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PubMed1979

DNA replication in Physarum polycephalum: electron microscopic and autoradiographic analysis of replicating DNA from defined stages of the S-period.

Electron microscopic and autoradiographic analysis of replicating DNA from Physarum showed that replication occurs at a rate of 0.4 micron/min/per replicon and that replicons of size 10--15 mu occur in temporal clusters with an average of about 4 replicons per cluster. These results are compared with previous hydrodynamic measurements and with those obtained in other organisms.

Autoradiography↗
PubMed1975

Replication of polyoma DNA in isolated nuclei. V. Complementation of in vitro DNA replication.

Nuclei from polyoma-infected 3T6 fibroblasts elongate in vitro the progeny strands of the replicative intermediates of polyoma DNA. When high concentrations of such nuclei were incubated, short DNA fragments were formed and subsequently added onto growing progeny strands. When nuclei were repeatedly washed with buffer containing detergent and then incubated at low concentrations. DNA synthesis was decreased. In particular, the joining process was reduced, resulting in an accumulation of short DNA fragments. All aspects of the synthetic capacity of the nuclei were restored by addition of cytoplasmic extract. Additions of purified enzymes (polynucleotide ligase from calf thymus or Escherichia coli together with E. coli DNA polymerase I) increased the joining function of the nuclei. The system can be used for the identification of the enzymatic steps concerned with polyoma DNA replication.

Animals↗
PubMed1979

Replication in Drosophila chromosomes. I. Replication of intranucleolar DNA in polytene cells of D. nasuta.

The organization and replication of intranucleolar DNA in polytene cells of Drosophila nasuta have been examined. Normal Giemsa and fluorescent (Hoechst 33258 and quinacrine mustard) staining reveal that in D. nasuta polytene cells, the intranucleolar DNA is organized into condensed and disperse forms and very often shows connexion to the alpha heterochromatin of the chromocentre. Results of [3H]thymidine autoradiography indicate that the known underreplication of rDNA sequences in polytene cells is due to the slower replication of the intranucleolar DNA. Some aspects of the organization of condensed and disperse intranucleolar DNA are discussed.

Animals↗
PubMed1977

In situ replication techniques: I. Preliminary screening and the negative replication technique.

Fourteen commercially available elastomeric materials were investigated for their suitability as in vivo replication media. After a preliminary screening on an annotated specimen, three materials were chosen for further study. Of all materials evaluated, Xantopren Blue and Silene silicone impression materials provided the best results in vivo. This study demonstrates that a high resolution (ca 1 micron) negative replication technique may prove useful for the clinical evaluation of single-surface phenomena.

Acetates↗
PubMed1978

Differences in the binding of methylated albumin to non-replicating, replicating and denatured DNA from Ehrlich ascites cells.

The binding of methylated albumin to DNA, the basis of the chromatography on columns of kieselguhr coated with methylated albumin (MAK chromatography), was investigated. Scatchard plots revealed only one mode of interaction with fully double-stranded DNA. The complexes should be completely dissociated by raising the NaCl concentration of the solution to 0.8 M, indicating a binding by electrostatic attraction between the oppositely charged protein and DNA molecules. In complexes with denatured and partially single-stranded replicating DNA an additional kind of binding was found which made these complexes more stable against salt dissociation. These secondary interactions were stronger at 23 degrees C than at 0 degrees C and could be weakened by the addition of 6 M urea. It was therefore concluded that apolar forces were involved in these interactions.

Animals↗
PubMed1975

Replication of colicinogenic factor E1 DNA in plasmolysed Escherichia coli cells. Coupling of DNA replication and RNA synthesis.

Plasmolysed chloramphenicol-treated Escherichia coli cells carrying the colicinogenic factor E1 utilize deoxynucleoside triphosphates for the semi-conservative synthesis of Col E1 DNA. Col E1 DNA replication in plasmolysed cells can be dissociated into two temporally separated processes: (a) a rifampicin-sensitive RNA synthesis, which is stimulated by adenosine 3':5'-monophosphate (cyclic AMP) and requires all four ribonucleoside triphosphates and (b) an ATP-dependent DNA synthesis, which is inhibited by arabinosylnucleoside triphosphates and sulfhydryl-blocking reagents. Thes two processes exhibit different sensitivities to inhibition by polyamines and actinomycin D.

Adenosine Triphosphate↗
PubMed1978

Virus-replicating T cells in the immune response of mice. II. Characterization of T cells capable of replicating vesicular stomatitis virus.

Immunocytological properties of the splenic T cell (Tv) which develop into virus plaque-forming cells in response to the antigenic challenge in vitro were investigated in relation to the properties of helper T cells and suppressor T cells in antibody response. Tv was observed in spleen around 1 wk after the intravenous injection of mice with 10(7) sheep erythrocytes. This contrasted with the finding that both helper T cells and suppressor T cells developed as early as 3 days after the immunization. Tv was proliferative in response to the antigenic stimulation, whereas helper T-cell activity could be expressed without cell division. Development of Tv to virus plaque-forming cells was much more dependent on macrophages than the generation of helper activity. Tv was found in nylon wool adherent fraction, whereas helper T cell was found in both nylon adherent and nonadherent fractions. Tv belongs to the short-lived and nonrecirculating T-cell population (T1), whereas the major part of helper T cells belongs to the long-lived and recirculating T-cell population (T2). These results strongly suggest that vesicular stomatitis virus infect and replicate in the different subset(s) of T cell(s) to which the major part of helper T cells belong.

Animals↗
PubMed1979

In vitro replication of a DNA fragment containing the vicinity of the origin of E. coli DNA replication.

The restriction nuclease cleavage pattern of E. coli DNA synthesized in vitro in the cellophane membrane system (Schaller et al., 1972) is similar to the one obtained after labelling E. coli in vivo. This is shown for exponentially growing cells and for cells synchronized by amino acid starvation followed by thymine starvation. In synchronized cells a piece of some 180 kilobase pairs is labelled containing oriC and neighbouring regions at 82 min on the genetic map of E. coli. A pulse label in vitro is incorporated into the same piece of DNA, but the center of this region, i.e. the EcoR1 fragment of 8.6 kbp length which contains the oriC region (Marsh and Worcel, 1977; v. Meyenburg et al., 1977; Yasuda and Hirota, 1977) is missing.

Amino Acids↗