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41.
George L. Vourlitis Francisco de Almeida Lobo Shelley Lawrence Kali Holt Anthony Zappia Osvaldo Borges Pinto Jr. Jose de Souza Nogueira 《Plant Ecology》2014,215(9):963-975
Nutrient limitation in Brazilian savanna (known as cerrado) presumably causes trees to maximize nutrient resorption from senesced leaves to reduce their dependence on nutrient availability. To assess patterns between nutrient resorption and soil fertility, we measured community-level nitrogen (N), phosphorus (P), and potassium (K) concentrations in mature and senesced leaves and soil fertility in the upper 50 cm soil layer in structurally diverse cerrado ecosystems in the Cuiaba Basin (CB) and Pantanal (PAN) of Mato Grosso, Brazil. Foliar nutrient concentration data were used to estimate resorption efficiency and proficiency, and correlation was used to determine whether resorption efficiency and proficiency varied across soil fertility gradients. We found that N and P resorption proficiency (NRP and PRP, respectively) and P resorption efficiency (PRE) increased significantly as total soil N (NRP) and extractable P (PRP and PRE) declined. In contrast, K resorption efficiency (KRE) declined as soil sand content and bulk density increased, which was likely due to a reduction in soil water-holding capacity. Leaf N/P ratios indicate potential N limitation and/or N + P co-limitation for ecosystems in the PAN and P limitation and/or N + P co-limitation for ecosystems in the CB, while trends in leaf N/K ratios indicate possible K or K + P co-limitation for the CB only. Our results illustrate that cerrado forests and woodlands have highly variable nutrient resorption capacities that vary predictably across soil fertility or textural gradients and indicate that cerrado communities have flexible nutrient resorption that can reduce their dependence on soil nutrient availability. 相似文献
42.
The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30?kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected. 相似文献
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44.
Miguel?PetrereJr.Email author Ronaldo?Borges?Barthem Edwin?Agudelo?Córdoba Bernardo?Corrales?Gómez 《Reviews in Fish Biology and Fisheries》2004,14(4):403-414
In this paper we describe the present status of the large migratory catfish fisheries in the Upper Amazon. We present biological information about the main species and we give strong evidence that the stock of piraíba (Brachyplatystoma filamentosum),the largest catfish in the Amazon Basin is probably over-exploited. In conclusion, we raise some hypotheses about the causes and prospects for the future. 相似文献
45.
Borges E Vuaden FC Cognato Gde P Fauth Mda G Bonan CD Turcato G Rossi IC Dias RD 《Journal of experimental zoology. Part A, Comparative experimental biology》2004,301(11):891-897
In the present study, the glucose concentration in the haemolymph and glycogen levels were determined in the various body parts of the Helix aspersa snail after feeding lettuce ad libitum and after various periods of starvation. To characterize the effect of starvation on nucleotidase activity, enzyme assays were performed on membranes of the nervous ganglia and digestive gland. Results demonstrated the maintenance of the haemolymph glucose concentration for up to 30 days of starvation, probably due to the consumption of glycogen from the mantle. In the nervous ganglia, depletion of glycogen occurs progressively during the different periods of starvation. No significant changes were observed on ATP and ADP hydrolysis in the membranes of nervous ganglia and no alterations in Ca2+ -ATPase and Mg2+ -ATPase occurred in the membranes of the digestive gland of H. aspersa during the different periods of starvation. Although there were no changes in the enzyme activities during starvation, they could be modulated by effectors in situ with concomitant changes in products/reactants during starvation. 相似文献
46.
Ribeiro-Dias F Shio MT Timenetsky J Oliane AP Metran CC Pessoa FB Jancar S 《Experimental cell research》2003,286(2):345-354
Mycoplasma arthritidis causes arthritis in rodents that resembles human rheumatoid arthritis. It produces a superantigen (MAM) that stimulates production of cytokines by making a bridge between lymphocyte T-cell receptor with the appropriate Vbeta chain, and H-2 1-Ealpha MHC class II molecules. Here we studied MAM-induced nitric oxide (NO) production in mouse peritoneal macrophages and found that it was: (1) time and concentration dependent, (2) possibly derived from inducible NOS synthase since it was reduced significantly by amino guanidine pretreatment, (3) restricted to H-2(K) (C3H/HePas and C3H/HeJ) and H-2(d) strains (BALB/c), (4) independent of TLR4 signaling since the coisogenic strains C3H/HePas and C3H/HeJ (TLR4 deficient) produced similar levels of NO following MAM stimulation, (5) potentiated by lipopolysaccharide, and (6) dependent on the presence of nonadherent peritoneal cells. Neutralization of interferon-gamma (IFNgamma in the peritoneal cell cultures with monoclonal antibodies abolished MAM-induced NO production. Addition of rIFNgamma to the adherent cells substituted the nonadherent cells for MAM-induced NO production. A macrophage cell line, J774A.1 (H-2(d)), also produced NO upon MAM stimulation but only when BALB/c spleen lymphocytes were added. Thus, in murine macrophages, MAM induces NO production that is dependent on signaling through MHC class II molecules and IFNgamma but independent of TLR4 expression. 相似文献
47.
Previous studies have demonstrated the absorption of porcine trypsin in isolated jejunal loops from male Wistar rats by open-loop perfusion. The possible routes of absorption were examined in the study reported here. Trypsin (0.5 mg/ml) was dissolved in tyrode solution and perfused at a rate of 0.5 ml/min, at 37 degrees C, for 40 min. Using immunoperoxidase and immunofluorescence techniques, strong reactivity towards anti-TLCK-trypsin antibody was demonstrated through out the enterocyte cytosol. The present data indicate that trypsin was absorbed by enterocytes, probably through a transcellular route. 相似文献
48.
Vonasek E Mateu L Luzzati V Marquez G Vargas R Céspedes G Cotúa M Borges J 《European biophysics journal : EBJ》2001,30(1):11-16
A sural nerve dissected from a recently dead patient displayed an unusual X-ray diffraction pattern, suggesting that in situ and at the time of the patient's death the myelin sheaths were in a swollen state. Diffraction patterns of the swollen type were also recorded from: (1) a sural nerve from the corpse of a neurologically healthy person after soaking the nerve with Ringer solution at pH 5.5; (2) sciatic nerves dissected from rat cadavers at increasing time after death. In all the cases the swollen patterns reversed to the native type upon superfusion with Ringer solution at pH 7.3. The postmortem effect is to decrease the pH of the fluids surrounding the nerves in the cadavers. Our experiments show that the early postmortem processes have the effect of acidifying PNS nerves and that as a consequence of acidification the myelin sheaths swell. 相似文献
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50.
Aspergillus is a very ubiquitous fungal in our environment, including hospitals, being the second in frequency in colonization and infection, just after Candida spp. Aspergillus nosocomial infections have increased, because the number of immunocompromised patients has also increased. Nosocomial infections can be caused by different species of Aspergillus, being pulmonary manifestations the most frequent. Primary or secondary nonpulmonary infections can affect the brain, heart, kidney, eyes and other organs. The mortality due to invasive aspergillosis is very high, and a clinical-radiological suspicion and, specially the instauration of a rapid treatment with high doses of amphotericin B or its new formulations (associated with surgery in many times) may modify the mortality observed in this patients. 相似文献