The future of our radiation protection profession.

There is widespread recognition of the challenge of an ageing profession and the need to recruit, train and retain the next generation of radiation protection professionals. This challenge was the topic of a special session at the International Radiation Protection Association IRPA15 International Congress. It is necessary to address three key aspects: capturing the future professional: gaining RP knowledge and skills: addressing retention, development and career progression. We must support the flow of students into science-based topics and attractively promote our profession. The availability of university and other training courses, together with research opportunities, must be supported. Mentoring of young professionals is key, supported by empathetic seniors in the profession. The overall challenge necessitates cooperation across a wide range of organisations at both international and national level.

The role of radiation protection societies in tackling the skills shortage and development of young professionals and researchers.

Over the last 10 years there have been increasing concerns raised about a potential skills gap in the field of radiation protection (RP). Noting these concerns in 2019, the Society for Radiological Protection, the UK's Chartered Professional Body, launched a study to determine the RP demand in the UK going forward along with the capacity of the profession. The initial results show that over 50% of the SRP membership retires in the next 10-15 years, coupled with an increase in RP demand across the nuclear fuel cycle, medical sector and advancement of new technologies or applications requiring RP advice. This provides strong evidence supporting the concerns of a future skills gap. This paper presents a framework highlighting three core objectives that need to be met to resolve the skills gap. A review of the existing initiatives being undertaken by the Society of Radiological Protection to meet these objectives is included, identifying both areas of good practice and areas for further work and development. A key theme in tackling this challenge has been identified as the need to foster greater collaboration between RP professionals, and organizations both within the UK and abroad, such as IRPA, national societies, employers, academia and industry. This brings a unique opportunity to direct efforts and resources toward a common goal, allowing the sharing of good practice, whilst reducing the strain and burden on any one organization. Another key output of the review was the need to embrace new and innovative solutions to developing our profession and importantly inspiring and communicating into the future of the profession.

Maternal Prenatal External Locus of Control and Reduced Mathematical and Science Abilities in Their Offspring: A Longitudinal Birth Cohort Study.

A personality scale that identifies individuals' general attitude to what happens to them as largely a matter of luck or fate or of powerful others (externality) or whether they feel they can influence the consequences (internality) is known as locus of control (LOC). A continuous scale can distinguish those who are more external from those who are more internal. Lower scholastic achievement is associated with externality and higher achievement with internality, but little is known about the association of parental LOC on children's academic performance. Data collected within the Avon Longitudinal Study of Parents and Children (ALSPAC) are analyzed to assess associations between mothers' LOC orientation, measured during pregnancy, and their children's abilities in mathematics and science reasoning. We found that maternal external LOC is associated with lower scores for her child assessed by tests measuring mental arithmetic as well as understanding of mathematical and scientific concepts. Additionally, we determined the extent to which three separate sets of factors previously found to positively influence the developing child's ability mediate these findings: (a) perinatal and infant exposures, such as prenatal smoking, binge drinking, consumption of oily fish, and postnatal breast feeding; (b) parenting attitudes and strategies; and (c) the interface of the parents with their child's school. The three factors identify at least 50% of the mechanism by which maternal externality is associated with poor academic outcomes in her child and may be candidates for further investigation as possible intervention targets.

Drosophila imaginal disc growth factor 2 is a trophic factor involved in energy balance, detoxification, and innate immunity.

Drosophila imaginal disc growth factor 2 (IDGF2) is a member of chitinase-like protein family (CLPs) able to induce the proliferation of imaginal disc cells in vitro. In this study we characterized physiological concentrations and expression of IDGF2 in vivo as well as its impact on the viability and transcriptional profile of Drosophila cells in vitro. We show that IDGF2 is independent of insulin and protects cells from death caused by serum deprivation, toxicity of xenobiotics or high concentrations of extracellular adenosine (Ado) and deoxyadenosine (dAdo). Transcriptional profiling suggested that such cytoprotection is connected with the induction of genes involved in energy metabolism, detoxification and innate immunity. We also show that IDGF2 is an abundant haemolymph component, which is further induced by injury in larval stages. The highest IDGF2 accumulation was found at garland and pericardial nephrocytes supporting its role in organismal defence and detoxification. Our findings provide evidence that IDGF2 is an important trophic factor promoting cellular and organismal survival.

NUCLEAR NEW BUILD-INTEGRATING CULTURAL DIFFERENCES IN RADIATION PROTECTION.

Across the world, we are seeing a resurgence in Nuclear New Build. In the UK alone, plans are under way for the construction of 10 new reactors, using 4 different reactor designs all of which are to be provided by foreign vendors, and operated by 3 newly formed licensees within the UK. As these new licensees embark on the task of establishing themselves and progressing the design and build of these reactors, there are challenges faced in integrating the Radiation Protection Requirements and Culture from the various Foreign Investors and Vendors into the UK 'Context'. The following paper identifies the origin of the Radiation Protection Requirements within the UK and foreign investor/vendor countries, in an attempt to integrate them into the UK licensing and approval process. Thus, allowing due credit to be taken for the regulatory regime of the foreign countries where these reactors originate.

Topoisomerase IIα levels and G2 radiosensitivity in T-lymphocytes of women presenting with breast cancer.

Previous studies from our laboratory have identified a link between intracellular topoisomerase IIα (topo IIα) levels and chromosomal radiosensitivity, as measured by the frequencies of chromatid breaks in the so-called G2-assay. Lower topo IIα levels were associated with reduced chromosomal radiosensitivity in cultured human cells. These findings supported a model, in which it is proposed that such chromatid breaks are the result of radiation-induced errors made by topoisomerase IIα during decatenation of chromatids. Studies from our and other laboratories, using the G2-assay, have shown that phytohaemagglutinin (PHA)-stimulated peripheral blood T-lymphocytes from 40% of female breast cancer cases show elevated chromatid break frequencies when exposed to a small standard dose of ionizing radiation, i.e. elevated above the 90th percentile of a group of female control samples. In the present study we have used a modified G2-assay to test whether elevated frequency of chromatid breaks in breast cancer cases is linked with elevated intracellular topo IIα level in PHA-stimulated T-lymphocytes, and also whether there is a general correlation between chromosomal radiosensitivity and topo IIα level. Our results confirm previous studies that 40% of breast cancer cases show elevated radiosensitivity as compared with controls. Also, the mean chromatid break frequency in breast cancer cases was significantly higher than in controls (P = 0.0001). We found that the mean topo IIα level in the cohort of breast cancer cases studied was significantly raised, as compared with controls (P = 0.0016), which could indicate a genetic propensity towards a raised intracellular production of topo IIα in these individuals. There was no direct correlation between chromosomal radiosensitivity and topo IIα level for individual samples either in the breast cancer cohort or in controls. However, a comparison between control and breast cancer samples shows a higher mean topo IIα level in breast cancer samples that correlates with the elevated mean chromatid break frequency seen in these patient samples. We found no meaningful correlations between either chromatid break frequency or topo IIα level and either tumour grade or hormone status. We conclude that elevated intracellular topo IIα level is likely to be a significant factor in determining the chromosomal response of stimulated T-lymphocytes from certain breast cancer cases.

Resolving the film-formation dilemma with infrared radiation-assisted sintering.

The film formation of an acrylate latex with a glass-transition temperature of 38 °C has been achieved through the use of near-infrared (NIR) radiative heating. A hard, crack-free coating was obtained without the addition of plasticizers. Sintering of acrylate particles was confirmed through measurements using atomic force microscopy. The addition of an NIR-absorbing polymer increased the rate of particle deformation such that it was significantly greater than obtained in a convection oven at 60 °C. The results are consistent with a lower polymer viscosity under infrared radiation, according to a simple analysis using a standard model of sintering.

Casein kinase I epsilon somatic mutations found in breast cancer cause overgrowth in Drosophila.

We are using a candidate gene approach to identify genes contributing to cancer through somatic mutation. Somatic mutations were found in breast cancer samples in the human casein kinase I epsilon (CKIepsilon) gene, a homolog of the Drosophila gene dco in which certain point mutations lead to imaginal disc overgrowth. We therefore created fly genotypes in which the dco gene carried point mutations homologous to those discovered in CKIepsilon, and tested them in vivo. The results show that the most frequent mutation discovered in breast cancer, L39Q, causes a striking overgrowth phenotype in flies. Further experiments show that this mutation affects the newly recognized Fat/Warts signaling pathway, which controls organ size and shape in both flies and mammals. Another mutation, S101R, modifies the mutant phenotype so that the affected tissue disintegrates, mimicking more aggressive forms of breast cancer. Our results thus strongly support the conclusion that CKIepsilon mutations play important roles in breast carcinogenesis.

Mechanisms of the formation of radiation-induced chromosomal aberrations.

Although much is now known about the mechanisms of radiation-induction of DNA double-strand breaks (DSB), there is less known about the conversion of DSB into chromosomal aberrations. In particular the induction and 'rejoining' of chromatid breaks has been a controversial topic for many years. However, its importance becomes clear in the light of the wide variation in the chromatid break response of human peripheral blood lymphocytes from different individuals when exposed to ionizing radiation, and the elevation of the frequency of radiation-induced chromatid breaks in stimulated peripheral blood lymphocytes of around 40% of breast cancer cases. A common assumption has been that chromatid breaks are merely expansions of initiating DSB, although the classic 'breakage-first' hypothesis (Sax, Ref. 44) was already challenged in the 50's by Revell [30] who maintained that chromatid breaks were formed as a result of an incomplete exchange process initiated by two interacting lesions of an unspecified nature. Here we argue that both these models of chromatid break formation are flawed and we suggest an alternative hypothesis, namely that a radiation-induced DSB initiates an indirect mechanism leading to a chromatid break. This mechanism we suggest involves the nuclear enzyme topoisomerase IIalpha and we present evidence from topoisomerase IIalpha expression variant human cell lines and from siRNA treatment of human cells that supports this hypothesis.

Suppression of topoisomerase IIalpha expression and function in human cells decreases chromosomal radiosensitivity.

The mechanism behind chromatid break formation is as yet unclear, although it is known that DNA double-strand breaks (DSBs) are the initiating lesions. Chromatid breaks formed in cells in the G2-phase of the cell-cycle disappear ('rejoin') as a function of time between radiation exposure and cell fixation. However, the kinetics of disappearance of chromatid breaks does not correspond to those of DSB rejoining, leading us to seek alternative models. We have proposed that chromatid breaks could be formed indirectly from DSB and that the mechanism involves topoisomerase IIalpha. In support of this hypothesis we have recently shown that frequencies of radiation-induced chromatid breaks are lower in two variant human promyelocytic leukaemic cell lines with reduced topoisomerase IIalpha expression. Here we report that suppression of topoisomerase IIalpha in human hTERT-RPE1 cells, either by its abrogation using specific siRNA or by inhibition of its catalytic activity with the inhibitor ICRF-193, causes a reduction in frequency of chromatid breaks in radiation-exposed cells. The findings support our hypothesis for the involvement of topoisomerase IIalpha in the formation of radiation-induced chromatid breaks, and could help explain inter-individual variation in human chromosomal radiosensitivity; elevation of which has been linked with cancer susceptibility.

An improved assay for radiation-induced chromatid breaks using a colcemid block and calyculin-induced PCC combination.

We report on a new method for the study of radiation-induced chromatid breaks in stimulated human peripheral blood T lymphocytes, involving a combination of a 1-h colcemid block and a short (15 min) calyculin A treatment. We find that this procedure eliminates the problem of centromere splitting when calyculin A is used alone for a longer period and produces metaphase spreads with superior quality. By this procedure, the chromosomes and the chromatid breaks are expanded and thereby make for improved break scoring. In a comparison of the new technique with the conventional colcemid block method, we show a close proportionality between the frequencies of chromatid breaks scored with the two methods. The frequency of chromatid breaks with the new method was found to be significantly higher than that with colcemid alone, adding a higher sensitivity to the assay as an additional advantage.

Casein Kinase I epsilon positively regulates the Akt pathway in breast cancer cell lines.

The Akt pathway is very important in both development and cancer. Here we show that, expression of Casein Kinase I epsilon (CKIepsilon) causes up-regulation of the Akt pathway despite normal protein expression of the pathway inhibitor phosphate and tensin homologue deleted on chromosome ten (PTEN). Conversely, we show that a CKIepsilon/delta-specific inhibitor can inhibit Akt phosphorylation at both Thr308 and Ser473 and drastically reduce phosphorylation of the Akt target Glycogen Synthase Kinase 3beta (GSK3beta). These conclusions were confirmed between MCF7 cells transiently transfected with CKIepsilon and Hs578T cells which already express endogenous CKIepsilon. The results suggest that CKIepsilon is a new positive regulator of the Akt pathway. Here we propose that, rather than inhibiting PTEN function, CKIepsilon positively regulates Akt possibly by inhibiting Protein Phosphatase 2A (PP2A).

Adaptive response: some underlying mechanisms and open questions: [review]

Organisms are affected by different DNA damaging agents naturally present in the environment or released as a result of human activity. Many defense mechanisms have evolved in organisms to minimize genotoxic damage. One of them is induced radioresistance or adaptive response. The adaptive response could be considered as a nonspecific phenomenon in which exposure to minimal stress could result in increased resistance to higher levels of the same or to other types of stress some hours later. A better understanding of the molecular mechanism underlying the adaptive response may lead to an improvement of cancer treatment, risk assessment and risk management strategies, radiation protection, e.g. of astronauts during long-term space flights. In this mini-review we discuss some open questions and the probable underlying mechanisms involved in adaptive response: the transcription of many genes and the activation of numerous signaling pathways that trigger cell defenses - DNA repair systems, induction of proteins synthesis, enhanced detoxification of free radicals and antioxidant production.

Radiation sensitivity of leukocytes from healthy individuals and breast cancer patients as measured by the alkaline and neutral comet assay.

Initial radiation-induced DNA damage, dose-response curves and kinetics of DNA repair in leukocytes from healthy volunteers and breast cancer patients, was assessed using alkaline and neutral comet assay after exposure to (60)Co gamma rays. Both versions of comet assay showed higher levels of baseline DNA damage in leukocytes of breast cancer cases than in controls. Gamma ray induced initial DNA damage in leukocytes of cancer cases was not significantly different from that of healthy donors. A similar dose-response was obtained with both versions of comets for two groups. After a repair time of 24h, following irradiation, samples from the healthy individuals showed no residual DNA damage in their leukocytes, whereas breast cancer patients revealed more than 20%. Although similar initial radiosensitivity was observed for both groups but the repair kinetics of radiation-induced DNA damage of leukocytes from breast cancer cases and healthy subjects was statistically different.

Expression of Wnt pathway components frizzled and disheveled in colon cancer arising in patients with inflammatory bowel disease.

Mutations in apc which lead to activation of the Wnt signaling pathway are a hallmark of sporadic colon cancers but occur infrequently in colon cancers arising in patients with inflammatory bowel disease (IBD). There is evidence, however, that other components of the Wnt pathway may be altered in IBD-related colon cancer. In this study, we examined the expression the Wnt pathway components frizzled (Fz), the cell surface receptor, and disheveled (DVL), a family of cytoplasmic signal transduction molecules, in IBD and IBD-related colon cancer. Paraffin sections of normal and malignant colon tissues were obtained from patients with a history of ulcerative colitis and from controls with sporadic colon cancer. Tissue sections were stained with antibodies directed against Fz1/2 receptors and DVL1, DVL2 and DVL3 and antigen expression visualized by immunohistochemistry. Fz1/2 receptors were minimally expressed in normal IBD mucosa, were not expressed in IBD colon cancer, but exhibited strong expression in dysplastic tissues adjacent to the cancers. DVL1 was not expressed in IBD normal mucosa or normal mucosa from non-IBD patients, but was expressed in all cancers. DVL2 and DVL3 were expressed in all normal mucosa samples tested, and in sporadic colon cancer, but were not expressed in colon cancers arising in IBD patients. The characteristics of Fz and DVL expression in IBD tissues reported herein provides evidence of the importance of Wnt signaling in IBD and IBD-related colon cancer and, specifically, the significance of non-APC components of this pathway. Fz may serve as a marker for dyspasia in IBD patients and DVL1 is a potential therapeutic target for IBD-related colon cancer.

A comparison of G2 phase radiation-induced chromatid break kinetics using calyculin-PCC with those obtained using colcemid block.

To study the possible influence of cell-cycle delay on cells reaching mitosis during conventional radiation-induced chromatid break experiments using colcemid as a blocking agent, we have compared the chromatid break kinetics following a single dose of gamma rays (0.75 Gy) in metaphase CHO cells using calyculin-induced premature chromosome condensation (PCC), with those using colcemid block. Calyculin-induced PCC causes very rapid condensation of G2 cell chromosomes without the need for a cell to progress to mitosis, hence eliminating any effect of cell-cycle checkpoint on chromatid break frequency. We found that the kinetics of the exponential first-order decrease in chromatid breaks with time after irradiation was similar (not significantly different) between the two methods of chromosome condensation. However, use of the calyculin-PCC technique resulted in a slightly increased rate of disappearance of chromatid breaks and thus higher frequencies of breaks at 1.5 and 2.5 h following irradiation. We also report on the effect of the nucleoside analogue ara A on chromatid break kinetics using the two chromosome condensation techniques. Ara A treatment of cells abrogated the decrease in chromatid breaks with time, both using the calyculin-PCC and colcemid methods. We conclude that cell-cycle delay may be a factor determining the absolute frequency of chromatid breaks at various times following irradiation of cells in G2 phase but that the first-order disappearance of chromatid breaks with time and its abrogation by ara A are not significantly influenced by the G2 checkpoint.

A Drosophila adenosine receptor activates cAMP and calcium signaling.

Adenosine receptors (AdoR) are members of the G protein-coupled receptor superfamily and mediate extracellular adenosine signaling, but the mechanism of adenosine signaling is still unclear. Here we report the first characterization of an insect AdoR, encoded by the Drosophila gene CG9753. Adenosine stimulation of Chinese hamster ovary cells carrying transiently expressed CG9753 led to a dose-dependent increase of intracellular cAMP and calcium, but untransfected controls showed no such response, showing that CG9753 encodes a functional AdoR. Endogenous CG9753 transcripts were detected in the brain, imaginal discs, ring gland and salivary glands of third-instar Drosophila larvae, and CG9753 overexpression in vivo caused lethality or severe developmental anomalies. These developmental defects were reduced by adenosine depletion, consistent with the proposed function of the CG9753 product as an AdoR. Overexpression of the G protein subunit Galpha(s) or of the catalytic subunit of protein kinase A (PKA) partially mimicked and enhanced the defects caused by ectopic expression of AdoR. Our results suggest that AdoR is an essential part of the adenosine signaling pathway and Drosophila offers a unique opportunity to use genetic analysis to study conserved aspects of the adenosine signaling pathway.

Mammalian stem cells.

Stem cells are quickly coming into focus of much biomedical research eventually aiming at the therapeutic applications for various disorders and trauma. It is important, however, to keep in mind the difference between the embryonic stem cells, somatic stem cells and somatic precursor cells when considering potential clinical applications. Here we provide the review of the current status of stem cell field and discuss the potential of therapeutic applications for blood and Immune system disorders, multiple sclerosis, hypoxic-ischemic brain injury and brain tumors. For the complimentary information about various stem cells and their properties we recommend consulting the National Institutes of Health stem cell resources (http://stemcells.nih.gov/info/basics).

A role for adenosine deaminase in Drosophila larval development.

Adenosine deaminase (ADA) is an enzyme present in all organisms that catalyzes the irreversible deamination of adenosine and deoxyadenosine to inosine and deoxyinosine. Both adenosine and deoxyadenosine are biologically active purines that can have a deep impact on cellular physiology; notably, ADA deficiency in humans causes severe combined immunodeficiency. We have established a Drosophila model to study the effects of altered adenosine levels in vivo by genetic elimination of adenosine deaminase-related growth factor-A (ADGF-A), which has ADA activity and is expressed in the gut and hematopoietic organ. Here we show that the hemocytes (blood cells) are the main regulator of adenosine in the Drosophila larva, as was speculated previously for mammals. The elevated level of adenosine in the hemolymph due to lack of ADGF-A leads to apparently inconsistent phenotypic effects: precocious metamorphic changes including differentiation of macrophage-like cells and fat body disintegration on one hand, and delay of development with block of pupariation on the other. The block of pupariation appears to involve signaling through the adenosine receptor (AdoR), but fat body disintegration, which is promoted by action of the hemocytes, seems to be independent of the AdoR. The existence of such an independent mechanism has also been suggested in mammals.