Determinação indireta de N-acetil-L-cisteína por injeção em fluxo empregando Ce(IV) e ferroína

An indirect flow injection spectrophotometric procedure is proposed for the determination of N-acetyl-L-cysteine in pharmaceutical formulations. In this system, ferroin ([Fe(II)-(fen)2]2+) in excess, with a strong absorption at 500 nm, is oxidized by cerium(IV) yielding cerium(III) and [Fe(III)-(fen)2]3+ (colorless), thus producing a baseline. When N-acetyl-L-cysteine solution is introduced into the flow injection system, it reacts with cerium(IV) increasing the analytical signal in proportion to the drug concentration. Under optimal experimental conditions, the linearity of the analytical curve for N-acetyl-L-cysteine ranged from 6.5x10-6 to 1.3x10-4 mol L-1. The detection limit was 5.0x10-6 mol L-1and recoveries between 98.0 and 106% were obtained. The sampling frequency was 60 determinations per hour and the RSD was smaller than 1.4% for 2.2x10-5 mol L-1 N-acetyl-L-cysteine.

Determinação dos parâmetros cinéticos e termodinâmicos da adsorção de L-cisteína em ouro por meio da técnica de microbalança a cristal de quartzo

This article discusses the adsorption kinetics of a L-cysteine monolayer onto a gold surface by means of information obtained through the QCM technique. The results indicate that the adsorption process is rapid and follows the Langmuir isotherm, in which adsorption and desorption are considered. From these measurements the following parameter values were obtained: k d = (4.2 ± 0.4) x 10-3 s-1, k a = 75 ± 6 M-1 s-1, Keq=(1.8 ± 0.3) x 10(4) M-1 and ΔGads = - (5.8 ± 0.2) kcal mol-1.

Preservation of minimally processed 'aurora-1' peaches using additives

'Aurora-1' peaches establishes an interesting alternative as a minimally processed product, due to its characteristics like flavor, color, smell, and also because of its handling resistance. However, it has a short shelf life after a fresh-cut due to enzymatic browning and stone cavity collapse. The main purpose of this research was to test the additive with antioxidant effect to prevent browning in minimally processed 'Aurora-1' peaches. The minimal processing consists of washing, sanitizing, peelings and fruit stone extraction. After that, longitudinal cuts were made to obtain eight segments per fruit. The slices were immersed into the following treatment solutions: control (immersion in 2% ascorbic acid); 2% ascorbic acid + 2% calcium chloride; 1% sodium isoascorbate; 1% citric acid; 1% L-cysteine hydrochloride. The products were placed into rigid polystyrene trays branded MEIWA M-54, covered with 14 µm PVC film (OmnifilmTM) and kept in cold storage at 3ºC ± 2ºC and 65% RH for twelve days, and evaluated each three days. Appraised variables were appearance, soluble solids, titratable acidity, soluble carbohydrates and reducing sugars, total and soluble pectin, ascorbic acid, and peroxidase and polyphenol oxidase enzyme activity. L-cysteine gave to the minimally processed products a shelf life of twelve days, limmited by off-flavor. The treatment with ascorbic acid was efficient to maintainthe ascorbic acid content, with a shelf-life of nine days, limited by enzymatic browning.

Metodologia para preservação do fungicida mancozebe em amostras de solo

The influence of temperature, storage time and the addition of hydrochloride L-cysteine in the preservation of the fungicide mancozeb was studied under field conditions in the surface layer of a Cambisol collected in an area planted with cabbage in Nova Friburgo - RJ, Brazil. The results of this study showed an efficiency of up to 42% in the preservation of the fungicide in the samples treated with cysteine and stored at low temperatures compared to those not treated and kept at room temperature

The myth of nitric oxide in central cardiovascular control by the nucleus tractus solitarii

Considerable evidence suggests that nitroxidergic mechanisms in the nucleus tractus solitarii (NTS) participate in cardiovascular reflex control. Much of that evidence, being based on responses to nitric oxide precursors or inhibitors of nitric oxide synthesis, has been indirect and circumstantial. We sought to directly determine cardiovascular responses to nitric oxide donors microinjected into the NTS and to determine if traditional receptor mechanisms might account for responses to certain of these donors in the central nervous system. Anesthetized adult Sprague Dawley rats that were instrumented for recording arterial pressure and heart rate were used in the physiological studies. Microinjection of nitric oxide itself into the NTS did not produce any cardiovascular responses and injection of sodium nitroprusside elicited minimal depressor responses. The S-nitrosothiols, S-nitrosoglutathione (GSNO), S-nitrosoacetylpenicillamine (SNAP), and S-nitroso-D-cysteine (D-SNC) produced no significant cardiovascular responses while injection of S-nitroso-L-cysteine (L-SNC) elicited brisk, dose-dependent depressor and bradycardic responses. In contrast, injection of glyceryl trinitrate elicited minimal pressor responses without associated changes in heart rate. It is unlikely that the responses to L-SNC were dependent on release of nitric oxide in that 1) the responses were not affected by injection of oxyhemoglobin or an inhibitor of nitric oxide synthesis prior to injection of L-SNC and 2) L- and D-SNC released identical amounts of nitric oxide when exposed to brain tissue homogenates. Although GSNO did not independently affect blood pressure, its injection attenuated responses to subsequent injection of L-SNC. Furthermore, radioligand binding studies suggested that in rat brain synaptosomes there is a saturable binding site for GSNO that is displaced from that site by L-SNC. The studies suggest that S-nitrosocysteine, not nitric oxide, may be an interneuronal messenger for cardiovascular neurons in the NTS

Perspectives of digestive pest control with proteinase inhibitors that mainly affect the trypsin-like activity of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)

The present study describes the main characteristics of the proteolytic activities of the velvetbean caterpillar, Anticarsia gemmatalis Hübner, and their sensitivity to proteinase inhibitors and activators. Midguts of last instar larvae reared on an artificial diet were homogenized in 0.15 M NaCl and centrifuged at 14,000 g for 10 min at 4ºC and the supernatants were used in enzymatic assays at 30ºC, pH 10.0. Basal total proteolytic activity (azocasein hydrolysis) was 1.14 ± 0.15 absorbance variation min-1 mg protein-1, at 420 nm; basal trypsin-like activity (N-benzoyl-L-arginine-p-nitroanilide, BApNA, hydrolysis) was 0.217 ± 0.02 mmol p-nitroaniline min-1 mg protein-1. The maximum proteolytic activities were observed at pH 10.5 using azocasein and at pH 10.0 using BApNA, this pH being identical to the midgut pH of 10.0. The maximum trypsin-like activity occurred at 50ºC, a temperature that reduces enzyme stability to 80 and 60% of the original, when pre-incubated for 5 and 30 min, respectively. Phenylmethylsulfonyl fluoride inhibited the proteolytic activities with an IC50 of 0.39 mM for azocasein hydrolysis and of 1.35 mM for BApNA hydrolysis. Benzamidine inhibited the hydrolysis with an IC50 of 0.69 and 0.076 mM for azocasein and BApNA, respectively. The absence of cysteine-proteinases is indicated by the fact that 2-mercaptoethanol and L-cysteine did not increase the rate of azocasein hydrolysis. These results demonstrate the presence of serine-proteinases and the predominance of trypsin-like activity in the midgut of Lepidoptera insects, now also detected in A. gemmatalis, and suggest this enzyme as a major target for pest control based on disruption of protein metabolism using proteinase inhibitors.

Prevention of enzymatic browning of yacon flour by the combined use of anti-browning agents and the study of its chemical composition

Yacon roots present functional properties because of the high levels of fructooligosaccharides (FOS), which are considered as prebiotic fibers. In addition, yacon roots are rich in phenolic compounds. During the processing of yacon, the freshly cut surface undergoes rapid enzymatic browning. Control of enzymatic browning during processing is very important to preserve the appearance of yacon flour. In this study, it was evaluated the combined effect of anti-browning agents (ascorbic acid, citric acid and L-cysteine) on the inhibition of enzymatic browning of yacon, using Response Surface Methodology. The yacon pre-treated with anti-browning agents in concentrations of 15.0 mM for ascorbic acid, 7.5 mM for citric acid and 10.0 mM for L-cysteine was used for the processing of flour. Yacon flour presented an attractive color and good sensory properties, without residual aroma. The contents of FOS and phenolic compounds obtained in yacon flour were 28.60 g.100 g- 1 and 1.35 g.100 g- 1. Yacon flour can be considered as a potential functional food, especially due to high levels of FOS, which allows for its use in formulation of various foods.

The effect of nitrogen and sulphur fertilization on yield and quality of kohlrabi (Brassica oleracea, L.)

In a greenhouse pot experiment with kohlrabi, variety Luna, we explored the joint effect of N (0.6 g N per pot = 6 kg of soil) and S in the soil (25-35-45 mg kg-1 of S) on yields, on N, S and NO3- content in tubers and leaves, and on alterations in the amino acids concentration in the tubers. S fertilisation had no effect on tuber yields. The ranges of N content in tubers and leaves were narrow (between 1.42-1.48 % N and 1.21-1.35 % N, respectively) and the effect of S fertilisation was insignificant. S concentration in the tubers ranged between 0.59 and 0.64 % S. S fertilisation had a more pronounced effect on the S concentration in leaf tissues where it increased from 0.50 to 0.58 or to 0.76 % S under the applied dose. The NO3- content was higher in tubers than in leaves. Increasing the S level in the soil significantly reduced NO3- concentrations in the tubers by 42.2-53.6 % and in the leaves by 8.8-21.7 %. Increasing the S content in the soil reduced the concentration of cysteine + methionine by 16-28 %. The values of valine, tyrosine, aspartic acid and serine were constant. In the S0, S1, and S2 treatments the levels of threonine, isoleucine, leucine, arginine, the sum of essential amino acids and alanine decreased from 37 to 9 %. The histidine concentration increased with increasing S fertilisation. S fertilisation of kohlrabi can be recommended to stabilize the yield and reduce the undesirable NO3- contained in the parts used for consumption.

Kaurene diterpene induces apoptosis in U87 human malignant glioblastoma cells by suppression of anti-apoptotic signals and activation of cysteine proteases

Gliomas are the most common and malignant primary brain tumors in humans. Studies have shown that classes of kaurene diterpene have anti-tumor activity related to their ability to induce apoptosis. We investigated the response of the human glioblastoma cell line U87 to treatment with ent-kaur-16-en-19-oic acid (kaurenoic acid, KA). We analyzed cell survival and the induction of apoptosis using flow cytometry and annexin V staining. Additionally, the expression of anti-apoptotic (c-FLIP and miR-21) and apoptotic (Fas, caspase-3 and caspase-8) genes was analyzed by relative quantification (real-time PCR) of mRNA levels in U87 cells that were either untreated or treated with KA (30, 50, or 70 µM) for 24, 48, and 72 h. U87 cells treated with KA demonstrated reduced viability, and an increase in annexin V- and annexin V/PI-positive cells was observed. The percentage of apoptotic cells was 9% for control cells, 26% for cells submitted to 48 h of treatment with 50 µM KA, and 31% for cells submitted to 48 h of treatment with 70 µM KA. Similarly, in U87 cells treated with KA for 48 h, we observed an increase in the expression of apoptotic genes (caspase-8, -3) and a decrease in the expression of anti-apoptotic genes (miR-21 and c-FLIP). KA possesses several interesting properties and induces apoptosis through a unique mechanism. Further experiments will be necessary to determine if KA may be used as a lead compound for the development of new chemotherapeutic drugs for the treatment of primary brain tumors.

Desfolha artificial simulando danos de pragas na cultura do girassol (Helianthus annuus L., Asteraceae)

O girassol está sujeito às perdas de área foliar por diferentes fatores, dentre eles os insetos desfolhadores, contra aos quais geralmente são dirigidas aplicações de inseticidas na cultura. A desfolha artificial em plantas de importância econômica é uma metodologia útil na simulação de ataques dessas pragas em lavouras na determinação dos níveis de dano econômico. O objetivo deste estudo foi avaliar componentes de produção das plantas de girassol submetidas a níveis crescentes de desfolha de 0, 10, 25, 50, 75 e 100%, realizada em três distintos estádios fenológicos da cultura, a saber: V6 (seis folhas com no mínimo 4,0 cm de comprimento), R1 (quando a inflorescência circundada pela bráctea imatura torna-se visível) e R5.5 (50% das flores do disco estão fertilizadas ou em antese), perfazendo um total de 18 tratamentos, os quais foram dispostos em blocos ao acaso, com quatro repetições. Para todos os componentes de produção avaliados (diâmetro do capítulo, biomassa total de sementes da planta e biomassa de 100 aquênios) houve efeito significativo da interação dos tratamentos, evidenciando que o efeito da desfolha será dependente do estágio fenológico da planta. O estádio R5.5 foi mais sensível à desfolha, ocasionando perdas em todos os componentes de produção avaliados.

Observações anatômicas em plantas de Coffea arabica L. obtidas por enraizamento de estacas

Uma forma para se obter diminuição significativa de tempo e recursos despendidos nos programas de melhoramento de Coffea arabica L. é a clonagem de híbridos F1 por meio de estacas caulinares. Alguns estudos, em diferentes instituições, foram realizados buscando-se definir um método eficiente para esse tipo de clonagem. Com o objetivo de verificar-se a presença de barreiras anatômicas ao enraizamento de estacas caulinares do cafeeiro e a origem das raízes adventícias, bem como compara-las às raízes provenientes de plantas obtidas por semeadura, foram realizadas análises anatômicas no Departamento de Biologia da Universidade Federal de Lavras (UFLA), Lavras, MG. Utilizaram-se estacas caulinares de cafeeiro dos cultivares Acaiá e Rubi e mudas obtidas por semeadura direta e por estaquia. Os cortes realizados nas estacas caulinares mostraram não existirem barreiras anatômicas ao enraizamento adventício. Nas estacas enraizadas, a origem do primórdio radicular foi próxima aos tecidos vasculares. Cortes histológicos nas raízes formadas nas estacas e nas raízes de mudas obtidas por semeadura confirmaram que elas apresentam as mesmas estruturas primárias.

Comparação do efeito do ácido etilenodiaminotetracético (EDTA) e da heparina sobre os eritrócitos de avestruzes (Struthio camelus L.)

Anticoagulantes com diferentes formas de ação têm sido utilizados na hematologia aviária. Entretanto, poucos estudos foram publicados sobre seu efeito e sobre os parâmetros hematológicos dos avestruzes. Visando a preencher essa lacuna, realizou-se um estudo em que foi comparado o efeito de dois anticoagulantes de rotina (EDTA - 2 mg/mL sangue e da Heparina -10U/mL sangue) sobre os eritrócitos de avestruzes. Para tanto, foram avaliados a integridade, o volume globular e a morfometria dos eritrócitos de amostras sanguíneas de 20 aves, tratadas com ambos os anticoagulantes. A integridade eritrocitária foi estimada pelo grau de hemoglobina livre no plasma, sendo o volume globular obtido pelo método de micro-hematócrito e os dados morfométricos (área, diâmetro maior e menor) calculados automaticamente em sistema computadorizado de imagem digital de alta resolução. A hemólise estimada pela dosagem de hemoglobina plasmática, o volume globular, a área e o diâmetro máximo dos eritrócitos foram significativamente maiores nas amostras tratadas com EDTA. Para melhor preservar a integridade e a morfometria dos eritrócitos, concluiuse que a heparina é um anticoagulante mais adequado que o EDTA para avaliar as discrasias eritrocitárias dos avestruzes.