Biomaterial Database

Mutation and inactivation of cultured mammalian cells exposed to beams of accelerated heavy ions. IV. Biophysical interpretation. 1980

D T Goodhead, and R J Munson, and J Thacker, and R Cox

A biophysical analysis is made of the results of recent experiments which used accelerated heavy ions of 20 to 470 keV micron-1 to induce inactivation and mutation (resistance to 6-thioguanine) in cultured V79 Chinese hamster cells and HF19 human diploid fibroblasts. It is shown that the discrete nature of the primary ions must be explicity taken into account before the numbers of induced lethal and mutagenic lesions can be deduced from the observed radiosensitivities. The measured numbers of lesions produced by the radiations of different LET are compared with the relative numbers predicted by various models of radiation action. The observations can be explained on the hypothesis that each lethal lesion is produced by a deposition of small energy (small number of ionizations) in a distance of about 3 nm. Two different lesions appear to be involved, one of which requires greater than or equal to 100 eV and is dominant with low-LET radiations, and the other requires greater than or equal to 300 eV and is dominant at high-LET. Similar conclusions may apply to mutagenic lesions except that the mechanism which dominates at high-LET requires significantly more than 300 eV. More precise assessments of the hypothesis and these numerical values must await detailed track structure calculations of the radiation on the nanometre scale. Alternative models which invoke 'accumulation of sublethal damage' or 'interaction between sublesions', over distances of the order of microns, do not provide a consistent explanation of the observations. This suggests that the frequently observed curvature of low-LET dose-responses is not due to interaction between sublesions but rather to some other mechanism such as a dose-dependent repair process. It is also shown that low velocity, high-LET ions produce an average of appreciably less than one lethal lesion in traversing the nucleus of the above mammalian cells; 90 keV micron-1 helium ions produce about 0.03-0.06 lethal lesions micron-1 of track through the nucleus of the cells of thickness about 7 microns. Some estimates are also made of the size of the nuclear region which is sensitive to the induction of mutation to 6-thioguanine-resistance; it is concluded that this region extends beyond the DNA of the structural gene itself.

UI	MeSH Term	Description	Entries
D007477	Ions	An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D007668	Kidney	Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.	Kidneys
D008168	Lung	Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.	Lungs
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009154	Mutation	Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.	Mutations
D011829	Radiation Dosage	The amount of radiation energy that is deposited in a unit mass of material, such as tissues of plants or animal. In RADIOTHERAPY, radiation dosage is expressed in gray units (Gy). In RADIOLOGIC HEALTH, the dosage is expressed by the product of absorbed dose (Gy) and quality factor (a function of linear energy transfer), and is called radiation dose equivalent in sievert units (Sv).	Sievert Units,Dosage, Radiation,Gray Units,Gy Radiation,Sv Radiation Dose Equivalent,Dosages, Radiation,Radiation Dosages,Units, Gray,Units, Sievert
D002467	Cell Nucleus	Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)	Cell Nuclei,Nuclei, Cell,Nucleus, Cell
D002470	Cell Survival	The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.	Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D003412	Cricetulus	A genus of the family Muridae consisting of eleven species. C. migratorius, the grey or Armenian hamster, and C. griseus, the Chinese hamster, are the two species used in biomedical research.	Hamsters, Armenian,Hamsters, Chinese,Hamsters, Grey,Armenian Hamster,Armenian Hamsters,Chinese Hamster,Chinese Hamsters,Grey Hamster,Grey Hamsters,Hamster, Armenian,Hamster, Chinese,Hamster, Grey