Determination of the cross-points of rat liver peroxisomes, peroxisomal core and the core components by cross-partition

Existence of fatty acyl-CoA oxidizing system in (micro)peroxisomes of rabbit aorta

A cyanide-insensitive palmitoyl-CoA oxidizing activity was detected in rabbit aorta. An assay developed for the arterial acyl-CoA oxidizing system was linear with respect to protein content of the homogenate between 12.5 and 100 micrograms and incubation time for at least 15 min. The system was shown to be localized in (micro)peroxisomes by centrifugation in sucrose density gradient. With a diet containing 1% (w/w) cholesterol and 3% (w/w) olive oil for 8 weeks the activity of peroxisomal beta-oxidation increased from 1.38 to 2.54 nmole/min/g aorta. These results show that the aortic catalase-positive particles have a capacity to oxidize fatty acyl-CoA and participate in fatty acid metabolism.

Changes in membrane surface properties of hepatic peroxisomes of rats under several conditions as determined by partition in aqueous polymer two-phase systems

Changes in membrane surface properties of hepatic peroxisomes of rats under several conditions were observed by aqueous polymer two-phase systems, which contained 6% (w/w) dextran T 500, 6% (w/w) polyethyleneglycol 4000, 250 mmol sucrose/kg and various concentrations of sodium phosphate buffer. The partition of peroxisomes into the upper phase depended to a large extent on their membrane surface charge. The cross-points of peroxisomes shifted from 5.55 to 5.25 and 5.2 after the administration of clofibrate and aspirin for 2 weeks, respectively, although that of alloxan-diabetic rat peroxisomes was not altered. The hydrophobic properties of peroxisomes, examined by means of a partition containing polyethyleneglycol monostearate, were altered by diabetes and starvation, but no change occurred in rats treated with clofibrate or aspirin. In the liver of rats fed a high-fat diet, the partition of peroxisomes was the same as that of the control. These findings indicate that hypolipidemic drugs such as clofibrate and aspirin induce the proliferation of peroxisomes and lead to the alteration of the surface charge of peroxisomal membranes. Diabetes or fasting lead to an alteration mainly of the hydrophobic properties. Both changes are probably due to alteration of content and/or composition of the proteins and the phospholipids in peroxisomal membrane under the conditions used.

Isoelectric points and surface hydrophobicity of Gram-positive cocci as determined by cross-partition and hydrophobic affinity partition in aqueous two-phase systems

Thirty-nine streptococcal strains belonging to groups A, C, and G and 12 staphylococcal strains were investigated with respect to surface charge and hydrophobicity. Isoelectric points of the bacteria were determined by cross-partition experiments in dextran-polyethylene glycol two-phase systems containing charged polymers. The results obtained indicate that group A, C, and G streptococci have isoelectric points of pH 3.75 +/- 0.15 standard deviation. Staphylococci show an isoelectric point of around pH 2 and thereby differ markedly from the streptococci. Pretreatment of bacteria with human serum resulted in a significant change in the isoelectric points of streptococci. In a second series of experiments, an aqueous dextran-polyethylene glycol two-phase system containing polyethylene glycol palmitate or stearate was used to study the hydrophobic surface properties of the bacterial cells. The partition of the staphylococci was not influenced by the addition of up to 1% (wt/wt) polyethylene glycol palmitate or stearate, whereas the streptococci showed a large variation in affinity for polyethylene glycol-bound hydrophobic groups. The bacterial strains included in the study were also tested for uptake of human serum proteins. A positive correlation was found between the hydrophobic affinity of group A streptococci and the density of receptors for aggregated beta-2-microglobulin.