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51.
Natural images were subjected to patchwise Fourier analysis, and the local amplitude and phase spectra were swapped between different images. When the patches were large relative to the image size, the appearance of the reconstructed image was similar to that of the image from which the phase information had been derived, in agreement with previous reports of phase-dominance in the global Fourier Transform. However, when the patch size was made sufficiently small, the appearance of reconstructed images was dominated by amplitude rather than phase. This was not simply due to the DC component of the amplitude spectrum. Prior low-pass filtering of the images enhanced the dominance of amplitude information in the patchwise transform. We conclude that patchwise-reconstructed images contain two quite distinct kinds of information for the human observer. The first is the positional information (local sign) of the patches themselves; the second is the textural information within patches, which is dominated by amplitude rather than phase. The reason why the global Fourier Transform is dominated by phase is that in the absence of any other information about local sign, phase is necessary to reconstruct localised features such as edges. 相似文献
52.
Protein and other compositional differences of the extracellular material from slimy and non-slimy colonies of non-mucoid Pseudomonas aeruginosa 总被引:1,自引:0,他引:1
The composition of extracellular material produced by non-mucoid strains of Pseudomonas aeruginosa differed when grown on surfaces that either did or did not induce the formation of slime under conditions where the medium was identical. The nature of the changes in protein composition indicated that protein expression differed in the course of growth on the two surfaces, and hence that there were physiological consequences associated with growth under conditions which do or do not lead to slime formation. The compositional differences also included elevated levels in extracellular material from the slimy colonies of two virulence factors, protease and rhamnolipids. 相似文献
53.
J Guzman M Hilgarth K J Bross A Ross U Wiehle V Kresin F Grunert S von Kleist 《Acta cytologica》1988,32(4):519-522
In 17 malignant peritoneal effusions due to papillary serous adenocarcinoma of the ovary, the reaction patterns of the tumor cells to monoclonal antibodies (MAbs) against surface antigens were studied and compared with the reaction patterns of mesothelial cells in the same effusions. The following surface markers were used with the adhesive slide method: epithelial membrane antigen (EMA), human epithelium-specific cell surface antigen (HEA-125), human endothelial antigen (BMA-120), carcinoembryonic antigen (CEA 3-13), an antibody against natural killer cells and cytotoxic cells (BMA-070), granulocyte antigen (Leu M1) and leukocyte antigen of class I (HLA-1). In all cases, from 30% to 95% of the tumor cells reacted with EMA and HEA-125. Tumor cells showed a positive staining with CEA 3-13 in only five cases. In all cases, from 75% to 95% of the tumor cells reacted positively with BMA-120. The reactivity of a few mesothelial cells with EMA and of all mesothelial cells with BMA-120 did not interfere with the identification of positive tumor cells since the reaction patterns were different. Interestingly, our study demonstrated that BMA-070, an MAb identifying natural killer cells and cytotoxic cells, is also a most useful tumor marker. The same was found to be true for Leu M1, an MAb originally thought to react only with granulocytes. The tumor cells showed a partial or total loss of the expression of HLA-1 reactivity. Since all cases were immunocytochemically positive for tumor cells while conventional cytology was positive in only 13 of the cases, the immunocytochemical analysis of malignant peritoneal effusions due to papillary serous adenocarcinoma of the ovary seems able to improve the cytologic diagnosis of the fluids. 相似文献
54.
J774 macrophages exposed to medium containing cholesterol-rich phospholipid dispersions accumulate cholesteryl ester. Supplementing this medium with 100 micrograms oleate/ml increased cellular cholesteryl ester contents 3-fold. Cell retinyl ester contents increased 8-fold when medium containing retinol dispersed in dimethyl sulfoxide was supplemented with oleate. These increases were not the result of increases in total lipid uptake by the cells but rather of redistribution of cholesterol and retinol into their respective ester pools. Effective oleate concentration of 15-30 micrograms/ml increased cellular retinyl and cholesteryl ester contents. The effective oleate concentration was reduced to 5 micrograms/ml when the fatty acid/albumin molar ratio was increased. The oleate-stimulated increase in cholesterol esterification was blocked by incubating cells with Sandoz 58-035, a specific inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), indicating that the effect of fatty acid exposure is mediated through changes in ACAT activity. When cholesterol or retinol was added to cells which had been exposed to oleate for 24 h to provide a triacylglycerol store, the cellular contents of cholesteryl or retinyl ester were also significantly increased compared to cells not previously exposed to oleate. The oleate-stimulated increase in the esterification of cholesterol and/or retinol was also observed in P388D1 macrophages, human (HepG2) and rat (Fu5AH) hepatomas, human fibroblasts, rabbit aortic smooth muscle cells and MCF-7 breast carcinoma cells. In addition to oleate, a number of other fatty acids increased retinol esterification in J774 macrophages; however, cellular cholesterol esterification in these cells was increased only by unsaturated fatty acids and was inhibited in the presence of saturated fatty acids. Although the cellular uptake of radiolabeled oleate and palmitate was similar, a significant difference in the distribution of these fatty acids among the lipid classes was observed. These data demonstrate that exogenous fatty acids are one factor that regulate cellular cholesteryl and retinyl ester contents in cultured cells. 相似文献
55.
Platelet-derived growth factor (PDGF), a powerful mitogen released by platelets, promoted the degradation of low-density lipoprotein (LDL) by cultured primate arterial smooth muscle cells and human skin fibroblasts by stimulating both receptor-mediated and LDL-receptor-independent uptake of LDL. Stimulation of LDL-receptor-independent LDL uptake and degradation by PDGF was demonstrated in three ways. First, the small amount of LDL that was degraded by LDL-receptor-negative skin fibroblasts was stimulated by PDGF. Second, PDGF led to increased degradation of LDL that had been reductively methylated to prevent its binding to LDL receptors. Third, 125I-labeled LDL degradation was stimulated by PDGF in the presence of high concentrations of unlabeled LDL, i.e., conditions under which the contribution of the LDL receptor to cellular uptake and degradation is reduced. These observations suggest that mitogens, as typified by PDGF, can facilitate the cellular delivery of LDL cholesterol by both LDL-receptor-mediated and non-LDL-receptor-mediated mechanisms to provide exogenous cholesterol for use during cell replication. 相似文献
56.
Steady-state and time-resolved fluorescence properties of the single tyrosyl residue in oxytocin and two oxytocin derivatives at pH 3 are presented. The decay kinetics of the tyrosyl residue are complex for each compound. By use of a linked-function analysis, the fluorescence kinetics can be explained by a ground-state rotamer model. The linked function assumes that the preexponential weighting factors (amplitudes) of the fluorescence decay constants have the same relative relationship as the 1H NMR determined phenol side-chain rotamer populations. According to this model, the static quenching of the oxytocin fluorescence can be attributed to an interaction between one specific rotamer population of the tyrosine ring and the internal disulfide bridge. 相似文献
57.
The interaction of the estrogen d-3-hydroxy-1,3,5(10),6,8-estrapentaen-17-one (equilenin) with the human and rabbit sex steroid binding proteins (hSBP and rSBP, respectively) has been investigated by using fluorescence and absorption spectroscopy. Equilenin competes for the binding of 5 alpha-dihydrotestosterone. The calculated binding constant of equilenin for rSBP is 1.9 X 10(7) M-1 at 4 degrees C, which can be compared with the binding constant of 5.7 X 10(7) M-1 reported for hSBP [Ross, J.B.A., Torres, R., & Petra, P.H. (1982) FEBS Lett. 149, 240]. The results of fluorescence quenching experiments with the collisional quenchers KI and acrylamide indicate that the bound steroid has limited accessibility to the bulk solvent and that there are no anionic surface groups near the steroid-binding site. The fluorescence excitation spectra of SBP-equilenin complexes are similar to the absorption spectra of equilenin in low-dielectric solvents. The fluorescence emission of the SBP-equilenin complexes, however, exhibits wavelength shifts (red shifts) opposite to those of the steroid in low-dielectric solvents or complexed with beta-cyclodextrin (blue shifts) but similar to the red shift produced by addition of the proton acceptor triethylamine to equilenin in cyclohexane. These data indicate that the steroid-binding site of hSBP and rSBP is a nonpolar cavity containing a proton acceptor that participates in a specific interaction, possibly a hydrogen bond, with the 3'-hydroxyl group of the bound steroid. 相似文献
58.
Myotubes were obtained in vitro from satellite cells of normal and dystrophic C57BL/6J/dydy mice. The acetylcholine sensitivity (mV/nC) of dystrophic myotubes determined with conventional electrophysiological techniques, was lower than that of normal myotubes. Incubation of dystrophic myotubes with liposomes containing phosphatidylcholine (a lipid present in higher amounts in normal adult muscle) significantly increased their acetylcholine sensitivity. 相似文献
59.
The role of oxidative processes in the cytotoxicity of substituted 1,4-naphthoquinones in isolated hepatocytes 总被引:1,自引:0,他引:1
D Ross H Thor M D Threadgill M S Sandy M T Smith P Moldéus S Orrenius 《Archives of biochemistry and biophysics》1986,248(2):460-466
In order to clarify the role of oxidative processes in cytotoxicity we have studied the metabolism and toxicity of 2-methyl-1,4-naphthoquinone (menadione) and its 2,3 dimethyl (DMNQ) and 2,3 diethyl (DENQ) analogs in isolated rat hepatocytes. The two analogs, unlike menadione, cannot alkylate nucleophiles directly and were considerably less toxic than menadione. This decreased toxicity was consistent with the inability of DMNQ and DENQ to alkylate but we also found them to undergo lower rates of redox cycling in hepatocytes and a higher ratio of two electron as opposed to one electron reduction relative to menadione. Thus, facile analysis of the respective roles of alkylation and oxidation in cytotoxicity was not possible using these compounds. In hepatocytes pretreated with bischloroethyl-nitrosourea (BCNU) to inhibit glutathione reductase, all three naphthoquinones caused a potentiation of reduced glutathione (GSH) removal/oxidized glutathione (GSSG) generation and cytotoxicity relative to that observed in control cells. These data show that inhibition of hepatocyte glutathione reductase by BCNU results in enhanced naphthoquinone-induced oxidative challenge and subsequent cellular toxicity. That DMNQ and DENQ are cytotoxic, albeit at high concentrations, and that this cytotoxicity is potentiated by BCNU pretreatment suggest that oxidative processes alone can be a determinant of cytotoxicity. 相似文献
60.
Isolation and characterization of a carcinoma-associated antigen 总被引:5,自引:0,他引:5
A H Ross D Herlyn D Iliopoulos H Koprowski 《Biochemical and biophysical research communications》1986,135(1):297-303
GA733 is a murine IgG2a monoclonal antibody (MAb) against human gastric carcinoma and is highly tumoricidal in nude mice. The GA733 antigen is a cell surface protein with two subunits of 30,000 and 40,000 daltons. The antigen isolated by immunoaffinity chromatography consists mainly of the 30,000-dalton subunit which bears the GA733 epitope. This subunit displayed several isoelectric points between 6.9 and 7.7. Anti-colon carcinoma MAb 17-1A also detects this antigen, but probably binds to a different epitope. 相似文献