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1.
The relationship between polyphosphoinositide hydrolysis and protein kinase C (PKC) activation was explored in rabbit platelets treated with the agonists platelet-activating factor (PAF), thrombin and 12-O-tetradecanoylphorbol 13-acetate (TPA), and with the anti-aggregant prostacyclin (PGI2). Measurement of the hydrolysis of radiolabelled inositol-containing phospholipids relied upon the separation of the products [3H]inositol mono-, bis- and tris-phosphates by Dowex-1 chromatography. PKC activity, measured in platelet cytosolic and Nonidet-P40-solubilized particulate extracts that were fractionated by MonoQ chromatography, was based upon the ability of the enzyme to phosphorylate either histone H1 in the presence of the activators Ca2+, diacylglycerol and phosphatidylserine, or protamine in the absence of Ca2+ and lipid. Treatment of platelets for 1 min with PAF (2 nM) or thrombin (2 units/ml) led to the rapid hydrolysis of inositol-containing phospholipids, a 2-3-fold stimulation of both cytosolic and particulate-derived PKC activity, and platelet aggregation. Exposure to TPA (200 nM) for 5 min did not stimulate formation of phosphoinositides, but translocated more than 95% of cytosolic PKC into the particulate fraction, and induced a slower rate of aggregation. PGI2 (1 microgram/ml) did not enhance phosphoinositide production, and at higher concentrations (50 micrograms/ml) it antagonized the ability of PAF, but not that of thrombin, to induce inositol phospholipid turnover, even though platelet aggregation in response to both agonists was blocked by PGI2. On the other hand, PGI2 alone also appeared to activate (by 3-5-fold) cytosolic and particulate PKC by a translocation-independent mechanism. The activation of PKC by PGI2 was probably mediated via cyclic AMP (cAMP), as this effect was mimicked by the cAMP analogue 8-chlorophenylthio-cAMP. It is concluded that this novel mechanism of PKC regulation by platelet agonists may operate independently of polyphosphoinositide turnover, and that activation of cAMP-dependent protein kinase represents another route leading to PKC activation. 相似文献
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Michael J. Barber Andrew S. Zektzer Gerald M. Rosen Helen A. Demos Elmer J. Rauckman 《生物化学与生物物理学报:生物膜》1984,776(1):159-168
Hepatic microsomal membranes, prepared under various conditions that yield either ‘intact’ or ‘disrupted’ microsomal vesicles, have been labeled via the sulfhydryl groups of intrinsic membrane proteins using nitroxide analogs of . Electron paramagnetic resonance spectra revealed the presence of two dominant classes of bound label corresponding to differing degrees of immobilization, the ratio of which were quantitated using a parameter designated the ‘’ ratio. For latent microsomes, the value of this parameter was determined to be and was influenced by factors such as label/protein ratio, incubation period, nitroxide structure, temperature and pH. The ratio was also sensitive to the degree of membrane integrity as revealed by the latency of mannose 6-phosphate activity of glucose-6-phosphohydrolase. In addition, membrane disruption resulted in a corresponding decrease in the order parameter for nitroxide-labeled fatty acids intercalated within the lipid bilayer. The ratio was observed to be dependent upon the method of microsome preparation yielding values of for ‘hypertonically disrupted’ vesicles and for ‘mechanically disrupted’ vesicles. Microsomal marker enzymes such as cytochrome and FAD-containing monooxygenase retained significant levels of functionally following nitroxide incorporation. 相似文献
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Summary In a previous article (Demos et al. 1981), we reported a significant and specific reduction of the activity index (AI) of the diphenoloxidases (DPox) in patients and heterozygotes with progressive Duchenne muscular dystrophy (DMD), which is transmitted genetically by female subjects by a sex-linked recessive mechanism (SLR). This same anomaly was detected in patients suffering from other types of dystrophy: Becker, limbgirdle, fascio-scapulo-humeral, and in heterozygotes, of either sex in diseases transmitted by an obviously recessive autosomic mechanism. These anomalies were detected using blood spots collected on absorbent paper and stored at 4°C for differnt periods. They were of the same type as had previously been detected using blood platelets (Demos 1973). 相似文献
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B Utete C Phiri SS Mlambo N Maringapasi N Muboko TB Fregene 《African Journal of Aquatic Science》2018,43(1):1-15
Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity. 相似文献
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Víctor Faundes William G. Newman Laura Bernardini Natalie Canham Jill Clayton-Smith Bruno Dallapiccola Sally J. Davies Michelle K. Demos Amy Goldman Harinder Gill Rachel Horton Bronwyn Kerr Dhavendra Kumar Anna Lehman Shane McKee Jenny Morton Michael J. Parker Julia Rankin Siddharth Banka 《American journal of human genetics》2018,102(1):175-187