a1_Reduced tolerance to ischemia/reperfusion (IR) injury has been shown in elder human and animal hearts, however, the onset of this unfavorable phenotype and cellular mechanisms behind remain unknown. Moreover, aging may interfere with the mechanisms of innate cardioprotection (preconditioning, PC) and cause defects in protective cell signaling. We studied the changes in myocardial function and response to ischemia, as well as selected proteins involved in “pro-survival” pathways in the hearts from juvenile (1.5 months), younger adult (3 months) and mature adult (6 months) male Wistar rats. In Langendorffperfused hearts exposed to 30-min ischemia/2-h reperfusion with or without prior PC (one cycle of 5-min ischemia/5-min reperfusion), we measured occurrence of reperfusion-induced arrhythmias, recovery of contractile function (left ventricular developed pressure, LVDP, in % of pre-ischemic values), and size of infarction (IS, in % of area at risk size, TTC staining and computerized planimetry). In parallel groups, LV tissue was sampled for the detection of protein levels (WB) of Akt kinase (an effector of PI3-kinase), phosphorylated (activated) Akt (p-Akt), its target endothelial NO synthase (eNOS) and protein kinase Cε (PKCε) as components of “pro-survival” cascades. Maturation did not affect heart function, however, it impaired cardiac response to lethal IR injury (increased IS) and promoted arrhythmogenesis. PC reduced the occurrence of malignant arrhythmias, IS and improved LVDP recovery in the younger animals, while its efficacy was attenuated in the mature adults. Loss of PC protection was associated with age-dependent reduced Akt phosphorylation and levels of eNOS and PKCε in the hearts of mature animals compared with the younger ones, as well as with a failure of PC to upregulate these proteins., a2_Agingrelated alterations in myocardial response to ischemia may be caused by dysfunction of proteins involved in protective cell signaling that may occur already during the process of maturation., L. Griecsová, V. Farkašová, I. Gáblovský, V. K. M. Khandelwal, I. Bernátová, Z. Tatarková, P. Kaplan, T. Ravingerová., and Obsahuje bibliografii
Melatonin has different functions in plant growth and development, especially in the protection of plants suffering from various forms of abiotic stress. We explored the effect of melatonin priming on photosynthetic activity of tomato (Lycopersicon esculentum L.) leaves. Our results showed that 100 µM is the optimal concentration used for alleviation of the damage to photosynthetic apparatus. Melatonin priming both in the form of leaf spray and direct root application was found to reduce the damage to photosynthetic apparatus, and increase the electron transfer rate and quantum yield of PSI and PSII photochemistry, to protect the thylakoid membrane from damage caused by low-temperature stress. Our study provides fundamental information for further research on the molecular mechanism of melatonin function in regulating photosynthesis., X. L. Yang, H. Xu, D. Li, X. Gao, T. L. Li, R. Wang., and Obsahuje bibliografii
Monosodium glutamate (MSG), the sodium salt of glutamate, is commonly used as a flavor enhancer in modern nutrition. Recent studies have shown th e existence of glutamate receptors on lymphocytes, thymoc ytes and thymic stromal cells. In this study, we evaluated the in vitro effect of different MSG concentr ations on rat thymocyte apoptosis and expression of two apoptosis-related proteins, Bcl-2 and Bax. Rat thymocytes, obtained from male Wistar rats, were exposed to increasing concentrations of MSG (ranging from 1 mM to 100 mM) for 24 h. Apoptosis was detected using the Annexin V-FITC/PI apoptosis detection kit and cells were analyzed using a flow cytometer. Expression of Bcl-2 and Bax proteins were determined with flow cytometry using respective monoclonal antibodies. Exposure to MSG resulted in a dose-dependent decrease in cell survival (as determined by trypan blue exclusion method). Annexin V- FITC/PI also confirmed that MSG incr eased, in a dose-dependent manner, ap optotic cell death in rat thymocyte cultures. MSG treatment induced downregulation of Bcl-2 protein, while Bax protein levels were not significantly changed. Our data showed that MSG significantly modulates thymocyte apoptosis rate in cultures. The temporal profile of Bcl-2 and Bax expression after MSG treatment suggests that downregulation of Bcl-2 protein and the resulting change of Bcl-2/Bax protein ratio may be an important event in thymocyte apoptosis triggered by MSG., V. Pavlović, S. Cekić, G. Kocić, D. Sokolović, V. Živković., and Obsahuje bibliografii a bibliografické odkazy
In a greenhouse experiment, the influence of arbuscular mycorrhizal fungi (Glomus mosseae and Glomus intraradices) and water stress [100% field capacity (FC), 75% FC, 50% FC and 25% FC] on maximal quantum yield of photosystem II (PSII) photochemistry (Fv/Fm) and some other ecophysiological characteristics of two pistachio cultivar (Pistacia vera cv.
Badami-Riz-Zarand and Pistacia vera cv. Qazvini) were investigated.
No difference was found in colonization rate between the two arbuscular mycorrhizal fungi (AMF) applied. Water stress reduced the mycorrhizal colonization in both cultivars at the same rate but the difference was significant just with severe water stress level (25% FC). The Fv/Fm was also adversely affected by water stress from 75% FC downwards in Qazvini cultivar while in Badami, increase in water-stress intensity had no significant effect on this parameter. Gasexchange parameters were decreased with increasing stress intensity and chlorophyll (Chl) pigments were increased with mild water stress (75% FC) compared with control (100% FC) and then decreased with increasing stress intensity. The carotenoids (Car) content increased significantly in the stressed leaves in all water-stress levels irrespective of AMF treatment and cultivar type.
The adverse effects of water stress were significantly reduced by AM inoculation and in the most of measured parameters, both AMF had an equal influence except with the intercellular CO2 concentration (Ci), where G. intraradices was superior. Results obtained from Chl fluorescence probe indicated that inoculated AMF enhanced photochemical efficiency of light reactions of the PSII in intact pistachio leaf tissues both under irrigation and waterstress conditions. Under mild and moderate water stress, mycorrhizal pistachio plants had higher relative Chl and Car content and higher gas-exchange capacity (increased photosynthesis and transpiration rate) but under severe water-stress condition (25% FC), the effects of mycorrhizal treatments were not noticeable. Data obtained in present study emphasized that Qazvini is more tolerant to water stress than Badami because photosynthesis activity in Qazvini was more efficiently protected than in the Badami, as indicated by related parameters. and V. Bagheri ... [et al.].
The effects of NaCl (200 mM) and osmotic stress generated by polyethylene glycol (PEG) on PSII maximal quantum efficiency, photosynthetic CO2/H2O gas exchange at two CO2 concentrations, content of chlorophyll, proline, and malondialdehyde were investigated in shoots of C4 xerohalophyte Haloxylon aphyllum (Chenopodiaceae). The PEG treatment induced a low water osmotic potential (-0.4 MPa) and inhibited photosynthesis (by a factor of 2) and transpiration (by a factor of 4). The NaCl treatment, at equal osmoticity conditions, reduced transpiration (by a factor of 2) and stimulated photosynthesis (by a factor of 2.5). Only the
PEG-treated plants showed osmotic stress effects, which were demonstrated by an increase in proline and malondialdehyde contents in the shoot tissue. The data indicated that the halophilic character of this species was essential for maintaining the plant water status and photosynthesis under osmoticity induced by NaCl treatment. Herewith, the presence of C4-type photosynthesis appeared to be just an auxiliary mechanism, because this xerohalophyte did not reveal the efficiency in water use typical for C4 plants under osmotic stress, in the absence of a saline substrate., Z. F. Rakhmankulova, P. Yu. Voronin, E. V. Shuyskaya, N .A. Kuznetsova, N. V. Zhukovskaya, K. N. Toderich., and Obsahuje bibliografii
Wheat (Triticum aestivum L.) genotypes K-65 (salt tolerant) and HD 2329 (salt sensitive) were grown in pots under natural conditions and irrigated with NaCl solutions of electrical conductivity (ECe) 4.0, 6.0, and 8.0 dS m-1. Control plants were irrigated without saline water. Observations were made on the top most fully expanded leaf at tillering, anthesis, and grain filling stages. The net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were reduced with the addition of NaCl. The reduction was higher in HD 2329 than in K-65. Salinity enhanced leaf to air temperature gradient (ΔT) in both the genotypes. NaCl increased the activities of superoxide dismutase (SOD) and peroxidase (POX); the percent increment was higher in K-65. The sodium and potassium contents were higher in the roots and leaves of K-65 over HD 2329. Thus at cellular level K-65 has imparted salt tolerance by manipulating PN, E, gs, and K accumulation in leaves along with overproduction of antioxidative enzyme activities (SOD and POX). and N. Sharma ... [et al.].
Calligonum caput-medusae is known to grow well when irrigated with water containing NaCl. The aim of this study was to investigate ecophysiological responses of C. caput-medusae to different NaCl concentrations. In our study, we examined the effect of 0, 50, 100, 200, and 400 mM NaCl. Our results demonstrated that maximum seedling growth occurred at 50 mM NaCl. Photosynthetic parameters, such as the photosynthetic pigment content and gas exchange parameters, correlated with growth response. High salinity (≥ 100 mM NaCl) resulted in a significant reduction of the plant growth. Similarly, marked declines in the pigment content, maximal efficiency of PSII photochemistry, net photosynthetic rate, transpiration rate, and stomatal conductance were also detected. However, intercellular CO2 concentration showed a biphasic response, decreasing with water containing less than 200 mM NaCl and increasing with NaCl concentration up to 400 mM. Water-use efficiency and intrinsic water-use efficiency exhibited the opposite response. The reduction of photosynthesis at the high NaCl concentration could be caused by nonstomatal factors. High salinity led also to a decrease in the relative water content and water potential. Correspondingly, an accumulation of soluble sugars and proline was also observed. Na+ and
Cl- concentrations increased in all tissues and K+ concentrations were maintained high during exposure to NaCl compared with the control. High salinity caused oxidative stress, which was evidenced by high malondialdehyde and hydrogen peroxide contents. In order to cope with oxidative stress, the activity of antioxidative enzymes increased to maximum after 50 mM NaCl treatment. The data reported in this study indicate that C. caput-medusae can be utilized in mild salinity-prone environments., Y. Lu, J.-Q. Lei, F.-J. Zeng, B. Zhang, G.-J. Liu, B. Liu, X.-Y. Li., and Obsahuje bibliografii
a1_The day-night variation of food intake and alkaline phosphatase (AP) activity was studied in the duodenum of rats neonatally treated with monosodium glutamate (MSG) and saline-treated (control) rats. The animals were kept under light-dark conditions (light phase from 09:00 h to 21:00 h) with free access to food. AP activity was cytophotometrically analyzed in the brush-border of enterocytes separated from the tip, middle and cryptal part of the villi every 6 h over a 24-hour period. In comparison with the controls, MSG-treated rats consumed about 40 % less food during the dark period and their 24-hour food intake was thus significantly lowered (P<0.001). On the other hand, the nocturnal feeding habit showed a similar pattern: food consumption was high during the night (65 % vs. 75 %) and the lowest consumption was found during the light phase (35 % vs. 25 %) in MSG-treated and control rats, respectively. In agreement with the rhythm of food intake, the highest AP activity was observed during the dark phase and was lowest during the light phase in both groups of animals. These significant day-night variations showed nearly the same pattern in the enterocytes of all observed parts along the villus axis. In comparison with the controls, a permanent increase of AP activity was observed in neonatal MSG-treated rats. This increase was more expressive during the dark phase of the day in the cryptal (P<0.001) and middle part of the villus (P<0.01). From the viewpoint of feeding, this enzyme in MSG-treated rats was enhanced in an inverse relation to the amount of food eaten i.e. despite sustained hypophagia the mean AP activity in the enterocytes along the villus axis was higher than in the control animals during all investigated periods., a2_The present results suggest that the increased AP activity in MSG-treated rats is probably not a consequence of actual day-night eating perturbations but could be a component of a more general effect of MSG. This information contributes to better understanding of the function of intestinal AP and its relation to day-night feeding changes especially in connection with the MSG syndrome., A. Martinková, Ľ. Lenhardt, Š. Mozeš., and Obsahuje bibliografii
The present investigation was directed to study the effect of in vitro or ex vivo NO donors, sodium nitroprusside and molsidomine, using isolated sliced adipose tissue or in the form of immobilized and perfused adipocytes on the basal and isoprenaline-stimulated lipolysis. The results demonstrated that 1) in vitro application of sodium nitroprusside to perfused adipocytes or molsidomine to sliced adipose tissues affects isoprenaline-induced lipolysis in two ways, an increase in lipolysis at low isoprenaline concentrations (which means the sensitization of adipose tissues to adrenergic effect by NO) and decreased adrenergic agonist-stimulated lipolysis at higher concentration of isoprenaline (a decrease in the maximum lipolytic effect of isoprenaline), 2) low concentrations of molsidomine alone induced lipolysis from adipose tissue which attained more than 60 % of that by isoprenaline (pD2 value for molsidomine = 11.2, while pD2 for isoprenaline = 8.17) while sodium nitroprusside did not affect the basal lipolysis significantly, 3) in vivo administration of molsidomine for 2 days reduced the maximum lipolytic effect of isoprenaline and (only non-significantly) increased the sensitivity to low doses of isoprenaline. In conclusion the present data demonstrate that NO plays an important role in adrenergic lipolysis in adipose tissues and further investigations are needed to unravel the exact role of NO in lipolysis., D. Lincová, D. Mišeková, E. Kmoníčková, N. Canová, H. Farghali., and Obsahuje bibliografii
As nitric oxide is considered a mediator of liver oxid ative metabolism during sepsis, we studied the effects of exogenous nitric oxide, produced by NO-donor, (±)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (NOR-3), on cell viability, urea biosynthesis and oxygen consumption in rat hepatocyte cultures. Nitric oxide release from NOR-3 was studied using 4,5-diaminofluorescein diacetate. Urea levels were measured by the spectrophotometric method. Cell viability was determined by the MTT test and trypan blue exclusion test, whereas oxygen consumption was measured by a polarographic technique. After 2 h treatment, NOR-3 induced an increase in the levels of nitric oxide. After 2 h of treatment and 24 h after the end of the treatment with NOR-3, both cell viability and urea synthesis were significantly reduced in comparison to the controls for NOR-3 concentrations equal to or greater than 50 μM. A reduction in oxygen consumption was observed in hepatocytes after 40 min treatment with 100 μM NOR-3, even if the cell viability was unchanged. Reduction of oxygen consumption is an early indicator of the metabolic alterations in hepatocytes exposed to nitric oxide. These findings suggest that nitric oxide accumulation acts on hepatocyte cultures inducing cell death and reduction of urea synthesis after 2 hours., R. Chimenti, G. Martino, S. Mazzulla, S. Sesti., and Obsahuje bibliografii a bibliografické odkazy