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DOSIMETRIE FOETALE : MESURE DES EFFETS INDUITS APRES IRRA- DIATION CHRONIQUE IN UTERO EN FONCTION DU DEBIT DE DOSE ET DE LA PERIODE DE GESTATION

Objective

THE EFFECTS OF AN INTENSIVE "IN UTERO" IRRADIATION ARE STUDIED DURING THE PHASES OF EXTREME SENSITIVITY OF A GIVEN ORGAN. FOR CERTAIN ORGANS, PERMANENT RADIATION INDUCED CHANGES ARE OBSERVED FOR DOSES OF X- OR GAMMA-RAYS IN THE REGION OF 0.1 GY.

THE EFFECTS INDUCED BY A CHRONIC IRRADIATION FOR ALL OR PART OF INTRA-UTERINE LIFE ARE STILL TO BE DETERMINED. THIS TYPE OF CHRONIC IRRADIATION INCLUDES EXTERNAL IRRADIATION AND ALSO THAT RESULTING FROM INTERNAL CONTAMINATION BY CERTAIN RADIONUCLIDES.

THE AIM OF THE CURRENT RESEARCH IS TO DETERMINE THE EFFECTS INDUCED BY CHRONIC GAMMA (60-CO) IRRADIATION OF RODENTS FOR ALL OR A PART OF THE INTRA-UTERINE LIFE. FOR A DOSE OF GAMMA IRRADIATION IN THE REGION OF 1.5 GY, A PRELIMINARY STUDY HAS SHOWN THE INFLUENCE OF THE STRENGTH OF DOSE. THUS AN INTENSE IRRADIATION OF A RAT BETWEEN J+12 AND J+17 P.C. CAUSES SIGNIFICANT MALFORMATIONS IN THE CENTRAL NERVOUS SYSTEM (CNS) WHEREAS AN IDENTICAL DOSE DELIVERED PROTRACTED OVER THE ENTIRE DAY DOES NOT CAUSE THIS TYPE OF MALFORMATION. THE CHANGES IN THE GONADS ARE, ON THE OTHER HAND, IDENTICAL AFTER INTENSE OR CHRONIC IRRADIATION. THE RESEARCH PROGRAMME FORESEEN FOR THE NEXT 18 MONTHS INTENDS TO DETERMINE THE DIFFERENT RESPONSES OBTAINED IN RADIATION SENSITIVE ORGANS AFTER INTENSE OR CHRONIC IRRADIATION.
Foetal body weights and adult brain weights are good parameters to estimate the dose of exposure received during intrauterine life.

No dose rate effect compatible with animals survival occurs with protracted irradiation during gestation.

A 1 Gy acute exposure in the middle of the brain organogenes is period shows a specific dose rate effect in adults on brain weight and histology in the range of dose rates from 4.75 Gy/day to 23.9 Gy/day.
THIS WORK WILL BE CARRIED OUT ON 2 SPECIES OF RODENT AND WILL CONSIST OF 2 PARTS:

A. INFLUENCE OF DOSE RATE OF AN IRRADIATION DELIVERED DURING THE WHOLE INTRA-UTERINE LIFE. THE DAILY DOSE WILL BE BETWEEN 0 AND 0.6 GY. IN ORDER TO VARY THE DOSE RATE, THE DAILY IRRADIATION WILL BE DELIVERED OVER A PERIOD OF 5 OR 24 HOURS.

B. INFLUENCE OF THE PERIOD OF EMBRYONIC OR FOETAL LIFE DURING WHICH IRRADIATION HAS TAKEN PLACE. THE STUDY OF RADIATION INDUCED EFFECTS WILL BE CARRIED OUT ON LETHALITY, WEIGHT GAIN AND RESEARCH OF MACRO- AND MICROSCOPIC LESIONS IN DIFFERENT TISSUES. LETHALITY WILL BE QUANTIFIED AT THE END OF THE GESTATION PERIOD AND WILL BE EXPRESSED IN TERMS OF PRE- AND POST-IMPLANTATION. WEIGHT GAIN WILL BE EVALUATED FROM THE END OF GESTATION TO MATURITY. THE EFFECTS INDUCED IN DIFFERENT ORGANS, I.E. CNS AND GONADS WILL BE DETERMINED ON THE BASIS OF ORGAN WEIGHT EITHER IN ABSOLUTE TERMS OR RELATED TO THE WHOLE ANIMAL AS WELL AS ON THE BASIS OF MORPHOLOGICAL AND HISTOLOGICAL EXAMINATION.
THESE RESULTS, PRESENTED AS DOSE-EFFECT RELATIONSHIP, WILL BE USED TO ESTIMATE DOSE AND EFFECTS FROM AN INTERNAL CONTAMINATION BY CERTAIN RADIONUCLIDES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

COMMISSARIAT A L'ENERGIE ATOMIQUE
Address
Rue De La Federation 31-33
75015 Paris
France