Heterologous production of bioactive xenoacremone analogs in Aspergillus nidulans / 中国天然药物

Tyrosine-decahydrofluorene derivatives are a class of hybrid compounds that integrate the properties of polyketides and nonribosomal peptides. These compounds feature a [6.5.6] tricarbocyclic core and a para-cyclophane ether moiety in their structures and exhibit anti-tumor and anti-microbial activities. In this study, we constructed the biosynthetic pathway of xenoacremones from Xenoacremonium sinensis ML-31 in the Aspergillus nidulans host, resulting in the identification of four novel tyrosine-decahydrofluorene analogs, xenoacremones I-L (1-4), along with two known analogs, xenoacremones A and B. Remarkably, compounds 3 and 4 contained a 12-membered para-cyclophane ring system, which is unprecedented among tyrosine-decahydrofluorene analogs in X. sinensis. The successful reconstruction of the biosynthetic pathway and the discovery of novel analogs demonstrate the utility of heterologous expression strategy for the generation of structurally diverse natural products with potential biological activities.

Efeito da Aloe arborescens Miller e da Aloe barbadensis Miller sobre o desenvolvimento vegetativo em Aspergillus nidulans / Effects of the Aloe arborescens Millerand Aloe barbadensis Milleron over vegetative growth in the Aspergillus nidulans

RESUMOA pesquisa de produtos naturais benéficos à saúde humana vem crescendo nos últimos 20 anos. Considerando que as plantas de Aloe são amplamente utilizadas pela população humana, em geral de maneira terapêutica, o objetivo deste estudo foi avaliar os efeitos de Aloearborescens Miller e Aloe barbadensis Miller, sobre o desenvolvimento vegetativo de linhagens normais e mutantes de Aspergillus nidulans. Conídios da linhagem biA1methG1, MSE e CLB3 de A. nidulans, foram inoculados em meio completo sem (Controle) e com extratos das duas espécies incubados por 2, 4, 6 e 8 horas a 37ºC, no escuro. Foi analisado em microscópio óptico, 200 conídios de cada tratamento. Para o desenvolvimento das colônias, as linhagens foram inoculadas no centro das placas juntamente com o meio de cultura sólido e sobre a membrana de diálise, visando a medição do diâmetro e do peso. A análise estatística foi baseada no teste de Tukey e todos os procedimentos experimentais foram conduzidos em triplicata. Todas as linhagens apresentaram interferências positivas quando expostas às plantas de Aloe, porém, de maneira variada. Ambas as espécies aceleraram a germinação em todas as linhagens testadas e atuaram na redução significativa de conídios mortos e/ou malformados. Em relação ao desenvolvimento vegetativo, todos os dados referentes ao peso úmido e diâmetro corrigido dos tratamentos demonstraram progressos, contudo, a razão diâmetro/peso apresentou somente na linhagem MSE, ação favorável dos tratamentos naturais. As informações deste estudo sugerem benefícios de A. arborescens e A. barbadensis, justificando a importância e continuidade da investigação, para melhor elucidar os mecanismos de ação dessas plantas.

ABSTRACTThe researches about natural products that arebeneficial to human health have been growing over the past 20 years. Since Aloe plants are broadly used by the general population, frequently due to therapeutic reasons, the objective of this study was to evaluate the effects of Aloe arborescens Millerand Aloe barbadensis Miller on the vegetative growth of normal and mutant strains of Aspergillus nidulans. The conidia of thebiA1methG1, MSE and CLB3 strains of A. nidulans were inoculated in complete environment without (control) and with extracts of two species of Aloeincubated for 2, 4, 6 and 8 hours at 37˚C. 200 conidia were analyzed by optical microscopy. For the development of the colonies, the strains were inoculated in the center of the plates together with the solid environment of the cultivation and over the dialysis membrane for measuring the diameter and weighing. The statistical analysis was based on the Tukey test and all experimental procedures were performed in triplicate. All strains showed positive interference when exposed to Aloe plants, however, through different manners. Both species have accelerated the germination in all tested strains and acted in the significant reduction of dead and / or malformed conidia. Regarding the vegetative growth, all data related to wet weight and corrected diameter of the treatments revealed progress, however, the ratio diameter/weightpresented improvement only in the MSE lineage, favorable action of natural treatments. The information from this study suggest that A. arborescens and A. barbadensis are beneficial, thus justifying the importance of research maintenance in order to better elucidate the action mechanisms of these plants.

Instituto de Radium de Minas Gerais: vanguarda da radioterapia no Brasil, 1923-1935 / Minas Gerais Radium Institute: at the forefront of radiotherapy in Brazil, 1923-1935

Este artigo propõe estudar os primeiros 12 anos de existência do Instituto de Radium de Minas Gerais, fundado em 1922. Sua atuação na luta contra o câncer no Brasil, ainda pouco conhecida, começa a ser esboçada pelo estudo de documentação institucional inédita. Através de um banco de dados elaborado com informações constantes em seu livro de registro de pacientes, foram feitos levantamentos estatísticos dos tipos de câncer e das formas de tratamento existentes entre 1923 e 1935. Esse livro faz parte de um conjunto de outros cinco recentemente descobertos no Centro de Memória da Medicina/UFMG. A documentação permite resgatar os primórdios das intervenções de radioterapia no país e acompanhar seu desenvolvimento e a influência exercida por esse hospital modelo.

This article proposes to study the first 12 years of the Minas Gerais Radium Institute, founded in 1922. Its work in the fight against cancer in Brazil, albeit still little known, is coming to light as its institutional documents are studied. A database has been prepared using information from its patient register, based on which statistical analyses have been done to identify the types of cancer and treatments available there between 1923 and 1935. This register is one of five recently unearthed at the Medicine Memory Center of the Universidade Federal de Minas Gerais. Through them, the earliest experiments in radiotherapy in Brazil can be reconstituted, and its development and the influence of this model hospital can be mapped out.

O coração irritável nos discursos médicos anglo-americanos no fim do século XIX / Irritable heart syndrome in Anglo-American medical thought at the end of the nineteenth century

Investiga o estatuto e as condições de emergência da categoria nosológica de síndrome do coração irritável presente nos discursos médicos anglo-americanos na segunda metade do século XIX. No contexto da Guerra Civil Americana, examina elementos sócio-históricos que configuraram a atenção médica sobre os sintomas de ordem cardíaca de soldados. Destacam-se os valores morais de médicos-militares frente aos sintomas de medo em combatentes, assim como as hipóteses etiológicas britânicas e norte-americanas que consolidaram o estatuto nosológico do sofrimento dos soldados com palpitações. Propõe análise da especificidade da síndrome do coração irritável frente às categorias nosológicas do medo descritas pela nosologia psiquiátrica atual.

This paper examines the characteristics and the conditions for the emergence of the nosological category known as irritable heart syndrome to be found in Anglo-American medical literature in the second half of the nineteenth century. In the context of the American Civil War, it looks at some of the socio-historical elements, which comprised the medical care given to certain cardiac symptoms shown by soldiers. It emphasizes the moral values influencing the medical attitudes of military physicians towards symptoms of fear experienced by combatants, as well as the British and American etiological theories, which contributed to the nosological characterization of the suffering of soldiers afflicted with palpitations. Finally, it offers a brief analysis of the specific nature of the medical category known as irritable heart syndrome in the light of the categories of fear described by current psychiatric nosology.

Mechanism of sterigmatocystin biosynthesis regulation by pH in Aspergillus nidulans

External pH constitutes one of the most important environmental factors that control growth, metabolism and differentiation in microorganisms, including fungi. We have analyzed the effect of external pH on sterigmatocystin biosynthesis in Aspergillus nidulans. It was observed in repeated experiments that alkaline pH, in opposition to acid pH, increased sterigmatocystin production and the transcript levels of aflR, the master gene that regulates expression of the sterigmatocystin cluster in A. nidulans. It is known that pH effects in fungi operate mostly through the Pal/Pac signaling pathway, originally described in Aspergillus nidulans. Accordingly, we studied the role of this signaling pathway in ST biosynthesis. It was observed that aflR transcript levels were increased in the "alkalinity mimicking" mutant pacCc14 and were minimal in the "acidity mimicking" mutant palA1. No sterigmatocystin was produced by palA1 or pacC- mutants at neither acid or alkaline pH of incubation. Finally, fluG and flbA, genes known to regulate both conidiation and sterigmatocystin synthesis upstream in the regulatory cascade, were up-regulated at alkaline pH.

Identification of nutrient-dependent changes in extracellular pH and acid phosphatase secretion in Aspergillus nidulans

The present study was designed to identify nutrient-dependent changes in extracellular pH and acid phosphatase secretion in the biA1 palC4 mutant strain of Aspergillus nidulans. The palC4 mutant was selected as lacking alkaline phosphatase, but having substantially increased acid phosphatase activity when grown on solid minimal medium under phosphate starvation, pH 6.5. Gene palC was identified as a putative member of a conserved signaling cascade involved in ambient alkaline sensing whose sole function is to promote the proteolytic activation of PacC at alkaline pH. We showed that both poor growth and conidiation of the palC4 mutant strain on solid medium, alkaline pH, were relative to its hypersensitivity to Tris (hydroxymethyl) aminomethane buffer. Also, the secretion of acid phosphatase was repressed when both the wild-type and palC4 mutant strains were grown in low-phosphate yeast extract liquid medium, pH 5.0, indicating that the secretion of this enzyme is not necessary to regenerate inorganic phosphate from the organic phosphate pool present in yeast extract.

Molecular characterization of ABC transporter-encoding genes in Aspergillus nidulans

As a preliminary step towards characterizing genes encoding ATP-binding cassette (ABC) transporters that confer pleiotropic drug resistance in Aspergillus, we used a PCR-based approach to isolate four DNA fragments corresponding to different ABC type transporter genes. DNA sequencing and Southern blot analysis confirmed that they were distinct genes, which were designated abcA-D. One of these genes, abcD, was cloned and characterized. It was found to have a predicted 1,452-amino acid translation product with a calculated molecular mass of 147,467 kDa. The abcD gene specifies a single transcript of approximately 5.0 kb; there was a two- to six-fold enhancement of mRNA levels following exposure to miconazole, camptothecin, methotrexate, and ethidium bromide

Intra and extracellular nuclease production by Aspergillus niger and Aspergillus nidulans

Intra and extracellular nuclease production by strains of "Aspergillus niger"and "Aspergillus nidulans" was estimated using a modified DNAse test agar and cell-0free extract assays. Differences in the production of nucleases by A. niger and A. nidulans were observed. These observations suggest that the DNAse test agar can be helpful for a quick screening for some types of nucleases in filamentous fungi. The assays using cell-free extracts can also be useful for initial characterization of other types of nucleases.

Kinetic studies of nitrite uptake by Aspergillus nidulans

1. In the filamentous mold Aspergillus nidulans, net nitrite uptake is inducible by nitrate and nitrite, is probably different from the nitrate uptake system and is partially repressed by ammonium. 2. The concentration dependence of net nitrite uptake by the biA1 facA303 strain of A. nidulans shows a saturation kinetics with an apparent Km value of 0.64 mM. 3. Strains of A. nidulans carrying the nihA1 and nihA1 chlA14 mutations considerably reduced the affinity of the nitrite uptake system for the substrate when nitrite concentrations ranging from 2.5 mM to 10.0 mM were tested (apparent Km values of 5.9 mM and 23.6 mM, respectively). 4. These results suggest that the toxic effect of nitrite on A. nidulans is due to enhanced nitrite uptake by nihA strains when high concentrations are present in the medium