Biomedical subjects

M J Chapman

Publications and source records attributed to M J Chapman.

At least 73 records · Page 4Linked to original sources

PubMed1997

Hepatitis C virus core protein shows a cytoplasmic localization and associates to cellular lipid storage droplets.

There is now abundant evidence to substantiate an important role of hepatitis C virus (HCV) core protein in cellular gene expression as well as in the viral cycle. Thus the subcellular localization of this protein has important implications. However, several studies have shown controversial results: the HCV core has been, indeed, described as cytoplasmic or nuclear depending on the size of the protein or on the genotype analyzed. We have studied the localization of the HCV core protein in two different cell lines, one nonhepatic (CHO) and the other hepatic (HepG2). Double immunofluorescence staining using a nuclear membrane marker and confocal analysis showed the core protein pattern to be cytoplasmic and globular. This pattern is not cell cycle-regulated. Electron microscopy analysis revealed the nature of the globular staining observed in immunofluorescence. The HCV core protein accumulated at the surface of lipid droplets that were also the unique morphological feature of nonhepatic core transfected cells. The lipid droplets were isolated by sequential ultracentrifugation on the basis of their density; biochemical analysis revealed a prevalence of triglycerides. In addition the core protein colocalized with apolipoprotein AII at the surface of the lipid droplets as revealed by confocal microscopy. Moreover analysis of liver biopsies from chronically HCV-infected chimpanzees revealed that HCV core is cytoplasmic and localized on the endoplasmic reticulum and on lipid droplets. These results clearly define the subcellular localization of the HCV core protein and suggest a relationship between the expression of the HCV core protein and cellular lipid metabolism.

Animals↗

PubMed1997

Effect of the oxidation state of LDL on the modulation of arterial vasomotor response in vitro.

Although it is established that highly oxidized LDL modify both vasodilator and vasoconstrictor responses in normal and atherosclerotic arterial tissue, there is a paucity of data on the relationship between the degree of the oxidative modification of LDL and vasomotor response. We therefore compared the impact of native LDL (Nat-LDL), and of partially (P-oxLDL), of moderately (M-oxLDL) and of highly oxidized LDL (H-oxLDL) on the vasomotor response of isolated human internal mammary artery and of rat thoracic aorta. Copper-mediated oxidative modification for up to 24 h at 37 degrees C was characterised by a progressive increase in the net negative electrical charge of LDL, and in the content of oxysterols; by contrast, lipid hydroperoxide and TBARS content peaked in M-oxLDL at 6 h. Neither basal vascular tone nor vasoconstriction induced by KCl (100 mmol/l) were modified significantly in arterial segments in relation to the degree of LDL oxidation. While Nat-LDL did not modify the contractile response of rat aorta to norepinephrine, increase in the degree of oxidative modification of LDL progressively and significantly shifted the norepinephrine response curve to the right (EC50 values for Nat-LDL, M-oxLDL and H-oxLDL: 1.2+/-0.5x10(-8), 3.5+/-1x10(-7), 1.3+/-0.4x10(-6) mol/l respectively) with reduction in the maximal effect (74.5+/-12.2 and 100.1+/-6.2% for H-oxLDL and M-oxLDL respectively, P < 0.05 versus controls). Similar findings were made in human arteries treated with H-oxLDL (P < 0.05 for EC50 and maximal response versus controls). The acetylcholine-induced, endothelial-dependent relaxation of rat aortic segments was significantly and progressively impaired with increase in the degree of LDL oxidation, maximal relaxation with H-oxLDL being 3-fold less (P < 0.05) than Nat-LDL at the same protein concentration (100 microg/ml). Acetylated LDL was without effect. Our data indicate that the increase in the degree of copper-mediated, oxidative modification of LDL parallels progressive reduction in the vasomotor response of the arterial wall to norepinephrine-induced contraction and to acetylcholine-induced relaxation subsequent to precontraction. Our data are consistent with the hypothesis that the major oxysterols (7-ketocholesterol, 7beta-hydroxycholesterol) present in Ox-LDL underlie such effects.

Animals↗

PubMed1997

Familial lecithin:cholesterol acyltransferase deficiency: molecular analysis of a compound heterozygote: LCAT (Arg147 --> Trp) and LCAT (Tyr171 --> Stop).

Lecithin:cholesterol acyltransferase (LCAT) is responsible for the formation of the majority of plasma cholesteryl esters. Familial LCAT deficiency is associated with corneal opacity, anemia and proteinurea and typically results in renal failure in the 4-5th decade; this syndrome is equally characterized by the quasi-absence of plasma LCAT activity with variable enzyme mass and very low levels of plasma cholesteryl esters. In this study, we report detailed analyses of plasma lipids and lipoprotein profile in two sisters (CM and ML) presenting classical homozygous LCAT-deficiency; the younger sibling (CM) had proteinurea from an early age whereas the older sister (ML) has never exhibited renal dysfunction. We investigated the molecular defect in the 45 year-old woman (proband CM) exhibiting all clinical and biochemical features of familial LCAT deficiency: a plasma cholesterol level of 105 mg/dl, of which 95% was unesterified, an HDL-cholesterol of 6.5 mg/dl and an apo A-I level of 52 mg/dl. The proband (CM) displayed a plasma cholesterol esterification rate which corresponded to 2% of normal LCAT activity; plasma LCAT protein concentration was 0.56 microg/ml and equivalent to approximately 10% of normal LCAT mass. Analysis by single strand conformation polymorphism (SSCP) of the PCR products corresponding to exons 4 and 5 of the LCAT gene revealed a visible band shift. Sequence analyses of exons 4 + 5 revealed two separate single point mutations: a C --> T transition replacing Arg147 by Trp and a T --> G transition converting Tyr171 to a stop codon. The presence of these two point mutations was confirmed by restriction enzyme analyses: the C --> T transition abolished a MwoI site whereas the T --> G transition created an AvrII site. The Arg147 mutation was associated with a non-secreted protein. The Tyr171 mutation resulted in formation of a truncated protein lacking the catalytic site. In summary, we have identified an LCAT deficient patient corresponding to a compound heterozygote for the Arg147 --> Trp mutation and a new molecular defect involving a Tyr171 --> Stop mutation in the LCAT gene.

Apolipoprotein A-I↗

PubMed1997

Antioxidant action of Vaccinium myrtillus extract on human low density lipoproteins in vitro: initial observations.

Oxidative modifications of low density lipoproteins (LDL) are now recognised as one of the major processes in atherogenesis. Various drugs, as well as a number of natural products, have been proposed to inhibit such processes. Among the naturally-occurring constituents of plants which appear to possess antioxidant activity are polyphenolic compounds such as flavonoids. The aqueous extract of Vaccinium myrtillus is rich in such molecules. In this report, we describe the in vitro antioxidative potential of this extract on human LDL. The copper-induced oxidative modification of these lipoproteins was assessed using 1) measurement of oxidative resistance as determined by the lag-phase preceding conjugated diene formation; 2) quantification of the amount of lipoperoxides and thiobarbituric acid-reactive substances generated, and measurement of the modification in the net negative electrical charge of the lipoproteins, over a 7-hour time course experiment. Trace amounts of V myrtillus extract (15 to 20 micrograms/mL) induce statistically significant changes in the oxidation behaviour of LDL, which include 1) prolongation of the lag-phase of conjugated diene production (P < 0.01); 2) reduction in the formation of lipoperoxides and of thiobarbituric acid-reactive substances up to 7 hours and especially between 1 and 5 hours (P < 0.01); and 3) inhibition of modification in the net negative charge of LDL. These results demonstrate that V myrtillus extract exerts potent protective action on LDL particles during in vitro copper-mediated oxidation. Calculation of IC50 values indicates that, on a molar basis, this extract may indeed be more potent than either ascorbic acid or butylated hydroxytoluene in the protection of LDL particles from oxidative stress.

Anthocyanins↗

PubMed1997

Oxidative degradation of cholesteryl esters in low-density lipoproteins: analysis by liquid chromatography-light scattering and protection by a new synthetic antioxidant, S20478.

Cholesteryl esters in the hydrophobic core of low-density lipoprotein (LDL) particles constitute a major molecular target during copper-mediated oxidation. To facilitate the rapid analysis and quantitation of the oxidative degradation of LDL cholesteryl esters, we describe a new approach based on light scattering detection following separation by HPLC. We have applied this approach to the evaluation of the protective capacity of a new synthetic antioxidant, S20478, during oxidation of LDL in the presence of copper ions. HPLC separation of cholesterol and the four major molecular species of cholesteryl esters (C16:0, C18:1, C18:2 and C20:4) of LDL was achieved in a single run of 20 min with high sensitivity (50 ng) and low background. Time course studies of the oxidative modification of LDL (ratio LDL protein: copper, 100 micrograms/mL: 1 microM) revealed that the content of unsaturated cholesteryl esters (C20:4 and C18:2) decreased (-30% and -15%, respectively) within 90 min of copper-mediated oxidation, while only minor degradation (up to 15%) of monounsaturated (C18:1) and saturated (C16:0) esters occurred. At 24 hours of oxidation, only traces (< 5%) of the C20:4 and C18:2 esters were detectable; whereas 52% of the C18:1 ester remained (P < 0.01). Of the saturated esters, only minor proportions (35% or less) underwent oxidative modification. In addition, some 81% of free cholesterol was conserved as the native sterol. The synthetic antioxidant, S20478 (50 microM) was capable of inhibiting the initiation and the propagation of copper-mediated LDL oxidation as determined by the time- and dose-dependent inhibition of the formation of conjugated dienes and thiobarbituric acid-reactive substances, as well as the conservation of the net electrical charge of LDL; indeed S20478 conserved cholesteryl esters in their native form up to 24 hours. However, after prolonged exposure to copper ions (48 hours), only 47% of the unsaturated esters remained (C18:2, P < 0.05). Nonetheless, S20478 (10 microM) was more efficient in inhibiting copper-mediated LDL oxidation as compared to probucol at the same concentration. These findings suggest that S20478 may be of potential interest in a new antioxidant approach to therapeutic stabilisation and regression of atherosclerotic plaques. Moreover, this method should prove useful in the assessment of the integrity of native LDL, and provides a new chemical marker of the degree of LDL oxidation.

Antioxidants↗

PubMed1997

Copper-catalyzed oxidation mediates PAF formation in human LDL subspecies. Protective role of PAF:acetylhydrolase in dense LDL.

Free radical-mediated oxidation of cholesterol-rich LDL plays a key role in atherogenesis and involves the formation of oxidized phospholipids with proinflammatory biological activity. We evaluated the production of platelet-activating factor (PAF), a potent inflammatory mediator, in human LDL subspecies on copper-initiated oxidation (4 mumol/L CuCl2, 80 micrograms/mL for hours at 37 degrees C). PAF formation was determined by biological assay of HPLC-purified lipid extracts of copper-oxidized lipoproteins; chemical identity was confirmed by gas chromatographic and mass spectrometric analyses. PAF, characterized as the C16:0 molecular species, was preferentially produced in intermediate LDL (d = 1.029 to 1.039 g/mL) (8.6 +/- 5.7 pmol PAF/3 h per mg LDL protein) and light LDL (d = 1.019 to 1.029 g/mL), but was absent from dense LDL particles (d = 1.050 to 1.063 g/mL). As PAF:acetylhydrolase inactivates PAF and oxidized forms of phosphatidylcholine, we evaluated the relationship of lipoprotein-associated PAF:acetylhydrolase to PAF formation. We confirmed that PAF:acetylhydrolase activity was elevated in native, dense LDL (41.5 +/- 9.5 nmol/min per mg protein) but low in LDL subspecies of light and intermediate density (d 1.020 to 1.039 g/mL) (3.5 +/- 1.6 nmol/min per mg protein) [Tselepis et al, Arterioscler Thromb Vasc Biol. 1995;15:1764-1773]. On copper-mediated oxidation for 3 hours at 37 degrees C, dense LDL particles conserved 20 +/- 14% of their initial enzymatic activity; in contrast, PAF:acetylhydrolase activity was abolished in light and intermediate LDL subspecies. Clearly, the elevated PAF:acetylhydrolase activity of dense LDL efficiently diminishes the potential inflammatory role of endogenously formed PAF; nonetheless, formation of proatherogenic lysophospholipids results. In contrast, LDL particles of the light and intermediate subclasses can accumulate PAF on oxidative modification.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1997

Plasma LDL and HDL subspecies are heterogenous in particle content of tocopherols and oxygenated and hydrocarbon carotenoids. Relevance to oxidative resistance and atherogenesis.

Epidemiological data indicate that dietary tocopherols and carotenoids can exert cardioprotective effects, which may be mediated by their antioxidant actions. The oxidative modification of LDL underlies the atherogenicity of these cholesterol-rich particles. The resistance of LDL to oxidation is influenced by several endogenous factors, among which the content of tocopherols and carotenoids is prominent. Of the exogenous factors, HDL inhibits oxidation of LDL via several mechanisms. In view of the paucity of data on the distribution of diverse tocopherol and carotenoid components among the apoB- and apoA-I-containing lipoproteins of human plasma, we evaluated the quantitative and qualitative features of the LDL and HDL particle subspecies in normolipidemic subjects. The bulk of tocopherols and hydrocarbon carotenoids (lycopene, alpha- and beta-carotene) was transported in LDL (45% and 76%, respectively), in contrast to the oxygenated carotenoids (lutein/zeaxanthin, canthaxanthin, and beta-cryptoxanthin), which were equally distributed between LDL and HDL. alpha-Tocopherol content was independently associated with lipid core size (cholesteryl ester and triglyceride) in VLDL, LDL, and HDL (P < .005); by contrast, the particle content of the oxygenated carotenoids lutein/zeaxanthin and canthaxanthin was strongly related to that of phospholipids. A significant and progressive decrease in the molar content of alpha- and gamma-tocopherols was found with increase in density from light to dense LDL subspecies (LDL1 to LDL5); a similar trend was observed in HDL subspecies. Furthermore, particle contents of lutein/zeaxanthin, beta-cryptoxanthin, beta-carotene, and lycopene were markedly reduced in small, dense LDL (LDL5, d = 1.050 to 1.065 g/mL). We conclude that diminished contents in such carotenoids as well as in tocopherols could underlie not only the diminished oxidative resistance of small, dense LDL but also reduced tissue targeting of antioxidants in subjects with a dense LDL phenotype.

Antioxidants↗

PubMed1997

Expression of the PAF receptor in human monocyte-derived macrophages is downregulated by oxidized LDL: relevance to the inflammatory phase of atherogenesis.

Human monocyte-derived macrophages play a major role in the initiation and progression of atherosclerotic lesions as a result of the production of a wide spectrum of proinflammatory and prothrombotic factors. Among such factors is a potent inflammatory phospholipid, platelet-activating factor (PAF), which is produced after macrophage activation. Because the cells involved in PAF biosynthesis are typically targets for the bioactions of PAF via specific cell surface receptors, we evaluated the expression of the PAF receptor in human monocyte-derived macrophages. Oxidized LDL (oxLDL) exerts multiple cellular effects that enhance lesion progression; we therefore investigated the potential modulation of expression of the macrophage PAF receptor by oxLDL. [3H]PAF bound to adherent human macrophages with a K(d) of 2.1 nmol/L and a B(max) of 19 fmol/10(6) cells; approximately 5300 binding sites per cell were detected. OxLDL (100 microg protein per milliliter) induced a twofold decrease in cellular PAF binding after 3 hours at 37 degrees C. Analysis of macrophage mRNA by reverse transcription-polymerase chain reaction (RT-PCR) revealed two forms corresponding to the PAF receptor, of which the leukocyte type (type 1 promoter) predominated. Expression of PAF receptor mRNA, evaluated by quantitative RT-PCR using an actin or a GAPDH mimic, was progressively reduced (up to 70%) by oxLDL up to 6 hours and remained low for at least 24 hours. Such downregulation was reversible after incubation of the cells for 24 hours in oxLDL-free medium. Addition of forskolin (3 micromol/L) or dibutyryl cAMP (1 mmol/L) to macrophage cultures reproduced the oxLDL-mediated inhibition of PAF receptor expression; carbamyl PAF reduced PAF binding and PAF mRNA to a similar degree (approximately 50%). These data demonstrate that atherogenic oxLDL downregulates the expression of both cellular PAF receptors and PAF receptor mRNA in macrophages, consistent with both a diminished bioresponse to PAF and decreased cell motility. Such diminished bioresponse to a powerful antacoid reflects the suppression of an acute inflammatory reaction, thereby leading to chronic, low-level inflammation, such as that characteristic of fatty streaks and more advanced atherosclerotic plaques.

Cyclic AMP↗

PubMed1997

Impact of a combination of a calcium antagonist and a beta-blocker on cell- and copper-mediated oxidation of LDL and on the accumulation and efflux of cholesterol in human macrophages and murine J774 cells.

Calcium antagonists and beta-blockers may retard or inhibit atherogenesis. In the absence of data pertaining to the potential cardioprotective action of an association of such agents, we have investigated the impact of nifedipine and atenolol, alone or in combination, on the capacity of monocyte-macrophages (ex vivo) and copper ions (in vitro) to oxidize LDL and on intracellular metabolism and efflux of free and esterified forms of cholesterol in human macrophages and foam cells. At concentrations up to 100 micromol/L, atenolol had no effect on the oxidative resistance of LDL; on the contrary, nifedipine displayed a significant dose-dependent capacity to protect LDL during copper-mediated oxidation (100 micromol/L; P<.001). Using a DPPH radical generating system, nifedipine was shown to exert free radical-trapping activity (molar ratio of scavenging activity, nifedipine:alpha-tocopherol, 1:114). The addition of atenolol to nifedipine was without effect on the antioxidant activity of the calcium antagonist. In experiments in which oxidative modification was mediated by monocyte-macrophages, nifedipine but not atenolol conserved its antioxidant capacity. Furthermore, we demonstrated that association of atenolol with nifedipine did not modify the antioxidant properties of nifedipine itself. Using a human monocyte-derived macrophage culture system, nifedipine, atenolol, or a combination of the two drugs was ineffective in inhibiting foam cell formation induced by acetylated LDL or oxidized LDL. However, atenolol (100 micromol/L) increased cellular accumulation of cholesteryl ester (+17%; P<.05), whereas nifedipine (100 micromol/L) decreased total cholesterol (-37.4%; P<.05) accumulation induced by acetylated LDL in the mouse macrophage cell line J774. A combination of the two drugs neutralized these antagonistic effects. None of these results were reproduced during the oxidized LDL-induced transformation of murine J774 cells into foam cells. Furthermore, cholesterol efflux from preloaded human macrophages was equally unaffected by the addition of the drugs alone or in combination. It therefore seems unlikely that the beneficial effect of atenolol on coronary heart disease is mediated by changes in either LDL oxidizability or cholesterol metabolism in human macrophages and foam cells. Our findings with nifedipine suggest, however, that this calcium antagonist may potentially exert antiatherosclerotic properties via a reduction of the oxidative modification of LDL, thereby affecting a reduction in foam cell formation and in the pathophysiological cellular activities of oxidized lipids, rather than by inducing a direct reduction in cholesterol accumulation in human foam cells of macrophage origin.

Adrenergic beta-Antagonists↗

PubMed1996

The complete cDNA sequence encoding plasminogen from the European hedgehog (Erinaceus europaeus).

Using a PCR-based strategy, we have determined the complete cDNA sequence encoding hedgehog plasminogen (Plg). The 2700-nucleotide cDNA (corresponding to a 2.9-kb liver-derived transcript) encodes an open reading frame of 811 amino acids which shares 74-76% identity with Plg characterized from mouse, human and rhesus monkey. Residues corresponding to the catalytic triad, tPA-cleavage site, as well as seven of the eight lysine-binding residues in kringle IV are conserved in the hedgehog. However, potential N-linked glycosylation sites which have been reported in human and rhesus Plg are not present in analogous positions in the hedgehog Plg sequence.

Amino Acid Sequence↗

PubMed1996

Pefabloc, 4-[2-aminoethyl]benzenesulfonyl fluoride, is a new, potent nontoxic and irreversible inhibitor of PAF-degrading acetylhydrolase.

We report here that 4-[2-aminoethyl]benzenesulfonyl fluoride (Pefabloc SC, Pefabloc), a new irreversible serine proteinase inhibitor, efficiently inhibits both human and rat platelet activating factor (PAF)-degrading acetylhydrolase (acetylhydrolase). Indeed, low concentrations of Pefabloc (0.1 mM) rapidly and totally inactivate both human plasma-, VLDL-, IDL-, LDL- and HDL-associated acetylhydrolase, and in addition, acetylhydrolase synthesized and released by human adherent monocytes in culture, as well as rat brain cytosolic acetylhydrolase. By contrast, Pefabloc only minimally inhibited the phospholipase A2 (PLA2) activity from Naja naja and from porcine pancreas. In addition, Pefabloc is relatively nontoxic, stable and convenient to use. Henceforth, Pefabloc may replace both DFP and PMSF and therefore constitutes a useful and valuable tool in future studies of acetylhydrolase.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1996

Phagocytic activation induces formation of platelet-activating factor in human monocyte-derived macrophages and in macrophage-derived foam cells. Relevance to the inflammatory reaction in atherogenesis.

Monocyte-derived macrophages and macrophage-derived foam cells in arterial tissue may undergo phagocytic activation and thereby contribute to an inflammatory reaction. We have investigated the effect of phagocytic activation on the formation of platelet-activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF-acether, PAF), a proinflammatory phospholipid, in human monocyte-derived macrophages (macrophages) and in cholesterol-loaded macrophage foam cells (foam cells). Adherent human monocyte-derived macrophages were transformed into foam cells upon incubation with acetylated low-density lipoproteins (Ac-LDL). Such foam cells characteristically displayed a markedly increased content of cholesteryl esters compared with macrophages (4.3 +/- 1.3 microgram/microgram DNA and 0.2 +/- 0.3 microgram/microgram DNA, n = 5, respectively). After phagocytic stimulation with serum-opsonized zymosan (OPZ), both macrophages and foam cells synthesized PAF transiently with maximal production (0.5-1.1 pmol PAF/microgram DNA, n = 5, corresponding to 4.0-8.8 pmol PAF/10(6) cells, as assessed by bioassay) occurring approximately 15 min after stimulation. A major fraction of the synthesized PAF remained cell-associated; such PAF was composed mainly of the hexadecyl (16:0 PAF, approximately 75%) and the octadecenyl (18:1 PAF) species and of trace amounts of octadecyl (18:0 PAF), as assessed by reverse-phase liquid chromatography. Addition of exogenous 16:0 lyso-PAF alone triggered PAF formation (0.9-1.7 pmol PAF/microgram DNA, after 15 min of cellular stimulation); simultaneous cellular stimulation with OPZ and 16:0 lyso-PAF increased PAF formation in an additive manner. Acetyltransferase, the enzyme which acetylates the precursor lyso-PAF and transforms it into PAF, displayed elevated activity both in macrophages and in foam cells, attaining 83-240 pmol PAF formed per min per mg DNA (n = 4); such elevated activity was not increased by OPZ-stimulation. The activity of acetylhydrolase, the PAF-degrading enzyme, was similar in macrophages and in foam cells, and varied between 120 pmol and 320 pmol PAF degraded per min per mg DNA (n = 5). Cell-associated acetylhydrolase activity was increased significantly by 40+/-15 % (P < 0.003, n = 5) after 15 - 30 min of activation with OPZ compared with non-stimulated cells and may account for the rapid decrease in cellular PAF content observed approximately 30 min after stimulation. These studies have established that metabolism of PAF in foam cells closely resembles that in macrophages, and thus PAF metabolism is largely independent of cellular cholesterol content. Moreover our data are consistent with the hypothesis that both macrophages and macrophage-derived foam cells upon phagocytic-activation constitute a significant transient source of PAF at inflammatory sites in the arterial intima where this phospholipidic mediator may exert potent proatherogenic and prothrombotic effects.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1996

The atherogenic role of triglycerides and small, dense low density lipoproteins: impact of ciprofibrate therapy.

Triglyceride levels greater than 150 mg/dl are associated with the atherogenic lipoprotein phenotype, represented by a predominance of small, dense low density lipoproteins (LDL) and diminished concentrations of high density lipoproteins. This phenotype is characteristic of patients with combined hyperlipidemia (CHL). We evaluated the impact of ciprofibrate therapy (100 mg daily) for 1 month on the quantitative and qualitative characteristics of the LDL particle profile in CHL patients (n = 9). Marked reductions in plasma levels of triglycerides (-33%), cholesterol (-15.5%), LDL-cholesterol (-15.2%) and apolipoprotein-B (-22.7%) were accompanied by a significant degree of normalisation in the LDL subspecies profile; such normalisation resulted from a preferential reduction in the elevated levels of dense LDL subspecies (LDL-4 and LDL-5, -43% and -54%, respectively; P < 0.03 and P < 0.006, respectively). Concentrations of light LDL (LDL-1) were also reduced significantly (-30%, P < 0.006), while those of LDL-3 of intermediate density (d = 1.029-1.039 g/ml) were moderately increased (+23%). The ciprofibate-induced normalisation of both the quantitative and qualitative features of the atherogenic LDL particle profile characteristic of combined hyperlipidemia is consistent with a reduction in the elevated cardiovascular risk in the patient group.

Cardiovascular Diseases↗

PubMed1996

A comparison of high-energy oblique lung irradiation techniques.

The lung cancer death rate in the U.S. rose 440% between 1957-59 and 1987-89, from 5.4 to 29.4 per 100,000. While surgical resection of small, localized carcinomas offers the best prognosis, only 15-20% of lung cancers fall into this category. The remaining 80-85% of patients are generally candidates for radiation therapy. Typically, the tumor volume (plus a 2 cm margin) and the mediastinum will be irradiated, using parallel opposed anterior and posterior ports, until the spinal cord has reached tolerance at 45 Gy. At this point, an off-cord lateral or oblique treatment technique will be used to complete the prescribed dose to the tumor. The depth to isocenter for oblique ports may easily be 15 cm. With this depth, a high-energy x-ray beam seems to be required; however, the beam may pass through a significant portion of lung tissue, reducing the equivalent depth. Another factor to consider is the build-up region beyond the lower density lung tissue. Two different energy beams, 6 MV and 18 MV, were compared for the oblique treatment ports. Plans were run using a thorax CT slice of an anthropomorphic phantom for parallel opposed oblique fields at these two energies, each with and without CT correction. Further data were collected for comparison by thermoluminescent dosimetry measurements. This paper describes the process and results obtained.

Humans↗

PubMed1996

Absence of cholesteryl ester transfer protein-mediated cholesteryl ester mass transfer from high-density lipoprotein to low-density lipoprotein particles is a major feature of combined hyperlipidaemia.

Elevated plasma cholesteryl ester transfer protein (CETP) mass is characteristic of combined hyperlipidaemia (CHL), an atherogenic dyslipidaemia characterized by increased levels of both very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) and subnormal levels of high-density lipoprotein (HDL). CETP remodels plasma lipoproteins by promoting the heteroexchange of neutral lipids. To determine the mechanism of the CETP-mediated redistribution of cholesteryl ester (CE) between plasma lipoprotein particles in CHL, we measured CE mass transfer and exchange from HDL to apoB-containing lipoproteins under physiological conditions in the plasmas of 14 CHL patients and compared the data with those in a group of normolipidaemic subjects (NLS; n = 9). The rate of CE mass transfer from HDL to VLDL was significantly increased in CHL patients (24.1 +/- 3.8 micrograms CE transferred h-1 mL-1 plasma) when compared with NLS (14.4 +/- 2.6 micrograms CE transferred h-1 mL-1 plasma, P = 0.0001). By contrast with control subjects, no net CE mass transfer from HDL to LDL was detected in CHL patients; transfer of radiolabelled CE to LDL was, however, observed, suggesting the occurrence of CE exchange between HDL and LDL in the absence of net CE mass transfer. The LDL fraction from CHL patients displayed a significant reduction (15%; P < 0.003) in its ability to accept cholesteryl ester from HDL when compared with normolipidaemic LDL. Moreover, a reduction of 10% (P < 0.02) was found in the capacity of hyperlipidaemic HDL to donate cholesteryl esters to apoB-containing lipoproteins as compared with control HDL; the reduced levels (-32%) of HDL2b particles in CHL plasmas may account for this effect. We conclude that the low affinity of hyperlipidaemic LDL particles for CETP, taken together with the elevated plasma concentrations of a qualitatively active CE acceptor, VLDL, and the low HDL levels in CHL patients, result in the absence of net CE mass transfer from HDL to LDL in Combined hyperlipidaemia.

Adult↗

PubMed1996

Fenofibrate reduces plasma cholesteryl ester transfer from HDL to VLDL and normalizes the atherogenic, dense LDL profile in combined hyperlipidemia.

The effect of fenofibrate on plasma cholesteryl ester transfer protein (CETP) activity in relation to the quantitative and qualitative features of apoB- and apoA-I-containing lipoprotein subspecies was investigated in nine patients presenting with combined hyperlipidemia. Fenofibrate (200 mg/d for 8 weeks) induced significant reductions in plasma cholesterol (-16%; P < .01), triglyceride (-44%; P < .007), VLDL cholesterol (-52%; P = .01), LDL cholesterol (-14%; P < .001), and apoB (-15%; P < .009) levels and increased HDL cholesterol (19%; P = .0001) and apoA-I (12%; P = .003) levels. An exogenous cholesteryl ester transfer (CET) assay revealed a marked decrease (-26%; P < .002) in total plasma CETP-dependent CET activity after fenofibrate treatment. Concomitant with the pronounced reduction in VLDL levels (37%; P < .005), the rate of CET from HDL to VLDL was significantly reduced by 38% (P = .0001), whereas no modification in the rate of cholesteryl ester exchange between HDL and LDL occurred after fenofibrate therapy. Combined hyperlipidemia is characterized by an asymmetrical LDL profile in which small, dense LDL subspecies (LDL-4 and LDL-5, d = 1.039 to 1.063 g/mL) predominate. Fenofibrate quantitatively normalized the atherogenic LDL profile by reducing levels of dense LDL subspecies (-21%) and by inducing an elevation (26%; P < .05) in LDL subspecies of intermediate density (LDL-3, d = 1.029 to 1.039 g/mL), which possess optimal binding affinity for the cellular LDL receptor. However, no marked qualitative modifications in the chemical composition or size of LDL particles were observed after drug treatment. Interestingly, the HDL cholesterol concentration was increased by fenofibrate therapy, whereas no significant change was detected in total plasma HDL mass. In contrast, the HDL subspecies pattern was modified as the result of an increase in the total mass (11.7%) of HDL2a, HDL3a, and HDL3b (d = 1.091 to 1.156 g/mL) at the expense of reductions in the total mass (-23%) of HDL2b (d = 1.063 to 1.091 g/mL) and HDL3c (d = 1.156 to 1.179 g/mL). Such changes are consistent with a drug-induced reduction in CETP activity. In conclusion, the overall mechanism involved in the fenofibrate-induced modulation of the atherogenic dense LDL profile in combined hyperlipidemia primarily involves reduction in CET from HDL to VLDL together with normalization of the intravascular transformation of VLDL precursors to receptor-active LDLs of intermediate density.

Adult↗

PubMed1996

Plasma lipoproteins in preruminant calves fed diets containing tallow or soybean oil with and without cholesterol.

Five-week-old, preruminant male calves were fed milk replacer containing tallow or soybean oil (230 g/ kg of dietary DM) with and without cholesterol (10 g/ kg of dietary DM) for 17 d in order to study changes in plasma lipids and lipoproteins. Dietary soybean oil induced higher cholesterolemia than did tallow because of a specific increase in plasma concentrations of large high density lipoproteins of type 1 (1.026 to 1.060 g/ml), but plasma concentrations of low and very low density lipoproteins were not modified. Addition of cholesterol to diets containing either tallow or soybean oil markedly increased plasma concentrations of intermediate and low density lipoproteins, suggesting partial inhibition of the low density lipoprotein receptor activity in tissue. By contrast, dietary cholesterol added to the diet containing soybean oil led to an increase in plasma concentrations of type 1 high density lipoproteins and of light high density (1.060 to 1.091 g/ml) lipoproteins. These data indicated that the soybean oil diet, which was rich in linoleic acid, did not reduce the effects of dietary cholesterol on the metabolism of low and high density lipoproteins in the preruminant calf.

Aging↗

PubMed1995

Core lipid structure is a major determinant of the oxidative resistance of low density lipoprotein.

The influence of thermally induced changes in the lipid core structure on the oxidative resistance of discrete, homogeneous low density lipoprotein (LDL) subspecies (d, 1.0297-1.0327 and 1.0327-1.0358 g/ml) has been evaluated. The thermotropic transition of the LDL lipid core at temperatures between 15 degrees C and 37 degrees C, determined by differential scanning calorimetry, exerted significant effects on the kinetics of copper-mediated LDL oxidation expressed in terms of intrinsic antioxidant efficiency (lag time) and diene production rate. Thus, the temperature coefficients of oxidative resistance and maximum oxidation rate showed break points at the core transition temperature. Temperature-induced changes in copper binding were excluded as the molecular basis of such effects, as the saturation of LDL with copper was identical below and above the core transition. At temperatures below the transition, the elevation in lag time indicated a greater resistance to oxidation, reflecting a higher degree of antioxidant protection. This effect can be explained by higher motional constraints and local antioxidant concentrations, the latter resulting from the freezing out of antioxidants from crystalline domains of cholesteryl esters and triglycerides. Below the transition temperature, the conjugated diene production rate was decreased, a finding that correlated positively with the average size of the cooperative units of neutral lipids estimated from the calorimetric transition width. The reduced accessibility and structural hindrance in the cluster organization of the core lipids therefore inhibits peroxidation. Our findings provide evidence for a distinct effect of the dynamic state of the core lipids on the oxidative susceptibility of LDL and are therefore relevant to the atherogenicity of these cholesterol-rich particles.

Calorimetry, Differential Scanning↗