Thyroid State and Tolerance of Mammalian Myocardium to Hypoxia

Thyroid hormone is known to affect myocardial glycogen stores and thereby possibly limit anaerobic performance of mammalian cardiac muscle. Thyroid hormone administration (3,5,T-triiodo-L-thyroxine, 300 mu g/kg/day, sc) for 10 days decreased left ventricle (LV) glycogen concentration relative to euthyroid animals (2.78 +/- 0.46 vs. 4.28 +/- 0.29 mg/g of LV (mean +/- SEM)) while increasing the percent of V(1) myosin isozyi-ne, contractile activity and cardiac mass. In contrast, thyroidectomy increased myocardial glycogen stores (8.50 +/- 0.56 mg/g of LV) and shifted the myosin isozyme toward V(3), prolonged contractile activity and decreased LV mass. Thyroxine administration for 3, 7 and 10 days to thyroidectomized animals progressively decreased contractile duration and increased LV mass. Thyroxine administration for 3 or 7 days to thyroidectomized rats did not reduce glycogen stores (7.75 +/- 1.02 and 9.62 +/- 1.16 mg/g of LV, respectively), whereas myocardial glycogen declined to 3.30 +/- 0.58 mg/g of LV after 10 days of treatment. During hypoxia, cardiac muscle from thyroidectomized rats maintained greater active force and developed less contracture relative to euthyroid and, to a greater extent, than hyperthyroid rats. Removal of glucose from the bath decreased anaerobic performance and impaired recovery; however, myocardium from thyroidectomized rats remained more tolerant to hypoxia than the euthyroid group. Overall, the intrinsic LV glycogen content was positively correlated to anaerobic performance. These data demonstrate that the thyroid state profoundly affects myocardial growth, contractility and anaerobic performance of rat myocardium. Although energy demand may affect function during hypoxia, anaerobic substrate reserve (cardiac glycogen concentration) appears to be the primary factor determining tolerance to hypoxic stress. J. Exp. Zool. 311A:399-407, 2009. (C) 2009 Wiley-Liss, Inc.

Drought tolerance of two field-grown clones of Coffea canephora

We compared tolerance to soil drought of two field-grown clones of Coffea canephora (clone 46, drought-sensitive; and clone 120, drought-tolerant). Under irrigation, there were no marked differences between the clones in water relation parameters, gas exchange and total leaf area. Under rainfed conditions, clone 46 showed osmotic adjustment and increased tissue rigidity. These adjustments, however, were incapable of preventing substantial decreases in xylem pressure potential. By contrast, clone 120 did not exhibit osmotic adjustment, but was able to increase tissue elasticity and to maintain xylem pressure potentials to a greater extent than clone 46 (despite having twice the total leaf area of this clone). Stomatal conductance was lowered by drought in clone 120 but not in clone 46. Carbon assimilation per unit leaf area in both clones remained unaffected under stress. Long-term water use efficiency (WUE), as estimated through carbon isotope discrimination, was consistently greater in clone 120 than in clone 46. Because of these traits, clone 120 was better able to postpone dehydration and to maintain whole-tree photosynthesis. It is proposed that these features should decisively contribute to buffer its productivity in drought-prone areas. © 2002 Elsevier Science Ireland Ltd. All rights reserved.

Toxicity of hypercaloric diet and monosodium glutamate: oxidative stress and metabolic shifting in hepatic tissue.

The present study examines the effects of a hypercaloric diet on hepatic glucose metabolism of young rats, with and without monosodium glutamate (MSG) administration, and the association of these treatments with evaluating markers of oxidative stress. Male weaned Wistar rats (21 days old) from mothers fed with a hypercaloric diet or a normal diet, were divided into four groups (n=6): control (C) fed with control diet; (MSG) treated with MSG (4 mg/g) and control diet; (HD) fed with hypercaloric diet and (MSG-HD) treated with MSG and HD. Rats were sacrificed after the oral glucose tolerance test (OGTT), at 45 days of treatments. Serum was used for insulin determination. Glycogen, hexokinase(HK), glucose-6-phosphatase(G6PH), lipid hydroperoxide, superoxide dismutase(SOD) and glutathione peroxidase(GSH-Px) were determined in liver. HD rats showed hypoglycemia, hyperinsulinemia, and high hepatic glycogen, HK and decreased G6PH. MSG and MSG-HD had hyperinsulinemia, hyperglycemia, decreased HK and increased G6PH in hepatic tissue. These animals had impaired OGTT. HD, MSG and MSG-HD groups had increased lipid hydroperoxide and decreased SOD in hepatic tissue. Hypercaloric diet and monosodium glutamate administration induced alterations in metabolic rate of glucose utilization and decreased antioxidant defenses. Therefore, the hepatic glucose metabolic shifting induced by HD intake and MSG administration were associated with oxidative stress in hepatic tissue.

Peroxidase enzyme (EC.1.11.1.7) activity as an indicator of water stress in sweet pepper plants

The present work was carried out at the Faculdade de Ciências Agronômicas - UNESP, Botucatu, SP. The purpose of the study was to evaluate the physiological and biochemical behavior of sweet pepper (Capsicum annuum L.) plants under different soil water availability conditions and the efficiency of the peroxidase (EC. 1.11.1.7) activity as an indicator of water stress in plants. Sweet pepper plants were grown for 230 days after transplanting of seedlings. The experiment was arranged in a completely randomized experimental design with 4 treatments, two irrigation managements (50 and 1500 kPa) and two soil surface managements (presence or absence of black polyethylene covering), and six replications. Physiological activities, such as stomatal transpiration and resistance to water vapor diffusion, were evaluated, as well as biochemical activities, such as peroxidase activity and total soluble protein in foliar tissues. It was observed that soil water availability may lead to physiological and biochemical alterations in plants. Successive water stress cycles may promote the development of characteristics responsible for improving the plant tolerance to periods of low water availability. The peroxidase enzyme activity showed to be an efficient indicator of water stress in sweet pepper plants.

Peroxidase activity as an indicator of water stress in sweet pepper plants

The purpose of the study was to evaluate the physiological and biochemical behavior of sweet pepper (Capsicum annuum L.) plants under different soil water availability conditions and the efficiency of the peroxidase (EC. 1.11. 1.7) activity as an indicator of water stress in plants. The experiment was carried out at the Faculdade de Ciências Agronômicas UNESP, Botucatu, SP. Sweet pepper plants were grown for 230 days after transplanting of seedlings and arranged in a completely randomized experimental design with 4 treatments, two irrigation managements (50 and 1500 kPa) and two soil surface managements (presence or absence of black polyethylene covering), and six replications. Physiological activities, such as stomatal transpiration and resistance to water vapor diffusion, were evaluated as well as biochemical activities, such as peroxidase activity and total soluble protein in foliar tissues. It was observed that soil water availability may lead to physiological and biochemical alterations in plants. Successive water stress cycles may promote the development of characteristics responsible for improving plant tolerance to periods of low water availability. The peroxidase enzyme activity showed to be an efficient indicator of water stress in sweet pepper plants.

QTL identification for tolerance to fruit set in tomato by FAFLP markers

This study aimed to detect quantitative trait loci (QTL) by fALP (Fluorescent Amplified Fragment Length Polymorphism) markers associated to the trait tomato fruit set at high temperatures. A biparental cross between line Jab-95 (heat-tolerant) and cultivar Caribe (heat-susceptible) was made. A total of 192 plants of the F2 generation were evaluated, generating 172 polymorphic markers through six primer combinations previously identified by the Bulked Segregant Analysis technique. To construct the genetic map, 106 of the 172 markers that segregated in the expected Mendelian segregation proportion (3:1) were used. The map covered 1191.46 cM of the genome. Six trait-linked QTL were identified in the analysis of simple markers and three others by the interval-mapping methodology. These results could be highly useful in improvement programs, since heat-tolerant plants can be selected rapidly, which improves tomato fruit set.

Use of Physiological Parameters in Screening Drought Tolerance in Sugarcane Genotypes

The physiological response of four commercial sugarcane genotypes to water stress was evaluated by measuring the photochemical efficiency of the photosystem II (chlorophyll a fluorescence ratio, F v/F m), estimated chlorophyll content (SPAD unit), leaf temperature (LT) and leaf relative water content (RWC). A field trial was established in the subtropical area with well-watered and water-stressed genotypes, in completely randomized blocks with four replicates in a 4 × 2 × 3 factorial design (genotype × irrigation × evaluation date). Physiological measurements were done during a 90 day-period of formative stage of plants. The analysis of variance showed that the interaction of genotype × irrigation × evaluation date had a significant effect for three physiological markers tested, F v/F m, SPAD unit and RWC. Under non-stressed conditions, all genotypes showed similar responses for the four markers. Under water deficiency stress, two drought-tolerant genotypes, HOCP01-523 and TCP89-3505 displayed higher values for F v/F m, SPAD unit and RWC, and lower values for LT, and could be classified as tolerant. It is therefore possible to use these physiological water stress associated traits as scorable marker traits for selecting drought-tolerant sugarcane genotypes in future breeding programs. © 2011 Society for Sugar Research & Promotion.

Evaluation of ornamental grasses submitted to water stress

The work was carried out at the College of Agricultural and Veterinary Sciences of the State University of São Paulo (UNESP/FCAV), Campus of Jaboticabal, Brazil, aiming to study the tolerance response to water stress and capacity of regeneration after mowing three different ornamental grasses used in Brazilian landscaping: Imperial zoysia grass (Zoysia japonica 'Imperial'), zoysia grass (Zoysia japonica) and St. Augustine grass (Stenotaphrum secundatum). The experimental design was entirely randomized in a factorial scheme 33 (three grass species: Zoysia japonica 'Imperial', Zoysia japonica and Stenotaphrum secundatum; in three water stress conditions: under full sun, with and without irrigation, and under greenhouse conditions without irrigation) with four replications per plot. The irrigation was performed using microsprinklers with a flow of 0.28 L s-1, and the grasses of all plots were mowed monthly. The evaluations were executed monthly, before mowing the grass, in the beginning of each season, that means, in October (for Spring evaluation), January (for Summer), April (for Autumn) and July (for Winter), considering the Brazilian climate conditions. The evaluated parameters were shoot height and total dry mass. The data were submitted to the variance analysis and the means were compared by the Tukey test at 5% confidence level. The grasses grown under greenhouse conditions, without irrigation, showed higher height and lower dry mass weight averages, what possibly indicates that the plants etiolated. The grasses grown under full sun, either with or without irrigation, showed a similar plant development. The S. secundatum species showed greater tolerance to water stress in October, month that followed the longest dry period. The total dry mass was gradually reduced during the experiment for all grasses grown under greenhouse conditions without irrigation; however, a great general tolerance to water stress was observed for all grasses because all of them survived along nine months without irrigation.

Identificação de regiões relacionadas ao déficit hídrico em Eucalyptus por meio de marcadores moleculares

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Atividade da redutase do nitrato e acúmulo de prolina livre em raízes de cana-de-açúcar submetidas aos estresses hídrico e ácido no solo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identificação e análise da expressão de genes relacioanados com tolerância à seca em soja através de microarranjos de DNA e PCR em tempo real

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Expressão de genes no embrião e endosperma durante a germinação de sementes de lobeira (Solanum lycocarpum St. Hill)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chlorophyll a fluorescence in Annona emarginata (Schltdl.) H. Rainer plants subjected to water stress and after rehydration

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photomorphogenic modulation of water stress in tomato (Solanum lycopersicum L.): the role of phytochromes A, B1, and B2

Phytochromes are red/far-red light photoreceptors that mediate a variety of photomorphogenic processes in plants, from germination to flowering. In addition, there is evidence that phytochromes are also part of the stress signalling response, especially in response to water deficit stress, which is the major abiotic factor limiting plant growth and crop productivity worldwide. In this study, we used the phyA (far red-insensitive; fri), phyB1 (temporary red-insensitive; tri) and phyB2 mutants of tomato (Solanum lycopersicum L.) to study the roles of these three phytochromes in drought stress responses. Compared to wild type (WT) plants grown under water-deficit stress conditions, the fri, tri, and phyB2 mutants did not exhibit altered dry weights, leaf areas, stomatal densities, or stomatal opening. The stomatal conductance of all three mutants was severely reduced under both fully-hydrated and water-deficit conditions. Although relative water contents did change after drought stress in each mutant, the most significant reduction in water potential during water stress was observed in the fri mutant. However, this mutant returned its water status to WT levels during rehydration. Although the phyB2 mutant lost more water from detached leaves during abscisic acid (ABA) treatment, phyB2 behaved like WT plants, indicating that this mutant was not insensitive to ABA. Overall, these results indicate that the phytochromes phyA, phyB1, and phyB2 modulate drought stress responses in tomato.

Tropical soils with high aluminum concentrations cause oxidative stress in two tomato genotypes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)