Ischemic postconditioning and remote conditioning are potentially useful tools for protecting ischemic myocardium. This study tested the hypothesis that 2,3-dehydrosilybin (DHS), a flavonolignan component of Silybum marianum , could attenuate cardiomyocyte damage following hypoxia/ reoxygenation by decreasing the generation of reactive oxygen species (ROS). After 5-6 days of cell culture in normoxic conditions the rat neonatal cardiomyocytes were divided into four groups. Control group (9 h at normoxic conditions), hypoxia/ reoxygenation group (3 h at 1 % O2 , 94 % N2 and 5 % CO2 followed by 10 min of 10 μmol·l -1 DHS and 6 h of reoxygenation in normoxia) and postconditioning group (3 h of hypoxia, three cycles of 5 min reoxygenation and 5 min hypoxia followed by 6 h of normoxia). Cell viability assess ed by propidium iodide staining was decreased after DHS treatment consistent with increased levels of lactatedehydrogenase (LDH) after reoxygenation. LDH leakage was significantly reduced when cardiomyocytes in the H/Re group were exposed to DHS. DHS treatment reduced H2O2 production and also decreased the generation of ROS in the H/Re group as evidenced by a fluorescence indicator. DHS treatment reduces reoxygenation-induced injury in cardiomyocytes by attenuation of ROS generation, H2O2 and protein carbonyls levels. In addition, we found that both the postconditioning protocol and the DHS treatment are associated with restored ratio of phosphorylated/total protein kinase C epsilon, relative to the H/Re group. In conclusion, our data support the protective role of DH S in hypoxia/reperfusion injury and indicate that DHS may act as a postconditioning mimic., E. Gabrielová, V. Křen, M. Jabůrek, M. Modrianský., and Obsahuje bibliografii
a1_Different parameters that vary during leaf development may be affected by light intensity. To study the influence of different light intensities on primary leaf senescence, sunflower (Helianthus annuus L.) plants were grown for 50 days under two photon flux density (PFD) conditions, namely high irradiance (HI) at 350 μmol(photon) m-2 s-1 and low irradiance (LI) at 125 μmol(photon) m-2 s-1. Plants grown under HI exhibited greater specific leaf mass referred to dry mass, leaf area and soluble protein at the beginning of the leaf development. This might have resulted from the increased CO2 fixation rate observed in HI plants, during early development of primary leaves. Chlorophyll a and b contents in HI plants were lower than in LI plants in young leaves. By contrast, the carotenoid content was significantly higher in HI plants. Glucose concentration increased with the leaf age in both treatments (HI and LI), while the starch content decreased sharply in HI plants, but only slightly in LI plants. Glucose contents were higher in HI plants than in LI plants; the differences were statistically significant (p<0.05) mainly at the beginning of the leaf senescence. On the other hand, starch contents were higher in HI plants than in LI plants, throughout the whole leaf development period. Nitrate reductase (NR) activity decreased with leaf ageing in both treatments. However, the NR activation state was higher during early leaf development and decreased more markedly in senescent leaves in plants grown under HI. GS activity also decreased during sunflower leaf ageing under both PFD conditions, but HI plants showed higher GS activities than LI plants. Aminating and deaminating activities of glutamate dehydrogenase (GDH) peaked at 50 days (senescent leaves). GDH deaminating activity increased 5-fold during the leaf development in HI plants, but only 2-fold in LI plants., a2_ The plants grown under HI exhibited considerable oxidative stress in vivo during the leaf senescence, as revealed by the substantial H2O2 accumulation and the sharply decrease in the antioxidant enzymes, catalase and ascorbate peroxidase, in comparison with LI plants. Probably, systemic signals triggered by a high PFD caused early senescence and diminished oxidative protection in primary leaves of sunflower plants as a result., L. De la Mata ... [et al.]., and Obsahuje bibliografii
Ascorbate is an important antioxidant involved in both enzymatic and nonenzymatic reactions in plant cells. To reveal the function of ascorbate associated with defense against photo-oxidative damage, responses of the ascorbate-deficient mutant vtc2-1 of Arabidopsis thaliana to high-light stress were investigated. After high-light treatment at 1,600 μmol(photon) m-2 s-1 for 8 h, the vtc2-1 mutant exhibited visible photo-oxidative damage. The total ascorbate content was lower, whereas accumulation of H2O2 was higher in the vtc2-1 mutant than that in the wild type. The chlorophyll (Chl) content and PSII Chl fluorescence parameters, such as maximal quantum yield of PSII photochemistry, yield, and electron transport rate, in vtc2-1 mutant decreased more than that in the wild type, whereas the nonphotochemical quenching coefficient increased more in the wild type than that in vtc2-1 mutant. Therefore, the vtc2-1 mutant was more sensitive to high-light stress than the wild type. Accumulation of reactive oxygen species was mainly responsible for the damage of PSII in the vtc2-1 mutant under high light. The results indicate that ascorbate plays a critical role in maintaining normal photosynthetic function in plants under high-light stress., L.-D. Zeng, M. Li, W. S. Chow, C.-L. Peng., and Obsahuje bibliografické odkazy
To test whether macrophages can play any role in hypoxic pulmonary vasoconstriction, we tested the in vitro response of rings from small pulmonary arteries to the activation of macrophages by FMLP, a substance stimulating predominantly membrane-bound NADPH oxidase. A small vessel myograph was used to measure the responses of rings from small pulmonary arteries (300-400 μ m) isolated from rat lungs. Rings from 5 rats were placed into both chambers of the myograph. The vessels were stabilized for 40 min and then normalized by automatic stretching to a wall tension equivalent to the intravascular pressure 30 mm Hg. At the start of each experiment, vessels were exposed to 80 mM K + to obtain maximal contractile response, which was used to normalize subsequent contractile responses. 2x10 6 viable macrophages, obtained by peritoneal lavage, were added into one chamber, then 5 μ M FMLP was administrated to both chambers and the tension measurement was started. The hydrogen peroxide concentration produced by stimulated macrophages was measured luminometrically. The concentrations of H 2 O 2 in specimens from chambers containing activated macrophages rose from 3.5±1.5 nM to 110±28 nM within 25 min of stimulation, while FMLP itself didn’t increase the H 2 O 2 concentration from the baseline value (4.5±3 nM) in samples from control chambers. After FMLP administration, the tension of the vessel rings in the presence of macrophages reached 0.23±0.07 of maximal contractile response, it did not change in controls. The additi on of ROS scavenger 4-hydroxy- TEMPO blocked the contractile response to the activation of macrophages. We conclude that the activation of macrophages stimulates the contraction of small pulmonary arteries and that this contraction is probably mediated by reactive oxygen species., M. Žaloudíková, J. Herget, M. Vízek., and Obsahuje bibliografii a bibliografické odkazy
A significant factor in the development of hypertension may be excessive vasoconstriction within the renal medulla. This study therefore investigated the role of superoxide dismutase (SOD) in the regulation of renal medullary and cortical blood perfusion (MBP and CBP, respectively) in both stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar rats. CBP and MBP were measured before and after intra-renal infusion of the SOD inhibitor, diethyldithio-carbamic acid (DETC). Under basal conditions, mean arterial pressure was significantly greater in SHRSP than Wistar rats, but both MBP and heart rate (HR) were significantly lower in SHRSP relative to Wistar rats (P<0.05, n=7 in both groups). Infusion of DETC (2 mg/kg/min) into the cortico-medullary border area of the kidney significantly decreased MBP in the SHRSPs (by 28±3 %, n=7, P<0.05), indicating a greater vasoconstriction within this vascular bed. However, DETC also significantly decreased MBP in Wistar rats to a similar extent (24±4 %, n=7, P<0.05). These results suggest that superoxide anions play a significant role in reducing renal vascular compliance within the renal medulla in both normotensive and hypertensive animals, although the responses are not greater in the hypertensive relative to the control animals., A. F. Ahmeda, M. G. Rae, L. M. Anweigi, M. F. Al Otaibi, A. A. Al-Masri, E. J. Johns., and Obsahuje bibliografii
Populus x euramericana cv. ‘Neva’ is an important tree species in northern China. In the study, we used its potted oneyear- old seedlings as experimental material and established three treatments (CK, 0.5X, and 1.0X) according to the concentrations of phenolic acids in order to examine the effects of different concentrations on the photosynthetic characteristics and growth of poplar. With increasing concentrations of phenolic acids, the net photosynthetic rate, stomatal limitation, transpiration rate, apparent quantum yield, photochemical quenching coefficient, electron transport rate, chlorophyll content, and total biomass decreased significantly. The intercellular CO2 concentration, light-compensation point, nonphotochemical quenching, malondialdehyde content, and root/shoot ratio increased significantly. Peroxidase and superoxide dismutase activities initially decreased and then increased. We concluded that phenolic acids significantly inhibited poplar’s photosynthesis and the higher phenolic acid concentration, the greater inhibition of photosynthesis occurred. This inhibition effect was mainly caused by nonstomatal factors. Phenolic acids induced noticeable photoinhibition, resulted in the irreversible damage of membrane structure, and then changed intracellular metabolic processes. To cope with phenolic acid stress, poplar seedlings increased dissipation of excess light energy and distributed relatively more biomass to underground parts within carbon allocation., D. F. Xie, G. C. Zhang, X. X. Xia, Y. Lang, S. Y. Zhang., and Obsahuje bibliografii
Calorie restriction (CR) has been shown to decrease reactive oxygen species (ROS) production an d retard aging in a variety of species. It has been proposed that alterations in membrane saturation are central to these ac tions of CR. As a step towards testing this theory, mice were assigned to 4 dietary groups (control and 3 CR groups) and fed AIN-93G diets at 95 % (control) or 60 % (CR) of ad libitum for 8 months. To manipulate membrane composition, the primary dietary fats for the CR groups were soybean oil (also used in the control diet), fish oil or lard. Skeletal muscle mitochondrial lipid composition, proton leak, and H 2 O 2 production were measured. Phospholipid fatty acid composition in CR mice was altered in a manner that reflected the n-3 and n-6 fatty acid profiles of their respective dietary lipid sources. Dietary lipid composition did not alter proton leak kinetics between the CR groups . However, the capacity of mitochondrial complex III to produce ROS was decreased in the CR lard compared to the other CR groups. The results of this study indicate that dietary lipid composition can influence ROS production in muscle mitochondria of CR mice. It remains to be determined if lard or other dietary oils can maximize the CR- induced decreases in ROS production., Y. Chen ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Endothelial dysfunction may be considered as the interstage between risk factors and cardiovascular pathology. An imbalance between the production of vasorelaxing and vasoconstricting factors plays a decisive role in the development of hypertension, atherosclerosis and target organ damage. Except vasorelaxing and antiproliferative properties per se, nitric oxide participates in antagonizing vasoconstrictive and growth promoting effects of angiotensin II, endothelins and reactive oxygen species. Angiotensin II is a potent activator of NAD(P)H oxidase contributing to the production of reactive oxygen species. Numerous signaling pathways activated in response to angiotensin II and endothelin-1 are mediated through the increased level of oxidative stress, which seems to be in casual relation to a number of cardiovascular disturbances including hypertension. With respect to the oxidative stress, the NO molecule seems to be of ambivalent nature. On the one hand, NO is able to reduce generation of reactive oxygen species by inhibiting association of NAD(P)H oxidase subunits. On the other hand, when excessively produced, NO reacts with superoxides resulting in the formation of peroxynitrite, which is a free radical deteriorating endothelial function. The balance between vasorelaxing and vasoconstricting substances appears to be the principal issue for the physiological functioning of the vascular bed., O. Pecháňová, F. Šimko., and Obsahuje bibliografii
Cadmium is often detected in areas contaminated by heavy metals and the incidence of this element in dangerous concentrations has been increasing due to anthropogenic activities. The aim of this research was to determine Cd concentrations in tissues, quantify compounds, pigments and enzymes, and to evaluate the gas exchange. Our aim was also to identify components that can modify and contribute to tolerance of Cassia alata against Cd toxicity. We used five Cd concentrations (0, 22, 44, 88, and 132 μM) to validate our hypothesis. The Cd concentrations in tissues of C. alata plants increased significantly, compared with the control treatment, in the following graduated sequence: root > leaf > stem. Progressive enhancement in glutathione (GSH) was verified in plants treated with all Cd concentrations used, when compared with treatment without Cd. Antioxidant enzyme activities presented similar patterns with progressive enhancements, being a desirable characteristic for plants with a potential to hyperaccumulate Cd. Our results suggest that C. alata plants can be used for phytoremediation programs. Their defense mechanism is based on Cd accumulation in roots, coupled with increase in GSH and the efficient activity of antioxidant enzymes that contribute to minimize the oxidative stress and consequently improve the protection of the metabolic machinery., J. R. R. Silva, A. R. Fernandes, M. L. Silva Junior, C. R. C. Santos, A. K. S. Lobato., and Obsahuje bibliografii
The aim of the study was to examine the potential impacts of bisphenol A (BPA) and its analogues BPB, BPF, and BPS on mice TM3 Leydig cells, with respect to basal cell viability parameters such as metabolic activity, cell membrane integrity, and lysosomal activity after 48-h exposure. In addition, monitoring of potential bisphenol´s actions included evaluation of ROS production and gap junctional intercellular communication (GJIC) complemented by determination of testosterone secretion. Obtained results revealed significant inhibition in mitochondrial activity started at 10 µg/ml of bisphenols after 48-h exposure. Cell membrane integrity was significantly decreased at 5 µg/ml of BPA and BPF and 10, 25, and 50 µg/ml of BPA and BPS. The lysosomal activity was significantly affected at 10, 25, and 50 µg/ml of applied bisphenols. A significant overproduction of ROS was recorded mainly at 5 and 10 µg/ml of tested compounds. In addition, significant inhibition of GJIC was observed at 5 µg/ml of BPB followed by a progressive decline at higher applied doses. In the case of testosterone production, a significant decline was confirmed at 10, 25 and 50 µg/ml.