This investigation addresses the interaction of insulin (INS) and glucocorticoid (GC) signaling in the hepatic regulation of tryptophan oxygenase (TO) enzyme activity in the rat. Male Wistar rats (200-250 g b.w) received an injection of the different doses of INS (10, 25, 50, 70 and 100 μg/200 g b.w., i.p.) and were used for experiments 3 h and 18 h after INS administration. This study shows that maximum of TO activity was found at dose of 50 μg of INS with peak increases observed at 3 h and 18 h after injection of INS, while INS had no effect on TO activity in adrenalectomized rats. The analysis of INS effects on glucocorticoid receptor-complex (GC/GR complex) stability shows that complexes from INS-treated rats are less stable than those from control animals. In addition, INS-stimulated stability of glucocorticoid receptor (GR) protein was significantly increased from the controls. Furthermore, the results show that GC/GR complexes from INS-treated rats could be activated and accumulated at higher rate in cell nuclei of control animals. These data support the involvement of INS in modulation of GC signaling pathway which mediates, in part, the activity of TO., E. R. Isenović, Z. Zakula, G. Koricanac, N. Ribarac-Stepić., and Obsahuje bibliografii a bibliografické odkazy
Under optimal conditions, most of the light energy is used to drive electron transport. However, when the light energy exceeds the capacity of photosynthesis, the overall photosynthetic efficiency drops down. The present study investigated the effects of high light on rice photooxidation-prone mutant 812HS, characterized by a mutation of leaf photooxidation 1 gene, and its wild type 812S under field conditions. Our results showed no significant difference between 812HS and 812S before exposure to high sunlight. However, during exposure to high light, shoot tips of 812HS turned yellow and their chlorophyll (Chl) content decreased. Transmission electron microscopy showed that photooxidation resulted in significant damage of chloroplast ultrastructure. It was confirmed also by inhibited photophosphorylation and reduced ATP content. The decreased coupling factor of ATP, Ca2+-ATPase and Mg2+-ATPase activities also verified these results. Further, significantly enhanced activities of antioxidative enzymes were observed during photooxidation. Malondialdehyde, hydrogen peroxide, and the superoxide generation rates also increased. Chl a fluorescence analysis found that the performance index and maximum quantum yield of PSII declined on August 4, 20 days after high-light treatment. Net photosynthetic rate also decreased and substomatal CO2 concentration increased in 812HS at the same time. In conclusion, our findings indicated that excessive energy triggered the production of toxic reactive oxygen species and promoted lipid peroxidation in 812HS plants, causing severe damage to cell membranes, degradation of photosynthetic pigments and proteins, and ultimately inhibition of photosynthesis., J. Ma, C. F. Lv, B. B. Zhang, F. Wang, W. J. Shen, G. X. Chen, Z. P. Gao, C. G. Lv., and Obsahuje seznam literatury
The relationships between drought response and anatomical/physiological properties were assessed in two poplar clones belonging to the Aigeros section: Populusxeuramericana clone Dorskamp (drought-tolerant) and clone Luisa Avanzo (drought-sensitive). Cuttings of both clones were exposed for 12 h to 0 mM (control). 50 mM (osmotic potential -0.112 MPa), and 150 mM (-0.336 MPa) mannitol. In control, Dorskamp had smaller stomata than Luisa Avanzo, one or two layers of palisade cells, a spongy mesophyll, and high concentrations of antioxidative compounds (ascorbate, glutathione). After exposure to 50 or 150 mM mannitol, both clones closed their stomata: leaf conductance and opening of stomata decreased. When exposed to 50 mM mannitol, net photosynthetic rate (PN) and chlorophyll (Chl) and total solute contents remained stable; ribulose-1,5-bisphosphate carboxylase/-oxygenase activity, Chl synthesis and turn-over, ascorbate peroxidase and glutathione reductase activities were less affected in Dorskamp than in Luisa Avanzo. Following an exposure to 150 mM mannitol, Dorskamp exhibited higher PN and higher contents of antioxidants (ascorbate, glutathione) and antioxidative enzymes (ascorbate peroxidase, glutathione reductase) than Luisa Avanzo. Hence the drought-tolerant poplar was able to better avoid and tolerate osmotic stress. and M. Courtois, E. Boudouresque, G. Guerrier.
Pendulum walnut leaves exhibited various adaptive responses related to the regulation of photon interception such as specific downward orientation, greater leaf area, and larger pigment pool. Changes in the regulation of PS2 such as higher thermal dissipation (NPQ) and lower quantum efficiency (ΦPS2) that protect the photosynthetic apparatus against damages were also found. The growth and photosynthetic features of pendulum walnut leaf are interpreted as adaptations that allow the pendulum walnut tree to compensate the impaired ability by appropriate growth to ensure the energy needs for photosynthesis, respectively for biomass formation. and L. Atanasova ... [et al.].
The aim of our study was to investigate the underlying molecular mechanisms of exogenously supplied trehalose affecting wheat photosynthesis under heat stress. The amount of ATP synthase (ATPase), oxygen-evolving enhancer protein (OEE), PsbP, Rubisco, chloroplast fructose-bisphosphate aldolase (FBPA), and ferredoxin-NADP(H) oxidoreductase (FNR) were downregulated, while PSI reaction center subunits were upregulated under heat stress. However, in the trehalose-pretreated groups, the amount of FNR, cytochrome b6f complex, PSI reaction center subunits, ATPase, FBPA, and Rubisco were upregulated under normal growth conditions and heat stress. Besides, during the recovery period, the upregulation in CAB, PsbP, OEE2, and ATPase suggested that trehalose pretreatment might help to the recovery of PSII and PSI. These results indicate that trehalose pretreatment effectively regulates the levels of the photosynthesis-related proteins and relieves the damage of heat stress to wheat chloroplast., Y. Luo, H. Y. Liu, Y. Z. Fan, W. Wang, Y. Y. Zhao., and Obsahuje bibliografii
Achtheres percarum von Nordmann, 1832 and Achtheres sandrae Gadd, 1901 (Lernaeopodidae) are common parasitic copepods infecting fishes in Eurasia. The former is specific to perch, Perca fluviatilis L., while the latter, to zander, Sander lucioperca (L.). Until recently these copepods have been regarded a single species. The present study was intended to analyse details of male morphology and provide their complete descriptions with differential diagnosis. Males of A. percarum and A. sandrae were collected from perch and zander at Lake Dąbie (north-western Poland). The males of A. sandrae are larger than those of A. percarum. They also differ in proportions of the first antenna, mandibular denticulation, structure of the first maxilla, and the armament of caudal ramus. The reported differences in male morphology constitute a conclusive confirmation of the separate identity of the two species.
The present piece of work highlights the comparative effects of two active forms of brassinosteroids (BRs), 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL), on growth parameters, carbonic anhydrase activity and photosynthetic parameters in Lycopersicon esculentum (cv. K-21) sampled at 45 (24 h after spray) and 60 days after sowing, under natural conditions. Out of the two active forms of BR, EBL proved better than HBL in improving the above parameters, when applied as foliar spray. Of the three concentrations (10-6 M, 10-8 M or 10-10 M) of HBL and EBL, 10-8M proved best in both cases. and S. Hayat ... [et al.].
In this study, cotton seedlings were subjected to osmotic-, salt- and alkali stresses. The growth, photosynthesis, inorganic ions, and organic acids in the stressed seedlings were measured, to compare the mechanisms by which plants adapt to these stresses and attempt to probe the mechanisms by which plants adapt to high pH stress. Our results indicated that, at high stress intensity, both osmotic and alkali stresses showed a stronger injurious effect on growth and photosynthesis than salt stress. Cotton accumulated large amount of Na+ under salt and alkali stresses, but not under osmotic stress. In addition, the reductions of K+, NO3 -, and H2PO4 - under osmotic stress were much greater than those under salt stress with increasing stress intensity. The lack of inorganic ions limited water uptake and was the main reason for the higher injury from osmotic-compared to salt stress on cotton. Compared with salt- and alkali stresses, the most dramatic response to osmotic stress was the accumulation of soluble sugars as the main organic osmolytes. In addition, we found that organic acid metabolism adjustment may play different roles under different types of stress. Under alkali stress, organic acids might play an important role in maintaining ion balance of cotton; however, under osmotic stress, malate might play an important osmotic role. and W. Chen ... [et al.].
We compared the effects of salt-stresses (SS, 1: 1 molar ratio of NaCl to Na2SO4) and alkali-stresses (AS, 1: 1 molar ratio of NaHCO3 to Na2CO3) on the growth, photosynthesis, solute accumulation, and ion balance of barley seedlings, to elucidate the mechanism of AS (high-pH) damage to plants and the physiological adaptive mechanism of plants to AS. The effects of SS on the water content, root system activity, membrane permeability, and the content of photosynthetic pigments were much less than those of AS. However, AS damaged root function, photosynthetic pigments, and the membrane system, led to the severe reductions in water content, root system activity, content of photosynthetic pigments, and net photosynthetic rate, and a sharp increase in electrolyte leakage rate. Moreover, with salinity higher than 60 mM, Na+ content increased slowly under SS and sharply under AS. This indicates that high-pH caused by AS might interfere with control of Na+ uptake in roots and increase intracellular Na+ to a toxic level, which may be the main cause of some damage emerging under higher AS. Under SS, barley accumulated organic acids, Cl-, SO4 2-, and NO3 - to balance the massive influx of cations, the contribution of inorganic ions to ion balance was greater than that of organic acids. However, AS might inhibit absorptions of NO3 - and Cl-, enhance organic acid synthesis, and SO4 2- absorption to maintain intracellular ion balance and stable pH. and C.-W. Wang ... [et al.].
Chlorophyll a fluorescence, water potential (Ψs), and root system of Juniperus oxycedrus ssp. macrocarpa, Juniperus phoenicea ssp. turbinata, and Pinus pinea were studied in Mediterranean coastal dunes of SW Spain during summer drought and after fall rains in 1999, the driest year in the 90's. A strong and reversible depression in the photochemical efficiency of photosystem 2 of the three species was recorded, which happened concomitantly with the diurnal increase and decrease in radiation. J. phoenicea, with superficial root system, was the most affected species by summer drought. It showed high rates of down-regulation of photosynthesis by photoinhibition and positive correlation between Ψs and Fv/Fp, with Ψs lower than -7 MPa. However, it tolerated this high stress, showing a fast recovery of its physiological state after fall rains. On the other hand, J. oxycedrus and P. pinea, both with deep root systems, kept their Ψs values up to -3 MPa, showing lower stress during summer drought. On the other hand, J. oxycedrus and J. phoenicea were more sensible to changes in edaphic water content than P. pinea. These specific responses to summer drought would be determined by their root distributions and stomatal control of transpiration, conditioning the efficiency in getting and using the available water resources. Ecophysiological responses indicate that these species are well-adapted to long periods of drought in Mediterranean climate areas, developing different strategies: J. phoenicea tolerates high stress with a fast recovery after fall rains, while J. oxycedrus and P. pinea are less affected by summer drought since their deep root systems would allow them to reach deep water resources. and J. M. Castillo ... [et al.].