Search results for "Diffusion"
showing 10 items of 1615 documents
Comparison of Diffusion MRI Acquisition Protocols for the In Vivo Characterization of the Mouse Spinal Cord: Variability Analysis and Application to …
2016
Diffusion-weighted Magnetic Resonance Imaging (dMRI) has relevant applications in the microstructural characterization of the spinal cord, especially in neurodegenerative diseases. Animal models have a pivotal role in the study of such diseases; however, in vivo spinal dMRI of small animals entails additional challenges that require a systematical investigation of acquisition parameters. The purpose of this study is to compare three acquisition protocols and identify the scanning parameters allowing a robust estimation of the main diffusion quantities and a good sensitivity to neurodegeneration in the mouse spinal cord. For all the protocols, the signal-to-noise and contrast-to noise ratios…
Buccal Delivery of Methimazole as an Alternative Means for Improvement of Drug Bioavailability: Permeation Studies and Matrix System Design
2012
The aim of this study was to investigate the potential for systemic administration of Methimazole (MMI) through the buccal mucosa as an alternative route for drug delivery. Considering that the most important restriction in buccal drug delivery could be the low permeability of the mucosa, the ability of MMI to cross the mucosal barrier was assessed. Permeation of MMI through porcine buccal mucosa was investigated ex vivo using Franz type diffusion cells, buffer solution simulating saliva or natural human saliva as donor phase. The collected data suggested that buccal mucosa does not hinder MMI diffusion and the drug crosses the membrane (J(s) = 0.068 mg cm(-2) h(-1) and K(p) = 0.065 cm h(-1…
Diffusion Tensor Imaging of the Hippocampus in MCI and Early Alzheimer's Disease
2011
The hippocampus is among the first brain structures to be affected by Alzheimer's disease (AD) pathology. Microstructural alterations within this region have been quantified in vivo using diffusion tensor imaging (DTI), a relatively novel MRI-based technique for mapping diffusion properties of water. Existing evidence indicates that DTI-derived mean diffusivity (MD) of the anterior hippocampus is more predictive than ordinary volumetric indices of the degree of episodic memory impairment in patients with early AD. Thus, altered MD of the (anterior) hippocampus might be highly indicative of hippocampal dysfunction, thereby potentially qualifying this measure as a candidate marker for monitor…
Isolation of a high spin form of cytochrome P-450 induced in rat liver by 3-methylcholanthrene.
1983
Abstract A form of cytochrome P-450 (P-450 MC1) has been isolated from the livers of 3-methylcholanthrene-treated rats. The molecular weight is 54,500 and the heme iron is in the high spin configuration which clearly differenciates this form from the other major cytochrome induced by 3-methylcholanthrene (P-450 MC2). Whilst MC2 actively dealkylated 7-ethoxycoumarin and 7-ethoxyresorufin, MC1 was only active with 7-ethoxyresorufin. Ouchterlony immunodiffusion analysis and ELISA showed that anti MC1 and anti MC2 reacted with both MC1 and MC2 but preferentially with the homologous antigen. Both anti MC1 and MC2 cross-reacted strongly with microsomes from 3-methylcholanthrene, Aroclor 1254 and …
Studies on the Biosynthesis of Microsomal Membrane Proteins. Site of Synthesis and Mode of Insertion of Cytochrome b5, Cytochrome b5 Reductase, Cytoc…
1982
The site of synthesis and mechanism of insertion into membranes of several microsomal polypeptides was studied using translation system programmed in vitro with polysomes or with mRNA extracted from free and membrane-bound rat liver polysomes. Primary translation products of cytochrome b5, NADH: cytochrome b5 oxidoreductase, NADPH: cytochrome P-450 oxidoreductase and epoxide hydrolase were isolated by specific immunoprecipitation and compared with the mature proteins. The following observations were made: 1 While cytochrome b5 and NADH: cytochrome b5 oxidoreductase are synthesized in free polysomes, NADPH: cytochrome P-450 oxidoreductase and epoxide hydrolase are made in membrane-bound poly…
Arthus type inflammation with rat immunoglobulins.
1971
Etude comparative des proprietes biologiques des anticorps IgM, IgG1 et IgG2 du rat. Les resultats montrent que le pouvoir agglutinant et lytique des anticorps IgM est respectivement 37 et 100 fois superieur a celui des deux classes d'anticorps IgG. Par contre, en ce qui concerne le phenomene d'Arthus, les anticorps IgM sont moins actifs que les anticorps IgG, si les rapports sont exprimes en poids. Si l'on calcule les rapports par nombre de molecules, les anticorps IgM sont aussi, dans ce cas, plus actifs que les IgG.
Endogenous role of epoxide-hydratase. Development of a steroid epoxide-hydratase assay and properties of the enzyme.
1979
A highly sensitive and rapid radiometric assay for the determination of specific epoxide hydratase activity with a steroid epoxide (16α, 17α-epoxy-1,3,5(10)-estratrien-3-ol, ‘estroxide’) has been developed. The unreacted substrate was separated from the product 1,3,5(10)-estratrien-3,16β,17α-triol by extraction into light petroleum. The product was then extracted into ethyl acetate and measured by scintillation spectrometry. Radiochromatography established that after subtraction of the blank the entire radioactivity measured in the ethyl acetate phase resulted from the product 1,3,5(10)-estratrien-3,16,17-triol, whilst high performance liquid chromatography with the four possible isomers of…
Correlation of brain white matter diffusion anisotropy and mean diffusivity with reaction time in an oddball task.
2008
<i>Background:</i> Reaction time (RT) is a frequently used measure of information processing speed, but the underlying physiological and anatomical conditions are not yet fully understood. A correlation between measures of white matter (WM) ultrastructural properties and RT is expected – particularly for those WM tracts that are involved in the attentional system of the brain. <i>Methods:</i> Diffusion tensor imaging data were acquired in 43 unrelated healthy subjects (age: 22.7 ± 1.8 years), and RT was measured during an attention-requiring visual oddball task in the same scanning session. Voxel-by-voxel and region of interest analyses were performed for the large a…
Improvement in survival of metastatic colorectal cancer: Are the benefits of clinical trials reproduced in population-based studies?
2012
To describe trends in survival of non-resectable metastatic colorectal cancer (MCRC) over a 34-year period in a French population-based registry taking into account major advances in medical therapy.3804 patients with non-resectable metastatic colorectal cancer diagnosed between 1976 and 2009 were included. Three periods (1976-96, 1997-2004 and 2005-09) were considered.The proportion of patients receiving chemotherapy dramatically increased from 19% to 57% between the first two periods, then increased steadily thereafter reaching 59% during the last period (p0.001). Median relative survival increased from 5.9 months during the 1976-96 period to 10.2 months during the 1997-2004 period but, d…
Increased cortical curvature reflects white matter atrophy in individual patients with early multiple sclerosis
2014
Objective White matter atrophy occurs independently of lesions in multiple sclerosis. In contrast to lesion detection, the quantitative assessment of white matter atrophy in individual patients has been regarded as a major challenge. We therefore tested the hypothesis that white matter atrophy (WMA) is present at the very beginning of multiple sclerosis (MS) and in virtually each individual patient. To find a new sensitive and robust marker for WMA we investigated the relationship between cortical surface area, white matter volume (WMV), and whole-brain-surface-averaged rectified cortical extrinsic curvature. Based on geometrical considerations we hypothesized that cortical curvature increa…