Vascular endothelial growth factor and angiopoietin-2 play a major role in the pathogenesis of vascular leakage in cirrhotic rats.

Background and aims: The extent and molecular mechanisms governing plasma extravasation and formation of ascites in cirrhosis are unknown. Vascular endothelial growth factor-A (VEGF-A) and angiopoietin-2 (Ang-2) are endogenous substances with powerful vascular permeability effects. We assessed regional blood flow, vascular leakage, mRNA and tissular expression of VEGF-A and Ang-2 and vascular permeability following VEGF receptor 2 blockade in control and cirrhotic rats to define the vascular territories showing altered vascular permeability in cirrhosis and to determine whether VEGF-A and Ang-2 are involved in this phenomenon. Methods: Arterial blood flow was analysed with the coloured microsphere method. Vascular leakage was measured and visualised with the dye Evan¿s Blue and colloidal carbon techniques, respectively. VEGF-A and Ang-2 expression were determined by real-time polymerase chain reaction (RT-PCR), immunohistochemistry and western blot. The effect on vascular permeability induced by VEGFR2 blockade was assessed by administration of the receptor inhibitor SU11248. Results: Arterial blood flow was increased in the mesentery, pancreas and small intestine but not in the kidney and spleen of cirrhotic rats as compared to controls. Increased vascular leakage was observed in the mesentery and liver, where colloidal carbon spread from microvessels to the adjacent fibrotic tracts. Increased hepatic and mesenteric expression of VEGF-A and Ang-2 was found in cirrhotic rats as compared to controls. Blockade of VEGFR2 markedly reduced hepatic and mesenteric vascular leakage in cirrhotic rats. Conclusions: Enhanced endothelial permeability is restricted to the hepatic and mesenteric vascular beds in cirrhotic rats with ascites and VEGF-A and Ang-2 are key factors in the signalling pathways regulating this dysfunction.

Analysis of leakage properties and guiding conditions of rib antiresonant reflecting optical waveguides

Power leakage properties and guiding conditions of rib antiresonant reflecting optical waveguides (rib-ARROW) have been theoretically and experimentally studied as a function of wavelength and polarization of the light for different geometrical and optical parameters that characterize the rib-ARROW structure. Obtained results show that rib-ARROWs can only be fabricated with low losses in a wavelength range when determined rib configurations are adopted. Furthermore, these waveguides exhibit a polarization sensitivity that largely depends on the core-substrate refractive index difference. Together with the experimental results, theoretical calculations from different modeling methods are also presented and discussed.

Effectiveness of fused magnesium potassium phosphate for marandu grass

The current high price of KCl and great dependence on importation to satisfy the Brazilian demand indicate the need for studies that evaluate the efficiency of other K sources, particularly those based on domestic raw material. For this purpose, a greenhouse experiment was conducted with samples of a sandy clay loam Typic Haplustox, in a completely randomized 4 x 3 x 2 factorial design: four K rates (0, 60, 120, and 180 mg kg-1), three sources (potassium chloride (KCl), fused magnesium potassium phosphate (FMPP) and a mixture of 70 % FMPP + 30 % KCl) and two particle sizes (100 and 60 mesh), with three replications. Potassium fertilization resulted in significant increases in shoot dry matter production and in K concentrations, both in soil and plants. The K source and particle size had no significant effect on the evaluated characteristics. Potassium critical levels in the soil and the shoots were 1.53 mmol c dm-3 and 19.1 g kg-1, respectively.

Potassium availability in a hapludalf soil under long term fertilization

In a system in which fertilization is recommended, diagnosis of soil K availability and the establishment of critical levels are made difficult by the possibility of a contribution of non-exchangeable forms of K for plant nutrition. Due to its magnitude, this contribution is well diagnosed in long term experiments and in those which compare fertilization systems with positive and negative balances in terms of replacement of the K extracted by plants. The objective of this study was to evaluate K availability in a Hapludalf under fertilization for sixteen years with the addition of K doses. The study was undertaken in an experiment set up in 1991 and carried out until 2007 in the experimental area of the Soil Department of the Federal University of Santa Maria (Universidade Federal de Santa Maria - UFSM), in Santa Maria (RS), Brazil. The soil was a Typic Hapludalf submitted to four doses of K (0, 60, 120 and 180 kg ha-1 K2O) and subdivided in the second year, when 60 kg ha-1 of K2O were reapplied in the subplots in 0, 1, 2 and 3 times. As of the fifth year, the procedure was repeated. Grain yield above ground dry matter and total K content contained in the plant tissue were evaluated. Soil samples were collected, oven dried, ground, passed through a sieve and submitted to exchangeable K analysis by the Mehlich-1 extractor; non-exchangeable K by boiling HNO3 1 mol L-1 and total K by HF digestion. Potassium fertilization guidelines should foresee the establishment of a critical level as of which the recommended dose should accompany crop needs, which coincides with the quantity exported by the grain, without there being the need for the creation of broad ranges of K availability to predict K fertilization. In adopting the K fertilization recommendations proposed in this manner, there will not be K translocation in the soil profile.

Nitrate reductase activity and spad readings in leaf tissues of guinea grass submitted to nitrogen and potassium rates

Nitrogen and K deficiency are among the most yield limiting factors in Brazilian pastures. The lack of these nutrients can hamper the chlorophyll biosynthesis and N content in plant tissues. A greenhouse experiment was carried out to evaluate the relationship among N and K concentrations, the indirect determination of chlorophyll content (SPAD readings), nitrate reductase activity (RNO3-) in newly expanded leaf lamina (NL) and the dry matter yield for plant tops of Mombaça grass (Panicum maximum Jacq.). A fractionated 5² factorial design was used, with 13 combinations of N and K rates in the nutrient solution. The experimental units were arranged in a randomized block design, with four replications. Plants were harvested twice. The first harvest occurred 36 days after seedling transplanting and the second 29 days after the first. Significance occurred for the interaction between the N and K rates to SPAD readings and to RNO3- assessment taken on the NL during the first growth. Besides, RNO3- and SPAD readings increased only with the NL N concentration, reaching the highest values of both variables up to about 25 g kg-1, but were ratively constant at higher leaf N. Significant relationships either between SPAD readings or RNO3- activity and shoot dry mass weight were also observed. The critical levels of N concentration in the NL were, respectively, 22 and 17g kg-1 in the first and second harvest. Thus, SPAD instrument and RNO3- assessment can be used as complementary tools to evaluate the N status in forage grass.

Effect of different potassium sources on the seasonal variation of potassium and free polyamines in scots pine needles

Summary

Effect of potassium sources and rates on arabica coffee yield, nutrition, and macronutrient export

The use of potassium (K) rock powder can be an alternative for K supply of crops. Thus, to reduce K fertilizer imports from abroad, possibilities of extracting this nutrient from Brazilian rocks are being studied. The objective was to evaluate the effect of phonolite rock powder (F2) as K source (Ekosil®) on the air-dried fruit yield, nutrition and macronutrient export of Arabica coffee. The experiment was carried out on a dystroferric Red Latosol (Typic Haplorthox), in Piraju, São Paulo State, Brazil, in the 2008/09 and 2009/10 growing seasons. The experimental design was a randomized complete block, in a factorial 2 × 3 + 1 arrangement, with four replications. The treatments consisted of two K sources (KCl - 58 % of K2O and F2 - 8.42 % K2O) and three rates ½-, 1-, and 2-fold the K2O rate recommended for coffee, i.e., 75, 150, and 300 kg ha-1 of K2O), plus a control (without K application). Potassium supply increased coffee yield, regardless of the source. Application of source F2 increased coffee yield similarly to KCl at the recommended K rate for coffee (150 kg ha-1 K2O), proving efficient as K supply for coffee. Potassium application increased macronutrient export in coffee, especially in the growing season with higher yield.

Effect of potassium fertilization on yield and nutrition of yerba mate (Ilex paraguariensis)

Yerba mate (Ilex paraguariensis) is a tree species native to the subtropical regions of South America, and is found in Brazil predominantly in the southern region. Despite the historical importance in this region, so far, studies on crop nutrition to improve yields are scarce. Thus, this study evaluated the effect of potassium rates on K soil availability, and the yield and nutritional status of yerba mate. The experiment was conducted in São Mateus do Sul, State of Paraná, on a Humox soil, where K2O rates of 0, 20, 40, 80, 160, and 320 kg ha-1 were tested on 7-year-old plantations. The experiment was harvested 24 months after installation by removing approximately 95 % of the canopy that had sprouted from the previous harvest. The soil was evaluated for K availability in the layers 0-10, 0-20, 10-20, and 20-40 cm. The plant parts leaf fresh matter (LM), twigs (TW), thick branches (BR) and commercial yerba mate (COYM), i.e., LM+TW, were analyzed. In addition, the relationship between fresh matter/dry matter (FM/DM) and K concentration in LM, AG and BR were evaluated. The fertilization increased K availability in all evaluated soil layers, indicating good mobility of the nutrient even at low rates. Yerba mate responded positively to increasing K2O rates with higher yields of all harvested components. The crop proved K-demanding, with a maximum COYM yield of 28.5 t ha-1, when 72 mg dm-3 K was available in the 0-20 cm layer. Yerba mate in the plant production stage requires soil K availability at medium to high level; in clayey soil with low K availability, a rate of 300 kg ha-1 K2O should be applied at 24 month intervals to obtain high yields. A leaf K concentration of 16.0 g ha-1 is suitable for yerba mate in the growth stage.

Effect of potassium sources on the antioxidant activity of eggplant¹

Potassium participates in the essential processes in plant physiology, however, the effects of K sources on plant metabolism have been little studied. Also, in certain cases, K sources and concentrations may cause undesirable effects, e.g., soil salinization. The objective was to evaluate the effect of K sources and levels on the enzyme activity of the antioxidant system and protein content in eggplant (Solanum melongena L.) leaves and to determine the most suitable K sources for these physiological characteristics. The experiment was conducted in randomized blocks, in a 2 × 4 factorial design, consisting of two K sources (KCl and K2SO4) and rates (250, 500, 750, and 1000 kg ha-1 K2O), with four replications. The following variables were evaluated: plant height, number of leaves per plant, superoxide dismutase (SOD), catalase (CAT), and leaf protein content. There was an increase in CAT activity with increasing K levels until 30 days after transplanting (DAT), when K2SO4 was applied and until 60 DAT, when KCl was used; after this period, the enzyme activity decreased under both sources. The activity of SOD increased in the presence of KCl, but was reduced with the application of K2SO4. For both K sources, increasing rates reduced the protein content and number of leaves per plant, and this reduction was greater under KCl application. Thus it was concluded that KCl tends more strongly to salinize the soil than K2SO4. Both for KCl and for K2SO4, the increasing rates adversely affected the activities of CAT and SOD and the levels of leaf protein in eggplant. The potential of KCl to reduce the enzyme activity of SOD and CAT, leaf protein content and plant growth of eggplant was stronger than that of K2SO4.

Effect of Nitrogen and Potassium Rates on Early Development of Macaw Palm

ABSTRACT The economic exploitation of macaw palm [Acrocomia aculeate(Jacq.) Lodd. ex Mart.] is currently in transition, from extractivism to agricultural cultivation, thus requiring studies on the fertilization of the crop. This study evaluated the response of three genotypes of macaw palm to increasing rates of nitrogen and potassium, grown in the field until the 2nd year and to establish reference contents of mineral nutrients in the leaf. The experiment was a split-plot randomized block design with five main treatments (N and K rates) and three secondary treatments (genotypes), with three replications, each plot containing three plants. Plant height, leaf number, vigor, and nutrient contents in leaf tissues were evaluated at the end of 2nd year of cultivation. Differential responses were observed among genotypes, indicating that some genotypes are more efficient in the use of mineral inputs. There was a differentiated and positive response to increasing side-dressed N and K rates in the vegetative development of macaw genotypes until the 2nd year of field cultivation, indicating variability in the species in terms of nutrient use efficiency. The N and K fertilization rate corresponding to 360 g N + 480 g K2O per plant, in four split applications over the two years of cultivation, was insufficient to induce maximum vegetative development in the three macaw genotypes. There was no variation in macro- and micronutrient contents in leaf dry matter of the three macaw genotypes.

Impact of preoperative embolization of the left gastric artery on the rate of anastomotic leakage after esophageal resection

Objective: Impaired blood flow of the gastric tube represents a major cause of anastomotic leakage after esophageal resection. In order to improve local vascularisation, preoperative embolization (PE) of the left gastric artery has recently been proposed. The aimof this study was to assess our initial experience of this novel approach with a particular focus on anastomotic leakage.Methods: A consecutive series of 102 patients (81 male, 21 female, median age 64 years) underwent resection (82 Ivor-Lewis procedures, 9 transhiatal resections, 11 triple incisions) for esophageal malignancies at our institution from 2000 to 2009. Since 2004, PE was used selectively in 19 patients 21 days prior to elective esophagectomy. Selection criteria were normal gastric vascular anatomy, no pre-existing vascular disease, i.e. atheromatosis of the celiac trunk or superior mesenteric artery, and resectability of the tumor. PE was performed under local anesthesia on a dedicated system in a standard fashion. Following percutaneous transfemoral visceral angiography to identify gastric vascular anatomy, embolization was performed either with 5-F or with coaxial 3-F catheters and fibered metal coils. We analyzed retrospectively patient's data, operative data, and outcome from a prospective database.Results: The overall anastomotic leakage rate was 18・6% (19/102 patients); cervical anastomosis had a leak rate of 25% compared to intrathoracic anastomosis leak rate of 18・2%. While 17 of 83 patients without PE developed anastomotic leakage (20・5%), there were only 2 of 19 patients after PE revealing an anastomotic leakage (10・5%). Otherwise, patients with PE had no more other complications. There was only one PE-related complication (i.e. partial splenic necrosis).Mean hospital stay was 25 days versus 27 days for patients with PE and without PE, respectively. The mortality rate was 7・8% (8/102 patients), whereby four deaths were related to anastomotic leakage (1 and 3 patients with PE and without PE, respectively).Conclusion: PE is an interesting novel approach to improve gastric blood flow in order to minimize anastomotic leakage. Its application is safe and technically easy. Our preliminary experience revealed a decrease of the anastomotic leakage rate of almost 50%.