Biomedical subjects

N C Shantha

Publications and source records attributed to N C Shantha.

6 recordsLinked to original sources

PubMed1995

Animal and plant fats selectively modulate oxidizability of rabbit LDL and LDL-mediated disruption of endothelial barrier function.

Enrichment of lipoproteins with fatty acids derived from animal and/or plant fats may modify the oxidizability of lipoproteins and their effects on endothelial barrier function. To test this hypothesis, rabbits were fed for 30 days diets containing 2 g corn oil/100 g diet (low fat diet) or low fat supplemented with 16 g/100 g diet of corn oil, corn oil with added cholesterol, milk fat, chicken fat, beef tallow or lard. Compared with those fed the low fat, serum and LDL cholesterol concentrations were significantly lower in rabbits fed corn oil and greater in animals fed corn oil with added cholesterol or chicken fat. In contrast to the cholesterol data, lipid hydroperoxide levels were highest in oxidized LDL derived from rabbits fed corn oil or lard. LDL vitamin E levels were highest in rabbits fed corn oil with added cholesterol. The significant elevations in linoleic acid [18:2(n-6)] in serum and LDL may partially explain the high oxidizability of LDL in rabbits fed corn oil. LDL isolated from animals fed corn oil, lard or milk fat had significantly greater albumin transfer across cultured endothelial monolayers compared with those of the low fat diet group. Their oxidative modification further contributed to endothelial barrier dysfunction. Dietary cholesterol supplementation to the corn oil diet decreased oxidizability of LDL and partially protected the oxidized LDL-mediated endothelial cell dysfunction as compared with the corn oil diet group. These data suggest that beef tallow and chicken fat are the least atherogenic fats if oxidative modification of LDL is a critical issue in atherosclerosis.

Animals↗

PubMed1993

Selective disruption of endothelial barrier function in culture by pure fatty acids and fatty acids derived from animal and plant fats.

Endothelial cell integrity has been suggested to play a role in the development of atherosclerosis. The effects of fatty acids on endothelial barrier function were tested by measuring albumin transport across endothelial monolayers cultured on polycarbonate filters. Compared with control cultures, a 24-h exposure to 90 mumol/L lauric (12:0) and linoleic acid (18:2) but not to butyric (4:0), hexanoic (6:0), octanoic (8:0), decanoic (10:0), myristic (14:0), palmitic (16:0) or stearic acid (18:0) caused an increase in albumin transfer across endothelial monolayers. Selective enrichment of a "physiological" serum fatty acid mixture (FA-Mix; 90 mumol/L) with 90 mumol/L of 12:0 or 18:2 significantly increased albumin transfer, whereas enrichment with 90 mumol/L of 4:0, 16:0 or 18:0 significantly decreased albumin transfer relative to 180 mumol/L FA-Mix. Only 12:0- or 18:2-treated cultures showed increased Ca(++)-ATPase activity and the presence of lipid droplets. Fatty acids (60 mumol/L) extracted from butter fat and beef tallow had no effect on albumin transfer, whereas fatty acids extracted from chicken fat and corn oil consistently disrupted endothelial barrier function. This fat-induced disruption of endothelial barrier function seems to be related to the amount of 18:2 present in each fat source. These data indicate that unsaturated fats cause cellular perturbations that result in a decrease in endothelial barrier function in this model system, and that high dietary levels of unsaturated fats may be detrimental to cell integrity.

Albumins↗

PubMed1992

Thin-layer chromatography-flame ionization detection Iatroscan system.

The thin-layer chromatography-flame ionization detection (TLC-FID) Iatroscan system is a technique which is still being evolved. Quantification with the TLC-FID system relies heavily on the accurate setting up and calibration of the instrument. An appreciation of the factors that influence the analysis can eliminate significant errors. At least a few of the numerous operating variables need to be fixed to obtain coherent results from different laboratories. Hydrogenation of the sample is recommended in order to improve quantification with the Iatroscan system. The improved reproducibility obtained with automatic sample spotters compared with manual spotting indicates that autosampling is highly advisable.

Chromatography, Thin Layer↗

PubMed1992

Gas chromatography of fatty acids.

Lipids in foods contain a wide variety of fatty acids differing in chain length, degree of unsaturation, position and configuration of double bonds and the presence of special functional groups. Modern capillary gas chromatography offers excellent separation of fatty acids. Fused-silica capillary columns with stationary phases of medium polarity and non-polar methylsilicone stationary phases successfully separate most of the natural fatty acids. Special applications, such as the separation of complex cis-trans fatty acid mixtures and cyclic fatty acids, required particular chromatographic conditions, including the use of very long capillary columns or more polar stationary phases. The derivatization methods for the preparation of fatty acid esters also need to be optimized to obtain accurate quantitative results. This paper reviews the derivatization techniques, capillary columns and stationary phases commonly used in the gas chromatography of fatty acids in food.

Chromatography, Gas↗

PubMed1990

Nervonic acid versus tricosanoic acid as internal standards in quantitative gas chromatographic analyses of fish oil longer-chain n-3 polyunsaturated fatty acid methyl esters.

Tricosanoic acid (23:0) and cis-15-tetracosenoic acid (nervonic acid, 24:1 n-9) were compared as choices suitable for use as internal standards in the quantitation of eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids. Experiments conducted included: (a) comparison of the flame ionisation detector responses of the two fatty acid methyl esters; (b) estimation of accurately weighed quantities of EPA and DHA using both 23:0 and 24:1 separately as internal standard; (c) determination of EPA and DHA contents of commercially available fish oil ethyl ester capsules using the two as internal standard. The results suggest that both 23:0 and 24:1 methyl esters behaved similarly in the flame ionization detector of the gas chromatograph and are comparable internal standards for use in quantitation of EPA and DHA. This includes the analysis of ethyl ester mixtures as long as interesterification of sample with solvent methanol is complete. The relatively poor solubility of the saturated 23:0 is countered by its greater stability. A possible drawback of 24:1 could be the presence of more than one positional isomer in either a 24:1n-9 standard or in the actual sample. In principle any fatty acid could serve as an internal standard as long as the limitations involved in the use of each are taken into account.

Chromatography, Gas↗

PubMedDate not supplied

Rapid, sensitive, iron-based spectrophotometric methods for determination of peroxide values of food lipids.

The official International Dairy Federation method for determination of the peroxide value of anhydrous milk fat was extended to poultry, meat, fish, and vegetable oils. The ferrous oxidation-xylenol orange method for determination of peroxide values of liposomes and lipoproteins was modified to make it simpler and more rapid. These 2 spectrophotometric methods were used successfully to determine the peroxide values of beef, chicken, butter, fish, and vegetable products. The results in most cases were consistent with those obtained by using the AOAC Official Method. The spectrophotometric methods have an assay time of less than 10 min, require < or = 0.3 g fat, and are capable of determining peroxide values as low as 0.1 mequiv/kg of sample.

Ferrous Compounds↗