The purpose of this study was to elucidate the intestinal serotonin (5-HT) receptor subtypes involved in fluid transport in the pig jejunum in uioo. The fluid accumulating effect of intraluminally administered 5-HT, renzapride, methysergide, ketanserin, granisetron, citalopram and intravenous indomethacin, was tested in tied- off loops in uiuo. 5-HT caused a dose-dependent fluid accumulation, which was reduced by indomethacin by about 30 %. Renzapride, methysergide, ketanserin, granisetron and citalopram all caused fluid accumulation. Taking into account these fluid accumulating effects, renzapride, methysergide, ketanserin and granisetron reduced the fluid accumulating effect of 5-HT, giving a maximal reduction of 70, 46, 76, and 80 %, respectively. These data suggest the existence of intestinal 5-HT receptor subtypes involved in fluid transport in the pig jejunum. The antagonistic effects of indomethacin, ketanserin and granisetron, suggest the involvement of prostangladins, as well as the 5-HT2 and the 5-HT3 receptor subtypes in the fluid accumulating response of 5-HT.
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
The aphid parasitoid Aphidius ervi was collected and subsequently reared on Sitobion avenae on wheat or Acyrthosiphon pisum on alfalfa. Parasitoids from both origins were exposed in an olfactometer to alfalfa or wheat volatiles after plant experience (wheat or alfalfa) or after oviposition experience (S. avenae on wheat or A. pisum on alfalfa). The results showed the importance of adult experience, conditioning and innate preferences on the responses of A. ervi toward volatiles and provided a mechanistic explanation to the high prevalence of A. ervi on aphids on cereals and legumes in central Chile.
a1_There is little systematic research on the effect of transgenic maize expressing Bacillus thuringiensis (Bt) toxins on insect survival and the response in vivo of their detoxification enzymes. Results of laboratory bioassays indicate that the whorl leaves of transgenic maize lines G03-2396 and G03-2739 significantly affected the survival of neonate and third instar larvae of the Asian corn borer, Ostrinia furnacalis (Güenée). Neonate mortality two days after being fed on G03-2739 was 72.5% and exceeded 92.5% four days later. The percentage mortality of third instar larvae six days after being fed whorl leaves from G03-2396 exceeded 65%. The resistance of whorl leaves to insect attack was greater than that of maize-ears, but less effective against attacks by third instar larvae. Neonate development was more prolonged when they were fed on whorl leaves of both the transgenic maize lines. In contrast, low pupation (<80% of that recorded in the controls), ecolosion and fecundity were recorded following ingestion of maize-ears, with pupal weights 10-14 mg lower than that of controls. The growth rates of third instar larvae recorded three and six days after feeding on whorl leaves were lower, but food utilization, conversion and relative metabolism were not significantly affected. Relative food ingestion, relative growth rate and other nutritional indicators of third instar larvae were significantly lower six days after the ingestion of ears and that of fifth instar larvae after three days. In vivo activity of carboxylesterase was decreased to a greater degree after three days when the larvae were fed on whorl leaves than ears, with no significant effect on fifth instar larvae. Furthermore, in vivo activity of glutathione S-transferase (GST) of third instar larvae was significantly affected following the ingestion of whorl leaves. These results are discussed in the context of the literature on the resistance, a2_of transgenic plants and of improving the resistance of plants to attack by the different larval stages of insects., and Min Juan Shi, Pei Ling Lu, Xiao Li Shi, Yi Zhong Yang.
After 8 weeks of intermittent fasting, mice fed both a standard laboratory diet and a high-fat diet became hyperphagic and showed an increased amount of glycogen storage in the liver. An important effect of the adaptation to intermittent feeding with a high-fat diet seems to be an activation of the oxidation of lipids. Lipid oxidation prevails over lipogenesis so that the protein levels in the liver and skeletal muscle are preserved and maintained constant.
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.
We investigated whether polyethylene glycol-coated Fe3O4 nanoparticles (IONs), acute stress and their combination modifies vascular functions, nitric oxide synthase (NOS) activity, mean arterial pressure (MAP) as well as hepcidin and ferritin H gene expressions in Wistar-Kyoto rats. Rats were divided into control, ION-treated rats (1 mg Fe/kg i.v.), repeated acute air jet stressexposed rats and IONs-and-stress co-exposed rats. Maximal acetylcholine (ACh)-induced and sodium nitroprusside (SNP)-induced relaxations in the femoral arteries did not differ among the groups. IONs alone significantly elevated the Nω-nitroL-arginine methyl ester (L-NAME)-sensitive component of ACh-induced relaxation and reduced the sensitivity of vascular smooth muscle cells to SNP. IONs alone also elevated NOS activity in the brainstem and hypothalamus, reduced NOS activity in the kidneys and had no effect in the liver. Acute stress alone failed to affect vascular function and NOS activities in all the tissues investigated but it elevated ferritin H expression in the liver. In the ION-and-stress group, NOS activity was elevated in the kidneys and liver, but reduced in the brainstem and hypothalamus vs. IONs alone. IONs also accentuated air jet stress-induced MAP responses vs. stress alone. Interestingly, stress reduced ION-originated iron content in blood and liver while it was elevated in the kidneys. In conclusion, the results showed that 1) acute administration of IONs altered vascular function, increased L-NAME-sensitive component of ACh-induced relaxation and had tissue-dependent effects on NOS activity, 2) ION effects were considerably reduced by co-exposure to repeated acute stress, likely related to decrease of ION-originated iron in blood due to elevated decomposition and/or excretion.
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