Bioassays for detecting residues of fungitoxic compounds through bioautography, bioelectrophoresis and thin-laver diffusion

Comparou-se a técnica de bioautografia em camada fina com bioeletroforese e difusão em camada fina na detecção de resíduos de fungicidas, tendo como fungo-teste, o Thielaviopsis paradoxa. O método de bioeletroforese e a técnica de difusão em camada fina modificada são descritos e utilizados pela primeira vez. Os métodos foram comparados em bioensaios empregando-se os fungicidas mancozeb, captafol, benomil e triadimefon em diferentes concentrações. As concentrações mínimas detectadas não variaram com as técnicas utilizadas, mas sim com os fungicidas. Obtiveram-se concentrações mínimas de 0,04, 0,06, 1,25 e 1,90 ppm para benomil, captafol, triadimefon e mancozeb, respectivamente. A técnica de bioeletroforese proporcionou maior zona de inibição do fungo-teste quando se empregou alta concentração de fungicidas. A técnica de difusão em camada fina, por não demandar aparelhagem sofisticada, foi tão eficiente como a bioautografia, constituindo-se em método simples e rápido para a detecção e avaliação de resíduos de compostos fungitóxicos.The bioautographic technique on thin-layer chromatograms was compared to bioelectrophoresis and thin-layer diffusion for detecting fungitoxic compound by using Thielaviopsis paradoxa as test fungus. The bioelectrophoresis and thin-layer diffusion methods were described and employed for the first time. The methods were illustrated by bioassaying the fungicides mancozeb, captafol, benomyl and triadimefon in different concentrations. The minimum concentration of fungitoxic compounds detected was the same for three techniques employed, but it did vary with the fungicides. The minimum concentrations detected of benomyl, captafol, triadimefon and mancozeb were 0.04, 0.06, 1.25 and 1.90 ppm, respectively. The bioelectrophoresis technique gave the highest inhibition zone of the test fungus by using higher concentrations of the fungicides. The thin-layer diffusion technique may be of great value, because it is a simple, rapid, sensitive as the bioautographic technique on the detection of fungitoxic compounds

Peptides Derived from Mycobacterium leprae ML1601c Discriminate between Leprosy Patients and Healthy Endemic Controls

The stable incidence of new leprosy cases suggests that transmission of infection continues despite worldwide implementation of MDT. Thus, specific tools are needed to diagnose early stage Mycobacterium leprae infection, the likely sources of transmission. M. leprae antigens that induce T-cell responses in M. leprae exposed and/or infected individuals thus are major targets for new diagnostic tools. Previously, we showed that ML1601c was immunogenic in patients and healthy household contacts (HHC). However, some endemic controls (EC) also recognized this protein. To improve the diagnostic potential, IFN-γ responses to ML1601c peptides were assessed using PBMC from Brazilian leprosy patients and EC. Five ML1601c peptides only induced IFN-γ in patients and HHC. Moreover, 24-hour whole-blood assay (WBA), two ML1601c peptides could assess the level of M. leprae exposure in Ethiopian EC. Beside IFN-γ, also IP-10, IL-6, IL-1β, TNF-α, and MCP-1 were increased in EC from areas with high leprosy prevalence in response to these ML1601c peptides. Thus, ML1601c peptides may be useful for differentiating M. leprae exposed or infected individuals and can also be used to indicate the magnitude of M. leprae transmission even in the context of various HLA alleles as present in these different genetic backgrounds

Context-dependence of race self-classification : results from a highly mixed and unequal middle-income country

Ethnic-racial classification criteria are widely recognized to vary according to historical, cultural and political contexts. In Brazil, the strong influence of individual socio-economic factors on race/colour self-classification is well known. With the expansion of genomic technologies, the use of genomic ancestry has been suggested as a substitute for classification procedures such as self-declaring race, as if they represented the same concept. We investigated the association between genomic ancestry, the racial composition of census tracts and individual socioeconomic factors and self-declared race/colour in a cohort of 15,105 Brazilians. Results show that the probability of self-declaring as black or brown increases according to the proportion of African ancestry and varies widely among cities. In Porto Alegre, where most of the population is white, with every 10% increase in the proportion of African ancestry, the odds of self-declaring as black increased 14 times (95%CI 6.08–32.81). In Salvador, where most of the population is black or brown, that increase was of 3.98 times (95%CI 2.96–5.35). The racial composition of the area of residence was also associated with the probability of selfdeclaring as black or brown. Every 10% increase in the proportion of black and brown inhabitants in the residential census tract increased the odds of self-declaring as black by 1.33 times (95%CI 1.24–1.42). Ancestry alone does not explain self-declared race/colour. An emphasis on multiple situational contexts (both individual and collective) provides a more comprehensive framework for the study of the predictors of self-declared race/colour, a highly relevant construct in many different scenarios, such as public policy, sociology and medicine

Pathogen-Specific Epitopes as Epidemiological Tools for Defining the Magnitude of Mycobacterium leprae Transmission in Areas Endemic for Leprosy

During recent years, comparative genomic analysis has allowed the identification of Mycobacterium leprae-specific genes with potential application for the diagnosis of leprosy. In a previous study, 58 synthetic peptides derived from these sequences were tested for their ability to induce production of IFN-γ in PBMC from endemic controls (EC) with unknown exposure to M. leprae, household contacts of leprosy patients and patients, indicating the potential of these synthetic peptides for the diagnosis of sub- or preclinical forms of leprosy. In the present study, the patterns of IFN-γ release of the individuals exposed or non-exposed to M. leprae were compared using an Artificial Neural Network algorithm, and the most promising M. leprae peptides for the identification of exposed people were selected. This subset of M. leprae-specific peptides allowed the differentiation of groups of individuals from sites hyperendemic for leprosy versus those from areas with lower level detection rates. A progressive reduction in the IFN-γ levels in response to the peptides was seen when contacts of multibacillary (MB) patients were compared to other less exposed groups, suggesting a down modulation of IFN-γ production with an increase in bacillary load or exposure to M. leprae. The data generated indicate that an IFN-γ assay based on these peptides applied individually or as a pool can be used as a new tool for predicting the magnitude of M. leprae transmission in a given population