title: Biological effects of field emission-type X-rays generated by nanotechnology.
abstract: Thermionic emission (TE)-type X-ray generators have been exclusively used in medicine, but there are many difficulties in making these X-ray sources compact. A field emission (FE)-type X-ray generator using carbon nanotubes is a newly-developed compact system that can be as small as several cm in length. Considering the compactness of the equipment, the FE-type X-ray generator may become a useful tool for endoscopic, intracavitary or intraoperative radiotherapy in the future. The aim of this study was to investigate the biological effects of X-rays generated by the FE-type X-ray source in comparison with those of conventional TE-type X-rays. Mouse thymic lymphoma 3SB cells were irradiated by an FE-type X-ray generator developed by our group and a conventional TE-type X-ray source under identical conditions. DNA damage after radiation was detected by foci formation of phospho-H2AX (gamma-H2AX). Effect on the cell cycle was analyzed by flow cytometry. Activation of the DNA damage checkpoint was analyzed by immunoblotting. Induction of apoptosis was studied using the TUNEL assay. In terms of induction of DNA damage (DNA double-strand breaks), activation of cell cycle checkpoints (p53 stabilization, p21 induction, Chk1 and Chk2 phosphorylations), and induction of apoptotic cell death, FE-type X-rays were as effective as TE-type X-rays, and FE-type X-rays appeared to be applicable to radiation therapy.
authors.affiliation: Department of Musculoskeletal Medicine, Nagoya City University, Graduate School of Medical Sciences, Japan.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Nakazato
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakanishi
authors.forename: Shigetomo
authors.initials: S
authors.lastname: Kita
authors.forename: Fumio
authors.initials: F
authors.lastname: Okuyama
authors.forename: Yuta
authors.initials: Y
authors.lastname: Shibamoto
authors.forename: Takanobu
authors.initials: T
authors.lastname: Otsuka
mesh_terms: D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D006657:Histones / Q000378:metabolism; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence; D036103:Nanotechnology / Q000379:methods*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D015739:Nocodazole / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011878:Radiotherapy / Q000379:methods*; D014965:X-Rays
chemical_list: D006657:Histones; D037742:Nanotubes, Carbon; C475961:gamma-H2AX protein, mouse; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse; C578633:Chek2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D015739:Nocodazole