Cytotoxicity of human T-lymphocytes sensitized by Epstein-Barr virus. Role of HLA antigens at the surface of target cells infected by the virus]

Peripheral T-lymphocytes from patients with infectious mononucleosis are cytotoxic towards target cells from Epstein-Barr virus-genome carrying human lumphoblastoid lines. Thus, these T-cells appear to be sensitized to viral coded determinants. Daudi cells, that carry EBV-genome, but lack HLA antigens are resistant to specific cytolysis in this model. These results suggest direct HLA involvement in the target structure recognized by birus-sensitized cytolytic T-lymphocytes in human.     

Density gradient centrifugation of cells separated from multicellular tumor spheroids

Summary Cells from a murine fibrosarcoma (FSa) have been grown in vitro as multicell tumor spheroids (MTS). The growth rate of these MTS was determined. Follwing selected periods of growth, MTS were made into a single cell suspension and separated on linear density gradients of Renografin. While only 1 population of cells was separated from small spheroids (400 m diameter), at least 3 subpopulations of tumor cells were separated and isolated from large spheroids (800 m in diameter).This investigation was supported in part by grants numbered CA-18628 and CA-06294, awarded by the National Cancer Institute, DHEW.     

Density gradient centrifugation of cells separated from multicellular tumor spheroids.

Cells from a murine fibrosarcome (FSa) have been grown in vitro as multicell tumor spheroids (MTS). The growth rate of these MTS was determined. Following selected periods of growth, MTS were made into a single cell suspension and separated on linear density gradients of Renografin. While only 1 population of cells were separated from small spheriods (400 mum diameter), at least 3 subpopulations of tumor cells were separated and isolated from large spheroids (800 mum in diameter).     

Limitations in the quantitative separation of DNA samples by density gradient centrifugation

Résumé Des mélanges de l'ADN («léger») et de l'ADN-¹⁴ C-BU («lourd») ont étés centrifugés dans le chloride de caesium pendant 65 h à 60,000g. Le résidu de l'ADN «lourd» dans l'ADN «léger» fut de l'ordre de 0.1 à 1%. La grandeur du résidu n'a pas correspondu à la proportion de l'ADN «lourd», ni à la concentration totale de l'ADN dans le chloride de caesium.     

Heterogeneity of HeLa cell DNA as evidenced by CsCl density gradient centrifugation

Summary HeLa cell DNA was analyzed through CsCl density gradient centrifugation and thermal denaturation. Neutral centrifugation without ionic treatment allowed the resolution of a main peak with density 1.699 g/ml and of 3 satellites DNAs with densities 1.683, 1.710 and 1.720. First derivatives of melting curves showed the presence of 4 DNA families, whose G+C content calculated from T_m values corresponded almost exactly to the G+C content expected from the previously densities. The extraction method seems particularly suitable for quantitative separation of DNA classes.     

Different primary structure of 2 variants of Friend virus p 30 polypeptide separated by isoelectric focusing]

Variants of p 30 (iso-p 30s), the 30,000 dalton major polypeptide of murine C-type retraviruses, have been characterized in all virus strains by isoelectric focusing. Several of these iso-p 30s have been found to coexist in a given virus strain. In the present study, two iso-p 30s, characteristic of the Friend-Rauscher subgroup, separated by preparative isoelectric focusing of p 30 in thin layers of polydextran gel, were subjected to tryptic peptide mapping and aminoacid analysis. The two iso-p 30s, with isoelectric points (pI) of 6.5 and 7.1, were found to possess a partially different primary structure, with about 50% homology. The results are discussed.     

Sampling of virus particles and macromolecules sedimented in an equilibrium density gradient

Résumé La distribution de composés macromoléculaires, stratifiés dans un gradient de densité de CsCl établi par une ultracentrifugation prolongée, est déterminée quantitativement par le recoupage du contenu du tube. Une courte aiguille hypodermique est tout simplement insérée dans le fond du tube. Le contenu du tube s'épanche goutte à goutte. Les fractions de recoupage peuvent être ensuite analysées une à une.

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This research was supported in part by the National Science Foundation.     

Isolation of plasmid DNA fromAgrobacterium by isopycnic density gradient centrifugation in vertical rotors

Summary Fixed angle and vertical rotors are compared in terms of their sample load, run time, and resolution for the preparation of plasmid DNA fromAgrobacterium.Acknowledgments. This work was supported by a CASE Studentship from the SRC and ICI Corporate Laboratories to J.D., and a grant from the SRC to M.R.D. and E.C.C. The authors thank Mr B.V. Case for photographic assistance.     

Attempt at activating mouse intracisternal type A particles by iododeoxyuridine and dexamethasone]

In this study we have compared the effects of Iododeoxyridine (IUdR) and dexamethasone on different Mouse cell lines to determine any differences in their actions on intracisternal A-type particles (IAP). Among the nine cell lines studied only four responded to IUdR stimulation by a subsequent augmentation of IAP. No similar activating effect was detected with dexamethasome treatment.     

Induction of dolykaryocytes by vesicular stomatitis virus in XC rat cells]

V.S.V. induced polycaryocytes in rat embryonic fibroblasts, transformed by the Prague strain of Sarcoma Rous (XC cells). This fusion is strictly dependent on the expression of the viral genome and is probably due to the incorporation of viral antigens in the cell membrane. The integrity of cellular RNA synthesis is however not required. The fusion is probably due to a membrane structure characteristic of these transformed cells.     

Detection of human antigens on the surface of mouse cells transformed by chromosome transfer]

Mouse embryo cells, transformed in vitro by the transfer of chromosomes from HeLa human tumour cells, express a surface antigen (s) also found on HeLa cells. This antigen(s), which has been detected both by indirect immunofluoresence and by a 125I-protein A binding assay, is not an antigen(s) shared by both Human and Mouse cells.     

Density gradient centrifugation of tumor cells from needle biopsies and their respective source tumors: a comparison of density distributions

Summary A needle biopsy technique was applied to a murine fibrosarcoma (FSa) tumor system. FSa tumors of 8 mm diameter in size were biopsied and then made into single cell suspensions. Resulting density profiles of cells from both sources were compared following centrifugation in Renografin gradients. In all cases, there was excellent agreement between the density profiles of the material from each of the biopsies and the corresponding solid tumors.This investigation was supported by grant CA-18628, awarded by the National Cancer Institute, Department of Health and Human Services.