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81.
82.
mRNAs encoding ribulose-1,5-bisphosphate carboxylase remain bound to polysomes but are not translated in amaranth seedlings transferred to darkness 总被引:20,自引:3,他引:17 下载免费PDF全文
Berry JO Carr JP Klessig DF 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(12):4190-4194
When light-grown seedlings of amaranth are transferred to total darkness, synthesis of the large subunit (LS) and small subunit (SS) of ribulose-1,5-bisphosphate carboxylase [RbuP2Case; 3-phospho-D-glycerate carboxylase (dimerizing), EC 4.1.1.39] is rapidly depressed. This reduction in RbuP2Case synthesis occurs in the absence of any corresponding changes in levels of functional mRNA for either subunit. Four hours after light-to-dark transition little, if any, changes in the distribution of LS and SS mRNAs on polysomes could be detected. The association of these mRNAs with polysomes was authenticated by treatment with RNase A or puromycin. Furthermore, polysomes were able to synthesize LS and SS precursor in cell-free translation systems supplemented with inhibitors of initiation. Therefore, during a light-to-dark transition LS and SS mRNAs remained bound to polysomes but were not translated in vivo, suggesting that control is exercised, in part, at the translational elongation step. 相似文献
83.
A gas-liquid chromatographic method for the determination of feprazone in various biological matrixes, employing a choice of detector options, is described. After rapid, micro-scale extraction of the sample with n-butyl acetate at physiological pH, the solution was injected directly onto the chromatograph. Separation was with either an OV7 column and flame ionisation or electron capture detection, or with a carbowax high polymer column and nitrogen specific detection. When 100 mul of plasma was extracted the limit of accurate measurement was 2 mg 1(-1) for F.I.D. and N.P.D. and 0.5 mg 1(-1) with E.C. detection. Quantification was by comparison with a range of plasma calibrators carried throughout the procedure, and determination of peak height ratios against an internal standard incorporated into the extracting solvent. The CV of the assay throughout the concentration range normally encountered in patients undergoing feprazone treatment, ranged between 2.4 and 7.8% for the various detector options. The analytical method has been applied to samples collected both from patients and normal volunteers undergoing treatment with a range of feprazone maintenance doses. 相似文献
84.
Enzymatic determination of potassium in serum 总被引:5,自引:0,他引:5
This is a kinetic assay for measuring K+ in serum, based on the activation of pyruvate kinase (EC 2.7.1.40) by K+. We eliminated interference from Na+ and NH4+ ions, which also activate this enzyme, by including Na+-binding and NH4+-consuming reagents in the reaction mixture. The assay was developed with and evaluated in the Cobas Fara centrifugal analyzer (and has been used in other kinetic analyzers). Within-run and between-run CVs were less than 1.4% and less than 1.6%, respectively. The reaction rate per millimole of K+ per liter (0.05 delta A/min) was more than double that of the reagent blank (0.02 delta A/min). Results correlated well with those by flame photometry, and interference from bilirubin, hemoglobin, lipids, heparin, and other cations was negligible. This method, in conjunction with a previous method we have reported in which beta-galactosidase is used for measuring Na+ in serum, offers a practical alternative to the use of ion-selective electrodes and flame photometry for measuring these clinically important monovalent cations in high-throughput or "stat" biochemical analyzers. 相似文献
85.
Besle J Fort A Giard MH 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2005,166(3-4):337-344
The mismatch negativity (MMN) component of auditory event-related brain potentials can be used as a probe to study the representation of sounds in auditory sensory memory (ASM). Yet it has been shown that an auditory MMN can also be elicited by an illusory auditory deviance induced by visual changes. This suggests that some visual information may be encoded in ASM and is accessible to the auditory MMN process. It is not known, however, whether visual information affects ASM representation for any audiovisual event or whether this phenomenon is limited to specific domains in which strong audiovisual illusions occur. To highlight this issue, we have compared the topographies of MMNs elicited by non-speech audiovisual stimuli deviating from audiovisual standards on the visual, the auditory, or both dimensions. Contrary to what occurs with audiovisual illusions, each unimodal deviant elicited sensory-specific MMNs, and the MMN to audiovisual deviants included both sensory components. The visual MMN was, however, different from a genuine visual MMN obtained in a visual-only control oddball paradigm, suggesting that auditory and visual information interacts before the MMN process occurs. Furthermore, the MMN to audiovisual deviants was significantly different from the sum of the two sensory-specific MMNs, showing that the processes of visual and auditory change detection are not completely independent. 相似文献
86.
87.
Specific antibody responses to three schistosome-related carbohydrate structures in recently exposed immigrants and established residents in an area of Schistosoma mansoni endemicity 下载免费PDF全文
Naus CW van Remoortere A Ouma JH Kimani G Dunne DW Kamerling JP Deelder AM Hokke CH 《Infection and immunity》2003,71(10):5676-5681
By the use of surface plasmon resonance spectroscopy, immunoglobulin G (IgG) subclass and IgM antibodies against three schistosome-derived carbohydrate structures, FLDN (Fucalpha1-3GalNAcbeta1-4GlcNAcbeta1-3Galalpha1), LDN-DF [GalNAcbeta1-4(Fucalpha1-2Fucalpha1-3)GlcNAcbeta1], and LDNF [GalNAcbeta1-4(Fucalpha1-3)GlcNAcbeta1-3Galalpha1], were measured in 184 previously unexposed Kenyan immigrants who moved into the Masongaleni area, where Schistosoma mansoni is endemic. They were sampled within their first year of exposure and again 2 years later. A cohort selected out of the original residents of the area, who had been exposed for many years, served as controls. Associations with responses to S. mansoni worm, egg (SEA), and cercarial (CERC) antigens were examined. In addition, we measured responses to keyhole limpet hemocyanin, a glycoprotein which carries glycan epitopes that are also expressed by schistosomes. Specific IgG1 responses were most pronounced against FLDN and LDN-DF and strongly associated with those previously measured to SEA and CERC. Similarly to previously published age profiles of IgG1 and IgG2 responses to SEA, levels of IgG1 against LDN-DF decreased with age. In contrast, specific IgM responses against the three schistosome-derived carbohydrate structures were most marked against LDNF. Our results indicate that, of the three glycan structures tested, the acute response against schistosome glycoconjugate antigens in young children is mainly directed against the LDN-DF epitope. The response to LDN-DF in older individuals and the responses to the two other epitopes were similar in the two cohorts, suggesting that these antigens are recognized in the early stages of infection and that the immune response persists. The biological significance of these observations needs further elucidation. 相似文献
88.
Rizzitelli A Vremec D Villadangos JA Mavaddat N Wright MD Shortman K 《European journal of immunology》2005,35(11):3209-3220
Freshly isolated quiescent splenic dendritic cell (DC) subtypes differ in their capacity to activate naive CD4 T cells in culture. The CD8+ DC showed a reduced capacity to stimulate T cell proliferation compared to either of the CD8- DC subsets, regardless of antigen and DC dose. In contrast to CD8- DC, the quiescent CD8+ DC did not induce IFN-gamma production from CD4 T cells. The difference between the DC subtypes appeared to be at the level of initial surface molecule interactions, but could not be attributed to differences in expression of MHC class II or B7 family molecules, or to the expression of Fas ligand on DC. However, when activated by inclusion of the Toll-like receptor 9 ligand CpG in culture, CD8+ DC became potent stimulators of both CD4 T cell proliferation and IFN-gamma production. In contrast, similar activation of CD8- DC produced a more modest increase in capacity to stimulate CD4 T cell proliferation and no increase in capacity to stimulate IFN-gamma production. The difference between a quiescent and an activated state is therefore more extreme for CD8+ than for CD8- DC. The especially tight regulation of the activity of CD8+ DC may be essential for the maintenance of self tolerance. 相似文献
89.
Laska M Fendt M Wieser A Endres T Hernandez Salazar LT Apfelbach R 《Physiology & behavior》2005,84(2):211-215
2,4,5-trimethylthiazoline (TMT) is a volatile component of the anal gland secretion of the red fox and elicits behavioral and physiological fear responses in the rat. Using instrumental conditioning paradigms, we determined olfactory detection thresholds for TMT in three rats, a natural prey species of the red fox, and compared their performance to that of three squirrel monkeys, three spider monkeys and four pigtail macaques, all non-prey species of the red fox. We found that the rats were able to discriminate concentrations between 0.04 and 0.10 ppt (parts per trillion) of TMT from the odorless solvent which is by far the lowest olfactory detection threshold for an odorant reported in rats so far. In contrast, the spider monkeys needed 0.14-1.38 ppb (parts per billion), the pigtail macaques 0.41-4.07 ppb, and the squirrel monkeys 4.07-13.80 ppb to detect TMT which does not rank among the lowest olfactory thresholds reported for these three primate species. Thus, these results support the assumption that the behavioral relevance of an odorant may be an important determinant of a species' olfactory sensitivity. 相似文献
90.
Mechanical Analysis of Atherosclerotic Plaques Based on Optical Coherence Tomography 总被引:8,自引:0,他引:8
Chau AH Chan RC Shishkov M MacNeill B Iftimia N Tearney GJ Kamm RD Bouma BE Kaazempur-Mofrad MR 《Annals of biomedical engineering》2004,32(11):1494-1503
Finite element analysis is a powerful tool for investigating the biomechanics of atherosclerosis and has thereby provided an improved understanding of acute myocardial infarction. Structural analysis of arterial walls is traditionally performed using geometry contours derived from histology. In this paper we demonstrate the first use of a new imaging technique, optical coherence tomography (OCT), as a basis for finite element analysis. There are two primary benefits of OCT relative to histology: 1) imaging is performed without excessive tissue handling, providing a more realistic geometry than histology and avoiding structural artifacts common to histologic processing, and 2) OCT imaging can be performed in vivo, making it possible to study disease progression and the effect of therapeutic treatments in animal models and living patients. Patterns of mechanical stress and strain distributions computed from finite element analysis based on OCT were compared with those from modeling based on "gold standard" histology. Our results indicate that vascular structure and composition determined by OCT provides an adequate basis for investigating the biomechanical factors relevant to atherosclerosis and acute myocardial infarction. 相似文献