Development and validation of a quantitative assay for cholesterol crystal growth in human gallbladder bile

A technique for isolation of rubella virus-like particles by sucrose gradient ultracentrifugation using Coomassie brilliant blue G crystals

An improved method for the isolation of rubella virus-like particles (RVLP) from cell culture supernatant of transfected Chinese hamster ovary (CHO24S) cells is described. It employs a combination of membrane filtration with sucrose gradient ultracentrifugation. It was found that staining the RVLP band with Coomassie brilliant blue G (CBB) resulted in the CBB crystals adsorbing RVLP. After ultracentrifugation (25,000 rpm, 3h, 4 degrees C) a sharp blue band with crystals (diameter 30-40 microm) was observed (at a density of 1.250 g/ml at 25 degrees C) in a 30-60% sucrose gradient. Using a combination of SDS-PAGE and Western blotting techniques, E1 rubella virus structural protein was detected only in the solutions derived from the sharp blue band. A decrease in crystal concentration a few millimeters above or below the main band was associated with a decrease in protein concentration. By dilution with a saturated ice-cold 30% sucrose solution it was possible to pellet the crystals by centrifugation (15,000 rpm, 10 min). SDS-PAGE showed a much higher concentration of RVLP structural protein in the pellet than in the supernatant. This RVLP-containing material is especially suitable for the preparation of rubella virus immunoblot stripes.

The role of the Concanavalin A-binding fraction in cholesterol crystallization in native human bile

BACKGROUND/AIMS

Many Concanavalin A-binding glycoproteins have been proposed to influence cholesterol crystallization in human bile. This has been studied mainly by addition of the Concanavalin A-binding fraction to model bile. The physiological relevance of the proteins in native bile is not yet known. The aim of this study was to establish the role of the Concanavalin A-binding fraction in cholesterol crystallization in native human gallbladder bile.

METHODS

To determine the effects of the removal of Concanavalin A-binding fraction, fresh human gallbladder bile was incubated with either Concanavalin A-Sepharose or Sepharose alone. Beads were sedimented and crystallization was studied in the supernatant.

RESULTS

Extraction of Concanavalin A-binding fraction decreased crystallization in fast-nucleating biles (Crystal Detection Time < or =4 days). Slow-nucleating biles were not affected. The effect could not be related to the content of known pronucleating proteins (IgA, IgM, haptoglobin, aminopeptidase N and alpha1-acid glycoprotein), since the slow-nucleating biles contained similar amounts of these proteins.

CONCLUSIONS

Although Concanavalin A-binding fraction always accelerated crystallization when added to model bile, removal of the same fraction from native bile often had no effect. We conclude that slow-nucleating biles in particular contain undetermined factors which regulate the activity of pronucleators.

Inducing cholesterol precipitation from pig bile with beta-cyclodextrin and cholesterol dietary supplementation

BACKGROUND/METHODS

In this study, pigs fed for 3 weeks a well-balanced semi-purified diet enriched with 0.3% cholesterol and 0, 5 or 10% beta-cyclodextrin were proposed as new animal donors of gallbladder bile exhibiting different rates of cholesterol crystallization, in order to gain insight into the early mechanisms underlying cholesterol precipitation in vivo. The appearance and growth of cholesterol crystals were monitored in the incubated freshly collected gallbladder biles through light microscopy and concomitant time-sequential determination of crystallized cholesterol concentration, and interpreted in terms of the composition of the bile.

RESULTS

Although the concentration of total lipids and proteins and the relative proportions of bile acids, phospholipids, and cholesterol remained unchanged under beta-cyclodextrin, the cholesterol crystallization increased in the following order: 0<<10<5% beta-cyclodextrin. Concomitantly, the proportion of chenodeoxycholic acid in bile, and the hydrophobicity index of the biliary bile acid mixture increased in the following order: 0<5<10% beta-cyclodextrin (the same as reported elsewhere for the decrease in the antinucleating ApoA1), while sn-2 arachidonoyl biliary lecithins were specifically increased with 5% beta-cyclodextrin in the diet.

CONCLUSIONS

We hypothesized that lecithin molecular species may be the determinant factor in modulating high cholesterol crystallization rates in biles otherwise enriched with hydrophobic bile acids.