RESUMEN
Cerebral cavernous malformations (CCMs) are described as vascular lesions consisting of endothelial-lined dilated vessels embedded in a connective tissue sheath without intervening parenchyma between them. Their anatomical connections with the normal blood vessels are still enigmatic and the fine three-dimensional (3-D) organization of these vascular lesions remains to be established. Two stacks of serial histological slices, obtained from two brainstem CCM lesions (from the necropsy of a CCM2 male patient), were stained using Masson's trichrome method and then digitized. Stacks of regions of interest underwent quasi-automatic processing: 1) propagative registering using blockmatching algorithms and Brain Visa programs; 2) 3-D segmentation using Aphelion; 3) display with Anatomist or ImageVis3D. These first histological 3-D reconstructions show the external limits of the caverns defined as the external limit of their collagen sheath. These pictures not only reveal the gross spatial organization of the lesions, but due to their high resolution (4 µm) and with the help of simple anaglyphic 3-D rendering, they also allow the visualization of connections between caverns and very small blood vessels.
Asunto(s)
Neoplasias del Tronco Encefálico/patología , Hemangioma Cavernoso del Sistema Nervioso Central/patología , Interpretación de Imagen Asistida por Computador/métodos , Imagenología Tridimensional/métodos , Autopsia , Humanos , MasculinoRESUMEN
Magnetic resonance imaging (MRI) applied to the hippocampus is challenging in studies of the neurophysiology of memory and the physiopathology of numerous diseases such as epilepsy, Alzheimer's disease, ischemia, and depression. The hippocampus is a well-delineated cerebral structure with a multi-layered organization. Imaging of hippocampus layers is limited to a few studies and requires high magnetic field and gradient strength. We performed one conventional MRI sequence on a 7T MRI in order to visualize and to delineate the multi-layered hippocampal structure ex vivo in rat brains. We optimized a volumic three-dimensional T2 Rapid Acquisition Relaxation Enhancement (RARE) sequence and quantified the volume of the hippocampus and one of its thinnest layers, the stratum granulare of the dentate gyrus. Additionally, we tested passive staining by gadolinium with the aim of decreasing the acquisition time and increasing image contrast. Using appropriated settings, six discrete layers were differentiated within the hippocampus in rats. In the hippocampus proper or Ammon's Horn (AH): the stratum oriens, the stratum pyramidale of, the stratum radiatum, and the stratum lacunosum moleculare of the CA1 were differentiated. In the dentate gyrus: the stratum moleculare and the stratum granulare layer were seen distinctly. Passive staining of one brain with gadolinium decreased the acquisition time by four and improved the differentiation between the layers. A conventional sequence optimized on a 7T MRI with a standard receiver surface coil will allow us to study structural layers (signal and volume) of hippocampus in various rat models of neuropathology (anxiety, epilepsia, neurodegeneration).
Asunto(s)
Hipocampo/anatomía & histología , Imagen por Resonancia Magnética/métodos , Animales , Medios de Contraste , Gadolinio , Imagenología Tridimensional/métodos , RatasRESUMEN
OBJECTIVE: Two clinical strains of Streptococcus pyogenes, 237 and 544, one isolated in Slovakia and the other in Croatia, that were resistant to azithromycin (MIC 8 and 2 mg/L, respectively) but susceptible to erythromycin (MIC 0.5 and 0.12 mg/L, respectively) did not contain any gene known to confer macrolide resistance by ribosomal modification (erm gene) or efflux [mef(A) and msr(A) genes]. The aim of the study was to determine the mechanisms of macrolide resistance in both strains. METHODS: Portions of genes encoding ribosomal proteins L22 and L4, and 23S rRNA (domains II and V) in the two macrolide-resistant strains and in control strains susceptible to macrolides, were analysed by PCR and single-strand conformational polymorphism, to screen for mutations. The DNA sequences of amplicons from resistant strains that differed from those of susceptible strains, in terms of their electrophoretic migration profiles, were determined. RESULTS: S. pyogenes 237 displayed a KG insertion after position 69 in ribosomal protein L4. S. pyogenes 544 contained a C2611U mutation in domain V of 23S rRNA. CONCLUSION: Mutations at a similar position in ribosomal protein L4 and 23S rRNA have been reported previously in macrolide-resistant pneumococci. This report shows that similar mutations can be found in macrolide-resistant S. pyogenes.
Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana/genética , Mutación/genética , Proteínas Ribosómicas/genética , Streptococcus pyogenes/efectos de los fármacos , Streptococcus pyogenes/genética , Adulto , Humanos , Lactante , Macrólidos , Pruebas de Sensibilidad Microbiana/métodos , Pruebas de Sensibilidad Microbiana/estadística & datos numéricos , Homología de Secuencia de Aminoácido , Infecciones Estreptocócicas/tratamiento farmacológico , Infecciones Estreptocócicas/microbiología , Streptococcus pyogenes/aislamiento & purificaciónRESUMEN
Mechanisms of resistance were studied in 22 macrolide-resistant mutants selected in vitro from 5 parental strains of macrolide-susceptible Streptococcus pneumoniae by serial passage in various macrolides (T. A. Davies, B. E. Dewasse, M. R. Jacobs, and P. C. Appelbaum, Antimicrob. Agents Chemother., 44:414-417, 2000). Portions of genes encoding ribosomal proteins L22 and L4 and 23S rRNA (domains II and V) were amplified by PCR and analyzed by single-strand conformational polymorphism analysis to screen for mutations. The DNA sequences of amplicons from mutants that differed from those of parental strains by their electrophoretic migration profiles were determined. In six mutants, point mutations were detected in the L22 gene (G95D, P99Q, A93E, P91S, and G83E). The only mutant selected by telithromycin (for which the MIC increased from 0.008 to 0.25 microg/ml) contained a combination of three mutations in the L22 gene (A93E, P91S, and G83E). L22 mutations were combined with an L4 mutation (G71R) in one strain and with a 23S rRNA mutation (C2611A) in another strain. Nine other strains selected by various macrolides had A2058G (n = 1), A2058U (n = 2), A2059G (n = 1), C2610U (n = 1), and C2611U (n = 4) mutations (Escherichia coli numbering) in domain V of 23S rRNA. One mutant selected by clarithromycin and resistant to all macrolides tested (MIC, >32 microg/ml) and telithromycin (MIC, 4 microg/ml) had a single base deletion (A752) in domain II. In six remaining mutants, no mutations in L22, L4, or 23S rRNA could be detected.