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Biomedical subjects

D N Buell

Publications and source records attributed to D N Buell.

At least 19 recordsLinked to original sources
PubMed1977

Viral reverse transcriptase suppression associated with erythroid differentiation of Friend leukemia cells.

The Friend erythroleukemia cell line T3-C12, which produces Friend murine leukemia virus (F-MuLV) and can be induced to synthesize hemoglobin by dimethyl sulfoxide (DMSO), was monitored for viral RNA-dependent DNA polymerase reverse transcriptase (RT) activity. The amount of viral 60-70S RNA released from DMSO-treated cells was unaffected or increased compared to that from control cells, while RT activity from treated cells was decreased. Accordingly, the specific activity in F-MuLV from DMSO-treated cells expressed as RT/70S RNA was decreased to 8% of the control activity. The 5-bromo-2'-deoxyuridine added to cultures containing DMSO reversed the differentiation process, and the F-MuLV thus treated did not exhibit the reduced RT activity normally observed in DMSO-treated virus. Cell-free F-MuLV incubated with and without DMSO showed the same RT activity, indicating that DMSO itself did not inhibit RT activity. However, when F-MuLV-containing pellets from control and DMSO-treated culture fluids were mixed, there was marked inhibition of the control RT activity, suggesting that RNase hybrid activity was stimulated or that an inhibitor was produced. Assays of F-MuLV-RNase hybrid released from control and DMSO-treated cells showed no difference in activity, indicating that a specific inhibitor of RT was produced or activated. Additions of certain nucleotide triphosphates to RT incubation mixtures did not result in any stimulation of RT activity in DMSO-treated F-MuLV, suggesting that phosphatase was not responsible for the observed inhibition. The results suggested that DMSO treatment of T3-C12 cells caused a reduction in viral RT activity by stimulating the production of an inhibitor, the nature of which is unknown.

Animals↗
PubMed1976

Insulin binding of acute lymphocytic leukemia cells.

Because of differences in insulin binding of cultured lymphoic cell lines, T- and B-cell surface receptor and 125I-insulin binding studies were performed on the bone marrow and peripheral blood leukocytes of 13 children with active acute lymphocytec leukemia. Based on surface receptors, nine patients had null-cell disease and four had T-cell disease. The mean per cent insulin binding of the bone marrow cells from the null-cell patients was 10.0% +/- 8.1 and from the T-cell patients was 0.18% +/- 0.13. The mean insulin binding of the cell suspensions of the peripheral blood from the null-cell patients was 7.3% +/- 7.5 and 0.07% +/- 0.06 from the T-cell patients. Displacement studies with nonradioactive insulin indicated that null leukemic cells bore specific binding sites. These results indicated that there may be metabolic as well as surface membrane heterogeneity among the acute lymphocytic leukemias of childhood.

B-Lymphocytes↗
PubMed1976

Erythroid differentiation in cultured Friend leukemia cells treated with metabolic inhibitors.

The induction of erythroid differentiation in the T3-C12 clone of Friend leukemia cells by dimethyl sulfoxide is accompanied by reduction in viral RNA-dependent DNA polymerase activity with increased cellular delta-aminolevulinic acid synthetase activity and hemoglobin synthesis. These cells were treated with a variety of compounds to determine whether other durgs are capable on inducing erythroid differentiation. While several hormones, inhibitors of RNA synthesis, organic solvents, inhibitors of DNA polymerase, sulfhydryl inhibitors, and inducers of delta-aminolevulinic acid synthetase administered singly did not stimulate hemoglobin synthesis like dimethyl sulfoxide, inhibitors of DNA and RNA synthesis such as adriamycin, mitomycin C, and hydroxyurea:mithramycin were synergistic in stimulating erythroid differentiation.

5-Aminolevulinate Synthetase↗
PubMed1976

Cell cycle and morphological changes during growth and differentiation of a rat basophilic leukemia cell line.

Cells of the rat basophilic leukemia cell line RBL-1 differentiated maximally when permitted to achieve growth arrest in a high-density stationary phase, in which the cell number is constant, and the cells are arrested in a G phase of the cycle. Features of differentiation are the accumulation of large basophilic granules and increases in membrane receptors for immunoglobulin E. However, changes in histamine content did not parallel granule development or changes in immunoglobulin receptor concentration. During rapid "forced exponential" growth, the cell number doubles every 8 hr, 50% of the cells are in S phase, and differentiation is minimal.

Animals↗
PubMed1975

Cell cycle-associated changes in receptors for IgE during growth and differentiation of a rat basophilic leukemia cell line.

The rat basophilic leukemia cell line (RBL-1) showed an inverse relationship between growth rate and expression of receptor activity for IgE. After prolonged exponential growth, the number of receptors per cell stabilized at 4-6 times 10-5. Cells in stationary cultures, which are arrested in the G1 phase of the cell cycle, continued to accumulate up to 0.9-1.7 times 10-6 receptors/cell with no increase in volume. Upon resuspension in fresh medium at low density, these cells were shown to lose up to 70% of the receptor activity within 4 h. Assessment of cultures synchronized by double thymidine block and cells fractionated by centrifugation of a Ficoll gradient indicated that the RBL-1 cells acquire receptors in the G1 phase of the cell cycle. No accumulation of active receptors occurred during the S and G2 phases, though the average cell volume increased. Cell division resulted in a drop in number of receptors per cell while the number of cell-bound receptors in the culture remained unchanged. This indicates that during mitosis receptors were simply distributed to daughter cells.

Animals↗
PubMed1974

Insulin-dependent regulation of insulin receptor concentrations: a direct demonstration in cell culture.

Chronic (5-16 hr) exposure of cultured human lymphocytes to 10(-8) M insulin at 37 degrees in vitro produced a decrease in insulin receptor concentrations unaccounted for by simple occupancy of sites; acute exposure (0-2 hr) was without effect. These results reproduced observations in vivo where chronic hyperinsulinemia (e.g., 10(-8) M insulin in the circulation of obese insulinresistant hyperglycemic mice) is associated with a substantial reduction in the concentration of insulin receptors per cell, while acute hyperinsulinemia in vivo has no effect on receptor concentration. These data suggest a reciprocal relationship between insulin in the extracellular fluid and the concentration of insulin receptors per cell, which is mediated at the target cell itself by intracellular insulin-sensitive regulatory processes and directly affects target-cell sensitivity to hormone.

Binding Sites↗
PubMed1973

Separation of human lymphoid cells into G 1 , S, and G 2 cell cycle populations by use of a velocity sedimentation technique.

Human lymphoid tissue culture cells can be separated according to cell size and corresponding cell cycle phase with a velocity sedimentation centrifugation method employing a continuous 5-20% wt/wt Ficoll gradient. A 7-fold increase in streaming limit was achieved by placing a buffer zone of isosmolar 5% Ficoll on top of the gradient before application of the cell load. The various pooled populations of cells from upper, middle, and lower areas of the gradient were characterized using autoradiographic, TCA-precipitable (3)H]thymidine incorporation, and Fuelgen microspectrophotometric methods. The upper range of the gradient contains cells in the G(1) cell cycle phase; the lower range, cells in the G(2) phase; cells found in the middle of the gradient belong largely to the S phase of the cell cycle. These gradient-separated cell pools contained relatively little contamination with cells from other phases of the cell cycle and, when explanted from the gradient into fresh growth media, showed growth patterns characteristic of synchronized cell populations. This system of cell separation provides a useful tool for investigating the relationship of the cell cycle to surface membrane and metabolic characteristics in human lymphoid cell culture systems.

Autoradiography↗
PubMed1972

Water-soluble insulin receptors from human lymphocytes.

Specific insulin receptors from human lymphocytes in culture have been prepared in aqueous solution without use of detergents or related compounds. Receptors prepared in this fashion exhibit characteristics identical to those reported in intact cells.

Adrenocorticotropic Hormone↗