Search results for "Retinol"

Retinol and retinyl esters in pigment epithelium of rats with inherited retinal degeneration

1976

A comparative study of the retinol and retinyl ester concentrations was performed in the retinal pigment epithelium of the normal and affected rats. Our findings indicate that in dystrophic rat retinol content increases, whereas the amount of retinyl esters is always lower than normal. An hypothesis can be made on the deficiency of enzymic activities which regulate retinol retinol and retinyl esters levels in the pigment epithelium.

Retinol-binding protein 4 (RBP4): A new marker of G1 HCV-induced steatosis

2008

Plasma Proteins, Yolk Proteins and Metal-Binding Proteins

1994

The extracellular fluid of the metazoans is not only a transport vehicle but also, for the majority of the body’s cells, their growth environment. Proteins play an important role here, providing colloid-osmotic pressure and acting as buffers. The most important parameter in this respect is their concentration which, depending upon the species, the developmental stage and the physiological conditions, can vary from less than 1 to more than 200 mg/ml (Table 5.1). In addition to these general functions, individual plasma proteins have various specific roles, e.g. in the transport of substances, in defence reactions, in blood clotting or in the solution of clots. At least in the case of the mor…

751 RETINOL-BINDING PROTEIN 4 (RBP4): A NEW MARKER OF G1 HCV-INDUCED STEATOSIS

2008

Development and validation of a fast and sensitive chromatographic assay for all-trans-retinol and tocopherols in human serum/plasma using liquid-liq…

2002

A sensitive HPLC assay for all-trans-retinol, a-tocopherol, and g-tocopherols in human serum and plasma is reported. Sample preparation is performed in one step and involves precipitation of proteins and extraction of lipids with two volumes of an ethanol–chloroform mixture (3:1, v/v) without I.S. addition. After removal of the precipitated protein, 20 ml aliquots of the supernatant (equivalent to 6.7 ml of serum or plasma) were injected into the HPLC system and analyzed using fluorometric detection. RP-HPLC was performed using a C18 S3 ODS2 column with a methanol–water step gradient (97:3 to 100) at 1.0 ml/min. The quantification limit expressed as nanograms of analyte per milliliter of se…

Determination of liposoluble vitamins in cooked meals, milk and milk products by liquid chromatography

2002

A method for the simultaneous determination of liposoluble vitamins in cooked meals was established. Saponification was performed with 50% (w/v) KOH at 80 degrees C, and ascorbic acid was added as antioxidant. The subsequent extraction was carried out with diethyl ether. This was followed by a liquid chromatographic separation on a reversed-phase C18 column with methanol-water (94:6, v/v as the mobile phase. Retinyl acetate was used as the internal standard. The analytical parameters linearity, detection limit (0.19 and 8.33 microg/100 g for retinol and alpha-tocopherol, respectively), precision of the method (RSD=5.24 and 6.99% for retinol and alpha-tocopherol, respectively) and recovery a…

Microparticles derived from marine sponge collagen (SCMPs): preparation, characterization and suitability for dermal delivery of all-trans retinol.

2002

Abstract Collagen microparticles were prepared using marine sponge collagen. For this purpose a previous method by Rossler et al. (J. Microencapsul. 12 (1995) 49) of emulsification and cross-linking of native calf collagen was modified. The modified method for sponge collagen microparticles (SCMPs) achieved a yield of 10%. Scanning electromicroscopic photographs showed spherical particles with a diameter of 120–300 nm and photon correlation spectroscopic measurements indicated particle size range from 126 (±2.9) to 2179 (±342) nm. This broad size distribution was caused by some agglomerates that could not be destroyed by ultrasonication. The surface charge was measured as a function of pH. …

Contribution of vitamin A to the oxidation resistance of human low density lipoproteins.

1995

This study investigated the antioxidant contribution of vitamin A in protecting human low density lipoprotein (LDL) against copper-stimulated oxidation. The presence of small amounts of retinol (0.033 ± 0.012 nmol/mol LDL) and retinyl palmitate (0.036 ± 0.021 nmol/mol LDL) was routinely ascertained in the LDL. A single oral supplementation with 20,000 IU vitamin A caused a two- to three-fold increase of retinol and retinyl palmitate in the LDL isolated 8 h after the supplementation. In comparison to autologous-control LDL, vitamin A-enriched LDL were more resistant to oxidation, as expressed both by a clear delay in the onset of lipid peroxidation and by a reduction of the rate of conjugate…

[37] Interactions between vitamin A and vitamin E in liposomes and in biological contexts

1999

Publisher Summary This chapter discusses the interactions between vitamin A and vitamin E in liposomes. The chapter reviews several studies carried out by incorporating a variable proportion of all- trans -retinol and α-tocopherol in soybean phosphatidylcholine liposomes. It discusses the antioxidant effectiveness of all- trans - retinol in retinal membranes, whether deprived of endogenous α-tocopherol. In the experiments discussed in the chapter, synergistic effects between all- trans -retinal and α -tocopherol are evident in chemical bilayer as well as in natural membranes. In addition, when all- trans -retinol and α –tocopherol are allowed to act in combination, consumption of both antio…

Vitamin A deficiency alters rat lung alveolar basement membrane: reversibility by retinoic acid.

2010

Vitamin A is essential for lung development and pulmonary cell differentiation and its deficiency results in alterations of lung structure and function. Basement membranes (BMs) are also involved in those processes, and retinoic acid, the main biologically active form of vitamin A, influences the expression of extracellular matrix macromolecules. Therefore, we have analyzed the ultrastructure and collagen content of lung alveolar BM in growing rats deficient in vitamin A and the recovering effect of all-trans retinoic acid. Male weanling pups were fed a retinol-adequate or -deficient diet until they were 60 days old. A group of vitamin A-deficient pups were recovered by daily intraperitonea…