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Biomedical subjects

G Camejo

Publications and source records attributed to G Camejo.

At least 73 records · Page 4Linked to original sources
PubMed1986

Effects of prazosin and propranolol on blood lipids and lipoproteins in hypertensive patients.

Prazosin and propranolol were compared in an open, crossover study to determine their effects on plasma lipids and lipoproteins. After a four-week placebo period, 10 hypertensive patients were randomly assigned to prazosin treatment (Group I) and another 10 to propranolol treatment (Group II) for eight weeks. After a second four-week placebo period, treatment in each group was switched to the alternative drug for eight weeks. The mean blood pressure was reduced to normal levels (diastolic blood pressure less than or equal to 90 mm Hg) by both drugs--prazosin (1 to 8 mg per day) and propranolol (40 to 240 mg per day). The results of the study indicate that prazosin decreases serum cholesterol levels. In contrast, propranolol not only increases serum triglyceride levels and very-low-density lipoprotein cholesterol, but decreases total high-density lipoprotein cholesterol, high-density lipoprotein2 cholesterol, high-density lipoprotein2, and apoprotein A-I. The data suggest that propranolol may induce significant, potentially atherogenic changes in lipid metabolism, whereas prazosin may represent an advantageous alternative as an antihypertensive agent, especially in subjects with an already atherogenic lipoprotein profile.

Adult↗
PubMed1985

Interaction of low density lipoproteins with arterial proteoglycans. The role of charge and sialic acid content.

The interaction of low density lipoproteins (LDL) with chondroitin sulfate-rich arterial proteoglycans appears to be initiated by coulombic interactions that lead to insoluble complexes. Once formed, large LDL aggregates are held together by non-polar associations. The irreversible formation of LDL proteoglycans aggregates was evaluated for different LDL preparations by definition of an avidity coefficient (Ar) using a Langmuir isotherm. LDL from different subjects, when tested against the same lipoprotein-complexing proteoglycan (LCP), gave Ar values ranging from 1-9 X 10(6) L/M. High avidity values were associated to lipoproteins with apparent isoelectric points above 6.5. These lipoproteins show low sialic acids content. The content of N-acetyl and N-acetyl,O-acetyl sialic acid was found inversely correlated with the avidity coefficient for the arterial LCP. Reductions of 42% on the LDL sialic acid content, by neuraminidase treatment, induced a 10-fold increment in their avidity for the lipoprotein complexing proteoglycan. The results indicate that at low ionic strength and physiological Ca2+-concentration and pH, the surface charge of LDL is an important modulator of the interaction with the arterial proteoglycan. Sialic acid, perhaps because of its exposure at the LDL surface, plays a determinant role in the in vitro association of LDL with the polyanionic proteoglycans. It is possible that in the intima-media the sialic residues of LDL and its balance of surface charges will control part of the interactions with the proteoglycans of the extracellular matrix.

Arteries↗
PubMed1985

Properties of lipoprotein complexes isolated by affinity chromatography from human aorta.

We have isolated from the same human aortic intima-media, using a sequential extraction procedure and affinity column chromatography, different ApoLDL-containing lipoprotein complexes. The neutral lipid composition of the fractions retained by the anti-ApoLDL immunoglobulin, from saline extracts and elastase-treated samples, was similar to that of plasma low density lipoproteins. The fatty acids of phosphatidylcholine, triglycerides and cholesterol esters of all three fractions have a lower content of linoleic acid than plasma low density lipoproteins. By electron microscope the three lipoprotein fractions appeared polydisperse. All the fractions contained particles in the density range of low density plasma lipoproteins but those from elastase extracts and guanidinium-HC1 extracts contained also lipoproteins with densities below 1.019 g/ml. We found large variation in the composition of fractions from different aortas. The lipoproteins isolated from buffered saline were found associated with 2 to 4 micrograms of glycosaminoglycan (GAG) per 100 micrograms of protein. The associated GAG was made of chondroitin-6-SO4, dermatan and chondroitin-4-SO4 in a 3:2:1 ratio.

Aorta, Thoracic↗
PubMed1984

The structural stability of low-density lipoprotein. A kinetic X-ray scattering study of its interaction with arterial proteoglycans.

The structural stability of human plasma low-density lipoproteins (LDL) has been studied kinetically by means of dynamic X-ray scattering techniques. At 37 degrees C, rapid deterioration of the lipoproteins present in the insoluble complex which is formed on mixing solutions of LDL and human arterial proteoglycans is observed. This is evidenced by the progressive blurring of the X-ray scattering spectra. At 4 degrees C the X-ray patterns from the insoluble complex show a single reflection centered at 34 A-1, which is characteristic of pure cholesteryl esters organized in a smectic phase. This behaviour contrasted with the high stability exhibited by free LDL at 37 degrees C. Our results show that, in the form of insoluble complex, the lipoprotein molecules are rapidly disrupted and that the neutral lipids segregated with formation of a lipid phase. This suggests that LDL particles become destabilized by their interaction with arterial proteoglycans.

Aorta, Thoracic↗
PubMed1984

Circulating immune complexes, immunoglobulins, complement, antibodies to dietary antigens, cholesterol and lipoproteins levels in patients with occlusive coronary lesions.

The presence of circulating immune complexes, serum immunoglobulins, C3 (the third component of complement), antibodies to alpha-lactalbumin, beta-lactoglobulin and bovine serum albumin was studied in 39 patients subjected to coronary arteriography. Total serum cholesterol and triglycerides and cholesterol in VLDL, LDL and HDL were also estimated. The results obtained in the group of patients found with occlusive lesions were compared with those found in the group without lesions. With one of the five assays used for the detection of immune complexes, higher and significant levels were found in the group with lesions. A negative and significant correlation was found between the number of vessels with lesions and the levels of serum C3.

Adult↗
PubMed1983

Partial structure of the active moiety of a lipoprotein complexing proteoglycan from human aorta.

Proteoglycans and glycosaminoglycans of the intima-media extracellular matrix have been stated to play a role in lipoprotein deposition associated with atherogenesis. It is therefore important to characterize the active lipoprotein-complexing moiety of these macromolecular aggregates. We have isolated a soluble proteoglycan aggregate of approximately 5 X 10(6) molecular weight after homogenization of human aortic intima-media in an isosmotic sucrose solution, sequential differential centrifugation, dialysis, exclusion chromatography and preparative electrophoresis. This proteoglycan aggregate, labelled lipoprotein-complexing proteoglycan (LCP), has been previously shown to form specific complexes with low density lipoproteins, either isolated or in sera. Density gradient centrifugation in dissociative conditions of the LCP, cellulose acetate acetate electrophoresis of the subfractions, chondroitinases treatment and high performance liquid chromatography of the unsaturated disaccharides indicated that the glycosaminoglycan moiety was composed of 56% chondroitin-6-SO4, 26% hyaluronate and/or undersulfated chondroitin and 17% chondroitin-4-SO4. In pore-gradient polyacrylamide gel electrophoresis, the hyaluronate monomer appeared to have a molecular weight of 250000 while that of the chondroitin sulfates ranged between 50000 and 70000 after extensive treatment with protease. The fractions enriched in the chondroitin sulfate monomers were the most reactive towards LDL and their reactivity was abolished by chondroitinase AC indicating that the lipoprotein-complexing capacity of the LCP aggregate is associated to these molecules.

Aorta↗
PubMed1982

ApoLDL: evidence for an aggregating system of heterogeneous subunits.

The protein moieties of low density lipoprotein (LDL) (d 1.019-1.063 g/ml) and subfractions: I (d 1.018-1.023 g/ml), II (d 1.023-1.028 g/ml), III (d 1.028-1.034 g/ml), and IV (d 1.034-1.052 g/ml) were obtained by a mild delipidation procedure involving attachment of LDL to an ionic-exchange column and a gradient of the non-ionic detergent Brij-36T (J. Lipid Res. 1979. 20: 631.). The apoLDL, eluted in the presence of 6 M urea, 0.1% SDS, or 4 M guanidine-HCl and analyzed by pore-gradient polyacrylamide gel electrophoresis and high performance gel exclusion chromatography, appeared to be made up of several polypeptide components with molecular weights between 250,000 and 14,000. The complex pattern was observed in the apoprotein of LDL subfractions I to IV; however the distribution of the most prominent components was different for each density range. These results, those from immunoelectrophoresis, N-terminal analysis, and measurements of tetramethylurea-soluble apoproteins discounted the possibility that the presence of bands with molecular weights below 250,000 could be caused by contamination with VLDL or HDL or nonspecific proteolysis. Delipidation of subfractions I to IV with organic solvents produced, on the other hand, simple patterns of highly aggregated apoLDL subfractions, where most of the protein had molecular weights above 250,000. The more disaggregated apoLDL preparations were those obtained from LDL rapidly isolated by single-spin centrifugation in KBr gradients, from fresh plasma immediately mixed with EDTA, phenylmethyl sulfonylfluoride, and chloramphenicol. ApoLDL fractionated by single-pore polyacrylamide gel electrophoresis appeared to be a system of heterogeneous antigens unevenly distributed on the different polypeptide components. These results, and those obtained by peptide maps of tryptic hydrolyzates from the major constituents, suggest that apoLDL is made of several polypeptides of different lengths with similar repetitive sequences but with some dissimilar segments specific for the major protein constituent of LDL. These polypeptides show a high tendency to form multiple aggregates with size distribution dependent on the preparation history.-Socorro, L., F. López, A. López, and G. Camejo. ApoLDL: evidence for an aggregating system of heterogeneous subunits.

Apolipoproteins↗
PubMed1981

Photometric measurement of lipoprotein-cholesterol after agarose electrophoresis: comparison with single-spin ultracentrifugal analysis.

A method is presented for the evaluation of lipoprotein-cholesterol after fractionation of 20 microliter of serum in agarose electrophoresis in a discontinuous buffer system. The prestained lipoprotein bands are separated in less tha 1 h, cut out and extracted with butanol. The cholesterol in the extract is measured by a simple colorimetric method. The recoveries of lipoprotein cholesterol were 95.3% +/- 13.0 (S.D.), and the average coefficient of variation was 8% for alphalipoprotein, 6.4% for betalipoprotein and 8.0% for pre-betalipoproteins. Lipoprotein cholesterol concentrations, determined by the proposed method correlated well with those analyzed following ultracentrifugation. The method can handle up to 4 serum samples run in duplicate per day and only requires equipment available in conventional clinical laboratories, and stable reagents.

Adult↗
PubMed1980

Characterization and properties of a lipoprotein-complexing proteoglycan from human aorta.

The preparation of a proteoglycan (PG) from human aortic intima-media is described. The PG was obtained from intima-media homogenates by differential centrifugation, exclusion chromatography and preparative agarose electrophoresis. Crude or purified preparations of the proteoglycan are capable of forming specific insoluble complexes with LDL, purified or in serum. This product has been labelled lipoprotein-complexing proteoglycan (LCP-3). On agarose and cellulose acetate electrophoresis LCP-3 appears as a single band. However, its glycosaminoglycan (GAG) moiety shows a composition and chromatographic behaviour compatible with hybrid or mixed chains of chondroitin-6-so4, dermatan sulfate and heparin and/or heparan sulfate. The specificity of LCP-3 for LDL disappears when it is treated with testicular hyaluronidase or proteolytic enzymes. Ionic strength, pH, Ca++ and Mg++ modulate the amount of LDL insolubilized. The amino acid composition of the protein from LCP-3 is that of a basic protein(s), perhaps bound covalently through xylose--serine residues to the GAG's. The estimated molecular weight of LCP-3 is 1 to 5 x 10(6) daltons. The presence of LCP-3 to intima-media and its specificity for interacting with LDL at conditions near to physiological ones are suggestive of the role that this type of structure may play in the association of the atherogenic lipoproteins with components of the arterial intima-media.

Aorta↗
PubMed1980

Factors modulating the interaction of LDL with an arterial lipoprotein complexing proteoglycan: the effect of HDL.

The presence of a lipoprotein complexing proteoglycan (LCP) in extracts of human arterial intima/media that forms specific complexes with low density lipoproteins (LDL) has suggested that it may play a role in the interaction of LDL with the arterial wall and the atherogenic process. The formation of insoluble LDL-LCP complexes by incubation of serum with arterial extracts appears directly related to the concentration of LDL and inversely to the content of high density lipoproteins (HDL), indicating that HDL may inhibit the interaction between LDL and LCP. This inhibition is clearly visible by addition of HDL to LCP containing extracts before their incubation with LDL. This effect is also shown by apoHDL but not by lipoprotein-free plasma. It is suggested that the HDL/LDL ratio of the plasma crossing the endothelial barrier may be an important modulator of the net accumulation of LDL in the intima/media and of its contribution to atherogenesis.

Adult↗
PubMed1979

Preparation and properties of soluble, immunoreactive apoLDL.

Immunoreactive apo-low density lipoprotein (LDL), soluble in mildly alkaline buffers of low ionic strength, was prepared by attaching LDL to a DEAE-Sepharose column and eluting the lipids with a 0--2% (w/v) gradient of nonionic detergents. Brij-36T, Nonidet P-40, and Triton X-100 gave similar results. After washing the detergent from the column, the bound apoLDL was eluted with 1 M NaCl, pH 7.4, with recoveries up to 85%. This apoLDL could be dialyzed extensively against low ionic strength solutions, and remained soluble as long as the pH was above 7. Spectrophotometric analysis showed that less than 0.1% %w/v) of cholesterol or phospholipids and less than 1% (w/v) of detergent remained associated with the protein. The apoLDL cross-reacted with LDL against antisera prepared vs. intact LDL. Pore-gradient polyacrylamide gel electrophoresis, with SDS and urea, showed that this preparation was less aggregated than organic solvent extracted apolLDL and appeared to be made of oligomers of two monomeric subunits, one with molecular weight around 22,700 and a smaller one of approximately 8000. Isoelectric focusing showed that there also was charge heterogeneity in the soluble apoLDL.

Apolipoproteins↗
PubMed1978

Small-angle X-ray scattering and differential scanning calorimetry studies on reversibly modified human-serum low density lipoproteins.

Small-angle x-ray scattering diagrams of human serum low density lipoprotein (LDL) were recorded at several temperatures in solutions of different freezing points. It was found that modifications of the x-ray patterns observed on cooling the lipoprotein samples below 0 degrees C are due to reversible alterations of the LDL surface structure induced by the freezing process (independent of temperature). With both intact and partially dehydrated LDL, differential scanning calorimetry (DSC) carried out in the body temperature range revealed a heat absorption characteristic of the transition from a liquid crystal to an isotropic liquid phase of cholesteryl esters within the lipoproteins (Deckelbaum, R. J., Shipley, R. J., Small, P. M., Lees, R. S., & George, P. K. (1975) Science 190, 392). However, small-angle x-ray scattering diagrams recorded with the same LDL sample before and after the partial removal of water were found to be very different: the scattering curve for intact LDL showed a strong band centered at (36 A)-1 which disappeared upon drying and reappeared upon restoring the water. Our results suggest that the presence of this signal strongly depends on the molecular structure of the lipoprotein surface.

Calorimetry, Differential Scanning↗
PubMed1977

Small-angle x-ray scattering study of human serum low-density lipoproteins with differential reactivity for an arterial proteoglycan.

The structure and thermal behavior of human serum low-density lipoproteins showing either a high or a low reactivity against a proteoglycan isolated from human arteries have been found to be different from each other. It is suggested that modifications in the lipoprotein surface structure induced by the physical state of the neutral lipids could modulate the affinity of the macromolecule for the arterial component.

Adult↗