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1.

001-es BibID:BIBFORM006026
Első szerző:Basu, Hirak S.
Cím:Effect of polyamine depletion on chromatin structure in U-87 MG human brain tumour cells / Basu, H. S., Sturkenboom, M. C., Delcros, J. G., Csokan, P. P., Szollosi, J., Feuerstein, B. G., Marton, L. J.
Dátum:1992
Megjegyzések:The chromatin structure of polyamine-depleted U-87 MG human brain tumour cells was studied by following the kinetics of digestion of cell nuclei by micrococcal nuclease and bovine pancreatic DNAase I. Cells growing in monolayers were treated with either alpha-difluoromethylornithine (DFMO), to deplete putrescine and spermidine, or N1,N14-bis(ethyl)homospermine (BE-4-4-4), to deplete putrescine, spermidine and spermine. BE-4-4-4 increased the initial rates of digestion and the magnitudes of limit digest by both enzymes; DFMO increased the limit digests without affecting initial digestion rates. Addition of 1 mM-putrescine 1 day after addition of DFMO reversed the effect of DFMO on limit digests. (Because polyamine uptake is low in cells treated with BE-4-4-4, and because putrescine does not reverse the growth-inhibitory effects of BE-4-4-4, reversal of the effects of BE-4-4-4 with putrescine was not attempted.) The increases in initial rates and limit digests did not result from changes in the lengths of nucleosomal or linker DNA, from blocks in cell-cycle progression, or from growth inhibition caused by DFMO or BE-4-4-4. Thus, because the limit digest is highest in cells with the lowest polyamine levels, it seems clear that the enhanced enzymic digestion of nuclei is caused by polyamine depletion and its possible effect on chromatin structure.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
analogs and derivatives
Brain Neoplasms
Cell Cycle
Cell Nucleus
Chromatin
Culture Media
Culture Media,Serum-Free
Deoxyribonuclease I
Dna
drug effects
Eflornithine
Enzymes
Human
Intracellular Fluid
Kinetics
metabolism
Micrococcal Nuclease
pathology
pharmacology
Polyamines
Putrescine
Spermidine
Spermine
Support,Non-U.S.Gov't
Support,U.S.Gov't,P.H.S.
Tumor Cells,Cultured
ultrastructure
Megjelenés:The Biochemical Journal. - 282 : Pt 3 (1992), p. 723-727. -
További szerzők:Sturkenboom, M. C. Delcros, J. G. Csokan, P. P. Szöllősi János (1953-) (biofizikus) Feuerstein, Burt G. Marton, Laurence J.
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2.

001-es BibID:BIBFORM006032
Első szerző:Delcros, J. G.
Cím:Differential effects of spermine and its analogues on the structures of polynucleotides complexed with ethidium bromide / Delcros J. G., Sturkenboom M. C., Basu, H. S., Shafer R. H., Szöllösi, J., Feuerstein, B. G., Marton, L. J.
Dátum:1993
Megjegyzések:The interactions of spermine and polyamine analogues with synthetic polynucleotides of various base sequences complexed with ethidium bromide (EB) were investigated using measurements of fluorescence intensity and steady-state fluorescence polarization. Spermine and polyamine analogues displaced some but not all of the EB bound to poly(dA-dT).poly(dA-dT) or poly(dG-dC).poly(dG-dC), suggesting that polyamines may stabilize these polynucleotides in a conformation with reduced affinity for EB. Modifications of the aliphatic backbone of spermine have pronounced effects on its ability to displace EB from poly(dA-dT).poly(dA-dT) but not from poly-(dG-dC).poly(dG-dC). Spermine and some but not all of the polyamine analogues caused fluorescence depolarization when they interacted with the complex of EB and poly(dA-dT).poly-(dA-dT). Neither spermine nor any of the analogues, however, induced fluorescence depolarization in the complex of EB with poly(dG-dC).poly(dG-dC) or poly(dA).poly(dT). This suggests that spermine and some spermine analogues induce structural changes specific to alternating A-T sequences.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
chemistry
Ethidium
Fluorescence
Fluorescence Polarization
Nucleic Acid Conformation
pharmacology
Poly dA-dT
Polyamines
Polydeoxyribonucleotides
Polynucleotides
Spectrometry,Fluorescence
Spermine
Support,Non-U.S.Gov't
Support,U.S.Gov't,P.H.S.
Megjelenés:The Biochemical Journal. - 291 : Pt 1 (1993), p. 269-274. -
További szerzők:Sturkenboom, M. C. Basu, Hirak S. Shafer, R. H. Szöllősi János (1953-) (biofizikus) Feuerstein, Burt G. Marton, Laurence J.
Internet cím:elektronikus változat
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3.

001-es BibID:BIBFORM006033
Első szerző:Feuerstein, Burt G.
Cím:alpha-Difluoromethylornithine alters calcium signaling in platelet-derived growth factor-stimulated A172 brain tumor cells in culture / Feuerstein, B. G., Szollosi, J., Basu, H. S., Marton, L. J.
Dátum:1992
Megjegyzések:alpha-Difluoromethylornithine (DFMO), an irreversible inhibitor of the polyamine biosynthetic enzyme ornithine decarboxylase, inhibits the growth of brain tumor cell lines and is undergoing clinical trials as a treatment for brain tumors. Platelet-derived growth factor (PDGF) is thought to regulate the growth and development of precursors of both normal and neoplastic astrocytic cells; calcium signaling is thought to play a role in the transduction of PDGF signals. Using laser fluorescence image cytometry, flow cytometry, and spectrofluorometry, we studied the effect of DFMO on the calcium signals induced by PDGF in A172 human glioblastoma cells. Four days of treatment with 5 mM DFMO substantially shortened PDGF-induced calcium signals. The effect was reversed more than 10 h but less than 24 h after putrescine treatment, even though polyamines were repleted 4 h after putrescine and spermidine were added. DFMO did not substantially affect intracellular calcium release or the timing of the opening and closing of plasma membrane calcium channels. These findings support the notion that calcium signaling may be a target for inhibitors of polyamine metabolism.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
analysis
Biogenic Polyamines
Brain Neoplasms
Calcium
Calcium Channels
Calcium Signaling
Cell Line
drug effects
Eflornithine
Flow Cytometry
Fluorescence
Glioblastoma
Human
Image Cytometry
Ion Channel Gating
metabolism
pathology
pharmacology
Platelet-Derived Growth Factor
Polyamines
Signal Transduction
Support, Non-U.S.Gov't
Support, U.S.Gov't,P.H.S.
Tumor Cells, Cultured
Megjelenés:Cancer Research. - 52 : 24 (1992), p. 6782-6789. -
További szerzők:Szöllősi János (1953-) (biofizikus) Basu, Hirak S. Marton, Laurence J.
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4.

001-es BibID:BIBFORM006053
Első szerző:Szöllősi János (biofizikus)
Cím:Attachment of A172 human glioblastoma cells affects calcium signalling : a comparison of image cytometry, flow cytometry, and spectrofluorometry / Szollosi, J., Feuerstein, B. G., Hyun, W. C., Das, M. K., Marton, L. J.
Dátum:1991
Megjegyzések:The intracellular free calcium concentration ([Ca2+]i) of indo-1 loaded A172 human glioblastoma cells stimulated by platelet-derived growth factor (PDGF) was studied in cell suspensions by flow cytometry and spectrofluorometry and in confluent monolayers by laser image cytometry and spectrofluorometry. With all three techniques, the percentage of responsive cells, peak [Ca2+]i, and the duration of response were directly related, and the delay time was inversely related to PDGF dose. The maximum response occurred at a PDGF concentration of about 20 ng/ml. Basal and peak [Ca2+]i did not differ significantly from method to method even though different calibration procedures were used. Cells in suspension monitored by both spectrofluorometry and flow cytometry displayed significantly shorter calcium responses than attached cells. This did not appear to be a direct effect of trypsinization. Spectral analysis of indo-1 in cytoplasm, 40% glycerol, and aqueous solutions showed significant differences in the isosbestic point and quantum efficiency. Calibration of [Ca2+]i with spectrofluorometry is more accurate using the ratio of fluorescence intensities than the fluorescence intensities measured at either 405 or 485 nm.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
analysis
Calcium
Cell Separation
Chelating Agents
Comparative Study
Cytoplasm
drug therapy
Dyes
Flow Cytometry
Fluorescence
Fluorescent Dyes
Glioblastoma
Glioma
Glycerol
Human
Image Cytometry
Indoles
metabolism
pharmacology
Platelet-Derived Growth Factor
Spectrometry,Fluorescence
Support,Non-U.S.Gov't
Support,U.S.Gov't,P.H.S.
Tumor Cells,Cultured
Megjelenés:Cytometry. - 12 : 8 (1991), p. 707-716. -
További szerzők:Feuerstein, Burt G. Hyun, William C. Das, M. K. Marton, Laurence J.
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5.

001-es BibID:BIBFORM006054
Első szerző:Szöllősi János (biofizikus)
Cím:Calcium channels in PDGF-stimulated A172 cells open after intracellular calcium release and are not voltage-dependent / Szollosi, J., Feuerstein, B. G., Vereb, G., Pershadsingh, H. A., Marton, L. J.
Dátum:1991
Megjegyzések:Using laser image cytometry and Indo-1 fluorescence, we investigated the intracellular free Ca2+ concentration ([Ca2+]i) of confluent A172 human glioblastoma cells stimulated by the BB homodimer of platelet-derived growth factor (PDGF-BB). The shape of the calcium transients and the delay time between stimulation and the beginning of the transient varied considerably. The percentage of responsive cells, the peak [Ca2+]i and the duration of the response were directly related to PDGF-BB dose, while the delay time was inversely related; the maximal response occurred at a PDGF-BB concentration of 20 ng/ml. Studies with EGTA and inorganic calcium-channel blockers (Ni2+, La3+) showed that the increase of [Ca2+]i resulted from initial release of intracellular stores and subsequent calcium influx across the plasma membrane. Opening of calcium channels in the plasma membrane, monitored directly by studying Mn2+ quenching of Indo-1 fluorescence, was stimulated by PDGF-BB and blocked by La3+; the opening occurred 55 +/- 10 s after the initial increase in [Ca2+]i. Therefore, in these tumor cells, intracellular release always occurs before channel opening in the plasma membrane. Depolarization of cells with high extracellular [K+] did not generally induce calcium transients but did decrease calcium influx. L-type calcium-channel blockers (verapamil, nifedipine, and diltiazem) had little or no effect on the calcium influx induced by PDGF-BB. These results indicate that PDGF-BB induces calcium influx by a mechanism independent of voltage-sensitive calcium channels in A172 human glioblastoma cells.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Calcium
Calcium Channel Blockers
Calcium Channels
Dyes
Egtazic Acid
Electrophysiology
Fluorescence
Fluorescent Dyes
Glioblastoma
Human
Image Cytometry
Image Processing,Computer-Assisted
Indoles
Lanthanum
metabolism
pharmacology
Platelet-Derived Growth Factor
Signal Transduction
Support,Non-U.S.Gov't
Support,U.S.Gov't,P.H.S.
Tumor Cells,Cultured
Verapamil
Megjelenés:Cell Calcium. - 12 : 7 (1991), p. 477-491. -
További szerzők:Feuerstein, Burt G. Vereb György (1965-) (biofizikus, orvos) Pershadsingh, Harrihar A. Marton, Laurence J.
Internet cím:elektronikus változat
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