Membranes, barrier function

M7. Marzo, I., Susin, S. A., Petit, P. X., Ravagnan, L., Brenner, C., Larochette, N., Zamzami, N., and Kroemer, G., Caspases disrupt mitochondrial membrane barrier function. FEBS Lett. 427, 198-202 (1998). 

Mutants of E. coli lacking the amine-containing lipids PE (psdA null) or PS and PE (pssA null) are viable when grown in the presence of millimolar concentrations of Ca ", Mg, and Sr but have a complex mixture of defects in cell division, growth rate, outer membrane barrier function, energy metabolism, assembly of membrane proteins, and sugar and amino acid transport [1]. 

Hamid K. A. Katsumi H. Sakane T. Yamamoto A. The effects of common solubihzing agents on the intestinal membrane barrier functions and membrane toxicity in rats. Int. J. Pharm. 2009,379, 100-108. 

A great deal of our current understanding of the structure and function of the outer membrane of Gram-negative bacteria has come from studies with Escherichia coli and Salmonella typhimurium. The permeability barrier function of the outer membrane can... 

The significance of the barrier function of membranes has been the topic of considerable research. The blood-brain barrier and the blood-retinal barrier are well understood, and the microscopic structures imparting and controlling barrier properties have been quite thoroughly investigated and the science reviewed [15, 154-155], The structures and functions of ocular membranes specific to transport associated with ophthalmic drug administration also have been topics of extensive research [15, 157-158],... 

Kramer, S. D. Begley, D. J. Abbott, N. J., Relevance of cell membrane hpid composition to blood-brain barrier function Lipids and fatty acids of different BBB models, Am. Assoc. Pharm. Sci. Ann. Mtg., 1999. 

Seams and overlaps must be carefully and completely sealed in order for membranes to function as radon barriers. The choice of seam material varies with the type of sealant. Manufacturers recommendations for sealant, procedure, and safety precautions should be followed. 

Tetra(o-aminophenyl)porphyrin, H-Co-Nl TPP, can for the purpose of electrochemical polymerization be simplistically viewed as four aniline molecules with a common porphyrin substituent, and one expects that their oxidation should form a "poly(aniline)" matrix with embedded porphyrin sites. The pattern of cyclic voltammetric oxidative ECP (1) of this functionalized metal complex is shown in Fig. 2A. The growing current-potential envelope represents accumulation of a polymer film that is electroactive and conducts electrons at the potentials needed to continuously oxidize fresh monomer that diffuses in from the bulk solution. If the film were not fully electroactive at this potential, since the film is a dense membrane barrier that prevents monomer from reaching the electrode, film growth would soon cease and the electrode would become passified. This was the case for the phenolically substituted porphyrin in Fig. 1. 

Wohnsland and Faller ([175] performed measurements using a thin (9-10 //in) supported, phospholipid-free hexadecane layer. To validate their model, they used 32 well-characterized chemically diverse compounds. The permeability values obtained with their model could be correlated with known human absorption values if the maximum permeability obtained at different pH was taken into account. However, several disadvantages are related to this method. For hydrophilic drugs, hexadecane by itself has an increased barrier function in comparison with membranes. In addition, the hexadecane layers are not very stable, which makes this assay difficult to apply as a routine screening method. The advantage of this PAMPA setup is that it appears to be a satisfactory substitute for obtaining alkane-water partition coefficients, which are usually very difficult to measure directly, due to the poor solubility of drug molecules in alkanes. 

The lipid bilayer forms a barrier to transport of matter into and out of the cell. This barrier function is essential since cells need to be able to control their internal milieu, regardless of the external environment. (Some antibiotics work by disrnpting the barrier function of bacterial membranes see Chapter 23). At the same time, some communication of signals and materials across the bilayer must occur. Special mechanisms to do this are a key property of biological membranes. More specifically, these mechanisms are the province of proteins that one finds in these membranes. 

Lowes, S., and N.L. Simmons. 2001. Human intestinal cell monolayers are preferentially sensitive to disruption of barrier function from basolateral exposure to cholic acid Correlation with membrane transport and transepithelial secretion. Pflugers Arch 443 265. 

Besides the biochemical characteristics of the buccal and sublingual membranes, which are responsible for the barrier function and permeability, various factors of the drug molecule influence the extent of permeation through the membranes. 

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