Biomedical subjects

H Straaten

Publications and source records attributed to H Straaten.

4 recordsLinked to original sources

PubMed1992

Protein synthesis in irradiated cells. I. Ultraviolet radiation.

Excision-deficient haploid yeast cells (Saccharomyces cerevisiae) were exposed to 254-nm UV radiation and protein synthesis inhibition was measured for a large number of different proteins resolved by two-dimensional gel electrophoresis. The derived UV-radiation sensitivities exhibited an overall increase with protein molar mass. Quantitatively, this behavior is compatible with a well known mechanism of transcription inactivation--termination of RNA chains at UV-radiation-induced pyrimidine dimers--if the respective target sizes are inferred from protein molar mass. The observed deviations from the predicted response suggest that (i) UV-radiation damage may also interfere with recognition/binding of RNA polymerase to regulatory sequences and (ii) the frequency of photolesions for a specific protein encoding gene may differ markedly from the mean induction rate for the total yeast genome.

Fungal Proteins↗

PubMed1989

Quantitative interpretation of heavy ions effects: models for the biological effects of heavy ions.

Heavy ions are an important part of space radiation. Although they contribute only about 1 percent in number the fraction in terms of energy deposited is much higher. Also the quality of radiation is different from the other components since the LET is generally quite high. This poses the problem of Relative Biological Effectiveness (RBE). It is considerably more important in space than on earth because shielding measures are costly and sometimes not even feasible. Radiation hazards appear to be the limiting factor In long term space flights and their evaluation constitutes a major task. There is still no general agreement about RBE of earthbound radiation, and even less concerning the biological weighting of very heavy and very energetic ions in space. Because of the lack of experimental data--particularly for risk estimates in humans-- theoretical approaches may be very helpful in this respect and provide the only means to judge the radiation protection situation in outer space. In order to be useful careful checks of their consistency are necessary. This paper summarizes some of the more common approaches in a critical manner. The unhappy conclusion at the end will be that at present it is not possible to understand even heavy ion action on survival quantitatively with an acceptable precision.

Animals↗

PubMed1986

A model of ion track structure based on classical collision dynamics.

The energy deposition in ion tracks as a function of radial distance is calculated on the basis of classical collision dynamics and using empirical range-energy relationships for electrons. The calculations show that the energy density (i.e. energy deposited per unit mass) varies according to an inverse-square function with distance from the track centre. The maximum extension, the 'penumbra radius', is a power function of the ion's kinetic energy divided by its mass. Comparison with experimental data demonstrates the applicability of the model for ion specific energies greater than 1 MeVu-1.

Animals↗

PubMed1982

Heavy ion effects on yeast cells: induction of canavanine-resistant mutants.

The induction of forward mutations (resistance to canavanine) by heavy ion bombardment was investigated in wild type haploid yeast Saccharomyces cerevisiae. Accelerated ions of argon, titanium, nickel, krypton, xenon, lead and uranium with specific energies between 1.7 and 9.25 MeV/u were obtained from the UNILAC machine at the Gesellschaft für Schwerionenforschung, Darmstadt/Germany. LET-values ranged from 1200 to about 15 000 keV/microns. There was no unequivocal dependence of mutation induction cross section on either LET or Z*2/beta 2, but also a prominent influence of ion specific energy. This is explained by the action of long-ranging delta-electrons.

Canavanine↗