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Exposure of rabbit polymorphonuclear leukocytes to micromolar concentrations of quin2-AM results in high intracellular concentrations of quin2, which lead to inhibition of chemotaxis. The loading efficiency of polymorphonuclear leukocytes, being the percentage of quin2-AM which is taken up by the cells and transformed intracellularly into quin2, is very high, reaches a maximum after 30 min, is independent of the presence of extracellular Ca2+ and is fairly independent of cell concentration. As a consequence, inhibition of chemotaxis is strongly dependent on experimental conditions: with a low cell density (3 X 10(6)/ml) exposure to 20 microM quin2-AM results in complete inhibition of chemotaxis, whereas the same concentration of quin2-AM is nearly without effect when an 8-fold higher cell concentration is used. Inhibition by quin2 is dependent on extracellular Ca2+; inhibition is more pronounced in the absence of extracellular Ca2+ than in its presence. It is suggested that quin2 inhibits chemotaxis by interference with intracellular Ca2+. 相似文献
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Energy transduction by electron transfer via a pyrrolo-quinoline quinone-dependent glucose dehydrogenase in Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter calcoaceticus (var. lwoffi). 总被引:13,自引:9,他引:4
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B J van Schie K J Hellingwerf J P van Dijken M G Elferink J M van Dijl J G Kuenen W N Konings 《Journal of bacteriology》1985,163(2):493-499
The coupling of membrane-bound glucose dehydrogenase (EC 1.1.99.17) to the respiratory chain has been studied in whole cells, cell-free extracts, and membrane vesicles of gram-negative bacteria. Several Escherichia coli strains synthesized glucose dehydrogenase apoenzyme which could be activated by the prosthetic group pyrrolo-quinoline quinone. The synthesis of the glucose dehydrogenase apoenzyme was independent of the presence of glucose in the growth medium. Membrane vesicles of E. coli, grown on glucose or succinate, oxidized glucose to gluconate in the presence of pyrrolo-quinoline quinone. This oxidation led to the generation of a proton motive force which supplied the driving force for uptake of lactose, alanine, and glutamate. Reconstitution of glucose dehydrogenase with limiting amounts of pyrrolo-quinoline quinone allowed manipulation of the rate of electron transfer in membrane vesicles and whole cells. At saturating levels of pyrrolo-quinoline quinone, glucose was the most effective electron donor in E. coli, and glucose oxidation supported secondary transport at even higher rates than oxidation of reduced phenazine methosulfate. Apoenzyme of pyrrolo-quinoline quinone-dependent glucose dehydrogenases with similar properties as the E. coli enzyme were found in Acinetobacter calcoaceticus (var. lwoffi) grown aerobically on acetate and in Pseudomonas aeruginosa grown anaerobically on glucose and nitrate. 相似文献
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J G Elferink 《Biochemical medicine and metabolic biology》1986,36(1):25-35
Microcrystals of hydroxyapatite cause severe membrane damage in human erythrocytes, as is evident from the strong hemolysis that is caused by these crystals. Hemolysis by hydroxyapatite crystals is time and concentration dependent, and is preceded by aggregation of erythrocytes. Polyvinylpyridine-N-oxide, a strong hydrogen acceptor, has no inhibiting effect on hydroxyapatite-induced hemolysis. This suggest that the mechanism of action of these crystals is different from that of urate crystals and silica particles, where hydrogen bonding interaction is supposed to be important. Negatively charged macromolecules, such as dextran sulfate, heparin, and polyglutamic acid, inhibit hydroxyapatite crystal-induced hemolysis, suggesting that positive charges, probably located on the crystals, play an important role in the membrane-damaging effect of these crystals. The structures with which these positive charges interact remain to be determined because removal of negative charges from the erythrocytes by treatment with neuraminidase does not affect crystal-induced hemolysis. 相似文献
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Transformation of the extremely thermoacidophilic archaeon Sulfolobus solfataricus via a self-spreading vector 总被引:1,自引:0,他引:1
Abstract The comparative chromosomal locations of polymeric β-fructosidase SUC genes have been determined by Southern blot hybridization with the SUC2 probe in 91 different strains of Saccharomyces cerevisiae . Most of the strains exhibited a single SUC2 gene, but in some strains two or three SUC genes were found. All Suc− strains carried a silent suc20 sequence. The accumulation of SUC genes was observed in populations derived from sources containing sucrose and seems to be absent in strains from sources promoting the MEL gene. 相似文献
8.
Sjoerd L. Bonting 《Origins of life and evolution of the biosphere》1984,14(1-4):777-783
A survey is given of the life sciences research program sponsored by the European Space Agency (ESA). This program rests on a number of facilities originated by ESA: Spacelab, Space sled, Biorack, Anthrorack, Eureca and its Botany — and Protein Crystallization facilities. They are all to be brough into space and returned by one of the NASA Space Shuttles. With these facilities a wide range of space biology research will be covered: cell biology, developmental biology, botany, human physiology, radio-biology, exobiology and biotechnology. Information is given on how to prepare, submit and execute an experiment proposal. 相似文献
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Gemma A.J. Kuijpers Irene G.P. Van Nooy Jan Joep H.H.M. De Pont Sjoerd L. Bonting 《生物化学与生物物理学报:生物膜》1984,774(2):269-276
The isolated rabbit pancreas secretes a fluid containing chloride and bicarbonate in about equal concentrations. Replacement of bicarbonate by acetate, phosphate or isethionate, replacement of Na+ by Li+ and addition of ouabain to the bathing medium of the pancreas inhibit the secretion of fluid, chloride and bicarbonate in a similar fashion and by maximally 100%. Replacement of chloride by isethionate inhibits fluid secretion by maximally 50%, chloride secretion by 90% and bicarbonate secretion by 20%. It is concluded that fluid secretion is based on a Na+-gradient-dependent bicarbonate influx or proton efflux in the ductular cell, and that the secretion of chloride is secondary to that of bicarbonate. 相似文献
10.
P.C. Noordam A. Killian R.F.M. Oude Elferink J. de Gier 《Chemistry and physics of lipids》1982,31(2):191-204
Comparative studies on bilayer systems of saturated phosphatidylcholines and phosphatidylethanolamines revealed a maximum in ionic permeability in phosphatidylcholine bilayers at the temperature of the gel to liquid-crystalline phase transition but such an increase in permeability was not detectable in bilayers of phosphatidylethanolamine. Furthermore, it was found that at the phase transition temperature the phosphatidylcholine bilayers are subject to rapid hydrolysis by pancreatic phospholipase A2 whereas phosphatidylethanolamine bilayers are not. These differences are discussed in view of detailed information on the molecular organization in the gel and liquid crystalline phases of the two phospholipid classes. 相似文献