Ongoing assembly and maintenance activities at the International Space Station (ISS) require much more extravehicular activity (EVA) than did the earlier U.S. Space Shuttle missions. It is thus desirable to determine and analyze, and possibly foresee, as accurately as possible what radiation exposures crew members involved in EVAs will experience in order to minimize risks and to establish exposure limits that must not to be exceeded. A detailed CAD model of the U.S. Space Shuttle EVA Spacesuit, developed at NASA Langley Research Center (LaRC), is used to represent the directional shielding of an astronaut; it has detailed helmet and backpack structures, hard upper torso, and multilayer space suit fabric material. The NASA Computerized Anatomical Male and Female (CAM and CAF) models are used in conjunction with the space suit CAD model for dose evaluation within the human body. The particle environments are taken from the orbit-averaged NASA AP8 and AE8 models at solar cycle maxima and minima. The transport of energetic particles through space suit materials and body tissue is calculated by using the NASA LaRC HZETRN code for hadrons and a recently developed deterministic transport code, ELTRN, for electrons. The doses within the CAM and CAF models are determined from energy deposition at given target points along 968 directional rays convergent on the points and are evaluated for several points on the skin and within the body. Dosimetric quantities include contributions from primary protons, light ions, and electrons, as well as from secondary brehmsstrahlung and target fragments. Directional dose patterns are displayed as rays and on spherical surfaces by the use of a color relative intensity representation.

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Intraperitoneal administration of diltiazem (DTZ), half an hour prior to whole body gamma irradiation (2.5, 5.0, & 7.5 Gy), showed the protection of animals from radiation-induced anaemia. Radiation exposure significantly (p < 0.001) reduced the number of pro- and normoblasts in bone marrow and RBC counts, hemoglobin (Hb), hematocrit (Hct ), and erythropoietin (EPO) level in blood, but increased myeloid / erythroid ratio. At all the radiation doses, the maximum decrease in these values was noted on the 3rd day, followed by a gradual recovery from the 7th day, but it was not recorded as normal even until the end of experimentation. In animals pretreated with DTZ, these values were measured higher at all the time periods in comparison to corresponding control, and these were almost normal at the last autopsy interval only at 2.5 Gy radiation dose. DTZ maintained the higher erythropoietin level in blood, which acted on bone marrow and spleen colony forming unit for erythroblast (CFU-E), and stimulated such cells to produce RBCs. These results confirm that DTZ has the potency to alter anaemic condition favorably through the protection of bone marrow stem cells, and subsequently it maintains the higher number of pro- and normoblasts in bone marrow, RBC counts, hemoglobin (Hb), hematocrit (Hct) percentage, and erythropoietin level in blood and the lower myeloid/erythroid ratio in bone marrow.

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Our previous study indicated that dermal multipotent cells with the differentiation capacity to form cells with the phenotypic properties of osteocytes, adipocytes, chondrocytes, and neurons in specific inducing media could be isolated from the enzymatically dissociated dermal cells of newborn rats by their adherence to culture dish plastic. We have also observed that the systemic transplantation of dermal multipotent cells could not repopulate the hematopoietic system in lethally irradiated rats. In this paper, we found that a transplantation of plastic-adherent dermal multipotent cells into sublethally irradiated rats led to a significant increase of white blood cells in peripheral blood, nucleated cells, CFU-GM, and CFU-F colonies in bone marrow. FISH analysis, using a Y-chromosome specific probe, showed that dermal multipotent cells could engraft into bone marrow in recipients. Flow cytometry (FACS) analysis also showed that the proportion of CD2 and CD25 positive lymphocytes in peripheral blood did not change significantly in two weeks after transplantation. By these results, we infer that dermal multipotent cells may represent an alternative origin of mesenchymal stem cells to restore marrow microenvironment and promote the survival, engraftment, and proliferation of hematopoietic cells.

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The murine genome has about 1,000 copies of DNA elements for the intracisternal A-particle (IAP) that resembles a retrovirus. We previously reported that the genomic DNA of the cells from radiation-induced acute myeloid leukemia (AML) lines derived from C3H/He inbred mice was frequently rearranged by the integration of the IAP element. In this study, 8 IAP elements from the characteristic integration sites in 6 cell lines of radiation-induced AML from different mice were characterized and compared in structure with 114 IAP elements isolated from the normal C3H/He genome. One of the 8 elements was a full-length type I IAP, and 7 were of type-IΔ1 with a common deletion site. Although the type IΔ1 form is a minor population accounting for about 6% of total genomic IAP elements, it is predominantly retrotransposed in the AML cells from different C3H/He mice. This indicates that limited populations of the IAP elements contribute to the unique retrotransposition in AML cells.

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We examined whether the increase of glutathione level induced by low dose γ-ray irradiation is involved in the appearance of enhanced natural killer (NK) activity and antibody-dependent cellular cytotoxicity (ADCC), leading to delayed tumor growth in Ehrlich solid tumor-bearing mice. NK activity in ICR mouse splenocytes significantly increased from 4 h to 6 h after whole-body γ-ray irradiation at 0.5 Gy, and thereafter decreased almost to the zero-time level by 24 h post-irradiation. ADCC also increased significantly in a similar way. Reduced glutathione exogenously added to splenocytes obtained from normal mice enhanced both NK activity and ADCC in a dose-dependent manner. Since immune functions were enhanced through the induction of cellular glutathione after low-dose irradiation, the inhibitory effect of the radiation on tumor growth was then examined in Ehrlich solid tumor-bearing mice. Tumor growth after inoculation was significantly delayed by the radiation. These results suggest that low-dose γ-rays activate immune functions via an induction of glutathione, leading to a delay of tumor growth.

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This paper discusses the results of the analysis of the relationship between dose and solid cancer incidence among nuclear workers (males) who worked as liquidators after the Chernobyl accident. Information on this cohort of individuals is available at the regional center of Russian National Medical and Dosimetric Registry operating at the RF State Research Centre-Institute of Biophysics. Medical and dosimetric information on 8,654 persons 18–60 years of age with documented external radiation doses is used for the analysis. These data were gathered in the period from 1996 to 2001 and cover a total of 45,166.5 follow-up person-years. In the cohort under study, 179 solid cancers occurred during this period. The average age of liquidators at the time of exposure was 35.8 years, and the average dose as a result of the Chernobyl exposure was about 0.05 Sv. For an analysis of the dose-effect relationship (induction of radiation-induced malignant neoplasms) the statistical software EPICURE was used. The results of the analysis show that the cancer incidence in this cohort does not exceed cancer incidence in relevant age groups of the Russian population. The mean value of SIR for all cancer diseases was 0.88 (0.76, 1.02, 95% CI) for the whole period of follow-up. Risks for the induction of radiation-related cancer diseases were not statistically meaningful. Excess relative risk per 1 Sv was 0.95 (–1.52, 4.49, 95% CI).

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Experiments on mongrel canines exposed to total body irradiation in free-in-air dose of 3.85 (LD 95/45) or 4.05 Gy were carried out to evaluate the therapeutic effectiveness of some of bone marrow immediate-after-irradiation extraction, incubation in the presence of protein synthesis inhibitor and reimplantation in the organism (the reimplantation method) or bone marrow extraction alone (the extraction method). There were tested various kinds of methods that differed in bone marrow-blood mix volume extracted, in large or in small volumes. It has been determined that the reimplantation method in large volumes and the extraction method in small volumes are equally effective. Being supplemented with supportive therapy by antibiotics during d8-d24, the methods allowed the rescue at 4.05 Gy irradiation significantly more animals than in the case of therapy alone or its combination with ineffective variants of the methods. The positive effect of the methods manifested in a higher level of leukocyte nadir on d17, earlier reaching 0.5 × 10⁹ and 1 × 10⁹ leukocytes per liter, and increasing 45 days survival.The mechanism of positive influence of the methods on the radiation injury of hemopoesis seems to be related to increased cytokine producing because of the irritation of bone marrow stromal cells and thus favorable interference in the early restoration processes.

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To determine the patterns of gene expression responsible for the radiosensitivity of glioblastoma cells, we analyzed transcriptional changes after ionizing radiation in different cell lines. After completing clonogenic survival assays, we selected two glioblastoma cell lines with different radiosensitivities. Subsequently, they were investigated by using the technique of DNA microarray, and we then categorized the upregulated genes into 10 groups. Between the two cell lines, the difference in the percentage of DNA repair/replication category was the largest, and this category was present at a greater percentage with radioresistant cell line U87MG. Moreover, among the commonly upregulated genes, the DNA repair/replication category was present in the largest percentage. These genes included G22P1 (Ku70) and XRCC5 (Ku80) genes known as important members of the nonhomologous end-joining (NHEJ) pathway of DNA double strand break (DSB) repair. Furthermore, cell line that specifically upregulated genes included the members of major pathways of DNA DSB or single strand damage repair. These pathways were not only NHEJ, but also homologous recombination (HR) and postreplication repair (PRR). In conclusion, the distribution of genes involved in the DNA repair/replication category was most different between two human glioblastoma cell lines of different radiosensitivities. Among commonly upregulated genes, the DNA repair/replication category was present in the largest percentage.

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A preparation of Tinospora cordifolia (RTc) administered i.p. (200 mg/kg b.w.) to strain "A" male mice 1 h before whole body gamma-irradiation was evaluated for its radioprotective efficacy in terms of whole body survival, spleen colony forming units (CFU), hematological parameters, cell cycle progression, and micronuclei induction. Preirradiation treatment with RTc rendered 76.3% survival (30 days), compared to 100% mortality in irradiated control and prevented radiation induced weight loss. On 10th postirradiation day, the endogenous CFU counts in spleen were decreased with increasing radiation doses 12.0 (5 Gy), 2.16 (7.5 Gy) and 0.33 (10 Gy) but pre-irradiation administration of 200 mg/kg b.w. of RTc increased CFU counts to 31.16, 21.83 and 3.00 respectively. Pre-irradiation RTc treatment could restore total lymphocyte counts (TLC) by the 15th day to normal. It also increased the S-phase cell population that was reduced following 2 Gy irradiation in a time dependent manner. 2 Gy irradiation-induced micronuclei were also decreased by a pre-irradiation administration of RTc from 2.9 to 0.52%. Because the radioprotective manifestation of RTc observed in several systems in experimental animals can be exploited for human applications.

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The tumor suppressor gene Tp53 was analyzed by polymerase chain reaction-amplification of genomic DNA extracted from paraffin-embedded tissue sections of rat lung tumors to compare mutations that occurred after inhalation exposures to plutonium dioxide, neptunium dioxide, or radon and radon progenies. Exons 5 to 8 of the gene were amplified in 16 plutonium-, 23 neptunium- and 15 radon-induced lung tumors, and their polymerase chain reaction products were examined for mutations by single strand conformational polymorphism analysis and direct sequencing method. Two point mutations were detected in the plutonium-induced tumors, i.e., a guanine to adenine transition at codon 219 of exon 6 and a cytosine to thymine transition at codon 266 of exon 8. Although only one point mutation was found at codon 175 of exon 5 (cytosine to thymine transition) from neptunium-induced tumors, no mutations were detectable from radon-induced tumors. These results indicate that the abnormalities of the Tp53 gene might not be so critical for the pulmonary carcinogenesis after the inhalation of different alpha emitters, even though the presence and frequencies of the Tp53 gene mutations were different.

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Wool fibers of different sample conditions were irradiated in different atmospheres by ⁶⁰Co γ-rays and were studied by electron spin resonance method (ESR). It was found that a large percentage of the α-carbon radicals of polymer main chain were more long-lived radicals. The ESR measurements of irradiated cortex samples of the wool fibers proved that most radicals from the cortex were long-lived ones. Low water content (as low as 27.5%) in the reaction system did not greatly affect the radical formation, but higher water contents would reduce the radical concentrations dramatically and accelerate their decaying process. The results will be of help in property modification of wool products by radiation graft copolymerization.

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The radioactive and thermal effects of radon hot spring were biochemically compared under a sauna room or hot spring conditions with a similar chemical component, using the parameters that are closely involved in the clinic for radon therapy. The results showed that the radon and thermal therapy enhanced the antioxidation functions, such as the activities of superoxide dismutase (SOD) and catalase, which inhibit lipid peroxidation and total cholesterol produced in the body. Moreover the therapy enhanced concanavalin A (ConA)-induced mitogen response and increased the percentage of CD4 positive cells, which is the marker of helper T cells, and decreased the percentage of CD8 positive cells, which is the common marker of killer T cells and suppressor T cells, in the white blood cell differentiation antigen (CD8/CD4) assay. Furthermore, the therapy increased the levels of α atrial natriuretic polypeptide (αANP), β endorphin, adrenocorticotropic hormone (ACTH), insulin and glucose-6-phosphate dehydrogenase (G-6-PDH), and it decreased the vasopression level. The results were on the whole larger in the radon group than in the thermal group. The findings suggest that radon therapy contributes more to the prevention of life-style-related diseases related to peroxidation reactions and immune suppression than to thermal therapy. Moreover, these indicate what may be a part of the mechanism for the alleviation of hypertension, osteoarthritis (pain), and diabetes mellitus brought about more by radon therapy than by thermal therapy.

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The catalase activities in blood and organs of the acatalasemic (C3H/AnLCs^bCs^b) mouse of C3H strain are lower than those of the normal (C3H/AnLCs ^aCs^a) mouse. We examined the effects of prior low-dose (0.5 Gy) X-ray irradiation, which reduced the oxidative damage under carbon tetrachloride-induced hepatopathy in the acatalasemic or normal mice. The acatalasemic mice showed a significantly lower catalase activity and a significantly higher glutathione peroxidase activity compared with those in the normal mice. Moreover, low-dose irradiation increased the catalase activity in the acatalasemic mouse liver to a level similar to that of the normal mouse liver. Pathological examinations and analyses of blood glutamic oxaloacetic and glutamic pyruvic transaminase activity and lipid peroxide levels showed that carbon tetrachloride induced hepatopathy was inhibited by low-dose irradiation. These findings may indicate that the free radical reaction induced by the lack of catalase and the administration of carbon tetrachloride is more properly neutralized by high glutathione peroxidase activity and low-dose irradiation in the acatalasemic mouse liver.

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Evidence has been accumulated for attached cells demonstrating that nonirradiated cells can have a response to the ionization events delivered to their neighbors. In the present study, we first investigated the bystander responses between suspension and neoplastic cells by coculturing L5178Y (LY) cells with human salivary gland (HSG) cells that had been irradiated with either 290 MeV/u carbon ions or X-rays. After this coculture, the survival of nonirradiated recipient LY cells showed dichotomous responses to the irradiation dose delivered to HSG cells. Apoptosis and necrosis were also produced in a 48 h subculture of the recipient LY cells, and their yield increased, but then had a tendency to decrease when the irradiation dose increased. Treatment of cells with PTIO, a nitric oxide specific scavenger, diminished apoptosis and necrosis of the recipient LY cells to the control level. As an oxidization product of NO, nitrite was detected in the coculture medium and its time course corresponded well to the decrease of the viability of irradiated HSG cells. Moreover, the relationship of the survival and the apoptotic and necrotic production of the recipient LY cells to the nitrite concentration followed a linear-quadratic model. The present findings of NO being involved in the radiation-induced bystander effect may have significance in terms of radiotherapy.

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We examined the delayed induction of telomere instability in hTERT-immortalized normal human fibroblast (BJ1-hTERT) cells exposed to X-rays. BJ1-hTERT cells were irradiated with 2 Gy of X-rays, and chromosome aberrations were analyzed 24 hours after irradiation and in the surviving cells 14 days after X-ray exposure. We found that the X-ray-surviving cells showed an increased frequency of chromatid gaps and breaks and chromosome fragments compared to the control cells. Furthermore, centromere- and telomere-FISH revealed that the frequency of telomere loss and duplication significantly increased in surviving cells compared to the control level. Because no induction of telomere abnormality was observed in cells 24 hours after irradiation, X-irradiation might not affect telomeres directly, but it specifically induces delayed telomere instability in normal human fibroblast cells.

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The radiosensitizing potential of gemcitabine (2′,2′-difluoro-2′-deoxycytidine) was studied in combination with pulsed low dose-rate irradiation. The experiments were carried out with a human lung carcinoma cell line SW1573. These were irradiated at pulsed low dose rate (p-LDR); the average dose rate was 1 Gy/h. In the experiments with gemcitabine, this drug was applied for 24 h at a concentration of 10 nM prior to irradiation. The response of the cells to treatment was tested by using the standard clonogenic assay. Next to the cell-killing effects, damage to chromosomes was also assayed by using by whole chromosome Fluorescent In Situ Hybridization (FISH). Damage in chromosomes 2 and 18 was visualized by whole chromosome FISH and scored according to the PAINT method. A clear enhancement of the effects of radiation on cell survival was observed by preincubation of the cells with gemcitabine. The enhancement factor obtained from the p-LDR data was 1.7, which is much lower than the enhancement factor of 2.9 at high-dose rate. We did not observe a consistent increase in color junctions concomitant with radiosensitization. In chromosome 2, a small increase, and in chromosome 18, a decrease, in the number of color junctions was observed after radiation combined with gemcitabine compared to irradiation alone. These differences were not statistically significant. However, for the (unstable) acentric chromosome fragments from both chromosomes, significant changes were observed: In the case of chromosome 2, an increase, and in the case of chromosome 18, a decrease. So these results indicate that gemcitabine has no large and consistent effect on the repair of genomic lesions that induce secondary chromosome breaks. Although it is clear that gemcitabine-induced radiosensitization can be expected when it is combined with brachytherapy, as with radiation at a high-dose rate, the mechanism of radiosensitization is so far not evident, and further experiments will be needed to elucidate this.

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The Ku protein is a complex of two subunits, Ku70 and Ku80, and it plays a role in multiple nuclear processes, e.g., nonhomologous DNA-end-joining (NHEJ), chromosome maintenance, and transcription regulation. On the other hand, several studies have reported a cytoplasmic or cell surface localization of Ku in various cell types. The mechanism underlying the regulation of all the diverse functions of Ku is still unclear, though the mechanism that regulates the nuclear localization of Ku70 and Ku80 appears to play, at least in part, a key role in regulating the physiological function of Ku. In this study, we generated cell lines expressing the human Ku80 tagged with the green fluorescent protein (GFP) color variants in Ku80-deficient cells, i.e., xrs-6 derived from CHO-K1. Although Ku70, as well as Ku80, was undetectable in xrs-6 cells, it was seen in these transformants at a level similar to the level of CHO-K1. Furthermore, etoposide- and radiosensitive phenotype of xrs-6 cells were corrected by an introduction of the tagged Ku80. Moreover, the tagged Ku80 suppressed apoptosis triggered by DNA damage. These results demonstrate that fusion to the GFP color variants does not interfere with the functions of the Ku80 in the Ku-dependent DSB repair. Therefore, these transformants might be useful not only in the analysis of Ku80 behavior, but also in an analysis of the dynamics of the NHEJ repair process.

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Various kinases, such as tyrosine, protein kinase C (PKC) and MAP kinase, play important role in the cellular response to radiation, but little is known about the specific response in the whole animal. Most studies, except a few, are based on single cells. There is a paucity of data where signaling following whole body irradiation is concerned. In this study a comparison has been made between the activities of these kinases following ex vivo and in vivo irradiation. Tyrosine kinase activity showed no difference in the lymphocytes irradiated ex vivo or in vivo. A significant differential dose-dependent response could be observed in PKC activity. PKC was seen to be activated at the higher dose, i.e., 1 Gy in, in vivo irradiated lymphocytes, whereas in ex vivo irradiated lymphocytes, PKC was seen to be activated at the lower dose, i.e., 0.1 Gy. MAP kinase activity was seen to decrease with an increasing dose in ex vivo irradiated lymphocytes. In vivo MAP kinase activity was seen to increase as the dose increased, with maximum activation at 3 Gy. These kinases are being used to manipulate the tumor response to radiotherapy. Thus it is essential to study the behavior of the above kinases in the whole animal because the difference in response of a single cell to the whole animal may be different.

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The radioprotective effect of an extract of the plant Phyllanthus amarus (P. amarus) was investigated in adult BALB/c mice. P. amarus extract (750 mg/kg b.wt and 250 mg/kg b.wt) was administered orally to mice for five days prior to whole body radiation (6 Gy) and for one month after radiation. The animals were sacrificed on days 3, 9, 12, and 30 after radiation. P. amarus significantly increased the total W.B.C count, bone marrow cellularity, and α-esterase activity as compared to untreated radiation-exposed animals. P. amarus treatment also increased the activity of various antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPX), and glutathione reductase (GR), both in blood and tissue, which were reduced by radiation treatment. There was also a significant increase in the glutathione (GSH) levels of blood and tissue. Lipid peroxidation levels, which were increased after radiation, were significantly reduced by P. amarus treatment, both in serum and liver. The results collectively indicate that P. amarus extract could increase the antioxidant defense mechanism in mice and there by protect the animals from radiation-induced cellular damage.

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We have investigated the role of insulin-like growth factor I receptor (IGF-IR) in heat shock-induced activation of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3 ′ kinase (PI3-K) pathways. We utilized mouse embryo fibroblasts (MEFs) devoid of endogenous IGF-IR (R-) and MEFs overexpressing human IGF-IR (WT) and examined the activation kinetics of extracellular signal-regulated kinase (ERK) and Akt following heat shock treatment. There were no differences in the kinetics or temperature dependence of activation of either ERK or Akt between the cell lines. As expected, heat shock failed to induce autophosphorylation of IGF-IR overexpressed in WT cells. Surprisingly, the autophosphorylation of endogenous epidermal growth factor receptor (EGFR), which is thought to play an important role in heat shock-induced activation of the MAPK and PI3-K pathways, was not observed in either WT or R-cells. These results suggest that neither IGF-IR nor EGFR contributes to the heat shock -induced activation of ERK and Akt in these cell lines.

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