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At least 415 records · Page 23Linked to original sources
PubMed1989

In-vivo radiotoxicity of DNA-incorporated 125I compared with that of densely ionising alpha-particles.

When the atomic nucleus of 125I decays by orbital electron capture followed by internal conversion, numerous very-low-energy electrons (Auger electrons) are emitted, so that the energy density in the immediate vicinity of the decay site is extremely high. 125I incorporated into DNA was as effective as densely ionising 5.3 MeV alpha-particles from 210Po in reducing the sperm-head population in mice. Hence the biological risks of Auger-electron emitting radionuclides widely used in biology and medicine ought to be reassessed.

Animals↗
PubMed2006

A comparison of cellular irradiation techniques with alpha particles using the Geant4 Monte Carlo simulation toolkit.

A comparison of three cellular irradiation techniques using the Monte Carlo simulation toolkit Geant4 is presented in this paper. They involve electrodeposited source of alpha particle-emitting radionuclides, random classical alpha beam irradiation and single cell targeted irradiation using a focused alpha microbeam line. The simulation allows the calculation of hit distributions among the cellular population as well as the absorbed dose for two typical cellular geometries.

Alpha Particles↗
PubMed2006

Effective cancer therapy with the alpha-particle emitter [211At]astatine in a mouse model of genetically modified sodium/iodide symporter-expressing tumors.

PURPOSE: The sodium/iodide symporter (NIS) gene is currently explored in several trials to eradicate experimental cancer with radiodine ((131)I) by its beta-emission. We recently characterized NIS-specific cellular uptake of an alternative halide, radioastatine ((211)At), which emits high-energy alpha-particles. The aim of this study was to investigate in vivo effects of the high linear energy transfer (LET) emitter (211)At on tumor growth and outcome in nude mice. EXPERIMENTAL DESIGN: We administered radioastatide in a fractionated therapy scheme to NMRI nude mice harboring rapidly growing solid tumors established from a papillary thyroid carcinoma cell line genetically modified to express NIS (K1-NIS). Animals were observed over 1 year. Tumor growth, body weight, blood counts, survival, and side effects were measured compared with control groups without therapy and/or lack of NIS expression. RESULTS: Within 3 months, radioastatide caused complete primary tumor eradication in all cases of K1-NIS tumor-bearing nude mice (n = 25) with no tumor recurrence during 1 year follow-up. Survival rates of the K1-NIS/(211)At group were 96% after 6 months and 60% after 1 year, in contrast to those of control groups (maximum survival 40 days). CONCLUSION: Our study indicates that (211)At represents a promising substrate for NIS-mediated therapy of various cancers either with endogenous or gene transfer-mediated NIS expression.

Animals↗
PubMed2004

Stable doubly charged positive molecular ions formed by direct attachment of alpha particles to HCN and HNC.

The existence of [HeNCH](2+) and [HeCNH](2+) is examined by reliable high-level ab initio methods. It is shown that both species are metastable with respect to the proton loss process, but the activation barriers are high enough to accommodate several resonant states. Their estimated lifetimes are practically infinite for v<3, implying that the attachment of alpha particles to HNC and HCN yields kinetically stable dications. This could be an important factor in the cyanide chemistry in interstellar and comet environments.

Journal Article↗
PubMed1992

Interlaboratory comparison of different alpha-particle and radon sources: cell survival and relative biological effectiveness.

Alpha radiation-induced cell killing was determined in four different laboratories in order to: 1) measure interlaboratory variability and 2) compare the effects of radon and radon daughter exposures with the effects of 238Pu (an often-used model for radon exposure). The results suggest that differences in handling from laboratory to laboratory can affect both low and high linear energy transfer responses and should be considered when comparing results from different laboratories.

Alpha Particles↗
PubMed1999

The track structures of ionizing particles and their application to radiation biophysics. II. Results for various organisms irradiated with protons, deuterons and alpha-particles.

Using knowledge of the track structure generated by ionizing particles together with details of the organisms being irradiated, the application of a new analytical method to two biophysical models to explain the inactivation of cells by radiation has been developed. It is shown that both models are equally successful in predicting experimental results and that good agreement is found with the data for single-strand phage, Bacillus subtilis spores, various strains of Escherichia coli, haploid and diploid yeast, and human diploid fibroblasts. The only significant discrepancy arose with T1-phage, for which a tentative explanation is offered. The differences in inherent radiosensitivity between organisms, after allowance is made for differences in target size, are attributed to differences in enzymatic repair systems and in the packing of the DNA.

Alpha Particles↗
PubMed1989

Cerebral glycogenosis, alpha particle type: morphologic and biochemical observations in an infant.

A 3-month-old infant with congenital hypotonia suffering from an unusual form of glycogenosis is reported. The most striking neuropathologic findings were vacuolation of neuropile and glycogen accumulation, especially in the cerebral cortex and cerebellar molecular layer. Ultrastructurally, glycogen accumulation was present mainly in neurites and astrocytic processes, and mostly appeared as rosettes (alpha glycogen particles). Biochemical analysis of glycogen in various regions of the central nervous system showed an increase of up to 100-fold. The cerebral cortex, deep nuclei, and cerebellar cortex had the highest glycogen elevations, while the cerebral white matter glycogen level was normal. Among other tissues, the heart showed a several-fold increase in glycogen content. Muscle, liver, and kidney glycogen levels were not elevated. Findings in this case and in three other reported patients with cerebral glycogenosis of alpha particle type are discussed.

Brain↗
PubMed1986

Lung cancer risk at low doses of alpha particles.

A survey of inhabitant exposures arising from the inhalation of 222Rn and 220Rn progeny, and lung cancer mortality has been carried out in two adjacent areas in Guangdong Province, People's Republic of China, designated as the "high background" and the "control" area. Annual exposure rates are 0.38 working level months (WLM) per year in the high background, and 0.16 WLM/yr in the control area. In 14 yr of continuous study, from 1970 to 1983, age-adjusted mortality rates were found to be 2.7 per 10(5) living persons of all ages in the high background area, and 2.9 per 10(5) living persons in the control area. From this data, we conclude that we are unable to determine excess lung cancers over the normal fluctuations below a cumulative exposure of 15 WLM. This conclusion is supported by lung cancer mortality data from Austrian and Finnish high-background areas. A theoretical analysis of epidemiological data on human lung cancer incidence from inhaled 222Rn and 220Rn progeny, which takes into account cell killing as competitive with malignant transformation, leads to the evaluation of a risk factor which is either a linear-exponential or a quadratic-exponential function of the alpha-particle dose. Animal lung cancer data and theoretical considerations can be supplied to support either hypothesis. Thus we conclude that at our current stage of knowledge both the linear-exponential and the quadratic-exponential extrapolation to low doses seem to be equally acceptable for Rn-induced lung cancer risk, possibly suggesting a linear-quadratic transformation function with an exponential cell-killing term, or the influence of risk-modifying factors such as repair or proliferation stimuli.

China↗