Tests statistiques et IRM cérébrales en classe de première S

International audienceLes images IRM fonctionnelles (IRMf) ont permis une avancée importante dans la compréhension du fonctionnement cérébral. Loin d’être de simples « photographies » du cerveau en fonctionnement, ces images résultent de protocoles de construction complexes et ont une signification statistique. La compréhension de leur nature statistique est difficile, mais nécessaire pour appréhender leur domaine de validité et construire une attitude critique face à leur utilisation, notamment dans les médias. Les représentations de ces images construites par les élèves ne prennent généralement pas en compte cette dimension statistique. Nous présentons et analysons une séquence d’apprentissage innovante mise en œuvre pour favoriser la compréhension de ce type d’image. Il s’agit d’une séance de modélisation comprenant le paramétrage d’IRMf à l’aide du logiciel EduAnatomist, précédée d’une activité d’appropriation de la notion de test statistique (test T). Nos résultats font apparaitre les difficultés inhérentes à la prise en compte par les élèves de l’aspect statistique des images biologiques. Nous proposons des pistes didactiques pour ouvrir, au moins en partie, certaines des boites noires qui correspondent à la construction de ce type d’image

Profiling Mycobacterium ulcerans with hsp65

Univ Fed Sao Paulo, Escola Paulista Med, Dept Microbiol, BR-04023062 Sao Paulo, BrazilInst Trop Med, B-2000 Antwerp, BelgiumUniv Fed Sao Paulo, Escola Paulista Med, Dept Microbiol, BR-04023062 Sao Paulo, BrazilWeb of Scienc

Plaidoyer pour une sylviculture du Pin d'Alep par les techniciens de terrain

Constatant qu'ils gèrent une forêt où le Pin d'Alep tient une place prédominante, les auteurs proposent d'en améliorer la sylviculture. Ils évoquent les modes de traitement qu'impose l'état des peuplements : la futaie régulière devant être traitée en priorité, la futaie d'aspect jardiné et les peuplements mélangés qui sont les plus délicats à aménager. Après avoir examiné les difficultés rencontrées dans ces aménagements, les auteurs concluent que le mode de sylviculture le plus approprié est la futaie régulière par parquets de 0,5 à 4 ha

Tuberculosis in the Caribbean: using spacer oligonucleotide typing to understand strain origin and transmission.

We used direct repeat (DR)-based spacer oligonucleotide typing (spoligotyping) (in association with double-repetitive element polymerase chain reaction, IS6110-restriction fragment length polymorphism [RFLP], and sometimes DR-RFLP and polymorphic GC-rich sequence-RFLP) to detect epidemiologic links and transmission patterns of Mycobacterium tuberculosis on Martinique, Guadeloupe, and French Guiana. In more than a third of the 218 strains we typed from this region, clusters and isolates shared genetic identity, which suggests epidemiologic links. However, because of limited epidemiologic information, only 14.2% of the strains could be directly linked. When spoligotyping patterns shared by two or more isolates were pooled with 392 spoligotypes from other parts of the world, new matches were detected, which suggests imported transmission. Persisting foci of endemic disease and increased active transmission due to high population flux and HIV-coinfection may be linked to the recent reemergence of tuberculosis in the Caribbean. We also found that several distinct families of spoligotypes are overrepresented in this region

Identificación molecular de micobacterias no tuberculosas mediante el análisis de los patrones de restricción, Colombia 1995-2005

Introduction. Nontuberculous mycobacteria can be saprophytic, pathogenic or opportunistic. The most common diseases produced by these microorganisms are the post-surgical infections due to anesthetic procedures, infections associated with catheters, disseminated cutaneous diseases and pulmonary and central nervous system diseases that especially affect HIV patients. Identification of the nontuberculous mycobacteria can take several weeks and even then, differentiation of complex members is not possible.Objective. The PCR-restriction analysis (PRA) technique was evaluated as a method for genotypic identification of nontuberculous mycobacteria isolated of clinical samples located in the culture collection of the Instituto Nacional de Salud (National Institute of Health), Bogotá, Colombia.Materials and methods. Seventy clinical isolates of nontuberculous mycobacteria stored in 50% glycerol at -70°C were identified by phenotypic techniques. The genotypic identification was made using the PCR-restriction analysis (PRA) using the restriction enzymes BstEII and HseIII, the restriction products were visualized on gels of agarose to 3%, and the concordance between the methodologies was evaluated.Results. A matching of 100% was obtained in the identification of Mycobacterium terrae, M. szulgai, M. avium, M. chelonae and M. scrofulaceum, the matching between M. fortuitum species, M. abscessus, M. gordonae and M. intracellulare varied from 44 to 89%; there was no concurrence in the identification of species M. flavescens and M. malmoense. Conclusions. PRA provided a fast, inexpensive and accurate alternative for the identification of nontuberculous mycobacteria that permited the differentiation among species of a complex and determining the subtype of each species sample.Introducción. Las micobacterias no tuberculosas pueden ser saprofitas, patógenas u oportunistas; las enfermedades más comunes producidas por estos microorganismos son las infecciones posquirúrgicas, principalmente por procedimiento estéticos, infecciones asociadas con catéteres, enfermedades cutáneas diseminadas, enfermedades pulmonares y del sistema nervioso central que afectan especialmente a pacientes infectados con el virus de la inmunodeficiencia humana. La identificación fenotípica de las micobacterias no tuberculosas incluye pruebas microbiológicas y bioquímicas, las cuales pueden tomar varias semanas y algunas veces no logran diferenciar entre los miembros de un complejo.Objetivo. El objetivo fue evaluar la metodología de reacción en cadena de la polimerasaanálisis de restricción, como método de identificación genotípica de micobacterias no tuberculosas aisladas de muestras clínicas que pertenecen a la colección del Instituto Nacional de Salud.Materiales y métodos. Se estudiaron 70 aislamientos clínicos de micobacterias no tuberculosas, criopreservados en glicerol al 50% e identificados mediante metodologías fenotípicas. La identificación genotípica se realizó por reacción en cadena de la polimerasa-análisis de restricción y se evaluó la concordancia entre las metodologías.Resultados. Se obtuvo una concordancia del 100% en la identificación de Mycobacterium terrae, M. szulgai, M. avium, M. chelonae y M. scrofulaceum, en las especies M. fortuitum, M. abscessus M. gordonae y M. intracellulare varió de 44% a 89%; no se obtuvo concordancia en la identificación de las especies M. flavescens y M. malmoense.Conclusiones. El análisis de restricción es una alternativa para la identificación de especies de micobacterias no tuberculosas, rápida, económica y segura para la identificación, que permite la diferenciación entre especies de un complejo y la determinación del subtipo de cada especie

Discovery of a Novel hsp65 Genotype within Mycobacterium massiliense Associated with the Rough Colony Morphology

So far, genetic diversity among strains within Mycobacterium massiliense has rarely been studied. To investigate the genetic diversity among M. massiliense, we conducted phylogenetic analysis based on hsp65 (603-bp) and rpoB (711-bp) sequences from 65 M. massiliense Korean isolates. We found that hsp65 sequence analysis could clearly differentiate them into two distinct genotypes, Type I and Type II, which were isolated from 35 (53.8%) and 30 patients (46.2%), respectively. The rpoB sequence analysis revealed a total of four genotypes (R-I to R-IV) within M. massiliense strains, three of which (R-I, R-II and R-III) correlated with hsp65 Type I, and other (R-IV), which correlated with Type II. Interestingly, genotyping by the hsp65 method agreed well with colony morphology. Despite some exceptions, Type I and II correlated with smooth and rough colonies, respectively. Also, both types were completely different from one another in terms of MALDI-TOF mass spectrometry profiles of whole lipid. In addition, we developed PCR-restriction analysis (PRA) based on the Hinf I digestion of 644-bp hsp65 PCR amplicons, which enables the two genotypes within M. massiliense to be easily and reliably separated. In conclusion, two distinct hsp65 genotypes exist within M. massiliense strains, which differ from one another in terms of both morphology and lipid profile. Furthermore, our data indicates that Type II is a novel M. massiliense genotype being herein presented for the first time. The disparity in clinical traits between these two hsp65 genotypes needs to be exploited in the future study