Acute, subchronic and chronic 2,4-dichlorophenoxyacetic acid (2,4-D) intoxication in rats

The acute, subchronic and chronic toxicities of 2,4- dichlorophenoxyacetic acid (2,4-D) were studied in rats. Animals were exposed acutely (600 mg/kg), subchronically (200 ppm for 30 d) and chronically (200 ppm for 180 d) to 2,4-D by the oral route. Clinical, laboratory and histopathological methods were used as indicators of toxicity. After acute exposure, the herbicide decreased locomotor activity and induced ataxia, sedation, muscular weakness (mainly of the hind quarters) and gasping for breath; increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), alkaline phosphatase (AP), amylase activities and creatinine levels; decreased total protein (TP) and glucose levels; and increased hematocrit values. Subchronic and chronic 2,4-D exposures did not induce overt clinical signs or symptoms of intoxication. However, subchronic herbicide exposure increased AST activity and albumin and hematocrit values, and chronic exposure increased AST, AP and LDH activities, decreased amylase and glucose levels, but did not change hematocrit values. Chromatographic analysis of the serum of chronically exposed rats showed the presence of the herbicide; the amount found (3.76 ± 1.16 mg/ml) suggested the absence of 2,4-D accumulation within the body. Although macroscopic or histopathological lesions were not observed in acutely, subchronically or chronically 2,4-D exposed rats, the laboratory data obtained suggest tissue injuries after dosing, since the results are considered early indicators of primarily hepatic and muscle tissue damage.

Alterations in the duodenum myenteric neurons of Wistar rats after ingesting of 2,4 dichlorophenoxyacetic acid

The 2,4 dichlorophenoxyacetic acid (2,4-D) is a systemic herbicide whose effects in animal organic systems have been examined in previous studies, being the neurotoxicity considered the predominant effect. However, the studies that detect the 2,4-D neurotoxicity have merely focused in the central nervous system, and therefore, little is known about the effect of this herbicide in the enteric nervous system. This study aimed to verifying the 2,4-D effects on the myenteric neurons in duodenum of Wistar rats. Ten 60-day-old male Wistar rats (Rattus norvegicus) were divided in two groups: control group (C) that did not receive 2,4-D and experimental group (E) that received 5.0 mg of 2,4-D/kg for 15 days. At the end of experimental period, the animal were euthanized, the duodenum was collected and processed for NADPH-diaphorase histochemical analysis in order to expose the nitrergic myenteric neurons (NADPH-dp). In the light microscopy analysis, the whole-mount preparation obtained from duodenum of each animal were image-captured in 120 and 40 fields, for quantitative and morphometric analyses of myenteric neurons, respectively. The neuronal density was not affected when comparing the two groups, but an increase (p > 0.05) of 8.5% was observed in the cell body area of neurons in the E group. In conclusion, the ingestion of 2,4-D at a dosage of 5.0 mg/kg body weight for 15 days does not change the neuronal density, but promotes the hypertrophy of NADPH-dp myenteric neurons in duodenum of the rats of this study.

2,4-Dichlorophenoxyacetic acid (2,4-D) degradation promoted by nanoparticulate zerovalent iron (nZVI) in aerobic suspensions

Reactive species generated by Fe0 oxidation promoted by O2 (catalyzed or not by ligands) are able to degrade contaminant compounds like the herbicide 2,4-dichlorophenoxyacetic acid. The degradation of 2,4-D was influenced by the concentrations of zero valent iron (ZVI) and different ligands, as well as by pH. In the absence of ligands, the highest 2,4-D degradation rate was obtained at pH 3, while the highest percentage degradation (50%) was achieved at pH 5 after 120 min of reaction. Among the ligands studied (DTPA, EDTA, glycine, oxalate, and citrate), only ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) significantly enhanced oxidation of 2,4-D. This increase in oxidation was observed at all pH values tested (including neutral to alkaline conditions), indicating the feasibility of the technique for treatment of contaminated water. In the presence of EDTA, the oxidation rate was greater at pH 3 than at pH 5 or 7. Increasing the EDTA concentration increased the rate and percentage of 2,4-D degradation, however increasing the Fe0 concentration resulted in the opposite behavior. It was found that degradation of EDTA and 2,4-D occurred simultaneously, and that the new methodology avoided any 2,4-D removal by adsorption/coprecipitation. © 2013 Elsevier Ltd.

Planejamento, síntese e avaliação farmacológica de novos compostos 1,2,5-oxadiazol-2-n-óxido úteis como preventivos de aterotrombose

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

Poly(2,5-bibenzimidazole) Membranes: Physico-Chemical Characterization Focused on Fuel Cell Applications

Membranes of Poly(2,5-benzimidazole) (ABPBI), prepared by polycondensation in polyphosphoric acid, were characterized from the fuel cell application point of view: mechanical properties of the membranes for different acid doping levels, thermal stability, permeability for the different gases/vapors susceptible of use in the cell (hydrogen, oxygen, methanol and ethanol), electro-osmotic water drag coefficient, oxidation stability to hydroxyl radicals, phosphoric acid leaching rate and, finally, in-plane membrane conductivity. ABPBI membranes presented an excellent thermal stability, above 500 degrees C in oxygen, suitable mechanical properties for high phosphoric acid doping levels, a low methanol and ethanol limiting permeation currents, and oxygen permeability compared to Nafion membranes, and a low phosphoric acid leaching rate when exposed to water vapor. On the contrary, hydrogen permeation current was higher than that of Nafion, and the chemical stability was very limited. Membrane conductivity achieved 0.07 S cm(-1) after equilibration with a humid environment. Fuel cell tests showed reasonable good performances, with a maximum power peak of 170 mW cm(-2) for H-2/air at 170 degrees C operating under a humidified hydrogen stream, 39.9 mW cm(-2) for CH3OH/O-2 at 200 degrees C for a methanol/water weight ratio of 1: 2, and 31.5 mW cm(-2) for CH3CH2OH/O-2 at the same conditions than for methanol. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.014207jes] All rights reserved.

Performance of a poly(2,5-benzimidazole)-based polymer electrolyte membrane fuel cell

The performance of an ABPBI-based High Temperature H-2/O-2 PEMFC system was studied under different experimental conditions. Increasing the temperature from 130 to 170 degrees C improved the cell performance, even though further increase was not beneficial for the system. Humidification of the H-2 stream ameliorated this behaviour, even though operating above 170 degrees C is not advisable in terms of cell performance. A significant electrolyte dehydration seems to negatively affect the fuel cell performance, especially in the case of the anode. In the presence of 2% vol. CO in the H-2 stream, the temperature exerted a positive effect on the cell performance, reducing the strong adsorption of this poison on the platinum sites. Moreover, humidification of the H-2 + CO stream increased the maximum power densities of the cell, further alleviating the CO poisoning effects. Actual CO-O-2 fuel cell results confirmed the significant beneficial effect of the relative humidity on the kinetics of the CO oxidation process. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Evidence of 5-aminolevulinic acid (ALA) penetration increase due to microdrilling in soft tissue using femtosecond laser ablation

Photodynamic therapy (PDT) is a therapeutic technique mainly applied to the treatment of malignant and pre-malignant lesions, which induces cell death by the combined effect of a photosensitizer, irradiation in a proper wavelength, and molecular oxygen. One of the main limitations of PDT using 5-aminolevulinic acid (ALA) is the superficial volume of treatment, mainly due to the limited penetration of topical photosensitization. In this context, the present study investigates if a laser micromachining producing microchannels on the tissue surface could improve ALA penetration and result in an increase in the treatment depth. The laser micromachining under femtosecond regime was performed on the tissue surface of rat livers. Conventional PDT was applied and the induced depth of necrosis with or without laser micromachining was compared. The results showed an increase of more than 20% in the depth of necrosis when the femtosecond laser micromachining was performed before the treatment with the PDT.

Valorizzazione di molecole da materie prime rinnovabili: la trasformazione del 2,5-diidrossimetilfurano con catalisi acida

The present work is part of a larger project aimed at obtaining compounds of industrial interest from renewable sources. The work is particularly aimed to investigate the reactivity of 2,5-bis-hydroxymethylfuran (BHMF), an important building block of organic nature easily obtainable from biomass, with acid catalysis. Through the study of the reactivity of BHMF in water, in the presence of an heterogeneous acid catalyst (Amberlyst 15), has been developed a new synthetic method for the preparation of α-6-hydroxy-6-methyl-4-enyl-2H-pyran-3-one a derivative whose molecular skeleton is similar to that of natural products which are used in pharmaceutical chemistry. The product is obtained in milder conditions and with better selectivity with respect to the strongly oxidizing conditions with which it is prepared in the literature starting from different precursors containing furan ring.

Sensitivity of osteoblasts, fibroblasts, bone marrow cells, and dendritic cells to 5-aminolevulinic acid based photodynamic therapy

INTRODUCTION: Photodynamic therapy with 5-aminolevulinic acid (5-ALA-PDT) exerts cell type specific effects on target cells. Since chondrocytes were found to be more resistant than osteoblasts to 5-ALA-PDT, the pre-treatment of osteochondral grafts with 5-ALA-PDT may represent a means to devitalize the osseous portion while maintaining functional cartilage. The present study was designed to determine the effects of 5-ALA-PDT in vitro on cell populations residing in skeletal tissues. METHODS: Osteoblasts, fibroblasts, bone marrow cells, and dendritic cells were incubated with 0.5 mM 5-ALA for 4 h. Protoporphyrin IX (PpIX) accumulation and after exposure to light cellular functions were assessed for up to 6 days. RESULTS: Accumulation of PpIX reached a plateau at 0.5 mM in osteoblasts, fibroblasts, and dendritic cells, and at 2.0 mM in bone marrow cells. At 0.5 mM 5-ALA, similar responses to illumination were observed in all cells with a survival rate of less than 12% at a light dose of 20 J/cm(2). The function of osteoblasts (proliferation, levels of mRNA encoding collagen type I, alkaline phosphatase activity) and fibroblasts (proliferation, levels of mRNAs encoding collagens type I and III) was not affected, when the cells were treated with 5-ALA and light doses of < or =10 J/cm(2). Paralleling the reduction of viable cells after 5-ALA-PDT, the capacity of dendritic cells to stimulate T cells in a mixed leukocyte reaction decreased to 4+/-2% at 20 J/cm(2). CONCLUSION: The investigated cell types were sensitive to 5-ALA-PDT and the residual cell debris did not elicit an allogenic response. These findings, together with the resistance of chondrocytes to 5-ALA-PDT, encourage the further investigation of this protocol in the pretreatment of osteochondral allografts.

In vitro resistance of articular chondrocytes to 5-Aminolevulinic acid based photodynamic therapy

OBJECTIVE: 5-Aminolevulinic acid based photodynamic therapy (5-ALA-PDT) has revealed promising results in the treatment of inflammatory joint diseases due to the sensitivity of inflamed synovial tissue. For 5-ALA-PDT to be safe and beneficial for intra-articular applications, resistance of chondrocytes is essential to prevent cartilage damage. As no data yet exist, the aim of the present study was to assess in vitro the response of the chondrocytes to 5-ALA-PDT and to compare with osteoblasts and synovial tissue derived cells. METHODS: Bovine articular chondrocytes, osteoblasts, and synovial cells were subjected to 5-ALA-PDT in cell culture. The PpIX accumulation and the function of the cells were assessed for up to 12 days. RESULTS: Bovine chondrocytes showed lower PpIX fluorescence upon incubation with 5-ALA (0.0-2.0 mM) for 4 hours as compared to osteoblasts and synovial cells suggesting a low PpIX accumulation. After incubation with 0.5 mM 5-ALA and application of light at a dose of 20 J/cm2, chondrocytes were functionally not affected (collagen type II and aggrecan mRNA, glycosaminoglycan synthesis) whereas a decrease in the proportion of viable cells was observed in osteoblasts and synovial cells (2+/-2% and 14+/-8%, respectively; chondrocytes 91+/-13%). Chondrocytes showed a 58% reduction of 5-ALA uptake using [3H]5-ALA as compared to osteoblasts and a lower mitochondrial content as assessed by the activity of the mitochondrial marker enzyme citrate synthase (9.2+/- 3.6 mU/mg protein) than osteoblasts (32.6+/-10.5 mU/mg) and synovial cells (60.0+/-10.8 mU/mg). The reduced uptake of 5-ALA and/or the low mitochondrial content, an adaptation to their in vivo environment and the site of PpIX synthesis, presumably explains the lower PpIX content in chondrocytes and their resistance against 5-ALA-PDT. CONCLUSION: 5-ALA-PDT might represent a treatment strategy in inflammatory joint diseases without endangering the cartilage function. However, further in vitro and in vivo experiments are required to confirm this data in the authentic environment of chondrocytes, the articular cartilage.

Differential response of porcine osteoblasts and chondrocytes in cell or tissue culture after 5-aminolevulinic acid-based photodynamic therapy

OBJECTIVE: Outcome in osteochondral allografting is limited by the immunological incompatibility of the grafted tissue. Based on a resistance of chondrocytes to photodynamic therapy in cell culture it is proposed that 5-aminolevulinic acid-based photodynamic therapy (5-ALA-PDT) might be used to inactivate bone while maintaining viability of chondrocytes and thus immunomodulate bone selectively. METHODS: Chondrocytes and osteoblasts from porcine humeral heads were either isolated (cell culture) or treated in situ (tissue culture). To quantify cytotoxic effects of 5-ALA-PDT (0-20J/cm(2), 100mW/cm(2)) an (3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide) (MTT)-assay was used in cell culture and in situ hybridization in tissue culture to assess metabolic active cells (functional osteoblasts: colalpha(1)(I) mRNA, functional chondrocytes: colalpha(1)(II) mRNA). RESULTS: In cell culture, survival after 5-ALA-PDT was significantly higher for chondrocytes (5J/cm(2): 87+/-12% compared to untreated cells) than for osteoblasts (5J/cm(2): 12+/-11%). In tissue culture, the percentage of functional chondrocytes in cartilage showed a decrease after 5-ALA-PDT (direct fixation: 92+/-2%, 20J/cm(2): 35+/-15%; P<0.0001). A significant decrease in the percentage of bone surfaces covered by functional osteoblasts was observed in freshly harvested (31+/-3%) compared to untreated tissues maintained in culture (11+/-4%, P<0.0001), with no further decrease after 5-ALA-PDT. CONCLUSION: Chondrocytes were more resistant to 5-ALA-PDT than osteoblasts in cell culture, while in tissue culture a loss of functional chondrocytes was observed after 5-ALA-PDT. Since osteoblasts - but not chondrocytes - were sensitive to the tissue culture conditions, devitalized bone with functional cartilage might already be achieved by applying specific tissue culture conditions even without 5-ALA-PDT.

Rhizodeposition and the enhanced mineralization of 2,4-dichlorophenoxyacetic acid in soil from the Trifolium pratense rhizosphere

Enhanced biodegradation of organic xenobiotic compounds in the rhizosphere is frequently recorded although the specific mechanisms are poorly understood. We have shown that the mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D) is enhanced in soil collected from the rhizosphere of Trifolium pratense[e.g. maximum mineralization rate = 7.9 days(-1) and time at maximum rate (t(1)) = 16.7 days for 12-day-old T. pratense soil in comparison with 4.7 days(-1) and 25.4 days, respectively, for non-planted controls). The purpose of this study was to gain a better understanding of the plant-microbe interactions involved in rhizosphere-enhanced biodegradation by narrowing down the identity of the T. pratense rhizodeposit responsible for stimulating the microbial mineralization of 2,4-D. Specifically, we investigated the distribution of the stimulatory component(s) among rhizodeposit fractions (exudates or root debris) and the influence of soil properties and plant species on its production. Production of the stimulatory rhizodeposit was dependent on soil pH (e.g. t(1) for roots grown at pH 6.5 was significantly lower than for those grown at pH 4.4) but independent of soil inorganic N concentration. Most strikingly, the stimulatory rhizodeposit was only produced by T. pratense grown in non-sterile soil and was present in both exudates and root debris. Comparison of the effect of root debris from plant species (three each) from the classes monocotyledon, dicotyledon (non-legume) and dicotyledon (legume) revealed that legumes had by far the greatest positive impact on 2,4-D mineralization kinetics. We discuss the significance of these findings with respect to legume-rhizobia interactions in the rhizosphere.

Solid base catalysed 5-HMF oxidation to 2,5-FDCA over Au/hydrotalcites:fact or fiction?

Nanoparticulate gold has emerged as a promising catalyst for diverse mild and efficient selective aerobic oxidations. However, the mechanism of such atom-economical transformations, and synergy with functional supports, remains poorly understood. Alkali-free Mg-Al hydrotalcites are excellent solid base catalysts for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furan dicarboxylic acid (FDCA), but only in concert with high concentrations of metallic gold nanoparticles. In the absence of soluble base, competitive adsorption between strongly-bound HMF and reactively-formed oxidation intermediates site-blocks gold. Aqueous NaOH dramatically promotes solution phase HMF activation, liberating free gold sites able to activate the alcohol function within the metastable 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) reactive intermediate. Synergistic effects between moderate strength base sites within alkali-free hydrotalcites and high gold surface concentrations can afford highly selective and entirely heterogeneous catalysts for aqueous phase aldehyde and alcohol cascade oxidations pertinent to biomass transformation.