Simian virus 40 chromatin showing nucleosomes in linear bead-like arrangements along extended closed circular DNA

Viral nucleoprotein complexes were extracted from nuclei of permissive cells (CV-1) infected with simian virus 40 (SV40) and examined by electron microscopy. SV40 nucleoprotein complexes (SV40 chromatin) showed nucleosomes in linear bead-like arrangements along the extended closed circular DNA. The contour length of the SV40 chromatin was only 1.0-1.8 times shorter than that of viral DNA obtained after deproteinization. The data suggest that the circular DNA in SV40 chromatin can be extended to nearly its full length without detachment of the histone complexes.</p

Swelling and Replicative DNA Synthesis of Detergent-treated Mouse Ascites Sarcoma Cells

Previous investigation showed that mouse ascites sarcoma cells permeabilized with appropriate concentrations of detergents (Triton X-100, Nonidet P-40 and Brij 58) had high replicative DNA synthesis in the presence of the four deoxyribonucleoside triphosphates, ATP, Mg2+ and proper ionic environment. The present study showed the optimum detergent concentration for DNA synthesis coincided closely with the minimum detergent concentration for inducing cell swelling. Phase contrast microscopy and electron microscopy of Triton-permeabilized cells showed the characteristic swollen cytoplasms and nucleus. Autoradiographic study showed that the DNA synthesis in permeable cells was confined to the nucleus. Cell viability and [3H] deoxythymidine uptake were impaired at much lower concentrations of Triton X-100 than the optimum concentration for in vitro DNA synthesis. In Triton-permeabilized cells, the minimum Triton concentration that produced cell swelling also seemed to produce high repliative DNA synthesis, which reflects the in vivo state of DNA synthesis.</p

Complete in vitro DNA replication of SV40 chromatin in digitonin-treated permeable cells.

A permeable cell system has been developed by treatment with digitonin for studying in vitro DNA replication of chromatin. DNA replication of simian virus 40 nucleoprotein complexes (SV40 chromatin) in digitonin-treated permeable cells was analyzed by electrophoresis in agarose-gel. Autoradiography of the agarose-gel revealed that [32P]dCTP was incorporated in SV40 DNA I, II and replicating intermediates. The time course of the incorporation indicated the complete replication of SV40 DNA and chromatin with a full number of nucleosomes. The digitonin-treated permeable cell system will serve as a useful system for studying in vitro DNA replication of chromatin.</p

Type C virus particles produced in human T-cell lines derived from acute lymphoblastic leukemia and a leukemic T-lymphoid malignancy.

Electron microscopy of four human T-cell lines revealed the production of type C virus particles in two T-cell lines: one derived from acute lymphoblastic leukemia and the other from a leukemic T-lymphoid malignancy. Virus particles isolated from these cells had reverse transcriptase activity and the major internal structural protein of 30,000 daltons (p30). The indirect immunofluorescence test of these virus-producing cells with sera of patients with adult T-cell leukemia (ATL) was negative. The data indicate that these retroviruses are different from adult T-cell leukemia virus (ATLV).</p

日本産アキギリ属の核形態学的比較

[論文

富山県産オオバコの染色体数

[短報

Finite-element analysis of laminated rubber bearing of building frame under seismic excitation

Finite element analysis is carried out for a building frame supported by laminated rubber bearings to simultaneously investigate global displacement and local stress responses under seismic excitation. The frame members and the rubber bearings are discretized into hexahedral solid elements with more than 3 million degrees of freedom. The material property of rubber is represented by the Ogden model, and the frame is assumed to remain in elastic range. It is shown that the time histories of non-uniform stress distribution and rocking behavior of the rubber bearings under a frame subjected to seismic excitation can be successfully evaluated, and detailed responses of base and frame can be evaluated through large-scale finite element analysi