Influence of respiration on photosynthesis in Synechocystis PCC6803 was studied by measuring the redox transients of cytochrome f (cyt f) upon excitation of the cells with repetitive single turnover flashes. Upon the addition of KCN the flash-induced oxidation of cyt f was increased and the rereduction of cyt f+ was accelerated. Dependence of these effects on the concentration of KCN clearly demonstrated the existence of two cyanide-sensitive oxidases interacting with photosynthesis: cyt aa3, which was sensitive to low concentrations of cyanide, and an alternative oxidase, which could be suppressed by using ≥1 mM KCN. The interaction between the photosynthetic and the respiratory electron transport chains was regulated mainly by the activity of the alternative cyanide-sensitive oxidase. The oxidative pathway involving the alternative cyanide-sensitive oxidase was insensitive to salicyl hydroxamic acid and azide. The close resemblance of the inhibition pattern reported here and that described for chlororespiration in algae and higher plants strongly suggest that an oxidase of the same type as the alternative cyanide-sensitive oxidase of cyanobacteria functions as a terminal oxidase in chloroplasts. and C. Büchel, O. Zsíros, G. Garab.
The total content of rat liver microsomal cytochrome P450 (CYP) significantly decreased after repeated i.p. administration of the antiviral agent tenofovir ((R)-9-[2-(phosphonomethoxy)propyl] adenine) and tenofovir disoproxil at a daily dose 25 mg/kg, although the content of liver microsomal protein did not change. The decrease of the CYP content was accompanied by concomitant increase of the amount of inactive CYP form, cytochrome P420. This effect was confirmed by a parallel study of the activities of selected CYP forms, CYP2E1 (p-nitrophenol hydroxylation) and CYP1A2 (7-ethoxyresorufin deethylation). The activity (expressed relatively to the protein content) of both CYP forms decreased significantly following the decrease of the total CYP. On the other hand, the CYP2E1 activity expressed relatively to the decreasing total CYP content remained unchanged. However, CYP1A2 activity also decreased when calculated relatively to the total native CYP content indicating lower stability of this form. Semiquantitative RT-PCR showed no significant changes in expression of major rat liver microsomal CYP forms after tenofovir treatment. In conclusion, repeated administration of tenofovir in higher doses led to significant decrease of the relative proportion of active liver microsomal CYPs accompanied by a conversion of these enzymes to the inactive form (CYP420) maintaining the sum of CYP proteins unchanged., E. Anzenbacherová, P. Anzenbacher, Z. Zídek, E. Buchar, E. Kmoníčková, P. Potměšil, J. Nekvindová, A. Veinlichová, A. Holý., and Obsahuje bibliografii a bibliografické odkazy
The effects of inclusion of sesamin / episesamin in Baltic Atlantic salmon ( Salmo salar L.) diets based on vegetable oils were studied. The study was designed as a dose response study with two control diets, one diet based on fish oil (FO) and one diet based on a mixture of linseed and sunflower oil (6:4 by vol.) (MO). As experimental diets three different levels of inclusion of sesamin / episesamin (hereafter named sesamin) to the MO based diet and one diet based on sesame oil and linseed oil (SesO) (1:1 by vol.) were used. Th e dietary oils were mirrored in the fatty acid profile of the white muscle. Sesamin significantly decreased the levels of 18:3n-3 in the white muscle phospholipid (PL) fraction of all groups fed sesamin, no significant differences were found in the triacylglycerol fraction (TAG). Slightly increased levels of docosahexaenoic acid (22:6n-3, DHA) in PL and TAG were found in some of the sesamin fed groups. Sesamin significantly affected the expressi on of peroxisome proliferator- activated receptor α , scavenger receptor type B and hormone sensitive lipase, in agreement wi th previous studies on rainbow trout ( Oncorhynchus mykiss ) and Atlantic salmon ( Salmo salar L.) hepatocytes published by our group. No significant effects on toxicological response measured as ethoxyresorufin O-deethylase activity was found. The total cytochrome P450 enzymes were significantly higher in MO 0.29 and SesO group. The amount of α - and γ -tocopherols in liver and the amount of γ -tocopherol in white muscle were significantly lower in fish fed the FO diet compared to the MO diet, but no difference after inclusion of sesamin was found in this study. Increased inclusion of sesamin increased the levels of sesamin and episesamin in the liver, but did not affect the amounts in white muscle., S. Trattner ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Effect of drought on the mechanisms of energy dissipation was evaluated in two-month-old Arachis hypogaea cvs. 57-422, 73-30, and GC 8-35. Plants were submitted to three treatments: control (C), mild water stress (S1), and severe water stress (S2). Photosynthetic performance was evaluated as the Hill and Mehler reactions. These activities were correlated with the contents of the low and high potential forms of cytochrome (cyt) b 559, plastoquinone, cyt b 563, and cyt f. Additionally, the patterns of carotenoids and chlorophylls (Chls), as well as the alterations of Chl a fluorescence parameters were studied. Under mild water stress the regulatory mechanism at the antennae level was effective for 57-422 and GC 8-35, while in the cv. 73-30 an overcharge of photosynthetic apparatus occurred. Relative to this cv., under S1 the stability of carotene and the dissipative cycle around photosystem (PS) 2 became an important factor for the effective protection of the PS2 reaction centres. The cyclic electron flow around PS1 was important for energy dissipation under S1 only for the cvs. 57-422 and 73-30. and J. A. Lauriano ... [et al.].
Polymorphic CYP2D6 is the enzyme that activates the opioid analgesic tramadol by O-demethylation to its active metabolite O-demethyltramadol (M1). Our objective was to determine the opioid effects measured by pupillary response to tramadol of CYP2D6 genotyped volunteers in relation to the disposition of tramadol and M1 in plasma. Tramadol displayed phenotypic pharmacokinetics and it was possible to identify poor metabolizers (PM) with >99 % confidence from the metabolic ratio (MR) in a single blood sample taken between 2.5 and 24 h post-dose. Homozygous extensive metabolizers (EM) differed from PM subjects by an almost threefold greater (P=0.0014) maximal pupillary constriction (Emax). Significant correlations between the AUC and Cmax values of M1 versus pupillary constriction were found. The corresponding correlations of pharmacokinetic parameters for tramadol itself were weaker and negative. The strongest correlations were for the single-point metabolic ratios at all sampling intervals versus the effects, with rs ranging from 0.85 to 0.89 (p‹0.01). It is concluded that the concept of dual opioid/non-opioid action of the drug, though considerably stronger in EMs, is valid for both EM and PM subjects. This is the theoretical basis for the frequent use and satisfactory efficacy of tramadol in clinical practice when given to genetically non-selected population., O. Slanař, M. Nobilis, J. Květina, R. Mikoviny, T. Zima, J. R. Idle, F. Perlík., and Obsahuje biblografii a bibliografické odkazy
Glutamate is a well-characterized excitatory neurotransmitter in the central nervous system (CNS). Recently, glutamate receptors (GluRs) were also found in peripheral tissues, including the heart. However, the function of GluRs in peripheral organs remains poorly understood. In the present study, we found that N-methyl-D-aspartate (NMDA) could increase intracellular calcium ([Ca2+]i) level in a dose-dependent manner in cultured neonatal rat cardiomyocytes. NMDA at 10-4 M increased the levels of reactive oxygen species (ROS), cytosolic cytochrome c (cyto c), and 17-kDa caspase-3, but depolarized mitochondrial membrane potential, leading to cardiomyocyte apoptosis. In addition, NMDA treatment induced an increase in ba x mRNA but a decrease in bcl-2 mRNA expression in the cardiomyocytes. The above effects of NMDA were bloc ked by the NMDA receptor antagonist (+)-5-methyl- 10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), and by ROS scavengers glutathione (GSH) and N-acetylcystein (NAC). These results suggest that stimulation of NMDA receptor in the cardiomyocyte may lead to apoptosis via a Ca2+, ROS, and caspase-3 mediated pathway. These findings suggest that NMDA receptor may play an important role in myocardial pathogenesis., X. Gao, X. Xu, J. Pang, C. Zhang, J. M. Ding, X. Peng, Y. Liu, J.-M. Cao., and Obsahuje bibliografii a bibliografické odkazy
The determination of cytochrome c oxidase (COX) activity represents an important indicator for the evaluation of cell oxidative capacity. However, it has been shown repeatedly that different factors modify the rate of COX activity under various experimental conditions. The most important concern the ionic concentrations of the medium and the application of various detergents for the solubilization of mitochondrial membranes. We found the highest activity of COX in rat heart homogenates and mitochondria at 40-60 mM potassium phosphate. The rate of COX activity is dependent on the detergent/protein (P) ratio. Using n-dodecyl-b-D-maltoside (lauryl maltoside, LM) as the detergent, we obtained the highest activity at LM/P ratios of (50:100):1. By kinetic measurements of low-affinity binding sites in heart mitochondria, we found Vlim values of 4.3 and 22.2 mmol cytochrome c per min per mg P in the presence or absence of lauryl maltoside, respectively. The Km values were 16.7 mmol in the presence or absence of lauryl maltoside. Our results thus indicate that 1) the exact assessment of COX activity in heart homogenates and mitochondria requires the determination of optimum phosphate concentrations in the medium used, and 2) even small modifications of the experimental procedure may induce significant differences in the maximum values of COX activity., A. Stieglerová, Z. Drahota, B. Ošťádal, J. Houštěk., and Obsahuje bibliografii
The concentrations of photosynthetic pigments decreased in both chilling stressed species but the ratios of chlorophyll (Chl) a/b and total carotenoids (Car)/Chls were depressed only in faba bean. The contents of α+β carotene and lutein+lutein-5,6-epoxide remained unaffected in both species, but the de-epoxidation state involving the components of xanthophyll cycle increased in pea. Under chilling stress the photosynthetic electron transport associated with photosystem 2, PS2 (with and without the water oxidising complex) decreased in both plant species, the inhibition being higher in faba bean. The intrachloroplast quinone pool also decreased in both stressed species, yet an opposite trend was found for cytochrome b559LP. Under stress an increasing peroxidation of thylakoid acyl lipids was detected in pea, but higher protein/Chl ratio was detected in faba bean. Thus the acceptor side of PS2 is mostly affected in both chilling stressed species, but faba bean is more sensitive. and F. C. Lidon ... [et al.].
The redox interaction of exogenous cytochrome c550 (Cyt) with PSII isolated from spinach was studied. Illumination of PSII particles in the presence of Cyt led to: (1) Cyt photooxidation by PSII reaction center (demonstrated at the first time), (2) Cyt photoreduction via O2- photoproduced on the acceptor side of PSII, and (3) Cyt photoreduction by reduced electron carriers of PSII. A step-by-step removal of components of water-oxidizing complex was accompanied by the appearance of Cyt photooxidation, an increase in the superoxide dismutase (SOD)-dependent Cyt photoreduction (related to O2- formation), and a decrease in the SOD-independent Cyt photoreduction. Re-addition of PsbO protein diminished the
Cyt-induced restoration of electron transfer in PSII. Addition of diuron led to inhibition of these photoprocesses, while exogenous Mn2+ inhibited only the Cyt c photooxidation. The results can be important for correct measurements of O2- photoproduction in PSII and for elucidation of the role of cytochrome c550 in cyanobacterial PSII., A. A. Khorobrykh, D. V. Yanykin, V. V. Klimov., and Obsahuje bibliografické odkazy
The activities of cytochrome c oxidase and FoF1-ATPase as well as the content of cytochromes cc1, aa3, and b were investigated in free brain mitochondria in the course of postnatal development and aging. The results show an increase of Vmax of both enzymes during postnatal development (between day 5 and 30). During the following phase ending at the age of 6 months, a decrease of FoF1-ATPase and cytochrome c oxidase activity occurs. From 6 to 12 months of age the activity of these enzymes did not change. The KM for both enzymes remained unchanged during the whole period observed. The content of cytochromes increased from the low values found in young rats, reached the highest values at around one month, and decreased till the age of 3 months. Later, their content in brain mitochondria did not markedly change. Our results suggest that the metabolic maturation of brain mitochondria differs in several aspects from the same process in other tissues, mainly in the time course. This is probably due to the unique role of neural tissue in the organism., M. Kalous, H. Rauchová, Z. Drahota., and Obsahuje bibliografii