We compared the effects of adaptation to intermittent high altitude (IHA) hypoxia of various degree and duration on ischemia-induced ventricular arrhythmias in rats. The animals were exposed to either relatively moderate hypoxia of 5000 m (4 or 8 h/day, 2-3 or 5-6 weeks) or severe hypoxia of 7000 m (8 h/day, 5-6 weeks). Ventricular arrhythmias induced by coronary artery occlusion were assessed in isolated buffer-perfused hearts or open-chest animals. In the isolated hearts, both antiarrhythmic and proarrhythmic effects were demonstrated depending on the degree and duration of hypoxic exposure. Whereas the adaptation to 5000 m for 4 h/day decreased the total number of premature ventricular complexes (PVCs), extending the daily exposure to 8 h and/or increasing the altitude to 7000 m led to opposite effects. On the contrary, the open-chest rats adapted to IHA hypoxia exhibited an increased tolerance to arrhythmias that was even more pronounced at the higher altitude. The distribution of PVCs over the ischemic period was not altered by any protocol of adaptation. It may be concluded that adaptation to IHA hypoxia is associated with enhanced tolerance of the rat heart to ischemic arrhythmias unless its severity exceeds a certain upper limit. The opposite effects of moderate and severe hypoxia on the isolated hearts cannot be explained by differences in the occluded zone size, heart rate or degree of myocardial fibrosis. The proarrhythmic effect of severe hypoxia may be related to a moderate left ventricular hypertrophy (27 %), which was present in rats adapted to 7000 m but not in those adapted to 5000 m. This adverse effect can be overcome by an unknown protective mechanism(s) that is absent in the isolated hearts., G. Asemu, J. Neckář, O. Szárszoi, F. Papoušek, B. Ošťádal, F. Kolář., and Obsahuje bibliografii
Photosynthetic electron flux allocation, stomatal conductance, and the activities of key enzymes involved in photosynthesis were investigated in Rumex K-1 leaves to better understand the role of nitric oxide (NO) in photoprotection under osmotic stress caused by polyethylene glycol. Gas exchange and chlorophyll fluorescence were measured simultaneously with a portable photosynthesis system integrated with a pulse modulated fluorometer to calculate allocation of photosynthetic electron fluxes. Osmotic stress decreased stomatal conductance, photosynthetic carbon assimilation, and nitrate assimilation, increased Mehler reaction, and resulted in photoinhibition. Addition of external NO enhanced the stomatal conductance, photosynthetic rate, activities of glutamine synthetase and nitrate reductase, and reduced Mehler reaction and photoinhibition. These results demonstrated that osmotic stress reduced CO2 assimilation, decreasing the use of excited energy via CO2 assimilation which caused significant photoinhibition. Improving stomatal conductance by the addition of external NO enhanced the use of excited energy via CO2 assimilation. As a result, less excited energy was allocated to Mehler reaction, which reduced production of reactive oxygen species via this pathway. We suppose that Mehler reaction is not promoted unless photosynthesis and nitrogen metabolism are prominently inhibited. and H. D. Li ... [et al.].
Benzodiazepines seem to be frequently abused in conjunction with opioids. Fluoxetine was reported to block morphine locomotor sensitization in rats. Sensitization has been implicated in some aspects of drug abuse. We have investigated the effect of alprazolam (0.25 mg/kg) and fluoxetine (5 mg/kg) on the development and expression of sensitization to the locomotor stimulant effect of morphine (10 mg/kg) in mice. Sensitization was produced by daily injections of morphine (10 mg/kg) for 10 days. There was a clear sensitization of locomotor activity produced by morphine in photocell activity cages but co-administration of alprazolam with morphine had no effect on the degree of sensitization. Alprazolam was also without effect on the expression of the sensitized response to morphine in mice sensitized with morphine alone. Fluoxetine partly reduced both the development and expression of morphine sensitization. In conclusion, the present experiments have not yielded evidence that alprazolam may influence the development or the expression of sensitization to morphine. However, they have corroborated and extended results indicating that fluoxetine can attenuate, to a certain level, the development and expression of morphine sensitization., M. Votava, M. Kršiak, V. Moravec., and Obsahuje bibliografii
Maize plant inbred lines, one Al-sensitive (B-73) and two Al-tolerant (F-2 and L-2039), were grown hydroponically in the presence of 200 µM Al. After 13 d of growth, root and shoot lengths, photosystem 2 (PS2) activity, chlorophyll (Chl) content, 5-aminolevulinic acid (5-ALA) synthesis rate, chlorophyllase (Chlase) activity, and N, Mg, Fe, and Mn contents in leaves were determined. PS2 activity and Chl content were most severely affected by Al in B-73, but F-2 was almost unaffected. This was in accordance with Al-accumulation in the plants. The observed changes in B-73 coincided with 5-ALA synthesis inhibition, Chlase activation, and leaf deprivation of Fe and Mg. In Al-treated L-2039 plants, the leaf Mg and Mn contents were decreased. Also, an excessive Chlase activation was found in Al-treated L-2039, without a substantial Chl loss. This may indicate the activation of different enzyme pools in tolerant and sensitive genotypes under low-stress conditions. and N. Mihailovic, G. Drazic, Z. Vucinic.
The current concentrations of O3 have been shown to cause significant negative effects on crop yield. The present levels of ozone may not induce visible symptoms in most of plants, but can result in substantial losses in reproductive output. This paper considers the impact of ambient O3 on gas exchange, photosynthetic pigments, chlorophyll (Chl) fluorescence and carbohydrate levels in the flag leaf of wheat plants during various stages of reproductive development using open-top chambers. Mean O3 concentration was 45.7 ppb during wheat growth and 50.2 ppb after flag leaf development. Reproductive stage showed higher exceedence of O3 above 40 ppb compared to the vegetative stage. Diurnal variations in net photosynthetic rate (PN) and stomatal conductance (gs), intercellular CO2 concentration (Ci), Fv/Fm ratio, photosynthetic pigments, soluble sugars, and starch were measured at 10, 30, and 50 days after flag leaf expansion (DAFE). The results showed reductions in PN, gs, Fv/Fm ratio, photosynthetic pigments and starch, and increases in Ci, F0, and soluble sugars in nonfiltered chambers (NFCs) compared to filtered chambers (FCs). Maximum changes in measured parameters were observed at 50 DAFE (i.e. grain filling and setting phase). Diurnal variation in PN showed double peaked curve in both FCs and NFCs, but delayed peak and early depression in NFCs. Stomatal conductance was significantly lower in NFCs. The study suggests that higher prevalence of ambient O3 during reproductive development led to significant alteration in physiological vitality of wheat having potential negative influence on yield. and R. Rai, M. Agrawal, S. B. Agrawal.
Effects of selective reagents of amino groups (fluorescamine, Fc) and thiol [5,5'-dithio-bis(2-nitrobenzoic) acid, DTNB] groups on the diaphorase activity of spinach ferredoxin:NADP+ oxidoreductase (FNR, E.C 1.18.1.2) in the presence of dibromothymoquinone (DBMIB) as an electron acceptor were studied. The incubation of FNR with 250 μM Fc in the time range from 0 to 120 min led to the gradual decrease of FNR activity according to biphasic kinetics. At the initial phase the activity (defined as the rate of NADPH oxidation) decreased about 4-time faster than at the subsequent second slower phase. Incubation of FNR simultaneously with Fc and DBMIB for more than 20 min caused restoration of the activity to about 80 % of the control. The inhibitory effect of Fc on the FNR-catalysed DBMIB reduction had non-competitive character. Incubation of FNR with DTNB led also to a gradual decrease of the enzyme activity, which reached about 45 % of the control after 2 h of incubation. Thus neither amino nor thiol groups in the FNR molecule are involved directly in the DBMIB reduction. However, the presence of DBMIB in the incubation medium influenced the inhibitory pattern of Fc and DTNB, and this suggests that DBMIB modified the conformational state of the FNR molecule. and J. Grzyb, M. Bojko, S. Więckowski.
Ultraviolet-radiation exerts a well-known role in the development of various ocular diseases and may contribute to the progress of age-related macular degeneration. Therefore, the use of compounds able to protect the eyes from UV-induced cellular damage is challenging. The aim of this study has been to test the protective effects of an antioxidant topical formulation against UV-induced damage in rabbit eyes. Twelve male rabbits were used. Animals were divided into 4 groups of 3 animals each. Control group (CG) did not receive any irradiation and/or eye drop. The other three experimental groups were treated as follows: the first group received only UVR irradiation for 30 min, without eye drop supplementation (Irradiation group, IG), the second (G30) and the third (G60) groups received UV irradiation for 30’ and 60’, respectively, and eye drop supplementation (riboflavin, d-α-tocopheryl polyethylene glycol, proline, glycine, lysine and leucine solution) every 15 min for three hours. In the IG group a significant increase of oxidized glutathione (GSSG) and hydrogen peroxide (H2O2) was recorded in the aqueous humor, whereas ascorbic acid levels were significantly lower when compared to control eyes. In the groups exposed to UVR rays for 30 min, and treated with the topical antioxidant formulation, the GSSG, H2O2 and ascorbic acid levels were similar to those recorded in controls, whereas in the G60 group the three markers significantly differ from control group. In the lens, a significant decrease of alpha tocopherol and total antioxidant capacity (TAC) was recorded in IG-animals as compared to control group, whereas malondialdehyde (MDA) levels were significantly higher in UV-induced eye than in control eyes. In the G30 groups the alpha tocopherol, MDA and TAC levels do not significantly differ from those recorded in controls, whereas in the G60 group these three markers significantly differ from control group. Present findings demonstrate that topical treatment with the antioxidant formulation used herein protects ocular structures from oxidative stress induced by UV exposure in in vivo animal model, F. Vizzarri, M. Palazzo, S. Bartollino, D. Casamassima, B. Parolini, P. Troiano, C. Caruso, C. Costagliola., and Obsahuje bibliografii
Isolated and interactive effects of angular leaf spot (caused by Phaeoisariopsis griseola) and rust (caused by Uromyces appendiculatus) on leaf gas exchange and yield was studied in common bean (Phaseolus vulgaris L. cv. Carioca) plants. Gas exchange was measured on 37, 44, 51, and 58 d after planting using a portable photosynthesis system. The inoculation of plants with P. griseola (P), U. appendiculatus (U), and the combination of both pathogens (P+U) caused a significant reduction of net photosynthetic rate (PN) and yield. The reduction of stomatal conductance (gs), PN, and yield was higher under P and combination of P+U than under U treatment. By effect of U, the reduction on yield was higher than the reductions on gas exchange parameters. On the treatment P+U, a reduction of 23 % in PN and a correspondent reduction of 32 % in yield was observed. The interactive effects of the pathogens on yield could be explained in part by the decreases in gs and in PN of diseased bean leaves. The combined effect of both diseases on yield and gas exchange parameters suggests an antagonistic interaction. and W. C. Jesus Junior ... [et al.].
Arbuscular mycorrhizal fungi (AMF) form symbioses with many plants. Black locust (Robinia pseudoacacia L.) is an important energy tree species that can associate with AMF. We investigated the effects of AMF (Rhizophagus irregularis and Glomus versiforme) on the growth, gas exchange, chlorophyll (Chl) fluorescence, carbon content, and calorific value of black locust seedlings in the greenhouse. The total biomass of the arbuscular mycorrhizal (AM) seedlings was 4 times greater than that of the nonmycorrhizal (NM) seedlings. AMF greatly promoted the photosynthesis of black locust seedlings. AM seedlings had a significantly greater leaf area, higher carboxylation efficiency, Chl content, and net photosynthetic rate (PN) than NM seedlings. AMF also significantly increased the effective photochemical efficiency of PSII and significantly enhanced the carbon content and calorific value of black locust seedlings. Seedlings inoculated with G. versiforme had the largest leaf area and highest biomass, Chl content, PN, and calorific value., X. Q. Zhu, C. Y. Wang, H. Chen, M. Tang., and Obsahuje bibliografii
Atrial natriuretic peptide antifibrotic properties are mainly described in cardiac myocytes or in induced cardiac myofibroblasts (Angiotensin II or TGF-β induced differentiation). In the present work, we investigate the effects of ANP/NPRA/cGMP system in modulating rat cardiac fibroblasts function. Cardiac fibroblasts were isolated from adult Wistar male rats and cultured in the presence of serum in order to induce fibroblasts differentiation. Cultures were then treated with ANP (1 μM), 8-Br-cGMP (100 μM) or IBMX (100 μM), a non-specific phosphodiesterases inhibitor. ANP significantly decreased proliferation rate and collagen secretion. Its effect was mimicked by t he c GMP a nalog, w hile c ombining A NP w ith 8 -Br-cGMP did not lead to additional effects. Moreover intracellular cGMP levels were elevated when cells were incubated with ANP confirming that ANP intracellular pathway is mediated by cGMP. Additionally, immunoblotting and immunofluorescence were used to confirm the presence of guanylyl cyclase specific natriuretic peptide receptors A and B. Finally we scanned specific cGMP dependent PDEs via RT-qPCR, and noticed that inhibiting all PDEs led to an important decrease in proliferation rate. Effect of ANP became more prominent after 10 culture days, confirming the importance of ANP in fibroblasts to myofibroblasts differentiation. Uncovering cellular aspects of ANP/NPRA/cGMP signaling system provided more elements to help understand cardiac fibrotic process., M. Moubarak, C. Magaud, Y. Saliba, A. Chatelier, P. Bois, J.-F. Faivre, N. Farès., and Obsahuje bibliografii