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SummaryThe exchange of free cholesterol of endogenous or exogenous origin between plasma and red blood cells has been studied. Using tritiated cholesterol and 14C-mevalonic acid or sodium-1-14C-acetate, it has been shown that after incubation of labeled plasma with control RBC or of labeled RBC with control plasma, the free cholesterol 3H/14C ratio in plasma or RBC is unchanged. This is true for incubation of 6 or 24 hr. In a parallel series of experiments it was observed that the plasma 3H/14C free cholesterol ratio was unchanged after 24 hr of incubation in the presence of native lecithin cholesterol acyl transferase. The data confirm the findings in man and baboon which suggest that it is not possible to distinguish between plasma free cholesterol of endogenous or exogenous origin.

1. 1. The major neutral lipid classes of Himasthla quissetensis rediae are sterols, free fatty acids, triglycerides and sterol esters. 2. 2. Sixteen fatty acid components of these classes have been resolved using gas-liquid chromatography. The major fatty acid in the sterol ester class is C 20:1 , in the triglyceride class is C 18:1 and in the free fatty acid class is C 16:0 . 3. 3. The fatty acid composition of the triglyceride class varies while the composition of the free fatty acid fraction shows a decrease in the relative proportions of C 18:1 and shorte chain fatty acids following in vitro starvation. The relative fatty acid composition of the sterol ester class shows no change after starvation.

Studies on the transport of exogenous and endogenous cholesterol in the baboon have been carried out using(14)C-acetate,(14)C-mevalonic acid, or(3)H-cholesterol. The results suggest the following characteristics of cholesterol metabolism in the baboon: the serum alpha- and beta-lipoproteins show no preference in the transport of exogenous or endogenous cholesterol; the half-life (t(1/2)) of disappearance of cholesterol from the whole animal varied between 31 and 50 days; the daily rate of whole body cholesterol biosynthesis in the baboon (47 mg/kg/day) is comparable with that rate observed in the human being (18-41 mg/kg/day); after administration of(14)C-acetate,(14)C-mevalonic acid, or(3)H-cholesterol to baboons, newly synthesized cholesterol esters appear to be incorporated to a greater extent into the serum alpha-lipoproteins.

Publisher Summary This chapter focuses on the analysis of lipid components of viruses. The primary function of the lipids present in viruses seems to be to maintain the structural integrity of their membrane. The lipids may also play an important role in the interaction of virus with host cells and in their agglutination of erythrocytes. The present state of development of lipid methodology makes possible the separation and identification of all classes of viral lipids. If less than 50 mg of a lipid extract is available, it is desirable to separate lipids by thin-layer chromatography (TLC). Alternately, this technique may be used as a tool to authenticate the homogeneity of lipid fractions obtained by column chromatography. TLC is a more convenient, more economical, and more rapid technique than column chromatography, as less solvent and much less time is required to achieve separations. The most widely used adsorbent for TLC is silica gel G, which is a mixture of silicic acid containing calcium sulfate as a binder. After chromatographic fractionation of the lipid extract is achieved, an estimate of the amount of each type of lipid may be obtained by colorimetry. The chapter highlights the colorimetric methods most commonly used for analysis of each type of lipid or for functional groups contained in the lipid.

The transport of exogenous and/or endogenous cholesterolin the baboon has been studied using [1-14C] acetate, [2-14C] mevalonic acid and 3H- and 14C-labeled cholesterol. The peak specific activity of the serum free cholesterol derived from [2-14C] mevalonic acid was reached in 4–10 h and the free and esterified forms equilibrated by 72 h. With the use of either [4-14C] cholesterol or [7δ-3H] cholesterol, peak specific activities of the free and esterified fractions were observed between 1–3 days. The free and ester specific activities were about equal over a 10-day period. The total cholesterol specific activity of the α and β lipoproteins was nearly the same over the period studied, regardless of whether derived from exogenous or endogenous sources. This finding was corroborated by simultaneous administration of [2-14C] mevalonic acid and [7α-3H] cholesterol to a baboon. Rate constants were deduced for the compartmentation of either exogenous or endogenous cholesterol. The slowest components of the free cholesterol specific activity curves of dietary or biosynthetic origin were found to have half-life values of 9.6 and 3.7 days, respectively. These studies indicate at least a qualitative parallel for the manner of transport of cholesterol in humans and baboons.

Evidence has accumulated in recent years which suggests that subtle differences may exist between the fractional turnover rates of the major classes of serum cholesterol esters. This subject has been reviewed recently by Goodman (1). Both Goodman (1,2) and Nester et al. (3) showed that, in the human, the fractional turnover rate of the cholesterol esters as a group was higher in the serum high-density lipoproteins than in the serum low-density lipoproteins. However, within each class of lipoprotein, a homogeneous turnover of all cholesterol esters was observed. On the other hand, Gidez et al. (4) have recently reported that, in the rat, the fractional turnover rate of each cholesterol ester class is heterogeneous both within and between the serum α- and β-lipoproteins. In recent years, there has been an increase in the use of primates, including the baboon, for experimental atherosclerosis research. In the course of our studies on cholesterol transport and metabolism in the baboon, we became interested in determining the degree of homogeneity in the turn-over of the different serum cholesterol ester classes and in comparing our results with similar studies obtained from other species and with humans. Toward this end, we undertook a study of the pattern of labeling of serum cholesterol esters at early sampling times (0 – 30 hr) after the administration of labeled substrates.

WHEN randomly labelled cholesterol (either with carbon-14 or tritium) was fed to rats, a small but appreciable amount of the administered radioactivity could be recovered in the carcass fatty acids1. In both cases it was assumed that the label was due to incorporation of the carbon atoms of the isopropyl group of the cholesterol side-chain into the isolated fatty acids. In the course of recent experiments involving cholesterol metabolism in baboons we administered cholesterol-6α-3H (5 mc.) to a male baboon (18 kg) which was killed 3 days later. The lipids of a number of tissues (liver, spleen, kidney, lung, adrenal) were extracted with chloroform–methanol 2: 1 (ref. 2), separated by chromatography on silicic acid3 and assayed for radioactivity by liquid scintillation spectrometry.

Histochemical and thin-layer chromatographic analyses were made on neutral lipids in Leucochloridiomorpha constantiae (Trematoda) metacercariae incubated in non-nutrient Locke's solution at 37.5 or 42 C for 24 hr. As determined by Oil Red O staining, lipid droplets accumulate mainly in the intestine of incubated worms. Attempts to distinguish specific neutral lipid fraction of metacercariae obtained directly from snails is free sterol. During incubation, metacercariae accumulate triglycerides and to a lesser extent cholesterol esters, and excrete free sterol into the medium.

A series of laboratory periods are devoted to the chemistry of intravenous solution in a one-semeter course for nursing students.

Thin-layer chromatographic analyses were made of phospholipids extracted from adult Echinostoma revolutum (Trematoda) and from the nonnutrient medium in which worms were maintained. Identity of phospholipids was based on comparison with authentic lipid standards and on specific chemical detection tests. The most abundant phospholipids in the extract were phosphatidyl choline, phosphatidyl ethanolamine and phosphatidyl serine; lesser amounts of cerebrosides and lysophosphatidyl choline were detected also. Phospholipids detected in the incubation medium were essentially as described for extracts.