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51.
AS Shashkov NA Paramonov SP Veremeychenko H Grosskurth GM Zdorovenko YA Knirel NK Kochetkov 《Canadian Metallurgical Quarterly》1998,306(1-2):297-303
The O-specific polysaccharide of Pseudomonas fluorescens biovar B, strain IMV 247, was studied by acid hydrolysis, GLC-MS and 1H and 13C NMR spectroscopy, including 1D and 2D NOE, 2D hybrid TOCSY and ROESY (TORO), and 2D H-detected heteronuclear multiple-bond correlation (HMBC) experiments. The polysaccharide was found to contain L-rhamnose, 3.6-dideoxy-3-[(S)-3-hydroxybutyramido]-D-glucose (D-Qui3NHb), 2-acetamido- 2,4,6-trideoxy-4-[(S)-3-hydroxybutyramido-D-glucose (D-QuiNAc4NHb) and 2-acetamido-2- deoxy-D-galacturonic acid (D-GalNAcA). Partial acid hydrolysis of the polysaccharide resulted in a non-reducing GalNAcA-->QuiNAc4NHb disaccharide with the 3-hydroxybutyryl group glycosylated intramolecularly by the QuiN4N residue. The following structure of the tetrasaccharide repeating unit of the polysaccharide was established:-->4) -alpha-D-GalpNAcA-(1-->3)- alpha-D-QuipNAc4NHb-(1-->2)-beta-D-Quip3NHb-(1-->2)-alpha-L- Rhap(1-->. 相似文献
52.
The binding of the calcium-regulatory protein calmodulin (CaM) to caldesmon (CaD) contributes to the regulation of smooth muscle contraction. Two regions of caldesmon have been identified as putative calmodulin-binding domains. We have earlier reported on the binding of one of these domains to calmodulin (Zhang & Vogel (1994) Biochemistry 33, 1163-1171). Here we have studied the binding of CaM to synthetic peptides of CaD which contain: (1) both the first and second CaM-binding domains; (2) the second CaM-binding domain; and (3) the sequence between the first and second CaM-binding domains. Two-dimensional transferred nuclear Overhauser enhancement proton NMR measurements as well as circular dichroism studies of a 22-residue peptide NKETAGLKVGVSSRINEWLTK, which contains the second CaM-binding domain, show that only the C-terminal half of the peptide becomes alpha-helical upon binding to CaM. Somewhat surprisingly, the shorter 9-residue peptide SRINEWLTK was sufficient to form a 1:1 complex with CaM; this peptide appears to bind as a 3(10)-helix. Proton-carbon-13 correlation NMR titration studies with specifically labeled [methyl-13C]methionine CaM were used to study the participation of the hydrophobic regions in both domains of the dumbbell shaped CaM in peptide binding. Binding of a 54-residue CaD peptide containing both CaM-binding domains affects all the 8 Met residues in the two hydrophobic domains of CaM (only Met 76 in the linker region of CaM is not involved), while binding of the second CaM-binding domain of CaD influences principally Met 51, 71, and Met 124, 144. Simultaneous binding to CaM of two peptides comprising the first and the second CaM-binding domains also caused changes to all Met residues except Met 76. Taken together, these data demonstrate that both CaM-binding domains of CaD can bind simultaneously to the two hydrophobic regions of CaM. 相似文献
53.
The goal of work was to investigate the electrogenic transport of Na ions by Na+,K(+)-ATPase in membrane fragments absorbed on a planar bilayer lipid membrane. The photorelease of ATP from an inactive precursor, caged ATP, induced a transient current and changes in the net system capacitance measured during the application of an alternating voltage. The increments of capacitance (delta c) decreased with the increase in the frequency of the applied voltage. The characteristic frequency F0 of the steepest slope of the curve significantly decreased in solutions with high ionic strength (either NaCl or choline chloride), in which Na+ transport is decelerated. The value of delta c correlated with the total charge delta q transported across the membrane. The capacitance increments decreased when the Na+ concentration in solution decreased. At a concentration below 2 mM the increment became negative. The increase in membrane capacitance can be attributed to the charge relaxation process inside the protein, as discovered in the cells by other methods. The characteristic frequency F0 depends on the time constants of charge redistribution. The nonlinear dependences of delta c on delta q were explained by a voltage bias across the membrane fragments resulting from pumping. The potentials corresponding to the maximum capacitance change were similar to the midpoint potentials of the equilibrium charge distribution and depended on the Na+ concentrations in solution. The model enabled also the determination of the total capacitance of the active region of a lipid membrane with the adsorbed protein containing membrane fragments. 相似文献
54.
A questionnaire concerning the detection and management of hypertension was presented to 265 hospital doctors, 114 medical students and 59 student nurses. Of these 75% were completed. Although only 76% thought that routine measurement was necessary in outpatients, 92% of respondents thought that blood pressure (BP) should be measured routinely in all in-patients. A total of 17% of all doctors and 11% of physicians indicated that they would not use drug treatment until the diastolic BP exceeded 105 mmHg. Thirty-four per cent of respondents still use diastolic phase IV and 84% felt that BP should be measured 2-4 times before deciding on treatment but the posture of the patient (lying, sitting or standing) during recording was inconsistent. Seventy-seven per cent of respondents indicated that they recorded BP to the nearest 5 mmHg and 4% to the nearest 10 mmHg. Despite the literature on the subject, there are still widely differing opinions amongst medical staff on how to record BP and at what level it should be treated. 相似文献
55.
AA al-Jafari MA Kamal NH Greig AS Alhomida ER Perry 《Canadian Metallurgical Quarterly》1998,248(1):180-185
The elastic properties of carotid arteries of spontaneously hypertensive rats (SHR) and normotensive controls (Wistar-Kyoto rats [WKY]) were examined in vivo, in situ, and in vitro. The changes of internal diameter were measured with a high-resolution A-mode echo-tracking device simultaneously with the intra-arterial pressure at the carotid. The internal diameter at mean arterial blood pressure (MBP) was substantially smaller in vitro than in vivo in SHR (-33.8%) and WKY (-48.3%). The arterial distensibility was lower in vitro in all arteries compared with in vivo conditions (SHR, -30.1%; WKY, -60.4%; at MBP) despite a reduced incremental elastic modulus in vitro (SHR, -56.9%; WKY, -45.1%; at MBP). However, the in vitro and in vivo measurements show consistent elastic behavior of the carotid arteries between both strains of rats. Carotid arteries from WKY were also examined in situ. Although no significant reduction in internal diameter could be observed in situ, distensibility was dramatically decreased (-87% at MBP). These results emphasize the importance of considering the original vascular geometry when determining elastic properties of arteries. We conclude that experimental conditions are likely to be a critical determinant for the assessment of the mechanical properties of conduit vessels. 相似文献
56.
JD Gilbert TF Greber JD Ellis A Barrish TV Olah C Fernández-Metzler AS Yuan CJ Burke 《Canadian Metallurgical Quarterly》1995,13(8):937-950
An analytical method based on radioimmunoassay (RIA) has been developed for the determination of the antiarrhythmic agent, MK-0499, in plasma and urine. Owing to the potency of the drug, the specificity of this assay in human plasma could not be adequately determined using conventional RIA procedures. A highly specific procedure, based on LC/MS-MS, was developed to cross-validate the RIA. The lower quantifiable limits of the RIA and LC/MS-MS-based methods were 0.05 and 0.013 ng ml-1, respectively. Cross-validation data, compared using paired student's t-test regression analysis, showed excellent correlation between methods. The mass spectrometric assay was also used to simultaneously measure plasma concentrations of unlabeled and 14C-labeled MK-0499 following administration of the drug at high specific activity to volunteers. 相似文献
57.
Past analysis of dysbaric-induced cerebral perfusion defects, demonstrated by 99Tcm-hexamethylpropylene amine oxime (99Tcm-HMPAO) single photon emission tomography in divers using quantitative and/or univariate techniques, has resulted i considerable controversy regarding the significance of these lesions compared to those seen in control subjects, correlations with clinical findings and the role of 99Tcm-HMPAO as a prognostic indicator in decompression sickness. We tried to address these problems by using a multivariate approach to a voxel-by-voxel analysis, involving the use of principal components, to determine ranges of normality in 50 reference controls. In subsequent images, abnormality was defined as 10 spatially connected voxels at an appropriate significance level of three standard deviations. The images of 50 divers with clinically diagnosed 'bends' were compared with those of a further 40 normal population controls with no previous history of loss of consciousness, head injury or dysbarism. The results showed that 19 of 50 divers with 'bends' and 3 of 40 population controls had significant perfusion defects, representing a significant difference between divers with dysbarism and population controls at the level P < 0.002. It is concluded that dysbarism causes significant cerebral cortical perfusion defects in affected divers both in 'silent' and symptomatic (clinically correlated) areas. 相似文献
58.
59.
Pathfinding mechanisms underlying retinal ganglion cell (RGC) axon growth from the optic chiasm into the optic tract are unknown. Previous work has shown that mouse embryos deficient in GAP-43 have an enlarged optic chiasm within which RGC axons were reportedly stalled. Here we have found that the enlarged chiasm of GAP-43 null mouse embryos appears subsequent to a failure of the earliest RGC axons to progress laterally through the chiasm-tract transition zone to form the optic tract. Previous work has shown that ventral diencephalon CD44/stage-specific embryonic antigen (SSEA) neurons provide guidance information for RGC axons during chiasm formation. Here we found that in the chiasm-tract transition zone, axons of CD44/SSEA neurons precede RGC axons into the lateral diencephalic wall and like RGC axons also express GAP-43. However unlike RGC axons, CD44/SSEA axon trajectories are unaffected in GAP-43 null embryos, indicating that GAP-43-dependent guidance at this site is RGC axon specific or occurs only at specific developmental times. To determine whether the phenotype results from loss of GAP-43 in RGCs or in diencephalon components such as CD44/SSEA axons, wild-type, heterozygous, or homozygous GAP-43 null donor retinal tissues were grafted onto host diencephalons of all three genotypes, and graft axon growth into the optic tract region was assessed. Results show that optic tract development requires cell autonomous GAP-43 function in RGC axons and not in cellular elements of the ventral diencephalon or transition zone. 相似文献
60.