Uncoupling effects

Substances that functionally separate oxidation and phosphorylation from one another are referred to as uncouplers. They break down the proton gradient by allowing ions to pass from the intermembrane space back into the mitochondrial matrix without the involvement of ATP synthase. Uncoupling effects are produced by mechanical damage... 

Another group of transmitters involved in the control of the cardiovascular system by the autonomous nervous system includes the catecholamines, adrenaline and noradrenaline. In acinar submandibular gland cells of the rat the administration of 10 4 mol/1 adrenaline elicits a reduction in dye coupling from 97 to 75.3% dye-coupled cells [Kanno et al., 1993]. This could not be mimicked with isoprenaline, but was inhibited with phenoxybenzamine. Thus, the uncoupling effect of adrenaline in this preparation is mediated by stimulation of the a-adre-noceptor, whereas a stimulation of the P-adrenoceptor has no effect. 

Obviously, there is some kind of cross-talk between PKC and cAMP in the modulation of intercellular coupling, since cAMP can inhibit the uncoupling effect of phorbol esters if cells are exposed to both agents from the start of the experiment [Kanno et al., 1984], but this protective effect can be abolished by the protein synthesis inhibitor cycloheximide [Enomoto et al., 1984] in Balb/ cells. 

It can be imagined that these uncoupling effects of the cardiac glycosides may contribute to the arrhythmogenic risk associated with digitalis therapy and intoxication. 

In psychosomatic reactions, benzodiazepines can exert an uncoupling effect. They Luellmann, Color Atlas of Pharmacology All rights reserved. Usage subject to terms... 

Fig. 10.14. The uncoupling effect of free fatty acids and their CoA derivatives on mitochondria. Brown fat mitochondria from co/4-accIimated or control rats, as well as Hver mitochondria, all at a protein concentration of 0.5 mg ml , were studied in the oxygen electrode in a medium containing 0.05% albumin and with 20 mM succinate as substrate. The stimulation of respiration caused by the addition of...

It has been criticized that the effect of acyl-CoA is unspecific and due to a general detergent action. However, acyl-CoA does not induce permeability in parallel with Cl permeability [85], and there are clearly effects of palmitoyl-CoA on brown fat mitochondria at concentrations below those that yield (definitely unspecific ) uncoupling in rat liver mitochondria. Further, the uncoupling effects of free fatty acids are clearly — at low concentrations — better if acyl-CoA formation is allowed to proceed than when it is hampered [81] (Fig. 10.14). 

Introductorily we examine a generally accepted momentum balance formulation for a small (point) particle generally referred to as Newton s second law. The net force is conventionally split into the uncoupled effects of drag, gravity (fc), body forces other than gravity hydrostatic pressure force... 

An investigation of the cardiovascular effects of 117 in dogs found that use of a low dose continual infusion, rather than a bolus administration, may reduce undesirable cardiovascular effects [336]. Arecoline increased mean arterial blood pressure [337] and selectively increased local cerebral glucose utilization in the hippocampus and median raphe [338], In general, the effect of 117 on local cerebral blood flow and glucose utilization correlated well, but uncoupled effects were observed in some regions, such as the hippocampus [339]. 

Fig. 4 Role of xylulose-borate complexation in the co-iimnobilized enzyme system. When sodium tetraborate (borax) is added to solution, it dissociates into tetrahydroxyborate (borate, B) ion and boric acid. In the pellet interior, higher pH favors tighter xylulose-borate binding, which effectively reduces the xylulose concentration in the interior and forces the isomerization forward. In the bulk, the lower pH has an uncoupling effect on the Xu-B complex, making the dissociated xylulose readily available to the yeast. Removal of xylulose via fermentation further forces dissociation of the xylulose-borate complex. Dashed lines represent transport of species solid lines represent reactions... 

Examples of PSII activities (oxygen production) after immobilization of thylakoids according to the procedure ate shown in Table 2. As the uncoupling effect of each method varies, an uncoupler (NH4CI) was added to the reaction medium in order to obtain a well defined activity yield. 

Fromenty B, Fisch C, Berson A, Letteron P, Larrey D, Pessayre D (1990b) Dual effect of amiodarone on mitochondrial respiration. Initial protonophoric uncoupling effect followed by inhibition of the respiratory chain at the levels of complex I and complex II. J Pharmacol Exp Ther 255 1377-1384... 

Petrescu, I. and Tarba, C., Uncoupling effects of diclofenac and aspirin in the perfused liver and isolated hepatic mitochondria of rat, Biochim. Biophys. Acta, 1318, 385-394, 1997. 

Toyomizu, M., Okamoto, K., Ishibashi, T., Chen, Z., and Nakatsu, T., Uncoupling effect of anacardic acids from cashew nut shell oil on oxidative phosphorylation of rat liver mitochondria. Life Sci., 66, 229-234, 2000. 

Barre, H., Nedergaard, J. Cannon, B. (1986). Increased respiration in skeletal muscle mitochondria from cold-acclimated ducklings uncoupling effects of free fatty acids. Comp. Biochem. Physiol, 85B, 343-8. 

The cessation of nitrate reduction on transfer of green algae to ammonium has been attributed to the uncoupling effect of this ion on noncyclic photo-phosphorylatim and a resultant increase in intracellular reducing power and ADP. Supporting this proposal are the findings that arsenate can duplicate the ammonium effect and the inactivation by anunonium ions can be prevented by treatment of cells with DCMU, an inhibitor of photosynthetic electron transfer (Losada, 1973, 1975 Chaparro et al., 1976). It has been demonstrated that ADP and/or NADH inactivate nitrate reductase in vitro... 

Their uncoupling effects (BR) on isolated mitochondria were found to be linearly related to their hydrophobicity and their to quantify the electron-withdrawing properties (Terada, 1990) ... 

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