References: Lecithin
J Microencapsul. 1995 Nov-Dec;12(6):609-15.
Multiple emulsion-based systems carrying insulin: development and characterization.
Singh S, Singh R, Vyas SP.
Pharmaceutics Laboratories, Department of Pharmaceutical Sciences, Sagar (M.P.), India.
An insulin delivery system based on liquid surfactant membranes has been developed. The formulation was based on a w/o/w emulsion where an organic membrane separated two aqueous phases and the internal aqueous phase contained insulin. Sesame and cotton seed oils were used as organic membranes. In order to facilitate the transportation of glucose across the organic membrane various additives such as calcium stearate, lecithin, cholesterol, hexamine, stearic acid and glyceryl tristearate were used. The additives were found to be successful carriers for the transportation of glucose to the internal aqueous phase. Similarly, viscosity enhancers, e.g. cetostearyl alcohol, in the organic phase enhanced the immobilization of insulin. Various parameters affecting the stability of the emulsions were established. The developed system was characterized for insulin activity and insulin efflux profile.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8558383&dopt=Abstract lecithin
Farmaco. 1997 Nov;52(11):645-52.
1-Thiopsoralen, a new photobiologically active heteropsoralen. Photophysical, photochemical and computer aided studies.
Vedaldi D, Piazza G, Moro S, Caffieri S, Miolo G, Aloisi GG, Elisei F, Dall'Acqua F.
Department of Pharmaceutical Sciences, University of Padova, Italy.
1-Thiopsoralen (7H-thieno[3,2-g]benzofuran-7-one) 1, a lead compound of a series of heteropsoralens, was investigated. The electronic transitions involved were studied. Fluorescence quantum yield is very low, while laser flash photolysis showed that the triplet state is practically the sole transient of 1. Fluorescence quantum yield (phi F) and triplet lifetime (tau F) as well as triplet quantum yield (phi T) and lifetime (tau T) were determined. The production of singlet oxygen was also evaluated by photophysical measurements. Photophysical data suggest that DNA photobinding of 1, owing to short fluorescence lifetime value and high triplet quantum yield, occurs likely through triplet mechanism. Interactions between 1 and DNA were studied both in the ground and the excited state. In the ground state 1 undergoes intercalation inside duplex DNA. This fact is also supported by molecular modeling studies. By UVA-light activation 1 photobinds covalently to DNA forming mono and diadducts. The furan side 1-thymine monoadduct, isolated from DNA photomodified by thiopsoralen, shows a cis-syn stereochemistry, in agreement with quantum mechanics studies. Compound 1 photobinds also with linolenic acid, component of lecithins, giving a C4-cycloaddition, and supporting that this compound also induces photolesions at the level of cell membrane, like psoralen. Compound 1 exhibits strong skin-phototoxicity.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9550088&dopt=Abstract lecithin
Biol Cell. 1989;66(1-2):149-53.
Cellular permeation pathways in a leaky epithelium: the human amniochorion.
Hardy MA, Leonardi RT, Scheide JI.
Department of Obstetrics, Gynecology & Reproductive Science, Mount Sinai School of Medicine, City University of New York.
The presence of cellular permeation pathways in human fetal membranes at term was evaluated. Electrical parameters (transepithelial potential [TEP], and conductance [Gt], and intracellular potentials [cell PD]), and water and urea diffusional coefficients (Pdw, Pdu), were determined in Ussing-like chambers. In amniochorion, the TEP was practically 0 (0.1 +/- 0.03 mV), and the Gt very high (144 +/- 14 mS/cm2). The Cell PD of amnion cells was -37 +/- 3 mV. Increasing the [K+] of the amniotic perfusate between 5.8 and 125.8 mM depolarized the cells with a slope of 23 mV. The deletion of Na+ hyperpolarized the cells, whereas amiloride and ouabain depolarized them. The Pdw and Pdu were determined in intact amnion and chorion and in their epithelial cell layers. The Pdw/Pdu ratio in amnion was 4.0, and 7.0 in its cell layer; the ratio in chorion was 2.5, and 3.3 in its cell layer. The amniochorion is a leaky structure, but its cellular layers possess definite transcellular permeation pathways. The ionic conductances in amnion cells are complex, with the Cell PD being determined by at least K+ and Na+ conductances, and ouabain- and amiloride-sensitive pathways. The amnion is a more effective diffusional barrier to water and urea than chorion is; its diffusional characteristics are comparable to those of nystatin-treated lecithin: cholesterol bilayers and the membranes of human erythrocytes.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2804455&dopt=Abstract lecithin
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