Number of results to display per page
Search Results
6362. Differential blockage of photosynthetic electron flow in young and mature leaves of Arabidopsis thaliana by exogenous proline
- Creator:
- Sperdouli, I. and Moustakas, M.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, photosynthesis, chlorophyll fluorescence, electron transport rate, leaf age, reactive oxygen species, 2, and 581
- Language:
- Multiple languages
- Description:
- Responses of the photosynthetic electron transport system of chloroplasts to exogenous proline application were evaluated in young and mature leaves of Arabidopsis thaliana plants under optimal growth conditions. Exogenous proline application (10 mM) during the 4th week of growth increased proline accumulation in young leaves more than in mature leaves, and possibly due to its degradation producing NADPH, decreased significantly the ratio of NADP+/NADPH in both leaf types compared with controls (without proline). However, the ratio of NADP+/NADPH remained significantly higher in the young leaves, suggesting lower proline degradation which resulted in less reduced plastoquinone pool than that in the mature leaves, under both low light [130 μmol(photon) m-2 s-1] and high light [1,200 μmol(photon) m-2 s-1] treatments. The young leaves seemed to adjust nonphotochemical fluorescence quenching in order to maintain a better PSII quantum yield. We concluded that under optimal growth conditions exogenous proline results in overreduction of the plastoquinone pool and blockage of photosynthetic electron flow due to accumulation of NADPH. We suggest that optimum concentrations of proline are required for optimal PSII photochemistry., I. Sperdouli, M. Moustakas., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6363. Differential effects of statins and alendronate on cholinesterases in serum and brain of rats
- Creator:
- Cibičková, Ľ., Vladimír Palička, Norbert Cibiček, Čermáková, E., Stanislav Mičuda, Ladislava Bartošová, and Daniel Jun
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Biochemie. Molekulární biologie. Biofyzika, biochemie, cholesterol, Alzheimerova choroba, biochemistry, Alzheimer's disease, simvastin, atorvastin, alendronate, acetylcholinesterase, 2, and 577
- Language:
- English
- Description:
- Acetylcholinesterase (AChE) inhibitors represent standard treatment of Alzheimer´s disease. Cholesterol plays an important role in Alzheimer´s disease development. Because cholesterol synthesis may be inhibited by statins or bisphosphonates, we hypothesized that these drugs might possibly have an influence on cholinesterases. Moreover, we also evaluated if the cholesterol-lowering agents that cross the blood-brain barrier (e.g. simvastatin) should be more effective than those which do not (e.g. atorvastatin). Four groups of rats were orally administered simvastatin, atorvastatin, alendronate or vehicle for seven days. Thereafter, blood samples were taken and the basal ganglia, septum, frontal cortex, and hippocampus were isolated from brains for measurement of acetylcholinesterase activity. In the blood, activities of neither acetyl- nor butyrylcholinesterase were influenced by any of the applied drugs. In the brain, no significant changes in AChE activity were observed after administration of atorvastatin. Both simvastatin and alendronate significantly suppressed the activity of AChE in the frontal cortex. In conclusion, our results confirmed the hypothesis that cholesterol-modifying drugs modulate AChE activity and it is more reasonable to use a blood-brain barrier penetrating drug., Ľ. Cibičková, V. Palička, N. Cibiček, E. Čermáková, S. Mičuda, L. Bartošová, D. Jun., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6364. Differential equations in metric spaces
- Creator:
- Tabor, Jacek
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- differential equation and tangent space
- Language:
- English
- Description:
- We give a meaning to derivative of a function u: R → X, where X is a complete metric space. This enables us to investigate differential equations in a metric space. One can prove in particular Gronwall’s Lemma, Peano and Picard Existence Theorems, Lyapunov Theorem or Nagumo Theorem in metric spaces. The main idea is to define the tangent space TxX of x ∈ X. Let u, v : [0, 1) → X, u(0) = v(0) be continuous at zero. Then by the definition u and v are in the same equivalence class if they are tangent at zero, that is if lim h→0+ d(u(h), v(h)) ⁄ h = 0. By TxX we denote the set of all equivalence classes of continuous at zero functions u: [0, 1) → X, u(0) = x, and by T X the disjoint sum of all TxX over x ∈ X. By u (t) ∈ Tu(t)X, where u: → X, we understand the equivalence class of a function [0, 1) h → u(t + h) ∈ X. Given a function F : X → T X such that F(x) ∈ TxX we are now able to investigate solutions to the differential equation u (t) = F(u(t)).
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6365. Differential evolution algorithm combined with chaotic pattern search
- Creator:
- He, Yaoyao, Zhou, Jian Zhong, Lu, Ning, Qin, Hui, and Lu, Youlin
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- hybrid algorithm, differential evolution (DE), chaotic pattern search, and global optimization
- Language:
- English
- Description:
- Differential evolution algorithm combined with chaotic pattern search(DE-CPS) for global optimization is introduced to improve the performance of simple DE algorithm. Pattern search algorithm using chaotic variables instead of random variables is used to accelerate the convergence of solving the objective value. Experiments on 6 benchmark problems, including morbid Rosenbrock function, show that the novel hybrid algorithm is effective for nonlinear optimization problems in high dimensional space. The comparisons with the standard particle swarm optimization (PSO), differential evolution (DE) and other hybrid algorithms verify DE-CPS algorithm has great superiority.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6366. Differential expression of photosynthesis-related genes of reed ecotypes in response to drought and saline habitats
- Creator:
- Wang, H. L., Hao, L. M., Wen, J. Q., Zhang, C. L., and Liang, H. G.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- cab, 16S rDNA, net photosynthetic rate, Phragmites communis, psbA, and stomatal conductance
- Language:
- Multiple languages
- Description:
- Three ecotypes of reed (Phragmites communis Trinius), swamp reed (SR), dune reed (DR), and heavy salt meadow reed (HSMR), growing in desert regions of northwest China were simultaneously investigated in their natural state for gas exchange patterns and the expression of three photosynthesis-related genes, cab (the gene for the light-harvesting chlorophyll a/b binding protein, LHC), psbA (the gene for the reaction centre D1 protein of photosystem 2, PS2), and 16S rDNA (the gene for plastid 16S rRNA). Stomatal conductance (gs) and intercellular CO2 concentration (ci) were markedly lower in the two terrestrial ecotypes (DR and HSMR) as compared to SR, paralleling a similar observed depression in net photosynthetic rate (PN). However, DR with the lowest measured gs and ci still exhibited a higher PN compared to HSMR. These results suggest that both stomatal and non-stomatal factors account for the comparatively low carbon assimilation in the terrestrial ecotypes. An increase in the expression of photosynthesis-related genes was observed in DR compared to SR, whereas the reverse situation was true in HSMR. The expression of photosynthesis-related genes may contribute to reed plants' photosynthetic capacity per leaf area under natural water deficits, but the levels of photosynthesis-related gene expression are not directly correlated with reed plants' general ability for survival and adaptation under water deficient conditions. and H. L. Wang ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6367. Differential host utilisation by different life history stages of the fish ectoparasite Argulus foliaceus (Crustacea: Branchiura)
- Creator:
- Walker, Peter D., Harris, Jack E., Velde, Gerard van der, and Wendelaar Bonga, Sjoerd E.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Argulus, ectoparasite, fish, host-choice, and specificity
- Language:
- English
- Description:
- In this study we examine differences in the occurrence of life history stages of the destructive fish ectoparasite Argulus foliaceus (L., 1758) on eight fish species (stickleback, rudd, roach, gudgeon, bream, tench, crucian carp and common carp) sampled from a mixed-species recreational fishing lake on nine occasions during late spring and summer. Total numbers of A. foliaceus, as well as the number of larval, juvenile and adult parasite stages, from each fish were recorded along with the fish species. Lice generally exhibited an aggregated distribution approximating a negative binomial distribution. Significant differences in the prevalence, intensity and intensity frequency distribution were observed between life history stages and between host species. In general, all life history stages of A. foliaceus exhibited an over-dispersed distribution. However, larval lice did show some degree of aggregation particularly within the stickleback samples. Infection data for parasite larval stages suggested that sticklebacks are more likely to be infected than other host species. For adult lice, however, carp appeared to be the main host. We propose that A. foliaceus infection characteristics are predominantly determined by the level of host exposure to the parasite and its life history stages (larval, juvenile and adult) rather than by an innate difference in host susceptibility related to individual host factors such as immune responses. We conclude that host exposure is determined by the parasite-host behavioural interplay related to species-specific ecology and behavioural traits such as microhabitat preference and normal swimming speed.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6368. Differential impact of acute bout of exercise on redox- and oxidative damage-related profiles between untrained subjects and amateur runners
- Creator:
- Falone, S., Mirabilio, A., Pennelli, A., Cacchio, CM., Di Baldassarre, A., Gallina, S., Passerini, A., and Amicarelli, F.
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, oxidační stres, tělesná kondice, oxidative stress, physical fitness, aerobic exercise, reactive oxygen species, lipid peroxidation, 14, and 612
- Language:
- English
- Description:
- Despite the demonstrated exercise -induced increase in reactive oxygen species (ROS) production, growing epidemiological evidence indicates that habitual, moderate physical activity reduces the incidence of several oxidative stress-based diseases. This apparent paradox can be explained taking into account that ROS produced during repeated ex ercise bouts may act as mild stressors able to trigger physiological and biomolecular hormetic responses through a number of redox-sensitive transcription pathways. Unfortunately, much more limited information is available from general population-based research, which could better reflect the condition of common people interested in achieving and maintaining good fitness levels. The present work aimed at investigatin g whether and how exercise-related habits in non-professional regular runners (n=33) can affect the systemic anti-oxidative capacity, and the resting serum levels of typical lipid peroxidation-related by-products and oxidatively- damaged proteins, in comparison with untrained sedentary individuals (n=25). We also anal yzed in both groups the redox response elicited by a modified Bruce-based maximal exercise test on the same parameters. Our findings indicated that long- term regular and moderate practice of aerobic physical activity can increase antioxidant defense systems, lower the resting protein oxidation processes and reduce the immediate up- regulation of lipid-targeting oxidative stress in response to an acute bout of exercise., S. Falone, A. Mirabilio, A. Pennelli, M. Cacchio, A. Di Baldassarre, S. Gallina, A. Passerini, F. Amicarelli., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6369. Differential inhibition of photosynthesis under drought stress in Flaveria species with different degrees of development of the C4 syndrome
- Creator:
- Dias, M. C. and Brüggemann, W.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- bundle sheath cells, C3, C4 metabolism, CO2 compensation concentration, malic enzyme, NADP-malate dehydrogenase, phosphoenolpyruvate carboxylase, pyruvate-orthophosphate dikinase, RuBP, RuBPCO, stromal fructose 1,6-bisphosphatase, and water potential
- Language:
- Multiple languages
- Description:
- The effect of drought stress (DS) on photosynthesis and photosynthesis-related enzyme activities was investigated in F. pringlei (C3), F. floridana (C3-C4), F. brownii (C4-like), and F. trinervia (C4) species. Stomatal closure was observed in all species, probably being the main cause for the decline in photosynthesis in the C3 species under ambient conditions. In vitro ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and stromal fructose 1,6-bisphosphatase (sFBP) activities were sufficient to interpret the net photosynthetic rates (PN), but, from the decreases in PN values under high CO2 (C a = 700 µmol mol- 1) it is concluded that a decrease in the in vivo rate of the RuBPCO reaction may be an additional limiting factor under DS in the C3 species. The observed decline in the photosynthesis capacity of the C3-C4 species is suggested to be associated both to in vivo decreases of RuBPCO activity and of the RuBP regeneration rate. The decline of the maximum PN observed in the C4-like species under DS was probably attributed to a decrease in maximum RuBPCO activity and/or to decrease of enzyme substrate (RuBP or PEP) regeneration rates. In the C4 species, the decline of both in vivo photosynthesis and photosynthetic capacity could be due to in vivo inhibition of the phosphoenolpyruvate carboxylase (PEPC) by a twofold increase of the malate concentration observed in mesophyll cell extracts from DS plants. and M. C. Dias, W. Brüggemann.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6370. Differential Laws of Left Ventricular Isovolumic Pressure Fall
- Creator:
- Stephan Langer
- Format:
- print, bez média, and svazek
- Type:
- article, studie, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie člověka, human physiology, Ventricular relaxation, Relaxation time constant, Rat, Guinea pig, Ferret, 14, and 612
- Language:
- English
- Description:
- An attempt has been made to test for a reliable method of characterizing the isovolumic left ventricular pressure fall in isolated ejecting hearts by one or two time constants, tau. Alternative nonlinear regression models (three- and four-parametric exponential, logistic, and power function), based upon the common differential law dp(t)/dt = - [p(t)-Ptau]/ tau(t) are compared in isolated ejecting rat, guinea pig, and ferret hearts. Intraventricular pressure fall data are taken from an isovolumic standard interval and from a subinterval of the latter, determined data-dependently by a statistical procedure. Extending the three-parametric exponential fitting function to four-parametric models reduces regression errors by about 20-30 %. No remarkable advantage of a particular four-parametric model over the other was revealed. Enhanced relaxation, induced by isoprenaline, is more sensitively indicated by the asymptotic logistic time constant than by the usual exponential. If early and late parts of the isovolumic pressure fall are discarded by selecting a subinterval of the isovolumic phase, ? remains fairly constant in that central pressure fall region. Physiological considerations point to the logistic model as an advantageous method to cover lusitropic changes by an early and a late tau. Alternatively, identifying a central isovolumic relaxation interval facilitates the calculation of a single ("central") tau; there is no statistical justification in this case to extend the three-parametric exponential further to reduce regression errors., S. F. J. Langer,., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public