-The-brain-S105-from-suckling-rats-contained-fewer-binding-sites-for-desmosterol-and-cholesterol-than-the-brain-S105-from-weaned-rats-k

However, the concentration of lanosterol binding sites in brain S105 did not show an age-dependent change. The receptor proteins in brain and liver appear to be identical.Molecular crowding and viscosity as determinants of translational diffusion of metabolites in subcellular organelles.The role of molecular crowding and viscosity on the apparent translational diffusion coefficient (ADC) of small metabolites was investigated in different subcellular organelles using the pulse-field gradient spin-echo 1H NMR technique. ADCs of metabolites with increasing radius of gyration (0 A < RG < 4 A) were measured in the cytoplasm of rat or chicken erythrocytes, in the nucleus of chicken erythrocytes, and in isolated rat liver mitochondria. Metabolite ADCs in these systems were compared with the corresponding ADCs determined in model solutions of increasing bulk viscosity but different molecular crowding.

For solutions having the same viscosity, metabolite ADCs decreased with increasing concentration of cosolutes. This effect is adequately described by the modified Stokes-Einstein relationship, ADC = k/RG (1 + 2Phi), where k is a constant for a given temperature and Phi is an obstruction factor reporting the fractional volume of solution occupied by cosolutes, a measure of the molecular crowding in the solution. Cytoplasmic values of Phi for metabolites of different sizes did not depend exclusively on metabolite RG but on additional factors including the chemical nature of the metabolite, the presence of diffusional barriers, and metabolite-specific binding sites. In the case of water, nuclear Phi values approached those of the extracellular space while mitochondrial Phi values were significantly higher than those of the cytoplasm. Taken together, these results reveal important differences in molecular crowding within the different subcellular compartments, suggesting considerable diffusional heterogeneity for small metabolites within the 10590/s0100-879x2003000800009. Epub 2003 Jul 23.Collagens and proteoglycans of the corneal extracellular matrix.

The cornea is a curved and transparent structure that provides the initial focusing of a light image into the eye. It consists of a central stroma that constitutes 90% of the corneal depth, covered anteriorly with epithelium and posteriorly with endothelium. Its transparency is the result of the regular spacing of collagen fibers with remarkably uniform diameter and interfibrillar space. Corneal collagen is composed of heterotypic fibrils consisting of type I and type V collagen molecules. The cornea also contains unusually high amounts of type VI collagen, which form microfibrillar structures, FACIT collagens (XII and XIV), and other nonfibrillar collagens (XIII and XVIII). FACIT collagens and other molecules, such as leucine-rich repeat proteoglycans, play important roles in modifying the structure and function of collagen fibrils.Proteoglycans are macromolecules composed of a protein core with covalently linked glycosaminoglycan side chains.

Four leucine-rich repeat proteoglycans are present in the extracellular matrix of corneal stroma: decorin, lumican, mimecan and keratocan. The first is a dermatan sulfate proteoglycan, and the other three are keratan sulfate proteoglycans. Experimental evidence indicates that the keratan sulfate proteoglycans are involved in the regulation of collagen fibril diameter, and dermatan sulfate proteoglycan participates in the control of interfibrillar spacing and in the lamellar adhesion properties of corneal collagens. Heparan sulfate proteoglycans are minor components of the cornea, and are synthesized mainly by epithelial cells. The effect of injuries on [Collagen. I. Natural condition, chemistry, physics, metabolism].

[ squalene of various types of collagen present in medium-sized arteries].Szymanovicz A, Laurain-Guillaume G, Randoux A, Borel JP.A technique using alternatively dithiothreitol reduction, sonication and pepsin digestions permits the extraction of 75% of the insoluble collagen from human common iliac arteries. The pattern of the collagen types obtained by acrylamide gel electrophoresis is far different from that of the aortic wall: type I averages 44 +/- 14% of the total, type III 48 +/- 14% and a supplementary fraction, probably belonging to type V, 9 +/- 5% of the total in females and 6 The influence of various oxygen tensions upon proline hydroxylation and the metabolism of collagenous and non-collagenous proteins in skin slices.Collagen biosynthesis by human skin fibroblasts. I. Optimization of the culture conditions for synthesis of type I and type III procollagens.

Skin fibroblasts in culture can provide a convenient means to study aberrations of collagen metabolism in a variety of clinical conditions. In Vitamin AD drugs , the culture conditions for the synthesis of procollagen by cultured human skin fibroblasts were optimized by independently varying parameters in the cell culture environment.