References: Lecithin
Eur Biophys J. 1993;22(1):5-11.
Halide permeation through three types of epithelial anion channels after reconstitution into giant liposomes.
Duszyk M, Liu D, French AS, Man SF.
Department of Medicine, University of Alberta, Edmonton, Canada.
Anion-selective channels from apical membranes of cultured CFPAC-1 cells were isolated and incorporated into giant liposomes for patch clamp recording. Liposomes were formed from L-alpha-lecithin by a dehydration-hydration method. Ion channels were characterized using the excised inside-out patch clamp configuration. The most commonly observed anion channels were similar to those observed in native epithelial tissues. The linear 20 pS Cl- channel had the halide permeability sequence Cl- > I- > or = Br- > F-, and showed anomalous mole-fraction behavior in solutions containing different proportions of Cl- and F- ions. The autwardly rectifying Cl- channel had the halide permeability sequence I- > Br- > Cl- > F-, and also showed anomalous mole-fraction behavior, indicating that both these channels probably contain multi-ion pores. The third, voltage-dependent anion channel showed at least five different substrates, had a conductance of 390 pS in the main state, and showed two types of kinetics, fast (openings and closings < 1 ms), and slow (openings and closings > 1 s). The channel was seen more frequently after reconstitution into giant liposomes than in intact cells. It was not selective amongst the halides, and there was no deviation from a linear dependence of relative current on molar fractions, indicating relatively simple permeation through the pore. Differences in halide permeabilities suggest that different anion channels may be related to different membrane proteins. Comparison with the chloride channel proteins isolated biochemically from epithelial cell membranes is discussed.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7685690&dopt=Abstract lecithin
Magn Reson Med. 1992 Feb;23(2):275-86.
Permeability of liposomal membranes to water: results from the magnetic field dependence of T1 of solvent protons in suspensions of vesicles with entrapped paramagnetic ions.
Koenig SH, Ahkong QF, Brown RD 3rd, Lafleur M, Spiller M, Unger E, Tilcock C.
IBM T. J. Watson Research Center, Yorktown Heights, New York 10598.
The diffusive permeability to water molecules, Pd, of lipid vesicles with entrapped paramagnetic solute ions can be determined rapidly from analysis of the magnetic field dependence (nuclear magnetic relaxation dispersion, or NMRD profile) of T1 of exterior solvent water protons. Such data yield tau, the mean lifetime of solvent molecules inside the vesicles, from tau = (fT1Para) - T1Ves, where f is the volume fraction of entrapped water, T1Para is the observed T1 corrected for buffer background, and T1Ves is the relaxation time of water protons in the entrapped solution. For small spherical unilamellar vesicles of inner radius R, Pd = R/3 tau, f can be obtained accurately from knowledge of both the concentration of Gd(DTPA)2- in the solution in which the vesicles were formed and the average concentration of ions in the final sample. At low temperatures, in the limit of slow exchange, T1Para becomes independent of field and tau = fT1Para; the observation of a field-independent profile is a control that confirms that no paramagnetic material is external to the vesicles. We have measured T1Para, using a field-cycling relaxometer, for suspensions of POPC (1-palmitoyl-2-oleoyl-lecithin) vesicles with 100-500 mM entrapped Gd(DTPA)2- and membrane concentrations of cholesterol ranging from 0 to 40 mol %. These profiles, which span the field range 0.01-50 MHz proton Larmor frequency, were taken at 5, 15, 25, and 35 degrees C. Concentrations of Gd(DTPA)2- were determined independently by both ICP analyses and NMRD methods. Values for Pd for vesicles with 100 mM Gd(DTPA)2- and outer diameters 100 nm +/- 20%, as determined by quasielastic light sc
Probl Khig. 1993;18:50-62.
[An experimental study of the atherogenic effect of the vanadium and nickel contained in drinking water when combined]
[Article in Bulgarian]
Vodichenska Ts, Budeva B.
During an annual toxicological experiment on white male rats, receiving orally vanadium (V) and nickel (Ni) in doses, equivalent to the accepted in Bulgaria, maximum allowable norms for ist category surface waters (respectively 0.005 mg/kg and 0.0025 mg/kg), 2 and 6 times and 20 and 60 times higher, is studied the atherogenic effect of the latter after the indices: total cholesterol, beta-lipoproteins, phospholipids, lecithin, total lipids, total protein and hexoses of glycoproteins in the serum; oxyproline, hexauranium acids and hexoses, hexosamines, connected with the proteins in the aorta. It is established that V and Ni in chronic combined effect in doses, equivalent to those accepted in Bulgaria, in maximum allowable concentrations for Ist category waters and surpassing them 2 and 6 time respectively, lead to no changes in the biochemical composition of the connective tissue of the aorta and to disorders in the lipidic and protein metabolism, while in higher doses is registered an increase of the glucoproteins and decrease in the glucosaminglycans in the aorta and decrease of the total lipids in the serum. The results point out, that V and Ni in the conditions of the experiment don't accelerate the processes of the natural ageing of the vessels and have no atherogenic effect. Juxtaposing the data for V and Ni concentrations in drinking waters in Bulgaria with our results give grounds to reckon, that their raised content in drinking waters in some regions do not represent a risk factor for the development of atherosclerosis.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7845974&dopt=Abstract lecithin
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