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J C Touchstone

Publications and source records attributed to J C Touchstone.

At least 19 recordsLinked to original sources
PubMed1995

Thin-layer chromatographic procedures for lipid separation.

This review focuses on the thin-layer chromatographic (TLC) separation aspects of lipid analysis. Since the space limitations do not permit, the quantitative aspects of the analyses are not discussed at length although some indications of appropriate methodology and detection reagents will be indicated. Many separations carried out by TLC have the prerequisite of proper sample preparation. Using proper sample clean-up prior to TLC enables one to carry out precise separation as well as sensitive quantitation. Thus, the discussions are divided into the two main topics--sample preparation and TLC. Examples of applications are limited to those which illustrate the capabilities of the technique as well as practicability. Since there are a number of reviews in the literature, the discussions herein are focused mainly on reports after 1985.

Chromatography, Thin Layer↗
PubMed1992

Separation of acidic and neutral lipids by aminopropyl-bonded silica gel column chromatography.

The separation of acidic and neutral lipids by aminopropyl-bonded silica gel column chromatography is presented. Total lipid extracts from Escherichia coli and human spermatozoa were loaded onto pre-packed aminopropyl-bonded silica gel columns and the lipids separated into four fractions. Non-polar lipids including cholesterol esters, triglycerides, diglycerides, monoglycerides and cholesterol, were eluted with 4 ml of isopropanol-chloroform (1:2, v/v) (fraction 1); free fatty acids were eluted with 4 ml of 2% acetic acid in diethyl ether (fraction 2); neutral polar lipids, including phosphophatidylethanolamine, phosphatidylcholine, sphingomyelin and neutral glycolipids, were eluted with 4 ml of methanol (fraction 3); and, finally, polar acidic lipids, including phosphatidylglycerol, cardiolipin, phosphatidylinositol, phosphatidylserine, seminolipid lipid A and acidic glycosphingolipids, were eluted with 4 ml of chloroform-methanol-0.8 M sodium acetate (60:30:4.5, v/V/V) (fraction 4). The recoveries for the different lipids ranged between 89 and 98% and the intra-assay variation, expressed as the standard deviation, was less than 5%.

Chromatography, Liquid↗
PubMed1991

Fluorometric labeling of tetrahydroprogesterones.

7-Diethylaminocourmarin-3-carbohydrazide was used to label the ketone group of the tetrahydroprogesterones to form fluorescent derivatives with high sensitivity. The four isomeric 3-hydroxypregnanes separated readily on high-performance, thin-layer chromatography after derivatization. This separation was not possible with the underivatized isomers. Standards and steroids from biologic mixtures were separated and showed similar characteristics. The methods used are described.

Chromatography, High Pressure Liquid↗
PubMed1988

Phospholipids in amniotic fluid with special reference to the lecithin/sphingomyelin ratio.

At the present time, it appears that the method of choice for determination of phospholipids in amniotic fluid is the thin-layer chromatographic method. Noteworthy is that presented by Touchstone et al in which a minimum of effort is required. With the direct application of the amniotic fluid the problems of recovery and time-consuming efforts are minimized, considering that extraction and chromatography are carried out on the same plate. Another approach to the problem is shown in the reports of Krauss et al. in which they showed that 24 samples can be accommodated on one plate. Sensitivity was obtained using 2,5-bis[5-tert.-butylbenzoxazolyl (2')] thiophene to form fluorescent derivatives. With development times of as little as 10 min this method has not yet been perfected for use with biological samples, but indicates that some future developments using high-performance thin-layer chromatography are perhaps coming.

Amniotic Fluid↗
PubMed1988

Amniotic fluid cholesteryl palmitate in pregnancies complicated by diabetes mellitus.

Amniotic fluid cholesteryl palmitate, as measured by thin-layer chromatography, appears to be a very sensitive and specific predictor for the risk of respiratory distress syndrome (RDS) in newborns of normal pregnancies. To assess the effect of diabetes mellitus on fetal pulmonary maturation, we measured cholesteryl palmitate concentration, the lung profile, and total phosphatidylcholine in amniotic fluid obtained from 35 well-controlled diabetic and 39 control pregnancies at term. In women with diabetes, the mean (+/- SD) third-trimester glycosylated hemoglobin level was 6.96 +/- 2.3% (normal 6-8%). Mean cholesteryl palmitate concentration in the diabetic population was 79.12 +/- 13.17 micrograms/mL, versus 153.71 +/- 16.77 micrograms/mL in the control group (P less than .001). The mean cholesteryl palmitate concentration was also significantly different for gestational diabetics and class B-R gravidas (112.75 +/- 26.2 versus 54.45 +/- 7.34 micrograms/mL; P less than .005). Cholesteryl palmitate was decreased despite the presence of a mature lecithin/sphingomyelin ratio and, in most cases, phosphatidylglycerol. These data suggest that even in well-controlled diabetic pregnancies, alterations in maternal metabolism may affect either the biosynthesis or degradation of cholesteryl palmitate.

Amniotic Fluid↗
PubMed1987

Cholesteryl palmitate as a predictor of fetal lung maturity.

Cholesteryl palmitate was measured by thin-layer chromatography in 98 amniotic fluid samples obtained from pregnancies ranging from 15 to 40 weeks. Pregnancies complicated by diabetes mellitus or Rh sensitization were excluded. Cholesteryl palmitate concentration increased with gestational age from values less than 5 micrograms/ml at 15 weeks to maximum values of 384 micrograms/ml at term. Seventy-three patients were delivered of their infants within 24 hours of sampling. The mean concentration of cholesteryl palmitate for 55 infants without respiratory distress syndrome was 123.70 +/- 12.21 micrograms/ml (SD). For neonates that developed respiratory distress syndrome (n = 18), the mean concentration was 22.66 +/- 6.16 micrograms/ml (SD). This difference is significant (p less than 0.001). For all patients delivered, respiratory distress syndrome was not seen when the cholesteryl palmitate concentration was greater than 41 micrograms/ml (mean + 3 SD). All infants with a concentration below 38 micrograms/ml developed respiratory distress syndrome. We conclude that measurement of cholesteryl palmitate concentration in amniotic fluid might be another reliable method of assessing fetal lung maturity and may often improve specificity when compared with other tests of fetal lung maturity.

Amniotic Fluid↗
PubMed1985

Evidence for diplasmalogen as the major component of rabbit sperm phosphatidylethanolamine.

The question of whether diplasmalogens [1,2-di(O-1'-alkenyl) phosphatidyl derivatives] make up part of the plasmalogen component of cell phospholipids was examined using rabbit epididymal spermatozoa. These cells are readily obtained as a highly homogeneous suspension and long have been known to have high plasmalogen content. Phospholipids were determined by thin layer chromatography (TLC) with CuSO4 staining. Plasmalogens were determined by hydrolysis of the phospholipids with TCA/HCl, followed by TLC and CuSO4 staining. Ethanolamine derivatives were determined by ninhydrin. The phosphatidylethanolamine (PE) content of these cells was 29 +/- 2 micrograms/10(8) cells, 90% of which was assayed as diplasmalogen and 10% as diacyl PE. No monoplasmalogen could be detected. The presence of diplasmalogen as the major component of PE was given further support from infrared and proton nuclear magnetic resonance (1H-NMR) spectroscopy, which showed the presence of O-1'-alkenyl substituents but near absence of O-acyl substituents. The phosphatidylcholine (PC) content of the cells was 104 +/- 5 mu/10(8) cells, of which 50% was monoplasmalogen with the 1'-alkenyl group on the 2 position of the glycerol moiety. No diplasmalogen was found in PC. The other phospholipids in rabbit sperm were phosphatidylglycerol (PG), cardiolipin (CL), sphingomyelin (SP) and lysophosphatidylcholine (LPC). Phosphatidylserine (PS) and phosphatidylinositol (PI) were present at the limits of detectability of the TLC method. None of these phospholipids contained plasmalogen. The PE component of rabbit sperm phospholipids appears to differ from that of the other cells in having the previously unreported diplasmalogen as its major constituent.

Animals↗
PubMed1984

A simplified procedure for separating amniotic fluid phospholipids with thin-layer chromatography.

A simple, unidimensional, thin-layer-chromatographic separation of amniotic fluid phospholipids involving detection with a phosphorus-specific spray was compared to the two-dimensional, thin-layer-chromatographic method described by Gluck et al. There were close correlations between the two techniques for lecithin/sphingomyelin ratios and for the presence of phosphatidylglycerol. The advantages of the unidimensional method are a shorter procedure time, the ability to analyze multiple samples on a single plate and the simplicity of a single-solvent system.

Amniocentesis↗
PubMed1983

(3-sn-Phosphatidyl)cholines (lecithins) in amniotic fluid.

Many currently used thin-layer chromatographic methods for phospholipid assay rely on charring the developed plate in the presence of cupric acetate. Saturated acyl phospholipids do not react. We find that substitution of cupric sulfate results in detection of both saturated and unsaturated phospholipids. By exploiting the difference with the two reagents, one can separately estimate the amounts of saturated phospholipid. The method described here is reproducible, and we illustrate its use in determinations of (3-sn-phosphatidyl)cholines (lecithins) in amniotic fluid from problem pregnancies.

Amniotic Fluid↗
PubMed1981

Theophylline analysis by direct application of serum to thin layer chromatograms.

The direct application of 20 microliters of serum to thin layer chromatograms was a rapid and sensitive method for the determination of theophylline. Ten common drugs were shown not to interfere. A comparison with the enzyme immunoassay values obtained in an independent laboratory showed the utility of the method.

Chromatography, Thin Layer↗
PubMed1978

Spectrodensitometry of nanogram quantities of cholesterol.

In studies of hydrolysis and synthesis of cholesterol esters by aortic enzymes, conventional methods (aside from isotope methodology) are too insensitive to measure reaction products when few aortas are used. High-performance thin-layer chromatography coupled with spectrodensitometry of plates charred after spraying with a cupric acetate-phosphoric acid reagent permitted quantitation of 10-ng amounts of cholesterol, cholesterol oleate oleate, and oleic acid. Linear calibration curves were obtained after spectrodensitometry of chromatograms containing 10-200 ng of lipid. The results were verified by radioassay.

Animals↗