Resumo Desde os estudos clássicos de Alexander Flemming, as cepas de Penicillium são conhecidas como uma fonte rica em substâncias antimicrobianas. Estudos recentes identificaram novos metabólitos produzidos pela espécie Penicillium sclerotiorum com atividades antibacteriana, anti-incrustante e farmacêutica. Aqui, relatamos o isolamento de uma colônia de P. sclerotiorum (LM 5679) do solo amazônico e relatamos também o estudo baseado em cultura para determinar se ele pode produzir qualquer novo metabólito (s) secundário (s) que não foram relatados até agora para este gênero. Usando um sistema de cultura submerso, os metabólitos secundários foram recuperados por extrato de solvente seguido por cromatografia em camada delgada, ressonância magnética nuclear e espectroscopia de massa. Um novo metabólito secundário foi isolado de P. sclerotiorum (LM 5679); o composto fenólico 5-pentadecil resorcinol que é amplamente conhecido como um antifúngico que é produzido por diversas espécies de plantas. Este metabólito não foi relatado anteriormente em nenhuma espécie de Penicillium, e foi encontrado apenas uma vez em fungos (Fusarium). Aqui, discutimos as atividades conhecidas do 5-pentadecil resorcinol no contexto de seu modo de ação como um estressor hidrofóbico (mediado pela caotropicidade).

Abstract Since the classic studies of Alexander Flemming, Penicillium strains have been known as a rich source of antimicrobial substances. Recent studies have identified novel metabolites produced by Penicillium sclerotiorum that have antibacterial, antifouling and pharmaceutical activities. Here, we report the isolation of a P. sclerotiorum (LM 5679) from Amazonian soil and carry out a culture-based study to determine whether it can produce any novel secondary metabolite(s) that are not thus-far reported for this genus. Using a submerged culture system, secondary metabolites were recovered by solvent extract followed by thin-layer chromatography, nuclear magnetic resonance, and mass spectroscopy. One novel secondary metabolite was isolated from P. sclerotiorum (LM 5679); the phenolic compound 5-pentadecyl resorcinol widely known as an antifungal, that is produced by diverse plant species. This metabolite was not reported previously in any Penicillium species and was only found once before in fungi (that time, in a Fusarium). Here, we discuss the known activities of 5-pentadecyl resorcinol in the context of its mode-of-action as a hydrophobic (chaotropicity-mediated) stressor.

RESUMO O método de homogeneização assintótica é aplicado para obter a solução assintótica formal e uma solução homogeneizada de um problema de valor de contorno de Dirichlet para uma equação elíptica com coeficientes rapidamente oscilantes. A proximidade da solução assintótica formal e a solução homogeneizada para a solução exata é provada, a qual fornece a justificativa matemática do processo de homogeneização. A preservação da simetria e definição positiva do coeficiente efetivo no problema homogeneizado é também provada. Um exemplo é apresentado para ilustrar os resultados teóricos.

ABSTRACT The asymptotic homogenization method is applied to obtain formal asymptotic solution and the homogenized solution of a Dirichlet boundary-value problem for an elliptic equation with rapidly oscillating coefficients. The proximity of the formal asymptotic solution and the homogenized solution to the exact solution is proved, which provides the mathematical justification of the homogenization process. Preservation of the symmetry and positive-definiteness of the effective coefficient in the homogenized problem is also proved. An example is presented in order to illustrate the theoretical results.

We study the charge transport by polarons in conjugated polymers in the presence of impurities. The effects on the polaron motion due to the symmetry of the chain is considered. The polaron dynamics in doped conjugated polymers is numerically studied using the Su-Schrieffer-Heeger (SSH) model combined with the Pariser-Parr-Pople (PPP) model modified to include an external electric field and the Brazovskii-Kirova (BK) symmetry breaking interaction. The time dependent Hartree-Fock approximation is used. The electric field is used to accelerate the polaron in a polymer chain. Polaron trapped by the impurity and polaron-impurity collisions are considered. When the polaron-structure is around the impurity site a charge oscillation can be observed. Nevertheless, when there are collisions between the polaron and the impurity, the polaron-structure can pass, be trapped or be reflected. These effects are determined by the strength of the radical parameter and by the electric field intensity. The effects on the polaron are analyzed and an effective potential is determined. Therefore, the effective potential determines the polaron behavior for each case, as the polaron pass, or it is trapped or reflected by an impurity.

Introduction: Colorectal cancer is the most common tumor in the developed countries, and the number of new cases annualy is aproximately equal for men and women. Several environmental factors can interact in all steps of carcinogenesis. Lately the balance between genetic predisposition and these factors, including nutritional components and lifestyle behaviors, determines individual susceptibility to develop colorectal cancer. The aim of this study is to revise the references about lifestyle include diet, physical exercise, tobacco smoking and use of alcohol, and the risk of colorectal cancer in databases published during 1994-2004. Dietary factors: According to the reports high intake of red meat, and particularly of processed meat and positive energetic balance (high intake of total fat and carbohydrate) was associated with a moderate but significant increase in colorectal cancer risk. Convincing preventive factors include increase consumption of a wide variety of fruit and vegetable, particularly, dark-green leafy, cruciferous, a deep-yellow on tones, and fibre. Lifestyle: Physical activity as a means for the primary prevention of colorectal cancer. There is a probable synergic effect among physical inactivity, high energy intake and obesity and incidence of colorectal cancer. A growing body of evidence supports that avoidance overweight and the use of tobacco and alcohol is recommended to prevent colorectal cancer. Conclusion: Current data suggest that lifestyle modification including proper diet such as the ones rich in vegetable and poor in red meat and fat, regular physical activity and maintaining an appropriate body weight and avoiding the use of tobacco and alcohol may lead to reduce colorectal cancer risk.

Introducción: el cáncer colorrectal es el tumor más frecuente de los países desarrollados, y el número anual de casos nuevos es aproximadamente igual en hombres que en mujeres. Diversos factores ambientales pueden interactuar en todas las etapas de la carcinogénesis. Últimamente, el equilibrio entre la predisposición y estos factores, incluyendo los componentes nutricionales y los hábitos de vida, determina la susceptibilidad individual para el desarrollo de cáncer colorrectal. El objetivo de este estudio es revisar las referencias acerca de los hábitos de vida, incluyendo la dieta, el ejercicio físico, el tabaquismo y el consumo de alcohol, y el riesgo de cáncer colorrectal en las bases de datos publicadas durante 1994-2004. Factores dietéticos: según los informes, la ingestión elevada de carne roja, y especialmente de carne procesada, y el balance energético positivo (ingestión elevada de hidratos de carbono y grasas totales) se asociaba con un aumento moderado pero significativo en el riesgo de cáncer colorrectal. Los factores preventivos convincentes incluyen el aumento de la ingestión de frutas y vegetales variados, particularmente los de hoja verde oscura, las crucíferas, los de tono amarillo oscuro y la fibra. Hábitos de vida: la actividad física como medida de prevención primaria del cáncer colorrectal. Probablemente, exista un efecto sinérgico entre la inactividad física, el consumo elevado de energía y la obesidad, y la incidencia de cáncer colorrectal. Un cuerpo de evidencia cada vez mayor apoya la recomendación de evitar el sobrepeso y el consumo de tabaco y alcohol para prevenir el cáncer colorrectal. Conclusión: los datos actuales sugieren que la modificación de los hábitos de vida, incluyendo una dieta adecuada, como las ricas en vegetales y bajas en carne roja y grasa, la actividad física habitual y el mantenimiento de un peso corporal adecuado, así como la evitación del consumo de tabaco y alcohol pueden reducir el riesgo de cáncer colorrectal.