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G Nalbone

Publications and source records attributed to G Nalbone.

68 records · Page 4Linked to original sources
PubMed1979

The apoprotein fraction of the bile lipoprotein complex: isolation, partial characterization and phospholipid binding properties.

A bile apoprotein fraction (Apo BLC) was isolated by preparative isoelectric focusing (I.E.F.) from the detergent-free form of the bile lipoprotein complex (BLC). Analytical I.E.F. of Apo BLC yields a characteristic and reproducible pattern of two narrow acidic bands (pI 4,8-5,0). This apoprotein presents a strong tendency to undergo self-aggregation in aqueous buffer. A low molecular weight constituent of Apo BLC has been isolated after gel filtration, its mean Mw is estimated by SDS-PAGE at 7,500 daltons. The binding capacity of Apo BLC for phospholipids was investigated on dimyristoylphosphatidylcholine liposomes by gel filtration and zone electrophoresis. The resulting structures, larger than the original single-shelled vesicles, acquire and anodic electrophoretic mobility. Apo BLC has a weaker affinity for lysophosphatidylcholines: these phospholipids decrease the degree of aggregation of the apoprotein. These studies contribute additional data concerning the high affinity of Apo BLC for phosphatidylcholines, which are the major phospholipid constituents of bile. The discussion deals with the fact that association of Apo BLC with bile phosphatidylcholines may present some implications in the pathogeny of LpX and in the process of intestinal fat absorption.

Apolipoproteins↗
PubMed1978

Possible roles of bile lipids and colipase in lipase adsorption.

The adsorption isotherms of bile salts, phospholipids, and cholesterol were determined with siliconized glass beads. It was observed that the molar fractions of cholesterol, phospholipid, and bile polypeptide fractions increased simultaneously and considerably on the surface of the beads in comparison to the corresponding fractions found in bile. The composition of the adsorbed film is approximately 1 cholesterol: 2 phospholipid: 3 bile salt molecules. The performed complex of lipase, colipase, and bile lipids behaves as an entity which determines lipase adsorption. The modification of the interface quality of a lipid substrate by a detergent is not perse the reason for the lack of lipase adsorption. A model is proposed according to which lipolysis under physiological conditions would occur in two steps requiring two cofactors. Colipase would be necessary for the formation of the lipase-bile lipoprotein complex, and bile lipids would be required to direct the adsorption of this lipolytic entity toward the emulsified substrate.

Adsorption↗
PubMed1978

Inhibition of lipase adsorption at interfaces. Role of bile salt micelles and colipase.

The effects of bile salts and colipase on the adsorption of lipase at an interface were studied by hydrophobic affinity chromatography on phenyl- and octyl-Sepharose. In the absence of bile salts, lipase or colipase binds separately to the gel. This is unchanged in the presence of adsorbed bile salts, when one bile salt molecule is associated per hydrophobic ligand. The same data are obtained in the presence of monomeric bile salt solutions. In contrast, lipase adsorption is totally prevented in a micellar bile salt solution. These results favor the idea that the formation of a lipase-bile salt complex in solution is responsible for the lack of interfacial lipase adsorption.

Adsorption↗
PubMed1977

A comparative in vivo study of intestinal absorption of biliary phosphatidylcholines and micellar phosphatidylcholines in the rat.

An in vivo study was performed using rats with the purpose of comparing the absorption of native biliary and purified phosphatidylcholines. The latter were purified from bile and solubilized in the form of mixed micelles of bile salts-phosphatidylcholines-cholesterol. The animals all bore bile duct diversions, and were divided into two groups: one had a normal pancreatic secretion while in the other group the pancreatic duct was ligated. Animals with normal pancreatic secretion showed comparable rates of absorption of micellar and biliary phosphatidylcholines. In the absence of normal pancreatic secretion, the rate of absorption of biliary phosphatidylcholines was unchanged, whereas that of micellar phosphatidylcholines markedly decreased. The results are consistent with the concept that some biliary phosphatidylcholines are absorbed independently of pancreatic secretion in an unhydrolyzed form.

Animals↗
PubMed1977

Zone electrophoresis study of the bile lipoprotein complex.

Sucrose gradient column electrophoresis was performed with human hepatic and gallbladder bile. It is shown that bile phosphatidylcholines exhibit a more rapid anodic mobility than do bile salts and serum albumin. This high mobility of bile phosphatidylcholines is not due to the negatively charged lipids which are present in bile, i.e. bile salts or free fatty acids. It is demonstrated that phosphatidylcholines are associated with anionic polypeptides. Electrophoresis of reassociations between these purified polypeptides and dilaurylphosphatidylcholine showed that these anionic polypeptides are primarily responsible for the high anodic mobility of the bile lipoprotein complex. This work describes a procedure for the purification of the bile lipoprotein complex which can be useful for the study of other kinds of lipid-polypeptide associations.

Amino Acids↗
PubMedDate not supplied

Stimulating effect of oxidized low density lipoproteins on plasminogen activator inhibitor-1 synthesis by endothelial cells.

Oxidized low density lipoproteins (ox-LDL) are thought to accelerate atherogenesis. It was recently demonstrated that patients with coronary heart disease have defects in plasma fibrinolysis due to increased plasminogen activator inhibitor-1 (PAI-1) levels. Investigation of PAI-1 synthesis by endothelial cells may allow insight into the effect of native LDL (N-LDL) and ox-LDL on endothelial cells. In the present study, secretion of PAI-1 by human umbilical vein endothelial cells (HUVEC) in culture was evaluated after incubation with N-LDL and ox-LDL. Ox-LDL were obtained by peroxidation under ultraviolet radiation, which induced compositional changes in LDL, namely, a decrease in the levels of arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and alpha-tocopherol and an increase in the malondialdehyde content. Ox-LDL induced a dose-dependent increase in PAI-1 secretion by HUVEC as assayed by an enzyme-linked immunosorbent assay. After a 24-hour incubation, a twofold increase in the PAI-1 content was observed with 50 micrograms/ml ox-LDL protein. Studies with inhibitors of protein synthesis and metabolic labeling with [35S]methionine confirmed that PAI-1 synthesis was stimulated by ox-LDL. N-LDL had no detectable effect on PAI-1 secretion. Binding studies with radiolabeled lipoproteins showed that the effect of ox-LDL was independent of the B/E receptor. Our experiments indicate that ox-LDL stimulate PAI-1 secretion from HUVEC and that this effect may involve a scavenger receptor.

Binding, Competitive↗