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121.
Delayed striate cortical activation during spatial attention 总被引:12,自引:0,他引:12
Noesselt T Hillyard SA Woldorff MG Schoenfeld A Hagner T Jäncke L Tempelmann C Hinrichs H Heinze HJ 《Neuron》2002,35(3):575-587
Recordings of event-related potentials (ERPs) and event-related magnetic fields (ERMFs) were combined with functional magnetic resonance imaging (fMRI) to study visual cortical activity in humans during spatial attention. While subjects attended selectively to stimulus arrays in one visual field, fMRI revealed stimulus-related activations in the contralateral primary visual cortex and in multiple extrastriate areas. ERP and ERMF recordings showed that attention did not affect the initial evoked response at 60-90 ms poststimulus that was localized to primary cortex, but a similarly localized late response at 140-250 ms was enhanced to attended stimuli. These findings provide evidence that the primary visual cortex participates in the selective processing of attended stimuli by means of delayed feedback from higher visual-cortical areas. 相似文献
122.
Schüngel J Passreiter CM 《Zeitschrift für Naturforschung. C, Journal of biosciences》2002,57(11-12):966-968
Melampodium divaricatum is a medicinal plant, which occurs in Central America. In a recent paper we reported the occurrence of acylated 2-hydroxy thymol glycosides as main constituents in this plant. This paper deals with the isolation of two new 2,5-dihydroxythymol ester derivatives. The formerly reported sesquiterpene lactone mikanokryptin was not found in our plant material. 相似文献
123.
Jasmonate-induced lipid peroxidation in barley leaves initiated by distinct 13-LOX forms of chloroplasts 总被引:1,自引:0,他引:1
Bachmann A Hause B Maucher H Garbe E Vörös K Weichert H Wasternack C Feussner I 《Biological chemistry》2002,383(10):1645-1657
In addition to a previously characterized 13-lipoxygenase of 100 kDa encoded by LOX2:Hv:1 [V?r?s et al., Eur. J. Biochem. 251 (1998), 36-44], two full-length cDNAs (LOX2:Hv:2, LOX2:Hv:3) were isolated from barley leaves (Hordeum vulgare cv. Salome) and characterized. Both of them encode 13-lipoxygenases with putative target sequences for chloroplast import. Immunogold labeling revealed preferential, if not exclusive, localization of lipoxygenase proteins in the stroma. The ultrastructure of the chloroplast was dramatically altered following methyl jasmonate treatment, indicated by a loss of thylakoid membranes, decreased number of stacks and appearance of numerous osmiophilic globuli. The three 13-lipoxygenases are differentially expressed during treatment with jasmonate, salicylate, glucose or sorbitol. Metabolite profiling of free linolenic acid and free linoleic acid, the substrates of lipoxygenases, in water floated or jasmonate-treated leaves revealed preferential accumulation of linolenic acid. Remarkable amounts of free 9- as well as 13-hydroperoxy linolenic acid were found. In addition, metabolites of these hydroperoxides, such as the hydroxy derivatives and the respective aldehydes, appeared following methyl jasmonate treatment. These findings were substantiated by metabolite profiling of isolated chloroplasts, and subfractions including the envelope, the stroma and the thylakoids, indicating a preferential occurrence of lipoxygenase-derived products in the stroma and in the envelope. These data revealed jasmonate-induced activation of the hydroperoxide lyase and reductase branch within the lipoxygenase pathway and suggest differential activity of the three 13-lipoxygenases under different stress conditions. 相似文献
124.
CSN1 N-terminal-dependent activity is required for Arabidopsis development but not for Rub1/Nedd8 deconjugation of cullins: a structure-function study of CSN1 subunit of COP9 signalosome
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Wang X Kang D Feng S Serino G Schwechheimer C Wei N 《Molecular biology of the cell》2002,13(2):646-655
The COP9 signalosome (CSN) is a multifunctional protein complex essential for arabidopsis development. One of its functions is to promote Rub1/Nedd8 deconjugation from the cullin subunit of the Skp1-cullin-F-box ubiquitin ligase. Little is known about the specific role of its eight subunits in deneddylation or any of the physiological functions of CSN. In the absence of CSN1 (the fus6 mutant), arabidopsis CSN complex cannot assemble, which destabilizes multiple CSN subunits and contributes, together with the loss of CSN1, to the phenotype of fus6. To distinguish CSN1-specific functions, we attempted to rescue the complex formation with deletion or point-mutation forms of CSN1 expressed as transgenes in fus6. We show that the central domain of CSN1 is critical for complex assembly, whereas the C-terminal domain has a supporting role. By expressing the C231 fragment, which contains the structural information but lacks the presumed functional domain located at the N terminus, we have rescued the complex formation and restored the Rub1/Nedd8 deconjugation activity on cullins (fus6/C231). Nonetheless, fus6/C231 exhibits pleiotropic phenotype, including photomorphogenic defects and growth arrest at seedling stage. We conclude that CSN1 N-terminal domain is not required for the Rub1/Nedd8 deconjugation activity of cullins, but contributes to a significant aspect of CSN functions that are essential for plant development. 相似文献
125.
Ishibashi Y Yoshimura K Nishikawa A Claus S Laudanna C Relman DA 《Cellular microbiology》2002,4(12):825-833
Bordetella pertussis, the causative agent of whooping cough, adheres to human monocytes by means of filamentous haemagglutinin (FHA), a bacterial surface protein that is recognized by complement receptor type 3 (CR3, alphaMbeta2 integrin). Previous work has shown that an FHA Arg-Gly-Asp (RGD, residues 1097-1099) site interacts with a complex composed of leucocyte response integrin (LRI, alphavbeta3 integrin) and integrin-associated protein (IAP, CD47) on human monocytes, resulting in enhancement of CR3-mediated bacterial binding. However, the pathway that mediates alphavbeta3-alphaMbeta2 integrin signalling remains to be characterized. Here we describe the involvement of phosphatidylinositol 3-kinase (PI3-K) in this pathway. Wortmannin and LY294002, inhibitors of PI3-K, reduced alphavbeta3/IAP-upregulated, CR3-associated bacterial binding to human monocytes. B. pertussis infection of human monocytes resulted in a marked recruitment of cellular PI3-K to the sites of B. pertussis contact. In contrast, cells infected with an isogenic strain carrying a G1098A mutation at the FHA RGD site did not show any recruitment of PI3-K. We found that ligation of FHA by alphavbeta3/IAP induced RGD-dependent tyrosine phosphorylation of a 60 kDa protein, which associated with IAP and PI3-K in human monocytes. These results suggest that PI3-K and a tyrosine phosphorylated 60 kDa protein may be involved in this biologically important integrin signalling pathway. 相似文献
126.
A new non-linear normalization method for reducing variability in DNA microarray experiments
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Workman C Jensen LJ Jarmer H Berka R Gautier L Nielser HB Saxild HH Nielsen C Brunak S Knudsen S 《Genome biology》2002,3(9):research0048.1-research004816
Background
Microarray data are subject to multiple sources of variation, of which biological sources are of interest whereas most others are only confounding. Recent work has identified systematic sources of variation that are intensity-dependent and non-linear in nature. Systematic sources of variation are not limited to the differing properties of the cyanine dyes Cy5 and Cy3 as observed in cDNA arrays, but are the general case for both oligonucleotide microarray (Affymetrix GeneChips) and cDNA microarray data. Current normalization techniques are most often linear and therefore not capable of fully correcting for these effects. 相似文献127.
The international meeting Light, Endocrine Systems and Cancer--Facts and Research Perspectives was convened because recent research suggests that ubiquitous light may have more serious cancer consequences than expected. Beyond the established causal link between (over) exposure to sunlight and skin cancer, many scientists consider a causal relationship between light, endocrine systems and internal cancers as biologically plausible. To identify options to turn biological plausibility of mechanisms into true understanding and to assess the possible public health relevance we chose to bring together leading specialists from clinical, experimental laboratory and epidemiological studies of these issues to stimulate a critical, multi-disciplinary discussion of published and new results. Presentations at the symposium covered the physics of light and evolutionary aspects and provided intriguing information about chronobiology, physiology and patho-physiology of endocrine systems and carcinogenesis. Experimental and epidemiological findings on light and skin cancer, and of very recent investigations of relationships between light and internal cancers such as breast cancer were presented. The meeting concluded with a lively discussion of future research options. The symposium's essence and constructive atmosphere are captured in these proceedings [Neuroendocrinol Lett 2002 Jul;23 Suppl 2:1-104] which contain: (i) original presentation papers [Vladimir Anisimov, David Blask, Roland B?ni, George Brainard, Thomas Erren, Alexander Lerchl, Sidney Perkowitz, Chris Portier, Russel Reiter, Richard Stevens, Günter Vollmer]; (ii) abstracts of oral and poster presentations; (iii) four commentaries [Charles Poole, Chris Portier, Till Roenneberg and Rob Lucas, Vladimir Anisimov and Johnni Hansen] on the presentations at the meeting and possible implications for research and public health. In our view, the biological plausibility of mechanistic links between light and hormones and cancer can serve as a unique basis for syn-disciplinary research and we expect that investigations in this area will become a higher priority research focus. 相似文献
128.
The cyclic somatostatin (SST) analogue, cyclo-(7-aminoheptanoyl-Phe-D-Trp-Lys-Thr[BZL]) (cSSTA), has been widely used as somatostatin antagonist. In the human neuroblastoma cell line SH-SY5Y the cyclopeptide acts as a somatostatin receptor agonist. Similar to SST, cSSTA inhibits cell proliferation, activates the protein tyrosine phosphatase SHP-2, and stimulates the activity of mitogen-activated protein kinase. These results suggest that in SH-SY5Y neuroblastoma cells somatostatin receptors may exist which exhibit altered antagonist binding properties. 相似文献
129.
Helledie T Jørgensen C Antonius M Krogsdam AM Kratchmarova I Kristiansen K Mandrup S 《Molecular and cellular biochemistry》2002,239(1-2):157-164
Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that are activated by a number of fatty acids and fatty acid derivatives. By contrast, we have recently shown that acyl-CoA esters display PPAR antagonistic properties in vitro. We have also shown that the adipocyte lipid binding protein (ALBP), the keratinocyte lipid binding protein (KLBP) and the acyl-CoA binding protein (ACBP) exhibit a prominent nuclear localization in differentiating 3T3-L1 adipocytes. Similarly, ectopic expression of these proteins in CV-1 cells resulted in a primarily nuclear localization. We therefore speculated that FABPs and ACBP might regulate the availability of PPAR agonists and antagonists by affecting not only their esterification in the cytoplasm but also their transport to and availability in the nucleus. We show here that coexpression of ALBP or ACBP exerts a negative effect on ligand-dependent PPAR transactivation, when tetradecylthioacetic (TTA) is used as ligand but not when the thiazolidinedione BRL49653 is used as ligand. The results presented here do not support the hypothesis that ALBP facilitates the transport of the fatty acid-type ligands to the nucleus, rather ALBP appears to sequester or increase the turn-over of the agonist. Similarly, our results are in keeping with a model in which ACBP increase the metabolism of these ligands. 相似文献
130.
European cultivars of white lupin (Lupinus albus L.) grow poorly in limed or calcareous soils. However, Egyptian genotypes are grown successfully in highly calcareous soil and show no stress symptoms. To examine their physiological responses to alkaline soil and develop potential screens for tolerance, three experiments were conducted in limed and non-limed (neutral pH) soil. Measurements included net CO2 uptake, and the partitioning of Fe2+ and Fe3+ and soluble and insoluble Ca in stem and leaf tissue. Intolerant plants showed clear symptoms of stress, whereas stress in the Egyptian genotypes and in L pilosus Murr. (a tolerant species) was less marked. Only the intolerant plants became chlorotic and this contributed to their reduced net CO2 uptake in the limed soil. In contrast, Egyptian genotypes and L pilosus showed no change in net CO2 uptake between the soils. The partitioning of Ca and Fe either resulted from the stress responses, or was itself a stress response. L pilosus and some Egyptian genotypes differed in soluble Ca concentrations compared with the intolerant cultivars, although no significant difference was apparent in the Ca partitioning of the Egyptian genotype Giza 1. In a limed soil, Giza 1 maintained its stem Fe3+ concentration at a level comparable with that of plants grown in non-limed soil, whereas stem [Fe3+] of an intolerant genotype increased. Gizal increased the percentage of plant Fe that was Fe2+ in its leaf tissue under these conditions; that of the intolerant genotype was reduced. The potential tolerance of the Egyptian genotypes through these mechanisms and the possibility of nutritional-based screens are discussed. 相似文献