Boei, J. J. W. A., Fomina, J., Darroudi, F., Nagelkerke, N. J. D. and Mullenders, L. H. F. Interphase Chromosome Positioning Affects the Spectrum of Radiation-Induced Chromosomal Aberrations. Radiat. Res. 166, 319–326 (2006).

In interphase, chromosomes occupy defined nuclear volumes known as chromosome territories. To probe the biological consequences of the described nonrandom spatial positioning of chromosome territories in human lymphocytes, we performed an extensive FISH-based analysis of ionizing radiation-induced interchanges involving chromosomes 1, 4, 18 and 19. Since the probability of exchange formation depends strongly on the spatial distance between the damage sites in the genome, a preferential formation of exchanges between proximally positioned chromosomes is expected. Here we show that the spectrum of interchanges deviates significantly from one expected based on random chromosome positioning. Moreover, the observed exchange interactions between specific chromosome pairs as well as the interactions between homologous chromosomes are consistent with the proposed gene density-related radial distribution of chromosome territories. The differences between expected and observed exchange frequencies are more pronounced after exposure to densely ionizing neutrons than after exposure to sparsely ionizing X rays. These experiments demonstrate that the spatial positioning of interphase chromosomes affects the spectrum of chromosome rearrangements.

Kennedy, A. R., Zhou, Z., Donahue, J. J. and Ware, J. H. Protection against Adverse Biological Effects Induced by Space Radiation by the Bowman-Birk Inhibitor and Antioxidants. Radiat. Res. 166, 327–332 (2006).

This study was undertaken to evaluate the protective effects of the soybean-derived Bowman-Birk inhibitor (BBI), BBI concentrate (BBIC) and/or antioxidants against the adverse biological effects induced by space radiation in cultured human epithelial cells. The effects of BBI, BBIC and a combination of ascorbic acid, co-enzyme Q10, l-selenomethionine (SeM) and vitamin E succinate on proton and HZE-particle [high-energy (high E) nuclei of heavier (high atomic number, Z) elements] radiation-induced cytotoxicity in MCF10 human breast epithelial cells and a phenotypic change associated with transformation in HTori-3 human thyroid epithelial cells were assessed with a clonogenic survival assay and a soft agar colony formation assay. The results demonstrate that BBIC and antioxidants are effective in protecting against space radiation-induced cytotoxicity in MCF10 cells and BBI, BBIC and antioxidants are effective in protecting against a space radiation-induced phenotypic change associated with transformation of HTori-3 cells.

Balagurumoorthy, P., Chen, K., Bash, R. C., Adelstein, S. J. and Kassis, A. I. Mechanisms Underlying Production of Double-Strand Breaks in Plasmid DNA after Decay of ¹²⁵I-Hoechst. Radiat. Res. 166, 333–344 (2006).

Previously, the kinetics of strand break production by ¹²⁵I-labeled m-iodo-p-ethoxyHoechst 33342 (¹²⁵IEH) in supercoiled (SC) plasmid DNA had demonstrated that ∼1 DSB is produced per ¹²⁵I decay both in the presence and absence of the hydroxyl radical scavenger DMSO. In these experiments, an ¹²⁵IEH:DNA molar ratio of 42:1 was used. We now hypothesize that this DSB yield (but not the SSB yield) may be an overestimate due to subsequent decays occurring in any of the 41 ¹²⁵IEH molecules still bound to nicked (N) DNA. To test our hypothesis, ¹²⁵IEH was incubated with SC pUC19 plasmids (¹²⁵IEH:DNA ratio of ∼3:1) and the SSB and DSB yields were quantified after the decay of ¹²⁵I. As predicted, the number of DSBs produced per ¹²⁵I decay is one-half that reported previously (∼0.5 compared to ∼1, ± DMSO) whereas the number of SSBs (∼3/¹²⁵I decay) is similar to that obtained previously (∼90% are generated by OH radicals). Direct visualization by atomic force microscopy confirms formation of L and N DNA after ¹²⁵IEH decays in SC DNA and supports the strand break yields reported. These findings indicate that although SSB production is independent of the number of ¹²⁵IEH bound to DNA, the DSB yield can be augmented erroneously by ¹²⁵I decays occurring in N DNA. Further analysis indicates that 17% of SSBs and 100% of DSBs take place within the plasmid molecule in which an ¹²⁵IEH molecule decays, whereas 83% of SSBs are formed in neighboring plasmid DNA molecules.

Kashiwakura, I., Inanami, O., Abe Y., Satoh, K., Takahashi, T. A. and Kuwabara, M. Regeneration of Megakaryocytopoiesis and Thrombopoiesis In Vitro from X-Irradiated Human Hematopoietic Stem Cells. Radiat. Res. 166, 345–351 (2006).

In the present study, we investigated whether X-irradiated hematopoietic stem cells can be induced to undergo megakaryocytopoiesis and thrombopoiesis in vitro using cytokine combinations that have been demonstrated to be effective for conferring increased survival on irradiated human CD34 megakaryocytic progenitor cells (colony-forming unit megakaryocytes; CFU-Meg), such as thrombopoietin (TPO), interleukin 3 (IL3), stem cell factor and FLT3 ligand. Culture of nonirradiated CD34 cells in serum-free medium supplemented with multiple cytokine combinations led to an approximately 200- to 600-fold increase in the total cell numbers by day 14 of culture. In contrast, the growth of X-irradiated cells was observed to be one-sixth to one-tenth that of the nonirradiated cultures. Similarly, total megakaryocytes were increased by 50- to 130-fold, while culture of X-irradiated cells yielded one-fourth to one-eighth of the control numbers. At this time, CD41 particles, which appeared to be platelets, were produced in the medium harvested from nonirradiated and irradiated cultures. Although radiation suppressed cell growth and megakaryocytopoiesis, there were no significant differences in thrombopoiesis between the two types of culture. These results suggest that X-irradiated CD34 cells can be induced to undergo nearly normal terminal maturation through megakaryocytopoiesis and thrombopoiesis by stimulation with appropriate cytokine combinations.

Liu, B., Zhao, L., Yu, X., Han, Z., Lu, S., Yang, R. and Han, Z. C. Live Attenuated Salmonella Carrying Platelet Factor 4 cDNAs as Radioprotectors. Radiat. Res. 166, 352–359 (2006).

To determine whether live attenuated Salmonella carrying platelet factor 4 cDNAs can protect mice from radiation damage, the attenuated Salmonella SL3261 was used as oral vector for targeted gene delivery. The recovery of mice receiving sublethal total-body irradiation (TBI) was investigated after the oral administration of attenuated Salmonella carrying cDNA for platelet factor 4 (PF4) or truncated PF4. This oral gene therapy protected mice from radiation damage after TBI. The number of bone marrow cells and high proliferative potential colony-forming cells (HPP-CFCs) increased significantly at day 7. Similarly, the administration of PF4 or PF4_17–70 protein also improved the survival of mice after TBI. Both PF4 gene therapy and protein administration accelerated hematopoietic recovery in vivo in mice after irradiation. In vitro, PF4 also promoted survival and proliferation of 5-fluorouracil-resistant hematopoietic stem/progenitor cells after irradiation. These data demonstrate a novel biological function of PF4 as a protector against radiation injury and suggest that attenuated Salmonella could be used in vivo as a PF4 DNA delivery vector in the management of radiation injury.

Hakoda, M., Kasagi, F., Kusunoki, Y., Matsuura, S., Hayashi, T., Kyoizumi, S., Akahoshi, M., Suzuki, G., Kodama, K. and Fujiwara, S. Levels of Antibodies to Microorganisms Implicated in Atherosclerosis and of C-Reactive Protein among Atomic Bomb Survivors. Radiat. Res. 166, 360–366 (2006).

Although it has been suggested that cardiovascular disease incidence is increased among atomic bomb survivors, the existence of a causal relationship between radiation exposure and atherosclerosis is unclear. Microbial infections, including those caused by Chlamydia pneumoniae, Helicobacter pylori and cytomegalovirus, have recently been implicated in atherosclerosis. Since immune function is somewhat impaired among atomic bomb survivors, their immune defense against such infections might be diminished. To investigate this possibility, we measured antibody levels to the above microorganisms in the sera of survivors. We found that the levels of IgG and IgA antibodies to Chlamydia pneumoniae decreased significantly with radiation dose, whereas the levels of IgG antibodies to Helicobacter pylori or cytomegalovirus remained unchanged. The inflammation marker C-reactive protein was significantly and positively associated with level of antibodies to Chlamydia pneumoniae only in heavily exposed (≥1000 mGy) survivors. These results may suggest that among atomic bomb survivors, immune response to Chlamydia pneumoniae is diminished and chronic inflammatory reactions related to Chlamydia pneumoniae infection are present.

Kopecky, K. J., Stepanenko, V., Rivkind, N., Voillequé, P., Onstad, L., Shakhtarin, V., Parshkov, E., Kulikov, S., Lushnikov, E., Abrosimov, A., Troshin, V., Romanova, G., Doroschenko, V., Proshin, A., Tsyb, A. and Davis, S. Childhood Thyroid Cancer, Radiation Dose from Chernobyl, and Dose Uncertainties in Bryansk Oblast, Russia: A Population-Based Case-Control Study. Radiat. Res. 166, 367–374 (2006).

A population-based case-control study was conducted to estimate the radiation-related risk of thyroid cancer in persons who were exposed in childhood to ¹³¹I from the Chernobyl accident of April 26, 1986 and to investigate the impact of uncertainties in individual dose estimates. Included were all 66 confirmed cases of primary thyroid cancer diagnosed from April 26, 1986 through September 1998 in residents of Bryansk Oblast, Russia, who were 0–19 years old at the time of the accident, along with two individually matched controls for each case. Thyroid radiation doses, estimated using a semi-empirical model based on environmental contamination data and individual characteristics, ranged from 0.00014 Gy to 2.73 Gy and had large uncertainties (median geometric standard deviation 2.2). The estimated excess relative risk (ERR) associated with radiation exposure, 48.7/Gy, was significantly greater than 0 (P = 0.00013) but had an extremely wide 95% confidence interval (4.8 to 1151/Gy). Adjusting for dose uncertainty nearly tripled the ERR to 138/Gy, although this was likely an overestimate due to limitations in the modeling of dose uncertainties. The radiation-related excess risk observed in this study is quite large, especially if the uncertainty of dose estimation is taken into account, but is not inconsistent with estimates previously reported for risk after ¹³¹I exposure or acute irradiation from external sources.

Likhtarov, I., Kovgan, L., Vavilov, S., Chepurny, M., Ron, E., Lubin, J., Bouville, A., Tronko, N., Bogdanova, T., Gulak, L., Zablotska, L. and Howe, G. Post-Chornobyl Thyroid Cancers in Ukraine. Report 2: Risk Analysis. Radiat. Res. 166, 375–386 (2006).

On April 26, 1986, the worst nuclear reactor accident to date occurred at the Chornobyl (Chernobyl) power plant in Ukraine. Millions of people in Ukraine, Belarus and Russia were exposed to radioactive nuclides, especially ¹³¹I. Since then, research has been conducted on various subgroups of the exposed population, and it has been demonstrated that the large increase in thyroid cancer is related to the ¹³¹I exposure. However, because of study limitations, quantified risk estimates are limited, and there remains a need for additional information. We conducted an ecological study to investigate the relationship between ¹³¹I thyroid dose and the diagnosis of thyroid cancer in three highly contaminated oblasts in Northern Ukraine. The study population is comprised of 301,907 persons who were between the ages of 1 and 18 at the time of the Chornobyl accident and were living in 1,293 rural settlements in the three study oblasts. Twenty-four percent of the study population had individual thyroid dose estimates and the other 76% had “individualized” estimates of thyroid dose based on direct thyroid measurements taken from a person of the same age and gender living in the same or nearby settlement. Cases include 232 thyroid cancers diagnosed from January 1990 through December 2001, and all were confirmed histologically. Dose–response analyses took into account differences in the rate of ultrasound examinations conducted in the three study oblasts. The estimated excess relative risk per gray was 8.0 (95% CI = 4.6–15) and the excess absolute risk per 10,000 person-year gray was estimated to be 1.5 (95% CI = 1.2–1.9). In broad terms, these estimates are compatible with results of other studies from the contaminated areas, as well as studies of external radiation exposure.

Trivillin, V. A., Heber, E. M., Nigg, D. W., Itoiz, M. E., Calzetta, O., Blaumann, H., Longhino, J. and Schwint, A. E. Therapeutic Success of Boron Neutron Capture Therapy (BNCT) Mediated by a Chemically Non-selective Boron Agent in an Experimental Model of Oral Cancer: A New Paradigm in BNCT Radiobiology. Radiat. Res. 166, 387–396 (2006).

The hypothesis of boron neutron capture therapy (BNCT) research has been that the short-range, high-linear energy transfer radiation produced by the capture of thermal neutrons by ¹⁰B will potentially control tumor and spare normal tissue only if the boron compound selectively targets tumor tissue within the treatment volume. In a previous in vivo study of low-dose BNCT mediated by GB-10 (Na₂¹⁰B₁₀H₁₀) alone or combined with boronophenylalanine (BPA) in the hamster cheek pouch oral cancer model that was primarily designed to evaluate safety and feasibility, we showed therapeutic effects but no associated normal tissue radiotoxicity. In the present study, we evaluated the response of tumor, precancerous and normal tissue to high-dose BNCT mediated by GB-10 alone or combined with BPA. Despite the fact that GB-10 does not target hamster cheek pouch tumors selectively, GB-10-BNCT induced a 70% overall tumor response with no damage to normal tissue. (GB-10 BPA)-BNCT induced a 93% overall tumor response with no normal tissue radiotoxicity. Light microscope analysis showed that GB-10-BNCT selectively damages tumor blood vessels, sparing precancerous and normal tissue vessels. In this case, selective tumor lethality would thus result from selective blood vessel damage rather than from selective uptake of the boron compound.

Heikkinen, P., Ernst, H., Huuskonen, H., Komulainen, H., Kumlin, T., Mäki-Paakkanen, J., Puranen, L. and Juutilainen, J. No Effects of Radiofrequency Radiation on 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone-Induced Tumorigenesis in Female Wistar Rats. Radiat. Res. 166, 397–408 (2006).

This study evaluated possible effects of radiofrequency (RF) radiation on tumorigenesis induced by the mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) given in drinking water. Female Wistar rats aged 7 weeks at the beginning of the experiments were randomly divided into four groups of 72 animals: a cage-control group and three MX-exposed groups (a daily average dose of 1.7 mg MX/kg body weight for 104 weeks), of which two were exposed to 900 MHz pulsed RF radiation and the third served as a sham-RF-radiation group. The RF-radiation groups were exposed 2 h per day, 5 days per week for 104 weeks at nominal whole-body average SARs of 0.3 W/kg and 0.9 W/kg. Complete histopathology was performed on the rats of the three MX-exposed groups. The tumor types and incidences observed in the MX-exposed animals were similar to those reported earlier in MX-exposed female Wistar rats. RF radiation did not statistically significantly affect mortality or organ-specific incidence of any tumor type. The only statistically significant difference was an increase in the combined frequency of vascular tumors of the mesenteric lymph nodes in the high-RF-radiation group compared to the sham-RF-radiation group. However, additional histopathological analysis of the cage-control animals suggested that this difference was due to unusually low frequency of this type of tumor in the sham-RF-radiation group rather than a high frequency in the high-RF-radiation group. With respect to non-neoplastic findings, statistically significant differences between the RF-radiation groups and the sham-RF-radiation group were observed only for single findings in the lacrimal glands, lungs, liver and skin. Such changes are commonly seen in aged rats and were considered to be unrelated to RF radiation. The results of the present study do not support co-carcinogenic effects of low-level long-term RF-radiation exposure in rats.

Thorlin, T., Rouquette, J.-M., Hamnerius, Y., Hansson, E., Persson, M., Björklund, U., Rosengren, L., Rönnbäck, L. and Persson, M. Exposure of Cultured Astroglial and Microglial Brain Cells to 900 MHz Microwave Radiation. Radiat. Res. 166, 409–421 (2006).

The rapid rise in the use of mobile communications has raised concerns about health issues related to low-level microwave radiation. The head and brain are usually the most exposed targets in mobile phone users. In the brain, two types of glial cells, the astroglial and the microglial cells, are interesting in the context of biological effects from microwave exposure. These cells are widely distributed in the brain and are directly involved in the response to brain damage as well as in the development of brain cancer. The aim of the present study was to investigate whether 900 MHz radiation could affect these two different glial cell types in culture by studying markers for damage-related processes in the cells. Primary cultures enriched in astroglial cells were exposed to 900 MHz microwave radiation in a temperature-controlled exposure system at specific absorption rates (SARs) of 3 W/kg GSM modulated wave (mw) for 4, 8 and 24 h or 27 W/kg continuous wave (cw) for 24 h, and the release into the extracellular medium of the two pro-inflammatory cytokines interleukin 6 (Il6) and tumor necrosis factor-alpha (Tnfa) was analyzed. In addition, levels of the astroglial cell-specific reactive marker glial fibrillary acidic protein (Gfap), whose expression dynamics is different from that of cytokines, were measured in astroglial cultures and in astroglial cell-conditioned cell culture medium at SARs of 27 and 54 W/kg (cw) for 4 or 24 h. No significant differences could be detected for any of the parameters studied at any time and for any of the radiation characteristics. Total protein levels remained constant during the experiments. Microglial cell cultures were exposed to 900 MHz radiation at an SAR of 3 W/kg (mw) for 8 h, and Il6, Tnfa, total protein and the microglial reactivity marker ED-1 (a macrophage activation antigen) were measured. No significant differences were found. The morphology of the cultured astroglial cells and microglia was studied and appeared to be unaffected by microwave irradiation. Thus this study does not provide evidence for any effect of the microwave radiation used on damage-related factors in glial cells in culture.

Kopp-Schneider, A., Haertel, T., Burkholder, I., Bannasch, P., Wesch, H., Groos, J. and Heeger, S. Investigating the Formation and Growth of α-Particle Radiation-Induced Foci of Altered Hepatocytes: A Model-Based Approach. Radiat. Res. 166, 422–430 (2006).

The effect of α-particle radiation on the formation and increase in volume of preneoplastic liver lesions was investigated in an animal experiment. Mice were divided into four groups; two groups received different doses of the α-particle-labeled antibody ²¹³Bi-anti CD19 (²¹³Bi-CD19), Thorotrast was administered to one group, and one group was left untreated. Hematoxylin and eosin-stained liver sections were evaluated for preneoplastic foci of altered hepatocytes 6, 12 and 17 months after treatment. The density and size distribution of focal transections were described by a mechanistic model for the formation and growth of foci of altered hepatocytes. The negative control and the ²¹³Bi-CD19 groups were combined to investigate the dose–response relationship for model parameters describing the formation and growth of foci of altered hepatocytes. Although ²¹³Bi-CD19 was given by single injection, the effect on formation of foci of altered hepatocytes lasted for the entire experiment. Likelihood-ratio tests comparing nested models showed that ²¹³Bi-CD19 increases the rates of both the formation and growth of foci of altered hepatocytes. Comparing the effects of Thorotrast with those of ²¹³Bi-CD19 revealed that Thorotrast had an effect similar to that of a low dose of ²¹³Bi-CD19, but the effect on focus formation was slightly smaller whereas the effect on focus growth was slightly higher for Thorotrast, in contrast to a low dose of ²¹³Bi-CD19.

Hawkins, R. B. Mammalian Cell Killing by Ultrasoft X Rays and High-Energy Radiation: An Extension of the MK Model. Radiat. Res. 166, 431–442 (2006).

An alternate formulation of the microdosimetric-kinetic (MK) model is presented that applies to irradiation of mammalian cells with ultrasoft X rays as well as high-energy radiations of variable linear energy transfer (LET). Survival and DNA double-strand break measurements for V79 cells from the literature are examined to illustrate application of the model. It is demonstrated that the linear component of the linear-quadratic survival relationship (α) is enhanced because repairable potentially lethal lesions formed from a single ultrasoft X-ray energy deposition event, when closer on average than for a single high-energy radiation event, are more likely to combine to form a lethal lesion. The quadratic component (β) of the linear-quadratic survival relationship is increased because the potentially lethal lesions formed by ultrasoft X rays are created with greater efficiency than those of high-energy radiation. In addition, potentially lethal lesions from very low-energy carbon K-shell X rays may be enriched in structural forms that favor combination to form lethal lesions instead of repair. These features account for the increased effectiveness of killing of V79 cells by ultrasoft X rays compared to cobalt-60 γ radiation. The importance of pairwise combination of potentially lethal lesions to form exchange chromosome aberrations that become lethal lesions is discussed. The extended MK model explains and reconciles differences between the MK model and the theory of dual radiation action on the one hand, and on the other, the view that variation in the RBE with radiation quality is explained by differences in energy deposition in nanometer- rather than micrometer-size volumes.