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C Fielding

Publications and source records attributed to C Fielding.

13 recordsLinked to original sources
PubMed2001

Apolipoprotein A-I stimulates the transport of intracellular cholesterol to cell-surface cholesterol-rich domains (caveolae).

We have studied the effect of lipid-free human plasma apolipoprotein A-I (apoA-I) on the transport of newly synthesized cholesterol to cell-surface cholesterol-rich domains, which in human skin fibroblasts are mainly represented by caveolae. Changes in transport of newly synthesized cholesterol were assessed after labelling cells with [(14)C]acetate at 15 degrees C and warming cells to permit the transfer of cholesterol, followed by the selective oxidation of cholesterol in cholesterol-rich domains (caveolae) in the plasma membrane before their partial purification. ApoA-I, but not BSA added in an equimolar concentration, enhanced the transport of cholesterol to the caveolae up to 5-fold in a dose- and time-dependent manner. The effect of apoA-I on cholesterol transport exceeded its effect on cholesterol efflux, resulting in an accumulation of intracellular cholesterol in caveolae. Methyl-beta-cyclodextrin, added at a concentration promoting cholesterol efflux to the same extent as apoA-I, also stimulated cholesterol trafficking, but was 3-fold less effective than apoA-I. Progesterone inhibited the transport of newly synthesized cholesterol to the caveolae. Treatment of cells with apoA-I stimulated the expression of caveolin, increasing the amount of caveolin protein and mRNA by approx. 2-fold. We conclude that apoA-I induces the transport of intracellular cholesterol to cell-surface caveolae, possibly in part through the stimulation of caveolin expression.

Apolipoprotein A-I↗
PubMed2001

Elimination of rabies from red foxes in eastern Ontario.

The province of Ontario (Canada) reported more laboratory confirmed rabid animals than any other state or province in Canada or the USA from 1958-91, with the exception of 1960-62. More than 95% of those cases occurred in the southern 10% of Ontario (approximately 100,000 km2), the region with the highest human population density and greatest agricultural activity. Rabies posed an expensive threat to human health and significant costs to the agricultural economy. The rabies variant originated in arctic foxes: the main vector in southern Ontario was the red fox (Vulpes vulpes), with lesser involvement of the striped skunk (Mephitis mephitis). The Ontario Ministry of Natural Resources began a 5 yr experiment in 1989 to eliminate terrestrial rabies from a approximately 30,000 km2 study area in the eastern end of southern Ontario. Baits containing oral rabies vaccine were dropped annually in the study area at a density of 20 baits/km2 from 1989-95. That continued 2 yr beyond the original 5 yr plan. The experiment was successful in eliminating the arctic fox variant of rabies from the whole area. In the 1980's, an average of 235 rabid foxes per year were reported in the study area. None have been reported since 1993. Cases of fox rabies in other species also disappeared. In 1995, the last bovine and companion animal cases were reported and in 1996 the last rabid skunk occurred. Only bat variants of rabies were present until 1999, when the raccoon variant entered from New York (USA). The success of this experiment led to an expansion of the program to all of southern Ontario in 1994. Persistence of terrestrial rabies, and ease of elimination, appeared to vary geographically, and probably over time. Ecological factors which enhance or reduce the long term survival of rabies in wild foxes are poorly understood.

Administration, Oral↗
PubMed1996

Endotoxin and cytokines decrease serum levels and extra hepatic protein and mRNA levels of cholesteryl ester transfer protein in syrian hamsters.

Endotoxin alters the metabolism of lipoproteins, including that of high density lipoprotein (HDL). Cholesteryl ester transfer protein (CETP) facilitates exchange of HDL cholesterol for very low density lipoprotein (VLDL) triglyceride, leading to catabolism of HDL. We investigated the effects of endotoxin and cytokines on CETP in Syrian hamsters. Endotoxin induced a rapid and progressive decrease in serum CETP levels, by 48 h CETP had decreased to < 20% of control levels. Endotoxin also decreased CETP mRNA and protein levels in adipose tissue, heart, and muscle, the tissues with highest levels of CETP mRNA, providing a plausible mechanism for the endotoxin-induced decrease in circulating CETP. Dexamethasone did not mimic the effects of endotoxin on CETP, but the combination of tumor necrosis factor and interleukin-1 did, indicating that these cytokines may in part mediate the effects of endotoxin on CETP. The endotoxin-induced decrease in CETP may help maintain HDL cholesterol levels during infection and inflammation when increased triglyceride levels could drive the exchange of HDL cholesteryl ester for VLDL triglyceride. Maintaining circulating HDL may be important because HDL protects against the toxic effects of endotoxin and provides cholesterol for peripheral cells involved in the immune response and tissue repair.

Adipose Tissue↗
PubMed1996

Effect of electrosurgical technique on wound healing and early complication rate following abdominal dermolipectomy.

Thirty-eight patients with significant weight loss after vertical banded gastroplasty were studied prospectively while undergoing abdominal dermolipectomy to determine if the current intensity used during electrosurgical dissection influenced wound complication rates after this surgery. Patients were assigned randomly to one of two groups: (1) a HI group, in which the electrosurgical current intensity was set at a level that easily allowed coagulation of all vessels smaller than 0.5 mm in diameter or (2) a LO group, in which the current intensity was set at a much lower level that allowed dissection, but required that nearly all visible vessels be ligated separately. A standardized procedure was employed for all patients. The patients in the LO (N = 14) and HI (N = 24) groups were well matched for age, weight history, nutritional parameters, operative times, surgical blood loss, and postoperative hospital stay. The overall complication rates of 36% and 21%, and wound complication rates of 36% and 13% for the LO and HI groups, respectively, were not significantly different. These data indicate that using a relatively high electrosurgical current intensity for dissection during abdominal lipectomy does not result in a higher wound complication rate.

Abdomen↗
PubMed1989

Distribution and functions of lecithin:cholesterol acyltransferase and cholesteryl ester transfer protein in plasma lipoproteins. Evidence for a functional unit containing these activities together with apolipoproteins A-I and D that catalyzes the esterification and transfer of cell-derived cholesterol.

The distribution of apolipoprotein A-I, apolipoprotein D, lecithin:cholesterol acyltransferase, and cholesteryl ester transfer protein in fasting normal human plasma was determined by two-dimensional electrophoresis followed by immunoblotting. The synthesis and transfer of labeled cholesteryl esters generated in plasma briefly incubated with [3H]cholesterol-labeled fibroblasts was followed in terms of the lipoprotein species containing these antigens. Following the early appearance of labeled free cholesterol in two pre beta-migrating apolipoprotein A-I species (Castro, G. R., and Fielding, C. J. (1988) Biochemistry 27, 25-29), labeled esters were first detected, after a 2-min delay, in a third pre beta-migrating species which also contained apolipoprotein D, lecithin:cholesterol acyltransferase, and cholesteryl ester transfer protein. Pulse-chase experiments determined that label generated in this fraction was the precursor of at least a major part of labeled cholesteryl esters in the bulk of alpha-migrating high density lipoprotein. Over the maximum time course of these experiments (15 min, 37 degrees C), less than 10% of labeled cholesteryl esters were recovered in low or very low density lipoproteins separated by electrophoresis, immunoaffinity, or heparin-agarose chromatography. These data suggest channeling of cell-derived cholesterol and cholesteryl esters derived from it through a preferred pathway involving several minor pre beta-migrating lipoproteins to alpha-migrating high density lipoprotein.

Antibodies, Monoclonal↗
PubMed1987

Isolation and specificity of a Mr 74,000 cholesteryl ester transfer protein from human plasma.

A cholesteryl ester transfer protein was isolated from human plasma whose ligand specificity, molecular weight, and amino acid composition are significantly different from those of proteins previously reported to have this activity. The protein, purified about 100,000-fold from plasma, is rich in hydrophobic amino acids, especially leucine. It has a molecular weight of 74,000 and an isoelectric point of 5.2. The protein's transfer rate for cholesteryl ester between each of the major plasma lipoprotein classes is similar, and rapid compared to the transfer of triacyglycerol, regardless of the overall lipid composition of the donor and acceptor lipoprotein. These data suggest that this protein functions primarily in the transfer of cholesteryl esters between plasma lipoproteins.

Amino Acid Sequence↗
PubMed1986

Cloning and expression of human apolipoprotein D cDNA.

The amino acid sequence of human apolipoprotein D, a component of high density lipoprotein, has been obtained from the cloned cDNA sequence. The 169-amino acid protein has no marked similarity to other apolipoprotein sequences, but has a high degree of homology to plasma retinol-binding protein and other members of the alpha 2u-globulin protein superfamily. Apolipoprotein D mRNA has been detected in human liver, intestine, pancreas, kidney, placenta, adrenal, spleen, and fetal brain tissue. Tissue culture cells transfected with the cloned cDNA secrete material that reacts with anti-apoD antibodies.

Amino Acid Sequence↗
PubMed1986

Human lecithin-cholesterol acyltransferase gene: complete gene sequence and sites of expression.

The human lecithin-cholesterol acyltransferase (LCAT) gene has been sequenced to completion. The gene is divided into six exons spanning approximately 4,200 bp. Exon five codes for amino acids homologous to the interfacial active site of several lipases, and also codes for an amphipathic alpha-helix resembling the carboxy terminus of apolipoprotein E. Blot hybridization data suggest that there is only one LCAT gene in humans. The 1550 base LCAT mRNA can be detected in liver and HepG2 (hepatocyte) cells, but not in small intestine, spleen, pancreas, placenta or adrenal tissue.

Base Sequence↗
PubMed1986

Cloning and expression of human lecithin-cholesterol acyltransferase cDNA.

cDNA and genomic cloning has been used to determine the mRNA and amino acid sequence of human plasma lecithin-cholesterol acyltransferase (LCATase; EC 2.3.1.43). The mature protein was found to contain 416 amino acid residues with a hydrophobic leader sequence of 24 amino acids. An unusual feature of the message is that the poly(A) signal AATAAA overlaps the COOH-terminal glutamic acid and stop codons, and the 3' untranslated region is only 23 bases. The protein itself is distinguished by a number of extended sequences of hydrophobic amino acids, one of which contains a hexapeptide identical with the interfacial binding segment of the active site of pancreatic lipase and is similar to the same site of lingual lipase. The cloned cDNA allows the expression of active LCATase by transfected tissue culture cells.

Amino Acid Sequence↗
PubMedDate not supplied

Cloning and sequencing of human cholesteryl ester transfer protein cDNA.

The transfer of insoluble cholesteryl esters among lipoprotein particles is a vital step in normal cholesterol homeostasis and may be involved in the development of atherosclerosis. Extrahepatic tissues lack the enzymes required for the degradation of sterols to the excretable form of bile acids. Cholesterol synthesized in these tissues in excess of that needed for the synthesis of cell membranes or steroid hormones must accordingly be returned through the plasma to the liver for catabolism. The series of reactions involved has been termed reverse cholesterol transport. Catalysed steps of this pathway are believed to include an efflux from peripheral cells, which generates a diffusion gradient between these membranes and extracellular fluid; esterification of this cholesterol by lecithin-cholesterol acyltransferase (LCAT) (phosphatidylcholine-sterol acyltransferase) acting on species of high-density lipoproteins; transfer of the cholesteryl esters formed (largely to low- and very low-density lipoproteins) (LDL and VLDL) by a cholesteryl ester transfer protein (CETP); and removal of these lipoproteins, together with their cholesteryl ester content, by the liver through receptor-mediated and nonspecific endocytosis. Of these steps, the CETP reaction is the least characterized. Several laboratories have reported the purification from human plasma of proteins active on cholesteryl ester transfer between lipoprotein particles and possibly between cells and plasma. However, the reported relative molecular mass (Mr), abundance and specificity of the purified activities have differed considerably. We have recently described the preparation of a highly active CETP of Mr 74,000 purified about 100,000-fold from human plasma, which may represent the functional component of earlier preparations. Using a partial amino-acid sequence from this purified protein, CETP complementary DNA derived from human liver DNA has been cloned and sequenced and the cloned DNA used to detect CETP messenger RNA in a number of human tissues.

Amino Acid Sequence↗