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Sample records for phospholipid turnover relevant

  1. Turnover of pancreas phospholipids in rats fed inadequate dietary protein.

    PubMed

    Bhutani, V; Kumar, V; Misra, U K

    1986-01-01

    Effect of feeding rice diets with and without lysine and threonine supplementation has been studied on phospholipid turnover of rat pancreas and compared to rats fed casein diet at 20% protein level. Rice diet without amino acid supplementation significantly reduced the levels of pancreas PC, PE, PI, PS and Sph and increased that of total cholesterol and TG. Incorporation of palmitate-1-14C, labelled choline, labelled methionine and NaH2(32)PO4 into PC and of palmitate-1-14C into TG was significantly reduced in rats fed unsupplemented rice diet. Incorporation of NaH2(32)PO4 into pancreas PI, DPI, TPI, PA, LPA and into IP, IP2', IP3 and GPI was significantly reduced in rats fed unsupplemented rice diet. PMID:3781752

  2. Phospholipid turnover during phagocytosis in human polymorphonuclear leucocytes

    PubMed Central

    García Gil, Merche; Alonso, Fernando; Alvarez Chiva, Vicente; Sánchez Crespo, Mariano; Mato, José M.

    1982-01-01

    We have previously observed that the phagocytosis of zymosan particles coated with complement by human polymorphonuclear leucocytes is accompanied by a time- and dose-dependent inhibition of phosphatidylcholine synthesis by transmethylation [García Gil, Alonso, Sánchez Crespo & Mato (1981) Biochem. Biophys. Res. Commun. 101, 740–748]. The present studies show that phosphatidylcholine synthesis by a cholinephosphotransferase reaction is enhanced, up to 3-fold, during phagocytosis by polymorphonuclear cells. This effect was tested by both measuring the incorporation of radioactivity into phosphatidylcholine in cells labelled with [Me-14C]choline, and by assaying the activity of CDP-choline:diacylglycerol cholinephosphotransferase. The time course of CDP-choline:diacylglycerol cholinephosphotransferase activation by zymosan mirrors the inhibition of phospholipid methyltransferase activity previously reported. The extent of incorporation of radioactivity into phosphatidylcholine induced by various doses of zymosan correlates with the physiological response of the cells to this stimulus. This effect was specific for phosphatidylcholine, and phosphatidyl-ethanolamine turnover was not affected by zymosan. The purpose of this enhanced phosphatidylcholine synthesis is not to provide phospholipid molecules rich in arachidonic acid. The present studies show that about 80% of the arachidonic acid generated in response to zymosan derives from phosphatidylinositol. A transient accumulation of arachidonoyldiacylglycerol has also been observed, which indicates that a phospholipase C is responsible, at least in part, for the generation of arachidonic acid. Finally, isobutylmethylxanthine and quinacrine, inhibitors of phosphatidylinositol turnover, inhibit both arachidonic acid generation and phagocytosis, indicating a function for this pathway during this process. PMID:6181780

  3. Hyperbaric hyperoxia reversibly inhibits erythrocyte phospholipid fatty acid turnover

    NASA Technical Reports Server (NTRS)

    Dise, Craig A.; Clark, James M.; Lambersten, Christian J.; Goodman, David B. P.

    1987-01-01

    The effect of hyperbaric hyperoxia on the acylation of membrane phospholipid was studied by measuring the rates of activation of exogenous tritiated oleic acid to acyl thioester and of transesterification of the thioester into membrane phospholipids in intact human erythrocytes obtained 1 h after an exposure of the subjects to a hyperbaric oxygen atmosphere (3.5 h, 100 pct O2, 3 ATA). Exposure to pure oxygen was found to inhibit both the acylation and transesterification reactions by more than 30 percent, with partial recovery detected 24 h later. On the other hand, no rate changes were observed when isolated membranes from the same batches of cells were used in similar experiments. It is suggested that the decrease in the incorporation of tritiated oleic acid after hyperbaric hyperoxia may reflect an early event in the pathogenesis of oxygen-induced cellular injury and that it may be a useful index for the assessment of the tolerance of tissues to hyperoxia.

  4. The turnover of myelin phospholipids in the adult and developing rat brain

    PubMed Central

    Jungalwala, F. B.; Dawson, R. M. C.

    1971-01-01

    1. Inorganic [32P]phosphate, [U-14C]glycerol and [2-14C]ethanolamine were injected into the lateral ventricles in the brains of adult rats, and the labelling of individual phospholipids was followed over 2–4 months in both a microsomal and a highly purified myelin fraction. 2. All the phospholipids in myelin became appreciably labelled, although initially the specific radioactivities of the microsomal phospholipids were somewhat higher. Eventually the specific radioactivities in microsomal and myelin phospholipids fell rapidly at a rate corresponding to the decline of radioactivity in the acid-soluble pools. 3. Equivalent experiments carried out in developing rats with [32P]phosphate administered at the start of myelination showed some persistence of phospholipid labelling in the myelin, but this could partly be attributed to the greater retention of 32P in the acid-soluble phosphorus pool and recycling. 4. It is concluded that a substantial part of the phospholipid molecules in adult myelin membranes is readily exchangeable, although a small pool of slowly exchangeable material also exists. 5. A slow incorporation into or loss of labelled precursor from myelin phospholipids does not necessarily give a good indication of the rate of renewal of the molecules in the membrane. As presumably such labelled molecules originate by exchange with those in another membrane site (not necessarily where synthesis occurs) it is only possible to calculate the turnover rate in the myelin membrane if the behaviour of the specific radioactivity with time of the phospholipid molecules in the immediate precursor pool is known. PMID:5124379

  5. Depletion of arachidonic acid from GH3 cells. Effects on inositol phospholipid turnover and cellular activation.

    PubMed Central

    Dudley, D T; Macfarlane, D E; Spector, A A

    1987-01-01

    We have adapted rat pituitary GH3 cells to grow in delipidated culture medium. In response, esterfied linoleic acid and arachidonic acid become essentially undetectable, whereas eicosa-5,8,11-trienoic acid accumulates and oleic acid increases markedly. These changes occur in all phospholipid classes, but are particularly pronounced in inositol phospholipids, where the usual stearate/arachidonate profile is replaced with oleate/eicosatrienoate (n - 9) and stearate/eicosatrienoate (n - 9). Incubation of arachidonate-depleted cells with 10 microM-arachidonic acid for only 24 h results in extensive remodelling of phospholipid fatty acids, such that close-to-normal compositions and arachidonic acid content are achieved for the inositol phospholipids. In comparison studies with arachidonic acid-depleted or -repleted cells, it was found that the arachidonate content does not affect thyrotropin-releasing-hormone (TRH)-stimulated responses measured at long time points, including [32P]Pi labelling of phosphatidylinositol and phosphatidic acid, stimulation of protein phosphorylation, and basal or TRH-stimulated prolactin release. However, transient events such as stimulated breakdown of inositol phospholipids and an initial rise in diacylglycerol are enhanced by the presence of arachidonate. These results show that arachidonic acid itself is not required for operation of the phosphatidylinositol cycle and is not an obligatory intermediate in TRH-mediated GH3 cell activation. It is possible that any structural or functional role of arachidonic acid in these processes is largely met by replacement with eicosatrienoate (n - 9). However, since arachidonate in inositol phospholipids facilitates their hydrolysis upon stimulation by TRH, arachidonic acid apparently may have a specific role in the recognition of these lipids by phospholipase C. Images Fig. 4. PMID:3120699

  6. Subcellular localization of yeast Sec14 homologues and their involvement in regulation of phospholipid turnover.

    PubMed

    Schnabl, Martina; Oskolkova, Olga V; Holic, Roman; Brezná, Barbara; Pichler, Harald; Zágorsek, Milos; Kohlwein, Sepp D; Paltauf, Fritz; Daum, Günther; Griac, Peter

    2003-08-01

    Sec14p of the yeast Saccharomyces cerevisiae is involved in protein secretion and regulation of lipid synthesis and turnover in vivo, but acts as a phosphatidylinositol-phosphatidylcholine transfer protein in vitro. In this work, the five homologues of Sec14p, Sfh1p-Sfh5p, were subjected to biochemical and cell biological analysis to get a better view of their physiological role. We show that overexpression of SFH2 and SFH4 suppressed the sec14 growth defect in a more and SFH1 in a less efficient way, whereas overexpression of SFH3 and SFH5 did not complement sec14. Using C-terminal yEGFP fusions, Sfh2p, Sfh4p and Sfh5p are mainly localized to the cytosol and microsomes similar to Sec14p. Sfh1p was detected in the nucleus and Sfh3p in lipid particles and in microsomes. In contrast to Sec14p, which inhibits phospholipase D1 (Pld1p), overproduction of Sfh2p and Sfh4p resulted in the activation of Pld1p-mediated phosphatidylcholine turnover. Interestingly, Sec14p and the two homologues Sfh2p and Sfh4p downregulate phospholipase B1 (Plb1p)-mediated turnover of phosphatidylcholine in vivo. In summary, Sfh2p and Sfh4p are the Sec14p homologues with the most pronounced functional similarity to Sec14p, whereas the other Sfh proteins appear to be functionally less related to Sec14p. PMID:12869188

  7. Phospholipid turnover in Torpedo marmorata electric organ during discharge in vivo.

    PubMed Central

    Bleasdale, J E; Hawthorne, J N; Widlund, L; Heilbronn, E

    1976-01-01

    One electric organ of anaesthetized Torpedo marmorata was stimulated through electrodes placed on the electric lobe of the brain. Nerves to the other electric organ were cut to provide an unstimulated control. Glucose 6-[32P]phosphate was injected into each organ 16h before electrical stimulation. After stimulation for 10 min at 5 Hz, the organs were removed homogenized and centrifuged on a density gradient for the preparation of subcellular fractions. Stimulation increased the incorporation of 32P into phosphatidate, phosphatidylinositol and phosphatidylcholine. The increased phosphatidate labelling, but not that of the other two lipids, was seen in fractions rich in synaptic vesicles. Stimulation had no effect on ATP labelling. The phosphatidate content of most fractions fell slightly after stimulation, but amounts of other phospholipids were not affected. Images PLATE 1 PLATE 2 PMID:825114

  8. Acyl-CoA Synthetase 1 Is Induced by Gram-negative Bacteria and Lipopolysaccharide and Is Required for Phospholipid Turnover in Stimulated Macrophages*

    PubMed Central

    Rubinow, Katya B.; Wall, Valerie Z.; Nelson, Joel; Mar, Daniel; Bomsztyk, Karol; Askari, Bardia; Lai, Marvin A.; Smith, Kelly D.; Han, Myoung Sook; Vivekanandan-Giri, Anuradha; Pennathur, Subramaniam; Albert, Carolyn J.; Ford, David A.; Davis, Roger J.; Bornfeldt, Karin E.

    2013-01-01

    The enzyme acyl-CoA synthetase 1 (ACSL1) is induced by peroxisome proliferator-activated receptor α (PPARα) and PPARγ in insulin target tissues, such as skeletal muscle and adipose tissue, and plays an important role in β-oxidation in these tissues. In macrophages, however, ACSL1 mediates inflammatory effects without significant effects on β-oxidation. Thus, the function of ACSL1 varies in different tissues. We therefore investigated the signals and signal transduction pathways resulting in ACSL1 induction in macrophages as well as the consequences of ACSL1 deficiency for phospholipid turnover in LPS-activated macrophages. LPS, Gram-negative bacteria, IFN-γ, and TNFα all induce ACSL1 expression in macrophages, whereas PPAR agonists do not. LPS-induced ACSL1 expression is dependent on Toll-like receptor 4 (TLR4) and its adaptor protein TRIF (Toll-like receptor adaptor molecule 1) but does not require the MyD88 (myeloid differentiation primary response gene 88) arm of TLR4 signaling; nor does it require STAT1 (signal transducer and activator of transcription 1) for maximal induction. Furthermore, ACSL1 deletion attenuates phospholipid turnover in LPS-stimulated macrophages. Thus, the regulation and biological function of ACSL1 in macrophages differ markedly from that in insulin target tissues. These results suggest that ACSL1 may have an important role in the innate immune response. Further, these findings illustrate an interesting paradigm in which the same enzyme, ACSL1, confers distinct biological effects in different cell types, and these disparate functions are paralleled by differences in the pathways that regulate its expression. PMID:23426369

  9. Disruption of G1-phase phospholipid turnover by inhibition of Ca2+-independent phospholipase A2 induces a p53-dependent cell-cycle arrest in G1 phase.

    PubMed

    Zhang, Xu Hannah; Zhao, Chunying; Seleznev, Konstantin; Song, Keying; Manfredi, James J; Ma, Zhongmin Alex

    2006-03-15

    The G1 phase of the cell cycle is characterized by a high rate of membrane phospholipid turnover. Cells regulate this turnover by coordinating the opposing actions of CTP:phosphocholine cytidylyltransferase and the group VI Ca2+-independent phospholipase A2 (iPLA2). However, little is known about how such turnover affects cell-cycle progression. Here, we show that G1-phase phospholipid turnover is essential for cell proliferation. Specific inhibition of iPLA2 arrested cells in the G1 phase of the cell cycle. This G1-phase arrest was associated with marked upregulation of the tumour suppressor p53 and the expression of cyclin-dependent kinase inhibitor p21cip1. Inactivation of iPLA2 failed to arrest p53-deficient HCT cells in the G1 phase and caused massive apoptosis of p21-deficient HCT cells, suggesting that this G1-phase arrest requires activation of p53 and expression of p21cip1. Furthermore, downregulation of p53 by siRNA in p21-deficient HCT cells reduced the cell death, indicating that inhibition of iPLA2 induced p53-dependent apoptosis in the absence of p21cip1. Thus, our study reveals hitherto unrecognized cooperation between p53 and iPLA2 to monitor membrane-phospholipid turnover in G1 phase. Disrupting the G1-phase phospholipid turnover by inhibition of iPLA2 activates the p53-p21cip1 checkpoint mechanism, thereby blocking the entry of G1-phase cells into S phase. PMID:16492706

  10. Clinical relevance of multiple antibody specificity testing in anti-phospholipid syndrome and recurrent pregnancy loss

    PubMed Central

    Tebo, A E; Jaskowski, T D; Hill, H R; Branch, D W

    2008-01-01

    We wanted to evaluate whether testing for anti-phosholipid antibodies other than anti-cardiolipin (aCL) and anti-beta-2 glycoprotein I (aβ2GPI) immunoglobulin (Ig)G and IgM identifies patients with recurrent pregnancy loss (RPL) who may be positive for anti-phospholipid syndrome (APS). In a cross-sectional study comprising 62 patients with APS, 66 women with RPL, 50 healthy blood donors and 24 women with a history of successful pregnancies, we tested IgM and IgG antibodies to phosphatidic acid, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol, phosphatidyl inositol and phosphatidyl serine with and without beta-2 glycoprotein I (β2GPI) from a single manufacturer as well as aCL and aβ2GPI antibodies. Diagnostic accuracies of individual and combined anti-phospholipid (aPL) assays were assessed by computing sensitivities, specificities, positive predictive values and negative predictive values together with their 95% confidence intervals. There was a general trend for increased sensitivities in the presence of β2GPI co-factor with significant effect for certain specificities. The overall combined sensitivity of the non-recommended aPL assays was not significantly higher than that of the aCL and aB2GPI tests. Multiple aPL specificities in RPL group is not significantly different from controls and therefore of no clinical significance. PMID:18826497

  11. Clinical relevance of multiple antibody specificity testing in anti-phospholipid syndrome and recurrent pregnancy loss.

    PubMed

    Tebo, A E; Jaskowski, T D; Hill, H R; Branch, D W

    2008-12-01

    We wanted to evaluate whether testing for anti-phosholipid antibodies other than anti-cardiolipin (aCL) and anti-beta-2 glycoprotein I (abeta2GPI) immunoglobulin (Ig)G and IgM identifies patients with recurrent pregnancy loss (RPL) who may be positive for anti-phospholipid syndrome (APS). In a cross-sectional study comprising 62 patients with APS, 66 women with RPL, 50 healthy blood donors and 24 women with a history of successful pregnancies, we tested IgM and IgG antibodies to phosphatidic acid, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol, phosphatidyl inositol and phosphatidyl serine with and without beta-2 glycoprotein I (beta2GPI) from a single manufacturer as well as aCL and abeta2GPI antibodies. Diagnostic accuracies of individual and combined anti-phospholipid (aPL) assays were assessed by computing sensitivities, specificities, positive predictive values and negative predictive values together with their 95% confidence intervals. There was a general trend for increased sensitivities in the presence of beta2GPI co-factor with significant effect for certain specificities. The overall combined sensitivity of the non-recommended aPL assays was not significantly higher than that of the aCL and aB2GPI tests. Multiple aPL specificities in RPL group is not significantly different from controls and therefore of no clinical significance. PMID:18826497

  12. Minimal Peptidoglycan (PG) Turnover in Wild-Type and PG Hydrolase and Cell Division Mutants of Streptococcus pneumoniae D39 Growing Planktonically and in Host-Relevant Biofilms

    PubMed Central

    Boersma, Michael J.; Kuru, Erkin; Rittichier, Jonathan T.; VanNieuwenhze, Michael S.; Brun, Yves V.

    2015-01-01

    as signals for bacteria to induce antibiotic resistance and as activators of innate immune responses. S. pneumoniae is a commensal bacterium that colonizes the human nasopharynx and opportunistically causes serious respiratory and invasive diseases. The results presented here demonstrate a distinct demarcation between regions of old PG and regions of new PG synthesis and minimal turnover of PG in S. pneumoniae cells growing in culture or in host-relevant biofilms. These findings suggest that S. pneumoniae minimizes the release of PG breakdown products by turnover, which may contribute to evasion of the innate immune system. PMID:26303829

  13. Platelet-activating factor induces phospholipid turnover, calcium flux, arachidonic acid liberation, eicosanoid generation, and oncogene expression in a human B cell line

    SciTech Connect

    Schulam, P.G.; Kuruvilla, A.; Putcha, G.; Mangus, L.; Franklin-Johnson, J.; Shearer, W.T. )

    1991-03-01

    Platelet-activating factor is a potent mediator of the inflammatory response. Studies of the actions of platelet-activating factor have centered mainly around neutrophils, monocytes, and platelets. In this report we begin to uncover the influence of platelet-activating factor on B lymphocytes. Employing the EBV-transformed human B cell line SKW6.4, we demonstrate that platelet-activating factor significantly alters membrane phospholipid metabolism indicated by the incorporation of 32P into phosphatidylcholine, phosphatidylinositol, and phosphatidic acid but not significantly into phosphatidylethanolamine at concentrations ranging from 10(-9) to 10(-6) M. The inactive precursor, lyso-platelet-activating factor, at a concentration as high as 10(-7) M had no effect on any of the membrane phospholipids. We also show that platelet-activating factor from 10(-12) to 10(-6) M induced rapid and significant elevation in intracellular calcium levels, whereas lyso-platelet-activating factor was again ineffective. We further demonstrate the impact of platelet-activating factor binding to B cells by measuring platelet-activating factor induced arachidonic acid release and 5-hydroxyeicosatetraenoic acid production. Moreover, platelet-activating factor was capable of inducing transcription of the nuclear proto-oncogenes c-fos and c-jun. Finally we explored the possible role of 5-hydroxyeicosatetraenoic acid as a regulator of arachidonic acid liberation demonstrating that endogenous 5-lipoxygenase activity modulates platelet-activating factor induced arachidonic acid release perhaps acting at the level of phospholipase A2. In summary, platelet-activating factor is shown here to have a direct and profound effect on a pure B cell line.

  14. Turnover Begets Turnover

    ERIC Educational Resources Information Center

    Castle, Nicholas G.

    2005-01-01

    Purpose: This study examined the association between turnover of caregivers and turnover of nursing home top management. The top managers examined were administrators and directors of nursing, and the caregivers examined were registered nurses, licensed practical nurses, and nurse aides. Design and Methods: The data came from a survey of 419…

  15. Phospholipid Scramblases

    PubMed Central

    Williamson, Patrick

    2015-01-01

    The distribution of phospholipid types between the two leaflets of a membrane bilayer is a controlled feature of membrane structure. One of the two membrane catalytic activities governing this distribution randomizes the composition of the two leaflets—the phospholipid scramblases. Two proteins (Xkr8 and TMEM16F) required for the activation of these activities have been identified. One of these proteins (TMEM16F) is quite clearly a scramblase itself and provides insight into the mechanism by which transbilayer phospholipid movement is facilitated. PMID:26843813

  16. Surfactant phospholipid metabolism.

    PubMed

    Agassandian, Marianna; Mallampalli, Rama K

    2013-03-01

    Pulmonary surfactant is essential for life and is composed of a complex lipoprotein-like mixture that lines the inner surface of the lung to prevent alveolar collapse at the end of expiration. The molecular composition of surfactant depends on highly integrated and regulated processes involving its biosynthesis, remodeling, degradation, and intracellular trafficking. Despite its multicomponent composition, the study of surfactant phospholipid metabolism has focused on two predominant components, disaturated phosphatidylcholine that confers surface-tension lowering activities, and phosphatidylglycerol, recently implicated in innate immune defense. Future studies providing a better understanding of the molecular control and physiological relevance of minor surfactant lipid components are needed. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism. PMID:23026158

  17. The use of natural and synthetic phospholipids as pharmaceutical excipients*

    PubMed Central

    van Hoogevest, Peter; Wendel, Armin

    2014-01-01

    In pharmaceutical formulations, phospholipids obtained from plant or animal sources and synthetic phospholipids are used. Natural phospholipids are purified from, e.g., soybeans or egg yolk using non-toxic solvent extraction and chromatographic procedures with low consumption of energy and minimum possible waste. Because of the use of validated purification procedures and sourcing of raw materials with consistent quality, the resulting products differing in phosphatidylcholine content possess an excellent batch to batch reproducibility with respect to phospholipid and fatty acid composition. The natural phospholipids are described in pharmacopeias and relevant regulatory guidance documentation of the Food and Drug Administration (FDA) and European Medicines Agency (EMA). Synthetic phospholipids with specific polar head group, fatty acid composition can be manufactured using various synthesis routes. Synthetic phospholipids with the natural stereochemical configuration are preferably synthesized from glycerophosphocholine (GPC), which is obtained from natural phospholipids, using acylation and enzyme catalyzed reactions. Synthetic phospholipids play compared to natural phospholipid (including hydrogenated phospholipids), as derived from the number of drug products containing synthetic phospholipids, a minor role. Only in a few pharmaceutical products synthetic phospholipids are used. Natural phospholipids are used in oral, dermal, and parenteral products including liposomes. Natural phospholipids instead of synthetic phospholipids should be selected as phospholipid excipients for formulation development, whenever possible, because natural phospholipids are derived from renewable sources and produced with more ecologically friendly processes and are available in larger scale at relatively low costs compared to synthetic phospholipids. Practical applications: For selection of phospholipid excipients for pharmaceutical formulations, natural phospholipids are preferred

  18. Turnover Time

    EPA Science Inventory

    Ecosystems contain energy and materials such as carbon, nitrogen, phosphorus, and water, and are open to their flow-through. Turnover time refers to the amount of time required for replacement by flow-through of the energy or substance of interest contained in the system, and is ...

  19. Phospholipid transport via mitochondria

    PubMed Central

    Tamura, Yasushi; Sesaki, Hiromi; Endo, Toshiya

    2014-01-01

    In eukaryotic cells, complex membrane structures called organelles are highly developed to exert specialized functions. Mitochondria are one of such organelles consisting of the outer and inner membranes with characteristic protein and phospholipid compositions. Maintaining proper phospholipid compositions of the membranes is crucial for mitochondrial integrity, thereby contributing to normal cell activities. Since cellular locations for phospholipid synthesis are restricted to specific compartments such as the endoplasmic reticulum (ER) membrane and the mitochondrial inner membrane, newly synthesized phospholipids have to be transported and distributed properly from the ER or mitochondria to other cellular membranes. Although understanding of molecular mechanisms of phospholipid transport are much behind those of protein transport, recent studies using yeast as a model system began to provide intriguing insights into phospholipid exchange between the ER and mitochondria as well as between the mitochondrial outer and inner membranes. In this review, we summarize the latest findings of phospholipid transport via mitochondria and discuss the implicated molecular mechanisms. PMID:24954234

  20. Phospholipid Metabolism in Ferrobacillus ferrooxidans

    PubMed Central

    Short, Steven A.; White, David C.; Aleem, M. I. H.

    1969-01-01

    The lipid composition of the chemoautotroph Ferrobacillus ferrooxidans has been examined. Fatty acids represent 2% of the dry weight of the cells and 86% of the total are extractable with organic solvents. About 25% of the total fatty acids are associated with diacyl phospholipids. Polar carotenoids, the benzoquinone coenzyme Q-8, and most of the fatty acids are present in the neutral lipids. The phospholipids have been identified as phosphatidyl monomethylethanolamine (42%), phosphatidyl glycerol (23%), phosphatidyl ethanolamine (20%), cardiolipin (13%), phosphatidyl choline (1.5%), and phosphatidyl dimethylethanolamine (1%) by chromatography of the diacyl lipids, by chromatography in four systems of the glycerol phosphate esters derived from the lipids by mild alkaline methanolysis, and by chromatographic identification of the products of acid hydrolysis of the esters. No trace of phosphatidylserine (PS), glycerolphosphorylserine, or serine could be detected in the lipid extract or in derivatives of that extract. This casts some doubt on the postulated involvement of PS in iron metabolism. After growth in the presence of 14C and 32P, there was essentially no difference in the turnover of either isotope in the glycerolphosphate ester derived from each lipid in cells grown at pH 1.5 or 3.5. Images PMID:5802599

  1. Tissue phospholipids (TPL) in avian tuberculosis (AT)

    SciTech Connect

    Nandedkar, A.K.N.; Malhotra, H.C.

    1986-05-01

    AT constitutes one of the major problems in animal husbandry. Chickens (white, leg horn, male, 400-600 g) were infected with Mycobacterium avium maintained on I.U.T. medium to induce clinical AT which was confirmed by histopathological examinations of the affected tissues. Fatty infiltration and tissue enlargement was visible in infected birds. After 4 wks, incorporation of i.v. /sup 32/P (50 uCi/100 g body wt.) in affected tissues was followed for 3,7,9,12 hr intervals. Lipids were extracted and fractionated by silicic acid (SA) column and SA impregnated paper chromatography. When compared with pair-fed controls, in AT slower turnover of TPL in liver, slightly higher in heart and significantly increased turnover of TPL in serum were observed. No appreciable change in total TPL content was noticed in brain, spleen and kidney. Further fractionation of TPL provided better understanding of the metabolism. Increase in lysophosphatidyl-choline (LPC) and -ethanolamine (LPE) content, powerful hemolytic agents, in liver may explain frequent occurrence of anemia in tuberculosis. Also, a concomitant marked increase in the ratio of total saturated/unsaturated fatty acids is observed in serum phosphatidyl choline fraction. This confirms the observation that the membrane phospholipid metabolism is significantly affected in tuberculosis infection.

  2. Measurement of Phospholipids May Improve Diagnostic Accuracy in Ovarian Cancer

    PubMed Central

    Davis, Lorelei; Han, Gang; Zhu, Weiwei; Molina, Ashley D.; Arango, Hector; LaPolla, James P.; Hoffman, Mitchell S.; Sellers, Thomas; Kirby, Tyler; Nicosia, Santo V.; Sutphen, Rebecca

    2012-01-01

    Background More than two-thirds of women who undergo surgery for suspected ovarian neoplasm do not have cancer. Our previous results suggest phospholipids as potential biomarkers of ovarian cancer. In this study, we measured the serum levels of multiple phospholipids among women undergoing surgery for suspected ovarian cancer to identify biomarkers that better predict whether an ovarian mass is malignant. Methodology/Principal Findings We obtained serum samples preoperatively from women with suspected ovarian cancer enrolled through a prospective, population-based rapid ascertainment system. Samples were analyzed from all women in whom a diagnosis of epithelial ovarian cancer (EOC) was confirmed and from benign disease cases randomly selected from the remaining (non-EOC) samples. We measured biologically relevant phospholipids using liquid chromatography/electrospray ionization mass spectrometry. We applied a powerful statistical and machine learning approach, Hybrid huberized support vector machine (HH-SVM) to prioritize phospholipids to enter the biomarker models, and used cross-validation to obtain conservative estimates of classification error rates. Results The HH-SVM model using the measurements of specific combinations of phospholipids supplements clinical CA125 measurement and improves diagnostic accuracy. Specifically, the measurement of phospholipids improved sensitivity (identification of cases with preoperative CA125 levels below 35) among two types of cases in which CA125 performance is historically poor - early stage cases and those of mucinous histology. Measurement of phospholipids improved the identification of early stage cases from 65% (based on CA125) to 82%, and mucinous cases from 44% to 88%. Conclusions/Significance Levels of specific serum phospholipids differ between women with ovarian cancer and those with benign conditions. If validated by independent studies in the future, these biomarkers may serve as an adjunct at the time of clinical

  3. Cell signalling and phospholipid metabolism

    SciTech Connect

    Boss, W.F.

    1990-01-01

    These studies explored whether phosphoinositide (PI) has a role in plants analogous to its role in animal cells. Although no parallel activity of PI in signal transduction was found in plant cells, activity of inositol phospholipid kinase was found to be modulated by light and by cell wall degrading enzymes. These studies indicate a major role for inositol phospholipids in plant growth and development as membrane effectors but not as a source of second messengers.

  4. Interactions of amelogenin with phospholipids.

    PubMed

    Lokappa, Sowmya Bekshe; Chandrababu, Karthik Balakrishna; Dutta, Kaushik; Perovic, Iva; Evans, John Spencer; Moradian-Oldak, Janet

    2015-02-01

    Amelogenin protein has the potential to interact with other enamel matrix proteins, mineral, and cell surfaces. We investigated the interactions of recombinant amelogenin rP172 with small unilamellar vesicles as model membranes, toward the goal of understanding the mechanisms of amelogenin-cell interactions during amelogenesis. Dynamic light scattering (DLS), fluorescence spectroscopy, circular dichroism (CD), and nuclear magnetic resonance (NMR) were used. In the presence of phospholipid vesicles, a blue shift in the Trp fluorescence emission maxima of rP172 was observed (∼334 nm) and the Trp residues of rP172 were inaccessible to the aqueous quencher acrylamide. DLS studies indicated complexation of rP172 and phospholipids, although the possibility of fusion of phospholipids following amelogenin addition cannot be ruled out. NMR and CD studies revealed a disorder-order transition of rP172 in a model membrane environment. Strong fluorescence resonance energy transfer from Trp in rP172 to DNS-bound-phospholipid was observed, and fluorescence polarization studies indicated that rP172 interacted with the hydrophobic core region of model membranes. Our data suggest that amelogenin has ability to interact with phospholipids and that such interactions may play key roles in enamel biomineralization as well as reported amelogenin signaling activities. PMID:25298002

  5. [Phospholipids: properties and health effects].

    PubMed

    Torres García, Jairo; Durán Agüero, Samuel

    2015-01-01

    Phospholipids are amphipathic lipids, which are found in all the cell membranes, organized as a lipid bilayer. They belong to the glycerol-derived lipids, showing a similar structure as triglycerides. The current interest of them comes from its effectiveness to incorporate different fatty acids in the cell membrane, as they exhibit better absorption and utilization than triglycerides. In this paper, the bibliographical data published about the benefits of the phospholipids in inflammatory processes, cancer, cardiovascular diseases, neurological disorders, liver disease and as an antioxidants transporter is reviewed. PMID:25561100

  6. Effect of gentamicin on phospholipid metabolism in cultured rabbit proximal tubular cells

    SciTech Connect

    Ramsammy, L.S.; Josepovitz, C.; Lane, B.; Kaloyanides, G.J.

    1989-01-01

    We examined the hypothesis that the accumulation of phospholipid in cells exposed to gentamicin is due to impaired degradation. Experiments were performed in rabbit proximal tubular cells grown in primary culture. Cells exposed to 10(-3) M gentamicin manifested myeloid body formation and a progressive increase in total phospholipid that by day 6 was 44% higher than that of control cells and reflected increases of phosphatidylinositol of 235%, phosphatidylcholine of 60%, phosphatidylethanolamine of 90%, and phosphatidylserine of 55% above control values. Gentamicin impaired the degradation of these phospholipids. The t1/2 of the phospholipid pool labeled with (3H)myoinositol increased 146% from 1.17 (control) to 2.88 days (gentamicin); the t1/2 of the (3H)choline pool increased 34% from 1.77 to 2.38 days; the t1/2 of the (3H)ethanolamine pool increased 57% from 3.14 to 4.93 days; the t1/2 of the (3H) serine pool increased 37% from 6.30 to 8.63 days. Exposure of cells to gentamicin for 2 days also stimulated increased incorporation of (3H)myoinositol (68%) and (3H)ethanolamine (59%) into phospholipid. The data are consistent with the hypothesis that gentamicin inhibits the activity of lysosomal phospholipases that results in the accumulation of phospholipid within the lysosome in the form of myeloid bodies. Increased phospholipid synthesis may represent a compensatory response to the impaired lysosomal degradation of phospholipid. We postulate that the preferential increase of phosphatidylinositol reflects the capacity of the polycationic gentamicin to interact electrostatically with the anionic phosphoinositides and inhibit their turnover.

  7. Phospholipid Metabolism and Membrane Synthesis During Sporulation in Bacillus megaterium

    PubMed Central

    Bacon, Karen; White, David

    1974-01-01

    In view of previously published reports of localized membrane growth in exponentially growing Bacillus megaterium and in sporulating Bacillus cereus, an attempt was made to describe phospholipid metabolism and the topology of membrane synthesis during sporulation in B. megaterium. The cells were pulsed with radioactive glycerol or acetate at the time of septum formation, and the specific activity of the lipid fraction was measured at various times through the free spore stage. The bulk of the material labeled during septation could not be recovered in the spore. Rather, it was found that the labeled lipid fraction underwent considerable turnover during spore development. Additionally, other experiments revealed that the lipid made before the initiation of sporulation was also subject to extensive turnover. In order to minimize both the confounding effects of lipid turnover and the possible presence of lateral diffusion of labeled lipid in the membrane, autoradiography of cells pulse labeled with radioactive glycerol at the time of septation was performed; a symmetrical grain distribution resulted. Thus, despite previously published suggestions to the contrary, the current experimental techniques could not demonstrate the existence of localized membrane synthesis in B. megaterium during sporulation. PMID:4206872

  8. Langmuir films containing ibuprofen and phospholipids

    NASA Astrophysics Data System (ADS)

    Geraldo, Vananélia P. N.; Pavinatto, Felippe J.; Nobre, Thatyane M.; Caseli, Luciano; Oliveira, Osvaldo N.

    2013-02-01

    This study shows the incorporation of ibuprofen, an anti-inflammatory drug, in Langmuir monolayers as cell membrane models. Significant effects were observed for dipalmitoyl phosphatidyl choline (DPPC) monolayers with relevant changes in the elasticity of the monolayer. Dipalmitoyl phosphatidyl glycerol (DPPG) monolayers were affected by small concentrations of ibuprofen, from 1 to 5 mol%. For both types of monolayer, ibuprofen could penetrate into the hydrophobic part of the monolayer, which was confirmed with polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). Brewster angle microscopy (BAM) images showed that ibuprofen prevents the formation of large domains of DPPC. The pharmacological action should occur primarily with penetration of ibuprofen via electrically neutral phospholipid headgroups of the membrane.

  9. Metabolism of the phospholipid precursor inositol and its relationship to growth and viability in the natural auxotroph Schizosaccharomyces pombe.

    PubMed Central

    Fernandez, S; Homann, M J; Henry, S A; Carman, G M

    1986-01-01

    Phospholipid metabolism in the fission yeast Schizosaccharomyces pombe was examined. Three enzymes of phospholipid biosynthesis, cytidine diphosphate diacylglycerol synthase (CDP-DG), phosphatidylinositol (PI) synthase, and phosphatidylserine (PS) synthase, were characterized in extracts of S. pombe cells. Contrary to an earlier report, we were able to demonstrate that CDP-DG served as a precursor for PI and PS biosynthesis in S. pombe. S. pombe is naturally auxotrophic for the phospholipid precursor inositol. We found that S. pombe was much more resistant to loss of viability during inositol starvation than artificially generated inositol auxotrophs of Saccharomyces cerevisiae. The phospholipid composition of S. pombe cells grown in inositol-rich medium (50 microM) was similar to that of S. cerevisiae cells grown under similar conditions. However, growth of S. pombe at low inositol concentrations (below 30 microM) affected the ratio of the anionic phospholipids PI and PS, while the relative proportions of other glycerophospholipids remained unchanged. During inositol starvation, the rate of PI synthesis decreased rapidly, and there was a concomitant increase in the rate of PS synthesis. Phosphatidic acid and CDP-DG, which are precursors to these phospholipids, also increased when PI synthesis was blocked by lack of exogenous inositol. The major product of turnover of inositol-containing phospholipids in S. pombe was found to be free inositol, which accumulated in the medium and could be reused by the cell. Images PMID:3011744

  10. [Relevance of metabolism of membrane phospholipids for Alzheimer dementia].

    PubMed

    Gattaz, W F; Levy, R; Cairns, N J; Förstl, H; Braus, D F; Maras, A

    1996-01-01

    We found a decreased activity of the enzyme phospholipase A2 (PLA2) in brain tissue from 23 patients with Alzheimer's disease (AD) compared to 20 non-demented controls. The decrement was more pronounced in patients with an early onset of disease and correlated significantly with higher counts of senile plaques and neurofibrillary tangles. Decreased PLA2 activity may inhibit the secretion of the amyloid precursor protein (APP) and thus contribute to the formation of the beta-amyloid peptide, the major component of the amyloid plaque in AD. Because PLA2 activity is under genetic control, it is conceivable that the enzyme activity in the brain is related to the activity in blood cells. To test this assumption we investigated PLA2 in platelet membranes from AD patients compared to healthy and psychiatric controls. Platelets are interesting peripheral models in AD research, because they contain and secrete APP. We determined the platelet PLA2 activity in 16 patients with a "probable" AD (NINCDS-ADRDA criteria) as compared to 13 healthy controls and to 14 psychiatric patients with a major depression. There were no significant differences between the three groups regarding age and sex distribution. In the AD patients the cognitive performance was assessed with the CAMCOG and the Mini Mental State Exam (MMSE). The radioenzymatic assay for the determination of PLA2 activity is described elsewhere. Platelet PLA2 activity was significantly reduced in AD patients as compared to healthy (p < 0.03) and to psychiatric controls (p < 0.002). The reduction of the enzyme activity correlated with an early onset of the disease (rs = .43, p < 0.10) and with the cognitive impairment in the CAMCOG (rs = .55, p < 0.05). AD patients with a MMSE-score lower than 10 (median) showed significantly lower PLA2 activity (11.8 +/- 3.1) than patients with MMSE-score higher than 10 (16.2 +/- 4.6, p < 0.05). These findings in platelets are in line with our previous results in brain tissue. In both studies decreased PLA2 activity was related to a more severe form of AD (early onset, more cognitive impairment and higher number of plaques and tangles). Moreover, reduced platelet PLA2 activity was specific for AD as compared to age-matched psychiatric controls. Further studies should clarify whether PLA2 activity in platelets could be useful as a peripheral marker for a subgroup of AD. PMID:8850090

  11. Calcium dependency of arachidonic acid incorporation into cellular phospholipids of different cell types.

    PubMed

    Daniele, J J; Fidelio, G D; Bianco, I D

    1999-07-01

    Ca2+ -independent phospholipase A2 (iPLA2) is involved in the incorporation of arachidonic acid (AA) into resting macrophages by the generation of the lysophospholipid acceptor. The role of iPLA2 in AA remodeling in different cells was evaluated by studying the Ca2+ dependency of AA uptake from the medium, the incorporation into cellular phospholipids, and the effect of the iPLA2 inhibitor bromoenol lactone on these events. Uptake and esterification of AA into phospholipids were not affected by Ca2+ depletion in human polymorphonuclear neutrophils and rat fibroblasts. The uptake was Ca2+ independent in chick embryo glial cells, but the incorporation into phospholipids was partially dependent on extracellular Ca2+. Both events were fully dependent on extra and intracellular Ca2+ in human platelets. In human polymorphonuclear neutrophils, the kinetics of incorporation in several isospecies of phospholipids was not affected by the absence of Ca2+ at short times (<30 min). The involvement of iPLA2 in the incorporation of AA from the medium was confirmed by the selective inhibition of this enzyme with bromoenol lactone, which reduced < or =50% of the incorporation of AA into phospholipids of human neutrophils. These data provide evidence that suggests iPLA2 plays a major role in regulating AA turnover in different cell types. PMID:10480488

  12. 13C- and 15N-Labeling Strategies Combined with Mass Spectrometry Comprehensively Quantify Phospholipid Dynamics in C. elegans

    PubMed Central

    Drechsler, Robin; Gafken, Philip R.; Olsen, Carissa Perez

    2015-01-01

    Membranes define cellular and organelle boundaries, a function that is critical to all living systems. Like other biomolecules, membrane lipids are dynamically maintained, but current methods are extremely limited for monitoring lipid dynamics in living animals. We developed novel strategies in C. elegans combining 13C and 15N stable isotopes with mass spectrometry to directly quantify the replenishment rates of the individual fatty acids and intact phospholipids of the membrane. Using multiple measurements of phospholipid dynamics, we found that the phospholipid pools are replaced rapidly and at rates nearly double the turnover measured for neutral lipid populations. In fact, our analysis shows that the majority of membrane lipids are replaced each day. Furthermore, we found that stearoyl-CoA desaturases (SCDs), critical enzymes in polyunsaturated fatty acid production, play an unexpected role in influencing the overall rates of membrane maintenance as SCD depletion affected the turnover of nearly all membrane lipids. Additionally, the compromised membrane maintenance as defined by LC-MS/MS with SCD RNAi resulted in active phospholipid remodeling that we predict is critical to alleviate the impact of reduced membrane maintenance in these animals. Not only have these combined methodologies identified new facets of the impact of SCDs on the membrane, but they also have great potential to reveal many undiscovered regulators of phospholipid metabolism. PMID:26528916

  13. Nanomechanics of electrospun phospholipid fiber

    SciTech Connect

    Mendes, Ana C. E-mail: ioach@food.dtu.dk; Chronakis, Ioannis S. E-mail: ioach@food.dtu.dk; Nikogeorgos, Nikolaos; Lee, Seunghwan

    2015-06-01

    Electrospun asolectin phospholipid fibers were prepared using isooctane as a solvent and had an average diameter of 6.1 ± 2.7 μm. Their mechanical properties were evaluated by nanoindentation using Atomic Force Microscopy, and their elastic modulus was found to be approximately 17.2 ± 1 MPa. At a cycle of piezo expansion-retraction (loading-unloading) of a silicon tip on a fiber, relatively high adhesion was observed during unloading. It is proposed that this was primarily due to molecular rearrangements at the utmost layers of the fiber caused by the indentation of the hydrophilic tip. The phospholipid fibers were shown to be stable in ambient conditions, preserving the modulus of elasticity up to 24 h.

  14. Interactions of Amelogenin with Phospholipids

    PubMed Central

    Lokappa, Sowmya Bekshe; Chandrababu, Karthik Balakrishna; Dutta, Kaushik; Perovic, Iva; Evans, John Spencer; Moradian-Oldak, Janet

    2015-01-01

    Amelogenin protein has the potential to interact with other enamel matrix proteins, mineral and cell surfaces. We investigated the interactions of recombinant amelogenin rP172 with small unilamellar vesicles as model membranes, towards the goal of understanding the mechanisms of amelogenin-cell interactions during amelogenesis. Dynamic light scattering (DLS), fluorescence spectroscopy, circular dichroism (CD) and nuclear magnetic resonance (NMR) were used. In the presence of phospholipid vesicles, a blue shift in the Trp fluorescence emission maxima of rP172 was observed (~334 nm) and the Trp residues of rP172 were inaccessible to the aqueous quencher acrylamide. Though in DLS studies we cannot exclude the possibility of fusion of liposomes as the result of amelogenin addition, NMR and CD studies revealed a disorder-order transition of rP172 in a model membrane environment. Strong FRET from Trp in rP172 to DNS–bound-phospholipid was observed, and fluorescence polarization studies indicated that rP172 interacted with the hydrophobic core region of model membranes. Our data suggest that amelogenin has ability to interact with phospholipids and that such interactions may play key roles in enamel biomineralization as well as reported amelogenin signaling activities. PMID:25298002

  15. Nutritional Deficiencies and Phospholipid Metabolism

    PubMed Central

    Gimenez, María S.; Oliveros, Liliana B.; Gomez, Nidia N.

    2011-01-01

    Phospholipids are important components of the cell membranes of all living species. They contribute to the physicochemical properties of the membrane and thus influence the conformation and function of membrane-bound proteins, such as receptors, ion channels, and transporters and also influence cell function by serving as precursors for prostaglandins and other signaling molecules and modulating gene expression through the transcription activation. The components of the diet are determinant for cell functionality. In this review, the effects of macro and micronutrients deficiency on the quality, quantity and metabolism of different phospholipids and their distribution in cells of different organs is presented. Alterations in the amount of both saturated and polyunsaturated fatty acids, vitamins A, E and folate, and other micronutrients, such as zinc and magnesium, are discussed. In all cases we observe alterations in the pattern of phospholipids, the more affected ones being phosphatidylcholine, phosphatidylethanolamine and sphingomyelin. The deficiency of certain nutrients, such as essential fatty acids, fat-soluble vitamins and some metals may contribute to a variety of diseases that can be irreversible even after replacement with normal amount of the nutrients. Usually, the sequelae are more important when the deficiency is present at an early age. PMID:21731449

  16. Integrating Turnover Reasons and Shocks with Turnover Decision Processes

    ERIC Educational Resources Information Center

    Maertz, Carl P., Jr.; Kmitta, Kayla R.

    2012-01-01

    We interviewed and classified 186 quitters from many jobs and organizations via a theoretically-based protocol into five decision process types. We then tested exploratory hypotheses comparing users of these types on their propensity to report certain turnover reasons and turnover shocks. "Impulsive-type quitters," with neither a job offer in hand…

  17. Modulation of Plasma Membrane Ca2+-ATPase by Neutral Phospholipids

    PubMed Central

    Pignataro, María Florencia; Dodes-Traian, Martín M.; González-Flecha, F. Luis; Sica, Mauricio; Mangialavori, Irene C.; Rossi, Juan Pablo F. C.

    2015-01-01

    The effects of lipids on membrane proteins are likely to be complex and unique for each membrane protein. Here we studied different detergent/phosphatidylcholine reconstitution media and tested their effects on plasma membrane Ca2+ pump (PMCA). We found that Ca2+-ATPase activity shows a biphasic behavior with respect to the detergent/phosphatidylcholine ratio. Moreover, the maximal Ca2+-ATPase activity largely depends on the length and the unsaturation degree of the hydrocarbon chain. Using static light scattering and fluorescence correlation spectroscopy, we monitored the changes in hydrodynamic radius of detergent/phosphatidylcholine particles during the micelle-vesicle transition. We found that, when PMCA is reconstituted in mixed micelles, neutral phospholipids increase the enzyme turnover. The biophysical changes associated with the transition from mixed micelles to bicelles increase the time of residence of the phosphorylated intermediate (EP), decreasing the enzyme turnover. Molecular dynamics simulations analysis of the interactions between PMCA and the phospholipid bilayer in which it is embedded show that in the 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer, charged residues of the protein are trapped in the hydrophobic core. Conversely, in the 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer, the overall hydrophobic-hydrophilic requirements of the protein surface are fulfilled the best, reducing the thermodynamic cost of exposing charged residues to the hydrophobic core. The apparent mismatch produced by a 1,2-dioleoyl-sn-glycero-3-phosphocholine thicker bilayer could be a structural foundation to explain its functional effect on PMCA. PMID:25605721

  18. Recent advances and future prospects of phyto-phospholipid complexation technique for improving pharmacokinetic profile of plant actives.

    PubMed

    Khan, Junaid; Alexander, Amit; Ajazuddin; Saraf, Swarnlata; Saraf, Shailendra

    2013-05-28

    The phyto-phospholipid complexation technique has emerged as one of the leading methods of improving bioavailability of phytopharmaceuticals having poor competency of solubilizing and crossing the biological membranes. Several plant actives in spite having potent in vitro pharmacological activities have failed to demonstrate similar in vivo response. Such plant actives have been made more effective systemically by incorporating them with dietary phospholipids forming new cellular structures which are amphipathic in nature. In the last few years phospholipids have been extensively explored for improved bioavailability and efficacy of plant drugs. Further, it is also much relevant to mention that phospholipids show unique compatibility with biological membranes and have inherent hepatoprotective activity. Different methods have been adopted to formulate phospholipid complexes of plant extractives utilizing varying solvent systems, molar ratios of drug/phospholipids and different drying techniques. Some methods of formulating such drug-phospholipid complexes have been patented as well. However, the stability of phyto-phospholipid complexes is still a matter of concern which needs attention. But still a number of products exploiting this technique are under clinical trials and some of them are now in market. The current review highlights key findings of recent years with our own viewpoints which can give the new directions to this strategy and also includes advancements in the technical aspects of phyto-phospholipid formulations which have been done in the recent past with future challenges. PMID:23474031

  19. Commitment Profiles and Employee Turnover

    ERIC Educational Resources Information Center

    Stanley, Laura; Vandenberghe, Christian; Vandenberg, Robert; Bentein, Kathleen

    2013-01-01

    We examined how affective (AC), normative (NC), perceived sacrifice (PS), and few alternatives (FA) commitments combine to form profiles and determine turnover intention and turnover. We theorized that three mechanisms account for how profiles operate, i.e., the degree to which membership is internally regulated, the perceived desirability and…

  20. Occupational stress and employee turnover.

    PubMed

    Bridger, Robert S; Day, Andrea J; Morton, Kate

    2013-01-01

    Questionnaire data captured in January-March 2007 were examined in relation to turnover in males and females during the next five years. In general, most of the workplace stressors (such as role conflict or peer support) were not antecedents of turnover in any group. Junior personnel with psychological strain in 2007 had an increased risk of turnover in the next five years. Low commitment to the service in 2007 increased the odds of turnover in male and female juniors and in female officers. Female juniors with less effective skills for coping with stress and who exercised less frequently on a weekly basis were more likely to leave. An incidental finding was that the odds of turnover were three times greater in female officers with children than in female officers with no children. Stress management interventions focusing on effective coping and sports and exercise participation which are targeted appropriately may improve retention. PMID:24047248

  1. Cell signalling and phospholipid metabolism

    SciTech Connect

    Boss, W.F.

    1989-01-01

    Our research for the past two years has involved the study of phosphoinositides and their potential role in regulating plant growth and development. Our initial goal was to document the sequence of events involved in inositol phospholipid metabolism in response to external stimuli. Our working hypothesis was that phosphatidylinositol bisphosphate (PIP/sub 2/) was in the plasma membrane of plants cells and would be hydrolyzed by phospholipase C to yield the second messengers inositol triphosphate (IP/sub 3/) and diacyglycerol (DAG) and that IP/sub 3/ would mobilize intracellular calcium as has been shown for animal cells. Our results with both carrot suspension culture cells and sunflower hypocotyl indicate that this paradigm is not the primary mechanism of signal transduction in these systems. We have observed very rapid, within 5 sec, stimulation of phosphatidylinositol monophosphate (PIP) kinase which resulted in an increase in PIP/sub 2/. However, there was no evidence for activation of phospholipase C. In addition, we have shown that PIP and PIP/sub 2/ can activate the plasma membrane ATPase. The results of these studies are described briefly in the paragraphs below. Inositol phospholipids are localized in distinct membrane fractions. If PIP and PIP/sub 2/ play a role in the transduction of external signals, they should be present in the plasma membrane. We used the fusogenic carrot suspension culture cells as a model system to study the distribution of inositol phospholipids in various membrane fractions and organelles. Cells were labeled 12 to 18 h with myo(2-/sup 3/H) inositol and the membranes were isolated by aqueous two-phase partitioning. The plasma membrane was enriched in PIP and PIP/sub 2/ compared to the intracellular membranes.

  2. Phospholipid liposomes functionalized by protein

    NASA Astrophysics Data System (ADS)

    Glukhova, O. E.; Savostyanov, G. V.; Grishina, O. A.

    2015-03-01

    Finding new ways to deliver neurotrophic drugs to the brain in newborns is one of the contemporary problems of medicine and pharmaceutical industry. Modern researches in this field indicate the promising prospects of supramolecular transport systems for targeted drug delivery to the brain which can overcome the blood-brain barrier (BBB). Thus, the solution of this problem is actual not only for medicine, but also for society as a whole because it determines the health of future generations. Phospholipid liposomes due to combination of lipo- and hydrophilic properties are considered as the main future objects in medicine for drug delivery through the BBB as well as increasing their bioavailability and toxicity. Liposomes functionalized by various proteins were used as transport systems for ease of liposomes use. Designing of modification oligosaccharide of liposomes surface is promising in the last decade because it enables the delivery of liposomes to specific receptor of human cells by selecting ligand and it is widely used in pharmacology for the treatment of several diseases. The purpose of this work is creation of a coarse-grained model of bilayer of phospholipid liposomes, functionalized by specific to the structural elements of the BBB proteins, as well as prediction of the most favorable orientation and position of the molecules in the generated complex by methods of molecular docking for the formation of the structure. Investigation of activity of the ligand molecule to protein receptor of human cells by the methods of molecular dynamics was carried out.

  3. Role of phospholipids in the actions of prolactin in the mammary gland

    SciTech Connect

    Etindi, R.O.N.

    1987-01-01

    These studies were designed to determine the role of phospholipid turnover in the mechanism of action of prolactin in mammary gland explants derived from 12-14 day pregnant mice. Prolactin stimulates phospholipid biosynthesis 12-16h after cultured mouse mammary tissues are exposed to it. Prolactin stimulates phospholipid biosynthesis at physiological concentrations and the response is maximal at all PRL concentrations above 25 ng/ml. p-Bromphenacyl bromide (BPB) at concentrations of 50 ..mu..M and above and quinacrine (50 ..mu..M) abolish the actions of prolactin on casein and lipid biosynthesis in cultured mouse mammary gland explants. In mouse mammary gland explants, binding of prolactin to its receptor leads to a phospholipase C type hydrolysis of inositol phospholipids, but this effect is transient and does not occur immediately after hormone exposure. Prolactin significantly stimulated the accumulation of (/sup 3/H)label in inositol monophosphate (IP/sub 1/), inositol bisphosphate (IP/sub 2/) and inositol trisphosphate (IP/sub 3/) 1-3 hours after addition of prolactin. Gossypol, a drug which has been shown to be an inhibitor of kinase C activity in mouse mammary tissues, is shown to abolish several of the actions of prolactin in cultured mouse mammary gland expalants.

  4. Phospholipid composition of cultured human endothelial cells.

    PubMed

    Murphy, E J; Joseph, L; Stephens, R; Horrocks, L A

    1992-02-01

    Detailed analyses of the phospholipid compositions of cultured human endothelial cells are reported here. No significant differences were found between the phospholipid compositions of cells from human artery, saphenous and umbilical vein. However, due to the small sample sizes, relatively large standard deviations for some of the phospholipid classes were observed. A representative composition of endothelial cells is: phosphatidylcholine 36.6%, choline plasmalogen 3.7%, phosphatidylethanolamine 10.2%, ethanolamine plasmalogen 7.6%, sphingomyelin 10.8%, phosphatidylserine 7.1%, lysophosphatidylcholine 7.5%, phosphatidylinositol 3.1%, lysophosphatidylethanolamine 3.6%, phosphatidylinositol 4,5-bisphosphate 1.8%, phosphatidic acid 1.9%, phosphatidylinositol 4-phosphate 1.5%, and cardiolipin 1.9%. The cells possess high choline plasmalogen and lysophosphatidylethanolamine contents. The other phospholipids are within the normal biological ranges expected. Phospholipids were separated by high-performance liquid chromatography and quantified by lipid phosphorus assay. PMID:1315902

  5. Extensive exchange of rat liver microsomal phospholipids.

    PubMed

    Zilversmit, D B; Hughes, M E

    1977-08-15

    Liver microsomal fractions were prepared from rats injected with a single dose of choline [14C]methylchloride or with single or multiple doses of 32Pi. Exchangeability of microsomal phospholipids was determined by incubation with an excess of mitochondria and phospholipid exchange proteins derived from beef heart, beef liver or rat liver. Labeled phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were found to act as a single pool and were 85--95% exchangeable in 1--2h. High latencies of mannose-6-phosphate phosphohydrolase activities and impermeability of microsomes to EDTA proved that phospholipid exchange proteins did not have access to the intracisternal space. If microsomal membranes are largely composed of phospholipid bilayers, the experiments suggest that one or more of the phospholipid classes in microsomal membranes undergo rapid translocation between the inner and outer portions of the bilayer. PMID:889827

  6. Patterning and characterization of model phospholipid membranes

    NASA Astrophysics Data System (ADS)

    Kassu, Aschalew; Calzzani, Fernando A., Jr.; Taguenang, Jean M.; Sileshi, Redahegn K.; Sharma, Anup

    2008-08-01

    Phospholipid, which is a building block of biological membranes, plays an important role in compartmentalization of cellular reaction environment and control of the physicochemical conditions inside the reaction environment. Phospholipid bilayer membrane has been proposed as a natural biocompatible platform for attaching biological molecules like proteins for biosensing related application. Due to the enormous potential applications of biomimetic model biomembranes, various techniques for depositions and patterning of these membranes onto solid supports and their possible biotechnological applications have been reported by different groups. In this work, patterning of phospholipid thin-films is accomplished by interferometric lithography as well as using lithographic masks in liquid phase. Surface Enhanced Raman Spectroscopy and Atomic Force microscopy are used to characterize the model phospholipid membrane and the patterning technique. We describe an easy and reproducible technique for direct patterning of azo-dye (NBD)-labeled phospholipid (phosphatidylcholine) in aqueous medium using a low-intensity 488 nm Ar+ laser and various kinds of lithographic masks.

  7. Peroxidase activation of cytoglobin by anionic phospholipids: Mechanisms and consequences.

    PubMed

    Tejero, Jesús; Kapralov, Alexandr A; Baumgartner, Matthew P; Sparacino-Watkins, Courtney E; Anthonymutu, Tamil S; Vlasova, Irina I; Camacho, Carlos J; Gladwin, Mark T; Bayir, Hülya; Kagan, Valerian E

    2016-05-01

    Cytoglobin (Cygb) is a hexa-coordinated hemoprotein with yet to be defined physiological functions. The iron coordination and spin state of the Cygb heme group are sensitive to oxidation of two cysteine residues (Cys38/Cys83) and/or the binding of free fatty acids. However, the roles of redox vs lipid regulators of Cygb's structural rearrangements in the context of the protein peroxidase competence are not known. Searching for physiologically relevant lipid regulators of Cygb, here we report that anionic phospholipids, particularly phosphatidylinositolphosphates, affect structural organization of the protein and modulate its iron state and peroxidase activity both conjointly and/or independently of cysteine oxidation. Thus, different anionic lipids can operate in cysteine-dependent and cysteine-independent ways as inducers of the peroxidase activity. We establish that Cygb's peroxidase activity can be utilized for the catalysis of peroxidation of anionic phospholipids (including phosphatidylinositolphosphates) yielding mono-oxygenated molecular species. Combined with the computational simulations we propose a bipartite lipid binding model that rationalizes the modes of interactions with phospholipids, the effects on structural re-arrangements and the peroxidase activity of the hemoprotein. PMID:26928591

  8. Effect of Cholesterol on the Structure of a Five-Component Mitochondria-Like Phospholipid Membrane

    PubMed Central

    Cathcart, Kelly; Patel, Amit; Dies, Hannah; Rheinstädter, Maikel C.; Fradin, Cécile

    2015-01-01

    Cellular membranes have a complex phospholipid composition that varies greatly depending on the organism, cell type and function. In spite of this complexity, most structural data available for phospholipid bilayers concern model systems containing only one or two different phospholipids. Here, we examine the effect of cholesterol on the structure of a complex membrane reflecting the lipid composition of mitochondrial membranes, with five different types of headgroups (phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS) and cardiolipin (CL)) and a variety of hydrocarbon tails. This particular system was chosen because elevated cholesterol contents in mitochondrial membranes have been linked to a breaking down of Bax-mediated membrane permeabilization and resistance to cancer treatments. High resolution electron density profiles were determined by X-ray reflectivity, while the area per phospholipid chain, Apc, and the chain order parameter, SX-ray, were determined by wide-angle X-ray scattering (WAXS). We show that chain order increases upon the addition of cholesterol, resulting in both a thickening of the lipid bilayer and a reduction in the average surface area per phospholipid chain. This effect, well known as cholesterol’s condensation effect, is similar, but not as pronounced as for single-component phospholipid membranes. We conclude by discussing the relevance of these findings for the insertion of the pro-apoptotic protein Bax in mitochondrial membranes with elevated cholesterol content. PMID:26529029

  9. Molecular Mechanisms for Biliary Phospholipid and Drug Efflux Mediated by ABCB4 and Bile Salts

    PubMed Central

    Terada, Tomohiro

    2014-01-01

    On the canalicular membranes of hepatocytes, several ABC transporters are responsible for the secretion of bile lipids. Among them, ABCB4, also called MDR3, is essential for the secretion of phospholipids from hepatocytes into bile. The biliary phospholipids are associated with bile salts and cholesterol in mixed micelles, thereby reducing the detergent activity and cytotoxicity of bile salts and preventing cholesterol crystallization. Mutations in the ABCB4 gene result in progressive familial intrahepatic cholestasis type 3, intrahepatic cholestasis of pregnancy, low-phospholipid-associated cholelithiasis, primary biliary cirrhosis, and cholangiocarcinoma. In vivo and cell culture studies have demonstrated that the secretion of biliary phospholipids depends on both ABCB4 expression and bile salts. In the presence of bile salts, ABCB4 located in nonraft membranes mediates the efflux of phospholipids, preferentially phosphatidylcholine. Despite high homology with ABCB1, ABCB4 expression cannot confer multidrug resistance. This review summarizes our current understanding of ABCB4 functions and physiological relevance, and discusses the molecular mechanism for the ABCB4-mediated efflux of phospholipids. PMID:25133187

  10. Localization of Anionic Phospholipids in Escherichia coli Cells

    PubMed Central

    Oliver, Piercen M.; Crooks, John A.; Leidl, Mathias; Yoon, Earl J.; Saghatelian, Alan

    2014-01-01

    Cardiolipin (CL) is an anionic phospholipid with a characteristically large curvature and is of growing interest for two primary reasons: (i) it binds to and regulates many peripheral membrane proteins in bacteria and mitochondria, and (ii) it is distributed asymmetrically in rod-shaped cells and is concentrated at the poles and division septum. Despite the growing number of studies of CL, its function in bacteria remains unknown. 10-N-Nonyl acridine orange (NAO) is widely used to image CL in bacteria and mitochondria, as its interaction with CL is reported to produce a characteristic red-shifted fluorescence emission. Using a suite of biophysical techniques, we quantitatively studied the interaction of NAO with anionic phospholipids under physiologically relevant conditions. We found that NAO is promiscuous in its binding and has photophysical properties that are largely insensitive to the structure of diverse anionic phospholipids to which it binds. Being unable to rely solely on NAO to characterize the localization of CL in Escherichia coli cells, we instead used quantitative fluorescence microscopy, mass spectrometry, and mutants deficient in specific classes of anionic phospholipids. We found CL and phosphatidylglycerol (PG) concentrated in the polar regions of E. coli cell membranes; depletion of CL by genetic approaches increased the concentration of PG at the poles. Previous studies suggested that some CL-binding proteins also have a high affinity for PG and display a pattern of cellular localization that is not influenced by depletion of CL. Framed within the context of these previous experiments, our results suggest that PG may play an essential role in bacterial physiology by maintaining the anionic character of polar membranes. PMID:25002539

  11. Analyzing plant signaling phospholipids through 32Pi-labeling and TLC.

    PubMed

    Munnik, Teun; Zarza, Xavier

    2013-01-01

    Lipidomic analyses through LC-, GC-, and ESI-MS/MS can detect numerous lipid species based on headgroup and fatty acid compositions but usually miss the minor phospholipids involved in cell signaling because of their low chemical abundancy. Due to their high turnover, these signaling lipids are, however, readily picked up by labeling plant material with (32)P-orthophosphate and subsequent analysis of the lipid extracts by thin layer chromatography. Here, protocols are described for suspension-cultured tobacco BY-2 cells, young Arabidopsis seedlings, Vicia faba roots, and Arabidopsis leaf disks, which can easily be modified for other plant species and tissues. PMID:23681518

  12. Mitochondrial phospholipids: role in mitochondrial function.

    PubMed

    Mejia, Edgard M; Hatch, Grant M

    2016-04-01

    Mitochondria are essential components of eukaryotic cells and are involved in a diverse set of cellular processes that include ATP production, cellular signalling, apoptosis and cell growth. These organelles are thought to have originated from a symbiotic relationship between prokaryotic cells in an effort to provide a bioenergetic jump and thus, the greater complexity observed in eukaryotes (Lane and Martin 2010). Mitochondrial processes are required not only for the maintenance of cellular homeostasis, but also allow cell to cell and tissue to tissue communication (Nunnari and Suomalainen 2012). Mitochondrial phospholipids are important components of this system. Phospholipids make up the characteristic outer and inner membranes that give mitochondria their shape. In addition, these membranes house sterols, sphingolipids and a wide variety of proteins. It is the phospholipids that also give rise to other characteristic mitochondrial structures such as cristae (formed from the invaginations of the inner mitochondrial membrane), the matrix (area within cristae) and the intermembrane space (IMS) which separates the outer mitochondrial membrane (OMM) and inner mitochondrial membrane (IMM). Phospholipids are the building blocks that make up these structures. However, the phospholipid composition of the OMM and IMM is unique in each membrane. Mitochondria are able to synthesize some of the phospholipids it requires, but the majority of cellular lipid biosynthesis takes place in the endoplasmic reticulum (ER) in conjunction with the Golgi apparatus (Fagone and Jackowski 2009). In this review, we will focus on the role that mitochondrial phospholipids play in specific cellular functions and discuss their biosynthesis, metabolism and transport as well as the differences between the OMM and IMM phospholipid composition. Finally, we will focus on the human diseases that result from disturbances to mitochondrial phospholipids and the current research being performed to help

  13. Microbial carbon turnover in the plant-rhizosphere-soil continuum

    NASA Astrophysics Data System (ADS)

    Malik, Ashish; Dannert, Helena; Griffiths, Robert; Thomson, Bruce; Gleixner, Gerd

    2014-05-01

    Soil microbial biomass contributes significantly to maintenance of soil organic matter (SOM). It is well known that biochemical fractions of soil microorganisms have varying turnover and therefore contribute differentially to soil C storage. Here we compare the turnover rates of different microbial biochemical fractions using a pulse chase 13CO2 plant labelling experiment. The isotope signal was temporally traced into rhizosphere soil microorganisms using the following biomarkers: DNA, RNA, fatty acids and chloroform fumigation extraction derived microbial biomass size classes. C flow into soil microbial functional groups was assessed through phospholipid and neutral lipid fatty acid (PLFA/NLFA) analyses. Highest 13C enrichment was seen in the low molecular weight (LMW) size class of microbial biomass (Δδ13C =151) and in nucleic acids (DNA: 38o RNA: 66) immediately after the pulse followed by a sharp drop. The amount of 13C in the high molecular weight (HMW) microbial biomass (17-81) and total fatty acids (32-54) was lower initially and stayed relatively steady over the 4 weeks experimental period. We found significant differences in turnover rates of different microbial biochemical and size fractions. We infer that LMW cytosolic soluble compounds are rapidly metabolized and linked to respiratory C fluxes, whereas mid-sized products of microbial degradation and HMW polymeric compounds have lower renewal rate in that order. The turnover of cell wall fatty acids was also very slow. DNA and RNA showed faster turnover rate; and as expected RNA renewal was the fastest due to its rapid production by active microorganisms independent of cell replication. 13C incorporation into different functional groups confirmed that mutualistic arbuscular mycorrhizal fungi rely on root C and are important in the initial plant C flux. We substantiated through measurements of isotope incorporation into bacterial RNA that rhizosphere bacteria are also important in the initial C conduit

  14. LIPID PEROXIDATION GENERATES BIOLOGICALLY ACTIVE PHOSPHOLIPIDS INCLUDING OXIDATIVELY N-MODIFIED PHOSPHOLIPIDS

    PubMed Central

    Davies, Sean S.; Guo, Lilu

    2014-01-01

    Peroxidation of membranes and lipoproteins converts “inert” phospholipids into a plethora of oxidatively modified phospholipids (oxPL) that can act as signaling molecules. In this review, we will discuss four major classes of oxPL: mildly oxygenated phospholipids, phospholipids with oxidatively truncated acyl chains, phospholipids with cyclized acyl chains, and phospholipids that have been oxidatively N-modified on their headgroups by reactive lipid species. For each class of oxPL we will review the chemical mechanisms of their formation, the evidence for their formation in biological samples, the biological activities and signaling pathways associated with them, and the catabolic pathways for their elimination. We will end by briefly highlighting some of the critical questions that remain about the role of oxPL in physiology and disease. PMID:24704586

  15. Vinculin acts as a sensor in lipid regulation of adhesion-site turnover.

    PubMed

    Chandrasekar, Indra; Stradal, Theresia E B; Holt, Mark R; Entschladen, Frank; Jockusch, Brigitte M; Ziegler, Wolfgang H

    2005-04-01

    The dynamics of cell adhesion sites control cell morphology and motility. Adhesion-site turnover is thought to depend on the local availability of the acidic phospholipid phosphatidylinositol-4,5-bisphosphate (PIP(2)). PIP(2) can bind to many cell adhesion proteins such as vinculin and talin, but the consequences of this interaction are poorly understood. To study the significance of phospholipid binding to vinculin for adhesion-site turnover and cell motility, we constructed a mutant, vinculin-LD, deficient in acidic phospholipid binding yet with functional actin-binding sites. When expressed in cells, vinculin-LD was readily recruited to adhesion sites, as judged by fluorescence recovery after photobleaching (FRAP) analysis, but cell spreading and migration were strongly impaired, and PIP(2)-dependent disassembly of adhesions was suppressed. Thus, PIP(2) binding is not essential for vinculin activation and recruitment, as previously suggested. Instead, we propose that PIP(2) levels can regulate the uncoupling of adhesion sites from the actin cytoskeleton, with vinculin functioning as a sensor. PMID:15769850

  16. [Phospholipids metabolism disorders in acute stroke].

    PubMed

    Solovieva, E Yu; Farrahova, K I; Karneev, A N; Chipova, D T

    2016-01-01

    The disturbances of cerebral circulation results in the violation of phospholipid metabolism. Activation of lipid peroxidation and protein kinase C and release of intracellular calcium leads to disruption of the homeostasis of phosphatidylcholine. The use of cytidine-5-diphosphocholine, which is used as an intermediate compound in the biosynthesis of phospholipids of the cell membrane, helps to stabilize cell membranes, and reduce the formation of free radicals. PMID:27045147

  17. Cell signalling and phospholipid metabolism. Final report

    SciTech Connect

    Boss, W.F.

    1990-12-31

    These studies explored whether phosphoinositide (PI) has a role in plants analogous to its role in animal cells. Although no parallel activity of PI in signal transduction was found in plant cells, activity of inositol phospholipid kinase was found to be modulated by light and by cell wall degrading enzymes. These studies indicate a major role for inositol phospholipids in plant growth and development as membrane effectors but not as a source of second messengers.

  18. Phospholipids and fatty acids of Neisseria gonorrhoeae.

    PubMed Central

    Sud, I J; Feingold, D S

    1975-01-01

    The phospholipids and fatty acids of two strains of Neisseria gonorrhoeae of different penicillin susceptibilities were examined. The phospholipids, which comprise about 8% of the dry weight of the cells, consisted of phosphatidylethanolamine (70%) and phosphatidylglycerol (20%); small amounts of phosphatidylcholine and traces of cardiolipin were also present. Growing and stationary-phase cells were similar in content and composition of phospholipids except for phosphatidylcholine, which increased two- to fivefold in the stationary-phase cells. The fatty acids of the phospholipids were characterized by two major acids, palmitic and a C16:1, with myristic and a C18:1 acid present in smaller amounts. The fatty acids present in purified phospholipid fractions varied considerably in relative proportions from fraction to fraction. No significant difference in the composition of phospholipids from the two strains was evident. Large amounts of beta-hydroxy lauric acid were detected only after saponification of the organisms. Differences in the lipid composition between the gonococcus and other gram-negative bacteria are discussed. PMID:810478

  19. Metabolomics annotates ABHD3 as a physiologic regulator of medium-chain phospholipids

    PubMed Central

    Long, Jonathan Z.; Cisar, Justin S.; Milliken, David; Niessen, Sherry; Wang, Chu; Trauger, Sunia A.; Siuzdak, Gary; Cravatt, Benjamin F.

    2011-01-01

    All organisms, including humans, possess a huge number of uncharacterized enzymes. Here, we describe a general cell-based screen for enzyme substrate discovery by untargeted metabolomics and its application to identify α/β-hydrolase domain-containing 3 (ABHD3) as a lipase that selectively cleaves medium-chain and oxidatively-truncated phospholipids. Abhd3−/− mice possess elevated myristoyl (C14)-phospholipids, including the bioactive lipid C14-lysophosphatidylcholine, confirming the physiological relevance of our substrate assignments. PMID:21926997

  20. Turnover in the Advancement Profession

    ERIC Educational Resources Information Center

    Iarrobino, Jon D.

    2006-01-01

    Recruitment and retention is an area with which most organizations are concerned. Excessive turnover has exorbitant costs and wastes valuable time. Institutions of higher education are no exception. One of the most vital operations in nonprofit colleges and universities is its Office of Institutional Advancement. More and more, an institution of…

  1. Co-ordination between membrane phospholipid synthesis and accelerated biosynthesis of cytoplasmic ribonucleic acid and protein

    PubMed Central

    Tata, J. R.

    1970-01-01

    1. The rate of synthesis of membrane phospholipid was studied in rat liver and seminal vesicles by following the incorporation of [32P]orthophosphate, [14C]choline and [14C]glycerol. Particular emphasis was laid on the endoplasmic reticulum, which was fractionated into smooth microsomal membranes, heavy rough membranes, light rough membranes and free polyribosomes. 2. Phospholipid labelling patterns suggested a heterogeneity in the synthesis and turnover of the different lipid moieties of smooth and rough endoplasmic membranes. The major phospholipids, phosphatidylcholine and phosphatidylethanolamine, were labelled relatively rapidly with 32P over a short period of time whereas incorporation of radioisotope into the minor phospholipids, sphingomyelin, lysolecithin and phosphatidylinositol proceeded slowly but over a longer period of time. 3. The incorporation of orotic acid into RNA and labelled amino acids into protein of the four submicrosomal fractions was also studied. 4. Rapid growth of the liver was induced by the administration of growth hormone and tri-iodothyronine to hypophysectomized and thyroidectomized rats and by partial hepatectomy. Growth of seminal vesicles of castrated rats was stimulated with testosterone propionate. 5. The rate of labelling of membrane phospholipids was enhanced in all major subcellular particulate fractions (nuclear, mitochondrial and microsomal) during induced growth. However, it was in the rough endoplasmic reticulum that the accumulation of phospholipids, RNA and protein was most marked. The effect of hormone administration was also to accelerate preferentially the labelling with 32P of sphingomyelin relative to that of phosphatidylcholine or phosphatidylethanolamine. 6. Time-course analyses showed that, in all four growth systems studied, the enhancement of the rate of membrane phospholipid synthesis coincided with the rather abrupt increase in the synthesis of RNA and protein of the rough endoplasmic reticulum. Growth

  2. Nonenzymatic Reactions above Phospholipid Surfaces of Biological Membranes: Reactivity of Phospholipids and Their Oxidation Derivatives

    PubMed Central

    Solís-Calero, Christian; Ortega-Castro, Joaquín; Frau, Juan; Muñoz, Francisco

    2015-01-01

    Phospholipids play multiple and essential roles in cells, as components of biological membranes. Although phospholipid bilayers provide the supporting matrix and surface for many enzymatic reactions, their inherent reactivity and possible catalytic role have not been highlighted. As other biomolecules, phospholipids are frequent targets of nonenzymatic modifications by reactive substances including oxidants and glycating agents which conduct to the formation of advanced lipoxidation end products (ALEs) and advanced glycation end products (AGEs). There are some theoretical studies about the mechanisms of reactions related to these processes on phosphatidylethanolamine surfaces, which hypothesize that cell membrane phospholipids surface environment could enhance some reactions through a catalyst effect. On the other hand, the phospholipid bilayers are susceptible to oxidative damage by oxidant agents as reactive oxygen species (ROS). Molecular dynamics simulations performed on phospholipid bilayers models, which include modified phospholipids by these reactions and subsequent reactions that conduct to formation of ALEs and AGEs, have revealed changes in the molecular interactions and biophysical properties of these bilayers as consequence of these reactions. Then, more studies are desirable which could correlate the biophysics of modified phospholipids with metabolism in processes such as aging and diseases such as diabetes, atherosclerosis, and Alzheimer's disease. PMID:25977746

  3. Mammalian Glucose Transporter Activity Is Dependent upon Anionic and Conical Phospholipids.

    PubMed

    Hresko, Richard C; Kraft, Thomas E; Quigley, Andrew; Carpenter, Elisabeth P; Hruz, Paul W

    2016-08-12

    The regulated movement of glucose across mammalian cell membranes is mediated by facilitative glucose transporters (GLUTs) embedded in lipid bilayers. Despite the known importance of phospholipids in regulating protein structure and activity, the lipid-induced effects on the GLUTs remain poorly understood. We systematically examined the effects of physiologically relevant phospholipids on glucose transport in liposomes containing purified GLUT4 and GLUT3. The anionic phospholipids, phosphatidic acid, phosphatidylserine, phosphatidylglycerol, and phosphatidylinositol, were found to be essential for transporter function by activating it and stabilizing its structure. Conical lipids, phosphatidylethanolamine and diacylglycerol, enhanced transporter activity up to 3-fold in the presence of anionic phospholipids but did not stabilize protein structure. Kinetic analyses revealed that both lipids increase the kcat of transport without changing the Km values. These results allowed us to elucidate the activation of GLUT by plasma membrane phospholipids and to extend the field of membrane protein-lipid interactions to the family of structurally and functionally related human solute carriers. PMID:27302065

  4. Mammalian Glucose Transporter Activity Is Dependent upon Anionic and Conical Phospholipids*

    PubMed Central

    Hresko, Richard C.; Kraft, Thomas E.; Quigley, Andrew; Carpenter, Elisabeth P.; Hruz, Paul W.

    2016-01-01

    The regulated movement of glucose across mammalian cell membranes is mediated by facilitative glucose transporters (GLUTs) embedded in lipid bilayers. Despite the known importance of phospholipids in regulating protein structure and activity, the lipid-induced effects on the GLUTs remain poorly understood. We systematically examined the effects of physiologically relevant phospholipids on glucose transport in liposomes containing purified GLUT4 and GLUT3. The anionic phospholipids, phosphatidic acid, phosphatidylserine, phosphatidylglycerol, and phosphatidylinositol, were found to be essential for transporter function by activating it and stabilizing its structure. Conical lipids, phosphatidylethanolamine and diacylglycerol, enhanced transporter activity up to 3-fold in the presence of anionic phospholipids but did not stabilize protein structure. Kinetic analyses revealed that both lipids increase the kcat of transport without changing the Km values. These results allowed us to elucidate the activation of GLUT by plasma membrane phospholipids and to extend the field of membrane protein-lipid interactions to the family of structurally and functionally related human solute carriers. PMID:27302065

  5. Filamentous Fungi with High Cytosolic Phospholipid Transfer Activity in the Presence of Exogenous Phospholipid

    PubMed Central

    Record, Eric; Lesage, Laurence; Cahagnier, Bernard; Marion, Didier; Asther, Marcel

    1994-01-01

    The phospholipid transfer activity of cell extracts from 15 filamentous fungus strains grown on a medium containing phospholipids as the carbon source was measured by a fluorescence assay. This assay was based on the transfer of pyrene-labeled phosphatidylcholines forming the donor vesicles to acceptor vesicles composed of egg phosphatidylcholines. The highest phosphatidylcholine transfer activity was obtained with cell extracts from Aspergillus oryzae. The presence of exogenous phospholipids in the culture medium of A. oryzae was shown to increase markedly the activity of phospholipid transfer as well as the pool of exocellular proteins during the primary phase of growth. Modifications in the biochemical marker activities of cellular organelles were observed: succinate dehydrogenase, a mitochondrial marker; inosine diphosphatase, a Golgi system marker; and cytochrome c oxidoreductase, an endoplasmic reticulum marker, were increased 7.3-, 2-, and 22-fold, respectively, when A. oryzae was grown in the presence of phospholipids. PMID:16349388

  6. Chronic Teacher Turnover in Urban Elementary Schools

    ERIC Educational Resources Information Center

    Guin, Kacey

    2004-01-01

    This study examines the characteristics of elementary schools that experience chronic teacher turnover and the impacts of turnover on a school's working climate and ability to effectively function. Based on evidence from staff climate surveys and case studies, it is clear that high turnover schools face significant organizational challenges.…

  7. Estimating Teacher Turnover Costs: A Case Study

    ERIC Educational Resources Information Center

    Levy, Abigail Jurist; Joy, Lois; Ellis, Pamela; Jablonski, Erica; Karelitz, Tzur M.

    2012-01-01

    High teacher turnover in large U.S. cities is a critical issue for schools and districts, and the students they serve; but surprisingly little work has been done to develop methodologies and standards that districts and schools can use to make reliable estimates of turnover costs. Even less is known about how to detect variations in turnover costs…

  8. Measuring Staff Turnover in Nursing Homes

    ERIC Educational Resources Information Center

    Castle, Nicholas G.

    2006-01-01

    Purpose: In this study the levels of staff turnover reported in the nursing home literature (1990-2003) are reviewed, as well as the definitions of turnover used in these prior studies. With the use of primary data collected from 354 facilities, the study addresses the various degrees of bias that result, depending on how staff turnover is defined…

  9. Using Turnover as a Recruitment Strategy

    ERIC Educational Resources Information Center

    Duncan, Sandra

    2009-01-01

    Teacher turnover is notoriously high in the field of early childhood education with an estimated 33% of staff exiting the workplace each year. Turnover is costly. Not only do high levels of turnover negatively impact children's growth and development, it also erodes the program's economic stability and wherewithal to provide effective operations…

  10. How Teacher Turnover Harms Student Achievement

    ERIC Educational Resources Information Center

    Ronfeldt, Matthew; Loeb, Susanna; Wyckoff, James

    2013-01-01

    Researchers and policymakers often assume that teacher turnover harms student achievement, though recent studies suggest this may not be the case. Using a unique identification strategy that employs school-by-grade level turnover and two classes of fixed-effects models, this study estimates the effects of teacher turnover on over 850,000 New York…

  11. Benchmarking of homogeneous electrocatalysts: overpotential, turnover frequency, limiting turnover number.

    PubMed

    Costentin, Cyrille; Passard, Guillaume; Savéant, Jean-Michel

    2015-04-29

    In relation to contemporary energy challenges, a number of molecular catalysts for the activation of small molecules, mainly based on transition metal complexes, have been developed. The time has thus come to develop tools allowing the benchmarking of these numerous catalysts. Two main factors of merit are addressed. One involves their intrinsic catalytic performances through the comparison of "catalytic Tafel plots" relating the turnover frequency to the overpotential independently of the characteristics of the electrochemical cell. The other examines the effect of deactivation of the catalyst during the course of electrolysis. It introduces the notion of the limiting turnover number as a second key element of catalyst benchmarking. How these two factors combine with one another to control the course of electrolysis is analyzed in detail, leading to procedures that allow their separate estimation from measurements of the current, the charge passed, and the decay of the catalyst concentration. Illustrative examples from literature data are discussed. PMID:25757058

  12. Polyhydroxyalkanoate (PHA) Granules Have no Phospholipids.

    PubMed

    Bresan, Stephanie; Sznajder, Anna; Hauf, Waldemar; Forchhammer, Karl; Pfeiffer, Daniel; Jendrossek, Dieter

    2016-01-01

    Polyhydroxybutyrate (PHB) granules, also designated as carbonosomes, are supra-molecular complexes in prokaryotes consisting of a PHB polymer core and a surface layer of structural and functional proteins. The presence of suspected phospholipids in the surface layer is based on in vitro data of isolated PHB granules and is often shown in cartoons of the PHB granule structure in reviews on PHB metabolism. However, the in vivo presence of a phospholipid layer has never been demonstrated. We addressed this topic by the expression of fusion proteins of DsRed2EC and other fluorescent proteins with the phospholipid-binding domain (LactC2) of lactadherin in three model organisms. The fusion proteins specifically localized at the cell membrane of Ralstonia eutropha but did not co-localize with PHB granules. The same result was obtained for Pseudomonas putida, a species that accumulates another type of polyhydroxyalkanoate (PHA) granules related to PHB. Notably, DsRed2EC-LactC2 expressed in Magnetospirillum gryphiswaldense was detected at the position of membrane-enclosed magnetosome chains and at the cytoplasmic membrane but not at PHB granules. In conclusion, the carbonosomes of representatives of α-proteobacteria, β-proteobacteria and γ-proteobacteria have no phospholipids in vivo and we postulate that the PHB/PHA granule surface layers in natural producers generally are free of phospholipids and consist of proteins only. PMID:27222167

  13. Polyhydroxyalkanoate (PHA) Granules Have no Phospholipids

    PubMed Central

    Bresan, Stephanie; Sznajder, Anna; Hauf, Waldemar; Forchhammer, Karl; Pfeiffer, Daniel; Jendrossek, Dieter

    2016-01-01

    Polyhydroxybutyrate (PHB) granules, also designated as carbonosomes, are supra-molecular complexes in prokaryotes consisting of a PHB polymer core and a surface layer of structural and functional proteins. The presence of suspected phospholipids in the surface layer is based on in vitro data of isolated PHB granules and is often shown in cartoons of the PHB granule structure in reviews on PHB metabolism. However, the in vivo presence of a phospholipid layer has never been demonstrated. We addressed this topic by the expression of fusion proteins of DsRed2EC and other fluorescent proteins with the phospholipid-binding domain (LactC2) of lactadherin in three model organisms. The fusion proteins specifically localized at the cell membrane of Ralstonia eutropha but did not co-localize with PHB granules. The same result was obtained for Pseudomonas putida, a species that accumulates another type of polyhydroxyalkanoate (PHA) granules related to PHB. Notably, DsRed2EC-LactC2 expressed in Magnetospirillum gryphiswaldense was detected at the position of membrane-enclosed magnetosome chains and at the cytoplasmic membrane but not at PHB granules. In conclusion, the carbonosomes of representatives of α-proteobacteria, β-proteobacteria and γ-proteobacteria have no phospholipids in vivo and we postulate that the PHB/PHA granule surface layers in natural producers generally are free of phospholipids and consist of proteins only. PMID:27222167

  14. Altered bone turnover during spaceflight

    NASA Technical Reports Server (NTRS)

    Turner, R. T.; Morey, E. R.; Liu, C.; Baylink, D. J.

    1982-01-01

    Modifications in calcium metabolism during spaceflight were studied, using parameters that reflect bone turnover. Bone formation rate, medullary area, bone length, bone density, pore size distribution, and differential bone cell number were evaluated in growing rate both immediately after and 25 days after orbital spaceflights aboard the Soviet biological satellites Cosmos 782 and 936. The primary effect of space flight on bone turnover was a reversible inhibition of bone formation at the periosteal surface. A simultaneous increase in the length of the periosteal arrest line suggests that bone formation ceased along corresponding portions of that surface. Possible reasons include increased secretion of glucocorticoids and mechanical unloading of the skeleton due to near-weightlessness, while starvation and immobilization are excluded as causes.

  15. Turnover: strategies for staff retention.

    PubMed

    SnowAntle, S

    1990-01-01

    This discussion has focused on a number of areas where organizations may find opportunities for more effectively managing employee retention. Given the multitude of causes and consequences, there is no one quick fix. Effective management of employee retention requires assessment of the entire human resources process, that is, recruitment, selection, job design, compensation, supervision, work conditions, etc. Regular and systematic diagnosis of turnover and implementation of multiple strategies and evaluation are needed (Mobley, 1982). PMID:10106673

  16. Phospholipids accumulation in mucolipidosis IV cultured fibroblasts.

    PubMed

    Bargal, R; Bach, G

    1988-01-01

    Cultured fibroblasts from mucolipidosis IV patients accumulated phospholipids when compared to normal controls or cells from other genotypes. The major stored compounds were identified as phosphatidylcholine, phosphatidylethanolamine and to a larger extent lysophosphatidylcholine and lysobisphosphatidic acid. Pulse chase experiments of 32P-labelled phospholipids showed increased retention of these compounds in the mucolipidosis IV lines throughout the pulse and chase periods. Phospholipase A1, A2, C, D and lysophospholipase showed normal activity in the mucolipidosis IV lines and thus the metabolic cause for this storage remains to be identified. PMID:3139925

  17. Phospholipid exchange reactions within the liver cell

    PubMed Central

    McMurray, W. C.; Dawson, R. M. C.

    1969-01-01

    1. Isolated rat liver mitochondria do not synthesize labelled phosphatidylcholine from CDP-[14C]choline or any phospholipid other than phosphatidic acid from [32P]phosphate. The minimal labelling of phosphatidylcholine and other phosphoglycerides can be attributed to microsomal contamination. However, when mitochondria and microsomes are incubated together with [32P]phosphate, the phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine of the reisolated mitochondria become labelled, suggesting a transfer of phospholipids between the two fractions. 2. When liver microsomes or mitochondria containing labelled phosphatidylcholine are independently incubated with the opposite un-labelled fraction, there is a substantial and rapid exchange of the phospholipid between the two membranes. Exchange of phosphatidylinositol also occurs rapidly, whereas phosphatidylethanolamine and phosphatidic acid exchange only slowly. There is no corresponding transfer of marker enzymes. The transfer of phosphatidylcholine does not occur at 0°, and there is no requirement for added substrate, ATP or Mg2+, but the omission of a heat-labile supernatant fraction markedly decreases the exchange. 3. After intravenous injection of [32P]phosphate, short-period labelling experiments of the individual phospholipids of rat liver microsomes and mitochondria in vivo give no evidence for a similar exchange process. However, the incubation of isolated microsomes and mitochondria with [32P]phosphate also fails on reisolation of the fractions to demonstrate a precursor–product relationship between the individual phospholipids of the two membranes. 4. The intraperitoneal injection of [32P]phosphate results in a far greater proportion of the dose entering the liver than does intravenous administration. After intraperitoneal administration of [32P]phosphate the specific radioactivities of the individual phospholipids are in the order microsomes > outer mitochondrial membrane > inner

  18. Supervisory Turnover in Outpatient Substance Abuse Treatment

    PubMed Central

    Knight, Danica K.; Broome, Kirk M.; Edwards, Jennifer R.; Flynn, Patrick M.

    2009-01-01

    Staff turnover is a significant issue within substance abuse treatment, with implications for service delivery and organizational health. This study examined factors associated with turnover among supervisors in outpatient substance abuse treatment. Turnover was conceptualized as being an individual response to organizational-level influences, and predictors represent aggregate program measures. Participants included 532 staff (including 467 counselors and 65 clinical/program directors) from 90 programs in four regions of the USA. Using logistic regression, analyses of structural factors indicated that programs affiliated with a parent organization and those providing more counseling hours to clients had higher turnover rates. When measures of job attitudes were included, only parent affiliation and collective appraisal of satisfaction were related to turnover. Subsequent analyses identified a trend toward increased supervisory turnover when satisfaction was low following the departure of a previous supervisor. These findings suggest that organizational-level factors can be influential in supervisory turnover. PMID:19949883

  19. Sex-chromosome turnovers induced by deleterious mutation load.

    PubMed

    Blaser, Olivier; Grossen, Christine; Neuenschwander, Samuel; Perrin, Nicolas

    2013-03-01

    In sharp contrast with mammals and birds, many cold-blooded vertebrates present homomorphic sex chromosomes. Empirical evidence supports a role for frequent turnovers, which replace nonrecombining sex chromosomes before they have time to decay. Three main mechanisms have been proposed for such turnovers, relying either on neutral processes, sex-ratio selection, or intrinsic benefits of the new sex-determining genes (due, e.g., to linkage with sexually antagonistic mutations). Here, we suggest an additional mechanism, arising from the load of deleterious mutations that accumulate on nonrecombining sex chromosomes. In the absence of dosage compensation, this load should progressively lower survival rate in the heterogametic sex. Turnovers should occur when this cost outweighs the benefits gained from any sexually antagonistic genes carried by the nonrecombining sex chromosome. We use individual-based simulations of a Muller's ratchet process to test this prediction, and investigate how the relevant parameters (effective population size, strength and dominance of deleterious mutations, size of nonrecombining segment, and strength of sexually antagonistic selection) are expected to affect the rate of turnovers. PMID:23461315

  20. Protein turnover, nitrogen balance and rehabilitation.

    PubMed

    Fern, E B; Waterlow, J C

    1983-01-01

    Not many studies have been done on protein turnover during recovery from malnutrition. Some relevant information can, however, be obtained from measurements on normal growing animals, since rehabilitation and normal growth have in common a rapid rate of net protein synthesis. The key question is the extent to which net gain in protein results from an increase in synthesis or a decrease in breakdown or both. Different studies have used different methods, and all methods for measuring protein turnover have some disadvantages and sources of error. It is important to bear this in mind in evaluating the results. Consequently, part of this paper will be devoted to questions of methodology. Whole body protein turnover has been measured in children recovering from severe malnutrition. During the phase of rapid catch-up growth the rate of protein synthesis is increased. As might be expected, it increases linearly with the rate of weight gain. At the same time there is a smaller increase in the rate of protein breakdown. The resultant of these two processes is that, over and above the basal rate of protein synthesis, 1.4 grams of protein have to be synthesized for 1 gram to be laid down. Very similar results have been obtained in rapidly growing young pigs. Experimental studies on muscle growth in general confirm the conclusion that, at least in muscle, rapid growth is associated with rapid rates of protein breakdown as well as of synthesis. This has been shown in muscles of young growing rats, as well as in muscles in which hypertrophy has been induced by stretch or other stimuli. In contrast, the evidence suggests that rapid growth involves a fall in the rate of protein degradation. The magnitude of the nitrogen balance under any conditions is determined by the difference between synthesis and breakdown. In the absence of any storage of amino acids, this must be the same as the difference between intake and excretion (S - B = I - E). A question of great interest is whether

  1. Multidisciplinary analytical investigation of phospholipids and triglycerides in offshore farmed gilthead sea bream (Sparus aurata) fed commercial diets.

    PubMed

    Anedda, Roberto; Piga, Carlo; Santercole, Viviana; Spada, Simona; Bonaglini, Elia; Cappuccinelli, Roberto; Mulas, Gilberto; Roggio, Tonina; Uzzau, Sergio

    2013-06-01

    In this work, a quantitative characterisation of lipid (both triglycerides and phospholipids) rearrangements in the muscle of offshore-raised gilthead sea bream was carried out as a function of fish growth between April and September. Relative percentages of lipid classes and fatty acids/acyls composition of the commercial feeds and fish dorsal muscles were assessed by means of an interdisciplinary analytical approach. A combination of preparative chemistry and experimental results from NMR spectroscopy, GC, 3D-TLC as well as proximate analysis permitted the observed growth parameters in key metabolic events to be linked with fish fattening and lipid turnover. While defined effects of feed composition on fatty acid profiles of fillets were ascertained, the relative increase of fatty acyls in triglycerides and phospholipids were also estimated enabling detailed evaluation of TAG:PL ratio in adult offshore-farmed gilthead sea bream. NMR was also used to quantify PUFA regiospecific distribution in TAG and PL. PMID:23411224

  2. Rpe65 Isomerase Associates with Membranes through an Electrostatic Interaction with Acidic Phospholipid Headgroups*

    PubMed Central

    Yuan, Quan; Kaylor, Joanna J.; Miu, Anh; Bassilian, Sara; Whitelegge, Julian P.; Travis, Gabriel H.

    2010-01-01

    Opsins are light-sensitive pigments in the vertebrate retina, comprising a G protein-coupled receptor and an 11-cis-retinaldehyde chromophore. Absorption of a photon by an opsin pigment induces isomerization of its chromophore to all-trans-retinaldehyde. After a brief period of activation, opsin releases all-trans-retinaldehyde and becomes insensitive to light. Restoration of light sensitivity to the apo-opsin involves the conversion of all-trans-retinaldehyde back to 11-cis-retinaldehyde via an enzyme pathway called the visual cycle. The critical isomerization step in this pathway is catalyzed by Rpe65. Rpe65 is strongly associated with membranes but contains no membrane-spanning segments. It was previously suggested that the affinity of Rpe65 for membranes is due to palmitoylation of one or more Cys residues. In this study, we re-examined this hypothesis. By two independent strategies involving mass spectrometry, we show that Rpe65 is not palmitoylated nor does it appear to undergo other post-translational modifications at significant stoichiometry. Instead, we show that Rpe65 binds the acidic phospholipids, phosphatidylserine, phosphatidylglycerol, and cardiolipin, but not phosphatidic acid. No binding of Rpe65 to basic phospholipids or neutral lipids was observed. The affinity of Rpe65 to acidic phospholipids was strongly pH-dependent, suggesting an electrostatic interaction of basic residues in Rpe65 with negatively charged phospholipid headgroups. Binding of Rpe65 to liposomes containing phosphatidylserine or phosphatidylglycerol, but not the basic or neutral phospholipids, allowed the enzyme to extract its insoluble substrate, all-trans-retinyl palmitate, from the lipid bilayer for synthesis of 11-cis-retinol. The interaction of Rpe65 with acidic phospholipids is therefore biologically relevant. PMID:19892706

  3. Phospholipid association with the bovine cardiac mitochondrial adenosine triphosphatase.

    PubMed Central

    Brown, R E; Montgomery, R I; Spach, P I; Cunningham, C C

    1985-01-01

    The association of different phospholipids with a lipid-depleted oligomycin-sensitive ATPase from bovine cardiac mitochondria [Serrano, Kanner & Racker (1976) J. Biol. Chem. 251, 2453-2461] has been examined using three approaches. First, reconstitution of the ATPase with different synthetic diacyl phospholipids resulted in a 2-10-fold stimulation of ATPase specific activity depending upon the particular phospholipid employed. The phospholipid headgroup region displayed the following order of ATPase reactivation potential: dioleoylphosphatidylglycerol greater than dioleoylphosphatidic acid greater than dioleoylphosphatidylcholine. Furthermore, the ATPase showed higher levels of specific activity when reconstituted with dioleoyl phospholipid derivatives compared with dimyristoyl derivatives. Second, examination of the phospholipid remaining associated with the lipid-depleted ATPase upon purification showed that phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol were present. No relative enrichment of any of these phospholipids (compared with their distribution in submitochondrial particles) was noted. Therefore, no preferential association between the ATPase and any one phospholipid could be found in the mitochondrial ATPase. Third, the sodium cholate-mediated phospholipid exchange procedure was employed for studying the phospholipid requirements of the ATPase. Replacement of about 50% of the mitochondrial phospholipid remaining with the lipid-depleted ATPase could be achieved utilizing either synthetic phosphatidic acid or phosphatidylcholine. Examination of the displaced mitochondrial phospholipid showed that phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol were replaced with equal facility. Images Fig. 3. PMID:3156584

  4. PLA2-responsive and SPIO-loaded phospholipid micelles

    PubMed Central

    Gao, Qiang; Yan, Lesan; Chiorazzo, Michael; Delikatny, E. James; Tsourkas, Andrew; Cheng, Zhiliang

    2015-01-01

    A PLA2-responsive and superparamagnetic iron oxide (SPIO) nanoparticle-loaded phospholipid micelle was developed. The release of phospholipid-conjugated dye from these micelles was triggered due to phospholipid degradation by phospholipase A2. High relaxivity of the encapsulated SPIO could enable non-invasive magnetic resonance imaging. PMID:26139589

  5. An evaluation of serum high density lipoproteins-phospholipids.

    PubMed

    Ide, H; Tsuji, M; Shimada, M; Kondo, T; Fujiya, S; Asanuma, Y; Agishi, Y

    1988-07-01

    Phospholipids in high density lipoproteins (HDL) is being used as a negative risk indicator of atherosclerosis. Phospholipids in HDL may not demonstrate the actual level of HDL-phospholipids when determined by the precipitation or ultracentrifugal methods, because HDL fractions contain very high density lipoproteins (VHDL) and albumin. In the present study, the true level of phospholipids in HDL was estimated using high performance liquid chromatography (HPLC), and it was compared with the level of phospholipids in HDL determined by the precipitation method. Sera from 18 healthy subjects were used as materials. In the HPLC method, the HDL fraction was extracted making sure that it contained no free albumin, which is albumin not bound to phospholipids. The HDL fraction was separated into subfractions. It was found that phospholipids in the VHDL fraction make a 20.2 +/- 7.3% (mean +/- S.D.) part of the total HDL-phospholipids. A large part of the VHDL fraction was constituted of albumin-bound phospholipids. A significant correlation was observed between HDL-phospholipids determined by the precipitation method, which contain albumin, and the actual HDL fraction phospholipids determined by HPLC, which do not contain VHDL (r = 0.903, p less than 0.01). These results suggest that HDL-phospholipids values determined by the precipitation method give useful clinical data. PMID:3176021

  6. Interaction of phospholipid with silver nanorods

    NASA Astrophysics Data System (ADS)

    Anju, K. N.; Mahesh, S.; Kalarikkal, Nandakumar

    2014-01-01

    Development of a simple method for incorporating phospholipids onto the surfaces of anisotropic silver nanorods as a stepping-stone for creating responsive and multifunctional nanocomposites. 1, 2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC)-silver nanorod composites were prepared by immobilizing liposomes onto the surface of cetyltrimethylammonium bromide (CTAB) capped silver nanorods. Here we report the role of phospholipids to control the self assembly of silver nanorods into agglomerate architectures ranging from open "end-to-end" networks to densely packed "side-to-side" arrays. The tuning of electrostatic interactions within the phospholipid layers is governed to lipid silver nanorod assembly and also about the organization of phospholipid layers themselves around nanorod surfaces. The initial studies on passive lipid functionalized nanorods could serve as the groundwork for introducing active components into these systems to make more switchable or reconfigurable nanocomposite material. Changing the surface species on silver nanorods from CTAB to DSPC is reflected in ξ- potential measurements. The surface morphology is studied using SEM and TEM. The optical studies are carried out using UV-Vis spectroscopy.

  7. Feruloyl Dioleoyglycerol Antioxidant Capacity in Phospholipid Vesicles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ferulic acid and its esters are known to be effective antioxidants. Feruloyl dioleoylglycerol was assessed for its ability to serve as an antioxidant in model membrane phospholipid vesicles. The molecule was incorporated into single-lamellar vesicles of 1,2-dioleoyl-sn-glycero-3-phosphocholine at ...

  8. Revisiting nurse turnover costs: adjusting for inflation.

    PubMed

    Jones, Cheryl Bland

    2008-01-01

    Organizational knowledge of nurse turnover costs is important, but gathering these data frequently may not always be feasible in today's fast-paced and complex healthcare environment. The author presents a method to inflation adjust baseline nurse turnover costs using the Consumer Price Index. This approach allows nurse executives to gain current knowledge of organizational nurse turnover costs when primary data collection is not practical and to determine costs and potential savings if nurse retention investments are made. PMID:18157000

  9. Guide to good practices for operations turnover

    SciTech Connect

    1998-12-01

    This Guide to Good Practices is written to enhance understanding of, and provide direction for, Operations Turnover, Chapter XII of Department of Energy (DOE) Order 5480.19, Conduct of Operations Requirements for DOE Facilities. The practices in this guide should be considered when planning or reviewing operations turnover programs. Contractors are advised to adopt procedures that meet the intent of DOE Order 5480.19. Operations Turnover is an element of an effective Conduct of Operations program. The complexity and array of activities performed in DOE facilities dictate the necessity for a formal operations turnover program to promote safe and efficient operations.

  10. Marine by-product phospholipids as booster of medicinal compounds.

    PubMed

    Takahashi, Koretaro; Inoue, Yoshikazu

    2012-01-01

    Marine phospholipids are defined as phospholipids containing docosahexaenoic acid (DHA) or eicosapentaenoic acid that would be more effective than fish oil, which is mostly composed of triacylglycerol, in exerting health benefits. Marine phospholipids would boost the effect of both the health-beneficial hydrophilic and the hydrophobic compounds such as cell differentiators, anticancer compounds, and antiobesity compounds. When marine phospholipids are served as liposomal drinks, they would be more effective than adding into solid foods or feeds. As long as the liposome bilayer is basically composed of marine phospholipids, they would promote the encapsulated functional compounds. And this is the principal advantage of choosing marine phospholipids as liposomal membrane. Bioconversion of marine phospholipid would also be advantageous in delivering DHA into the desired tissue. For example, lysophosphatidylserine obtained through phospholipase D-mediated transphosphatidylation and phospholipase A₁ or sn-1 positional specific lipase-mediated partial hydrolysis seemed to be the most effective chemical form in delivering DHA into brain. PMID:22361179

  11. Relevancy 101

    NASA Technical Reports Server (NTRS)

    Lynnes, Chris; Newman, Doug

    2016-01-01

    Where we present an overview on why relevancy is a problem, how important it is and how we can improve it. The topic of relevancy is becoming increasingly important in earth data discovery as our audience is tuned to the accuracy of standard search engines like Google.

  12. Polyunsaturated Fatty Acid Composition of Maternal Diet and Erythrocyte Phospholipid Status in Chilean Pregnant Women

    PubMed Central

    Bascuñán, Karla A.; Valenzuela, Rodrigo; Chamorro, Rodrigo; Valencia, Alejandra; Barrera, Cynthia; Puigrredon, Claudia; Sandoval, Jorge; Valenzuela, Alfonso

    2014-01-01

    Chilean diets are characterized by a low supply of n-3 polyunsaturated fatty acids (n-3 PUFA), which are critical nutrients during pregnancy and lactation, because of their role in brain and visual development. DHA is the most relevant n-3 PUFA in this period. We evaluated the dietary n-3 PUFA intake and erythrocyte phospholipids n-3 PUFA in Chilean pregnant women. Eighty healthy pregnant women (20–36 years old) in the 3rd–6th month of pregnancy were included in the study. Dietary assessment was done applying a food frequency questionnaire, and data were analyzed through the Food Processor SQL® software. Fatty acids of erythrocyte phospholipids were assessed by gas-liquid chromatography. Diet composition was high in saturated fat, low in mono- and PUFA, high in n-6 PUFA (linoleic acid) and low in n-3 PUFA (alpha-linolenic acid and DHA), with imbalance in the n-6/n-3 PUFA ratio. Similar results were observed for fatty acids from erythrocyte phospholipids. The sample of Chilean pregnant women showed high consumption of saturated fat and low consumption of n-3 PUFA, which is reflected in the low DHA content of erythrocyte phospholipids. Imbalance between n-6/n-3 PUFA could negatively affect fetal development. New strategies are necessary to improve n-3 PUFA intake throughout pregnancy and breast feeding periods. Furthermore, it is necessary to develop dietary interventions to improve the quality of consumed foods with particular emphasis on n-3 PUFA. PMID:25386693

  13. Tracking synthesis and turnover of triacylglycerol in leaves

    PubMed Central

    Tjellström, Henrik; Strawsine, Merissa; Ohlrogge, John B.

    2015-01-01

    Triacylglycerol (TAG), typically represents <1% of leaf glycerolipids but can accumulate under stress and other conditions or if leaves are supplied with fatty acids, or in plants transformed with regulators or enzymes of lipid metabolism. To better understand the metabolism of TAG in leaves, pulse–chase radiolabelling experiments were designed to probe its synthesis and turnover. When Arabidopsis leaves were incubated with [14C]lauric acid (12:0), a major initial product was [14C]TAG. Thus, despite low steady-state levels, leaves possess substantial TAG biosynthetic capacity. The contributions of diacylglycerol acyltransferase1 and phospholipid:diacylglycerol acyltransferase1 to leaf TAG synthesis were examined by labelling of dgat1 and pdat1 mutants. The dgat1 mutant displayed a major (76%) reduction in [14C]TAG accumulation whereas pdat1 TAG labelling was only slightly reduced. Thus, DGAT1 has a principal role in TAG biosynthesis in young leaves. During a 4h chase period, radioactivity in TAG declined 70%, whereas the turnover of [14C]acyl chains of phosphatidylcholine (PC) and other polar lipids was much lower. Sixty percent of [14C]12:0 was directly incorporated into glycerolipids without modification, whereas 40% was elongated and desaturated to 16:0 and 18:1 by plastids. The unmodified [14C]12:0 and the plastid products of [14C]12:0 metabolism entered different pathways. Although plastid-modified 14C-labelled products accumulated in monogalactosyldiacylglycerol, PC, phosphatidylethanolamine, and diacylglcerol (DAG), there was almost no accumulation of [14C]16:0 and [14C]18:1 in TAG. Because DAG and acyl-CoA are direct precursors of TAG, the differential labelling of polar glycerolipids and TAG by [14C]12:0 and its plastid-modified products provides evidence for multiple subcellular pools of both acyl-CoA and DAG. PMID:25609824

  14. Dynamic Aspects of Voluntary Turnover: An Integrated Approach to Curvilinearity in the Performance-Turnover Relationship

    ERIC Educational Resources Information Center

    Becker, William J.; Cropanzano, Russell

    2011-01-01

    Previous research pertaining to job performance and voluntary turnover has been guided by 2 distinct theoretical perspectives. First, the push-pull model proposes that there is a quadratic or curvilinear relationship existing between these 2 variables. Second, the unfolding model of turnover posits that turnover is a dynamic process and that a…

  15. Employee Turnover among Full-time Public Librarians.

    ERIC Educational Resources Information Center

    Rubin, Richard

    1989-01-01

    A study of employee turnover in 31 public libraries in the American Midwest established baseline turnover rates and examined the relationship of gender to turnover behavior. Findings showed that: turnover rates are low compared to other occupations; and turnover rates of males and females are similar. (28 references) (Author/MES)

  16. Adsorption of ruthenium red to phospholipid membranes.

    PubMed Central

    Voelker, D; Smejtek, P

    1996-01-01

    We have measured the distribution of the hexavalent ruthenium red cation (RuR) between water and phospholipid membranes, have shown the critical importance of membrane negative surface charge for RuR binding, and determined the association constant of RuR for different phospholipid bilayers. The studies were performed with liposomes made of mixtures of zwitterionic L-alpha-phosphatidylcholine (PC), and one of the negatively charged phospholipids: L-alpha-phosphatidylserine (PS), L-alpha-phosphatidylinositol (PI), or L-alpha-phosphatidylglycerol (PG). Lipid composition of PC:PX membranes was 1:0, 19:1, 9:1, and 4:1. Liposomes were processed using freeze-and-thaw treatment, and their size distribution was characterized by light scattering and electron microscopy. Experimental distribution isotherms of RuR obtained by ultracentrifugation and spectrophotometry can be reproduced with the Langmuir-Stern-Grahame model, assuming that RuR behaves in the diffuse double layer as an ion with effective valency < 6. In terms of this model, PC-PS, PC-PI, and PC-PG membranes were found to be electrostatically equivalent and the intrinsic association constants of RuR were obtained. RuR has highest affinity to PS-containing membranes; its association constant for PC-PI and PC-PG membranes is about 5 times smaller than that for PC-PS membranes. From the comparison of RuR binding to mixed negatively charged phospholipid membranes and RuR binding to sarcoplasmic reticulum (SR), we conclude that the low-affinity RuR binding sites may indeed be associated with the lipid bilayer of SR. PMID:8789099

  17. Bolaamphiphiles Promote Phospholipid Translocation Across Vesicle Membranes

    PubMed Central

    Forbes, Christopher C.; DiVittorio, Kristy M.; Smith, Bradley D.

    2008-01-01

    A series of membrane-spanning bolaamphiphiles (molecules with two hydrophilic end-groups connected by a hydrophobic linker) were prepared by a modular synthetic method and evaluated for their abilities to affect the dynamics of a surrounding bilayer membrane. The goal was to determine if the bolaamphiphiles promote the translocation of phospholipids across vesicle membranes. The bolaamphiphiles were incorporated at low levels (up to 5 mol%) in vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Inward translocation assays were performed using fluorescent, NBD-labeled phospholipid probes with phosphocholine (PC) or phosphoglycerol (PG) head-groups. The membrane-spanning bolaamphiphiles promote the translocation of both phospholipid probes in the order PG > PC, while shorter bolaamphiphiles (structures that must adopt a U-shape and keep both end-groups in the same leaflet of the membrane), and regular amphiphiles with one hydrophilic end-group, are inactive. These results are an exception to the rule-of-thumb that membrane-spanning bolaamphiphiles are inherently membrane stabilizing molecules that inhibit all types of membrane transport. PMID:16834395

  18. Employee Turnover: An Empirical and Methodological Assessment.

    ERIC Educational Resources Information Center

    Muchinsky, Paul M.; Tuttle, Mark L.

    1979-01-01

    Reviews research on the prediction of employee turnover. Groups predictor variables into five general categories: attitudinal (job satisfaction), biodata, work-related, personal, and test-score predictors. Consistent relationships between common predictor variables and turnover were found for four categories. Eight methodological problems/issues…

  19. Principal Turnover. Information Capsule. Volume 0914

    ERIC Educational Resources Information Center

    Blazer, Christie

    2010-01-01

    Recent studies indicate that school districts are facing increasing rates of principal turnover. Frequent principal changes deprive schools of the leadership stability they need to succeed, disrupt long-term school reform efforts, and may even be linked to increased teacher turnover and lower levels of student achievement. This Information Capsule…

  20. Employee Turnover: Evidence from a Case Study.

    ERIC Educational Resources Information Center

    Borland, Jeff

    1997-01-01

    Patterns of employee turnover from a medium-sized law firm in Australia were examined in regard to theories of worker mobility (matching, sectoral shift, and incentive). Results support a role for matching effects, but personnel practices affect the timing of turnover. Matching and incentive-based theories do not explain the high rates of turnover…

  1. Contextual Factors Related to Elementary Principal Turnover

    ERIC Educational Resources Information Center

    Partlow, Michelle C.

    2007-01-01

    The issue of school leadership instability and how it affects schools and student achievement has been studied. The question of how to predict turnover of the principal remains an unknown. The purpose of this research was to search for possible relationships between certain contextual variables and principal turnover and to test the independent…

  2. Predicting Employee Turnover from Communication Networks.

    ERIC Educational Resources Information Center

    Feeley, Thomas H.; Barnett, George A.

    1997-01-01

    Investigates three social network models of employee turnover: a structural equivalence model, a social influence model, and an erosion model. Administers a communication network questionnaire to all 170 employees of an organization. Finds support for all three models of turnover, with the erosion model explaining more of the variance than do the…

  3. Mitochondrial Turnover in the Heart

    PubMed Central

    Gustafsson, Åsa B.

    2010-01-01

    Mitochondrial quality control is increasingly recognized as an essential element in maintaining optimally functioning tissues. Mitochondrial quality control depends upon a balance between biogenesis and autophagic destruction. Mitochondrial dynamics (fusion and fission) allows for the redistribution of mitochondrial components. We speculate that this permits sorting of highly functional components into one end of a mitochondrion, while damaged components are segregated at the other end, to be jettisoned by asymmetric fission followed by selective mitophagy. Ischemic preconditioning requires autophagy/mitophagy, resulting in selective elimination of damaged mitochondria, leaving behind a population of robust mitochondria with a higher threshold for opening of the mitochondrial permeability transition pore. In this review we will consider the factors that regulate mitochondrial biogenesis and destruction, the machinery involved in both processes, and the biomedical consequences associated with altered mitochondrial turnover. PMID:21147177

  4. Social Disadvantage and Network Turnover

    PubMed Central

    2015-01-01

    Objectives. Research shows that socially disadvantaged groups—especially African Americans and people of low socioeconomic status (SES)—experience more unstable social environments. I argue that this causes higher rates of turnover within their personal social networks. This is a particularly important issue among disadvantaged older adults, who may benefit from stable networks. This article, therefore, examines whether social disadvantage is related to various aspects of personal network change. Method. Social network change was assessed using longitudinal egocentric network data from the National Social Life, Health, and Aging Project, a study of older adults conducted between 2005 and 2011. Data collection in Wave 2 included a technique for comparing respondents’ confidant network rosters between waves. Rates of network losses, deaths, and additions were modeled using multivariate Poisson regression. Results. African Americans and low-SES individuals lost more confidants—especially due to death—than did whites and college-educated respondents. African Americans also added more confidants than whites. However, neither African Americans nor low-SES individuals were able to match confidant losses with new additions to the extent that others did, resulting in higher levels of confidant network shrinkage. These trends are partly, but not entirely, explained by disadvantaged individuals’ poorer health and their greater risk of widowhood or marital dissolution. Discussion. Additional work is needed to shed light on the role played by race- and class-based segregation on group differences in social network turnover. Social gerontologists should examine the role these differences play in explaining the link between social disadvantage and important outcomes in later life, such as health decline. PMID:24997286

  5. Antidiabetic phospholipid-nuclear receptor complex reveals the mechanism for phospholipid-driven gene regulation

    SciTech Connect

    Musille, Paul M; Pathak, Manish C; Lauer, Janelle L; Hudson, William H; Griffin, Patrick R; Ortlund, Eric A

    2013-01-31

    The human nuclear receptor liver receptor homolog-1 (LRH-1) has an important role in controlling lipid and cholesterol homeostasis and is a potential target for the treatment of diabetes and hepatic diseases. LRH-1 is known to bind phospholipids, but the role of phospholipids in controlling LRH-1 activation remains highly debated. Here we describe the structure of both apo LRH-1 and LRH-1 in complex with the antidiabetic phospholipid dilauroylphosphatidylcholine (DLPC). Together with hydrogen-deuterium exchange MS and functional data, our studies show that DLPC binding is a dynamic process that alters co-regulator selectivity. We show that the lipid-free receptor undergoes previously unrecognized structural fluctuations, allowing it to interact with widely expressed co-repressors. These observations enhance our understanding of LRH-1 regulation and highlight its importance as a new therapeutic target for controlling diabetes.

  6. Effects of chronic ethanol administration and withdrawal on incorporation of arachidonate into membrane phospholipids.

    PubMed

    Sun, G Y; Kelleher, J A; Sun, A Y

    1985-01-01

    A plasma membrane fraction isolated from cerebral cortex of control and ethanol-treated rats was used to study the effects of chronic ethanol administration on uptake of arachidonate by membrane phospholipids. Upon incubation of the membranes with [(14)C] arachidonic acid in the presence of ATP, Mg(2+), and CoA, radioactivity was incorporated into all of the phospholipids, although a large proportion of the label was found in phosphatidylinositols (PI, 60%) and phosphatidylcholines (PC, 20%). Rats given ethanol (8-10 g/kg body wt) via intubation in the form of a liquid diet for 4 weeks showed an increase (17-20%) in arachidonate incorporation into PI and PC as compared to phosphatidylethanolamines (PE) and phosphatidylserines (PS). A similar increase in uptake activity was observed at 2 or 24 h upon withdrawal of ethanol, but uptake activity returned readily to that of control level by 72 h. The method described in this study is a sensitive and reliable procedure for monitoring the arachidonoyl turnover activity in neural membranes with respect to chronic ethanol induction and withdrawal. PMID:20492952

  7. The herpes simplex virus 1 U{sub S}3 regulates phospholipid synthesis

    SciTech Connect

    Wild, Peter; Oliveira, Anna Paula de; Sonda, Sabrina; Schraner, Elisabeth M.; Ackermann, Mathias; Tobler, Kurt

    2012-10-25

    Herpes simplex virus type 1 capsids bud at nuclear and Golgi membranes for envelopment by phospholipid bilayers. In the absence of U{sub S}3, nuclear membranes form multiple folds harboring virions that suggests disturbance in membrane turnover. Therefore, we investigated phospholipid metabolism in cells infected with the U{sub S}3 deletion mutant R7041({Delta}U{sub S}3), and quantified membranes involved in viral envelopment. We report that (i) [{sup 3}H]-choline incorporation into nuclear membranes and cytoplasmic membranes was enhanced peaking at 12 or 20 h post inoculation with wild type HSV-1 and R7041({Delta}U{sub S}3), respectively, (ii) the surface area of nuclear membranes increased until 24 h of R7041({Delta}U{sub S}3) infection forming folds that equaled {approx}45% of the nuclear surface, (iii) the surface area of viral envelopes between nuclear membranes equaled {approx}2400 R7041({Delta}U{sub S}3) virions per cell, and (iv) during R7041({Delta}U{sub S}3) infection, the Golgi complex expanded dramatically. The data indicate that U{sub S}3 plays a significant role in regulation of membrane biosynthesis.

  8. Neutral Lipid Metabolism Influences Phospholipid Synthesis and Deacylation in Saccharomyces cerevisiae

    PubMed Central

    Mora, Gabriel; Scharnewski, Michael; Fulda, Martin

    2012-01-01

    Establishment and maintenance of equilibrium in the fatty acid (FA) composition of phospholipids (PL) requires both regulation of the substrate available for PL synthesis (the acyl-CoA pool) and extensive PL turnover and acyl editing. In the present study, we utilize acyl-CoA synthetase (ACS) deficient cells, unable to recycle FA derived from lipid deacylation, to evaluate the role of several enzymatic activities in FA trafficking and PL homeostasis in Saccharomyces cerevisiae. The data presented show that phospholipases B are not contributing to constitutive PL deacylation and are therefore unlikely to be involved in PL remodeling. In contrast, the enzymes of neutral lipid (NL) synthesis and mobilization are central mediators of FA trafficking. The phospholipid:DAG acyltransferase (PDAT) Lro1p has a substantial effect on FA release and on PL equilibrium, emerging as an important mediator in PL remodeling. The acyl-CoA dependent biosynthetic activities of NL metabolism are also involved in PL homeostasis through active modulation of the substrate available for PL synthesis. In addition TAG mobilization makes an important contribution, especially in cells from stationary phase, to FA availability. Beyond its well-established role in the formation of a storage pool, NL metabolism could play a crucial role as a mechanism to uncouple the pools of PL and acyl-CoAs from each other and thereby to allow independent regulation of each one. PMID:23139841

  9. Selective acceleration of arachidonic acid reincorporation into brain membrane phospholipid following transient ischemia in awake gerbil.

    PubMed

    Rabin, O; Chang, M C; Grange, E; Bell, J; Rapoport, S I; Deutsch, J; Purdon, A D

    1998-01-01

    Awake gerbils were subjected to 5 min of forebrain ischemia by clamping the carotid arteries for 5 min and then allowing recirculation. Radiolabeled arachidonic or palmitic acid was infused intravenously for 5 min at the start of recirculation, after which the brains were prepared for quantitative autoradiography or chemical analysis. Dilution of specific activity of the acyl-CoA pool was independently determined for these fatty acids in control gerbils and following 5 min of ischemia and 5 min of reperfusion. Using a quantitative method for measuring regional in vivo fatty acid incorporation into and turnover within brain phospholipids and determining unlabeled concentrations of acyl-CoAs following recirculation, it was shown that reperfusion after 5 min of ischemia was accompanied by a threefold increase compared with the control in the rate of reincorporation of unlabeled arachidonate that had been released during ischemia, whereas reincorporation of released palmitate was not different from the control. Selective and accelerated reincorporation of arachidonate into brain phospholipids shortly after ischemia may ameliorate specific deleterious effects of arachidonate and its metabolites on brain membranes. PMID:9422378

  10. A method for the modulation of membrane fluidity: homogeneous catalytic hydrogenation of phospholipids and phospholipids and phospholipid-water model biomembranes.

    PubMed Central

    Chapman, D; Quinn, P J

    1976-01-01

    The fatty acids associated with phospholipids of cell membranes, and particularly their degree of unsaturation, contribute to the fluidity of their structure and hance determine many of their biological properties. We describe a technique for modulating membrane fluidity which consists of hydrogenating the unsaturated double bonds of membrane phospholipids. This has been accomplished using a homogeneous catalyst. The process has been applied to phospholipids in organic solvents, to phospholipids dispersed as multibilayers in aqueous systems, and also to sonicated preparations of phospholipids arranged as single bilayer vesicles. Preliminary experiments have also been performed with biological membranes. These results indicate that the process of homogeneous catalysis for the modulation of lipid fluidity of biological cell membranes may have considerable future biological and biochemical application. PMID:1069280

  11. Effect of acute thioacetamide administration on rat brain phospholipid metabolism

    SciTech Connect

    Osada, J.; Aylagas, H.; Miro-Obradors, M.J.; Arce, C.; Palacios-Alaiz, E.; Cascales, M. )

    1990-09-01

    Brain phospholipid composition and the ({sup 32}P)orthophosphate incorporation into brain phospholipids of control and rats treated for 3 days with thioacetamide were studied. Brain phospholipid content, phosphatidylcholine, phosphatidylethanolamine, lysolecithin and phosphatidic acid did not show any significant change by the effect of thioacetamide. In contrast, thioacetamide induced a significant decrease in the levels of phosphatidylserine, sphingomyelin, phosphatidylinositol and diphosphatidylglycerol. After 75 minutes of intraperitoneal label injection, specific radioactivity of all the above phospholipids with the exception of phosphatidylethanolamine and phosphatidylcholine significantly increased. After 13 hours of isotope administration the specific radioactivity of almost all studied phospholipid classes was elevated, except for phosphatidic acid, the specific radioactivity of which did not change and for diphosphatidylglycerol which showed a decrease in specific radioactivity. These results suggest that under thioacetamide treatment brain phospholipids undergo metabolic transformations that may contribute to the hepatic encephalopathy induced by thioacetamide.

  12. PHOSPHOLIPIDS IN VEGETATIVE CELLS AND SPORES OF BACILLUS POLYMYXA1

    PubMed Central

    Matches, Jack R.; Walker, Homer W.; Ayres, John C.

    1964-01-01

    Matches, Jack R. (Iowa State University of Science and Technology, Ames), Homer W. Walker, and John C. Ayres. Phospholipids in vegetative cells and spores of Bacillus polymyxa. J. Bacteriol. 87:16–23. 1964.—The same types of phospholipids were recovered from both vegetative cells and spores of Bacillus polymyxa 1A39. Nitrogen-containing phospholipids were identified as phosphatidyl ethanolamine, lysophosphatidyl ethanolamine, lysophosphatidyl serine, and lysolecithin. Acidic phosphatides containing no nitrogen were identified as phosphatidic acid, phosphatidyl glycerol, and a fraction appearing to be bis (phosphatidic) acid. The major phosphatide fraction in both cells and spores was phosphatidyl ethanolamine. Smaller amounts of phosphatidyl glycerol and bis (phosphatidic) acid were present; the other acidic phospholipid components were present only in trace amounts. Heat resistance of the spore as compared to the vegetative cell could not be attributed to a specific phospholipid, since no difference in the type of phospholipids present was observed. PMID:14102851

  13. Essential phospholipids in fatty liver: a scientific update

    PubMed Central

    Gundermann, Karl-Josef; Gundermann, Simon; Drozdzik, Marek; Mohan Prasad, VG

    2016-01-01

    Aim Although essential phospholipids (EPL) from soybean are often used in membrane-associated disorders and diseases, their high quality of purification and effects on prevalent liver diseases, especially on fatty liver diseases (FLDs) of different origin, are still widely unknown and a matter of continuous active research. The aim of this article is to review, discuss, and summarize the available results of EPL in the treatment of FLD. Methods Database research was carried out on Medline, Embase, Cochrane Library, country-specific journals, and follow-up literature citations for relevant hepatogastroenterological articles published between 1988 and 2014. We searched for and reviewed only those papers that indicated minimum extraction amount of 72% (3-sn-phosphatidyl)choline from soybean as being necessary to treat patients with a considerable amount of 1,2-dilinoleoylphosphatidylcholine as a key component in EPL. Results EPL has a well-established mode of action, therapeutic effectiveness, and lack of toxicity, which ensures clinically relevant efficacy-to-safety ratio. It influences membrane- dependent cellular functions and shows anti-inflammatory, antioxidant, antifibrogenic, anti apoptotic, membrane-protective, and lipid-regulating effects. Due to its positive effects on membrane composition and functions, it accelerates the improvement or normalization of subjective symptoms; pathological, clinical, and biochemical findings; hepatic imaging; and liver histology. It is justified to administer EPL together with other therapeutic measurements in the liver. Conclusion Pharmacological and clinical results confirm the efficacy of EPL in the treatment of FLD. PMID:27217791

  14. Critical assessment of phospholipid measurement in amniotic fluid.

    PubMed

    Badham, L P; Worth, H G

    1975-09-01

    We assessed several methods of inorganic phosphate assay for their suitability in estimating phospholipids in digested extracts of amniotic fluids. The extraction and digestion procedures used for phospholipids from amniotic fluid were also examined critically. The effect of contamination by blood or obstetric cream has been examined. Accordingly, we suggest a method for measuring total phospholipids in amniotic fluids, and results of it are compared with the lecithin/sphingomyelin ratio measurement in some clinical situations. PMID:1157310

  15. Looking Beyond Structure: Membrane Phospholipids of Skeletal Muscle Mitochondria.

    PubMed

    Heden, Timothy D; Neufer, P Darrell; Funai, Katsuhiko

    2016-08-01

    Skeletal muscle mitochondria are highly dynamic and are capable of tremendous expansion to meet cellular energetic demands. Such proliferation in mitochondrial mass requires a synchronized supply of enzymes and structural phospholipids. While transcriptional regulation of mitochondrial enzymes has been extensively studied, there is limited information on how mitochondrial membrane lipids are generated in skeletal muscle. Herein we describe how each class of phospholipids that constitute mitochondrial membranes are synthesized and/or imported, and summarize genetic evidence indicating that membrane phospholipid composition represents a significant modulator of skeletal muscle mitochondrial respiratory function. We also discuss how skeletal muscle mitochondrial phospholipids may mediate the effect of diet and exercise on oxidative metabolism. PMID:27370525

  16. Platelet activating factor activity in the phospholipids of bovine spermatozoa

    SciTech Connect

    Parks, J.E.; Hough, S.; Elrod, C. )

    1990-11-01

    Platelet activating factor (PAF) has been detected in sperm from several mammalian species and can affect sperm motility and fertilization. Because bovine sperm contain a high percentage of ether-linked phospholipid precursors required for PAF synthesis, a study was undertaken to determine the PAF activity of bovine sperm phospholipids. Total lipids of washed, ejaculated bull sperm were extracted, and phospholipids were fractionated by thin-layer chromatography. Individual phospholipid fractions were assayed for PAF activity on the basis of (3H)serotonin release from equine platelets. PAF activity was detected in the PAF fraction (1.84 pmol/mumol total phospholipid) and in serine/inositol (PS/PI), choline (CP), and ethanolamine phosphoglyceride (EP) and cardiolipin (CA) fractions. Activity was highest in the CP fraction (8.05 pmol/mumol total phospholipid). Incomplete resolution of PAF and neutral lipids may have contributed to the activity in the PS/PI and CA fractions, respectively. Phospholipids from nonsperm sources did not stimulate serotonin release. Platelet activation by purified PAF and by sperm phospholipid fractions was inhibited by the receptor antagonist SRI 63-675. These results indicate that bovine sperm contain PAF and that other sperm phospholipids, especially CP and EP, which are high in glycerylether components, are capable of receptor-mediated platelet activation.

  17. Specific heating power of fatty acid and phospholipid stabilized magnetic fluids in an alternating magnetic field

    NASA Astrophysics Data System (ADS)

    DeCuyper, M.; Hodenius, M.; Ivanova, G.; Baumann, M.; Paciok, E.; Eckert, T.; Soenen, S. J. H.; Schmitz-Rode, T.

    2008-05-01

    Magnetic fluids (MFs) with a similar narrow size distribution of the iron oxide core were stabilized with lauric acid (MF 1), oleate (MF 2) or, after dialysis in the presence of liposomes, with phospholipid molecules (MF 3 and MF 4, respectively). The hydrodynamic sizes of the MF 1 and MF 3 were half those found for MF 2 and MF 4. The MFs were exposed to inductive heating in an alternating magnetic field at a frequency of 200 kHz and a maximum magnetic field strength of 3.8 kA m-1. Specific absorption rates (SAR) of 294 ± 42 (MF 1), 214 ± 16 (MF 2), 297 ± 13 (MF 3) and 213 ± 6 W g-1 Fe (MF 4) were obtained. The data for MF 2 and MF 4 were identical to those found for the commercially available ferucarbotran. The biomedical relevance of the phospholipid-coated MFs is briefly discussed.

  18. Drug induced `softening' in phospholipid monolayers

    NASA Astrophysics Data System (ADS)

    Basak, Uttam Kumar; Datta, Alokmay; Bhattacharya, Dhananjay

    2015-06-01

    Compressibility measurements on Langmuir monolayers of the phospholipid Dimystoryl Phospatidylcholine (DMPC) in pristine form and in the presence of the Non-steroidal Anti-inflammatory Drug (NSAID) Piroxicam at 0.025 drug/lipid (D/L) molecular ratio at different temperatures, show that the monolayer exhibits large increase (and subsequent decrease) in compressibility due to the drug in the vicinity of the Liquid Expanded - Liquid Condensed (LE-LC) phase transition. Molecular dynamics simulations of the lipid monolayer in presence of drug molecules show a disordering of the tail tilt, which is consistent with the above result.

  19. Improvements to Kramers turnover theory

    NASA Astrophysics Data System (ADS)

    Pollak, Eli; Ankerhold, Joachim

    2013-04-01

    The Kramers turnover problem, that is, obtaining a uniform expression for the rate of escape of a particle over a barrier for any value of the external friction was solved in the 1980s. Two formulations were given, one by Mel'nikov and Meshkov (MM) [V. I. Mel'nikov and S. V. Meshkov, J. Chem. Phys. 85, 1018 (1986), 10.1063/1.451844], which was based on a perturbation expansion for the motion of the particle in the presence of friction. The other, by Pollak, Grabert, and Hänggi (PGH) [E. Pollak, H. Grabert, and P. Hänggi, J. Chem. Phys. 91, 4073 (1989), 10.1063/1.456837], valid also for memory friction, was based on a perturbation expansion for the motion along the collective unstable normal mode of the particle. Both theories did not take into account the temperature dependence of the average energy loss to the bath. Increasing the bath temperature will reduce the average energy loss. In this paper, we analyse this effect, using a novel perturbation theory. We find that within the MM approach, the thermal energy gained from the bath diverges, the average energy gain becomes infinite implying an essential failure of the theory. Within the PGH approach increasing the bath temperature reduces the average energy loss but only by a finite small amount of the order of the inverse of the reduced barrier height. Then, this does not seriously affect the theory. Analysis and application for a cubic potential and Ohmic friction are presented.

  20. The aminosterol antibiotic squalamine permeabilizes large unilamellar phospholipid vesicles.

    PubMed

    Selinsky, B S; Zhou, Z; Fojtik, K G; Jones, S R; Dollahon, N R; Shinnar, A E

    1998-03-13

    The ability of the shark antimicrobial aminosterol squalamine to induce the leakage of polar fluorescent dyes from large unilamellar phospholipid vesicles (LUVs) has been measured. Micromolar squalamine causes leakage of carboxyfluorescein (CF) from vesicles prepared from the anionic phospholipids phosphatidylglycerol (PG), phosphatidylserine (PS), and cardiolipin. Binding analyses based on the leakage data show that squalamine has its highest affinity to phosphatidylglycerol membranes, followed by phosphatidylserine and cardiolipin membranes. Squalamine will also induce the leakage of CF from phosphatidylcholine (PC) LUVs at low phospholipid concentrations. At high phospholipid concentrations, the leakage of CF from PC LUVs deviates from a simple dose-response relationship, and it appears that some of the squalamine can no longer cause leakage. Fluorescent dye leakage generated by squalamine is graded, suggesting the formation of a discrete membrane pore rather than a generalized disruption of vesicular membranes. By using fluorescently labeled dextrans of different molecular weight, material with molecular weight /=10,000 is retained. Negative stain electron microscopy of squalamine-treated LUVs shows that squalamine decreases the average vesicular size in a concentration-dependent manner. Squalamine decreases the size of vesicles containing anionic phospholipid at a lower squalamine/lipid molar ratio than pure PC LUVs. In a centrifugation assay, squalamine solubilizes phospholipid, but only at significantly higher squalamine/phospholipid ratios than required for either dye leakage or vesicle size reduction. Squalamine solubilizes PC at lower squalamine/phospholipid ratios than PG. We suggest that squalamine complexes with phospholipid to form a discrete structure within the bilayers of LUVs, resulting in the transient leakage of small encapsulated molecules. At higher

  1. Plagued by Turnover? Train Your Managers.

    ERIC Educational Resources Information Center

    Dobbs, Kevin

    2000-01-01

    Dissatisfaction with managers is a major cause of employee turnover The Charles Schwab Corporation surveys employees annually and holds employee focus groups and online town meetings. The information is used for the coaching and training of department heads. (JOW)

  2. Coping with Turnovers in School Food Service.

    ERIC Educational Resources Information Center

    Pannell, Dorothy V.

    1988-01-01

    Labor shortages, cost increases, and turnover have prompted Fairfax County Schools, Virginia, food service managers to offer training programs and recruitment bonuses, to use more convenience foods, and to price out every service. (MLF)

  3. Biomimetic catalysis: Taking on the turnover challenge

    NASA Astrophysics Data System (ADS)

    Hooley, Richard J.

    2016-03-01

    Emulating the efficiency with which enzymes catalyse reactions has often been used as inspiration to develop self-assembled cages. Now two studies present approaches to achieving catalyst turnover -- one of the biggest challenges in achieving truly biomimetic catalysis.

  4. Phospholipid/aromatic thiol hybrid bilayers.

    PubMed

    Li, Chao; Wang, Mingming; Ferguson, Matthew; Zhan, Wei

    2015-05-12

    Gold-supported hybrid bilayers comprising phospholipids and alkanethiols have been found to be highly useful in biomembrane mimicking as well as biosensing ever since their introduction by Plant in 1993 (Plant, A. L. Langmuir 1993, 9, 2764-2767). Generalizing the mechanism (i.e., hydrophobic/hydrophobic interaction) that primarily drives bilayer formation, we report here that such a bilayer structure can also be successfully obtained when aromatic thiols are employed in place of alkanethiols. Four aromatic thiols were studied here (thiophenol, 2-naphthalene thiol, biphenyl-4-thiol, and diphenylenevinylene methanethiol), all affording reliable bilayer formation when 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes were incubated with self-assembled monolayers of these thiols. Characterization of the resultant structures, using cyclic voltammetry, impedance analysis, and atomic force microscopy, confirms the bilayer formation. Significant differences in electrochemical blocking and mechanical characteristics of these new bilayers were identified in comparison to their alkanethiol counterparts. Taking advantage of these new features, we present a new scheme for the straightforward biorecognition of a lipolytic enzyme (phospholipase A2) using these phospholipid/aromatic thiol bilayers. PMID:25896646

  5. The costs of nurse turnover, part 2: application of the Nursing Turnover Cost Calculation Methodology.

    PubMed

    Jones, Cheryl Bland

    2005-01-01

    This is the second article in a 2-part series focusing on nurse turnover and its costs. Part 1 (December 2004) described nurse turnover costs within the context of human capital theory, and using human resource accounting methods, presented the updated Nursing Turnover Cost Calculation Methodology. Part 2 presents an application of this method in an acute care setting and the estimated costs of nurse turnover that were derived. Administrators and researchers can use these methods and cost information to build a business case for nurse retention. PMID:15647669

  6. Spatial turnover in the global avifauna

    PubMed Central

    Gaston, Kevin J; Davies, Richard G; Orme, C. David L; Olson, Valerie A; Thomas, Gavin H; Ding, Tzung-Su; Rasmussen, Pamela C; Lennon, Jack J; Bennett, Peter M; Owens, Ian P.F; Blackburn, Tim M

    2007-01-01

    Despite its wide implications for many ecological issues, the global pattern of spatial turnover in the occurrence of species has been little studied, unlike the global pattern of species richness. Here, using a database on the breeding distributions of birds, we present the first global maps of variation in spatial turnover for an entire taxonomic class, a pattern that has to date remained largely a matter of conjecture, based on theoretical expectations and extrapolation of inconsistent patterns from different biogeographic realms. We use these maps to test four predictions from niche theory as to the form that this variation should take, namely that turnover should increase with species richness, towards lower latitudes, and with the steepness of environmental gradients and that variation in turnover is determined principally by rare (restricted) species. Contrary to prediction, we show that turnover is high both in areas of extremely low and high species richness, does not increase strongly towards the tropics, and is related both to average environmental conditions and spatial variation in those conditions. These results are closely associated with a further important and novel finding, namely that global patterns of spatial turnover are driven principally by widespread species rather than the restricted ones. This complements recent demonstrations that spatial patterns of species richness are also driven principally by widespread species, and thus provides an important contribution towards a unified model of how terrestrial biodiversity varies both within and between the Earth's major land masses. PMID:17472910

  7. On gigahertz spectral turnovers in pulsars

    NASA Astrophysics Data System (ADS)

    Rajwade, K.; Lorimer, D. R.; Anderson, L. D.

    2016-01-01

    Pulsars are known to emit non-thermal radio emission that is generally a power-law function of frequency. In some cases, a turnover is seen at frequencies around 100 MHz. Kijak et al. have reported the presence of a new class of `Gigahertz Peaked Spectrum' (GPS) pulsars that show spectral turnovers at frequencies around 1 GHz. We apply a model based on free-free thermal absorption to explain these turnovers in terms of surrounding material such as the dense environments found in H II regions, pulsar wind nebulae, or in cold, partially ionized molecular clouds. We show that the turnover frequency depends on the electron temperature of the environment close to the pulsar, as well as the emission measure along the line of sight. We fitted this model to the radio fluxes of known GPS pulsars and show that it can replicate the GHz turnover. From the thermal absorption model, we demonstrate that normal pulsars would exhibit a GPS-like behaviour if they were in a dense environment. We discuss the application of this model in the context of determining the population of neutron stars within the central parsec of the Galaxy. We show that a non-negligible fraction of this population might exhibit high-frequency spectral turnovers, which has implications on the detectability of these sources in the Galactic Centre.

  8. Doxorubicin enhances nucleosome turnover around promoters.

    PubMed

    Yang, Fan; Kemp, Christopher J; Henikoff, Steven

    2013-05-01

    Doxorubicin is an anthracycline DNA intercalator that is among the most commonly used anticancer drugs. Doxorubicin causes DNA double-strand breaks in rapidly dividing cells, although whether it also affects general chromatin properties is unknown. Here, we use a metabolic labeling strategy to directly measure nucleosome turnover to examine the effect of doxorubicin on chromatin dynamics in squamous cell carcinoma cell lines derived from genetically defined mice. We find that doxorubicin enhances nucleosome turnover around gene promoters and that turnover correlates with gene expression level. Consistent with a direct action of doxorubicin, enhancement of nucleosome turnover around promoters gradually increases with time of exposure to the drug. Interestingly, enhancement occurs both in wild-type cells and in cells lacking either the p53 tumor suppressor gene or the master regulator of the DNA damage response, ATM, suggesting that doxorubicin action on nucleosome dynamics is independent of the DNA damage checkpoint. In addition, another anthracycline drug, aclarubicin, shows similar effects on enhancing nucleosome turnover around promoters. Our results suggest that anthracycline intercalation promotes nucleosome turnover around promoters by its effect on DNA topology, with possible implications for mechanisms of cell killing during cancer chemotherapy. PMID:23602475

  9. Rapid Lateral Diffusion of Phospholipids in Rabbit Sarcoplasmic Reticulum

    PubMed Central

    Scandella, Carl J.; Devaux, Philippe; McConnell, Harden M.

    1972-01-01

    Phospholipid spin labels incorporated in the sarcoplasmic reticulum from rabbit-skeletal muscle undergo rapid lateral diffusion within the plane of the membrane. The diffusion constant, D, is 6×10-8 cm2/sec at 37°. With this diffusion constant, a phospholipid molecule can diffuse a distance of the order of 5000 nm in 1 sec. PMID:4506073

  10. Different oxidized phospholipid molecules unequally affect bilayer packing.

    PubMed

    Megli, Francesco M; Russo, Luciana

    2008-01-01

    The aim of this study was to gain more detailed knowledge about the effect of the presence of defined oxidized phospholipid molecules in phospholipid bilayers. After chromatographic and mass spectrometry analysis, the previously used product of the Fenton reaction with unsaturated lecithins proved to consist of a plethora of oxidatively modified lecithins, useless either for the detailed study of the effects brought about in the bilayer or as the source of defined oxidized phospholipid molecules. The latter, particularly 2-(omega-carboxyacyl)- and 2-(n-hydroperoxyacyl)-lecithins, can be more conveniently prepared by chemical or enzymatic synthesis rather than by chemical or physical oxidation. The effect of those molecules and of commercially available 12-hydroxy-stearic and dodecanedioic acid was studied in planar supported phospholipid bilayers (SPBs) by use of EPR spectrometry. The SPBs also contained 2-(5-doxylstearoyl)-lecithin as the spin probe, and the EPR spectral anisotropy loss, indicative of bilayer disordering, was measured as a function of the molar percentage of oxidized lipid. Most oxidized lipid molecules examined in this study were able to induce bilayer disordering, while hydroperoxyl group-bearing acyl chains appeared to be much less effective. It is concluded that the effects of different oxidized phospholipids on phospholipid bilayer structure cannot be generalized, as happens with batch-oxidized phospholipids, and that the use of defined oxidized phospholipid molecular species for membrane oxidative stress guarantees a more reliable and detailed response. PMID:18054893

  11. The costs of nurse turnover: part 1: an economic perspective.

    PubMed

    Jones, Cheryl Bland

    2004-12-01

    Nurse turnover is costly for healthcare organizations. Administrators and nurse executives need a reliable estimate of nurse turnover costs and the origins of those costs if they are to develop effective measures of reducing nurse turnover and its costs. However, determining how to best capture and quantify nurse turnover costs can be challenging. Part 1 of this series conceptualizes nurse turnover via human capital theory and presents an update of a previously developed method for determining the costs of nurse turnover, the Nursing Turnover Cost Calculation Method. Part 2 (January 2005) presents a recent application of the methodology in an acute care hospital. PMID:15632752

  12. Regulation of lung surfactant phospholipid synthesis and metabolism.

    PubMed

    Goss, Victoria; Hunt, Alan N; Postle, Anthony D

    2013-02-01

    The alveolar type II epithelial (ATII) cell is highly specialised for the synthesis and storage, in intracellular lamellar bodies, of phospholipid destined for secretion as pulmonary surfactant into the alveolus. Regulation of the enzymology of surfactant phospholipid synthesis and metabolism has been extensively characterised at both molecular and functional levels, but understanding of surfactant phospholipid metabolism in vivo in either healthy or, especially, diseased lungs is still relatively poorly understood. This review will integrate recent advances in the enzymology of surfactant phospholipid metabolism with metabolic studies in vivo in both experimental animals and human subjects. It will highlight developments in the application of stable isotope-labelled precursor substrates and mass spectrometry to probe lung phospholipid metabolism in terms of individual molecular lipid species and identify areas where a more comprehensive metabolic model would have considerable potential for direct application to disease states. PMID:23200861

  13. Regulation of Phospholipid Synthesis in Escherichia coli by Guanosine Tetraphosphate

    PubMed Central

    Merlie, John P.; Pizer, Lewis I.

    1973-01-01

    Phospholipid synthesis has been reported to be subject to stringent control in Escherichia coli. We present evidence that demonstrates a strict correlation between guanosine tetraphosphate accumulation and inhibition of phospholipid synthesis. In vivo experiments designed to examine the pattern of phospholipid labeling with 32P-inorganic phosphate and 32P-sn-glycerol-3-phosphate suggest that regulation must occur at the glycerol-3-phosphate acyltransferase step. Assay of phospholipid synthesis by cell-free extracts and semipurified preparations revealed that guanosine tetraphosphate inhibits at least two enzymes specific for the biosynthetic pathway, sn-glycerol-3-phosphate acyltransferase as well as sn-glycerol-3-phosphate phosphatidyl transferase. These findings provide a biochemical basis for the stringent control of lipid synthesis as well as regulation of steady-state levels of phospholipid in growing cells. Images PMID:4583220

  14. Addressing employee turnover and retention: keeping your valued performers.

    PubMed

    McConnell, Charles R

    2011-01-01

    Employee turnover and employee retention are inextricably linked; to control turnover is to enhance retention. Turnover is a relatively simple concept; however, considerable confusion often results when addressing turnover because of differences in how it is defined; that is, what is counted, how it is counted, and how the turnover rates are expressed. Turnover is also costly, although not enough attention is paid to its cost because so much of it is indirect and thus not readily visible. There are a variety of causes of turnover, some that can be corrected and some that cannot be avoided. Reducing or otherwise controlling turnover requires continuing management attention to its causes and constant recognition of what can and should be controlled and what cannot be controlled. Ongoing attention to turnover is an essential part of the department manager's role; every improvement in turnover is a direct improvement in retention, with eventual positive effects on the bottom line. PMID:21808181

  15. Phospholipid Species in Newborn and 4 Month Old Infants after Consumption of Different Formulas or Breast Milk

    PubMed Central

    Uhl, Olaf; Fleddermann, Manja; Hellmuth, Christian; Demmelmair, Hans; Koletzko, Berthold

    2016-01-01

    Introduction Arachidonic acid (AA) and docosahexaenoic acid (DHA) are important long-chain polyunsaturated fatty acids for neuronal and cognitive development and are ingredients of infant formulae that are recommended but there is no evidence based minimal supplementation level available. The aim of this analysis was to investigate the effect of supplemented AA and DHA on phospholipid metabolism. Methods Plasma samples of a randomized, double-blind infant feeding trial were used for the analyses of phospholipid species by flow-injection mass spectrometry. Healthy term infants consumed isoenergetic formulae (intervention formula with equal amounts of AA and DHA—IF, control formula without additional AA and DHA—CF) from the first month of life until the age of 120 days. A group of breast milk (BM) -fed infants was followed as a reference. Results The plasma profile detected in newborns was different from 4 month old infants, irrespective of study group. Most relevant changes were seen in higher level of LPC16:1, LPC20:4, PC32:1, PC34:1 and PC36:4 and lower level of LPC18:0, LPC18:2, PC32:2, PC36:2 and several ether-linked phosphatidylcholines in newborns. The sum of all AA and DHA species at 4 month old infants in the CF group showed level of 40% (AA) and 51% (DHA) of newborns. The supplemented amount of DHA resulted in phospholipid level comparable to BM infants, but AA phospholipids were lower than in BM infants. Interestingly, relative contribution of DHA was higher in ether-linked phosphatidylcholines in CF fed infants, but IF and BM fed infants showed higher overall ether-linked phosphatidylcholines levels. Conclusion In conclusion, we have shown that infant plasma phospholipid profile changes remarkably from newborn over time and is dependent on the dietary fatty acid composition. A supplementation of an infant formula with AA and DHA resulted in increased related phospholipid species. PMID:27571269

  16. Fibrillation of β amyloid peptides in the presence of phospholipid bilayers and the consequent membrane disruption.

    PubMed

    Qiang, Wei; Yau, Wai-Ming; Schulte, Jürgen

    2015-01-01

    Fibrillation of β amyloid (Aβ) peptides and the accumulation of amyloid plaques are considered as an important clinical hallmark to identify Alzheimer's disease (AD). The physiological connection between Aβ plaques and the disruption of neuronal cells has not been clearly understood. One hypothesis to explain the Aβ neurotoxicity is that the fibrillation process induces disruption to the cellular membrane. We studied the Aβ fibrillation process in two biologically relevant conditions with the peptide either pre-incorporated into or externally added to the synthetic phospholipid bilayers. These two sample preparation conditions mimic the physiological membrane proximities of Aβ peptides before and after the enzymatic cleavage of amyloid precursor protein (APP). Using thioflavin T (ThT) fluorescence and transmission electron microscopy (TEM), we were able to monitor the kinetics and morphological evolution of fibril formation, which was highly sensitive to the two sample preparation protocols. While the external addition protocol generates long and mature fibrils through normal fibrillation process, the pre-incubation protocol was found to stabilize the immature protofibrils. Fluorescence spectroscopy studies with doubly-labeled phospholipids indicated that there may be a lipid uptake process associated with the fibril formation. Solid state nuclear magnetic resonance (NMR) spectroscopy provided evidence for high resolution structural variations in fibrils formed with different protocols, and in particular the stabilization of long-range contact between N- and C-terminal β strands. In addition, disruption of phospholipid bilayers was supported by measurements with ³¹P chemical shifts and relaxation time constants. PMID:24769158

  17. The effect of hydroxylated fatty acid-containing phospholipids in the remodeling of lipid membranes.

    PubMed

    Piotto, Stefano; Trapani, Alfonso; Bianchino, Erminia; Ibarguren, Maitane; López, David J; Busquets, Xavier; Concilio, Simona

    2014-06-01

    The synthetic fatty acid 2-hydroxyoleic acid (2OHOA) is an antitumor drug that regulates membrane lipid composition and structure. An important effect of this drug is the restoration of sphingomyelin (SM) levels in cancer cell membranes, where the SM concentration is lower than in non-tumor cells. It is well known that free fatty acid concentration in cell membranes is lower than 5%, and that fatty acid excess is rapidly incorporated into phospholipids. In a recent work, we have considered the effect of free 2OHOA in model membranes in liquid ordered (Lo) and liquid disordered (Ld) phases, by using all-atom molecular dynamics. This study concerns membranes that are modified upon incorporation of 2OHOA into different phospholipids. 2OHOA-containing phospholipids have a permanent effect on lipid membranes, making a Ld membrane surface more compact and less hydrated, whereas the opposite effect is observed in Lo domains. Moreover, the hydroxyl group of fatty acid chains increases the propensity of Ld model membranes to form hexagonal or other non-lamellar structures. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy. PMID:24463068

  18. Allosteric regulation of G protein-coupled receptor activity by phospholipids.

    PubMed

    Dawaliby, Rosie; Trubbia, Cataldo; Delporte, Cédric; Masureel, Matthieu; Van Antwerpen, Pierre; Kobilka, Brian K; Govaerts, Cédric

    2016-01-01

    Lipids are emerging as key regulators of membrane protein structure and activity. These effects can be attributed either to the modification of bilayer properties (thickness, curvature and surface tension) or to the binding of specific lipids to the protein surface. For G protein-coupled receptors (GPCRs), the effects of phospholipids on receptor structure and activity remain poorly understood. Here we reconstituted purified β2-adrenergic receptor (β2R) in high-density lipoparticles to systematically characterize the effect of biologically relevant phospholipids on receptor activity. We observed that the lipid headgroup type affected ligand binding (agonist and antagonist) and receptor activation. Specifically, phosphatidylgycerol markedly favored agonist binding and facilitated receptor activation, whereas phosphatidylethanolamine favored antagonist binding and stabilized the inactive state of the receptor. We then showed that these effects could be recapitulated with detergent-solubilized lipids, demonstrating that the functional modulation occurred in the absence of a bilayer. Our data suggest that phospholipids act as direct allosteric modulators of GPCR activity. PMID:26571351

  19. Cholesterol transfer between lipid vesicles. Effect of phospholipids and gangliosides.

    PubMed Central

    Thomas, P D; Poznansky, M J

    1988-01-01

    The effect of lipid composition on the rate of cholesterol movement between cellular membranes is investigated using lipid vesicles. The separation of donor and acceptor vesicles required for rate measurement is achieved by differential centrifugation so that the lipid effect can be quantified in the absence of a charged lipid generally used for ion-exchange-based separation. The rate of cholesterol transfer from small unilamellar vesicles (SUVs) containing 50 mol% cholesterol to a common large unilamellar vesicle (LUV) acceptor containing 20 mol% cholesterol decreases with increasing mol% of sphingomyelin in the SUVs, while phosphatidylethanolamine and phosphatidylserine have no appreciable effect at physiologically relevant levels. There is a large decrease in rate when phosphatidylethanolamine constitutes 50 mol% of donor phospholipids. Interestingly, gangliosides which have the same hydrocarbon moiety as sphingomyelin exert an opposite effect. The effect of spingomyelin seems to be mediated by its ability to decrease the fluidity of the lipid matrix, while that of gangliosides may arise from a weakening of phosphatidylcholine-cholesterol interactions or from a more favourable (less polar) microenvironment for the desorption of cholesterol provided by the head-group interactions involving sugar residues. If the effect of asymmetric transbilayer distribution of lipids is taken into consideration, the observed composition-dependent rate changes could partly account for the large difference in the rates of cholesterol desorption from the inner and outer layers of plasma membrane. Such rate differences may be responsible for an unequal steady-state distribution of cholesterol among various cellular membranes and lipoproteins. PMID:3390160

  20. The impact of phospholipids and phospholipid removal on bioanalytical method performance.

    PubMed

    Carmical, Jennifer; Brown, Stacy

    2016-05-01

    Phospholipids (PLs) are a component of cellmembranes, biological fluids and tissues. These compounds are problematic for the bioanalytical chemist, especially when PLs are not the analytes of interest. PL interference with bioanalysis highly impacts reverse-phase chromatographic methods coupled with mass spectrometric detection. Phospholipids are strongly retained on hydrophobic columns, and can cause significant ionization suppression in the mass spectrometer, as they outcompete analyte molecules for ionization. Strategies for improving analyte detection in the presence of PLs are reviewed, including in-analysis modifications and sample preparation strategies. Removal of interfering PLs prior to analysis seems to be most effective atmoderating thematrix effects fromthese endogenous cellular components, and has the potential to simplify chromatography and improve column lifetime. Products targeted at PL removal for sample pre-treatment, as well as products that combine multiplemodes of sample preparation (i.e. Hybrid SPE), show significant promise inmediating the effect on PL interference in bioanalysis. PMID:26773720

  1. Predictors of Staff Turnover and Turnover Intentions within Addiction Treatment Settings: Change Over Time Matters

    PubMed Central

    Garner, Bryan R; Hunter, Brooke D

    2014-01-01

    This study examined the extent to which changes over time in clinicians’ responses to measures of work attitude (eg, job satisfaction) and psychological climate (eg, supervisor support) could predict actual turnover and turnover intentions above and beyond absolute levels of these respective measures. Longitudinal data for this study were collected from a sample of clinicians (N = 96) being trained to implement an evidence-based treatment for adolescent substance use disorders. Supporting findings from a recent staff turnover study, we found job satisfaction change was able to predict actual turnover above and beyond average levels of job satisfaction. Representing new contributions to the staff turnover literature, we also found that change over time in several other key measures (eg, job satisfaction, role manageability, role clarity) explained a significant amount of variance in turnover intentions above and beyond the absolute level of each respective measure. A key implication of the current study is that organizations seeking to improve their ability to assess risk for staff turnover may want to consider assessing staff at multiple points in time in order to identify systematic changes in key employee attitudes like turnover intentions and job satisfaction. PMID:25336960

  2. Predictors of Staff Turnover and Turnover Intentions within Addiction Treatment Settings: Change Over Time Matters.

    PubMed

    Garner, Bryan R; Hunter, Brooke D

    2014-01-01

    This study examined the extent to which changes over time in clinicians' responses to measures of work attitude (eg, job satisfaction) and psychological climate (eg, supervisor support) could predict actual turnover and turnover intentions above and beyond absolute levels of these respective measures. Longitudinal data for this study were collected from a sample of clinicians (N = 96) being trained to implement an evidence-based treatment for adolescent substance use disorders. Supporting findings from a recent staff turnover study, we found job satisfaction change was able to predict actual turnover above and beyond average levels of job satisfaction. Representing new contributions to the staff turnover literature, we also found that change over time in several other key measures (eg, job satisfaction, role manageability, role clarity) explained a significant amount of variance in turnover intentions above and beyond the absolute level of each respective measure. A key implication of the current study is that organizations seeking to improve their ability to assess risk for staff turnover may want to consider assessing staff at multiple points in time in order to identify systematic changes in key employee attitudes like turnover intentions and job satisfaction. PMID:25336960

  3. Phospholipid monolayers between fluid and solid states.

    PubMed Central

    Helm, C A; Möhwald, H; Kjaer, K; Als-Nielsen, J

    1987-01-01

    Monolayers of the phospholipid dimyristoyl phosphatidic acid on the surface of water have been studied by a combination of the new techniques of synchrotron x-ray diffraction and fluorescence microscopy with classical surface pressure data. The pressure vs. area isotherm changes slope at the surface pressures pi c and pi s. The optical technique demonstrates that between pi c and pi s the fluid phase coexists with a denser "gel" phase. Electron diffraction data have shown that the gel phase has bond orientational order over tens of micrometers. However, the x-ray data demonstrate that positional correlations extend only over tens of angstroms. Thus, the gel phase is not crystalline. Above pi s a solid phase is formed with a positional correlation range that is eight times longer for the chemically purest films. Images FIGURE 1 FIGURE 2 PMID:3651557

  4. Simulations of zwitterionic and anionic phospholipid monolayers.

    PubMed

    Kaznessis, Yiannis N; Kim, Sangtae; Larson, Ronald G

    2002-04-01

    Results of atomistic molecular dynamics simulations of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol monolayers at the air/water interface are presented. Dipalmitoylphosphatidylcholine is zwitterionic and dipalmitoylphosphatidylglycerol is anionic at physiological pH. NaCl and CaCl2 water subphases are simulated. The simulations are carried out at different surface densities, and a simulation cell geometry is chosen that greatly facilitates the investigation of phospholipid monolayer properties. Ensemble average monolayer properties calculated from simulation are in agreement with experimental measurements. The dependence of the properties of the monolayers on the surface density, the type of the headgroup, and the ionic environment are explained in terms of atomistically detailed pair distribution functions and electron density profiles, demonstrating the strength of simulations in investigating complex, multicomponent systems of biological importance. PMID:11916834

  5. Retaining your high performers: moderators of the performance-job satisfaction-voluntary turnover relationship.

    PubMed

    Nyberg, Anthony

    2010-05-01

    Two divergent ideas explain the relationship between performance and voluntary turnover. One suggests that higher performing employees, who are rewarded for their superior work product, will desire to remain with an organization that values their performance and will, consequently, be less likely than lower performing employees to voluntarily leave. An alternative idea suggests that higher performing employees, who are more desirable to external companies as a result of their superior work product, will have more external job opportunities and will, consequently, be more likely than their lower performing colleagues to voluntarily leave. The current study evaluated the behaviors and attitudes of 12,545 insurance employees over a 3-year period to examine how these 2 divergent expectations influence the performance-voluntary turnover relationship. Results show that both pay growth and the relevant unemployment rate interact with performance to influence the performance-voluntary turnover relationship and that they work independently of employee job satisfaction influences. PMID:20476825

  6. Phospholipids at the Interface: Current Trends and Challenges

    PubMed Central

    Pichot, Roman; Watson, Richard L.; Norton, Ian T.

    2013-01-01

    Phospholipids are one of the major structural elements of biological membranes. Due to their amphiphilic character, they can adopt various molecular assemblies when dispersed in water, such as bilayer vesicles or micelles, which give them unique interfacial properties and render them very attractive in terms of foam or emulsion stabilization. This article aims at reviewing the properties of phospholipids at the air/water and oil/water interfaces, as well as the recent advances in using these natural components as stabilizers, alone or in combination with other compounds such as proteins. A discussion regarding the challenges and opportunities offered by phospholipids-stabilized structure concludes the review. PMID:23736688

  7. Comparative Proteome Analysis of hAT-MSCs Isolated from Chronic Renal Failure Patients with Differences in Their Bone Turnover Status

    PubMed Central

    Akpinar, Gurler; Tuncay, Mehmet; Aksoy, Ayça; Karaoz, Erdal

    2015-01-01

    The relationship between the stem cells and the bone turnover in uremic bone disease due to chronic renal failure (CRF) is not described. The aim of this study was to investigate the effect of bone turnover status on stem cell properties. To search for the presence of such link and shed some light on stem-cell relevant mechanisms of bone turnover, we carried out a study with mesenchymal stem cells. Tissue biopsies were taken from the abdominal subcutaneous adipose tissue of a CRF patient with secondary hyperparathyroidism with the high turnover bone disease. This patient underwent parathyroidectomy operation (PTX) and another sample was taken from this patient after PTX. A CRF patient with adynamic bone disease with low turnover and a healthy control were also included. Mesenchymal stem cells isolated from the subjects were analyzed using proteomic and molecular approaches. Except ALP activity, the bone turnover status did not affect common stem cell properties. However, detailed proteome analysis revealed the presence of regulated protein spots. A total of 32 protein spots were identified following 2D gel electrophoresis and MALDI-TOF/TOF analyzes. The identified proteins were classified into seven distinct groups and their potential relationship to bone turnover were discussed. Distinct protein expression patterns emerged in relation to the bone turnover status indicate a possible link between the stem cells and bone turnover in uremic bone disease due to CRF. PMID:26575497

  8. Docosahexaenoate-containing molecular species of glycerophospholipids from frog retinal rod outer segments show different rates of biosynthesis and turnover

    SciTech Connect

    Louie, K.; Wiegand, R.D.; Anderson, R.E.

    1988-12-13

    The authors have studied the de novo synthesis and subsequent turnover of major docosahexaenoate-containing molecular species in frog rod outer segment (ROS) phospholipids following intravitreal injection of (2-/sup 3/H)glycerol. On selected days after injection, ROS were prepared and phospholipids extracted. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) were isolated and converted to diradylglycerols with phospholipase C. Diradylglycerols were derivatized with benzoic anhydride and resolve into diacylglycerobenzoates and ether-linked glycerobenzoates. The diacylglycerobenzoates were fractionated into molecular species by HPLC, quantitated, and counted for radioactivity. Label was incorporated into ROS phospholipids by day 1 and was followed up through the eighth day. The dipolyenoic species 22:6-22:6 from PC showed 1 3-5 times higher radiospecific activity than the same species from either PE or PS. The rate of decline was determined by calculating the half-life of each molecular species, which was used as a measure of the turnover of the species. The percent distribution of radioactivity in the molecular species of PC and PE was quite different from the relative mass distribution at day 1. However, percent dpm approached the mole percent by 31 days. In PS, percent dpm and mole percent were the same at all time points. These results indicate that the molecular species composition of PC and PE in frog retinal ROS is determined by a combination of factors, which include rate of synthesis, rate of degradation, and selective interconversions. In contrast, PS composition appears to be determined at the time of synthesis.

  9. Quantification of isotopic turnover in agricultural systems

    NASA Astrophysics Data System (ADS)

    Braun, A.; Auerswald, K.; Schnyder, H.

    2012-04-01

    The isotopic turnover, which is a proxy for the metabolic rate, is gaining scientific importance. It is quantified for an increasing range of organisms, from microorganisms over plants to animals including agricultural livestock. Additionally, the isotopic turnover is analyzed on different scales, from organs to organisms to ecosystems and even to the biosphere. In particular, the quantification of the isotopic turnover of specific tissues within the same organism, e.g. organs like liver and muscle and products like milk and faeces, has brought new insights to improve understanding of nutrient cycles and fluxes, respectively. Thus, the knowledge of isotopic turnover is important in many areas, including physiology, e.g. milk synthesis, ecology, e.g. soil retention time of water, and medical science, e.g. cancer diagnosis. So far, the isotopic turnover is quantified by applying time, cost and expertise intensive tracer experiments. Usually, this comprises two isotopic equilibration periods. A first equilibration period with a constant isotopic input signal is followed by a second equilibration period with a distinct constant isotopic input signal. This yields a smooth signal change from the first to the second signal in the object under consideration. This approach reveals at least three major problems. (i) The input signals must be controlled isotopically, which is almost impossible in many realistic cases like free ranging animals. (ii) Both equilibration periods may be very long, especially when the turnover rate of the object under consideration is very slow, which aggravates the first problem. (iii) The detection of small or slow pools is improved by large isotopic signal changes, but large isotopic changes also involve a considerable change in the input material; e.g. animal studies are usually carried out as diet-switch experiments, where the diet is switched between C3 and C4 plants, since C3 and C4 plants differ strongly in their isotopic signal. The

  10. Phospholipid synthesis in HeLa cells exposed to immunoglobulin G and complement

    PubMed Central

    Güttler, Flemming

    1972-01-01

    1. HeLa cells were cultured in the presence of heterologous immunoglobulin G and guinea-pig serum together with [32P]phosphate. 2. Incorporation of [32P]phosphate was significantly stimulated by anti-HeLa immunoglobulin G and complement-sufficient serum compared with immunoglobulin G from unimmunized rabbits and complement. Within 2.5h heat-inactivated guinea-pig serum and anti-HeLa immunoglobulin G stimulated [32P]phosphate incorporation to the same extent as heat-inactivated complement and immunoglobulin G from unimmunized rabbits. 3. Compared with cells exposed to immunoglobulin G from unimmunized rabbits together with complement, anti-HeLa immunoglobulin G with complement increased the phospholipid content of HeLa cells twofold within 5h of incubation. 4. Exposure of HeLa cells to anti-HeLa immunoglobulin G and complement for 5–22h resulted in a twofold increase in the net accumulation of [32P]phosphate in sphingomyelin and phosphatidylcholine and a 50% increase in the net accumulation of [32P]phosphate in phosphatidylethanolamine, compared with cultures exposed to immunoglobulin G from unimmunized rabbits and complement. 5. A transient accumulation of 32P-labelled lysophosphoglycerides in HeLa cells exposed to antibody and complement was detected, confirming previous findings (Güttler & Clausen, 1969b). 6. The stimulation of [32P]phosphate turnover occurred in cells filling up their cytoplasma with vacuoles. This supports the suggestion that the accumulation of phospholipid in these cells may be concerned with the synthesis and function of cytomembranes. PMID:4674125

  11. Mitochondrial protein turnover: methods to measure turnover rates on a large scale

    PubMed Central

    Chan, X’avia CY; Black, Caitlin M; Lin, Amanda J; Ping, Peipei; Lau, Edward

    2016-01-01

    Mitochondrial proteins carry out diverse cellular functions including ATP synthesis, ion homeostasis, cell death signaling, and fatty acid metabolism and biogenesis. Compromised mitochondrial quality control is implicated in various human disorders including cardiac diseases. Recently it has emerged that mitochondrial protein turnover can serve as an informative cellular parameter to characterize mitochondrial quality and uncover disease mechanisms. The turnover rate of a mitochondrial protein reflects its homeostasis and dynamics under the quality control systems acting on mitochondria at a particular cell state. This review article summarizes some recent advances and outstanding challenges for measuring the turnover rates of mitochondrial proteins in health and disease. PMID:25451168

  12. Herpes simplex virus 1 induces de novo phospholipid synthesis

    SciTech Connect

    Sutter, Esther; Oliveira, Anna Paula de; Tobler, Kurt; Schraner, Elisabeth M.; Sonda, Sabrina; Kaech, Andres; Lucas, Miriam S.; Ackermann, Mathias; Wild, Peter

    2012-08-01

    Herpes simplex virus type 1 capsids bud at nuclear membranes and Golgi membranes acquiring an envelope composed of phospholipids. Hence, we measured incorporation of phospholipid precursors into these membranes, and quantified changes in size of cellular compartments by morphometric analysis. Incorporation of [{sup 3}H]-choline into both nuclear and cytoplasmic membranes was significantly enhanced upon infection. [{sup 3}H]-choline was also part of isolated virions even grown in the presence of brefeldin A. Nuclei expanded early in infection. The Golgi complex and vacuoles increased substantially whereas the endoplasmic reticulum enlarged only temporarily. The data suggest that HSV-1 stimulates phospholipid synthesis, and that de novo synthesized phospholipids are inserted into nuclear and cytoplasmic membranes to i) maintain membrane integrity in the course of nuclear and cellular expansion, ii) to supply membrane constituents for envelopment of capsids by budding at nuclear membranes and Golgi membranes, and iii) to provide membranes for formation of transport vacuoles.

  13. A phospholipid uptake system in the model plant Arabidopsis thaliana.

    PubMed

    Poulsen, Lisbeth R; López-Marqués, Rosa L; Pedas, Pai R; McDowell, Stephen C; Brown, Elizabeth; Kunze, Reinhard; Harper, Jeffrey F; Pomorski, Thomas G; Palmgren, Michael

    2015-01-01

    Plants use solar energy to produce lipids directly from inorganic elements and are not thought to require molecular systems for lipid uptake from the environment. Here we show that Arabidopsis thaliana Aminophospholipid ATPase10 (ALA10) is a P4-type ATPase flippase that internalizes exogenous phospholipids across the plasma membrane, after which they are rapidly metabolized. ALA10 expression and phospholipid uptake are high in the epidermal cells of the root tip and in guard cells, the latter of which regulate the size of stomatal apertures to modulate gas exchange. ALA10-knockout mutants exhibit reduced phospholipid uptake at the root tips and guard cells and are affected in growth and transpiration. The presence of a phospholipid uptake system in plants is surprising. Our results suggest that one possible physiological role of this system is to internalize lysophosphatidylcholine, a signalling lipid involved in root development and stomatal control. PMID:26212235

  14. p53 attenuates AKT signaling by modulating membrane phospholipid composition

    PubMed Central

    Rueda-Rincon, Natalia; Bloch, Katarzyna; Derua, Rita; Vyas, Rajesh; Harms, Amy; Hankemeier, Thomas; Khan, Niamat Ali; Dehairs, Jonas; Bagadi, Muralidhararao; Binda, Maria Mercedes; Waelkens, Etienne; Marine, Jean-Christophe; Swinnen, Johannes V.

    2015-01-01

    The p53 tumor suppressor is the central component of a complex network of signaling pathways that protect organisms against the propagation of cells carrying oncogenic mutations. Here we report a previously unrecognized role of p53 in membrane phospholipids composition. By repressing the expression of stearoyl-CoA desaturase 1, SCD, the enzyme that converts saturated to mono-unsaturated fatty acids, p53 causes a shift in the content of phospholipids with mono-unsaturated acyl chains towards more saturated phospholipid species, particularly of the phosphatidylinositol headgroup class. This shift affects levels of phosphatidylinositol phosphates, attenuates the oncogenic AKT pathway, and contributes to the p53-mediated control of cell survival. These findings expand the p53 network to phospholipid metabolism and uncover a new molecular pathway connecting p53 to AKT signaling. PMID:26061814

  15. Inhibition by calmodulin of calcium/phospholipid-dependent protein phosphorylation.

    PubMed Central

    Albert, K A; Wu, W C; Nairn, A C; Greengard, P

    1984-01-01

    Calmodulin was previously found to inhibit the Ca2+/phospholipid-dependent phosphorylation of an endogenous substrate, called the 87-kilodalton protein, in a crude extract prepared from rat brain synaptosomal cytosol. We investigated the mechanism of this inhibition, using Ca2+/phospholipid-dependent protein kinase and the 87-kilodalton protein, both of which had been purified to homogeneity from bovine brain. Rabbit brain calmodulin and some other Ca2+-binding proteins inhibited the phosphorylation of the 87-kilodalton protein by this kinase in the purified system. Calmodulin also inhibited the Ca2+/phospholipid-dependent phosphorylation of H1 histone, synapsin I, and the delta subunit of the acetylcholine receptor, with use of purified components. These results suggest that calmodulin may be a physiological regulator of Ca2+/phospholipid-dependent protein kinase. Images PMID:6233611

  16. Supported phospholipid/alkanethiol biomimetic membranes: insulating properties.

    PubMed Central

    Plant, A L; Gueguetchkeri, M; Yap, W

    1994-01-01

    A novel model lipid bilayer membrane is prepared by the addition of phospholipid vesicles to alkanethiol monolayers on gold. This supported hybrid bilayer membrane is rugged, easily and reproducibly prepared in the absence of organic solvent, and is stable for very long periods of time. We have characterized the insulating characteristics of this membrane by examining the rate of electron transfer and by impedance spectroscopy. Supported hybrid bilayers formed from phospholipids and alkanethiols are pinhole-free and demonstrate measured values of conductivity and resistivity which are within an order of magnitude of that reported for black lipid membranes. Capacitance values suggest a dielectric constant of 2.7 for phospholipid membranes in the absence of organic solvent. The protein toxin, melittin, destroys the insulating capability of the phospholipid layer without significantly altering the bilayer structure. This model membrane will allow the assessment of the effect of lipid membrane perturbants on the insulating properties of natural lipid membranes. PMID:7811924

  17. Evidence that phospholipid turnover is the signal transducing system coupled to serotonin-S2 receptor sites

    SciTech Connect

    de Chaffoy de Courcelles, D.; Leysen, J.E.; De Clerck, F.; Van Belle, H.; Janssen, P.A.

    1985-06-25

    Upon stimulation with serotonin of washed human platelets prelabeled with (/sup 32/P)orthophosphate, the authors found an approximately 250% increase in (/sup 32/P)phosphatidic acid (PA) formation, a small decrease in (/sup 32/P)phosphatidylinositol 4,5-bisphosphate, and a concomitant increase in (/sup 32/P)phosphatidylinositol 4-phosphate. Using (/sup 3/H)arachidonate for prelabeling, (/sup 3/H)diacylglycerol accumulated transiently at 10 s after addition of the agonist, (/sup 3/H)PA increased but to a lower extent compared to /sup 32/P-labeled lipid, and the formation of both (/sup 3/H)polyphosphoinositides increased. The serotonin-induced dose-dependent changes in (/sup 32/P)PA correlate with its effect on the changes in slope of aggregation of platelets. The potency of 13 drugs to antagonize the serotonin-induced PA formation closely corresponds to both their potency to inhibit platelet aggregation and their binding affinity for serotonin-S2 receptor sites. It is suggested that at least part of the signal transducing system following activation of the serotonin-S2 receptors involves phospholipase C catalyzed inositol lipid breakdown yielding diacylglycerol which is subsequently phosphorylated to PA.

  18. Novel Phospholipid-Protein Conjugates Allow Improved Detection of Antibodies in Patients with Autoimmune Diseases

    PubMed Central

    Nybo, Mads; Macaubas, Claudia; Lønstrup, Lars; Balboni, Imelda M.; Mellins, Elizabeth D.; Astakhova, Kira

    2016-01-01

    Reliable measurement of clinically relevant autoimmune antibodies toward phospholipid-protein conjugates is highly desirable in research and clinical assays. To date, the development in this field has been limited to the use of natural heterogeneous antigens. However, this approach does not take structural features of biologically active antigens into account and leads to low reliability and poor scientific test value. Here we describe novel phospholipid-protein conjugates for specific detection of human autoimmune antibodies. Our synthetic approach includes mild oxidation of synthetic phospholipid cardiolipin, and as the last step, coupling of the product with azide-containing linker and copper-catalyzed click chemistry with β2-glycoprotein I and prothrombin. To prove utility of the product antigens, we used enzyme-linked immunosorbent assay and three cohorts of samples obtained from patients in Denmark (n = 34) and the USA (n = 27 and n = 14). Afterwards we analyzed correlation of the obtained autoantibody titers with clinical parameters for each patient. Our results prove that using novel antigens clinically relevant autoantibodies can be detected with high repeatability, sensitivity and specificity. Unlike previously used antigens the obtained autoantibody titers strongly correlate with high disease activity and in particular, with arthritis, renal involvement, anti-Smith antibodies and high lymphocyte count. Importantly, chemical composition of antigens has a strong influence on the correlation of detected autoantibodies with disease activity and manifestations. This confirms the crucial importance of antigens’ composition on research and diagnostic assays, and opens up exciting perspectives for synthetic antigens in future studies of autoimmunity. PMID:27257889

  19. Effects of gamma irradiation on solid and lyophilised phospholipids

    NASA Astrophysics Data System (ADS)

    Stensrud, G.; Redford, K.; Smistad, G.; Karlsen, J.

    1999-11-01

    The effects of gamma irradiation (25 kGy) as a sterilisation method for phospholipids (distearoylphosphatidylcholine and distearoylphosphatidylglycerol) were investigated. 31P-NMR revealed minor chemical degradation of the phospholipids but lower dynamic viscosity and pseudoplasticity, lower turbidity, higher diffusion constant, smaller size, more negative zeta potential and changes in the phase transition behaviour of the subsequently produced liposomes were observed. The observed changes could to some extent be explained by the irradiation-induced degradation products (distearoylphosphatidic acid, fatty acids, lysophospholipids).

  20. Uncoupling binding of substrate CO from turnover by vanadium nitrogenase

    PubMed Central

    Lee, Chi Chung; Fay, Aaron W.; Weng, Tsu-Chien; Krest, Courtney M.; Hedman, Britt; Hodgson, Keith O.; Hu, Yilin; Ribbe, Markus W.

    2015-01-01

    Biocatalysis by nitrogenase, particularly the reduction of N2 and CO by this enzyme, has tremendous significance in environment- and energy-related areas. Elucidation of the detailed mechanism of nitrogenase has been hampered by the inability to trap substrates or intermediates in a well-defined state. Here, we report the capture of substrate CO on the resting-state vanadium-nitrogenase in a catalytically competent conformation. The close resemblance of this active CO-bound conformation to the recently described structure of CO-inhibited molybdenum-nitrogenase points to the mechanistic relevance of sulfur displacement to the activation of iron sites in the cofactor for CO binding. Moreover, the ability of vanadium-nitrogenase to bind substrate in the resting-state uncouples substrate binding from subsequent turnover, providing a platform for generation of defined intermediate(s) of both CO and N2 reduction. PMID:26515097

  1. A Turnover Model for the Mexican Maquiladoras.

    ERIC Educational Resources Information Center

    Maertz, Carl P.; Stevens, Michael J.; Campion, Michael A.

    2003-01-01

    From interviews with 47 Mexican maquiladora workers, a model of voluntary turnover was created and compared with models from the United States, Canada, England, and Australia. Despite similarities, the cultural and economic environment affected the precise content of antecedents in the Mexican model. (Contains 63 references.) (SK)

  2. Home Visitor Job Satisfaction and Turnover.

    ERIC Educational Resources Information Center

    Buchbinder, Sharon B.; Duggan, Anne K.; Young, Elizabeth; Fuddy, Loretta; Sia, Cal

    This paper summarizes findings of a 3-year study of the job satisfaction and turnover of home visitors, both professional and paraprofessional, in programs which link families-at-risk for impaired functioning to medical home care and other resources. Specifically, the study examined: (1) home visitor personal characteristics that influence…

  3. Job Turnover Intentions Among Pharmacy Faculty

    PubMed Central

    Conklin, Mark H.

    2007-01-01

    Objectives To determine the primary reasons why pharmacy faculty intend to remain or leave their current institution and why they left their most recent academic institution, and the relative contribution of various organizational and individual characteristics toward explaining variance in turnover intentions. Methods A survey instrument was e-mailed to pharmacy faculty members asking respondents to indicate up to 5 reasons for their intentions and up to 5 reasons why they left a previous institution. The survey also elicited perceptions on quality of work life in addition to demographic and institutional data, upon which turnover intentions were regressed using a forward-conditional procedure. Organizational commitment as a moderator of turnover intentions was regressed over the remaining variables not acting directly on employer intentions. Results Just over 1 in 5 respondents indicated intentions to leave their current academic institution. Excessive workload, seeking a new challenge, poor salary, and poor relationships with college or school administrators were frequently cited as reasons for leaving. Turnover intentions are influenced directly by department chair support and organizational commitment, which moderates various support and satisfaction variables. Conclusions Pharmacy faculty members’ decision to remain or leave an institution is dependent upon developing a sense of commitment toward the institution. Commitment is facilitated by support from the institution and department chair, in addition to a sense of satisfaction with the teaching environment. PMID:17786250

  4. Teacher Turnover in Charter Schools. Research Brief

    ERIC Educational Resources Information Center

    Stuit, David; Smith, Thomas M.

    2010-01-01

    The current study aimed to contribute to a deeper understanding of the organizational conditions of charter schools by examining teacher turnover. Using data from the National Center for Education Statistics (NCES) 2003-04 Schools and Staffing Survey (SASS) and the Teacher Follow-Up Survey (TFS), researchers from the National Center on School…

  5. Turnover of Public School Superintendents in Arizona

    ERIC Educational Resources Information Center

    Meyer, Joyce Ntsoaki

    2013-01-01

    This study used a descriptive qualitative design utilizing a phenomenological approach to determine and examine the reasons behind the voluntary or involuntary turnover of Arizona school superintendents. Open-ended questions were used to interview five superintendents who had left their districts between 2008 and 2013 about their perceptions on…

  6. Cusp catastrophe model of employee turnover.

    PubMed

    Sheridan, J E; Abelson, M A

    1983-09-01

    A cusp catastrophe model is developed to explain job turnover of nursing employees. The temporal dynamics of the catastrophe model suggest that leavers experience lower organization commitment than do stayers prior to termination. Leavers' perceptions of job tension and commitment appear to cross the threshold levels prior to the termination dates. PMID:10262614

  7. Employee Development and Turnover Intention: Theory Validation

    ERIC Educational Resources Information Center

    Rahman, Wali; Nas, Zekeriya

    2013-01-01

    Purpose: This study aims to examine the pattern of behavior of turnover intentions in developing countries "vis-a-vis" the one in advanced countries through the empirical data from public universities in Khyber Pakhtunkhwa, Pakistan. The study provides empirical evidence from academia in Pakistan, thereby enriching the understanding of…

  8. Antecedents of Norwegian Beginning Teachers' Turnover Intentions

    ERIC Educational Resources Information Center

    Tiplic, Dijana; Brandmo, Christian; Elstad, Eyvind

    2015-01-01

    This study aims at exploring several individual, organizational, and contextual factors that may affect beginning teachers' turnover intentions during their first years of practice. The sample consists of 227 beginning teachers (69% female and 31% male) from 133 schools in Norway. The results show four important antecedents of beginning teachers'…

  9. Normal Bone Turnover in Transient Hyperphosphatasemia

    PubMed Central

    Kutilek, Stepan; Cervickova, Barbora; Bebova, Pavla; Kmonickova, Marie; Nemec, Vladimir

    2012-01-01

    Transient hyperphosphatasemia of infancy and early childhood (THI) is characterized by a temporary isolated elevation of serum alkaline phosphatase activity (ALP), predominantly its bone or liver isoform, in either sick or healthy children under 5 years of age. Return to normal ALP levels usually occurs within four months. Spontaneous rise of ALP might concern the physician, especially when treating seriously ill children. However, THI is considered a benign biochemical disorder with no clinical consequences. Some existing reports support the hypothesis that THI is a result of increased bone turnover. We present evidence of normal bone turnover in two children with THI. In a one-year-old girl and a boy of the same age, high ALP levels (31 and 109 μkat/L, respectively) were accidentally detected. The children had no signs of metabolic bone disease or of liver disease. The high ALP levels returned to normal in two months, thus fulfilling the diagnosis of THI. In both patients, serum parathyroid hormone and bone turnover markers, serum CrossLaps, and serum osteocalcin were neither elevated, nor did these markers follow the ALP dynamics, thus reflecting normal bone turnover in THI. Children with THI should be spared from extensive investigations and unnecessary vitamin D treatment. Conflict of interest:None declared. PMID:22664360

  10. Costing Child Protective Services Staff Turnover.

    ERIC Educational Resources Information Center

    Graef, Michelle I.; Hill, Erick L.

    2000-01-01

    Details process of determining a child welfare agency's actual dollar costs directly attributed to protective services staff turnover, using the agency's human resources database and interviews with administrative personnel. Provides formulas and process for calculating specific cost elements due to employee separation, replacement, and training.…

  11. Director Turnover: An Australian Academic Development Study

    ERIC Educational Resources Information Center

    Fraser, Kym; Ryan, Yoni

    2012-01-01

    Although it can be argued that directors of central academic development units (ADUs) are critical to the implementation of university teaching and learning strategies, it would appear there is a high director turnover rate. While research in the USA, the UK, and Australia illustrates that ADUs are frequently closed or restructured, that research…

  12. Hyaluronan and phospholipid association in biolubrication.

    PubMed

    Wang, Min; Liu, Chao; Thormann, Esben; Dėdinaitė, Andra

    2013-12-01

    It is becoming increasingly clear that the outstanding lubrication of synovial joints is achieved by a sophisticated hierarchical structure of cartilage combined with synergistic actions of surface-active components present in the synovial fluid. In this work we focus on the association of two components of the synovial fluid, hyaluronan and dipalmitoyl phosphatidyl choline (DPPC), in bulk solution and at interfaces. We demonstrate that hyaluronan associates with DPPC vesicles and adsorbs to supported DPPC bilayers. The association structures formed at the interface are sufficiently stable to allow sequential adsorption of DPPC and hyaluronan, whereby promoting the formation of thick composite layers of these two components. The lubricating ability of such composite layers was probed by the AFM colloidal probe technique and found to be very favorable with low friction coefficients and high load bearing capacity. With DPPC as the last adsorbed component, a friction coefficient of 0.01 was found up to pressures significantly above what is encountered in healthy synovial joints. Hyaluronan as the last added component increases the friction coefficient to 0.03 and decreases the load bearing capacity somewhat (but still above what is needed in the synovial joint). Our data demonstrate that self-assembly structures formed by hyaluronan and phospholipids at interfaces are efficient aqueous lubricants, and it seems plausible that such self-assembly structures contribute to the exceptional lubrication of synovial joints. PMID:24171653

  13. Millimeter-area, free standing, phospholipid bilayers.

    PubMed

    Beltramo, Peter J; Van Hooghten, Rob; Vermant, Jan

    2016-05-11

    Minimal model biomembrane studies have the potential to unlock the fundamental mechanisms of cellular function that govern the processes upon which life relies. However, existing methods to fabricate free-standing model membranes currently have significant limitations. Bilayer sizes are often tens of micrometers, decoupling curvature or substrate effects, orthogonal control over tension, and solvent exchange combined with microscopy techniques is not possible, which restricts the studies that can be performed. Here, we describe a versatile platform to generate free standing, planar, phospholipid bilayers with millimeter scale areas. The technique relies on an adapted thin-film balance apparatus allowing for the dynamic control of the nucleation and growth of a planar black lipid membrane in the center of an orifice surrounded by microfluidic channels. Success is demonstrated using several different lipid types, including mixtures that show the same temperature dependent phase separation as existing protocols, moreover, membranes are highly stable. Two advantages unique to the proposed method are the dynamic control of the membrane tension and the possibility to make extremely large area membranes. We demonstrate this by showing how a block polymer, F68, used in drug delivery increases the membrane compliance. Together, the results demonstrate a new paradigm for studying the mechanics, structure, and function of model membranes. PMID:27050618

  14. Specific RNA binding to ordered phospholipid bilayers

    PubMed Central

    Janas, Tadeusz; Janas, Teresa; Yarus, Michael

    2006-01-01

    We have studied RNA binding to vesicles bounded by ordered and disordered phospholipid membranes. A positive correlation exists between bilayer order and RNA affinity. In particular, structure-dependent RNA binding appears for rafted (liquid-ordered) domains in sphingomyelin-cholesterol-1,2-dioleoyl-sn-glycero-3-phosphocholine vesicles. Binding to more highly ordered gel phase membranes is stronger, but much less RNA structure-dependent. All modes of RNA-membrane association seem to be electrostatic and headgroup directed. Fluorometry on 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes indicates that bound RNA broadens the gel-fluid melting transition, and reduces lipid headgroup order, as detected via fluorometric measurement of intramembrane electric fields. RNA preference for rafted lipid was visualized and confirmed using multiple fluorophores that allow fluorescence and fluorescence resonance energy transfer microscopy on RNA molecules closely associated with ordered lipid patches within giant vesicles. Accordingly, both RNA structure and membrane order could modulate biological RNA–membrane interactions. PMID:16641318

  15. Enhancement by cytidine of membrane phospholipid synthesis

    NASA Technical Reports Server (NTRS)

    G-Coviella, I. L.; Wurtman, R. J.

    1992-01-01

    Cytidine, as cytidine 5'-diphosphate choline, is a major precursor in the synthesis of phosphatidylcholine in cell membranes. In the present study, we examined the relationships between extracellular levels of cytidine, the conversion of [14C]choline to [14C]phosphatidylcholine, and the net syntheses of phosphatidylcholine and phosphatidylethanolamine by PC12 cells. The rate at which cytidine (as [3H]cytidine) was incorporated into the PC12 cells followed normal Michaelis-Menten kinetics (Km = 5 microM; Vmax = 12 x 10(-3) mmol/mg of protein/min) when the cytidine concentrations in the medium were below 50 microM; at higher concentrations, intracellular [3H]cytidine nucleotide levels increased linearly. Once inside the cell, cytidine was converted mainly into cytidine triphosphate. In pulse-chase experiments, addition of cytidine to the medium caused a time- and dose-dependent increase (by up to 30%) in the incorporation of [14C]choline into membrane [14C]-phosphatidylcholine. When the PC12 cells were supplemented with both cytidine and choline for 14 h, small but significant elevations (p less than 0.05) were observed in their absolute contents of membrane phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine, all increasing by 10-15% relative to their levels in cells incubated with choline alone. Exogenous cytidine, acting via cytidine triphosphate, can thus affect the synthesis and levels of cell membrane phospholipids.

  16. Molecular Insights into Phospholipid -- NSAID Interactions

    NASA Astrophysics Data System (ADS)

    Babu Boggara, Mohan; Krishnamoorti, Ramanan

    2007-03-01

    Non steroidal anti inflammatory drugs (NSAIDs) e.g. Aspirin and Ibuprofen, with chronic usage cause gastro intestinal (GI) toxicity. It has been shown experimentally that NSAIDs pre-associated with phospholipids reduce the GI toxicity and also increase the therapeutic activity of these drugs compared to the unmodified ones. Using all atomistic simulations and two different methodologies, we studied the partitioning behavior of two model NSAIDs (Aspirin and Ibuprofen) as a function of pH and drug loading. The results from two methodologies are consistent in describing the equilibrium drug distribution in the bilayers. Additionally, the heterogeneity in density and polarity of the bilayer in the normal direction along with the fact that NSAIDs are amphiphilic (all of them have a carboxylic acid group and a non-polar part consisting of aromatic moieties), indicate that the diffusion mechanism in the bilayer is far different compared to the same in a bulk medium. This study summarizes the various effects of NSAIDs and their behavior inside the lipid bilayer both as a function of pH and drug concentration.

  17. Effects of phospholipids on renal function.

    PubMed

    Buckalew, V M; Strandhoy, J W; Handa, R K

    1993-01-01

    The effects of two classes of phospholipids (PL) on renal function have been studied. Bolus injections of 1 ng (10 pmol) of lysophosphatidylcholine (LPC) caused natriuresis and diuresis in rats. Natriuretic activity was eliminated by substituting unsaturated bonds in the 1-acyl group and by removing the choline group on the sn-3 position. Natriuretic activity was not affected by substitution of 1-alkyl for 1-acyl groups. In the dog, LPC was natriuretic when given as a bolus of 3.0 micrograms/kg or as a constant infusion at 5 ng/kg/min. To explore further the effect of alkyl PLs on renal function, a series of studies with platelet activating factor (PAF) was performed. PAF injected directly into the renal artery (IR) in bolus doses of 0.5-10 ng/kg caused renal vasodilation that was blocked by a specific PAF receptor antagonist. This effect was not due to release of vasodilatory eicosanoids, dopamine, or nitric oxide (NO). PAF given IR as a continuous infusion at 2.5 ng/kg/min attenuated the renal vasoconstrictor effects of angiotensin II and norepinephrine but not vasopressin. This effect to attenuate vasoconstriction was blocked by the NO inhibitor N-monomethyl-L-arginine. These studies using picomolar amounts of PL suggest a physiologic role for these compounds in control of renal function. PMID:7508037

  18. Lipid metabolizing enzyme activities modulated by phospholipid substrate lateral distribution.

    PubMed

    Salinas, Dino G; Reyes, Juan G; De la Fuente, Milton

    2011-09-01

    Biological membranes contain many domains enriched in phospholipid lipids and there is not yet clear explanation about how these domains can control the activity of phospholipid metabolizing enzymes. Here we used the surface dilution kinetic theory to derive general equations describing how complex substrate distributions affect the activity of enzymes following either the phospholipid binding kinetic model (which assumes that the enzyme molecules directly bind the phospholipid substrate molecules), or the surface-binding kinetic model (which assumes that the enzyme molecules bind to the membrane before binding the phospholipid substrate). Our results strongly suggest that, if the enzyme follows the phospholipid binding kinetic model, any substrate redistribution would increase the enzyme activity over than observed for a homogeneous distribution of substrate. Besides, enzymes following the surface-binding model would be independent of the substrate distribution. Given that the distribution of substrate in a population of micelles (each of them a lipid domain) should follow a Poisson law, we demonstrate that the general equations give an excellent fit to experimental data of lipases acting on micelles, providing reasonable values for kinetic parameters--without invoking special effects such as cooperative phenomena. Our theory will allow a better understanding of the cellular-metabolism control in membranes, as well as a more simple analysis of the mechanisms of membrane acting enzymes. PMID:21108012

  19. Biomimetic surface modification of polyurethane with phospholipids grafted carbon nanotubes.

    PubMed

    Tan, Dongsheng; Liu, Liuxu; Li, Zhen; Fu, Qiang

    2015-08-01

    To improve blood compatibility of polyurethane (PU), phospholipids grafted carbon nanotubes (CNTs) were prepared through zwitterion-mediated cycloaddition reaction and amide condensation, and then were added to the PU as fillers via solution mixing to form biomimetic surface. The properties of phospholipids grafted CNTs (CNT-PC) were investigated by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and proton nuclear magnetic resonance ((1) H NMR). The results indicated that the phospholipids were grafted onto CNTs in high efficiency, and the hydrophilicity and dispersibility of the modified CNTs were improved effectively. The structures and properties of composites containing CNT-PC were investigated by optical microscope, XPS, and water contact angles. The results indicated that phospholipids were enriched on the surface with addition of 0.1 wt % of CNT-PC, which significantly reduced protein adsorption and platelet adhesion. The method of carrying phospholipids on the nanofiller to modify polymers has provided a promising way of constructing biomimetic phospholipid membrane on the surface to improve blood compatibility. PMID:25630300

  20. Looking for a Challenge? Watch That Labour Turnover!

    ERIC Educational Resources Information Center

    Wilkinson, Roderick

    1975-01-01

    Low labor turnover is an essential factor in the success of an enterprise. Steps in dealing with the turnover problem include: establish the objective, get the facts, decide what to do, take action, and check results. (MW)

  1. Staff turnover: occasional friend, frequent foe, and continuing frustration.

    PubMed

    McConnell, C R

    1999-09-01

    Turnover appears to be a relatively simple concept. However, considerable confusion results when discussing turnover because of differences in how it is defined--what is counted, how it is counted, and how the rate of turnover is expressed. Turnover is also costly, although not enough attention is paid to turnover's cost because so much of it is indirect and thus not readily visible. There are a variety of causes of turnover, some which can be corrected and some which cannot be avoided. Reducing or otherwise controlling turnover requires continuing management attention to its causes and constant recognition of what can and should be controlled and what cannot be controlled. Ongoing attention to turnover is an essential part of the department manager's role. PMID:10747463

  2. A concept analysis of turnover intention: implications for nursing management.

    PubMed

    Takase, Miyuki

    2010-01-01

    This paper provides a review and concept analysis of turnover intention. The aim was to promote Nurse Managers' understanding of the meanings and mechanisms of turnover intention, which could help them counteract nurse turnover. Sixty-six papers published between January 1998 and August 2007 were collected from CINAHL, PubMed, and PsycINFO databases, and were subjected to Rogers' concept analysis. The results showed that turnover intention is a multi-stage process involving the voluntary departure of employees from their current position, and is triggered by negative psychological responses to internal/external job context. These psychological responses evolve into withdrawal cognition and behaviours, and lead to actual turnover. To prevent nurse turnover, Nurse Managers should closely observe the internal and external causes of turnover, and the stage of nurses' turnover intention. PMID:20394269

  3. Work-Related Variables and Turnover Intention among Registered Nurses.

    ERIC Educational Resources Information Center

    Pooyan, Abdullah; And Others

    1990-01-01

    Health institutions have become more interested in the causes of job turnover among registered nurses. Proper management of job turnover can improve the financial health and long-term survival of health care institutions. (Author)

  4. Gaussian Process Modeling of Protein Turnover.

    PubMed

    Rahman, Mahbubur; Previs, Stephen F; Kasumov, Takhar; Sadygov, Rovshan G

    2016-07-01

    We describe a stochastic model to compute in vivo protein turnover rate constants from stable-isotope labeling and high-throughput liquid chromatography-mass spectrometry experiments. We show that the often-used one- and two-compartment nonstochastic models allow explicit solutions from the corresponding stochastic differential equations. The resulting stochastic process is a Gaussian processes with Ornstein-Uhlenbeck covariance matrix. We applied the stochastic model to a large-scale data set from (15)N labeling and compared its performance metrics with those of the nonstochastic curve fitting. The comparison showed that for more than 99% of proteins, the stochastic model produced better fits to the experimental data (based on residual sum of squares). The model was used for extracting protein-decay rate constants from mouse brain (slow turnover) and liver (fast turnover) samples. We found that the most affected (compared to two-exponent curve fitting) results were those for liver proteins. The ratio of the median of degradation rate constants of liver proteins to those of brain proteins increased 4-fold in stochastic modeling compared to the two-exponent fitting. Stochastic modeling predicted stronger differences of protein turnover processes between mouse liver and brain than previously estimated. The model is independent of the labeling isotope. To show this, we also applied the model to protein turnover studied in induced heart failure in rats, in which metabolic labeling was achieved by administering heavy water. No changes in the model were necessary for adapting to heavy-water labeling. The approach has been implemented in a freely available R code. PMID:27229456

  5. Relating microbial community structure to functioning in forest soil organic carbon transformation and turnover.

    PubMed

    You, Yeming; Wang, Juan; Huang, Xueman; Tang, Zuoxin; Liu, Shirong; Sun, Osbert J

    2014-03-01

    Forest soils store vast amounts of terrestrial carbon, but we are still limited in mechanistic understanding on how soil organic carbon (SOC) stabilization or turnover is controlled by biotic and abiotic factors in forest ecosystems. We used phospholipid fatty acids (PLFAs) as biomarker to study soil microbial community structure and measured activities of five extracellular enzymes involved in the degradation of cellulose (i.e., β-1,4-glucosidase and cellobiohydrolase), chitin (i.e., β-1,4-N-acetylglucosaminidase), and lignin (i.e., phenol oxidase and peroxidase) as indicators of soil microbial functioning in carbon transformation or turnover across varying biotic and abiotic conditions in a typical temperate forest ecosystem in central China. Redundancy analysis (RDA) was performed to determine the interrelationship between individual PFLAs and biotic and abiotic site factors as well as the linkage between soil microbial structure and function. Path analysis was further conducted to examine the controls of site factors on soil microbial community structure and the regulatory pathway of changes in SOC relating to microbial community structure and function. We found that soil microbial community structure is strongly influenced by water, temperature, SOC, fine root mass, clay content, and C/N ratio in soils and that the relative abundance of Gram-negative bacteria, saprophytic fungi, and actinomycetes explained most of the variations in the specific activities of soil enzymes involved in SOC transformation or turnover. The abundance of soil bacterial communities is strongly linked with the extracellular enzymes involved in carbon transformation, whereas the abundance of saprophytic fungi is associated with activities of extracellular enzymes driving carbon oxidation. Findings in this study demonstrate the complex interactions and linkage among plant traits, microenvironment, and soil physiochemical properties in affecting SOC via microbial regulations. PMID

  6. Structure and interactive properties of highly fluorinated phospholipid bilayers.

    PubMed Central

    McIntosh, T J; Simon, S A; Vierling, P; Santaella, C; Ravily, V

    1996-01-01

    Because liposomes containing fluoroalkylated phospholipids are being developed for in vivo drug delivery, the structure and interactive properties of several fluoroalkylated glycerophosphocholines (PCs) were investigated by x-ray diffraction/osmotic stress, dipole potential, and hydrophobic ion binding measurements. The lipids included PCs with highly fluorinated tails on both alkyl chains and PCs with one hydrocarbon chain and one fluoroalkylated chain. Electron density profiles showed high electron density peaks in the center of the bilayer corresponding to the fluorine atoms. The height and width of these high density peaks varied systematically, depending on the number of fluorines and their position on the alkyl chains, and on whether the bilayer was in the gel or liquid crystalline phase. Wide-angle diffraction showed that in both gel and liquid crystalline bilayers the distance between adjacent alkyl chains was greater in fluoroalkylated PCs than in analogous hydrocarbon PCs. For interbilayer separations of less than about 8 A, pressure-distance relations for fluoroalkylated PCs were similar to those previously obtained from PC bilayers with hydrocarbon chains. However, for bilayer separations greater than 8A, the total repulsive pressure depended on whether the fluoroalkylated PC was in a gel or liquid-crystalline phase. We argue that these pressure-distance relations contain contributions from both hydration and entropic repulsive pressures. Dipole potentials ranged from -680 mV for PCs with both chains fluoroalkylated to -180 mV for PCs with one chain fluoroalkylated, compared to +415 mV for egg PC. The change in dipole potential as a function of subphase concentration of tetraphenyl-boron was much larger for egg PC than for fluorinated PC monolayers, indicating that the fluorine atoms modified the binding of this hydrophobic anion. Thus, compared to conventional liposomes, liposomes made from fluoroalkylated PCs have different binding properties, which

  7. New insights into water-phospholipid model membrane interactions.

    PubMed

    Milhaud, Jeannine

    2004-05-27

    Modulating the relative humidity (RH) of the ambient gas phase of a phospholipid/water sample for modifying the activity of phospholipid-sorbed water [humidity-controlled osmotic stress methods, J. Chem. Phys. 92 (1990) 4519 and J. Phys. Chem. 96 (1992) 446] has opened a new field of research of paramount importance. New types of phase transitions, occurring at specific values of this activity, have been then disclosed. Hence, it is become recognized that this activity, like the temperature T, is an intensive parameter of the thermodynamical state of these samples. This state can be therefore changed (phase transition) either, by modulating T at a given water activity (a given hydration level), or, by modulating the water activity, at a given T. The underlying mechanisms of these two types of transition differ, especially when they appear as disorderings of fatty chains. In lyotropic transitions, this disordering follows from two thermodynamical laws. First, acting on the activity (the chemical potential) of water external to a phospholipid/water sample, a transbilayer gradient of water chemical potential is created, leading to a transbilayer flux of water (Fick's law). Second, water molecules present within the hydrocarbon region of this phospholipid bilayer interact with phospholipid molecules through their chemical potential (Gibbs-Duhem relation): the conformational state of fatty chains (the thermodynamical state of the phospholipid molecules) changes. This process is slow, as revealed by osmotic stress time-resolved experiments. In thermal chain-melting transitions, the first rapid step is the disordering of fatty chains of a fraction of phospholipid molecules. It occurs a few degrees before the main transition temperature, T(m), during the pretransition and the sub-main transition. The second step, less rapid, is the redistribution of water molecules between the different parts of the sample, as revealed by T-jump time-resolved experiments. Finally, in

  8. Superintendent Turnover in Kentucky. Issues & Answers. REL 2011-No. 113

    ERIC Educational Resources Information Center

    Johnson, Jerry; Huffman, Tyler; Madden, Karen; Shope, Shane

    2011-01-01

    This study examines superintendent turnover in Kentucky public school districts for 1998/99-2007/08, looking at how turnover varies by rural status, Appalachian and non-Appalachian region, and 2007/08 school district characteristics. Key findings include: (1) Kentucky school districts averaged one superintendent turnover during 1998/99-2007/08;…

  9. Salary and Ranking and Teacher Turnover: A Statewide Study

    ERIC Educational Resources Information Center

    Garcia, Cynthia Martinez; Slate, John R.; Delgado, Carmen Tejeda

    2009-01-01

    This study examined three years of data obtained from the Academic Excellence Indicator System of the State of Texas regarding teacher turnover rate and teacher salary. Across all public school districts, teacher salary was consistently negatively related to teacher turnover; that is, where salary was lower, turnover rate was higher When data were…

  10. A Ministudy of employee turnover in US hospitals.

    PubMed

    Collins, Sandra K; McKinnies, Richard C; Matthews, Eric P; Collins, Kevin S

    2015-01-01

    A ministudy was conducted to collect self-reported employee turnover rates in US hospitals. The results indicate many hospitals are struggling with high employee turnover rates. Widespread variances in ratings were observed across hospitals, which may be due to lack of consistency in how they each calculate their employee turnover. This makes benchmarking for the purposes of performance improvement challenging. PMID:25627851

  11. Investing in Leadership: The District's Role in Managing Principal Turnover

    ERIC Educational Resources Information Center

    Mascall, Blair; Leithwood, Kenneth

    2010-01-01

    This article presents the results of research into the impact of principal turnover on schools, and the ability of schools to mitigate the negative effects of frequent turnover by distributing leadership in the schools. The findings from this qualitative and quantitative analysis show that rapid principal turnover does indeed have a negative…

  12. Job Turnover and Job Satisfaction among Nursing Home Aides.

    ERIC Educational Resources Information Center

    Waxman, Howard M.; And Others

    1984-01-01

    Interviewed 234 aides in seven nursing homes concerning job turnover rate, job satisfaction, and perception of milieu. A positive association found between turnover rate and aides' perceptions of the homes' order, organization, and control suggested that job turnover would lessen with more involvement in the decision-making process. (JAC)

  13. Employee Turnover in the Federal Government. A Special Study.

    ERIC Educational Resources Information Center

    Musell, R. Mark

    A study of employee turnover in the Federal government showed that in 1984, about 195,000 full-time, nonpostal Federal workers with permanent appointments left Federal jobs or transferred to other Federal agencies--representing a turnover rate of 11.5 percent. The turnover was about three percentage points higher for white-collar workers than for…

  14. High School Band Students' Perspectives of Teacher Turnover

    ERIC Educational Resources Information Center

    Kloss, Thomas E.

    2013-01-01

    Teacher turnover remains an important issue in education. The least researched perspectives, though, are those of the students who experience teacher turnover. The purpose of this study was to examine how high school band students experience teacher turnover. A total of twelve students were interviewed, representing three schools that experienced…

  15. Job Satisfaction, Commitment, Withdrawal Cognitions and Turnover: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Kerber, Kenneth W.; Campbell, James P.

    Recent research on organizational turnover has examined the validity of the turnover decision process, in particular, the model of employee turnover proposed by Mobley (1977). This study followed-up on a previous (Kerber and Campbell, 1986) study of new employees of a large computer company in which participants completed a questionnaire that…

  16. Phase behavior and permeability properties of phospholipid bilayers containing a short-chain phospholipid permeability enhancer.

    PubMed

    Risbo, J; Jørgensen, K; Sperotto, M M; Mouritsen, O G

    1997-10-01

    The thermodynamic phase behavior and trans-bilayer permeability properties of multilamellar phospholipid vesicles containing a short-chain DC10PC phospholipid permeability enhancer have been studied by means of differential scanning calorimetry and fluorescence spectroscopy. The calorimetric scans of DC14PC lipid bilayer vesicles incorporated with high concentrations of DC10PC demonstrate a distinct influence on the lipid bilayer thermodynamics manifested as a pronounced freezing-point depression and a narrow phase coexistence region. Increasing amounts of DC10PC lead to a progressive lowering of the melting enthalpy, implying a mixing behavior of the DC10PC in the bilayer matrix similar to that of a substitutional impurity. The phase behavior of the DC10PC-DC14PC mixture is supported by fluorescence polarization measurements which, furthermore, in the low-temperature gel phase reveal a non-monotonic concentration-dependent influence on the structural bilayer properties; small concentrations of DC10PC induce a disordering of the acyl chains, whereas higher concentrations lead to an ordering. Irreversible fluorescence quench measurements demonstrate a substantial increase in the trans-bilayer permeability over broad temperature and composition ranges. At temperatures corresponding to the peak positions of the heat capacity, a maximum in the trans-bilayer permeability is observed. The influence of DC10PC on the lipid bilayer thermodynamics and the associated permeability properties is discussed in terms of microscopic effects on the lateral lipid organization and heterogeneity of the bilayer. PMID:9370247

  17. Rhizosphere bacterial carbon turnover is higher in nucleic acids than membrane lipids: implications for understanding soil carbon cycling

    PubMed Central

    Malik, Ashish A.; Dannert, Helena; Griffiths, Robert I.; Thomson, Bruce C.; Gleixner, Gerd

    2015-01-01

    Using a pulse chase 13CO2 plant labeling experiment we compared the flow of plant carbon into macromolecular fractions of rhizosphere soil microorganisms. Time dependent 13C dilution patterns in microbial cellular fractions were used to calculate their turnover time. The turnover times of microbial biomolecules were found to vary: microbial RNA (19 h) and DNA (30 h) turned over fastest followed by chloroform fumigation extraction-derived soluble cell lysis products (14 days), while phospholipid fatty acids (PLFAs) had the slowest turnover (42 days). PLFA/NLFA 13C analyses suggest that both mutualistic arbuscular mycorrhizal and saprophytic fungi are dominant in initial plant carbon uptake. In contrast, high initial 13C enrichment in RNA hints at bacterial importance in initial C uptake due to the dominance of bacterial derived RNA in total extracts of soil RNA. To explain this discrepancy, we observed low renewal rate of bacterial lipids, which may therefore bias lipid fatty acid based interpretations of the role of bacteria in soil microbial food webs. Based on our findings, we question current assumptions regarding plant-microbe carbon flux and suggest that the rhizosphere bacterial contribution to plant assimilate uptake could be higher. This highlights the need for more detailed quantitative investigations with nucleic acid biomarkers to further validate these findings. PMID:25914679

  18. SEC14 Phospholipid Transfer Protein Is Involved in Lipid Signaling-Mediated Plant Immune Responses in Nicotiana benthamiana

    PubMed Central

    Kiba, Akinori; Galis, Ivan; Hojo, Yuko; Ohnishi, Kouhei; Yoshioka, Hirofumi; Hikichi, Yasufumi

    2014-01-01

    We previously identified a gene related to the SEC14-gene phospholipid transfer protein superfamily that is induced in Nicotiana benthamiana (NbSEC14) in response to infection with Ralstonia solanacearum. We here report that NbSEC14 plays a role in plant immune responses via phospholipid-turnover. NbSEC14-silencing compromised expression of defense–related PR-4 and accumulation of jasmonic acid (JA) and its derivative JA-Ile. Transient expression of NbSEC14 induced PR-4 gene expression. Activities of diacylglycerol kinase, phospholipase C and D, and the synthesis of diacylglycerol and phosphatidic acid elicited by avirulent R. solanacearum were reduced in NbSEC14-silenced plants. Accumulation of signaling lipids and activation of diacylglycerol kinase and phospholipases were enhanced by transient expression of NbSEC14. These results suggest that the NbSEC14 protein plays a role at the interface between lipid signaling-metabolism and plant innate immune responses. PMID:24845602

  19. Camptothecin-catalyzed phospholipid hydrolysis in liposomes.

    PubMed

    Saetern, Ann Mari; Skar, Merete; Braaten, Asmund; Brandl, Martin

    2005-01-01

    Hydrolysis of phospholipid (PL) within camptothecin (CPT)-containing liposomes was studied systematically, after elevated lyso-phosphatidylcholine (LPC)-concentrations in pH 5, CPT-containing liposomes (22.1+/-0.9 mol%) relative to control-liposomes (7.3+/-0.5 mol%) occasionally had been observed after four months storage in fridge. Liposomes were prepared by dispersing freeze-dried PL/CPT mixtures in 25 mM phosphate buffered saline (PBS) of varying pH (5.0-7.8) and CPT concentrations (0, 3 and 6 mM). PL-hydrolysis was monitored by HPTLC, quantifying LPC. In an accelerated stability study (60 degrees C), a catalytic effect of CPT on PL-hydrolysis was observed after 40 h, but not up to 30 h of incubation. The pH profile of the hydrolysis indicated a stability optimum at pH 6.0 for the liposomes independent of CPT. The equilibrium point between the more active lactone- and the carboxylate-form of CPT was found to be pH 6.8. As a compromise, pH 6.0 was chosen, assuring >85% CPT to be present in the lactone form. At this pH, both control- and CPT-liposomes showed only minor hydrolysis after autoclaving (121 degrees C, 15 min). Storage at room temperature and in fridge (2 months), as well as accelerated ageing (70 degrees C, 25 h), gave a significant elevation of LPC content in CPT-liposomes relative to control-liposomes. This study demonstrates a catalytic effect of CPT on PL-hydrolysis, the onset of which seems to require a certain threshold level of hydrolytic degradation. PMID:15607259

  20. The Charge Properties of Phospholipid Nanodiscs.

    PubMed

    Her, Cheng; Filoti, Dana I; McLean, Mark A; Sligar, Stephen G; Alexander Ross, J B; Steele, Harmen; Laue, Thomas M

    2016-09-01

    Phospholipids (PLs) are a major, diverse constituent of cell membranes. PL diversity arises from the nature of the fatty acid chains, as well as the headgroup structure. The headgroup charge is thought to contribute to both the strength and specificity of protein-membrane interactions. Because it has been difficult to measure membrane charge, ascertaining the role charge plays in these interactions has been challenging. Presented here are charge measurements on lipid Nanodiscs at 20°C in 100 mM NaCl, 50 mM Tris, at pH 7.4. Values are also reported for measurements made in the presence of Ca(2+) and Mg(2+) as a function of NaCl concentration, pH, and temperature, and in solvents containing other types of cations and anions. Measurements were made for neutral (phosphatidylcholine and phosphatidylethanolamine) and anionic (phosphatidylserine, phosphatidic acid, cardiolipin, and phosphatidylinositol 4,5-bisphosphate (PIP2)) PLs containing palmitoyl-oleoyl and dimyristoyl fatty acid chains. In addition, charge measurements were made on Nanodiscs containing an Escherichia coli lipid extract. The data collected reveal that 1) POPE is anionic and not neutral at pH 7.4; 2) high-anionic-content Nanodiscs exhibit polyelectrolyte behavior; 3) 3 mM Ca(2+) neutralizes a constant fraction of the charge, but not a constant amount of charge, for POPS and POPC Nanodiscs; 4) in contrast to some previous work, POPC only interacts weakly with Ca(2+); 5) divalent cations interact with lipids in a lipid- and ion-specific manner for POPA and PIP2 lipids; and 6) the monovalent anion type has little influence on the lipid charge. These results should help eliminate inconsistencies among data obtained using different techniques, membrane systems, and experimental conditions, and they provide foundational data for developing an accurate view of membranes and membrane-protein interactions. PMID:27602726

  1. Identification of phospholipid species affected by miltefosine action in Leishmania donovani cultures using LC-ELSD, LC-ESI/MS, and multivariate data analysis.

    PubMed

    Imbert, L; Ramos, R G; Libong, D; Abreu, S; Loiseau, P M; Chaminade, P

    2012-01-01

    Leishmaniasis is a widespread parasitic disease principally treated by intravenous drugs. Hexadecylphosphocholine (miltefosine) has recently proved its efficacy by oral route. Although its mechanism of action has been investigated, and principally relies on perturbations of the metabolism of lipids and especially phospholipids, further studies need to be conducted to detect precisely which metabolic pathways are impacted. For this purpose, the present work proposes a complete lipidomic study focused on membrane phospholipids of clones of Leishmania donovani non-treated (NT), treated (T) and resistant (R) to miltefosine. Firstly, a separation of phospholipids in normal phase high-performance liquid chromatography (NP-HPLC) was coupled to a mass spectrometer (MS) equipped with an electrospray (ESI) ion source, and response was compared to evaporative light scattering detection (ELSD). Secondly, a quantification of phospholipid classes was performed using NP-HPLC/ESI/MS on NT, T and R clones of L. donovani. Thirdly, full-scan acquisitions of analyzed samples were compared using orthogonal signal correction-partial least square-discriminant analysis (OSC-PLS-DA) to highlight phospholipid molecular species of interest between the three types of clones. Structural determination of the most relevant species has finally been performed using tandem mass spectrometry. A first hypothesis on the effect of miltefosine on lipid metabolic pathways is then proposed. PMID:22065347

  2. Organisation turnover among registered nurses: an exploratory model.

    PubMed

    Bloom, J R; Alexander, J A; Flatt, S

    1988-11-01

    In light of current concerns over nursing shortages and productivity, turnover among hospital nurses has assumed renewed importance as a managerial issue. This study examines the thesis that organisation of hospital work is a determinant of voluntary turnover among registered nurses. This perspective differs from previous work in this area in that both turnover and its determinants are conceptualised at the organisational rather than individual level, thus opening the way for administrative intervention to reduce turnover. The conceptual model is tested using multiple regression techniques on a sample of 310 community hospitals. Results suggest the importance of administrative work structures and the professionalisation of the workforce as contributors to higher turnover. PMID:10296903

  3. Turnover intention in new graduate nurses: a multivariate analysis

    PubMed Central

    Beecroft, Pauline C; Dorey, Frederick; Wenten, Madé

    2008-01-01

    Title Turnover intention in new graduate nurses: a multivariate analysis Aim This paper is a report of a study to determine the relationship of new nurse turnover intent with individual characteristics, work environment variables and organizational factors and to compare new nurse turnover with actual turnover in the 18 months of employment following completion of a residency. Background Because of their influence on patient safety and health outcomes nurse turnover and turnover intent have received considerable attention worldwide. When nurse staffing is inadequate, especially during nursing shortages, unfavourable clinical outcomes have been documented. Method Prospective data collection took place from 1999 to 2006 with 889 new paediatric nurses who completed the same residency. Scores on study instruments were related to likelihood of turnover intent using logistic regression analysis models. Relationships between turnover intent and actual turnover were compared using Kaplan–Meier survivorship. Results The final model demonstrated that older respondents were more likely to have turnover intent if they did not get their ward choice. Also higher scores on work environment and organizational characteristics contributed to likelihood that the new nurse would not be in the turnover intent group. These factors distinguish a new nurse with turnover intent from one without 79% of the time. Increased seeking of social support was related to turnover intent and older new graduates were more likely to be in the turnover intent group if they did not get their ward choice. Conclusion When new graduate nurses are satisfied with their jobs and pay and feel committed to the organization, the odds against turnover intent decrease. What is already known about this topic There is concern in many countries about nurse turnover and the resulting effects on patient safety and quality of care. Decreasing ability to recruit experienced nurses has increased the emphasis on

  4. Replicator dynamics with turnover of players

    NASA Astrophysics Data System (ADS)

    Juul, Jeppe; Kianercy, Ardeshir; Bernhardsson, Sebastian; Pigolotti, Simone

    2013-08-01

    We study adaptive dynamics in games where players abandon the population at a given rate and are replaced by naive players characterized by a prior distribution over the admitted strategies. We demonstrate how such a process leads macroscopically to a variant of the replicator equation, with an additional term accounting for player turnover. We study how Nash equilibria and the dynamics of the system are modified by this additional term for prototypical examples such as the rock-paper-scissors game and different classes of two-action games played between two distinct populations. We conclude by showing how player turnover can account for nontrivial departures from Nash equilibria observed in data from lowest unique bid auctions.

  5. Role of Cholesterol and Phospholipids in Amylin Misfolding, Aggregation and Etiology of Islet Amyloidosis

    PubMed Central

    Singh, Sanghamitra; Trikha, Saurabh; Bhowmick, Diti Chatterjee; Sarkar, Anjali A.

    2015-01-01

    Amyloidosis is a biological event in which proteins undergo structural transitions from soluble monomers and oligomers to insoluble fibrillar aggregates that are often toxic to cells. Exactly how amyloid proteins, such as the pancreatic hormone amylin, aggregate and kill cells is still unclear. Islet amyloid polypeptide, or amylin, is a recently discovered hormone that is stored and co-released with insulin from pancreatic islet β-cells. The pathology of type 2 diabetes mellitus (T2DM) is characterized by an excessive extracellular and intracellular accumulation of toxic amylin species, soluble oligomers and insoluble fibrils, in islets, eventually leading to β-cell loss. Obesity and elevated serum cholesterol levels are additional risk factors implicated in the development of T2DM. Because the homeostatic balance between cholesterol synthesis and uptake is lost in diabetics, and amylin aggregation is a hallmark of T2DM, this chapter focuses on the biophysical and cell biology studies exploring molecular mechanisms by which cholesterol and phospholipids modulate secondary structure, folding and aggregation of human amylin and other amyloid proteins on membranes and in cells. Amylin turnover and toxicity in pancreatic cells and the regulatory role of cholesterol in these processes are also discussed. PMID:26149927

  6. Health Care Workplace Discrimination and Physician Turnover

    PubMed Central

    Nunez-Smith, Marcella; Pilgrim, Nanlesta; Wynia, Matthew; Desai, Mayur M.; Bright, Cedric; Krumholz, Harlan M.; Bradley, Elizabeth H.

    2013-01-01

    Objective To examine the association between physician race/ethnicity, workplace discrimination, and physician job turnover. Methods Cross-sectional, national survey conducted in 2006–2007 of practicing physicians [n = 529] randomly identified via the American Medical Association Masterfile and The National Medical Association membership roster. We assessed the relationships between career racial/ethnic discrimination at work and several career-related dependent variables, including 2 measures of physician turnover, career satisfaction, and contemplation of career change. We used standard frequency analyses, odds ratios and χ2 statistics, and multivariate logistic regression modeling to evaluate these associations. Results Physicians who self-identified as nonmajority were significantly more likely to have left at least 1 job because of workplace discrimination (black, 29%; Asian, 24%; other race, 21%; Hispanic/Latino, 20%; white, 9%). In multivariate models, having experienced racial/ethnic discrimination at work was associated with high job turnover [adjusted odes ratio, 2.7; 95% CI, 1.4–4.9]. Among physicians who experienced work-place discrimination, only 45% of physicians were satisfied with their careers (vs 88% among those who had not experienced workplace discrimination, p value < .01], and 40% were con-templating a career change (vs 10% among those who had not experienced workplace discrimination, p value < .001). Conclusion Workplace discrimination is associated with physician job turnover, career dissatisfaction, and contemplation of career change. These findings underscore the importance of monitoring for workplace discrimination and responding when opportunities for intervention and retention still exist. PMID:20070016

  7. Strategies to manage low-bone turnover.

    PubMed

    Spasovski, G

    2009-01-01

    A change in paradigm occurred lately whereby not hypocalcemia but hypercalcemia and positive calcium balance were considered negative factors. Namely, the use of calcium- based binders in combination with vitamin D analogues, has been shown to lead to an over-suppression of parathyroid hormone (PTH) and development of low-bone turnover adynamic bone disease (ABD). The changing prevalence of various types of bone diseases from a high to low-bone turnover goes in line with the presence of increased risk for vascular calcification (VC), morbidity and mortality in the dialysis population. The attenuation of the previous great expectations in calcium-based phosphate binders and vitamin D-analogues entailed a new treatment strategy to preserve bone and vascular health. Hence, a new evidence for treatment of ABD with various types of non calcium based binders and low calcium dialysate is presented. Sevelamer treatment has reduced calcium concentration and increased PTH levels, resulting in the improvement of markers of bone turnover, increased bone formation and improved trabecular architecture, providing a slower progression of VC. Data on lanthanum beneficial effect on ABD histology have been demonstrated in long-term clinical studies. Although there is a slow release of lanthanum from its bone deposits after discontinuation of the treatment and no association with aluminium- like bone toxicity, there is still an ongoing scientific debate about its long-term toxic potential. Finally, reducing the number of calcium based binders and low calcium dialysate (1.25 mmol/l) has been reported to have an impact on the evolution towards markers reflecting higher bone turnover. Then, adoption of the non calcium-based binders should be reserved to high risk patients with ABD and progression of vascular calcifications associated with increased morbidity and mortality. PMID:19668299

  8. Turnover of soil monosaccharides: Recycling versus Stabilization

    NASA Astrophysics Data System (ADS)

    Basler, Anna; Dyckmans, Jens

    2014-05-01

    Soil organic matter (SOM) represents a mixture of differently degradable compounds. Each of these compounds are characterised by different dynamics due to different chemical recalcitrance, transformation or stabilisation processes in soil. Carbohydrates represent one of these compounds and contribute up to 25 % to the soil organic matter. Vascular plants are the main source of pentose sugars (Arabinose and Xylose), whereas hexoses (Galactose and Mannose) are primarily produced by microorganisms. Several studies suggest that the mean turnover times of the carbon in soil sugars are similar to the turnover dynamics of the bulk carbon in soil. The aim of the study is to characterise the influence of stabilisation and turnover of soil carbohydrates. Soil samples are collected from (i) a continuous maize cropping experiment ('Höhere Landbauschule' Rotthalmünster, Bavaria) established 1979 on a Stagnic Luvisol and (ii) from a continuous wheat cropping, established 1969, as reference site. The effect of stabilisation is estimated by the comparison of turnover times of microbial and plant derived soil carbohydrates. As the dynamics of plant derived carbohydrate are solely influenced by stabilisation processes, whereas the dynamics of microbial derived carbohydrates are affected by recycling of organic carbon compounds derived by C3 plant substrate as well as stabilisation processes. The compound specific isotopic analysis (CSIA) of soil carbohydrates was performed using a HPLC/o/IRMS system. The chromatographic and mass spectrometric subunits were coupled with a LC-Isolink interface. Soil sugars were extracted after mild hydrolysis using 4 M trifluoroacetic acid (TFA). Chromatographic separation of the sugars was achieved using a low strength 0.25 mM NaOH solution as mobile phase at a ?ow rate of 250 μL min-1 at 10 ° C.

  9. Forest turnover rates follow global and regional patterns of productivity

    USGS Publications Warehouse

    Stephenson, N.L.; van Mantgem, P.J.

    2005-01-01

    Using a global database, we found that forest turnover rates (the average of tree mortality and recruitment rates) parallel broad-scale patterns of net primary productivity. First, forest turnover was higher in tropical than in temperate forests. Second, as recently demonstrated by others, Amazonian forest turnover was higher on fertile than infertile soils. Third, within temperate latitudes, turnover was highest in angiosperm forests, intermediate in mixed forests, and lowest in gymnosperm forests. Finally, within a single forest physiognomic type, turnover declined sharply with elevation (hence with temperature). These patterns of turnover in populations of trees are broadly similar to the patterns of turnover in populations of plant organs (leaves and roots) found in other studies. Our findings suggest a link between forest mass balance and the population dynamics of trees, and have implications for understanding and predicting the effects of environmental changes on forest structure and terrestrial carbon dynamics. ??2005 Blackwell Publishing Ltd/CNRS.

  10. Phospholipids of subcellular organelles isolated from cultured BHK cells.

    PubMed

    Brotherus, J; Renkonen, O

    1977-02-23

    Mitochondrial and nuclei were purified from cultured hamster fibroblasts (BHK21 cells) by centrifugation in sucrose gradients. The phospholipid compositions of the preparations were compared to those of the previously purified plasma membranes, endoplasmic reticulum and lysosomes. The mitochondria had a characteristically high content (approx. 16% of lipid phosphorus) of cardiolipin, which was practically absent from the other purified organelles. The nuclei were enriched in phosphatidylcholine and phosphatidylinositol (approx. 68% and 5% of lipid phosphorus, respectively). Lysobisphosphatidic acid was almost absent from the mitochondria and nuclei, as well as from the plasma membrane and endoplasmic reticulum, which suggests that this phospholipid is confined to the lysosomes of the BHK cell. The nuclei and the mitochondria contained relatively little sphingomyelin, a characteristic lipid of the plasma membrane. The distributions of the total cellular phospholipid and protein between the various organelles were calculated and compared to the corresponding data estimated for the rat liver. The BHK cell contained relatively more phospholipids in the nucleus and the lysosomes than the liver. All the organelles of the BHK cell contained less protein per phospholipid than the equivalent organelles of the liver. PMID:836856

  11. Ibuprofen-phospholipid solid dispersions: improved dissolution and gastric tolerance.

    PubMed

    Hussain, M Delwar; Saxena, Vipin; Brausch, James F; Talukder, Rahmat M

    2012-01-17

    Solid dispersions of ibuprofen with various phospholipids were prepared, and the effect of phospholipids on the in vitro dissolution and in vivo gastrointestinal toxicity of ibuprofen was evaluated. Most phospholipids improved the dissolution of ibuprofen; dimyristoylphosphatidyl-glycerol (DMPG) had the greatest effect. At 45 min, the extent of dissolution of ibuprofen from the ibuprofen-DMPG system (weight ratio 9:1) increased about 69% compared to ibuprofen alone; the initial rate of dissolution increased sevenfold. Increasing the DMPG content from 9:1 to 4:1 in this system did not significantly increase the rate and the extent of dissolution. X-ray diffraction and scanning electron micrograph indicated a smaller crystallite size of ibuprofen with fairly uniform distribution in the ibuprofen-DMPG solid dispersion. A small amount of carrier phospholipid significantly increases the rate and the extent of dissolution, which may increase the bioavailability of ibuprofen. The number of ulcers >0.5mm in size formed in the gastric mucosa of rats following ibuprofen, DMPG, DMPC and DPPC solid dispersions (ibuprofen and phospholipid weight ratio 4:1) were 8.6 ± 6.2, 3.9 ± 5.3, 5.3 ± 4.9 and 9.1 ± 7.4, respectively. Solid dispersion of ibuprofen with DMPG was significantly less irritating to the gastric mucosa than ibuprofen itself (one-way ANOVA, p<0.05). Solid dispersion of ibuprofen and DMPG decreases the gastric side effects of ibuprofen. PMID:22101290

  12. Tracing Viable Bacteria in Wadden Sea Sediments Using Phospholipid Analysis

    NASA Astrophysics Data System (ADS)

    Ruetters, H.; Sass, H.; Cypionka, H.; Rullkotter, J.

    2001-12-01

    Lipid analysis is a commonly used tool for chemotaxonomical characterization of bacterial strains. In particular, phospholipids - determined as polar lipid fatty acids (PLFA) - have proven to be appropriate biomarkers for viable bacterial cells. In this study the lipid content of different bacterial isolates from an intertidal mudflat (Wadden Sea, NW Germany) was investigated. To identify the phospholipids present in the isolated bacteria, fractionated lipid extracts were studied using HPLC-ESI-MS and -MS-MS. This technique gives information on types of phospholipids and their corresponding fatty acid substituents. It could be shown by cluster analyses that the combined information of phospholipid types and corresponding fatty acids allows a better differentiation of bacterial groups than fatty acid patterns determined after whole cell hydrolysis. Sedimentary microbial communities were studied by an interdisciplinary approach using microbiological as well as geochemical techniques. Characteristic phospholipids were traced in the sediment cores (0-70 cm) in order to estimate the relative contributions of different bacterial groups to the sedimentary microbial communities. Seasonal variations of environmental parameters (temperature, sulfate concentrations, oxygen availability etc.) and their influence on the microbial communities were studied.

  13. Morphological and Physical Analysis of Natural Phospholipids-Based Biomembranes

    PubMed Central

    Jacquot, Adrien; Francius, Grégory; Razafitianamaharavo, Angelina; Dehghani, Fariba; Tamayol, Ali; Linder, Michel; Arab-Tehrany, Elmira

    2014-01-01

    Background Liposomes are currently an important part of biological, pharmaceutical, medical and nutritional research, as they are considered to be among the most effective carriers for the introduction of various types of bioactive agents into target cells. Scope of Review In this work, we study the lipid organization and mechanical properties of biomembranes made of marine and plant phospholipids. Membranes based on phospholipids extracted from rapeseed and salmon are studied in the form of liposome and as supported lipid bilayer. Dioleylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) are used as references to determine the lipid organization of marine and plant phospholipid based membranes. Atomic force microscopy (AFM) imaging and force spectroscopy measurements are performed to investigate the membranes' topography at the micrometer scale and to determine their mechanical properties. Major Conclusions The mechanical properties of the membranes are correlated to the fatty acid composition, the morphology, the electrophoretic mobility and the membrane fluidity. Thus, soft and homogeneous mechanical properties are evidenced for salmon phospholipids membrane containing various polyunsaturated fatty acids. Besides, phase segregation in rapeseed membrane and more important mechanical properties were emphasized for this type of membranes by contrast to the marine phospholipids based membranes. General Significance This paper provides new information on the nanomechanical and morphological properties of membrane in form of liposome by AFM. The originality of this work is to characterize the physico-chemical properties of the nanoliposome from the natural sources containing various fatty acids and polar head. PMID:25238543

  14. Identification of a Plasmodium falciparum Phospholipid Transfer Protein*

    PubMed Central

    van Ooij, Christiaan; Withers-Martinez, Chrislaine; Ringel, Alessa; Cockcroft, Shamshad; Haldar, Kasturi; Blackman, Michael J.

    2013-01-01

    Infection of erythrocytes by the human malaria parasite Plasmodium falciparum results in dramatic modifications to the host cell, including changes to its antigenic and transport properties and the de novo formation of membranous compartments within the erythrocyte cytosol. These parasite-induced structures are implicated in the transport of nutrients, metabolic products, and parasite proteins, as well as in parasite virulence. However, very few of the parasite effector proteins that underlie remodeling of the host erythrocyte are functionally characterized. Using bioinformatic examination and modeling, we have found that the exported P. falciparum protein PFA0210c belongs to the START domain family, members of which mediate transfer of phospholipids, ceramide, or fatty acids between membranes. In vitro phospholipid transfer assays using recombinant PFA0210 confirmed that it can transfer phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, and sphingomyelin between phospholipid vesicles. Furthermore, assays using HL60 cells containing radiolabeled phospholipids indicated that orthologs of PFA0210c can also transfer phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine. Biochemical and immunochemical analysis showed that PFA0210c associates with membranes in infected erythrocytes at mature stages of intracellular parasite growth. Localization studies in live parasites revealed that the protein is present in the parasitophorous vacuole during growth and is later recruited to organelles in the parasite. Together these data suggest that PFA0210c plays a role in the formation of the membranous structures and nutrient phospholipid transfer in the malaria-parasitized erythrocyte. PMID:24043620

  15. Generational differences in registered nurse turnover.

    PubMed

    LeVasseur, Sandra A; Wang, Chen-Yen; Mathews, Barbara; Boland, Mary

    2009-08-01

    The chronic nature of the nursing workforce shortage in the United States is a continuing concern. As the nationwide gap between supply and demand grows, it remains unknown what impact turnover will have on nursing, access to care, and efforts to improve quality and safety of health care. It also remains unclear whether the recent turnover trends among new graduate registered nurses differ from past generational cohorts of new nurses. The aims of this study were to identify the reasons why registered nurses turnover by generational cohort (Veterans, Baby Boomers, and GenXMs) and to compare the length of time nurses were employed in their first five nursing positions by generational cohort. The findings suggest the three generational cohorts displayed similar reasons for leaving nursing positions with relocation, career advancement, and personal/family reasons reported most frequently. Except for the first nursing position, significant generational effects were found in the length of time Veterans, Baby Boomer, and GenXMs stayed employed in their nursing positions. It remains unknown why the GenXMs displayed a significantly shorter length of employment time in their second, third, fourth, and fifth nursing positions. The decline in length of employment time displayed in both the Baby Boomers and GenXMs may be an issue of concern requiring future research. PMID:20026454

  16. THE RELATIONSHIP BETWEEN ORGANIZATIONAL JUSTICE AND TURNOVER INTENTION OF HOSPITAL NURSES IN IRAN

    PubMed Central

    Tourani, Sogand; Khosravizadeh, Omid; Omrani, Amir; Sokhanvar, Mobin; Kakemam, Edris; Najafi, Behnam

    2016-01-01

    Background: Despite advances in science and technology, human resources are of the major capital for organizations. Workforce retention is required to improve organizational efficiencies. Objective: Therefore, in this study, the relationship between organizational justice (as one of the most influential factors) and turnover intention was investigated. Methods: This descriptive-analytic study was done in the Comprehensive Jame Women’s Hospital of Tehran in 2015. The statistical sample consisted of 135 nursing staff members. The data were collected using a questionnaire of Beugre’s organizational justice and analyzed by the use of Spearman’s and Anova statistical tests. Results: Averages of organizational justice was obtained to be 68.85 ± 7.67 . Among different sorts of organizational justice, the highest average score of 75.24 ± 16.68 was achieved relevant to interactional justice. A significant relationship was observed between organizational justice (r = -0.36), interactional justice (r = -0.38), and procedural justice (r = -0.36) and turnover intention, but no relation was found between turnover intention and systemic and distributive justice. Furthermore, there was no relationship between demographic variables, organizational justice, and turnover intention. Conclusion: Considering the prominent role of organizational justice in the personnel’s intention to stay or leave and due to the high costs of recruiting and training new staff, managers should pay especial attention to justice and provide their employees’ satisfaction and stability in their organizations by creating a positive mindset in them. PMID:27482163

  17. Phosphocreatine Interacts with Phospholipids, Affects Membrane Properties and Exerts Membrane-Protective Effects

    PubMed Central

    Tokarska-Schlattner, Malgorzata; Epand, Raquel F.; Meiler, Flurina; Zandomeneghi, Giorgia; Neumann, Dietbert; Widmer, Hans R.; Meier, Beat H.; Epand, Richard M.; Saks, Valdur; Wallimann, Theo; Schlattner, Uwe

    2012-01-01

    A broad spectrum of beneficial effects has been ascribed to creatine (Cr), phosphocreatine (PCr) and their cyclic analogues cyclo-(cCr) and phospho-cyclocreatine (PcCr). Cr is widely used as nutritional supplement in sports and increasingly also as adjuvant treatment for pathologies such as myopathies and a plethora of neurodegenerative diseases. Additionally, Cr and its cyclic analogues have been proposed for anti-cancer treatment. The mechanisms involved in these pleiotropic effects are still controversial and far from being understood. The reversible conversion of Cr and ATP into PCr and ADP by creatine kinase, generating highly diffusible PCr energy reserves, is certainly an important element. However, some protective effects of Cr and analogues cannot be satisfactorily explained solely by effects on the cellular energy state. Here we used mainly liposome model systems to provide evidence for interaction of PCr and PcCr with different zwitterionic phospholipids by applying four independent, complementary biochemical and biophysical assays: (i) chemical binding assay, (ii) surface plasmon resonance spectroscopy (SPR), (iii) solid-state 31P-NMR, and (iv) differential scanning calorimetry (DSC). SPR revealed low affinity PCr/phospholipid interaction that additionally induced changes in liposome shape as indicated by NMR and SPR. Additionally, DSC revealed evidence for membrane packing effects by PCr, as seen by altered lipid phase transition. Finally, PCr efficiently protected against membrane permeabilization in two different model systems: liposome-permeabilization by the membrane-active peptide melittin, and erythrocyte hemolysis by the oxidative drug doxorubicin, hypoosmotic stress or the mild detergent saponin. These findings suggest a new molecular basis for non-energy related functions of PCr and its cyclic analogue. PCr/phospholipid interaction and alteration of membrane structure may not only protect cellular membranes against various insults, but could

  18. Oxidized phospholipids as biomarkers of tissue and cell damage with a focus on cardiolipin

    PubMed Central

    Samhan-Arias, Alejandro K.; Ji, Jing; Demidova, Olga M.; Sparvero, Louis J.; Feng, Weihong; Tyurin, Vladimir; Tyurina, Yulia Y.; Epperly, Michael W.; Shvedova, Anna A.; Greenberger, Joel S.; Bayir, Hülya; Kagan, Valerian E.; Amoscato, Andrew A.

    2012-01-01

    Oxidized phospholipid species are important, biologically relevant, lipid signaling molecules that usually exist in low abundance in biological tissues. Along with their inherent stability issues, these oxidized lipids present themselves as a challenge in their detection and identification. Often times, oxidized lipid species can co-chromatograph with non-oxidized species making the detection of the former extremely difficult, even with the use of mass spectrometry. In this study, a normal-phase and reverse-phase two dimensional HPLC-mass spectrometric system was applied to separate oxidized phospholipids from their non-oxidized counterparts, allowing unambiguous detection in a total lipid extract. We have utilized bovine heart cardiolipin as well as commercially available tetralinoleoyl cardiolipin oxidized with cytochrome c (cyt c) and hydrogen peroxide as well as with lipoxygenase to test the separation power of the system. Our findings indicate that oxidized species of not only cardiolipin, but other phospholipid species, can be effectively separated from their non-oxidized counterparts in this two dimensional system. We utilized three types of biological tissues and oxidative insults, namely rotenone treatment of lymphocytes to induce mitochondrial damage and cell death, pulmonary inhalation exposure to single walled carbon nanotubes, as well as total body irradiation, in order to identify cardiolipin oxidation products, critical to the cell damage/cell death pathways in these tissues following cellular stress/injury. Our results indicate that selective cardiolipin (CL) oxidation is a result of a non-random free radical process. In addition, we assessed the ability of the system to identify CL oxidation products in the brain, a tissue known for its extreme complexity and diversity of CL species. The ability of the two-dimensional HPLC-mass spectrometric system to detect and characterize oxidized lipid products will allow new studies to be formulated to probe

  19. Plasma phospholipid mass transfer rate: relationship to plasma phospholipid and cholesteryl ester transfer activities and lipid parameters.

    PubMed

    Cheung, M C; Wolfbauer, G; Albers, J J

    1996-09-27

    Human plasma phospholipid transfer protein (PLTP) has been shown to facilitate the transfer of phospholipid from liposomes or isolated very low and low density lipoproteins to high density lipoproteins. Its activity in plasma and its physiological function are presently unknown. To elucidate the role of PLTP in lipoprotein metabolism and to delineate factors that may affect the rate of phospholipid transfer between lipoproteins, we determined the plasma phospholipid mass transfer rate (PLTR) in 16 healthy adult volunteers and assessed its relationship to plasma lipid levels, and to phospholipid transfer activity (PLTA) and cholesteryl ester transfer activity (CETA) measured by radioassays. The plasma PLTR in these subjects was 27.2 +/- 11.8 nmol/ml per h at 37 degrees C (mean +/- S.D.), and their PLTA and CETA were 13.0 +/- 1.7 mumol/ml per h and 72.8 +/- 15.7 nmol/ml per h, respectively. Plasma PLTR was correlated directly with total, non-HDL, and HDL triglyceride (rs = 0.76, P < 0.001), total and non-HDL phospholipid (rs > 0.53, P < 0.05), and inversely with HDL free cholesterol (rs = -0.54, P < 0.05), but not with plasma PLTA and CETA. When 85% to 96% of the PLTA in plasma was removed by polyclonal antibodies against recombinant human PLTP, phospholipid mass transfer from VLDL and LDL to HDL was reduced by 50% to 72%, but 80% to 100% of CETA could still be detected. These studies demonstrate that PLTP plays a major role in facilitating the transfer of phospholipid between lipoproteins, and suggest that triglyceride is a significant modulator of intravascular phospholipid transport. Furthermore, most of the PLTP and CETP in human plasma is associated with different particles. Plasma PLTA and CETA were also measured in mouse, rat, hamster, guinea pig, rabbit, dog, pig, and monkey. Compared to human, PLTA in rat and mouse was significantly higher and in rabbit and guinea pig was significantly lower while the remaining animal species had PLTA similar to humans. No

  20. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    SciTech Connect

    Bradshaw, J.P.; Gilchrist, P.J.; Duff, K.C.; Saxena, A.M.

    1994-12-31

    The structural feature which is thought to facilitate the interaction of many peptides with phospholipid bilayers is the ability to fold into an amphipathic helix. In most cases the exact location and orientation of this helix with respect to the membrane is not known, and may vary with factors such as pH and phospholipid content of the bilayer. The growing interest in this area is stimulated by indications that similar interactions can contribute to the binding of certain hormones to their cell-surface receptors. We have been using the techniques of neutron diffraction from stacked phospholipid bilayers in an attempt to investigate this phenomenon with a number of membrane-active peptides. Here we report some of our findings with three of these: the bee venom melittin; the hormone calcitonin; and a synthetic peptide representing the ion channel fragment of influenza A M2 protein.

  1. The role of lamellate phospholipid bilayers in lubrication of joints.

    PubMed

    Pawlak, Zenon; Urbaniak, Wiesław; Gadomski, Adam; Yusuf, Kehinde Q; Afara, Isaac O; Oloyede, Adekunle

    2012-01-01

    This study aims to determine the effect of progressive loss of the surface active phospholipids on the characteristics, and hence tribological function of articular cartilage. In accordance to Hill's hypothesis, 3-7 lipid bilayers at pH 7.4 operate as the solid lubricant in the cartilage-cartilage interface during physiological function. These bilayers are known to be depleted during cartilage degeneration. This study models this loss of phospholipid bilayers, studying experimentally both wet and dry cartilage surfaces, measuring surface wettability, and friction coefficient under a constant stress of 1.2 MPa. The results demonstrate that the friction coefficient increases gradually with loss of the phospholipid bilayers, and gains in value with decrease in wettability. PMID:23394101

  2. Intestinal interaction of bile acids, phospholipids, dietary fibers, and cholestyramine.

    PubMed

    Gallaher, D; Schneeman, B O

    1986-04-01

    Binding of bile acids and phospholipids to a number of dietary fibers and cholestyramine (CH) within the small intestine was determined. The fibers used were cellulose, wheat bran, oat bran, guar gum (GG), and lignin (LG). GG, LG, and CH bound significant quantities of bile acids. However, only the CH reduced the bile acid concentration within the aqueous phase of the intestinal contents. Significant phospholipid binding was found only with CH. None of the test substances significantly reduced the quantity of solubilized lipid. Multiple regression analysis indicated that the total quantity of bile acids and phospholipids in the aqueous phase of the intestinal contents was a significant predictor of the quantity of lipid solubilized within the contents (r2 = 0.67). The failure of GG and LG to significantly decrease the amount of solubilized lipid suggests that the hypocholesterolemic effect of these fibers is due more to their bile acid binding capacity than to an effect on lipid solubilization. PMID:3008573

  3. Shear-induced morphology in mixed phospholipid films

    NASA Astrophysics Data System (ADS)

    Hirsa, Amir; Young, James; Posada, David; Lopez, Juan

    2014-11-01

    Flow of mixed phospholipid films on liquid surfaces plays a significant role in biological processes ranging from lipid bilayer fluidity and the associated behavior of cellular membranes, to flow on the liquid lining in the lungs. Phospholipid films are also central to the process of two-dimensional protein crystallization below a ligand-bearing film. Here, we study a binary mixture of phospholipids that form an insoluble monolayer on the air-water interface. Brewster angle microscopy reveals that a shearing flow induces a phase separation in the binary film, resulting in the appearance of 10 micron-scale dark domains. Hydrodynamic response of the binary film is quantified at the macro-scale by measurements of the surface shear viscosity, via a deep-channel surface viscometer. Reynolds number was shown to be a state variable, along with surface pressure, controlling the surface shear viscosity of a biotinylated lipid film.

  4. Possible mechanism of adhesion in a mica supported phospholipid bilayer

    SciTech Connect

    Pertsin, Alexander; Grunze, Michael

    2014-05-14

    Phospholipid bilayers supported on hydrophilic solids like silica and mica play a substantial role in fundamental studies and technological applications of phospholipid membranes. In both cases the molecular mechanism of adhesion between the bilayer and the support is of primary interest. Since the possibilities of experimental methods in this specific area are rather limited, the methods of computer simulation acquire great importance. In this paper we use the grand canonical Monte Carlo technique and an atomistic force field to simulate the behavior of a mica supported phospholipid bilayer in pure water as a function of the distance between the bilayer and the support. The simulation reveals a possible adhesion mechanism, where the adhesion is due to individual lipid molecules that protrude from the bilayer and form widely spaced links with the support. Simultaneously, the bilayer remains separated from the bilayer by a thin water interlayer which maintains the bilayer fluidity.

  5. Phospholipid flippases: building asymmetric membranes and transport vesicles

    PubMed Central

    Sebastian, Tessy T.; Baldridge, Ryan D.; Xu, Peng; Graham, Todd R.

    2012-01-01

    Phospholipid flippases in the type IV P-type ATPase family (P4-ATPases) are essential components of the Golgi, plasma membrane and endosomal system that play critical roles in membrane biogenesis. These pumps flip phospholipid across the bilayer to create an asymmetric membrane structure with substrate phospholipids, such as phosphatidylserine and phosphatidylethanolamine, enriched within the cytosolic leaflet. The P4-ATPases also help form transport vesicles that bud from Golgi and endosomal membranes, thereby impacting the sorting and localization of many different proteins in the secretory and endocytic pathways. At the organismal level, P4-ATPase deficiencies are linked to liver disease, obesity, diabetes, hearing loss, neurological deficits, immune deficiency and reduced fertility. Here, we review the biochemical, cellular and physiological functions of P4-ATPases, with an emphasis on their roles in vesicle-mediated protein transport. PMID:22234261

  6. The mechanism of acyl specific phospholipid remodeling by tafazzin

    PubMed Central

    Schlame, Michael; Acehan, Devrim; Berno, Bob; Xu, Yang; Valvo, Salvatore; Ren, Mindong; Stokes, David L.; Epand, Richard M.

    2013-01-01

    Cardiolipin is a mitochondrial phospholipid with a characteristic acyl chain composition that depends on the function of tafazzin, a phospholipid-lysophospholipid transacylase, although the enzyme itself lacks acyl specificity. We incubated isolated tafazzin with various mixtures of phospholipids and lysophospholipids, characterized the lipid phase by 31P-NMR, and measured newly formed molecular species by mass spectrometry. Significant transacylation was observed only in non-bilayer lipid aggregates and the substrate specificity was highly sensitive to the lipid phase. In particular, tetralinoleoyl-cardiolipin, a prototype molecular species, formed only under conditions that favor the inverted hexagonal phase. In isolated mitochondria, <1 percent of lipids participated in transacylations, suggesting that the action of tafazzin is limited to privileged lipid domains. We propose that tafazzin reacts with non-bilayer type lipid domains that occur in curved or hemifused membrane zones, and that acyl specificity is driven by the packing properties of these domains. PMID:22941046

  7. NMR analyses of deuterated phospholipids isolated from Pichia angusta

    NASA Astrophysics Data System (ADS)

    Massou, S.; Augé, S.; Tropis, M.; Lindley, N. D.; Milon, A.

    1998-02-01

    The phospholipid composition of methylotrophic yeasts grown on deuterated and hydrogenated media has been determined by proton and phosphorus NMR. By using a line narrowing solvent, we could obtain linewidth lower than 2 Hz, and all the resonances could be resolved. Phospholipids were identified on the basis of their chemical shift and by 31P - H correlations (HMQC - HOHAHA gradient enhanced experiments). We have thus analysed qualitatively and quantitatively lipids mixtures directly after chloroform-methanol extraction. The lipid composition is deeply modified after growth in deuterated medium were phosphatidyl Inositol (PI) becomes the major lipid, instead of a PC, PS, PI mixture in hydrogenated conditions. La composition en phospholipides de levures méthylotrophes ayant poussé sur des milieux de cultures hydrogénés et deutériés a été déterminée par RMN du proton et du phosphore31. L'utilisation d'un solvant d'affinement a permis d'obtenir des largeurs de raies inférieures à 2Hz et de résoudre toutes les classes de phospholipides. Ils sont ensuite identifiés par leur déplacement chimique et par des corrélations phosphore - proton spécifiques (expériences HMQC-HOHAHA gradients). Cette approche a permis une analyse qualitative et quantitative de mélanges de phospholipides directement après extraction au chloroforme-méthanol. La composition en phospholipides est profondément modifiée lors de la croissance en milieu perdeutérié où l'on observe un lipide majoritaire, le phosphatidyl Inositol (PI), au lieu d'un mélange PC, PS PI en milieu hydrogéné.

  8. Dynamic aspects of voluntary turnover: an integrated approach to curvilinearity in the performance-turnover relationship.

    PubMed

    Becker, William J; Cropanzano, Russell

    2011-03-01

    Previous research pertaining to job performance and voluntary turnover has been guided by 2 distinct theoretical perspectives. First, the push-pull model proposes that there is a quadratic or curvilinear relationship existing between these 2 variables. Second, the unfolding model of turnover posits that turnover is a dynamic process and that a downward performance change may increase the likelihood of organizational separation. Drawing on decision theory, we propose and test an integrative framework. This approach incorporates both of these earlier models. Specifically, we argue that individuals are most likely to voluntarily exit when they are below-average performers who are also experiencing a downward performance change. Furthermore, the interaction between this downward change and performance partially accounts for the curvilinear relationship proposed by the push-pull model. Findings from a longitudinal field study supported this integrative theory. PMID:20853945

  9. Genetic Analysis of Digestive Physiology Using Fluorescent Phospholipid Reporters

    NASA Astrophysics Data System (ADS)

    Farber, Steven A.; Pack, Michael; Ho, Shiu-Ying; Johnson, Iain D.; Wagner, Daniel S.; Dosch, Roland; Mullins, Mary C.; Hendrickson, H. Stewart; Hendrickson, Elizabeth K.; Halpern, Marnie E.

    2001-05-01

    Zebrafish are a valuable model for mammalian lipid metabolism; larvae process lipids similarly through the intestine and hepatobiliary system and respond to drugs that block cholesterol synthesis in humans. After ingestion of fluorescently quenched phospholipids, endogenous lipase activity and rapid transport of cleavage products results in intense gall bladder fluorescence. Genetic screening identifies zebrafish mutants, such as fat free, that show normal digestive organ morphology but severely reduced phospholipid and cholesterol processing. Thus, fluorescent lipids provide a sensitive readout of lipid metabolism and are a powerful tool for identifying genes that mediate vertebrate digestive physiology.

  10. Saturated anionic phospholipids enhance transdermal transport by electroporation.

    PubMed Central

    Sen, Arindam; Zhao, Ya-Li; Hui, Sek Wen

    2002-01-01

    Anionic phospholipids, but not cationic or neutral phospholipids, were found to enhance the transdermal transport of molecules by electroporation. When added as liposomes to the milieus of water-soluble molecules to be delivered through the epidermis of porcine skin by electroporation, these phospholipids enhance, by one to two orders of magnitude, the transdermal flux. Encapsulation of molecules in liposomes is not necessary. Dimyristoylphosphatidylserine (DMPS), phosphatidylserine from bovine brain (brain-PS), dioleoylphosphatidylserine (DOPS), and dioleoylphosphatidylglycerol (DOPG) were used to test factors affecting the potency of anionic lipid transport enhancers. DMPS with saturated acyl chains was found to be a much more potent transport enhancer than those with unsaturated acyl chains (DOPS and DOPG). There was no headgroup preference. Saturated DMPS was also more effective in delaying resistance recovery after pulsing, and with a greater affinity in the epidermis after pulsing. Using fluorescent carboxyl fluorescein and fluorescein isothiocyanate (FITC)-labeled Dextrans as test water-soluble molecules for transport, and rhodamine-labeled phospholipids to track anionic phospholipids, we found, by conventional and confocal fluorescence microscopy, that transport of water-soluble molecules was localized in local transport spots or regions (LTRs) created by the electroporation pulses. Anionic phospholipids, especially DMPS, were located at the center of the LTRs and spanned the entire thickness of the stratum corneum (SC). The degree of saturation of anionic phospholipids made no difference in the densities of LTRs created. We deduce that, after being driven into the epidermis by negative electric pulses, saturated anionic phospholipids mix and are retained better by the SC lipids. Anionic lipids prefer loose layers or vesicular rather than multilamellar forms, thereby prolonging the structural recovery of SC lipids to the native multilamellar form. In the

  11. Light and phospholipid driven structural transitions in nematic microdroplets

    NASA Astrophysics Data System (ADS)

    Dubtsov, A. V.; Pasechnik, S. V.; Shmeliova, D. V.; Kralj, Samo

    2014-10-01

    We studied the UV-irradiation and phospholipid driven bipolar-radial structural transitions within azoxybenzene nematic liquid crystal (LC) droplets dispersed in water. It was found that the UV-irradiation induced trans-cis isomerisation of LC molecules could enable structural transitions into radial-type configurations at a critical UV-irradiation time tc. In particular, we show that under appropriate conditions, a value of tc could sensitively fingerprint the concentration of phospholipid molecules present in LC-water dispersions. This demonstrated proof-of-principle mechanism could be exploited for development of sensitive detectors for specific nanoparticles (NPs), where value of tc reveals concentration of NPs.

  12. Profiling of phospholipids and related lipid structures using multidimensional ion mobility spectrometry-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Trimpin, Sarah; Tan, Bo; Bohrer, Brian C.; O'Dell, David K.; Merenbloom, Samuel I.; Pazos, Mauricio X.; Clemmer, David E.; Walker, J. Michael

    2009-10-01

    Increasingly comprehensive questions related to the biosynthesis of lipids relevant to understanding new signaling pathways have created daunting tasks for their chemical analysis. Here, ion mobility spectrometry (IMS) and mass spectrometry (MS) techniques combined with electrospray ionization have been used to examine mixtures of closely related lipid structures. The drift time distributions of sphingomyelins show baseline separations for ethylene chain length differences ([Delta] ~ 1.2 ms) and partial separations in single unsaturation differences ([Delta] ~ 0.3 ms) revealing that the most compact structures are observed with shorter chains and increasing unsaturation. Drift time distributions of different ionizations frequently fall into families with the same drift times (isodrifts) indicating that the ion attached to the lipid has little structural influence. The present data show that phospholipids, especially phosphatidylinositol, aggregate to form inverted micelles. Phospholipids (phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and phosphatidylinositol) are effectively separated according to their polar head groups. This method also provides information about the mixture composition of the chemically different lipids N-palmitoyl glycine, N-arachidonoyl ethanolamide, and phosphatidylcholine existing over an array of charge states and sizes (inverted micelles) depending on mixture concentration. Multidimensional IMS3-MS introduces an additional dimension to fragmentation analysis by separating the fragmented ions into groups related to size, shape and charge and allows determination of sn-1 and sn-2 substitution as is shown for phosphatidylglycerols. This contribution provides evidence for extending the targeted approach to global lipidomics analysis using the high-efficiency gas-phase separation afforded by multidimensional IMS-MS.

  13. Stability of Monodisperse Phospholipid-Coated Microbubbles Formed by Flow-Focusing at High Production Rates.

    PubMed

    Segers, Tim; de Rond, Leonie; de Jong, Nico; Borden, Mark; Versluis, Michel

    2016-04-26

    Monodisperse microbubble ultrasound contrast agents may dramatically increase the sensitivity and efficiency in ultrasound imaging and therapy. They can be produced directly in a microfluidic flow-focusing device, but questions remain as to the interfacial chemistry, such as the formation and development of the phospholipid monolayer coating over time. Here, we demonstrate the synthesis of monodisperse bubbles with radii of 2-10 μm at production rates ranging from 10(4) to 10(6) bubbles/s. All bubbles were found to dissolve to a stable final radius 2.55 times smaller than their initial radius, independent of the nozzle size and shear rate, indicating that the monolayer self-assembles prior to leaving the nozzle. The corresponding decrease in surface area by a factor 6.6 reveals that lipid molecules are adsorbed to the gas-liquid interface in the disordered expanded state, and they become mechanically compressed by Laplace pressure-driven bubble dissolution to a more ordered condensed state with near zero surface tension. Acoustic characterization of the stabilized microbubbles revealed that their shell stiffness gradually increased from 0.8 to 2.5 N/m with increasing number of insonations through the selective loss of the more soluble lipopolymer molecules. This work therefore demonstrates high-throughput production of clinically relevant monodisperse contrast microbubbles with excellent control over phospholipid monolayer elasticity and microbubble resonance. PMID:27006083

  14. The role of anti-phospholipid antibodies in autoimmune reproductive failure.

    PubMed

    Pantham, Priyadarshini; Abrahams, Vikki M; Chamley, Lawrence W

    2016-05-01

    Anti-phospholipid antibodies (aPL) are autoantibodies that are associated with thrombosis and a range of pregnancy complications including recurrent pregnancy loss and pre-eclampsia. The three clinically relevant, well-characterized aPL are anti-cardiolipin antibodies, lupus anticoagulant and anti-beta-2-glycoprotein I (β2GPI) antibodies. aPL do not bind directly to phospholipids but instead bind to a plasma-binding 'cofactor'. The most extensively studied cofactor is β2GPI, whose role in pregnancy is not fully elucidated. Although the pathogenicity of aPL in recurrent pregnancy loss is well established in humans and animal models, the association of aPL with infertility does not appear to be causative. aPL may exert their detrimental effects during pregnancy by directly binding trophoblast cells of the placenta, altering trophoblast signalling, proliferation, invasion and secretion of hormones and cytokines, and by increasing apoptosis. Heparin is commonly used to treat pregnant women with aPL; however, as thrombotic events do not occur in the placentae of all women with aPL, it may exert a protective effect by preventing the binding of aPL to β2GPI or by acting through non-thrombotic pathways. The aim of this review is to present evidence summarizing the current understanding of this field. PMID:26884418

  15. Fish Oil Supplementation in Humans: Effects on Platelet Responses, Phospholipid Composition and Metabolism.

    NASA Astrophysics Data System (ADS)

    Skeaff, Clark Murray

    Platelets are believed to play a significant role in the development of occlusive vascular diseases. Epidemiological reports have correlated the high intake of marine foods, rich in omega3 fatty acids, with diminished platelet responses and a low incidence of arterial thrombosis and myocardial infarction. The activation of platelet responses is mediated by the accelerated metabolism of membrane phospholipid; therefore, it was of interest to examine, in human volunteers, the effect of a dietary fish oil concentrate (MaxEPA), enriched in omega 3 polyunsaturated fatty acids, on platelet aggregation and phospholipid composition/metabolism. For the complete separation of cellular phospholipids, a one-dimensional thin-layer chromatography system using silica-gel pre-coated glass plates was developed. The solvent system consisted of CHCl_3/CH_3OH/CH _3COOH/H_2O (50/37.5/3.5/2.0, by vol), required approximately 90-120 minutes for full phospholipid separation, and was highly reproducible even under conditions of variable humidity and temperature. The consumption of a fish oil concentrate (MaxEPA) for 6 weeks (3.6 g of 20:5omega 3 and 2.4 g of 22:6omega3 per day) diminished both the collagen- and platelet activating factor-induced maximum aggregation responses in washed human platelet suspensions by 50.1% and 27.2%, respectively, as compared to initial unsupplemented baseline responses. Thrombin -induced aggregation remained unchanged. Thrombin stimulation of intact human platelets produced a significant decrease in the mass of phosphatidylinositol in plasma membrane. In platelets pre-labelled with (2-^3H) glycerol and stimulated with either thrombin or low-dose collagen, the loss of (^3H) phosphatidylinositol did not differ between those subjects consuming olive oil or fish oil. Likewise, the thrombin-stimulated accumulation of diacylglycerol, an activator of protein kinase C, was unaffected by fish oil consumption. The ratio of collagen -induced increase in radioactivity

  16. Oxidized phospholipids as biomarkers of tissue and cell damage with a focus on cardiolipin.

    PubMed

    Samhan-Arias, Alejandro K; Ji, Jing; Demidova, Olga M; Sparvero, Louis J; Feng, Weihong; Tyurin, Vladimir; Tyurina, Yulia Y; Epperly, Michael W; Shvedova, Anna A; Greenberger, Joel S; Bayır, Hülya; Kagan, Valerian E; Amoscato, Andrew A

    2012-10-01

    Oxidized phospholipid species are important, biologically relevant, lipid signaling molecules that usually exist in low abundance in biological tissues. Along with their inherent stability issues, these oxidized lipids present themselves as a challenge in their detection and identification. Often times, oxidized lipid species can co-chromatograph with non-oxidized species making the detection of the former extremely difficult, even with the use of mass spectrometry. In this study, a normal-phase and reverse-phase two dimensional high performance liquid chromatography (HPLC)-mass spectrometric system was applied to separate oxidized phospholipids from their non-oxidized counterparts, allowing unambiguous detection in a total lipid extract. We have utilized bovine heart cardiolipin as well as commercially available tetralinoleoyl cardiolipin oxidized with cytochrome c (cyt c) and hydrogen peroxide as well as with lipoxygenase to test the separation power of the system. Our findings indicate that oxidized species of not only cardiolipin, but other phospholipid species, can be effectively separated from their non-oxidized counterparts in this two dimensional system. We utilized three types of biological tissues and oxidative insults, namely rotenone treatment of lymphocytes to induce mitochondrial damage and cell death, pulmonary inhalation exposure to single walled carbon nanotubes, as well as total body irradiation, in order to identify cardiolipin oxidation products, critical to the cell damage/cell death pathways in these tissues following cellular stress/injury. Our results indicate that selective cardiolipin (CL) oxidation is a result of a non-random free radical process. In addition, we assessed the ability of the system to identify CL oxidation products in the brain, a tissue known for its extreme complexity and diversity of CL species. The ability of the two dimensional HPLC-mass spectrometric system to detect and characterize oxidized lipid products will

  17. Organizational commitment and turnover of nursing home administrators.

    PubMed

    Castle, Nicholas G

    2006-01-01

    In this investigation, the associations between organizational commitment (OC), intent-to-turnover, and actual turnover of a large sample of nursing home administrators (NHAs) are examined. Data used come from a mail survey, from which 632 responses were received from the NHAs (response rate = 63%). The one-year turnover rate of NHAs was 39 percent, and in almost all cases (87%) these NHAs had also exhibited low OC scores. The intent-to-turnover results show thinking about quitting comes before searching for a new position, which in turn both comes before the intention to quit. Multivariate analyses show work overload has a strong and robust association with both intent-to-turnover and turnover of NHAs, and may indicate that NHAs are leaving their positions because they are understaffed. PMID:16648695

  18. The implications of linking the dynamic performance and turnover literatures.

    PubMed

    Sturman, M C; Trevor, C O

    2001-08-01

    This article examines how the literatures of dynamic performance and the performance-turnover relationship inform each other. The nonrandom performance turnover relationship suggests that dynamic performance studies may be biased by their elimination of participants who do not remain for the entire study period. The authors demonstrated that the performance slopes of those who leave an organization differ from the performance slopes of those who remain. This finding suggests that studies of the performance-turnover relationship need to consider employee performance trends when predicting turnover. Replicating and extending the research of D. A. Harrison, M. Virick, and S. William (1996), the authors found that performance changes from the previous month and performance trends measured over a longer time period explained variance in voluntary turnover beyond current performance. Finally, the authors showed that performance trends interacted with current performance in the prediction of voluntary turnover. PMID:11519652

  19. The experience of work and turnover intentions: interactive effects of value attainment, job satisfaction, and positive mood.

    PubMed

    George, J M; Jones, G R

    1996-06-01

    The researchers proposed that the phenomenological experience of work is multifaceted and that simultaneously considering the combined effects of the different aspects of the work experience holds considerable promise for increasing understanding of turnover intentions and other organizationally relevant outcomes. Research in subjective well-being and other areas suggests that there are 3 important aspects of the experience of work: attainment of values, attitudes, and moods. It was hypothesized and found that the relationship between job satisfaction and turnover intentions is jointly moderated by value attainment and positive mood. The nature of this triple interaction was such that the job satisfaction-turnover intention relationship was strongest when workers' jobs did not help them to attain terminal values and positive moods were experienced, and the relationship was weakest when jobs helped workers to attain terminal values and positive moods were experienced. PMID:8690691

  20. Dietary DHA supplementation causes selective changes in phospholipids from different brain regions in both wild type mice and the Tg2576 mouse model of Alzheimer's disease.

    PubMed

    Bascoul-Colombo, Cécile; Guschina, Irina A; Maskrey, Benjamin H; Good, Mark; O'Donnell, Valerie B; Harwood, John L

    2016-06-01

    Alzheimer's disease (AD) is of major concern in ageing populations and we have used the Tg2576 mouse model to understand connections between brain lipids and amyloid pathology. Because dietary docosahexaenoic acid (DHA) has been identified as beneficial, we compared mice fed with a DHA-supplemented diet to those on a nutritionally-sufficient diet. Major phospholipids from cortex, hippocampus and cerebellum were separated and analysed. Each phosphoglyceride had a characteristic fatty acid composition which was similar in cortex and hippocampus but different in the cerebellum. The biggest changes on DHA-supplementation were within ethanolamine phospholipids which, together with phosphatidylserine, had the highest proportions of DHA. Reciprocal alterations in DHA and arachidonate were found. The main diet-induced alterations were found in ethanolamine phospholipids, (and included their ether derivatives), as were the changes observed due to genotype. Tg mice appeared more sensitive to diet with generally lower DHA percentages when on the standard diet and higher relative proportions of DHA when the diet was supplemented. All four major phosphoglycerides analysed showed age-dependent decreases in polyunsaturated fatty acid contents. These data provide, for the first time, a detailed evaluation of phospholipids in different brain areas previously shown to be relevant to behaviour in the Tg2576 mouse model for AD. The lipid changes observed with genotype are consistent with the subtle alterations found in AD patients, especially for the ethanolamine phospholipid molecular species. They also emphasise the contrasting changes in fatty acid content induced by DHA supplementation within individual phospholipid classes. PMID:26968097

  1. Dietary DHA supplementation causes selective changes in phospholipids from different brain regions in both wild type mice and the Tg2576 mouse model of Alzheimer's disease

    PubMed Central

    Bascoul-Colombo, Cécile; Guschina, Irina A.; Maskrey, Benjamin H.; Good, Mark; O'Donnell, Valerie B.; Harwood, John L.

    2016-01-01

    Alzheimer's disease (AD) is of major concern in ageing populations and we have used the Tg2576 mouse model to understand connections between brain lipids and amyloid pathology. Because dietary docosahexaenoic acid (DHA) has been identified as beneficial, we compared mice fed with a DHA-supplemented diet to those on a nutritionally-sufficient diet. Major phospholipids from cortex, hippocampus and cerebellum were separated and analysed. Each phosphoglyceride had a characteristic fatty acid composition which was similar in cortex and hippocampus but different in the cerebellum. The biggest changes on DHA-supplementation were within ethanolamine phospholipids which, together with phosphatidylserine, had the highest proportions of DHA. Reciprocal alterations in DHA and arachidonate were found. The main diet-induced alterations were found in ethanolamine phospholipids, (and included their ether derivatives), as were the changes observed due to genotype. Tg mice appeared more sensitive to diet with generally lower DHA percentages when on the standard diet and higher relative proportions of DHA when the diet was supplemented. All four major phosphoglycerides analysed showed age-dependent decreases in polyunsaturated fatty acid contents. These data provide, for the first time, a detailed evaluation of phospholipids in different brain areas previously shown to be relevant to behaviour in the Tg2576 mouse model for AD. The lipid changes observed with genotype are consistent with the subtle alterations found in AD patients, especially for the ethanolamine phospholipid molecular species. They also emphasise the contrasting changes in fatty acid content induced by DHA supplementation within individual phospholipid classes. PMID:26968097

  2. Work–family climate, organizational commitment, and turnover: Multilevel contagion effects of leaders ⋆

    PubMed Central

    O’Neill, John W.; Harrison, Michelle M.; Cleveland, Jeannette; Almeida, David; Stawski, Robert; Crouter, Anne C.

    2009-01-01

    This paper presents empirical research analyzing the relationship between work–family climate (operationalized in terms of three work–family climate sub-scales), organizational leadership (i.e., senior manager) characteristics, organizational commitment and turnover intent among 526 employees from 37 different hotels across the US. Using multilevel modeling, we found significant associations between work–family climate, and both organizational commitment and turnover intent, both within and between hotels. Findings underscored the importance of managerial support for employee work–family balance, the relevance of senior managers’ own work–family circumstances in relation to employees’ work outcomes, and the existence of possible contagion effects of leaders in relation to work–family climate. PMID:19412351

  3. Protein turnover in Azotobacter vinelandii during encystment and germination.

    PubMed

    Ruppen, M E; Garner, G; Sadoff, H L

    1983-12-01

    Protein turnover occurs during differentiation of Azotobacter vinelandii 12837 to the extent of 50% during encystment and 7% during germination. The addition of rifampin at the initiation of encystment prevents encystment and inhibits turnover. In germinating cysts, protein turnover is essential owing to an apparent lack of certain amino acid biosynthetic enzymes. The capacity to synthesize sulfur-containing amino acids from inorganic precursors is regained about halfway through the germination process. PMID:6643391

  4. Skeletal Muscle Phospholipid Metabolism Regulates Insulin Sensitivity and Contractile Function.

    PubMed

    Funai, Katsuhiko; Lodhi, Irfan J; Spears, Larry D; Yin, Li; Song, Haowei; Klein, Samuel; Semenkovich, Clay F

    2016-02-01

    Skeletal muscle insulin resistance is an early defect in the development of type 2 diabetes. Lipid overload induces insulin resistance in muscle and alters the composition of the sarcoplasmic reticulum (SR). To test the hypothesis that skeletal muscle phospholipid metabolism regulates systemic glucose metabolism, we perturbed choline/ethanolamine phosphotransferase 1 (CEPT1), the terminal enzyme in the Kennedy pathway of phospholipid synthesis. In C2C12 cells, CEPT1 knockdown altered SR phospholipid composition and calcium flux. In mice, diet-induced obesity, which decreases insulin sensitivity, increased muscle CEPT1 expression. In high-fat diet-fed mice with skeletal muscle-specific knockout of CEPT1, systemic and muscle-based approaches demonstrated increased muscle insulin sensitivity. In CEPT1-deficient muscles, an altered SR phospholipid milieu decreased sarco/endoplasmic reticulum Ca(2+) ATPase-dependent calcium uptake, activating calcium-signaling pathways known to improve insulin sensitivity. Altered muscle SR calcium handling also rendered these mice exercise intolerant. In obese humans, surgery-induced weight loss increased insulin sensitivity and decreased skeletal muscle CEPT1 protein. In obese humans spanning a spectrum of metabolic health, muscle CEPT1 mRNA was inversely correlated with insulin sensitivity. These results suggest that high-fat feeding and obesity induce CEPT1, which remodels the SR to preserve contractile function at the expense of insulin sensitivity. PMID:26512026

  5. Comparative Phospholipid Profiles of Control and Glaucomatous Human Trabecular Meshwork

    PubMed Central

    Aribindi, Katyayini; Guerra, Yenifer; Lee, Richard K.; Bhattacharya, Sanjoy K.

    2013-01-01

    Purpose. We compared phospholipid (phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, and phosphatidylinositol) profiles of control and glaucomatous trabecular meshwork (TM) derived from human donors. Methods. Control TM and most primary open angle glaucoma (POAG) TM were collected from cadaver donors. A select subset of POAG surgical TM samples also were collected for analyses. Lipid extraction was performed using a modification of the Bligh and Dyer method, protein concentrations were determined using the Bradford method, and for select samples confirmed with densitometry of PHAST gels. Lipids were identified and subjected to ratiometric quantification using a TSQ quantum Access Max triple quadrupole mass spectrometer with precursor ion scan (PIS) or neutral ion loss scan (NLS), using appropriate class specific lipid standards. Results. The comparative profiles of phosphatidylcholine, phosphatidylserine, phosphoethanolamine, and phosphatidylinositol between control and glaucomatous TM showed several species common between them. A number of unique lipids in all four phospholipid classes also were identified in control TM that were absent in glaucoma TM and vice versa. Conclusions. A number of phospholipids were found to be uniquely present in control but absent in glaucomatous TM and vice versa. Compared to a previous study of control and POAG blood, a number of these phospholipids are absent locally (TM), as well as systemically (in blood). PMID:23557733

  6. Synthetic phospholipids as specific substrates for plasma endothelial lipase.

    PubMed

    Papillon, Julien P N; Pan, Meihui; Brousseau, Margaret E; Gilchrist, Mark A; Lou, Changgang; Singh, Alok K; Stawicki, Todd; Thompson, James E

    2016-08-01

    We designed and prepared synthetic phospholipids that generate lyso-phosphatidylcholine products with a unique mass for convenient detection by LC-MS in complex biological matrices. We demonstrated that compound 4, formulated either as a Triton X-100 emulsion or incorporated in synthetic HDL particles can serve as a substrate for plasma EL with useful specificity. PMID:27344207

  7. Dictyostelium uses ether-linked inositol phospholipids for intracellular signalling

    PubMed Central

    Clark, Jonathan; Kay, Robert R; Kielkowska, Anna; Niewczas, Izabella; Fets, Louise; Oxley, David; Stephens, Len R; Hawkins, Phillip T

    2014-01-01

    Inositol phospholipids are critical regulators of membrane biology throughout eukaryotes. The general principle by which they perform these roles is conserved across species and involves binding of differentially phosphorylated inositol head groups to specific protein domains. This interaction serves to both recruit and regulate the activity of several different classes of protein which act on membrane surfaces. In mammalian cells, these phosphorylated inositol head groups are predominantly borne by a C38:4 diacylglycerol backbone. We show here that the inositol phospholipids of Dictyostelium are different, being highly enriched in an unusual C34:1e lipid backbone, 1-hexadecyl-2-(11Z-octadecenoyl)-sn-glycero-3-phospho-(1'-myo-inositol), in which the sn-1 position contains an ether-linked C16:0 chain; they are thus plasmanylinositols. These plasmanylinositols respond acutely to stimulation of cells with chemoattractants, and their levels are regulated by PIPKs, PI3Ks and PTEN. In mammals and now in Dictyostelium, the hydrocarbon chains of inositol phospholipids are a highly selected subset of those available to other phospholipids, suggesting that different molecular selectors are at play in these organisms but serve a common, evolutionarily conserved purpose. PMID:25180230

  8. Porphyrin–phospholipid liposomes permeabilized by near-infrared light

    PubMed Central

    Carter, Kevin A.; Shao, Shuai; Hoopes, Matthew I.; Luo, Dandan; Ahsan, Bilal; Grigoryants, Vladimir M.; Song, Wentao; Huang, Haoyuan; Zhang, Guojian; Pandey, Ravindra K.; Geng, Jumin; Pfeifer, Blaine A.; Scholes, Charles P.; Ortega, Joaquin; Karttunen, Mikko; Lovell, Jonathan F.

    2014-01-01

    The delivery of therapeutic compounds to target tissues is a central challenge in treating disease. Externally controlled drug release systems hold potential to selectively enhance localized delivery. Here we describe liposomes doped with porphyrin–phospholipid that are permeabilized directly by near-infrared light. Molecular dynamics simulations identified a novel light-absorbing monomer esterified from clinically approved components predicted and experimentally demonstrated to give rise to a more stable porphyrin bilayer. Light-induced membrane permeabilization is enabled with liposomal inclusion of 10 molar % porphyrin–phospholipid and occurs in the absence of bulk or nanoscale heating. Liposomes reseal following laser exposure and permeability is modulated by varying porphyrin–phospholipid doping, irradiation intensity or irradiation duration. Porphyrin–phospholipid liposomes demonstrate spatial control of release of entrapped gentamicin and temporal control of release of entrapped fluorophores following intratumoral injection. Following systemic administration, laser irradiation enhances deposition of actively loaded doxorubicin in mouse xenografts, enabling an effective single-treatment antitumour therapy. PMID:24699423

  9. Structural intermediates during α-synuclein fibrillogenesis on phospholipid vesicles

    PubMed Central

    Comellas, Gemma; Lemkau, Luisel R.; Zhou, Donghua H.; George, Julia M.

    2012-01-01

    α-Synuclein (AS) fibrils are the main protein component of Lewy Bodies, the pathological hallmark of Parkinson’s disease and other related disorders. AS forms helices that bind phospholipid membranes with high affinity, but no atomic level data for AS aggregation in the presence of lipids is yet available. Here, we present direct evidence of a conversion from α-helical conformation to β-sheet fibrils in the presence of anionic phospholipid vesicles and direct conversion to β-sheet fibrils in their absence. We have trapped intermediate states throughout the fibril formation pathways to examine the structural changes using solid-state NMR spectroscopy and electron microscopy. The comparison between mature AS fibrils formed in aqueous buffer and those derived in the presence of anionic phospholipids demonstrates no major changes in the overall fibril fold. However, a site-specific comparison of these fibrillar states demonstrates major perturbations in the N-terminal domain with a partial disruption of the long β-strand located in the 40’s and small perturbations in residues located in the “non-β amyloid component” (NAC) domain. Combining all these results, we propose a model for AS fibrillogenesis in the presence of phospholipid vesicles. PMID:22352310

  10. Hexamodal imaging with porphyrin-phospholipid-coated upconversion nanoparticles.

    PubMed

    Rieffel, James; Chen, Feng; Kim, Jeesu; Chen, Guanying; Shao, Wei; Shao, Shuai; Chitgupi, Upendra; Hernandez, Reinier; Graves, Stephen A; Nickles, Robert J; Prasad, Paras N; Kim, Chulhong; Cai, Weibo; Lovell, Jonathan F

    2015-03-11

    Hexamodal imaging using simple nanoparticles is demonstrated. Porphyrin-phospholipids are used to coat upconversion nanoparticles in order to generate a new biocompatible material. The nanoparticles are characterized in vitro and in vivo for imaging via fluorescence, upconversion, positron emission tomography, computed tomography, Cerenkov luminescence, and photoacoustic tomography. PMID:25640213

  11. Porphyrin-phospholipid liposomes permeabilized by near-infrared light.

    PubMed

    Carter, Kevin A; Shao, Shuai; Hoopes, Matthew I; Luo, Dandan; Ahsan, Bilal; Grigoryants, Vladimir M; Song, Wentao; Huang, Haoyuan; Zhang, Guojian; Pandey, Ravindra K; Geng, Jumin; Pfeifer, Blaine A; Scholes, Charles P; Ortega, Joaquin; Karttunen, Mikko; Lovell, Jonathan F

    2014-01-01

    The delivery of therapeutic compounds to target tissues is a central challenge in treating disease. Externally controlled drug release systems hold potential to selectively enhance localized delivery. Here we describe liposomes doped with porphyrin-phospholipid that are permeabilized directly by near-infrared light. Molecular dynamics simulations identified a novel light-absorbing monomer esterified from clinically approved components predicted and experimentally demonstrated to give rise to a more stable porphyrin bilayer. Light-induced membrane permeabilization is enabled with liposomal inclusion of 10 molar % porphyrin-phospholipid and occurs in the absence of bulk or nanoscale heating. Liposomes reseal following laser exposure and permeability is modulated by varying porphyrin-phospholipid doping, irradiation intensity or irradiation duration. Porphyrin-phospholipid liposomes demonstrate spatial control of release of entrapped gentamicin and temporal control of release of entrapped fluorophores following intratumoral injection. Following systemic administration, laser irradiation enhances deposition of actively loaded doxorubicin in mouse xenografts, enabling an effective single-treatment antitumour therapy. PMID:24699423

  12. 21 CFR 862.1575 - Phospholipid test system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Phospholipid test system. 862.1575 Section 862.1575 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... treatment of disorders involving lipid (fat) metabolism. (b) Classification. Class I (general controls)....

  13. 21 CFR 862.1575 - Phospholipid test system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Phospholipid test system. 862.1575 Section 862.1575 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... treatment of disorders involving lipid (fat) metabolism. (b) Classification. Class I (general controls)....

  14. Lysosomal phospholipids from rat liver after treatment with different drugs.

    PubMed

    Tjiong, H B; Lepthin, J; Debuch, H

    1978-01-01

    Rats were treated with 5 different drugs p-ethoxyacetanilide (I), indometacin (II) and nor-amidopyrine-methanesulfonate (III), O,O'-bis(diethylaminoethyl)hexestrol(IV) and choloroquine (V) for 3 - 4 weeks. Liver cell fractions were isolated by discontinuous gradient centrifugation and the specific activity of acid phosphatase was determined in each. Lysosomal fractions contained widely varying amounts of this marker enzyme, indicating that the concentration of lysosomes within these fractions differed. The amounts and patterns of phospholipids reflected this fact. Since we assumed bis(monoacylglycero)phosphate [(MAG)2-P; synonym:lysobisphosphatidic acid] is a marker lipid for secondary lysosomes, we expected and found significant quantities of this acidic phospholipid only in those lysosomal fractions which were also rich in acid phosphatase activity. 12% of the lysosomal phospholipids from animals receiving the hexestrol derivative (IV), and 19% of those from the chloroquine (V) experiment were present as (MAG)2P. The fatty acid compositions of this lysosomal phospholipid were not the same in all lysosome fractions. The more (MAG)2P present in the lysosomes, the more unsaturated are the fatty acids. Thus, after treatment with chloroquine, more than 90% of the fatty acids from (MAG)2P are unsaturated; C22:6 represents about 70% of the total. PMID:627402

  15. 21 CFR 862.1575 - Phospholipid test system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... treatment of disorders involving lipid (fat) metabolism. (b) Classification. Class I (general controls). The... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Phospholipid test system. 862.1575 Section 862.1575 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES...

  16. 21 CFR 862.1575 - Phospholipid test system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... treatment of disorders involving lipid (fat) metabolism. (b) Classification. Class I (general controls). The... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Phospholipid test system. 862.1575 Section 862.1575 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES...

  17. 21 CFR 862.1575 - Phospholipid test system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... treatment of disorders involving lipid (fat) metabolism. (b) Classification. Class I (general controls). The... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Phospholipid test system. 862.1575 Section 862.1575 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES...

  18. Temperature Control of Phospholipid Biosynthesis in Escherichia coli

    PubMed Central

    Sinensky, Michael

    1971-01-01

    The higher the growth temperature of Escherichia coli cultures the greater is the proportion of saturated fatty acids in the bacterial phospholipids. When fatty acids are exogenously supplied to E. coli, higher growth temperatures will likewise increase the relative incorporation of saturated fatty acids into phospholipids. One of the steps in the utilization of fatty acids for phospholipid biosynthesis is, therefore, temperature-controlled. The temperature effect observed in vivo with mixtures of 3H-oleate and 14C-palmitate is demonstrable in vitro by using mixtures of the coenzyme A derivative of these fatty acids for the acylation of α-glycerol phosphate to lysophosphatidic and phosphatidic acids. In E. coli extracts, the relative rates of transacylation of palmityl and oleyl coenzyme A vary as a function of incubation temperature in a manner which mimics the temperature control observed in vivo. The phosphatidic acid synthesized in vitro shows a striking enrichment of oleate at the β position analogous to the positional specificity observed in phospholipids synthesized in vivo. PMID:4324806

  19. Phospholipid Motional Characteristics in a Dry Biological System 1

    PubMed Central

    Priestley, David A.; de Kruijff, B.

    1982-01-01

    Analysis of the proton-decoupled 31P-nuclear magnetic resonance (NMR) spectrum of fully hydrated Typha latifolia pollen revealed the presence of two main peaks: A broad asymmetrical component of a `bilayer' lineshape and a much narrower symmetrical component originating from phosphorus compounds undergoing rapid isotropic motion. From (a) 31P-NMR experiments on the hydrated total pollen phospholipids, (b) saturation transfer 31P-NMR experiments, and (c) the fraction of lipid phosphate in the pollen, it can be concluded that the great majority of the endogenous phospholipids are arranged in extended bilayers in which the lipid phosphates undergo fast (τc < 10−6 second) long axis rotation. This bilayer arrangement of phospholipids was observed in the pollen down to hydration levels of at least 10.9% moisture content. At the lowest level of pollen hydration examined (5.2%) the 31P-NMR spectrum had a solid state lineshape demonstrating that all the phosphorus-containing compounds (including the phospholipids) were virtually immobile. PMID:16662616

  20. An improved SPE method for fractionation and identification of phospholipids.

    PubMed

    Fauland, Alexander; Trötzmüller, Martin; Eberl, Anita; Afiuni-Zadeh, Somaieh; Köfeler, Harald; Guo, Xinghua; Lankmayr, Ernst

    2013-02-01

    This work reports an efficient and universal SPE method developed for separation and identification of phospholipids derived from complex biological samples. For the separation step, sequential combination of silica gel-aminopropyl-silica gel SPE cartridges is applied. This setup enables separation of phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidic acid, phosphatidylinositol, phosphatidylserine, cardiolipin, and sphingomyelin into four fractions according to the polarity of their headgroups. Sample acquisition of the SPE fractions is performed by a high-resolution LC-MS system consisting of a hybrid linear IT Fourier transform ion cyclotron resonance mass spectrometer coupled to RP-HPLC. The unequivocal advantage of our SPE sample preparation setup is avoidance of analyte peak overlapping in the determination step done by RP-HPLC. Overlapping phospholipid signals would otherwise exert adverse ion suppression effects. An additional benefit of this method is the elimination of polar and nonpolar (e.g. neutral lipids) contaminants from the phospholipid fractions, which highly reduces contamination of the LC-MS system. The method was validated with fermentation samples of organic waste, where 78 distinct phospholipid and sphingomyelin species belonging to six lipid classes were successfully identified. PMID:23349108

  1. PHOSPHOLIPIDS OF FIVE PSEUDOMONAD ARCHETYPES FOR DIFFERENT TOLUENE DEGRADATION PATHWAYS

    EPA Science Inventory

    Liquid chromatography/electrospray ionization/mass spectrometry (LC/ESI/MS) was used to determine phospholipid profiles for five reference pseudomonad strains harboring distinct toluene catabolic pathways: Pseudomonas putida mt-2, Pseudomonas putida F1, Burkholderia cepacia G4, B...

  2. Dynamical and Phase Behavior of a Phospholipid Membrane Altered by an Antimicrobial Peptide at Low Concentration.

    PubMed

    Sharma, V K; Mamontov, E; Tyagi, M; Qian, S; Rai, D K; Urban, V S

    2016-07-01

    The mechanism of action of antimicrobial peptides is traditionally attributed to the formation of pores in the lipid cell membranes of pathogens, which requires a substantial peptide to lipid ratio. However, using incoherent neutron scattering, we show that even at a concentration too low for pore formation, an archetypal antimicrobial peptide, melittin, disrupts the regular phase behavior of the microscopic dynamics in a phospholipid membrane, dimyristoylphosphatidylcholine (DMPC). At the same time, another antimicrobial peptide, alamethicin, does not exert a similar effect on the DMPC microscopic dynamics. The melittin-altered lateral motion of DMPC at physiological temperature no longer resembles the fluid-phase behavior characteristic of functional membranes of the living cells. The disruptive effect demonstrated by melittin even at low concentrations reveals a new mechanism of antimicrobial action relevant in more realistic scenarios, when peptide concentration is not as high as would be required for pore formation, which may facilitate treatment with antimicrobial peptides. PMID:27232190

  3. Enzymatic synthesis and modification of structured phospholipids: recent advances in enzyme preparation and biocatalytic processes.

    PubMed

    Hama, Shinji; Ogino, Chiaki; Kondo, Akihiko

    2015-10-01

    Phospholipids (PLs) containing specific polar head groups and fatty acids, artificially synthesized from a complex mixture of natural PLs, have considerable industrial applications. The biocatalytic approaches to synthesizing structured PLs are of great interest because the enzymes used show high selectivity and performance under mild conditions, leading to the generation of products that cannot easily be obtained by chemical catalysis. Although the limited supply of phospholipases (e.g., phospholipase D) has thus far been an obstacle to the widespread use of enzymatic processing, recent advances in enzyme preparation have opened up various applications for PL modification. In this review, attempts to increase the productivity and utility of microbial phospholipases and lipases are presented. We also summarize recent developments in enzyme-catalyzed modification of PLs, focusing particularly on the relevant reactions, bioreactor design, and novel proof-of-concept experiments. PMID:26245679

  4. Turnover intentions and voluntary turnover: the moderating roles of self-monitoring, locus of control, proactive personality, and risk aversion.

    PubMed

    Allen, David G; Weeks, Kelly P; Moffitt, Karen R

    2005-09-01

    This article explores moderators of the relationship between turnover intentions and turnover behavior to better explain why some employees translate intentions into behavior and other employees do not. Individual differences in self-monitoring, locus of control, proactive personality, and risk aversion were examined. Results indicate that self-monitoring and risk aversion moderate the intentions-turnover link. Specifically, the relationship between turnover intentions and turnover is stronger for low self-monitors and those lower in risk aversion. Locus of control moderated the relationship in 1 of 2 samples such that the relationship was stronger for those with an internal locus of control. Proactive personality, however, did not directly moderate the relationship between intentions and turnover behaviors. PMID:16162070

  5. 14C in cropland soil of a long-term field trial - experimental variability and implications for estimating carbon turnover

    NASA Astrophysics Data System (ADS)

    Leifeld, J.; Mayer, J.

    2015-07-01

    Because of their controlled nature, the presence of independent replicates, and their known management history, long-term field experiments are key to the understanding of factors controlling soil carbon. Together with isotope measurements, they provide profound insight into soil carbon dynamics. For soil radiocarbon, an important tracer for understanding these dynamics, experimental variability across replicates is usually not accounted for; hence, a relevant source of uncertainty for quantifying turnover rates is missing. Here, for the first time, radiocarbon measurements of five independent field replicates, and for different layers, of soil from the 66-year-old controlled field experiment ZOFE in Zurich, Switzerland, are used to address this issue. 14C variability was the same across three different treatments and for three different soil layers between the surface and 90 cm depths. On average, experimental variability in 14C content was 12 times the analytical error but still, on a relative basis, smaller than variability in soil carbon concentration. Despite a relative homogeneous variability across the field and along the soil profile, the curved nature of the relationship between radiocarbon content and modelled carbon mean residence time implies that the absolute error of calculated soil carbon turnover time increases with soil depth. In our field experiment findings on topsoil carbon turnover variability would, if applied to subsoil, tend to underweight turnover variability even if experimental variability in the subsoil isotope concentration is the same. Together, experimental variability in radiocarbon is an important component in an overall uncertainty assessment of soil carbon turnover.

  6. Dynamics of Adipocyte Turnover in Humans

    SciTech Connect

    Spalding, K; Arner, E; Westermark, P; Bernard, S; Buchholz, B; Bergmann, O; Blomqvist, L; Hoffstedt, J; Naslund, E; Britton, T; Concha, H; Hassan, M; Ryden, M; Frisen, J; Arner, P

    2007-07-16

    Obesity is increasing in an epidemic fashion in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. Owing to the increase in obesity, life expectancy may start to decrease in developed countries for the first time in recent history. The factors determining fat mass in adult humans are not fully understood, but increased lipid storage in already developed fat cells is thought to be most important. We show that adipocyte number is a major determinant for the fat mass in adults. However, the number of fat cells stays constant in adulthood in lean and obese and even under extreme conditions, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analyzing the integration of {sup 14}C derived from nuclear bomb tests in genomic DNA. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in obesity, suggesting a tight regulation of fat cell number that is independent of metabolic profile in adulthood. The high turnover of adipocytes establishes a new therapeutic target for pharmacological intervention in obesity.

  7. Cytoplasmic mRNA turnover and ageing

    PubMed Central

    Borbolis, Fivos; Syntichaki, Popi

    2015-01-01

    Messenger RNA (mRNA) turnover that determines the lifetime of cytoplasmic mRNAs is a means to control gene expression under both normal and stress conditions, whereas its impact on ageing and age-related disorders has just become evident. Gene expression control is achieved at the level of the mRNA clearance as well as mRNA stability and accessibility to other molecules. All these processes are regulated by cis-acting motifs and trans-acting factors that determine the rates of translation and degradation of transcripts. Specific messenger RNA granules that harbor the mRNA decay machinery or various factors, involved in translational repression and transient storage of mRNAs, are also part of the mRNA fate regulation. Their assembly and function can be modulated to promote stress resistance to adverse conditions and over time affect the ageing process and the lifespan of the organism. Here, we provide insights into the complex relationships of ageing modulators and mRNA turnover mechanisms. PMID:26432921

  8. Sponge mesoporous silica formation using disordered phospholipid bilayers as template.

    PubMed

    Galarneau, Anne; Sartori, Federica; Cangiotti, Michela; Mineva, Tzonka; Di Renzo, Francesco; Ottaviani, M Francesca

    2010-02-18

    Lecithin/dodecylamine/lactose mixtures in ethanol/aqueous media led to the formation of sponge mesoporous silica (SMS) materials by means of tetraethoxysilane (TEOS) as silica source. SMS materials show a "sponge-mesoporous" porosity with a pore diameter of about 5-6 nm, in accordance to the length of a lecithin bilayer. SMS synthesis was developed to create a new class of powerful biocatalysts able to efficiently encapsulate enzymes by adding a porosity control to the classical sol-gel synthesis and by using phospholipids and lactose as protecting agents for the enzymes. In the present study, the formation of SMS was investigated by using electron paramagnetic resonance (EPR) probes inserted inside phospholipid bilayers. The influence of progressive addition of each component (ethanol, dodecylamine, lactose, TEOS) on phospholipid bilayers was first examined; then, the time evolution of EPR spectra during SMS synthesis was studied. Parameters informative of mobility, structure, order, and polarity around the probes were extracted by computer analysis of the EPR line shape. The results were discussed on the basis of solids characterization by X-ray diffraction, nitrogen isotherm, transmission electron microscopy, and scanning electron microscopy. The results, together with the well-known ability of ethanol to promote membrane hemifusion, suggested that the templating structure is a bicontinuous phospholipid bilayer phase, shaped as a gyroid, resulting of multiple membrane hemifusions induced by the high alcohol content used in SMS synthesis. SMS synthesis was compared to hexagonal mesoporous silica (HMS) synthesis accomplished by adding TEOS to a dodecylamine/EtOH/water mixture. EPR evidenced the difference between HMS and SMS synthesis; the latter uses an already organized but slowly growing mesophase of phospholipids, never observed before, whereas the former shows a progressive elongation of micelles into wormlike structures. SMS-type materials represent a new

  9. Calcium-phospholipid enhanced protein phosphorylation in human placenta

    SciTech Connect

    Moore, J.J.; Moore, R.; Cardaman, R.C.

    1986-07-01

    Calcium-activated, phospholipid-dependent protein phosphorylation has not been studied in placenta. Human placental cytosol was subjected to an endogenous protein phosphorylation assay using (..gamma..-/sup 32/P)ATP in the presence of calcium and phosphatidylserine. Protein phosphorylation was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. When compared to basal levels, calcium (10/sup -6/ M) in combination with phosphatidylserine (50 ..mu..g/ml) significantly enhanced (P < 100) /sup 32/P incorporation into phosphoproteins having mol wt 47,000, 43,000, and 37,000. Half-maximal /sup 22/P incorporation was observed with 3.5 x 10/sup -7/ M Ca/sup 2 +/ in the presence of phosphatidylserine (50 ..mu..g/ml). The effect of phosphatidylserine was biphasic. In the presence of Ca 10/sup -6/ M, /sup 32/P incorporation increased to a maximum at 70 /sup +/g/ml of phosphatidylserine. The increase was suppressed at 150 ..mu..g/ml. Tetracaine caused a dose-dependent inhibition of calcium-activated, phospholipid-dependent enhancement of the three phosphoproteins. Calcium in the absence of phospholipid enhanced the phosphorylation of a protein of 98,000 mol wt. Phosphatidylserine suppressed this enhancement. Calmodulin (10/sup -6/ M) had no detectable effect upon phosphorylation beyond that of calcium alone, but the calmodulin inhibitor R-24571 specifically inhibited the calcium-stimulated 98,000 mol wt phosphoprotein. Calcium-activated, phospholipid-dependent phospholipid-dependent phosphoproteins are present in human placental cytosol; whether calcium-activated, calmodulin-dependent phosphoproteins also are present remains a question.

  10. Binding of Diphtheria Toxin to Phospholipids in Liposomes

    NASA Astrophysics Data System (ADS)

    Alving, Carl R.; Iglewski, Barbara H.; Urban, Katharine A.; Moss, Joel; Richards, Roberta L.; Sadoff, Jerald C.

    1980-04-01

    Diphtheria toxin bound to the phosphate portion of some, but not all, phospholipids in liposomes. Liposomes consisting of dimyristoyl phosphatidylcholine and cholesterol did not bind toxin. Addition of 20 mol% (compared to dimyristoyl phosphatidylcholine) of dipalmitoyl phosphatidic acid, dicetyl phosphate, phosphatidylinositol phosphate, cardiolipin, or phosphatidylserine in the liposomes resulted in substantial binding of toxin. Inclusion of phosphatidylinositol in dimyristol phosphatidylcholine / cholesterol liposomes did not result in toxin binding. The calcium salt of dipalmitoyl phosphatidic acid was more effective than the sodium salt, and the highest level of binding occurred with liposomes consisting only of dipalmitoyl phosphatidic acid (calcium salt) and cholesterol. Binding of toxin to liposomes was dependent on pH, and the pattern of pH dependence varied with liposomes having different compositions. Incubation of diphtheria toxin with liposomes containing dicetyl phosphate resulted in maximal binding at pH 3.6, whereas binding to liposomes containing phosphatidylinositol phosphate was maximal above pH 7. Toxin did not bind to liposomes containing 20 mol% of a free fatty acid (palmitic acid) or a sulfated lipid (3-sulfogalactosylceramide). Toxin binding to dicetyl phosphate or phosphatidylinositol phosphate was inhibited by UTP, ATP, phosphocholine, or p-nitrophenyl phosphate, but not by uracil. We conclude that (a) diphtheria toxin binds specifically to the phosphate portion of certain phospholipids, (b) binding to phospholipids in liposomes is dependent on pH, but is not due only to electrostatic interaction, and (c) binding may be strongly influenced by the composition of adjacent phospholipids that do not bind toxin. We propose that a minor membrane phospholipid (such as phosphatidylinositol phosphate or phosphatidic acid), or that some other phosphorylated membrane molecule (such as a phosphoprotein) may be important in the initial binding of

  11. Phospholipid transfer from vesicles to high density lipoproteins, catalyzed by human plasma phospholipid transfer protein

    SciTech Connect

    Sweeny, S.A.

    1985-01-01

    Human plasma phospholipid transfer protein (PLTP) catalyzes the mass transfer of phosphatidylcholine (PC). Partial purification of PLTP yielded proteins with apparent M/sub r/ = 59,000 and 40,000 by SDS-PAGE. PLTP activity was measured by transfer of (/sup 14/C)L-..cap alpha..-dipalmitoyl PC from egg-PC vesicles to HDL. Activity was enhanced at low pH (4.5) upon addition of ..beta..-mercaptoethanol while Ca/sup +2/ and Na/sup +/ had no effect. E/sub act/ for facilitated PC transfer was 18.2 +/- 2 kcal/mol. The donor specificity of PLTP was examined using vesicles containing egg-PC plus cholesterol or sphingomyelin. The fluidity of the donor membrane (measured by fluorescence polarization of diphenylhexatriene) correlated strongly with a decrease in PLTP activity. Phosphatidic acid did not affect activity. Increase in vesicle size reduced activity. The acceptor specificity of PLTP was examined using chemically modified HDL. PLTP activity increased up to 1.7-fold with an initial increase in negative charge and then decreased upon extensive modification. A mechanism is proposed where PLTP binds to vesicls and enhances the diffusion of PC into the medium where it is adsorbed by HDL.

  12. Quantification of fatty acids as methyl esters and phospholipids in cheese samples after separation of triacylglycerides and phospholipids.

    PubMed

    Hauff, Simone; Vetter, Walter

    2009-03-23

    Determination of the individual fatty acid composition of neutral- and phospholipids as well as the phospholipid content of dairy food and other foodstuffs are important tasks in life sciences. For these purposes, a method was developed for the separation of lipids (standards of triolein and diacylphosphatidylcholines as well as three cheese samples) by solid-phase extraction using a self-packed column filled with partly deactivated silica. Non-halogenated solvents were used for the elution of the lipid classes. Cyclohexane/ethyl acetate (1:1, v/v) served for the elution of neutral lipids, while polar lipids were eluted with three solvents (ethyl acetate/methanol, methanol, and methanol/water) into one fraction. The separated lipid fractions were transesterified and the individual fatty acids were quantified by using gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) in the selected ion monitoring (SIM) mode. The recovery rate for standard phosphatidylcholines was approximately 90% and cross-contamination from neutral lipids was negligible. The method was applied to cheese samples. Quantitative amounts of individual fatty acids in the phospholipid fraction were <0.002-0.29% of total lipids from camembert, <0.002-0.12% of total lipids from mozzarella, and <0.002-0.18% of total lipids in a goat cream cheese. Differences in the fatty acid pattern of neutral and polar lipids were detected. The quantity of the fatty acids determined in the phospholipid fraction was divided by the factor 0.7 in order to convert the fatty acid content into the phospholipid content of the cheese samples. This factor is based on the contribution of 16:0 to dipalmitoylphosphatidylcholine (DPPC). The resulting DPPC equivalents (DPPC(eq)) were found to be representative for the average contribution of fatty acids to all classes of phospholipids in dairy products. Using this approach, the phospholipid content of lipids from mozzarella, camembert, and goat cream

  13. Phospholipid decoration of microcapsules containing perfluorooctyl bromide used as ultrasound contrast agents.

    PubMed

    Díaz-López, Raquel; Tsapis, Nicolas; Libong, Danielle; Chaminade, Pierre; Connan, Carole; Chehimi, Mohamed M; Berti, Romain; Taulier, Nicolas; Urbach, Wladimir; Nicolas, Valérie; Fattal, Elias

    2009-03-01

    We present here an easy method to modify the surface chemistry of polymeric microcapsules of perfluorooctyl bromide used as ultrasound contrast agents (UCAs). Capsules were obtained by a solvent emulsification-evaporation process with phospholipids incorporated in the organic phase before emulsification. Several phospholipids were reviewed: fluorescent, pegylated and biotinylated phospholipids. The influence of phospholipid concentration on microcapsule size and morphology was evaluated. Only a fraction of the phospholipids is associated to microcapsules, the rest being dissolved with the surfactant in the aqueous phase. Microscopy shows that phospholipids are present within the shell and that the core/shell structure is preserved up to 0.5 mg fluorescent phospholipids, up to about 0.25 mg pegylated phospholipids or biotinylated phospholipids (for 100 mg of polymer, poly(lactide-co-glycolide) (PLGA)). HPLC allows quantifying phospholipids associated to capsules: they correspond to 10% of pegylated phospholipids introduced in the organic phase. The presence of pegylated lipids at the surface of capsules was confirmed by X-ray photon electron spectroscopy (XPS). The pegylation did not modify the echographic signal arising from capsules. Finally biotinylated microcapsules incubated with neutravidin tend to aggregate, which confirms the presence of biotin at the surface. These results are encouraging and future work will consist of nanocapsule surface modification for molecular imaging. PMID:19097640

  14. Sexual selection affects local extinction and turnover in bird communities

    USGS Publications Warehouse

    Doherty, P.F., Jr.; Sorci, G.; Royle, J. Andrew; Hines, J.E.; Nichols, J.D.; Boulinier, T.

    2003-01-01

    Predicting extinction risks has become a central goal for conservation and evolutionary biologists interested in population and community dynamics. Several factors have been put forward to explain risks of extinction, including ecological and life history characteristics of individuals. For instance, factors that affect the balance between natality and mortality can have profound effects on population persistence. Sexual selection has been identified as one such factor. Populations under strong sexual selection experience a number of costs ranging from increased predation and parasitism to enhanced sensitivity to environmental and demographic stochasticity. These findings have led to the prediction that local extinction rates should be higher for species/populations with intense sexual selection. We tested this prediction by analyzing the dynamics of natural bird communities at a continental scale over a period of 21 years (1975-1996), using relevant statistical tools. In agreement with the theoretical prediction, we found that sexual selection increased risks of local extinction (dichromatic birds had on average a 23% higher local extinction rate than monochromatic species). However, despite higher local extinction probabilities, the number of dichromatic species did not decrease over the period considered in this study. This pattern was caused by higher local turnover rates of dichromatic species, resulting in relatively stable communities for both groups of species. Our results suggest that these communities function as metacommunities, with frequent local extinctions followed by colonization. Anthropogenic factors impeding dispersal might therefore have a significant impact on the global persistence of sexually selected species.

  15. Microbial Turnover of Fixed Nitrogen Compounds in Oceanic Crustal Fluids

    NASA Astrophysics Data System (ADS)

    Kraft, B.; Wankel, S. D.; Glazer, B. T.; Huber, J. A.; Girguis, P. R.

    2014-12-01

    Oceanic crust is the largest aquifer on Earth, with a massive volume of seawater advecting through the basaltic crust. The microbiome of this deep marine subsurface biosphere has been estimated to be substantial, and consequently their metabolic activity may have major influences on global biogeochemical cycles. While earlier and recent studies provide insight into the microbial community composition of oceanic crustal fluids, information on the microbial ecophysiology is broadly missing. Therefore, to investigate the microbial transformation of fixed nitrogen compounds in crustal aquifer fluids, fluids were sampled from different horizons of two neighbouring CORK (Circulation Obviation Retrofit Kit) observatories at the North Pond sediment pond. This site is located on the western flank of the Mid Atlantic Ridge and is characterized by relatively young oceanic crust and cold fluids. The crustal fluids contain oxygen and nitrate, which potentially both may serve as electron acceptor for respiration. In a multidisciplinary approach we combined stable isotope incubations, determination of the natural isotopic compositions and plan to analyse relevant functional genes from a metagenomic dataset to investigate the nitrogen cycling at North Pond. The turnover of fixed nitrogen in oceanic crustal fluids may have important implications for the understanding of the global nitrogen cycle.

  16. Earthdata Search: The Relevance of Relevance

    NASA Technical Reports Server (NTRS)

    Quinn, Patrick

    2016-01-01

    Through recent usability studies, the issue of relevance became increasingly clear in the Earthdata Search Client. After all, if a user can't find the data they are looking for, nothing else we do matters. This presentation walks through usability testing findings and recent relevance improvements made to the Earthdata Search Client.

  17. Analysis of follicular fluid total phospholipids in women undergoing in-vitro fertilisation.

    PubMed

    Fayezi, S; Darabi, M; Darabi, M; Nouri, M; Rahimipour, A; Mehdizadeh, A

    2014-04-01

    Follicular fluid (FF) samples were obtained from 100 patients referred to the University Hospital. A total of 79 subjects underwent IVF and the remaining 21 underwent ICSI. The levels of apoA-I and total phospholipid were measured using turbidometric and colorimetric phosphorus assays, respectively. Correlation analysis showed a significant inverse association of total phospholipid in FF with fertilisation ratio (r = -0.24, p = 0.04). Furthermore, the ratio of phospholipid/apoA-I in patients with a percentage of fertilised oocytes ≤ 50% was significantly higher (> 2.5%, p < 0.05) than in those with higher percentages of fertilised oocytes. The amounts of phospholipid and phospholipid/apoA-I ratio in FF were associated negatively to the percentage of oocyte fertilisation. Therefore, the change in the phospholipid and phospholipid/apoA-I ratio of FF might be regarded as indicators of female fertility. PMID:24476398

  18. Job Search, Intentions, and Turnover: The Mismatched Trilogy.

    ERIC Educational Resources Information Center

    Kirschenbaum, Alan; Weisberg, Jacob

    1994-01-01

    Interviews with 477 Israeli blue-collar workers showed that neither intent to leave nor actual job search significantly explained actual turnover, resulting from lack of available opportunities. "Passive" search seems to occur before intent emerges; active search may bring together perceived and actual opportunities and lead to turnover. (SK)

  19. How Multiple Interventions Influenced Employee Turnover: A Case Study.

    ERIC Educational Resources Information Center

    Hatcher, Timothy

    1999-01-01

    A 3-year study of 46 textile industry workers identified causes of employee turnover (supervision, training, organizational communication) using performance analysis. A study of multiple interventions based on the analysis resulted in changes in orientation procedures, organizational leadership, and climate, reducing turnover by 24%. (SK)

  20. Estimating Cause: Teacher Turnover and School Effectiveness in Michigan

    ERIC Educational Resources Information Center

    Keesler, Venessa; Schneider, Barbara

    2010-01-01

    The purpose of this paper is investigate issues related to within-school teacher supply and school-specific teacher turnover within the state of Michigan using state administrative data on Michigan's teaching force. This paper 1) investigates the key predictors of teacher turnover and mobility, 2) develops a profile of schools that are likely to…

  1. Analysis of the Educational Personnel System: IV. Teacher Turnover.

    ERIC Educational Resources Information Center

    Keeler, Emmett B.

    This report attempts to predict the rates of teacher turnover in the 1970s, which teachers will leave the profession, and what the effects of turnover will be on the educational personnel system. The overall termination rate has varied from six to 11 percent over the last 15 years. An analysis of recent changes in the teaching profession is used…

  2. Re-Examining the Relationship between Age and Voluntary Turnover

    ERIC Educational Resources Information Center

    Ng, Thomas W. H.; Feldman, Daniel C.

    2009-01-01

    In their quantitative review of the literature, Healy, Lehman, and McDaniel [Healy, M. C., Lehman, M., & McDaniel, M. A. (1995). Age and voluntary turnover: A quantitative review. "Personnel Psychology, 48", 335-345] concluded that age is only weakly related to voluntary turnover (average r = -0.08). However, with the significant changes in…

  3. The Link between Training Satisfaction, Work Engagement and Turnover Intention

    ERIC Educational Resources Information Center

    Memon, Mumtaz Ali; Salleh, Rohani; Baharom, Mohamed Noor Rosli

    2016-01-01

    Purpose: The purpose of this paper is to examine the casual relationship between training satisfaction, work engagement (WE) and turnover intention and the mediating role of WE between training satisfaction and turnover intention. Design/methodology/approach: Data were collected from 409 oil and gas professionals using an email survey…

  4. Organizational Characteristics Associated with Staff Turnover in Nursing Homes

    ERIC Educational Resources Information Center

    Castle, Nicholas G.; Engberg, John

    2006-01-01

    Purpose: The association between certified nurse aide, licensed practical nurse, and registered nurse turnover and the organizational characteristics of nursing homes are examined. Design and Methods: Hypotheses for eight organizational characteristics are examined (staffing levels, top management turnover, resident case mix, facility quality,…

  5. Predicting Turnover: Validating the Intent to Leave Child Welfare Scale

    ERIC Educational Resources Information Center

    Auerbach, Charles; Schudrich, Wendy Zeitlin; Lawrence, Catherine K.; Claiborne, Nancy; McGowan, Brenda G.

    2014-01-01

    A number of proxies have been used in child welfare workforce research to represent actual turnover; however, there have been no psychometric studies to validate a scale specifically designed for this purpose. The Intent to Leave Child Welfare Scale is a proxy for actual turnover that measures workers' intention to leave. This scale was…

  6. Understanding the Impacts of Induction Programs on Beginning Teacher Turnover

    ERIC Educational Resources Information Center

    Kang, Seok

    2010-01-01

    This study examines impacts of mentoring and induction activities on beginning teacher turnover using the School and Staffing Survey (SASS) of 1999-2000 and the Teacher Follow-up Survey (TFS) of 2000-2001. In order to improve understanding of the influence of induction programs on beginning teacher turnover, three models are developed to achieve…

  7. Voluntary Turnover and Women Administrators in Higher Education

    ERIC Educational Resources Information Center

    Jo, Victoria H.

    2008-01-01

    A salient characteristic about the U.S. workforce is the continual process of voluntary employee turnover, which can be problematic for employers who invest a substantial amount of time and money in recruiting and training employees. This paper discusses the effects of workplace policies and practices on the voluntary turnover of women…

  8. Pexophagy and peroxisomal protein turnover in plants.

    PubMed

    Young, Pierce G; Bartel, Bonnie

    2016-05-01

    Peroxisomes are dynamic, vital organelles that sequester a variety of oxidative reactions and their toxic byproducts from the remainder of the cell. The oxidative nature of peroxisomal metabolism predisposes the organelle to self-inflicted damage, highlighting the need for a mechanism to dispose of damaged peroxisomes. In addition, the metabolic requirements of plant peroxisomes change during development, and obsolete peroxisomal proteins are degraded. Although pexophagy, the selective autophagy of peroxisomes, is an obvious mechanism for executing such degradation, pexophagy has only recently been described in plants. Several recent studies in the reference plant Arabidopsis thaliana implicate pexophagy in the turnover of peroxisomal proteins, both for quality control and during functional transitions of peroxisomal content. In this review, we describe our current understanding of the occurrence, roles, and mechanisms of pexophagy in plants. PMID:26348128

  9. RHIZOSPHERE MICROBIOLOGY OF CHLORINATED ETHENE CONTAMINATED SOILS: EFFECTS ON PHOSPHOLIPID FATTY ACID CONTENT

    SciTech Connect

    Brigmon, R. L.; Stanhopc, A.; Franck, M. M.; McKinsey, P. C.; Berry, C. J.

    2005-05-26

    Microbial degradation of chlorinated ethenes (CE) in rhizosphere soils was investigated at seepline areas impacted by CE plumes. Successful bioremediation of CE in rhizosphere soils is dependent on microbial activity, soil types, plant species, and groundwater CE concentrations. Seepline soils were exposed to trichloroethylene (TCE) and perchloroethylene (PCE) in the 10-50 ppb range. Greenhouse soils were exposed to 2-10 ppm TCE. Plants at the seepline were poplar and pine while the greenhouse contained sweet gum, willow, pine, and poplar. Phospholipid fatty acid (PLFA) analyses were performed to assess the microbial activity in rhizosphere soils. Biomass content was lowest in the nonvegetated control soil and highest in the Sweet Gum soil. Bacterial rhizhosphere densities, as measured by PLFA, were similar in different vegetated soils while fungi biomass was highly variable. The PLFA soil profiles showed diverse microbial communities primarily composed of Gram-negative bacteria. Adaptation of the microbial community to CE was determined by the ratio of {omega}7t/{omega}7c fatty acids. Ratios (16:1{omega}7v16:1{omega}7c and 18:l{omega}7t/18:1{omega}7c) greater than 0.1 were demonstrated in soils exposed to higher CE concentrations (10-50 ppm), indicating an adaptation to CE resulting in decreased membrane permeability. Ratios of cyclopropyl fatty acids showed that the vegetated control soil sample contained the fastest microbial turnover rate and least amount of environmental stress. PLFA results provide evidence that sulfate reducing bacteria (SRB) are active in these soils. Microcosm studies with these soils showed CE dechlorinating activity was occurring. This study demonstrates microbial adaptation to environmental contamination and supports the application of natural soil rhizosphere activity as a remedial strategy.

  10. Water level changes affect carbon turnover and microbial community composition in lake sediments

    PubMed Central

    Weise, Lukas; Ulrich, Andreas; Moreano, Matilde; Gessler, Arthur; E. Kayler, Zachary; Steger, Kristin; Zeller, Bernd; Rudolph, Kristin; Knezevic-Jaric, Jelena; Premke, Katrin

    2016-01-01

    Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. 13C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions. PMID:26902802

  11. Water level changes affect carbon turnover and microbial community composition in lake sediments.

    PubMed

    Weise, Lukas; Ulrich, Andreas; Moreano, Matilde; Gessler, Arthur; Kayler, Zachary E; Steger, Kristin; Zeller, Bernd; Rudolph, Kristin; Knezevic-Jaric, Jelena; Premke, Katrin

    2016-05-01

    Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. (13)C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions. PMID:26902802

  12. Migration of phospholipid vesicles in response to OH(-) stimuli.

    PubMed

    Kodama, Atsuji; Sakuma, Yuka; Imai, Masayuki; Oya, Yutaka; Kawakatsu, Toshihiro; Puff, Nicolas; Angelova, Miglena I

    2016-03-21

    We demonstrate migration of phospholipid vesicles in response to a pH gradient. Upon simple micro-injection of a NaOH solution, the vesicles linearly moved to the tip of the micro-pipette and the migration velocity was proportional to the gradient of OH(-) concentration. Vesicle migration was characteristic of OH(-) ions and no migration was observed for monovalent salts or nonionic sucrose solutions. The migration of vesicles is quantitatively described by the surface tension gradient model where the hydrolysis of the phospholipids by NaOH solution decreases the surface tension of the vesicle. The vesicles move toward a direction where the surface energy decreases. Thus the chemical modification of lipids produces a mechanical force to drive vesicles. PMID:26883729

  13. Hormetic and anti-inflammatory properties of oxidized phospholipids.

    PubMed

    Mauerhofer, Christina; Philippova, Maria; Oskolkova, Olga V; Bochkov, Valery N

    2016-06-01

    Oxidized phospholipids are generally recognized as deleterious factors involved in disease pathogenesis. This review summarizes the data suggesting that under certain biological conditions the opposite is correct, namely that OxPLs can also induce protective effects. Examples that are discussed in the review include upregulation of antioxidant genes, inhibition of inflammatory signaling pathways through Nrf2-dependent and -independent mechanisms, antagonism of Toll-like receptors, immuno-modulating and immuno-suppressive action of OxPLs in adaptive immunity and autoimmune disease, activation of PPARs known for their anti-inflammatory action, as well as protective action against lung edema in acute lung inflammation. The data support the notion that oxidation of phospholipids provides a negative feedback preventing damage to host tissues due to uncontrolled inflammation and oxidative stress. PMID:26948981

  14. A Cholesterol Recognition Motif in Human Phospholipid Scramblase 1

    PubMed Central

    Posada, Itziar M.D.; Fantini, Jacques; Contreras, F. Xabier; Barrantes, Francisco; Alonso, Alicia; Goñi, Félix M.

    2014-01-01

    Human phospholipid scramblase 1 (SCR) catalyzes phospholipid transmembrane (flip-flop) motion. This protein is assumed to bind the membrane hydrophobic core through a transmembrane domain (TMD) as well as via covalently bound palmitoyl residues. Here, we explore the possible interaction of the SCR TMD with cholesterol by using a variety of experimental and computational biophysical approaches. Our findings indicate that SCR contains an amino acid segment at the C-terminal region that shows a remarkable affinity for cholesterol, although it lacks the CRAC sequence. Other 3-OH sterols, but not steroids lacking the 3-OH group, also bind this region of the protein. The newly identified cholesterol-binding region is located partly at the C-terminal portion of the TMD and partly in the first amino acid residues in the SCR C-terminal extracellular coil. This finding could be related to the previously described affinity of SCR for cholesterol-rich domains in membranes. PMID:25229146

  15. Light and phospholipid driven structural transitions in nematic microdroplets

    SciTech Connect

    Dubtsov, A. V. Pasechnik, S. V.; Shmeliova, D. V.; Kralj, Samo

    2014-10-13

    We studied the UV-irradiation and phospholipid driven bipolar-radial structural transitions within azoxybenzene nematic liquid crystal (LC) droplets dispersed in water. It was found that the UV-irradiation induced trans-cis isomerisation of LC molecules could enable structural transitions into radial-type configurations at a critical UV-irradiation time t{sub c}. In particular, we show that under appropriate conditions, a value of t{sub c} could sensitively fingerprint the concentration of phospholipid molecules present in LC-water dispersions. This demonstrated proof-of-principle mechanism could be exploited for development of sensitive detectors for specific nanoparticles (NPs), where value of t{sub c} reveals concentration of NPs.

  16. The influence of plant hormones on phospholipid monolayer stability.

    PubMed

    Gzyl-Malchera, Barbara; Filek, Maria; Brezesinski, Gerald; Fischer, Antje

    2007-01-01

    The influence of hormones in water subphase on the stability of monolayers built of phospholipid mixtures extracted from embryogenic (PLE) and nonembryogenic (PLNE) wheat calli was examined. Additionally, experiments on individual lipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidic acid (DPPA), were performed. DPPC was chosen because it was the main phospholipid present in both calli. Negatively charged DPPA could mimic a negatively charged natural mixture of lipids. As hormones, auxins (IAA and 2,4-D), cytokinins (zeatin and kinetin) and zearalenone were chosen. The time of monolayer stability for PLNE calli was much longer than for PLE calli. Kinetics of monolayer stability of PLNE was similar to DPPA, whereas that of PLE was similar to DPPC. Generally, hormones increased the time after which the monolayer stability was reached and decreased the surface pressure. The greatest effect was observed for auxins (especially IAA), whereas cytokinins affected the monolayer stability to a lesser degree. PMID:17425106

  17. Large-scale variation in boreal and temperate forest carbon turnover rate related to climate

    NASA Astrophysics Data System (ADS)

    Thurner, Martin; Beer, Christian; Carvalhais, Nuno; Forkel, Matthias; Santoro, Maurizio; Tum, Markus; Schmullius, Christiane

    2016-05-01

    Vegetation carbon turnover processes in forest ecosystems and their dominant drivers are far from being understood at a broader scale. Many of these turnover processes act on long timescales and include a lateral dimension and thus can hardly be investigated by plot-level studies alone. Making use of remote sensing-based products of net primary production (NPP) and biomass, here we show that spatial gradients of carbon turnover rate (k) in Northern Hemisphere boreal and temperate forests are explained by different climate-related processes depending on the ecosystem. k is related to frost damage effects and the trade-off between growth and frost adaptation in boreal forests, while drought stress and climate effects on insects and pathogens can explain an elevated k in temperate forests. By identifying relevant processes underlying broadscale patterns in k, we provide the basis for a detailed exploration of these mechanisms in field studies, and ultimately the improvement of their representations in global vegetation models (GVMs).

  18. Does a Corresponding Set of Variables for Explaining Voluntary Organizational Turnover Transfer to Explaining Voluntary Occupational Turnover?

    ERIC Educational Resources Information Center

    Blau, Gary

    2007-01-01

    This study proposed and tested corresponding sets of variables for explaining voluntary organizational versus occupational turnover for a sample of medical technologists. This study is believed to be the first test of the Rhodes and Doering (1983) occupational change model using occupational turnover data. Results showed that corresponding job…

  19. Differential Intrahepatic Phospholipid Zonation in Simple Steatosis and Nonalcoholic Steatohepatitis

    PubMed Central

    Wattacheril, Julia; Seeley, Erin H.; Angel, Peggi; Chen, Heidi; Bowen, Benjamin P.; Lanciault, Christian; M.Caprioli, Richard; Abumrad, Naji; Flynn, Charles Robb

    2013-01-01

    Nonalcoholic fatty liver disease (NAFLD) occurs frequently in a setting of obesity, dyslipidemia and insulin resistance, but the etiology of the disease, particularly the events favoring progression to nonalcoholic steatohepatitis (NASH) as opposed to simple steatosis (SS), are not fully understood. Based on known zonation patterns in protein, glucose and lipid metabolism, coupled with evidence that phosphatidylcholine may play a role in NASH pathogenesis, we hypothesized that phospholipid zonation exists in liver and that specific phospholipid abundance and distribution may be associated with histologic disease. A survey of normal hepatic protein expression profiles in the Human Protein Atlas revealed pronounced zonation of enzymes involved in lipid utilization and storage, particularly those facilitating phosphatidylcholine (PC) metabolism. Immunohistochemistry of obese normal, SS and NASH liver specimens with anti-phosphatidylethanomine N-methyltransferase (PEMT) antibodies showed a progressive decrease in the zonal distribution of this PC biosynthetic enzyme. Phospholipid quantitation by liquid chromatography mass spectrometry (LC-MS) in hepatic extracts of Class III obese patients with increasing NAFLD severity revealed that most PC species with 32, 34 and 36 carbons as well as total PC abundance was decreased with SS and NASH. Matrix assisted laser desorption ionization - imaging mass spectrometry (MALDI-IMS) imaging revealed strong zonal distributions for 32, 34 and 36 carbon PCs in controls (minimal histologic findings) and SS that was lost in NASH specimens. Specific lipid species such as PC 34∶1 and PC 36∶2 best illustrated this phenomenon. These findings suggest that phospholipid zonation may be associated with the presence of an intrahepatic proinflammatory phenotype and thus have broad implications in the etiopathogenesis of NASH. PMID:23451176

  20. Inhibition of phospholipid methylation by a cytosolic factor.

    PubMed Central

    Alvarez Chiva, V; Mato, J M

    1984-01-01

    Rat liver cytosol contains a heat-stable factor which inhibits phospholipid methylation by rat liver microsomes. The effect of this factor on lipid methylation was dose- and pH-dependent. This factor has an Mr of approx. 3200 as estimated by gel filtration. It could not be extracted by chloroform/methanol (2:1, v/v), and its action was inhibited by incubation with subtilisin. PMID:6712636

  1. Phospholipid biosynthesis in the oyster protozoan parasite, Perkinsus marinus.

    PubMed

    Lund, Eric D; Chu, Fu-Lin E

    2002-05-01

    Perkinsus marinus is a protozoan parasite that causes high mortality in its commercially and ecologically important host, the Eastern oyster Crassostrea virginica. In order to understand the host-parasite relationship in lipid metabolism, the ability of P. marinus to synthesize phospholipids from polar headgroup precursors was investigated. Pulse/chase experiments were conducted using radiolabled serine, choline, ethanolamine and inositol. Timecourse incubations revealed that in vitro cultured P. marinus meronts can utilize the cytidine diphosphate-diacylglycerol (CDP-DAG) pathway to synthesize phosphatidylinositol (PI) from inositol and phosphatidylserine (PS) from serine. Serine label was also incorporated into phosphatidylethanolamine (PE), phosphatidylcholine (PC) and lysophosphatidylcholine (LPC). Incubations of P. marinus cells with increasing concentrations of radiolabeled serine resulted in more radioactivity recovered in neutral lipids than in polar lipids at the highest substrate concentration tested (344 microM). This suggests that excess serine label was being utilized for fatty acid synthesis and stored as triacylglycerols. Additional incubations were conducted with radiolabeled choline and ethanolamine at concentrations equimolar to the highest serine concentration tested. Ethanolamine label was also incorporated into PE, PS, PC and LPC. Choline label was incorporated into PC. These results suggest the presence of three pathways for de novo synthesis of phospholipids in P. marinus: CDP-choline, CDP-ethanolamine and CDP-DAG. At equivalent substrate concentrations (344 microM) the highest incorporation of labeled substrate into total phospholipids was with serine followed by ethanolamine and choline, respectively. P. marinus phospholipid biosynthetic capabilities appear to be similar to those of Plasmodium and Trypanosoma species. PMID:12034458

  2. NMR Structures of Membrane Proteins in Phospholipid Bilayers

    PubMed Central

    Radoicic, Jasmina; Lu, George J.; Opella, Stanley J.

    2014-01-01

    Membrane proteins have always presented technical challenges for structural studies because of their requirement for a lipid environment. Multiple approaches exist including X-ray crystallography and electron microscopy that can give significant insights into their structure and function. However, nuclear magnetic resonance (NMR) is unique in that it offers the possibility of determining the structures of unmodified membrane proteins in their native environment of phospholipid bilayers under physiological conditions. Furthermore, NMR enables the characterization of the structure and dynamics of backbone and side chain sites of the proteins alone and in complexes with both small molecules and other biopolymers. The learning curve has been steep for the field as most initial studies were performed under non-native environments using modified proteins until ultimately progress in both techniques and instrumentation led to the possibility of examining unmodified membrane proteins in phospholipid bilayers under physiological conditions. This review aims to provide an overview of the development and application of NMR to membrane proteins. It highlights some of the most significant structural milestones that have been reached by NMR spectroscopy of membrane proteins; especially those accomplished with the proteins in phospholipid bilayer environments where they function. PMID:25032938

  3. Enteropathogenic Escherichia coli Infection Triggers Host Phospholipid Metabolism Perturbations

    PubMed Central

    Wu, Y.; Lau, B.; Smith, S.; Troyan, K.; Barnett Foster, D. E.

    2004-01-01

    Enteropathogenic Escherichia coli (EPEC) specifically recognizes phosphatidylethanolamine (PE) on the outer leaflet of host epithelial cells. EPEC also induces apoptosis in epithelial cells, which results in increased levels of outer leaflet PE and increased bacterial binding. Consequently, it is of interest to investigate whether EPEC infection perturbs host cell phospholipid metabolism and whether the changes play a role in the apoptotic signaling. Our findings indicate that EPEC infection results in a significant increase in the epithelial cell PE level and a corresponding decrease in the phosphatidylcholine (PC) level. PE synthesis via both the de novo pathway and the serine decarboxylation pathway was enhanced, and de novo synthesis of phosphatidylcholine via CDP-choline was reduced. The changes were transitory, and the maximum change was noted after 4 to 5 h of infection. Addition of exogenous PC or CDP-choline to epithelial cells prior to infection abrogated EPEC-induced apoptosis, suggesting that EPEC infection inhibits the CTP-phosphocholine cytidylyltransferase step in PC synthesis, which is reportedly inhibited during nonmicrobially induced apoptosis. On the other hand, incorporation of exogenous PE by the host cells enhanced EPEC-induced apoptosis and necrosis without increasing bacterial adhesion. This is the first report that pathogen-induced apoptosis is associated with significant changes in PE and PC metabolism, and the results suggest that EPEC adhesion to a host membrane phospholipid plays a role in disruption of host phospholipid metabolism. PMID:15557596

  4. Hydrophobic Silica Nanoparticles Induce Gel Phases in Phospholipid Monolayers.

    PubMed

    Orsi, Davide; Rimoldi, Tiziano; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Cristofolini, Luigi

    2016-05-17

    Silica nanoparticles (SiNP) can be incorporated in phospholipid layers to form hybrid organic-inorganic bidimensional mesostructures. Controlling the dynamics in these mesostructures paves the way to high-performance drug-delivery systems. Depending on the different hydrophobicity/hydrophilicity of SiNP, recent X-ray reflectivity experiments have demonstrated opposite structural effects. While these are reasonably well understood, less is known about the effects on the dynamics, which in turn determine molecular diffusivity and the possibility of drug release. In this work we characterize the dynamics of a mixed Langmuir layer made of phospholipid and hydrophobic SiNP. We combine X-ray photon correlation spectroscopy and epifluorescence discrete Fourier microscopy to cover more than 2 decades of Q-range (0.3-80 μm(-1)). We obtain evidence for the onset of an arrested state characterized by intermittent stress-relaxation rearrangement events, corresponding to a gel dominated by attractive interactions. We compare this with our previous results from phospholipid/hydrophilic SiNP films, which show an arrested glassy phase of repulsive disks. PMID:27133453

  5. Bile salt-phospholipid aggregation at submicellar concentrations.

    PubMed

    Baskin, Rebekah; Frost, Laura D

    2008-04-01

    The aggregation behavior of the bile salts taurodeoxycholate (NaTDC) and sodium cholate (NaC), are followed at concentrations below critical micelle concentrations (CMCs) using the environment sensitive, fluorescent-labeled phospholipid, 2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl-1-hexadecanoyl-sn-glycero-3-phosphocholine (NBD-C(6)-HPC). A buffer solution containing NBD-C(6)-HPC is titrated with increasing NaC or NaTDC and the fluorescence changes followed. Both bile salts induced fluorescence changes below their critical micelle concentration indicating the presence of a bile salt-phospholipid aggregate. A critical control experiment using 6-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino) hexanoic acid (NBD-X) shows that the bile salts are interacting with the longer, C16 hydrocarbon tail, not the NBD probe. The fluorescence curves were fitted to the Hill equation as a model for cooperative aggregation. The cooperativity model provides a minimum estimate for the number of bile salts to give maximal fluorescence. This number was calculated for NaC and NaTDC to have a minimum value of approximately 2. A small aggregation number supports the existence of primary micellar aggregates at submicellar concentrations for bile salt-phospholipid aqueous solutions. PMID:18035524

  6. THE CATION CONTENT OF PHOSPHOLIPIDES FROM SWINE ERYTHROCYTES

    PubMed Central

    Kirschner, Leonard B.

    1958-01-01

    Phospholipides from swine erythrocytes were isolated and separated into four reproducible fractions. One of the fractions seems to be pure phosphatidylserine. The others are almost certainly not single compounds, although the analytical data indicate that they represent mixtures considerably simpler than the parent mixture extracted from the cells. All four fractions contained Na+ and K+, but very little Ca2+. Sodium was the predominant cation in two of the fractions under all conditions although the major intracellular cation was potassium. In the other two fractions the ratio Na/K varied with the extraction procedure largely because the quantity of K+ seemed to depend on the solvent system used. There appear to be reasons to believe that the entire system of phospholipides binds Na+ preferentially. In addition, it was observed that the quantity of Na+ found in the lipide extracts varied when the extrusion of Na+ from the cells was made to vary. Both of these observations are consistent with the possibility that the phospholipides play some part in the extrusion of Na+ from these cells. PMID:13587908

  7. The innate immune response to products of phospholipid peroxidation.

    PubMed

    Weismann, David; Binder, Christoph J

    2012-10-01

    Lipid peroxidation occurs in the context of many physiological processes but is greatly increased in various pathological situations. A consequence of phospholipid peroxidation is the generation of oxidation-specific epitopes, such as phosphocholine of oxidized phospholipids and malondialdehyde, which form neo-self determinants on dying cells and oxidized low-density lipoproteins. In this review we discuss evidence demonstrating that pattern recognition receptors of the innate immune system recognize oxidation-specific epitopes as endogenous damage-associated molecular patterns, allowing the host to identify dangerous biological waste. Oxidation-specific epitopes are important targets of both cellular and soluble pattern recognition receptors, including toll-like and scavenger receptors, C-reactive protein, complement factor H, and innate natural IgM antibodies. This recognition allows the innate immune system to mediate important physiological house keeping functions, for example by promoting the removal of dying cells and oxidized molecules. Once this system is malfunctional or overwhelmed the development of diseases, such as atherosclerosis and age-related macular degeneration is favored. Understanding the molecular components and mechanisms involved in this process, will help the identification of individuals with increased risk of developing chronic inflammation, and indicate novel points for therapeutic intervention. This article is part of a Special Issue entitled: Oxidized phospholipids-their properties and interactions with proteins. PMID:22305963

  8. Ultraviolet radiation alters choline phospholipid metabolism in human keratinocytes

    SciTech Connect

    DeLeo, V.; Scheide, S.; Meshulam, J.; Hanson, D.; Cardullo, A.

    1988-10-01

    Ultraviolet radiation B (UVB-290-320 nm) induces inflammation and hyperproliferation in human epidermis. This response is associated with the recovery from irradiated skin of inflammatory mediators derived from membrane phospholipids. We have previously reported that UVB stimulates the production of such mediators by human keratinocytes (HK) in culture. In these studies we examined the effect of UVB on the metabolism of choline containing phospholipids in HK prelabeled with (/sup 3/H) choline. UVB (400-1600J/m2) stimulated a dose dependent release of (/sup 3/H) choline from HK within minutes of irradiation. Examination of media extracts by paper chromatography revealed that the released (/sup 3/H) choline was predominately in the form of glycerophosphorylcholine. Examination of label remaining in membranes of cells after irradiation by acid precipitation and HPLC revealed that the origin of the released (/sup 3/H) choline was the membrane phosphatidylcholine/lysophosphatidylcholine. These data support a concept of UVB stimulation of both a phospholipase A (1 or 2) and a lysophospholipase. These UVB induced alterations of HK membrane phospholipid metabolism likely have profound effects on UVB-induced inflammation and control of cell growth in human skin.

  9. Hybrid electrospun chitosan-phospholipids nanofibers for transdermal drug delivery.

    PubMed

    Mendes, Ana C; Gorzelanny, Christian; Halter, Natalia; Schneider, Stefan W; Chronakis, Ioannis S

    2016-08-20

    Chitosan (Ch) polysaccharide was mixed with phospholipids (P) to generate electrospun hybrid nanofibers intended to be used as platforms for transdermal drug delivery. Ch/P nanofibers exibithed average diameters ranging from 248±94nm to 600±201nm, depending on the amount of phospholipids used. Fourier Transformed Infra-Red (FTIR) spectroscopy and Dynamic Light Scattering (DLS) data suggested the occurrence of electrostatic interactions between amine groups of chitosan with the phospholipid counterparts. The nanofibers were shown to be stable for at least 7days in Phosphate Buffer Saline (PBS) solution. Cytotoxicity studies (WST-1 and LDH assays) demonstrated that the hybrid nanofibers have suitable biocompatibility. Fluorescence microscopy, also suggested that L929 cells seeded on top of the CH/P hybrid have similar metabolic activity comparatively to the cells seeded on tissue culture plate (control). The release of curcumin, diclofenac and vitamin B12, as model drugs, from Ch/P hybrid nanofibers was investigated, demonstrating their potential utilization as a transdermal drug delivery system. PMID:27286632

  10. Linking Phospholipid flippases to vesicle-mediated protein transport

    PubMed Central

    Muthusamy, Baby-Periyanayaki; Natarajan, Paramasivam; Zhou, Xiaoming; Graham, Todd R.

    2013-01-01

    Type IV P-type ATPases (P4-ATPases) are a large family of putative phospholipid translocases (flippases) implicated in the generation of phospholipid asymmetry in biological membranes. P4-ATPases are typically the largest P-type ATPase subgroup found in eukaryotic cells, with five members in Saccharomyces cerevisiae, six members in Caenorhabditis elegans, 12 members in Arabidopsis thaliani and 14 members in humans. In addition, many of the P4-ATPases require interaction with a noncatalytic subunit from the CDC50 gene family for their transport out of the endoplasmic reticulum (ER). Deficiency of a P4-ATPase (Atp8b1) causes liver disease in humans, and studies in a variety of model systems indicate that P4-ATPases play diverse and essential roles in membrane biogenesis. In addition to their proposed role in establishing and maintaining plasma membrane asymmetry, P4-ATPases are linked to vesicle-mediated protein transport in the exocytic and endocytic pathways. Recent studies have also suggested a role for P4-ATPases in the nonvesicular intracellular trafficking of sterols. Here, we discuss the physiological requirements for yeast P4-ATPases in phospholipid translocase activity, transport vesicle budding and ergosterol metabolism, with an emphasis on Drs2p and its noncatalytic subunit, Cdc50p. PMID:19286470

  11. Reconstitution of rat liver vasopressin receptors into phospholipid vesicles

    SciTech Connect

    Dickey, B.; Navarro, J.; Fishman, J.; Fine, R.

    1986-05-01

    Isolation and characterization of the hepatic vasopressin (V1) receptor has been hampered by the loss of vasopressin binding when the receptor is solubilized. An alternative to a soluble binding assay is reconstitution of solubilized receptors into phospholipid vesicles. They report here the initial reconstitution of solubilized vasopressin receptors. Rat liver microsomes were solubilized with 3% 3-((3-cholamido-propyl)dimethyl-ammonio)-1-propanesulfonate (CHAPS) in 20mM HEPES (pH 7.4). The solubilized protein was combined with an equal volume of 7% soybean phospholipids dissolved in 3% CHAPS. This solution was passed over a column of Sephadex G50 equilibrated with 30 mM HEPES, 5mM MgCl/sub 2/ (pH 7.4). Reconstituted vesicles containing the microsomal proteins were recovered in the void volume. Binding of (/sup 3/H)-Vasopressin to the reconstituted vesicles at pH 7.4 was 80% specific, saturable, reversible and required magnesium. Solubilization of microsomes in the presence of glycerol, prebound ligand, phospholipids or magnesium did not improve subsequent binding. This reconstitution procedure will allow examination of signal transduction mechanisms and may be used as a functional assay in isolating the receptor.

  12. Label free detection of phospholipids by infrared absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahmed, Tahsin; Foster, Erick; Vigil, Genevieve; Khan, Aamir A.; Bohn, Paul; Howard, Scott S.

    2014-08-01

    We present our study on compact, label-free dissolved lipid sensing by combining capillary electrophoresis separation in a PDMS microfluidic chip online with mid-infrared (MIR) absorption spectroscopy for biomarker detection. On-chip capillary electrophoresis is used to separate the biomarkers without introducing any extrinsic contrast agent, which reduces both cost and complexity. The label free biomarker detection could be done by interrogating separated biomarkers in the channel by MIR absorption spectroscopy. Phospholipids biomarkers of degenerative neurological, kidney, and bone diseases are detectable using this label free technique. These phospholipids exhibit strong absorption resonances in the MIR and are present in biofluids including urine, blood plasma, and cerebrospinal fluid. MIR spectroscopy of a 12-carbon chain phosphatidic acid (PA) (1,2-dilauroyl-snglycero- 3-phosphate (sodium salt)) dissolved in N-methylformamide, exhibits a strong amide peak near wavenumber 1660 cm-1 (wavelength 6 μm), arising from the phosphate headgroup vibrations within a low-loss window of the solvent. PA has a similar structure to many important phospholipids molecules like phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylserine (PS), making it an ideal molecule for initial proof-of-concept studies. This newly proposed detection technique can lead us to minimal sample preparation and is capable of identifying several biomarkers from the same sample simultaneously.

  13. Synaptogenesis: Modulation by Availability of Membrane Phospholipid Precursors.

    PubMed

    Cansev, Mehmet

    2016-09-01

    Phospholipids are the main constituents of brain membranes. Formation of new membranes requires that uridine, the omega-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA), and choline, the three circulating precursors of major phospholipids, interact via the Kennedy pathway. Supplementation of laboratory rodents with uridine, DHA and choline enhances the amount of brain membranes as well as synaptic proteins and increases the number of dendritic spines, the essential cytological precursor of new synapses. Hence, the newly formed membranes are utilized for synaptogenesis which underlies increased synaptic functioning evidenced by enhanced neurotransmission and cognition. In addition, this supplementation ameliorates the degeneration in a rat model of Parkinson's disease and mouse models of Alzheimer's disease (AD) when used in combination with several vitamins and cofactors. Hence, accumulating evidence shows that increasing the availability of phospholipid precursors, vitamins and cofactors to the brain through dietary supplementation enhances the formation of new synapses and provides protection under neurodegenerative conditions. The combination has been tested in clinical trials and a medication has been marketed for early-stage AD patients. PMID:27250850

  14. Proton/hydroxide conductance and permeability through phospholipid bilayer membranes.

    PubMed Central

    Gutknecht, J

    1987-01-01

    Proton/hydroxide (H+/OH-) permeability of phospholipid bilayers is several orders of magnitude higher than alkali or halide ion permeabilities at pH 7. The objective of this study was to determine the mechanism(s) of H+/OH- conductance and permeability through planar phospholipid bilayer membranes. Membranes were formed from decane solutions of bacterial phosphatidylethanolamine, diphytanoyl phosphatidylcholine, or egg phosphatidylcholine plus cholesterol. At pH 7, H+/OH- conductance (GH/OH) ranged from 2 to 6 nS.cm-2, corresponding to H+/OH- "net" permeabilities of (0.4-1.6) X 10(-5) cm.sec-1. GH/OH was inhibited by serum albumin (fatty acid-free), phloretin, and low pH. GH/OH was increased by chlorodecane, long-chain fatty acids, and voltages greater than 80 mV. Water permeability and GH/OH were not correlated. The results suggest that the H+/OH- charge carrier (i) is primarily anionic, (ii) crosses the membrane via nonpolar pathway(s), and (iii) can be removed from the membrane by "washing" with serum albumin. The simplest explanation is that the phospholipids contain weakly acidic contaminants that act as proton carriers at neutral pH. However, at low pH or in the presence of inhibitors, a "background" GH/OH remains that may be due to other mechanisms. PMID:2819878

  15. Staff turnover in statewide implementation of ACT: relationship with ACT fidelity and other team characteristics

    PubMed Central

    Rollins, Angela L.; Salyers, Michelle P.; Tsai, Jack; Lydick, Jennifer M.

    2010-01-01

    Staff turnover on assertive community treatment (ACT) teams is a poorly understood phenomenon. This study examined annual turnover and fidelity data collected in a statewide implementation of ACT over a 5-year period. Mean annual staff turnover across all observations was 30.0%. Turnover was negatively correlated with overall fidelity at Year 1 and 3. The team approach fidelity item was negatively correlated with staff turnover at Year 3. For 13 teams with 3 years of follow-up data, turnover rates did not change over time. Most ACT staff turnover rates were comparable or better than other turnover rates reported in the mental health and substance abuse literature. PMID:20012481

  16. Understanding the factors that determine registered nurses' turnover intentions.

    PubMed

    Osuji, Joseph; Uzoka, Faith-Michael; Aladi, Flora; El-Hussein, Mohammed

    2014-01-01

    Turnover among registered nurses (RNs) produces a negative impact on the health outcomes of any health care organization. It is also recognized universally as a problem in the nursing profession. Little is known about the turnover intentions and career orientations of RNs working in Calgary, Alberta, Canada. The aim of this study is to contribute to the knowledge of and to advance the discussion on the turnover of nursing professionals. The study population consisted of RNs employed in the five major hospitals in Calgary. There were 193 surveys returned, representing a response rate of 77.2%. The results show that age and education have a negative effect on turnover intention. Education was found to have a significant negative effect on career satisfaction but not on job satisfaction and organizational commitment. Length of service has a significant negative effect on turnover intention. Role ambiguity has significant highly negative effect on career satisfaction. Growth opportunity and supervisor support have a very significant positive effect on job satisfaction, career satisfaction, and organizational commitment. External career opportunities and organizational commitment do not seem to have a significant effect on turnover intention. Career satisfaction, on the other hand, had negative significant effects on turnover intention. PMID:25087326

  17. Turnover of metallothioneins in rat liver.

    PubMed Central

    Andersen, R D; Winter, W P; Maher, J J; Bernstein, I A

    1978-01-01

    Two electrophoretically distinguishable metallothioneins were isolated from the livers of Cd2+-treated rats and had thiol group/metal ratios of 3:1, a total metal content, in each of these proteins, of 3.6 atoms of Cd2+ + 2.4 atoms of Zn2+/molecule and 4.2 atoms of Cd2+ + 2.8 atoms of Zn2+/molecule and respective apoprotein mol.wts. of 5844 and 6251. Studies with 1 h pulse labels of [3H]cysteine, given after a single injection of ZnCl2 or CdCl2, showed that these metals stimulated radioactive isotope incorporation into the metallothioneins over the control value by 10- and 15-fold respectively. This stimulation was maximal at 4 h after a single CdCl2 injection and decreased to control values by 16 h, suggesting that either a translational event is responding to free intracellular Cd2+ or a short-lived mRNA is being produced or stabilized in response to the metal treatment. In rats chronically exposed to CdCl2, the metallothioneins increased to 0.2% of the liver wet weight from a control value of 2--4 mumol/kg of liver, with a maximum rate of accumulation of 2--3 mumol/h per kg of liver. The turnover of these proteins in control animals was 0.3--0.6 mumoles/h per kg of liver, measured by the rate of disappearance of 203Hg2+, which binds irreversibly to the metallothioneins. Pretreatment with CdCl2 completely stopped the rapid 203Hg turnover observed in untreated animals. Unlike CdCl2, treatment with ZnCl2 increased the concentration of metallothioneins to a new steady-state pool, 11 mumole/kg of liver, after 10 h. The increase in the zinc-thionein pool by exposure to ZnCl2 in vivo was determined to be primarily due to a stimulation of metallothionein biosynthesis. PMID:697759

  18. Investigating Histone Acetylation Stoichiometry and Turnover Rate.

    PubMed

    Fan, J; Baeza, J; Denu, J M

    2016-01-01

    Histone acetylation is a dynamic epigenetic modification that functions in the regulation of DNA-templated reactions, such as transcription. This lysine modification is reversibly controlled by histone (lysine) acetyltransferases and deacetylases. Here, we present methods employing isotopic labeling and mass spectrometry (MS) to comprehensively investigate histone acetylation dynamics. Turnover rates of histone acetylation are determined by measuring the kinetics of labeling from (13)C-labeled precursors of acetyl-CoA, which incorporates (13)C-carbon onto histones via the acetyltransferase reaction. Overall histone acetylation states are assessed from complete protease digestion to single amino acids, which is followed by MS analysis. Determination of site-specific acetylation stoichiometry is achieved by chemically acetylating endogenous histones with isotopic acetic anhydride, followed by trypsin digestion and LC-MS analysis. Combining metabolic labeling with stoichiometric analysis permits determination of both acetylation level and acetylation dynamics. When comparing genetic, diet, or environmental perturbations, these methods permit both a global and site-specific evaluation of how histone acetylation is dynamically regulated. PMID:27423860

  19. Triacylglycerol turnover in the failing heart.

    PubMed

    Carley, Andrew N; Lewandowski, E Douglas

    2016-10-01

    No longer regarded as physiologically inert the endogenous triacylglyceride (TAG) pool within the cardiomyocyte is now recognized to play a dynamic role in metabolic regulation. Beyond static measures of content, the relative rates of interconversion among acyl intermediates are more closely linked to dynamic processes of physiological function in normal and diseased hearts, with the potential for both adaptive and maladaptive contributions. Indeed, multiple inefficiencies in cardiac metabolism have been identified in the decompensated, hypertrophied and failing heart. Among the intracellular responses to physiological, metabolic and pathological stresses, TAG plays a central role in the balance of lipid handling and signaling mechanisms. TAG dynamics are profoundly altered from normal in both diabetic and pathologically stressed hearts. More than just expansion or contraction of the stored lipid pool, the turnover rates of TAG are sensitive to and compete against other enzymatic pathways, anabolic and catabolic, for reactive acyl-CoA units. The rates of TAG synthesis and lipolysis thusly affect multiple components of cardiomyocyte function, including energy metabolism, cell signaling, and enzyme activation, as well as the regulation of gene expression in both normal and diseased states. This review examines the multiple etiologies and metabolic consequences of the failing heart and the central role of lipid storage dynamics in the pathogenic process. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk. PMID:26993578

  20. Turnover of cytokeratin polypeptides in mouse hepatocytes

    SciTech Connect

    Denk, H.; Lackinger, E.; Zatloukal, K. ); Franke, W.W. )

    1987-11-01

    The turnover of cytokeratin polypeptides A (equivalent to No. 8 of the human cytokeratin catalog) and D (equivalent to human cytokeratin No. 18) of mouse hepatocytes was studied by pulse-labeling of mouse liver proteins after intraperitoneal injection of L-(guanido{sup 14}C)arginine and ({sup 14}C)sodium bicarbonate. With L-(guanido-{sup 14}C)arginine a rapid increase in the specific radioactivity of both cytokeratins was observed which reached a plateau between 12 and 24 h. With ({sup 14}C)sodium bicarbonate maximal specific radioactivity was obtained at 6 h followed by a rapid decrease to half maximum values within the subsequent 6 h and then a slower decrease. Half-lives were determined from the decrease of specific radioactivities after pulse-labeling by least-squares plots and found to be 84 h (for cytokeratin component A) and 104 h (component D) for arginine labeling . Values obtained after bicarbonate labeling were similar (95 h for A and 98 h for D). These results show that liver cytokeratins are relatively stable proteins and suggest that components A and D are synthesized and degraded at similar rates, probably in a coordinate way.

  1. Environmental and historical imprints on beta diversity: insights from variation in rates of species turnover along gradients

    PubMed Central

    Fitzpatrick, Matthew C.; Sanders, Nathan J.; Normand, Signe; Svenning, Jens-Christian; Ferrier, Simon; Gove, Aaron D.; Dunn, Robert R.

    2013-01-01

    A common approach for analysing geographical variation in biodiversity involves using linear models to determine the rate at which species similarity declines with geographical or environmental distance and comparing this rate among regions, taxa or communities. Implicit in this approach are weakly justified assumptions that the rate of species turnover remains constant along gradients and that this rate can therefore serve as a means to compare ecological systems. We use generalized dissimilarity modelling, a novel method that accommodates variation in rates of species turnover along gradients and between different gradients, to compare environmental and spatial controls on the floras of two regions with contrasting evolutionary and climatic histories: southwest Australia and northern Europe. We find stronger signals of climate history in the northern European flora and demonstrate that variation in rates of species turnover is persistent across regions, taxa and different gradients. Such variation may represent an important but often overlooked component of biodiversity that complicates comparisons of distance–decay relationships and underscores the importance of using methods that accommodate the curvilinear relationships expected when modelling beta diversity. Determining how rates of species turnover vary along and between gradients is relevant to understanding the sensitivity of ecological systems to environmental change. PMID:23926147

  2. Autoradiographic imaging of phosphoinositide turnover in the brain

    SciTech Connect

    Hwang, P.M.; Bredt, D.S.; Snyder, S.H. )

    1990-08-17

    With ({sup 3}H)cytidine as a precursor, phosphoinositide turnover can be localized in brain slices by selective autoradiography of the product ({sup 3}H)cytidine diphosphate diacylglycerol, which is membrane-bound. In the cerebellum, glutamatergic stimulation elicits an increase of phosphoinositide turnover only in Purkinje cells and the molecular layer. In the hippocampus, both glutamatergic and muscarinic cholinergic stimulation increase phosphoinositide turnover, but with distinct localizations. Cholinergic stimulation affects CA1, CA3, CA4, and subiculum, whereas glutamatergic effects are restricted to the subiculum and CA3. Imaging phosphoinositide turnover in brain slices, which are amenable to electrophysiologic studies, will permit a dynamic localized analysis of regulation of this second messenger in response to synaptic stimulation of specific neuronal pathways.

  3. Loading of lipophorin particles with phospholipids at the midgut of Rhodnius prolixus.

    PubMed

    Atella, G C; Gondim, C; Masuda, H

    1995-01-01

    32P-Labelled midguts (32P-midguts) of Rhodnius prolixus females were incubated in the presence of nonradioactive purified lipophorin and the release of radioactivity to the medium was analysed. The radioactivity found in the medium was associated with lipophorin phospholipids. When the 32P-midguts were incubated in the absence of lipophorin, no 32P-phospholipids were found in the medium. Comparative analysis by thin-layer chromatography of 32P-phospholipids derived from metabolically labelled 32P-midgut or lipophorin particles after incubation with 32P-midgut showed some differences, revealing a possible selectivity in the process of phospholipids transfer. The transfer of phospholipids to lipophorin was linear with time up to 45 min, was saturable with respect to the concentration of lipophorin, and was half-maximal at about 5 mg/ml. The binding of 32P-lipophorin to the midgut at 0 degrees C reached the equilibrium at about 1 h of incubation. The binding of 32P-lipophorin was inhibited by an excess of nonradioactive lipophorin, which suggests a specific receptor for lipophorin. The capacity of midguts and fat bodies to transfer phospholipids to lipophorin varied during the days following the meal. When lipophorin enzymatically depleted of phospholipids by treatment with phospholipase A2 was incubated with 32P-midguts, the same amount of phospholipids was transferred, indicating a net gain of phospholipids by the particle. PMID:11488302

  4. Formation of oil-in-water emulsions from natural emulsifiers using spontaneous emulsification: sunflower phospholipids.

    PubMed

    Komaiko, Jennifer; Sastrosubroto, Ashtri; McClements, David Julian

    2015-11-18

    This study examined the possibility of producing oil-in-water emulsions using a natural surfactant (sunflower phospholipids) and a low-energy method (spontaneous emulsification). Spontaneous emulsification was carried out by titrating an organic phase (oil and phospholipid) into an aqueous phase with continuous stirring. The influence of phospholipid composition, surfactant-to-oil ratio (SOR), initial phospholipids location, storage time, phospholipid type, and preparation method was tested. The initial droplet size depended on the nature of the phospholipid used, which was attributed to differences in phospholipid composition. Droplet size decreased with increasing SOR and was smallest when the phospholipid was fully dissolved in the organic phase rather than the aqueous phase. The droplets formed using spontaneous emulsification were relatively large (d > 10 μm), and so the emulsions were unstable to gravitational separation. At low SORs (0.1 and 0.5), emulsions produced with phospholipids had a smaller particle diameter than those produced with a synthetic surfactant (Tween 80), but at a higher SOR (1.0), this trend was reversed. High-energy methods (microfluidization and sonication) formed significantly smaller droplets (d < 10 μm) than spontaneous emulsification. The results from this study show that low-energy methods could be utilized with natural surfactants for applications for which fine droplets are not essential. PMID:26528859

  5. A retrospective: Use of Escherichia coli as a vehicle to study phospholipid synthesis and function

    PubMed Central

    Dowhan, William

    2012-01-01

    Although the study of individual phospholipids and their synthesis began in the 1920’s first in plants and then mammals, it was not until the early 1960’s that Eugene Kennedy using Escherichia coli initiated studies of bacterial phospholipid metabolism. With the base of information already available from studies of mammalian tissue, the basic blueprint of phospholipid biosynthesis in E. coli was worked out by the late 1960’s. In 1970’s and 1980’s most of the enzymes responsible for phospholipid biosynthesis were purified and many of the genes encoding these enzymes were identified. By the late 1990’s conditional and null mutants were available along with clones of the genes for every step of phospholipid biosynthesis. Most of these genes had been sequenced before the complete E. coli genome sequence was available. Strains of E. coli were developed in which phospholipid composition could be changed in a systematic manner while maintaining cell viability. Null mutants, strains in which phospholipid metabolism was artificially regulated, and strains synthesizing foreign lipids not found in E. coli have been used to this day to define specific roles for individual phospholipid. This review will trace the findings that have led to the development of E. coli as an excellent model system to study mechanisms underlying the synthesis and function of phospholipids that are widely applicable to other prokaryotic and eukaryotic systems. PMID:22925633

  6. Flow of glucose carbon into cholesterol and phospholipids in various regions of the adult rat brain: enhanced incorporation into hypothalamic phospholipids

    SciTech Connect

    Barkai, A.I.

    1981-01-01

    The contribution of glucose carbon to the biosynthesis of cholesterol and phospholipids in distinct brain regions was studied quantitatively in the adult male rat. Rates of flow of glucose carbon into the lipids in vivo were calculated from two measurements: the curve representing the decrease in plasma /sup 14/C-glucose with time and the specific activity of the cerebral lipid 180 minutes after a rapid intravenous injection of a tracer dose of D-U /sup 14/C-glucose. The following brain regions were studied: cerebral cortex, hypothalamus, medulla, and corpus callosum and cerebellum. The values for carbon flow into phospholipids were significantly higher in the hypothalamus than in the whole brain, whereas small, but insignificant, regional differences were found for carbon flow into cholesterol. The conversion of U-/sup 14/C-glucose to individual phospholipids of both hypothalamus and cerebral cortex was further investigated in vitro in order to establish whether the higher rate of carbon flow into hypothalamic phospholipids resulted from enhanced synthesis of a particular phospholipid. In agreement with the results obtained in vivo, the rate of incorporation of /sup 14/C into total phospholipids was 60% higher in hypothalamic tissue. The results indicate that the higher rate of carbon flow into hypothalamic phospholipids might be attributed to enhanced incorporation of glucose carbon to phosphatidyl-choline and phosphatidyl-ethanolamine following a faster conversion of glucose to glycerol in this brain region.

  7. Phospholipid and Hydrocarbon Interactions with a Charged Electrode Interface.

    PubMed

    Levine, Zachary A; DeNardis, Nadica Ivošević; Vernier, P Thomas

    2016-03-22

    Using a combination of molecular dynamics simulations and experiments we examined the interactions of alkanes and phospholipids at charged interfaces in order to understand how interfacial charge densities affect the association of these two representative molecules with electrodes. Consistent with theory and experiment, these model systems reveal interfacial associations mediated through a combination of Coulombic and van der Waals forces. van der Waals forces, in particular, mediate rapid binding of decane to neutral electrodes. No decane binding was observed at high surface charge densities because of interfacial water polarization, which screens hydrophobic attractions. The positively charged choline moiety of the phospholipid palmitoyloleoylphosphatidylcholine (POPC) is primarily responsible for POPC attraction by a moderately negatively charged electrode. The hydrocarbon tails of POPC interact with the hydrophobic electrode interface similarly to decane. Previously reported electrochemical results confirm these findings by demonstrating bipolar displacement currents from PC vesicles adhering to moderately negatively charged interfaces, originating from the choline interactions observed in simulations. At more negatively charged interfaces, choline-to-surface binding was stronger. In both simulations and experiments the maximal interaction of anionic PS occurs with a positively charged interface, provided that the electrostatic forces outweigh local Lennard-Jones interactions. Direct comparisons between the binding affinities measured in experiments and those obtained in simulations reveal previously unobserved atomic interactions that facilitate lipid vesicle adhesion to charged interfaces. Moreover, the implementation of a charged interface in molecular dynamics simulations provides an alternative method for the generation of large electric fields across phospholipid bilayers, especially for systems with periodic boundary conditions, and may be useful for

  8. Sphingophosphonolipids, phospholipids, and fatty acids from Aegean jellyfish Aurelia aurita.

    PubMed

    Kariotoglou, D M; Mastronicolis, S K

    2001-11-01

    The goal of this study is to elucidate and identify several sphingophosphonolipids from Aurelia aurita, an abundant but harmless Aegean jellyfish, in which they have not previously been described. Total lipids of A. aurita were 0.031-0.036% of fresh tissue, and the lipid phosphorus content was 1.3-1.7% of total lipids. Phosphonolipids were 21.7% of phospholipids and consisted of a major ceramide aminoethylphosphonate (CAEP-I; 18.3%), as well as three minor CAEP (II, III, IV) methyl analogs at 1.3, 1.1, and 1.0%, respectively. The remaining phospholipid composition was: phosphatidylcholine, 44.5%, including 36.2% glycerylethers; phosphatidylethanolamine, 18.6%, including 4.5% glycerylethers; cardiolipin, 5.6%; phosphatidylinositol, 2.6%; and lysophosphatidylcholine, 5.0%. In CAEP-I, saturated fatty acids of 14-18 carbon chain length were 70.8% and were combined with 57.3% dihydroxy bases and 23.4% trihydroxy bases. The suite of the three minor CAEP methyl analogs were of the same lipid class based on the head group, but they separated into three different components because of their polarity as follows: CAEP-II and CAEP-III differentiation from the major CAEP-I was mainly due to the increased fatty acid unsaturation and not to a different long-chain base, but the CAEP-IV differentiation from CAEP-I, apart from fatty acid unsaturation, was due to the increased content of hydroxyl groups originated from both hydroxy fatty acids and trihydroxy long-chain bases. Saturated fatty acids were predominant in total (76.7%), polar (83.0%), and neutral lipids (67.6%) of A. aurita. The major phospholipid components of A. aurita were comparable to those previously found in a related organism (Pelagia noctiluca), which can injure humans. PMID:11795859

  9. Phospholipid Signaling Responses in Salt-Stressed Rice Leaves

    PubMed Central

    Darwish, Essam; Testerink, Christa; Khalil, Mohamed; El-Shihy, Osama; Munnik, Teun

    2009-01-01

    Salinity is one of the major environmental factors limiting growth and productivity of rice plants. In this study, the effect of salt stress on phospholipid signaling responses in rice leaves was investigated. Leaf cuts were radiolabeled with 32P-orthophosphate and the lipids extracted and analyzed by thin-layer chromatography, autoradiography and phosphoimaging. Phospholipids were identified by co-migration of known standards. Results showed that 32Pi was rapidly incorporated into the minor lipids, phos-phatidylinositol bisphosphate (PIP2) and phosphatidic acid (PA) and, interestingly, also into the structural lipids phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), which normally label relatively slowly, like phosphatidylcholine (PC) and phosphatidylinositol (PI). Only very small amounts of PIP2 were found. However, in response to salt stress (NaCl), PIP2 levels rapidly (<30 min) increased up to 4-fold, in a time- and dose-dependent manner. PA and its phosphorylated product, diacylglyc-erolpyrophosphate (DGPP), also increased upon NaCl stress, while cardiolipin (CL) levels decreased. All other phospholipid levels remained unchanged. PA signaling can be generated via the combined action of phospholipase C (PLC) and diacylglycerol kinase (DGK) or directly via phospholipase D (PLD). The latter can be measured in vivo, using a transphosphatidylation assay. Interestingly, these measurements revealed that salt stress inhibited PLD activity, indicating that the salt stress-induced PA response was not due to PLD activity. Comparison of the 32P-lipid responses in salt-tolerant and salt-sensitive cultivars revealed no significant differences. Together these results show that salt stress rapidly activates several lipid responses in rice leaves but that these responses do not explain the difference in salt tolerance between sensitive and tolerant cultivars. PMID:19369274

  10. Islet amyloid polypeptide inserts into phospholipid monolayers as monomer.

    PubMed

    Engel, Maarten F M; Yigittop, HaciAli; Elgersma, Ronald C; Rijkers, Dirk T S; Liskamp, Rob M J; de Kruijff, Ben; Höppener, Jo W M; Antoinette Killian, J

    2006-02-24

    Amyloid deposits in the pancreatic islets of Langerhans are thought to be a main factor responsible for death of the insulin-producing islet beta-cells in type 2 diabetes. It is hypothesized that beta-cell death is related to interaction of the 37 amino acid residue human islet amyloid polypeptide (hIAPP), the major constituent of islet amyloid, with cellular membranes. However, the mechanism of hIAPP-membrane interactions is largely unknown. Here, we study the nature and the molecular details of the initial step of hIAPP-membrane interactions by using the monolayer technique. It is shown that both freshly dissolved hIAPP and the non-amyloidogenic mouse IAPP (mIAPP) have a pronounced ability to insert into phospholipid monolayers, even at lipid packing conditions that exceed the conditions that occur in biological membranes. In contrast, the fibrillar form of hIAPP has lost the ability to insert. These results, combined with the observations that both the insertion kinetics and the dependence of insertion on the initial surface pressure are similar for freshly dissolved hIAPP and mIAPP, indicate that hIAPP inserts into phospholipid monolayers most likely as a monomer. In addition, our results suggest that the N-terminal part of hIAPP, which is nearly identical with that of mIAPP, is largely responsible for insertion. This is supported by experiments with hIAPP fragments, which show that a peptide consisting of the 19 N-terminal residues of hIAPP efficiently inserts into phospholipid monolayers, whereas an amyloidogenic decapeptide, consisting of residues 20-29 of hIAPP, inserts much less efficiently. The results obtained here suggest that hIAPP monomers might insert with high efficiency in biological membranes in vivo. This process could play an important role as a first step in hIAPP-induced membrane damage in type 2 diabetes. PMID:16403520

  11. Transfer of oleic acid between albumin and phospholipid vesicles

    SciTech Connect

    Hamilton, J.A.; Cistola, D.P.

    1986-01-01

    The net transfer of oleic acid between egg phosphatidylcholine unilamellar vesicles and bovine serum albumin has been monitored by TC NMR spectroscopy and 90% isotopically substituted (1- TC)oleic acid. The carboxyl chemical shifts of oleic acid bound to albumin were different from those for oleic acid in phospholipid vesicles. Therefore, in mixtures of donor particles, the equilibrium distribution of oleic acid was determined from chemical shift and peak intensity data without separation of donor and acceptor particles. In a system containing equal masses of albumin and phospholipid and a stoichiometry of 4-5 mol of oleic acid per mol of albumin, the oleic acid distribution was pH dependent, with greater than or equal to80% of the oleic acid associated with albumin at pH 7.4; association was greater than or equal to90% at pH 8.0. Decreasing the pH below 7.4 markedly decreased the proportion of fatty acid bound to albumin. The distribution was reversible with pH and was independent of whether vesicles or albumin acted as a donor. These data suggest that pH may strongly influence the partitioning of fatty acid between cellular membranes and albumin. The TC NMR method is also advantageous because it provides information about the structural environments of oleic acid bound to albumin or phospholipid, the ionization state of oleic acid in each environment, and the structural integrity of the vesicles. In addition, minimum and maximum limits for the exchange rates of oleic acid among different environments were obtained from the NMR data.

  12. Warming Effects Enzyme Turnover During Decomposition of Subtropical Peat

    NASA Astrophysics Data System (ADS)

    Sihi, D.; Inglett, P.; Inglett, K. S.

    2015-12-01

    Extracellular enzymes are the proximate agents for organic matter degradation, but the turnover rate of enzymes is often assumed in most decomposition models without direct observations. Here, we assess turnover rates of C (ß-D-glucosidase), N (Leucine aminopeptidase), and P (Phosphomonoesterase) degrading enzymes by spiking commercially available enzymes to the dissolved organic matter of two subtropical peats incubated at 15°C and 25°C and monitoring of net activity of spiked enzymes (i.e. the difference between the spiked and the non-spiked samples) over time. Turnover rates of all three enzymes were greater in the samples incubated at 25°C (ranged between 0.006 hr-1 to 0.014 hr-1) as compared to those incubated at 15°C (ranged between 0.002 hr-1 to 0.009 hr-1). Concentrations of dissolved organic matter were positively correlated with the turnover rates (R2 ranged between 0.71-0.77) of all enzyme groups. To our knowledge, this is the first attempt to evaluate the turnover rates of enzymes in wetland soils as a function of warming and dissolved organic matter concentration. The findings suggest that warming-induced changes in the size of soil enzyme pool due to direct (by increasing protease activity) and indirect (by increasing concentrations of dissolved organic matter) effects on their turnover rates has potential to alter soil C stocks in a warmer world.

  13. CERAMIDE SYNTHASE 1 IS REGULATED BY PROTEASOMAL MEDIATED TURNOVER

    PubMed Central

    Sridevi, Priya; Alexander, Hannah; Laviad, Elad L.; Pewzner-Jung, Yael; Hannink, Mark; Futerman, Anthony H.; Alexander, Stephen

    2009-01-01

    Ceramide is an important bioactive lipid, intimately involved in many cellular functions, including the regulation of cell death, and in cancer and chemotherapy. Ceramide is synthesized de novo from sphinganine and acyl CoA via a family of 6 ceramide synthase enzymes, each having a unique preference for different fatty acyl CoA substrates and a unique tissue distribution. However, little is known regarding the regulation of these important enzymes. In this study we focus on ceramide synthase 1 (CerS1) which is the most structurally and functionally distinct of the enzymes, and describe a regulatory mechanism that specifically controls the level of CerS1 via ubiquitination and proteasome dependent protein turnover. We show that both endogenous and ectopically expressed CerS1 have rapid basal turnover and that diverse stresses including chemotherapeutic drugs, UV light and DTT can induce CerS1 turnover. The turnover requires CerS1 activity and is regulated by the opposing actions of p38 MAP kinase and protein kinase C (PKC). p38 MAP kinase is a positive regulator of turnover, while PKC is a negative regulator of turnover. CerS1 is phosphorylated in vivo and activation of PKC increases the phosphorylation of the protein. This study reveals a novel and highly specific mechanism by which CerS1 protein levels are regulated and which directly impacts ceramide homeostasis. PMID:19393694

  14. Phospholipids do not have lipolytic activity. A critical review.

    PubMed

    Motolese, Pasquale

    2008-06-01

    This article re-examines and refutes the theories of intra-adipocyte lipolysis activated by phosphatidylcholine and by phospholipids in general, when injected into adipose tissue to reduce localized adiposity. These theories have not been confirmed and at times they conflict with current, although incomplete, knowledge relative to adipocyte metabolism. In particular, those regarding adipose tissues with little-known biochemical characteristics such as the primary localized adiposities. The use of the term 'lipolysis' is considered inappropriate; instead, these types of treatments should be indicated by the term 'adipocytolysis', given the demonstrated lytic activity of sodium deoxycholate on cell membranes, whose action, if not unique, is certainly prominent. PMID:18569265

  15. Predicted Relative Metabolomic Turnover (PRMT): determining metabolic turnover from a coastal marine metagenomic dataset

    PubMed Central

    2011-01-01

    Background The world's oceans are home to a diverse array of microbial life whose metabolic activity helps to drive the earth's biogeochemical cycles. Metagenomic analysis has revolutionized our access to these communities, providing a system-scale perspective of microbial community interactions. However, while metagenome sequencing can provide useful estimates of the relative change in abundance of specific genes and taxa between environments or over time, this does not investigate the relative changes in the production or consumption of different metabolites. Results We propose a methodology, Predicted Relative Metabolic Turnover (PRMT) that defines and enables exploration of metabolite-space inferred from the metagenome. Our analysis of metagenomic data from a time-series study in the Western English Channel demonstrated considerable correlations between predicted relative metabolic turnover and seasonal changes in abundance of measured environmental parameters as well as with observed seasonal changes in bacterial population structure. Conclusions The PRMT method was successfully applied to metagenomic data to explore the Western English Channel microbial metabalome to generate specific, biologically testable hypotheses. Generated hypotheses linked organic phosphate utilization to Gammaproteobactaria, Plantcomycetes, and Betaproteobacteria, chitin degradation to Actinomycetes, and potential small molecule biosynthesis pathways for Lentisphaerae, Chlamydiae, and Crenarchaeota. The PRMT method can be applied as a general tool for the analysis of additional metagenomic or transcriptomic datasets. PMID:22587810

  16. Uncoupling of bone turnover following hip replacement.

    PubMed

    Whitson, H; DeMarco, D; Reilly, D; Murphy, S; Yett, H S; Mattingly, D; Greenspan, S L

    2002-07-01

    Studies using total hip replacement surgery as a model for acute hip injury have shown that bone mineral density of the proximal femur decreases 6-18% in the 6 months following surgery. To examine the acute biochemical mechanism associated with bone loss, we measured two indicators of bone formation [serum osteocalcin (OC), serum bone-specific alkaline phosphatase (BSAP)], as well as two markers for bone resorption [urine and serum N-telopeptide cross-linked collagen type 1 (NTx)], in 20 patients (10 men, 10 women, mean age 59.4 years) prior to hip replacement and 1-2 days postsurgery. The average OC value (ng/ml) decreased by 57.3% following surgery (7.5 +/- 4.3 to 3.2 +/- 1.1, P <0.001), and the average BSAP level (U/L) decreased by 27.6% (19.9 +/- 5.6 to 14.4 +/- 3.7, P <0.001). In contrast, levels of urine NTx (nmol BCE/mmol Cr) did not change significantly after the surgery (73.9 +/- 47.2 to 70.1 +/- 29.7). In addition, there was no change in serum NTx (nmol BCE) after surgery (11.8 +/- 2.3 to 11.8 +/- 3.0). Six months after surgery, bone mass had not changed significantly from baseline. These findings suggest that there is an uncoupling of bone turnover following hip replacement surgery which is characterized by significant reductions in bone formation without compensatory decreases in bone resorption, potentially leading to bone loss. Longer periods of follow-up are needed to assess long-term bone mass changes. PMID:12200656

  17. The phospholipid code: a key component of dying cell recognition, tumor progression and host-microbe interactions.

    PubMed

    Baxter, A A; Hulett, M D; Poon, I K H

    2015-12-01

    A significant effort is made by the cell to maintain certain phospholipids at specific sites. It is well described that proteins involved in intracellular signaling can be targeted to the plasma membrane and organelles through phospholipid-binding domains. Thus, the accumulation of a specific combination of phospholipids, denoted here as the 'phospholipid code', is key in initiating cellular processes. Interestingly, a variety of extracellular proteins and pathogen-derived proteins can also recognize or modify phospholipids to facilitate the recognition of dying cells, tumorigenesis and host-microbe interactions. In this article, we discuss the importance of the phospholipid code in a range of physiological and pathological processes. PMID:26450453

  18. Explaining the Gap in Charter and Traditional Public School Teacher Turnover Rates

    ERIC Educational Resources Information Center

    Stuit, David A.; Smith, Thomas M.

    2012-01-01

    This study uses national survey data to examine why charter school teachers are more likely to turnover than their traditional public school counterparts. We test whether the turnover gap is explained by different distributions of factors that are empirically and theoretically linked to turnover risk. We find that the turnover rate of charter…

  19. The Cost of Teacher Turnover in Five School Districts: A Pilot Study

    ERIC Educational Resources Information Center

    Barnes, Gary; Crowe, Edward: Schaefer, Benjamin

    2007-01-01

    In this paper, we report the results of a pilot study of the cost of teacher turnover in five school districts. We examine the rate of turnover, the relationship between turnover and teacher and school characteristics, and the costs associated with recruiting, hiring, and training replacement teachers. We find evidence that turnover costs,…

  20. Reviewing Employee Turnover: Focusing on Proximal Withdrawal States and an Expanded Criterion

    ERIC Educational Resources Information Center

    Hom, Peter W.; Mitchell, Terence R.; Lee, Thomas W.; Griffeth, Rodger W.

    2012-01-01

    We reconceptualize employee turnover to promote researchers' understanding and prediction of why employees quit or stay in employing institutions. A literature review identifies shortcomings with prevailing turnover dimensions. In response, we expand the conceptual domain of the turnover criterion to include multiple types of turnover (notably,…

  1. Perceptions of document relevance

    PubMed Central

    Bruza, Peter; Chang, Vivien

    2014-01-01

    This article presents a study of how humans perceive and judge the relevance of documents. Humans are adept at making reasonably robust and quick decisions about what information is relevant to them, despite the ever increasing complexity and volume of their surrounding information environment. The literature on document relevance has identified various dimensions of relevance (e.g., topicality, novelty, etc.), however little is understood about how these dimensions may interact. We performed a crowdsourced study of how human subjects judge two relevance dimensions in relation to document snippets retrieved from an internet search engine. The order of the judgment was controlled. For those judgments exhibiting an order effect, a q–test was performed to determine whether the order effects can be explained by a quantum decision model based on incompatible decision perspectives. Some evidence of incompatibility was found which suggests incompatible decision perspectives is appropriate for explaining interacting dimensions of relevance in such instances. PMID:25071622

  2. Warming Alters the Routing of Labile and Slower-Turnover Carbon Through Distinct Microbial Groups in Boreal Forest Organic Soils

    NASA Astrophysics Data System (ADS)

    Ziegler, S. E.; Billings, S. A.; Lane, C. S.; Li, J.; Fogel, M. L.

    2012-12-01

    Increased temperature has been linked to greater losses of soil organic carbon (SOC) via microbial respiration and potentially greater relative increases in mineralization of more complex, slow-turnover SOC pools. Though critical for predicting climate feedbacks, our mechanistic understanding of these temperature responses remains limited. Here we report results from a warming experiment using organic horizon soils from two mesic, boreal forest sites with contrasting climate regimes. We replaced extant Oi soil sub-horizons with another coniferous Oi possessing a distinct δ13C signature, and tracked incorporation of the replaced Oi-C and, by difference, the more humified Oea sub-horizon C into microbial phospholipid fatty acids (PLFA) following 120 day incubations at 15C and 20C. We demonstrate how regional climate (site effects) and experimental warming (temperature effects) influence microbial incorporation of Oi versus slower-turnover Oea SOC pools. Congruent with increased mineralization in these soils, the quantity of total PLFA, a proxy for microbial biomass, increased by 32-60% with experimental warming and was 20-42% higher within soils from the warmer versus cooler site. The proportion of Gram-positive bacterial PLFA-C derived from Oi-C more than doubled and coincided with a reduction in the incorporation of Oi-C into fungal relative to bacterial PLFA with laboratory warming and in soils from the warmer site. In conjunction with the relative decrease in fungal incorporation of Oi-C, warming led to an increase of 22-31% in the proportion of fungal PLFA-C derived from the Oea-C. This is consistent with site effects and an increased incorporation of this slower-turnover SOC pool in soils from the warmer site. The increase in microbial biomass and shift in routing of Oi and Oea pools through PLFA indicate that warming increases fungal mineralization of more slow-turnover C pools in these boreal organic soils. This increased exploitation of low C:N Oea by fungi

  3. Identification of Two Legionella pneumophila Effectors that Manipulate Host Phospholipids Biosynthesis

    PubMed Central

    Viner, Ram; Chetrit, David; Ehrlich, Marcelo; Segal, Gil

    2012-01-01

    The intracellular pathogen Legionella pneumophila translocates a large number of effector proteins into host cells via the Icm/Dot type-IVB secretion system. Some of these effectors were shown to cause lethal effect on yeast growth. Here we characterized one such effector (LecE) and identified yeast suppressors that reduced its lethal effect. The LecE lethal effect was found to be suppressed by the over expression of the yeast protein Dgk1 a diacylglycerol (DAG) kinase enzyme and by a deletion of the gene encoding for Pah1 a phosphatidic acid (PA) phosphatase that counteracts the activity of Dgk1. Genetic analysis using yeast deletion mutants, strains expressing relevant yeast genes and point mutations constructed in the Dgk1 and Pah1 conserved domains indicated that LecE functions similarly to the Nem1-Spo7 phosphatase complex that activates Pah1 in yeast. In addition, by using relevant yeast genetic backgrounds we examined several L. pneumophila effectors expected to be involved in phospholipids biosynthesis and identified an effector (LpdA) that contains a phospholipase-D (PLD) domain which caused lethal effect only in a dgk1 deletion mutant of yeast. Additionally, LpdA was found to enhance the lethal effect of LecE in yeast cells, a phenomenon which was found to be dependent on its PLD activity. Furthermore, to determine whether LecE and LpdA affect the levels or distribution of DAG and PA in-vivo in mammalian cells, we utilized fluorescent DAG and PA biosensors and validated the notion that LecE and LpdA affect the in-vivo levels and distribution of DAG and PA, respectively. Finally, we examined the intracellular localization of both LecE and LpdA in human macrophages during L. pneumophila infection and found that both effectors are localized to the bacterial phagosome. Our results suggest that L. pneumophila utilize at least two effectors to manipulate important steps in phospholipids biosynthesis. PMID:23133385

  4. Phospholipid and glycolipid composition of acidocalcisomes of Trypanosoma cruzi

    PubMed Central

    Salto, María Laura; Kuhlenschmidt, Theresa; Kuhlenschmidt, Mark; de Lederkremer, Rosa M.; Docampo, Roberto

    2008-01-01

    Highly purified acidocalcisomes from Trypanosoma cruzi epimastigotes were obtained by differential centrifugation and iodixanol gradient ultracentrifugation. Lipid analysis of acidocalcisomes revealed the presence of low amounts of 3β-hydroxysterols and predominance of phospholipids. Alkylacyl phosphatidylinositol (16:0/18:2), diacyl phosphatidylinositol (18:0/18:2), diacyl phosphatidylcholine (16:0/18:2; 16:1/18:2; 16:2/18:2, 18:1/18:2, and 18:2/18:2), and diacyl phosphatidylethanolamine (16:0/18:2 and 16:1/18:2) were the only phospholipids characterized by electrospray ionization-mass spectrometry (ESI-MS). Incubation of epimastigotes with [3H]-mannose and isolation of acidocalcisomes allowed the detection of a glycoinositolphospholipid (GIPL) in these organelles. The sugar content of the acidocalcisomal GIPL was similar to that of the GIPL present in a microsomal fraction but the amount of galactofuranose and inositol with respect to the other monosaccharides was lower, suggesting a different chemical structure. Taken together, these results indicate that acidocalcisomes of T. cruzi have a distinct lipid and carbohydrate composition. PMID:18207579

  5. Interleaflet mixing and coupling in liquid-disordered phospholipid bilayers.

    PubMed

    Capponi, Sara; Freites, J Alfredo; Tobias, Douglas J; White, Stephen H

    2016-02-01

    Organized as bilayers, phospholipids are the fundamental building blocks of cellular membranes and determine many of their biological functions. Interactions between the two leaflets of the bilayer (interleaflet coupling) have been implicated in the passage of information through membranes. However, physically, the meaning of interleaflet coupling is ill defined and lacks a structural basis. Using all-atom molecular dynamics simulations of fluid phospholipid bilayers of five different lipids with differing degrees of acyl-chain asymmetry, we have examined interleaflet mixing to gain insights into coupling. Reasoning that the transbilayer distribution of terminal methyl groups is an appropriate measure of interleaflet mixing, we calculated the transbilayer distributions of the acyl chain terminal methyl groups for five lipids: dioleoylphosphatidylcholine (DOPC), palmitoyloleoylphosphatidylcholine (POPC), stearoyloleoylphosphatidylcholine (SOPC), oleoylmyristoylphosphatidylcholine (OMPC), and dimyristoylphosphatidylcholine (DMPC). We observed in all cases very strong mixing across the bilayer midplane that diminished somewhat with increasing acyl-chain ordering defined by methylene order parameters. A hallmark of the interleaflet coupling idea is complementarity, which postulates that lipids with short alkyl chains in one leaflet will preferentially associate with lipids with long alkyl chains in the other leaflet. Our results suggest a much more complicated picture for thermally disordered bilayers that we call distributed complementarity, as measured by the difference in the peak positions of the sn-1 and sn-2 methyl distributions in the same leaflet. PMID:26657692

  6. Metformin Decouples Phospholipid Metabolism in Breast Cancer Cells

    PubMed Central

    Smith, Tim A. D.; Phyu, Su M.

    2016-01-01

    Introduction The antidiabetic drug metformin, currently undergoing trials for cancer treatment, modulates lipid and glucose metabolism both crucial in phospholipid synthesis. Here the effect of treatment of breast tumour cells with metformin on phosphatidylcholine (PtdCho) metabolism which plays a key role in membrane synthesis and intracellular signalling has been examined. Methods MDA-MB-468, BT474 and SKBr3 breast cancer cell lines were treated with metformin and [3H-methyl]choline and [14C(U)]glucose incorporation and lipid accumulation determined in the presence and absence of lipase inhibitors. Activities of choline kinase (CK), CTP:phosphocholine cytidylyl transferase (CCT) and PtdCho-phospholipase C (PLC) were also measured. [3H] Radiolabelled metabolites were determined using thin layer chromatography. Results Metformin-treated cells exhibited decreased formation of [3H]phosphocholine but increased accumulation of [3H]choline by PtdCho. CK and PLC activities were decreased and CCT activity increased by metformin-treatment. [14C] incorporation into fatty acids was decreased and into glycerol was increased in breast cancer cells treated with metformin incubated with [14C(U)]glucose. Conclusion This is the first study to show that treatment of breast cancer cells with metformin induces profound changes in phospholipid metabolism. PMID:26959405

  7. Spontaneous structural transition in phospholipid-inspired aromatic phosphopeptide nanostructures.

    PubMed

    Pellach, Michal; Atsmon-Raz, Yoav; Simonovsky, Eyal; Gottlieb, Hugo; Jacoby, Guy; Beck, Roy; Adler-Abramovich, Lihi; Miller, Yifat; Gazit, Ehud

    2015-01-01

    Phospholipid membranes could be considered a prime example of the ability of nature to produce complex yet ordered structures, by spontaneous and efficient self-assembly. Inspired by the unique properties and architecture of phospholipids, we designed simple amphiphilic decapeptides, intended to fold in the center of the peptide sequence, with a phosphorylated serine "head" located within a central turn segment, and two hydrophobic "tails". The molecular design also included the integration of the diphenylalanine motif, previously shown to facilitate self-assembly and increase nanostructure stability. Secondary structure analysis of the peptides indeed indicated the presence of stabilized conformations in solution, with a central turn connecting two hydrophobic "tails", and interactions between the hydrophobic strands. The mechanisms of assembly into supramolecular structures involved structural transitions between different morphologies, which occurred over several hours, leading to the formation of distinctive nanostructures, including half-elliptical nanosheets and curved tapes. The phosphopeptide building blocks appear to self-assemble via a particular combination of aromatic, hydrophobic and ionic interactions, as well as hydrogen bonding, as demonstrated by proposed constructed simulated models of the peptides and self-assembled nanostructures. Molecular dynamics simulations also gave insight into mechanisms of structural transitions of the nanostructures at a molecular level. Because of the biocompatibility of peptides, the phosphopeptide assemblies allow for expansion of the library of biomolecular nanostructures available for future design and application of biomedical devices. PMID:25802000

  8. Microarrays of phospholipid bilayers generated by inkjet printing.

    PubMed

    Yamada, Misato; Imaishi, Hiromasa; Morigaki, Kenichi

    2013-05-28

    We report an efficient and reproducible method to generate a microarray of model biological membranes on a solid substrate by applying the inkjet printing technology. Although inkjet printing is currently widely used for industrial fabrication processes, including biological materials, printing lipid membranes remains technically challenging due to the hydrophobic nature of droplets and instability of the lipid bilayer structure against dehydration. In the present study, we printed lipids onto a glass substrate covered with a micropatterned membrane of a polymeric phospholipid bilayer. Polymeric bilayers were formed by the lithographic photopolymerization of a diacetylene-containing phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC). After removal of nonpolymerized DiynePC with a detergent solution, natural lipid membranes were incorporated into the polymer-free regions (corrals) by using an electric-field-based inkjet printing device that can eject subfemtoliter volume droplets. To avoid rapid dehydration and destabilization, we preprinted an aqueous solution containing agarose and trehalose onto the corrals and subsequently printed lipid suspensions ("two-step-printing method"). After rinsing, stable lipid bilayer membranes were formed in the corrals. The bilayers were continuous and fluid as confirmed by fluorescence recovery after photobleaching. We could introduce multiple bilayer patches having different lipid compositions into the neighboring corrals. The present results demonstrate that the combination of a patterned polymeric bilayer and inkjet printing technology enables efficient, reliable, and scalable generation of the model membrane microarrays having varied compositions. PMID:23627772

  9. Phospholipid vesicle fusion on micropatterned polymeric bilayer substrates.

    PubMed

    Okazaki, Takashi; Morigaki, Kenichi; Taguchi, Takahisa

    2006-09-01

    As an approach to create versatile model systems of the biological membrane we have recently developed a novel micropatterning strategy of substrate-supported planar lipid bilayers (SPBs) based on photolithographic polymerization of a diacetylene phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine. The micropatterned SPBs are composed of a polymeric bilayer matrix and embedded fluid lipid bilayers. In this study, we investigated the incorporation of fluid bilayers into micropatterned polymeric bilayer matrices through the adsorption and reorganization of phospholipid vesicles (vesicle fusion). Total internal reflection fluorescence microscopy observation showed that vesicle fusion started at the boundary of polymeric bilayers and propagated into the central part of lipid-free regions. On the other hand, quartz crystal microbalance with dissipation monitoring revealed that the transformation from adsorbed vesicles into SPBs was significantly accelerated for substrates with micropatterned polymeric bilayers. These results indicate that the edges of polymeric bilayers catalyze the formation of SPBs by destabilizing adsorbed vesicles and also support the premise that polymeric bilayers and embedded fluid bilayers are forming a continuous hybrid bilayer membrane, sealing energetically unfavorable bilayer edges. PMID:16766614

  10. Cationic Polyene Phospholipids as DNA Carriers for Ocular Gene Therapy

    PubMed Central

    Machado, Susana; Calado, Sofia; Bitoque, Diogo; Oliveira, Ana Vanessa; Øpstad, Christer L.; Zeeshan, Muhammad; Sliwka, Hans-Richard; Partali, Vassilia; Pungente, Michael D.; Silva, Gabriela A.

    2014-01-01

    Recent success in the treatment of congenital blindness demonstrates the potential of ocular gene therapy as a therapeutic approach. The eye is a good target due to its small size, minimal diffusion of therapeutic agent to the systemic circulation, and low immune and inflammatory responses. Currently, most approaches are based on viral vectors, but efforts continue towards the synthesis and evaluation of new nonviral carriers to improve nucleic acid delivery. Our objective is to evaluate the efficiency of novel cationic retinoic and carotenoic glycol phospholipids, designated C20-18, C20-20, and C30-20, to deliver DNA to human retinal pigmented epithelium (RPE) cells. Liposomes were produced by solvent evaporation of ethanolic mixtures of the polyene compounds and coformulated with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) or cholesterol (Chol). Addition of DNA to the liposomes formed lipoplexes, which were characterized for binding, size, biocompatibility, and transgene efficiency. Lipoplex formulations of suitable size and biocompatibility were assayed for DNA delivery, both qualitatively and quantitatively, using RPE cells and a GFP-encoding plasmid. The retinoic lipoplex formulation with DOPE revealed a transfection efficiency comparable to the known lipid references 3β-[N-(N′,N′-dimethylaminoethane)-carbamoyl]-cholesterol (DC-Chol) and 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EPC) and GeneJuice. The results demonstrate that cationic polyene phospholipids have potential as DNA carriers for ocular gene therapy. PMID:25147812

  11. The innate immune response to products of phospholipid peroxidation☆

    PubMed Central

    Weismann, David; Binder, Christoph J.

    2012-01-01

    Lipid peroxidation occurs in the context of many physiological processes but is greatly increased in various pathological situations. A consequence of phospholipid peroxidation is the generation of oxidation-specific epitopes, such as phosphocholine of oxidized phospholipids and malondialdehyde, which form neo-self determinants on dying cells and oxidized low-density lipoproteins. In this review we discuss evidence demonstrating that pattern recognition receptors of the innate immune system recognize oxidation-specific epitopes as endogenous damage-associated molecular patterns, allowing the host to identify dangerous biological waste. Oxidation-specific epitopes are important targets of both cellular and soluble pattern recognition receptors, including toll-like and scavenger receptors, C-reactive protein, complement factor H, and innate natural IgM antibodies. This recognition allows the innate immune system to mediate important physiological house keeping functions, for example by promoting the removal of dying cells and oxidized molecules. Once this system is malfunctional or overwhelmed the development of diseases, such as atherosclerosis and age-related macular degeneration is favored. Understanding the molecular components and mechanisms involved in this process, will help the identification of individuals with increased risk of developing chronic inflammation, and indicate novel points for therapeutic intervention. This article is part of a Special Issue entitled: Oxidized phospholipids—their properties and interactions with proteins. PMID:22305963

  12. Mutagenicity of diesel exhaust soot dispersed in phospholipid surfactants

    SciTech Connect

    Wallace, W.; Keane, M.; Xing, S.; Harrison, J.; Gautam, M.; Ong, T.

    1994-06-01

    Organics extractable from respirable diesel exhaust soot particles by organic solvents have been known for some time to be direct acting frameshift mutagens in the Ames Salmonella typhimurium histidine reversion assay. Upon deposition in a pulmonary alveolus or respiratory bronchiole, respirable diesel soot particles will contact first the hypophase which is coated by and laden with surfactants. To model interactions of soot and pulmonary surfactant, the authors dispersed soots in vitro in the primary phospholipid pulmonary surfactant dipalmitoyl glycerophosphorylcholine (lecithin) (DPL) in physiological saline. They have shown that diesel soots dispersed in lecithin surfactant can express mutagenic activity, in the Ames assay system using S. typhimurium TA98, comparable to that expressed by equal amounts of soot extracted by dichloromethane/dimethylsulfoxide (DCM/DMSO). Here the authors report additional data on the same system using additional exhaust soots and also using two other phospholipids, dipalmitoyl glycerophosphoryl ethanolamine (DPPE), and dipalmitoyl phosphatidic acid (DPPA), with different ionic character hydrophilic moieties. A preliminary study of the surfactant dispersed soot in an eucaryotic cell test system also is reported.

  13. Inositol Depletion Restores Vesicle Transport in Yeast Phospholipid Flippase Mutants

    PubMed Central

    Yamagami, Kanako; Yamamoto, Takaharu; Sakai, Shota; Mioka, Tetsuo; Sano, Takamitsu; Igarashi, Yasuyuki; Tanaka, Kazuma

    2015-01-01

    In eukaryotic cells, type 4 P-type ATPases function as phospholipid flippases, which translocate phospholipids from the exoplasmic leaflet to the cytoplasmic leaflet of the lipid bilayer. Flippases function in the formation of transport vesicles, but the mechanism remains unknown. Here, we isolate an arrestin-related trafficking adaptor, ART5, as a multicopy suppressor of the growth and endocytic recycling defects of flippase mutants in budding yeast. Consistent with a previous report that Art5p downregulates the inositol transporter Itr1p by endocytosis, we found that flippase mutations were also suppressed by the disruption of ITR1, as well as by depletion of inositol from the culture medium. Interestingly, inositol depletion suppressed the defects in all five flippase mutants. Inositol depletion also partially restored the formation of secretory vesicles in a flippase mutant. Inositol depletion caused changes in lipid composition, including a decrease in phosphatidylinositol and an increase in phosphatidylserine. A reduction in phosphatidylinositol levels caused by partially depleting the phosphatidylinositol synthase Pis1p also suppressed a flippase mutation. These results suggest that inositol depletion changes the lipid composition of the endosomal/TGN membranes, which results in vesicle formation from these membranes in the absence of flippases. PMID:25781026

  14. Purification of phospholipid methyltransferase from rat liver microsomal fraction.

    PubMed Central

    Pajares, M A; Villalba, M; Mato, J M

    1986-01-01

    Phospholipid methyltransferase, the enzyme that converts phosphatidylethanolamine into phosphatidylcholine with S-adenosyl-L-methionine as the methyl donor, was purified to apparent homogeneity from rat liver microsomal fraction. When analysed by SDS/polyacrylamide-gel electrophoresis only one protein, with molecular mass about 50 kDa, is detected. This protein could be phosphorylated at a single site by incubation with [alpha-32P]ATP and the catalytic subunit of cyclic AMP-dependent protein kinase. A less-purified preparation of the enzyme is mainly composed of two proteins, with molecular masses about 50 kDa and 25 kDa, the 50 kDa form being phosphorylated at the same site as the homogeneous enzyme. After purification of both proteins by electro-elution, the 25 kDa protein forms a dimer and migrates on SDS/polyacrylamide-gel electrophoresis with molecular mass about 50 kDa. Peptide maps of purified 25 kDa and 50 kDa proteins are identical, indicating that both proteins are formed by the same polypeptide chain(s). It is concluded that rat liver phospholipid methyltransferase can exist in two forms, as a monomer of 25 kDa and as a dimer of 50 kDa. The dimer can be phosphorylated by cyclic AMP-dependent protein kinase. Images Fig. 3. Fig. 4. Fig. 6. PMID:3800912

  15. [Some peculiarities of brain phospholipids in deep sea fishes].

    PubMed

    Pomazanskaia, L F; Pravdina, N I; Chirkovskaia, E V

    1975-01-01

    Total phospholipids (PL) as well as the content of various phospholipid classes and their fatty acid composition have been investigated in the brain of mesopelagic and abyssal marine teleosts. These species were compared to shallow water ones. The brain of deep sea fishes was found to be very poor in PL as compared to the brain of mesopelagic ans surface water species. No differences concerning the brain PL content were revealed between the two last mentioned groups. The relative content of separate PL classes was very similar in all the species studied irrespectively of the depth of their habitat. Peculiarities were found in fatty acid composition of individual PL from deep sea species as compared to surface ones. The deeper the habitat, the lower the content of saturated fatty acids, especially of the stearic acid. The lowest content of saturated fatty acids, maximum level of polyenoic fatty acids as well as some peculiarities in the relative content of particular fatty acids were found in the brain of ultraabyssal (6, 000 m) Leucicorus sp. PMID:1217333

  16. Human autoreactive T cells recognize CD1b and phospholipids

    PubMed Central

    Van Rhijn, Ildiko; van Berlo, Twan; Hilmenyuk, Tamara; Cheng, Tan-Yun; Wolf, Benjamin J.; Tatituri, Raju V. V.; Uldrich, Adam P.; Napolitani, Giorgio; Cerundolo, Vincenzo; Altman, John D.; Willemsen, Peter; Huang, Shouxiong; Rossjohn, Jamie; Besra, Gurdyal S.; Brenner, Michael B.; Godfrey, Dale I.; Moody, D. Branch

    2016-01-01

    In contrast with the common detection of T cells that recognize MHC, CD1a, CD1c, or CD1d proteins, CD1b autoreactive T cells have been difficult to isolate in humans. Here we report the development of polyvalent complexes of CD1b proteins and carbohydrate backbones (dextramers) and their use in identifying CD1b autoreactive T cells from human donors. Activation is mediated by αβ T-cell receptors (TCRs) binding to CD1b-phospholipid complexes, which is sufficient to activate autoreactive responses to CD1b-expressing cells. Using mass spectrometry and T-cell responses to scan through the major classes of phospholipids, we identified phosphatidylglycerol (PG) as the immunodominant lipid antigen. T cells did not discriminate the chemical differences that distinguish mammalian PG from bacterial PG. Whereas most models of T-cell recognition emphasize TCR discrimination of differing self and foreign structures, CD1b autoreactive T cells recognize lipids with dual self and foreign origin. PG is rare in the cellular membranes that carry CD1b proteins. However, bacteria and mitochondria are rich in PG, so these data point to a more general mechanism of immune detection of infection- or stress-associated lipids. PMID:26621732

  17. Structure and organization of phospholipid/polysaccharide nanoparticles

    NASA Astrophysics Data System (ADS)

    Gerelli, Y.; Di Bari, M. T.; Deriu, A.; Cantù, L.; Colombo, P.; Como, C.; Motta, S.; Sonvico, F.; May, R.

    2008-03-01

    In recent years nanoparticles and microparticles composed of polymeric or lipid material have been proposed as drug carriers for improving the efficacy of encapsulated drugs. For the production of these systems different materials have been proposed, among them phospholipids and polysaccharides due to their biocompatibility, biodegradability, low cost and safety. We report here a morphological and structural investigation, performed using cryo-TEM, static light scattering and small angle neutron and x-ray scattering, on phospholipid/saccharide nanoparticles loaded with a lipophilic positively charged drug (tamoxifen citrate) used in breast cancer therapy. The lipid component was soybean lecithin; the saccharide one was chitosan that usually acts as an outer coating increasing vesicle stability. The microscopy and scattering data indicate the presence of two distinct nanoparticle families: uni-lamellar vesicles with average radius 90 Å and multi-lamellar vesicles with average radius 440 Å. In both families the inner core is occupied by the solvent. The presence of tamoxifen gives rise to a multi-lamellar structure of the lipid outer shell. It also induces a positive surface charge into the vesicles, repelling the positively charged chitosan molecules which therefore do not take part in nanoparticle formation.

  18. Chemical modification of proteins during peroxidation of phospholipids.

    PubMed

    Januszewski, Andrzej S; Alderson, Nathan L; Jenkins, Alicia J; Thorpe, Suzanne R; Baynes, John W

    2005-07-01

    Chemical modification of proteins by advanced glycation and lipoxidation end products is implicated in the pathogenesis of macrovascular disease in aging and diabetes. To identify biomarkers of the lipoxidative modification of protein, we studied the oxidation of phospholipids in the presence of the model protein RNase A and compared protein-bound products formed in these reactions with those formed during oxidation of plasma proteins. Metal-catalyzed oxidation of 1-palmitoyl-2-arachidonoyl-phosphatidylcholine or 1-palmitoyl-2-linoleoyl-phosphatidylcholine in the presence of RNase led to the loss of amino groups in RNase and the incorporation of phosphate, hexanoate, pentanedioate, nonanedioate, and palmitate into protein. Protein-bound palmitate and phosphate correlated strongly with one another, and protein-bound pentanedioate and nonanedioate, derived from arachidonate and linoleate, respectively, accounted for approximately 20% of the cross-linking of lipid phosphorus to protein. Similar results were obtained on oxidation of total plasma or isolated LDL. We conclude that alkanedioic acids are quantitatively important linkers of oxidized phospholipids to proteins and that measurement of protein-bound phosphate and long-chain fatty acids may be useful for assessing long-term lipid peroxidative damage to proteins in vivo. Analyses of plasma proteins from control and diabetic patients indicated significant increases in lipoxidative modification of protein in diabetic compared with control subjects. PMID:15805546

  19. Choline phospholipid metabolism: a target in cancer cells?

    PubMed

    Ackerstaff, Ellen; Glunde, Kristine; Bhujwalla, Zaver M

    2003-10-15

    The experience of treating cancer over the past several decades overwhelmingly demonstrates that the disease continues to evade the vast array of drugs and treatment modalities available in the twenty-first century. This is not surprising in view of the complexity of this disease, and the multiplicities of pathways available to the cancer cell to enable its survival. Although the progression of cancer arrives at a common end point of cachexia, organ failure, and death, common pathways are rare in cancer. Identifying and targeting common pathways that would act across these levels of multiplicity is essential for the successful treatment of this disease. Over the past decade, one common characteristic consistently revealed by magnetic resonance spectroscopic studies is the elevation of phosphocholine and total choline-containing compounds in cancer cells and solid tumors. This elevation has been observed in almost every single cancer type studied with NMR spectroscopy and can be used as an endogenous biomarker of cancer. In this article, we have summarized some of the observations on the choline phospholipid metabolism of cancer cells and tumors, and make a case for targeting the aberrant choline phospholipid metabolism of cancer cells. PMID:14523987

  20. Rigor, Relevance and Relationships

    ERIC Educational Resources Information Center

    McNulty, Raymond J.; Quaglia, Russell J.

    2007-01-01

    Rigor, relevance, and relationships are three elements that provide the hallmark for education today. These three elements are integrally connected; if one is missing in a teacher's teaching practices, he or she is not doing his or her best to prepare students for success in school and in life. To ensure the inclusion of both rigor and relevance,…

  1. Making Science Relevant

    ERIC Educational Resources Information Center

    Eick, Charles; Deutsch, Bill; Fuller, Jennifer; Scott, Fletcher

    2008-01-01

    Science teachers are always looking for ways to demonstrate the relevance of science to students. By connecting science learning to important societal issues, teachers can motivate students to both enjoy and engage in relevant science (Bennet, Lubben, and Hogarth 2007). To develop that connection, teachers can help students take an active role in…

  2. Culturally Relevant Pedagogy

    ERIC Educational Resources Information Center

    Irvine, Jacqueline Jordan

    2010-01-01

    Many teachers have only a cursory understanding of culturally relevant pedagogy, and their efforts to bridge the cultural gap often fall short. Culturally relevant pedagogy is a term that describes effective teaching in culturally diverse classrooms. It can be a daunting idea to understand and implement. Yet people tend to appreciate culturally…

  3. Similar Processes but Different Environmental Filters for Soil Bacterial and Fungal Community Composition Turnover on a Broad Spatial Scale

    PubMed Central

    Chemidlin Prévost-Bouré, Nicolas; Dequiedt, Samuel; Thioulouse, Jean; Lelièvre, Mélanie; Saby, Nicolas P. A.; Jolivet, Claudy; Arrouays, Dominique; Plassart, Pierre; Lemanceau, Philippe; Ranjard, Lionel

    2014-01-01

    Spatial scaling of microorganisms has been demonstrated over the last decade. However, the processes and environmental filters shaping soil microbial community structure on a broad spatial scale still need to be refined and ranked. Here, we compared bacterial and fungal community composition turnovers through a biogeographical approach on the same soil sampling design at a broad spatial scale (area range: 13300 to 31000 km2): i) to examine their spatial structuring; ii) to investigate the relative importance of environmental selection and spatial autocorrelation in determining their community composition turnover; and iii) to identify and rank the relevant environmental filters and scales involved in their spatial variations. Molecular fingerprinting of soil bacterial and fungal communities was performed on 413 soils from four French regions of contrasting environmental heterogeneity (Landesturnovers. The relative importance of processes and filters was assessed by distance-based redundancy analysis. This study demonstrates significant community composition turnover rates for soil bacteria and fungi, which were dependent on the region. Bacterial and fungal community composition turnovers were mainly driven by environmental selection explaining from 10% to 20% of community composition variations, but spatial variables also explained 3% to 9% of total variance. These variables highlighted significant spatial autocorrelation of both communities unexplained by the environmental variables measured and could partly be explained by dispersal limitations. Although the identified filters and their hierarchy were dependent on the region and organism, selection was systematically based on a common group of environmental variables: pH, trophic resources, texture and land use. Spatial autocorrelation was also important at coarse (80 to

  4. Nature of the charged headgroup determines the fusogenic potential and membrane properties of lithocholic acid phospholipids.

    PubMed

    Bhargava, Priyanshu; Singh, Manish; Sreekanth, Vedagopuram; Bajaj, Avinash

    2014-08-01

    Phospholipids play a crucial role in many cellular processes ranging from selective membrane permeability, to membrane fission and fusion, to cellular signaling. Headgroups of phospholipids determine the membrane properties and fusogenicity of these lipids with target cell membranes. We studied the fusogenic and membrane properties of phospholipids possessing unnatural charged headgroups with model membranes using laurdan based membrane hydration studies, DPH based membrane fluidity, and differential scanning calorimetry. We unravel that fusogenicity, membrane hydration, and fluidity of membranes are strongly contingent on the nature of the phospholipid charged headgroup. Our studies unraveled that introduction of bulky headgroups like dimethylamino pyridine induces maximum membrane hydration and perturbations with high fusogenicity as compared to small headgroup based phospholipids. These phospholipids also have the capability of high retention in DPPC membranes. Hydration and fluidity of these phospholipid-doped DPPC membranes are contingent on the nature of the charged headgroup. This study would help in future design of phospholipid based nanomaterials for effective drug delivery. PMID:25029367

  5. Characterization and localization of in vivo phospholipid methylation in the hamster testis

    SciTech Connect

    Schlegel, P.N.; Wright, W.W.; Chang, T.S.

    1989-06-01

    Although previous studies have demonstrated that phospholipid methylation occurs in the testis and may be involved in Leydig cell function, phospholipid methylation in spermatogenic cells has not been characterized. In this study we describe the occurrence, time course, and localization of phospholipid methylation in the hamster testis following intratesticular injection of radioactive methyl precursor. Adult and pubertal (seven day old) hamsters were injected intratesticularly with (/sup 3/H-methyl)-methionine and sacrificed 10 min. to 31 hours thereafter. The testes were then removed and homogenized or dispersed into cell suspensions. Spermatogenic cell and Leydig cell enriched preparations were isolated from the dispersed cell preparations using elutriation and Percoll gradient centrifugation and assayed for methylated phospholipids and proteins. These experiments demonstrated that (1) phospholipid methylation occurs in the hamster testis at a level seven-fold greater than protein methylation, (2) the incorporation of radioactivity associated with phospholipid methylation is progressive over time, and (3) in vivo, spermatogenic cell preparations enriched with pachytene spermatocytes have an almost four-fold higher level of measurable phospholipid methylation when compared to whole testis preparations. Taken together, these results suggest that phospholipid methylation may play an important stage-specific role in spermatogenesis.

  6. 31P magnetic resonance phospholipid profiles of neoplastic human breast tissues.

    PubMed Central

    Merchant, T. E.; Meneses, P.; Gierke, L. W.; Den Otter, W.; Glonek, T.

    1991-01-01

    Phospholipids from malignant, benign and noninvolved human breast tissues were extracted by chloroform-methanol (2:1) and analysed by 31P MR spectroscopy at 202.4 MHz. Thirteen phospholipids were identified as constituents of the profiles obtained among the 55 tissue specimens analysed. Observed patterns in phospholipid tissues profiles were distinct, allowing qualitative characterisation of the three tissue groups. Multivariate analysis of lysophosphatidylcholine (LPC) and an uncharacterised phospholipid were shown to be independently significant in predicting benign tissue histology as either fibrocystic disease or fibroadenoma in 92% of cases. Univariate analysis of relative mole-percentage of phosphorus concentrations of individual phospholipids using the Scheffé comparison procedure revealed that in malignant tissues, phosphatidylethanolamine was significantly elevated compared to benign (+ 32%) and noninvolved tissues (+ 22%). Phosphatidylinositol (+ 33%) and phosphatidylcholine plasmalogen (PC plas) (+ 25%) were increased in malignant compared to benign and LPC was decreased (-44%) in malignant compared to noninvolved. LPC was significantly depressed (-39%) in benign tissue compared to normal. Phospholipid indices computed to further characterise the three tissue groups showed PC plas/PC elevated in malignant tissue compared to benign and PE plas/PE depressed in malignant tissue compared to noninvolved. These findings support previous investigations reporting that the alkyl-phospholipid analogues of phosphatidylcholine are released by malignant tissues and that levels of ethanolamine are elevated in malignant tissues. Indices describing the choline-containing phospholipids showed that these lipids are depressed significantly in malignant tissue relative to healthy tissue. PMID:2039694

  7. Plasma phospholipid pentadecanoic acid, EPA, and DHA, and the frequency of dairy and fish product intake in young children

    PubMed Central

    Lund-Blix, Nicolai A.; Rønningen, Kjersti S.; Bøås, Håkon; Tapia, German; Andersen, Lene F.

    2016-01-01

    Background There is a lack of studies comparing dietary assessment methods with the biomarkers of fatty acids in children. Objective The objective was to evaluate the suitability of a food frequency questionnaire (FFQ) to rank young children according to their intake of dairy and fish products by comparing food frequency estimates to the plasma phospholipid fatty acids pentadecanoic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Design Cross-sectional data for the present study were derived from the prospective cohort ‘Environmental Triggers of Type 1 Diabetes Study’. Infants were recruited from the Norwegian general population during 2001–2007. One hundred and ten (age 3–10 years) children had sufficient volumes of plasma and FFQ filled in within 2 months from blood sampling and were included in this evaluation study. The quantitative determination of plasma phospholipid fatty acids was done by fatty acid methyl ester analysis. The association between the frequency of dairy and fish product intake and the plasma phospholipid fatty acids was assessed by a Spearman correlation analysis and by investigating whether participants were classified into the same quartiles of distribution. Results Significant correlations were found between pentadecanoic acid and the intake frequency of total dairy products (r=0.29), total fat dairy products (r=0.39), and cheese products (r=0.36). EPA and DHA were significantly correlated with the intake frequency of oily fish (r=0.26 and 0.37, respectively) and cod liver/fish oil supplements (r=0.47 for EPA and r=0.50 DHA). To a large extent, the FFQ was able to classify individuals into the same quartile as the relevant fatty acid biomarker. Conclusions The present study suggests that, when using the plasma phospholipid fatty acids pentadecanoic acid, EPA, and DHA as biomarkers, the FFQ used in young children showed a moderate capability to rank the intake frequency of dairy products with a high-fat content

  8. STRUCTURAL DETERMINATION AND QUANTITATIVE ANALYSIS OF BACTERIAL PHOSPHOLIPIDS USING LIQUID CHROMATOGRAPHY/ELECTROSPRAY IONIZATION/MASS SPECTROMETRY

    EPA Science Inventory

    This report presents a comprehensive spectral analysis of common bacterial phospholipids using electrospray/mass spectrometry (ESI/MS) under both negative and positive ionization conditions. Phospholipids under positive ionization yield sodium-adduct molecular ions which are mos...

  9. Effect of long-term aluminum feeding on lipid/phospholipid profiles of rat brain myelin.

    PubMed

    Pandya, Jignesh D; Dave, Kunjan R; Katyare, Surendra S

    2004-06-22

    Effect of long-term (90-100 days) exposure of rats to soluble salt of aluminum (AlCl3) on myelin lipid profile was examined. The long-term exposure to AlCl3 resulted in a 60% decrease in the total phospholipid (TPL) content while the cholesterol (CHL) content increased by 55%. Consequently the TPL/CHL molar ratio decreased significantly by 62%. The phospholipid composition of the myelin membrane changed drastically; the proportion of practically all the phospholipid classes decreased by 32 to 60% except for phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Of the latter two, proportion of PC was unchanged while PE increased in proportion by 47%. Quantitatively, all phospholipid classes decreased by from 42 to 76% with no change in the PE content. However the membrane fluidity was not altered in Al-treated rats. Many of the changes we observe here show striking similarities with the reported phospholipid profiles of Alzheimer brains. PMID:15212698

  10. Phospholipid Membrane Protection by Sugar Molecules during Dehydration-Insights into Molecular Mechanisms Using Scattering Techniques

    SciTech Connect

    Garvey, Christopher J.; Lenné, Thomas; Koster, Karen L.; Kent, Ben; Bryant, Gary

    2014-09-24

    Scattering techniques have played a key role in our understanding of the structure and function of phospholipid membranes. These techniques have been applied widely to study how different molecules (e.g., cholesterol) can affect phospholipid membrane structure. However, there has been much less attention paid to the effects of molecules that remain in the aqueous phase. One important example is the role played by small solutes, particularly sugars, in protecting phospholipid membranes during drying or slow freezing. In this paper, we present new results and a general methodology, which illustrate how contrast variation small angle neutron scattering (SANS) and synchrotron-based X-ray scattering (small angle (SAXS) and wide angle (WAXS)) can be used to quantitatively understand the interactions between solutes and phospholipids. Specifically, we show the assignment of lipid phases with synchrotron SAXS and explain how SANS reveals the exclusion of sugars from the aqueous region in the particular example of hexagonal II phases formed by phospholipids.

  11. Self-reproducing catalyst drives repeated phospholipid synthesis and membrane growth

    PubMed Central

    Hardy, Michael D.; Yang, Jun; Selimkhanov, Jangir; Cole, Christian M.; Tsimring, Lev S.; Devaraj, Neal K.

    2015-01-01

    Cell membranes are dynamic structures found in all living organisms. There have been numerous constructs that model phospholipid membranes. However, unlike natural membranes, these biomimetic systems cannot sustain growth owing to an inability to replenish phospholipid-synthesizing catalysts. Here we report on the design and synthesis of artificial membranes embedded with synthetic, self-reproducing catalysts capable of perpetuating phospholipid bilayer formation. Replacing the complex biochemical pathways used in nature with an autocatalyst that also drives lipid synthesis leads to the continual formation of triazole phospholipids and membrane-bound oligotriazole catalysts from simpler starting materials. In addition to continual phospholipid synthesis and vesicle growth, the synthetic membranes are capable of remodeling their physical composition in response to changes in the environment by preferentially incorporating specific precursors. These results demonstrate that complex membranes capable of indefinite self-synthesis can emerge when supplied with simpler chemical building blocks. PMID:26100914

  12. Effect of Vesicle-to-Micelle Transition on the Interactions of Phospholipid/Sodium Cholate Mixed Systems with Curcumin in Aqueous Solution.

    PubMed

    Zhang, Sha; Wang, Xiaoyong

    2016-08-01

    The role of vesicle-to-micelle transition has been investigated in the interactions of phospholipid vesicles, phospholipid/sodium cholate (NaC) mixed vesicles, and phospholipid/NaC mixed micelles with curcumin in aqueous solution. The addition of NaC causes phospholipid vesicles to transit into phospholipid/NaC mixed vesicles and phospholipid/NaC mixed micelles. Turbidity measurement reveals that the presence of curcumin increases the NaC concentration for the solubilization of phospholipid vesicles, which indicates that the bound curcumin tends to suppress the vesicle-to-micelle transition. The pyrene polarity index and curcumin fluorescence anisotropy measurements suggest that phospholipid/NaC mixed micelles have a more compact structure than that of phospholipid vesicles and phospholipid/NaC mixed vesicles. Curcumin associated with phospholipid vesicles, phospholipid/NaC mixed vesicles, and phospholipid/NaC mixed micelles often results in higher intensities of absorption and fluorescence than those of free curcumin. However, phospholipid/NaC mixed vesicles lead to the highest values of absorption and fluorescence intensities, binding constant, and radical-scavenging capacity with curcumin. The different structures in the phospholipid bilayer of phospholipid/NaC mixed vesicles and the hydrophobic part of phospholipid/NaC mixed micelles where curcumin located are discussed to explain the interaction behaviors of phospholipid/NaC mixed systems with curcumin. PMID:27403579

  13. Enhancing Phospholipid Fatty Acid Profiling of Soil Bacterial Communities via Substrate- Specific 13C-labelling

    NASA Astrophysics Data System (ADS)

    Evershed, R. P.; Maxfield, P. J.; Bingham, E. M.; Dildar, N.; Brennand, E. L.; Hornibrook, E.

    2008-12-01

    A range of culture-independent methods, has recently emerged to study environmental microorganisms in situ[1]. One such method is phospholipid fatty acid (PLFA) analysis, wherein these ubiquitous membrane lipids provide a powerful tool for the study of unculturable soil microorganisms. PLFA analyses have been used to investigate the impacts of a wide range of environmental factors on the soil microbial community. An acknowledged shortcoming of the PLFAs approach is the lack the chemotaxonoic specificity, which restricts the ability of the method to probe the activities of specific functional groups of the microbial community selectively. However, the selectivity of PLFAs analyses can be enhanced by incubating soils with 13C- labelled substrates followed by gas chromatography-combustion-isotope ratio mass spectrometry to reveal the specific PLFAs incorporating the 13C-label. The application of this approach will be demonstrated through our recent work on methanotrophic bacteria in soils. We applied this approach initially to mineral soils[2] and then extended chemotaxonomic assessments by using a combination of 13C-labelled PLFAs and hopanoids [3]. We have used this approach to explore the properties of high affinity methanotrophs in a range of environments, investigating the relationship between methane oxidation rates and the nature and magnitude of the methanotrophic community for the first time[4,5] More recently we extended the technique using a novel time series 13C-labelling of PLFAs[6] to estimate the rate and progression of 13C- label incorporation and turnover of methanotrophic populations. This modified approach has been used to investigate the impacts of various environmental variables, e.g. soil type, vegetation cover and land use, on the methanotrophic biomass[7.8]. The unique nature of the 13CH4 as a gaseous substate/carbon source means that can be readily introduced into soils via a specific subset of the soil microbial biomass, thereby offering many

  14. Cost of nursing turnover in a Teaching Hospital.

    PubMed

    Ruiz, Paula Buck de Oliveira; Perroca, Marcia Galan; Jericó, Marli de Carvalho

    2016-02-01

    OBJECTIVE To map the sub processes related to turnover of nursing staff and to investigate and measure the nursing turnover cost. METHOD This is a descriptive-exploratory study, classified as case study, conducted in a teaching hospital in the southeastern, Brazil, in the period from May to November 2013. The population was composed by the nursing staff, using Nursing Turnover Cost Calculation Methodology. RESULTS The total cost of turnover was R$314.605,62, and ranged from R$2.221,42 to R$3.073,23 per employee. The costs of pre-hire totaled R$101.004,60 (32,1%), and the hiring process consumed R$92.743,60 (91.8%) The costs of post-hire totaled R$213.601,02 (67,9%), for the sub process decreased productivity, R$199.982,40 (93.6%). CONCLUSION The study identified the importance of managing the cost of staff turnover and the financial impact of the cost of the employee termination, which represented three times the average salary of the nursing staff. PMID:27007427

  15. Counselor emotional exhaustion and turnover intention in therapeutic communities.

    PubMed

    Knudsen, Hannah K; Ducharme, Lori J; Roman, Paul M

    2006-09-01

    Counselor turnover is a significant problem facing substance abuse treatment agencies. Understanding the role of organizational culture in predicting burnout and turnover intention may yield important information on how to address turnover in treatment organizations. Using data collected from 817 counselors employed in a national sample of 253 therapeutic communities (TCs), structural equation modeling was used to estimate the associations between emotional exhaustion, turnover intention, and three measures of organizational culture: centralized decision making, distributive justice, and procedural justice. The model controlled for counselor demographics, credentials, and earnings. Counselors' emotional exhaustion scores were higher in TCs with greater centralized decision making (p < .01) but lower in TCs where greater distributive justice (p < .05) and procedural justice (p < .001) were reported. Likewise, turnover intention was positively associated with centralized decision making (p < .05) and inversely associated with the workplace justice measures (p < .001). These data suggest that management practices in TCs and perhaps in other types of substance abuse treatment facilities likely play a substantial role in counselors' well-being and in their decisions to leave their jobs. Because these practices are not structural features of organizations, they may be targeted for intervention and change. PMID:16919745

  16. Evolution of phospholipid contents during the production of quark cheese from buttermilk.

    PubMed

    Ferreiro, T; Martínez, S; Gayoso, L; Rodríguez-Otero, J L

    2016-06-01

    We report the evolution of phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), phosphatidylserine (PS), and sphingomyelin (SM) contents during the production of quark cheese from buttermilk by successive ultrafiltration concentration, enrichment with cream, concurrent homogenization and pasteurization, fermentative coagulation, and separation of quark from whey by further ultrafiltration. Buttermilk is richer than milk itself in phospholipids that afford desirable functional and technological properties, and is widely used in dairy products. To investigate how phospholipid content is affected by end-product production processes such as ultrafiltration, homogenization, pasteurization or coagulation, we measured the phospholipids at several stages of each of 5 industrial-scale quark cheese production runs. In each run, 10,000L of buttermilk was concentrated to half volume by ultrafiltration, enriched with cream, homogenized, pasteurized, inoculated with lactic acid bacteria, incubated to coagulation, and once more concentrated to half volume by ultrafiltration. Phospholipid contents were determined by HPLC with evaporative light scattering detection in the starting buttermilk, concentrated buttermilk, ultrafiltrate, cream-enriched concentrated buttermilk (both before and after concurrent homogenization and pasteurization), coagulate, and quark, and also in the rinsings obtained when the ultrafiltration equipment was washed following initial concentration. The average phospholipid content of buttermilk was approximately 5 times that of milk, and the phospholipid content of buttermilk fat 26 to 29 times that of milk fat. Although phospholipids did not cross ultrafiltration membranes, significant losses occurred during ultrafiltration (due to retention on the membranes) and during the homogenization and pasteurization process. During coagulation, however, phospholipid content rose, presumably as a consequence of the proliferation of the

  17. Changes during hibernation in different phospholipid and free and esterified cholesterol serum levels in black bears

    USGS Publications Warehouse

    Chauhan, V.; Sheikh, A.; Chauhan, A.; Tsiouris, J.; Malik, M.; Vaughan, M.

    2002-01-01

    During hibernation, fat is known to be the preferred source of energy. A detailed analysis of different phospholipids, as well as free and esterified cholesterol, was conducted to investigate lipid abnormalities during hibernation. The levels of total phospholipids and total cholesterol in the serum of black bears were found to increase significantly in hibernation as compared with the active state. Both free and esterified cholesterol were increased in the hibernating state in comparison with the active state (P < 0.05). The percentage increase during hibernation was more in free cholesterol (57%) than in esterified cholesterol (27%). Analysis of subclasses of serum phospholipids showed that choline containing phospholipids, i.e., sphingomyelin (SPG) (14%) and phosphatidylcholine (PC) (76%), are the major phospholipids in the serum of bear. The minor phospholipids included 8% of phosphatidylserine (PS) + phosphatidylinositol (PI), while phosphatidylethanolamine (PE) was only 2% of the total phospholipids. A comparison of phospholipid subclasses showed that PC, PS + PI and SPG were significantly increased, while PE was significantly decreased (P < 0.05) in the hibernating state as compared with the active state in black bears. These results suggest that the catabolism of phospholipids and cholesterol is decreased during hibernation in black bears, leading to their increased levels in the hibernating state as compared with the active state. In summary, our results indicate that serum cholesterol and phospholipid fractions (except PE) are increased during hibernation in bears. It is proposed that the increase of these lipids may be due to the altered metabolism of lipoproteins that are responsible for the clearance of the lipids. ?? 2002 E??ditions scientifiques et me??dicales Elsevier SAS and Socie??te?? franc??aise de biochimie et biologie mole??culaire. All rights reserved.

  18. Disease-associated mutations of TDP-43 promote turnover of the protein through the proteasomal pathway.

    PubMed

    Araki, Wataru; Minegishi, Seiji; Motoki, Kazumi; Kume, Hideaki; Hohjoh, Hirohiko; Araki, Yumiko M; Tamaoka, Akira

    2014-12-01

    TAR DNA-binding protein (TDP-43) is a major component of most ubiquitin-positive neuronal and glial inclusions of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). A number of missense mutations in the TARDBP gene have been identified in patients with familial and sporadic ALS, as well as familial FTLD with ALS. In the diseased states, TDP-43 proteins exhibit characteristic alterations, including truncation, abnormal phosphorylation, and altered subcellular distribution. However, the mechanisms by which TDP-43 mutations induce neurodegeneration remain unclear at present. In the current study, we analyzed protein turnover and subcellular distribution of wild-type TDP-43 and two disease-associated mutants (G298S and A382T) in human neuroblastoma SH-SY5Y cells stably expressing TDP-43 with a C-terminal tag. Cycloheximide chase experiments revealed more rapid turnover of TDP-43 mutant proteins than their wild-type counterpart. The decrease in the TDP-43 level after cycloheximide treatment was partially recovered upon co-treatment with the proteasome inhibitor, epoxomicin, but not the lysosomotropic agent, chloroquine, suggesting involvement of the proteasomal pathway in TDP-43 degradation. Analysis of the subcellular distribution of TDP-43 revealed predominant localization in the nuclear fraction, whereas the relative level in the cytoplasm remained unaltered in cells expressing either mutant protein, compared with wild-type protein. Our results suggest that higher turnover of disease-associated mutant TDP-43 proteins through the ubiquitin proteasome system is pathogenetically relevant and highlight the significance of proteolysis in the pathogenetic mechanism of TDP-43 proteinopathy. PMID:24477737

  19. Accelerated bone turnover identifies hemiplegic patients at higher risk of demineralization.

    PubMed

    Del Puente, A; Pappone, N; Servodio Iammarrone, C; Esposito, A; Scarpa, R; Costa, L; Caso, F; Bardoscia, A; Del Puente, A

    2016-01-01

    Immobilization osteoporosis represents a severe complication in hemiplegic patients (HPs), causing fragility fractures, which may occur during rehabilitation reducing functional recovery and survival. The aim of the study was to investigate determinants of bone loss, independent from length of immobilization, which may be useful in early identification of HPs at higher risk of demineralization. Forty-eight HPs of both sexes underwent anthropometric measurements, evaluation of scores of spasticity and of lower limb motory capacity. Laboratory tests were performed. On serum: calcium; phosphorus; creatinine; ALP; iPTH; 25(OH) vitamin-D; sex hormones; Δ4-androstenedione; DHEA-S; insulin; IGF-1; FT3; FT4; TSH; c-AMP. On urine: c-AMP and calcium/creatinine ratio. Two bone turnover markers were measured: serum osteocalcin (BGP) and urinary deoxypyridinoline (DPD). Bone mineral density was determined at both femoral necks, defining a percentage difference in bone loss between paretic and non-paretic limb, thus controlling for the complex cofactors involved. Only bone turnover markers significantly and directly correlated with the entity of demineralization, controlling for age, sex and length of immobilization in the multivariate analysis (BGP coefficient estimate=0.008; SE=0.003; p=0.020; DPD coefficient estimate=0.005; SE=0.002; p=0.036). BGP and DPD are not dependent on anthropometric and endocrine-metabolic parameters, disability patterns and duration of immobilization, thus represent independent determinants of the degree of demineralization. A cutoff was defined for BGP and DPD above which subjects show significantly greater risk of demineralization. The immobilization event generates more severe bone loss when it occurs in subjects with higher bone turnover. BGP and DPD measurements may be of primary importance for early identification of HPs at risk, with relevant preventive implications. PMID:27049105

  20. Characteristics of the binding of tacrine to acidic phospholipids.

    PubMed Central

    Lehtonen, J Y; Rytömaa, M; Kinnunen, P K

    1996-01-01

    Tacrine (1,2,3,4-tetrahydro-9-acridinamine monohydrate) is an inhibitor of acetylcholinesterase currently used in the treatment of the symptoms of Alzheimer's disease. The present study demonstrates preferential binding of this drug to acidic phospholipids, as revealed by fluorescence polarization, penetration into lipid monolayers, and effects on the thermal phase behavior of dimyristoyl phosphatidic acid (DMPA). A fivefold enhancement in the polarization of tacrine emission is evident above the main phase transition temperature (T(m)) of DMPA vesicles, whereas below T(m) only a 0.75-fold increase is observed. In contrast, the binding of tacrine to another acidic phospholipid, dimyristoylphosphatidylglycerol, did not exhibit strong dependence on T(m). In accordance with the electrostatic nature of the membrane association of tacrine, the extent of binding was augmented with increasing contents of egg PG in phosphatidylcholine liposomes. Furthermore, [NaCl] > 50 mM dissociates tacrine (albeit incompletely) from the liposomes composed of acidic phospholipids. Inclusion of the cationic amphiphile sphingosine in egg PG vesicles decreased the membrane association of tacrine until at 1:1 sphingosine: egg PG stoichiometry binding was no longer evident. Tacrine also penetrated into egg PG but not into egg PC monolayers. Together with broadening of the main transition and causing a shoulder on its high temperature side, the binding of tacrine to DMPA liposomes results in a concentration-dependent reduction both in the combined enthalpy delta H of the above overlapping endotherms and the main transition temperature T(m). Interestingly, these changes in the thermal phase behavior of DMPA as a function of the content of the drug in vesicles were strongly nonlinear. More specifically, upon increasing [tacrine], T(m) exhibited stepwise decrements. Simultaneously, sharp minima in delta H were observed at drug:lipid stoichiometries of approximately 2:100 and 25:100, whereas a

  1. Association of the polioviral RNA polymerase complex with phospholipid membranes.

    PubMed Central

    Butterworth, B E; Shimshick, E J; Yin, F H

    1976-01-01

    Polioviral RNA polymerase complex, which consists of enzyme, template, and nascent RNA, is membrane bound in vivo. The solubilized RNA polymerase complex associated spontaneously in vitro with phospholipid bilayer membranes (liposomes) of defined composition. The degree of association at 37 degrees C was greater for those membranes that were more fluid, suggesting that the binding involves the interaction of the RNA polymerase complex with the hydrocarbon chains in the interior of the lipid bilayer. The polymerase activity was not enhanced by addition of the lipid; in fact, the addition of some of the longer-chain lipids resulted in up to a 40% inhibition of the polymerase activity. Spin-label electron paramagnetic resonance experiments, which measured the membrane fluidity, and kinetic experiments on the rate of incorporation of tritiated UTP into RNA by the polymerase were performed as a function of temperature. The results indicated that the activity of the polymerase was not affected by the physical state of the phospholipid membrane and that its active site was not intimately associated with the membrane. Analysis of both the viral and host polypeptides associated with the smooth membrane-bound polymerase indicated that X was the primary viral polypeptide present. In addition, host polypeptides of molecular weight 86,000, 62,000, 54,000, and 46,000 were also present. If the membrane was disrupted with detergent, polypeptide X was released from the polymerase activity, suggesting that X may play a role in binding the polymerase to the membrane. In an analogous manner, polypeptide X associated spontaneously with phospholipid membranes to a greater extent than the capsid polypeptides. Analysis of both the host and viral polypeptides associated with the viral RNA polymerase purified by precipitation in 2 M LiCl indicated that host polypeptides of molecular weight 106,000, 38,000, 33,000, and 14,000 were the major constituents, whereas relatively small amounts of

  2. Anatomical Location of LPA1 Activation and LPA Phospholipid Precursors in Rodent and Human Brain

    PubMed Central

    González de San Román, E; Manuel, I; Giralt, MT; Chun, J; Estivill-Torrús, G; Rodriguez de Fonseca, F; Santín, LJ; Ferrer, I; Rodriguez-Puertas, R

    2016-01-01

    Lysophosphatidic acid (LPA) is a signaling molecule that binds to six known G protein-coupled receptors (GPCRs): LPA1–LPA6. LPA evokes several responses in the CNS including cortical development and folding, growth of the axonal cone and its retraction process. Those cell processes involve survival, migration, adhesion proliferation, differentiation and myelination. The anatomical localization of LPA1 is incompletely understood, particularly with regard to LPA binding. Therefore, we have used functional [35S]GTPγS autoradiography to verify the anatomical distribution of LPA1 binding sites in adult rodent and human brain. The greatest activity was observed in myelinated areas of the white matter such as corpus callosum, internal capsule and cerebellum. MaLPA1-null mice (a variant of LPA1-null) lack [35S]GTPγS basal binding in white matter areas, where the LPA1 receptor is expressed at high levels, suggesting a relevant role of the activity of this receptor in the most myelinated brain areas. In addition, phospholipid precursors of LPA were localized by MALDI-IMS in both rodent and human brain slices identifying numerous species of phosphatides (PA) and phosphatidylcholines (PC). Both PA and PC species represent potential LPA precursors. The anatomical distribution of these precursors in rodent and human brain may indicate a metabolic relationship between LPA and LPA1 receptors. PMID:25857358

  3. Dynamical and phase behavior of a phospholipid membrane altered by an antimicrobial peptide at low concentration

    DOE PAGESBeta

    Mamontov, Eugene; Tyagi, M.; Qian, Shuo; Rai, Durgesh K.; Urban, Volker S.; Sharma, V. K.

    2016-05-27

    Here we discuss that the mechanism of action of antimicrobial peptides is traditionally attributed to the formation of pores in the lipid cell membranes of pathogens, which requires a substantial peptide to lipid ratio. However, using incoherent neutron scattering, we show that even at a concentration too low for pore formation, an archetypal antimicrobial peptide, melittin, disrupts the regular phase behavior of the microscopic dynamics in a phospholipid membrane, dimyristoylphosphatidylcholine (DMPC). At the same time, another antimicrobial peptide, alamethicin, does not exert a similar effect on the DMPC microscopic dynamics. The melittin-altered lateral motion of DMPC at physiological temperature nomore » longer resembles the fluid-phase behavior characteristic of functional membranes of the living cells. The disruptive effect demonstrated by melittin even at low concentrations reveals a new mechanism of antimicrobial action relevant in more realistic scenarios, when peptide concentration is not as high as would be required for pore formation, which may facilitate treatment with antimicrobial peptides.« less

  4. Stressful work, psychological job strain, and turnover: a 2-year prospective cohort study of truck drivers.

    PubMed

    de Croon, Einar M; Sluiter, Judith K; Blonk, Roland W B; Broersen, Jake P J; Frings-Dresen, Monique H W

    2004-06-01

    Based on a model that combines existing organizational stress theory and job transition theory, this 2-year longitudinal study examined antecedents and consequences of turnover among Dutch truck drivers. For this purpose, self-reported data on stressful work (job demands and control), psychological strain (need for recovery after work and fatigue), and turnover were obtained from 820 drivers in 1998 and 2000. In agreement with the model, the results showed that strain mediates the influence of stressful work on voluntary turnover. Also in conformity with the model, job movement to any job outside the trucking industry (i.e., interoccupational turnover) resulted in a larger strain reduction as compared to job movement within the trucking industry (intraoccupational turnover). Finally, strain was found to stimulate interoccupational turnover more strongly than it stimulated intraoccupational turnover. These findings provide a thorough validation of existing turnover theory and give new insights into the turnover (decision) process. PMID:15161404

  5. Methionine deficiency does not increase polyamine turnover through depletion of hepatic S-adenosylmethionine in juvenile Atlantic salmon.

    PubMed

    Espe, Marit; Andersen, Synne Marte; Holen, Elisabeth; Rønnestad, Ivar; Veiseth-Kent, Eva; Zerrahn, Jens-Erik; Aksnes, Anders

    2014-10-28

    During the last few decades, plant protein ingredients such as soya proteins have replaced fishmeal in the diets of aquacultured species. This may affect the requirement and metabolism of methionine as soya contains less methionine compared with fishmeal. To assess whether methionine limitation affects decarboxylated S-adenosylmethionine availability and polyamine status, in the present study, juvenile Atlantic salmon were fed a methionine-deficient plant protein-based diet or the same diet supplemented with dl-methionine for 8 weeks. The test diets were compared with a fishmeal-based control diet to assess their effects on the growth performance of fish. Methionine limitation reduced growth and protein accretion, but when fish were fed the dl-methionine-supplemented diet their growth and protein accretion equalled those of fish fed the fishmeal-based control diet. Methionine limitation reduced free methionine concentrations in the plasma and muscle, while those in the liver were not affected. S-adenosylmethionine (SAM) concentrations were higher in the liver of fish fed the methionine-deficient diet, while S-adenosylhomocysteine concentrations were not affected. Putrescine concentrations were higher and spermine concentrations were lower in the liver of fish fed the methionine-deficient diet, while the gene expression of SAM decarboxylase (SAMdc) and the rate-limiting enzyme of polyamine synthesis ornithine decarboxylase (ODC) was not affected. Polyamine turnover, as assessed by spermine/spermidine acetyltransferase (SSAT) abundance, activity and gene expression, was not affected by treatment. However, the gene expression of the cytokine TNF-α increased in fish fed the methionine-deficient diet, indicative of stressful conditions in the liver. Even though taurine concentrations in the liver were not affected by treatment, methionine and taurine concentrations in muscle decreased due to methionine deficiency. Concomitantly, liver phospholipid and cholesterol

  6. Light-stimulated inositolphospholipid turnover in Samanea saman leaf pulvini

    SciTech Connect

    Morse, M.J.; Crain, R.C.; Satter, R.L.

    1987-10-01

    Leaflets of Samanea saman open and close rhythmically, driven by an endogenous circadian clock. Light has a rapid, direct effect on the movements and also rephases the rhythm. The authors investigated whether light signals might be mediated by increased inositolphospholipid turnover, a mechanism for signal transduction that is widely utilized in animal systems. Samanea motor organs (pulvini) labeled with (/sup 3/H)inositol were irradiated briefly (5-30 sec) with white light, and membrane-localized phosphatidylinositol phosphates and their aqueous breakdown products, the inositol phosphates, were examined. After a 15-sec or longer light pulse, labeled phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate decreased and their labeled metabolic products inositol 1,4-biphosphate and inositol 1,4,5-trisphosphate increased changes characteristic of inositolphospholipid turnover. The authors conclude that inositolphospholipid turnover may act as a phototransduction mechanism in Samanea pulvini in a manner that is similar to that reported in animal systems.

  7. Quality of Working Life: An Antecedent to Employee Turnover Intention

    PubMed Central

    Mosadeghrad, Ali Mohammad

    2013-01-01

    Background: The purpose of this study was to measure the level of quality of work life (QWL) among hospital employees in Iran. Additionally, it aimed to identify the factors that are critical to employees’ QWL. It also aimed to test a theoretical model of the relationship between employees’ QWL and their intention to leave the organization. Methods: A survey study was conducted based on a sample of 608 hospital employees using a validated questionnaire. Face, content and construct validity were conducted on the survey instrument. Results: Hospital employees reported low QWL. Employees were least satisfied with pay, benefits, job promotion, and management support. The most important predictor of QWL was management support, followed by job proud, job security and job stress. An inverse relationship was found between employees QWL and their turnover intention. Conclusion: This study empirically examined the relationships between employees’ QWL and their turnover intention. Managers can take appropriate actions to improve employees’ QWL and subsequently reduce employees’ turnover. PMID:24596835

  8. Factors related to job turnover in physical therapy.

    PubMed

    Harkson, D G; Unterreiner, A S; Shepard, K F

    1982-10-01

    The purpose of this study was to determine the relative importance of personal and work-related factors in relation to job turnover in the physical therapy profession. A survey questionnaire was mailed to a nationwide sample of 820 physical therapists, and 567 responses (69%) were used in the data analyses. The two most important reasons for leaving a job were "desire to pursue a different area of physical therapy" and "insufficient salary to meet financial needs." Significant differences were found in the relative importance of job-turnover factors when the sample was stratified according to physical therapy education level, percentage of time in direct patient care, years in the physical therapy profession, and sex. A careful look at the factors contributing to job turnover will help physical therapy administrators retain staff members. PMID:7122704

  9. Dynamics of Cell Generation and Turnover in the Human Heart.

    PubMed

    Bergmann, Olaf; Zdunek, Sofia; Felker, Anastasia; Salehpour, Mehran; Alkass, Kanar; Bernard, Samuel; Sjostrom, Staffan L; Szewczykowska, Mirosława; Jackowska, Teresa; Dos Remedios, Cris; Malm, Torsten; Andrä, Michaela; Jashari, Ramadan; Nyengaard, Jens R; Possnert, Göran; Jovinge, Stefan; Druid, Henrik; Frisén, Jonas

    2015-06-18

    The contribution of cell generation to physiological heart growth and maintenance in humans has been difficult to establish and has remained controversial. We report that the full complement of cardiomyocytes is established perinataly and remains stable over the human lifespan, whereas the numbers of both endothelial and mesenchymal cells increase substantially from birth to early adulthood. Analysis of the integration of nuclear bomb test-derived (14)C revealed a high turnover rate of endothelial cells throughout life (>15% per year) and more limited renewal of mesenchymal cells (<4% per year in adulthood). Cardiomyocyte exchange is highest in early childhood and decreases gradually throughout life to <1% per year in adulthood, with similar turnover rates in the major subdivisions of the myocardium. We provide an integrated model of cell generation and turnover in the human heart. PMID:26073943

  10. Negatively cooperative binding of melittin to neutral phospholipid vesicles

    NASA Astrophysics Data System (ADS)

    Torrens, Francisco; Castellano, Gloria; Campos, Agustín; Abad, Concepción

    2007-05-01

    The association of basic amphipathic peptides to neutral phospholipid membranes is investigated in terms of binding and partition models. The binding of native and modified melittin to egg-yolk phosphatidylcholine vesicles is studied by steady-state fluorescence spectroscopy. The effect of the ionic strength shows an enhancement of the association as the ionic strength increases. After correction for electrostatic effects by the Gouy-Chapman theory, the melittin binding isotherms could be described by a partition model. In terms of conventional binding mechanisms, which do not take into account electrostatic effects, this would correspond to a negative cooperativity. A plausible way in which the interaction occurs is proposed, based on the calculated Hill coefficient.

  11. Marine Omega-3 Phospholipids: Metabolism and Biological Activities

    PubMed Central

    Burri, Lena; Hoem, Nils; Banni, Sebastiano; Berge, Kjetil

    2012-01-01

    The biological activities of omega-3 fatty acids (n-3 FAs) have been under extensive study for several decades. However, not much attention has been paid to differences of dietary forms, such as triglycerides (TGs) versus ethyl esters or phospholipids (PLs). New innovative marine raw materials, like krill and fish by-products, present n-3 FAs mainly in the PL form. With their increasing availability, new evidence has emerged on n-3 PL biological activities and differences to n-3 TGs. In this review, we describe the recently discovered nutritional properties of n-3 PLs on different parameters of metabolic syndrome and highlight their different metabolic bioavailability in comparison to other dietary forms of n-3 FAs. PMID:23203133

  12. Sarcolemmal phospholipid N-methylation in genetically determined hamster cardiomyopathy

    SciTech Connect

    Okumura, K.; Panagia, V.; Jasmin, G.; Dhalla, N.S.

    1987-02-27

    The heart sarcolemmal phosphatidylethanolamine N-methylation in UM-X7.1 strain of cardiomyopathic hamsters was examined by using 0.055, 10 and 150 microM S-adenosyl-L-(methyl-/sup 3/H) methionine as methyl donor for sites I, II and III, respectively. In comparison with control values, methylation activities at site I was increased in 40, 120 and 250 days old cardiomyopathic hamsters. On the other hand, methylation activities at sites II and III in 120 and 250 days old cardiomyopathic animals were depressed without any change in the 40 days old group. The alterations in N-methylation activities were associated with kinetic changes in apparent Vmax values without any changes in the apparent Km. These results indicate a defect in the phospholipid N-methylation process in heart sarcolemma during the development of genetically determined cardiomyopathy.

  13. Equation of State for Phospholipid Self-Assembly.

    PubMed

    Marsh, Derek

    2016-01-01

    Phospholipid self-assembly is the basis of biomembrane stability. The entropy of transfer from water to self-assembled micelles of lysophosphatidylcholines and diacyl phosphatidylcholines with different chain lengths converges to a common value at a temperature of 44°C. The corresponding enthalpies of transfer converge at ∼-18°C. An equation of state for the free energy of self-assembly formulated from this thermodynamic data depends on the heat capacity of transfer as the sole parameter needed to specify a particular lipid. For lipids lacking calorimetric data, measurement of the critical micelle concentration at a single temperature suffices to define an effective heat capacity according to the model. Agreement with the experimental temperature dependence of the critical micelle concentration is then good. The predictive powers should extend also to amphiphile partitioning and the kinetics of lipid-monomer transfer. PMID:26745421

  14. Substrate trajectory through phospholipid-transporting P4-ATPases.

    PubMed

    Williamson, Patrick

    2014-10-01

    A difference in the lipid composition between the two leaflets of the same membrane is a relatively simple instance of lipid compositional heterogeneity. The large activation energy barrier for transbilayer movement for some (but not all) membrane lipids creates a regime governed by active transport processes. An early step in eukaryote evolution was the development of a capacity for generating transbilayer compositional heterogeneity far from equilibrium by directly tapping energy from the ATP pool. The mechanism of the P-type ATPases that create lipid asymmetry is well understood in terms of ATP hydrolysis, but the trajectory taken by the phospholipid substrate through the enzyme is a matter of current active research. There are currently three different models for this trajectory, all with support by mutation/activity measurements and analogies with known atomic structures. PMID:25233416

  15. Interactions of lauryl gallate with phospholipid components of biological membranes.

    PubMed

    Jurak, Małgorzata; Miñones, José

    2016-08-01

    The effect of different amounts of lauryl gallate (LG) on properties of the model membranes of phosphatidylcholines (PC), differing in the presence of double bonds in the hydrocarbon chains, and phosphatidylglycerol (PG) was described in terms of phase behaviour of mixtures, interactions between both components, monolayers stability and their organization. The Langmuir monolayer technique was used to monitor the surface thermodynamics (i.e. the excess area and excess Gibbs energy of mixing) on the basis of surface pressure-area per molecule (π-A) isotherms. Simultaneously, morphology of the studied monolayers was visualized by the Brewster angle microscopy (BAM). This allowed evaluating the kind and magnitude of interactions which influence on the phase behaviour and structural properties of the monolayers. The obtained results can be helpful to reveal the mechanism of phospholipid antioxidant protection and important pharmacological (antimicrobial) role of lauryl gallate for production of effective therapeutic substances. PMID:27117642

  16. Bioinspired interface for nanobiodevices based on phospholipid polymer chemistry

    PubMed Central

    Ishihara, Kazuhiko; Takai, Madoka

    2009-01-01

    This review paper describes novel biointerfaces for nanobiodevices. Biocompatible and non-biofouling surfaces are designed largely based on cell membrane structure, and the preparation and functioning of the bioinspired interface are evaluated and compared between living and artificial systems. A molecular assembly of polymers with a phospholipid polar group has been developed as the platform of the interface. At the surface, protein adsorption is effectively reduced and the subsequent bioreactions are suppressed. Through this platform, biomolecules with a high affinity to the specific molecules are introduced under mild conditions. The activity of the biomolecules is retained even after immobilization. This bioinspired interface is adapted to construct bionanodevices, that is, microfluidic chips and nanoparticles for capturing target molecules and cells. The interface functions well and has a very high efficiency for biorecognition. This bioinspired interface is a promising universal platform that integrates various fields of science and has useful applications. PMID:19324688

  17. Interesterification activity of Rhizopus delemar lipase in phospholipid microemulsions.

    PubMed

    Komatsu, Takayoshi; Nagayama, Kazuhito; Imai, Masanao

    2004-11-15

    The interesterification of olive oil with palmitic acid catalyzed by Rhizopus delemar lipase was investigated in phospholipid microemulsion systems. Soybean lecithin was used as the amphiphilic component. The maximal reaction rate was obtained at a buffer pH of 5.5-6.0. The reaction rate was also dependent on the W(L) (= [H2O]/[lecithin]) value and attained a maximum at W(L)=5. The reaction rate reached a maximum at a palmitic acid concentration of 350 mM. The molar fraction of the interesterified product 1,3-dipalmitoyl-3-oleoyl glycerol (POP) in the olive oil was enhanced from 2.8 to 65.6 mol% after 24 h of the reaction. PMID:15542321

  18. Copper-deficient mice have higher cardiac norepinephrine turnover

    SciTech Connect

    Gross, A.M.; Prohaska, J.R. )

    1989-02-01

    Male Swiss albino mice were studied at 6 weeks of age. Their dams were fed a copper-deficient diet (modified AIN-76A) starting 4 days after birth and given deionized water (-Cu) or water with CuSO{sub 4} added (+Cu) (20 {mu}g Cu/ml). When 3 weeks of age mice were weaned and housed in stainless steel cages on the respective treatment of their dams. Turnover of norepinephrine (NE) was studied in 8 experiments using 2 separate techniques. The first procedure used {alpha}-methyl-p-tyrosine methyl ester (300 mg/kg i.p.) to inhibit tyrosine hydroxlase activity. The loss of residual NE was determined by HPLC with electrochemical detection. Regression lines were constructed and fractional turnover (%/h) and calculated turnover (ng/g/h) were determined for heart, cerebellum and adrenal gland. In 4 experiments loss of NE in cerebellum of -Cu ad +Cu mice was equivalent. Loss of NE from adrenal gland could not be detected in the 8 h time course. Loss of NE, both fractional turnover and calculated turnover, from heart of -Cu mice was 4-5 fold higher compared to +Cu controls. A second method using m- hydroxybenzylhydrazine (NSD-1015) (100 mg/kg i.p.), which inhibits aromatic amino acid decarboxylase, confirmed the results. For all 4 experiments the cardiac accumulation of L-DOPA (measured by HPLC) was faster in -Cu mice compared to controls. The higher turnover rate of NE in heart and perhaps other sympathetic nerves may contribute to the higher urinary NE output observed previously.

  19. Human turnover dynamics during sleep: Statistical behavior and its modeling

    NASA Astrophysics Data System (ADS)

    Yoneyama, Mitsuru; Okuma, Yasuyuki; Utsumi, Hiroya; Terashi, Hiroo; Mitoma, Hiroshi

    2014-03-01

    Turnover is a typical intermittent body movement while asleep. Exploring its behavior may provide insights into the mechanisms and management of sleep. However, little is understood about the dynamic nature of turnover in healthy humans and how it can be modified in disease. Here we present a detailed analysis of turnover signals that are collected by accelerometry from healthy elderly subjects and age-matched patients with neurodegenerative disorders such as Parkinson's disease. In healthy subjects, the time intervals between consecutive turnover events exhibit a well-separated bimodal distribution with one mode at ⩽10 s and the other at ⩾100 s, whereas such bimodality tends to disappear in neurodegenerative patients. The discovery of bimodality and fine temporal structures (⩽10 s) is a contribution that is not revealed by conventional sleep recordings with less time resolution (≈30 s). Moreover, we estimate the scaling exponent of the interval fluctuations, which also shows a clear difference between healthy subjects and patients. We incorporate these experimental results into a computational model of human decision making. A decision is to be made at each simulation step between two choices: to keep on sleeping or to make a turnover, the selection of which is determined dynamically by comparing a pair of random numbers assigned to each choice. This decision is weighted by a single parameter that reflects the depth of sleep. The resulting simulated behavior accurately replicates many aspects of observed turnover patterns, including the appearance or disappearance of bimodality and leads to several predictions, suggesting that the depth parameter may be useful as a quantitative measure for differentiating between normal and pathological sleep. These findings have significant clinical implications and may pave the way for the development of practical sleep assessment technologies.

  20. [Pharmacological agents and transport nanosystems based on plant phospholipids].

    PubMed

    Medvedeva, N V; Prosorovskiy, V N; Ignatov, D V; Druzilovskaya, O S; Kudinov, V A; Kasatkina, E O; Tikhonova, E G; Ipatova, O M

    2015-01-01

    A new generation of plant phosphatidylcholine (PC)-based pharmacological agents has been developed under academician A.I. Archakov leadership at the Institute of Biomedical Chemistry (IBMC). For their production a unique technology allowing to obtain dry lyophilized phospholipid nanoparticles of 30 nm was elaborated. The successful practical application of PC nanoparticles as a drug agent may be illustrated by Phosphogliv (oral and injection formulations). Being developed at IBMC for the treatment of liver diseases, including viral hepatitis, Phosphogliv (currently marketed by the "Pharmstandard" company) is approved for clinical application in 2000, and is widely used in medical practice. Based on the developed and scaled in IBMC technology of prerparation of ultra small size phospholipid nanoparticles without the use of detergents/surfactants and stabilizers another drug preparation, Phospholipovit, exhibiting pronounced hypolipidemic properties has been obtained. Recently completed preclinical studies have shown that PC nanoparticles of 20-30 nm activate reverse cholesterol transport (RCT) and in this context it is more active than well known foreign preparation Essentiale. Phospholipovit is now at the stage of clinical trials (phase 1 completed). PC was also used as a basis for the development of a transport nanosystem with a particles size of 20-25 nm in diameter and incorporation of various drug substances from various therapeutic groups. Using several drugs substances as an example, increased bioavailability and specific activity were demonstrated for the formulations equipped with such transport nanosystem. Formulations equipped with the transport nanosystems have been developed for such pharmacological agents as doxorubicin, rifampin, budesonide, chlorin E6, prednisone, and others. PMID:25978388

  1. Membrane-derived phospholipids control synaptic neurotransmission and plasticity.

    PubMed

    García-Morales, Victoria; Montero, Fernando; González-Forero, David; Rodríguez-Bey, Guillermo; Gómez-Pérez, Laura; Medialdea-Wandossell, María Jesús; Domínguez-Vías, Germán; García-Verdugo, José Manuel; Moreno-López, Bernardo

    2015-05-01

    Synaptic communication is a dynamic process that is key to the regulation of neuronal excitability and information processing in the brain. To date, however, the molecular signals controlling synaptic dynamics have been poorly understood. Membrane-derived bioactive phospholipids are potential candidates to control short-term tuning of synaptic signaling, a plastic event essential for information processing at both the cellular and neuronal network levels in the brain. Here, we showed that phospholipids affect excitatory and inhibitory neurotransmission by different degrees, loci, and mechanisms of action. Signaling triggered by lysophosphatidic acid (LPA) evoked rapid and reversible depression of excitatory and inhibitory postsynaptic currents. At excitatory synapses, LPA-induced depression depended on LPA1/Gαi/o-protein/phospholipase C/myosin light chain kinase cascade at the presynaptic site. LPA increased myosin light chain phosphorylation, which is known to trigger actomyosin contraction, and reduced the number of synaptic vesicles docked to active zones in excitatory boutons. At inhibitory synapses, postsynaptic LPA signaling led to dephosphorylation, and internalization of the GABAAγ2 subunit through the LPA1/Gα12/13-protein/RhoA/Rho kinase/calcineurin pathway. However, LPA-induced depression of GABAergic transmission was correlated with an endocytosis-independent reduction of GABAA receptors, possibly by GABAAγ2 dephosphorylation and subsequent increased lateral diffusion. Furthermore, endogenous LPA signaling, mainly via LPA1, mediated activity-dependent inhibitory depression in a model of experimental synaptic plasticity. Finally, LPA signaling, most likely restraining the excitatory drive incoming to motoneurons, regulated performance of motor output commands, a basic brain processing task. We propose that lysophospholipids serve as potential local messengers that tune synaptic strength to precedent activity of the neuron. PMID:25996636

  2. Factors influencing α-crystallin association with phospholipid vesicles

    PubMed Central

    Cobb, Brian A.; Petrash, J. Mark

    2010-01-01

    Purpose Lens lipids undergo a number of changes with age, including an overall increase in phospholipid acyl chain saturation and a decrease in length. In addition, the amount of membrane bound α-crystallin increases dramatically with age and with the onset of cataract. The aim of this study was to determine if a link exists between age and cataract associated changes in lens lipids and the changes in α-crystallin membrane association. Methods Protein-free lipid vesicles composed of a wide variety of synthetic and lens-derived lipid vesicles were formed by sonication. These vesicles were used with fluorescent native and recombinant α-crystallin conjugates in vesicle binding assays. Vesicles were collected by centrifugation and bound α-crystallin was quantified with fluorescence intensity measurements. Results α-Crystallin complexes showed remarkably similar binding profiles for all lipid vesicles tested, regardless of lipid origin, phospholipid head group, acyl chain length or saturation, and inclusion of cholesterol. In addition, recombinant α-crystallin complexes bind to these vesicles in a manner that is essentially indistinguishable from that of native human and bovine α-crystallins. Unlike α-crystallin binding to lens membranes containing intrinsic proteins, binding of α-crystallin to protein-free vesicles was very high capacity and unsaturable. Conclusions We conclude from these data that the binding of α-crystallin to lens membranes is not lipid-specific. Furthermore, protein post-translational changes, such as phosphorylation, do not appear to alter α-crystallin binding to these vesicles. Given the linearity of the binding curves, we propose that the only limiting factor for normal α-crystallin membrane binding is available surface area on the bilayer. Finally, the present data suggests that increased in vivo membrane association of α-crystallin is not a result of lipid changes, but more likely a result of non-lipid factors such as the

  3. PPAR-β/δ activation promotes phospholipid transfer protein expression.

    PubMed

    Chehaibi, Khouloud; Cedó, Lídia; Metso, Jari; Palomer, Xavier; Santos, David; Quesada, Helena; Naceur Slimane, Mohamed; Wahli, Walter; Julve, Josep; Vázquez-Carrera, Manuel; Jauhiainen, Matti; Blanco-Vaca, Francisco; Escolà-Gil, Joan Carles

    2015-03-15

    The peroxisome proliferator-activated receptor (PPAR)-β/δ has emerged as a promising therapeutic target for treating dyslipidemia, including beneficial effects on HDL cholesterol (HDL-C). In the current study, we determined the effects of the PPAR-β/δ agonist GW0742 on HDL composition and the expression of liver HDL-related genes in mice and cultured human cells. The experiments were carried out in C57BL/6 wild-type, LDL receptor (LDLR)-deficient mice and PPAR-β/δ-deficient mice treated with GW0742 (10mg/kg/day) or a vehicle solution for 14 days. GW0742 upregulated liver phospholipid transfer protein (Pltp) gene expression and increased serum PLTP activity in mice. When given to wild-type mice, GW0742 significantly increased serum HDL-C and HDL phospholipids; GW0742 also raised serum potential to generate preβ-HDL formation. The GW0742-mediated effects on liver Pltp expression and serum enzyme activity were completely abolished in PPAR-β/δ-deficient mice. GW0742 also stimulated PLTP mRNA expression in mouse J774 macrophages, differentiated human THP-1 macrophages and human hepatoma Huh7. Collectively, our findings demonstrate a common transcriptional upregulation by GW0742-activated PPAR-β/δ of Pltp expression in cultured cells and in mouse liver resulting in enhanced serum PLTP activity. Our results also indicate that PPAR-β/δ activation may modulate PLTP-mediated preβ-HDL formation and macrophage cholesterol efflux. PMID:25662586

  4. Structure of the Chemokine Receptor CXCR1 in Phospholipid Bilayers

    PubMed Central

    Park, Sang Ho; Das, Bibhuti B.; Casagrande, Fabio; Tian, Ye; Nothnagel, Henry J.; Chu, Mignon; Kiefer, Hans; Maier, Klaus; De Angelis, Anna; Marassi, Francesca M.; Opella, Stanley J.

    2013-01-01

    CXCR1 is one of two high-affinity receptors for the CXC chemokine interleukin-8 (IL-8), a major mediator of immune and inflammatory responses implicated in many disorders, including tumor growth1-3. IL-8, released in response to inflammatory stimuli, binds to the extracellular side of CXCR1. The ligand-activated intracellular signaling pathways result in neutrophil migration to the site of inflammation2. CXCR1 is a class-A, rhodopsin-like G-protein-coupled receptor (GPCR), the largest class of integral membrane proteins responsible for cellular signal transduction and targeted as drug receptors4-7. Despite its importance, its molecular mechanism is poorly understood due to the limited structural information available. Recently, structure determination of GPCRs has advanced by tailoring the receptors with stabilizing mutations, insertion of the protein T4 lysozyme and truncations of their amino acid sequences8, as well as addition of stabilizing antibodies and small molecules9 that facilitate crystallization in cubic phase monoolein mixtures10. The intracellular loops of GPCRs are critical for G-protein interactions11 and activation of CXCR1 involves both N-terminal residues and extracellular loops2,12,13. Our previous NMR studies indicate that IL-8 binding to the N-terminal residues is mediated by the membrane, underscoring the importance of the phospholipid bilayer for physiological activity14. Here we report the three-dimensional structure of human CXCR1 determined by NMR spectroscopy. The receptor is in liquid crystalline phospholipid bilayers, without modification of its amino acid sequence and under physiological conditions. Features important for intracellular G-protein activation and signal transduction are revealed. PMID:23086146

  5. Protein turnover and cellular autophagy in growing and growth-inhibited 3T3 cells

    SciTech Connect

    Papadopoulos, T.; Pfeifer, U. )

    1987-07-01

    The relationship between growth, protein degradation, and cellular autophagy was tested in growing and in growth-inhibited 3T3 cell monolayers. For the biochemical evaluation of DNA and protein metabolism, growth-inhibited 3T3 cell monolayers with high cell density and growing 3T3 cell monolayers with low cell density were labeled simultaneously with ({sup 14}C)thymidine and ({sup 3}H)leucine. The evaluation of the DNA turnover and additional ({sup 3}H)thymidine autoradiography showed that 24 to 5% of 3T3 cells continue to replicate even in the growth-inhibited state, where no accumulation of protein and DNA can be observed. Cell loss, therefore, has to be assumed to compensate for the ongoing cell proliferation. When the data of protein turnover were corrected for cell loss, it was found that the rate constant of protein synthesis in nongrowing monolayers was reduced to half the value found in growing monolayers. Simultaneously, the rate constant of protein degradation in nongrowing monolayers was increased to about 1.5-fold the value of growing monolayers. These data are in agreement with the assumption that cellular autophagy represents a major pathway of regulating protein degradation in 3T3 cells and that the regulation of autophagic protein degradation is of relevance for the transition from a growing to a nongrowing state.

  6. Dynamic phospholipid interaction of β2e subunit regulates the gating of voltage-gated Ca2+ channels

    PubMed Central

    Kim, Dong-Il; Park, Yongsoo; Jang, Deok-Jin

    2015-01-01

    High voltage-activated Ca2+ (CaV) channels are protein complexes containing pore-forming α1 and auxiliary β and α2δ subunits. The subcellular localization and membrane interactions of the β subunits play a crucial role in regulating CaV channel inactivation and its lipid sensitivity. Here, we investigated the effects of membrane phosphoinositide (PI) turnover on CaV2.2 channel function. The β2 isoform β2e associates with the membrane through electrostatic and hydrophobic interactions. Using chimeric β subunits and liposome-binding assays, we determined that interaction between the N-terminal 23 amino acids of β2e and anionic phospholipids was sufficient for β2e membrane targeting. Binding of the β2e subunit N terminus to liposomes was significantly increased by inclusion of 1% phosphatidylinositol 4,5-bisphosphate (PIP2) in the liposomes, suggesting that, in addition to phosphatidylserine, PIs are responsible for β2e targeting to the plasma membrane. Membrane binding of the β2e subunit slowed CaV2.2 current inactivation. When membrane phosphatidylinositol 4-phosphate and PIP2 were depleted by rapamycin-induced translocation of pseudojanin to the membrane, however, channel opening was decreased and fast inactivation of CaV2.2(β2e) currents was enhanced. Activation of the M1 muscarinic receptor elicited transient and reversible translocation of β2e subunits from membrane to cytosol, but not that of β2a or β3, resulting in fast inactivation of CaV2.2 channels with β2e. These results suggest that membrane targeting of the β2e subunit, which is mediated by nonspecific electrostatic insertion, is dynamically regulated by receptor stimulation, and that the reversible association of β2e with membrane PIs results in functional changes in CaV channel gating. The phospholipid–protein interaction observed here provides structural insight into mechanisms of membrane–protein association and the role of phospholipids in ion channel regulation. PMID

  7. Anatomical location of LPA1 activation and LPA phospholipid precursors in rodent and human brain.

    PubMed

    González de San Román, Estibaliz; Manuel, Iván; Giralt, María Teresa; Chun, Jerold; Estivill-Torrús, Guillermo; Rodríguez de Fonseca, Fernando; Santín, Luis Javier; Ferrer, Isidro; Rodríguez-Puertas, Rafael

    2015-08-01

    Lysophosphatidic acid (LPA) is a signaling molecule that binds to six known G protein-coupled receptors: LPA1 -LPA6 . LPA evokes several responses in the CNS, including cortical development and folding, growth of the axonal cone and its retraction process. Those cell processes involve survival, migration, adhesion proliferation, differentiation, and myelination. The anatomical localization of LPA1 is incompletely understood, particularly with regard to LPA binding. Therefore, we have used functional [(35) S]GTPγS autoradiography to verify the anatomical distribution of LPA1 binding sites in adult rodent and human brain. The greatest activity was observed in myelinated areas of the white matter such as corpus callosum, internal capsule and cerebellum. MaLPA1 -null mice (a variant of LPA1 -null) lack [(35) S]GTPγS basal binding in white matter areas, where the LPA1 receptor is expressed at high levels, suggesting a relevant role of the activity of this receptor in the most myelinated brain areas. In addition, phospholipid precursors of LPA were localized by MALDI-IMS in both rodent and human brain slices identifying numerous species of phosphatides and phosphatidylcholines. Both phosphatides and phosphatidylcholines species represent potential LPA precursors. The anatomical distribution of these precursors in rodent and human brain may indicate a metabolic relationship between LPA and LPA1 receptors. Lysophosphatidic acid (LPA) is a signaling molecule that binds to six known G protein-coupled receptors (GPCR), LPA1 to LPA6 . LPA evokes several responses in the central nervous system (CNS), including cortical development and folding, growth of the axonal cone and its retraction process. We used functional [(35) S]GTPγS autoradiography to verify the anatomical distribution of LPA1 -binding sites in adult rodent and human brain. The distribution of LPA1 receptors in rat, mouse and human brains show the highest activity in white matter myelinated areas. The basal and

  8. Fluorometric High-Throughput Screening Assay for Secreted Phospholipases A2 Using Phospholipid Vesicles.

    PubMed

    Ewing, Heather; Fernández-Vega, Virneliz; Spicer, Timothy P; Chase, Peter; Brown, Steven; Scampavia, Louis; Roush, William R; Riley, Sean; Rosen, Hugh; Hodder, Peter; Lambeau, Gerard; Gelb, Michael H

    2016-08-01

    There is interest in developing inhibitors of human group III secreted phospholipase A2 (hGIII-sPLA2) because this enzyme plays a role in mast cell maturation. There are no potent inhibitors for hGIII-sPLA2 reported to date, so we adapted a fluorescence-based enzyme activity monitoring method to a high-throughput screening format. We opted to use an assay based on phospholipid substrate present in phospholipid vesicles since this matrix more closely resembles the natural substrate of hGIII-sPLA2, as opposed to phospholipid/detergent mixed micelles. The substrate is a phospholipid analogue containing BODIPY fluorophores dispersed as a minor component in vesicles of nonfluorescent phospholipids. Action of hGIII-sPLA2 liberates a free fatty acid from the phospholipid, leading to a reduction in quenching of the fluorophore and hence an increase in fluorescence. The assay uses optical detection in a 1536-well plate format with an excitation wavelength far away from the UV range so as to minimize false-positive library hits that result from quenching of the fluorescence. The high-throughput screen was successfully carried out on a library of 370,276 small molecules. Several hits were discovered, and data have been uploaded to PubChem. This study describes the first high-throughput optical screening assay for secreted phospholipase A2 inhibitors based on a phospholipid vesicle substrate. PMID:27146384

  9. Eutectic mixed monolayers in equilibrium with phospholipid-bilayers and triolein-liquid phase.

    PubMed Central

    Handa, T; Saito, H; Miyajima, K

    1993-01-01

    Triolein (TO) and phospholipids (egg yolk phosphatidylcholine, egg yolk phosphatidylethanolamine, and bovine brain phosphatidylserine) had low mutual solubilities and separated into the TO-liquid phase and phospholipid-bilayers. Spreading pressures of the TO-phospholipid mixture (i.e., surface pressures of the mixed monolayer in equilibrium with the phase-separating lipid mixture) at the air/saline interface were independent of the lipid composition. On the other hand, collapse pressures of the mixed monolayer of TO and phospholipid (i.e., surface pressures of the mixed monolayer in equilibrium with the TO-liquid phase) at the interface changed with the monolayer composition and were lower than the spreading pressure. The experimental data indicated the spreading and collapse pressures as offering a phase diagram for the presence of equilibrium between the mixed monolayer, the phospholipid-bilayers and the TO-liquid phase. The diagram showed that TO and the phospholipids were miscible in the mixed monolayer, forming an eutectic mixed monolayer. When the mixed monolayer initially had the eutectic composition, no collapse of the monolayer was detected until the surface pressure reached the value of the spreading pressure. No specific complex between TO and the phospholipid is required to explain the stability and collapse of the mixed monolayers. The bulk immiscibility of the lipids elucidated by the spreading pressure-measurements, immediately leads to the phase behaviors observed. PMID:8369406

  10. [sup 31]P NMR study of immobilized artificial membrane surfaces. Structure and dynamics of immobilized phospholipids

    SciTech Connect

    Qiu, X.; Pidgeon, C. )

    1993-11-25

    Chromatography surfaces were prepared by immobilizing a single-chain ether phospholipid at approximately a monolayer density on silica particles. The chromatography particles are denoted as [sup ether]IAM.PC[sup C10/C3], and they are stable to all solvents. The structure and dynamics of the interphase created by immobilizing phospholipids on silica particles were studied by [sup 31]P NMR methods. [sup ether]IAM.PC[sup C10/C3] spontaneously wets when suspended in both aqueous and organic solvents, and [sup 31]P NMR spectra were obtained in water, methanol, chloroform, acetonitrile, and acetone. [sup 31]P NMR spectra were subjected to line-shape analysis. From line-shape analysis, the correlation times for rapid internal motion ([tau]-PLL) and wobbling ([tau]-PRP) of the phospholipid headgroup were calculated for each solvent. Immobilized phospholipid headgroups comprising the IAM interfacial region undergo rapid reorientation similar to the case of the phospholipids forming liposome membranes with [tau]-PLL approximately 1 ns. Phospholipids in liposome membranes exhibit slower wobbling motion ([tau]-PRP approximately 1 ms) in the plane of the membrane. However, the immobilized phospholipids on [sup ether]IAM.PC[sup C10/C3] surfaces wobble with correlation times [tau]-PRP that depend on the solvent bathing the [sup ether]IAM.PC[sup C10/C3] surface. 41 refs., 9 figs., 2 tabs.

  11. A phospholipid transfer function of ER-mitochondria encounter structure revealed in vitro

    PubMed Central

    Kojima, Rieko; Endo, Toshiya; Tamura, Yasushi

    2016-01-01

    As phospholipids are synthesized mainly in the endoplasmic reticulum (ER) and mitochondrial inner membranes, how cells properly distribute specific phospholipids to diverse cellular membranes is a crucial problem for maintenance of organelle-specific phospholipid compositions. Although the ER-mitochondria encounter structure (ERMES) was proposed to facilitate phospholipid transfer between the ER and mitochondria, such a role of ERMES is still controversial and awaits experimental demonstration. Here we developed a novel in vitro assay system with isolated yeast membrane fractions to monitor phospholipid exchange between the ER and mitochondria. With this system, we found that phospholipid transport between the ER and mitochondria relies on membrane intactness, but not energy sources such as ATP, GTP or the membrane potential across the mitochondrial inner membrane. We further found that lack of the ERMES component impairs the phosphatidylserine transport from the ER to mitochondria, but not the phosphatidylethanolamine transport from mitochondria to the ER. This in vitro assay system thus offers a powerful tool to analyze the non-vesicular phospholipid transport between the ER and mitochondria. PMID:27469264

  12. Stable and fluid multilayer phospholipid-silica thin films: mimicking active multi-lamellar biological assemblies.

    PubMed

    Gupta, Gautam; Iyer, Srinivas; Leasure, Kara; Virdone, Nicole; Dattelbaum, Andrew M; Atanassov, Plamen B; López, Gabriel P

    2013-06-25

    Phospholipid-based nanomaterials are of interest in several applications including drug delivery, sensing, energy harvesting, and as model systems in basic research. However, a general challenge in creating functional hybrid biomaterials from phospholipid assemblies is their fragility, instability in air, insolubility in water, and the difficulty of integrating them into useful composites that retain or enhance the properties of interest, therefore limiting there use in integrated devices. We document the synthesis and characterization of highly ordered and stable phospholipid-silica thin films that resemble multilamellar architectures present in nature such as the myelin sheath. We have used a near room temperature chemical vapor deposition method to synthesize these robust functional materials. Highly ordered lipid films are exposed to vapors of silica precursor resulting in the formation of nanostructured hybrid assemblies. This process is simple, scalable, and offers advantages such as exclusion of ethanol and no (or minimal) need for exposure to mineral acids, which are generally required in conventional sol-gel synthesis strategies. The structure of the phospholipid-silica assemblies can be tuned to either lamellar or hexagonal organization depending on the synthesis conditions. The phospholipid-silica films exhibit long-term structural stability in air as well as when placed in aqueous solutions and maintain their fluidity under aqueous or humid conditions. This platform provides a model for robust implementation of phospholipid multilayers and a means toward future applications of functional phospholipid supramolecular assemblies in device integration. PMID:23706112

  13. Carbonothioate phospholipids as substrate for a spectrophotometric assay of phospholipase A2.

    PubMed

    Yu, L; Ternansky, R J; Crisologo, J F; Chang, J; Baker, B L; Coutts, S M

    1998-12-01

    A continuous spectrophotometric assay for phospholipase A2 (PLA2) was developed using novel carbonothioate phospholipids. These phospholipid analogues contain a carbonothioate bond in the place of the sn-2 ester of the natural substrates of phospholipase A2 and were synthesized in a one-pot two-step reaction. Phospholipase A2 from cobra venom (Naja naja atra) hydrolyzes carbonothioate phospholipids and liberates a free thiol, alkylmercaptan, which is reacted with 5,5'-dithiobis(2-nitrobenzoic acid) to yield a product that absorbs at 412 nm. The kinetic studies on PLA2 hydrolysis of carbonothioate phospholipids were carried out in pure phospholipid forms and in Triton X-100 mixed micelles. The hydrolysis of pure carbonothioate phospholipids exhibits an interfacial activation phenomenon. The hydrolysis of phospholipid in mixed Triton X-100 micelles follows classical Michaelis-Menten kinetics. In a mixed micellar system, the catalytic efficiency observed with this series of substrates is two orders of magnitude lower than that of the hydrolysis of the natural substrate dipalmitoyl phosphocholine. However, these substrates bind to the enzyme over 10 times tighter than does the natural substrate. Application of this carbonothioate assay to screen both reversible and irreversible enzyme inhibitors of phospholipase A2 is also demonstrated. PMID:9866705

  14. A phospholipid transfer function of ER-mitochondria encounter structure revealed in vitro.

    PubMed

    Kojima, Rieko; Endo, Toshiya; Tamura, Yasushi

    2016-01-01

    As phospholipids are synthesized mainly in the endoplasmic reticulum (ER) and mitochondrial inner membranes, how cells properly distribute specific phospholipids to diverse cellular membranes is a crucial problem for maintenance of organelle-specific phospholipid compositions. Although the ER-mitochondria encounter structure (ERMES) was proposed to facilitate phospholipid transfer between the ER and mitochondria, such a role of ERMES is still controversial and awaits experimental demonstration. Here we developed a novel in vitro assay system with isolated yeast membrane fractions to monitor phospholipid exchange between the ER and mitochondria. With this system, we found that phospholipid transport between the ER and mitochondria relies on membrane intactness, but not energy sources such as ATP, GTP or the membrane potential across the mitochondrial inner membrane. We further found that lack of the ERMES component impairs the phosphatidylserine transport from the ER to mitochondria, but not the phosphatidylethanolamine transport from mitochondria to the ER. This in vitro assay system thus offers a powerful tool to analyze the non-vesicular phospholipid transport between the ER and mitochondria. PMID:27469264

  15. Transfer of phospholipids from fat body to lipophorin in Rhodnius prolixus.

    PubMed

    Atella, G C; Gondim, K C; Masuda, H

    1992-01-01

    32P-Labeled fat bodies (32P-fat bodies) of Rhodnius prolixus females were incubated in the presence of non radioactive purified lipophorin and the release of radioactivity to the medium was analysed to answer the question of whether lipophorin is a reusable shuttle for phospholipids. The radioactivity found in the medium was associated with lipophorin phospholipids. When the 32P-fat bodies were incubated in the absence of lipophorin, only a small amount of radioactivity was released and it was not associated with lipophorin, indicating that there was no release of pre-labeled 32P-lipophorin by the tissue. Analysis of 32P-phospholipids transferred from fat bodies to the lipophorin particles by thin-layer chromatography revealed a predominance of phosphatidylethanolamine and phosphatidylcholine, with minor amounts of phosphatidylserine, phosphatidylinositol, and sphingomyelin. The transfer of phospholipids to lipophorin was linear with time up to 45 min and the process was inhibited at low temperature and by the metabolic inhibitors azide and fluoride. The transfer of phospholipids from the fat bodies to lipophorin was saturable with respect to the concentration of lipophorin, which was half-maximal at about 8 mg/ml. A directional movement of phospholipids from the fat body to lipophorin was observed. The net gain of phospholipids in 2 h of incubation with fat body was 8.54 nmol per insect, which corresponds to 6.69% of increase in the lipophorin phospholipid content. The rate of 32P-phospholipid transfer from fat body to lipophorin particles varied during the days after a blood meal increasing up to day 10 and then decreasing in parallel with the process of oogenesis. PMID:11488301

  16. Effects of analogues of ethanolamine and choline on phospholipid metabolism in rat hepatocytes

    PubMed Central

    Åkesson, Björn

    1977-01-01

    1. Analogues of ethanolamine and choline were incubated with different labelled precursors of phospholipids and isolated hepatocytes and the effects on phospholipid synthesis were studied. 2. 2-Aminopropan-1-ol and 2-aminobutan-1-ol were the most efficient inhibitors of [14C]ethanolamine incorporation into phospholipids, whereas the incorporation of [3H]choline was inhibited most extensively by NN-diethylethanolamine and NN-dimethylethanolamine. 3. When the analogues were incubated with [3H]glycerol and hepatocytes, the appearance of 3H in unnatural phospholipids indicated that they were incorporated, at least in part, via CDP-derivatives. The distribution of [3H]glycerol among molecular species of phospholipids containing 2-aminopropan-1-ol and 1-aminopropan-2-ol was the same as in phosphatidylethanolamine. In other phospholipid analogues the distribution of 3H was more similar to that in phosphatidylcholine. 4. NN-Diethylethanolamine stimulated both the conversion of phosphatidylethanolamine into phosphatidylcholine and the incorporation of [Me-14C]methionine into phospholipids. Other N-alkyl- or NN-dialkyl-ethanolamines also stimulated [14C]methionine incorporation, but inhibited the conversion of phosphatidylethanolamine into phosphatidylcholine. This indicates that phosphatidyl-NN-diethylethanolamine is a poor methyl acceptor, in contrast with other N-alkylated phosphatidylethanolamines. 5. These results on the regulation of phospholipid metabolism in intact cells are discussed with respect to the possible control points. They also provide guidelines for future experiments on the manipulation of phospholipid polar-headgroup composition in primary cultures of hepatocytes. PMID:606244

  17. Serum Phospholipid Docosahexaenoic Acid Is Inversely Associated with Arterial Stiffness in Metabolically Healthy Men

    PubMed Central

    Lee, Mi-Hyang; Kwon, Nayeon; Yoon, So Ra

    2016-01-01

    We hypothesized that lower proportion of serum phospholipid docosahexaenoic acid (DHA) is inversely associated with increased cardiovascular risk and vascular function in metabolically healthy men. To elucidate it, we first compared serum phospholipid free fatty acid (FA) compositions and cardiovascular risk parameters between healthy men (n = 499) and male patients with coronary artery disease (CAD, n = 111) (30-69 years) without metabolic syndrome, and then further-analyzed the association of serum phospholipid DHA composition with arterial stiffness expressed by brachial-ankle pulse wave velocity (ba-PWV) in metabolically healthy men. Basic parameters, lipid profiles, fasting glycemic status, adiponectin, high sensitivity C-reactive protein (hs-CRP) and LDL particle size, and serum phospholipid FA compositions were significantly different between the two subject groups. Serum phospholipid DHA was highly correlated with most of long-chain FAs. Metabolically healthy men were subdivided into tertile groups according to serum phospholipid DHA proportion: lower (< 2.061%), middle (2.061%-3.235%) and higher (> 3.235%). Fasting glucose, insulin resistance, hs-CRP and ba-PWVs were significantly higher and adiponectin and LDL particle size were significantly lower in the lower-DHA group than the higher-DHA group after adjusted for confounding factors. In metabolically healthy men, multiple stepwise regression analysis revealed that serum phospholipid DHA mainly contributed to arterial stiffness (β′-coefficients = -0.127, p = 0.006) together with age, systolic blood pressure, triglyceride (r = 0.548, p = 0.023). Lower proportion of serum phospholipid DHA was associated with increased cardiovascular risk and arterial stiffness in metabolically healthy men. It suggests that maintaining higher proportion of serum phospholipid DHA may be beneficial for reducing cardiovascular risk including arterial stiffness in metabolically healthy men. PMID:27482523

  18. Purification, characterization and substrate specificity of rabbit lung phospholipid transfer proteins.

    PubMed

    Tsao, F H; Tian, Q; Strickland, M S

    1992-05-01

    Three phospholipid transfer proteins, namely proteins I, II and III, were purified from the rabbit lung cytosolic fraction. The molecular masses of phospholipid transfer proteins I, II and III are 32 kilodaltons (kDa), 22 kDa and 32 kDa, respectively; their isoelectric point values are 6.5, 7.0 and 6.8, respectively. Phospholipid transfer proteins I and III transferred phosphatidylcholine (PC) and phosphatidylinositol (PI) from donor unilamellar liposomes to acceptor multilamellar liposomes; protein II transferred PC but not PI. All the three phospholipid transfer proteins transferred phosphatidylethanolamine poorly and showed no tendency to transfer triolein. The transfer of [14C]PC from unilamellar liposomes to multilamellar liposomes facilitated by each protein was affected differently by the presence of acidic phospholipids in the PC unilamellar liposomes. In an equal molar ratio of acidic phospholipid and PC, phosphatidylglycerol (PG) reduced the activities of proteins I and III by 70% (P = 0.0004 and 0.0032, respectively) whereas PI and phosphatidylserine (PS) had an insignificant effect. In contrast, the protein II activity was stimulated 2-3-times more by either PG (P = 0.0024), PI (P = 0.0006) or PS (P = 0.0038). In addition, protein II transferred dioleoylPC (DOPC) about 2-times more effectively than dipalmitoylPC (DPPC) (P = 0.0002), whereas proteins I and III transferred DPPC 20-40% more effectively than DOPC but this was statistically insignificant. The markedly different substrate specificities of the three lung phospholipid transfer proteins suggest that these proteins may play an important role in sorting intracellular membrane phospholipids, possibly including lung surfactant phospholipids. PMID:1596521

  19. Differences in Bone Quality between High versus Low Turnover Renal Osteodystrophy

    SciTech Connect

    Porter, Daniel S.; Pienkowski, David; Faugere, Marie-Claude; Malluche, Hartmut H.

    2012-01-01

    Abnormal bone turnover is common in chronic kidney disease (CKD), but its effects on bone quality remain unclear. This study sought to quantify the relationship between abnormal bone turnover and bone quality. Iliac crest bone biopsies were obtained from CKD-5 patients on dialysis with low (n=18) or high (n=17) turnover, and from volunteers (n=12) with normal turnover and normal kidney function. Histomorphometric methods were used to quantify the microstructural parameters; Fourier transform infrared spectroscopy and nanoindentation were used to quantify the material and mechanical properties in bone. Reduced mineral-to-matrix ratio, mineral crystal size, stiffness and hardness were observed in bone with high turnover compared to bone with normal or low turnover. Decreased cancellous bone volume and trabecular thickness were seen in bone with low turnover compared to bone with normal or high turnover. Bone quality, as defined by its microstructural, material, and mechanical properties, is related to bone turnover. These data suggest that turnover related alterations in bone quality may contribute to the known diminished mechanical competence of bone in CKD patients, albeit from different mechanisms for bone with high (material abnormality) vs. low (microstructural alteration) turnover. The present findings suggest that improved treatments for renal osteodystrophy should seek to avoid low or high bone turnover and aim for turnover rates as close to normal as possible.

  20. Relevance, Derogation and Permission

    NASA Astrophysics Data System (ADS)

    Stolpe, Audun

    We show that a recently developed theory of positive permission based on the notion of derogation is hampered by a triviality result that indicates a problem with the underlying full-meet contraction operation. We suggest a solution that presupposes a particular normal form for codes of norms, adapted from the theory of relevance through propositional letter sharing. We then establish a correspondence between contractions on sets of norms in input/output logic (derogations), and AGM-style contractions on sets of formulae, and use it as a bridge to migrate results on propositional relevance from the latter to the former idiom. Changing the concept accordingly we show that positive permission now incorporates a relevance requirement that wards off triviality.

  1. Effect of the nature of phospholipids on the degree of their interaction with isobornylphenol antioxidants

    NASA Astrophysics Data System (ADS)

    Marakulina, K. M.; Kramor, R. V.; Lukanina, Yu. K.; Plashchina, I. G.; Polyakov, A. V.; Fedorova, I. V.; Chukicheva, I. Yu.; Kutchin, A. V.; Shishkina, L. N.

    2016-02-01

    The parameters of complexation between natural phospholipids (lecithin, sphingomyelin, and cephalin) with antioxidants of a new class, isobornylphenols (IBPs), were determined by UV and IR spectroscopy. The self-organization of phospholipids (PLs) was studied depending on the structure of IBPs by dynamic light scattering. The nature of phospholipids and the structure of IBPs was found to produce a substantial effect both on the degree of complexation and on the size of PL aggregates in a nonpolar solvent. Based on the obtained data it was concluded that the structure of biological membranes mainly depends on the complexation of IBP with sphingomyelin.

  2. Investigating the protective properties of milk phospholipids against ultraviolet light exposure in a skin equivalent model

    NASA Astrophysics Data System (ADS)

    Russell, Ashley; Laubscher, Andrea; Jimenez-Flores, Rafael; Laiho, Lily H.

    2010-02-01

    Current research on bioactive molecules in milk has documented health advantages of bovine milk and its components. Milk Phospholipids, selected for this study, represent molecules with great potential benefit in human health and nutrition. In this study we used confocal reflectance and multiphoton microscopy to monitor changes in skin morphology upon skin exposure to ultraviolet light and evaluate the potential of milk phospholipids in preventing photodamage to skin equivalent models. The results suggest that milk phospholipids act upon skin cells in a protective manner against the effect of ultraviolet (UV) radiation. Similar results were obtained from MTT tissue viability assay and histology.

  3. Microfluidics fabrication of monodisperse biocompatible phospholipid vesicles for encapsulation and delivery of hydrophilic drug or active compound.

    PubMed

    Kong, Feng; Zhang, Xu; Hai, Mingtan

    2014-04-01

    We encapsulate the hydrophilic anti-cancer drug doxurubicin hydrochloride (DOX) with about 94% drug encapsulation efficiency, either alone or with nanomagnetite, in monodisperse biocompatible phospholipid vesicles. Glass capillary microfluidics is used to generate monodisperse water in oil in water (w/o/w) double-emulsion templates with a core-shell structure by using a mixture of liquid unsaturated phospholipids and powdered saturated phospholipid. This combination would overcome the low transition temperature of unsaturated powdered phospholipid and the solubility limitation of saturated phospholipid, as well as improving the fabrication of stable monodisperse phospholipid vesicles. The double-emulsion droplet is controlled from 50 to 200 μm according to different flow rates, and the final phospholipid vesicles are retained after a solvent removal step by dewetting. DOX-loaded phospholipid vesicles show sustained release compared with free DOX water solution. The in vitro cell viability of 100 μg/mL phospholipid vesicles on HeLa or MCF-7 cells after 24 h incubation at 310 K is above 90%, confirming the excellent biocompatibility of the phospholipid vesicles. These biocompatible phospholipid vesicles are promising oral drug delivery vehicles for biomedical applications and magnetic resonance imaging contrast agents for biomedical diagnosis. PMID:24552433

  4. Teacher Turnover: An Issue of Workgroup Racial Diversity

    ERIC Educational Resources Information Center

    Sohn, Kitae

    2009-01-01

    One neglected aspect of the teacher labor supply is a recent increase in the proportion of minority teachers. Using the Schools and Staffing Survey and the Teacher Follow-up Survey, one can estimate the relationship between workgroup racial diversity and the turnover of White teachers. This approach finds that young White teachers are more likely…

  5. An intrinsic mechanism of secreted protein aging and turnover

    PubMed Central

    Yang, Won Ho; Aziz, Peter V.; Heithoff, Douglas M.; Mahan, Michael J.; Smith, Jeffrey W.; Marth, Jamey D.

    2015-01-01

    The composition and functions of the secreted proteome are controlled by the life spans of different proteins. However, unlike intracellular protein fate, intrinsic factors determining secreted protein aging and turnover have not been identified and characterized. Almost all secreted proteins are posttranslationally modified with the covalent attachment of N-glycans. We have discovered an intrinsic mechanism of secreted protein aging and turnover linked to the stepwise elimination of saccharides attached to the termini of N-glycans. Endogenous glycosidases, including neuraminidase 1 (Neu1), neuraminidase 3 (Neu3), beta-galactosidase 1 (Glb1), and hexosaminidase B (HexB), possess hydrolytic activities that temporally remodel N-glycan structures, progressively exposing different saccharides with increased protein age. Subsequently, endocytic lectins with distinct binding specificities, including the Ashwell–Morell receptor, integrin αM, and macrophage mannose receptor, are engaged in N-glycan ligand recognition and the turnover of secreted proteins. Glycosidase inhibition and lectin deficiencies increased protein life spans and abundance, and the basal rate of N-glycan remodeling varied among distinct proteins, accounting for differences in their life spans. This intrinsic multifactorial mechanism of secreted protein aging and turnover contributes to health and the outcomes of disease. PMID:26489654

  6. Employees as Customers: Exploring Service Climate, Employee Patronage, and Turnover

    ERIC Educational Resources Information Center

    Abston, Kristie A.; Kupritz, Virginia W.

    2011-01-01

    The role of retail employees as customers was explored by quantitatively examining the influence of service climate and employee patronage on employee turnover intentions. Employees representing all shifts in two stores of a national retailer participated. Results indicated that employee patronage partially mediates the effects of service climate…

  7. Quantifying Assemblage Turnover and Species Contributions at Ecologic Boundaries

    PubMed Central

    Hayek, Lee-Ann C.; Wilson, Brent

    2013-01-01

    Not all boundaries, whether stratigraphical or geographical, are marked by species-level changes in community composition. For example, paleodata for some sites do not show readily discernible glacial-interglacial contrasts. Rather, the proportional abundances of species can vary subtly between glacials and interglacials. This paper presents a simple quantitative measure of assemblage turnover (assemblage turnover index, ATI) that uses changes in species' proportional abundances to identify intervals of community change. A second, functionally-related index (conditioned-on-boundary index, CoBI) identifies species contributions to the total assemblage turnover. With these measures we examine benthonic foraminiferal assemblages to assess glacial/interglacial contrasts at abyssal depths. Our results indicate that these measures, ATI and CoBI, have potential as sequence stratigraphic tools in abyssal depth deposits. Many peaks in the set of values of ATI coincide with terminations at the end of glaciations and delineate peak-bounded ATI intervals (PATIs) separated by boundaries that approximate to glacial terminations and to transgressions at neritic depths. These measures, however, can be used to evaluate the assemblage turnover and composition at any defined ecological or paleoecological boundary. The section used is from Ocean Drilling Program (OPD) Hole 994C, drilled on the Blake Ridge, offshore SE USA. PMID:24130679

  8. Organizational Career Growth, Affective Occupational Commitment and Turnover Intentions

    ERIC Educational Resources Information Center

    Weng, Qingxiong; McElroy, James C.

    2012-01-01

    Survey data, collected from the People's Republic of China, were used to test Weng's (2010) four facet model of career growth and to examine its effect on occupational commitment and turnover intentions. Weng conceptualized career growth as consisting of four factors: career goal progress, professional ability development, promotion speed, and…

  9. Principal Turnover: Upheaval and Uncertainty in Charter Schools?

    ERIC Educational Resources Information Center

    Ni, Yongmei; Sun, Min; Rorrer, Andrea

    2015-01-01

    Purpose: Informed by literature on labor market and school choice, this study aims to examine the dynamics of principal career movements in charter schools by comparing principal turnover rates and patterns between charter schools and traditional public schools. Research Methods/Approach: This study uses longitudinal data on Utah principals and…

  10. An Investigation of Chief Administrator Turnover in International Schools

    ERIC Educational Resources Information Center

    Benson, John

    2011-01-01

    This article explores chief administrator turnover in international schools. Quantitative and qualitative data from the 83 chief administrators who participated in the study suggests that the average tenure of an international school chief administrator is 3.7 years and that the main reason chief administrators leave international schools is…

  11. Relationships between Emotional Labor, Job Performance, and Turnover

    ERIC Educational Resources Information Center

    Goodwin, Robyn E.; Groth, Markus; Frenkel, Stephen J.

    2011-01-01

    The present study investigates the relationship between the emotional labor strategies surface acting and deep acting and organizational outcomes, specifically, employees' overall job performance and turnover. Call center employees from two large financial service organizations completed an online survey about their use of surface and deep acting.…

  12. Chinese Teachers' Work Stress and Their Turnover Intention

    ERIC Educational Resources Information Center

    Liu, Shujie; Onwuegbuzie, Anthony J.

    2012-01-01

    This survey study employed qualitative dominant mixed research to explore the sources of teacher stress in China and the possible reasons for Chinese teachers' turnover intention. The data were collected in Jilin Province of China, and 510 teachers participated in the survey. Quantitatively, 40.4% of the surveyed teachers reported that they…

  13. The Effects of Turnover: What We Know about Teacher Attrition

    ERIC Educational Resources Information Center

    DeAngelis, Karen

    2012-01-01

    School business officials are likely to know better than anyone else about the financial costs to districts and schools associated with teacher attrition. Perhaps less well-known, though, is what else has been learned about this issue in recent years--information that may affect how one thinks about teacher turnover. Here is some of that research:…

  14. The High Cost of Teacher Turnover. Policy Brief

    ERIC Educational Resources Information Center

    National Commission on Teaching and America's Future, 2007

    2007-01-01

    In 2007, the National Commission on Teaching and America's Future (NCTAF) completed an 18-month study of the costs of teacher turnover in five school districts. The selected districts varied in size, location, and demographics enabling exploration of how these variations affected costs. Costs of recruiting, hiring, processing, and training…

  15. Faculty Turnover: Discipline-Specific Attention Is Warranted

    ERIC Educational Resources Information Center

    Xu, Yonghong Jade

    2008-01-01

    This study investigated the importance of discipline variations in understanding faculty turnover behaviors. A representative sample of university faculty in Research and Doctoral universities was obtained from a national database. Faculty members, self-identified into a primary academic area, were grouped into eight discipline clusters according…

  16. Prediction of Military Turnover Using Intentions, Satisfaction, and Performance.

    ERIC Educational Resources Information Center

    Knapp, Deirdre J.; And Others

    Although researchers have examined the link between job attitudes and turnover, some studies claim that civilian samples may not be generalizable to military personnel. This paper addresses two central questions: (1) To what extent does job satisfaction, job performance, and reenlistment intentions predict reenlistment behavior?; (2) To what…

  17. Attitudes toward Money, Intrinsic Job Satisfaction, and Voluntary Turnover.

    ERIC Educational Resources Information Center

    Tang, Thomas Li-Ping; Tang, Theresa Li-Na

    A study was conducted to determine whether employees' attitudes toward money (money ethic endorsement) moderates the relationships between intrinsic job satisfaction on the one hand and thoughts of withdrawal and voluntary turnover on the other. Data were collected from workers in the Department of Mental Health and Mental Retardation in a…

  18. Turnover at the Top: Superintendent Vacancies and the Urban School

    ERIC Educational Resources Information Center

    Buchanan, Bruce

    2006-01-01

    The leadership turnover in America's largest school districts has increased so rapidly that the average urban superintendent tenure is only about two years. In fact, many urban superintendents are hired knowing that they will either be terminated or forced to resign in a short period of time. This cycle has created a class of superintendents who…

  19. Faculty Turnover: An Analysis by Rank, Gender, Ethnicity and Reason.

    ERIC Educational Resources Information Center

    Honeyman, David S., Jr.; Summers, Susan Robinson

    In spring 1992, a study was conducted to determine factors associated with the attrition of faculty at the University of Florida (UF) from fiscal year (FY) 1989 through FY 1990. Specifically, the study sought to determine the relative level of turnover at UF compared to other institutions, the demographics of and motives given by leaving faculty,…

  20. Sustaining Effective Practices in the Face of Principal Turnover

    ERIC Educational Resources Information Center

    Strickland-Cohen, M. Kathleen; McIntosh, Kent; Horner, Robert H.

    2014-01-01

    In the face of principal turnover, a common approach taken by staff is to simply wait until the new school year begins and hope that the new administrator will continue to support current programs. It is our experience that this passive strategy is not as helpful, because there are proactive approaches that are more likely to be successful. The…

  1. High Classroom Turnover: How Children Get Left Behind.

    ERIC Educational Resources Information Center

    Hartman, Chester

    This book chapter discusses the problem of transiency, or high classroom turnover, in education. Research shows that a disproportionate number of schools with predominantly low-income African American and Hispanic students have low stability, and that such students are much more likely than white, middle-income students to switch schools in the…

  2. Some Determinants of Employee Turnover in a Psychiatric Facility.

    ERIC Educational Resources Information Center

    Zautra, Alex J.; And Others

    1987-01-01

    Used research from illness-prevention and job-enrichment approaches to enhancing quality of work environments to create instruments assessing number of job stressors and level of task interest on psychiatric hospital units. Instruments successfully predicted employee turnover during one year. Job stress and interaction between job stress and task…

  3. Ectomycorrhizal fungal mycelia turnover in a longleaf pine forest.

    PubMed

    Hendricks, Joseph J; Mitchell, Robert J; Kuehn, Kevin A; Pecot, Stephen D

    2016-03-01

    Elucidation of the patterns and controls of carbon (C) flow and nitrogen (N) cycling in forests has been hindered by a poor understanding of ectomycorrhizal fungal mycelia (EFM) dynamics. In this study, EFM standing biomass (based on soil ergosterol concentrations), production (based on ergosterol accrual in ingrowth cores), and turnover rate (the quotient of annual production and average standing biomass estimates) were assessed in a 25-yr-old longleaf pine (Pinus palustris) plantation where C flow was manipulated by foliar scorching and N fertilization for 5 yr before study initiation. In the controls, EFM standing biomass was 30 ± 7 g m(-2) , production was 279 ± 63 g m(-2)  yr(-1) , and turnover rate was 10 ± 3 times yr(-1) . The scorched × fertilized treatment had significantly higher EFM standing biomass (38 ± 8 g m(-2) ), significantly lower production (205 ± 28 g m(-2)  yr(-1) ), and a trend of decreased turnover rate (6 ± 1 times yr(-1) ). The EFM turnover estimates, which are among the first reported for natural systems, indicate that EFM are a dynamic component of ecosystems, and that conventional assessments have probably underestimated the role of EFM in C flow and nutrient cycling. PMID:26537020

  4. 41 CFR 109-27.5002 - Stores inventory turnover ratio.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Stores inventory... PROCUREMENT 27-INVENTORY MANAGEMENT 27.50-Inventory Management Policies, Procedures, and Guidelines § 109-27.5002 Stores inventory turnover ratio. Comparison of investment in stores inventories to annual...

  5. Actin Turnover-Mediated Gravity Response in Maize Root Apices

    PubMed Central

    Mancuso, Stefano; Barlow, Peter W; Volkmann, Dieter

    2006-01-01

    The dynamic actin cytoskeleton has been proposed to be linked to gravity sensing in plants but the mechanistic understanding of these processes remains unknown. We have performed detailed pharmacological analyses of the role of the dynamic actin cytoskeleton in gravibending of maize (Zea mays) root apices. Depolymerization of actin filaments with two drugs having different mode of their actions, cytochalasin D and latrunculin B, stimulated root gravibending. By contrast, drug-induced stimulation of actin polymerization and inhibition of actin turnover, using two different agents phalloidin and jasplakinolide, compromised the root gravibending. Importantly, all these actin drugs inhibited root growth to similar extents suggesting that high actin turnover is essential for the gravity-related growth responses rather than for the general growth process. Both latrunculin B and cytochalasin D treatments inhibited root growth but restored gravibending of the decapped root apices, indicating that there is a strong potential for effective actin-mediated gravity sensing outside the cap. This elusive gravity sensing outside the root cap is dependent not only on the high rate of actin turnover but also on weakening of myosin activities, as general inhibition of myosin ATPases induced stimulation of gravibending of the decapped root apices. Collectively, these data provide evidence for the actin turnover-mediated gravity sensing outside the root cap. PMID:19521476

  6. Diagnosing turnover times of carbon in terrestrial ecosystems to address global climate co-variability and for model evaluation

    NASA Astrophysics Data System (ADS)

    Carvalhais, Nuno; Thurner, Martin; Forkel, Matthias; Beer, Christian; Reichstein, Markus

    2016-04-01

    formulations. Despite the challenges in underpinning the exact dynamics behind the observed relationships these findings highlight the relevance of the hydrological cycle in controlling the mean turnover times of carbon in terrestrial ecosystems. Overall we acknowledge that carbon turnover times are an emergent property that translates different aspects of ecosystem dynamics, which enable diagnosing ecosystem functioning as well as evaluating model behavior.

  7. OPTIMIZING MINIRHIZOTRON SAMPLE FREQUENCY FOR ESTIMATING FINE ROOT PRODUCTION AND TURNOVER

    EPA Science Inventory

    The most frequent reason for using minirhizotrons in natural ecosystems is the determination of fine root production and turnover. Our objective is to determine the optimum sampling frequency for estimating fine root production and turnover using data from evergreen (Pseudotsuga ...

  8. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces.

    PubMed

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-01-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems. PMID:26658474

  9. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    PubMed Central

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-01-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems. PMID:26658474

  10. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    NASA Astrophysics Data System (ADS)

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-12-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems.

  11. Blending Rigor and Relevance

    ERIC Educational Resources Information Center

    Siri, Diane K.; Zinner, Jane; Lezin, Nicole

    2011-01-01

    A collaborative at several sites across the state of California will offer evidence of how successful linked learning, which connects academics to real-world work, can be. This article presents examples that illustrate the powerful connections and linkages that are generated by combining academic rigor with the relevance of applying learning to…

  12. Is Information Still Relevant?

    ERIC Educational Resources Information Center

    Ma, Lia

    2013-01-01

    Introduction: The term "information" in information science does not share the characteristics of those of a nomenclature: it does not bear a generally accepted definition and it does not serve as the bases and assumptions for research studies. As the data deluge has arrived, is the concept of information still relevant for information…

  13. The Relevance of Literature.

    ERIC Educational Resources Information Center

    Dunham, L. L.

    1971-01-01

    The "legacy" of the humanities is discussed in terms of relevance, involvement, and other philosophical considerations. Reasons for studying foreign literature in language classes are developed in the article. Comment is also made on attitudes and ideas culled from the writings of Clifton Fadiman, Jean Paul Sartre, and James Baldwin. (RL)

  14. Reading, Writing and Relevance.

    ERIC Educational Resources Information Center

    Hoffman, Mary

    This monograph presents classroom activities that were designed to encourage children to read and write in a self-reliant and responsible manner. The activities were chosen for their relevance to the children involved and because the vocabulary involved was interesting, familiar, and worth remembering and using again. The topics are arranged in…

  15. Whole body and tissue cholesterol turnover in the baboon

    SciTech Connect

    Dell, R.B.; Mott, G.E.; Jackson, E.M.; Ramakrishnan, R.; Carey, K.D.; McGill, H.C. Jr.; Goodman, D.S.

    1985-03-01

    Cholesterol turnover was studied in four baboons by injecting (/sup 14/C)cholesterol 186 days and (/sup 3/H)cholesterol 4 days before necropsy, and fitting a two- or three-pool model to the resulting specific activity-time data. At necropsy, cholesterol mass and specific activity were determined for the total body and for many tissues. The principal aim of this study was to estimate the extent of cholesterol synthesis in the side pools of the model, by computing the amount of side pool synthesis needed to equal the measured total body cholesterol. Central pool synthesis varied from 61 to 89% of the total cholesterol production rate. Moreover, the finding that the measured total body cholesterol fell within the range obtained from the kinetic analysis by using reasonable assumptions, provides evidence for the physiological validity of the model. A second aim of this study was to explore cholesterol turnover in various tissues. A pool model predicts that rapidly turning over tissues will have higher specific activities at early times and lower specific activities at later times after injection of tracer relative to slowly turning over tissues, except where significant synthesis occurs. Results in all four baboons were similar. Turnover rates for the different tissues loosely fell into three groups which were turning over at fast, intermediate, and slow rates. Finally, the magnitude of variation of cholesterol specific activity was moderate for several distributed tissues (fat, muscle, arteries, and the alimentary tract), but was small for liver. Cholesterol turnover in serial biopsies of skin, muscle, and fat could, however, be fitted with a single pool to estimate tissue turnover rates.

  16. Hypoxic cell turnover in different solid tumor lines

    SciTech Connect

    Ljungkvist, Anna S.E. . E-mail: a.ljungkvist@rther.umcn.nl; Bussink, Johan; Kaanders, Johannes H.A.M.; Rijken, Paulus F.J.W.; Begg, Adrian C.; Raleigh, James A.; Kogel, Albert J. van der

    2005-07-15

    Purpose: Most solid tumors contain hypoxic cells, and the amount of tumor hypoxia has been shown to have a negative impact on the outcome of radiotherapy. The efficacy of combined modality treatments depends both on the sequence and timing of the treatments. Hypoxic cell turnover in tumors may be important for optimal scheduling of combined modality treatments, especially when hypoxic cell targeting is involved. Methods and Materials: Previously we have shown that a double bioreductive hypoxic marker assay could be used to detect changes of tumor hypoxia in relation to the tumor vasculature after carbogen and hydralazine treatments. This assay was used in the current study to establish the turnover rate of hypoxic cells in three different tumor models. The first hypoxic marker, pimonidazole, was administered at variable times before tumor harvest, and the second hypoxic marker, CCI-103F, was injected at a fixed time before harvest. Hypoxic cell turnover was defined as loss of pimonidazole (first marker) relative to CCI-103F (second marker). Results: The half-life of hypoxic cell turnover was 17 h in the murine C38 colon carcinoma line, 23 h and 49 h in the human xenograft lines MEC82 and SCCNij3, respectively. Within 24 h, loss of pimonidazole-stained areas in C38 and MEC82 occurred concurrent with the appearance of pimonidazole positive cell debris in necrotic regions. In C38 and MEC82, most of the hypoxic cells had disappeared after 48 h, whereas in SCCNij3, viable cells that had been labeled with pimonidazole were still observed after 5 days. Conclusions: The present study demonstrates that the double hypoxia marker assay can be used to study changes in both the proportion of hypoxic tumor cells and their lifespan at the same time. The present study shows that large differences in hypoxic cell turnover rates may exist among tumor lines, with half-lives ranging from 17-49 h.

  17. Therapeutic Outcomes of Pectoralis Major Muscle Turnover Flap in Mediastinitis

    PubMed Central

    Bagheri, Reza; Tashnizi, Mohammad Abbasi; Haghi, Seyed Ziaollah; Salehi, Maryam; Rajabnejad, Ata’ollah; Safa, Mohsen Hatami Ghale; Vejdani, Mohammad

    2015-01-01

    Background This study aimed to evaluate the therapeutic results and safety of pectoralis major muscle turnover flaps in the treatment of mediastinitis after coronary artery bypass grafting (CABG) procedures. Methods Data regarding 33 patients with post-CABG deep sternal wound infections (DSWIs) who underwent pectoralis major muscle turnover flap procedures in the Emam Reza and Ghaem Hospitals of Mashhad, Iran were reviewed in this study. For each patient, age, sex, hospital stay duration, remission, recurrence, and associated morbidity and mortality were evaluated. Results Of the 2,447 CABG procedures that were carried out during the time period encompassed by our study, DSWIs occurred in 61 patients (2.5%). Of these 61 patients, 33 patients (nine females [27.3%] and 24 males [72.7%]) with an average age of 63±4.54 years underwent pectoralis major muscle turnover flap placement. Symptoms of infection mainly occurred within the first 10 days after surgery (mean, 10.24±13.62 days). The most common risk factor for DSWIs was obesity (n=16, 48.4%) followed by diabetes mellitus (n=13, 39.4%). Bilateral and unilateral pectoralis major muscle turnover flaps were performed in 20 patients (60.6%) and 13 patients (39.4%), respectively. Complete remission was achieved in 25 patients (75.7%), with no recurrence in the follow-up period. Four patients (12.1%) needed reoperation. The mean hospitalization time was 11.69±6.516 days. Four patients (12.1%) died during the course of the study: three due to the postoperative complication of respiratory failure and one due to pulmonary thromboembolism. Conclusion Pectoralis major muscle turnover flaps are an optimal technique in the treatment of post-CABG mediastinitis. In addition to leading to favorable therapeutic results, this flap is associated with minimal morbidity and mortality, as well as a short hospitalization time. PMID:26290837

  18. Biophysical studies of cholesterol in unsaturated phospholipid model membranes

    NASA Astrophysics Data System (ADS)

    Williams, Justin Adam

    Cellular membranes contain a staggering diversity of lipids. The lipids are heterogeneously distributed to create regions, or domains, whose physical properties differ from the bulk membrane and play an essential role in modulating the function of resident proteins. Many basic questions pertaining to the formation of these lateral assemblies remain. This research employs model membranes of well-defined composition to focus on the potential role of polyunsaturated fatty acids (PUFAs) and their interaction with cholesterol (chol) in restructuring the membrane environment. Omega-3 (n-3) PUFAs are the main bioactive components of fish oil, whose consumption alleviates a variety of health problems by a molecular mechanism that is unclear. We hypothesize that the incorporation of PUFAs into membrane lipids and the effect they have on molecular organization may be, in part, responsible. Chol is a major constituent in the plasma membrane of mammals. It determines the arrangement and collective properties of neighboring lipids, driving the formation of domains via differential affinity for different lipids. The molecular organization of 1-[2H31]palmitoyl-2-eicosapentaenoylphosphatidylcholine (PEPC-d31) and 1-[2H31]palmitoyl-2-docosahexaenoylphosphatidylcholine (PDPC-d31) in membranes with sphingomyelin (SM) and chol (1:1:1 mol) was compared by solid-state 2H NMR spectroscopy. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids are the two major n-3 PUFAs found in fish oil, while PEPC-d31 and PDPC-d31 are phospholipids containing the respective PUFAs at the sn-2 position and a perdeuterated palmitic acid at the sn-1 position. Analysis of spectra recorded as a function of temperature indicates that in both cases, formation of PUFA-rich (less ordered) and SM-rich (more ordered) domains occurred. A surprisingly substantial proportion of PUFA was found to infiltrate the more ordered domain. There was almost twice as much DHA (65%) as EPA (30%). The implication is that n-3

  19. Examining the job search-turnover relationship: the role of embeddedness, job satisfaction, and available alternatives.

    PubMed

    Swider, Brian W; Boswell, Wendy R; Zimmerman, Ryan D

    2011-03-01

    This study examined factors that may help explain under what conditions employee job search effort may most strongly (or weakly) predict subsequent turnover. As predicted, the job search-turnover relationship was stronger when employees had lower levels of job embeddedness and job satisfaction and higher levels of available alternatives. These findings suggest that there may be a number of factors interacting to influence employees' turnover decisions, indicating greater complexity to the process than described in prominent sequential turnover models. PMID:21142342

  20. Cell cycle progression is an essential regulatory component of phospholipid metabolism and membrane homeostasis.

    PubMed

    Sanchez-Alvarez, Miguel; Zhang, Qifeng; Finger, Fabian; Wakelam, Michael J O; Bakal, Chris

    2015-09-01

    We show that phospholipid anabolism does not occur uniformly during the metazoan cell cycle. Transition to S-phase is required for optimal mobilization of lipid precursors, synthesis of specific phospholipid species and endoplasmic reticulum (ER) homeostasis. Average changes observed in whole-cell phospholipid composition, and total ER lipid content, upon stimulation of cell growth can be explained by the cell cycle distribution of the population. TORC1 promotes phospholipid anabolism by slowing S/G2 progression. The cell cycle stage-specific nature of lipid biogenesis is dependent on p53. We propose that coupling lipid metabolism to cell cycle progression is a means by which cells have evolved to coordinate proliferation with cell and organelle growth. PMID:26333836

  1. Forty five years with membrane phospholipids, phospholipases and lipid mediators: A historical perspective.

    PubMed

    Chap, Hugues

    2016-06-01

    Phospholipases play a key role in the metabolism of phospholipids and in cell signaling. They are also a very useful tool to explore phospholipid structure and metabolism as well as membrane organization. They are at the center of this review, covering a period starting in 1971 and focused on a number of subjects in which my colleagues and I have been involved. Those include determination of phospholipid asymmetry in the blood platelet membrane, biosynthesis of lysophosphatidic acid, biochemistry of platelet-activating factor, first attempts to define the role of phosphoinositides in cell signaling, and identification of novel digestive (phospho)lipases such as pancreatic lipase-related protein 2 (PLRP2) or phospholipase B. Besides recalling some of our contributions to those various fields, this review makes an appraisal of the impressive and often unexpected evolution of those various aspects of membrane phospholipids and lipid mediators. It is also the occasion to propose some new working hypotheses. PMID:27059515

  2. Effect of chlorphentermine on incorporation of (/sup 14/C)choline in the rat lung phospholipids

    SciTech Connect

    Gonmori, K.; Morita, T.; Mehendale, H.M.

    1986-03-01

    The effect of chlorphentermine (CP) treatment (50 mg/kg/day, per os (po)) on the incorporation of (/sup 14/C)choline into rat lung phospholipid was studied. Total phospholipid content was increased 2.0-fold and 1.7-fold after seven and /sup 14/ days, respectively, compared with the pair-fed rats. The incorporation of (14C)choline into phosphatidylcholine (PC) was significantly inhibited by either seven or 14 days of CP treatment. Nevertheless, the PC content was significantly increased by day 7 and stayed elevated at day 14 of CP treatment. Choline and phosphorylcholine contents were significantly decreased by the CP treatment. These results suggest that the higher accumulation of PC is due to inhibition of enzymes involved in the hydrolysis of phospholipids rather than to a stimulation of the phospholipid synthesis.

  3. Effect of oral treatment with pantethine on platelet and plasma phospholipids in IIa hyperlipoproteinemia.

    PubMed

    Prisco, D; Rogasi, P G; Matucci, M; Paniccia, R; Abbate, R; Gensini, G F; Neri Serneri, G G

    1987-03-01

    In a single-blind, crossover, completely randomized study, the effects of oral treatment with pantethine or placebo on fatty acid composition of plasma and platelet phospholipids were investigated in 10 IIa hyperlipoproteinemic patients. A significant decrease of total cholesterol and total phospholipids was observed both in plasma and in platelets after a twenty-eight-day treatment. In plasma, pantethine induced a decrease of the ratio sphingomyelin/phosphatidylcholine. Moreover, a relative increase of n3-polyunsaturated fatty acids both in plasma and in platelet phospholipids and a decrease of arachidonic acid in plasma phospholipids were observed. These results indicate that pantethine can affect plasma and platelet lipid composition with possibly favorable influences on the determinants of cell membrane fluidity. PMID:3551695

  4. Inhomogeneous translational diffusion of monoclonal antibodies on phospholipid Langmuir-Blodgett films.

    PubMed Central

    Wright, L L; Palmer, A G; Thompson, N L

    1988-01-01

    The translational mobility of fluorescent-labeled monoclonal antibodies specifically bound to supported phospholipid bilayers containing hapten-conjugated phospholipids has been measured as a function of the surface concentration of bound antibodies using fluorescence recovery after photobleaching. Fluorescence recovery curves are fit well by a model that assumes the presence of two populations of antibodies with different lateral diffusion coefficients. The larger diffusion coefficient equals 3.5 x 10(-9) cm2/s, the smaller diffusion coefficient ranges from 1.5 x 10(-9) cm2/s to 2.5 x 10(-10) cm2/s, and the fractional fluorescence recovery associated with the smaller coefficient increases from approximately 0 to approximately 0.7 with increasing concentration of bound antibody. These results suggest that complexes of haptenated phospholipids and antibodies in phospholipid Langmuir-Blodgett films form clusters or domains in a concentration-dependent fashion. PMID:3207834

  5. Superintendent Turnover in Kentucky. Summary. Issues & Answers. REL 2011-No. 113

    ERIC Educational Resources Information Center

    Johnson, Jerry; Huffman, Tyler; Madden, Karen; Shope, Shane

    2011-01-01

    This study examines superintendent turnover in Kentucky public school districts for 1998/99-2007/08, looking at how turnover varies by rural status, Appalachian and non-Appalachian region, and 2007/08 school district characteristics. Key findings include: (1) Kentucky school districts averaged one superintendent turnover during 1998/99-2007/08;…

  6. How Teacher Turnover Harms Student Achievement. NBER Working Paper No. 17176

    ERIC Educational Resources Information Center

    Ronfeldt, Matthew; Lankford, Hamilton; Loeb, Susanna; Wyckoff, James

    2011-01-01

    Researchers and policymakers often assume that teacher turnover harms student achievement, but recent evidence calls into question this assumption. Using a unique identification strategy that employs grade-level turnover and two classes of fixed-effects models, this study estimates the effects of teacher turnover on over 600,000 New York City 4th…

  7. Blind Spots: Small Rural Communities and High Turnover in the Superintendency

    ERIC Educational Resources Information Center

    Kamrath, Barry; Brunner, C. Cryss

    2014-01-01

    This article examines high superintendency turnover through rural community members' perceptions of such attrition in their districts. Findings indicate that community members perceived high turnover as negative and believed that turnover was created by financial pressures, rural community resistance to educational trends, and bias against…

  8. Factors Affecting Turnover among Family Child Care Providers: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Todd, Christine M., Deery-Schmitt, Deanna M.

    1996-01-01

    This study investigated 57 family child caregivers longitudinally to identify turnover precursors. Providers most likely to leave had more education, less training, and more stress than providers who stayed. Training and caring for one's own children indirectly affected turnover through job stress. Job satisfaction was unrelated to turnover. Job…

  9. Measuring Worker Turnover in Long-Term Care: Lessons from the Better Jobs Better Care Demonstration

    ERIC Educational Resources Information Center

    Piercy, Kathleen Walsh, Ed.; Barry, Theresa; Kemper, Peter; Brannon, S. Diane

    2008-01-01

    Purpose: Turnover among direct-care workers (DCWs) continues to be a challenge in long-term care. Both policy makers and provider organizations recognize this issue as a major concern and are designing efforts to reduce turnover among these workers. However, there is currently no standardized method of measuring turnover to define the scope of the…

  10. A Review of the Literature on Administrator Turnover: Why They Move on or Are Displaced.

    ERIC Educational Resources Information Center

    Shields, Bruce A.

    Employee turnover contributes to lost production, disrupts normal business practices, and is expensive. This literature review examines turnover of three administrator positions: the school superintendent, the executive director of nonprofit agencies, and the chief executive officer of for-profit corporations. The most cited reason for turnover of…

  11. When the Going Gets Tough: Direct, Buffering and Indirect Effects of Social Support on Turnover Intention

    ERIC Educational Resources Information Center

    Pomaki, Georgia; DeLongis, Anita; Frey, Daniela; Short, Kathy; Woehrle, Trish

    2010-01-01

    We examined the role of social support in turnover intention among new teachers. First, we tested and found evidence for a direct negative relationship between social support and turnover intention. Second, we tested the social support buffer hypothesis, and found that teachers with higher social support had lower turnover intention in the face of…

  12. Phospholipid mass is increased in fibroblasts bearing the Swedish amyloid precursor mutation.

    PubMed

    Murphy, Eric J; Huang, Hsueh-Meei; Cowburn, Richard F; Lannfelt, Lars; Gibson, Gary E

    2006-03-15

    Phospholipid changes occur in brain regions affected by Alzheimer disease (AD), including a marked reduction in plasmalogens, which could diminish brain function either by directly altering signaling events or by bulk membrane effects. However, model systems for studying the dynamics of lipid biosynthesis in AD are lacking. To determine if fibroblasts bearing the Swedish amyloid precursor protein (swAPP) mutation are a useful model to study the mechanism(s) associated with altered phospholipid biosynthesis in AD, we examined the steady-state phospholipid mass and composition of fibroblasts, including plasmalogens. We found a 15% increase in total phospholipid mass, accounted for by a 24% increase in the combined total of phosphatidylethanolamine and plasmanylethanolamine mass and a 19% increase in the combined total of phosphatidylcholine (PtdCho) and plasmanycholine (PakCho) mass in the swAPP mutant bearing fibroblasts. Cholesterol mass was unchanged in these cells. The changes in phospholipid mass did not alter the cellular molar composition of the phospholipids nor the cholesterol to phospholipid ratio. While plasmalogen mass was not altered, the ratio of choline plasmalogen (PlsCho) mass to PtdCho+PakCho mass was decreased 16% and there was a 14% reduction in the proportion of PlsCho as a percent of total phospholipids in the swAPP mutant bearing fibroblasts. This change in choline plasmalogen is consistent with the reported decreases in plasmalogen proportions in affected regions of AD brain, suggesting that these cells may serve as a useful model to determine the mechanism underlying changes in plasmalogen biosynthesis in AD brain. PMID:16464688

  13. A unique antioxidant activity of phosphatidylserine on iron-induced lipid peroxidation of phospholipid bilayers.

    PubMed

    Dacaranhe, C D; Terao, J

    2001-10-01

    The relationship between the antioxidant effect of acidic phospholipids, phosphatidic acid (PA), phosphatidylglycerol (PG) and phosphatidylserine (PS), on iron-induced lipid peroxidation of phospholipid bilayers and their abilities to bind iron ion was examined in egg yolk phosphatidylcholine large unilamellar vesicles (EYPC LUV). The effect of each acidic phospholipid added to the vesicles at 10 mol% was assessed by measuring phosphatidylcholine hydroperoxides (PC-OOH) and thiobarbituric acid-reactive substances. The addition of dipalmitoyl PS (DPPS) showed a significant inhibitory effect, although the other two acidic phospholipids, dipalmitoyl PA (DPPA) and dipalmitoyl PG (DPPG), did not exert the inhibition. Neither dipalmitoyl PC (DPPC) nor dipalmitoyl phophatidylethanolamine (DPPE) showed any remarkable inhibition on this system. None of the tested phospholipids affected the lipid peroxidation rate remarkably when the vesicles were exposed to a water-soluble radical generator. The iron-binding ability of each phospholipid was estimated on the basis of the amounts of iron recovered in the chloroform/methanol phase after separation of the vesicle solution to water/methanol and chloroform/methanol phases. EYPC LUV containing DPPS, DPPA, and DPPG had higher amounts of bound iron than those containing DPPC and DPPE, indicating that these three acidic phospholipids possess an iron-binding ability at a similar level. Nevertheless, only DPPS suppressed iron-dependent decomposition of PC-OOH significantly. Therefore, it is likely that these three acidic phospholipids possess a significant iron-binding ability, although this ability per se does not warrant them antioxidative activities. The ability to suppress the iron-dependent decomposition of PC-OOH may explain the unique antioxidant activity of PS. PMID:11768154

  14. Detergent solubilization of phospholipid vesicle. Effect of electric charge.

    PubMed Central

    Urbaneja, M A; Alonso, A; Gonzalez-Mañas, J M; Goñi, F M; Partearroyo, M A; Tribout, M; Paredes, S

    1990-01-01

    In order to explore the effect of electric charge on detergent solubilization of phospholipid bilayers, the interaction of nine electrically charged surfactants with neutral or electrically charged liposomes has been examined. The detergents belonged to the alkyl pyridinium, alkyl trimethylammonium or alkyl sulphate families. Large unilamellar liposomes formed by egg phosphatidylcholine plus or minus stearylamine or dicetyl phosphate were used. Solubilization was assessed as a decrease in light-scattering of the liposome suspensions. The results suggest that electrostatic forces do not play a significant role in the formation of mixed micelles and that hydrophobic interactions are by far the main forces involved in solubilization. In addition, from the study of thirty different liposome-surfactant systems, we have derived a series of empirical rules that may be useful in predicting the behaviour of untested surfactants: (i) the detergent concentration producing the onset of solubilization (Don) decreases as the alkyl chain length increases; the decrease follows a semi-logarithmic pattern in the case of alkyl pyridinium compounds; (ii) for surfactants with critical micellar concentrations (cmc) less than 6 x 10(-3) M, Don. is independent of the nature of the detergent and the bilayer composition; for detergents having cmc greater than 6 x 10(-3) M, Don. increases linearly with the cmc; and (iii) Don. varies linearly with the surfactant concentration that produces maximum solubilization. PMID:2400390

  15. Anisotropic metal growth on phospholipid nanodiscs via lipid bilayer expansion

    NASA Astrophysics Data System (ADS)

    Oertel, Jana; Keller, Adrian; Prinz, Julia; Schreiber, Benjamin; Hübner, René; Kerbusch, Jochen; Bald, Ilko; Fahmy, Karim

    2016-05-01

    Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the “outer shape” of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of ~10 nm diameter containing a lipid bilayer ~5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials.

  16. Probing Lipid Membrane Rafts (Microdomains) with Fluorescent Phospholipids

    NASA Astrophysics Data System (ADS)

    Gu, Yongwen; Mitchel, Drake

    2011-10-01

    Membrane rafts are enriched in sphingolipids and cholesterol, they exist in a more ordered state (the liquid-ordered phase; lo) than the bulk membrane (the liquid-disordered phase; ld). Ternary mixtures of palmitoyl-oleoyl-phosphocholine (POPC; 16:0,18:1 PC), sphingomyelin (SPM), and cholesterol (Chol) form membrane rafts over a wide range of molar ratios. We are examining the ability of two fluorescent probes, NBD linked to di-16:0 PE which partitions into the lo phase, and NBD linked to di-18:1 PE which partitions into the ld phase, to detect these two phases. We are also examining the effect of the highly polyunsaturated phospholipid stearoyl-docosahexanoyl-phosphocholine (SDPC; 18:0, 22:6 PC) on the size and stability of POPC/SPM/Chol membrane rafts. We report on the fluorescence lifetime and anisotropy decay dynamics of two fluorescent probes. Data were acquired via frequency-domain measurements from 5 to 250 MHz.

  17. VISUALIZATION AND ANALYSIS OF LPS DISTRIBUTION IN BINARY PHOSPHOLIPID BILAYERS

    PubMed Central

    Florencia, Henning María; Susana, Sanchez; Laura, Bakás

    2010-01-01

    Lipopolysaccharide (LPS) is an endotoxin released from the outer membrane of Gram negative bacteria during infections. It have been reported that LPS may play a rol in the outer membrane of bacteria similar to that of cholesterol in eukaryotic plasma membranes. In this article we compare the effect of introducing LPS or cholesterol in liposomes made of dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine on the solubilization process by Triton X-100. The results show that liposomes containing LPS or Cholesterol are more resistant to solubilization by Triton X-100 than the binary phospholipid mixtures at 4°C. The LPS distribution was analyzed on GUVs of DPPC:DOPC using FITC-LPS. Solid and liquid-crystalline domains were visualized labeling the GUVs with LAURDAN and GP images were acquired using a two-photon microscope. The images show a selective distribution of LPS in gel domains. Our results support the hypothesis that LPS could aggregate and concentrate selectively in biological membranes providing a mechanism to bring together several components of the LPS-sensing machinery. PMID:19324006

  18. Visualization and analysis of lipopolysaccharide distribution in binary phospholipid bilayers

    SciTech Connect

    Henning, Maria Florencia; Sanchez, Susana; Bakas, Laura

    2009-05-22

    Lipopolysaccharide (LPS) is an endotoxin released from the outer membrane of Gram-negative bacteria during infections. It have been reported that LPS may play a role in the outer membrane of bacteria similar to that of cholesterol in eukaryotic plasma membranes. In this article we compare the effect of introducing LPS or cholesterol in liposomes made of dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine on the solubilization process by Triton X-100. The results show that liposomes containing LPS or cholesterol are more resistant to solubilization by Triton X-100 than the binary phospholipid mixtures at 4 {sup o}C. The LPS distribution was analyzed on GUVs of DPPC:DOPC using FITC-LPS. Solid and liquid-crystalline domains were visualized labeling the GUVs with LAURDAN and GP images were acquired using a two-photon microscope. The images show a selective distribution of LPS in gel domains. Our results support the hypothesis that LPS could aggregate and concentrate selectively in biological membranes providing a mechanism to bring together several components of the LPS-sensing machinery.

  19. Nutritional Properties of Dietary Omega-3-Enriched Phospholipids

    PubMed Central

    Murru, Elisabetta; Carta, Gianfranca

    2013-01-01

    Dietary fatty acids regulate several physiological functions. However, to exert their properties, they have to be present in the diet in an optimal balance. Particular attention has been focused on tissue highly polyunsaturated fatty acids (HPUFAs) n-6/n-3 ratio, influenced by the type and the esterified form of dietary fatty acids. Dietary EPA and DHA when esterified to phospholipids (PLs) are more efficiently incorporated into tissue PLs and seem to possess peculiar properties through specific mechanism(s) of action, such as the capacity to affect endocannabinoid biosynthesis at much lower doses than EPA and DHA in triglyceride form, probably because of the above mentioned higher incorporation into tissue PLs. Downregulation of the endocannabinoid system seems to mediate the positive effects exerted by omega-3-enriched PLs on several parameters of metabolic syndrome. PLs are one of the major dietary forms of EPA and DHA we are exposed to with the everyday diet; therefore, it is not surprising that it guarantees an effective EPA and DHA nutritional activity. Future studies should address whether EPA and DHA in PL form are also more effective than other formulations in ameliorating other pathological conditions where n-3 HPUFAs seem to exert beneficial activities such as cancer and psychiatric disorders. PMID:23984423

  20. Lysophosphatidic acid synthesis and phospholipid metabolism in rat mast cells

    SciTech Connect

    Fagan, D.L.

    1986-01-01

    The role of lysophosphatidic acid in mast cell response to antigen was investigated using an isolated rat serosal mast cell model. The cells were incubated with monoclonal murine immunoglobulin E to the dinitrophenyl hapten and prelabeled with /sup 32/P-orthophosphate or /sup 3/H-fatty acids. Lysophosphatidic acid was isolated form cell extracts by 2-dimensional thin-layer chromatography, and the incorporated radioactivity was assessed by liquid scintillation counting. Lysophosphatidic acid labeling with /sup 32/P was increased 2-4 fold within 5 minutes after the addition of antigen or three other mast cell agonists. Functional group analyses unequivocally showed that the labeled compound was lysophosphatidic acid. Lysophosphatidic acid synthesis was dependent on the activity of diacylglycerol lipase, suggesting formation from monoacylglycerol. In addition, the studies of lysophosphatidic acid synthesis suggest that the addition of antigen to mast cells may initiate more than one route of phospholipid degradation and resynthesis. Whatever the origin of lysophosphatidic acid, the results of this study demonstrated that lysophosphatidic acid synthesis is stimulated by a variety of mast cell agonists. Dose-response, kinetic, and pharmacologic studies showed close concordance between histamine release and lysophosphatidic acid labeling responses. These observations provide strong evidence that lysophosphatidic acid plays an important role in mast cell activation.

  1. Fusion of Boar Sperm with Nanoliposomes Prepared from Synthetic Phospholipids.

    PubMed

    Kasimanickam, V R; Buhr, M M

    2016-08-01

    Liposomes are artificial membrane vesicles that can be used to test and model the functions and interactions of various biological membranes, or as a carrier system to deliver biologically active substances into the cells, or to incorporate lipids into the plasma membrane of target cells to modify membrane structure-function relationships. Sperm plasma membrane undergoes lipid modification during maturation in epididymis and during capacitation in the female reproductive tract to facilitate fertilization. Natural variation in the amounts and composition of lipids in the sperm plasma membrane may also contribute to the species-specific sperm sensitivities to handling and storage conditions. Boar sperm are notoriously susceptible to membrane damage and are resistant to compositional alteration by artificial liposomes. This study used flow cytometry to demonstrate stable incorporation of nanoliposomes prepared from a complex mixture of various phospholipids (phosphatidylcholine : phosphatidylethanolamine : sphingomyelin : phosphatidylserine : phosphatidylinositol) with high fusion efficiency. Over 90% of sperm rapidly took up fluorescently labelled liposomes and retained the lipids for at least 60 min, in a significant time- and concentration-dependent manner. This unique fusion efficacy could be used to alter sperm plasma membrane composition and hence membrane-based functional responses. PMID:27217373

  2. Phospholipid Composition of Membranes Directs Prions Down Alternative Aggregation Pathways

    PubMed Central

    Robinson, Philip J.; Pinheiro, Teresa J.T.

    2010-01-01

    Abstract Prion diseases are neurodegenerative disorders of the central nervous system that are associated with the misfolding of the prion protein (PrP). PrP is glycosylphosphatidylinositol-anchored, and therefore the hydrophobic membrane environment may influence the process of prion conversion. This study investigates how the morphology and mechanism of growth of prion aggregates on membranes are influenced by lipid composition. Atomic force microscopy is used to image the aggregation of prions on supported lipid bilayers composed of mixtures of the zwitterionic lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and the anionic lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS). Circular dichroism shows that PrP interactions with POPS membranes result in an increase in β-sheet structure, whereas interactions with POPC do not influence PrP structure. Prion aggregation is observed on both zwitterionic and anionic membranes, and the morphology of the aggregates formed is dependent on the anionic phospholipid content of the membrane. The aggregates that form on POPC membranes have uniform dimensions and do not disrupt the lipid bilayer. The presence of POPS results in larger aggregates with a distinctive sponge-like morphology that are disruptive to membranes. These data provide detailed information on the aggregation mechanism of PrP on membranes, which can be described by classic models of growth. PMID:20409471

  3. Fluorescently labeled pulmonary surfactant protein C in spread phospholipid monolayers.

    PubMed Central

    Nag, K; Perez-Gil, J; Cruz, A; Keough, K M

    1996-01-01

    Pulmonary surfactant, a lipid-protein complex, secreted into the fluid lining of lungs prevents alveolar collapse at low lung volumes. Pulmonary surfactant protein C (SP-C), an acylated, hydrophobic, alpha-helical peptide, enhances the surface activity of pulmonary surfactant lipids. Fluorescein-labeled SP-C (F-SP-C) (3, 6, 12 wt%) in dipalmitoylphosphatidylcholine (DPPC), and DPPC:dipalmitoylphosphatidylglycerol (DPPG) [DPPC:DPPG 7:3 mol/mol] in spread monolayers was studied by epifluorescence microscopy. Mass spectometry of F-SP-C indicated that the protein is partially deacylated and labeled with 1 mol fluorescein/1 mol protein. The protein partitioned into the fluid, or liquid expanded, phase. Increasing amounts of F-SP-C in DPPC or DPPC:DPPG monolayers decreased the size and total amounts of the condensed phase at all surface pressures. Calcium (1.6 mM) increased the amount of the condensed phase in monolayers of DPPC:DPPG but not of DPPC alone, and such monolayers were also perturbed by F-SP-C. The study indicates that SP-C perturbs the packing of neutral and anionic phospholipid monolayers even when the latter systems are condensed by calcium, indicating that interactions between SP-C and the lipids are predominantly hydrophobic in nature. Images FIGURE 2 FIGURE 4 FIGURE 7 PMID:8804608

  4. Observation of Iron Specific Interaction with a Charge Neutral Phospholipid

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Zhang, Honghu; Feng, Shuren; San Emeterio, Josue; Kuzmenko, Ivan; Nilsen-Hamilton, Marit; Mallapragada, Surya; Vaknin, David

    2015-03-01

    Using surface sensitive X-ray scattering and spectroscopic techniques we show that phosphatidyl choline (PC) head groups attract positively charged iron ions and complexes even at pH values that are lower than 3. DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) is a zwitterionic lipid typically used as a model system for cell membranes. Within a large pH range (3 -11), it carries a negative charge on the phosphate group and a positive charge on the quaternary ammonium cation, thus appears charge neutral. Further lowering the pH, i.e. adding a proton to the phosphate group, results in a positively charged headgroup. Surprisingly, we detect significant enrichment of iron at the interface of the DPPC monolayer and the aqueous subphase with the pH maintained at 3 or even lower. With a supposedly charge neutral or even positive surface, the observation of surface bound, charge positive iron ions or iron hydroxides is counter-intuitive and suggests iron-specific interaction with the phospholipid headgroup, which is not governed by electrostatic interaction. The effect of the integration of Mms6, a membrane protein that promotes the formation of magnetic nanocrystals, into the DPPC monolayer will also be discussed. Research supported by the U.S. Department of Energy under Contract No. DE-AC02-07CH11358 and DE-AC02-06CH11357.

  5. Isolation and Analysis of Phospholipids in Dairy Foods

    PubMed Central

    Pimentel, Lígia; Gomes, Ana; Pintado, Manuela

    2016-01-01

    The lipid fraction of milk is one of the most complex matrixes in foodstuffs due to the presence of a high number of moieties with different physical and chemical properties. Glycerolipids include glycerol and two fatty acids esterified in positions sn-1 and sn-2 with higher concentration of unsaturated fatty acids than in the triglyceride fraction of milk. Sphingolipids consist of a sphingoid base linked to a fatty acid across an amide bond. Their amphiphilic nature makes them suitable to be added into a variety of foods and recent investigations show that phospholipids, mainly phosphatidylserine and sphingomyelin, can exert antimicrobial, antiviral, and anticancer activities as well as positive effects in Alzheimer's disease, stress, and memory decline. Polar lipids can be found as natural constituents in the membranes of all living organisms with soybean and eggs as the principal industrial sources, yet they have low contents in phosphatidylserine and sphingomyelin. Animal products are rich sources of these compounds but since there are legal restrictions to avoid transmission of prions, milk and dairy products are gaining interest as alternative sources. This review summarizes the analysis of polar lipids in dairy products including sample preparation (extraction and fractionation/isolation) and analysis by GC or HPLC and the latest research works using ELSD, CAD, and MS detectors. PMID:27610267

  6. Anisotropic metal growth on phospholipid nanodiscs via lipid bilayer expansion.

    PubMed

    Oertel, Jana; Keller, Adrian; Prinz, Julia; Schreiber, Benjamin; Hübner, René; Kerbusch, Jochen; Bald, Ilko; Fahmy, Karim

    2016-01-01

    Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the "outer shape" of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of ~10 nm diameter containing a lipid bilayer ~5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials. PMID:27216789

  7. Plasmalogen phospholipids protect internodal myelin from oxidative damage.

    PubMed

    Luoma, Adrienne M; Kuo, Fonghsu; Cakici, Ozgur; Crowther, Michelle N; Denninger, Andrew R; Avila, Robin L; Brites, Pedro; Kirschner, Daniel A

    2015-07-01

    Reactive oxygen species (ROS) are implicated in a range of degenerative conditions, including aging, neurodegenerative diseases, and neurological disorders. Myelin is a lipid-rich multilamellar sheath that facilitates rapid nerve conduction in vertebrates. Given the high energetic demands and low antioxidant capacity of the cells that elaborate the sheaths, myelin is considered intrinsically vulnerable to oxidative damage, raising the question whether additional mechanisms prevent structural damage. We characterized the structural and biochemical basis of ROS-mediated myelin damage in murine tissues from both central nervous system (CNS) and peripheral nervous system (PNS). To determine whether ROS can cause structural damage to the internodal myelin, whole sciatic and optic nerves were incubated ex vivo with a hydroxyl radical-generating system consisting of copper (Cu), hydrogen peroxide (HP), and ortho-phenanthroline (OP). Quantitative assessment of unfixed tissue by X-ray diffraction revealed irreversible compaction of myelin membrane stacking in both sciatic and optic nerves. Incubation in the presence of the hydroxyl radical scavenger sodium formate prevented this damage, implicating hydroxyl radical species. Myelin membranes are particularly enriched in plasmalogens, a class of ether-linked phospholipids proposed to have antioxidant properties. Myelin in sciatic nerve from plasmalogen-deficient (Pex7 knockout) mice was significantly more vulnerable to Cu/OP/HP-mediated ROS-induced compaction than myelin from WT mice. Our results directly support the role of plasmalogens as endogenous antioxidants providing a defense that protects ROS-vulnerable myelin. PMID:25801291

  8. Characteristic responses of a phospholipid molecular layer to polyols.

    PubMed

    Nakata, Satoshi; Deguchi, Ayano; Seki, Yota; Furuta, Miyuki; Fukuhara, Koichi; Nishihara, Sadafumi; Inoue, Katsuya; Kumazawa, Noriyuki; Mashiko, Shun; Fujihira, Shota; Goto, Makiko; Denda, Mitsuhiro

    2015-12-01

    Polyols (sugar alcohols) are widely used in foods, pharmaceutical formulations and cosmetics, and therefore it is important to understand their effects on cell membranes and skin. To address this issue, we examined the effect of polyols (1,2-ethanediol (ethylene glycol), 1,3-butanediol, 1,2,3-propanetriol (glycerol), and 1,2,3,4-butanetetraol) on artificial membrane systems (liposomes, monolayers, or dry films) prepared from phospholipid (1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)). 1,2-Ethanediol and 1,3-butanediol had little effect on the size of the DMPC liposomes or the surface pressure (π)-surface area (A) isotherm of DMPC monolayers at an air-water interface, whereas 1,2,3-propanetriol or 1,2,3,4-butanetetraol increased both liposome size and surface pressure. Attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) and differential scanning calorimetry (DSC) were used to evaluate the interaction between DMPC and polyols. These experimental results suggest that the chemical structure of polyol plays an important role in the characteristic interaction between polyol and DMPC. PMID:26454550

  9. Active microrheology and simultaneous visualization of sheared phospholipid monolayers.

    PubMed

    Choi, S Q; Steltenkamp, S; Zasadzinski, J A; Squires, T M

    2011-01-01

    Two-dimensional films of surface-active agents-from phospholipids and proteins to nanoparticles and colloids-stabilize fluid interfaces, which are essential to the science, technology and engineering of everyday life. The 2D nature of interfaces present unique challenges and opportunities: coupling between the 2D films and the bulk fluids complicates the measurement of surface dynamic properties, but allows the interfacial microstructure to be directly visualized during deformation. Here we present a novel technique that combines active microrheology with fluorescence microscopy to visualize fluid interfaces as they deform under applied stress, allowing structure and rheology to be correlated on the micron-scale in monolayer films. We show that even simple, single-component lipid monolayers can exhibit viscoelasticity, history dependence, a yield stress and hours-long time scales for elastic recoil and aging. Simultaneous visualization of the monolayer under stress shows that the rich dynamical response results from the cooperative dynamics and deformation of liquid-crystalline domains and their boundaries. PMID:21587229

  10. Active microrheology and simultaneous visualization of sheared phospholipid monolayers

    PubMed Central

    Choi, S.Q.; Steltenkamp, S.; Zasadzinski, J.A.; Squires, T.M.

    2011-01-01

    Two-dimensional films of surface-active agents—from phospholipids and proteins to nanoparticles and colloids—stabilize fluid interfaces, which are essential to the science, technology and engineering of everyday life. The 2D nature of interfaces present unique challenges and opportunities: coupling between the 2D films and the bulk fluids complicates the measurement of surface dynamic properties, but allows the interfacial microstructure to be directly visualized during deformation. Here we present a novel technique that combines active microrheology with fluorescence microscopy to visualize fluid interfaces as they deform under applied stress, allowing structure and rheology to be correlated on the micron-scale in monolayer films. We show that even simple, single-component lipid monolayers can exhibit viscoelasticity, history dependence, a yield stress and hours-long time scales for elastic recoil and aging. Simultaneous visualization of the monolayer under stress shows that the rich dynamical response results from the cooperative dynamics and deformation of liquid-crystalline domains and their boundaries. PMID:21587229

  11. Metal ion binding to phospholipid bilayers evaluated by microaffinity chromatography.

    PubMed

    Ross, Eric E; Hoag, Christian; Pfeifer, Zach; Lundeen, Christopher; Owens, Sarah

    2016-06-17

    Group I and II ion binding to phospholipid membranes was evaluated by affinity chromatography utilizing a new stationary phase system based on lipid bilayers supported within large-pore particles composed of Stöber silica spheres. Using an inductively coupled plasma mass spectrometer for detection, robust determination of binding selectivity within group II ions is achieved with capillary columns containing nanomole quantities of lipid and using picomoles of metal analyte. Columns with a unique lipid formulation can be prepared within three hours using a solvent-casting assembly method. The observable thermotropic phase behavior of dipalmitoylphosphatidylcholine has a significant effect on alkaline metal binding and demonstrates the dynamic nature of the supported bilayers. Of the group I ions, only lithium exhibits retention with neutral phosphatidylcholine bilayer stationary phases. A comparison of Stöber-based supports with two commercially available large-pore silicas reveals the effect that particle structure has on analyte accessibility to the bilayer surface as evaluated by retention per supported lipid mass. PMID:27189434

  12. Isolation and Analysis of Phospholipids in Dairy Foods.

    PubMed

    Pimentel, Lígia; Gomes, Ana; Pintado, Manuela; Rodríguez-Alcalá, Luis Miguel

    2016-01-01

    The lipid fraction of milk is one of the most complex matrixes in foodstuffs due to the presence of a high number of moieties with different physical and chemical properties. Glycerolipids include glycerol and two fatty acids esterified in positions sn-1 and sn-2 with higher concentration of unsaturated fatty acids than in the triglyceride fraction of milk. Sphingolipids consist of a sphingoid base linked to a fatty acid across an amide bond. Their amphiphilic nature makes them suitable to be added into a variety of foods and recent investigations show that phospholipids, mainly phosphatidylserine and sphingomyelin, can exert antimicrobial, antiviral, and anticancer activities as well as positive effects in Alzheimer's disease, stress, and memory decline. Polar lipids can be found as natural constituents in the membranes of all living organisms with soybean and eggs as the principal industrial sources, yet they have low contents in phosphatidylserine and sphingomyelin. Animal products are rich sources of these compounds but since there are legal restrictions to avoid transmission of prions, milk and dairy products are gaining interest as alternative sources. This review summarizes the analysis of polar lipids in dairy products including sample preparation (extraction and fractionation/isolation) and analysis by GC or HPLC and the latest research works using ELSD, CAD, and MS detectors. PMID:27610267

  13. sup 31 Phosphorus NMR studies of renal membrane phospholipids

    SciTech Connect

    Boylan, J.G.

    1988-01-01

    A research program was undertaken in order to study the effects of toxin-induced acute renal failure and streptozotozin-induced diabetes mellitus on the organization and motion of phospholipids in kidney membranes. The method of study included {sup 31}P NMR and computer simulated lineshape analyses and apparent lipid diffusion rate measurements. These were performed with selected tissue samples and disease models, and the results were compared with those of healthy renal tissues in order to identify changes associated with the diseased state. A new selective-excitation NMR pulse sequence was developed in which a portion of the lipid molecules were excited with a series of short equally-spaced RF pulses. As the position of the molecules changed on the membrane by lateral diffusion, the shape of the hole was seen to change. Experimental spectra were compared with calculated lineshapes in order to obtain estimates of useful molecular parameters including relation times and lateral lipid diffusion rates. The lineshape calculations were based on a solution to the Bloch equations for complex magnetization components with exchange terms added for diffusion.

  14. In vivo phospholipid biosynthesis in cotton cotyledons during glyoxysome enlargement

    SciTech Connect

    Chapman, K.D.; Trelease, R.N. )

    1990-05-01

    The surface are of cottonseed glyoxysomes increases about 4 fold within 36 h after imbibition. Membrane phospholipid must become available to glyoxysomes to accommodate expansion. Incubation of cotyledons (18-h-old) in 14C-choline (1 h) resulted in at least 85% recovery of 14C-phosphatidylcholine (PC) in membranes comigrating on sucrose gradients (20-59% w/w) with antimycin A-insensitive cytochrome c reductase (CCR) activity and choline- and ethanolaminephosphotransferase (CPT and EPT) activities (ER at about 24% w/w sucrose). Chase experiments with 3.4 M choline chloride for 2, 12, or 24 h led to increasing proportions of 14C-PC (36% after 24 h) recovery in mitochondria. No transfer of 14C-PC to enlarging glyoxysomes was detected. Incubations in 14C-ethanolamine yielded ER labeling after only 30 min. 14C-PE chased into mitochondria membranes more rapidly than PC (45% after 12 h), and no 14C-PE chased into glyoxysome membranes. Evidence for synthesis of 14C-PC from 14C-PE was found after 12 h chase with 1 M ethanolamine hydrochloride. Our results indicate that ER is the primary site of PC and PE synthesis in vivo and that ER contributes newly synthesized PC and PE to mitochondrial membranes but not to expanding glyoxysomal membranes. This is different from membrane biogenesis of glyoxysomes proliferating in castor bean endosperm.

  15. BROADBAND ATTENUATION MEASUREMENTS OF PHOSPHOLIPID-SHELLED ULTRASOUND CONTRAST AGENTS

    PubMed Central

    Raymond, Jason L.; Haworth, Kevin J.; Bader, Kenneth B.; Radhakrishnan, Kirthi; Griffin, Joseph K.; Huang, Shao-Ling; McPherson, David D.; Holland, Christy K.

    2014-01-01

    The aim of this study was to characterize the frequency-dependent acoustic attenuation of three phospholipid-shelled ultrasound contrast agents (UCAs): Definity, MicroMarker and echogenic liposomes. A broadband through-transmission technique allowed for measurement over 2 to 25 MHz with a single pair of transducers. Viscoelastic shell parameters of the UCAs were estimated using a linearized model developed by N. de Jong, L. Hoff, T. Skotland and N. Bom (Ultrasonics 1992; 30:95–103). The effect of diluent on the attenuation of these UCA suspensions was evaluated by performing attenuation measurements in 0.5% (w/v) bovine serum albumin and whole blood. Changes in attenuation and shell parameters of the UCAs were investigated at room temperature (25°C) and physiologic temperature (37°C). The attenuation of the UCAs diluted in 0.5% (w/v) bovine serum albumin was found to be identical to the attenuation of UCAs in whole blood. For each UCA, attenuation was higher at 37°C than at 25°C, underscoring the importance of conducting characterization studies at physiologic temperature. Echogenic liposomes exhibited a larger increase in attenuation at 37°C versus 25°C than either Definity or MicroMarker. PMID:24262056

  16. Anisotropic metal growth on phospholipid nanodiscs via lipid bilayer expansion

    PubMed Central

    Oertel, Jana; Keller, Adrian; Prinz, Julia; Schreiber, Benjamin; Hübner, René; Kerbusch, Jochen; Bald, Ilko; Fahmy, Karim

    2016-01-01

    Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the “outer shape” of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of ~10 nm diameter containing a lipid bilayer ~5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials. PMID:27216789

  17. Incorporation of peptides in phospholipid aggregates using ultrasound.

    PubMed

    Silva, Raquel; Little, Collin; Ferreira, Helena; Cavaco-Paulo, Artur

    2008-09-01

    This study presents the highlights of ultrasonic effects on peptides incorporated on phospholipid aggregates (liposomes). These liposomes or vesicles are known as transport agents in skin drug delivery and for hair treatment. They might be a good model to deliver larger peptides into hair to restore fibre strength after hair coloration, modelling, permanent wave and/or straightening. The preparation of liposomes 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) with peptides (LLLLK LLLLK LLLLK LLLLK; LLLLL LCLCL LLKAK AK) was made by the thin film hydration method. The LUVs (uni-lamellar vesicles) were obtained by sonication, applying different experimental conditions, such as depth (mm) and power intensity (%). Photon-correlation spectroscopy (PCS) and electronic microscopy (EM) results confirmed that the incorporation of these peptides, with different sequence of amino acids, presented differences on the diameter, zeta-potential of membrane surface and shape of liposomes. The liposomes that included peptide LLLLK LLLLK LLLLK LLLLK present an increased in zeta-potential values after using ultrasound and an "amorphous" aspect. Conversely, the liposomes that incorporated the peptide LLLLL LCLCL LLKAK AK presented a define shape (rod shape) and the potential surface of liposome did not change significantly by the use of ultrasound. PMID:18467154

  18. Analytical Characterization of the Role of Phospholipids in Platelet Adhesion and Secretion

    PubMed Central

    2015-01-01

    The cellular phospholipid membrane plays an important role in cell function and cell–cell communication, but its biocomplexity and dynamic nature presents a challenge for examining cellular uptake of phospholipids and the resultant effects on cell function. Platelets, small anuclear circulating cell bodies that influence a wide variety of physiological functions through their dynamic secretory and adhesion behavior, present an ideal platform for exploring the effects of exogenous phospholipids on membrane phospholipid content and cell function. In this work, a broad range of platelet functions are quantitatively assessed by leveraging a variety of analytical chemistry techniques, including ultraperformance liquid chromatography–tandem electrospray ionization mass spectrometry (UPLC–MS/MS), vasculature-mimicking microfluidic analysis, and single cell carbon-fiber microelectrode amperometry (CFMA). The relative enrichments of phosphatidylserine (PS) and phosphatidylethanolamine (PE) were characterized with UPLC–MS/MS, and the effects of the enrichment of these two phospholipids on both platelet secretory behavior and adhesion were examined. Results show that, in fact, both PS and PE influence platelet adhesion and secretion. PS was enriched dramatically and decreased platelet adhesion as well as secretion from δ-, α-, and lysosomal granules. PE enrichment was moderate and increased secretion from platelet lysosomes. These insights illuminate the critical connection between membrane phospholipid character and platelet behavior, and both the methods and results presented herein are likely translatable to other mammalian cell systems. PMID:25439269

  19. Effect of phospholipids on the structure of Triatoma infestans lipophorin studied by fluorescence methods.

    PubMed

    Rimoldi, O J; Garda, H A; Brenner, R R

    1996-10-01

    To study the role of phospholipids in the lipophorin structure, they were removed by phospholipase A2 treatment. Fluorescence lifetimes and accessibility to acrylamide quenching of different diphenylhexatrienyl derivatives, which were used as analogues of the different lipid components, indicate a surface localization of phospholipids and a distribution of diacylglycerols between the core and the surface, the surface fraction being increased by the phospholipase A2 treatment. The rotational behavior of these probes, studied by differential polarized phase fluorescence, indicates a high lipid order not only in the surface layer where phospholipids are located, but also in the core occupied by diacylglycerols and hydrocarbons. Phospholipid depletion increases the order only in the external region of the surface layer. Energy transfer from apolipoprotein tryptophan residues to several fluorescent acceptors indicates that phospholipid depletion produces a re-accommodation of the apoproteins. A decreased mobility of the water in the interfacial region is also produced by the phospholipase A2 treatment as it is reported by the fluorescence of 6-lauroyl-2-dimethylaminonaphthalene. This work shows that phospholipase A2 treatment of T. infestans lipophorin results in stable particles with an increased diacylglycerol to phospholipid ratio in the surface lipid layer. The modified particles are possibly stabilized by a conformational change in the apolipoproteins. PMID:8906590

  20. Lipidomic analysis of fibroblasts from Zellweger spectrum disorder patients identifies disease-specific phospholipid ratios.

    PubMed

    Herzog, Katharina; Pras-Raves, Mia L; Vervaart, Martin A T; Luyf, Angela C M; van Kampen, Antoine H C; Wanders, Ronald J A; Waterham, Hans R; Vaz, Frédéric M

    2016-08-01

    Peroxisomes are subcellular organelles involved in various metabolic processes, including fatty acid and phospholipid homeostasis. The Zellweger spectrum disorders (ZSDs) represent a group of diseases caused by a defect in the biogenesis of peroxisomes. Accordingly, cells from ZSD patients are expected to have an altered composition of fatty acids and phospholipids. Using an LC/MS-based lipidomics approach, we show that the phospholipid composition is characteristically altered in cultured primary skin fibroblasts from ZSD patients when compared with healthy controls. We observed a marked overall increase of phospholipid species containing very long-chain fatty acids, and a decrease of phospholipid species with shorter fatty acid species in ZSD patient fibroblasts. In addition, we detected a distinct phosphatidylcholine profile in ZSD patients with a severe and mild phenotype when compared with control cells. Based on our data, we present a set of specific phospholipid ratios for fibroblasts that clearly discriminate between mild and severe ZSD patients, and those from healthy controls. Our findings will aid in the diagnosis and prognosis of ZSD patients, including an increasing number of mild patients in whom hardly any abnormalities are observed in biochemical parameters commonly used for diagnosis. PMID:27284103