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At least 883 records · Page 49Linked to original sources
PubMed2005

Light-induced decrease in DCF fluorescence of wheat leaves in the presence of salicyl hydroxamate.

5-(and-6)-Carboxy-2',7'-dichlorodihydrofluorescein diacetate (DCF-DA), a permeative indicator of oxidative stress, was loaded into dissected leaves of wheat in order to monitor the temporal development of reactive oxygen species. DCF fluorescence was found to be constant under dark conditions. Upon loading the leaves with salicyl hydroxamate, a blocker of the alternative oxidase, DCF fluorescence linearly increased in the dark. This indicates a function of alternative oxidase in preventing reactive oxygen radicals in the mitochondria. Upon illumination, the DCF signal decreased within 5 min. As illuminated chloroplasts would increase the load of reactive oxygen species, the observed decrease cannot be assigned to the production of reactive oxygen species in the chloroplasts. Three different putative mechanisms are considered which all assign an important role to light-induced delivery of NAD(P)H: (1) direct quenching of DCF fluorescence by light-generated NAD(P)H, (2) light-stimulated activation of scavenging enzymes, or (3) redirection of mitochondrial electron fluxes as caused by the delivery of excess redox equivalents (NADH) from the chloroplasts.

Chloroplasts↗
PubMed2002

Effects of the intrastriatal administration of selective dopaminergic agonists on Fos expression in the rat brain.

In this study, we mapped the cerebral expression of Fos protein following intrastriatal stimulation of D(1) or D(2) receptors, in freely moving animals. Animals treated with the D(1) agonist SKF 38393 showed massive Fos increases in the cerebral cortex, ipsilaterally to the injected striatum, which were counteracted by systemic administration of D(1) antagonist SCH 23390. Conversely, D(2) agonist quinpirole suppressed cortical expression of Fos, while systemic administration of D(2) antagonist eticlopride relieved this blockade. As for the basal ganglia, Fos was consistently expressed only in the injected striatum of rats receiving SKF 38393. These results show that striatal dopamine receptors may play a role in the modulation of cortical activity. They also provide new information on a class of drugs--the dopamine agonists--whose role in the therapeutic strategy of Parkinson's disease is continuously evolving.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2005

Lipoxygenase pathway of arachidonic acid metabolism in growth control of tumor cells of different type.

The influence of inhibitors of different lipoxygenases (LOX) on the growth of human tumor cells with different profiles of synthesized eicosanoids was studied. The studied LOX inhibitors had virtually no influence on the growth of A549 cells actively synthesizing cyclooxygenase and lipoxygenase metabolites of arachidonic acid (AA). The inhibitor of 12-LOX, baicalein, significantly inhibited proliferation in cultures of A431 epidermoid carcinoma cells with a characteristic domination of the major lipoxygenase metabolite of AA, 12-hydroxyeicosatetraenoic acid (12-HETE), in the profile of synthesized eicosanoids and reduced to 70% the incorporation of [3H]thymidine into DNA. Treatment of these cultures with 12-HETE virtually restored the growth potential of the tumor cells. The findings suggest that the lipoxygenase metabolite of AA, 12-HETE, is a growth-limiting factor for tumor cells of definite type.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2005

The effects of cholinergic and dopaminergic antagonists on nicotine-induced cerebral neurotransmitter changes.

In a continuing study of nicotine-induced mechanisms in brain areas associated with cognitive processes, the effects of cholinergic and dopaminergic antagonists on nicotine-induced changes in dopamine, norepinephrine, and serotonin were examined. These effects were measured via in vivo microdialysis in the dorsal and ventral hippocampus and in the prefrontal and medial temporal cortex of conscious, freely moving, adult male rats. Nicotine (0.3 mg/kg, free base) was administered subcutaneously and the antagonists were infused locally via the microdialysis probe. Nicotine alone induced an increase of dopamine and its metabolites in all areas, an increase of norepinephrine in the cortex, and an increase of the norepinephrine metabolite 4-hydroxy-3-methoxy-phenylglycol in all areas. Serotonin was decreased in the hippocampus and increased in the cortex. Nicotine-induced dopamine increases were inhibited by nicotinic (mecamylamine 100 microM, methyllycaconitine 500 microM), muscarinic (atropine 100 microM), and dopaminergic D1 (SCH23390 100 microM) and D2 (eticlopride 100 microM) antagonists, in the hippocampal and cortical areas. In the hippocampal areas, these antagonists had less significant effect on norepinephrine and serotonin. However, in the cortical areas, all antagonists inhibited the nicotine-induced increase of serotonin to varying degrees; and some, primarily nicotinic and dopamine D1 antagonists, inhibited the induced increase of norepinephrine. In the hippocampal and cortical areas, the mechanisms of nicotine-induced dopamine increase seem to be similar, but the mechanisms seem to be different for noradrenergic and serotonergic systems, as shown by the fact that nicotine induces no change in norepinephrine and a decrease in serotonin in the hippocampus, while it induces an increase in both in the cortex. Nicotine-induced dopamine release seems to be mediated, in part locally, by nicotinic and muscarinic receptors on dopaminergic cells. In contrast, nicotine's effect on norepinephrine and serotonin is at least partially mediated by initial changes at other than local sites, and through different receptors. Thus, the effects of nicotine and the mechanisms involved differ for different neurotransmitters and in different brain areas.

Aconitine↗
PubMed1986

3-Hydroxybenzo[a]pyrene glucuronidation by cells: a direct fluorometric assay in culture medium.

A direct fluorometric assay for measuring the glucuronidation by cultured cells using 3-hydroxybenzo[a]pyrene (less than 1 microM) as substrate is described. The method is based on the different characteristics in the fluorescence spectra of 3-hydroxybenzo[a]pyrene and benzo[a]pyrene-3-glucuronide. The analytical procedure operates directly on the culture medium without extraction steps. The sensitivity of detection is 1 nmol glucuronide/1 mumol substrate.

Animals↗
PubMed1989

Regulation of alternative pathway activity in plant mitochondria: nonlinear relationship between electron flux and the redox poise of the quinone pool.

The dependence of respiratory flux via the alternative pathway on the redox poise of the ubiquinone (Q) pool was investigated in soybean cotyledon mitochondria. A marked nonlinear relationship was observed between Q-pool reduction level and O2 uptake via the alternative oxidase. Significant engagement of the alternative pathway was not apparent until Q-pool reduction level reached 35-40% but increased disproportionately on further reduction. Similar results were obtained with electron donation from either Complex 1 or Complex 2. Close agreement was obtained over a range of experimental conditions between the estimated contribution of the alternative pathway to total respiratory flux, as measured with salicylhydroxamic acid, and that predicted from the redox poise of the Q-pool. These results are discussed in terms of existing models of the regulation of respiratory flux via the alternative pathway.

Electron Transport↗
PubMed1975

On the stoichiometry between uncouplers of oxidative phosphorylation and respiratory chains. The catalytic action of SF 6847 (3,5-di-tert-butyl-4-hydroxy-benzylidenemalononitrile).

Titration of State 4 rat-liver mitochondria at pH 7.2 with the uncoupler 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (SF 6847) at various concentrations of mitochondria and using various substrates indicates that under optimal conditions less than 0.2 molecule of 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile per respiratory chain is sufficient to induce complete uncoupling. This result suggests that there is not a stoichiometric relationship between uncoupler molecules and cytochrome c oxidase, involved in oxidative phosphorylation, or between the former and phosphorylation assemblies. Experiments on the release by 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile of azide-inhibited respiration of State 3 mitochondria and titrations with 5-chloro-3-tert-butyl-2'-chloro-4'-nitrosalicylanilide (S13) of State 4 mitochondria at various mitochondrial concentrations confirm this conclusion.

Aniline Compounds↗
PubMed1977

EPR studies of higher plant mitochondria. I Ubisemiquinone and its relation to alternative respiratory oxidations.

An EPR investigation of the region of the higher plant respiratory chain involving ubiquinone and Center S-3 of succinate dehydrogenase is reported. At temperatures close to those of liquid helium, first derivative spectra corresponding to Center S-3 (gmax = 2.017) and a signal split around g = 2.00 (major features of peaks and troughs at g values of 2.045, 2.03, 1.985, 1.97 and 1.96) were observed in mung bean (Phaseolus aureus), Arum maculatum spadix, Sauromatum guttatum spadix and tulip bulb (Tulipa gesnerana) mitochondria. The split signal was small or absent in potato tuber and Symplocarpus foetidus spadix mitochondria. The redox behavior of these signals in mung bean mitochondria in a variety of respiratory steady-state conditions suggested that the components giving rise to them were an integral part of the respiratory chain and were located on the substrate side of coupling Site II. The split signal could be removed by addition of hydroxamic acids in all tissues tested, although the Ks of this effect was an order of magnitude higher than the Ki of inhibition of the alternative respiratory pathway in mung bean and Sauromatum guttatum spadix mitochondria. The results are discussed in relation to the current ideas on the ordering of components in the region around the classical Site II of the respiratory chain and in relation to the location of the alternative respiratory oxidase pathway of higher plants.

Cyanides↗
PubMed1988

Structural requirements of salicylanilides for uncoupling activity in mitochondria: quantitative analysis of structure-uncoupling relationships.

The uncoupling activities of more than 20 salicylanilides were measured in rat liver mitochondria. The activities, expressed as the minimum concentrations required for full release of state-4 respiration, ranged over three orders of magnitude. The acid dissociation constant, pKA, and the partition coefficient between octanol and water (Poct) of some of the salicylanilides were determined. These two parameters were found to be well expressed in terms of the Hammett constant, sigma, and the hydrophobic substituent coefficient, II, respectively. The pKA and log Poct values of all the salicylanilides were predicted according to these relationships. Furthermore, the capacity factor, k', on high-performance liquid chromatography was determined on glyceryl-coated-controlled pore glass (gly-CPG). Values of log k' correlated well with those of log Poct. The uncoupling activities of the salicylanilides were analyzed in terms of these three parameters. Both hydrophobic and electron-withdrawing properties were found to be essential for induction of potent uncoupling activity. The correlations using log k' were better than those using log Poct.

Animals↗
PubMed1993

Comparison between the properties of 3-nitrosalicyl-N-alkylamide and antimycin A acting on QH2:cytochrome c reductase.

3-Nitrosalicyl N-alkylamide was found to be an inhibitor different from antimycin A not only in its inhibitory nature but also in many other aspects. This difference indicated that the 11 kDa component, which was identified as the antimycin A (AA) binding factor in the QH2: cytochrome c reductase of Rhodopseudomonas sphaeroides by Wilson et al. ((1985) J. Biol. Chem. 260, 10288-10292) using the radioactive photoaffinity analogue 3-azidosalicyl N-octadecylamide, was not the genuine binding site of AA. Based on the observations that the 3-azidosalicyl N-alkylamide specifically inhibits the reactions of ubiquinone catalyzed by Q-related enzymes of the respiratory chain, the labeled 11 kDa factor might be one of the ubiquinone binding proteins in QH2:cytochrome c reductase.

Antimycin A↗
PubMed1979

The interaction of 3,3',4',5-tetrachlorosalicylanilide with phosphatidylcholine bilayers.

1. The interaction of the germicide 3,3',4',5-tetrachlorosalicylanilide (T4CS) with vesicles and dispersions of egg phosphatidylcholine has been studied by gel permeation chromatography, electron microscopy, electron spin resonance spin labelling and ion permeability measurements. 2. Incorporation of T4CS into vesicles of egg phosphatidylcholine gives rise to a large increase in the permeability rate of the paramagnetic cation N,N-dimethyl-N-(1'-oxyl-2',2',6',6'-tetramethyl-4'-piperidyl)-2-hydroxyethylammonium chloride through the lipid bilayer but has no significant effect on the vesicle sizes as measured by gel permeation chromatography or electron microscopy. 3. ESR studies using a spin-labelled fatty acid have demonstrated the presence of two different environments for the spin label when T4CS is incorporated into phosphatidylcholine bilayers. These two environments are identified as (a) highly ordered areas of the bilayer, rich in T4CS and (b) areas with very similar ordering to that in pure egg phosphatidylcholine. 4. The effectiveness of very low concentrations of the germicide in increasing vesicle permeability is explained in terms of its clustering to give rigid patches, rich in T4CS, rather than being evenly distributed throughout the bilayer. It is proposed that the increased ion permeability arises from leakage at the interfaces between the rigid and flexible regions of the lipid bilayer. 5. Comparisons between the effective levels of T4CS in phosphatidylcholine vesicles and its minimum inhibitory concentration with a Gram-positive bacterium confirm the validity of phospholipid vesicles as a model for studies of germicidal activity.

Chromatography, Gel↗