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K Lippel

Publications and source records attributed to K Lippel.

At least 37 records · Page 2Linked to original sources
PubMed1978

Analytical performance and comparability of the determination of triglycerides by 12 Lipid Research Clinic laboratories.

Twelve Lipid Research Clinic laboratories performed automated fluorometric triglyceride analyses on four control serum pools of known concentration by a modified Hantzsch reaction. The analyses were done during a two-year period, with use of common standards, methodology, and quality-control procedures. Estimates of analytical bias, variability, and short- and long-term trends for each instrument and for the entire group of LRC instruments are presented. High accuracy, precision, and interlaboratory comparability were achieved through rigorous standardization and control of the entire analytical procedure. Individual instrument biases varied from an average of 4.9% below to 1.0% above reference values. Between-run variability was often less than within-run variability and interlaboratory variation was substantially less than intralaboratory variation. The total standard deviation for all instruments ranged from 37 to 63 mg/liter. Only 5 to 14% of this variation was due to differences among instruments. The among-instruments standard deviation ranged from 12 to 17 mg/liter; the between-run, within-instrument standard deviation ranged from 29 to 46 mg/liter, and within-run standard deviation from 27 to 40 mg/liter. The significance of the results for long-term collaborative studies is discussed.

Analysis of Variance↗
PubMed1978

External quality-control survey of cholesterol analyses performed by 12 lipid research clinics.

We report accuracy and precision achieved in the automated analysis for cholesterol in a long-term multilaboratory study, presenting and evaluating the significance of data accumulated by 12 Lipid Research Clinics (LRC's) in the analysis of 18 unknown surveillance pools during three years. The average bias for all pools and for 13 autoAnalyzer II (Technicon Instruments Corp., Tarrytown, N.Y. 10591) instruments in the 12 clinics was -0.41% (range -1.2 to +0.3%), as compared to values established by reference methodology. The regression equation relating observed cholesterol values (y) to reference values (x) was: y = 0.35 + 0.977x. The bias varied from pool to pool (-2.3 to +5.3%), positive biases being observed for pools with cholesterol concentrations less than 1.4 g/liter, and negative biases for those pools with higher concentrations. Total standard deviations ranged between 25 and 75 mg/liter, and total CV's for most individual instruments were between 1 and 3%. Of the variability for a particular pool, less than 20% was due to differences among instruments, and within- and between-run variabilities were approximately equal. These trends were the same as those previously observed [Clin. Chem. 23, 1744 (1977)] in the analysis of bench control pools of known cholesterol concentration.

Autoanalysis↗
PubMed1977

Analytical performance and comparability of the determination of cholesterol by 12 Lipid-Research Clinics.

Twelve Lipid-Research Clinic laboratories performed automated cholesterol analyses on four control-serum pools of known cholesterol concentration, using the Liebermann-Burchard reaction. The analyses were done during a two-year period, with the same standards, methodology, and quality-control procedures. Estimates of analytical bias, variability, and short- and long-term trends for each instrument and for the entire group of LRC instruments are presented. High accuracy, precision, and interlaboratory comparability were achieved through the rigorous standardization and control of the entire analytical procedure. The significance of these results for long-term collaborative studies is discussed. Individual laboratory biases averaged from 0.5 to 2.0% below Abell-Kendall reference values. Between-run variability was about equal to within-run variability and inter-laboratory variation was substantially less than intra-laboratory variation. The total standard deviation for all instruments was about 0.04 g/liter. Only 8-15% of this variation was due to differences between instruments. The between-instrument standard deviation ranged from 0.011 to 0.015 g/liter; the between-run, within-instrument standard deviation ranged from 0.023 to 0.030 g/liter; and within-run standard deviation ranged from 0.023 to 0.028 g/liter. The significance of the achieved results for long-term collaborative studies is discussed.

Cholesterol↗
PubMed1973

Activation of branched and other long-chain fatty acids by rat liver microsomes.

Acyl coenzyme A synthetase (EC 6.2.1.3) of rat liver microsomes activates iso- and anteiso-branched long-chain fatty acids containing 12 to 20 carbon atoms. Fatty acid chain length appears to be the major determinant of the maximum rate of acyl CoA biosynthesis of branched, or saturated, or cis monounsaturated long-chain fatty acids. Based on activation studies conducted at 22-45 degrees C, it is concluded that the rate of activation is a function of long-chain fatty acid solubility. The shape of the in vitro activation curve with respect to fatty acid concentration appears to be determined by fatty acid melting point as well as by the presence and position of double bonds. Differently shaped activation curves were observed for cis or trans Delta(6) to Delta(12) central positional isomers of octadecenoic acid and for Delta(3), Delta(4), Delta(13) to Delta(15) terminal isomers of octadecenoic acid. The relationships between fatty acid structure, melting point, solubility, and shape of the activation curve observed during in vitro measurement of acyl CoA formation are discussed.

Animals↗
PubMed1968

Biosynthesis of beta-glucuronides of retinol and of retinoic acid in vivo and in vitro.

After the intraportal injection of retinol-6,7-(14)C to rats, the O-ether derivative of retinol, retinyl -glucosiduronate, appears in the bile. Both retinoyl -glucuronide and retinyl -glucosiduronate are also synthesized in vitro when washed rat liver microsomes are incubated with uridine diphosphoglucuronic acid (UDPGA) and either retinoic acid or retinol, respectively. The synthesis of retinoyl -glucuronide was also demonstrated in microsomes of the kidney and in particulate fractions of the intestinal mucosa. The glucuronides were characterized by their UV absorption spectra, by their quenching of UV light or fluorescence under it, by their thin-layer chromatographic behavior in two solvent systems, and by the identification of products released during their hydrolysis by -glucuronidase. With retinoic acid as the substrate, the UDP glucuronyl transferase of rat liver microsomes had a pH optimum of 7.0, a temperature optimum of 38 degrees C, and a marked dependence on the concentrations of both retinoic acid and UDPGA, but was unaffected by a number of possible inhibitors, protective agents, and competitive substrates. The conversion of retinal to retinoic acid and the synthesis of retinoyl -glucuronide from retinoic acid could not be detected in whole homogenates, cell fractions, or outer segments of the bovine retina.

Animals↗
PubMed1968

Origin of some derivatives of retinoic acid found in rat bile.

After the intraportal injection of retinoic acid-15-(14)C into rats, all-trans methyl retinoate, a cis isomer of methyl retinoate, retinoyl beta-glucurono-gamma-lactone, retinoic acid, and retinoyl beta-glucuronide were isolated from methanol extracts of rat bile by chromatography on anion-exchange resin and silicic acid columns and characterized on thin-layer plates of Silica Gel G. On the other hand, when bile was extracted with n-butanol or analyzed directly by thin-layer chromatography, only retinoyl beta-glucuronide and a very small amount of retinoic acid could be detected. Butanol extracts of the liver and the intestine, however, still contained a small radioactive nonpolar fraction. When retinoyl beta-glucuronide was incubated with an anion-exchange resin in the presence of methanol, several nonpolar products appeared. Apparently the methyl retinoate, retinoyl beta-glucurono-gamma-lactone, and most of the retinoic acid previously found in bile after retinoic acid administration are produced from retinoyl beta-glucuronide during the isolation procedure.

Acids↗