Biomedical subjects
J G Hamilton
Publications and source records attributed to J G Hamilton.
Rapid separation of neutral lipids, free fatty acids and polar lipids using prepacked silica Sep-Pak columns.
A method is described for the separation of neutral lipid, free fatty acid and polar lipid classes using small (600 mg), prepacked silica Sep-Pak columns. Combinations of hexane and methyltertiarybutylether were used to progressively elute cholesteryl ester first then triglyceride from the column. After column acidification, fatty acids were eluted followed by cholesterol. Recoveries of these lipids were 96% or greater. Polar lipids were eluted from the column using combinations of methyltertiarybutylether, methanol and ammonium acetate. Phospholipid classes could not be separated completely from each other. Phosphatidylethanolamine and phosphatidylinositol eluted together, whereas the more polar phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were eluted as a second fraction. Recoveries of each phospholipid was greater than 98%.
Separation of neutral lipid, free fatty acid and phospholipid classes by normal phase HPLC.
Normal phase high performance liquid chromatography methods are described for the separation of neutral lipid, fatty acid and five phospholipid classes using spectrophotometric detection at 206 nm. Separations were accomplished in less than 10 min for each lipid class. A mobile phase consisting of hexane/methyltertiarybutylether/acetic acid (100:5:0.02) proved effective in separating cholesteryl ester and triglyceride with recoveries of 100% for radiolabeled cholesteryl oleate and 98% for radiolabeled triolein. Free fatty acid and cholesterol were separated by two different mobile phases. The first, hexane/methyltertiarybutylether/acetic acid (70:30:0.02) effectively separated free fatty acids and cholesterol, but did not separate cholesterol from 1,2-diglyceride. A mobile phase consisting of hexane/isopropanol/acetic acid (100:2:0.02) effectively separated free fatty acid, cholesterol, 1,2-diglyceride and 1,3-diglyceride. Recoveries of oleic acid and cholesterol were 100% and 97%, respectively. Five phospholipid classes were separated using methyltertiarybutylether/methanol/aqueous ammonium acetate (pH 8.6) (5:8:2) as the mobile phase. The recoveries of phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were each greater than 96%.
Congenital dermal sinus presenting as anaerobic meningitis.
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Separation of neutral lipids and free fatty acids by high-performance liquid chromatography using low wavelength ultraviolet detection.
Normal phase, isocratic high-performance liquid chromatography methods are described for the separation of neutral lipid and fatty acid classes using low wavelength detection. Prior to high-performance liquid chromatography, methods were developed and are described for the separation of phospholipids from neutral lipids and fatty acids using small (600 mg) silica Sep-PaksTM. Recoveries of cholesteryl esters, triglycerides, fatty acids, and phospholipids from the silica columns were greater than 95%. Two mobile phases are described for lipid class separation by high-performance liquid chromatography. The first mobile phase, hexane-2-propanol-acetic acid 100:0.5:01, resulted in incomplete separation of cholesteryl ester and triglyceride but excellent separations of fatty acids and cholesterol. The second mobile phase, hexane-n-butyl chloride-acetonitrile-acetic acid 90:10:1.5:0.01, resulted in complete separation of the four lipid classes. This mobile phase also separated individual triglycerides and fatty acids based on the number of double bonds. Recoveries of radiolabeled lipids for the four lipid classes from high-performance liquid chromatography was greater than 95% with both mobile phases.
High performance liquid chromatography (HPLC) of arachidonic acid metabolites.
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Intracranial haemorrhage in association with pseudoephedrine overdose.
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Inhibition of antigen-induced histamine release and thromboxane synthase by FPL 55712, a specific SRA-A antagonist?
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Fatty acid and cholesterol synthesis from specifically labeled leucine by isolated rat hepatocytes.
Hepatocytes isolated from female rats meal-fed a high-glucose diet were incubated in Krebs-Henseleit bicarbonate medium containing 16.5 mM glucose, 3H2O, and 14C-labeled amino acids (-)-Hydroxycitrate depressed the incorporation of 3H2O and [14C] alanine into fatty acids and cholesterol. Incorporation of [U-14C]leucine into lipids was not affected but incorporation of 3H2O into lipids was decreased significantly by (-)-hydroxycitrate. (-)-Hydroxycitrate depressed the incorporation of radioactivity from [2-14C]leucine into fatty acids and cholesterol by 61 and 38%, respectively, and stimulated the incorporation of radioactivity from [4,5-3H]leucine 35 and 28%. As [2-14C]leucine labels the acetyl-CoA pool and [4,5-3H]leucine labels the acetoacetate pool, it was concluded that mitochondrial 3-hydroxy-3-methylglutaryl-CoA is not incorporated intact into cholesterol, and that acetoacetate can be activated effectively in the liver cytosol for support of cholesterol and fatty acid synthesis.
An improved competitive protein binding assay for 1,25-dihydroxyvitamin D.
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Sinus headache: a psychophysiological study.
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Inhibition of arachidonate metabolism by selected compounds in vitro with particular emphasis on the thromboxane A2 synthase pathway.
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The effect of 5,8,11,14-eicosatetraynoic acid on lipid metabolism.
The purpose of this presentation is to review the current state of knowledge regarding 5,8,11,14-eicosatetraynoic acid (ETYA, Ro 3-1428) and its effects on lipid metabolism. Accordingly, the topics discussed include hypocholesterolemic and dermatological studies involving ETYA in both animals and man, as well as the effects of ETYA on desaturase enzymes. Metabolic studies involving ETYA are also noted. Primary interest is focused on the effects of ETYA on selected processes of arachidonate metabolism, and the effect of ETYA on inflammation, platelet aggregation and tumor growth are discussed, keeping in mind the relevance of arachidonate metabolism to these processes.
Some effects of deoxycholate administration on the metabolism of cholesterol in man.
Hypercholesterolemic subjects in a metabolic ward were kept under uniform dietary conditions until constant levels of serum cholesterol were observed. Oral dosage with deoxycholate (1.5 to 3 g daily for a period of 4 to 10 weeks) resulted in a marked reduction of serum cholesterol concentration. Studies with 14C-labeled cholesterol demonstrated that deoxycholate administration decreased absorption of cholesterol from the human intestinal tract. In these subjects, the turnover rate of serum cholesterol was more rapid during therapy with deoxycholate than during control periods. Deoxycholate appeared to influence the intestinal flora as assessed indirectly by analysis of the types of neutral sterols eliminated with the feces. Decreased synthesis of cholesterol during deoxycholate administration uas demonstrated in a study with 14C-mevalonate. It is concluded that deoxycholic acid can have an important role in the regulation of cholesterol metabolism in humans.
Determination of xylitol in human urine by gas-liquid chromatography.
A rapid and specific method for the quantitative determination of xylitol in human urine has been developed. The method consists of the gas-liquid chromatographic analysis of the acetate ester derivative of the alditol in deionized urine using dulcitol as an internal standard. As little as 20 ng xylitol can be detected. At concentrations ranging from 25 to 400 micrograms/ml urine, the accuracy is +/- 4.0%.
Anthracene 1,2-oxide: synthesis and role in the metabolism of anthracene by mammals.
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Comparative effects of saturated and unsaturated lipids on hepatic lipogenesis and cholesterogenesis in vivo in the meal-fed rat.
The effects of saturated and unsaturated lipids on in vivo rates of hepatic lipogenesis and cholesterogenesis were compared. Lipogenic and cholesterogenic rates were determined in meal-fed rats either after feeding 1%, 5%, 10%, or 20% dietary corn oil or hydrogenated soybean oil for 14 days, or after intrgastric administration of fatty acyl ethyl esters (18:0, 18:1, or 18:2) for 1 and 3 days. Dietary hydrogenated soybean oil was not absorbed, whereas dietary corn oil and the intragastrically administered fatty acyl ethyl esters were well absorbed. Fatty acid synthesis measured from 3H2O and [14C] alanine was inversely correlated with unsaturated dietary fat content, but was unchanged by saturated dietary fat. A single daily administration of 18:0, 18:1, or 18:2 was ineffective in altering lipogenic rates. However, fatty acid synthesis was decreased by three consecutive daily doses of 18:1 or 18:2 (5 g/kg), but not by 18:0. Hepatic rates of cholesterogenesis from 3H2O and [14C] alanine were markedly enhanced by the administration of 10% or 20% saturated dietary fat. Feeding 1%, 5%, or 10% corn oil diets did not have an effect on cholesterogenesis. The 20% corn oil diet reduced the rate of conversion of [14C]anine into cholesterol while the rate of conversion of 3H2O remained unchanged. Neither the 1 day not 3 day oral administration of 18:0 or 18:1 had any effect on cholesterol synthesis; thereas the administration of 18:2 increased the conversion of [14C] alanine into cholesterol by 30% but did not after the rates of cholesterogenesis from 3H2O. These data suggest the following: a) fatty acid synthesis responds selectively to 18:0, 18:1, and 18:2; b) the inhibition of fatty acid synthesis by unsaturated fatty acids is time dependent; c) the rate of fatty acid synthesis is inversely proportional to the concentration of unsaturated dietary fat; d) prolonged feeding with a completely saturated diet will increase fecal fat excretion and hepatic cholesterol synthesis; and e) the regulation of fatty acid synthesis by dietary lipid is independent of the regulation of cholesterol synthesis.
Hupolipidemic activity of (--)-hydroxycitrate.
The influence of (--)-hydroxycitrate, a potent competitive inhibitor of adenosine triphosphate (ATP) citrate lyase, on serum triglyceride and cholesterol levels, and in vitro and in vivo rates of hepatic fatty acid and chloesterol synthesis was investigated in normal and hyperlipidemic rat model systems. (--)-Hydroxycitrate reduced equivalently the biosynthesis of triglycerides, phospholipids, cholesterol, diglycerides, cholesteryl esters, and free fatty acids in isolated liver cells. In vivo hepatic rates of fatty acid and cholesterol synthesis determined in meal-fed normolipidemic rats were suppressed significantly by the oral administration of (--)-hydroxycitrate for 6 hr, when control animals exhibited maximal rates of lipid synthesis; serum triglyceride and cholesterol levels were significantly reduced by (--)-hydroxycitrate. In two hypertriglyceridemic models-the genetically obese Zucker rat and the fructose-treated rat-elevated triglyceride levels were due, in part, to enhance hepatic rates of fatty acid synthesis. (--)-Hydroxycitrate significantly reduced the hypertriglyceridemia and hyperlipogensisi in both models. the marked hypertriglyceridemia exhibited by the triton-treated rat was only minimally due to increased hepatic lipogenesis;(--)-hydroxycitrate significantly inhibited both serum triglyceride levels and lipogenesis in this model.