Preston, D. L., Shimizu, Y., Pierce, D. A., Suyama, A. and Mabuchi, K. Studies of Mortality of Atomic Bomb Survivors. Report 13: Solid Cancer and Noncancer Disease Mortality: 1950–1997. Radiat. Res. 160, 381–407 (2003).

This continues the series of general reports on mortality in the cohort of atomic bomb survivors followed up by the Radiation Effects Research Foundation. This cohort includes 86,572 people with individual dose estimates, 60% of whom have doses of at least 5 mSv. We consider mortality for solid cancer and for noncancer diseases with 7 additional years of follow-up. There have been 9,335 deaths from solid cancer and 31,881 deaths from noncancer diseases during the 47-year follow-up. Of these, 19% of the solid cancer and 15% of the noncancer deaths occurred during the latest 7 years. We estimate that about 440 (5%) of the solid cancer deaths and 250 (0.8%) of the noncancer deaths were associated with the radiation exposure. The excess solid cancer risks appear to be linear in dose even for doses in the 0 to 150-mSv range. While excess rates for radiation-related cancers increase throughout the study period, a new finding is that relative risks decline with increasing attained age, as well as being highest for those exposed as children as noted previously. A useful representative value is that for those exposed at age 30 the solid cancer risk is elevated by 47% per sievert at age 70. There is no significant city difference in either the relative or absolute excess solid cancer risk. Site-specific analyses highlight the difficulties, and need for caution, in distinguishing between site-specific relative risks. These analyses also provide insight into the difficulties in interpretation and generalization of LSS estimates of age-at-exposure effects. The evidence for radiation effects on noncancer mortality remains strong, with risks elevated by about 14% per sievert during the last 30 years of follow-up. Statistically significant increases are seen for heart disease, stroke, digestive diseases, and respiratory diseases. The noncancer data are consistent with some non-linearity in the dose response owing to the substantial uncertainties in the data. There is no direct evidence of radiation effects for doses less than about 0.5 Sv. While there are no statistically significant variations in noncancer relative risks with age, age at exposure, or sex, the estimated effects are comparable to those seen for cancer. Lifetime risk summaries are used to examine uncertainties of the LSS noncancer disease findings.

Stram, D. O. and Kopecky, K. J. Power and Uncertainty Analysis of Epidemiological Studies of Radiation-Related Disease Risk in which Dose Estimates are Based on a Complex Dosimetry System: Some Observations. Radiat. Res. 160, 408–417 (2003).

This paper discusses practical effects of dosimetry error relevant to the design and analysis of an epidemiological study of disease risk and exposure. It focuses on shared error in radiation dose estimates for such studies as the Hanford Thyroid Disease Study or the Utah Thyroid Cohort Study, which use complex dosimetry systems that produce multiple replications of possible dose for the cohort. We argue that a simple estimation of shared multiplicative error components through direct examination of the replications of dose for each person provides information useful for estimating the power of a study to detect a radiation effect and illustrate this with an example based on the doses used for the Hanford Thyroid Disease Study. Uncertainty analysis (construction of confidence intervals) can be approached in the same way in simple cases. We also offer some suggestions for Monte Carlo-based confidence intervals.

Wu, H., Durante, M., Furusawa, Y., George, K., Kawata, T. and Cucinotta, F. A. Truly Incomplete and Complex Exchanges in Prematurely Condensed Chromosomes of Human Fibroblasts Exposed In Vitro to Energetic Heavy Ions. Radiat. Res. 160, 418–424 (2003).

Confluent human fibroblast cells (AG1522) were irradiated with γ rays, 490 MeV/nucleon silicon ions, or iron ions at either 200 or 500 MeV/nucleon. The cells were allowed to repair at 37°C for 24 h after exposure, and a chemically induced premature chromosome condensation (PCC) technique was used to condense chromosomes in the G₂ phase of the cell cycle. Incomplete and complex exchanges were analyzed in the irradiated samples. To verify that chromosomal breaks were truly unrejoined, chromosome aberrations were analyzed using a combination of whole-chromosome specific probes and probes specific for the telomere region of the chromosome. Results showed that the frequency of unrejoined chromosome breaks was higher after irradiation with the heavy ions of high LET, and consequently the ratio of incomplete to complete exchanges increased steadily with LET up to 440 keV/μm, the highest LET included in the present study. For samples exposed to 200 MeV/nucleon iron ions, chromosome aberrations were analyzed using the multicolor FISH (mFISH) technique, which allows identification of both complex and truly incomplete exchanges. Results of the mFISH study showed that 0.7 and 3 Gy iron ions produced similar ratios of complex to simple exchanges and incomplete to complete exchanges; these ratios were higher than those obtained after exposure to 6 Gy γ rays. After 0.7 Gy of iron ions, most complex aberrations were found to involve three or four chromosomes, which is a likely indication of the maximum number of chromosome domains traversed by a single iron-ion track.

George, K., Durante, M., Willingham, V., Wu, H., Yang, T. C. and Cucinotta, F. A. Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage Measured in Metaphase and Interphase Human Lymphocytes. Radiat. Res. 160, 425–435 (2003).

Chromosome aberrations were investigated in human lymphocytes after in vitro exposure to ¹H-, ³He-, ¹²C-, ⁴⁰Ar-, ²⁸Si-, ⁵⁶Fe-, or ¹⁹⁷Au-ion beams, with LET ranging from approximately 0.4-1393 keV/μm in the dose range of 0.075–3 Gy. Dose–response curves for chromosome exchanges, measured at the first mitosis postirradiation using fluorescence in situ hybridization (FISH) with whole-chromosome probes, were fitted with linear or linear-quadratic functions. The relative biological effectiveness (RBE) was estimated from the initial slope of the dose–response curve for chromosomal damage with respect to low- or high-dose-rate γ rays. Estimates of RBE_max values for mitotic spreads, which ranged from near 0.7 to 11.1 for total exchanges, increased with LET, reaching a maximum at about 150 keV/μm, and decreased with further increase in LET. RBEs for complex aberrations are undefined due to the lack of an initial slope for γ rays. Additionally, the effect of mitotic delay on RBE values was investigated by measuring chromosome aberrations in interphase after chemically induced premature chromosome condensation (PCC), and values were up to threefold higher than for metaphase analysis.

Kadosawa, T., Ohashi, F., Nishimura, R., Sasaki, N., Saito, I., Wakabayashi, H. and Takeuchi, A. Relative Biological Effectiveness and Tolerance Dose of Fission Neutrons in Canine Skin for a Potential Combination of Neutron Capture Therapy and Fast-Neutron Therapy. Radiat. Res. 160, 436–442 (2003).

To investigate the potential efficacy of fission neutrons from a fast-neutron reactor for the treatment of radioresistant tumors, the relative biological effectiveness (RBE) and tolerance dose of fission neutrons in canine skin were determined. The forelimbs of 34 healthy mongrel dogs received a single dose of fission neutrons (5.6, 6.8, 8.2, 9.6 or 11 Gy) or ¹³⁷Cs γ rays (10, 15, 20, 25 or 30 Gy). Based on observations of radiodermatitis for each radiation, the single-fraction RBE of fission neutrons in the sixth month was calculated as approximately 3. The tolerance doses of fission neutrons and γ rays, defined as the highest doses giving no moist desquamation on the irradiated skin in the recovery phase, were estimated as 7.6 Gy and 20 Gy, respectively. The tolerance dose of 7.6 Gy of fission neutrons included 5.0 Gy of fast neutrons possessing high anti-tumor effects and 1.4 × 10¹² n/cm² of thermal neutrons, which could be applicable to neutron capture therapy (NCT). The combination of fast-neutron therapy and NCT using a fast-neutron reactor might be useful for the treatment of radioresistant tumors.

Cordelli, E., Fresegna, A. M., Leter, G., Eleuteri, P., Spanò, M. and Villani, P. Evaluation of DNA Damage in Different Stages of Mouse Spermatogenesis after Testicular X Irradiation. Radiat. Res. 160, 443–451 (2003).

To evaluate whether DNA alterations in mature spermatozoa could stem from DNA damage induced in immature germ cells, testis cells and spermatozoa were analyzed by the comet assay and by the sperm chromatin structure assay 14, 45 and 100 days after in vivo X irradiation of the testes. These times were selected, according to the mouse seminiferous epithelium cycle, to follow the DNA damage induced in different germ cell compartments. The cytotoxic action was assessed by DNA flow cytometric analysis of testicular cells. A dose-dependent increase of DNA damage in testis cells was observed 14 days after irradiation, whereas mature sperm cells were not affected. On the other hand, an increase in DNA strand breaks was seen in spermatozoa 45 days after treatment. DNA damage returned to the control levels 100 days after irradiation. The methods used to evaluate DNA damage gave comparable results, emphasizing the correlation between DNA fragmentation and susceptibility of sperm chromatin to denaturation. Both techniques showed the high radiosensitivity of differentiating spermatogonia. The overall results showed that DNA damage induced in pre-meiotic germ cells is detectable in primary spermatocytes and is still present in mature spermatozoa.

Chen, B., Pogue, B. W., Goodwin, I. A., O'Hara, J. A., Wilmot, C. M., Hutchins, J. E., Hoopes, P. J. and Hasan, T. Blood Flow Dynamics after Photodynamic Therapy with Verteporfin in the RIF-1 Tumor. Radiat. Res. 160, 452–459 (2003).

In the present study, the effects of photodynamic therapy (PDT) with verteporfin on tumor blood flow and tumor regrowth were compared as verteporfin distributed in different compartments within the RIF-1 tumor. Tissue distribution of verteporfin was examined by fluorescence microscopy, and blood flow measurements were taken with a laser Doppler system. It was found that, at 15 min after drug administration, when verteporfin was mainly confined within the vasculature, PDT induced a complete arrest of blood flow by 6 h after treatment. PDT treatment at a longer drug–light interval (3 h), which allowed the drug to diffuse to the tumor interstitium, caused significantly less flow decrease, only to 50% of the initial flow in 6 h. A histological study and Hoechst 33342 staining of functional tumor vasculature confirmed the primary vascular damage and the decrease in tumor perfusion. The regrowth rate of tumors treated with 15-min interval PDT was 64% of that of the control group. However, when tumors were treated with 3-h interval PDT, the regrowth rate was not significantly different from that of the control, indicating that only the 15-min interval PDT caused serious damage to the tumor vascular bed. These results support the hypothesis that temporal pharmacokinetic changes in the distribution of the photosensitizer between the tumor parenchyma and blood vessels can significantly alter the tumor target of PDT.

Kang, Z., Scott, T. M., Wesolowski, C., Feng, L., Wang, J., Wang, L. and Liu, H. Ex Vivo Evaluation of a Novel Polyiodinated Compound for Early Detection of Atherosclerosis. Radiat. Res. 160, 460–466 (2003).

Atherosclerosis is a primary cause of heart disease and stroke; it is the underlying cause of about 50% of all deaths in Western countries. It is known that early detection of atherosclerotic lesions would significantly reduce the risk of mortality. The objective of this study was to develop a radioimaging method for early detection of atherosclerotic plaques. A novel polyiodinated cholesterol analog, cholesteryl 1,3-diiopanoate glyceryl ether (C2I, patent pending), was synthesized and radiolabeled with ¹²⁵I. ¹²⁵I-C2I was incorporated into acetylated low-density lipoprotein (AcLDL), which is considered to be an atherosclerotic plaque-seeking carrier. ¹²⁵I-C2I was also prepared as a chylomicron-like emulsion. Transgenic mice deficient in apoE and low-density lipoprotein receptors (LDLR), known as apoE/LDLR double knockout, were used as an animal model of early atherosclerosis. ¹²⁵I-C2I/AcLDL or ¹²⁵I-C2I emulsion was injected into the apoE/LDLR knockout mice via the tail vein, and the mice were killed humanely 24 h after injection. Various tissues including aorta were removed and radioactivity was determined. The aorta samples were also imaged to determine the accumulation of radioactivity from C2I. The images were compared to the atherosclerotic lesions revealed by histological studies. It was found that both ¹²⁵I-C2I/AcLDL and ¹²⁵I-C2I emulsion resulted in accumulation of radioactivity at the site of early atherosclerotic lesions, and they therefore may be useful for early detection of atherosclerosis.

Tomita, M., Suzuki, N., Matsumoto, Y., Enomoto, A., Yin, H. L., Hosoi, Y., Hirano, K. and Sakai, K. Wortmannin-Enhanced X-Ray-Induced Apoptosis of Human T-Cell Leukemia MOLT-4 Cells Possibly through the JNK/SAPK Pathway. Radiat. Res. 160, 467–477 (2003).

We demonstrated that enhancement of X-ray-induced apoptosis/rapid cell death by wortmannin accompanied by increased activation of JNK/SAPK in human leukemia MOLT-4 cells. Rapid cell death/apoptosis was determined either by the dye exclusion test or by the appearance of Annexin V-positive cells and cleaved PARP fragments. Enhancement was observed only at higher concentrations of wortmannin, i.e. 1 μM or more. At these high concentrations, both DNA-PK and ATM were inhibited. X-ray-induced phosphorylation of Ser 15 of p53/TP53, accumulation of both p53/TP53 and p21/WAF1/CDKN1A, and phosphorylation of XRCC4 were all suppressed. The enhancement of apoptosis/rapid cell death by wortmannin was prevented by addition of caspase inhibitors, Z-VAD-FMK or Ac-DEVD-CHO, or by transfection and overexpression of mouse Bcl2, which is known as an anti-apoptosis protein. The requirement for a high concentration of wortmannin, i.e. 1 μM or more, indicates that inhibition of both DNA-PK and ATM was necessary for the enhanced apoptosis/rapid cell death. Phosphorylation of AKT/PKB was completely suppressed at a much lower concentration, i.e. 0.1 μM wortmannin, where no enhancement of X-ray-induced apoptosis/rapid cell death was observed. On the other hand, X-ray-induced phosphorylation of JNK and its kinase activity as well as apoptosis/rapid cell death were all significantly enhanced only at high concentrations of wortmannin, i.e. 1 μM or more. Furthermore, the extent of enhancement of both JNK phosphorylation and of apoptosis/rapid cell death by wortmannin was less in Rh1a cells, which are ceramide- and radiation-resistant variant cells compared to the parental MOLT-4 cells. Therefore, activation of the JNK pathway was considered important for the enhancement of X-ray-induced apoptosis/rapid cell death of MOLT-4 cells by wortmannin, because of the requirement for a higher concentration of wortmannin than that required for inhibition of AKT phosphorylation. The suppression of the AKT-dependent pathway by wortmannin may have some underlying role in activating the JNK pathway toward the enhancement of cell death in the current system.

Shankar, B., Santosh Kumar, S. and Sainis, K. B. Generation of Reactive Oxygen Species and Radiation Response in Lymphocytes and Tumor Cells. Radiat. Res. 160, 478–487 (2003).

Several types of lymphoid and myeloid tumor cells are known to be relatively resistant to radiation-induced apoptosis compared to normal lymphocytes. The intracellular generation of reactive oxygen species was measured in irradiated spleen cells from C57BL/6 and BALB/c mice and murine tumor cells (EL-4 and P388) by flow cytometry using dichlorodihydrofluoresceindiacetate and dihydrorhodamine 123 as fluorescent probes. The amount of reactive oxygen species generated per cell was low in the tumor cells compared to spleen cells exposed to 1 to 10 Gy of γ radiation. This could be due to the higher total antioxidant levels in tumor cells compared to normal cells. Further, the changes in mitochondrial membrane potential and cytoplasmic Ca² content were appreciable in lymphocytes even at a dose of 1 Gy. In EL-4 cells, no such changes were observed at any of the doses used. About 65% of spleen cells underwent apoptosis 24 h after 1 Gy irradiation. However, under the same conditions, EL-4 and P388 cells failed to undergo apoptosis, but they accumulated in G₂/M phase. Thus the intrinsic radioresistance of tumor cells may be due to a decreased generation of reactive oxygen species after irradiation and down-regulation of the subsequent events leading to apoptosis.

Desta, A. B., Owen, R. D. and Cress, L. W. Non-thermal Exposure to Radiofrequency Energy from Digital Wireless Phones does not Affect Ornithine Decarboxylase Activity in L929 Cells. Radiat. Res. 160, 488–491 (2003).

L929 murine fibroblast cells were exposed to radiofrequency (RF) radiation from a time division multiple access wireless phone operating at 835 MHz frequency to determine the effect of RF-radiation energy emitted by wireless phones on ornithine decarboxylase (ODC) activity in cultured cells. Exposure was for 8 h to an average specific absorption rate (SAR) from <1 W/kg up to 15 W/kg. After exposure, cells were harvested and ODC activity was measured. No statistically significant difference in ODC activity was found between RF-radiation-exposed and sham-exposed cells at non-thermal specific absorption rates. At SARs which resulted in measurable heating of the medium, a dose-dependent decrease in enzymatic activity was observed and was shown to be consistent with a comparable decrease caused by non-RF-radiation heating. Thus we observed only the well-known enzyme inhibition due to heating, rather than the previously reported enhancement attributed to RF-radiation exposure.

Anane, R., Dulou, P-E., Taxile, M., Geffard, M., Crespeau, F. and Veyret, B. Effects of GSM-900 Microwaves on DMBA-Induced Mammary Gland Tumors in Female Sprague-Dawley Rats. Radiat. Res. 160, 492–497 (2003).

The aim of this investigation was to test the hypothesis that sub-chronic whole-body exposure to GSM-900 microwaves had an effect on tumor promotion and progression. Mammary tumors were induced by ingestion of a single 10-mg dose of 7,12-dimethylbenz(a)anthracene (DMBA) in female Sprague-Dawley rats (Ico:OFA-SD; IOPS Caw). In two independent experiments, DMBA-treated animals were divided into four groups: sham-exposed (16) and exposed (three groups of 16 animals). The specific absorption rates (SARs), averaged over the whole body, were 3.5, 2.2 and 1.4 W/kg in the first experiment (May–July) and 1.4, 0.7 and 0.1 W/kg in the second experiment (September–November). Exposure started 10 days after DMBA treatment and lasted 2 h/day, 5 days/week for 9 weeks. Animals were exposed to plane waves with the electric field parallel to the long axis of the animals. Body weight and the number, location and size of the tumors were recorded at regular intervals. Rats were killed humanely 3 weeks after the end of exposure. The results are negative in terms of latency, multiplicity and tumor volume. With regard to tumor incidence, in the first experiment there was an increase in the rate of incidence at 1.4 W/kg but less at 2.2 W/kg and none at 3.5 W/kg. Overall, these results, which are rather inconsistent, do not bring new evidence of a co-promoting effect of exposure to GSM-900 signals using the DMBA rat model.