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Difference in microviscosity induced by different cholesterol levels in the surface membrane lipid layer of normal lymphocytes and malignant lymphoma cells 总被引:32,自引:0,他引:32
Microviscosity (gh) in the surface membrane lipid layer of normal lymphocytes and malignant lymphoma cells, and in liposomes prepared from their lipid extracts, was determined with the aid of the fluorescence polarization properties of 1,6-diphenyl 1,3,5-hextriene embedded in it. The gh values, both in intact cells and in the liposomes, are distinctively greater for normal lymphocytes than for the lymphoma cells, whereas the fusion activation energy in both types of cells and liposomes is 8 ± 0.5 kcal/mol. Determination of cholesterol revealed that its relative amount in a lymphoma cell is about half of that of a normal lymphocyte, a difference that may account for the above difference in fluidity. This thesis is supported by the observed changes in gh, which follow artificial changes in cholesterol contents in the surface membrane of both cell types. Introduction of exogeneous cholesterol into the cell surface membranes was performed with lecithin-cholesterol (1:1) liposomes, and in lymphoma cells resulted in an increase of gh to a level of normal lymphocytes. Extraction of native cholesterol from the cell surface membranes was carried out with lecithin liposomes, and in normal lymphocytes results in a decrease of gh to a value similar to that of lymphoma cells. The induced changes in cholesterol contents are practically reversible for both cell types. By virtue of controlling the microviscosity of lipid layers, the level of cholesterol in cell surface membranes may play an important role in determining biological activities of normal and malignant cells. 相似文献
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Kinya Koizumi Satoru Shimizu Keiko T. Koizumi Keiko Nishida Chikako Sato Kazuo Ota Naoki Yamanaka 《生物化学与生物物理学报:生物膜》1981,649(2):393-403
A rapid isolation method was developed for plasma membranes from mouse lymphoid cells such as lymph node lymphocytes, thymocytes, radiation-induced thymoma cells and L1210 cells. Lysates of these lymphoid cells were prepared by Dounce homogenization under hypotonic conditions and directly layered on sucrose step density gradients containing 2 mM CaCl2 and 5 mM MgCl2, and centrifuged at for 1 h. Plasma membrane fractions appeared at the interface between 20 and 42% sucrose in the gradients. The procedure permitted purified membranes from cells to be obtained within 3 h, and the preparations appeared to be uniform by electron microscopy. Specific activities of (, Mg2+-ATPase and 5′-nucleotidase of the isolated plasma membranes were enriched 23- to 61-fold, 12- to 15-fold and 18- to 34-fold, respectively, in comparison with those of the corresponding cell homogenates. Cholesterol content of the malignant cell membranes was lower than that of the normal membranes and the molar ratio of cholesterol to phospholipid of the malignant cell membranes was also lower than that of the normal membranes. A decreased plasmalogen content was observed in the malignant plasma membranes, together with a higher percentage of phosphatidylethanolamine and a lower percentage of phosphatidylserine. In the normal cell membranes, thymocytes contained a higher percentage of phosphatidylcholine and a lower percentage of sphingomyelin than those of the lymph node lymphocytes. At all temperature ranges (5 to 40°C) the plasma membranes of the malignant cells had lower microviscosity than those of the normal cells. 相似文献
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Haydn E. Edwards J.Kerry Thomas Gary R. Burleson Charles F. Kulpa 《生物化学与生物物理学报:生物膜》1976,448(3):451-459
The fluorescent probes pyrene, pyrene butyric acid and 1-naphthylamine have been used to investigate the changes that accompany in vitro transformation of a baby hamster kidney cell line using Rous sarcoma virus. The fluorescent probes which reside in the membrane were used to compare the changes in microviscosity and polarity of the membranes of normal cells with two transformed cell lines. The spectrofluorimetric data indicate that following transformation the probe 1-naphthylamine resides in a more polar environment. However, using the probe pyrene, the yield of excimer indicates decreased mobility of this probe in the membrane of transformed cells. The data also indicate differences between the two transformed cell lines. Laser photolysis was used to study the lifetime of the pyrne probes and the quenching of the pyrene fluorescence in the membrane by several different quenching molecules. The data indicate differences between the three cell lines and suggest that transformation decreases movement within the membrane. 相似文献
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Snake venom phosphodiesterase from and 5′-nucleotide phosphodiesterase from were incubated with the 1-naphthyl ester of 5′-[methyl-3H]thymidylic acid. After short-time incubation the enzymes were denatured by extraction into phenol and chromatographed on Sephadex G-25. Protein fractions containing radioactivity were collected, dialysed and subjected to ultra-thin-layer isoelectric focussing and autoradiography. The results obtained indicate a hydrolytic course via a covalently-bound intermediate. 相似文献
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M E Christensen A L Beyer B Walker W M Lestourgeon 《Biochemical and biophysical research communications》1977,74(2):621-629
A nuclear protein apparently homologous to the two major proteins of 40S heterogeneous nuclear ribonucleoprotein particles from mammalian cells has been isolated from the lower eukaryote , purified, and found to contain a substantial amount of the unusual amino acid NG, NG-dimethylarginine. The apparent homology is based on similar molecular weights, basic isoelectric points and amino acid compositions including the dimethylarginine and a high content of glycine. The implications of the presence of this protein in and the possible significance of the NG, NG-dimethylarginine are discussed. 相似文献