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At least 865 records · Page 48Linked to original sources
PubMed1984

Effects of alpha-difluoromethylornithine on the growth of 9L rat brain tumor multicellular spheroids and their response to 1,3-bis(2-chloroethyl)-1-nitrosourea.

9L rat brain tumor cell spheroids were treated with alpha-difluoromethylornithine (DFMO) and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) alone and in combination. In contrast to results obtained with 9L monolayer culture cells, very low concentrations of DFMO killed spheroid cell within 0.5 day after the start of treatment; cell kill was maximum within 2 to 3 days. DFMO cytotoxicity could be prevented by adding putrescine (to a final concentration of 1 mM) to the culture medium. DFMO also significantly slowed and eventually stopped the growth of spheroids in a dose-dependent manner. Cells in all regions of DFMO-pretreated spheroids were sensitized to BCNU as measured by colony-forming efficiency; this sensitization was prevented when putrescine was added to culture medium before BCNU treatment. When used as single agents, either a 3-day treatment with 10 mM DFMO or a 1-hr treatment with BCNU (1.5 micrograms/ml) produced similar growth delay, but used in combination, the two agents produced a much longer growth delay than produced by either agent alone. Growth of spheroids treated continuously for up to 28 days with 10 mM DFMO ceased at approximately 7 times the volume at the time of treatment. When spheroid cells were treated for 1 hr with BCNU (1.5 micrograms/ml) and then were treated continuously with DFMO, growth plateaued at approximately 3.5 times the volume at the time of treatment; when spheroids were treated first with DFMO for 3 days, then with BCNU (1.5 micrograms/ml) for 1 hr, and then treated continuously with DFMO, growth plateaued at approximately 1.5 times the volume at the time of treatment. The number of clonogenic cells per spheroid that survived combination treatment also reflected the cytotoxic effects of the two drugs. Thus, the combined drug treatment was very effective in inhibiting the growth of spheroids and in preventing an increase in the number of clonogenic cells per spheroid.

Animals↗
PubMed1984

Development of multicellular spheroids of HeLa cells cocultured with fibroblasts and their response to X-irradiation.

HeLa cells cocultured with human diploid fibroblasts developed a more stable and tightly packed spheroid than did HeLa cells alone. Mature spheroids with central necrosis resembled the cord structure of solid tumors in histological appearance and distribution of cells labeled by [3H]thymidine. Electron microscopy showed that HeLa cells in the spheroid are in close contact with each other and have abundant intercellular junctions. The rate of cell loss from spheroid surface, expressed as cells lost per sq mm of spheroid surface per hr, was twice as high for spheroids of HeLa cells alone as for cocultured spheroids. The radiation dose-survival curve for cells in small spheroids without central necrosis was characterized by a wide shoulder than that for cells grown in monolayer or that for single-cell suspension from the same batch of the spheroids, but the terminal slope was similar for all survival curves. Development of central necrosis in larger spheroids coincided with a further increase in radioresistance, and the terminal D0 in the survival curve was 3 times that of single-cell suspension from the spheroids of the same batch. The radioresistant tail in the survival curve, however, disappeared when the spheroids were irradiated in medium containing a hypoxic cell radiosensitizer, misonidazole. These findings suggest that spheroids of HeLa cells cocultured with fibroblasts simulate the cord structure of solid tumors not only in structure but also in response to radiation.

Cell Division↗
PubMed1984

Human mixed cell colonies: unicellular or multicellular origin--analysis by G-6-PD.

Marrow and peripheral blood cells from normal women heterozygous (GdB/GdA) at the X-chromosome-linked glucose-6-phosphate dehydrogenase (G-6-PD) locus were cultured at cell concentrations ranging from 2 X 10(4)/ml to 4 X 10(5)/ml to test formally the plating conditions necessary for reliable enumeration of multipotent stem cells (CFU-mix). The culture system was rigorously tested by plating cells obtained after velocity sedimentation and the G-6-PD enzyme type of individual colonies was determined. At cell concentrations less than or equal to 7.5 X 10(4)/ml for marrow and less than or equal to 1 X 25 X 10(5)/ml for peripheral blood, mixed-cell colonies had either type A or type B enzyme, but not both. At higher cell concentrations, significant numbers of colonies showed both enzyme types and therefore arose from more than one cell. These studies demonstrate that enumeration of CFU-mix by in vitro colony assay is accurate only at low cell concentrations. Studies of haematopoietic differentiation relying on in vitro colony assays of multipotent stem cells must be carefully analysed in light of these data.

Bone Marrow Cells↗