Search results for "permeability"
showing 10 items of 596 documents
Gliadin, zonulin and gut permeabilità: effects on celiac and non-celiac intestinal mucosa and intestinal cell lines.
2006
Objective. Little is known about the interaction of gliadin with intestinal epithelial cells and the mechanism(s) through which gliadin crosses the intestinal epithelial barrier. We investigated whether gliadin has any immediate effect on zonulin release and signaling. Material and methods. Both ex vivo human small intestines and intestinal cell monolayers were exposed to gliadin, and zonulin release and changes in paracellular permeability were monitored in the presence and absence of zonulin antagonism. Zonulin binding, cytoskeletal rearrangement, and zonula occludens-1 (ZO-1) redistribution were evaluated by immunofluorescence microscopy. Tight junction occludin and ZO-1 gene expression …
Comparative study of the performance of spherical and angular silica and alumina supports in the 1-10-μm size range
1978
Summary Columns packed with four different sets of well characterized packings, spherical silica, angular silica, spherical alumina and angular alumina, varying in mean particle diameter ( d p ) between 1 and 10 μm, were compared. On these columns, the chromatographic permeability ( K 10 ), the column resistance parameter (Φ) and the reduced plate height-velocity dependences were determined under identical and comparable conditions. Discrepancies were found for K 10 and Φ depending on the type of packing and the particle shape. The courses of the h versus v plot, however, were nearly identical for packings with d p > 4 μm, showing a minimum at v ≅ 5 and h = 1.5–2.5 for solutes of k ′ ≅ 0.2 …
Factors affecting the moisture permeability of lipid-based edible films: a review.
2002
Moisture transfers inside food products could be controlled or limited by the use of edible films. These are usually based on hydrophobic substances such as lipids to improve barrier efficiency. Water permeability of films is affected by many factors, depending on both the nature of barrier components, the film structure (homogeneous, emulsion, multilayer, etc.), crystal type, shape, size and distribution of lipids, and thermodynamics such as temperature, vapor pressure, or the physical state of water in contact to the films. After a brief presentation of lipids and hydrophobic substances used as moisture barrier, cited in the scientific literature, this article reviews all of the parameter…
New method to determine the true transmissibilities and permeabilities of oxygen in hydrogel membranes
1999
In the present paper, an electrochemical method to obtain the true transmissibilities and permeabilities of hydrogels to oxygen is proposed. The method involves the measurement of the electric current arising from the flow of oxygen through a potentiostat cell integrated by a top water layer, the hydrogel membrane, and a thin water layer between the membrane and the cathode, where the oxygen is reduced. Varying the thickness of the top water layer, the true permeation characteristics of the hydrogels are obtained. A parallel study was carried out in which the transmissibilities and permeation coefficients were obtained from the variation of the steady state current with the thickness of the…
Influence of sodium lauryl sulphate on the in vitro percutaneous absorption of compounds with different lipophilicity
1997
Abstract The effects of sodium lauryl sulphate (SLS) at different concentrations on the “in vitro” percutaneous absorption of a number of compounds (5-fluorouracil, antipyrine, pentoxifylline, salicylamide, 4-ethylaniline, 4-n-butylaniline and indomethacin) with a wide range of lipophilicity values (log POCT from −0.95 to 4.42) through rat skin were analysed. After pretreatment of the skin with SLS (1% and 5%, w/w) the permeability coefficients increased only for compounds having a log POCT
Permeability and toxicological profile estimation of organochlorine compounds by biopartitioning micellar chromatography
2008
This paper points out the usefulness of biopartitioning micellar chromatography (BMC) as a high-throughput primary screening tool providing key information about the oral absorption, skin permeability (Kp), brain–blood distribution coefficient (BB) and ecotoxicological parameters such as median lethal concentration (LC50) and bioconcentration factors of 15 organochloride compounds. The retention data of compounds in BMC conditions were interpolated in previously developed quantitative–retention activity relationships by our research group. Results show that the compounds studied readily cross the intestinal barrier (oral absorption >ercnt;) and the blood–brain barrier (log BB >p;0.4). In ad…
New Insights of Oral Colonic Drug Delivery Systems for Inflammatory Bowel Disease Therapy
2020
[EN] Colonic Drug Delivery Systems (CDDS) are especially advantageous for local treatment of inflammatory bowel diseases (IBD). Site-targeted drug release allows to obtain a high drug concentration in injured tissues and less systemic adverse effects, as consequence of less/null drug absorption in small intestine. This review focused on the reported contributions in the last four years to improve the effectiveness of treatments of inflammatory bowel diseases. The work concludes that there has been an increase in the development of CDDS in which pH, specific enzymes, reactive oxygen species (ROS), or a combination of all of these triggers the release. These delivery systems demonstrated a th…
Preclinical models for colonic absorption, application to controlled release formulation development.
2018
Oral controlled release (CR) formulations have many benefits and have become a valuable resource for the local and systemic administration of drugs. The most important characteristic of these pharmaceutical products is that drug absorption occurs mainly in the colon. Therefore, this review analyses the physiological and physicochemical features that may affect an orally administered CR product, as well as the different strategies to develop a CR dosage form and the methods used to evaluate the formulation efficacy. The models available to study the intestinal permeability and their applicability to colonic permeability determinations are also discussed.
Lattice-Boltzmann and finite difference simulations for the permeability of three-dimensional porous media
2002
Numerical micropermeametry is performed on three dimensional porous samples having a linear size of approximately 3 mm and a resolution of 7.5 $\mu$m. One of the samples is a microtomographic image of Fontainebleau sandstone. Two of the samples are stochastic reconstructions with the same porosity, specific surface area, and two-point correlation function as the Fontainebleau sample. The fourth sample is a physical model which mimics the processes of sedimentation, compaction and diagenesis of Fontainebleau sandstone. The permeabilities of these samples are determined by numerically solving at low Reynolds numbers the appropriate Stokes equations in the pore spaces of the samples. The physi…
The study of correlation between microstructure of ferrites and their complex permeability spectra
2013
Theoretical model for complex permeability of polycrystalline ferrite (based on effects arising from realities of typical microstructure of sample) is correlated with experimental data. In the case of NiZn-ferrites there is observed a close agreement with the model and the data; for samples of MnZn-ferrites this agreement is only for small-sized cores; for bigger ones the dimensional effects (dimensional resonance) appear and the model cease to be valid.