An important mechanism underlying cochlear hair cell (HC) susceptibility to hypoxia/ischemia is the influx of Ca2+. Two main ATP-dependent mechanisms contribute to maintaining low Ca2+ levels: uptake of Ca2+ into intracellular stores via smooth endoplasmic reticulum calcium ATPase (SERCA) and extrusion of Ca2+ via plasma membrane calcium ATPase (PMCA). The effects of the SERCA inhibitors thapsigargin (10 nM-10 μM) and cyclopiazonic acid (CPA; 10-50 μM) and of the PMCA blockers eosin (1.5-10 μM) and o-vanadate (1-5 mM) on inner and outer hair cells (IHCs/OHCs) were examined in normoxia and ischemia using an in vitro model of the newborn rat cochlea. Exposure of the cultures to ischemia resulted in a significant loss of HCs. Thapsigargin and CPA had no effect. Eosin decreased the numbers of IHCs and OHCs by up to 25 % in normoxia and significantly aggravated the ischemia-induced damage to IHCs at 5 and 10 μM and to OHCs at 10 μM. o-Vanadate had no effect on IHC and OHC counts in normoxia, but aggravated the ischemia-induced HC loss in a dose-dependent manner. The effects of eosin and o-vanadate indicate that PMCA has an important role to play in protecting the HCs from ischemic cell death., N. Amarjargal, B. Mazurek, H. Haupt, N. Andeeva, J. Fuchs, J. Gross., and Obsahuje bibliografii a bibliografické odkazy
The effects of exposing winter-grown tomato {Lycopersicon esculentum L.) to various sunlight irradiances and CO2 concentrations, on dark respiration (Ro), night respiration (/?},}), net photosynthetic' rate (P^), dry matter production (DMP), yield earliness and yield amount were studied. Plants were grown in greenhouses under controlled temperatures and exposed to: fiill (FS) oř half (HS) sunlight irradiance in combination with atmospheric (A) oř enriched (E) concentrations of 300-330 or 1400-1500 g(C02) m'^, respectively. The of intact leaves at noontime reached 10.7, 15.2, 5.9 and 9.6 pmol(C02) m-2 s-i in treatments of FSA, FSE, HSA and HSE, respectively. The irradiances on the upper leaf surface during the measurements ranged between 160-190 and 450-550 pmol s'^ in the HS and FS treatments, respectively. of leaves which were kept in darkness following the measurement amved at efflux of 2.6, 2.5, 1.4 and 1.4 pmol(C02) m‘2 s'* while their Pn G^etween 20:00 and 24:00) reached values of 0.9, 1.3, 0.8 and 0.8 pmol(C02) treatments of FSA, FSE, HSA and HSE, respectively. Elevating the CO2 concentration from 300 to 1500 g m'^ increased P^ by 16, 28, 30 and 46 % under an irradiance of 160 pmol m‘2 s'*, and 19, 34, 59 and 44 % under irradiance of 320 pmol m-2 s'* in the FSA, FSE, HSA and HSE treatments, respectively. Increasing the measurement irradiance from 160 to 320 pmol m'2 s'* enhanced P^ by 69, 78, 23 and 49 % in an atmosphere of 300 g m-^ CO2, and by 73, 84, 49 and 47 % in an atmosphere of 1500 g m-^ CO2, in the FSA, FSE, HSA and HSE treatments, respectively. DMP was strongly influenced by the different environmental conditions and the total dry matter accumulation in the shoot per plant during 145 d reached 580, 347, 398 and 235 g in the FSA, FSE, HSA and HSE treatments, respectively. CO2 emichment promoted early yield under both full and partial sunlight irradiance. The HSE treatment led to earlier yield harvesting than the FSA and HSA treatments. The yield of the seven first trusses reached 6.8, 4.6, 5.7 and 3.2 kg per plant in the FSA, FSE, HSA and HSE treatments, respectively. Some increase in fruit fresh matter and diameter of fruits was detected in the C02-enrichéd treatments as compared to the non-enriched ones. Thus the combination of moderate shading and CO2 enrichment might provide a more productive option for winter- grown tomatoes in regions of subtropical climate, even in the winter, than the conventional management of aerated greenhouses without CO2 enrichment which are exposed to fiill sunlight.
Crop plants in Closed Ecological Life Support Systems (CELSS), for future extended manned space missions, might use for photosynthesis natural sunlight rather than an artificial irradiation. In a low earth orbit (LEO: 300-600 km) space station CELSS, these plants would have to deal with very short light/dark cycles. As a result of the 90 min revolution period of the station around the earth, they would be subjected to approximately 60 min sunlight followed by 30 min darkness in the earth's shade. These orbital light/dark cycles were simulated in growth chambers, which was accompanied by control experiments under long-day conditions (16/8 h light/dark). In Phaseolus mungo L., Glycine max L. and Sorghum bicolor L. the net C02-uptake (PN) and stomatal conductance (gs), as well as 02-production and quantum yield (QY) were measured. P. mungo grown under orbital cycles was strongly affected by slow induction of photosynthesis and stomatal limitation, resulting in the photodestruction of pigment systems and leaf chlorosis. Stomata of G. max opened faster upon onset of irradiation, which resulted in a sufficient C02-supply to prevent photoinhibition. Stomata of S. bicolor opened very rapidly, and Pn resumed steady-state similar to that before the dark break, within the first minutes of the irradiation, thus utilizing the major part of the 60 min "day" for net carbon gain. These findings were supported by QY measurements of oxygen evolution. Strongly decreased QY in P. mungo compared to long-day grown plants indicated destruction in light-harvesting pigments and electron transport chains. No reduction in QY was observed in G. max and S. bicolor.
a1_We investigated the influence of salinity (0, 25, 50, or 75 mM NaCl) on gas exchange and physiological characteristics of nine citrus rootstocks (Cleopatra mandarin, Carrizo citrange, Macrophylla, Iranian mandarin Bakraii, Rangpur lime, Rough lemon, Sour orange, Swingle citrumelo, and Trifoliate orange) in a greenhouse experiment. Total plant dry mass, total chlorophyll (Chl) content, and gas-exchange variables, such as net photosynthetic rate (PN), stomatal conductance (g s), intercellular CO2 concentration, were negatively affected by salinity. In addition, ion concentrations of Cl- and Na+ increased by salinity treatments. Salinity also increased Mg2+ content in roots and reduced Ca2+ and Mg2+ concentrations in leaves. The K+ concentration in leaves was enhanced at low salinity (25 mM NaCl), whereas it decreased with increasing salinity stress. Salinity caused a decline in K+ contents in roots., a2_The rootstocks showed major differences in the extent of Cl- and Na+ accumulation in leaves and in their ability to maintain the internal concentrations of essential nutrients in response to different salinity. Therefore, in addition to inhibitory effects of high concentrations of Cl- and Na+, an imbalance of essential nutrients may also contribute to the reduction in gas exchange under saline conditions. Higher tolerance of rootstocks to salinity could be associated with the reduction of Cl- and Na+ uptake and transport to leaves, ability to keep higher Chl, gs, PN, and better maintenance of nutrient uptake even under high salinity. We found that Sour orange and Cleopatra mandarin were the rootstocks most tolerant to salinity of all nine studied. In addition, Trifoliate orange, Carrizo citrange, and Swingle citrumelo were the rootstocks most sensitive to salt stress followed by the Rough lemon and Macrophylla that showed a low-to-moderate tolerance, and Rangpur lime and Bakraii, with a moderate-to-high tolerance to high salinity., D. Khoshbakht, A.A. Ramin, B. Baninasab., and Obsahuje bibliografii
This study investigated the effect of solar ultraviolet radiation (UVR) and temperature on a chain length and photosynthetic performance of diatom Chaetorceros curvisetus. The cells were cultured in large quartz tubes and exposed to PAR, PAR + UV-A (PA), or PAR + UV-A + UV-B (PAB) radiation at 20°C and 28°C for six days, respectively. After recovery for 1 h, the cells were exposed again to three different radiations for 1 h. Then, a change in the photochemical efficiency (FPSII) was examined and UVR-induced photoinhibition was calculated. The percentage of long chains (more than five single cells per chain) in C. curvisetus significantly increased from 8.2% (PAR) to 38.9% (PAB) at 20°C; while it was not notably affected at 28°C. Mycosporine-like amino acids (MAAs) concentration obviously increased by irradiance increment from PAR to PAB at 20°C. Chlorophyll (Chl) a concentration significantly declined with increasing irradiance at 20°C. Both MAAs and Chl a concentrations were not obviously changed by irradiance at 28°C. Before and after reexposure, FPSII was significantly reduced both at 20°C and 28°C. UVR-induced photoinhibition at 20°C (39%) was higher than that at 28°C (30.9%). Solar UV radiation, especially UV-B, could significantly influence the percentage of long chains of C. curvisetus, especially at low temperature. UVR-induced photoinhibition can be alleviated by higher temperatures., W. Guan, X. Peng, S. Lu., and Obsahuje seznam literatury
The chlorophyll (Chl) and protein degradation during dark incubation of leaf discs was reduced by Sr2+, Ca^^, and spermine (Spm) treatments. Sr2+ inhibited most effectively the Chl degradation, which was remarkable 48 h after the treatment. The Chl degradation appeared in control discs within 24 h in the dark and Chl content decreased by about 50 % during 96 h. The proteins retained at least during 48 h of dark treatment in the presence of Sr2+, Ca2+, or Spm. The retardation effect of Sr2+, Ca2+ and Spm on the Chl loss and the disintegration of thylakoid membrane proteins may be due to a cationic protection of thylakoid membranes.
Effects of electromagnetic fields (EMFs) on human cell lines were described in numerous studies, but still many questions remain unanswered. Our experiment was designed with the aim of studying the effects of EMFs on the metabolic activity of chondrocytes in vitro. Human chondrocyte in vitro cultures, cultured in medium supplemented with 20 % fetal calf serum, were exposed to static magnetic field (SMF) (intensity of 0.6 T) and pulsed electromagnetic fields (PEMF) (21.2 MHz period of 15 ms, burst duration of 2 ms, amplification 3 dBm (0.1 V) and maximum output of 250 W) continually for 72 h. After the exposure, viability was determined using the MTT test and compared with a nonexposed control culture. As compared to the control sample the exposure to SMF resulted in a statistically significant increase (p<0.001) in viability. However, the increase of viability after PEMF exposure was not significant. This could be due to the frequency dependent effect on human cells. The experiments demonstrated that magnetic fields, using the above parameters, have a positive effect on the viability of human chondrocytes cultured in vitro., Š. Štolfa, M. Škorvánek, P. Štolfa, J. Rosocha, G. Vaško, J. Sabo., and Obsahuje bibliografii
We investigated the effects of supplementary KNO3 and NaCl on one-year-old, potted Valencia orange (Citrus sinensis) scions grafted on Iranian mandarin Bakraii [Citrus reticulate × Citrus limetta] (Valencia/Bakraii) and Carrizo citrange [C. sinensis × Poncirus trifoliata] (Valencia/Carrizo) rootstocks. After watering plants for 60 days with 50 mM NaCl, the lowest reduction in dry mass, stomatal conductance, and chlorophyll (Chl) content was found in Valencia/Bakraii. Bakraii accumulated more Cl- and Na+ in roots and transferred less to Valencia leaves compared with Carrizo rootstock. Moreover, higher net photosynthetic rate was found in Valencia/Bakraii than those on Carrizo rootstock. NaCl caused a decrease in the maximal efficiency of PSII photochemistry (Fv/Fm) and effective quantum yield (ΦPSII) but elevated coefficient of nonphotochemical quenching. Salinity reduced Ca2+, Mg2+, and total N contents, and increased Na+/K+ ratio in leaves and roots of both grafting combinations. Salinity increased K+ and proline content in leaves and decreased K+ concentrations in roots of both grafting combinations. In salinized plants, nitrate supplementation (10 mM KNO3) reduced leaf abscission, Cl-, Na+, Na+/K+, and Ca2+ concentrations in leaves and roots of both combinations. K+ and N concentrations and proline increased in leaves of the nitrate-supplemented salinized plants. Supplementary nitrate increased leaf number and area, stem elongation, Chl content, Fv/Fm, and ΦPSII and stimulated photosynthetic activity. Thus, nitrate ameliorated the deleterious effects of NaCl stress and stimulated the plant metabolism and growth. It can be used as a vital treatment under such condition., D. Khoshbakht, A. Ghorbani, B. Baninasab, L. A. Naseri, M. Mirzaei., and Obsahuje bibliografii
Energy-dependent quenching of chlorophyll fluorescence and its reversion in intact isolated spinách chloroplasts were recorded at temperatures between 0 and 20 ®C. A temperature-dependence of Ihe quenching formation (and of quenching relaxation) corresponding to Qio values between 2 and 3 was found. Long-term cold acclimation of the plants resulted in a decrease of die fluorescence dechne half-time. The finál steady-state extent of quenching (q^) was not influenced by temperature shifts or cold acclimation.
Application of the electrostatic precipitator (ESP) dust to soil and leaves of Cajanus cajan, Vigna mungo, Vigna radiata, Vigna catjung and Glycina max increased biomass, chloroplast pigments, Chemical constituents and enzyme activities of leaves, besides crop productivity evidently indicating that the dust acted as a fertilizer. The net photosynthetic rate, photosystem 2 activity and rate of transpiration were not altered in špite of the dust forming a thin uniform coating ověř the leaf surface. The contents of intermediary N-compounds like allantoin, allantoic acid and total ureides of the leaves, which might serve as an indirect evidence of symbiotic N2-fixation, were higher in the treated plants. There were increments in free proline, soluble proteins, total nitrogen, nitrates, nitrites, soluble sugars and phenols in the treated plants. The concentrations of ffee amino acids, soluble starch, total sucrose and water soluble SH compounds of the leaves of the control and treated plants did not show any significant difference. The activity of superoxide dismutase was significantly higher which possibly indicated its role in alleviation of H2O2 and Oj toxicity. Enzymes like nitráte reductase, nitrite reductase, glutamine S3mthetase, acid and alkaline phosphatases, carbonic anhydrase, catalase, glutathione reductase and ascorbate peroxidase also functioned normally. In the treated plants, the concentration of ascorbic acid was significantly higher in the roots and nodules indicating the possible role of ascorbic acid in stress alleviation.