Lipid labelling

Figure 3. Retention of immunoliposomes in lung. Immunoliposomes (200 /ig lipid) labeled with lxlIn-DTPA-SA were injected iv. The percent initial accumulation in lung was calculated at indicated time intervals. Bar is S.D. (n=3) Data taken with permission from reference 14. Key , 34A-liposomes (PC chol GMx=10 5 l), Ab lipid= 1 11 (w/w), 297 nm in average diameter A, 34A-liposomes (PC chol GM.=10 5 1), Ab lipid=l 37 (w/w), 292 nm in average diameter , 34A-liposomes (PC chol PS=10 5 1), Ab lipid=l 8 (w/w), 253 nm in average diameter A, 34A-liposomes (PC chol PS=10 5 1), Ab lipid=l 31 (w/w), 255 nm in average diameter.

Figure 3 Planar scintigraphic images acquired at various times of a normal rat intravenously injected with Tc-Doxil (17MBq) Tc, 2 mg doxorubicin, and 16 mg total lipid labeled using Tc-iV,iV-bis(2-mercaptoethyl)-Af, Af diethyl-ethylenediamine method. Abbreviations-. H, heart L, liver K, kidney B, bowel.

The dyes used for probing lipid membranes consist of a fluorophore with a long lipophilic tail. The lipophilic tail inserts itself into the membrane thus locating the fluorophore label on the membrane. These products are used as lipid labels and in cell tracking as part of biophysical studies. There are two main classes of fluorophore, aminostyryls and indocarbocyanines. The most widely used indocarbocya-nine is the 18-carbon derivative of Cy3 known as dil, (3.72). 

It is difficult to identify the lipid moiety as a polyprenol, because of the small amounts present in tissues. Nevertheless, some information can be obtained by using glycosylated lipids labelled in the sugar moiety. The first indication of the presence of polyprenyl glycosyl phosphates comes from study of the properties just mentioned, namely, lability to mild acid, stability to mild alkali, and acidic properties. Information on the polyprenyl nature of the lipid may be obtained by labelling the lipid with radioactive 2,4-dideoxyO-C-methyl-D-g/ycero-pentono-l.S-lactone (mevalonic acid ). 

This question of direct interaction with nerve proteins or indirect interaction via membrane perturbation has also been tackled by ESR spectroscopy. Two types of labeling have been used fatty acids for lipid labeling and maleimide for frog nerve proteins. The anesthetics used were halothane as an example of a general anesthetic and procaine, lidocaine, and tetracaine as examples of local anesthetics. The latter interact primarily with head groups but can also merge into the hydrophobic hydrocarbon... 

GlycoUpids, Synthesis of Imaging Techniqnes Lipids Labeling Techniqnes Lipids Lipidomics Lipids, Semi-synthetic Steroid and Triterpene Biosynthesis PHYSICAL PROPERTIES PHASE BEHAVIOR AND PHASE TRANSITIONS... 

Lipids Label Fluorescence of factor II Fluorescence of factor IX... 

Paper radiochromatography has been employed to determine vitamin B12 labeled with cobalt-60 in foods, to follow its metabolism, and for various other studies. Thin-layer chromatography has been used for the determination of lipids labeled with H, or in foods. 

An interesting feature of lipid labeling by C02 in photosynthetic tissue is the rapid incorporation into compounds (PC and PG) which in vitro work indicates cannot be made in the chloroplast. The products of CO2 fixation in the chloroplast, e.g., lipid precursors, glycerol-3-P, and fatty acids, must be rapidly transported into the cytoplasmic compartment, and in some cases processed and rapidly returned to the chloroplast. 

Addition of radiolabeled [l,2- C]choline to plant tissue rather specifically labels PC. Marshall and Kates (1974) found 10% of the labeled lipid as lyso-phosphatidylcholine. (LPC). Tang and Castelfranco (1968) have published chromatograms of lipids from potato (Solanum tuberosum L.) tuber slices labeled by choline. In addition to PC there were minor spots which could correspond to LPC. Moore (1977) used [l,2- C]choline to label PC in soybean suspension cultures. The only lipid labeled was PC, and its degradation was followed after a 2-h pulse of radioactivity. The cells grew exponentially and then entered stationary phase turnover half-times in these two phases were 36 and 96 h. 

Ethanolamine is not as specific a label as choline. Willemot and Boll (1967) supplied excised tomato Lycopersicon esculentum L.) roots with [ CJeth-anolamine and found modest amounts of radioactivity in lipids other than PE [PC and an unknown compound in the region of lysophosphatidylethanol-amine (LPE)]. Marshall and Kates (1974) found that [ diethanolamine was incorporated into neutral lipid (10-20% of lipid label) and phosphatidylcholine (up to 10%). Waring et al. (1976) reported the metabolism of [ dletha-nolamine into tomato seedling lipids. After a 2-h exposure 70-75% of the radioactivity taken up by cotyledons or hypocotyl sections was still water-soluble, 5-12% was found as CO2, and 12-22% as phospholipid. Of the latter fraction 60% was PE, 26% PC, 3-4% each MMPE and DMPE, and... 

Schaeffer and Sharpe (1971) have reported an effect of cytokinin on the metabolism of [mer/iy/- C]methionine. There is an increase in lipid labeling, but there is also a marked decrease in the conversion of methyl groups to CO2 in the presence of cytokinin. Phosphatidylcholine was isolated from the lipid fraction and found to be more labeled in the cytokinin-treated samples. However, PC was by no means the only lipid labeled, and the position of label was not determined. 

Fig. 1. Lipid exchange between potato microsomes and mitochondria in vitro, (a) Incubation of radioactive lipid-labeled microsomes with unlabeled mitochondria, followed by reisolation of each organelle and determination of the specific radioactivity of its lipid, (b) Incubation of radioactive lipid-labeled mitochondria with unlabeled microsomes, and then as in (a). Mic, Microsomes Mit, mitochondria Sum, cytoplasmic supernatant , initial fraction of radioactive lipid (from Ben Abdelkader and Mazliak, 1970).

Similarly, it was recently found (Mazliak et al., 1977) that, in etiolated germinated sunflower cotyledons, newly synthesized radioactive lipids (labeled from [ C]acetate) accumulated first in the microsomes, second in the mitochondria, and much more slowly in the nuclei, which also suggests a lipid transfer from microsomes toward other cell organelles, such as mitochondria and nuclei. 

The necessity to add an x-VLDL radioactivity attributed in part to lipid label or to partially denatured material (x is external to the main exchange processes)... 

In this paper we describe lipid labeling from C-glycerol, C-acetate and C-glycero 1 3-phosphate during amphibian embryo-genesis. In addition the fatty acid pattern of phospholipids in microsomal and mitochondrial fractions is presented. 

Table 2. Changes due to different concentrations of propranolol or phentolamine on -glycerol lipid labeling in retina...

Postdecapitation ischemia also deeply inhibits the entrance of C-arachidonic acid into brain lipids. Ten minutes after the onset of blood shortage a deep inhibition of lipid labeling was observed and only 12% of radioactivity was in the polar lipids. Ischemia produced a larger decrease in lipid labeling than electro--shock however, in the latter a tendency toward recovery in the incorporation can be seen 10 min after application of the stimulus (Table 1). 

Table 2. Effects of varying the divalent cations concentration on cattle retina lipids labeling by C-glycerol...

Table 4. Percent of inhibition in retina lipid labeling from...

The shifts in ion concentration may alter the lipid labeling by either a secondary effect or a direct action on the metabolic steps. In either case, the early time-course of the labeling suggests that the precursor can enter different pools of retina lipids and that different branches of the de novo biosynthesis of retina glycerolipids are very sensitive to shifts in the ionic environment. Further experiments with lower concentrations of X-537A as well as with another carboxylic acid lipid soluble ionophore will likely help in clarifying the dual effect shown here to be exerted by this antibiotic. 

Although the media used make widely different ionic environments, similar lipid labeling profiles were found when the early time-course of C-glycerol uptake was followed. In both cases a temperature-dependent incorporation, higher for the Ames-Hastings medium, is evident. The precursor uptake Increases up to 23 C. Hereafter all the experiments were carried out at this temperature (Fig. 1). Phosphatidic acid and phosphatidylinositol were the highest labeled lipids under all these conditions (Fig. 2). 

In both media light flashes stimulated polar lipid labeling (Fig. 4). The effect was clearly observed after 20 minutes of incubation. The largest increments produced by light were found in PI and PA. 

Table 1 Effect of monensin on the distribution of the lipid label in the different subcellular membrane fractions.

Membrane fractions g.cm -3 Characterization according to ref. 2 3 lipid label -mon + mon fatly acid - mon + label mon... 

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