Eurados review of retrospective dosimetry techniques for internal exposures to ionising radiation and their applications.

This work presents an overview of the applications of retrospective dosimetry techniques in case of incorporation of radionuclides. The fact that internal exposures are characterized by a spatially inhomogeneous irradiation of the body, which is potentially prolonged over large periods and variable over time, is particularly problematic for biological and electron paramagnetic resonance (EPR) dosimetry methods when compared with external exposures. The paper gives initially specific information about internal dosimetry methods, the most common cytogenetic techniques used in biological dosimetry and EPR dosimetry applied to tooth enamel. Based on real-case scenarios, dose estimates obtained from bioassay data as well as with biological and/or EPR dosimetry are compared and critically discussed. In most of the scenarios presented, concomitant external exposures were responsible for the greater portion of the received dose. As no assay is available which can discriminate between radiation of different types and different LETs on the basis of the type of damage induced, it is not possible to infer from these studies specific conclusions valid for incorporated radionuclides alone. The biological dosimetry assays and EPR techniques proved to be most applicable in cases when the radionuclides are almost homogeneously distributed in the body. No compelling evidence was obtained in other cases of extremely inhomogeneous distribution. Retrospective dosimetry needs to be optimized and further developed in order to be able to deal with real exposure cases, where a mixture of both external and internal exposures will be encountered most of the times.

[Using mFISH and mBAND for Bioindication of Internal α-Radiation].

This study was aimed to compare mFISH and mBAND techniques in assessment of the yield of chromosomal aberrations induced by high-LET ionizing radiation. The study group included Mayak workers (46 individuals), for whom the yield of chromosomal aberrations was assessed using two methods: mFISH and mBAND. It was shown that both methods are applicable for biological indication of internal α-radiation exposure. Nevertheless, in case when the source of ionizing radiation is unknown or in terms of a mixed exposure, mFISH appeared as more informative technique that allows identification of markers both external γ-rays (translocations) and internal α-radiation (complex chromosomal rearrangements).

[Structural genomic damages in workers of plutonium production].

The research objective is assessment of structural genomic damages in plutonium workers. The study group included the Mayak nuclear workers subject to chronic occupational exposure to incorporated 239Pu and/or external gamma-rays. The analysis was performed based on the culture of lymphocytes in peripheral blood. The yield of intra-chromosomal exchange aberrations of chromosomal type on stained slides was analyzed using in situ fluorescent hybridization, mBAND. Linear relationships were revealed between (a) the total yield of chromosomal type aberrations (e.g. intra- and inter-chromosomal ones) and an absorbed dose from external exposure of the red bone marrow to gamma-rays, an absorbed dose from internal exposure to a-radiation from incorporated 239Pu; and (b) the yield of intra-chromosomal exchange aberrations of chromosomal type and an absorbed dose from exposure of the red bone marrow to 239Pu and 239Pu body burden.

Intensity of in vitro incorporation of 3H-melatonin in the thyroid gland of rabbits with pineal gland hypofunction.

The structure and hormonal activity of the thyroid gland and its capacity to bind (3)H-melatonin were studied in young adult Chinchilla rabbits with pineal gland hypofunction induced by 2-month exposure to constant illumination. After 2 months of constant exposure to light, the experimental animals exhibited signs of the so-called "latent hypothyroidism" and more intense binding of (3)H-melatonin by the thyroid gland. This fact indicated intactness of its receptor system underlying the possibility of restoring activity of the thyroid gland under conditions of melatonin replacement therapy in hypothyroidism induced by chronic melatonin insufficiency.

[Long round-the-clock illumination as a factor of accelerated ageing of pineal gland].

On sexually matured male rabbits of Shinhilla breed kept in round-the-clock illumination within 5 months, dynamic of changes of structure of pineal gland was investigated. It was found the gradual, progressing in time loss of pinealocytes amount, arising due to their apoptosis, which points out hypolinealism development. Round-the-clock illumination should be considered as the factor promoting accelerated aging of pineal gland.