LIPIDS OF SUBCELLULAR PARTICLES

Effect of fluorescent products from reaction of malonaldehyde with phosphatidylethanolamine on lipids in plasma and liver of rats

Effect of fluorescent products from the reaction of malonaldehyde with dipalmitoyl phosphatidylethanolamine on the content of lipids in plasma and liver of rats was examined, and the results are as follows: Growth of rats was suppressed by daily intraperitoneal administration of fluorescent products (10 or 50 mg/kg) for 7 days. Levels of triglycerides and total cholesterol in the plasma tended to decrease but that of phospholipids increased significantly by the administration of fluorescent products in a dose of 50 mg/kg/day. On the other hand, content of triglycerides in liver decreased by about 26% at a dose of 10 mg/kg and 23% at a dose of 50 mg/kg. Total cholesterol and phospholipids showed a slight diminution. Free fatty acid content in the liver was almost constant. Thiobarbituric acid values in the plasma and liver increased significantly by treatment with the fluorescent products, especially the values at a rate of increase were higher in the plasma than in the liver. No significant changes were observed in the relative fluorescence intensity between control animals and groups treated with fluorescent products. Serum lipoprotein patterns after Agarose gel electrophoresis revealed diffuse bands in the pre-beta and beta-regions.

[Chicken erythrocyte nuclei: composition and analysis of phospholipids]

While many works analyse lipid composition of cellular nuclei, essentially of liver, few describe bird erythrocyte nuclei. For them very discordant results are reported due to very different methods of preparation. In the method we adopted a good reproducibility is controlled by electron microscopy, evaluation of specific enzymatic activities and by protein, RNA and DNA determinations. Total lipid content and phospholipid composition were determined showing, in agreement with other works, the predominance of phosphatidylcholine and phosphatidylethanolamine. On the contrary, the nuclear fraction is poor in sphingomyelin, which is essentially a plasma membrane phospholipid.

Lipid composition and protein profiles of outer and inner membranes from pig heart mitochondria. Comparison with microsomes

1. Mitochondria, inner and outer mitochondrial membranes and microsomes were isolated and purified from pig heart. Their lipid composition and protein components were studied. 2. The fatty acid distribution in the main phospholipids seemed specific rather of a given phospholipid and not of one type of membrane. 3. Inner mitochondrial membranes were characterized by a high content in cardiolipin and a very low level of triglycerides together with a high degree of unsaturation and C18 acids. Gel electrophoresis revealed 13 different polypeptide subunits of which 5 were major ranging in molecular weights from 10000 to 215000. 4. In outer mitochondrial membranes, total lipid, phosphatidylcholine, phosphatidylinositol, plasmologen and triglyceride contents were much higher than in inner membranes. Fatty acids of phospholipids were mostly saturated and the polypeptide pattern showed 12 components, of which 4 were major of mol. wt 75000, 60000, 20000 and below 10000. 5. Compared to outer membrane, microsomes exhibited a much higher cholesterol content and markedly different protein profiles. They contained significant amounts of cardiolipin and phosphatidylserine, this latter phospholipid being exclusively located in microsomes. However odd similarities were observed in some lipid components of microsomes and inner mitochondrial membranes, but fatty acids were more saturated in microsomes and electrophoretic profiles of protein components appeared very different and revealed components of high mol. wt.

Distribution of cholesteryl esters and other lipids in subcellular fractions of the adrenal gland of the pig

Total lipids from whole pig adrenal glands as well as from their mitochondria, microsomes, liposomes, and cell sap were extracted and fractionated first into neutral lipids and phospholipids. The highest percentage of neutral lipids was found in the cell sap, and the lowest in the microsomal fraction. Neutral lipids were subfractionated into cholesteryl esters, free cholesterol, triglycerides, and free fatty acids. Cholesteryl esters were distributed throughout the liposomes. Free fatty acids represented a substantial part of cell sap lipids, but were present also in the mitochondria, microsomes, and liposomes. Fatty acids of all fractions were analyzed by gas liquid chromatography. Free fatty acids and cholesteryl ester fatty acids from all cellular fractions were similar in composition and were characterized by considerable quantities of linoleic and arachidonic acid. Triglycerides were characterized by an increased percentage of palmitic and a low content of arachidonic acid. Phosphatidyl choline, phosphatidyl ethanolamine, diphosphatidyl glycerol, and sphingomyelin plus phosphatidyl inositol were isolated from the lipids by preparative thin layer chromatography, and their fatty acids analyzed by gas liquid chromatography. Phosphatidyl choline and phosphatidyl ethanolamine from mitochondria, microsomes, and cell sap were very similar in respect of their fatty acid composition. Sphingomyelin plus phosphatidyl inositol was characterized by a high content of C22:2omega6. Diphosphatidyl glycerol was present in mitochondria and in the cell sap.

Fractionation and analysis of fluorescent products of lipid peroxidation

The fluorescence excitation spectrum of model conjugated Schiff base compounds that arise from the reaction of malonaldehyde with amino acids was shown to contain a maximum at 260-280 nm in addition to the previously observed maximum at 350-390 nm. Excitation at either maximum results in emission at a single maximum at 440-480 nm. The excitation and emission maxima of the model fluorescent compounds, together with the characteristic reductions in fluorescence intensity caused by alkaline pH or heavy metal coordination provide criteria with which to examine lipid peroxidation products for the presence of the conjugated Schiff base fluorophore. Silicic acid column chromatography and silica gel thin layer chromatography were employed to fractionate the fluorescent products of model lipid peroxidation systems and of rat testicular lipid soluble extracts. These products contained large families of compounds whose fluorescence characteristics were the same as those of the Schiff base fluorophores. The fractionation methods used enabled more thorough fluorescence characterization of many of the products of lipid peroxication, but the fluorescence criteria available do not provide definitive proof of structure.

Mitochondria and nuclei of pig and human epidermis: isolation and lipid composition

Pig and human epidermis were mechanically disrupted with a Polytron homogenizer and mitochondria and nuclei were isolated from homogenates in buffered sucrose and 2.5% citric acid solution, respectively, by differential and density-gradient centrifugation. Examination of the mitochondrial preparations by electron microscopy and the assay of several marker enzymes indicated that they consisted mostly of mitochondria with some microsomal contamination. The nuclear preparations were substantially free from contaminants as judged by particle counts with the aid of phase and electron microscopy. The lipid compositions of the mitochondria from both species were characterized by a high concentration of cardiolipin and low concentration of cholesterol and sphingomyelin and an absence of glycosphingolipids as compared with the lipid composition of the whole epidermal cell. The lipid compositions of the nuclei were characterized by a high proportion of phosphatidyl choline and an absence of glycosphingolipids. The neutral lipids accounted for an unusually high proportion of the total lipids especially in human epidermal nuclei. Although the technical difficulties in isolating subcellular organelles from mammalian epidermis limit the yield and quality of the mitochondria, these preparations as well as those of nuclei are superior to preparations reported previously and are pure enough for a valid comparison with other membrane systems of the epidermal cell.

Lipid composition of the Golgi apparatus of rat kidney and liver in comparison with other subcellular organelles

Golgi apparatus isolated from both rat liver and rat kidney have been characterized with respect to their neutral and phospholipid content and their phosphopipid composition and compared with mitochondria, rough endoplasmic reticulum and plasma membranes. In addition, the distribution of sulfatide in the subcellular fractions of rat kidney was determinich are rich in cholesterol esters and ubiquinone. Removal of about 75% of the cisternal contents of rat liver Golgi reduced its content of cholesterol esters but not of ubiquinone. The Golgi complex of liver most closely resembles endoplasmic reticulum in its phospholipid composition except for a higher content of sphingomyelin. Removal of most of the contents of the Golgi cisternae did not appreciably alter the phospholipid composition of the Golgi apparatus of liver. Goligi apparatus from kidney has a phospholipid composition which resembles liver Golgi much more closely than it does any other cell fraction from kidney. The sulfatide content of kidney Golgi, the cell fraction richest in this glycolipid, is about 14% of the total lipid present in this fraction. Sulfatide was present in plasma membranes, mitochondria and rough microsomes, but at about one-third the level found in Golgi. Sulfatide is the main glycosphingolipid present in all the cell fractions from kidney which were studied.

Isolation and characterization of lamellar bodies and tubular myelin from rat lung homogenates

Three surface-active fractions which differ in their morphology have been isolated from rat lung homogenates by ultracentrifugation in a discontinuous sucrose density gradient. In order of increasing density, the fractions consisted, as shown by electron microscopy, primarily of common myelin figures, lamellar bodies, and tubular myelin figures. The lipid of all three fractions contained approximately 94% polar lipids and 2% cholesterol. In the case of the common myelin figures and the lamellar bodies, the polar lipids consisted of 73% phosphatidylcholines, 9% phosphatidylserines and inositols, and 8% phosphatidylethanolamines. In the case of the tubular myelin figures, the respective percentages were 58, 19, and 5. Over 90% of the fatty acids of the lecithins of all three fractions were saturated. Electrophoresis of the proteins of the fractions in sodium dodecyl sulfate or Triton X-100 revealed that the lamellar bodies and the tubular myelin figures differed in the mobilities of their proteins. The common myelin figures, however, contained proteins from both of the other fractions. These data indicate that, whereas the lipids of the extracellular, alveolar surfactant(s) originate in the lamellar bodies, the proteins arise from another source. It is further postulated that the tubular myelin figures represent a liquid crystalline state of the alveolar surface-active lipoproteins.

Phospholipids in artificially induced muscular dystrophy of calves

1. Phospholipds were studied in the heart muscles, skeletal muscles and livers of seven Ayrshire calves which received vitamin E-free maize oil (in filled milk) with and without supplementary α-tocopherol from 1 week old for 17 d. The calves that were not given vitamin E developed muscular dystrophy.

2. Decreased amounts of cardiolipin and increased amounts of sphingomyelin were found in the skeletal muscles of vitamin E-deficient calves. There was a significant decrease of phosphatidyl choline in the livers of vitamin E-deficient calves.

3. The decrease in cardiolipin concentration confirmed the electron-microscopical picture (reported elsewhere) of preferential destruction of mitochondria in muscular dystrophy of calves.

Determination of Phospholipid Fractions in Red Blood Cells in Retarded Physically Handicapped Children

Phospholipids from the red cells of 85 children, both normal and belonging to various clinical groups, have been extracted and subjected to silica gel chromatography. The several phospholipids have been quantitated. The results have not proved to be useful in diagnosis and hence do not confirm earlier reports. The problems associated with analysis of phospholipids by this type of method are discussed.