Recent trend of research on the nongenotoxic mechanisms of chemical carcinogenesis

本総説は,筆者らが進めている｢低線量放射線の健康への影響と医療への応用｣に関する研究に資するために調査した,化学発がんの非遺伝毒性的メカニズムの解明に関する最近の動向の概要についてまとめたものである｡即ち,非遺伝毒性的発がんにおける細胞増殖,シトクロムP450誘導,酸化的ストレス,および遺伝子発現のそれぞれの役割,並びに量的な応答性について言及した｡また,後成的発がんにおけるアポトーシス,およびギャップ結合による情報伝達のそれぞれの役割についても触れた｡その結果,非遺伝毒性的な発がん物質の作用の様式とメカニズムやこれによる後成的な影響などについては解明さ れつつあり,特に,これらの発がん物質がゲノムDNAに対し直接的な相互作用,突然変異,修飾などを行う発がん物質とは機能的に異なった作用をすることが明らかになった｡また,これらは放射線発がんなど低線量放射線の健康への影響などについて研究する上で,重要な知見となっていることもわかった。To elucidate the health effects by low dose radiation, we reviewed the recent trend of research on the epigenetic mechanisms of chemical carcinogenesis. The following view were obtained. It has become apparent that chemical and physical agents that induce cancer may do so through different cellular and molecular mechanisms. Investigators, recognizing the apparent differences in the ways compounds participate in the carcinogenesis process, coined the phrases "genotoxic" and "epigenetic" in describing activities of chemicals and physical agents that induced cancer. The term "nongenotoxic" has to some extent replaced "epigenetic" and thus, classification of chemical carcinogens has been frequently delegated to either the genotoxic or nongenotoxic categories. Moreover, while much work remains in the understanding of the modes and mechanisms of action of nongenotoxic carcinogens and the epigenetic effects of these agents, it is apparent that this category of chemicals are functionally different than those compounds which directly interact, mutate, and modify genomic DNA

Characteristic of GAFCHROMIC XR TYPE T dosimetry film

医療の高度化に伴い,近年では長時間のⅩ線透視を行うInterventional Radiology(IVR)手技が頻繁に行われ,副作用としての難治性放射線皮膚障害例の報告が増加している｡確定的影響である放射線皮膚障害はしきい値を超えると発症し,線量に依存して障害の程度が重篤となるため,患者被曝線量の測定が重要である｡しかし,IVRでは照射部位が多彩で,焦点-皮膚間距離が不安定なため,その測定方法は確立されていない｡本研究では,近年IVR等低エネルギー線量測定用フイルムとして開発されたCAFCHROMIC XR TYPE T について性能評価を行い,患者皮膚入射面の被曝線量測定への応用の可能性について検討した｡その結果,線量特性,線質特性,ネット値の安定性に良好な特性を示し,臨床に使用可能であったので報告する｡In recent years, interventional radiology (IVR) using which uses prolomged fluoroscopy has been performed frequently in clinical radiology. Also, reports of radiation skin injuries whose symptoms occur after IVR has been also increasing. These symptoms will become worse if the radiation induced skin injuries are caused by doses which are above the designated threshold, and the grade of injuries are dependent on dose. Therefore, it is important that patient skin dose is measured correctly. But when perfoming IVR, irradiation is complex pricedure, and there is a measurement error with an unfixed source-to-skin distance. So. in this paper, characteristics of GAFCHROMIC XR TYPE T (which are film for low energy X-rays) are performed. Then, they are decided whether the application to the skin surface incidence dose measurement whoud be posible. From these results usefull data can be obtainned; for exanmpe film characteristics, energy factors and stability of sensivility