Attenuation of radiation-induced gastrointestinal damage by epidermal growth factor and bone marrow transplantation in mice

Purpose: We examined the effect of epidermal growth factor (EGF) and bone marrow transplantation (BMT) on gastrointestinal damage after high-dose irradiation of mice.

Material and methods: C57Black/6 mice were used. Two survival experiments were performed (12 and 13 Gy; ⁶⁰Co, 0.59–0.57 Gy/min). To evaluate BMT and EGF action, five groups were established – 0 Gy, 13 Gy, 13 Gy + EGF (at 2 mg/kg, first dose 24 h after irradiation and then every 48 h), 13 Gy + BMT (5 × 10⁶ cells from green fluorescent protein [GFP] syngenic mice, 4 h after irradiation), and 13 Gy + BMT + EGF. Survival data, blood cell counts, gastrointestine and liver parameters and GFP positive cell migration were measured.

Results: BMT and EGF (three doses, at 2 mg/kg, administered 1, 3 and 5 days after irradiation) significantly increased survival (13 Gy). In blood, progressive cytopenia was observed with BMT, EGF or their combination having no improving effect early after irradiation. In gastrointestinal system, BMT, EGF and their combination attenuated radiation-induced atrophy and increased regeneration during first week after irradiation with the combination being most effective. Signs of systemic inflammatory reaction were observed 30 days after irradiation.

Conclusions: Our data indicate that BMT together with EGF is a promising strategy in the treatment of high-dose whole-body irradiation damage.     

Protective effect of an extract from Periplaneta americana on hematopoiesis in irradiated rats

Purpose: To investigate the protective effect of W₁₁-a₁₂, an extract from Periplaneta americana, on hematopoiesis in irradiated rats.

Materials and methods: Wistar rats receiving total body irradiation of ⁶⁰Co γ-rays alone or with combined radiation and skin wound injury were used in this study. W₁₁-a₁₂ was applied either topically into the skin wounds or systemically by intraperitoneal injection. The numbers of white blood cells in peripheral blood, the nucleated cells and the colony-forming unit of granulocyte/macrophage progenitors (CFU-GM) in bone marrow were measured, respectively.

Results: Topical application of W₁₁-a₁₂ into skin wounds in rats with combined 6 Gy total body irradiation and skin wound injury could increase the neutrophils and macrophages in the wounded area and the nucleated cells in bone marrow at 24 h and 48 h, while the peripheral white blood cells did not show significant change. However, in rats with 4 Gy total body irradiation alone, the peripheral white blood cells, bone marrow nucleated cells and the number of colony-forming unit of granulocyte-macrophage progenitors were all significantly higher in the treatment groups by intraperitoneal injection of W₁₁-a₁₂ than those in the control groups by injection of normal saline at days 3 and days 5 after radiation.

Conclusions: W₁₁-a₁₂ showed a protective effect on hematopoiesis after total body irradiation and could increase the inflammatory cells in wounded tissues at the initiation stage after irradiation, which will benefit the management of combined radiation and skin wound injury.     

Investigations of antioxidant-mediated protection and mitigation of radiation-induced DNA damage and lipid peroxidation in murine skin

Abstract

Purpose: Radioprotection and mitigation effects of the antioxidants, Eukarion (EUK)-207, curcumin, and the curcumin analogs D12 and D68, on radiation-induced DNA damage or lipid peroxidation in murine skin were investigated. These antioxidants were studied because they have been previously reported to protect or mitigate against radiation-induced skin reactions.

Methods: DNA damage was assessed using two different assays. A cytokinesis-blocked micronucleus (MN) assay was performed on primary skin fibroblasts harvested from the skin of C3H/HeJ male mice 1 day, 1 week and 4 weeks after 5 Gy or 10 Gy irradiation. Local skin or whole body irradiation (100 kVp X-rays or caesium (Cs)-137 γ-rays respectively) was performed. DNA damage was further quantified in keratinocytes by immunofluorescence staining of γ-histone 2AX (γ-H2AX) foci in formalin-fixed skin harvested 1 hour or 1 day post-whole body irradiation. Radiation-induced lipid peroxidation in the skin was investigated at the same time points as the MN assay by measuring malondialdehyde (MDA) with a Thiobarbituric acid reactive substances (TBARS) assay.

Results: None of the studied antioxidants showed significant mitigation of skin DNA damage induced by local irradiation. However, when EUK-207 or curcumin were delivered before irradiation they provided some protection against DNA damage. In contrast, all the studied antioxidants demonstrated significant mitigating and protecting effects on radiation-induced lipid peroxidation at one or more of the three time points after local skin irradiation.

Conclusion: Our results show no evidence for mitigation of DNA damage by the antioxidants studied in contrast to mitigation of lipid peroxidation. Since these agents have been reported to mitigate skin reactions following irradiation, the data suggest that changes in lipid peroxidation levels in skin may reflect developing skin reactions better than residual post-irradiation DNA damage in skin cells. Further direct comparison studies are required to confirm this inference from the data.     

Structural and functional alterations in the rat lung following whole thoracic irradiation with moderate doses: Injury and recovery

Purpose:?To characterize structural and functional injuries following a single dose of whole-thorax irradiation that might be survivable after a nuclear attack/accident.

Methods:?Rats were exposed to 5 or 10 Gy of X-rays to the whole thorax with other organs shielded. Non-invasive measurements of breathing rate and arterial oxygen saturation, and invasive evaluations of bronchoalveolar lavage fluid, (for total protein, Clara cell secretory protein), vascular reactivity and histology were conducted for at least 6 time points up to 52 weeks after irradiation.

Results:?Irradiation with 10 Gy resulted in increased breathing rate, a reduction in oxygen saturation, an increase in bronchoalveolar lavage fluid protein and attenuation of vascular reactivity between 4–12 weeks after irradiation. These changes were not observed with the lower dose of 5 Gy. Histological examination revealed perivascular edema at 4–8 weeks after exposure to both doses, and mild fibrosis beyond 20 weeks after 10 Gy.

Conclusions:?Single-dose exposure of rat thorax to 10 but not 5 Gy X-irradiation resulted in a decrease in oxygen uptake and vasoreactivity and an increase in respiratory rate, which paralleled early pulmonary vascular pathology. Vascular edema resolved and was replaced by mild fibrosis beyond 20 weeks after exposure, while lung function recovered.     

A biosafety evaluation of synchrotron radiation X-ray to skin and bone marrow: single dose irradiation study of rats and macaques

Purpose: Very limited experimental data is available regarding the safe dosages related to synchrotron radiation (SR) procedures. We used young rats and macaques to address bone marrow and skin tolerance to various doses of synchrotron radiation.

Methods: Rats were subjected to 0, 0.5, 2.5, 5, 25 or 100?Gy local SR X-ray irradiation at left hind limb. Rat blood samples were analyzed at 2–90 days after irradiation. The SR X-ray irradiated skin and tibia were sectioned for morphological examination. For non-human primate study, three male macaques were subjected to 0.5 or 2.5?Gy SR X-ray on crus. Skin responses of macaques were observed.

Results: All rats that received SR X-ray irradiation doses greater than 2.5?Gy experienced hair loss and bone-growth inhibition, which were accompanied by decreased number of follicles, thickened epidermal layer, and decreased density of bone marrow cells (p?<?0.05). Macaque skin could tolerate 0.5?Gy SR X-ray but showed significant hair loss when the dose was raised above 2.5?Gy.

Conclusion: The safety threshold doses of SR X-ray for rat skin, bone marrow and macaque skin are between 0.5 and 2.5?Gy. Our study provided essential information regarding the biosafety of SR X-ray irradiation.     

A small fish model for quantitative analysis of radiation effects using visualized thymus responses in GFP transgenic medaka

Abstract

Purpose: The aim of this study was to establish a new method of real-time, in vivo detection of radiation damage and recovery.

Methods: The thymus was observed under fluorescent light in a green fluorescent protein transgenic medaka. After irradiation, medaka thymus images were analyzed to quantify the effects of radiation by measuring changes in thymus size. A single acute irradiation of X-rays (0–30?Gy) or heavy Fe ions (0–10?Gy) was delivered to the medaka. Images were captured 0, 1, 2, 3, 5, 7, 11, and 21 d after irradiation. Dose-response assessment was conducted to provide a direct measurement of the effects of the radiation.

Conclusion: A biomonitoring system to detect the effects of radiation in real time was established. Using this system, the threshold doses for the induction of thymic atrophy by acute X-rays and Fe ions were 2–5?Gy and 0.5–1?Gy, respectively. The Relative Biological Effectiveness (RBE) of Fe-ion to X-rays was estimated to be around 3. This system may be used to evaluate the risk from concurrent exposure to hazards, such as chemicals and radiation, and for aging research.     

Differential response to acute low dose radiation in primary and immortalized endothelial cells

Abstract

Purpose: The low dose radiation response of primary human umbilical vein endothelial cells (HUVEC) and its immortalized derivative, the EA.hy926 cell line, was evaluated and compared.

Material and methods: DNA damage and repair, cell cycle progression, apoptosis and cellular morphology in HUVEC and EA.hy926 were evaluated after exposure to low (0.05–0.5 Gy) and high doses (2 and 5 Gy) of acute X-rays.

Results: Subtle, but significant increases in DNA double-strand breaks (DSB) were observed in HUVEC and EA.hy926 30 min after low dose irradiation (0.05 Gy). Compared to high dose irradiation (2 Gy), relatively more DSB/Gy were formed after low dose irradiation. Also, we observed a dose-dependent increase in apoptotic cells, down to 0.5 Gy in HUVEC and 0.1 Gy in EA.hy926 cells. Furthermore, radiation induced significantly more apoptosis in EA.hy926 compared to HUVEC.

Conclusions: We demonstrated for the first time that acute low doses of X-rays induce DNA damage and apoptosis in endothelial cells. Our results point to a non-linear dose-response relationship for DSB formation in endothelial cells. Furthermore, the observed difference in radiation-induced apoptosis points to a higher radiosensitivity of EA.hy926 compared to HUVEC, which should be taken into account when using these cells as models for studying the endothelium radiation response.     

Detection of radiation‐induced lung injury using hyperpolarized 13C magnetic resonance spectroscopy and imaging

Radiation‐induced lung injury limits radiotherapy of thoracic cancers. Detection of radiation pneumonitis associated with early radiation‐induced lung injury (2–4 weeks postirradiation) may provide an opportunity to adjust treatment, before the onset of acute pneumonitis and/or irreversible fibrosis. In this study, localized magnetic resonance (MR) spectroscopy and imaging of hyperpolarized ¹³C‐pyruvate (pyruvate) and ¹³C‐lactate (lactate) were performed in the thorax and kidney regions of rats 2 weeks following whole‐thorax irradiation (14 Gy). Lactate‐to‐pyruvate signal ratio was observed to increase by 110% (P < 0.01), 57% (P < 0.02), and 107% (P < 0.01), respectively, in the thorax, lung, and heart tissues of the radiated rats compared with healthy age‐matched rats. This was consistent with lung inflammation confirmed using cell micrographs of bronchioalveolar lavage specimens and decreases in arterial oxygen partial pressure (p_aO₂), indicative of hypoxia. No statistically significant difference was observed in either lactate‐to‐pyruvate signal ratios in the kidney region (P = 0.50) between the healthy (0.215 ± 0.100) and radiated cohorts (0.215 ± 0.054) or in blood lactate levels (P = 0.69) in the healthy (1.255 ± 0.247 mmol/L) and the radiated cohorts (1.325 ± 0.214 mmol/L), confirming that the injury is localized to the thorax. This work demonstrates the feasibility of hyperpolarized ¹³C metabolic MR spectroscopy and imaging for detection of early radiation‐induced lung injury. Magn Reson Med 70:601–609, 2013. © 2012 Wiley Periodicals, Inc.     

Arginine glutamate improves healing of radiation-induced skin ulcers in guinea pigs

Abstract

Purpose: The increase in the incidence of the radiation-induced skin injury cases and the absence of standard treatments escalate the interest in finding new and effective drugs for these lesions. We studied the effect of a 40% solution of arginine glutamate on the healing of radiation-induced skin ulcers in guinea pigs.

Materials and methods: Radiation skin injury was produced on the thigh of guinea pigs by 60 Gy local X-ray irradiation. Treatment was started 6 weeks after the irradiation when ulcers had been formed. Arginine glutamate was administered by subcutaneous injections around the wound edge. Methyluracil was chosen as the comparison drug. The animals were sacrificed on day 21 after the start of treatment and the irradiated skin tissues were subjected to histological evaluation, cytokines analysis, lipid peroxidation and antioxidant enzymes analysis.

Results: We have shown that arginine glutamate significantly (p < 0.05) decreased levels of pro-inflammatory cytokines in the wound, restored the balance between lipid peroxidation formation and antioxidant enzymes activity and promoted cell proliferation as well as collagen synthesis.

Conclusions: These results demonstrate that arginine glutamate successfully improves the healing of radiation-induced skin ulcers. In all probability, the curative effect is associated with the interaction of arginine with nitric oxide synthase II and arginase I, but further investigations are needed to validate this.     

10 Gy total body irradiation increases risk of coronary sclerosis,degeneration of heart structure and function in a rat model

Purpose:?To determine the impact of 10?Gy total body irradiation (TBI) or local thorax irradiation, a dose relevant to a radiological terrorist threat, on lipid and liver profile, coronary microvasculature and ventricular function.

Materials and methods:?WAG/RijCmcr rats received 10?Gy TBI followed by bone marrow transplantation, or 10?Gy local thorax irradiation. Age-matched, non-irradiated rats served as controls. The lipid profile and liver enzymes, coronary vessel morphology, nitric oxide synthase (NOS) isoforms, protease activated receptor (PAR)-1 expression and fibrinogen levels were compared. Two-dimensional strain echocardiography assessed global radial and circumferential strain on the heart.

Results:?TBI resulted in a sustained increase in total and low density lipoprotein (LDL) cholesterol (190?±?8 vs. 58?±?6; 82?±?8 vs. 13?±?3?mg/dl, respectively). The density of small coronary arterioles was decreased by 32%. Histology revealed complete blockage of some vessels while cardiomyocytes remained normal. TBI resulted in cellular peri-arterial fibrosis whereas control hearts had symmetrical penetrating vessels with less collagen and fibroblasts. TBI resulted in a 32?±?4% and 28?±?3% decrease in endothelial NOS and inducible NOS protein, respectively, and a 21?±?4% and 35?±?5% increase in fibrinogen and PAR-1 protein respectively, after 120 days. TBI reduced radial strain (19?±?8 vs. 46?±?7%) and circumferential strain (?8?±?3 vs. ?15?±?3%) compared to controls. Thorax-only irradiation produced no changes over the same time frame.

Conclusions:?TBI with 10?Gy, a dose relevant to radiological terrorist threats, worsened lipid profile, injured coronary microvasculature, altered endothelial physiology and myocardial mechanics. These changes were not manifest with local thorax irradiation. Non-thoracic circulating factors may be promoting radiation-induced injury to the heart.     

The effect of Captopril on benign and malignant reactions in irradiated rat skin

The effect of the angiotensin converting enzyme inhibitor Captopril on the severity of radiation-induced epilation and moist desquamation and the incidence of skin tumours was determined for up to 52 weeks in male rats. The irradiation consisted of a range of single doses (0, 10, 20, 30 Gy) of 60Co gamma rays to a 3.5 cm2 right hemithorax port. Half of each radiation dose group consumed control powdered chow, and half consumed chow containing Captopril (50 mg/kg/day) continuously after irradiation. There were time- and radiation-dose-dependent increases in all three skin reactions. Rats exposed to 10 Gy exhibited a mild and transient epilation, but no moist desquamation or neoplasia in the radiation port. In animals exposed to 30 Gy, however, epilation began at 2 weeks after irradiation, reached a peak at approximately 7 weeks, then persisted essentially unchanged through 52 weeks. Captopril had no significant effect on the epilation reaction. Two waves of moist desquamation were observed after 30 Gy. The first appeared at 3 weeks after irradiation, reached a peak from 6-10 weeks, then subsided partially but significantly from 12-26 weeks. The second wave of moist desquamation began at 26-28 weeks, often was ulcerative, and occasionally was accompanied by the appearance of tumours in the irradiated volume. Captopril significantly (p less than 0.05) reduced the severity of both phases of the moist desquamation reaction after 30 Gy, and reduced the percentage of animals exhibiting the most severe desquamation score (involving 50% of the radiation port). Of particular interest was the observation that Captopril also reduced the incidence of tumours. Of the 14 tumours detected, all were malignant (fibrosarcomas, squamous cell carcinomas), and only three (p less than 0.05) occurred in rats receiving Captopril. Multiple tumours (three cases), tumours induced by 20 Gy (three cases), and tumours appearing before 6 months (one case) were observed only in rats consuming control diet, never in Captopril-treated animals. Animals which developed tumours in the second 6 months post-irradiation exhibited significantly more severe moist desquamation during the first 6 months than did the tumour-free members of their treatment group. Thus Captopril, known to ameliorate acute lung damage in irradiated rats, also reduces chronic benign and malignant skin reactions in the radiation treatment field.     

The autophagy-inducing drug carbamazepine is a radiation protector and mitigator

Abstract

Purpose: To determine whether Carbamazepine (CBZ) is a radiation protector and/or mitigator.

Materials and methods: Murine hematopoietic progenitor 32D cl 3 cells were incubated in 1, 10, or 100 μM CBZ 1 h before or immediately after 0–8 Gy irradiation and assayed for clonogenic survival. Autophagy was assayed by immunoblot for microtubule-associated protein light chain 3 (LC3). In vivo radioprotection and mitigation were determined with C57BL/6NTac mice.

Results: CBZ treatment at 1, 10 or 100 μM for 1 h prior to irradiation increased radioresistance (the dose for 37% survival or D₀) from control 1.5 ± 0.1 Gy to 2.1 ± 0.2 Gy (P = 0.012), 2.3 ± 0.1 Gy (P = 0.010), and 3.6 ± 0.7 Gy (P = 0.003), respectively; after irradiation increased the extrapolation number (ñ) from 1.5 ± 0.3 to 10.1 ± 4.2 (P = 0.011), 5.5 ± 1.7 (P = 0.019), and 3.6 ± 0.8 (P = 0.014), respectively, and increased autophagy. CBZ treated mice 10 min or 24 h before or 10 min or 12 h after 9.25 Gy total body irradiation (TBI) showed increased survival (P = 0.012, 0.011, 0.0002, and 0.017, respectively).

Conclusion: CBZ may be a useful radiation protector and mitigator.     

Role of ethanolic extract of Morus alba leaves on some biochemical and hematological alterations in irradiated male rats

Purpose: The present study aimed to evaluate the protective role of “Morus alba Linn (Family: Moraceae) commonly known as mulberry” leaves extract against hazardous effects of gamma rays in male rats.

Materials and methods: Thirty six male albino rats were divided into six groups (six rats/group); (1) control group received 1?ml distilled water, (2) low dose of extract (100?mg/kg) group treated daily with low oral dose of ethanolic extract of mulberry leaves (100?mg/kg body weight (b.wt.)) for 21 consecutive days, (3) high dose of extract (200?mg/kg) group treated daily with high oral dose of ethanolic extract of mulberry leaves (200?mg/kg b.wt.) for the same period, (4) irradiated group rats were subjected to whole body gamma irradiation at a shot dose of 7?Gy, (5) low dose of extract?+?irradiated group treated daily with low oral dose of ethanolic extract of mulberry leaves (100?mg/kg b.wt.) for 21 consecutive days then rats were exposed to gamma irradiation at a single dose of 7?Gy, (6) high dose of extract?+?irradiation group treated daily with high oral dose of ethanolic extract of mulberry leaves (200?mg/kg b.wt.) for 21 consecutive days then rats were exposed to gamma irradiation at a single dose of 7?Gy. Rats were sacrificed 1, 7, 15 days post gamma irradiation in all groups. Blood samples were taken at three intervals time in the six groups.

Results: The results showed that whole body irradiation of rats induced significant decrease (p?p?Conclusions: Mulberry leaves extract prior to exposure to gamma irradiation has radio protector against hazardous effect of irradiation in male rats.     

Radiation tolerance in the tardigrade Milnesium tardigradum

Purpose: Tardigrades are known to survive high doses of ionizing radiation. However, there have been no reports about radiation effects in tardigrades under culture conditions. In this study, we investigated tolerance of the tardigrade, Milnesium tardigradum, against gamma-rays and heavy ions by determining short-term or long-term survival, and reproductive ability after irradiation.

Materials and methods: Hydrated and anhydrobiotic animals were exposed to gamma-rays (1000 – 7000 Gy) or heavy ions (1000 – 8000 Gy) to evaluate short-term survival at 2, 24 and 48 h post-irradiation. Long-term survival and reproduction were observed up to 31 days after irradiation with gamma-rays (1000 – 4000 Gy).

Results: At 48 h after irradiation, median lethal doses were 5000 Gy (gamma-rays) and 6200 Gy (heavy ions) in hydrated animals, and 4400 Gy (gamma-rays) and 5200 Gy (heavy ions) in anhydrobiotic ones. Gamma-irradiation shortened average life span in a dose-dependent manner both in hydrated and anhydrobiotic groups. No irradiated animals laid eggs with one exception in which a hydrated animal irradiated with 2000 Gy of gamma-rays laid 3 eggs, and those eggs failed to hatch, whereas eggs produced by non-irradiated animals hatched successfully.

Conclusion: M. tardigradum survives high doses of ionizing radiation in both hydrated and anhydrobiotic states, but irradiation with >1000 Gy makes them sterile.     

Protective effect of the herbal preparation,STW 5, against intestinal damage induced by gamma radiation in rats

Abstract

Purpose: STW 5 (marketed as Iberogast^®, Steigerwald Arzneimittelwerk GmbH, Darmstadt, Germany) is a herbal preparation reported to possess anti-inflammatory properties and antioxidant activity. We investigated the effect of STW 5 against intestinal injury induced after whole body exposure to ionizing radiation (IR).

Materials and methods: Intestinal mucositis was induced in rats by irradiation at a level of 6 Gy. STW 5 (5 ml/kg) was delivered orally for 5 days before irradiation and 2 days after. Rats were sacrificed, jejunum homogenates were tested to assess biochemical parameters indicating intestinal injury and jejunum segments were exposed to semi-quantitative histological examination.

Results: IR led to an increase in overall damage severity (ODS) score associated with a significant rise in tumor necrosis factor (TNF-α) and thiobarbituric acid reactive substances (TBARS) by 46% and 50% (p ≤ 0.05), respectively, whereas the reduced glutathione (GSH), sucrase and alkaline phosphatase enzyme activities were significantly decreased by 68%, 76% and 25% (p ≤ 0.05), respectively, in intestinal homogenates. IR led to a reduction of plasma citrulline. Pre-treatment with STW 5 guarded against the changes in ODS score and in all parameters measured.

Conclusion: Pre-treatment with STW 5 has the potential to decrease the severity of radiation-induced mucositis.     

Radioprotective and radiomitigative effects of BP-C2, a novel lignin-derived polyphenolic composition with ammonium molybdate,in two mouse strains exposed to total body irradiation

Purpose: There remains an unmet medical need for radioprotective and mitigative agents. BP-C2 is a novel lignin-derived polyphenolic composition with ammonium molybdate, developed as radioprotector/radiomitigator.

Objectives: The present study evaluated BP-C2 for the mitigation of acute radiation syndrome (ARS).

Methods: A total-body irradiation mouse model (TBI, 4.0–8.0?Gy) was used in the study.

Results: In a 30-day survival study, performed in CBA mice, BP-C2, at a dosage of 81.0?mg/kg, improved survival (dose reduction factor (DRF)?=?1.1) and increased the formation of endogenous spleen colony-forming units (CFU). In C57BL/6 mice, BP-C2, when administered daily for 7 days, starting 24?hours after TBI, also improved survival. In animals irradiated with 5.0?Gy, BP-C2 increased the number of CFUs (6.7?±?5.1) compared to the 5.0?Gy placebo group (2.3?±?2.3, p?=?.0245). The number of surviving intestinal crypts was maintained in the 5.0?Gy BP-C2 group (133.7?±?13.9), in contrast to the 5.0?Gy placebo group (124.2?±?10.5, p?Conclusion: BP-C2 mitigates radiation-induced damage in mid-lethal range of radiation doses. Effects are mediated by enhancement of extramedullar hematopoiesis in the spleen and a protective effect on the intestinal epithelium.     

Lesion evolution after gamma knife irradiation observed by magnetic resonance imaging

Purpose: Our study is focused on the magnetic resonance imaging (MRI) observation of lesion development and hippocampus related functional impairments in rats after irradiation with a Leksell Gamma knife (LGK).

Materials and methods: We exposed 32 three-month-old Long-Evans rats to various radiation doses (25 Gy, 50 Gy or 75 Gy). The rats were scanned by a 4.7 T magnetic resonance (MR) spectrometer at several timepoints (1 – 18 months) after irradiation. The lesion size was evaluated by manual segmentation; the animals were behaviorally tested in a Morris water maze and examined histologically.

Results: We found that a dose of 25 Gy induced no edema, necrosis or behavioral change. The response of the rats to higher doses was not uniform; the first occurrence of lesions in the rat brains irradiated with 50 and 75 Gy was detected six months post-irradiation. Functional impairment correlated well with the lesion size and histology.

Conclusions: Rat brains showed the development of expanding delayed lesions after 50 or 75 Gy doses from the LGK during the first year after irradiation.     

Genetic changes in progeny of bystander human fibroblasts after microbeam irradiation with X-rays,protons or carbon ions: The relevance to cancer risk

Abstract

Purpose: Radiation-induced bystander effects have important implications in radiotherapy. Their persistence in normal cells may contribute to risk of health hazards, including cancer. This study investigates the role of radiation quality and gap junction intercellular communication (GJIC) in the propagation of harmful effects in progeny of bystander cells.

Materials and methods: Confluent human skin fibroblasts were exposed to microbeam radiations with different linear energy transfer (LET) at mean absorbed doses of 0.4 Gy by which 0.036–0.4% of the cells were directly targeted by radiation. Following 20 population doublings, the cells were harvested and assayed for micronucleus formation, gene mutation and protein oxidation.

Results: Our results showed that expression of stressful effects in the progeny of bystander cells is dependent on LET. The progeny of bystander cells exposed to X-rays (LET ～6 keV/μm) or protons (LET ～11 keV/μm) showed persistent oxidative stress, which correlated with increased micronucleus formation and mutation at the hypoxanthine-guanine phosphoribosyl-transferase (HPRT) locus. Such effects were not observed after irradiation by carbon ions (LET ～103 keV/μm). Interestingly, progeny of bystander cells from cultures exposed to protons or carbon ions under conditions where GJIC was inhibited harbored reduced oxidative and genetic damage. This mitigating effect was not detected when the cultures were exposed to X-rays.

Conclusions: These findings suggest that cellular exposure to proton and heavy charged particle with LET properties similar to those used here can reduce the risk of lesions associated with cancer. The ability of cells to communicate via gap junctions at the time of irradiation appears to impact residual damage in progeny of bystander cells.     

Protection of mice against X-ray injuries by the post-irradiation administration of guanosine and inosine

Purpose:?To examine the radioprotective action of guanosine (Guo) and inosine (Ino) administered to mice after irradiation with X-rays.

Materials and methods:?Survival of mice exposed to lethal and sublethal doses of X-rays was studied. Peripheral blood cells were counted using a light microscope. The damage to bone marrow cells was assessed by micronucleus (MN) test. Damage and repair of DNA in blood leukocytes were estimated using the comet assay.

Results:?Mice injected intraperitoneally (i.p.) with Guo or Ino (～30 μg g^?1, i.e., ～0.6 mg per 20-g mouse) 15 min after acute whole-body irradiation with 7 Gy recovered from X-ray injury. On the 30th day after irradiation, 50 and 40% of mice injected with Guo and Ino, respectively, remained alive. The dose reduction factor (DRF) was 1.23 for Guo and 1.15 for Ino. The protective effect gradually decreased as the time interval between the irradiation and injection was increased to 3, 5, 8 h. Guo and Ino facilitated the restoration of peripheral blood cell counts. These compounds protected bone marrow cells from damage and normalized erythropoiesis. Guo and Ino contributed to a more rapid and complete repair of DNA in mouse leukocytes irradiated both in vitro and in vivo.

Conclusion:?Guo and Ino introduced shortly after irradiation reduce leukopenia and thrombocytopenia and offer promise as therapeutic agents for treatment of radiation injuries.     

The inhibitory effect of meadowsweet (Filipendula ulmaria) on radiation-induced carcinogenesis in rats

Purpose: To examine the ability of the meadowsweet preparation to inhibit carcinogenesis induced by ionizing radiation in female rats.

Materials and methods: The chemical composition of meadowsweet (Filipendula ulmaria) raw material (ethanol and aqueous extracts of meadowsweet flowers) has been studied for the presence of flavonoids, tannins and catechins. Adult female LIO strain rats were subjected to a single whole body γ-irradiation at a dose of 4?Gy in animal experiments. One group of irradiated rats served as control while the other group, starting from the 10th day after irradiation and until the end of the experiment, was given meadowsweet as a decoction of the flowers instead of drinking water. The average daily intake of meadowsweet (dry raw material) was 1?g/kg body weight. Rats were observed for 16 months.

Results: The analyzed meadowsweet extracts showed a sufficiently high content of flavonoids and tannins. In irradiated rats after 16 months the overall incidence of tumors was 79.6% (in 82 of 103 rats), the incidence of malignant tumors was 43.7% and the overall tumor multiplicity was 1.48. Most tumors were localized in the mammary gland – 57.3%. In rats that received meadowsweet, the incidence of all malignant tumors and overall multiplicity of tumors were significantly decreased by 1.5 and 1.3 times, respectively. The greatest reduction of many parameters has been identified for breast tumors: the overall incidence was decreased by 1.5 (p?=?0.0174) and the overall multiplicity and multiplicity of malignant tumors – by 1.6 (p?=?0.0002) and 2.2 (p?=?0.0383) times, respectively.

Conclusions: Meadowsweet preparation showed inhibiting activity on radiation carcinogenesis.