The RNA interference revolution

The discovery of double-stranded RNA-mediated gene silencing has rapidly led to its use as a method of choice for blocking a gene, and has turned it into one of the most discussed topics in cell biology. Although still in its infancy, the field of RNA interference has already produced a vast array of results, mainly in Caenorhabditis elegans, but recently also in mammalian systems. Micro-RNAs are short hairpins of RNA capable of blocking translation, which are transcribed from genomic DNA and are implicated in several aspects from development to cell signaling. The present review discusses the main methods used for gene silencing in cell culture and animal models, including the selection of target sequences, delivery methods and strategies for a successful silencing. Expected developments are briefly discussed, ranging from reverse genetics to therapeutics. Thus, the development of the new paradigm of RNA-mediated gene silencing has produced two important advances: knowledge of a basic cellular mechanism present in the majority of eukaryotic cells and access to a potent and specific new method for gene silencing.

Formação de estratégia nas micro e pequenas empresas: um estudo no centro-oeste mineiro

Muito se tem dito e escrito sobre as peculiaridades da administração estratégica nas micro e pequenas empresas (MPE). Pouco, entretanto, tem sido feito em termos de trabalho empírico, de cunho quantitativo, quando comparado com o volume de pesquisa que trata de grandes empresas. Nesse sentido, o presente artigo buscou explorar o processo de formação de estratégias nessas empresas, descrevendo seus principais aspectos e, principalmente, verificando se há características desse processo que podem ser associadas a níveis de desempenho acima (e/ou abaixo) da média. Para tanto, utilizou-se a análise de regressão linear múltipla para entender as relações existentes entre as variáveis do processo de formação da estratégia consideradas no estudo e o desempenho; e, ainda, a análise discriminante para determinar os indicadores que diferenciam os grupos de empresas com desempenho acima e abaixo da média. Os resultados apontaram uma tendência à utilização de processos de formação de estratégia deliberados e formais. Por outro lado, reconhecemos também, uma tendência de inovação e mudança. O desempenho acima da média das micro e pequenas empresas, ao que parece, é resultado de uma receita balanceada desses dois ingredientes.

Gestão de capital de giro: contribuição para as micro e pequenas empresas no Brasil

Este artigo trata da importância das questões de capital de giro na gestão das micro e pequenas empresas (MPE) no Brasil. Apresenta-se uma revisão dos conceitos de capital de giro e da importância das MPE no Brasil, além de uma discussão sobre a relevância de uma gestão financeira de curto prazo eficiente para o sucesso de um empreendimento de pequeno porte. Com características bem definidas, as micro e pequenas empresas são responsáveis pela geração da maior parte dos empregos formais no Brasil; apesar disso, ainda não contam com uma estrutura formal de apoio de crédito. O trabalho aponta como fator relevante para o sucesso das micro e pequenas empresas ter um bom gerenciamento do capital de giro. O mau gerenciamento desse fator contribui para o alto índice de mortalidade dessas empresas. Para que o administrador de capital de giro tenha êxito, é importante que haja um forte entrelaçamento com a administração estratégica, para uma solução definitiva do problema, isto é, que consista numa recuperação de lucratividade da empresa e as consequentes recomposições de seu fluxo de caixa, fazendo com que as micro e pequenas empresas consigam chegar à fase de maturidade.

Tecnologia da informação como ferramenta para a análise econômica e financeira em apoio à tomada de decisão para as micro e pequenas empresas

Este artigo apresenta como a tecnologia de informação pode auxiliar na análise econômica e financeira em uma organização, favorecendo a apreciação dos resultados e de seu desempenho, com vistas à garantia da eficiência e da celeridade desse processo, e oferecendo, ainda, visibilidade das demonstrações financeiras para gestores e sócios. Também analisa como a contabilidade gerencial auxilia as micro e pequenas empresas no processo de planejamento e controle, focalizando a estrutura e o funcionamento dos elementos fundamentais para análise das demonstrações financeiras no apoio à decisão.

Estágios de desenvolvimento econômico e políticas públicas de empreendedorismo e de micro, pequenas e médias empresas (MPMEs) em perspectiva comparada: os casos do Brasil, do Canadá, do Chile, da Irlanda e da Itália

Esta pesquisa explora em perspectiva comparada as políticas públicas de empreendedorismo e Micro, Pequenas e Médias Empresas (MPMEs) no Brasil, no Canadá, no Chile e na Itália. A hipótese fundamental é que economias no estágio de inovação tendem a desenvolver mais políticas de empreendedorismo do que as de países no estágio da eficiência. Da mesma forma, países no estágio de inovação tendem a usar menos instrumentos de políticas de MPMEs do que países em estágio de eficiência, quase sempre para incentivar grupos, setores ou regiões em específico. O artigo contribui com a literatura de empreendedorismo ao analisar na prática a convergência/divergência das escolhas de política pública e estágio de desenvolvimento.

Dificuldades e perspectivas no acesso de micro e pequenas empresas a linhas de crédito públicas: o caso de Chapecó

Estas linhas se constituem em políticas que pretendem promover o desenvolvimento econômico e social através da geração de trabalho e renda. Este artigo tem como objetivo analisar se as linhas de crédito públicas - Proger e BNDES/Finame - foram acessadas pelas microempresas no município de Chapecó (SC), suas dificuldades e perspectivas. Caracteriza-se como um estudo exploratório descritivo, com abordagem qualitativa. Do universo investigado constatou-se um baixo índice de acesso, existindo mais dificuldades do que perspectivas concretas de que essas linhas se constituam em políticas de inclusão social que promovam o desenvolvimento para o município e região. A ausência de informações dos públicos-alvo a serem beneficiados por essas políticas mostra a necessidade de reformular as diretrizes de exigência necessárias para o acesso ao crédito.

Arbitrarily primed PCR fingerprinting of RNA and DNA in Entamoeba histolytica

Differences were detected in the gene expression of strains of E. histolytica using RNA (RAP-PCR) and DNA fingerprinting (RAPD). Analysis of the electrophoretic profiles of the gels revealed some polymorphic markers that could be used in the individual characterization of the strains. The 260 bands generated by using five different primers for RAP-PCR, as well as RAPD, were employed in the construction of dendograms. The dendogram obtained based on the RAPD products permitted the distinction of symptomatic and asymptomatic isolates, as well the correlation between the polymorphism exhibited and the virulence of the strains. The dendogram obtained for the RAP-PCR products did not show a correlation with the virulence of the strains but revealed a high degree of intraspecific transcriptional variability that could be related to other biological features, whether or not these are involved in the pathogenesis of amebiasis.

High prevalence of GB Virus C/Hepatitis G Virus RNA among Brazilian blood donors

The aim of this study was to investigate the presence of the Hepatitis G Virus on a population of blood donors from São Paulo, Brazil and to evaluate its association to sociodemographic variables. Two RT-PCR systems targeting the putative 5'NCR and NS3 regions were employed and the former has shown a higher sensitivity. The observed prevalence of HGV-RNA on 545 blood donors was 9.7% (CI 95% 7.4;12.5). Statistical analysis depicted an association with race/ethnicity, black and mulatto donors being more frequently infected; and also with years of education, less educated donors presenting higher prevalences. No association was observed with other sociodemographic parameters as age, gender, place of birth and of residence. DNA sequencing of nine randomly chosen isolates demonstrated the presence of genotypes 1, 2 and 3 among our population but clustering of these Brazilian isolates was not detected upon phylogenetic analysis.

Detection of HIV and HCV RNA in semen from Brazilian coinfected men using multiplex PCR before and after semen washing

INTRODUCTION: Prolonged survival of patients under HAART has resulted in new demands for assisted reproductive technologies. HIV serodiscordant couples wish to make use of assisted reproduction techniques in order to avoid viral transmission to the partner or to the newborn. It is therefore essential to test the effectiveness of techniques aimed at reducing HIV and HCV loads in infected semen using molecular biology tests. METHODS: After seminal analysis, semen samples from 20 coinfected patients were submitted to cell fractioning and isolation of motile spermatozoa by density gradient centrifugation and swim-up. HIV and HCV RNA detection tests were performed with RNA obtained from sperm, seminal plasma and total semen. RESULTS: In pre-washing semen, HIV RNA was detected in 100% of total semen samples, whereas HCV RNA was concomitantly amplified in only one specimen. Neither HIV nor HCV were detected either in the swim-up or in the post-washing semen fractions. CONCLUSIONS: Reduction of HIV and/or HCV shedding in semen by density gradient centrifugation followed by swim-up is an efficient method. These findings lead us to believe that, although semen is rarely found to contain HCV, semen processing is highly beneficial for HIV/HCV coinfected individuals.

Detection of Trypanosoma cruzi and Trypanosoma rangeli infection in triatomine vectors by amplification of the histone H2A/SIRE and the sno-RNA-C11 genes

Trypanosoma rangeli is non pathogenic for humans but of important medical and epidemiological interest because it shares vertebrate hosts, insect vectors, reservoirs and geographic areas with T. cruzi, the etiological agent of Chagas disease. Therefore, in this work, we set up two PCR reactions, TcH2AF/R and TrFR2, to distinguish T. cruzi from T. rangeli in mixed infections of vectors based on amplification of the histone H2A/SIRE and the small nucleolar RNA Cl1 genes, respectively. Both PCRs were able to appropriately detect all T. cruzi or T. rangeli experimentally infected-triatomines, as well as the S35/S36 PCR which amplifies the variable region of minicircle kDNA of T. cruzi. In mixed infections, whereas T. cruzi DNA was amplified in 100% of samples with TcH2AF/R and S35/S36 PCRs, T. rangeli was detected in 71% with TrF/R2 and in 6% with S35/S36. In a group of Rhodnius colombiensis collected from Coyaima (Colombia), T. cruzi was identified in 100% with both PCRs and T. rangeli in 14% with TrF/R2 and 10% with S35/S36 PCR. These results show that TcH2AF/R and TrF/R2 PCRs which are capable of recognizing all T. cruzi and T. rangeli strains and lineages could be useful for diagnosis as well as for epidemiological field studies of T. cruzi and T. rangeli vector infections.

Primary screening of blood donors by nat testing for HCV-RNA: development of an "in-house" method and results

An "in-house" RT-PCR method was developed that allows the simultaneous detection of the RNA of the Hepatitis C Virus (HCV) and an artificial RNA employed as an external control. Samples were analyzed in pools of 6-12 donations, each donation included in two pools, one horizontal and one vertical, permitting the immediate identification of a reactive donation, obviating the need for pool dismembering. The whole process took 6-8 hours per day and results were issued in parallel to serology. The method was shown to detect all six HCV genotypes and a sensitivity of 500 IU/mL was achieved (95% hit rate). Until July 2005, 139,678 donations were tested and 315 (0.23%) were found reactive for HCV-RNA. Except for five false-positives, all 310 presented the corresponding antibody as well, so the yield of NAT-only donations was zero, presenting a specificity of 99.83%. Detection of a window period donation, in the population studied, will probably demand testing of a larger number of donations. International experience is showing a rate of 1:200,000 - 1:500,000 of isolated HCV-RNA reactive donations.

Analysis of correlation between cerebrospinal fluid and plasma HIV-1 RNA levels in patients with neurological opportunistic diseases

The question of whether HIV-1 RNA in cerebrospinal fluid (CSF) is derived from viral replication in the central nervous system or simply reflects the transit of infected lymphocytes from the blood compartment has long been a matter of debate. Some studies found no correlation between CSF and plasma viral load, whereas others did. The lack of a correlation between the two compartments suggests that the presence of HIV-1 RNA is not simply due to the passive passage of the virus from blood to CSF but rather due to intrathecal replication. To evaluate the correlation between plasma and CSF HIV-1 RNA levels and to identify situations in which there is no correlation between the two compartments, seventy patients were prospectively studied. The association between CSF and plasma viral load was evaluated in the total population and in subgroups of patients with similar characteristics. A correlation between the CSF and plasma compartments was observed for patients undergoing highly active antiretroviral therapy (HAART), those with a CD4 T lymphocyte count lower than 200 cells/mm³, and those with increased CSF protein content. On the other hand, no correlation was observed for patients without adequate virological control, who had a CD4 count higher than 200 cells/mm³ and who did not use HAART. The correlation between the two compartments observed in some patients suggests that CSF HIV-1 RNA levels may reflect plasma levels in these subjects. In contrast, the lack of a correlation between the two compartments in patients who were not on HAART and who had normal CSF proteins and a poor virological control possibly indicates compartmentalization of the virus in CSF and, consequently, plasma-independent intrathecal viral replication.