencing of 15 kb in and around the F7 gene identified 49 polymorphisms, which were then genotyped in 398 people. Using a Bayesian quantitative trait nucleotide (BQTN) method, we identified four to seven functional variants that completely account for this QTL. These variants include both rare coding variants and more common, potentially regulatory polymorphisms in intronic and promoter regions. 相似文献
998.
Frédéric?SantoulEmail author Nicolas?Mengin Régis?Céréghino Jordi?Figuerola Sylvain?Mastrorillo 《Hydrobiologia》2005,544(1):347-355
We investigated the relationships between different environmental variables and the spatial distribution patterns of the stoneloach (Barbatula barbatula) at the stream system, the stream site, and the mesohabitat (riffle/pool) scales in south-western France. Stoneloach occurred at 240 sites (out of 554 sampling sites), chiefly close to the source, in areas at low elevation and with weak slopes. Population density at a site was primarily influenced by physical conditions. Stream width was positively related to the probability of presence of stoneloach within the stream system, but negatively related to local density. These results indicate that stoneloaches can occur in a wide range of streams, but they are less abundant in wide rivers, probably because of lower habitat heterogeneity. Slope was negatively correlated to both fish presence at the regional scale and local density, suggesting that stoneloach’s swimming performance were weak under greater erosive forces. These results suggested that the distribution of populations and the density of stoneloach were governed by the suitability of physical habitat. Multi-scale studies of factors influencing a species’distribution allow to integrate patterns observed at different scales, and enhance our understanding of interactions between animals and their environment. The use of few pertinent variables in successful final models could reduce the effort and cost of data collection for water management applications. 相似文献
999.
The conformational properties of polygamain and morelensin, two aryltetralin lignan lactones, have been investigated in both the gas-phase and chloroform solution using DFT calculations at the B3LYP/6-311G(d,p) level. Results indicate that the conformation of polygamain is very rigid. Thus, the conformational flexibility of its five-membered rings is considerably restricted as reflects the pseudorotational parameters of the corresponding envelope conformations. On the other hand, morelensin shows a notable conformational flexibility, which is mainly due to its two methoxy groups. Accordingly, 16 minimum energy conformations with relative energies smaller than 2.4 kcal/mol were detected. Furthermore, chemical shifts for 13C nuclei have been calculated using the GIAO method, results being compared with experimental data. A good agreement was found for both polygamain and morelensin. 相似文献
1000.
In order to assess the factors that determine the dynamics of bacteria with high nucleic acid content in aquatic systems, we (i) conducted 24-h in situ dialysis experiments, involving different fractions of plankton and unfiltered water and (ii) examined empirical relationships between bacteria and both abiotic factors and protists, in boreal humic freshwaters (reservoir and lakes) in the James Bay region (Québec, Canada). Bacteria were subdivided into two subgroups on the basis of their nucleic acid content assessed by flow cytometry. The abundance of bacteria with the highest nucleic acid content and high light scatter (HNA-hs) was significantly correlated, across sites, to bacterial production, whereas bacteria with lower nucleic acid content (LNA) and total bacteria were not. In addition, HNA-hs growth was higher and more variable than LNA growth, indicating that HNA-hs were the most dynamic bacteria. Heterotrophic nanoflagellate and ciliate biomass represented, on average, 5 and 13% of bacterial biomass, respectively. Both in ambient waters and in experiments, ciliates were significantly and negatively correlated with bacteria, whereas heterotrophic nanoflagellates, likely under the grazing pressure from ciliates and metazooplankton, were not. Among ciliates, Cyclidium glaucoma appeared to play an important role. Its growth was significantly and negatively correlated to that of HNA-hs but not to that of LNA. In ambient waters, the abundance of this species explained 56% of the variations in HNA-hs abundance and only 27% of those for LNA. The abundances of total bacteria and LNA significantly increased with chlorophyll a, whereas those of HNA-hs did not. In addition, during the experiments, the estimated potential losses of HNA-hs significantly increased with the initial abundance of C. glaucoma. These results suggest selective removal of the most dynamic bacteria by C. glaucoma and indicate that ciliates may play an important role in the dynamics of active bacteria in natural waters. These findings suggest the existence, within the aquatic microbial food webs, of keystone species that are very important in regulating the activity structure of bacteria. 相似文献