Lipid and phospholipid content and fatty acid composition of the chick lung during embryonic development

Summary The evolution of total phospholipid, phosphatidylcholine and phosphatidylethanolamine content of chick lung during embryonic development is in good agreement with morphological data. Saturated fatty acids are predominant. A sex-linked difference is observed in the evolution of phosphatidylcholine.     

Hepatic phosphatidylcholine synthesis in deficiency of lysine and threonine: effect of malathion

Rats fed on a rice diet deficient in lysine and threonine showed increased activities of CDP-Choline pathway enzymes and incorporation of (methyl-3H)-choline into hepatic microsomal phosphatidylcholine, compared to rats fed on the same diet supplemented with lysine and threonine. However, the amount of microsomal phosphatidylcholine was significantly decreased in rats fed a deficient rice diet. These results suggest an enhanced phosphatidylcholine catabolism in rats fed on a rice diet deficient in lysine and threonine. Malathion administration reduced the amount of phosphatidylcholine in all the groups.     

Hepatic phosphatidylcholine synthesis in deficiency of lysine and threonine: effect of malathion

Summary Rats fed on a rice diet deficient in lysine and threonine showed increased activities of CDP-Choline pathway enzymes and incorporation of (methyl-³H)-choline into hepatic microsomal phosphatidylcholine, compared to rats fed on the same diet supplemented with lysine and threonine. However, the amount of microsomal phosphatidylcholine was significantly decreased in rats fed a deficient rice diet. These results suggest an enhanced phosphatidylcholine catabolism in rats fed on a rice diet deficient in lysine and threonine. Malathion administration reduced the amount of phosphatidylcholine in all the groups.     

Metabolism and signaling activities of nuclear lipids

Apart from the lipids present in the nuclear envelope, the nucleus also contains lipids which are located further inside and are resistant to treatment with nonionic detergents. Evidence is being accumulated on the importance of internal nuclear lipid metabolism. Nuclear lipid metabolism gives rise to several lipid second messengers that function within the nucleus. Moreover, it is beginning to emerge that nuclear lipids not only act as precursors of bioactive second messengers but may be directly involved in regulation of nuclear structure and gene expression. Over the last 10years, especially the role of the inositol lipid cycle in nuclear signal transduction has been extensively studied. This cycle is activated following a variety of stimuli and is regulated independently from the inositide cycle located at the plasma membrane. However, the nucleus contain other lipids, such as phosphatidylcholine, sphingomyelin, fatty acids and eicosanoids. There are numerous reports which suggest that these classes of nuclear lipids may play roles in the nucleus as important as those of phosphoinositides. This review aims at highlighting the most important aspects regarding the metabolism and signaling activities of nuclear phosphatidylcholine, sphingomyelin, fatty acids and eicosanoids.Received 7 November 2003; received after revision 18 December 2003; accepted 29 December 2003     

Effect of taurine administration on liver lipids in guinea pig

The oral administration of 0.4% taurine in drinking water for 14 consecutive days showed the following hepatic effects in male guinea pig. The percentage of tauro-conjugated biliary bile acids was increased from 17.2-54.2%; the ratio liver weight/body weight was increased, and fatty change was induced. Liver triglyceride concentration was accordingly increased; diglyceride and phosphatidylcholine concentrations were reduced by the treatment, while phosphatidylethanolamine level was not affected. These changes suggest an adverse effect of taurine administration on phosphatidylcholine hepatic synthesis.     

Changes of the phosphatidylcholine content and the number of synaptic vesicles in relation to the neurohumoral transmission in sympathetic ganglia.

In sympathetic ganglia stimulated in the presence of HC-3, the reduction in number of synaptic vesicles was observed to be accompanied by a significant decrease of the ganglionic phosphatidylcholine content.     

Effect of taurine administration on liver lipids in guinea pig

Summary The oral administration of 0.4% taurine in drinking water for 14 consecutive days showed the following hepatic effects in male guinea pig. The percentage of tauro-conjugated biliary bile acids was increased from 17.2–54.2%; the ratio liver weight/body weight was increased, and fatty change was induced. Liver triglyceride concentration was accordingly increased; diglyceride and phosphatidylcholine concentrations were reduced by the treatment, while phosphatidylethanolamine level was not affected. These changes suggest an adverse effect of taurine administration on phosphatidylcholine hepatic synthesis.     

Enhancement of fluorescence of pyrene-containing lipids by polar media, detergents and phospholipids

The fluorescence intensities of a medium-chain fatty acid and of several amphiphilic lipids, each containing pyrene in covalent linkage, were enhanced considerably by: 1) Dissolving in mixtures of a polar solvent (e.g. methanol, ethanol, tetrahydrofuran or dimethylsulfoxide) and water; for each individual compound, a certain ratio of solvent to water provided maximal fluorescence intensity. 2) Incorporating into micelles of reduced Triton X-100; an excess of detergent was used so that, statistically, only one molecule of lipid resided in one micelle of the Triton X-100. 3) Incorporating into liposomes of egg phosphatidylcholine; maximal fluorescence was observed using a large excess of phosphatidylcholine. When related to the fluorescence intensities in chloroform/methanol (2:1, by vol.) or water, the enhancement of fluorescence in the above three systems was about 2-6-fold or up to 60-fold, respectively.     

Phospholipid composition of cardiac (Na+ + K+)-ATPases from various species

There is a difference in phospholipid composition of cardiac (Na+ + K+)-ATPase preparations between species which are sensitive to ouabain and those which are not. Sphingomyelin is higher and phosphatidylcholine is lower in the enzymes from sensitive species than in those from insensitive ones. Lysophosphatidylcholine is detectable only in the latter preparations.     

Lipid transport in microorganisms

Summary Microorganisms are useful model systems for the study of intracellular transport of lipids. Eukaryotic microorganisms, such as the yeastSaccharomyces cerevisiae, are similar to higher eukaryotes with respect to organelle structure and membrane assembly. Experiments in vivo showed that transport of phosphatidylcholine between yeast microsomes and mitochondria is energy independent; transfer of phosphatidylinositol to the plasma membrane and the flux of secretory vesicles take place by different mechanisms. Linkage of transfer and biosynthesis of phospholipids was demonstrated in the case of intramitochondrial phospholipid transfer. A yeast phosphatidylinositol/phosphatidylcholine transfer protein, which is essential for cell viability, was isolated and characterized. Another phospholipid transfer protein present in yeast cytosol, which has a different specificity, is currently under investigation. Transfer of phospholipids between cellular membranes was also demonstrated with prokaryotes. The cytoplasm and the periplasma of the gram-negative facultative photosynthetic bacteriumRhodopseudomonas sphaeroides contain phospholipid transfer proteins; these seem to be involved in the biosynthesis of prokaryotic membranes.     

Enhancement of fluorescence of pyrene-containing lipids by polar media,detergents and phospholipids

Summary The fluorescence intensities of a medium-chain fatty acid and of several amphiphilic lipids, each containing pyrene in covalent linkage, were enhanced considerably by: 1) Dissolving in mixtures of a polar solvent (e.g. methanol, ethanol, tetrahydrofuran or dimethylsulfoxide) and water; for each individual compound, a certain ratio of solvent to water provided maximal fluorescence intensity. 2) Incorporating into micelles of reduced Triton X-100; an excess of detergent was used so that, statistically, only one molecule of lipid resided in one micelle of the Triton X-100. 3) Incorporating into liposomes of egg phosphatidylcholine; maximal fluorescence was observed using a large excess of phosphatidylcholine. When related to the fluorescence intensities in chloroform/methanol (21, by vol.) or water, the enhancement of fluorescence in the above three systems was about 2-6-fold or up to 60-fold, respectively.     

Phospholipid composition of cardiac (Na++K+)-ATPases from various species

Summary There is a difference in phospholipid composition of cardiac (Na⁺+K⁺)-ATPase preparations between species which are sensitive to ouabain and those which are not. Sphingomyelin is higher and phosphatidylcholine is lower in the enzymes from sensitive species than in those from insensitive ones. Lysophosphatidylcholine is detectable only in the latter preparations.     

Pressure acclimation of the eel and liver membrane composition

Homeoviscous adaptation of membrane fluidity is known to exist in fish living at great depths. Is this adaptation also present in fish living near the surface but experimentally acclimated to high pressure? The composition of mitochondria-rich fractions extracted from the livers of eels acclimated for 15 days at 101 ATA was determined. The results show that pressure induced a significant increase (+100%) of total phospholipids (PL) and cholesterol without a change in their ratio. The increase of PL content was accompanied by a decrease in phosphatidylcholine in favour of phosphatidyl ethanolamine which, due to its preference for the H₁₁ form, is able to compensate for the loss in fluidity induced by pressure.     

Phospholipid and fatty acid composition of lamellar bodies isolated from chicken lungs at different stages of development]

In order to elucidate whether the lamellar body content represents functional surfactant as soon as these bodies appear in lung epithelium during fetal development, lamellar bodies were isolated from lungs of Chicken at various developmental stages. Their content was analyzed and compared to extra-cellular functionnal surfactant. The results show that this content undergoes gradual changes in the phospholipid/protein ratio, as well as in the relative phosphatidylcholine amount. Thus, in the Chicken, nascent lamellar bodies do not represent the final form of extracellular surfactant.     

Properties and modes of action of specific and non-specific phospholipid transfer proteins

We have described the mode of action of the phosphatidylcholine transfer protein (PC-TP), the phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) isolated from bovine and rat tissues. PC-TP and PI-TP specifically bind one phospholipid molecule to be carried between membranes. PC-TP, and most likely PI-TP as well, have independent binding sites for the sn-1- and sn-2-fatty acyl chains. These sites have different properties, which may explain the ability of PC-TP and PI-TP to discriminate between positional phospholipid isomers. nsL-TP, which is identical to sterol carrier protein 2, transfers all common phospholipids, cholesterol and oxysterol derivatives between membranes. This protein is very efficient in mediating a net mass transfer of lipids to lipid-deficient membranes. Models for its mode of action, which is clearly different from that of PC-TP and PI-TP, are presented.     

Incorporation of 32P into renal phospholipids of mice during postnatal growth

During the first 40 days of life the rate of incorporation of 32P into total phospholipids and into phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, diphosphatidylglycerol, phosphatidic acid and phosphatidylinositol of mouse kidney was by some 25-35% higher than in older animals. Results suggest a different involvement of cellular membranes during of normal and compensatory renal growth.     

Properties and modes of action of specific and non-specific phospholipid transfer proteins

Summary We have described the mode of action of the phosphatidylcholine transfer protein (PC-TP), the phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) isolated from bovine and rat tissues. PC-TP and PI-TP specifically bind one phospholipid molecule to be carried between membranes. PC-TP, and most likely PI-TP as well, have independent binding sites for thesn-1- andsn-2-fatty acyl chains. These sites have different properties, which may explain the ability of PC-TP and PI-TP to discriminate between positional phospholipid isomers. nsL-TP, which is identical to sterol carrier protein 2, transfers all common phospholipids, cholesterol and oxysterol derivatives between membranes. This protein is very efficient in mediating a net mass transfer of lipids to lipid-deficient membranes. Models for its mode of action, which is clearly different from that of PC-TP and PI-TP, are presented.     

On the location of the tetrapyrrole macrocycle of chlorophyll a in phospholipid vesicles and in hexadecane

Summary The state of chlorophyll a in phosphatidylcholine vesicles was examined. The results indicate that the chlorophylls are present in monomeric form. A kinetic study of chlorophyll reactions with K₂S₂O₈ and piperidine showed that these substances react with the porphyrin rings of pigments located on both vesicle faces, most probably within the polar headgroup region.Acknowledgments. This work was supported by the Research Committee and the Biophysics Research Group, University of Québec at Trois-Rivières.     

Age-dependent changes of rat liver plasma membrane composition

The chemical composition of liver plasma membrane was studied in Wistar rats aged between 3 and 24 months. Results obtained indicate a significant age-dependent positive correlation of both the protein: phospholipid and cholesterol: phospholipid ratios, whereas the protein: cholesterol ratio seems to remain unaffected. Phospholipid analysis of liver plasma membrane reveals that only the phosphatidylcholine content has a significant negative correlation with age; all other phospholipid species remain basically unchanged.     

Incorporation of32P into renal phospholipids of mice during postnatal growth

Summary During the first 40 days of life the rate of incorporation of³²P into total phospholipids and into phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, diphosphatidylglycerol, phosphatidic acid and phosphatidylinositol of mouse kidney was by some 25–35% higher than in older animals. Results suggest a different involvement of cellular membranes during of normal and compensatory renal growth.