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PubMed1985

Effect of 1,25-dihydroxyvitamin D3 on phospholipid metabolism in a clonal osteoblast-like rat osteogenic sarcoma cell line.

The effect of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on phospholipid metabolism was examined in clonal rat osteogenic sarcoma cells, UMR 106, of osteoblastic phenotype. Treatment of UMR 106 cells with 10(-8)M 1,25-(OH)2D3 for 48 h caused an increase in [14C]serine incorporation into phosphatidylserine (PS) and a decrease in [3H]ethanolamine, [3H]linositol, and [14C]choline incorporation into phosphatidylethanolamine (PE), phosphatidylinositol, and phosphatidylcholine, respectively; the decrease in [3H]ethanolamine incorporation into PE was the largest. The total contents of phospholipids were similarly affected by 10(-8)M 1,25-(OH)2D3 treatment, suggesting that the effects of 1,25-(OH)2D3 are due largely to alterations in the synthesis of these phospholipids. The effects of 1,25-(OH)2D3 were evident at 10(-10) M 1,25-(OH)2D3, and 10(-8)M 1,25-(OH)2D3 caused a maximal stimulation of [14C]PS synthesis (167% of control) and a maximal reduction in the [3H]PE synthesis (41% of control). The [14C]PS/[3H]PE ratio increased gradually and reached a maximum after 70 h of treatment with 10(-8)M 1,25-(OH)2D3. When the cells were cultured in calcium-free medium containing 0.5 mM EGTA or when 5 microM cycloheximide was added to the medium, the effect of 1,25-(OH)2D3 on phospholipid metabolism was almost completely inhibited. Neither 25-hydroxyvitamin D3 nor 24,25-dihydroxyvitamin D3 caused significant changes in phospholipid metabolism. These results suggest that 1,25-(OH)2D3 alters phospholipid metabolism by enhancing PS synthesis through a calcium-dependent stimulation of the base exchange reaction of serine with other phospholipids and that the effect of 1,25-(OH)2D3 requires the synthesis of new proteins. Because PS is thought to be important for apatite formation and bone mineralization by binding calcium and phosphate to form calcium-PS-phosphate complexes, the present data suggest that 1,25-(OH)2D3 may stimulate bone mineralization by a direct effect on osteoblasts, stimulating PS synthesis.

Animals↗
PubMed1986

Phospholipid binding and biophysical activity of pulmonary surfactant-associated protein (SAP)-35 and its non-collagenous COOH-terminal domains.

Surfactant-associated protein of Mr = 35,000, SAP-35, is the major glycoprotein present in mammalian pulmonary surfactants. In this study, canine SAP-35 and several of its COOH-terminal peptides were purified and characterized by amino acid composition and NH2-terminal sequencing analysis. These proteins were then studied in terms of their specific lipid-binding characteristics and surface activity when combined with a synthetic phospholipid mixture, SM, chosen as an approximation of lung surfactant phospholipids. Purified, delipidated SAP-35 bound SM strongly. In contrast, SAP-21 (a non-collagenous fragment generated by collagenase digestion) bound phospholipid weakly; SAP-18 (an acidic COOH-terminal fragment comprising residues Gly-118 to Phe-231) did not bind phospholipid, demonstrating the importance of hydrophobic amino acid residues Gly-81 to Val-117 and the NH2-terminal collagenous domain in interaction of the SAP-35 with phospholipids. In surface activity experiments, purified SAP-35 enhanced the adsorption of SM phospholipids in terms of both rate and overall surface tension lowering. However, the adsorption facility of the SM-SAP-35 mixture did not approach that of either whole surfactant or the surfactant extract preparations, calf lung surfactant extract or surfactant-TA, used in exogenous surfactant replacement therapy for the neonatal respiratory distress syndrome. In addition, the dynamic surface activity of the SM-SAP-35 mixture was well below that of natural surfactant or surfactant extracts. This was also true of mixtures of SM phospholipids combined with the SAP-18 and SAP-21 fragments of SAP-35.

Amino Acid Sequence↗
PubMed1987

Reconstitution of rabbit thrombomodulin into phospholipid vesicles.

The influence of phospholipid on thrombin-thrombomodulin-catalyzed activation of protein C has been studied by incorporating thrombomodulin into vesicles by dialysis from octyl glucoside-phospholipid mixtures. Thrombomodulin was incorporated into vesicles ranging from neutral (100% phosphatidylcholine) to highly charged (30% phosphatidylserine and 70% phosphatidylcholine). Thrombomodulin is randomly oriented in vesicles of different phospholipid composition. Incorporation of thrombomodulin into phosphatidylcholine, with or without phosphatidylserine, alters the Ca2+ concentration dependence of protein C activation. Soluble thrombomodulin showed a half-maximal rate of activation at 580 microM Ca2+, whereas half-maximal rates of activation of liposome-reconstituted thrombomodulin were obtained between 500 microM Ca2+ and 2 mM Ca2+, depending on the composition (protein:phospholipid) of the liposomes. The Ca2+ dependence of protein C activation fits a simple hyperbola for the soluble activator, while the Ca2+ dependence of the membrane-associated complex is distinctly sigmoidal with a Hill coefficient greater than 2.4. In contrast, the Ca2+ dependence of gamma-carboxyglutamic acid (Gla) domainless protein C activation is unchanged by membrane reconstitution (1/2 max = 53 +/- 10 microM) and fits a simple rectangular hyperbola. Incorporation of thrombomodulin into pure phosphatidylcholine vesicles reduces the Km for protein C from 7.6 +/- 2 to 0.7 +/- 0.2 microM. Increasing phosphatidylserine to 20% decreased the Km for protein C further to 0.1 +/- 0.02 microM. Membrane incorporation has no influence on the activation of protein C from which the Gla residues are removed proteolytically (Km = 6.4 +/- 0.5 microM). The Km for protein C observed on endothelial cells is more similar to the Km observed when thrombomodulin (TM) is incorporated into pure phosphatidylcholine vesicles than into negatively charged vesicles, suggesting that the protein C-binding site on endothelial cells does not involve negatively charged phospholipids. In support of this concept, we observed that prothrombin and fragment 1, which bind to negatively charged phospholipids, do not inhibit protein C activation on endothelial cells or TM incorporated into phosphatidylcholine vesicles, but do inhibit when TM is incorporated into phosphatidylcholine:phosphatidylserine vesicles. These studies suggest that neutral phospholipids lead to exposure of a site, probably on thrombomodulin, capable of recognizing the Gla domain of protein C.

Animals↗
PubMed1986

Interaction of the cytoskeletal component vinculin with bilayer structures analyzed with a photoactivatable phospholipid.

The cytoskeletal component vinculin has been proposed to act as an actin-plasma membrane linker. In order to demonstrate a possible direct interaction of vinculin with bilayers, photolabeling with a phospholipid generating a highly reactive carbene was used. This phosphatidylcholine analogue (1-palmitoyl-2-[10-[4-[(trifluoromethyl)diazirinyl]phenyl]-[3H] 9-oxaundecanoyl]-sn-glycero-3-phosphocholine), with the photoactivatable diazirine group on its apolar portion, has been shown to label selectively membrane-embedded domains of membrane proteins. Vinculin is significantly labeled upon incubation and photolysis with liposomes containing trace amounts of this photoactivatable phospholipid, but only when the liposomes also contain acidic phospholipids. Labeling of vinculin is markedly increased (5-17-fold) by all acidic phospholipids tested so far (30%, w/w), compared to labeling in neutral phospholipids. Labeling is high at low ionic strength, but significant vinculin labeling can still be observed at physiological salt concentrations and acidic phospholipid content of the membrane. Our results provide evidence that vinculin inserts into the hydrophobic part of the bilayer by interacting with acidic phospholipids. A similar interaction may be of importance in vivo.

Actins↗
PubMed1988

Comparison of the effects of carbisocaine and other local anesthetics on 32P incorporation into individual and total phospholipids in synaptosomes.

The aim of the paper was to study the effect of carbisocaine, a new local anesthetic with high liposolubility on incorporation of 32P into individual and total phospholipids and to compare its effect with that of other local anesthetics (procaine, lidocaine, cinchocaine, heptacaine). Carbisocaine decreased 32P incorporation into neutral phospholipids and increased the incorporation into acid phospholipids, presumably by inhibiting phosphatidate phosphohydrolase, similarly as reported for other anesthetics (Brindley and Bowley 1975). The increased incorporation of 32P into phosphatidylserine induced by carbisocaine suggests that this phospholipid is also synthetised from phosphatidic acid. At low concentrations, the local anesthetics studies were found to increase 32P incorporation into total phospholipids, whereas at high concentrations they reduced 32P incorporation. This biphasic effect is in agreement with the incorporation of 14C from glucose into lipids (Lassánová et al. 1984) and with the effect of cinchocaine on glycerol incorporation into phospholipids (Allan and Michell 1975), suggesting that local anesthetics affect de novo synthesis of phosphatidic acid. Carbisocaine increased 32P incorporation into phospholipids, in concentrations lower by several orders of magnitude as compared to the other local anesthetics studied. A rough correlation was observed between the concentrations at which the local anesthetics showed stimulatory effect on 32P incorporation, and the average effective concentrations of the respective anesthetics. No such correlation could be found for carbisocaine.

Anesthetics, Local↗
PubMed1987

Cytochemical and autoradiographic studies of the localization and turnover of chromatin and nucleolar associated phospholipids in plant and animal tissues.

The localization of chromatin-associated phospholipids has been demonstrated on chromosomes and on chromatin of interphase nuclei by cytochemical methods either in plant and in animal tissues. Three methods of fixation are suggested which can be combined which two cytochemical methods for phospholipids detection. An additional method is represented by autoradiographic technique after incorporation of a radioactive precursor such as [3H] ethanolamine. This method has been used with good results in nuclei of lateral root apices of Vicia faba on 1 micron thick section, thus avoiding any possible contamination by nuclear membrane. In these nuclei the phospholipids appear associated with the chromatin and more intensely with the nucleolar regions. The positivity of the cytochemical reaction disappears after extraction of fixed tissue with acidified methanol chloroform and after treatment of unfixed sections with phospholipase D. The use of phospholipid precursor has allowed the study of chromatin-phospholipids synthesis in root apices of Vicia faba with respect to timings of the cell cycle. The results show that there is a strong case for a pattern of chromatin phospholipid synthesis which operates during S phase. Concerning the role of phospholipids it is suggested that they may be linked to acidic protein and may have a structural function, particularly on the nucleoli.

Animals↗
PubMed1986

Influence of phospholipids on the formation and stability of vimentin-type intermediate filaments.

The interaction of vesicles produced from individual phospholipids and mixtures thereof with preformed vimentin filaments as well as the influence of these vesicles on filament assembly were investigated employing negative stain electron microscopy and sucrose density gradient equilibrium centrifugation. Liposomes with a phospholipid composition characteristic of Ehrlich ascites tumor cells were able to bind efficiently to vimentin filaments without significantly affecting their morphology at higher concentrations. However, in sucrose density gradient centrifugation partial disintegration of the filaments was observed. In addition, larger quantities of phospholipid mixture totally blocked intermediate filament (IF) formation. Using vesicles of individual phospholipids, these effects could be shown to be due to the presence of negatively charged lipid species in the phospholipid mixture. While these were highly active in preventing filament assembly and in dissociating preformed filaments, electrically uncharged phospholipids were virtually inactive. The highest efficiency was shown by phosphatidylinositol-4,5-diphosphate. These results demonstrate that a negative surface charge of liposomes is an essential prerequisite for their successful and tight association with vimentin filaments. However, the high susceptibility of these filaments to photoaffinity labeling with the membrane-penetrating reagent 1-azidopyrene in the presence of phospholipid vesicles, points to additional interactions between hydrophobic regions of both reactants. Finally, the data also suggest a direct relationship between IFs and the lipid bilayer as the active principle underlying the association of IFs with natural membranes as observed by electron and immunofluorescence microscopy.

Animals↗
PubMed1985

22-Carbon polyenoic acids. Incorporation into platelet phospholipids and the synthesis of these acids from 20-carbon polyenoic acid precursors by intact platelets.

The types of unsaturated fatty acids found in platelet phospholipids must be regulated by a series of controls which include specificity for activation and acylation as well as modification of circulating fatty acids by platelets prior to incubation into phospholipids. In this study we show that washed human platelets not only incorporate [1-14C]6,9,12-18:3, [1-14C]6,9,12,15-18:4, [1-14C]5,8,11-20:3, [1-14C]5,8,11,14-20:4, and [1-14C]5,8,11,14,17-20:5 into their phospholipids but also chain elongate each of these acids with subsequent acylation of the chain elongated products into phospholipids. Platelets incubated alone with 1-14C-labeled 5,8,11-20:3, 5,8,11,14-20:4, 5,8,11,14,17-20:5, 7,10,13,16,19-22:5, or 4,7,10,13,16,19-22:6 incorporated each of these acids into individual phosphoglycerides with phosphatidylinositol having the highest specific activity followed by phosphatidylcholine with phosphatidylserine approximately equal to phosphatidylethanolamine. The incorporation specificity of 4,7,10,13,16,19-22:6 was atypical since it was a relatively poor substrate for acylation into all phospholipids except phosphatidylethanolamine. The 20-carbon acids were better substrates for incorporation into phospholipids than were the 22-carbon compounds. Simultaneous incubation of 10 microM [1-14C]5,8,11,14-20:4 with increasing levels (5 to 15 microM) of each of the above five other 1-14C-labeled acids showed a concentration-dependent increase in the amount of the second fatty acid incorporated into platelet phospholipids. Dietary fat modification thus has the potential of increasing the plasma pool of 22-carbon acids for incorporation into platelets. In addition the activation of 20-carbon eicosanoid precursors by the high affinity platelet activating enzyme (Wilson, D. B., Prescott, S. M. and Majerus, P. W. (1982) J. Biol. Chem. 257, 3510-3515) will yield an acyl-CoA for both acylation and chain elongation followed by subsequent incorporation of 22-carbon acids into phosphoglycerides.

Arachidonic Acid↗
PubMed1985

The relationship between valinomycin-induced alterations in membrane phospholipid fatty acid turnover, membrane potential, and cell volume in the human erythrocyte.

The relationship between alterations in transmembrane potential, cell volume, and phospholipid fatty acid turnover has been examined in human erythrocytes by treating the cells with the monovalent cation ionophore valinomycin. Valinomycin increases the cellular uptake of tetra[3H]phenylphosphonium ion by erythrocytes, indicating membrane hyperpolarization, and causes net loss of potassium chloride and water from the cells leading to a decrease in cell volume. Treatment of erythrocytes with valinomycin also enhances incorporation of [9, 10-(3)H]oleic acid into phospholipids, primarily diacylphosphatidylethanolamine. After replacing intracellular chloride with sulfate and treating cells with the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonate, exposure to valinomycin results in uptake of tetra[3H]phenylphosphonium ion and stimulation of [9, 10-(3)H]oleic acid incorporation, but, because anion efflux is prevented, no decrease in cell volume occurs. When tetra[3H]phenylphosphonium ion uptake is also prevented by suspending these cells in 125 mM KCl to dissipate the transmembrane potassium gradient, valinomycin still enhances [9, 10-(3)H] oleic acid incorporation into phospholipid. These results suggest that the presence of valinomycin in the membrane directly alters phospholipid fatty acid turnover and that some of the effects of this ionophore on cellular function previously attributed to alterations in transmembrane potential or cellular potassium content may instead be due to altered phospholipid turnover. Since it is possible that valinomycin may directly perturb phospholipid fatty acid turnover in other cells, the possibility that valinomycin-induced alterations in cellular function are due to altered phospholipid turnover rather than membrane hyperpolarization or altered potassium content should be considered in the interpretation of studies employing this ionophore.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMedDate not supplied

The role of phospholipids in platelet function.

Platelet phospholipids undergo significant alterations during aggregation induced by thrombin or other agents. There is an early increase in phosphatidic acid, with a decrease in phosphatidyl inositol. De novo synthesis of most phospholipids from 14C-glycerol is decreased. Thrombin stimulates 32P-phosphate incorporation into di- and triphosphoinositides, suggesting increased phosphorylation of phosphatidyl inositol during aggregation. Arachidonic acid for prostaglandin synthesis is released from platelet phospholipids. Thrombin induced aggregation results in release of arachidonic acid primarily from phosphatidyl choline and phosphatidyl inositol. The availability of free arachidonic acid may be regulated by platelet phospholipase A2 activity. The latter activity is stimulated by thrombin, requires calcium ions, and is inhibited by agents which elevate cyclic adenosine monophosphate. Phospholipids are probably an essential component of the platelet surface lipoprotein procoagulant activity known as platelet factor 3. There is evidence that calcium ions may mediate binding between gamma carboxyglutamic acid residues on the amino terminal portion of prothrombin and negatively charged phosphate groups on phospholipid micelles. Binding of prothrombin to phospholipid on the platelet surface may orient the former such as to facilitate the prothrombinase activity of Factor Xa. Platelet phospholipids and platelet factor 3 activity are decreased in some congenital and myeloproliferative disorders. Increases in these factors may be associated with thrombotic and arterial occlusive disorders.

Animals↗
PubMed1984

Effects of starvation on phospholipid metabolism of pancreatic islets.

It was the aim of the present study to examine the extent to which starvation-induced impairment of glucose-stimulated insulin secretion is linked to changes of islet phospholipid metabolism. For this purpose both islets isolated from mice starved for 60 hr and islets maintained in culture for 1 week in a low (3.3 mM) glucose medium were studied together with relevant control islets. When challenged with a high glucose concentration the insulin response of both groups of islets was totally blunted. The effect of food restriction on 14C-glucose incorporation into different phospholipid classes was less prominent. On a percentage basis phosphatidylserine biosynthesis of islets isolated from starved mice was most affected, whereas the biosynthesis of phosphatidylcholine was only marginally impaired. Culture of islets for 1 week at the low glucose concentration affected the phospholipid biosynthesis even less and there was only a small decrease of 14C-glucose incorporation into phosphatidylcholine. In general, cultured islets synthesized more phospholipids than the freshly isolated ones. No dose-response relationship was found between various degrees of glucose-stimulated insulin secretion and 14C-glucose incorporation into different phospholipid classes of islets isolated from fed mice. The present data thus provided no evidence that an impairment of the islet phospholipid turnover contributes to the starvation-induced impairment of insulin secretion. There was also no close correlation between phospholipid biosynthesis in terms of 14C-glucose incorporation and glucose-stimulated insulin secretion.

Animals↗
PubMed1984

[Cytology and phospholipid content of the bronchoalveolar lavage liquid in diffuse interstitial pneumopathies and in sarcoidosis. Apropos of 96 lavages].

The phospholipid content of bronchoalveolar lavage (LBA) has been little studied till now. This work involved 96 LBA on 7 cases of allergic alveolitis, 11 cases of diffuse interstitial fibrosis (FID) and 42 of sarcoidosis. The liquid collected was submitted to a cellular study (cellularity, total and differential) and biochemical (total proteins, total phospholipids separated into their different fractions by chromatography which enabled the identification of phosphatidyl-choline, phosphatidyl-serine and phosphatidyl-inositol in particular). The cytological results were close to the classical data, a rise in the lymphocyte level in allergic alveolitis and active sarcoid, a rise in polymorphonuclear cells in FID. Biochemical analysis showed a fall in total phospholipids for the whole group, the drop being the greatest in the FID. Phosphatidyl-choline, the principle phospholipid of surfactant in normals, was reduced in all three groups of patient when expressed as a percentage of total phospholipids. This fall was greatest with an allergic alveolitis and occurred on a pro rata basis with a rise in phosphatidyl-serine and inositol. The protein phospholipid ratio (PL/P) expressed in micrograms of phospholipid and milligrams of protein fell in a significant fashion in all the pathological groups. This fall was significantly larger in allergic alveolitis than FID and active sarcoid. The PL/P ratio seems to be a good marker of active sarcoid, correlating with the activity of the disease inversely with the lymphocyte level, and was unchanged by steroids unlike the lymphocyte count. A rise in this ratio correlates with an improvement in the radiological and clinical state.

Adolescent↗
PubMed1984

[Phospholipids of the subcellular fractions of brain and liver tissues in rats in total oxygen starvation of the body].

The rate of phospholipid turnover in brain subcellular fractions differ from that in the liver tissue. Hypoxia of medium severity (pressure chamber 240 mm Hg) influences neither the content nor the turnover rate of phospholipids in liver subcellular fractions. Meanwhile in brain subcellular fractions, it results in a decreased phospholipid turnover rate. Severe hypoxia (less than 200 mm Hg) leads only to the suppression of the phospholipid turnover rate in the liver, whereas in the brain, it results in the decline of the phospholipid turnover rate as well as in the reduction of phospholipid content. Thus, the well-known concept of the higher brain sensitivity to oxygen deficiency as compared to the liver is exemplified by phospholipid turnover in subcellular fractions.

Animals↗
PubMed1983

Restoration by phospholipids of dolichol pyrophosphate N-acetylglucosamine synthesis in delipidated rat lung microsomes.

The effects of phospholipids on the reaction catalyzed by UDP-GlcNAc:dolichol phosphate GlcNAc-1-phosphate transferase have been studied with delipidated rat lung microsomes. Deoxycholate-solubilized enzyme was depleted of measurable phospholipid by either gel filtration on Sephadex G-100 or affinity chromatography on pentyl-agarose. The latter procedure also removed nucleotide and sugar nucleotide hydrolases. Delipidated protein fractions were devoid of GlcNAc-1-phosphate transferase activity unless supplemented with phospholipids. Maximal recovery of enzyme activity was obtained with an approximate 1:1 weight ratio of phosphatidylglycerol:phosphatidylcholine, with the observed rate being synergistic as compared to rates observed for each individual phospholipid. Variable recoveries of enzyme activity were obtained with mixtures containing other acidic phospholipids and phosphatidylcholine. Enzyme activity in the fraction eluted from pentyl-agarose could be recovered, after removal of Triton X-100, with sedimented phospholipid vesicles. Significant stabilization of enzyme activity associated with the phospholipid vesicles was obtained by the inclusion of dolichol phosphate.

Animals↗
PubMedDate not supplied

Maternal diabetes mellitus and changes in neonatal rat lung and alveolar surfactant phospholipids.

We investigated the extent of the influence of maternal diabetes on the phospholipid composition and exchange activity of the neonatal lung alveolar surfactant. The results show that each phospholipid fraction (as well as the total phospholipid content) of the surfactant of neonates with diabetic mothers are decreased to about 30% of the control values. Phosphatidylcholine and phosphatidylglycerol, which are the most important surface active phospholipid fractions, were decreased to 27% and 34% respectively. In lung tissue of the neonates with diabetic mothers, all phospholipid fractions were increased. We found that the phosphatidylcholine-exchange activity in the alveolar surfactant does not exist in neonates with diabetic mothers. This inhibited phospholipid-exchange activity may be the reason for the decrease in the surfactant phospholipids and their increase in the lungs of neonates with diabetic mothers. The cholesterol content in the surfactant of such neonates decreased by almost half in comparison with the controls, while in lung tissue it remained unchanged. Producing an experimental respiratory distress syndrome could permit to study more deeply the causes which provoke it and the accompanying metabolic changes.

Animals↗
PubMed1984

Mechanism for adaptive modification during cold acclimation of phospholipid acyl chain composition in Tetrahymena. I. Principal involvement of deacylation-reacylation.

The purpose of the present studies with in vivo isotope labeling was to explore the mechanism by which the fatty acyl composition of membrane phospholipids was altered quickly after a downward temperature-shift in Tetrahymena pyriformis. 1. When 39 degrees C-grown Tetrahymena cells were shifted to 15 degrees C, unsaturated fatty acids, especially gamma-linolenic acid, were increased, with compensating decrease of palmitic acid in phospholipids. 2. However, in the [32P]Pi-prelabeled cells, the specific radioactivities of major membrane phospholipids, phosphatidylethanolamine, phosphatidylcholine and 2-aminoethylphosphonolipid, were not changed within 10 h after shift-down. Furthermore, in the [14C]palmitic acid-prelabeled cells, the specific radioactivities toward phospholipids also did not change after temperature-shift. 3. After the shift, the rate of incorporation of [14C]acetate into fatty acids was reduced to less than one-tenth and the principal fatty acid newly synthesized was linoleic acid, and palmitic and gamma-linolenic acids were also formed to almost same degree. 4. In contrast, when cells prelabeled with both [32P]Pi and [14C]palmitic acid were shifted to 15 degrees C and then linoleic and gamma-linolenic acids, which are known to increase during cold acclimation, were added to the medium, the 14C/32P ratios of major phospholipids were progressively decreased until 5 h after the shift. These results suggest the mechanism for the alteration of phospholipid fatty acyl composition at lowered growth temperature by which preexisting fatty acids of membrane phospholipids would be deacylated and then, after modification to adequate unsaturated fatty acids by desaturation and/or elongation, be reacylated again into lysophospholipids.

Acclimatization↗
PubMed1983

Biosynthesis of phosphatidylcholine from serum phospholipids in Chinese hamster ovary cells deprived of choline.

We report that Chinese hamster ovary cells assemble membrane phospholipids from choline-linked lipid present in fetal calf serum. This was examined by testing the ability of various serum preparations to satisfy the choline requirement of the cells. Chinese hamster ovary cells divided in growth medium containing lipoprotein-deficient serum and approximately 8 microM lysolecithin. Identical results were obtained in growth medium supplemented with solvent-extracted (delipidated) serum reconstituted with purified egg lysolecithin and the uptake of lipid was inhibited by the addition of bovine serum albumin. Analysis of the phospholipid composition of cells incubated with 32Pi and egg lysolecithin in place of choline revealed that approximately 30% of the phosphorus moieties of the cellular phospholipids were derived from the added lipid, while in the presence of choline less than 10% arose in this fashion. Choline starvation enhanced the formation of lecithin from [32P]lysolecithin without affecting phospholipid turnover and labeled lecithin was converted to other phospholipids, especially sphingomyelin and phosphatidylserine. Unlike endogenous serum lysolecithin, lipoproteins obtained from human and fetal calf sera failed to satisfy the choline requirement of Chinese hamster ovary cells, even though 95% of the lipoprotein phospholipid was phosphatidylcholine and sphingomyelin. Together, these results demonstrate that animal cells can derive all of the choline required for membrane phospholipid synthesis from serum lysolecithin and that its conversion to lecithin within the cell is regulated by the availability of choline. In contrast, serum lipoproteins do not normally serve as a major source of choline moieties.

Animals↗
PubMed1983

Effect of undernutrition and vitamin A deficiency on the phospholipid composition of rat tissues at 21 days of age. -- I. Liver, spleen and kidney.

Studies were made of the effects of undernutrition and Vitamin A deficiency on the phospholipid composition of liver, spleen and kidney in rat. Undernutrition and vitamin A deficiency cause a significant deficit in body and tissue weights. But the deficit seems to be more in undernourished rats. Significant deficits were found in the concentration of total phospholipid in livers from both the experimental groups. This decrease in total phospholipid was reflected in most of the phospholipids with a significant decrease in phosphatidyl serine and inositol fraction of undernourished rats. The concentration of total phospholipid in the spleen was increased in undernourished rats. This increase was mainly confined to the sphingomyelin fraction. However the phosphatidyl choline was found to decrease in undernourished rats. No major changes were observed in the concentration of different phospholipids of kidney from the experimental rats. These results suggest that undernutrition and vitamin A deficiency have differential effects on the phospholipid composition of different tissues and the effects of vitamin A deficiency seems to be due to general growth retardation rather than the specific effect of vitamin A per se.

Animals↗