P. P. A. Oliveira

Fertilização com N e S na recuperação de pastagem de Brachiaria brizantha cv. Marandu em neossolo quartzarênico

An experiment was carried out during two years on Cerrado soil with the objective of evaluating the response of degraded Brachiaria brizantha cv. Marandu pastures to different N and S fertilization doses. Seven treatments, six with different N and S combinations and a control (degraded pasture), were compared in a randomized complete blocks design. The combinations were: 70 kg ha-1 N without sulphur, 140 kg ha-1 N without sulphur, 210 kg ha-1 N without sulphur, 70 kg ha-1 N and 77 kg ha-1 S, 140 kg ha-1 N and 153 kg ha-1 S, 210 kg ha-1 N and 230 kg ha-1 S. Herbage yield response to nitrogen rates was linear, and the best efficiency of nitrogen use was obtained in the second year. The highest herbage yield was associated with higher extraction of N and smaller soil organic matter content. The sulfur extraction was lower than S doses. The N:S ratio as a criterion of the forage mineral nutrition was effective only in the rainy season. There was sulphur accumulation in deeper layers of soil.

CYCLOOXYGENASE INHIBITION REDUCES BLOOD PRESSURE ELEVATION AND VASCULAR REACTIVITY DYSFUNCTION CAUSED BY INHIBITION OF NITRIC OXIDE SYNTHASE IN RATS

In the present study we investigated the role of cyclooxygenase (COX)-dependent vasoconstrictors in the hypertension and altered vascular reactivity following prolonged nitric oxide (NO) synthase inhibition. Male Wistar rats (250–270g) were divided into four groups and treated for 7 days with Placebo (control), L-NAME (48 mg/kg/day), indomethacin (4 mg/kg/day) and L-NAME in combination with indomethacin. L-NAME treatment induced arterial hypertension, in vitro aortic hyperresponsiveness to phenylephrine, impaired vasodilatory response to acetylcholine and no significant change in response to sodium nitroprusside. Indomethacin co-treatment partially prevented blood pressure elevation, restored responsiveness to phenylephrine and improved sensitivity to acetylcholine. Indomethacin treatment alone did not modify blood pressure and aortic vascular reactivity. Both enhanced phenylphrine-induced contraction and impaired acetylcholine-evoked vasodilation induced by acute NO synthase inhibition with L-NAME (10−4M) in normal rat aortas were not modified by indomethacin (10−5M). These results are consistent with the hypothesis that constricting factors, which arise from the COX pathway, contribute to hypertension and altered vascular reactivity following continued inhibition of NO synthase.

Molecular basis for the improvement in muscle metaboreflex and mechanoreflex control in exercise-trained humans with chronic heart failure

Previous studies have demonstrated that muscle mechanoreflex and metaboreflex controls are altered in heart failure (HF), which seems to be due to changes in cyclooxygenase (COX) pathway and changes in receptors on afferent neurons, including transient receptor potential vanilloid type-1 (TRPV1) and cannabinoid receptor type-1 (CB1). The purpose of the present study was to test the hypotheses: 1) exercise training (ET) alters the muscle metaboreflex and mechanoreflex control of muscle sympathetic nerve activity (MSNA) in HF patients. 2) The alteration in metaboreflex control is accompanied by increased expression of TRPV1 and CB1 receptors in skeletal muscle. 3) The alteration in mechanoreflex control is accompanied by COX-2 pathway in skeletal muscle. Thirty-four consecutive HF patients with ejection fractions <40% were randomized to untrained (n = 17; 54 ± 2 yr) or exercise-trained (n = 17; 56 ± 2 yr) groups. MSNA was recorded by microneurography. Mechanoreceptors were activated by passive exercise and metaboreceptors by postexercise circulatory arrest (PECA). COX-2 pathway, TRPV1, and CB1 receptors were measured in muscle biopsies. Following ET, resting MSNA was decreased compared with untrained group. During PECA (metaboreflex), MSNA responses were increased, which was accompanied by the expression of TRPV1 and CB1 receptors. During passive exercise (mechanoreflex), MSNA responses were decreased, which was accompanied by decreased expression of COX-2, prostaglandin-E2 receptor-4, and thromboxane-A2 receptor and by decreased in muscle inflammation, as indicated by increased miRNA-146 levels and the stable NF-κB/IκB-α ratio. In conclusion, ET alters muscle metaboreflex and mechanoreflex control of MSNA in HF patients. This alteration with ET is accompanied by alteration in TRPV1 and CB1 expression and COX-2 pathway and inflammation in skeletal muscle.

Liming and fertilization to restore degraded Brachiaria decumbens pastures grown on an entisol

The reconstitution of soil fertility is essential in the process of pasture restoring, liming being the first action to be taken in this direction. The liming recommendation for pastures needs more technical information as the application method and rate. A field experiment was carried out to evaluate the liming and fertilization practices to restore a degraded Brachiaria decumbens pasture. The following factors were studied: liming method (incorporated in soil by disking or not); level of base saturation (40, 50 or 80%) and lime type (55, 70 or 90 of ECC). Liming and fertilization (NPK and micronutrients) increased both the forage yield and its root system, these being more evident in the second year, even using the same rates of lime and fertilizer used during the first year. After two years the levels of base saturation aimed for the 0 to 0.20 m soil layer were not achieved, neither was the neutralization of the Al. The disking impaired the development of the root system of B. decumbens and promoted the decrease of soil organic matter. The lime with the lowest ECC increased root growth and led to higher concentrations of Ca and Mg in the soil. Studies in other conditions are necessary to define liming requirements in established and degraded pastures.

Eficiência da fertilização nitrogenada com uréia (15N) em Brachiaria brizantha cv. Marandu associada ao parcelamento de superfosfato simples e cloreto de potássio

Em pastagens, a avaliacao da eficiencia do processo de fertilizacao com N-ureia e importante em virtude das altas doses utilizadas. Varios trabalhos relatam que a aplicacao de ureia associada com cloreto de potassio (KCl) e superfosfato simples (SFS) pode melhorar a sua eficiencia. Na recuperacao de pastagens degradadas ou em sistemas de exploracao intensiva, as quantidades de KCl e SFS empregadas como fertilizacao corretiva sao altas e aplicadas em novembro, no inicio da estacao das aguas. O parcelamento do KCl e SFS associado as coberturas nitrogenadas com ureia seria de facil adocao sem custos adicionais. Com o objetivo de avaliar este manejo, foi desenvolvido um experimento em que se realizou o balanco anual da aplicacao de 15N da ureia quando o SFS e, ou, o KCl foram parcelados, associados a aplicacao da ureia em cinco coberturas, ou quando ambos foram aplicados de uma so vez, no mes de novembro. A maior producao de forragem ocorreu quando o SFS foi parcelado, seguido pelo parcelamento do KCl, da aplicacao unica de ambos e, finalmente, do parcelamento dos dois. A recuperacao do N-ureia na parte aerea e no sistema solo-pastagem nao diferiu com os tratamentos. Entretanto, a recuperacao na coroa da planta e no sistema radicular diferiu entre os tratamentos e mostrou-se positivamente correlacionada com a producao de forragem. A recuperacao de fertilizante na liteira foi favorecida pelo parcelamento do KCl. Apesar de nao ter sido verificado aumento na recuperacao total do sistema entre os tratamentos, o parcelamento do KCl e do SFS tem sido indicado por melhorar a recuperacao do N-ureia em varias estruturas da planta, refletindo em maior producao da forrageira.

Balanço do nitrogênio (15N) da uréia nos componentes de uma pastagem de capim-marandu sob recuperação em diferentes épocas de calagem

In order to evaluate the use of urea nitrogen, the balance of nitrogen (15N) in Brachiaria brizantha pastures was obtained when urea was applied either incorporated or in the soil surface (in four applications beginning in November of 1998) and the lime was applied in two periods (March and August of 1998). The recovery and retention of the N-urea were obtained for each plant structure of the soil-pasture system, and indicated that the plant crown is a very important storage organ for the N applied via Urea. Liming in March favored forage mass production and improved the efficiency of N use when urea was incorporated. The incorporation of urea improved both, the recovery and retention of nitrogen in most Brachiaria structures. Difference in N recovery between the best (lime application in March with urea incorporated) and the worst treatment (liming in March with urea-N on the soil-surface) was around 50 kg N.ha-1 after one year.

Modelos empíricos para estimar o acúmulo de matéria seca de capim‑marandu com variáveis agrometeorológicas

The objective of this work was to test empirical linear regression models, to predict dry matter accumulation rates (DMAR) of Urochloa brizantha cv. Marandu, using agrometeorological variables. To generate the models, the average dry matter accumulation under rainfed conditions, between 1998 and 2002, was used. The evaluated variables were: minimum, maximum and average temperatures, global radiation (GR), degree-days, actual (AET) and potential evapotranspiration (PET) obtained from the water balance, photothermal units (PU) and the climatic growth index (CGI). Except for the PU, the univariate and multivariate regressions showed good predictive ability. The best results were for the multivariate regression, with Tmin, GR and AET: R 2 , 0.84; root mean square residual (RMSR), 14.72; and Akaikes information criterium (AIC), 222.5. In the univariate regression, the following variables stood out: corrected degree-days (R 2 , 0.75; RMSR, 17.84; CIA, 242.6), corrected minimum temperature (R 2 , 0.75; RMSR, 17.82; AIC, 244.1); and CGI (R 2 , 0.74; RMSR, 17.85; AIC, 236.9). The correction of the agrometeorological variables using the relation between real and potential evapotranspiration (AET/PET) enhances, in general, the model prediction of DMAR.

New methods to quantify NH3 volatilization from fertilized surface soil with urea

Gaseous N losses from soil are considerable, resulting mostly from ammonia volatilization linked to agricultural activities such as pasture fertilization. The use of simple and accessible measurement methods of such losses is fundamental in the evaluation of the N cycle in agricultural systems. The purpose of this study was to evaluate quantification methods of NH3 volatilization from fertilized surface soil with urea, with minimal influence on the volatilization processes. The greenhouse experiment was arranged in a completely randomized design with 13 treatments and five replications, with the following treatments: (1) Polyurethane foam (density 20 kg m-3) with phosphoric acid solution absorber (foam absorber), installed 1, 5, 10 and 20 cm above the soil surface; (2) Paper filter with sulfuric acid solution absorber (paper absorber, 1, 5, 10 and 20 cm above the soil surface); (3) Sulfuric acid solution absorber (1, 5 and 10 cm above the soil surface); (4) Semi-open static collector; (5) 15N balance (control). The foam absorber placed 1 cm above the soil surface estimated the real daily rate of loss and accumulated loss of NH3N and proved efficient in capturing NH3 volatized from urea-treated soil. The estimates based on acid absorbers 1, 5 and 10 cm above the soil surface and paper absorbers 1 and 5 cm above the soil surface were only realistic for accumulated N-NH3 losses. Foam absorbers can be indicated to quantify accumulated and daily rates of NH3 volatilization losses similarly to an open static chamber, making calibration equations or correction factors unnecessary.

Efeito residual de fertilizantes fosfatados solúveis na recuperação de pastagem de Brachiaria brizantha cv. Marandu em Neossolo Quartzarênico

Dois experimentos foram realizados, por um periodo de dois anos, para avaliar a resposta de um sistema solo-pastagem a fertilizantes fosfatados de diferentes velocidades de solubilizacao (superfosfato simples, superfosfato triplo e termofosfato magnesiano) associados ou nao a calagem. Nao houve diferenca em producao de forragem entre as varias fontes de fosforo, quando as adubacoes fosfatadas foram feitas nos dois anos. A associacao de fertilizantes pode ser vantajosa, porque o termofosfato promoveu as maiores producoes de forragem quando se suprimiu a adubacao fosfatada no segundo ano, enquanto as adubacoes com superfosfatos resultaram nas maiores producoes no primeiro ano. A calagem favoreceu a producao de forragem e proporcionou aumento nos teores de nutrientes e reducao do aluminio no solo. A resposta a adubacao foi melhor no segundo ano, porque a pastagem estava em recuperacao.

Impaired Pulmonary Function is an Additional Potential Mechanism for the Reduction of Functional Capacity in Clinically Stable Fontan Patients

Central factors negatively affect the functional capacity of Fontan patients (FP), but “non-cardiac” factors, such as pulmonary function, may contribute to their exercise intolerance. We studied the pulmonary function in asymptomatic FP and its correlations with their functional capacity. Pulmonary function and cardiopulmonary exercise tests were performed in a prospective study of 27 FP and 27 healthy controls (HC). Cardiovascular magnetic resonance was used to evaluate the Fontan circulation. The mean age at tests, the mean age at surgery, and the median follow-up time of FP were 20(±6), 8(±3), and 11(8–17) years, respectively. Dominant ventricle ejection fraction was within normal range. The mean of peak VO2 expressed in absolute values (L/min), the relative values to body weight (mL/kg/min), and their predicted values were lower in FP compared with HC: 1.69 (±0.56) vs 2.81 (±0.77) L/min; 29.9 (±6.1) vs 41.5 (±9.3) mL/kg/min p < 0.001 and predicted VO2 Peak [71% (±14) vs 100% (±20) p < 0.001]. The absolute and predicted values of the forced vital capacity (FVC), forced expiratory volume in one second (FEV1), inspiratory capacity (IC), total lung capacity (TLC), diffusion capacity of carbon monoxide of the lung (DLCO), maximum inspiratory pressure (MIP), and sniff nasal inspiratory pressure (SNIP) were also significantly lower in the Fontan population compared to HC. An increased risk of restrictive ventilatory pattern was found in patients with postural deviations (OD:10.0, IC:1.02–97.5, p = 0.042). There was a strong correlation between pulmonary function and absolute peak VO2 [FVC (r = 0.86, p < 0.001); FEV1 (r = 0.83, p < 0.001); IC (r = 0.84, p < 0.001); TLC (r = 0.79, p < 0.001); and DLCO (r = 0.72, p < 0.001). The strength of the inspiratory muscles in absolute and predicted values was also reduced in FP [−79(±28) vs −109(±44) cmH2O (p = 0.004) and 67(±26) vs 89(±36) % (p = 0.016)]. Thus, we concluded that the pulmonary function was impaired in clinically stable Fontan patients and the static and dynamic lung volumes were significantly reduced compared with HC. We also demonstrated a strong correlation between absolute Peak VO2 with the FVC, FEV1, TLC, and DLCO measured by complete pulmonary test.