Expression of catalase, alcohol dehydrogenase, and malate dehydrogenase in rot grains upon fungicide use on maize hybrids grown at different spacings.

In this study, we evaluated the fungicide effect on the incidence of rot grains and expression of catalase (CAT), alcohol dehydrogenase (ADH), and malate dehydrogenase (MDH) enzymes in commercial maize hybrids grown with conventional and reduced spacing in Guarapuava, PR, Brazil. The experiment was designed in random blocks with a 3 × 8-factorial scheme, totaling 24 treatments. The first factor constituted three levels, the first with foliar fungicide application [150.0 g/L trifloxystrobin (15.0%, w/v) + 175.0 g/L prothioconazole (17.5%, w/v)] at a dose of 0.4 L/ha at V8-stage eight expanded leaves and the second with an application of 0.5 L/ha at VT-tasseling and check (no fungicide application) stage. The second factor comprised eight maize hybrids that were divided into two groups, complex (AG 9045PRO, AG 8041PRO, DKB245PRO2, and 2B707PW) and susceptible (P 32R48H, DKB390PRO, P 30F53H, and P 30R50H), according to their reaction to the causative fungus, totaling 72 plots at each site in the crop of 2013/2014. The percentage of rot grains and the expression of CAT, ADH, and MDH were evaluated for each hybrid. The percentage of rot grains was influenced by the hybrid and fungicide used. The (trifloxystrobin + prothioconazole) reduced the incidence of rot grains, with relatively higher reduction in the hybrids considered susceptible. The higher expression of CAT enzyme was related to the higher incidence of rot grains because of grain deterioration, depending on the hybrids evaluated. A higher expression of ADH and MDH enzymes was observed in the maize hybrids belonging to the group considered tolerant.

Lower values of handgrip strength and adductor pollicis muscle thickness are associated with hepatic encephalopathy manifestations in cirrhotic patients.

Hepatic encephalopathy (HE) is a late complication of liver cirrhosis and is clearly associated with poor outcomes. Chronic liver insufficiency leads to progressive muscle wasting, impairing ammonia metabolism and thus increasing the risk for HE. Given the association between lean mass and adductor pollicis muscle thickness (APMT), it has been used to predict outcome and complications in many conditions, but not yet in cirrhotic patients. Therefore, this article aimed to study the association between HE manifestations and measures related to muscle mass and strength. This cross-sectional study included 54 cirrhotic outpatients with HE varying from subclinical to grade II according to the West-Haven criteria, who were submitted to neuropsychometric tests, electroencephalogram, brain Single Photon Emission Computed Tomography (SPECT), anthropometric measurements, handgrip strength (HGS) and dual energy X-ray absorptiometry exam (DXA). Multiple logistic regression analysis was performed to investigate the association between body composition measures and HE grade. Analysis of the area under the receiver operator characteristic (AUROC) curve revealed the values related to neurological manifestations (HE grades I and II). Reductions in APMT and HGS were associated with higher HE grades, suggesting a big impact caused by the loss of muscle mass and function on HE severity. The link between HE manifestations and anthropometric measures, namely APMT and HGS, point to a significant relation concerning skeletal muscles and the neurological impairment in this population.

Ex vivo evaluation of artifacts mimicking fracture lines on cone-beam computed tomography produced by different root canal sealers.

AIM: To evaluate streaking artifacts produced by several root canal sealers on CBCT images with variations in voxel resolution. METHODOLOGY: Single-rooted premolars were selected and root filled using gutta-percha cones and one of the following sealers: Endofill, Sealer 26, Fillapex or AH Plus. Root canals filled only with gutta-percha were used as control. Scans of teeth using a small-volume CBCT were performed, and the images acquired were evaluated by two calibrated observers (k > 0.75). Artifacts were identified as streaks and dark bands on root dentine in axial slices with 2 voxel sizes (0.076 and 0.2 mm). Fisher's exact test (P < 0.05) was used to compare the presence/absence ratio of artifacts considering the factors 'sealer' and 'voxel size'. RESULTS: For the 0.20 mm voxel size, Sealer 26 had significantly more artifacts than Fillapex (P = 0.006) or AH Plus (P = 0.017). No differences existed between the sealers when the 0.07 mm voxel size was used. Sealer 26 (P = 0.042) and Endofill (P = 0.035) had significantly more artifacts in the 0.20 mm voxel size than with the 0.076 mm voxel size, whilst no difference was noted for other filling conditions. CONCLUSIONS: The material used for root filling and the voxel resolution can influence the presence of streaking artifacts observed in CBCT images.

Status epilepticus-Therapeutic management at the pediatric emergency department.

INTRODUCTION: Status epilepticus is an important cause of pediatric neurological emergency. Immediate treatment is essential to prevent definitive neurological damage. Several antiepileptic drugs are available for the management of status epilepticus. METHODS: Retrospective study of patients admitted at the emergency department of a tertiary hospital for 5 years (2014-2019). We analyzed the compliance to the treatment guidelines for pediatric status epilepticus. RESULTS: One hundred and seventeen admissions were identified, 23.9% of these were febrile status epilepticus. Among the other cases, the most frequent cause was genetic (22.2%). The majority were convulsive status epilepticus (93.1%), 58.7% of which were generalized tonic-clonic seizures. Benzodiazepines were the most used first and second line drug (98.2% and 94.8%). The most frequent third drug used was diazepam (56.4%) followed by phenytoin (18.2%). An infra-therapeutic antiepileptic drug dose was given in 48.7% of cases. 49.6% presented with a prolonged status epilepticus and 6.8% needed intensive care. Incorrect sequence of drugs and infra-therapeutic doses were associated with prolonged status (p<0.001 and p<0.05) and an increased number of antiepileptic drugs used (p<0.001 and p<0.05). CONCLUSIONS: Benzodiazepines were the most frequently first and second line drugs used for status epilepticus management. Surprisingly, the most frequently third line drugs used were also benzodiazepines. These findings were partially explained by the misuse of infra-therapeutic doses of these drugs. Noncompliance with the implemented guidelines was associated with unfavorable outcomes.

Land use around influences the entomological community in lettuce horticultural systems.

The complexity of the agroecosystem can also be assessed by the different land uses in the system and the surroundings, being a relevant way to assess the heterogeneity of the landscape and the effects on the community of interest, in this case, entomofauna. Thus, the objective of this work is to verify how the use of soil in the surroundings of Chilean lettuce horticultural systems, in the Coquimbo Region, alters the entomological community of the crop. Insect sampling was conducted (February 2021 to March 2022) using yellow pan traps. Two sites will be sampled on each of the seven studied lettuce crops. Land use and land cover classes were defined: Forests, water bodies, shrub vegetation, grasslands, barren lands, impermeable surfaces, and urban areas. After land use and land cover classification, buffers of 500 to 5,000 m were created around each data collection point. For data analysis, the percentages of land use of different classes were compared with the ecological attributes: Abundance of insects, abundance of insect pests, richness of entomological families and types of oral apparatus (licker-sucker, mandible, picker-sucker, and sucker). Land uses at different distances from horticultural systems affected the entomological community.

Physical properties of a generalized model of multilayer adsorption of dimers.

We investigate the transport properties of a complex porous structure with branched fractal architectures formed due to the gradual deposition of dimers in a model of multilayer adsorption. We thoroughly study the interplay between the orientational anisotropy parameter p_{0} of deposited dimers and the formation of porous structures, as well as its impact on the conductivity of the system, through extensive numerical simulations. By systematically varying the value of p_{0}, several critical and off-critical scaling relations characterizing the behavior of the system are examined. The results demonstrate that the degree of orientational anisotropy of dimers plays a significant role in determining the structural and physical characteristics of the system. We find that the Einstein relation relating to the size scaling of the electrical conductance holds true only in the limiting case of p_{0}→1. Monitoring the fractal dimension of the interface of the multilayer formation for various p_{0} values, we reveal that in a wide range of p_{0}>0.2 interface shows the characteristic of a self-avoiding random walk, compared to the limiting case of p_{0}→0 where it is characterized by the fractal dimension of the backbone of ordinary percolation cluster at criticality. Our results thus can provide useful information about the fundamental mechanisms underlying the formation and behavior of wide varieties of amorphous and disordered systems that are of paramount importance both in science and technology as well as in environmental studies.

Transport properties in multilayer adsorption of dimers.

In this paper, we study the transport properties (percolation and conductivity) of a two-dimensional structure created by depositing dimers on a one-dimensional substrate where multilayer deposition is allowed. Specifically, we are interested in studying how the mentioned properties vary as a function of the height of the multilayer. The critical parameters of the percolation transition are calculated using finite-size scaling analysis, obtaining the scaling laws for the probability of percolation and the conductivity of the system. To calculate the electrical conductivity of the multilayer, we use the Frank-Lobb algorithm.

Massive pleural effusion due to metastasis of prostate cancer.

We describe the case of a 72-year old male with pleural effusion associated with prostate cancer. There was a previous history of tobacco smoking (pack/year: 47) and of total prostatectomy followed by external beam radiation therapy seven years previously for prostate cancer. Furthermore, he was submitted to orchiectomy plus non-steroidal anti-androgen blockage, in addition to docetaxel-based chemotherapy and prednisone. After the beginning of chemotherapy, a progressive elevation in prostate specific antigen (PSA) levels was observed. On admission, he presented with fever, weight loss, and respiratory symptoms due to a massive right pleural effusion. Fluid samples obtained by needle aspiration showed haemorrhagic exudates without malignant cells. Pleural metastasis were detected by thorax imaging studies, and biopsy samples revealed prostate adenocarcinoma as the origin of his pleural effusion. Pleural fluid was drained and talc pleurodesis was performed. This report aims to describe the occurrence of massive pleural effusion due to metastasis of prostate cancer and emphasizes the role of pleural biopsy with immunohistochemical studies to characterize this diagnosis.

Inappropriate screening of obstructive coronary artery disease during pre-anesthesia assessment of candidates for non-cardiac surgery.

Preoperative evaluation in elective surgeries has been associated with successful surgical treatment. However, there is no solid scientific evidence that screening for coronary artery disease (CAD) reduces surgical risk. The aims of this study were to describe the frequency of inappropriate investigation of obstructive CAD induced by pre-anesthetic assessment in individuals without cardiovascular symptoms (candidates for low- to intermediate-risk surgeries) and to evaluate predictors of this conduct. We performed a retrospective evaluation of medical records of anesthesiology services from patients undergoing pre-anesthesia assessment between May 2015 and May 2016, including those with functional capacity ≥4 metabolic equivalents without a diagnosis of heart disease. A total of 778 medical records (47±16 years of age, 62.6% female) were studied. A private hospital performed 50.1% of the surgeries and 60.4% were of intermediate risk. Only 2.7% (95%CI: 1.7-4.1%) were screened for CAD, and 91% of these requests were mediated by cardiology consultations performed during pre-anesthetic testing visits. Factors associated with screening for CAD were hypertension, diabetes, moderate systemic disease (ASA III), cardiac consultation, previous diagnosis of CAD, and admission to a private hospital. Independent predictors were private hospitals (OR: 3.9; 95%CI: 1.3-11.0), ASA III (OR: 5.3; 95%CI: 1.7-16.2), and hypertension (OR: 3.8; 95%CI: 1.5-9.8). The frequency of inappropriate requests for CAD screening in asymptomatic individuals without untreated systemic diseases was low in pre-anesthetic visits. Although infrequent, screening for CAD is more common in the private setting, in patients with poorer health status, and is usually prescribed during cardiology consultation.

A Physiological behavior and tolerance of Lactuca sativa to lead nitrate and silver nitrate heavy metals.

This study goal to evaluate the effects of different concentrations of lead (Pb) and silver (Ag) on germination, initial growth and anatomical alterations of Lactuca sativa L. Plants use various mechanisms to reduce the impacts caused by anthropic action, such as xenobiotic elements of soils and water contaminated by heavy metals. These metals were supplied as lead nitrate and silver nitrate and the following treatments were established: control for both metals, maximum dose of heavy metals, for arable soils, allowed by the National Council of the Environment (Ag = 25 mg. Kg-1, Pb = 180 mg. Kg-1), double (Ag = 50 mg. Kg-1, Pb = 360 mg. Kg-1) and triple (Ag = 75 mg. Kg-1, Pb = 540 mg. Kg -1) of this dosage. Vigor and germination tests of the seeds and possible anatomical changes in the leaves and roots of lettuce plants were performed. The species showed a high capacity to germinate under Pb and Ag stress, and the germination was never completely inhibited; however, the germination decreased with increasing Pb concentrations, but not under Ag stress. The use of increasing doses of metals reduced seed vigor and increased chlorophyll content. An increase in biomass was also observed in plants from treatments submitted to Pb. The phytotoxic effects of metals were more pronounced at 15 days after sowing. Anatomically, L. sativa was influenced by metal concentrations, and had a reduction of up to 79.9% in root epidermis thickness at the highest Pb concentration, although some structures did not suffer significant changes. The results suggest that L. sativa presents tolerance to high concentrations of heavy metals, showing possible mechanisms to overcome the stress caused by these metals. In this research lettuce possibly used the mechanism of exclusion of metals retaining Pb and Ag in the roots preserving the photosynthetic apparatus in the aerial part of the plants. In general, the chemical element Pb was more toxic than Ag, in these experimental conditions.

Evolutionary characterization of the West Nile Virus complete genome.

The spatial dynamics of the West Nile Virus epidemic in North America are largely unknown. Previous studies that investigated the evolutionary history of the virus used sequence data from the structural genes (prM and E); however, these regions may lack phylogenetic information and obscure true evolutionary relationships. This study systematically evaluated the evolutionary patterns in the eleven genes of the WNV genome in order to determine which region(s) were most phylogenetically informative. We found that while the E region lacks resolution and can potentially result in misleading conclusions, the full NS3 or NS5 regions have strong phylogenetic signal. Furthermore, we show that geographic structure of WNV infection within the US is more pronounced than previously reported in studies that used the structural genes. We conclude that future evolutionary studies should focus on NS3 and NS5 in order to maximize the available sequences while retaining maximal interpretative power to infer temporal and geographic trends among WNV strains.

Chemical and physical properties of nanocrystalline chitosan by the method: Modified nanochitosan complex and process of obtaining modified nanochitosan.

Nanocrystalline chitosan (NCC) is a modified form of chitosan, prepared from the method for obtaining chitosan acetate (CA). Due to the greater crystallinity of chitosan nanoparticles in relation to CA, NCC is more thermally stable and thus has great potential in the development of a new generation of biomaterials potentially useful in regenerative medicine and tissue engineering. NCC is also characterized by having similar properties to its precursor chitosan, such as its biocompatibility, bioactivity, ability to be bioabsorbed and lack of toxicity. One of the major problems associated with obtaining NCC is the low productivity of the methods. While known methods of obtaining nanostructures produce small amounts (milligrams), the method of synthesis for creating NCC from its salt is often more productive and less costly, and is patented by the authors of this work (registration number: BR10201702272). Thus, the objective of this study was to characterize NCC obtained through this innovative method, and analyze its chemical and physical properties using Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and mechanical property analysis with the mean values for the elasticity module, the resistance to tensile strength and the tensile strength. The results indicate that this new process of obtaining the NCC did not modify the chemical structure of the chitosan. The structure of the film surface created was homogeneous and the mechanical properties emphasized the plastifying effect of glycerol under NCC. The thermogravimetric analysis of NCC indicated greater stability in the polysaccharide structure of the nanocrystalline, due to an increased crystalline region compared to the CA which was confirmed by DSC.

Multinodular neurilemmoma of the tongue: a case report with differential immunohistochemical profile.

Neurilemmoma is a distinctive, encapsulated, benign tumor, derived from Schwann cells. It is the most common neurogenic tumor, eventually occurring in the mouth, particularly the tongue. It occurs most often during the second or third decades of life, with predilection in females. Clinically, neurilemmomas present as a solitary circumscribed nodule, rarely being multinodular. We report a case of a 46 year-old female who presented a multinodular neurilemmoma of the tongue. She had a sessile nodule with two months of evolution. The presumptive diagnosis was of a benign mesenchymal neoplasm and an excisional biopsy was performed. During the excision it was found that the lesion was formed by two well-delimitated firm yellowish-white nodules. Histopathologic evaluation revealed an encapsulated benign tissue, formed by spindle cells forming irregular Antoni A and Antoni B patterns, not easily recognizable. Immunostaining was strongly positive for S-100 protein and negative for neurofilament. The lesion was excised and after 12 months of follow-up there was no recurrence.

Direct costs of asthma in Brazil: a comparison between controlled and uncontrolled asthmatic patients.

Asthma is a common chronic illness that imposes a heavy burden on all aspects of the patient's life, including personal and health care cost expenditures. To analyze the direct cost associated to uncontrolled asthma patients, a cross-sectional study was conducted to determine costs related to patients with uncontrolled and controlled asthma. Uncontrolled patient was defined by daytime symptoms more than twice a week or nocturnal symptoms during two consecutive nights or any limitations of activities, or need for relief rescue medication more than twice a week, and an ACQ score less than 2 points. A questionnaire about direct cost stratification in health services, including emergency room visits, hospitalization, ambulatory visits, and asthma medications prescribed, was applied. Ninety asthma patients were enrolled (45 uncontrolled/45 controlled). Uncontrolled asthmatics accounted for higher health care expenditures than controlled patients, US$125.45 and US$15.58, respectively [emergency room visits (US$39.15 vs US$2.70) and hospitalization (US$86.30 vs US$12.88)], per patient over 6 months. The costs with medications in the last month for patients with mild, moderate and severe asthma were US$1.60, 9.60, and 25.00 in the uncontrolled patients, respectively, and US$6.50, 19.00 and 49.00 in the controlled patients. In view of the small proportion of uncontrolled subjects receiving regular maintenance medication (22.2%) and their lack of resources, providing free medication for uncontrolled patients might be a cost-effective strategy for the public health system.

In situ synthesis and characterization of hydroxyapatite/natural rubber composites for biomedical applications.

In this work, a biomimetic synthesis reaction for the production of hydroxyapatite (HA)/natural rubber (NR) composites is presented. HA was synthesized in the presence of solubilized NR in tetrahydrofuran (THF), which permits that negatively charged domains in proteins and lipids in NR work as nucleation sites for hydroxyapatite. The mechanical and physicochemical properties of composites containing 10, 20 and 30wt% HA were studied. NR influenced HA crystallite morphology, shape and size and was able to disperse the HA particles in THF. The dispersion of HA in the composites promoted the enhancement of mechanical properties and loss of solubility of composites, which is believed to be macroscopic manifestations of the physical adsorption of NR to HA particles, known as the bound rubber phenomenon. Preliminary cell studies indicated that HepG2 cells presented viabilities ranging from 71.6 to 91.3%, with cell proliferation positively influenced by HA content at shorter culture times. The good dispersion of HA in the composites is expected to improve NR bioactivity and direct its use towards bone applications.

α-TCP cements prepared by syringe-foaming: Influence of Na2HPO4 and surfactant concentration.

The lack of intrinsic open porosity in calcium phosphate cements slows down the resorption rate and bone ingrowth when implanted In Vivo. In this study, macroporous structures were obtained by mixing α-TCP cement with a foamed liquid phase containing different concentrations of sodium hydrogen phosphate and a nonionic surfactant. The cement paste was prepared by hand mixing in a novel system of two syringes connected by a tube. Two different liquid to powder (L/P) ratios were used to prepare the cement paste. The cement samples showed open macropores with diameters>100µm. The specimens prepared with lower L/P ratio showed smaller porosity, macroporosity and pore size distribution. The cohesion of the cement paste in liquid solutions was assessed by adding 2wt% sodium alginate to the liquid phase. This study suggests that the final macrostructure of the foamed cements can be controlled by varying the phosphate and surfactant concentrations in the liquid phase and the L/P ratio.

Recurrent dislocation: scientific evidence and management following a systematic review.

Recurrent mandibular dislocation is a rare condition that can have a negative impact on quality of life. Different surgical techniques are employed in the treatment of this condition, and the demand for maximum healthcare quality has contributed to the implementation of evidence-based clinical practice. The objective of this study was to determine the level of scientific evidence in articles reporting open surgical treatment for recurrent mandibular dislocation. A comprehensive search strategy was conducted to locate relevant articles in the PubMed and Web of Science databases on open surgical treatment for recurrent mandibular dislocation published between January 1974 and August 2014. These were classified into one of the five established levels/sublevels of evidence: the level of evidence was determined based on the classification proposed by the Oxford Centre for Evidence-Based Medicine. One hundred and fourteen articles were identified, 91 of which were excluded based on the eligibility criteria. Thus, 23 articles were selected for inclusion in the review. All of the selected articles were rated as level 4 (low quality) regarding the level of evidence. The present review revealed that articles on open surgical treatment for recurrent mandibular dislocation exhibit a low level of scientific evidence. Thus, further studies on this topic with greater methodological rigour are needed.

A Physiological behavior and tolerance of Lactuca sativa to lead nitrate and silver nitrate heavy metals / Comportamento fisiológico e tolerância de Lactuca sativa aos metais pesados nitrato de chumbo e nitrato de prata

This study goal to evaluate the effects of different concentrations of lead (Pb) and silver (Ag) on germination, initial growth and anatomical alterations of Lactuca sativa L. Plants use various mechanisms to reduce the impacts caused by anthropic action, such as xenobiotic elements of soils and water contaminated by heavy metals. These metals were supplied as lead nitrate and silver nitrate and the following treatments were established: control for both metals, maximum dose of heavy metals, for arable soils, allowed by the National Council of the Environment (Ag = 25 mg. Kg-¹, Pb = 180 mg. Kg-¹), double (Ag = 50 mg. Kg-¹, Pb = 360 mg. Kg-¹) and triple (Ag = 75 mg. Kg-¹, Pb = 540 mg. Kg-¹) of this dosage. Vigor and germination tests of the seeds and possible anatomical changes in the leaves and roots of lettuce plants were performed. The species showed a high capacity to germinate under Pb and Ag stress, and the germination was never completely inhibited; however, the germination decreased with increasing Pb concentrations, but not under Ag stress. The use of increasing doses of metals reduced seed vigor and increased chlorophyll content. An increase in biomass was also observed in plants from treatments submitted to Pb. The phytotoxic effects of metals were more pronounced at 15 days after sowing. Anatomically, L. sativa was influenced by metal concentrations, and had a reduction of up to 79.9% in root epidermis thickness at the highest Pb concentration, although some structures did not suffer significant changes. The results suggest that L. sativa presents tolerance to high concentrations of heavy metals, showing possible mechanisms to overcome the stress caused by these metals. In this research lettuce possibly used the mechanism of exclusion of metals retaining Pb and Ag in the roots preserving the photosynthetic apparatus in the aerial part of the plants. In general, the chemical element Pb was more toxic than Ag, in these experimental conditions.

Este estudo teve como objetivo avaliar os efeitos de diferentes concentrações de chumbo (Pb) e prata (Ag) na germinação, crescimento inicial e alterações anatômicas de Lactuca sativa L. As plantas utilizam vários mecanismos para reduzir os impactos causados pela ação antrópica, como elementos xenobióticos de solos e água contaminada por metais pesados. Esses metais foram fornecidos como nitrato de chumbo e nitrato de prata e foram estabelecidos os seguintes tratamentos:controle para ambos os metais, dose máxima de metais pesados, para solos cultiváveis, permitida pelo Conselho Nacional do Meio Ambiente (Ag = 25mg.Kg-¹, Pb = 180mg.Kg-¹), dobro (Ag = 50mg.Kg-¹, Pb = 360mg.Kg-¹) e triplo (Ag = 75mg.Kg-¹, Pb = 540 mg.Kg-¹) desta dosagem. Foram realizados testes de vigor e germinação das sementes e possíveis alterações anatômicas nas folhas e raízes das plantas de alface. A espécie apresentou alta capacidade de germinar sob estresse de Ag e Pb, e a germinação nunca foi completamente inibida; entretanto, a germinação diminuiu com o aumento das concentrações de Pb, mas não sob estresse de Ag. O uso de doses crescentes dos metais, reduziu o vigor das sementes e aumentou o teor de clorofila. Também foi observado aumento da biomassa nas plantas a partir dos tratamentos submetidos ao Pb. Os efeitos fitotóxicos dos metais foram mais acentuados aos 15 dias após a semeadura. Anatomicamente, L. sativa foi influenciada pelas concentrações de metais, e teve uma redução de até 79,9% na espessura da epiderme radicular na maior concentração de Pb, embora algumas estruturas não tenham sofrido alterações significativas. Os resultados sugerem que L. sativa apresenta tolerância a altas concentrações de metais pesados, mostrando possíveis mecanismos para superar o estresse causado por esses metais. Nesta pesquisa a alface possivelmente utilizou o mecanismo de exclusão de metais retendo Pb e Ag nas raízes preservando o aparato [...].

A Physiological behavior and tolerance of Lactuca sativa to lead nitrate and silver nitrate heavy metals

Abstract This study goal to evaluate the effects of different concentrations of lead (Pb) and silver (Ag) on germination, initial growth and anatomical alterations of Lactuca sativa L. Plants use various mechanisms to reduce the impacts caused by anthropic action, such as xenobiotic elements of soils and water contaminated by heavy metals. These metals were supplied as lead nitrate and silver nitrate and the following treatments were established: control for both metals, maximum dose of heavy metals, for arable soils, allowed by the National Council of the Environment (Ag = 25 mg. Kg-1, Pb = 180 mg. Kg-1), double (Ag = 50 mg. Kg-1, Pb = 360 mg. Kg-1) and triple (Ag = 75 mg. Kg-1, Pb = 540 mg. Kg -1) of this dosage. Vigor and germination tests of the seeds and possible anatomical changes in the leaves and roots of lettuce plants were performed. The species showed a high capacity to germinate under Pb and Ag stress, and the germination was never completely inhibited; however, the germination decreased with increasing Pb concentrations, but not under Ag stress. The use of increasing doses of metals reduced seed vigor and increased chlorophyll content. An increase in biomass was also observed in plants from treatments submitted to Pb. The phytotoxic effects of metals were more pronounced at 15 days after sowing. Anatomically, L. sativa was influenced by metal concentrations, and had a reduction of up to 79.9% in root epidermis thickness at the highest Pb concentration, although some structures did not suffer significant changes. The results suggest that L. sativa presents tolerance to high concentrations of heavy metals, showing possible mechanisms to overcome the stress caused by these metals. In this research lettuce possibly used the mechanism of exclusion of metals retaining Pb and Ag in the roots preserving the photosynthetic apparatus in the aerial part of the plants. In general, the chemical element Pb was more toxic than Ag, in these experimental conditions.

Resumo Este estudo teve como objetivo avaliar os efeitos de diferentes concentrações de chumbo (Pb) e prata (Ag) na germinação, crescimento inicial e alterações anatômicas de Lactuca sativa L. As plantas utilizam vários mecanismos para reduzir os impactos causados pela ação antrópica, como elementos xenobióticos de solos e água contaminada por metais pesados. Esses metais foram fornecidos como nitrato de chumbo e nitrato de prata e foram estabelecidos os seguintes tratamentos: controle para ambos os metais, dose máxima de metais pesados, para solos cultiváveis, permitida pelo Conselho Nacional do Meio Ambiente (Ag = 25 mg.Kg-1, Pb = 180 mg.Kg-1), dobro (Ag = 50 mg.Kg-1, Pb = 360 mg.Kg-1) e triplo (Ag = 75 mg.Kg-1, Pb = 540 mg.Kg -1) desta dosagem. Foram realizados testes de vigor e germinação das sementes e possíveis alterações anatômicas nas folhas e raízes das plantas de alface. A espécie apresentou alta capacidade de germinar sob estresse de Ag e Pb, e a germinação nunca foi completamente inibida; entretanto, a germinação diminuiu com o aumento das concentrações de Pb, mas não sob estresse de Ag. O uso de doses crescentes dos metais, reduziu o vigor das sementes e aumentou o teor de clorofila. Também foi observado aumento da biomassa nas plantas a partir dos tratamentos submetidos ao Pb. Os efeitos fitotóxicos dos metais foram mais acentuados aos 15 dias após a semeadura. Anatomicamente, L. sativa foi influenciada pelas concentrações de metais, e teve uma redução de até 79,9% na espessura da epiderme radicular na maior concentração de Pb, embora algumas estruturas não tenham sofrido alterações significativas. Os resultados sugerem que L. sativa apresenta tolerância a altas concentrações de metais pesados, mostrando possíveis mecanismos para superar o estresse causado por esses metais. Nesta pesquisa a alface possivelmente utilizou o mecanismo de exclusão de metais retendo Pb e Ag nas raízes preservando o aparato fotossintético na parte aérea das plantas. De forma geral o elemento químico Pb se mostrou mais tóxico que Ag, nestas condições experimentais.