Immobilization of phospholipid micelles on modified apoHDL-Sepharose]

There was developed a procedure for immobilization of phosphatidyl cholines (Egg yolk phosphatidyl choline and polyunsaturated soya beams phosphatidyl choline) on the modified apoHDL-Sepharose. The formation of phospholipid micelles was proved by linear dependence of the content of the sorbed phosphatidyl choline versus, the content of apoHDL bound to Sepharose. Incubation of apoHDL/PC-Sepharose with human plasma was shown to change the plasma lipid composition. The apoHDL/PC-Sepharose might be used for correction of the plasma lipid composition on vitro experiments.     

The Electrical Capacitance of Phospholipid Membranes

As one of the methods of finding out the structural change of lipid bilayers due to change of environmental solution, the capacitances of phosphatidyl choline (egg lecithin) and phosphatidyl serine (bovine brain) bilayer membranes in solutions of various pH and salt contents were measured. It was found that the capacitance of the bilayer depended upon pH and salt content. The capacitance had a minimum value around pH 4 for phosphatidyl choline and around pH 3-4 for phosphatidyl serine bilayers, respectively. The value of the capacitance increased as the pH of the solution became lower or higher. As the concentration of cholesterol in the phosphatidyl choline bilayer increased, the capacitance increased and reached a saturation value. A DC voltage across the phosphatidyl choline bilayer did not affect the value of the capacitance practically.     

Frost-induced phospholipid changes in cold-acclimated and non-acclimated rape leaves

Freezing and thawing of winter rape leaves was found to cause a marked decrease of total phospholipid content in general, and that of phosphatidyl choline in particular. In the highly injured leaves the decrease of phosphatidyl choline was irreversible, and it was accompanied by a marked increase of phosphatidic acid. In the slightly damaged leaves no phosphatidic acid accumulation was detected, irrespective of phosphatidyl choline decrease. Instead of phosphatidic acid, the phosphatidyl glycerol or an unidentified P-containing lipid increased after thawing in leaves hardened to the first (T_k50=?8°C) or to the second (T_k50=?13.5°C) level, respectively. Frost hardening was found to promote phospholipid recovery after freezing and to increase phospholipid content, including that of phosphatidyl choline and phosphatidyl ethanolamine. Possible association of frost hardening with modified phospholipase-D properties is suggested.     

Phospholipid and ether linked phospholipid content alter with cellular resistance to vinblastine

The phospholipid and ether linked phospholipid content of leukaemic lymphocytes alters when the cells become resistant to low levels of the anti-cancer drug, vinblastine. Sphingomyelin and cardiolipin increase, and phosphatidyl ethanolamine and serine decrease in resistant cells. In addition, increases in 1-alkyl-2-acyl phosphatidyl choline and 1-alkenyl-2-acyl-phosphatidyl ethanolamine are concomitant with decreased 1,2-diacyl phosphatidyl choline and ethanolamine. Changes to the ultrastructure of the inner half of the plasma membrane bilayer, as a consequence of drug resistance, are illustrated by freeze-fracture electron microscopy.     

Characterization of gastric mucosal membranes: lipid composition of purified gastric microsomes from pig, rabbit, and frog

The lipid compositions of the gradient-purified gastric microsomal membranes from the fundic mucosa of pig, rabbit, and frog were determined. The total lipid content varied widely. Compared to the rabbit (21.6 ± 0.6 mg/100 mg protein), the pig had about twice as much and the frog about three times as much lipid. The levels of cholesterol were higher in both mammalian species (about 32% of the lipid) compared to frog (23%). Phospholipids accounted for about 45, 54, and 52% of the total microsomal lipids from pig, rabbit, and frog and the molar ratios of cholesterol to phospholipid in the three species were 1.95, 1.6, and 1.17, respectively. Phosphatidyl choline and phosphatidyl ethanolamine together constituted about 75% of the total phospholipids in pig and frog and 93% in rabbit gastric microsomes. Sphingomyelin comprised 19.3, 3.2, and 1.5% in pig, rabbit, and frog, respectively. Phosphatidyl inositol constituted 5, 2.7, and 23.6% in pig, rabbit, and frog, respectively. The ratios of phosphatidyl ethanolamine to phosphatidyl choline were 1.17, 1.1, and 0.85 in pig, rabbit, and frog, respectively. The saturated fatty acids 16:0 and 18:0 and the unsaturated fatty acid 18:1 and 18:2 were the predominant fatty acids in all phospholipids. The ratios of saturated to unsaturated fatty acids were between 0.8 and 0.9 in phosphatidyl choline and 0.27 and 0.5 in phosphatidyl ethanolamine from all three species. The contributions by saturated fatty acids were much more in phosphatidyl inositol and sphingomyelin than in phosphatidyl choline and phosphatidyl ethanolamine from all species. Position 1 of phosphatidyl choline had 63% saturated and 37% unsaturated fatty acids; while the reverse was true for position 2. Phosphatidyl ethanolamine, however, had 85% saturated fatty acids in position 1 compared to only 25% in position 2. Arachidonic acid (20:4) was present in significant amounts in all species located exclusively at position 2 of both phosphatidyl choline and phosphatidyl ethanolamine.     

Inhibition of chilling-induced photooxidative damage to leaves of Cucumis sativus L. by treatment with amino alcohols

The effect of pretreatment of cucumber (Cucumis sativus L.) roots with choline chloride or ethanolamine on leaf phospholipid composition and light-induced leaf damage during chilling was studied. Photooxidative chlorophyll degradation was similarly inhibited by both amino alcohols. The decrease of the chlorophyll a/chlorophyll b ratio and the increase of polyunsaturated-fatty-acid degradation during chilling in the light were equally inhibited by pretreatment with choline chloride or ethanolamine. Treatment with choline chloride and ethanolamine caused, respectively, 43% and 26% increases in the total phospholipid contents of the leaves. After treatment with choline chloride, the phosphatidylcholine content was higher than the content of phosphatidylethanolamine; the reverse was true after treatment with ethanolamine. The chlorophyll concentration increased less than the phospholipid concentration, resulting in a decreased chlorophyll/phospholipid ratio of treated leaves. During chilling in the light, degradation of phosphatidylcholine, ethanolamine and phosphatidyl glycerol occurred. Phosphatidyl glycerol was less sensitive than phosphatidylcholine and ethanolamine. The degradation was equally inhibited by pretreatment with either amino alcohol. Possible connections between the phospholipid content of leaf membranes and the inhibition of chilling-induced photooxidative leaf damage are discussed.Abbreviations CC choline chloride - Chl chlorophyll - EA ethanolamine - PC phosphatidyl choline - PE phosphatidyl ethanolamine - PG phosphatidyl glycerol     

Effect of acute hypobaric hypoxia on 32-P incorporation into phospholipids of alveolar surfactant, lung, liver and plasma of rat.

Exposure of adult rats to hypobaric hypoxia caused hypolipidemia, hypotriglyceridemia and hypophospholipidemia. Hypobaric hypoxia produced an increase in liver triglyceride and cholesterol levels and a decrease in lung triglyceride, total phospholipid and phosphatidyl choline. The proportion of phosphatidyl choline in the pulmonary surfactant fraction I phospholipids (responsible for reducing surface tension) decreased (55.2% as compared to 80.4% in control animals). Incorporation of 32-P into liver phosphatidyl ethanolamine was significantly increased, incorporation into lung phosphatidyl choline and phosphatidyl ethanolamine was increased whereas a decreased incorporation into plasma phosphatidyl choline was observed. The data suggest an enhanced lipid synthesis in liver with a probable impairment of mobilization into plasma.     

Cytolysis of nucleated cells by complement: inhibition of membrane-transmethylation enhances cell death by C5b-9

Inhibition of transmethylation, i.e., enzymatic transfer of methyl groups to phosphatidyl ethanolamine resulting in generation and translocation of phosphatidyl choline, enhances the killing of nucleated cells by complement. Furthermore, under complement attack, transmethylation measured as incorporation of [3H]methyl groups into phosphatidyl choline is enhanced, suggesting that transmethylation functions as a membrane defense mechanism either by increasing the phosphatidyl choline synthesis or by transducing a signal that might trigger another membrane repair process.     

The molecular organization of nerve membranes

Summary The lipid content and composition from an axolemma-rich preparation isolated from squid retinal axons was analyzed.The lipids, which accounted for 45.5% of the dry weight of this membrane, were composed of 22% cholesterol, 66.7% phospholipids and 5.2% free fatty acids. The negatively charged species phosphatidyl ethanolamine (37%), phosphatidyl serine (10%) and lysophosphatidyl ethanolamine (4%) made up 51% of the phospholipids. The amphoteric phosphatidyl choline and sphingomyelin accounted for 39% and 4%, respectively.The relative distribution of fatty acids in each of the isolated phospholipids was studied. The most remarkable feature of these phospholipids was the large proportion of long-chain polyunsaturated fatty acids. The 226 acyl chain accounted for 37% in phosphatidyl ethanolamine, 21.7% in phosphatidyl choline, 17.5% on phosphatidyl serine and 20.3% in sphingomyelin (all expressed as area %).The molar fraction of unsaturated fatty acids reached 65% in phosphatidyl ethanolamine and 42.0 and 44.8% in phosphatidyl choline and phosphatidyl serine, respectively. The double bond index in these species varied between 1.0 and 2.6.The lipid composition of the axolemma-rich preparation isolated from squid retinal axons appears to be similar to other excitable plasma membranes in two important features: (a) a low cholesterol/phospholipid molar ratio of 0.61; and (b) the polyunsaturated nature of the fatty acid of their phospholipids.This particular chemical composition may contribute a great deal to the molecular unstability of excitable membranes.The preceding papers of this series were published inArchives of Biochemistry and Biophysics.     

Lipids of the Spirochaetales: Comparison of the Lipids of Several Members of the Genera Spirochaeta, Treponema, and Leptospira

The lipid compositions of 17 spirochetes belonging to the genera Spirochaeta and Treponema were investigated and compared with data previously derived from 11 strains of Leptospira. The lipid compositions and lipid metabolism of any of these genera is sufficiently different to be characteristic of that genus and to differentiate it from the other two genera. Members of the genus Leptospira are characterized by their ability to beta-oxidize long chain fatty acids as their major carbon and energy source. With few exceptions, they are incapable of synthesizing fatty acids de novo. The major phospholipid found was phosphatidyl ethanolamine. No glycolipid or phosphatidyl choline was found in these organisms. Members of the genus Treponema studied were incapable of beta-oxidation as well as de novo synthesis of fatty acids. Phosphatidyl choline is the major phospholipid of this genus. The glycolipid, monogalactosyl diglyceride, is a major component of the Treponema. Members of the Spirochaeta did synthesize fatty acids de novo. Although these spirochetes contain a monoglycosyl diglyceride, the hexose content of the glycolipid varied from species to species. Neither phosphatidyl ethanolamine nor phosphatidyl choline was found in the Spirochaeta.     

Effect of Feeding Defatted Millet (Sorghum vulgarie) Flour at Different Protein Levels on Phospholipids of Rat Liver

Effect of feeding defatted millet flour at 5, 10 and 14.5 percent protein levels respectively to rats for 6 weeks has been studied on their liver phospholipids. Feeding of millet at these protein levels significantly increased liver total lipids and total glycerides as compared to control rats fed casein at 10 percent level. Liver phospholipids and phosphatidyl choline were significantly increased in rats fed millet at 10 and 14.5 percent protein levels whereas phosphatidyl ethanolamine was increased in all millet protein fed groups. Incorporation of (counts/liver/100 g body weight) into liver total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine was significantly increased in M–5 and M–15% groups and it was decreased in phosphatidyl choline in rats of M–10% groups as compared to control. The effects of feeding millet on liver phospholipids are due to the quantity as well as quality of the millet protein.     

Lipid monolayers: action of phospholipase A of Crotalus atrox and Naja naja venoms on phosphatidyl choline and phosphatidal choline

The activity of phospholipase A on phosphatidyl choline and phosphatidal choline spread as monolayers on phosphate buffers containing snake venom (Crotalus atrox or Naja naja) was studied by measuring the fall of surface potential as a function of time, pH, film pressure, temperature, and concentrations of phosphate and venom. At 25 degrees C, pH 7.0, and 0.2 micrograms of venom per ml, optimal activity was observed with both venoms on both substrates at 12 dynes/cm film pressure on 0.04 m phosphate. Under these conditions, the pH optimum for C. atrox was broad (6.6-7.4) and that for N. naja was sharp (8.0) for the action on phosphatidyl choline, whereas both venoms had a sharp optimum at pH 8.0 in their action on phosphatidal choline. The optimal temperature with phosphatidyl choline was 27.5 degrees C for N. naja and 40 degrees C for C. atrox. In line with studies of phospholipase A activity in bulk phase in ether, phosphatidal choline was attacked much more slowly than phosphatidyl choline by C. atrox. Under conditions where both venoms had equal activity on phosphatidyl choline, C. atrox was only half as active as N. naja on phosphatidal choline. The studies suggest that the linkage of the hydrophobic chains in glycerophosphatides may affect their interaction with proteins.     

Activation of phosphorylating vesicles by net transfer of phosphatidyl choline by phospholipid transfer protein

Vesicles formed with phosphatidyl ethanolamine, phosphatidyl choline, cardiolipin, coupling factors and hydrophobic proteins from bovine heart mitochondria catalyzed a rapid³²P_i-ATP exchange. When phosphatidyl choline was deleted during the assembly of the vesicles, little³²P_i-ATP exchange was observed. Exchange activity was induced by incubating such deficient vesicles with phosphatidyl choline liposomes in the presence of a phosphatidyl choline transfer protein isolated from bovine heart. Transfer of [³²P] phosphatidyl choline was demonstrated by isolation of the activated vesicles by sucrose density centrifugation.     

Lipids from nerve tissues of the horseshoe crab, Limulus polyphemus.

1. The predominant lipids of nerve cords, ganglion and brain from horseshoe crabs were cholesterol (11% of lipid) and phospholipid (81% of lipid). 2. Major phospholipids were phosphatidyl ethanolamine and phosphatidyl choline with lesser amounts of phosphatidyl serine and phosphatidyl inositol and sphingomyelin. 3. The phospholipid fraction was characterized by a high content of plasmalogen, i.e. alk-1-enyl acyl phosphatides, so that 42% of the ethanolamine phosphatides were the plasmalogen, phosphatidal ethanolamine. 4. Phosphatidyl choline and phosphatidyl ethanolamine were high in polyunsaturation with 20:4 and 20:5 major fatty acids. Sphingomyelin had predominantly long chain saturated fatty acids. 5. Cerebrosides and gangliosides, which are associated with vertebrate nerve tissues, were absent from nerves of horseshoe crabs.     

The manipulation of polar head group composition of phospholipids in the wheat Miranovskaja 808 affects frost tolerance

Caryopses of the frost-resistant cultivar of the wheat Triticum aestivum L., Miranovskaja 808, were germinated and grown in the presence of various concentrations of choline chloride. Changes in the composition of leaf total phospholipids and leaf total fatty acids at two extreme temperatures (25°C and 2°C) as well as changes in frost resistance were followed. A choline chloride concentration-dependent accumulation of phosphatidyl choline was observed in the leaves. Seedlings grown at 2°C accumulated more phosphatidyl choline at each choline chloride concentration than those grown at 25°C. There was an inverse relationship between the contents of phosphatidyl choline and phosphatidic acid in the leaves. Neither the temperature nor choline chloride seemed to affect fatty-acid composition. Modification of polar-head group composition of phospholipids affected frost tolerance: Seedlings grown in the presence of 15 mM choline chloride at 25°C exhibited a freezing resistance equal to that of hardened controls. The data indicate that the polar-head group composition of membrane phospholipids in plants can be easily manipulated and point to the importance of phosphatidyl choline in cold adaptation processes.     

Control of the potassium ion-stimulated adenosine triphosphatase of pig gastric microsomes: effects of lipid environment and the endogenous activator

The K⁺-stimulated ATPase activity associated with the purified gastric microsomes from the pig gastric mucosa can be completely inactivated by treatment with 15% ethanol for 60 s at 37 °C but not at 25 °C. Sequential exposure of the microsomes to 15% ethanol at 25 and 37 °C caused the release of 2.9 and 4.3% of the total membrane phospholipids, respectively, consisting entirely of phosphatidyl choline and phosphatidyl ethanolamine. The ethanol-treated (37 °C) membrane had high basal (with Mg²⁺ as the only cation in the assay mixture) activity, which was further enhanced during reconstitution with phosphatidyl choline or phosphatidyl ethanolamine. The high basal activities could be reduced to the normal control level by assaying the enzyme in presence of the “activator protein,” partially purified from the soluble supernatant of the pig gastric cells. Phosphatidyl choline was somewhat more effective than phosphatidyl ethanolamine in the restoration of the activity of the ethanol-treated enzyme while phosphatidyl serine, phosphatidyl inositol, and sphingomyelin were without any effect. Synthetic phosphatidyl choline with various fatty acid substitutions were tested for their effectiveness in the restoration of the ethanol-inactivated enzyme. The distearoyl (18:0), dioleoyl (18:1), and dilinoleoyl (18:2) derivatives of phosphatidyl choline were almost equally effective while dipalmitoyl (16:0) phosphatidyl choline was somewhat less effective in the reconstitution process. Cholesterol appeared to interfere with phosphatidyl choline in the restoration of the activity of ethanol-treated enzyme. The fatty acid composition of phosphatidyl choline and phosphatidyl ethanolamine extracted by 15% ethanol at 37 °C was clearly different than those of the total microsome. Our data suggest that the phospholipids extracted by 15% ethanol at 37 °C are derived primarily from the immediate lipid environment of the enzyme and ATP together with Mg²⁺ and K⁺ help the partially delipidated enzyme to retain the appropriate conformation for the subsequent reconstitution. Furthermore, ethanol appears to either release or inactivate the membrane-associated activator protein, demonstrated to be essential for the K⁺-stimulated activity of the pig gastric ATPase.     

Hepatic Subcellular Fractions Lipids in Rats Fed Millet (Sorghum vulgarie) at Different Protein Levels

Effect of feeding defatted millet (Sorghum vulgarie) flour at 5, 10 and 14.5% protein levels respectively for six weeks has been studied on rat liver mitochondrial, microsomal and supernatant fractions total lipids, cholesterol, triglycerides, total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine. The results have been compared with rats fed casein at 10% level for the same period. The metabolism of liver subcellular fractions lipids of millet diet and casein diet fed rats has been studied by the incorporation of acetate-1-¹⁴C and . A significant increase in mitochondrial triglycerides of rats fed millet diet at 5 and 10% protein level, in microsomes of rats fed millet diet at 5, 10 and 15% protein levels and in supernatant fractions of rats fed millet diet at 5 and 15% protein levels was observed. A significant increase in total cholesterol in mitochondria and microsomes and a significant decrease in supernatant fraction of rats fed millet diet at 10% protein level was observed. A significant increase in mitochondrial total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine in rats fed millet diet at 10% protein level and a decrease in these in rats fed millet diet at 5 per cent protein level was observed. In microsomes total phospholipids were increased in rats millet diet at 10% protein level and phosphatidyl choline was increased in rats fed millet diet at 15% protein level. Total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine were significantly reduced in the supernatant fraction of rats fed millet at 10% protein level.

Incorporation of acetate-1-¹⁴C into nonsaponifiable fraction of mitochondria, microsomes and supernatant fractions of rats fed millet diet at 5 and 15 % protein levels was significantly greater, and in saponifiable fractions of the above subcellular fractions was greater in rats fed millet diet at 5 per cent protein level. The specific activity (counts/min/mg) of free cholesterol in mitochondria, microsomes and supernatant fractions of millet diet fed rats was significantly greater, whereas the specific activity of triglycerides was not significantly different from the controls. The acetate-1-¹⁴C specific activity of phosphatidyl choline and phosphatidyl ethanolamine was significantly greater in all the above subcellular fractions of millet diet fed rats (except of phosphatidyl choline in rats fed millet diet at 5 % protein level). The specific activities of phosphatidyl choline were significantly greater in mitochondria of rats fed millet diet at 5 % protein level and of phosphatidyl choline and phosphatidyl ethanolamine in microsomes and supernatant fractions of rats fed millet diet at 5 and 15% protein levels. The specific activities of phosphatidyl choline were significantly decreased in mitochondria and microsomes of rats fed millet diet at 10% protein level. The total acetate-1-¹⁴C activities (counts/min/g equivalent wet liver) of free and esterified cholesterol triglycerides, phosphatidyl choline and phosphatidyl ethanolamine showed that their synthesis from acetate-1-¹⁴C was either enhanced in millet diet fed rats or was comparable to the controls. The total activity of (counts/min/g equivalent wet liver) into phosphatidyl choline and phosphatidyl ethanolamine showed that their synthesis was decreased in microsomes of rats fed millet diet at 10% protein level, increased in rats fed millet diet at 5 and 15% protein levels.     

Effect of cryopreservation on lipids and some physiological features of spermatozoa from rams pastured in highlands and in valleys

The effect of low temperature preservation on the motility and morphology of acrosomes, acrosomal proteolytic activity, phospholipid and fatty acid composition of phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE), and the cholesterol/phospholipid molar ratio in sperm from rams housed in the highlands or in the valleys, were studied. The indices of motility and morphological integrity of sperm from highland rams were much greater compared with those of valley rams. Phosphatidyl choline (PC) of the highland rams was more unsaturated, while PE was more saturated compared with those of valley rams. Cryopreservation of the sperm from highland rams significantly increased the content of choline plasmalogen, accompanied by a slight rise in the levels of lysophosphatidyl choline (LPC) and phosphatidyl inositol (PI) in their sperm. The fatty acid composition altered following cryopreservation. These variations were mainly due to a decrease in the amount of docosahexaenic acid and an increase in the amounts of linoleic and palmitic fatty acids. The results may be indicative of the fact that the alterations in the sperm of the valley rams were more pronounced and they may be attributed to the structural features of the sperm, as well as a reduced concentration of oxygen in the organs and tissues of the highland rams.     

Phospholipids in the nuclei and chromatin of the rat thymus at long periods following gamma-irradiation

The phospholipid content of the homogenate, nuclei and chromatin of rat thymus was being studied during three months after fractionated gamma-irradiation (2 Gy X 3 at a week interval). The number of phospholipids in the total fraction of phosphatidyl choline + phosphatidyl serine and phosphatidyl ethanolamine in the nuclei and chromatin of rat thymus was shown to decrease 60 min following the last exposure. In a month the phospholipid content in the nuclei and chromatin increased up to the control level keeping it throughout the entire period of observation.     

Electrical conductivity in lipid bilayer membranes induced by pentachlorophenol.

Electrical conductivity induced in thin lipid bilayer membranes by pentachlorophenol has been studied. The membranes were formed from phosphatidyl choline, phosphatidyl ethanolamine, or phosphatidyl glycerol and various amounts of cholesterol. The position and the magnitude of the maximum of the conductivity vs. pH curve depend on the type of lipids and cholesterol content. At low pentachlorophenol concentrations and low pH the concentration dependence of conductivity is quadratic and becomes linear at higher pH. Above 10(-5) M of pentachlorophenol the concentration dependence of the membrane conductivity tends to saturate. Presence of pentachlorophenol enhances membrane transport of nonactin-K+ complex. Increase of cholesterol content increases pentachlorophenol induced conductivity in all membranes and shifts the conductivity toward lower pH. For phosphatidyl choline the largest rate of change of membrane conductivity with cholesterol occurs at 1:1 phospholipid to cholesterol molar ratio. Pentachlorophenol is found to be a class II uncoupler and the experimental results are consistent with the hypothesis that the membrane permeable species are dimers formed by combination of neutral and dissociated pentachlorophenol molecules. Several schemes of membrane conduction, including dimer formation in the aqueous phase as well as at the membrane-water interface have been considered. Arguments are given in favor of the formation of dimers within the membrane surface.