The influence of various concentrations of imazapic residues (0-800 μg kg-1) on the growth, chlorophyll content, and photosynthetic characteristics of maize seedlings was studied in a greenhouse pot experiment. Plant height, root length, shoot dry mass, root dry mass, and total dry mass of maize declined with the increase of imazapic residue concentrations. The root/shoot ratio initially decreased and then increased in presence of imazapic, which indicated that the effects of imazapic residues on plant height and root length might differ in maize seedlings. Lowered chlorophyll content and net photosynthetic rate were observed in leaves of maize seedlings in all treatments and indicated a dose-response relationship to imazapic concentrations. Intercellular carbon dioxide concentration, transpiration rate, and stomatal conductance also declined to varying extents, but the chlorophyll a/b ratio increased gradually together with the increase of imazapic residue concentrations. Generally, the maize seedlings were negatively affected by the imazapic residues in soil. Response of root length and biomass to imazapic residues could be the important index for maize variety selection., W. C. Su, L. L. Sun, R. H. Wu, Y. H. Ma, H. L. Wang, H. L. Xu, Z. L. Yan, C. T. Lu., and Obsahuje bibliografii
Potential changes in the activity of endocrine axes related to growth as a result of leptin administration during embryonic development of birds were evaluated in the Japanese quail as a model bird with fast growth and development. On day 5 of incubation, 0.1 µg or 1 µg of recombinant mice leptin in 50 µl of phosphate buffered saline were injected into the albumen of eggs. Animals from each group were killed by decapitation on day 0, 2, 5, 7, 14, 21, 28, 35, 42, 49 and 56 of life. Plasma concentrations of triiodothyronine (T3), thyroxin (T4), corticosterone, testosterone, total lipids, triacylglycerols, cholesterol, glucose and alkaline phosphatase activity were measured. Quail treated by leptin hatched earlier (5-24 hours) and had a higher body weight than the control group (P<0.05-0.001). Mean body weight across the whole observed period was higher in both treated groups as compared to the control group (P<0.05). Leptin in ovo administration was accompanied by changes of endocrine and metabolic parameters during postembryonic development. The most prominent changes appeared immediately after hatching (T3, T4, total lipids, triacylglycerols) and before sexual maturity. It is suggested that leptin acts as a general signal of low energy status to neuroendocrine systems in birds which improves utilization of nutrients., D. Lamošová, M. Máčajová, M. Zeman, Š. Mózeš, D. Ježová., and Obsahuje bibliografii
Area and fresh and dry masses of flag leaf show two phases of development during grain filling in Triticum aestivum. The initial large increase in leaf size is mainly due to water intake. Contents of chlorophylls and carotenoids, reducing sugars, and sucrose, Hill reaction rate, and photosynthetic activity increased during leaf growth, but a noticeable decline in these parameters followed throughout leaf senescence. The maximum accumulation of polysaccharides and proteins occurred at the beginning of grain set, but a continuous decline in their absolute values was manifested during grain filling. Grain priming with indol-3-yl acetic acid (IAA) at 25 mg kg-1 stimulated the flag leaf growth, namely its fresh and dry masses and its area. Furthermore, the stimulatory effect was mainly due to the increase in the pigment formation that in turn increased the photosynthetic activity of flag leaf during grain filling. On the other hand, the highest dose of IAA (50 mg kg-1) attenuated the growth and physiological activity of flag leaf through its inhibitory action on leaf fresh and dry masses, leaf area, pigments, saccharides and protein formation, as well as its effect on 14CO2 assimilation.
Vasodilator prostaglandins (PGE2, PGI2) play an important role in the regulation of renal blood flow. Hence, inhibition of their production with nonsteroidal anti-inflammatory drugs increases renal vascular resistance and exerts adverse renal effects. It has been reported that besides endothelium-derived prostaglandin products, nitric oxide (NO) may be mainly involved in regulation of renal functions. The aim of our study was to evaluate the effect of cyclooxygenase inhibition with indomethacin and endothelium removal on vascular responses of the renal artery as a model vessel. Isolated segments of rabbit renal arteries were perfused at constant flow. Indomethacin administration (10-5mol.l-1) significantly increased the responses to single doses (0.1, 1, 10 m g) of noradrenaline (NA) as compared with the controls. In indomethacin-pretreated vessels, subsequent deendothelisation by air bubbles enhanced the constrictor responses to NA. In reversed order, when deendothelisation was followed by indomethacin administration, the responses to NA were similar in character. A comparison of renal artery responses to NA in both experimental situations did not reveal any significant differences. It can be supposed that endothelial and non-endothelial factors may be involved in local regulation of renal vascular tone., V. Kristová, M. Kriška, R. Vojtko, A. Kurtanský., and Obsahuje bibliografii
The effects of soil salt-alkaline (SA) stress on leaf physiological processes are well studied in the laboratory, but less is known about their effect on leaf, bark and branch chlorenchyma and no reports exist on their effect on C4 enzymes in field conditions. Our results demonstrated that activities of C4 enzymes, such as phospholenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), pyruvate orthophosphate dikinase (PPDK), and NADP-dependent malate dehydrogenase (NADP-MDH), could also be regulated by soil salinity/alkalinity in poplar (Populus alba × P. berolinensis) trees, similarly as the already documented changes in activities of antioxidative enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), pigment composition, photosynthesis, and respiration. However, compared with 50-90% changes in a leaf and young branch chlorenchyma, much smaller changes in malondialdehyde (MDA), antioxidative enzymes, and C4 enzymatic activities were observed in bark chlorenchyma, showing that the effect of soil salinity/alkalinity on enzymatic activities was organ-dependent. This suggests that C4 enzymatic ratios between nonleaf chlorenchyma and leaf (the commonly used parameter to discern the operation of the C4 photosynthetic pathway in nonleaf chlorenchyma), were dependent on SA stress. Moreover, much smaller enhancement of these ratios was seen in an improved soil contrary to SA soil, when the fresh mass (FM) was used as the unit compared with a calculation on a chlorophyll (Chl) unit. An identification of the C4 photosynthesis pathway via C4 enzyme difference between chlorenchyma and leaf should take this environmental regulation and unit-based difference into account., H. M. Wang ... [et al.]., and Obsahuje bibliografii
Hypoxia has been identified as an important stimulus for gene expression during embryogenesis and in various pathological situations. Its influence under physiological conditions, however, has only been studied occasionally. We therefore investigated the effect of intermittent high altitude hypoxia on the mRNA expression of different cytokines and protooncogenes, but also of other genes described to be regulated by hypoxia, in the left ventricle (LV), the right ventricle (RV), atria and the lung of adult rats after simulation of hypoxia in a barochamber (5000 m, 4 hours to 10 days). Heme oxygenase-1 as well as transforming growth factor-β1 showed an increased expression in all regions of the heart and the lung at different periods of hypoxia. For lactate dehydrogenase-A, we found a significant up-regulation in the RV and the lung, for lactate dehydrogenase-B up-regulation in the RV, but down-regulation in the LV and the atria. Vascular endothelial growth factor was up-regulated in the RV, the LV and the lung, but down-regulated in the atria. Its receptor Flk-1 mRNA was significantly increased in the atria and RV only. Expression of c-fos was found in the LV and RV only after 4 hours of hypoxia. The level of c-jun was significantly increased in the LV but decreased in the atria. Our data clearly demonstrate that intermittent hypoxia is a modulator of gene expression under physiological conditions. It differently regulates the expression of distinct genes not only in individual organs but even within one organ, i.e. in the heart., E. Deindl, F. Kolář, E. Neubauer, S Vogel, W. Schaper, B. Ošťádal., and Obsahuje bibliografii
The transverse (t-) tubular system serves to bring electrical signals deep inside the muscle cells to control mechanical responses. Our preliminary mathematical model of human ventricular cardiomyocyte incorporating t-tubular system [1] was improved by introducing description of latest experimental data related to morphology of human t-tubules and to specific properties of ionic currents. To describe the ion diffusion within t-tubular lumen, we partitioned the t-tubule compartment into nine concentric cylindrical segments. Using the model, we studied the effect of activity-induced concentration changes in the t-tubules on Ca2+ entry into the cell and the intracellular Ca2+ transients controlling the strength of cellular contraction. The values of some crucial parameters, unknown in human cardiomyocytes to date, were regarded as independent variables. The simulations confirmed the tendency of the activity-induced t-tubular concentration changes of Ca2+ to reduce the Ca2+ entry into the cell as well as the intracellular Ca2+ transient. The effect rose with the increase of t-tubular fraction of L-type Ca2+ channels (fCa,t), with the decrease of t-tubular fraction of Ca2+ pump (fpCa,t) and with the increase of the time constant of Ca2+ exchange between external space and t-tubule lumen (TCa,extt). Significant effect simultaneously fCa,t ≥ 0.64, fpCa,t ≤ 0.2 and TCa,extt ≥ 240 ms. and Obsahuje Appendix se seznamy literatury, užitých zkratek a symbolů
The effect of iron deficiency on photosynthetic pigments, ribulose-1,5-bisphosphate carboxylase (RuBPC), and photosystem activities were investigated in field grown grapevine (Vitis vinifera L. cv. Pinot noir) leaves. The contents of chlorophyll (Chl) (a+b) and carotenoids per unit fresh mass showed a progressive decrease upon increase in iron deficiency. Similar results were also observed in content of total soluble proteins and RuBPC activity. The marked loss of large (55 kDa) and small (15 kDa) subunits of RuBPC was also observed in severely chlorotic leaves. However, when various photosynthetic electron transport activities were analysed in isolated thylakoids, a major decrease in the rate of whole chain (H2O → methyl viologen) electron transport was observed in iron deficient leaves. Such reduction was mainly due to the loss of photosystem 2 (PS2) activity. The same results were obtained when Fv/Fm was evaluated by Chl fluorescence measurements in leaves. Smaller inhibition of photosystem 1 (PS1) activity was also observed in both mild and severely chlorotic leaves. The artificial electron donors, diphenyl carbazide and NH2OH, markedly restored the loss of PS2 activity in severely chlorotic leaves. The marked loss of PS2 activity was evidently due to the loss of 33, 23, 28-25, and 17 kDa polypeptides in iron deficient leaves. and M. Bertamini, N. Nedunchezhian, B. Borghi.
Although the beneficial role of Fe, Zn, and Mn on many physiological and biochemical processes is well established, effects of each of these elements on chlorophyll (Chl) a fluorescence and photosynthetic pigment contents is not well studied. The objective of this study was to evaluate effects of Fe, Zn, and Mn deficiency in two lettuce cultivars. The parameters investigated could serve also as physiological and biochemical markers in order to identify stress-tolerant cultivars. Our results indicated that microelement shortage significantly decreased contents of photosynthetic pigments in both lettuce cultivars. Chl a fluorescence parameters including maximal quantum yield of PSII photochemistry and performance index decreased under micronutrient deficiency, while relative variable fluorescence at J-step and minimal fluorescence yield of the dark-adapted state increased under such conditions in both cultivars. Micronutrient deficiency also reduced all parameters of quantum yield and specific energy fluxes excluding quantum yield of energy dissipation, quantum yield of reduction of end electron acceptors at the PSI, and total performance index for the photochemical activity. Osmoregulators, such as proline, soluble sugar, and total phenols were enhanced in plants grown under micronutrient deficiency. Fe, Zn, and Mn deficiency led to a lesser production of dry mass. The Fe deficiency was more destructive than that of Zn and Mn on the efficiency of PSII in both lettuce cultivars. Our results suggest that the leaf lettuce, which showed a higher efficiency of PSII, electron transport, quantum yield, specific energy fluxes, and osmoregulators under micronutrient deficiency, was more tolerant to stress conditions than crisphead lettuce., H. R. Roosta, A. Estaji, F. Niknam., and Obsahuje bibliografii
Thermal stability of thylakoid membranes isolated from acclimated and non-acclimated wheat (Triticum aestivum L. cv. HD 2329) leaves under irradiation was studied. Damage to the photosynthetic electron transport activity was more pronounced in thylakoid membranes isolated from non-acclimated leaves as compared to thylakoid membrane isolated from acclimated wheat leaves at 35 °C. The loss of D1 protein was faster in non-acclimated thylakoid membrane as compared to acclimated thylakoid membranes at 35 °C. However, the effect of elevated temperature on the 33 kDa protein associated with oxygen evolving complex in these two types of thylakoid membranes was minimal. Trypsin digestion of the 33 kDa protein in the thylakoid membranes isolated from control and acclimated seedlings suggested that re-organisation of 33 kDa protein occurs before its release during high temperature treatment. and A. K. Singh, G. S. Singhal.