Search results for " permeability"
showing 10 items of 341 documents
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.
Cell inactivation and membrane damage after long-term treatments at sub-zero temperature in the supercooled and frozen states.
2008
The survival of cells subjected to cooling at sub-zero temperature is of paramount concern in cryobiology. The susceptibility of cells to cryopreservation processes, especially freeze-thawing, stimulated considerable interest in better understanding the mechanisms leading to cell injury and inactivation. In this study, we assessed the viability of cells subjected to cold stress, through long-term supercooling experiments, versus freeze-thawing stress. The viability of Escherichia coli, Saccharomyces cerevisiae, and leukemia cells were assessed over time. Supercooled conditions were maintained for 71 days at -10 degrees C, and for 4 h at -15 degrees C, and -20 degrees C, without additives or…
Intracellular pH-dependent efflux of the fluorescent probe pyranine in the yeast Yarrowia lipolytica.
2001
International audience; 8-Hydroxypyrene-1,3,6-trisulfonic acid (pyranine) can be used as a vital intracellular pH (pH(i)) indicator. In the yeast Yarrowia lipolytica, a partial efflux of the probe was detected by using the pH-independent wavelength of 415 nm. A simplified correction of the fluorescent signals was applied, enabling to show for this species a good near-neutral pH(i) maintenance capacity in a pH 3.9 medium. Octanoic acid, which is known to have toxic effects on yeast, decreased the pH(i) and increased the 260-nm-absorbing compounds leakage. However, this acid inhibited the fluorescent probe efflux linearly with its concentration suggesting a pH(i)-dependent efflux of pyranine …
T-T cell interactions during in vitro cytotoxic T lymphocyte responses. III. Antigen-specific T helper cells release nonspecific mediator(s) able to …
1980
T helper cell induction and the specificity of T cell-mediated help as generated during alloreactive and H-2-restricted, virus- or hapten-specific cytotoxic T lymphocyte (CTL) responses have been compared. With the use of a double-chamber culture system, it was possible to dissect and separately analyze the induction phase of T helper cells from the T helper cell effector function. The data obtained revealed that during alloreactive as well as H-2-restricted T cell responses, antigen-specific T helper cells are induced. Upon specific restimulation of T helper cells, helper cell function is mediated across a cell-impermeable membrane via soluble products in an apparently nonspecific and nonr…
An improved protocol for electroporation ofOenococcus oeniATCC BAA-1163 using ethanol as immediate membrane fluidizing agent
2008
Aims: To finalize an effective and reproducible electroporation procedure to transform Oenococcus oeni ATCC BAA-1163 strain. Methods and Results: The vector pGID052 was selected to optimize the electroporation procedure. Transformation efficiency was 5·8 × 103 per μg of DNA. Transformation was improved when competent cells were prepared with exponential phase cultures; optimum electroporation parameters were an electric pulse of 12·5 kV cm−1, under a resistance of 200 Ω and the presence of 10% (v/v) ethanol in the electroporation buffer (EPB). Conclusions: An effective protocol to transform O. oeni ATCC BAA-1163 strain by electroporation has been obtained by addition of ethanol to the EP…
Adipokines and Endotoxemia Correlate with Hepatic Steatosis in Non-Alcoholic Fatty Liver Disease (NAFLD)
2020
(1) Background: The etiology of non-alcoholic fatty liver disease (NAFLD) is multifactorial. Dietary composition has been implicated as a factor modulating intestinal barrier and could affect disease severity. The aim of this study was to evaluate dietary intake and markers of intestinal permeability in patients with NAFLD. (2) Methods: We enrolled 63 patients with NAFLD and compared them to age-matched controls. (3) Results: body mass index (BMI) and leptin to adiponectin ratio&mdash
Vibrio cholerae cytolysin: assembly and membrane insertion of the oligomeric pore are tightly linked and are not detectably restricted by membrane fl…
2000
AbstractHemolytic strains of Vibrio cholerae secrete a cytolysin that, upon binding as a monomer, forms pentameric pores in animal cell membranes. Pore formation is inhibited at low temperature and in the absence of cholesterol. We here posed the following questions: firstly, can oligomerization be observed in the absence of pore formation? Secondly, is membrane fluidity responsible for the effect of temperature or of cholesterol upon pore formation? The first issue was approached by chemical cross-linking, by electrophoretic heteromer analysis, and by electron microscopy. None of these methods yielded any evidence of a non-lytic pre-pore oligomer. The second question was addressed by the u…
Intestinal drug efflux: formulation and food effects
2001
The intestine, primarily regarded as an absorptive organ, is also prepared for the elimination of certain organic acids, bases and neutral compounds depending on their affinity to intestinal carrier systems. Several of the transport systems known to mediate efflux in the major clearing organs--liver and kidney--are also expressed in the intestine. Examples of secretory transporters in the intestine are P-glycoprotein, members of the multidrug resistance associated protein family, breast cancer resistance protein, organic cation transporters and members of the organic anion polypeptide family. In this communication, the P-glycoprotein mediated intestinal secretion of talinolol, a model compo…
Drug gastrointestinal absorption in rat: Strain and gender differences.
2015
Predictive animal models of intestinal drug absorption are essential tools in drug development to identify compounds with promising biopharmaceutical properties. In situ perfusion absorption studies are routinely used in the preclinical setting to screen drug candidates. The objective of this work is to explore the differences in magnitude and variability on intestinal absorption associated with rat strain and gender. Metoprolol and Verapamil absorption rate coefficients were determined using the in situ closed loop perfusion model in four strains of rats and in both genders. Strains used were Sprague-Dawley, Wistar-Han, Wistar-Unilever, Long-Evans and CD∗IGS. In the case of Metoprolol only…
Provisional Classification and in Silico Study of Biopharmaceutical System Based on Caco-2 Cell Permeability and Dose Number
2013
Today, early characterization of drug properties by the Biopharmaceutics Classification System (BCS) has attracted significant attention in pharmaceutical discovery and development. In this direction, the present report provides a systematic study of the development of a BCS-based provisional classification (PBC) for a set of 322 oral drugs. This classification, based on the revised aqueous solubility and the apparent permeability across Caco-2 cell monolayers, displays a high correlation (overall 76%) with the provisional BCS classification published by World Health Organization (WHO). Current database contains 91 (28.3%) PBC class I drugs, 76 (23.6%) class II drugs, 97 (31.1%) class III d…