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PubMed1983

Membrane biogenesis in the sprouting neuron. I. Selective transfer of newly synthesized phospholipid into the growing neurite.

Our goal was to elucidate the pathway of newly synthesized phospholipid into the growing neurite. This was accomplished in pulse-chase studies with the phospholipid precursor [3H]glycerol, using sprouting explant cultures of rat superior cervical ganglion as an experimental system. After the pulse with the precursor and various chase periods, we separated perikarya and neurites microsurgically and extracted their phospholipids. The phospholipid extract from the perikarya exhibited a steep rise followed by a rapid decline in specific radioactivity. In contrast, an increase in neuritic specific radioactivity of phospholipid was observed only after a lag period of approximately 60 min. Nearly quantitative transfer of newly synthesized phospholipid from the perikarya into the neurites could be demonstrated. Both the decline in perikaryal specific radioactivity and the increase in its neuritic counterpart, i.e., the proximodistal transfer, could be blocked with the microtubule drug colchicine and the metabolic uncoupler, 2,4-dinitrophenol. These observations indicate preferential export of newly synthesized phospholipid from the perikaryon (the major or exclusive site of synthesis) into the growing neurites, most likely by rapid axoplasmic transport of formed elements.

2,4-Dinitrophenol↗
PubMed1984

Comparison of the phospholipid composition of breast milk from mothers of term and preterm infants during lactation.

Phospholipids were determined in milk on postpartum day 3 (colostrum) and days 7, 21, 42, and 84 from mothers of 18 very premature (26 to 30 wk gestation age), 28 premature (31 to 36 wk), and 6 term (37 to 40 wk) infants. Lipids were analyzed by thin-layer and gas-liquid chromatography. Total fat content increased during lactation whereas phospholipids and cholesterol declined. Phospholipids were separated from neutral lipids by column chromatography and distributed by preparative thin-layer chromatography into classes, sphingomyelin, phosphatidyl choline, serine, inositol, and ethanolamine for fatty acid analysis. Phospholipids exhibited a remarkable constancy in class percentages in milks from mothers giving birth prematurely or at term. Changes were observed in fatty acid composition within each of the phospholipid classes as secretion progressed from colostrum (3d) to transitional (7d) to mature milk (21, 42, 84d). These changes in phospholipid fatty acid composition occurred only during the first 3 wk of lactation. Mature milk was found to be relatively constant in phospholipid composition.

Colostrum↗
PubMed1996

Dietary fatty acid profile influences the composition of skeletal muscle phospholipids in rats.

Changes in dietary fatty acid composition alter phospholipid fatty acid composition in a variety of tissues, but little attention has been paid to skeletal muscle. In this study, rats were fed for 9 wk one of three isoenergetic diets: an essential fatty acid-deficient diet, a diet high in (n-6) fatty acids, and a diet enriched with (n-3) fatty acids. Some rats from each group were fed a nonpurified diet for a further 2 or 6 wk. Neither body mass nor food consumption varied among the dietary groups at any stage. Analyses of total phospholipids in soleus (a "slow" twitch muscle) and extensor digitorum longus (a "fast" twitch muscle) revealed that after 9 wk of test diet consumption, muscle phospholipids from rats fed the essential fatty acid-deficient diet were deficient in essential polyunsaturated fatty acids (triene:tetraene ratio >0.5), whereas the polyunsaturated fatty acids in muscle phospholipids from rats fed the high (n-6) fatty acid and high (n-3) fatty acid diets reflected the composition of their respective diets. Nevertheless, phospholipid fatty acid compositions of seemed to be selectively dynamic. After recovery, although the phospholipid fatty acid compositions of all groups were similar, they all contained a much higher proportion of (n-3) fatty acid than provided in the diets. Overall, these results demonstrate that in rats, the fatty acid profile of skeletal muscle phospholipids is strongly influenced by dietary changes, with most effects being reversible after short periods of adequate dietary intake.

Analysis of Variance↗
PubMed1987

The chemical carcinogen-induced enzyme, GDP-fucose: GM1 alpha 1----2 fucosyltransferase in rat liver and hepatoma: modulation by and association with phospholipids.

The enzyme GDPFuc:GM1 alpha 1----2 fucosyltransferase, induced by chemical carcinogens in precancerous rat liver as well as rat hepatoma cells, was found previously to be membrane bound, and was inactivated by various detergents, while the activities of many other transferases are generally enhanced by detergents (Holmes, E.H. & Hakomori, S. (1983) J. Biol. Chem. 258, 3706-3717). The effects of phospholipids and detergents on rat hepatoma H35 cells, the conditions of solubilization and subsequent affinity chromatography of the enzyme, and a possible association of phospholipids with the enzyme have been studied with the following major results: The alpha 1----2 fucosyltransferase activity in Golgi membrane was diminished on treatment of membranes with phospholipase A1 or phospholipase C. The enzyme activity was stimulated 7-fold in the presence of cardiolipin or phosphatidylglycerol (and 3-fold by phosphatidylethanolamine) but not other phospholipids. The stimulatory effect of phosphatidylglycerol was eliminated when a variety of ionic or non-ionic detergents were added to the reaction mixture, with the exception of the cationic detergent G-3634-A, which provided a 10-fold total stimulation in the presence of phosphatidylglycerol. The kinetic analysis indicated that addition of phosphatidylglycerol has a negligible effect on apparent Km values but increases the Vmax of the enzyme 5- to 6-fold. The enzyme activity was solubilized by the dialyzable detergent CHAPSO without inhibition of the enzyme activity, and the solubilized enzyme in the presence of 0.4% CHAPSO is partially purified by chromatography on GDP-hexanolamine-Sepharose. Removal of CHAPSO from the affinity purified enzyme by dialysis resulted in a 66% loss of the original activity, which was restored by addition of phosphatidylglycerol. Chromatography of the affinity-purified enzyme with 3H-labeled phosphatidylglycerol on a Biogel A0.5 column indicated an association of the enzyme with the phospholipid that occurred only in the absence of detergent. These results suggest that phospholipid has a direct effect on the enzyme and that the inhibitory effect of detergents can be ascribable to disturbing interaction between phospholipids and the enzyme. A possible role of specific phospholipids on in vivo transferase activity for glycolipids is discussed.

2-Acetylaminofluorene↗
PubMed1983

Structural studies of fc receptors. II. The effect of dissociation and reassociation of phospholipids on the activity of Fc gamma receptors of macrophages.

The receptor for the Fc portion of immunoglobulin G (Fc receptor) of guinea pig macrophages was solubilized with a detergent and partially delipidated to the point where the ligand binding activity was essentially lost. Delipidation of the Fc receptor was done by fractionating the macrophage lysate by gel filtration in the presence of detergent. The elution behavior of Fc receptor-detergent complex and phospholipid-detergent mixed micelles varied depending on the kind of detergents used for membrane solubilization and for gel filtration. Separation of phospholipids from Fc receptor was best achieved when octylglucoside-solubilized fraction was chromatographed on Sepharose CL-6B in the presence of deoxycholate; the phospholipid peak emerged at Kav = 0.55 and the Fc receptor at Kav = 0.45. The fraction of Kav = 0.45 showed only a marginal activity when the activity was measured after removal of detergents, but activity was clearly shown when phospholipid fraction was added to this fraction prior to removal of the detergents. Reappearance of the Fc receptor activity was shown to be due to association of phospholipids with the Fc receptor. Three kinds of phospholipids with different polar head groups examined, phosphatidylcholine, phosphatidylserine, and phosphatidylethanolamine, were all able to reconstitute active Fc receptor, although phosphatidylethanolamine was somewhat less effective than the others. Thus, our study demonstrated the amphipathic nature of the Fc receptor, the binding of which is dependent on the interaction with phospholipids.

Animals↗
PubMed1986

Membrane phospholipid synthesis in Escherichia coli: alteration by glycerol and physiological consequences in a pss mutant.

Escherichia coli mutants harboring the pss-1 allele (coding for a temperature-sensitive phosphatidylserine synthase) are temperature sensitive for growth and synthesize less phosphatidylethanolamine at higher temperatures, giving rise to abnormal membrane phospholipid compositions. To obtain information concerning the determinant for the phospholipid polar headgroup composition and the lethal factor in the defective membranes, we have examined the effect of increased supply of sn-glycerol 3-phosphate on the phospholipid synthesis and the growth ability of a pss-1 mutant. For this purpose, a pair of E. coli K-12 derivatives isogenic except for the pss-1 allele was constructed from strain BB26-36 to harbor the mutations related to glycerol metabolism (glpD3, glpR2, glpKi, and phoA8). Pulse- and uniform-labeling of phospholipids with 32P at 42 degrees C in a synthetic medium with (0.2%) or without glycerol showed that glycerol further lowered the temperature-sensitive formation of phosphatidylethanolamine, removed the phosphatidate and CDP-diacylglycerol accumulated in the absence of glycerol, and resulted in an increase in cardiolipin content in the pss-1 mutant. The phospholipid synthesis and contents in the pss+ strain were not significantly affected by glycerol. Glycerol in the medium markedly enhanced the growth defect of the pss-1 mutant, which was remediable by sucrose. The results indicate that the intracellular pool of sn-glycerol 3-phosphate is the limiting factor for acidic phospholipid synthesis in the pss-1 mutant, and cardiolipin unusually accumulated is injurious to the functional E. coli membranes. Possible determinants for the phospholipid composition of the wild-type E. coli cells are also discussed on the basis of the present observations.

CDPdiacylglycerol-Serine O-Phosphatidyltransferase↗
PubMed1997

Dietary safflower phospholipid reduces liver lipids in laying hens.

This experiment was conducted to determine the effects of dietary safflower phospholipids (crude safflower phospholipid and purified safflower phospholipid) on performance and lipid metabolism of laying hens. Sixty-week-old Single Comb White Leghorn laying hens were divided into four groups of seven birds each, and were given one of four experimental diets containing 5% beef tallow (served as a control, tallow), a mixture of safflower oil and palm oil (SP-oil), crude safflower phospholipid (Saf-PLcrude), or purified safflower phospholipid (Saf-PL) for 7 wk. Egg production ratio and daily egg mass were significantly higher in hens fed Saf-PLcrude diets than in hens of the other diet groups. There were no significant differences in egg weight among groups. Liver cholesterol and triglyceride contents were significantly decreased in all treated groups as compared with the control. The activity of hepatic 3-hydroxy-3 methylglutaryl coenzyme A reductase was the highest in hens fed the Saf-PLcrude diet. Serum esterified cholesterol concentration was decreased by feeding of SP-oil, Saf-PLcrude, or Saf-PL diets. Serum lecithin-cholesterol acyltransferase activity was highest in hens fed the tallow diet. Excreta neutral steroid excretion was significantly increased in the Saf-PLcrude or Saf-PL diet groups, although acidic steroid excretion was not affected by dietary treatments. Total cholesterol, triglyceride, and phospholipid contents in egg yolks were not different for any dietary treatments. The fatty acid compositions of egg yolks from hens fed Saf-PLcrude diets were not different with those fed the SP-oil diet, although eggs of hens fed the Saf-PL diet showed lower total polyunsaturated fatty acids. These results suggest that dietary safflower phospholipids may be a valuable ingredient to layers for reducing liver triglycerides and serum cholesterol without any adverse effects.

Animals↗
PubMed1983

Phospholipid methylation increases during capacitation of golden hamster sperm in vitro.

The present report describes in vitro experiments with golden hamster sperm designed to determine whether there is any relationship between sperm phospholipid methylation and capacitation and/or the acrosome reaction. Washed cauda epididymal hamster sperm were incubated in a capacitation medium containing [methyl-3H] methionine. After 0.5, 1.5, 2.5 and 3.5 h of incubation, sperm were extracted with a chloroform:methanol:2 N HCl mixture to extract total phospholipids. Liquid scintillation counting revealed that the methyl-3H-group was incorporated into phospholipids with maximum incorporation at 3.5 h and an increase of 50% between 2.5 and 3.5 h. Uptake of labeled methionine by sperm reached its plateau by 1.5 h of incubation. Some sperm were capacitated by 3.5 h because that is the time at which the rate of acrosome reactions began to increase and because at least 50% of them were able to undergo the acrosome reaction 10 min after the addition of the fusogen lysophophatidylcholine (LPC) at 3.5 h but not at 2.5 h. Homocysteine thiolactone and 3-deazadenosine, inhibitors of transmethylation, inhibited incorporation of methyl-3H into phospholipids at 3.5 h by approximately 90% and also inhibited LPC-induced acrosome reactions by 60%. Separation of methylated sperm phospholipid by thin-layer chromatography demonstrated the presence of 3H-labeled phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine, and to a lesser extent phosphatidylcholine. In addition, an unidentified lipid was also highly labeled. These results strongly suggest a positive correlation between phospholipid methylation and capacitation and/or the acrosome reaction of hamster sperm in vitro. Possible mechanisms for phospholipid methylation involvement in these events are discussed.

Animals↗
PubMed1996

Inspired oxygen concentration alters the phospholipids and protein content in the bronchoalveolar lavage-accessible space.

OBJECTIVE: To examine the effect of FIO2 on the contents of total protein, total phospholipids, phosphatidylcholine, and phosphatidylglycerol in the bronchoalveolar lavage-accessible space in male and female rats in vivo. DESIGN: Prospective, controlled trial. SETTING: Research laboratory. SUBJECTS: Adult male and female Sprague-Dawley rats. INTERVENTIONS: After animals were anesthetized with an intraperitoneal injection of pentobarbitol (50 mg/kg), a 24-gauge catheter was placed in the femoral artery. Determinations of arterial pH and PaO2 and PaCO2 were performed before tracheostomy, and all animals were then ventilated for 3 mins with an FIO2 of 0.21, followed by a reduction bronchoalveolar lavage. The animals were randomly divided equally by gender and given either an FIO2 of 0.21, 0.50, or 1.00. All subjects were ventilated in the same manner. Sampling bronchoalveolar lavage was performed 80 and 160 mins after institution of the variable FIO2. Bronchoalveolar lavage samples were analyzed for protein and phospholipid content. Arterial blood was obtained for determination of arterial pH and the PaO2 and PaCO2 immediately and 40 mins after each sampling bronchoalveolar lavage. MEASUREMENTS AND MAIN RESULTS: At the times of bronchoalveolar sampling lavage, the PaCO2 increased and the PaO2 decreased, as did the pH. In the 40-min samples obtained between sampling lavages, the arterial pH and PaCO2 and PaO2 returned to pretracheostomy values (animals ventilated with an FIO2 of 0.21) and/or higher pO2 values (animals ventilated with an FIO2 of 0.5 or 1.0). No differences were found between genders in amounts of total protein and phospholipid content in reduction and zero time bronchoalveolar lavage fluid. Males and females ventilated with an FIO2 of 0.21 differed in the amounts of total protein, total phospholipids, phosphatidylcholine, and phosphatidylglycerol found in sampling bronchoalveolar lavage at 80 and 160 mins. Amounts of total protein and total phospholipids also demonstrated gender differences with the administration of an FIO2 of 1.0, but no differences with the administration of and FIO2 of 0.5. In terms of the phospholipids, males had greater amounts in the sampling bronchoalveolar lavage at 80 mins, and females at 160 mins. Administration of an FIO2 of 0.5 or 1.0 resulted in decreased amounts of total phospholipids in both males and females when compared with and FIO2 of 0.21. In males, administration of both FIO2 of 0.5 and 1.0 resulted in decreased amounts of phosphtidylcholine found in the bronchoalveolar lavage-accessible space; in females, amounts of phosphatidylcholine were only decreased when and FIO2 of 1.0 was administered. In males, administration of and FIO2 of 1.0 also resulted in decreased amounts of phosphatidylglycerol. The decreased amount of phosphatidylglycerol occurred in females given an FIO2 of 0.5. Amounts of total protein in males and females given an FIO2 of 0.5 and in females given an FIO2 of 1.0 were found to be increased. CONCLUSIONS: Our findings support the hypothesis that hyperoxia alters surfactant composition. Further investigation is warranted to determine the mechanisms affecting secretion of phosphatidylcholine and phosphatidylglycerol into the bronchoalveolar space and to explore the gender difference in secretion.

Animals↗
PubMedDate not supplied

Pretreatment with chlorpromazine prevents phospholipid degradation and creatine kinase depletion in isoproterenol-induced myocardial damage in rats.

We investigated the effect of chlorpromazine on myocardial phospholipid content and composition and on myocardial creatine kinase (CK) activity in rats with isoproterenol-induced myocardial damage. A single subcutaneous injection of isoproterenol (40 mg/kg) increased heart weight but decreased myocardial phospholipid content and CK activity 24 h after administration. Total phospholipid content was significantly correlated with myocardial CK activity. The decrease of total phospholipid content was accompanied by an increase of the lysophosphatidylcholine (LPC)/phosphatidylcholine (PC) ratio, indicating that conversion from PC to LPC had occurred. Intraperitoneal injection of chlorpromazine (30 mg/kg) prior to isoproterenol injection inhibited the decrease in total phospholipid content and CK activity and the increase in the LPC/PC ratio, but did not affect the increase in heart weight. Pretreatment with propranolol (20 mg/kg) reversed the effects of isoproterenol. On the other hand, dexamethasone (12 mg/kg) and verapamil (50 mg/kg) had no significant effects on the above parameters of myocardial damage. These results suggest that prevention of myocardial phospholipid disruption inhibits enzyme depletion from the myocardium and that chlorpromazine helps to prevent isoproterenol-induced myocardial damage by improving phospholipid metabolism.

Animals↗
PubMed1989

Accumulation of sulphite by Saccharomyces cerevisiae and Zygosaccharomyces bailii as affected by phospholipid fatty-acyl unsaturation and chain length.

Analyses were made of the fatty-acyl composition of phospholipids from each of two strains of Saccharomyces cerevisiae and Zygosaccharomyces bailii grown aerobically. Residues of C16:0, C16:1 and C18:1 predominated in phospholipids from strains of the first yeast, while phospholipids from Z. bailii contained mainly C16:0, C18:1 and C18:2 residues. S. cerevisiae NCYC 431, grown anaerobically in media supplemented with ergosterol and C14:1, C16:1, C18:1, C18:2, C18:3 or C20:1 fatty acids, contained phospholipids enriched with residues of the exogenously provided acid, to a greater extent with shorter chain than longer chain acids. A plot of the permeability coefficient for sulphite, derived from Woolf-Eadie plots, against the degree of unsaturation in phospholipids (expressed as delta mol-1 value) showed that the coefficient was greater the lower the degree of unsaturation in the phospholipids. A plot of the permeability coefficient against values for the mean fatty-acyl chain length divided by the delta mol-1 value, which is an approximation of the cross-section surface area of a phospholipid molecule, showed that the permeability coefficient tended to increase the greater the surface-area value.

Cell Membrane Permeability↗
PubMed1982

Phospholipid interconversions in Mycoplasma capricolum.

Mycoplasma capricolum cells increase their phospholipid content by incorporating exogenous phospholipids from the growth medium. Growing the cells in media with increasing serum concentrations resulted in a massive incorporation of phosphatidylcholine and sphingomyelin (up to about 50% of total phospholipids) into the cell membrane. The incorporation of the exogenous phospholipids had essentially no effect on the rate of cell growth and did not decrease the overall phospholipid biosynthesis of the cells. Thus, the ratio of phospholipid to protein in membranes from cells grown with 5% horse serum was 0.5 (mumol/mg) compared to 0.3 (mumol/mg) in cells grown without serum, and the relative content of charged polar lipids was apparently decreased. The consequence of the incorporation of exogenous phosphatidylcholine was an alteration in the relative amount of the major end-products of the de novo phospholipid biosynthesis; a marked increase in the ratio of diphosphatidylglycerol to phosphatidylglycerol was observed. The possibility that the increase in the ratio of diphosphatidylglycerol to phosphatidylglycerol is part of a control mechanism to maintain a mixture of bilayer and non-bilayer lipids is discussed.

Animals↗
PubMed1983

Interaction of alpha-1,2-mannosidase with anionic phospholipids.

A partially purified microsomal alpha-1,2-mannosidase from rabbit liver binds to vesicles that contain anionic phospholipids. The affinity of the enzyme for the phospholipid vesicles is dependent upon the negative charge density of the vesicles rather than the concentration of the anionic phospholipid or the phospholipid specificity. A phosphatidylinositol/phosphatidylcholine ratio of 1:3 is sufficient to bind all of the enzyme. The association of enzyme with anionic phospholipids involves ionic interactions and can be readily reversed by high ionic strength or changes in pH. The alpha-mannosidase is inhibited when bound to the anionic phospholipid vesicles, but the enzyme can be reactivated when released by NaCl or CaCl2. When bound to anionic phospholipid vesicles, the enzyme was also found to undergo a slow inactivation process that was time and temperature dependent and could not be reversed by the addition of CaCl2.

Animals↗
PubMed1986

Characterization of the phosphorylation of rat mammary ATP-citrate lyase and acetyl-CoA carboxylase by Ca2+ and calmodulin-dependent multiprotein kinase and Ca2+ and phospholipid-dependent protein kinase.

ATP-citrate lyase and acetyl-CoA carboxylase purified from lactating rat mammary gland are phosphorylated stoichiometrically by the calmodulin-dependent multiprotein kinase from rabbit skeletal muscle. The reactions are completely dependent on the presence of both Ca2+ and calmodulin. ATP-citrate lyase and acetyl-CoA carboxylase are also phosphorylated stoichiometrically by the Ca2+- and phospholipid-dependent protein kinase (protein kinase C) purified from bovine brain. Phosphorylation of these substrates is stimulated 6-fold and 40-fold respectively by Ca2+ and phosphatidylserine. The calmodulin-dependent and phospholipid-dependent protein kinases phosphorylate the same serine residue on ATP-citrate lyase that is phosphorylated by cyclic-AMP-dependent protein kinase. The sequence of the tryptic peptide containing this site on the mammary enzyme is identical with the sequence of the peptide containing the site on ATP-citrate lyase that is phosphorylated in isolated hepatocytes in response to insulin and/or glucagon. The calmodulin-dependent, phospholipid-dependent and cyclic-AMP-dependent protein kinases phosphorylate distinct sites on acetyl-CoA carboxylase. However, one of the three phosphorylated tryptic peptides derived from enzyme treated with the phospholipid-dependent kinase is identical with the major phosphopeptide (T1) derived from enzyme treated with cyclic-AMP-dependent protein kinase. Phosphorylation of acetyl-CoA carboxylase by the phospholipid-dependent protein kinase inactivates acetyl-CoA carboxylase in a similar manner to cyclic-AMP-dependent protein kinase. With either protein kinase slightly greater phosphorylation and inactivation is seen after pretreatment of acetyl-CoA carboxylase with protein phosphatase-2A, but the effects of the protein phosphatase treatment are not completely reversed. Inactivation by the phospholipid-dependent protein kinase is Ca2+- and phospholipid-dependent, is reversed by protein phosphatase-2A, and correlates with the degree of phosphorylation. The relevance of these findings to insulin- and growth-factor-promoted phosphorylation of ATP-citrate lyase and acetyl-CoA carboxylase in intact cells is discussed.

ATP Citrate (pro-S)-Lyase↗
PubMed1986

Activation of phosphorylase kinase through autophosphorylation by membrane component phospholipids.

Phosphatidic acid (PtdOH) has been shown not only to stimulate autophosphorylation and autoactivation of phosphorylase kinase of rabbit skeletal muscle but also to decrease the apparent Ka for Ca2+ on autophosphorylation sharply [Negami et al. (1985) Biochem. Biophys. Res. Commun. 131, 712-719]. In this study we investigated the interaction between PtdOH and other phospholipids on autophosphorylation and autoactivation of this enzyme. Acidic phospholipids, such as phosphatidylserine (PtdSer), phosphatidylinositol (PtdIns) and PtdOH, stimulated this reaction about 2-4-fold, and the approximate Ka values of this reaction were 10 micrograms/ml, 6.3 micrograms/ml and 30 micrograms/ml respectively. The molar ratio of PtdIns and PtdSer with maximal effect on autophosphorylation was about 1:1. Under these conditions PtdOH stimulated the initial velocity of autophosphorylation about 5.2-fold. When fully autophosphorylated, about 12-13 mol phosphate per tetramer (alpha beta gamma delta) were incorporated in the presence of mixed acidic phospholipids (PtdOH:PtdIns:PtdSer = 2:1:1), which was about twice as much as values observed without effectors. In the presence of mixed acidic phospholipids there was a concomitant enhancement of kinase activity, about 30-40-fold at pH 6.8 and 2.5-3-fold at pH 8.2. Mixed acidic phospholipids sharply decreased an apparent Ka for Ca2+ from 4 X 10(-5) M to 8 X 10(-7) M. With mixed acidic phospholipids as effectors this autophosphorylation occurred through an intramolecular mechanism. Based on these results, autophosphorylation and autoactivation of phosphorylase kinase in the presence of acidic phospholipids may account for an important regulatory mechanism of glycogenolysis in muscle contraction.

Adenosine Triphosphate↗
PubMed1994

A study on the efficacy of a phospholipid solution in dogs with aspirin-induced thrombocytopathy.

The aim of the present study was to test the haemostyptic properties of a phospholipid complex with platelet factor-3 (PF-3) activity in platelet-dependent haemostatic disorders. The substance was investigated in an animal model comprising six investigational groups (five dogs each). A thrombocytopathy was created in the dogs belonging to groups 1-5 by intravenous administration of 20 mg/kg body weight (BW) acetylsalicylic acid (ASA). Two hours later a human albumin solution (5%) (control group) or a phospholipid complex with PF-3 activity was injected or infused intravenously in different dosages. In dogs pre-treated with ASA, injection of 2 ml/kg BW of the phospholipid complex shortened capillary bleeding time, which was prolonged as a consequence of ASA-treatment. This effect lasted for 4 h at least. The capability of the platelets to aggregate increased 5 min after intravenous injection of the phospholipid without differences in the respective groups. At the same time platelet counts dropped to approximately 50%, but increased again distinctly after 30 min. When the phospholipid complex was administered to clinically healthy dogs who had not been treated with ASA, this resulted in prolongation of the capillary bleeding time as well as a significant platelet drop in the peripheral blood. Although these were only short-term effects after administration of the phospholipid complex, a disadvantageous effect cannot be excluded in patients suffering from haemorrhagic diathesis. For this reason, a phospholipid complex with PF-3 activity cannot be recommended as a therapeutic agent for platelet-dependent coagulation disorders in the dog.

Animals↗
PubMed1985

Effects of short- and long-term protriptyline treatment on phospholipid metabolism in rat brain.

Wistar rats were injected intraperitoneally with 10 mg/kg of protriptyline according to one of the following schedules: a single dose or daily for 4 days (short-term), or daily for 2 or 13 weeks (long-term). Total lipid, total phospholipid, and individual phospholipid contents in the brain were determined. Further, the incorporation of 32P into individual phospholipids in vivo and the fatty acid composition of phosphatidylethanolamine in the brains of rats treated with protriptyline for 13 weeks were studied. Three alternative phases of changes of total and individual phospholipid contents in the brain during 13 weeks of experimentation were distinguished. An increase of phospholipid contents after 4 days, a decrease after 2 weeks, and a further increase after 13 weeks of protriptyline administration were found. However, phosphatidylinositol and phosphatidic acid levels after 13 weeks of protriptyline administration were diminished. The decrease of specific radioactivity of phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine and the increase of phosphatidylinositol, phosphatidic acid, and sphingomyelin in rats treated with the drug for a longer period of time were noted. No greater differences in fatty acid composition of phosphatidylethanolamine in the brains of the same group of rats were observed as compared to control. These results indicate that during long-term treatment with protriptyline the contents of lipids and phospholipids in rat brain are altered. The modification of the biological function of phospholipids in brain cell membranes is suggested.

Animals↗
PubMed1985

Retrograde axonal transport of phospholipid in rat sciatic nerve.

Retrograde axonal transport of phospholipid was studied in rat sciatic motoneuron axons by placing collection crushes on the nerve at intervals after injection of [methyl-3H]choline into the lumbosacral spinal cord, and allowing labelled material undergoing anterograde or retrograde movement to accumulate adjacent to the collection crushes. Control experiments showed that the accumulations of label were not a result of local uptake of circulating precursor. The majority of the 3H label was associated with phosphatidylcholine. Accumulation of label at the distal collection crush, representing retrograde transport, was observed subsequent to the anterograde transport of phospholipid. In comparison with a previous study on retrograde transport of protein, the following points were noted: (1) onset of retrograde transport occurred at approximately the same time after precursor injection (10-20 h) for both protein and phospholipid; (2) retrograde transport of lipids was more prolonged: maximum retrograde transport occurred later for phospholipid (approximately 30 h) than for protein (15-20 h), and declined to half-maximum between 49 and 99 h, compared to a corresponding value of 24-28 h for protein; (3) the proportion of total anterograde-transported activity subsequently undergoing retrograde transport was less in the case of phospholipid, at least over the time interval studied (up to 99 h after precursor injection). The similar times of onset of retrograde transport of phospholipid and protein support the concept of retrograde transport as a recycling mechanism returning to the cell body membrane fragments that were earlier transported into the axon. Coordinated retrograde transport of labelled protein and phospholipid components of the recycled membranes would be predicted.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗