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Biomedical subjects

G Camejo

Publications and source records attributed to G Camejo.

101 records · Page 6Linked to original sources
PubMed1968

Lipid monolayers: interactions with the apoprotein of high density plasma lipoprotein.

Monolayer techniques were used to study the interactions of various lipids (cholesterol, lysophosphatidyl choline, phosphatidal ethanolamine, phosphatidyl choline, sphingomyelin, stearic acid, and lipids extracted from plasma high density lipoproteins and very low density lipoprotein) with the lipid-free protein subunit of rat plasma high density lipoprotein and with rat plasma albumin. The proteins were injected under the lipid monolayer at fixed area, and the increase in surface pressure (decrease in surface tension) was measured as a function of time. With all lipids, both the rate and magnitude of this increase were greater with the apolipoprotein than with albumin. The degree of film penetration of pure lipid films (at an initial film pressure of 15 dynes/cm) by the two proteins followed the same order: cholesterol > phosphatidal ethanolamine > phosphatidyl choline > stearic acid > sphingomyelin > lysophosphatidyl choline. Other variables studied were protein concentration, initial film pressure, and pH. Two distinctive properties of the apolipoprotein were the penetration of lipid films at pressures above the collapse pressure of the protein, and the formation of a film even at low salt concentration. High surface activity and strong interaction of HDL-protein with lipid monolayers may be associated with the flexibility of the protein molecule due to absence of disulfide bridges. The unusual surface activity of HDL-protein may be intimately related to the mechanism of formation of the lipoprotein.

Animals↗
PubMed1967

Serum lipoproteinemia in pregnant and lactating rats.

Serum lipoproteins of pregnant and puerperal rats were studied by preparative and analytical ultracentrifugation. The concentration for the fraction with density less than 1.019 was markedly elevated in rats during the 3rd wk of gestation and in lactating rats. This fraction showed similar triglyceride fatty acid composition and immunoelectrophoretic behavior whether it was derived from pregnant or nonpregnant rats, and when partially delipidized, the lipoproteins from both groups showed similar immunoelectrophoretic characteristics and sedimentation rates. When lactation was interrupted during puerperium, serum lipoproteins returned to control levels; but in lactating rats, high levels of serum very low density lipoprotein persisted up to 3 wk post partum.

Animals↗
PubMedDate not supplied

The participation of aortic proteins in the formation of complexes between low density lipoproteins and intima-media extracts.

SUMMARY: A factor of protein nature that forms specific complexes with low density lipoproteins (LDL) has been detected in extracts of aortic intima-media from men and rabbits. Although the formation of complexes is maximal at low ionic strength, it is still observed under physiological conditions. Gel electrophoresis of the complex formed between the extracts and LDL proteins indicates that the insoluble material is an aggregate of the lipoproteins with some of the proteins present in the extracts. Pretreatment of the intima-media extract with proteases greatly diminishes its complexing ability. The interaction was also observed between the extracts and sera. The sera from patients with myocardial infarct formed more insoluble complexes than the sera from a control group. The lipoprotein complexing agent was found in intima-media of aorta and coronary arteries but not in that of veins, pulmonary arteries or in the adventitia of arteries or veins.

Animals↗
PubMedDate not supplied

Cationic polypeptides modulate in vitro association of low density lipoprotein with arterial proteoglycans, fibroblasts, and arterial tissue.

Polymers of lys (plys) and arg (parg) were found to be efficient inhibitors of the formation of complexes between low density lipoprotein (LDL) and human chondroitin-6-sulfate-rich proteoglycans. Displacement curves indicate that efficiency was dependent on molecular weight. Inclusion of alanine in the polymer up to a 1:1 molar ratio (plys,ala) has a moderate effect on displacing capacity. Poly-L-lys (plys) and poly-L-arg (parg) exhibited similar displacing ability. Inclusion of tryptophan in plys and parg diminished their effect, whereas inclusion of serine in plys,ser (3:1) improved it. Plys (18.3 kD) stimulates LDL binding to human fibroblasts. This may be due to the association of polylysine to LDL, leading to an increase in its positive charge. These more positively charged LDL may have an increased association with the negatively charged region of the apolipoprotein B/E receptor. Perfusion experiments on rabbit aortic segments were used to measure the influx of 125I-LDL into the intima and to study the effect of basic polypeptides. Plys in a 10:1 molar ratio decreased the LDL uptake by approximately 25% when added to the system together with the LDL or in experiments in which the tissue segments were pre-perfused with plys, and LDL was added after elimination of the plys. The results suggest that polycationic polypeptides, due to their strong affinity for sulfated proteoglycans, interfere with the interactions of LDL with components of the arterial extracellular matrix.

Arteries↗
PubMedDate not supplied

Identification of Apo B-100 segments mediating the interaction of low density lipoproteins with arterial proteoglycans.

The interactions of low density lipoprotein (LDL) and apolipoprotein (apo) B-100 segments with chondroitin-6-SO4 rich aortic proteoglycans aggregate (CSPG) were studied by using quantitative frontal elution affinity chromatography. The affinity of the agarose-CSPG was higher for LDL than for very low density lipoprotein and high density lipoprotein was not bound. LDL from different individuals had dissociation coefficients (Kd) from 28 to 179 nM. Experiments with tryptic hydrolysates of apo B suggested that the capacity of LDL to bind with CSPG resides in the protein. Nine apo B-100 hydrophilic peptides, 12 to 26 amino acids long, were selected, and three were found to interact with the agarose-bound CSPG: apo B P-1 (LRKHKLIDVISMYRELLKDLSKEA, residues 4230 to 4254), apo B P-2 (RLTRKRGLKLATALSLSNK, residues 3359 to 3377), and apo B P-11 (RQVSHAKEKLTALTKK, residues 2106 to 2121). These peptides competed with LDL for binding to the agarose-bound and soluble CSPG; apo B P-2 was the most effective. This correlates with Kd values: 63, 86, and 82 microM for apo B P-2, P-1, and P-11, respectively. The peptides shared an excess of positive-charged side chains. Apo B P-2 belongs to the lys- and arg-rich, LDL-receptor domain. Apo E also binds to the agarose-proteoglycan. The results suggest that apo B regions with sequences and charge distributions analogous to those of residues 3359 to 3377, 4230 to 4254, and 2106 and 2121 are among those responsible for the interaction of LDL with intima-media CSPG.

Aorta↗