Tissues, permeability

Although the pH-partition hypothesis and the absorption potential concept are useful indicators of oral drug absorption, physiologically based quantitative approaches need to be developed to estimate the fraction of dose absorbed in humans. We can reasonably assume that a direct measure of tissue permeability, either in situ or in vitro, will be more likely to yield successful predictions of drug absorption. Amidon et al. [30] developed a simplified film model to correlate the extent of absorption with membrane permeability. Sinko et al. [31] extended this approach by including the effect of solubility and proposed a macroscopic mass balance approach. That approach was then further extended to include facili-... 

Several mechanisms have been proposed to explain HIAR the cleavage of protein-protein cross-links,3,6 the disruption of cross-links involving calcium ions,5 an increase in tissue permeability for antibodies, and the removal of trace amounts of paraffin in the tissues. However, recent studies have indicated that the fundamental mechanism of HIAR is based on the cleavage of protein-protein cross-links. 

Grass GM, Sweetana SA (1988) In vitro measurement of gastrointestinal tissue permeability using a new diffusion cell. Pharm Res 5 372-376... 

Protein kinase Connexin Tissue Permeability g. Reference... 

Nasal tissue from animals can be mounted in Ussing chambers, permitting experiments similar to those performed in cell cultures to be performed in intact tissues. The nasal tissues of rabbits, dog, sheep, and cattle have been used and such experiments provide the reassurance that the ex vivo system is representative of the nasal mucosa in vivo. The limitations of this technique are the requirement for the use of fresh tissue, the limited duration of tissue viability, and interspecies variation in tissue permeability and metabolic capacity. 

Special properties of polyvinyl acetate are the very high hydrogen bonding and adherence to moist surfaces, and the self-plastization by absorption of less than 10% by weight of water. The absorption of water is sufficient to make the polyvinyl acetate flexible with natural body movement, pliable on moist tissue, permeable to water vapor and air, but not permeable to bacteria. Therefore, copolymers comprising polyvinyl acetate were synthesized for nonaqueous barrier dressings. Monomers were included to lightly crosslink the polyvinyl acetate. 

Abstract Electrical conductivity of agarose gels in 0.15 M KC1 was measured. From the experimental data, a functional relation of solute diffusivity to tissue permeability and solute size was derived. This relationship agreed with the experimental results on macromolecule diffusivity in agarose gel published in the literature. 

One of the earliest indications of ozone injury on several plant species is an upper surface discoloration with a waxy appearance. This symptom often disappears completely a few hours after exposure is terminated. High dosages of ozone cause permanent necrotic lesions on susceptible leaf tissue. Permeability of cell membranes is apparently disrupted, and cell contents are allowed to leak into the intercellular spaces producing a water-soaked appearance. Upon drying, the tissue will totally collapse and turn white or various shades of brown. Lesions which extend through the entire thickness of the leaf are commonly referred to as bifacial... 

Sutton, S.C. Forbes, A.E. Cargill, R. Hochman, J.H. LeCluyse, E.L. Simultaneous in vitro measurement of intestinal tissue permeability and transepithelial electrical-resistance (teer) using sweetana grass diffusion cells. Pharm. Res. 1992, 9, 316-319. 

In pharmaceutical research there is a need for cell-based assays that have some predictive capability with regard to tissue permeability properties of lead compounds. These assays are generally used after high-throughput screening procedures have identified compounds with the desired pharmacological properties. Cell-based assays can be used to identify those leads that have the desired properties with regard to tissue permeability, and then animal models may be used as a final screen. This approach is not only more cost-effective but also minimizes the use of animal resources. 

Grass GM and Sweetana SA. In vitro Measurement of Gastrointestinal Tissue Permeability Using a New Diffusion Cell. Pharm Res 1988 5(6) 372-376. 

Prolactin, growth hormone, and estradiol appear to be important accessory regulators for prostatic tissue permeability, receptor binding, and testosterone synthesis. 

Experimentally Determined Tumor Normal Tissue Permeability Ratios3... 

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