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At least 523 records · Page 29Linked to original sources
PubMed1975

Interaction of phospholipid vesicles with cells. Endocytosis and fusion as alternate mechanisms for the uptake of lipid-soluble and water-soluble molecules.

Depending on their phospholipid composition, liposomes are endocytosed by, or fuse with, the plasma membrane, of Acanthamoeba castellanii. Unilamellar egg lecithin vesicles are endocytosed by amoeba at 28 degrees C with equal uptake of the phospholipid bilayer and the contents of the internal aqueous space of the vesicles. Uptake is inhibited almost completely by incubation at 4 degrees C or in the presence of dinitrophenol. After uptake at 28 degrees C, the vesicle phospholipid can be visualized by electron microscope autoradiography within cytoplasmic vacuoles. In contrast, uptake of unilamellar dipalmitoyl lecithin vesicles and multilamellar dipalmitoyl lecithin liposomes is only partially inhibited at 4 degrees C, by dinitrophenol and by prior fixation of the amoebae with glutaraldehyde, each of which inhibits pinocytosis. Vesicle contents are taken up only about 40% as well as the phospholipid bilayer. Electron micrographs are compatible with the interpretation that dipalmitoyl lecithin vesicles fuse with the amoeba plasma membrane, adding their phospholipid to the cell surface, while their contents enter the cell cytoplasm. Dimyristoyl lecithin vesicles behave like egg lecithin vesicles while distearoyl lecithin vesicles behave like dipalmitoyl lecithin vesicles.

Amoeba↗
PubMed1997

Olestra dose response on fat-soluble and water-soluble nutrients in humans.

Ninety normal healthy adults were given 0, 8, 20 or 32 g/d olestra for 8 wk as part of a diet that provided 1 +/- 0.2 of the recommended dietary allowance (RDA) of vitamins A, D, E and K, folate zinc, calcium and iron. In addition, a 20 microg/d supplement of vitamin D was supplied. The diet provided 15% of energy from protein, 35% from fat and 55% from carbohydrate. The purpose of the study was to determine the dose response of olestra on vitamins D, E and K, carotenoids, vitamin B12, folate and zinc. Circulating concentrations of retinol, carotenoids, tocopherols, 25-hydroxy- and 1,25-dihydroxyvitamin D metabolites, phylloquinone, des-gamma-carboxyprothrombin, prothrombin, folate and hematological parameters were measured biweekly, as were urine concentrations of zinc and gamma-carboxyglutamic acid (Gla). Clinical chemistry, urinalysis and vitamin B12 absorption were measured at wk 0 and 8. Olestra reduced serum concentrations of carotenoids, alpha-tocopherol, 25-hydroxyergocalciferol and phylloquinone in a dose-responsive manner. Olestra did not affect Gla excretion, plasma des-gamma-carboxyprothrombin or prothrombin concentrations, prothrombin time, vitamin B12 absorption, overall vitamin D status or the status of folate or zinc. Laboratory evaluations showed no health-related effects of olestra. Subjects in all groups reported common gastrointestinal symptoms such as loose stools, fecal urgency and flatulence, which were transient and generally mild to moderate in severity. These symptoms did not affect protocol compliance or the ability to measure the potential for olestra to affect nutrient availability.

25-Hydroxyvitamin D 2↗