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At least 541 records · Page 30Linked to original sources
PubMed1993

Postirradiation exposure to hypotonic saline shows normal damage processing in radiation-sensitive cell lines.

Three pairs of cell lines (one human and two Chinese hamster ovary (CHO) cell lines) each comprising a cell line with a normal radiation response and a radiation-sensitive mutant, were evaluated for recovery of potentially lethal damage (PLDR) and recovery of sublethal damage (SLDR). In all cases, the normal cell lines (GM1522, human; AA8-4 and K1, CHO) exhibited capacity for PLDR and SLDR was also normal in the two CHO lines. For the mutants (GM3395, human AT; V3 and 5-11, CHO) there was no ability for PLDR and SLDR was also absent in the two CHO cell lines. Postirradiation exposure to hypotonic NaCl solutions resulted in fixation of radiation damage in all the cell lines. This form of damage is repaired if left unperturbed after irradiation. This shows that cells have a large capacity for repair of this form of damage which accounts for much greater changes in survival than those observed in conventional PLDR experiments. These data show that the mutant cell lines retained their capacity to repair the damage which was susceptible to postirradiation fixation by anisotonic salt solutions. In addition, initial (i.e. preirradiation) DNA polymerase activities were measured in the four CHO cell lines; they were not correlated to radiation sensitivity.

Animals↗
PubMed2000

Molecular phylogenetics and biogeography of galaxiid fishes (Osteichthyes: Galaxiidae): dispersal, vicariance, and the position of Lepidogalaxias salamandroides.

The galaxiid fishes exhibit a gondwanan distribution. We use mitochondrial DNA sequences to test conflicting vicariant and dispersal biogeographic hypotheses regarding the Southern Hemisphere range of this freshwater group. Although phylogenetic resolution of cytochrome b and 16S rRNA sequences is largely limited to more recent divergences, our data indicate that the radiation can be interpreted as several relatively recent dispersal events superimposed on an ancient gondwanan radiation. Genetic relationships contradict the findings of recent morphological analyses of galaxioid fishes. In particular, we examine several hypotheses regarding phylogenetic placement of the enigmatic Lepidogalaxias. Although most workers consider Lepidogalaxias to be an unusual scaled member of the Southern Hemisphere galaxioids, it has also been suggested that this species is related to the Northern Hemisphere esocoids. Our data strongly suggest that this species is not a galaxiid, and the alternative hypothesized esocoid relationship cannot be rejected. The species-rich genus Galaxias is shown to be polyphyletic and the generic taxonomy of the Galaxiinae is reassessed in the light of phylogenetic relationships. Juvenile saltwater-tolerance is phylogenetically distributed throughout the Galaxiinae, and the loss of this migratory phase may be a major cause of speciation.

Animals↗
PubMed1990

The 1986 and 1988 UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) reports: findings and implications.

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has published a substantive series of reports concerning sources, effects, and risks of ionizing radiation. This article summarizes the highlights and conclusions from the most recent 1986 and 1988 reports. The present annual per person effective dose equivalent for the world's population is about 3 mSv. The majority of this (2.4 mSv) comes from natural background, and 0.4 to 1 mSv is from medical exposures. Other sources contribute less than 0.02 mSv annually. The worldwide collective effective dose equivalent annually is between 13 and 16 million person-Sv. The Committee assessed the collective effective dose equivalent to the population of the northern hemisphere from the reactor accident at Chernobyl and concluded that this is about 600,000 person-Sv. The Committee also reviewed risk estimates for radiation carcinogenesis which included the new Japanese dosimetry at Hiroshima and Nagasaki. These data indicate that risk coefficient estimates for high doses and high dose rate low-LET radiation in the Japanese population are approximately 3-10% Sv-1, depending on the projection model utilized. The Committee also indicated that, in calculation of such risks at low doses and low dose rates, a risk-reduction factor in the range of 2-10 may be considered.

Accidents↗
PubMed1995

Mutant frequencies in workers at the Sellafield installation.

The frequency of hypoxanthine-guanine phosphoribosyltransferase (hprt) mutations has been determined in the peripheral T-lymphocytes of 18 workers at the Sellafield nuclear reprocessing installation with cumulative recorded radiation doses of about 500 mSv or more in comparison with a matched control group of 18 workers with doses less than 50 mSv. The mean dose of the exposed group was 663 mSv (range 449.3-880.8), and of the unexposed group 10.9 mSv (range 0-46.5). During the most recent 6 y the mean doses were 40.1 mSv (range 1.9-93.9) and 2.3 mSv (range 0-8.7), respectively. The logarithmic mean mutant frequency of the exposed group (9.3 x 10(-6)) was lower than that of the unexposed group (12.4 x 10(-6)). The apparent inverse association of mutant frequency and exposure varied in statistical significance tests from borderline to p < 0.01 depending on how the analysis was performed and whether recent or total exposure was considered.

Humans↗