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51.
G.W. Meijer J.E.M. Groener A.C. Beynen A. Van Tol 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》1996,114(4):403-407
We investigated the relationship between the development of hypercholesterolemia in rabbits and cholesteryl ester transfer protein (CETP) activity secretion by their perfused livers. Two inbred strains of rabbits were compared which differ markedly in their hypercholesterolemic response to dietary cholesterol. Feeding a high-cholesterol (0.3%) diet, increased plasma and liver cholesterol levels in the two strains, the increments being 15 mM and 30 μmol/g greater in the hyperresponders, respectively. The high-cholesterol diet caused an about 2-fold increased hepatic secretion of CETP activity, but there was no difference between the two rabbit strains. Feeding a lower amount of dietary cholesterol (0.08%) also caused higher cholesterolemic (2 mM) and hepatocholesterolic (28 μmol/g) responses in hyper- than in hyporesponsive rabbits. The activity of hepatic CETP secretion was not increased by the low-cholesterol diet, and there was no difference between hypo- and hyperresponsive rabbits. Cholesterol feeding increased plasma CETP activity by 90% in both rabbit strains, but there was no difference between the strains. Our combined data suggest that with increasing plasma cholesterol levels, hepatic CETP secretion may be increased in a parabolic manner, reaching its maximum rate far before plasma cholesterol concentrations are maximal. There were no differences in hepatic CETP activity secretion or plasma CETP activity levels between the genetically different strains of hypo- and hyperresponsive rabbits. 相似文献
52.
Jean L. Sarcich H. David Fischer Merrill S. Babcock Joseph W. Leone Alfredo G. Tomasselli 《Journal of Protein Chemistry》1995,14(2):73-80
Cholesteryl ester transfer protein (CETP) mediates the transfer of cholesteryl ester from high- and low-density lipoproteins to triglyceride-rich lipoproteins, and reciprocally mediates triglyceride transfer. The gene for cynomolgus monkey CETP was expressed in serum-free CHO culture with 2g/ml insulin as its only exogenous protein supplement. Cell growth was facilitated by immobilizing the CHO cells in alginate beads. Recombinant CETP (rCETP) was purified 176-fold with a three-step protocol resulting in a 60% final yield as measured by a fluorescent CETP activity assay. Typically, 3.4 mg of rCETP was purified from 1700 ml of media by affinity-gel chromatography involving Reactive Red 120 (RR120) followed by concanavalin A Sepharose 4B and rechromatography on RR120. SDS-PAGE shows a single broad band ofM
r
, ranging from 68,000 to 74,000 which immunoreacts in Western blot analysis. Amino acid analysis and protein sequencing of the purified protein agree with the theoretical amino acid composition and sequence of cynomolgus CETP. 相似文献
53.
The study addressed to understand whether or not lipoproteins at low concentrations could modulate Receptor-C dependent platelet signalling revealed that LDL, like exogneous cholesterol, had the capacity to initiate PLD-dependent platelet signalling in a dose dependent fashion and this effect was inhibited in presence of HDL; cAMP; DTT; Zn++ and butanol whereas cGMP had no effect upon this PLD-dependent signalling. Further Receptor C from platelet in the purified-form displayed LDL-or cholesterol-dependent autophosphorylation at the tyrosine residues and this Receptor-C tyrosine kinase (Receptor-Ck) activity contributed to the observed LDL-or cholesterol-dependent PLD activity in human platelets. Based upon these results coupled with earlier results, an attempt was made to define the lipoprotein-dependent platelet signalling pathway. 相似文献
54.
Judith K. Woodford William D. Behnke Friedhelm Schroeder 《Molecular and cellular biochemistry》1995,152(1):51-62
Among the large family of fatty acid binding proteins, the liver L-FABP is unique in that it not only binds fatty acids but also interacts with sterols to enhance sterol transfer between membranes. Nevertheless, the mechanism whereby L-FABP potentiates intermembrane sterol transfer is unknown. Both fluorescence and dialysis data indicate L-FABP mediated sterol transfer between L-cell fibroblast plasma membranes occurs by a direct membrane effect: First, dansylated-L-FABP (DNS-L-FABP) is bound to L-cell fibroblast plasma membranes as indicated by increased DNS-L-FABP steady state polarization and phase resolved limiting anisotropy. Second, coumarin-L-FABP (CPM-L-FABP) fluorescence lifetimes were significantly increased upon interaction with plasma membranes. Third, dialysis studies with3H-cholesterol loaded plasma membranes showed that L-FABP added to the donor compartment of the dialysis cell stimulated3H-cholesterol transfer whether or not the dialysis membrane was permeable to L-FABP. However, L-FABP mediated intermembrane sterol transfer did require a sterol binding site on L-FABP. Chemically blocking the ligand binding site also inhibited L-FABP activity in intermembrane sterol transfer. Finally, L-FABP did not act either as an aqueous carrier or in membrane fusion. The fact that L-FABP interacted with plasma membrane vesicles and required a sterol binding site was consistent with a mode of action whereby L-FABP binds to the membrane prior to releasing sterol from the bilayer.Abbreviations
3H-CHO
[1,2-3H(N)]-cholesterol
- ANTS
8-aminonaphthalene-1,3,6-trisulfonic acid
- CF
carboxyfluorescein
- CHO
cholesterol
- CPM (coumarin maleimide)
7-diethylamino-3-(4-maleimidylphenyl)-4-methylcoumarin
- cPNA
cisparinaric acid
- DHE (dehydroergosterol)
5,7,9(11),22-ergostatetraen-3-ol
- DMF
dimethyl formamide
- DMPOPOP
1,4-bis[4-methyl-5-phenyl-2-oxazolyl]benzene
- DNS (dansyl chloride)
5-dimethylaminonaphthalene-1-sulfonylchloride
- DPX
p-xylene-bis-pyridinium bromide
- FBS
fetal bovine serum
- fluorescamine
4-phenylspiro[furan-2(3H), 1 phthalan]-3,3-dione
- L-FABP
liver fatty acid binding protein
- NPG
p-nitrophenylglyoxal
- PIPES
piperazine-N,N-bis(2-ethanesulfonic acid)
- POPC
1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine
- SUV
small unilamellar vesicle(s)
- TNM
tetranitromethane
This work was supported in part by the National Institutes of Health United States Public Health Service (GM31651 and DK41402) and the American Heart Association (Postdoctoral Fellowship to JKW). The helpful assistance of Dr. Scott M. Colles and Mr. Daniel R. Prows in isolating L-FABP was much appreciated. 相似文献
55.
Y-organs are the ecdysial glands of crustaceans, responsible for synthesis and secretion of ecdysteroid hormones. For this purpose, the glands acquire cholesterol as obligate precursor entirely from circulating high-density lipoprotein (HDL). A preceding study provided evidence for the mechanism of acquisition: Y-organs take up cholesterol bound to HDL by an energy-requiring process, receptor-mediated absorptive endocytosis. The present study characterized the receptors involved utilizing isolated Y-organ membranes. HDL binding was saturable and specific; a dissociation constant (Kd) of 1.08 × 10?7 M and a binding maximum at equilibrium (Bmax) of 70 μg HDL protein/mg membrane protein, were obtained. Binding was decreased by protease and was dependent upon calcium. Y-organs are regulated negatively by a peptide hormone from the eystalks, molt-inhibiting hormone (MIH). Y-organ membranes from de-eyestalked crabs (MIH absent) exhibited the same Kd value as membranes from intact crabs, but a Bmax 17% higher. Thus, MIH activity apparently does not change the binding affinity of HDL, but decreases the number of binding sites. These results agree with our previous findings that MIH depresses ecdysteroid synthesis in part by inhibiting cholesterol uptake. Generally, Y-organ cells appear to contain receptors for HDL that are of high affinity and high binding capacity, similar to the characteristics reported for the binding of insect HDL (vitellogenin) to fat bodies and oocytes. © 1995 Wiley-Liss, Inc. 相似文献
56.
The effect of lipid lowering agents of plant origin garlic oil and guggulipid on the levels of catecholamine and dopamine
Β-hydroxylase activity of normal and cholesterol fed rabbit tissues has been studied. The catecholamine levels and enzyme
activity were found to be decreased in cholesterol (500 mg/kg body wt) fed animals. The feeding of garlic oil (5 mg/kg body
wt) and guggulipid (100 mg/kg body wt) an exudate ofCommiphora mukul, to normal rabbits caused significant increase in the dopamine-Β-hydroxylase activity and catecholamine levels, while the
feed helped the hypercholesterolemic rabbits to recover the decrease in catecholamine biosynthesis
C.D.R.I. Communication No. 3435. 相似文献
57.
S P Verma J R Philippot B Bonnet J Sainte-Marie Y Moschetto D F Wallach 《Biochemical and biophysical research communications》1984,122(2):867-875
Low-density lipoproteins isolated between density 1.02 and 1.063 g/cm3 from normal fasting human plasma, show strong resonance Raman spectra due to the presence of beta-carotene. Three intense bands, at 1010, 1160 and 1530 cm-1, are assigned to the stretching vibrations of -C-CH3, = C-C = and -C = C- bonds, respectively, of beta-carotene. High-resolution spectra of the 1500-1600 cm-1 region reveal multiple features, suggesting the coexistence of several structural populations of beta-carotene. The modifications of lipoproteins with pH and temperature (30 degrees-42 degrees) change the resonance Raman spectra of beta-carotene. The specific binding of LDL at pH 7.0 by fibroblast cells is suppressed. Our experiments thus suggest that physical and chemical perturbations of plasma lipoproteins modify the lipid-protein interactions and thereby alter the configurational distribution of beta-carotene molecules within these particles. 相似文献
58.
A complete synthesis of 1-O-hexadecyl-2-O-N-(heptadec-8-cis-enyl)carbamyl-sn-glycero-3-Phosphocholine, a novel analog of phosphatidylcholine, has been described. Each step is simple to perform and gives the desired products in high yield. Also, some of the intermediates formed during the synthesis have been efficiently utilized to prepare 1-O-hexadecyl-2-O-oleyl-sn-glycero-3-phosphocholine, 1-O-hexadecyl-2-oleoyl-sn-glycero-3-phosphochloine and 3-O-hexadecyl-2-oeloyl-sn-glycero-1-phosphocholine. These phosphatidylcholine (PC) analogs are useful for studying the possible role of phospholipases in the capture and lyses of liposomes in vivo. 相似文献
59.
David B. Fenske Robert J. Cushley 《Biochemical and biophysical research communications》1984,121(3):871-877
[2H]Chondroitin sulfate was prepared by partial -deacetylation of chondroitin sulfate ( hydrazinolysis) followed by treatment with [2H6]acetic anhydride. 2H NMR spectra of [2H]chondroitin sulfate in the presence of human plasma low density lipoprotein provide evidence for a soluble complex stoichiometry of 3 (and possibly 2) lipoproteins per polysaccharide molecule, and allow a rough estimation of the dissociation constant Kd. 相似文献
60.