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At least 307 records · Page 17Linked to original sources
PubMed1993

Phosphorylation of the Na,K-ATPase by Ca,phospholipid-dependent and cAMP-dependent protein kinases. Mapping of the region phosphorylated by Ca,phospholipid-dependent protein kinase.

Ca,phospholipid-dependent (PKC) and cAMP-dependent (PKA) protein kinases phosphorylate the alpha-subunit of the Na,K-ATPase from duck salt gland with the incorporation of 0.3 and 0.5 mol 32P/mol of alpha-subunit, respectively. PKA (in contrast to PKC) phosphorylates the alpha-subunit only in the presence of detergents. Limited tryptic digestion of the Na,K-ATPase phosphorylated by PKC demonstrates that 32P is incorporated into the N-terminal 41-kDa fragment of the alpha-subunit. Selective chymotrypsin cleavage of phosphorylated enzyme yields a 35-kDa radioactive fragment derived from the central region of the alpha-subunit molecule. These findings suggest that PKC phosphorylates the alpha-subunit of the Na,K-ATPase within the region restricted by C3 and T1 cleavage sites.

Animals↗
PubMed1983

Theoretical conformational analysis of phospholipids. I. Study of the interactions between phospholipid molecules by use of semi-empirical methods with the explicit introduction of polar headgroup interactions.

We present a theoretical conformational analysis of a system composed of seven dipalmitoylphosphatidylethanolamine molecules in interaction. The combined use of classical semi-empirical methods for the polar headgroup region with mechanical statistical calculations for the aliphatic chains permits the evaluation of the free energy for a phospholipids molecule. The free energy variation in function of the mean intermolecular interchain distance gives information about the main lipid bilayer phase transition. It appears, however, necessary to take into account the hydration of the polar headgroups.

Calorimetry↗
PubMed1983

Theoretical conformational analysis of phospholipids. II. Role of hydration in the gel to liquid crystal transition of phospholipids.

To obtain a satisfactory agreement between computed transition temperatures and those determined experimentally, we introduce explicitly water molecules which hydrate the polar headgroup of dipalmitoylphosphatidylethanolamine molecules. The calculated free energy curves as a function of the intermolecular interchain distance and the degree of hydration of the polar groups permit the determination of the transition of the phospholipid system from the gel to the liquid crystalline phase. The detailed structure of the hydration shell is defined using the supermolecular approach.

Calorimetry↗
PubMed1991

Binding and mobility of anti-dinitrophenyl monoclonal antibodies on fluid-like, Langmuir-Blodgett phospholipid monolayers containing dinitrophenyl-conjugated phospholipids.

The association of a fluorescently labelled anti-dinitrophenyl monoclonal antibody (ANO2) with Langmuir-Blodgett monolayers composed of three different binary mixtures of phosphatidylcholine and dinitrophenyl-conjugated phosphatidylethanolamine has been characterized. Quantitative fluorescence microscopy measurements demonstrated that measurable amounts of antibodies bound to the monolayers only at high molar fractions of dinitrophenyl-conjugated lipid (greater than or equal to 5 mol%). Fluorescence pattern photobleaching recovery measurements showed that the apparent translational diffusion coefficients and mobile fractions of a fluorescent lipid were high for all monolayer compositions and that the antibody translational mobility was measurable but slow and depended on the two-dimensional antibody density. The results demonstrate that the ANO2-binding characteristics of Langmuir-Blodgett monolayers containing dinitrophenyl-conjugated phospholipids are substantially different from those of similar model systems but that the ANO2 antibodies, when bound, display similar diffusive behavior.

Antibodies, Monoclonal↗
PubMed1988

Electrical oscillation and fluctuation in phospholipid membranes. Phospholipids can form a channel without protein.

Fluctuations and/or step-wise changes in membrane potential and electrical current were observed in bilayer membranes of dioleoylphosphatidylcholine (DOPC) in the absence of any channel protein. The DOPC membranes consisted of three types: black lipid membranes, pipette-clamp membranes and lipid membranes transferred to porous filter paper by conventional Langmuir-Blodgett techniques. This finding is significant since phospholipids are the main constituents of biomembranes. Lipid molecules with a cis double bond in their carbon skeleton are suggested to be important in the gating or excitation of biomembranes.

Electric Conductivity↗
PubMed1985

Fluorimetric detection of phospholipid vesicles bound to planar phospholipid membranes.

The first step in the fusion of two phospholipid membranes culminates in the aggregation of the two lipid bilayers. We have used a custom-built fluorimeter to detect multilamellar vesicles (liposomes) containing the fluorescent dye, 6-carboxyfluorescein (6-CF), bound to a planar lipid bilayer (BLM). Liposomes were added to one side of the BLM, and unbound vesicles were perfused out. This left a residual fluorescence from the BLM, but only when the membranes contained anionic lipids, and then only when millimolar levels of calcium were present. This residual fluorescence was consistently detected only when calcium was included in the buffer during the perfusion. This residual fluorescence originated from liposomes bound to the BLM. Breaking the BLM or lysing the adsorbed vesicles with distilled water abolished it. free 6-CF and/or calcium in the absence of liposomes resulted in no residual fluorescence. No residual fluorescence was detected when both the liposomes and the BLM were composed entirely of zwitterionic lipids. This was found to result from the insensitivity of the fluorimeter to a small number of liposomes adsorbed to the BLM. For this system, we conclude that calcium is necessary for both the initiation and maintenance of the state in which the vesicle membrane is bound to the planar bilayer when the membranes contain negatively charged lipids. This attachment is stronger than the interaction between zwitterionic membranes.

Fluoresceins↗
PubMed1996

Evidence for phospholipid bilayer formation in solid lipid nanoparticles formulated with phospholipid and triglyceride.

PURPOSE: Solid lipid nanoparticles (SLN) are comprised of a high-melting point triglyceride (TG) core with a phospholipid (PL) coating. This study has investigated the possible formation of multiple PL bilayers on the TG core of SLN's as a function of increasing the PL:TG molar ratio. METHODS: Trilaurin (TL) was used as the SLN core. Dipalmitoylphos-phatdylcholine (DPPC) or a mixture of DPPC and dimyristoylphosphatidylglycerol (DMPG) were used to produce neutral and negatively charged SLN's. The volume of aqueous phase associated with the PL was determined using calcein and 6-carboxyfluorescein (6-CF) as hydrophilic markers incorporated during the preparation of the SLN's. RESULTS: The diameter of the SLN's decreased as the molar ratio of PL to TL was increased, until a PL:TL ratio of 0.15 was reached. After this point the diameter was not affected by further increases in the molar ratio. The experimental amount of PL required to prepare SLN's was significantly higher than the theoretical amount required to form a single monolayer on the surface. The aqueous volume associated with the PL was increased with increasing PL:TL molar ratios. CONCLUSIONS: The results obtained suggest that the formation of multiple PL bilayers is probable in SLN's prepared with a high molar ratio of PL to TL. The volume of the aqueous phase between the PL-bilayers, estimated from the amount of the hydrosoluble markers trapped in this phase, provides an indication of the relative number of bilayers at different PL:TL ratios.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1970

Zymogen secretion and phospholipid metabolism in the pancreas. Phospholipids of the zymogen granule.

1. Acetylcholine produced a fivefold increase in the specific radioactivity of phosphatidylinositol in guinea-pig pancreas slices incubated in the presence of [(32)P]-orthophosphate, but did not affect the specific radioactivity of the terminal phosphate of ATP. 2. The secretagogues acetylcholine and pancreozymin had no direct effect on the enzymes of phosphatidylinositol biosynthesis in guinea-pig pancreas homogenates. 3. Pancreozymin in vivo increased the incorporation of [(32)P]orthophosphate into phosphatidylinositol but not into phosphatidylcholine, phosphatidylethanolamine or phosphatidylserine. 4. The zymogen-granule membrane contained no unusual phospholipids or lysophospholipids, although its high cholesterol/phospholipid ratio resembled that of plasma membrane. 5. Phospholipase A activity during fractionation sometimes produced lysophospholipids in mitochondrial, microsomal and zymogen-granule fractions.

Acetylcholine↗
PubMed1987

Stimulation of adipocyte phospholipid methyltransferase activity by phorbol 12-myristate 13-acetate. Differential regulation of phospholipid methyltransferase and lipolysis.

The present studies demonstrate that treatment of rat adipocytes with the phorbol ester phorbol 12-myristate 13-acetate (PMA) causes a dose-dependent stimulation of phospholipid methyltransferase (PLMT) activity. The stimulatory effect of PMA was not additive with that of isoprenaline or forskolin. The sensitivity of stimulated PLMT activity to inhibition by insulin, however, was decreased in the presence of PMA. The inhibitory effect of a maximal concentration of insulin on PLMT was unchanged in the presence of PMA. In contrast with the effects on PLMT, the lipolytic response of adipocytes to isoprenaline and the anti-lipolytic response to insulin were unaffected by PMA. These data suggest that PLMT is, whereas hormone-sensitive lipase is not, an intracellular target for the action of PMA. The lack of effect of PMA on lipolysis suggests that PLMT and hormone-sensitive lipase can be regulated by separate mechanisms. Furthermore, phorbol esters do not interfere in the regulatory pathway whereby insulin inhibits PMLT or lipolysis.

Adipose Tissue↗
PubMed2002

Inositol phospholipid metabolism in Arabidopsis. Characterized and putative isoforms of inositol phospholipid kinase and phosphoinositide-specific phospholipase C.

Phosphoinositides (PIs) constitute a minor fraction of total cellular lipids in all eukaryotic cells. They fulfill many important functions through interaction with a wide range of cellular proteins. Members of distinct inositol lipid kinase families catalyze the synthesis of these phospholipids from phosphatidylinositol. The hydrolysis of PIs involves phosphatases and isoforms of PI-specific phospholipase C. Although our knowledge of the roles played by plant PIs is clearly limited at present, there is no doubt that they are involved in many physiological processes during plant growth and development. In this review, we concentrate on inositol lipid-metabolizing enzymes from the model plant Arabidopsis for which biochemical characterization data are available, namely the inositol lipid kinases and PI-specific phospholipase Cs. The biochemical properties and structure of characterized and genome-predicted isoforms are presented and compared with those of the animal enzymes to show that the plant enzymes have some features clearly unique to this kingdom.

1-Phosphatidylinositol 4-Kinase↗
PubMed2006

Neuroendocrine manifestations of phospholipid antibody disease identified by long-term follow-up study of patients with phospholipid antibodies.

UNLABELLED: Recurrent clinical thrombotic episodes and/or recurrent fetal wastage are the clinical features of phospholipid antibody (aPL) syndrome, which is characterized by a bland thrombosis, but is not inflammatory, as is found in other connective tissue diseases such as systemic lupus erythematosus (SLE). Previous reports have suggested that some patients with primary aPL syndrome may progress to develop other autoimmune diseases, including inflammatory diseases such as SLE. The aim of this study was to determine the long-term outcome of women with aPL antibodies, with regard to progression of their underlying autoimmune disease. To that end, a retrospective study was made of women with aPL and primary aPL syndromes who had been followed at our institution for a minimum of 3 years. Charts were reviewed, patients interviewed, and laboratory tests were performed to determine whether the clinical nature of the disease and/or its autoantibody profile had changed. Thirty patients were enrolled into the study (29 with aPL syndrome, 1 with consistent aPL and no syndrome). Follow-up ranged from 3 to 22 years. Results were as follows: The autoimmune clinical features were unchanged in 27 patients, but 3 patients developed inflammatory disease, presenting with nasal chondritis (2), cutaneous vasculitis (3), and mucosal ulcer (1). In each case, these changes occurred during pregnancy or the immediate postpartum period. One patient fulfilled criteria for SLE as seen by a change in her autoantibody profile. Another incidental finding was that three other patients were diagnosed with papillary thyroid cancer, two being diagnosed during the follow-up period. IN CONCLUSION: (1) Inflammatory disease may develop in some patients with aPL and appears to be set off by pregnancy, a known trigger for clinical thrombotic events in aPL patients. (2) Thyroid cancer may be associated with aPL, and this association warrants further study with larger number of patients.

Adolescent↗