Skip to main content

RBE-VALUES OF MONOENERGETIC ELECTRONS IN THE RANGE OF SEVERAL 100 eV TO 10 keV FOR CELL TRANSFORMATION

Objective

CYTOGENETIC AND EPIDEMIOLOGICAL STUDIES SUGGEST THAT DNA REARRANGEMENTS ARE THE MAIN CAUSE FOR CANCER INDUCTION. EVIDENCE DERIVED FROM SEVERAL SOURCES IMPLICATES THE DNA DOUBLE STRAND BREAKS (DSB) IN DNA REARRANGEMENTS. INVESTIGATIONS WITH ULTRASOFT X-RAYS SHOW THAT THE RBE - VALUES FOR BOTH DSB AND CHROMOSOME ABERRATION INDUCTION INCREASE WITH DECREASING ELECTRON ENERGY. THE FOLLOWING INVESTIGATIONS WITH LOW ENERGY ELECTRONS ARE PROPOSED IN ORDER TO CONTRIBUTE TO RISK ASSESSMENTS AND IN SETTING UP EXPOSURE LIMITS.
Relative biological effectiveness (RBE) values, for cell transformations, of monoenergetic electrons in the range of several 100 eV to 10 keV have been determined.

Studies included:
determination of the transformation frequency in C3H10T1/2 cells using cobalt-60 gamma-rays as a reference radiation;
determination of the OER value for transformation of C3H10T1/2 cells;
evaluation of deoxyribonucleic acid (DNA) lesions involved in radiation induced cell transformation by comparing RBE and OER values for DNA lesions and cell transformation.
RBE - VALUES OF ELECTRONS OF DEFINITE ENERGIES WILL BE DETERMINED FOR CELL TRANSFORMATION. MONOENERGETIC ELECTRONS ARE PRODUCED WITHIN CELLS BY IRRADIATION WITH CHARACTERISTIC ULTRASOFT X-RAYS OF ENERGIES RANGING FROM SEVERAL HUNDRED EV UP TO ABOUT 10 KEV.

THESE X-RAYS ARE GENERATED BY BOMBARDING SUITABLE TARGETS WITH ACCELERATED PROTONS. THE USE OF PROTONS INSTEAD OF ELECTRONS PROVIDES AN ULTRASOFT X-RAY BEAM WITH NEGLIGIBLE BREMSSTRAHLUNG CONTAMINATION. THE INVESTIGATIONS WILL BE STARTED WITH CHROMIUM K CHARACTERISTIC X-RAYS (4.55 KEV) FOLLOWED BY ALUMINIUM K CHARACTERISTIC X-RAYS (1.5 KEV). THE RELATIVE BIOLOGICAL EFFECTIVENESS OF THESE CHARACTERISTIC X-RAYS (OR LOW ENERGY ELECTRONS) ARE RELATED TO THAT OF 60-CO GAMMA-RAYS.

BECAUSE OF THE DEFINED ENERGY AND SHORT RANGE OF THE PRODUCED ELECTRONS ULTRASOFT X-RAYS ARE AN EXCELLENT TOOL FOR PROBING THE SUBCELLULAR MECHANISMS OF RADIATION CARCINOGENESIS AND THE ROLE OF THE LOW ENERGETIC SECONDARY ELECTRONS WHICH ARE PRODUCED BY MOST RADIATIONS. CR K AND AL K CHARACTERISTIC X-RAYS OF PHOTON ENERGIES 4.55 AND 1.5 KEV RESPECTIVELY GENERATE SECONDARY ELECTRONS OF RANGES 600 NM AND 70 NM.

IT IS PLANNED TO USE C3H/10TI/2 MOUSE EMBRYO CELLS WHICH ARE ESTABLISHED FOR ONCOGENIC TRANSFORMATION STUDIES. IN DETAIL THE PROCEDURE IS AS FOLLOWS: FOR SURVIVAL STUDIES A SUFFICIENT NUMBER OF CELLS IS NEEDED PER DISH FOR EVALUATION OF THE COLONY FORMING ABILITY. FOR TRANSFORMATION SCORING ABOUT 300 VIABLE CELLS PER DISH ARE SEEDED. AFTER 6 WEEKS OF (CONFLUENT AND POST CONFLUENT) INCUBATION TRANSFORMED FOCI CAN BE IDENTIFIED. FROM THE TRANSFORMATION FREQUENCIES VERSUS ABSORBED DOSES THE RBE - VALUES CAN BE EVALUATED WHICH MAY BE DOSE DEPENDENT.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

GSF - FORSCHUNGSZENTRUM FUER UMWELT UND GESUNDHEIT GMBH
Address
Ingolstaedter Landstrasse 1
85764 Neuherberg
Germany