O comportamento do metilmercúrio (metilHg) no ambiente

Methylmercury is the most hazardous mercury species known. Due to its high stability, lipid solubility, and ionic properties, this compound shows a high ability to cross membranes in living organisms, damaging the central nervous system, mainly the brain, and the effects of chronic poisoning are progressive. In this paper some aspects related to the toxicity and the cases of methylmercury poisoning are described. Other aspects related to the behavior of methylmercury and the environmental factors that influence the transformation of mercury in the water and sediment, with emphasis on the methylation/demethylation reactions and the mercury cycle are discussed.

Sobre uma degenerescência acidental nos deslocamentos químicos de RMN de 31P{¹H} em complexos difosfínicos de rutênio

The [RuCl(bipy)(dppb)(4-pic)]PF6 complex was prepared and fully characterized. The X-ray crystal structure of this complex was determined in order to make an unambiguous distinction between the two possible positions of the 4-methylpyridine ligand (4-pic) in the compound: trans to phosphorus atom or trans to nitrogen atom. The [RuCl(bipy)(dppb)(4-pic)]PF6 complex exhibits an unusual temperature-dependent accidental degeneracy of the 31P chemical shifts in its solution NMR spectrum.

Activity and sulfur resistance of Rh(I) and Pd(II) complexes

Two complexes of Rh(I) and Pd(II) with chloride and tridecylamine ligands were obtained and characterized by Elementary Analysis and by XPS and FTIR spectroscopies. Complexes anchored on γ-Al2O3 were tested in the styrene semi-hydrogenation reaction carried out in the absence or presence of a sulfur poison. Although both low loaded catalysts were highly selective, the Pd(II) complex was three times more active than the Rh(I) complex. The rhodium complex was more sulfur resistant but less active than the palladium complex. Differences in conversion and sulfur resistance between both complexes could be related to electronic and/or geometric effects.

Determinação de compostos carbonilados e carboxilados em derivados de petróleo

Although metals and nitrogen/sulfur compounds have been the main concern of the petroleum industry, issues concerning the harmful effects on catalysts poisoning and product contamination by other contaminants such as oxygen-containing compounds have been raised. Trace amounts of carbonyl and carboxyl compounds in petroleum products can lead to catalyst poisoning. Additionally, oxygenates may be present in final polyethylene and polypropylene resins, affecting the quality of food packaging. In this work, we reviewed potential analytical approaches for oxygenates determination in petroleum products and report the features of each potential technique.

PREPARAÇÃO DE PONTOS DE CARBONO E SUA CARACTERIZAÇÃO ÓPTICA: UM EXPERIMENTO PARA INTRODUZIR NANOCIÊNCIA NA GRADUAÇÃO

Carbon dots (CDs) constitute a new class of carbon-based nanomaterials that measure less than 10 nm and display attractive physical and chemical features such as fluorescence. CDs have been considered the new “power” carbon nanomaterials since their accidental discovery in 2004. This study reports a simple, easy, and accessible experiment for undergraduate courses. The experiment involves the preparation of CDs by pyrolysis using commercial gelatin as a low cost precursor as well as CD purification and optical characterization. The optical properties of CDs such as absorption and emission properties make them a promising material for teaching the basic concepts and techniques used for characterization of nanomaterials. Also, the reactants and final product are suitable for undergraduate courses since they are non-toxic materials. The prepared CDs can be used in such applications as bioimaging, solar cells, and photocatalysis.

Occurrence of Euplatypus parallelus, Euplatypus sp. (col.: Euplatypodidae) and Xyleborus affinis (col.: Scolytidae) in Pinus sp. in Ribas do Rio Pardo, Mato Grosso do Sul, Brazil

Wood borer species of the families Euplatypodidae and Scolytidae were observed attacking trees of Pinus sp. in the Municipality of Ribas do Rio Pardo, state of Mato Grosso do Sul, Brazil, in March 2000. This plantation had been previously burned in an accidental fire in January 2000, causing the trees to become partially or totally unhealthy, rendering them more susceptible to attack of these pests. Galleries of these wood borers were opened with a chisel to observe parameters such as their direction and form of these galleries. Species observed as wood borers of Pinus sp. were Euplatypus parallelus, Euplatypus sp. (Coleoptera: Euplatypodidae) and Xyleborus affinis (Coleoptera: Scolytidae).

DIFFERENTIAL RESPONSE OF CLONES OF EUCALYPT TO GLYPHOSATE1

Weed control is commonly performed by the inter-row mechanical weeding associated to intrarow glyphosate directed spraying, causing a risk for drift or accidental herbicide application, that can affect the crop of interest. The objective was to evaluate the response of clones C219, GG100, I144, and I224 of eucalypt (Eucalyptus grandis x E. urophylla) to glyphosate doses of 0, 18, 36, 72, 180, 360, and 720 g of acid equivalent per hectare. The clones showed different growth patterns with regard to height, leaf number, stem dry weight, relative growth rate, net assimilation rate, and relative leaf growth rate. The clones I144 and GG100 were more susceptible to glyphosate, showing the doses required to reduce dry weight by 50% of 113.4 and 119.6 g acid equivalent per hectare, respectively. The clones C219 and I224 were less susceptible to glyphosate, showing the doses required to reduce dry weight by 50% of 237.5 and 313.5 g acid equivalent per hectare, respectively. Eucalyptus clones respond differently to glyphosate exposure, so that among I224, C219, GG100, and I144, the susceptibility to the herbicide is increasing.

Warning system based on theoretical-experimental study of dispersion of soluble pollutants in rivers

Information about capacity of transport and dispersion of soluble pollutants in natural streams are important in the management of water resources, especially in planning preventive measures to minimize the problems caused by accidental or intentional waste, in public health and economic activities that depend on the use of water. Considering this importance, this study aimed to develop a warning system for rivers, based on experimental techniques using tracers and analytical equations of one-dimensional transport of soluble pollutants conservative, to subsidizing the decision-making in the management of water resources. The system was development in JAVA programming language and MySQL database can predict the travel time of pollutants clouds from a point of eviction and graphically displays the temporal distribution of concentrations of passage clouds, in a particular location, downstream from the point of its launch.

Ingestão de corpo estranho

The great majority of the ingested foreign bodies (92,5%) enters into the gastrointestinal tract, and only a few of cases go to the respiratory tract. Eighty to 90% of those that go into the gastrointestinal tract are spontaneously eliminated but 10- 20% must be removed by endoscopy and 1% needs to be surgically removed. The authors report a case of accidental ingestion of a foreign body (toothbrush) by a 20-year-old patient.

Abscesso hepático piogênico por corpo estranho

Pyogenic hepatic abscess by a foreign body is a rare disease and its diagnosis is habitually made during necropsy. The authors present a case of a woman operated because of a pyogenic hepatic abscess, in the interior of which bristle made of material of vegetable origin were encountered and identified in the laboratory as the principal rib of a leaf, known in Brazil as piaçava. The hepatic abscess was drained and the patient was discharged. The probable mechanism for the formation of the hepatic abscess consisted of the accidental ingestion, perforation of the intestines and penetration in the liver.

Experimental intoxication by the leaves of Melia azedarach (Meliaceae) in cattle

Green leaves of Melia azedarach were administered at single doses ranging from 5 to 30 g/kg bw to 11 calves. Clinical signs were depression, ruminal stasis, dry feces with blood, ataxia, muscle tremors, sternal recumbency, hypothermia and abdominal pain. Serum AST and CPK were increased. Signs appeared from 8 to 24 hours after dosing, and the clinical course lasted from 2 to 72 hours. Three calves dosed with 30g/kg bw died. The macroscopic findings included intestinal congestion, yellow discoloration of the liver, brain congestion and dry feces with blood in the rectum. The liver showed swollen and vacuolated hepatocytes. Necrotic hepatocytes were scattered throughout the parenchyma or concentrated in the periacinar zone. Degenerative and necrotic changes were observed in the epithelium of the forestomachs. There was also necrosis of the lymphoid tissue. Skeletal muscles showed hyaline degeneration and fiber necrosis. The necrotic fragments contained floccular or granular debris with infiltration by macrophages and satellite cells.

Crystal-associated cholangiopathy in sheep grazing Brachiaria decumbens containing the saponin protodioscin

An outbreak of hepatogenous photosensitization is reported in a flock of 28 sheep grazing Brachiaria decumbens in Mato Grosso do Sul State, Central-Western Brazil. Seven lambs and an adult sheep were affected and 6 of them died. Two surviving affected lambs and one lamb without clinical signs had increased serum values of gamma glutamyltransferase, bilirubin, and cholesterol. In two adult unaffected sheep those parameters were within normal values. An adult sheep submitted to necropsy presented moderate body condition, unilateral corneal opacity, drying of the muzzle, moderate jaundice, increased lobular pattern of the liver, and a distended gallbladder. Histological lesions were epithelial degeneration, necrosis, and hyperplasia of small bile ducts. Mild amounts of foamy macrophages were observed, mainly in the centroacinar zone. Diffuse swelling and vacuolation were observed in hepatocytes. Crystal negative images were found within bile ducts, foamy macrophages, and the lumen of some renal tubules. The heart showed multifocal areas of degeneration and necrosis of the muscle fibers. Pasture samples (Brachiaria decumbens) contained 2.36% of protodioscin. No Pithomyces chartarum spores were found in the pasture. Samples from a similar neighboring B. decumbens pasture grazed by cattle without photosensitization contained 1.63% of protodioscin isomers. Outbreaks of photosensitization caused by Brachiaria spp. are common in cattle in the Brazilian Cerrado (savanna) with about 51 million hectares of Brachiaria spp pastures. Sheep farming has been recently developed in this region, and the number of sheep is increasing significantly. Because sheep are more susceptible than cattle to lithogenic saponins, poisoning by Brachiaria should be an important limiting factor for the sheep industry.

Development of conditioned taste aversion to Mascagnia rigida in goats

The aim of this study was to determine whether goats could be averted from consuming Mascagnia rigida, a toxic plant found in the semiarid region of northeastern Brazil. Fourteen male goats not previously familiarized to M. rigida were randomly allocated to two treatment groups: control (treated with 5.5mL water orally by a drenching gun) and lithium group (treated with 100mg LiCl/kg body weight orally by a drenching gun). For conditioning, goats were allowed to feed on M. rigida leaves for 15 min, followed by LiCl or water administration. The time spent on eating M. rigida leaves was measured. The conditioning was repeated daily until the LiCl-treated goats stopped eating M. rigida. On the 10th, 17th, and 24th day after conditioning, extinction trials of the M. rigida aversion were performed in goats by using single-choice tests. There was no difference between the two treatment groups with respect to the consumption of M. rigida on the first day of aversion conditioning, however, controls ingested increasing amounts of the plant on consecutive conditioning days. On the second day, five out of the seven goats in the lithium group did not eat the leaves, but on the third day, all the goats in the lithium group did not ingest M. rigida. This aversion persisted throughout all evaluated days. This indicates that goats can be easily conditioned by using lithium chloride to avoid eating M. rigida temporarily.

Thymic atrophy in cattle poisoned with Solanum glaucophyllum

Solanum glaucophyllum (Sg) [= S. malacoxylon] is a calcinogenic plant inducing "Enzootic Calcinosis" in cattle. The 1,25-dihydroxyvitamin D3, its main toxic principle, regulates bone and calcium metabolism and also exerts immunomodulatory effects. Thymocyte precursors from bone marrow-derived progenitor cells differentiate into mature T-cells. Differentiation of most T lymphocytes is characterized not only by the variable expression of CD4/CD8 receptor molecules and increased surface density of the T cell antigen receptor, but also by changes in the glycosylation pattern of cell surface glycolipids or glycoproteins. Thymocytes exert a feedback influence on thymic non-lymphoid cells. Sg-induced modifications on cattle thymus T-lymphocytes and on non-lymphoid cells were analysed. Heifers were divided into 5 groups (control, intoxicated with Sg during 15, 30 or 60 days, and probably recovered group). Histochemical, immunohistochemical, lectinhistochemical and morphometric techniques were used to characterize different cell populations of the experimental heifers. Sg-poisoned heifers showed a progressive cortical atrophy that was characterized using the peanut agglutinin (PNA) lectin that recognizes immature thymocytes. These animals also increased the amount of non-lymphoid cells per unit area detected with the Picrosirius technique, WGA and DBA lectins, and pancytokeratin and S-100 antibodies. The thymus atrophy found in intoxicated animals resembled that of the physiological aging process. A reversal effect on these changes was observed after suppression of the intoxication. These findings suggest that Sg-intoxication induces either directly, through the 1,25-dihydroxyvitamin D3 itself, or indirectly through the hypercalcemia, the observed alteration of the thymus.

Diagnose of the ingestion of Asclepias mellodora St. Hil. by sheep through microhistological analysis of their digestive contents

Asclepias mellodora St. Hil. is a native acute toxic species frequent in the grasslands of the Buenos Aires province, Argentina, whose toxicity had not been assessed until now. This study evaluates the minimal lethal dose of this species for sheep, and the possibility of microscopically recognizing its fragments in gastrointestinal contents as a complementary diagnostic tool in necropsies. Three Frisona sheep (average LW=55±4.5 kg) were dosed via an esophageal tube with each one of the following doses of asclepias: 8.0, 5.0, 2.0 and 0.8 g DM.kg LW-1. Sheep poisoned with the three higher doses died between 10 and 85 h after intoxication, but those receiving the lower dose did not. During necropsies we: 1) determined the dry weight of the contents of rumen+reticulum, omasum+abomasum, and large intestine, 2) estimated the percentages of asclepias fragments by microanalysis correcting for digestion effects on fragment recognition, and 3) calculated the total mass of asclepias in the digestive tract of each animal. For the three higher doses, the mass of asclepias identified in the total ingesta was 12.3±3.4% of the amount supplied, possibly because of the strong diarrhea its ingestion produced. The percentages of asclepias in rumen+reticulum did not differ from the average quantified for the entire tract. The results of this study indicate that the minimal lethal doses of asclepias for sheep is between 2.0 and 0.8g DM·kg LW-1, and that the microhistological analysis of the rumen+reticulum, the easiest region to sample, can be used to confirm the ingestion of this toxic species, although the estimated percentage will be not a good estimator of the ingested percentage.