V oblasti magnetického cielenia buniek, liečiv alebo génov, využívajúc princíp magnetickej separácie vel'kým gradientom, boli navrhnuté a teoreticky analyzované nové systémy, ako aj jednoduché usporiadania magnetov, už skôr študované Halbachovo pole. Na modelovanie magnetického pol'a sa s úspechom použiva metóda konečných prvkov. Táto metóda je predmetom tohto referátu. Novým potenciálnym systémom na magnetickú separáciu v mikrometrických rozemroch je nami študované pole s ve'lkým gradientom v okolí mikrometrických diskov zo silného feromagnetika v pôvodne homogénnom poli. Bol určený približný efektívny dosah takéhoto systému v prípade nanočastíc rádovo v mikrometroch. Obdobná analýza bola vykonaná aj pre magnetické částice v prúdiacom viskóznom tekutom prostredí. Účinná separácia, resp. cielenie, v prípade malých magnetov milimetrových rozmerov v priamom kontakte s kapilárou bola dosiahnutá pre mikročastice. V podobných systémoch v centimetrových rozemroch boli pozorované porovnatel'né výsledky. Kombinácia vel'kejj intenzity a gradientu je dosiahnutá len v blízkom okolí magnetov. Väčší dosah bol pozorovaný v prípade študovaného symetrického Halbachovho pol'a., The magnetic particles play an important role as magnetic drug, gene or cell carriers, in biomedicine and biotechnology. Their combination with a strongly non-homogeneous magnetic field is considered as a powerful way to target them to desired sites in living organism. It is important to know the potential applicability of these systems for magnetic drug targeting in living organism. For these purposes we have developed and evaluated a numerical model of magnetic targeting using finite element method applied to solve Maxwell equations describing electromagnetic field coupled with Newton law of particle motion., Andrej Krafčík, Melánia Babincová, Peter Babinec., and Obsahuje bibliografii
The altitudinal effects on photosynthesis were measured on progenies of three populations of Rosa platyacantha Schrenk from altitudes of 1,170 (L); 1,580 (M); and 1,920 (H) m a. s. l. During the day, net photosynthetic rate (PN) decreased in all populations due to the high air temperature in the summer. The H population showed a significantly lower PN at noon compared to other populations. The midday depression of PN occurred in L and M populations due to stomatal limitations, while PN inhibition was associated with PSII activity decline in the H population. In order to avoid photodamage, the plants of H population triggered active antioxidant defenses with a higher enzyme activity and redox ratio of ascorbate at midday compared to the L and M populations. However, more oxidative injury still occurred in the H plants at noon due to higher lipid peroxidation. Our results indicated that the provenance significantly affected photosynthesis in R. platyacantha from northwestern China., S. H. Yang, J. J. Wei, H. Ge., and Obsahuje bibliografii
Photoinhibition is a significant constraint for improvement of radiation-use efficiency and yield potential in cereal crops. In this work, attached fully expanded leaves of seedlings were used to assay the factors determining photoinhibition and for evaluation of tolerance to photoinhibition in wheat (Triticum aestivum L.). Our results showed that even 1 h under PPFD of 600 µmol(photon) m-2 s-1 could significantly reduce maximal quantum yield of PSII photochemistry (Fv/Fm) and performance index (PI) compared to low light [300 µmol(photon) m-2 s-1]. The decrease of Fv/Fm and PI was more noticeable with the increase of light intensity; irradiance higher than 800 µmol(photon) m-2 s-1 resulted in photoinhibition. Compared to 25°C, lower (20°C) or higher temperature (≥ 35°C) aggravated photoinhibition, while slightly high temperature (28°) alleviated photoinhibition. At 25°C, irradiance of 1,000 µmol(photon) m-2 s-1 for 1 h was enough to cause photoinhibition and a significant decrease of Fv/Fm, PI, trapped energy flux, electron transport flux, and density of reaction center as well as increase of dissipated energy flux per cross section were observed. In addition, seedlings at 21-32 days after planting showed a relatively stable phenotype, while the younger or older seedlings indicated an increased susceptibility to photoinhibition, especially in senescing leaves. Finally, six wheat varieties with relative tolerance to photoinhibition were identified from 22 Chinese winter wheat varieties by exposing attached leaves of the 25-d old seedlings for 1 h to 1,000 µmol(photon) m-2 s-1 at 25°C. Therefore, our work established a possible method for development of new wheat varieties with enhanced tolerance to photoinhibition., H. Li, Q. Zheng, J. Zhang, B. Li, Z. Li., and Obsahuje bibliografii
We identified and characterised the deep red state (DRS), an optically-absorbing charge transfer state of PSII, which lies at lower energy than P680, in the red algae Cyanidioschyzon merolae by means of low temperature absorption and magnetic circular dichroism spectroscopies. The photoactive DRS has been previously studied in PSII of the higher plant Spinacia oleracea, and in the cyanobacterium Thermosynechococcus vulcanus. We found the DRS in PSII of C. merolae has similar spectral properties. Treatment of PSII with dithionite leads to reduction of cytochrome (cyt) b559 and the PsbV-based cyt c550 as well as the disassembly of the oxygen-evolving complex. Whereas the overall visible absorption spectrum of PSII was little affected, the DRS absorption in the reduced sample was no longer seen. This bleaching of the DRS is discussed in terms of a corresponding lack of a DRS feature in D1D2/cyt b559 reaction centre preparations of PSII., J. Langley, J. Morton, R. Purchase, L. Tian, L. Shen, G. Han, J.-R. Shen, E. Krausz., and Obsahuje bibliografické odkazy
C-type natriuretic peptides (CNP) play an inhibitory role in smooth muscle motility of the gastrointestinal tract, but the effect of CNP on delayed rectifier potassium currents is still unclear. This study was designed to investigate the effect of CNP on delayed rectifier potassium currents and its mechanism by using conventional whole-cell patch- clamp technique in guinea-pig gastric myocytes isolated by collagenase. CNP significantly inhibited delayed rectifier potassium currents [IK (V)] in dose-dependent manner, and CNP inhibited the peak current elicited by depolarized step pulse to 86.1±1.6 % (n=7, P<0.05), 78.4±2.6 % (n=10, P< 0.01) and 67.7±2.3 % (n=14, P<0.01), at concentrations of 0.01 μmol/l, 0.1 μmol/l and 1 μmol/l, respectively, at +60 mV. When the cells were preincubated with 0.1 μmol/l LY83583, a guanylate cyclase inhibitor, the 1 μmol/l CNP-induced inhibition of IK (V) was significantly impaired but when the cells were preincubated with 0.1 μmol/l zaprinast, a cGMP-sensitive phosphodiesterase inhibitor, the 0.01 μmol/l CNP-induced inhibition of IK (V) was significantly potentiated. 8-Br-cGMP, a membrane permeable cGMP analogue mimicked inhibitory effect of CNP on IK (V). CNP-induced inhibition of IK (V) was completely blocked by KT5823, an inhibitor of cGMP-dependent protein kinase (PKG). The results suggest that CNP inhibites the delayed rectifier potassium currents via cGMP-PKG signal pathway in the gastric antral circular myocytes of the guinea-pig., H. Y. Xu, X. Huang, M. Yang, J.-B. Sun, L.-H. Piao, Y. Zhang, L. Gao, W.-X. Xu., and Obsahuje bibliografii a bibliografické odkazy
The study investigated the effects of different CaCl2 concentrations (2, 5, and 10 mM) on photosynthetic enzymatic activities, photosynthesis, and chlorophyll fluorescence of tung tree seedlings under drought conditions. Plants were sprayed with either CaCl2 or distilled water until run-off. Irrigation was then withheld to induce drought stress. The strength of drought stress was evaluated by relative leaf water content and soil water content, which was 27.3 and 9.5% on day 0 and day 12, respectively. Drought stress decreased activities of ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase, chlorophyll (a+b) content, net photosynthetic rate, stomatal conductance, transpiration rate, electron transport rate, the maximal quantum yield of PSII photochemistry, and effective quantum yield of PSII in tung tree seedlings. The CaCl2 pretreatments alleviated the negative effect of drought stress to some degree on all the parameters mentioned above., Z. Li, X. F. Tan, K. Lu, Z. M. Liu, L. L. Wu., and Obsahuje bibliografii
Changes of chlorophyll (Chl) a fluorescence and photosynthetic pigment contents were analysed in galled leaves (visibly damaged and undamaged parts) and intact leaves. The values of minimal fluorescence of the dark-adapted state, maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemical conversion, and photochemical quenching coefficient decreased in Ulmus pumila L. leaves galled by Tetraneura ulmi (L.) and in U. glabra Huds. galled by Eriosoma ulmi (L.). Colopha compressa (Koch.) feeding affected these parameters only in damaged parts of U. laevis Pall. galled leaves. The increasing number of T. ulmi galls progressively decreased photosynthetic performance. In gall tissues of all analysed aphid species, the lowest photosynthetic pigment content was found, indicating that the photosynthetic capacity must have been low in galls. Significant reduction of Chl and carotenoid contents were observed in damaged and undamaged portions of galled leaves only in the case of T. ulmi feeding., K. Kmieć, K. Rubinowska, W. Michałek, H. Sytykiewicz., and Obsahuje bibliografii
The aim of our study was to test the in fluence of short exposure (6 h) of preimplantation rabbit embryos to elevated temperatures (41.5 ºC or 42.5 ºC) in vitro on their developmental capacity. Fertilized eggs recovered from female oviducts at the pronuclear stage (19 hpc) were cultured at standard temperature (37.5 ºC) until the morula stage (72 hpc). Afterwards, the embryos were divided into two groups, cultured for 6 h either at hyperthermic (41.5 ºC or 42.5 ºC) or standard temperature (control 37.5 ºC), post-incubated overnight (16-20 h) at 37.5 ºC and then evaluated for developmental stages, apoptosis (TUNEL), proliferation (cell number), actin cytoskeleton and presence of heat-shock proteins Hsp70. It was observed that hyperthermia at 41.5 ºC did not alter progression of embryos to higher preimplantation stages (expanded and hatching/hatched blastocysts), rate of apoptosis, total cell number of blastocysts and structure of actin filament compared to 37.5 ºC. We stern-blotting revealed the presence of heat stress-induced 72 kDa fraction of Hsp70 proteins in granulosa cells (exposed to 41 ºC) and embryos (exposed to 41.5 ºC). Following the elevation of temperature to 42.5 ºC embryo development was dramati cally compromised. The embryos were arrested at the morula or early blastocyst stage, showed an increased rate of apoptosis and decreased total cell number compared to control. The structure of actin filaments in most of blastomeres was damaged and such blastomeres often contained apoptotic nuclei. In this group a presence of heat-stress-induced fraction of Hsp70 proteins had not been confirmed. This is the first report demonstrating a threshold of thermotolerance of rabbit preimplantation embryos to hyperthermic exposure in vitro. A detrimental effect of higher temperature on the embryo is probably associated with the loss of their ability to produce Hsp70 de novo, which leads to cytoskeleton alterations and enhanced apoptosis., A. V. Makarevich, L. Olexiková, P. Chrenek, E. Kubovičová, K. Fréharová, J. Pivko., and Obsahuje bibliografii a bibliografické odkazy
High irradiance promotes decreases in the quantum yield in plants, which reduce the photosynthetic rate. The excess of light in combination with water deficit can intensify the response of plants to stress, especially in species susceptible to those factors. The aim of the present study was to characterize the photosynthetic activity of young jatobá-do-cerrado (Hymenaea stigonocarpa Mart. ex Hayne) trees under different irradiance conditions, both alone and/or in combination with water deficit. Four irradiances [45, 230, 510, and 1,700 μmol(photon) m-2 s-1] and two levels of water in soil (90% and 50% of field capacity) were used. Gas exchange, water potential, and chlorophyll a fluorescence were measured. The highest rates of photosynthesis were observed under irradiances of 230 and 510 μmol(photon) m-2 s-1. Irradiance of 1,700 μmol(photon) m-2 s-1 led to the photoinhibition of photosynthesis, as indicated by a reduced maximum quantum yield of PSII, effective quantum yield ratio, and electron transport rate, as well as higher nonphotochemical quenching. The most stressful to young H. stigonocarpa plants was high irradiance, while water deficit did not intensify the response to light stress., A. C. Costa, S. L. Rezende-Silva, C. A. Megguer, L. M. F. Moura, M. Rosa, A. A. Silva., and Obsahuje bibliografii
This study was designed to investigate effect of alpha-lipoic acid (LA) on lipid peroxidation, nitric oxide production and antioxidant systems in rats exposed to chronic restraint stress. Twenty four male Wistar rats, aged three months, were divided into four groups: control (C), the group treated with LA (L), the group exposed to restraint stress (S) and the group exposed to stress and treated with LA (LS). Restraint stress was applied for 21 days (1 h/day) and LA (100 mg/kg/day) was injected intraperitonally to the L and LS groups for the same period. Restraint stress significantly decreased brain copper/zinc superoxide dismutase (Cu,Zn-SOD) and brain and retina glutathione peroxidase (GSH-Px) and catalase (CAT) activities compared with the control group. Thiobarbituric acid reactive substances (TBARS), nitrite and nitrate levels were significantly increased in the tissues of the S group compared with the C group. LA produced a significant decrease in brain and retina TBARS, nitrite and nitrate levels of the L and LS groups compared to their corresponding control groups. LA increased all enzyme activities in the tissues of the LS group compared to the S group. Our study indicated that LA is an ideal antioxidant candidate for the prevention of stress-induced lipid peroxidation., D. Akpinar, P. Yargiçoğlu, N. Derin, Y. Alicigüzel, A. Ağar., and Obsahuje bibliografii a bibliografické odkazy