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81.
The polyene antibiotic amphotericin B acts as a Ca2+ ionophore in sterol-containing liposomes 总被引:3,自引:0,他引:3
Amphotericin B (AmB) was shown to induce a Ca2+ influx across ergosterol- and cholesterol-containing large unilamellar liposomes, by following spectrophotometrically the formation of the Arsenazo III-Ca2+ complex. At equivalent antibiotic concentrations the Ca2+ influx was much more extensive through ergosterol-containing membranes (almost 100% with 1 microM AmB, 160 microM lipid) than through cholesterol-containing membranes (below 0.5 microM the influx of Ca2+ was negligible). In the presence of ergosterol-containing membranes the initial rate of Ca2+ influx had the same linear dependence on the ratio antibiotic/lipid whatever the lipid concentration, which was not the case in cholesterol-containing membranes. These results suggest that the channels responsible for the AmB-induced Ca2+ permeability across cholesterol- and ergosterol-containing liposomes have different structures. 相似文献
82.
Structural analysis of the mouse mdr1a (P-glycoprotein) promoter reveals the basis for differential transcript heterogeneity in multidrug-resistant J774.2 cells. 总被引:5,自引:2,他引:3
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S I Hsu D Cohen L S Kirschner L Lothstein M Hartstein S B Horwitz 《Molecular and cellular biology》1990,10(7):3596-3606
83.
Position effects on the timing of replication of chromosomally integrated simian virus 40 molecules in Chinese hamster cells. 总被引:2,自引:1,他引:1
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Simian virus 40 (SV40) DNA molecules chromosomally integrated at different sites in three Chinese hamster lung fibroblast lines replicated during the middle portion of S phase but not precisely at the same time in all three cell lines. The time of replication was unrelated to the presence of T antigen or to its relative activity in promoting SV40 replication. SV40 sequences and chromosomal DNA sequences adjacent to the SV40 insert in one cell line expressing a temperature-sensitive T antigen showed a T-antigen-independent difference in replication timing from the homologous, allelic locus not linked to SV40. Our results indicate that the timing of replication of these integrated SV40 molecules is dependent upon the site of integration and is not determined by the level of T antigen replication-promoting activity. 相似文献
84.
Marion Laig Michael Pape Joachim Hundrieser Gebhard Flatz Torpong Sanguansermsri B. M. Das Ranjan Deka Puangrat Yongvanit Naret Mularlee 《Human genetics》1990,84(2):188-190
Summary The distribution of the hemoglobin Constant Spring (Hb CS) gene in eight populations in Southeast Asia (including Assam) was determined using oligonucleotide hybridization. Hb CS was absent in two Assamese populations with a high prevalence of Hb E. The Hb CS gene frequency was 0.033 in northern Thailand and near 0.01 in central Thailand and Cambodia. High frequencies, between 0.05 and 0.06, were observed in northeastern Thailand. The present data and a similar study in Laotians suggest that the Lao-speaking populations of the Mekong River basin in northeastern Thailand and Laos have the highest frequencies of the Hb CS gene in Southeast Asia. 相似文献
85.
I. Lerer S. Cohen M. Chemke A. Sanilevich J. Rivlin A. Golan J. Yahav A. Friedman D. Abeliovich 《Human genetics》1990,85(4):416-417
Summary We have analysed the distribution of the ΔF508 mutation and the haplotypes of cystic fibrosis (CF) bearing chromosomes among
the Israeli CF population. The population was classified according to its ethnic origin and included 3 groups, Ashkenazi Jews,
Sephardic/Oriental Jews and Arabs. Haplotype B (KM19 allele 2, XV2c allele 1) was found to be the predominant haplotype in
all groups but in each of them the haplotype distribution was different. The ΔF508 mutation was present in all groups and
accounts for 32% of the CF mutations. It was mainly associated with the B haplotype but only one third of the CF chromosomes
with this haplotype carry the ΔF508 mutation.
This work is dedicated to Dr. Ruth Voss who initiated the CF study in Israel and was tragically killed in a car accident on
7 August 1988 相似文献
86.
The enzyme acetyl-CoA: 17-O-deacetylvindoline 17-O-acetyltransferase which terminates vindoline biosynthesis has been isolated from Catharanthus roseus leaves, further characterized and purified to homogeneity by three step column chromatography and subsequent preparative isoelectric focusing. Kinetic properties concerning the enzyme reaction are discussed. Five multiple forms of the acetyl-transferase could be observed, each consisting of two subunits. This enzyme is now the best characterized of the enzymes involved in vindoline biosynthesis.Abbreviations DTE
dithiothreitol
- EDTA
ethylenediamine-tetraacetic acid
- HEPES
N-(2-hydroxyethyl)-piperazine-N-2-ethanesulfonic acid
- IEF
isoelectric focusing
- KPi
potassium phosphate
- Mr
rel.molecular mass
- PEG
polyethylene glycol
- SDS-PAGE
sodium dodecylsulfate polyacrylamide gel electrophoresis
- Tris
2-amino-2-(hydroxymethyl)-1,3-propandiol 相似文献
87.
Evolution of isopenicillin N synthase genes may have involved horizontal gene transfer 总被引:3,自引:0,他引:3
G Landan G Cohen Y Aharonowitz Y Shuali D Graur D Shiffman 《Molecular biology and evolution》1990,7(5):399-406
The isopenicillin N synthase genes from three fungal species, three Gram-positive species, and one Gram-negative bacterial species share an unusually high sequence similarity. A phylogenetic analysis was carried out to determine which type of evolutionary scenario best accounts for this similarity. The most plausible scenario is one in which a horizontal gene-transfer event, from the prokaryotes to the eukaryotes, occurred at a time close to the divergence between the Gram-positive and the Gram-negative bacteria. 相似文献
88.
A simultaneous increase is found in the level of protein synthesis and the major regulatory glycolytic enzyme, phosphofructokinase (PFK), in early phytohemagglutinin exposure of human lymphocytes. The induction of DNA synthesis is demonstrated to be a much later event. This indicates that the increase of glycolysis in mitogen-stimulated cells precedes cell proliferation, but occurs simultaneously with a general increase in protein synthesis. Chemical inhibitors are used to clarify the interrelationship of protein synthesis, glycolytic enzymes levels, and DNA synthesis. Inhibition of protein synthesis with cycloheximide in the mitogen-exposed lymphocytes prevents any increase in PFK levels, implicating protein synthesis as a cause for the increased glycolysis. Cycloheximide also prevents entry into S phase in mitogen-stimulated lymphocytes which may be due to inhibition of the synthesis of enzymes necessary for DNA synthesis, such as DNA polymerase. Aphidicolin, a specific DNA polymerase inhibitor, is found to have no effect on the increase in protein synthesis and PFK levels that precedes DNA synthesis. The increase in glycolysis in mitogen-stimulated lymphocytes occurs simultaneously with, and is dependent upon, increased protein synthesis, and precedes DNA synthesis and lymphocyte proliferation; thus, the high glycolytic rate of mitogen-stimulated cells is not merely a secondary manifestation of rapid cell proliferation as has been previously reported. 相似文献
89.
90.
Neurite outgrowth in response to transfected N-CAM changes during development and is modulated by polysialic acid 总被引:32,自引:0,他引:32
We have used monolayers of control 3T3 cells and 3T3 cells transfected with a cDNA encoding human N-CAM as a culture substrate for embryonic chick retinal ganglion cells (RGCs). At embryonic day 6 (E6), but not at E11, RGCs extended longer neurites on monolayers of N-CAM-transfected cells. This loss of RGC responsiveness was not associated with substantial changes in the level of N-CAM expression on RGC growth cones. The neurite outgrowth response from E6 RGCs could be inhibited by removal of N-CAM from the monolayer, by removal of alpha 2-8-linked polysialic acid from neuronal N-CAM, or by antibodies that bind exclusively to chick (neuronal) N-CAM. In contrast, the response was not dependent on neuronal beta 1 integrin function. These data provide substantive evidence for a homophilic binding mechanism directly mediating N-CAM-dependent neurite outgrowth, and suggest that changes in polysialic acid expression on neuronal N-CAM may modulate N-CAM-dependent axonal growth during development. 相似文献