References: Lecithin
J Steroid Biochem. 1989 Aug;33(2):257-62.
Formation of lipoidal steroids in follicular fluid.
Roy R, Belanger A.
MRC Group in Molecular Endocrinology, Le Centre Hospitalier de l'Universite Laval, Ste-Foy, Quebec, Canada.
The presence of high levels of lipoidal pregnenolone in follicular fluid has recently been established although no evidence has been presented concerning its possible origin. The following investigation focuses on the enzymatic conversion of non-conjugated steroids into their lipoidal derivatives in preovulatory follicular fluid obtained from women undergoing in vitro fertilization. Our observations indicated that pregnenolone, an important precursor steroid, was acylated at a similar rate as cholesterol in follicular fluid. Similar studies were subsequently conducted with serum obtained from a pool of normal women and women undergoing follicular stimulation which showed little difference to the results obtained in follicular fluid. Further studies using dehydroepiandrosterone, androst-5-ene-3 beta,17 beta-diol, estradiol and dihydrotestosterone were were also performed to monitor their respective lipoidal conversion percentages in follicular fluid which revealed a marked difference of conversion rates between steroids. The indirect identification of the lipoidal pregnenolone derivatives formed in follicular fluid was also conducted by incubating radiolabelled pregnenolone in follicular fluid. The fatty acid components of the resulting lipoidal pregnenolone derivatives showed a marked resemblance to those of cholesteryl esters formed in plasma by the enzymatic activity of lecithin:cholesterol acyltransferase. The pregnenolone derivatives were comprised predominantly of unsaturated fatty acids such as linoleate, palmitoleate, oleate, linolenate and arachidonate while saturated fatty acids, namely palmitate, constituted 20% of the total lipoidal pregnenolone.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2770299&dopt=Abstract lecithin
Chirality. 2003 Oct;15(8):703-8.
Study of chiral recognition of bilayered phosphatidylcholine vesicles using a helicene probe: characteristic function of cholesterol.
Nakagawa H, Yoshida M, Kobori Y, Yamada K.
Faculty of Pharmaceutical Sciences, Josai University, Saitama, Japan.
Incorporated into bilayered chiral phosphatidylcholine (PC) vesicles, 2-hydroxymethyl[5]thiaheterohelicene (5HM) having a labile helix that functioned as a chirality probe, exhibited induced CD absorptions. The Cotton effects of these absorptions demonstrated opposite signs according to the difference in chirality of PC applied, indicating the chiral recognition of the vesicles. The vesicles formed by PCs with unsaturation or acyl chains shorter than dipalmitoyl-PC (DPPC) exhibited a slightly stronger CD absorptions of 5HM, presumably because of an increase in the constraint by the vesicles. The phenomenon that an increase in fluidity results in a decrease in the CD intensity was examined by CD measurements at various temperatures. The vesicles formed with egg lecithin and bovine heart lecithin also induced CD absorptions of 5HM similar to those of (L)PC vesicles. The influence of cholesterol (Cho) and four kinds of analogs with different structures at the 3- or 5-position of a Cho molecule on the CD intensities was investigated. Following addition of Cho, the CD intensities of 5HM decreased slightly in the (L)DPPC vesicles and increased moderately in the (D)DPPC vesicles. On the other hand, by addition of Cho analogs the CD intensities of 5HM were nearly unchanged in (L)DPPC vesicles and weakened moderately in the (D)DPPC vesicles. Copyright 2003 Wiley-Liss, Inc.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12923808&dopt=Abstract lecithin
Biochim Biophys Acta. 1993 Apr 7;1167(2):142-6.
Fatty acid composition of lecithin is a key factor in bile metastability in supersaturated model bile systems.
Tao S, Tazuma S, Kajiyama G.
First Department of Internal Medicine, Hiroshima University School of Medicine, Japan.
We studied the effect of fatty acid saturation of biliary lecithin on bile metastability, determined by nucleation time, using model bile solutions with identical lipid compositions except for the lecithin species (total lipid concentration, 9 g/dl; cholesterol, 12 mM; lecithin, 31 mM, bile salts, 116 mM). Gel permeation chromatographic studies revealed that nonmicellar cholesterol distribution was inversely related to the degree of unsaturation of the lecithin species. Differential interference contrast microscopy and cholesterol crystal growth assay showed that a lower degree of saturation of the lecithin species was associated with a faster nucleation time and crystal growth rate. These results suggest that vesicular lecithin containing more unsaturated fatty acyl chains binds less tightly to cholesterol as compared with lecithin containing predominantly saturated fatty acids and that the biliary lecithin species modulates cholesterol crystal nucleation in bile. Also, the high ratio of cholesterol to lecithin (more than 1.0) was found in the crystal forming model biles, although the vesicle aggregation was not always observed prior to the cholesterol crystal formation. These findings indicated that there are different processes in cholesterol crystal nucleation, with or without vesicle aggregation, and that such processes depend, in part, on lecithin species in vesicles.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8466941&dopt=Abstract lecithin
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