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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cholesteryl esters are a transport and storage form of cholesterol in normal physiology but also a significant lipid in atherosclerotic plaques. To understand better the molecular properties of cholesteryl esters in tissues and plaques, we have studied the polymorphic and mesomorphic features of pure and mixed cholesteryl esters by solid state C-13 NMR with magic angle sample spinning (MASNMR). The temperature-dependent properties of two single components (cholesteryl linoleate (CL, C18:2) and cholesteryl linolenate (CLL, C18:3)), four binary systems (cholesteryl palmitate (CP, C16:0) with CL, CLL or cholesteryl oleate (CO, C18:1), and CO/CL), one ternary system (CO/CP/CL), and one quaternary system (CO/CP/CL/CLL) were studied. The mixing ratios were based on the composition of an atherosclerosis plaque dissected from a cholesterol-fed New Zealand white rabbit. C-13 MASNMR determined the phase transition temperatures, identified the phases present in all systems, and provided novel information about molecular structures. For example, solid CL exhibited a disordered structure with multiple molecular conformations, whereas pure CLL had a crystalline structure different from the three most commonly characterized forms (MLII, MLI, BL). In binary mixtures, the crystalline structure of each cholesteryl ester species was identified by its own characteristic resonances. It was found that CP always existed in its native BL form, but CL and CO were influenced by the composition of the mixture. CL was induced to form MLII crystals by the coexisting CP (55 wt%). When CO was cooled from the isotropic phase, it existed as a mixture of MLII and an amorphous form. The presence of CP significantly accelerated the conversion of the amorphous form to the MLII form. For the ternary mixture co-dried from chloroform, CL cocrystallized with CO in the MLII form and CP existed in BL form. Addition of a small amount of CLL slightly increased the heterogeneity of the solid mixture, but had little effect on the crystal structures or the phase transitions. C-13 MASNMR represents a powerful method for physical characterization of cholesteryl ester mixtures reflecting the composition of biological samples.
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PMID:Phase behavior and crystalline structures of cholesteryl ester mixtures: a C-13 MASNMR study. 764 42

The dipolar-decoupled, natural abundance Fourier transform and cross polarization [13C] NMR spectra of human elastin isolated from atherosclerotic aorta and aortas free of atherosclerotic lesions, bovine insoluble elastin and bovine kappa-elastin were obtained at 75 MHz, with 5-7 kHz magic angle sample spinning. Spin-lattice rotating frame relaxation parameters were measured for protons (T1pH) and for carbons (T1pC) at room temperature. Proton relaxation times were shorter for bovine kappa-elastin (T1pH = 1.7 ms) than for bovine elastin (T1pH) = 3.5 ms). Calculation of T1pH showed no differences between human normal and atherosclerotic elastins. T1pC were shorter for bovine kappa-elastin than for bovine elastin. While alpha-carbons of human atherosclerotic elastin had shorter T1pC than normal elastin alpha carbons, carbons from hydrophobic amino acid side chains had longer T1pC for atherosclerotic then for normal elastin. Biochemical studies of aortic wall and purified elastin showed significantly increased content of lipids (atherosclerotic 67.7 mmol/g elastin, control 54.7 mmol/g elastin) and calcium (atherosclerotic 38.3 mmol/g elastin, control 19.6 mmol/g elastin). Changes in relaxation parameter values may be caused by the structural and biochemical changes in human elastin. Increased mobility of polypeptide chains as based on the model kappa-elastin studies is caused by the action of elastase. Restriction of mobility is expected to be caused by the accumulation of lipids and calcium.
Atherosclerosis 1995 May
PMID:Changes in elastin in human atherosclerotic aorta: carbon-13 magic angle sample-spinning NMR studies. 766 85

A case of bilateral blindness in a 47-year-old patient after buccal tumorectomy and bilateral neck dissection is reported. The diagnosis of posterior optic ischaemia was substantiated by the features of blindness and the negativity of cerebral CT-scanography and NMR imaging. The respective roles of atherosclerosis, arterial hypotension, acute anaemia and increased intracranial pressure are discussed. Preventive measures include a strict control of blood pressure, blood loss and head position.
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PMID:[Postoperative blindness after buccal tumorectomy and bilateral radical neck dissection]. 767 84

Oxidatively modified LDL (oLDL) is thought to play a key role in the pathogenesis of atherosclerosis. We have studied Cu(2+)-induced peroxidation reactions of LDL and have elucidated the sequence of events which subsequently occur within LDL particles by 1H-NMR spectroscopy. Studies of chloroform/methanol extracts show that LDL arachidonate is oxidised by Cu2+ at a higher rate and to a greater extent than linoleate, giving isomeric hydroperoxides with predominantly trans,trans double-bonds, whilst only cis,trans isomers were detected as intrinsic hydroperoxides in control LDL samples. These intrinsic hydroperoxides were not degraded during peroxidation, suggesting that they are not involved in the initiation of Cu(2+)-induced peroxidation. Aldehydes arising from the decomposition of hydroperoxides were also detected, as well as saturated fatty acids which were released into the external aqueous medium. Decomposition pathways of the two major isomeric hydroperoxides are discussed. Cu(2+)-induced oxidation of LDL cholesterol appears to occur only after hydroperoxide breakdown, with esterified cholesterol being oxidised to a greater extent than free cholesterol. Phospholipid hydrolysis appeared to parallel the peroxidation of arachidonic acid, and the released lysophosphatidylcholine may become associated with apoB. These results suggest that hydroperoxide breakdown (probably in phospholipids) may be a key event in the peroxidation process, leading to the oxidation of cholesterol and propagation into the core of LDL.
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PMID:Copper-induced LDL peroxidation investigated by 1H-NMR spectroscopy. 776 90

The lipid peroxidation product trans-4-hydroxy-2-nonenal (HNE) has been implicated in the covalent modification of low-density lipoproteins (LDL) thought to contribute to the over-accumulation of LDL in the arterial wall in the initial stages of atherosclerosis. Proposals for the exact structures of "early" protein side-chain modifications until now have been based on indirect evidence. In this paper, the structures of first-formed His- and Lys-based adducts were elucidated by correlating NMR spectral properties with those obtained on models with reduced chiral center content, in some cases following hydride reduction. In this manner, we could confirm unambiguously the structure of a HNE-His imidazole(N tau) Michael adduct, stabilized as a cyclic hemiacetal and isolated from a neutral aqueous 1:1 stoichiometry reaction mixture. In the case of Lys/amine reactivity, where an excess of amine is needed to avert HNE aldol condensation, the predominance of a 1:1 Michael adduct in homogeneous aqueous solution and a 1:2 Michael-Schiff base adduct under two-phase aqueous-organic conditions could be verified by isolation of the respective borohydride-reduced forms. The 1:2 adduct, shown to exist as the cyclic hemiaminal, could represent a stable lysine-based cross-link in certain protein microenvironments.
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PMID:Structural definition of early lysine and histidine adduction chemistry of 4-hydroxynonenal. 776 13

Ultrasonic dopplerography and rheoencephalography were employed to investigate cerebral circulation in patients (n-123) with carotid artery atherosclerosis having transient disturbances of cerebral circulation or ischemic apoplexy. The ischemic foci were measured and localized at computed and NMR tomography. The above complex of examinations allowed evaluation of local, regional and overall blood filling of the brain, of collateral flow as well as conclusion on the type of cerebral hemodynamics. Focal lesions seem to arise in inadequate functioning of collateral circulation, that is in patients with unstable and decompensated hemodynamics. Active collateral circulation shown by the absence of noticeable interhemispheric asymmetry proved prognostically favourable. Administration of vasoactive drugs to patients with decompensated cerebral hemodynamics may induce stealing syndrome and aggravation of neurological symptoms.
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PMID:[A clinico-instrumental evaluation of cerebral hemodynamics in patients with occlusive lesions of the carotid arteries (its diagnostic and prognostic importance)]. 794 92

Because cerebral atrophy and white substance of the cerebral hemispheres became typical findings at NMR-tomography of the brain in Parkinson's disease, the authors initiated a study to quantify the observed defects. A combination of neurological, neuropsychological and NMR-tomography methods with addition of formalized scales has been utilized. The severity of cerebral atrophy and that of neurological and psychic disorders were related. Internal atrophy was more frequently observed in older patients, the external one was more characteristic for patients with systemic atherosclerosis. Multiple focal lesions of the white substance were encountered in associated arterial hypertension and was present in all the patients with distinct cerebral atrophy. Diffuse lesions of the white substance (leukareosis) showed no relationship to any of the factors studied.
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PMID:[Magnetic resonance tomography of the brain in Parkinson's disease]. 816 Apr 96

Fatty acid composition of lipid classes and NMR spectra of lipoproteins were compared in 6 young (24-35-year-old) and 6 elderly (79-90-year-old) women. Cholesteryl ester, triglyceride and protein content of LDL in elderly women were significantly higher (+52-57% and +20% for lipids and proteins, respectively) than those observed in young women. HDL lipid levels were similar in the two groups. The proportion of linoleic acid (mainly in cholesteryl esters and phospholipids) of each lipoprotein species was always lower in octogenarians when compared with young females (lowering of 13-28% and 27-46% for cholesteryl esters and phospholipids, respectively). Conversely, the proportions of mono-unsaturated fatty acids (mainly oleic acid) increased in all lipid classes, although this was only significant in cholesteryl esters from each lipoprotein species. NMR spectra of lipoproteins showed a restricted mobility of acyl chain terminal CH3 groups in old women which was significant only in VLDL and HDL3. This suggests that the decrease of linoleic acid could affect the lipid mobility in lipoproteins of elderly women.
Atherosclerosis 1993 Jan 25
PMID:Variations in the fatty acid composition of lipid classes from lipoproteins in elderly women. 845 63

Myeloperoxidase, a heme protein secreted by activated phagocytes, may be a catalyst for lipoprotein oxidation in vivo. Active myeloperoxidase is a component of human atherosclerotic lesions, and atherosclerotic tissue exhibits selective enrichment of protein dityrosine cross-links, a well characterized product of myeloperoxidase. Tyrosylation of lipoproteins with peroxidase-generated tyrosyl radical generates multiple protein-bound tyrosine oxidation products in addition to dityrosine. The structural characterization of these products would thus serve as an important step in determining the role of myeloperoxidase in lipoprotein oxidation in the artery wall. We now report the identification and characterization of four distinct tyrosyl radical addition products generated by human phagocytes. Activated neutrophils synthesized three major fluorescent products from -tyrosine; on reverse phase HPLC, each compound coeluted with fluorescent oxidation products formed by myeloperoxidase. We purified the oxidation products to apparent homogeneity by cation and anion exchange chromatographies and identified the compounds as dityrosine (3,3'-dityrosine), trityrosine (3,3',5',3"-trityrosine) and pulcherosine (5-[4"-(2-carboxy-2-aminoethyl)phenoxy]3, 3'-dityrosine) by high resolution NMR spectroscopy and mass spectrometry. Additionally, we have found that dityrosine is a precursor to trityrosine, but not pulcherosine. In a search for a precursor to pulcherosine, we identified isodityrosine (3-[4'-(2-carboxy-2-aminoethyl)phenoxy]tyrosine), a non-fluorescent product of L-tyrosine oxidation by human phagocytes. Our results represent the first identification of this family of tyrosyl radical addition products in a mammalian system. Moreover, these compounds may serve as markers specific for tyrosyl radical-mediated oxidative damage in atherosclerosis and other inflammatory conditions.
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PMID:Human phagocytes employ the myeloperoxidase-hydrogen peroxide system to synthesize dityrosine, trityrosine, pulcherosine, and isodityrosine by a tyrosyl radical-dependent pathway. 870 10

An attempt was undertaken to analyze the phase changes in the transverse magnetization component, M[perp], determined in NMR response by an elastic wave in the presence of two pulses with opposite magnetic field gradient directions. The obtained theoretical results indicate that such changes are significant in biologic tissues. Their measurement by NMR opens up new possibilities for detecting the displacement and some viscoelastic properties such as the adiabatic compressibility coefficient, amplitude wave damping coefficient, frequency and dispersion strength of elastic relaxation processes, etc. The method may be useful in basic applied research and in medical diagnosis of some diseases resulting in the variation of elastic properties of biological tissues, eg, atherosclerosis.
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PMID:Viscoelastic property detection by elastic displacement NMR measurements. 883 59


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