Effect of colicin E3 on leukemia cells P388 in vitro.

Proliferation of murine leukemia cells P388 is stimulated by less than 1.0 mg/ml colicin E3, while being inhibited by higher concentrations. By 1.6 mg/ml colicin E3, uptake of thymidine into cold TCA-precipitable fraction is decreased by 59% during 24 h, uptake of uridine by 29%.     

Effect of methotrexate on glycolysis of leukemia L 1210 cells cultivated in vitro]

Methotrexate, at non lethal doses, alters the glycolysis of leukaemic L 1210 cells. Glucose uptake and lactate excretion are increased but lactate/glucose ratio remains constant. The activity of glycolytic enzymes in the cytoplasm is increased and the level of intracellular ATP is greatly enhanced.     

Cytogenetic evidence for hemizygosity at the thymidine kinase locus in P388 mouse lymphoma cells

A detailed cytogenetic investigation was carried out on P388 mouse lymphoma cells. The cells have a mean chromosome number of 36.86 with a mode and median of 37 chromosomes. G-banding analysis of 12 spreads revealed a total of 15 marker chromosomes with chromosome 11, the determinant of thymidine kinase, being present only in single copy per cell. It is therefore concluded that the P388 cell line is hemizygous at the thymidine kinase locus. Thymidine kinase activities were assayed in P388 cells and two other malignant cell lines, clone 707 Friend mouse leukaemia cells and L5178Y mouse lymphoma cells. No clear relationship was observed between enzyme activity and gene dosage.     

Presence of oncornavirus-like particles in the P388 murine leukemic cell line

Summary A culture of P388 murine lymphoblastoid cells has been shown to contain type C oncornavirus-like particles budding at the plasma membrane. Occasionally intracytoplasmic type A and immature type B particles were also observed by electron microscope techniques. The discovery of oncornavirus-like particles in the P388 cell line increases the utility of this neoplastic system for detecting potential antineoplastic agents.Supported by Contract NO1-CM-67048 from the Division of Cancer Treatment (DCT), National Cancer Institute (NCI), National Institutes of Health, Department of Health, Education, and Welfare. The fannie E. Rippel Foundation, Talley Industries, and the Phoenix Coca Cola Bottling Co. We are also grateful to Miss Linda M. Lange for technical assistance.     

Presence of oncornavirus-like particles in the P388 murine leukemic cell line

A culture of P388 murine lymphoblastoid cells has been shown to contain type C oncornavirus-like particles budding at the plasma membrane. Occasionally intracytoplasmic type A and immature type B particles were also observed by electron microscope techniques. The discovery of oncornavirus-like particles in the P388 cell line increases the utility of this neoplastic system for detecting potential antineoplastic agents.     

Antiproliferative effects of 4',5'-unsaturated adenine nucleosides on leukemia L1210 cells in vitro

Several 4',5'-unsaturated adenine nucleosides were shown to have antiproliferative activity against L1210 leukemia cells in vitro. The active nucleosides were cytotoxic to the L1210 cells as demonstrated by Trypan Blue uptake. The cytotoxicity was not induced by alterations in the ribonucleoside and deoxyribonucleoside triphosphate levels of the L1210 cells.     

Effect of infection of mice with Friend leukemia complex viruses on background antibody-forming cell production in vitro

Summary Friend leukemia complex (FLC) and Rowson-Parr virus (RPV) infections of donor mice depress the production of background antibody-forming cells by splenocytes cultured in the absence of specific antigenic stimulation.Supported in part by a grant from the Italian Research Council (Progetto finalizzato virus, CT 77.00248.84).     

Effect of infection of mice with Friend leukemia complex viruses on background antibody-forming cell production in vitro

Friend leukemia complex (FLC), and Rowson-Parr virus (RPV) infections of donor mice depress the production of background antibody-forming cells by splenocytes cultured in the absence of specific antigenic stimulation.     

Effect of calcitonin on glycosaminoglycan synthesis by embryo calf bone cells in vitro

Zusammenfassung Es wurde gefunden, dass rohe Calcitoninpräparate die Inkorporation von¹⁴C-Glucose in die Glycosaminoglycan-(GAG)-Synthese fördern. Unter denselben Zellkulturbedingungen wurde Calcitonin mit stark spezifischer Aktivität rasch inaktiviert und zeigte keine stimulierende Wirkung; wurde aber der Serumgehalt im Milieu stark eingeschränkt, so verursachte das Calcitonin (50 Einheiten/mg) eine hundertprozentige Erhöhung der¹⁴C-GAG-Synthese.     

Effect of temperature on in vitro proliferative activity of human umbilical vein endothelial cells

Human umbilical vein endothelial cells, skin fibroblasts, and retinal pigment epithelial cells are cultivated in medium supplemented with 15 to 20% serum in our laboratory. The effects of various incubation temperatures on the proliferation of these cells was examined. Our study shows that the mitogenic response of the endothelial cells to a change of temperature differed markedly from that of the fibroblasts and epithelial cells. Cultivation of human umbilical vein endothelial at 37°C required seeding densities as high as 1–2×10⁴ cells/cm², and yet resulted in a low growth rate and premature senescence. However, under the same culture conditions, but at 33°C, the proliferative capacity of these endothelial cells was potentiated. The results were striking; at 33°C the cells grew actively and the life span was extended. The number of cumulative population doublings increased fourfold compared with that for the same cells cultivated at 37°C. The inoculum size could be reduced, since at 33°C the endothelial cells were able to replicate at seeding densities as low as 20 cells/cm². The cells serially subcultured at 33°C retained morphological features and specific immunological markers of endothelial cells.     

The role of the bacterial cell wall in the development of the lethal effect of colicin E1

Zusammenfassung Es konnte wahrscheinlich gemacht werden, dass Zellwände von Bakterien die Wirkung bestimmter Colicine hemmen.