Some problems and errors in cytogenetic biodosimetry

Human radiosensitivity is a quantitative trait that is generally subject to binomial distribution. Individual radiosensitivity, however, may deviate significantly from the mean (by 2-3 standard deviations). Thus, the same dose of radiation may result in different levels of genotoxic damage (commonly measured as chromosome aberration rates) in different individuals. There is significant genetic component in individual radiosensitivity. It is related to carriership of variant alleles of various single-nucleotide polymorphisms (most of these in genes coding for proteins functioning in DNA damage identification and repair); carriership of different number of alleles producing cumulative effects; amplification of gene copies coding for proteins responsible for radioresistance, mobile genetic elements, and others. Among the other factors influencing individual radioresistance are: radioadaptive response; bystander effect; levels of endogenous substances with radioprotective and antimutagenic properties and environmental factors such as lifestyle and diet, physical activity, psychoemotional state, hormonal state, certain drugs, infections and others. These factors may have radioprotective or sensibilising effects. Apparently, there are too many factors that may significantly modulate the biological effects of ionising radiation. Thus, conventional methodologies for biodosimetry (specifically, cytogenetic methods) may produce significant errors if personal traits that may affect radioresistance are not accounted for.

Effects of handling regime and sex on changes in cortisol, thyroid hormones and body mass in fasting grey seal pups

Survival of seal pups may be affected by their ability to respond appropriately to stress. Chronic stress can adversely affect secretion of cortisol and thyroid hormones, which contribute to the control of fuel utilisation. Repeated handling could disrupt the endocrine response to stress and/or negatively impact upon mass changes during fasting. Here we investigated the effects of handling regime on cortisol and thyroid hormone levels, and body mass changes, in fasting male and female grey seal pups (Halichoerus grypus). Females had higher thyroid hormone levels than males throughout fasting and showed a reduction in cortisol midway through the fast that was not seen in males. This may reflect sex-specific fuel allocation or development. Neither handling frequency nor cumulative contact time affected plasma cortisol or thyroid hormone levels, the rate of increase in cortisol over the first five minutes of physical contact or the pattern of mass loss during fasting in either sex. The endocrine response to stress and the control of energy balance in grey seal pups appear to be robust to repeated, short periods of handling. Our results suggest that routine handling should have no additional impact on these animals than general disturbance caused by researchers moving around the colony.