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排序方式: 共有392条查询结果,搜索用时 15 毫秒
1.
Senescence-induced alteration in cell surface carbohydrates correlated using proton NMR spectroscopy and a lectin-based affinity-binding assay 总被引:1,自引:0,他引:1
Changes in the cell surface oligosaccharides in human fetal lung fibroblasts (IMR-90) are studied as the cells progress to senescence using nuclear magnetic resonance spectroscopy (NMR) and a biochemical assay. A lectin-based affinity-binding technique is used which measures the organization of carbohydrates on the cell surface. Proton NMR studies of the water in samples of frozen cell suspensions of young and old cells provide information on the local dynamics of the cell surface by monitoring the motion of bound water. Changes in the lectin binding density and affinity class distribution correlate with a decrease in the water proton linewidth in frozen cells. These observations reflect alterations in the conformation or structure of the cell surface oligosaccharides and local constituent water. 相似文献
2.
Generation of nitric oxide by human neutrophils 总被引:25,自引:0,他引:25
C D Wright A Mülsch R Busse H Osswald 《Biochemical and biophysical research communications》1989,160(2):813-819
Human neutrophils were evaluated for their ability to generate nitric oxide. Neutrophils incubated with superoxide dismutase at 37 degrees C produce nitrite anion at a rate of 1.8 nmols/2 x 10(6) cells/30 min, providing indirect evidence of nitric oxide production. Incubation of the neutrophils with concentrations of serum-opsonized zymosan, N-formyl-methionyl-leucyl-phenylalanine, or phorbol myristate acetate sufficient to stimulate the respiratory burst and lysosomal enzyme release caused no additional nitrite anion production. Glass wool-adherent neutrophils exhibited a similar dissociation of nitrite anion production from the respiratory burst and lysosomal enzyme release. Direct evidence for nitric oxide production was also obtained using nitric oxide-specific chemiluminescence. These results demonstrate that human neutrophils are capable of generating nitric oxide. 相似文献
3.
We have isolated the delta-globin gene of the New-World spider monkey,
Ateles geoffroyi, and compared its nucleotide sequence with those of other
primate delta- and beta-globin genes. Among primate delta-globin genes, the
rate of nonsynonymous substitutions is much less than the rate of
synonymous substitutions. This suggests that primate delta- globin genes
may remain under evolutionary conservation, perhaps because hemoglobin A2
has an as yet unknown physiological importance.
相似文献
4.
The phagovar variability of Listeria strains under the influence of virulent and temperate bacteriophages 总被引:1,自引:1,他引:0
Selected strains of Listeria spp. were challenged against a variety of bacteriophages usually employed for phage typing. The resistant mutants derived were characterized by the loss of sensitivity to defined groups of phages. When different phages were used in succession multiple mutants could be obtained. They eventually became insensitive to all phages employed. Our results indicate the possibility of shifting phagovars among Listeria strains grown in mixed culture, due to the potential action of free bacteriophages. 相似文献
5.
Long term oscillation in glycolysis 总被引:3,自引:0,他引:3
To increase the period of glycolytic oscillations in yeast extracts (Saccharomyces uvarum), the dependence of the period on pH, on concentrations of phosphate and enzymes, and on temperature has been studied. Stable oscillatory trans were obtained at a pH value of about 6.5. Increasing the phosphate and decreasing the enzyme concentrations as well as decreasing temperature lengthened the period. By dilution of the extract with buffer while maintaining the metabolite concentrations at their initial level the period could be successively prolonged from 20 min to about 6 h. 相似文献
6.
Biochemical pathways in prokaryotes can be traced backward through evolutionary time 总被引:10,自引:0,他引:10
For the first time, a credible prokaryotic phylogenetic tree is being
assembled by Woese and others using quantitative sequence analysis of
oligonucleotides in the highly conservative rRNA. This provides an
evolutionary scale against which the evolutionary steps that led to the
arrangement and regulation of contemporary biochemical pathways can be
measured. This paper presents an emerging evolutionary picture of aromatic
amino acid biosynthesis within a large superfamily assemblage of
prokaryotes that is sufficiently developed to illustrate a new perspective
that will be applicable to many other biochemical pathways.
相似文献
7.
Induction and activity of NO synthase in bone-marrow-derived macrophages are independent of Ca2+.
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S Hauschildt A Lückhoff A Mülsch J Kohler W Bessler R Busse 《The Biochemical journal》1990,270(2):351-356
The aim of the present study was to analyse whether an increase in the intracellular free Ca2+ concentration ([Ca2+]i) plays a role as a signal mediating synthesis of nitric oxide (NO) in bone-marrow-derived macrophages, either by stimulating induction of NO synthase or by regulating the activity of the enzyme. Therefore we compared the effects of various synthetic analogues of bacterial lipopeptide and of lipopolysaccharide (LPS) on NO production (assessed as nitrite formation during an incubation for 24 h) and on [Ca2+]i [measured with the fluorescent probe indo-1 (1-[2-amino-5-(6-carboxyindol-2-yl)phenoxy]-2- 2-(2'-amino-5'-methylphenoxy)ethane-NNN'N'-tetra-acetic acid)]. Strongly dissociating effects were evoked on nitrite formation and on [Ca2+]i by the stimuli. LPS was preferentially effective on nitrite formation, whereas the Ca2+ ionophore ionomycin and AlF3 induced increases only in [Ca2+]i. The lipopeptides N-palmitoyl-(S)-[2,3-bis(palmitoyloxy)-(2RS)- propyl]-(R)-cysteinylalanylglycine, N-palmitoyl-(S)-[2,3-bis(palmitoyloxy)- (2RS)-propyl]-(R)-cysteinylseryl-lysyl-lysyl-lysine and (S)-(1,2- dicarboxyhexadecyl)ethyl-N-palmitoylcysteinylseryl-lysyl-lys yl-lysine stimulated both parameters, but the maximal effects on nitrite formation and the shape of the dose-response curves did not parallel the effects on [Ca2+]i. Reduction of extracellular Ca2+ with EGTA significantly inhibited increases in [Ca2+]i, but did not change nitrite formation. Furthermore, NO synthesis in the cytosolic fraction of stimulated macrophages was not affected by Ca2+ over the concentration range 10 nM-2 microM. We conclude that increases in [Ca2+]i are not required for NO production in bone-marrow-derived macrophages. Thus the cellular regulation of NO production strikingly differs from that in the vascular endothelium, brain and adrenal gland. 相似文献
8.
9.
Paracrine functions of the coronary vascular endothelium 总被引:5,自引:0,他引:5
Ingrid Fleming Johann Bauersachs Rudi Busse 《Molecular and cellular biochemistry》1996,157(1-2):137-145
10.
In Drosophila pseudoobscura, the amylase (Amy) multigene family is
contained within a series of inversions, or gene arrangements, on the third
chromosome. The Standard (ST), Santa Cruz (SC), and Tree Line (TL)
inversions are central to the phylogeny of arrangements, and have clusters
of other arrangements derived from them. The gene arrangements belonging to
each of these three clusters have a characteristic number of Amy genes,
ranging from three in ST to two in SC to one in TL. This distribution
pattern can reflect a history of either duplications or deletions, although
the data available in the past did not permit a decision between these
alternatives. We provide unambiguous evidence that three Amy genes were
present before the divergence of the ST, SC, and TL arrangements. Thus, the
current status of the Amy multigene family is the result of deletions in
the TL and SC arrangements, which created three new pseudogenes: TL
Amy2-psi, TL Amy3-psi, and SC Amy3- psi. Analysis of pseudogene sequences
revealed that, in the SC and ST arrangements, pseudogene evolution has been
retarded, most likely due to the homogenization effect of gene conversion.
Finally, by determining the original copy number, we have reconstructed the
evolutionary history of the Amy multigene family and linked it with the
evolution of the central gene arrangements.
相似文献