Indicator Of Radiation Exposure Research Articles

Biodosimetry of ionizing radiations at different LET levels through cytogenetic endpoints in Allium cepa meristems

- This paper aims to enhance our understanding of the effects of ionizing radiation using radiobiology and biodosimetry techniques applied to living plant organisms. Plants are particularly suitable for this purpose as they are highly sensitive to detecting potential genotoxic agents in the environment and their use allows us to avoid using animals in research in compliance with the 3R principle. Currently, the onion (Allium cepa) is recognized as a valid model for the analysis of environmental pollutants but has been relatively unexplored as an indicator of radiation exposure. In this study, analyses of the genotoxicity of X and alpha radiation were conducted using the micronucleus test and mitotic index analysis. Our results indicate that Allium cepa can be considered a valid alternative model to animal use for assessing the effects of ionizing radiation. In particular, it was found that alpha radiation caused significant damage, as evidenced by an increased number of micronuclei, which was 20 times higher compared to X-ray radiation. This was further confirmed through the observation of the effective dose parameter, as determined by the analysis of various weight factors associated with different types of radiation.

Serum microRNA profile of rhesus macaques following ionizing radiation exposure and treatment with a medical countermeasure, Ex-Rad

Exposure to ionizing radiation (IR) presents a formidable clinical challenge. Total-body or significant partial-body exposure at a high dose and dose rate leads to acute radiation syndrome (ARS), the complex pathologic effects that arise following IR exposure over a short period of time. Early and accurate diagnosis of ARS is critical for assessing the exposure dose and determining the proper treatment. Serum microRNAs (miRNAs) may effectively predict the impact of irradiation and assess cell viability/senescence changes and inflammation. We used a nonhuman primate (NHP) model—rhesus macaques (Macaca mulatta)—to identify the serum miRNA landscape 96 h prior to and following 7.2 Gy total-body irradiation (TBI) at four timepoints: 24, 36, 48, and 96 h. To assess whether the miRNA profile reflects the therapeutic effect of a small molecule ON01210, commonly known as Ex-Rad, that has demonstrated radioprotective efficacy in a rodent model, we administered Ex-Rad at two different schedules of NHPs; either 36 and 48 h post-irradiation or 48 and 60 h post-irradiation. Results of this study corroborated our previous findings obtained using a qPCR array for several miRNAs and their modulation in response to irradiation: some miRNAs demonstrated a temporary increased serum concentration within the first 24–36 h (miR-375, miR-185-5p), whereas others displayed either a prolonged decline (miR-423-5p) or a long-term increase (miR-30a-5p, miR-27b-3p). In agreement with these time-dependent changes, hierarchical clustering of differentially expressed miRNAs showed that the profiles of the top six miRNA that most strongly correlated with radiation exposure were inconsistent between the 24 and 96 h timepoints following exposure, suggesting that different biodosimetry miRNA markers might be required depending on the time that has elapsed. Finally, Ex-Rad treatment restored the level of several miRNAs whose expression was significantly changed after radiation exposure, including miR-16-2, an miRNA previously associated with radiation survival. Taken together, our findings support the use of miRNA expression as an indicator of radiation exposure and the use of Ex-Rad as a potential radioprotectant.

Assessment of Environmental Risk from Radioactive Pollution of the Environment

T e article presents a methodology for assessing the risk of radioactive contamination of the environment according to the data of radiation monitoring. T e methodology is based on the indicators of radiation exposure and control levels of radionuclides in environmental components, the non-exceeding of which ensures the safety of natural environment. T e risk assessment methodology uses three indicators: an environmental risk index, based on radiation dose rates to reference biota; an integral indicator of pollution of the territory; a generalized risk indicator, estimated in scores, considering both the area and time dynamics of pollution. Examples of methodology application are given, presenting risk assessment for Chernobyl contaminated territories, also risk assessment for radiation hazardous facilities. T e proposed risk assessment procedure can be used to analyzing and interpreting information about radiation risks on the territory of the Russian Federation based on radiation monitoring data, taking into account the requirements of environmental protection, assessment of the state and changes in the radiation situation under the inf uence of natural and anthropogenic factors, including radiation facilities. T e methodology produces reliable integral information about radiation impact on the environment and its interpretation based on the concept of environmental risk. T e results of the risk assessment from radioactive pollution of the environment are used in the development and decision-making on the need for environmental protection measures, and also make it possible to rank the factors of radiation exposure and rationally organize monitoring of the radiation situation.

R400: A novel gene signature for dose prediction in radiation exposure studies in humans

Radiation’s harmful effects on biological organisms have long been studied through mainly evaluating pathological changes in cells, tissues, or organs. Recently, there have been more accessible gene expression datasets relating to radiation exposure studies. This provides an opportunity to analyze responses at the molecular level toward revealing phenotypic differences. Biomarkers in toxicogenomics have been suggested as indicators of radiation exposure and seem to react differently to various dosages of radiation. This study proposes a predictive gene signature specific to radiation exposure and can be used in automatically diagnosing the exposure dose. In searching for a reliable gene set that will correctly identify the exposure dose, consideration needs to be given to the size of the set. For this reason, we experimented with the number of genes used for training and testing. Gene set sizes of 28, 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1,000 were tested to find the size that provided the best accuracy across three datasets. Models were then trained and tested using multiple datasets in various ways, including an external validation. The dissimilarities between these datasets provide an analogy to real-world conditions where data from multiple sources are likely to have variances in format, settings, time parameters, participants, processes, and machine tolerances, so a robust training dataset from many heterogeneous samples should provide better predictability. All three datasets showed positive results with the correct classification of the radiation exposure dose. The average accuracy of all three models was 88% for gene sets of both 400 and 1,000 genes. R400 provided the best results when testing the three datasets used in this study. A literature validation of top selected genes shows high relevance of perturbations to adverse effects reported during cancer radiotherapy.

Ensuring radiation safety in medical institutions of the dental profile

The analysis of indicators of radiation exposure of medical workers of the dental profile of the Samara region during medical procedures for the period from 2004 to 2019 is carried out in comparison with the quantitative dynamics of X-ray diagnostic studies. The main directions of occupational safety indicators of medical workers of the dental profile when working with X-ray diagnostic equipment have been determined. The purpose was to conduct a comparative analysis of the radiation exposure indicators of medical workers of the dental profile of the Samara region during medical procedures for the period from 2004 to 2019, to characterize the radiation safety of personnel. An analytical work was carried out on the indicators of the average radiation dose of medical workers of the dental profile of the Samara region during medical procedures according to the data of radiation and hygienic certification of the territory of the Samara region for the period from 2004 to 2019. In the framework of this study, the number and demand for X-ray diagnostic procedures in medical institutions of the dental profile among the population. A retrospective analysis of the dynamics of X-ray studies and the values of the average individual dose of radiation for personnel working with X-ray dental devices in 10 large medical institutions of the dental profile of various forms of ownership in the territory of Samara and the Samara region (C1-C10) for the period from 2004 to 2019 was carried out…. on the basis of the annual forms of statistical reporting of the radiation-hygienic passport of the organization (RGPO). The decrease in radiation exposure is due to the replacement of outdated equipment with more modern ones, the transition from film types of research to digital ones, an increase in personnel literacy in the field of radiation safety, which characterizes the improvement of radiation safety indicators for dental personnel in Samara and the Samara region.

Lethal and Sub-Lethal Irradiation of Sprague-Dawley Rats Causes Development of Dense Red Blood Cells

Background: In vitro irradiation of blood produces morphologic and rheologic changes in the red blood cells. These changes may have clinicla significance, and if the changes are prolonged beyond hematologic recovery, serve as an indication of radiation exposure. However, no rheological studies have been performed on blood from irradiated animals.Objective: Determine the effect of lethal and sub lethal radiation treatment (RT) on whole blood rheology in a rodent model.Methods: 3 SD rats were subjected to lethal doses of irradiation (7.5 Gy), and 3 untreated; ten days following RT, the animals were sacrificed, and their blood analyzed by an ADVIA hematology analyzer, a cone and plate viscometer, and a RheoScan ektacytometer.Next, following baseline CBC and dense cell measurements, 6 rats were subjected to whole body RT at 6 Gy; 6 were subjected to 7.5 Gy with one leg shielded, and 2 were not irradiated. Percent dense red blood cells (%DRBC), CBC, reticulocyte count, and red cell deformability were measured 4 hours, 5 days and then every 10 days post RT.11 week old Sprague Dawley (SD) rats were used in all experiments. Peripheral blood smears were prepared and analyzed from each blood draw to assess RBC morphology.Results: SD rats who received lethal irradiation at 7.5 Gy exhibited a marked rise in %DRBC; 17.1% ±10.5% compared to 0.5%±0.3% in untreated SD rats (p=0.025). The hematocrit to viscosity ratio (HVR), a measure of oxygen carrying capacity, was calculated at two shear rates, 45 s-1 and 225 s-1, to mimic venous and arterial circulation. There was no significant difference in HVR at 45 s-1, but the HVR at 225s-1 was significantly lower in the RT group, p=0.018, suggesting impairment of oxygen carrying capacity due to intrinsic red cell defects caused by lethal RT. Deformability was reduced in the RT group as well (p=0.039).In longitudinally followed SD rats subjected to sub lethal RT, %DRBC rose 4 hours after irradiation, peaked at 5 days post-irradiation, and remained elevated 31 days after RT. At 31 days post-RT, hematologic recovery was observed in both the sub lethal and shielded groups, but %DRBC remained elevated. RBC morphology revealed anisocytosis in the RT groups, but few spherocytes were noted.Conclusions: In vivo RT impairs red cell rheology in SD rats; lethal doses cause a marked rise in %DRBC, reduction in red cell deformability, and reduction in oxygen carrying capacity as measured by HVR. Longitudinal examination of sub lethal RT reveals a rapid rise in %DRBC, without spherocytosis, suggesting that this change may be due to a KCl channel leak rather than spherocytosis from splenic fibrosis. Obese SD rats have higher %DRBC at baseline, and show a significantly higher increase in %DRBC in response to RT, compared to normal weight SD rats. This suggests that obesity may exacerbate the rheological complications of RT.The persistence of %DRBC after hematologic recovery is a significant observation, suggesting that radiation exposure after the window of hematologic recovery has passed could be detected by a point of care test for %DRBC, already available, as a rapid field test. DisclosuresNo relevant conflicts of interest to declare.

Gene Expression as a Dosimeter in Irradiated Drosophila melanogaster.

Biological indicators would be of use in radiation dosimetry in situations where an exposed person is not wearing a dosimeter, or when physical dosimeters are insufficient to estimate the risk caused by the radiation exposure. In this work, we investigate the use of gene expression as a dosimeter. Gene expression analysis was done on 15,222 genes of Drosophila melanogaster (fruit flies) at days 2, 10, and 20 postirradiation, with X-ray exposures of 10, 1000, 5000, 10,000, and 20,000 roentgens. Several genes were identified, which could serve as a biodosimeter in an irradiated D. melanogaster model. Many of these genes have human homologues. Six genes showed a linear response (R2 > 0.9) with dose at all time points. One of these genes, inverted repeat-binding protein, is a known DNA repair gene and has a human homologue (XRCC6). The lowest dose, 10 roentgen, is very low for fruit flies. If the lowest dose is excluded, 13 genes showed a linear response with dose at all time points. This includes 5 of 6 genes that were linear with all radiation doses included. Of these 13 genes, 4 have human homologues and 8 have known functions. The expression of this panel of genes, particularly those with human homologues, could potentially be used as the biological indicator of radiation exposure in dosimetry applications.

Human serum miR-34a as an indicator of exposure to ionizing radiation.

Radiation exposure in industrial accidents or nuclear device attacks is a major public health concern. There is an urgent need for markers that rapidly identify people exposed to ionizing radiation (IR). Finding a blood-based marker is advantageous because of the ease of sample collection. This study was designed to test the hypothesis that serum miR-34a could serve as an indicator of exposure to IR. Therefore, 44 women with breast cancer, where radiotherapy was part of their therapeutic protocol, were investigated in this study. After demonstrating the appropriateness of our microRNA (miRNA) extraction efficiency and miRNA assay in human serum, we analyzed the miR-34a level in paired serum samples before and after radiotherapy. Fifty Gy X-ray irradiation in daily dose fractions of 2Gy, 5days per week, was used in this study. We demonstrated that IR significantly increased serum level of miR-34a. By measuring miR-34a in serum, we could distinguish irradiated patients with sensitivity of 65% and specificity of 75%. According to this study, serum miR-34a has the potential to be used as an indicator of radiation exposure.

Tissue-specific effects of acute aluminium exposure on the radiation-induced bystander effect in rainbow trout (Oncorhynchus mykiss, Walbaum)

Purpose: To investigate if aluminium (Al) modifies the rainbow trout response to radiation exposure and/or the induction of a radiation-induced bystander effect.Methods: Rainbow trout were exposed to 100 or 200 μg l−1 Al (for 3 h), a 0.5 Gy X-ray dose or Al followed immediately by irradiation. The exposed fish were then swum with completely untreated bystander fish. A human reporter cell clonogenic assay was used to determine whether Al exposure modified the effects of irradiation on the skin and gills from directly exposed fish and also the radiation-induced bystander effect in untreated fish.Results: Al exposure did not modify the response to direct irradiation by the skin, or the gill. Al did not modify the bystander effect in the skin. However Al did modify the bystander effect in the gill. Gills of bystander fish swum with fish exposed to 200 μg l−1 Al, followed by irradiation, caused a greater reduction in HPV-G cell survival than was caused by irradiation only. Interestingly Al exposure only also caused a bystander effect (reduced HPV-G survival) in the gill.Conclusion: This study shows that, in a multiple stressor scenario, the communication of radiation-induced stress signals is modified on a tissue-specific basis by acute Al exposure. Aside from the implications this has for radiological protection this response may also have potential for environmental monitoring where detection of the bystander effect could act as an indicator of radiation exposure when direct exposure responses are not evident.

Metabolic phenotyping reveals a lipid mediator response to ionizing radiation.

Exposure to ionizing radiation has dramatically increased in modern society, raising serious health concerns. The molecular response to ionizing radiation, however, is still not completely understood. Here, we screened mouse serum for metabolic alterations following an acute exposure to γ radiation using a multiplatform mass-spectrometry-based strategy. A global, molecular profiling revealed that mouse serum undergoes a series of significant molecular alterations following radiation exposure. We identified and quantified bioactive metabolites belonging to key biochemical pathways and low-abundance, oxygenated, polyunsaturated fatty acids (PUFAs) in the two groups of animals. Exposure to γ radiation induced a significant increase in the serum levels of ether phosphatidylcholines (PCs) while decreasing the levels of diacyl PCs carrying PUFAs. In exposed mice, levels of pro-inflammatory, oxygenated metabolites of arachidonic acid increased, whereas levels of anti-inflammatory metabolites of omega-3 PUFAs decreased. Our results indicate a specific serum lipidomic biosignature that could be utilized as an indicator of radiation exposure and as novel target for therapeutic intervention. Monitoring such a molecular response to radiation exposure might have implications not only for radiation pathology but also for countermeasures and personalized medicine.

Development of a Qualitative Dose Indicator for Gamma Radiation Using Lyophilized Deinococcus

The feasibility of using Deinococcus showing strong resistance to both desiccation and ionizing radiation as a dose indicator of gamma radiation exposure was evaluated. Three Deinococcus strains having different levels of radiation resistance, Deinococcus radiodurans (DRD), Deinococcus radiopugnans (DRP), and the DRD pprI mutant (DRM), were selected to develop an appropriate dose indicator for a broad range of exposures. DRD, DRP, and DRM cultures with different numbers of cells [~10(7) to 10(3) colony forming units (CFU)/100 microliter] were lyophilized and subjected to various doses of gamma radiation to determine a critical dose that inhibited bacterial growth completely. Finally, a combination of DRD at ~10(7) and ~10(6) CFU, DRP at ~10(5) CFU, and DRM at ~10(4) CFU successfully indicated exposure to 5, 10, 20, and 30 kGy of gamma radiation, respectively. This study shows the possibility of developing a qualitative indicator of radiation exposure using Deinococcus.

How cytogenetical methods help victims prove radiation exposure and claim right for social support: NCERM experience

Abstract Russian citizens who were irradiated because of radiation disasters, nuclear weapons testing and some other sources have a right to some social support and financial compensation. In order to get this compensation people have to prove that they were irradiated. As it is, not all victims for a variety of reasons have formal documents. Thus they apply for cytogenetic investigation to prove irradiation months, years and even decades after irradiation. Since 1992 the cytogenetic investigations related to radiation exposure were performed in NRCERM for more than 700 people. At the beginning of this investigation FISH method was not certified as a biodosimenty test in Russia. Only dicentric analysis was approved as a proof of irradiation. It is known that the rate of dicentrics decrease in time, but the residual level of cytogenetical markers could be revealed a long time after a radiation accident. Thus the dicentric analysis was performed for the people who applied for biological indication of radiation exposure at that time. Rates of dicentrics exceeding control levels were revealed in half the people who applied for radiation conformation. Now FISH method is certified in Russia and both cytogenetic tests of biodosimetry (dicentrics and FISH) are available for all comers. Increased levels of translocations were found in 8 cases (the dose rate from 0.16 to 0.64 Gy). On the basis of the results of cytogenetic tests official documents were supplied to these people and they were entitled to apply for radiation exposure compensation. Thus cytogenetic tests are very effective and in some cases the only possible way for the victims to prove irradiation exposure and to apply for radiation exposure compensation a long time after an accident.

Ionizing radiation exposure and cancer risk among Norwegian nurses

The influence of occupational exposure to ionizing radiation on risk of radiation-related cancers was studied among Norwegian nurses. A cohort of 43 316 nurses who graduated between 1914 and 1984, and were registered by the Norwegian Board of Health's registry of nurses, was followed up from 1953 through 2002 by linkage to the Norwegian Cancer Registry by unique personal identification numbers. Indicators of radiation exposure were developed from data on work history. Internal analyses were performed with Poisson regression, according to time since first potential radiation exposure, duration of exposure, and period of first exposure, using unexposed nurses as reference group. No clear association was found between exposure to ionizing radiation and cancers of the breast, thyroid, ovary, or leukemia, malignant melanoma or other skin cancer. Increased risk of lung cancer was found in the subgroups of nurses first exposed after 1950 (rate ratio=1.47, 95% confidence interval: 0.97-2.23, 26 cases), and in nurses with less than 20 years since first exposure (rate ratio=3.41, 95% confidence interval: 1.67-6.99, 9 cases), but the most likely explanation was confounding by smoking. No firm evidence that nurses potentially exposed to ionizing radiation had increased risk of radiation-related cancer was found.

Total gene deletions and mutant frequency of the HPRT gene as indicators of radiation exposure in Chernobyl liquidators

This study was conducted to determine the utility of deletion spectrum and mutant frequency (MF) of the hypoxanthine phosphoribosyl transferase gene ( HPRT) as indicators of radiation exposure in Russian Liquidators who served in 1986 or 1987 in the clean up effort following the nuclear power plant accident at Chernobyl. HPRT MF was determined using the cloning assay for 117 Russian Controls and 122 Liquidators whose blood samples were obtained between 1991 and 1998. Only subjects from whom mutants were obtained for deletion analysis are included. Multiplex PCR analysis was performed on cell extracts of 1080 thioguanine resistant clones from Controls and 944 clones from Liquidators. Although the deletion spectra of Liquidators and Controls were similar overall, the Liquidator deletion spectrum was heterogeneous over time. Most notable, the proportion of total gene deletions was higher in 1991–1992 Liquidators than in Russian Controls ( χ 2=10.5, p=0.001) and in 1993–1994 Liquidators ( χ 2=8.3, p=0.004), and was marginally elevated relative to 1995–1996 Liquidators ( χ 2=3.3, p=0.07). This type of mutation has been highly associated with radiation exposure. Total gene deletions were not increased after 1992. Band shift mutations were also increased in the 1991–1992 Liquidators but were associated with increased MF of both Liquidators and Controls ( p=0.009), not with increased MF in 1991–1992 Liquidators ( p=0.7), and hence are not believed to be associated with radiation exposure. Regression analysis demonstrated that relative to Russian Controls HPRT MF was elevated in Liquidators overall when adjusted for age and smoking status (37%, p=0.0001), and also was elevated in Liquidators sampled in 1991–1992 (72%, p=0.0076), 1993–1994 (22%, p=0.037), and 1995–1996 (62%, p=0.0001). In summary, HPRT MF was found to be the more sensitive and persistent indicator of radiation exposure, but the specificity of total gene deletions led to detection of probable heterogeneity of radiation exposure within the exposed population.

Changes in the cellularity of the cortex of human hairs as an indicator of radiation exposure

Growing hair follicles with their rapid cell proliferation would be expected to be sensitive organs to cytotoxic agents such as radiation. Various abnormalities in the hair and hair follicles have been reported in the past. Changes in the number of cells in the newly forming hair cortex have been shown in the mouse to be one of the more sensitive assays for radiation effects, and this approach could provide a basis for a biological dosimeter. Here we show for the first time using hair cortex cell counts some preliminary data indicating that the number of cell nuclei in a unit of length (140 microns) of the cortex of human hairs from the chest and scalp of patients undergoing fractionated radiotherapy falls significantly (P = 0.005) by 5%-10% 3 days after the first dose in a fractionated sequence of irradiations. The first dose was delivered on a Friday, and no further exposures were delivered until after the hair sample was taken on the 3rd day (Monday). No significant effect of radiation dose could be detected over the available. limited range of doses studied (5-6.5 Gy with one exit dose sample at 2.6 Gy). Also, the width varies from hair to hair. If the width of the hair is taken into account and the cortical nuclei counts are normalised to the width of each hair, the effects seen at day 3 become slightly more significant (P = 0.002), and those at day 5 also become significant (P = 0.012). Samples taken on the 5th day after the first (Friday) exposure were also 2 days after the second exposure and 1 day after the third exposure. However, little expression of damage attributable to the 2nd and 3rd exposures was anticipated since their effects would take some time to be expressed in the cortical region examined, which is some distance from the proliferative region of the follicle

Changes in the cellularity of the cortex of human hairs as an indicator of radiation exposure.

Growing hair follicles with their rapid cell proliferation would be expected to be sensitive organs to cytotoxic agents such as radiation. Various abnormalities in the hair and hair follicles have been reported in the past. Changes in the number of cells in the newly forming hair cortex have been shown in the mouse to be one of the more sensitive assays for radiation effects, and this approach could provide a basis for a biological dosimeter. Here we show for the first time using hair cortex cell counts some preliminary data indicating that the number of cell nuclei in a unit of length (140 microns) of the cortex of human hairs from the chest and scalp of patients undergoing fractionated radiotherapy falls significantly (P = 0.005) by 5%-10% 3 days after the first dose in a fractionated sequence of irradiations. The first dose was delivered on a Friday, and no further exposures were delivered until after the hair sample was taken on the 3rd day (Monday). No significant effect of radiation dose could be detected over the available. limited range of doses studied (5-6.5 Gy with one exit dose sample at 2.6 Gy). Also, the width varies from hair to hair. If the width of the hair is taken into account and the cortical nuclei counts are normalised to the width of each hair, the effects seen at day 3 become slightly more significant (P = 0.002), and those at day 5 also become significant (P = 0.012). Samples taken on the 5th day after the first (Friday) exposure were also 2 days after the second exposure and 1 day after the third exposure. However, little expression of damage attributable to the 2nd and 3rd exposures was anticipated since their effects would take some time to be expressed in the cortical region examined, which is some distance from the proliferative region of the follicle.

Influence of Irradiation on Development of Caribbean Fruit Fly (Diptera: Tephritidae) Larvae

Larvae of the Caribbean fruit fly, Anastrepha suspensa (Loew), were irradiated at hatching with 0, 5, 10, 20, 50, 75, 100 and 150 Gy doses from a Cesium-137 source and dissected for measurements of the supraesophageal ganglion (brain) and proventriculus (B/Prv) as mature third instars. Cross-sectional area of a plane through the brain and proventriculus, and simple dorsal width measurements of the two organs were evaluated as indicators of radiation exposure. Brain area, brain width, and brain/proventriculus (B/Prv) ratios were significantly different from controls in insects treated with a dose {ge}20 Gy. Detailed dissections of hatching larvae exposed to 50 Gy revealed reductions in brain growth, small and misshapen compound eye and leg imaginal disks, and a ventral nerve cord that was elongated and sinuous. Larvae irradiated on the 1st d of each of the three instars had smaller brains, with the percentage of reduction in brain size being greater the younger the larvae were at the time of exposure. Brain and proventriculus measurements and calculated B/Prv values are indicative of irradiation in Caribbean fruit fly larvae, but the procedure may not be adaptable for routine use by quarantine inspectors. 14 refs., 4 figs., 2 tabs.

The influence of film processing temperature and time on mammographic image quality

High image quality and low radiation levels are essential in mammography. This study investigates the effect of changes in processor temperatures and developing times on sensitometric findings. These findings were matched with the changes in the image quality during similar changes in the developing parameters. Temperatures ranging between 35 degrees C and 40 degrees C and developing times from 20 s and 50 s were investigated. Higher developing temperatures and increased developing times resulted in an increase in film speed and film contrast. A definite pattern of change could be demonstrated in film speed and film contrast during sensitometry. The same pattern of change could, however, not be demonstrated in the quality of phantom images under similar circumstances. The base plus fog level was not adversely affected. Sensitometric findings of film speed can be effectively used as an indicator of radiation exposure to the patient, but cannot be used to establish the developing parameters that will give the best image quality. Both these methods should be used to determine which processing variables should be used to obtain a combination of the best image with radiation as low as possible. Recommendations for optimum processing parameters are made for the films and processing chemistry investigated.

Chromosome Aberrations as a Biological Dose-Response Indicator of Radiation Exposure in Uranium Miners

Cultured peripheral blood lymphocytes of controls and uranium miners were analyzed for the prevalence of structural chromosomal aberrations. The frequency data are compared between controls and five groups of miners with exposures expressed in working level months (WLM). The results demonstrate: (i) the prevalence of dicentrics + rings is not a good biological dose-response indicator; (ii) there is a marked decrease in the prevalence of deletions or dicentrics + rings + deletions in the most highly exposed individuals (Group V; >3000 WLM); (iii) apart from the Group V results, all aberration categories except dicentrics + rings demonstrate a significant and monotonic biological response increasing uniformly with estimated radiation dose through Group IV (1740-2890 WLM); (iv) including Group V individuals, the aberration category which shows the most consistent pattern of increase with dose is the pericentric inversions + translocations grouping (Spearman's $r_{{\rm s}}=0.943$ ; P = 0.0...

The effect of isotopic (I131) radiation and x-radiation on the total coproporphyrin excretion in humans.

THE application of radioactive isotopes to the diagnosis and treatment of a number of pathologic conditions has led. to an increasing interest in the study and evaluation of the biologic effects of irradiation. Among the physiologic systems which are most sensitive to ionizing radiation are the hematopoietic, the gastro-intestinal and the gonadal (1). Of these, the one which lends itself most readily to study and which consequently has been subjected to a more detailed analysis, has been that of the blood and the blood-forming organs. The analytic procedures which might serve as indices of radiation effect on this system have been screened by the Medical and Biology Divisions of the Manhattan Project. Painter and Brues (1) have concluded that “a reduction in the number of circulating lymphocytes is the most sensitive indicator of radiation exposure yet found.” Schwartz, Cohen, and Watson (2), who were cooperating in. this project, studied the urinary coproporphyrin excretion in dogs receiving varying dose...