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K L Carpenter

Publications and source records attributed to K L Carpenter.

At least 37 records · Page 2Linked to original sources
PubMed1995

Toxicity of oxysterols to human monocyte-macrophages.

We have investigated the toxicity of the cholesterol oxidation products (oxysterols), 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, 7-ketocholesterol, 25-hydroxycholesterol and 26-hydroxycholesterol to human monocyte-macrophages in vitro. The 7-position derivatives are present in low density lipoprotein (LDL) oxidised with copper (II) sulphate and macrophages, and in extracts of human atherosclerotic lesions, which also contain 26-hydroxycholesterol. We have also assessed 25-hydroxycholesterol for toxicity because it has often been used in studies of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibition and LDL receptor down-regulation. Measurement of radioactivity release from monocyte-macrophages preloaded with tritiated adenine, as a means of assessing cytotoxicity that all the oxysterols showed time- and concentration-dependent toxicity. The cytotoxic potency of 26-hydroxycholesterol was the greatest. The 7-position derivatives also produced marked cell damage, though at higher concentrations than for 26-hydroxycholesterol. Of the oxysterols assessed, the toxicity of 25-hydroxycholesterol was the least. The cytotoxicity of 7 beta-hydroxycholesterol and 26-hydroxycholesterol was also shown using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) dye reduction assay which confirmed that 26-hydroxycholesterol was more toxic than 7 beta-hydroxycholesterol. Incubation of monocyte-macrophages with cholesterol added to the different oxysterols gave varying results. Cholesterol, which was not itself toxic, inhibited the toxicity of 25-hydroxycholesterol and 26-hydroxycholesterol, but the toxicity of the 7-position derivatives was not affected. The possible relevance of these molecules to the death of macrophages seen in atherosclerosis is discussed.

Cells, Cultured↗
PubMed1995

Reference states and reversals: undoing actions with verbs.

The purpose of these studies is to characterize children's conception of reversal and its relation to a reference state. A reversal is the move from one state to some prior state of affairs. For example, shoes that have been TIED can be UNTIED, parcels WRAPPED then UNWRAPPED, and dishes COVERED then UNCOVERED. The present studies were designed to find out how children (aged 1;0 to 5;0) describe reversals of action that restore objects to a prior, less constrained, state. In English, the prefix un- offers the most productive device for this, but, initially, children rely on a verb like open, on general purpose undo, and on particles like out and off. As they acquire un-, English-speaking children must learn that this prefix applies primarily to verbs for change-of-state, often for enclosing, covering and attaching. In German, there is no reversal prefix, but there are productive particles. German-speaking children also begin with a verb like open and then turn to verb particles on a course similar to that in English to express reversals.

Child Language↗
PubMed1995

Macrophages, lipid oxidation, ceroid accumulation and alpha-tocopherol depletion in human atherosclerotic lesions.

Necropsy samples of atherosclerotic lesions of different histological stages have been analysed. Ceroid was present in all the lesions, within lipid-laden macrophage foam cells and extracellularly in the atheromatous core of advanced lesions. Mean levels of 7 beta-hydroxycholesterol, 26-hydroxycholesterol and hydroxyoctadecadienoic acids were all significantly greater in lesions than in normal intima. Levels of hydroxycholesterols were very low or undetectable in normal intima. Fatty streaks showed the highest ratio of 7 beta-hydroxycholesterol to cholesterol, and the lowest ratio of linoleate to oleate, suggesting that this type of lesion experiences the greatest free radical activity. Levels of 26-hydroxycholesterol, a product of the cytochrome P-450 enzyme sterol 26-hydroxylase, and the ratio of 26-hydroxycholesterol to cholesterol were significantly higher in advanced lesions than in intermediate lesions or fatty streaks. The ratio of alpha-tocopherol to cholesterol levels varied widely in normal intima but was consistently low in lesions, especially those rich in macrophage foam cells, suggesting that oxidative activity in the lesion may lead to significant oxidation of the lesion constituents only after alpha-tocopherol has been depleted. Macrophage death was a characteristic feature of advanced lesions, with apoptotic bodies present, and occasionally, intact apoptotic cells were seen in lesions. These striking correlations between macrophages, lipid oxidation, alpha-tocopherol depletion, ceroid accumulation, and macrophage death in advanced lesions, strongly support a role for oxidative damage in atherosclerosis, and lend credence to the idea that alpha-tocopherol dietary supplementation may slow the progression of atherosclerosis in humans.

Aorta, Abdominal↗
PubMed1995

Depletion of alpha-tocopherol in human atherosclerotic lesions.

Estimations of alpha-tocopherol content were made on a series of human necropsy samples of normal arterial wall and of atherosclerotic lesions. The results were compared with stage of lesion, shown by histology, and with the amounts of cholesterol and hydroxycholesterols in the same lesions. The ratio of alpha-tocopherol to cholesterol levels varied widely in normal arterial wall but was consistently low in lesions, especially in lesions rich in macrophage foam cells. The results suggested that significant accumulation of hydroxycholesterols, found almost exclusively in lesions, only occurred when alpha-tocopherol levels were low in relation to the cholesterol content. This suggests that oxidative activity in the lesion may lead to significant oxidation of constituents of low-density lipoprotein only after alpha-tocopherol has been depleted.

Adolescent↗
PubMed1994

Production of oxidized lipids during modification of low-density lipoprotein by macrophages or copper.

The oxidation of low-density lipoprotein (LDL) is implicated in atherosclerosis. Lipids and oxidized lipids were analysed by gas chromatography and gas chromatography-mass spectrometry in human LDL incubated with mouse peritoneal macrophages (MPM) or copper (II) sulphate in Ham's F-10 medium or medium alone (control). MPM-modification and copper-catalysed oxidation of LDL resulted in the formation of oxysterols, mainly cholest-5-en-3 beta,7 beta-diol (7 beta-OH-CHOL); 7%-19% of the initial cholesterol was converted to 7 beta-OH-CHOL in 24 h. 7 beta-OH-CHOL levels in control LDL were very low. The increase in 7 beta-OH-CHOL in MPM and copper-oxidized LDL was accompanied by decreases in linoleate and arachidonate and increases in the electrophoretic mobility and degradation of LDL protein by 'target' macrophages. The concerted occurrence of these processes and their similarity in both MPM-modification and copper-catalysed oxidation of LDL were suggested by the highly significant cross-correlations. The fall in polyunsaturated fatty acid (PUFA) was accompanied by a directly proportional increase in electrophoretic mobility of the LDL. Production of 7 beta-OH-CHOL and protein degradation by macrophages showed modest elevations during the initial steep fall in PUFA, and showed their greatest increases as the levels of PUFA slowly approached zero. The levels of 7 beta-OH-CHOL and the degradation of LDL by macrophages were directly proportional. The degradation of LDL by macrophages increased rapidly as the electrophoretic mobility of LDL was slowly approaching its maximum level.

Animals↗
PubMed1993

Lipids and oxidised lipids in human atheroma and normal aorta.

Lipids and oxidised lipids were analysed by GC and GC-MS in samples of human atheroma (necrotic gruel from the interior of advanced atherosclerotic plaques in the aorta) and human normal aorta (lesion-free intima plus inner media) from necropsy subjects. Cholest-5-en-3 beta,26-diol and cholest-5-en-3 beta,7 beta-diol were detected in all the atheroma samples examined but not in significant amounts in normal aorta. In atheroma, cholest-5-en-3 beta,26-diol was approximately proportional to cholesterol. Several isomeric hydroxy-octadecadienoic acids were detected in atheroma, and, in smaller amounts, in normal aorta. Many of the components of atheroma showed a high degree of cross-correlation on linear regression analysis, whilst cross-correlations were somewhat weaker for normal aorta. Atheroma showed a vast accumulation of lipid, especially cholesterol, in comparison to normal aorta. The atheroma samples contained a larger proportion of linoleate relative to oleate than the normal aorta. Levels of fatty acids relative to cholesterol were lower for atheroma than for normal aorta. The chemical composition of atheroma appeared unrelated to the age of the subject, whereas age-related increases in linoleate, oleate and cholesterol content were seen in the samples of normal aorta.

Age Factors↗
PubMed1993

Flow cytometric measurement of ceroid accumulation in macrophages.

Flow cytometry has been examined as a method for quantitative measurement of the accumulation in macrophages of ceroid, an autofluorescent polymer composed of oxidised protein and lipid. Murine peritoneal macrophages were cultured in the presence of cholesteryl linoleate- or arachidonate-bovine serum albumin (CL/BSA or CA/BSA) complexes. Ceroid accumulation was greater from CA/BSA than from CL/BSA and was dependent upon both time and cell plating density. Inclusion of vitamin E with the complexes diminished the accumulation of ceroid fluorescence after exposure to either CL/BSA or CA/BSA. Controls included exposure of macrophages to BSA, alone and with vitamin E, both of which led to some fluorescence at a similar wavelength to that used to monitor ceroid accumulation (Ex: 351.1-363.8 nm/Em: 490 nm and upwards). Ceroid accumulation can be monitored semi-quantitatively by staining techniques. However, such methods are relatively crude and give little information about the amount of ceroid within cells. Flow cytometry, on the other hand, can give a quantitative assessment of cellular ceroid accumulation, provided experiments are conducted with appropriate controls. The findings are discussed in the context of human atherosclerosis and of future investigation of cell-mediated lipid oxidation and its potential antagonists.

Animals↗
PubMed1991

Oxygen radicals and atherosclerosis.

There is increasing evidence that lipids, especially those in low density lipoprotein, may be oxidised during the development of atherosclerotic lesions. The lipid-laden "foam cells" of atherosclerosis are macrophages, which are known to produce oxygen radicals in their microbicidal role. The same process could result in oxidation of lipid or lipoprotein in atherosclerosis. In human atherosclerotic lesions, many of the macrophage foam cells also contain ceroid, an insoluble polymer formed by oxidation of mixtures of lipid and protein. Using in vitro systems, we have studied the possibility that macrophages may be responsible for the oxidation of lipid and/or lipoprotein. Experiments are described in which mouse peritoneal macrophages and human monocyte-derived macrophages have been shown to oxidise cholesteryl linoleate, added to the cultures in the form of an artificial lipoprotein, with the production of soluble oxidised lipids, including oxidised sterols, and, in the case of mouse peritoneal macrophages, abundant ceroid. The oxidation was inhibited by radical scavengers. Oxidised sterols are cytotoxic. It is thus conceivable that oxidised sterols produced by monocyte-macrophages may lead to necrosis and progression of the lesion. Possibilities for prevention of this oxidation are discussed.

Animals↗
PubMed1990

Oxidation of cholesteryl linoleate by human monocyte-macrophages in vitro.

The amount of cholest-5-en-3 beta,7 beta-diol (CD) was significantly higher in cultures of human monocytes incubated with cholesteryl linoleate-bovine serum albumin (CL/BSA) artificial lipoproteins than in no-cell control incubations of CL/BSA. CD production by monocytes was almost completely inhibited by the radical scavengers butylated hydroxytoluene (BHT), probucol, and alpha-tocopherol, and was partially inhibited by the metal chelator EDTA. The production of CD was accompanied by decrease in linoleic acid. CD amounts were negligible in incubations of monocytes with cholesteryl oleate/BSA (CO/BSA) or cholesterol/BSA (C/BSA). Ability to produce CD from CL/BSA appeared to increase with age in culture of human monocyte-macrophages. Considerable variations were observed in the CD production from CL/BSA by monocytes from different blood donations. Higher levels of CD production appeared more common with monocytes from men than from women. The significance of these results in the context of human atherosclerosis is discussed.

Arteriosclerosis↗
PubMed1990

Macrophages and ceroid in human atherosclerosis.

It is proposed that atherosclerosis is a chronic inflammatory disease in which monocyte-derived macrophages are doing harm and smooth muscle cells are essentially reparative. Activities of macrophages that might be contributory to the development of atherosclerosis are tabulated. Observations and experiments are described that suggest macrophages may be contributing to lipoprotein oxidation within the plaque and that individual humans vary in their macrophage oxidative capacity. The possibility of intervention with antioxidants is discussed.

Animals↗