Shape-Controlled Iron-Paraffin Composites as γ- and X-ray Shielding Materials Formable by Warmth-of-Hands-Derived Plasticity

The design of shielding materials against ionizing radiation while simultaneously displaying enhanced multifunctional characteristics remains challenging. Here, for the first time, we present moldable paraffin-based iron nano- and microcomposites attenuating γ- and X-radiation. The moldability was gained by the warmth-of-hands-driven plasticity, which allowed for obtaining a specific shape of the composites at room temperature. The manufactured composites contained iron particles of various sizes, ranging from 22 nm to 63 μm. The target materials were widely characterized using XRD, NMR, Raman, TGA, SEM, and EDX. In the case of microcomposites, the shielding properties were developed at two concentrations: 10 and 50 wt %. The statistically significant results indicate that the iron particle size has a negligible effect on the shielding properties of the nano- and microcomposites. On the other hand, the higher iron particle contents significantly affected the attenuating ability, which emerged even as superior to the elemental aluminum in the X-ray range: at a 70 kV anode voltage, the half value layer was 6.689, 1.882, and 0.462 cm for aluminum, paraffin + 10 wt % Fe 3.5-6.5 μm, and paraffin + 50 wt % Fe 3.5-6.5 μm microcomposites, respectively. Importantly, the elaborated methodology-in situ cross-verified in the hospital studies recording real-life sampling-opens the pathway to high-performance, eco-friendly, lightweight, and recyclable shields manufactured via fully reproducible and scalable protocols.

A large-scale whole-exome sequencing mutant resource for functional genomics in wheat

Hexaploid wheat (Triticum aestivum), a major staple crop, has a remarkably large genome of ~14.4 Gb (containing 106 913 high-confidence [HC] and 159 840 low-confidence [LC] genes in the Chinese Spring v2.1 reference genome), which poses a major challenge for functional genomics studies. To overcome this hurdle, we performed whole-exome sequencing to generate a nearly saturated wheat mutant database containing 18 025 209 mutations induced by ethyl methanesulfonate (EMS), carbon (C)-ion beams, or γ-ray mutagenesis. This database contains an average of 47.1 mutations per kb in each gene-coding sequence: the potential functional mutations were predicted to cover 96.7% of HC genes and 70.5% of LC genes. Comparative analysis of mutations induced by EMS, γ-rays, or C-ion beam irradiation revealed that γ-ray and C-ion beam mutagenesis induced a more diverse array of variations than EMS, including large-fragment deletions, small insertions/deletions, and various non-synonymous single nucleotide polymorphisms. As a test case, we combined mutation analysis with phenotypic screening and rapidly mapped the candidate gene responsible for the phenotype of a yellow-green leaf mutant to a 2.8-Mb chromosomal region. Furthermore, a proof-of-concept reverse genetics study revealed that mutations in gibberellic acid biosynthesis and signalling genes could be associated with negative impacts on plant height. Finally, we built a publically available database of these mutations with the corresponding germplasm (seed stock) repository to facilitate advanced functional genomics studies in wheat for the broad plant research community.

Low-dose ionizing radiation: Effects on the proliferation and migration of lens epithelial cells via activation of the Wnt/β-catenin pathway

Eye lens opacification (cataract) induced by ionizing radiation is an important concern for radiation protection. Human lens epithelial cells (HLE-B3) were irradiated with γ-rays and radiation effects, including cell proliferation, cell migration, cell cycle distribution, and other changes related to the β-catenin pathway, were determined after 8-72 h and 7 d. In an in vivo model, mice were irradiated; DNA damage (γH2AX foci) in the cell nucleus of the anterior capsule of the lens was detected within 1 h, and radiation effects on the anterior and posterior lens capsules were observed after 3 months. Low-dose ionizing radiation promoted cell proliferation and migration. The expression levels of β-catenin, cyclin D1, and c-Myc were significantly increased in HLE-B3 cells after irradiation and β-catenin was translocated into the cell nucleus (activation of the Wnt/β-catenin pathway). In C57BL/6 J mouse lens, even a very low irradiation dose (0.05 Gy) induced the formation of γH2AX foci, 1 h after irradiation. At 3 months, migratory cells were found in the posterior capsule; expression of β-catenin was increased and it was clustered at the nucleus in the epithelial cells of the lens anterior capsule. The Wnt/β-catenin signaling pathway may an important role in promoting abnormal proliferation and migration of lens epithelial cells after low-dose irradiation.

Effect of curcumin on γ-ray-induced cell response

The purpose of the present study is to evaluate the effect of curcumin as a natural compound against radiation induced γ-foci and stable chromosome aberrations. Whole blood samples form three human volunteers were pretreated with curcumin at different concentrations (0.5, 10, 20 and 100 μg/ml). After 1-hour incubation, the lymphocytes were exposed to γ-rays (0.05, 0.5, 1 and 2 Gy). Radiation induced changes in cells were quantified using γ-H2AX/53BP1 assay and FISH analysis. Our results have shown that curcumin significantly reduced the frequency of both γ-foci and translocations. We found concentration-dependent increase of curcumin protective effect on γ-H2AX/53BP1 foci formation at all radiation doses. Concerning the translocations, after 0.05 and 0.5 Gy γ-rays the values of genomic frequencies are comparable within each dose and we did not observe any impact of curcumin. The most protective effect after 1 Gy exposure was found at 100 μg/ml curcumin. At 2 Gy irradiation, the maximum protection was achieved at 0.5 and 10 μg/ml of curcumin. Concentrations of 20 and 100 μg/ml also prevent lymphocytes but to less extent. Our in vitro study indicates radioprotective efficacy of curcumin against γ-ray induced damages in human lymphocytes. This observation suggests that curcumin may play a role to protect patients undergoing radiological procedures.

Preparation and characterization of tin chloride-based polymeric composite for gamma shielding applications

Thin films of Poly (ethylene-co-vinyl acetate)/tin chloride different weight (w/w) ratios were prepared using a spin-coating method. The diameter, height, grain size, and other morphological and structural features of the prepared thin films were studied using atomic force microscope (AFM) system. Moreover, the maximum surface roughness and average diameter of the prepared thin films were reported to weight ratio of 0.3%Sn Also, the shielding properties of adding tin chloride inside the polymer matrix were investigated. In addition, the impact of adding the tin-dopant to the targeted polymer on the attenuation parameters, including the linear attenuation coefficient (μ), half-value layer (HVL), screening ratios, and the mean free path, were theoretically calculated. The results show that the properties of the prepared thin films can be improved significantly by introducing a small amount of tin chloride to the host polymer promoting the crystallinity of the produced material and enhancing the shielding property for gamma-rays. The better linear attenuation coefficient of the produced thin films was reported to the weight ratio of 0.3% Sn. The produced Poly (ethylene-co-vinyl acetate)/tin chloride thin films can be suggested as one of the significant shielding materials to be used in a wide range of applications in the field of radiation.

Adaptive Response in Rat Retinal Cell Cultures Irradiated with γ-rays

Retina can receive incidental γ-ray exposure from various sources. For example, although radiation therapy is a crucial tool for managing head and neck tumors, patients may develop ocular complications as collateral damage from accidental irradiation. Recently, there has been concern that retinal irradiation during space flight may compromise mission goals and long-term quality of life after space travel. Previously, in our in vitro model, we proved that immature retinal cells are more vulnerable to γ-radiation than differentiated neurons. Here, we investigate if a low-dose pre-irradiation (0.025 Gy), known to have a protective effect in various contexts, can affect DNA damage and oxidative stress in cells exposed to a high dose of γ-rays (2 Gy). Our results reveal that pre-irradiation reduces 2 Gy effects in apoptotic cell number, H2AX phosphorylation and oxidative stress. These defensive effects are also evident in glial cells (reduction in GFAP and ED1 levels) and antioxidant enzymes (catalase and CuZnSOD). Overall, our results confirm that rat retinal cultures can be an exciting tool to study γ-irradiation toxic effects on retinal tissue and speculate that low irradiation may enhance the skill of retinal cells to reduce damage induced by higher doses.

Withania somnifera Alter BCL2/Bax signaling and trigger apoptosis of MCF-7 and MDA-MB231 breast cancer cells exposed to γ-radiation

Treatment strategies encompass synchronization of more than one therapy with specific dependence on zeroing side effects of natural products that might represent a niche in the continuous struggle against cancer. Thus, this study aimed at assessing the role of Withania somnifera; WS (Ashwagandha) in forcing MCF7 or MDA-MB 231 irradiated breast cancer cells to outweigh the route of programmed cell death. We check to what extent SIRT1-BCL2/Bax signaling pathway was interrelated to form apoptotic cancer cells. MDA or MCF7 cells are categorized into four groups: gp1, Control (C): MDA-MB-231 or MCF7 cells not treated with WS or exposed to γ-rays, gp2 (WS): cells challenged with WS for MDA-MB-231 or MCF7 cells respectively, gp3: irradiated (R) MDA-MB-231 or MCF7 cells exposed to γ-rays (4 Gy; one shot) and gp4 WS and irradiated (WS + R): cells challenged with WS as in gp2 and exposed to gamma rays as in gp3. The results revealed that, WS established IC₅₀ equivalent to 4897.8 μg/ml in MDA-MB-231 cells or equivalent to 3801.9 μg/ml in MCF7 cells. The flowcytometric analysis (Annexin V and cell cycle) showed that WS induces apoptosis at pre-G phase and induces cell arrest at G2/M and preG1 phases for MDA-MB-231 and at the preG1 for MCF7 cells. Furthermore, the WS + R group of cells (MDA-MB-231 and MCF7) showed significant increases in the expression of SIRT1, and BCL2 and a decrease in BAX compared with WS or R group. It could be concluded that WS has an anti-proliferative action on MDA-MB-231 and MCF7 cells because of its capability to enhance apoptosis.

Synthesis of Small Peptide Nanogels Using Radiation Crosslinking as a Platform for Nano-Imaging Agents for Pancreatic Cancer Diagnosis

Nanoparticle-based drug delivery systems (DDS) have been developed as effective diagnostic and low-dose imaging agents. Nano-imaging agents with particles greater than 100 nm are difficult to accumulate in pancreatic cancer cells, making high-intensity imaging of pancreatic cancer challenging. Peptides composed of histidine and glycine were designed and synthesized. Additionally, aqueous peptide solutions were irradiated with γ-rays to produce peptide nanogels with an average size of 25-53 nm. The mechanisms underlying radiation-mediated peptide crosslinking were investigated by simulating peptide particle formation based on rate constants. The rate constants for reactions between peptides and reactive species produced by water radiolysis were measured using pulse radiolysis. HGGGHGGGH (H9, H-histidine; G-glycine) particles exhibited a smaller size, as well as high formation yield, stability, and biodegradability. These particles were labeled with fluorescent dye to change their negative surface potential and enhance their accumulation in pancreatic cancer cells. Fluorescent-labeled H9 particles accumulated in PANC1 human pancreatic cancer cells, demonstrating that these particles are effective nano-imaging agents for intractable cancers.

Development and Applications of Compton Camera-A Review

The history of Compton cameras began with the detection of radiation sources originally for applications in astronomy. A Compton camera is a promising γ-ray detector that operates in the wide energy range of a few tens of keV to MeV. The γ-ray detection method of a Compton camera is based on Compton scattering kinematics, which is used to determine the direction and energy of the γ-rays without using a mechanical collimator. Although the Compton camera was originally designed for astrophysical applications, it was later applied in medical imaging as well. Moreover, its application in environmental radiation measurements is also under study. Although a few review papers regarding Compton cameras have been published, they either focus very specifically on the detectors used in such cameras or the particular applications of Compton cameras. Thus, the aim of this paper is to review the features and types of Compton cameras and introduce their applications, associated imaging algorithms, improvement scopes, and their future aspects.

Effects of gamma irradiation on morphology and protein differential in M1V1 population of Vanilla planifolia Andrews

PURPOSE

Lower doses (1-10 Krad) of gamma-rays (γ) are frequently used in obtaining useful mutants in diverse plant species, whereas no report on gamma (γ) irradiation being used to develop new varieties of vanilla from vanilla cuttings. This study assessed the potential of lower doses of gamma-rays for vanilla mutation breeding.

MATERIALS AND METHODS

We compared the morphological differences between vanilla plants irradiated at different lower doses of gamma radiation (10, 30, 40, and 50 Gy). We quantified protein and compared variation from the extracted protein of vanilla shoots regenerated between treatments.

RESULTS AND CONCLUSIONS

After 44 weeks, the results showed that the growth of M1V1 (mutation 1 in vegetative cycle 1) plants at 0 Gy (control) is highest compared with other doses of gamma radiation in terms of plant height and the number of shoots. However, the highest measurement for root length is at 10 Gy. The slowest growth rate was obtained from 40 to 50 Gy. Based on the unique band of protein that appears on the SDS-PAGE gel, 10 Gy has three unique bands at loci 0.105 RF, two bands lie at loci between 0.164 RF and 0.234 RF. While 30 Gy is absent two unique bands at loci 0.234 RF compared to 0 Gy. Thus, the dose of gamma rays at 10 Gy gave the highest number of protein fragments, which detected polymorphisms between the control (0 Gy) and the plants treated. To our knowledge, this is the first report of the protein variation in M1V1 of irradiated vanilla plants.

Effect of Low-Dose Gamma Radiation and Lipoic Acid on High- Radiation-Dose Induced Rat Brain Injuries

Aim

This work aims to investigate the possible radio-adaptive mechanisms induced by low-dose (LD) whole-body γ-irradiation alone or combined with alpha-lipoic acid (ALA) administration in modulating high-dose (HD) head irradiation–induced brain injury in rats.

Materials and Methods

Rats were irradiated with LD (.25 Gy) 24 hours prior HD (20 Gy), and subjected to ALA (100 mg/kg/day) 5 minutes after HD and continued for 10 days. At the end of the experiment, animals were sacrificed and brain samples were dissected for biochemical and histopathological examinations.

Results

HD irradiation-induced brain injury as manifested by elevation of oxidative stress, DNA damage, apoptotic, and inflammatory markers in brain tissue. Histological examination of brain sections showed marked alterations. However, LD alone or combined with ALA ameliorated the changes induced by HD.

Conclusion

Under the present experimental conditions, LD whole-body irradiation exhibited neuroprotective activity against detrimental effects of a subsequent HD head irradiation. This effect might be due to the adaptive response induced by LD that activated the anti-oxidative, anti-apoptotic, and anti-inflammatory mechanisms in the affected animals making them able to cope with the subsequent high-dose exposure. However, the combined LD exposure and ALA supplementation produced a further modulating effect in the HD-irradiated rats.

Reduce and concentrate graphene quantum dot size via scissors: vacancy, pentagon-heptagon and interstitial defects in graphite by gamma rays

Graphene quantum dots (GQDs) with ultrafine particle size and centralized distribution have advantages of small size, narrow size distribution and large specific surface area, which make it be better applied in bioimaging, drug delivery and so on. In our research, we used graphite irradiated byγ-rays to successfully prepare GQDs with ultrafine particle size, narrow size distribution and high quantum yields through solvothermal method. Vacancy defects, pentagon-heptagon defects and interstitial defects were introduced to graphite structure after irradiation, which caused the abundance and concentrated distribution of defects. The defects generated by irradiation could damage the lattice structure of graphite to make it easy for introduction of C-O-C inside graphite sheets. The oxygen-containing functional groups in graphene oxide (GO) increased and centrally distributed after irradiation in graphite, especially for C-O-C group, which were beneficial for cutting of GO and grafting of functional groups in GQDs. Therefore, average size of GQDs was successfully reduced to 1.43 nm and concentrated to 0.6-2.4 nm. After irradiation in graphite, the content of carbonyl and C-N in GQDs had a promotion, which suppressed non-radiative recombination and upgraded the quantum yields to 13.9%.

Impact of γ-rays Irradiation on Hybrid TiO2-SiO2 Sol-Gel Films Doped with RHODAMINE 6G

In the present paper, we investigate how the optical and structural properties, in particular the observed photoluminescence (PL) of photocurable and organic-inorganic TiO₂-SiO₂ sol-gel films doped with Rhodamine 6G (R6G) are affected by γ-rays. For this, four luminescent films, firstly polymerized with UV photons (365 nm), were submitted to different accumulated doses of 50 kGy, 200 kGy, 500 kGy and 1 MGy while one sample was kept as a reference and unirradiated. The PL, recorded under excitations at 365 nm, 442 nm and 488 nm clearly evidences that a strong signal peaking at 564 nm is still largely present in the γ-irradiated samples. In addition, M-lines and Fourier-transform infrared (FTIR) spectroscopies are used to quantify the radiation induced refractive index variation and the chemical changes, respectively. Results show that a refractive index decrease of 7 × 10^-3 at 633 nm is achieved at a 1 MGy accumulated dose while a photo-induced polymerization occurs, related to the consumption of CH=C, Si-OH and Si-O-CH₃ groups to form Ti-O and Si-O bonds. All these results confirm that the host matrix (TiO₂-SiO₂) and R6G fluorophores successfully withstand the hard γ-ray exposure, opening the way to the use of this material for sensing applications in radiation-rich environments.

DNA double-strand breaks in cancer cells as a function of proton linear energy transfer and its variation in time

PURPOSE

The complex relationship between linear energy transfer (LET) and cellular response to radiation is not yet fully elucidated. To better characterize DNA damage after irradiations with therapeutic protons, we monitored formation and disappearance of DNA double-strand breaks (DNA DSB) as a function of LET and time. Comparisons with conventional γ-rays and high LET carbon ions were also performed.

MATERIALS AND METHODS

In the present work, we performed immunofluorescence-based assay to determine the amount of DNA DSB induced by different LET values along the 62 MeV therapeutic proton Spread out Bragg peak (SOBP) in three cancer cell lines, i.e. HTB140 melanoma, MCF-7 breast adenocarcinoma and HTB177 non-small lung cancer cells. Time dependence of foci formation was followed as well. To determine irradiation positions, corresponding to the desired LET values, numerical simulations were carried out using Geant4 toolkit. We compared γ-H2AX foci persistence after irradiations with protons to that of γ-rays and carbon ions.

RESULTS

With the rise of LET values along the therapeutic proton SOBP, the increase of γ-H2AX foci number is detected in the three cell lines up to the distal end of the SOBP, while there is a decrease on its distal fall-off part. With the prolonged incubation time, the number of foci gradually drops tending to attain the residual level. For the maximum number of DNA DSB, irradiation with protons attain higher level than that of γ-rays. Carbon ions produce more DNA DSB than protons but not substantially. The number of residual foci produced by γ-rays is significantly lower than that of protons and particularly carbon ions. Carbon ions do not produce considerably higher number of foci than protons, as it could be expected due to their physical properties.

CONCLUSIONS

In situ visualization of γ-H2AX foci reveal creation of more lesions in the three cell lines by clinically relevant proton SOBP than γ-rays. The lack of significant differences in the number of γ-H2AX foci between the proton and carbon ion-irradiated samples suggests an increased complexity of DNA lesions and slower repair kinetics after carbon ions compared to protons. For all three irradiation types, there is no major difference between the three cell lines shortly after irradiations, while later on, the formation of residual foci starts to express the inherent nature of tested cells, therefore increasing discrepancy between them.

The dose-, LET-, and gene-dependent patterns of DNA changes underlying the point mutations in spermatozoa of Drosophila melanogaster. I. Autosomal gene black

Sequence analysis of 7 spontaneous, 27 γ-ray- and 20 neutron/neutron+γ-ray-induced black (b) point mutants was carried out. All these mutants were isolated as non-mosaic transmissible recessive visibles in the progeny of irradiated males from the wild-type high-inbred laboratory D32 strain of Drosophila melanogaster. Among spontaneous mutants, there were two (28.5 %) mutants with copia insertion in intron 1 and exon 2, three (42.8 %) with replacement of b^+D32 paternal sequence with maternal b¹ sequence (gene conversion), one (14.3 %) with 142-bp-long insertion in exon 2, and one (14.3 %) with a short deletion and two single-base substitutions in exon 3. Among γ-ray-induced mutants, there were 1 (3.7 %) with copia insertion in intron 2, 6 (22.2 %) with gene conversion, and the remaining 20 (74.1 %) mutants had 37 different small-scale DNA changes. There were 20 (54.1 %) single- or double-base substitutions, 7 (18.9 %) frameshifts (indels), 9 (24.3 %) extended deletions or insertions, and 1(2.7 %) mutant with a short insertion instead of a short deletion. Remarkably, clusters of independent small-scale changes inside the gene or within one DNA helical turn were recovered. The spectrum of DNA changes in 20 neutron/ neutron+γ-ray-induced mutants was drastically different from that induced by γ-rays in that 18 (90.0 %) mutants had the b¹sequence. In addition, 2 (10.0 %) with gene conversion had 600- or 19-bp-long deletion in exon 3 and 1 (5.0 %) mutant with a short insertion instead of a short deletion. Analysis of all 27 mutants with gene conversion events shows that 20 (74.1 %) had full b¹ sequence whereas 7 others (25.9 %) contained a partial b¹ sequence. These data are the first experimental evidence for gene conversion in the early stages of animal embryogenesis in the first diploid cleavage nucleus after male and female pronuclei have united. The gene conversion, frameshifts (indels), and deletions between short repeats were considered as products of a relevant DNA repair pathways described in the literature. As the first step, the gametic doubling doses for phenotypic black point mutations and for intragenic base substitution mutations in mature sperm cells irradiated by 40 Gy of γ-rays were estimated as 5.8 and 1.2 Gy, respectively, showing that doubling dose for mutations at the molecular level is about 5 times lower than that at the phenotypic level.

Carbon nitride/positive carbon black anchoring PtNPs assembled byγ-rays as ORR catalyst with excellent stability

Electrocatalytic performance of low-cost graphitic carbon nitride (CN) is greatly limited by its limited conductivity and small specific surface area. Herein, a simple and cost-effective idea to produce novel nanocomposite is constructed by the CN and cetyl trimethyl ammonium bromide functionalized carbon black (CB) anchored platinum nanoparticles as highly efficient oxygen reduction catalysts based on gamma irradiation. The assembled carbon nitride/positive carbon black anchoring PtNPs (Pt/CN₂-CB⁺₁) catalyst exhibits significantly improved specific surface area, high graphitization, and uniformly dispersed ultra-small platinum nanoparticles. For the oxygen reduction reaction (ORR) performance, the catalyst shows more positive onset-potential (0.93 V versus RHE) and larger diffusion limiting current density (5.65 mA cm^-2) compared with benchmark Pt/C catalysts in alkaline medium. Moreover, the Pt/CN₂-CB⁺₁catalyst exhibits a small Tafel slope (92 mV dec^-1). Besides, the catalyst was demonstrated the remarkable methanol tolerance and good long-term stability under working conditions. This work provides a new and effectiveγ-rays irradiation for synthesizing the carbon nitride catalysts for energy conversion and storage applications.

Radiation Crosslinked Smart Peptide Nanoparticles: A New Platform for Tumor Imaging

Nanoparticles have been employed to develop nanosensors and drug carriers that accumulate in tumors. Thus, it is necessary to control the particle size, surface potential, and biodegradability of these nanoparticles for effective tumor accumulation and safe medical application. In this study, to form a nanoparticle platform suitable for diagnostic and drug delivery system (DDS) applications, peptides composed of aromatic amino acid residues were designed and synthesized based on the radiation crosslinking mechanism of proteins. The peptide nanoparticles, which were produced by γ-ray irradiation, displayed a positive surface potential, maintained biodegradability, and were stable in water and phosphoric buffer solution during actual diagnosis. The surface potential of the peptide nanoparticles could be changed to negative by using a fluorescent labeling reagent, so that the fluorescent-labeled peptide nanoparticles were uptaken by HeLa cells. The radiation-crosslinked nanoparticles can be applied as a platform for tumor-targeting diagnostics and DDS therapy.

Sterilization of Semiconductive Nanomaterials: The Case of Water-Suspended Poly-3-Hexylthiophene Nanoparticles

In this work, the feasibility of sterilizing a water suspension of poly-3-hexylthiophene nanoparticles (P3HT-NPs) is investigated using ionizing radiation, either γ-rays or high-energy electrons (e-beam). It is found that regardless of the irradiation source, the size, polydispersity, aggregation stability, and morphology of the NPs are not affected by the treatment. Furthermore, the impact of ionizing radiation on the physicochemical properties of NPs at different absorbed radiation doses (10-25 kGy) and dose rates (kGy time^-1 ) is evaluated through different spectroscopic techniques. The results indicate that delivering a high dose of radiations (25 kGy) at a high dose rate, that is, kGy s^-1 , as achieved by e-beam irradiation, preserves the characteristics of the polymeric NPs. Differently, the same radiation dose but delivered at a lower dose rate, that is, kGy h^-1 , as attained by using a γ-source, can modify the physicochemical properties of the polymer. Sterility tests indicate that an absorbed dose of 10 kGy, delivered either with γ-rays or e-beam, is already sufficient for effective sterilization of the colloidal suspension and for reducing the endotoxin content. Finally, NPs irradiated at different doses, exhibit the same cytocompatibility and cell internalization characteristics in human neuroblastoma SH-SY5Y cells of NPs prepared under aseptic conditions.

Involvement of DNA Repair Genes and System of Radiation-Induced Activation of Transposons in Formation of Transgenerational Effects

The study of the genetic basis of the manifestation of radiation-induced effects and their transgenerational inheritance makes it possible to identify the mechanisms of adaptation and possible effective strategies for the survival of organisms in response to chronic radioactive stress. One persistent hypothesis is that the activation of certain genes involved in cellular defense is a specific response of the cell to irradiation. There is also data indicating the important role of transposable elements in the formation of radiosensitivity/radioresistance of biological systems. In this work, we studied the interaction of the systems of hobo transposon activity and DNA repair in the cell under conditions of chronic low-dose irradiation and its participation in the inheritance of radiation-induced transgenerational instability in Drosophila. Our results showed a significant increase of sterility and locus-specific mutability, a decrease of survival, fertility and genome stability (an increase the frequency of dominant lethal mutations and DNA damage) in non-irradiated F1/F2 offspring of irradiated parents with dysfunction of the mus304 gene which is responsible for excision and post-replicative recombination repair and repair of double-stranded DNA breaks. The combined action of dysfunction of the mus309 gene and transpositional activity of hobo elements also led to the transgenerational effects of irradiation but only in the F1 offspring. Dysfunction of the genes of other DNA repair systems (mus101 and mus210) showed no visible effects inherited from irradiated parents subjected to hobo transpositions. The mei-41 gene showed specificity in this type of interaction, which consists in its higher efficiency in sensing events induced by transpositional activity rather than irradiation.

Genetic polymorphisms in mutagenesis progeny of Arabidopsis thaliana irradiated by carbon-ion beams and γ-rays irradiations

Purpose: Heavy-ion beams and γ-rays are popular physical mutagenesis to generate mutations in higher plants. It has been found that they show different mutation frequencies and spectrums of phenotype induction, however, the characteristics of heavy-ion beams on genetic polymorphism have not been clarified by comparing with γ-rays.Materials and methods: In the present study, seeds of Arabidopsis thaliana were exposed to carbon-ion beams (with linear energy transfer (LET) of 50 keV/μm) and γ-rays (with average LET of 0.2 keV/μm) irradiation. By using inter-simple sequence repeat (ISSR) and random amplified polymorphic DNA (RAPD) analysis, the genetic polymorphism of both M₁ and M₃ plants were investigated, respectively.Results: Carbon-ion beams induced relatively higher polymorphism rate in both M₁ and M₃ generation than γ-rays: the polymorphism rates of M₁ plants derived from carbon-ion beams irradiation are 12.87% (ISSR-C) and 9.01% (RAPD-C), while are 7.67% (ISSR-γ) and 1.45% (RAPD-γ) of plants derived from γ-rays. In M₃ generation, the polymorphism rates of ISSR-C, RAPD-C, ISSR-γ, and RAPD-γ are 17.64%, 22.79%, 12.10%, and 2.82%, respectively.Conclusions: In summary, the exposure to carbon-ion beams and γ-rays lead to the change of genomic DNA of A. thaliana, which could be tested in M₁ plants and M₃ plants by ISSR and RAPD technology. So, both carbon-ion beams and γ-rays can induce variations of genetic polymorphisms in M₁ plants and M₃ plants. The genetic polymorphisms of M₁ plants and M₃ plants induced by carbon-ion beams are higher than γ-rays, indicating that heavy-ion beams irradiations mutation breeding is more advantageous than conventional ionizing radiations. Average molecular polymorphism of M₁ plants is lower than M₃ mutants, by nearly 4.77% (ISSR-C), 13.78% (RAPD-C), 4.43% (ISSR-γ), and 1.37% (RAPD-γ). We hope our study will provide basic information for understanding the effects of carbon-ion beams and γ-rays for plant mutation breeding.

Possible curative role of curcumin and silymarin against nephrotoxicity induced by gamma-rays in rats

Curcumin (CUR) and silymarin (SLM) are powerful antioxidant and anti-inflammatory compounds with beneficial protective effects against renal diseases. The purpose of this study was to evaluate the efficacy of CUR and SLM alone or in combination on radiation (IR) induced kidney injury. The results showed that CUR and SLM alone or in combination attenuated the oxidative stress denoted by a reduction in the level of malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and advanced oxidation protein products (AOPP) along with a marked increase of glutathione GSH content and total antioxidant capacity (TAC). Additionally, a significant decrease in the level of blood urea nitrogen (BUN), creatinine, Cystatin-C (CYT-C), neutrophil gelatinase-associated lipocalin (N-GAL) and Kidney Injury Molecule-1 (Kim-1) was recorded. Moreover, the treatment resulted in a remarkable decline in the serum levels of interleukin-18(IL-18), tumor necrosis factor- alpha (TNF-α), C reactive protein (CRP), BCL2 associated X protein (Bax), Factor-related Apoptosis (FAS) and the activity of Caspase-3 associated by an increase of B-cell CLL/lymphoma 2 (Bcl2) level. The results were confirmed with the histopathological examination. Kidney of irradiated showed glomerular atrophy, massive necrotic changes of expanded tubules with hyaline cast inside some tubules and apoptotic changes were recorded in some renal tubules. While irradiated rats treated with CUR and SLM exhibited marked preservation of the cellular structure of their kidney tissue. In conclusion, the combination of CUR and SLM could be more potent than a single agent on the biochemical and histological changes of the irradiated rat renal tissue.

Synthesis and thermoluminescent response to γ-rays and neutrons of MgB4O7:Dy and MgB4O7:Dy,Na

MgB₄O₇ doped with rare earths and alkaline elements has been reported as a good TLD because of its high sensitivity, effective atomic number close to that of biological tissue and low fading. In this work, thermoluminescent matrices were synthesized of MgB₄O₇:Dy and MgB₄O₇:Dy, Na to evaluate their thermoluminescent response (TL) when exposed to γ-rays and neutrons. The amount of Dy was studied in a concentration range of 0.01-1.5 mol% of total doping, while for Na the concentration of 0.5 mol% was established to determine the TL response as a function of doping. The synthesis of the powders was carried out by the method of wet reaction assisted by heat treatment and the samples were characterized by techniques of scanning electron microscopy and X-ray diffraction to determine the size of grain and crystallographic phase. For the dosimetric study, thermoluminescent phosphors were irradiated with a source of ¹³⁷Cs at an estimated dose 6.8 ± 0.4 mGy to evaluate their response to γ-rays exposure, while for neutrons a source of ²⁴¹AmBe was used (estimated dose of 3.1 ± 0.1 mGy). The thermoluminescent responses are similar for all materials exposed to γ-rays as for neutrons, the differences are shown to 280 °C, where a peak of high temperature is observed in materials exposed to neutrons.

Biological outcomes of γ-radiation induced DNA damages in breast and lung cancer cells pretreated with free radical scavengers

PURPOSE

Investigation of effects on DNA of γ-irradiated human cancer cells pretreated with free radical scavengers is aimed to create reference data which would enable assessment of the relative efficiency of high linear energy transfer (LET) radiations used in hadron therapy, i.e. protons and carbon ions.

MATERIALS AND METHODS

MCF-7 breast and HTB177 lung cancer cells are irradiated with γ-rays. To minimize indirect effects of irradiation, dimethyl sulfoxide (DMSO) or glycerol are applied as free radical scavengers. Biological response to irradiation is evaluated through clonogenic cell survival, immunocytochemical and cell cycle analysis, as well as expression of proteins involved in DNA damage response.

RESULTS

Examined cell lines reveal similar level of radioresistance. Application of scavengers leads to the rise of cell survival and decreases the number of DNA double strand breaks in irradiated cells. Differences in cell cycle and protein expression between the two cell lines are probably caused by different DNA damage repair mechanisms that are activated.

CONCLUSION

The obtained results show that DMSO and glycerol have good scavenging capacity, and may be used to minimize DNA damage induced by free radicals. Therefore, they will be used as the reference for comparison with high LET irradiations, as well as good experimental data suitable for validation of numerical simulations.

The Effect of p53 Status on Radio-Sensitivity of Quiescent Tumor Cell Population Irradiated With γ-Rays at Various Dose Rates

Background

The aim of the study was to clarify the effect of p53 status of tumor cells on radio-sensitivity of solid tumors following γ-ray irradiation at various dose rates, referring to the response of intratumor quiescent (Q) cells.

Methods

Human head and neck squamous cell carcinoma cells transfected with mutant TP53 (SAS/mp53) or with neo vector (SAS/neo) were injected subcutaneously into hind legs of nude mice. Tumor bearing mice received 5-bromo-2’-deoxyuridine (BrdU) continuously to label all intratumor proliferating (P) cells. They received γ-rays at a high, middle or low dose rate. Immediately or 9 h after the high dose-rate irradiation (HDR, 2.5 Gy/min), or immediately after the middle (MDR, 0.039 Gy/min) or low (LDR, 0.00098 Gy/min) dose-rate irradiation, the tumor cells were isolated and incubated with a cytokinesis blocker, and the micronucleus (MN) frequency in cells without BrdU labeling (Q cells) was determined using immunofluorescence staining for BrdU.

Results

Following γ-ray irradiation, SAS/neo tumor cells, especially intratumor Q cells, showed a marked reduction in sensitivity due to the recovery from radiation-induced damage, compared with the total or Q cells within SAS/mp53 tumors that showed little repair capacity. The recovery capacities following γ-ray irradiation were greater in Q than total cell population and increased in the following order of 9 h after HDR < MDR < LDR. Thus, the difference in radio-sensitivity between the total (P + Q) and Q cells after γ-ray irradiation increased in the same order.

Conclusion

To secure controlling solid tumors as a whole, difference in sensitivity between total and Q tumor cells especially in solid tumors irrespective of p53 status has to be suppressed as irradiation dose rate decreases, for instance, through employing combined method for enhancing the response of Q tumor cells.

The Moss Physcomitrella patens Is Hyperresistant to DNA Double-Strand Breaks Induced by γ-Irradiation

The purpose of this study was to investigate whether the moss Physcomitrella patens cells are more resistant to ionizing radiation than animal cells. Protoplasts derived from P. patens protonemata were irradiated with γ-rays of 50–1000 gray (Gy). Clonogenicity of the protoplasts decreased in a γ-ray dose-dependent manner. The dose that decreased clonogenicity by half (LD₅₀) was 277 Gy, which indicated that the moss protoplasts were 200-times more radioresistant than human cells. To investigate the mechanism of radioresistance in P. patens, we irradiated protoplasts on ice and initial double-strand break (DSB) yields were measured using the pulsed-field gel electrophoresis assay. Induced DSBs linearly increased dependent on the γ-ray dose and the DSB yield per Gb DNA per Gy was 2.2. The DSB yield in P. patens was half to one-third of those reported in mammals and yeasts, indicating that DSBs are difficult to induce in P. patens. The DSB yield per cell per LD₅₀ dose in P. patens was 311, which is three- to six-times higher than those in mammals and yeasts, implying that P. patens is hyperresistant to DSBs. Physcomitrella patens is indicated to possess unique mechanisms to inhibit DSB induction and provide resistance to high numbers of DSBs.

Radioprotective effects of Silymarin on the sperm parameters of NMRI mice irradiated with γ-rays

Free radicals and reactive oxygen species (ROS) are generated using various endogenous systems or from external sources such as exposure to different physiochemicals. Ionizing radiation damage to the cell can be caused by the direct or indirect effects of radiotherapy processes. Silymarin (SM), a flavanolignan compound, has been identified as a natural potent antioxidant with cytoprotection activities due to scavenging free radicals. The aim of the present study was to evaluate the radioprotective effect of SM on sperm parameters of mice induced by γ-rays. A total number of 40 adult, male NMRI mice were randomly divided into four equal groups. The control group was neither treated with SM nor irradiated by γ-rays. The second group was only irradiated with 2Gy of γ-rays. The third group was firstly treated with 50mg/kg of SM for 7 consecutive days, and one day later, last injections were irradiated by 2Gy of γ-rays. The fourth groups received only 50mg/kg of SM for 7 consecutive days. All the animals were treated intraperitoneally. Histopathological and morphometrical examinations were performed. The data were analyzed using ANOVA and Tukey post hoc test. A value of p<0.05 was considered significant. The results showed that in the radiation-only group when compared with those treated with SM and irradiated, a significant different was observed in testicular parameters and DNA damage (p<0.05). In conclusion, SM can be considered as a promising herbal radioprotective agent in complementary medicine which may play an important role to protect normal spermatocytes against possible effects of γ-radiation-induced cellular damage.

Exposing primary rat retina cell cultures to γ-rays: An in vitro model for evaluating radiation responses

Retinal tissue can receive incidental γ-rays exposure during radiotherapy either of tumors of the eye and optic nerve or of head-and-neck tumors, and during medical diagnostic procedures. Healthy retina is therefore at risk of suffering radiation-related side effects and the knowledge of pathophysiological response of retinal cells to ionizing radiations could be useful to design possible strategies of prevention and management of radiotoxicity. In this study, we have exploited an in vitro model (primary rat retinal cell culture) to study an array of biological effects induced on retinal neurons by γ-rays. Most of the different cell types present in retinal tissue - either of the neuronal or glial lineages - are preserved in primary rat retinal cultures. Similar to the retina in situ, neuronal cells undergo in vitro a maturational development shown by the formation of polarized neuritic trees and operating synapses. Since 2 Gy is the incidental dose received by the healthy retina per fraction when the standard treatment is delivered to the brain, retina cell cultures have been exposed to 1 or 2 Gy of γ-rays at different level of neuronal differentiation in vitro: days in vitro (DIV)2 or DIV8. At DIV9, retinal cultures were analyzed in terms of viability, apoptosis and characterized by immunocytochemistry to identify alterations in neuronal differentiation. After irradiation at DIV2, MTT assay revealed an evident loss of cell viability and βIII-tubulin immunostaining highlighted a marked neuritic damage, indicating that survived neurons showed an impaired differentiation. Differentiated cultures (DIV8) appeared to be more resistant with respect to undifferentiated, DIV2 cultures, both in terms of cell viability and differentiation. Apoptosis evaluated with TUNEL assay showed that irradiation at both DIV2 and DIV8 induced a significant increase in the apoptotic rate. To further investigate the effects of γ-rays on retinal neurons, we evaluated the expression of synaptic proteins, such as SNAP25 and synaptophysin. WB and immunofluorescence analysis showed an altered expression of these proteins in particular when cultures were irradiated at DIV2. To evaluate the effect of γ-rays on photoreceptors, we studied the expression of rhodopsin in WB analysis and immunofluorescence. Our results confirm data from the literature that differentiated photoreceptors appear to be more resistant to irradiation respect to other retinal cell types present in cultures. The results obtained suggest that γ-rays exposure of primary retinal cultures may contribute to shed further light on the mechanisms involved in γ-radiation-induced neurodegeneration.

Effects of gamma rays on the regeneration of murine hair follicles in the natural hair cycle

PURPOSE

This review evaluates the effects of γ-rays on the regeneration of murine hair follicles in the natural hair cycle. A series of studies were performed to investigate this issue, in which the whole bodies of C57BL/10JHir mice in the 1st telogen phase of the hair cycle were irradiated with γ-rays.

RESULTS

The dermis of the irradiated skin showed a decrease in hair follicle density and induction of curved hair follicles along with the presence of white hairs and hypopigmented hair bulbs in the 2nd and 3rd anagen phases. An increased frequency of hypopigmented hair bulbs was still observed in the later hair cycle at postnatal day 200. There was no significant difference in the number of stem cells in the hair bulge region between control and irradiated skin.

CONCLUSIONS

These results show that the effects of γ-rays on the pigmentation of murine hair follicles are persistently carried over to later hair cycles, although those on the number and structure of hair follicles appear to be hidden by the effects of aging. Our findings may be important for understanding the mechanisms of the actions of stem cells on hair regeneration in connection with age-related phenotypes.

Epimerization of Alanyl-Alanine Induced by γ-Rays Irradiation in Aqueous Solutions

Living organisms have homochiral L-amino acids in proteins and homochiral D-mononucleotides in nucleic acids. The chemical evolutionary process to protein homochirality has been discussed for many years. Although many scenarios have been proposed for homochirality in the monomeric compounds, homochirality in amino acids and mononucleotides does not always guarantee homochirality in polypeptides and polynucleotides. Integrated scenarios containing the pathways from monomer to polymer should be proposed because in the pathways oligomers and polymers as well as monomers racemize (or epimerize), degrade, and condense. This research addresses epimerization and degradation of dipeptides under γ-rays irradiation by a cobalt-60 (60Co) radiation source. The different rate constants of epimerization between diastereomeric dipeptides in the research suggest that the potential pathway toward homochirality could be much more complex.

An FT-IR Spectral Analysis of the Effects of γ-Radiation on Normal and Cancerous Cartilage

In the present study we used non-distractive physicochemical methods to investigate the effect of γ-radiation on human articular cartilage. Comparison between the FT-IR (Fourier transform infrared) spectra before and after irradiation of the cartilage with different doses of radiation showed considerable changes in the spectra. It was found that for doses up to 2 Gy the collagen helices changed their structure from α-helix to random coil. By increasing the radiation dose it was found that the proteins' structure changed further to amyloid-like protein formation and to fragments of glycosaminoglycan chains, which were indicated in the IR spectra. Furthermore, comparison between the spectra of normal and irradiated cartilage, cancerous cartilage and cartilage from patients who received radiotherapy showed similarities in the spectra together with the formation of an aldehyde absorption band at 1740 cm(-1) suggesting that in all cases of cartilage examined,oxidative stress played major role in the damage progression of cartilage.

The impact of autophagy on cell death modalities in CRL-5876 lung adenocarcinoma cells after their exposure to γ-rays and/or erlotinib

In most patients with lung cancer radiation treatment is used either as single agent or in combination with radiosensitizing drugs. However, the mechanisms underlying combined therapy and its impact on different modes of cell death have not yet been fully elucidated. We aimed to examine effects of single and combined treatments with γ-rays and erlotinib on radioresistant CRL-5876 human lung adenocarcinoma cells with particular emphasis on cell death. CRL-5876 cells were treated with γ-rays and/or erlotinib and changes in cell cycle, DNA repair dynamics, ultrastructure, nuclear morphology and protein expression were monitored at different time points. To reveal the relationship between types of cell death that arise after these treatments, autophagy was blocked with chloroquine. We found that higher dose of γ-rays causes G2/M arrest while adding of erlotinib to this treatment decreases the number of cells in S phase. Impact of erlotinib on kinetics of disappearance of irradiation-induced DNA double strand breaks is reflected in the increase of residual γ-H2AX foci after 24 h. γ-rays provoke cytoprotective autophagy which precedes development of senescence. Erlotinib predominantly induces apoptosis and enlarges the number of apoptotic cells in the irradiated CRL-5876 cells. Chloroquine improved cytotoxicity induced by radiation and erlotinib, increased apoptosis and decreased senescence in the CRL-5876 cells. The results obtained on CRL-5876 cells indicate significant radiosensitizing effect of erlotinib and suggest that chloroquine in the combination with the above treatments may have an additional antitumor effect in lung adenocarcinoma.

The Effect of p53 Status of Tumor Cells on Radiosensitivity of Irradiated Tumors With Carbon-Ion Beams Compared With γ-Rays or Reactor Neutron Beams

Background

The aim of the study was to clarify the effect of p53 status of tumor cells on radiosensitivity of solid tumors following accelerated carbon-ion beam irradiation compared with γ-rays or reactor neutron beams, referring to the response of intratumor quiescent (Q) cells.

Methods

Human head and neck squamous cell carcinoma cells transfected with mutant TP53 (SAS/mp53) or with neo vector (SAS/neo) were injected subcutaneously into hind legs of nude mice. Tumor-bearing mice received 5-bromo-2’-deoxyuridine (BrdU) continuously to label all intratumor proliferating (P) cells. They received γ-rays or accelerated carbon-ion beams at a high or reduced dose-rate. Other tumor-bearing mice received reactor thermal or epithermal neutrons at a reduced dose-rate. Immediately or 9 hours after the high dose-rate irradiation (HDRI), or immediately after the reduced dose-rate irradiation (RDRI), the tumor cells were isolated and incubated with a cytokinesis blocker, and the micronucleus (MN) frequency in cells without BrdU labeling (Q cells) was determined using immunofluorescence staining for BrdU.

Results

The difference in radiosensitivity between the total (P + Q) and Q cells after γ-ray irradiation was markedly reduced with reactor neutron beams or carbon-ion beams, especially with a higher linear energy transfer (LET) value. Following γ-ray irradiation, SAS/neo tumor cells, especially intratumor Q cells, showed a marked reduction in sensitivity due to the recovery from radiation-induced damage, compared with the total or Q cells within SAS/mp53 tumors that showed little repair capacity. In both total and Q cells within both SAS/neo and SAS/mp53 tumors, carbon-ion beam irradiation, especially with a higher LET, showed little recovery capacity through leaving an interval between HDRI and the assay or decreasing the dose-rate. The recovery from radiation-induced damage after γ-ray irradiation was a p53-dependent event, but little recovery was found after carbon-ion beam irradiation. With RDRI, the radiosensitivity to reactor thermal and epithermal neutron beams was slightly higher than that to carbon-ion beams.

Conclusion

For tumor control, including intratumor Q-cell control, accelerated carbon-ion beams, especially with a higher LET, and reactor thermal and epithermal neutron beams were very useful for suppressing the recovery from radiation-induced damage irrespective of p53 status of tumor cells.

Possible modulating impact of glutathione disulfide mimetic on physiological changes in irradiated rats

Glutathione disulfide mimetic (NOV-002) is a complex of oxidized glutathione (GSSG) formulated with cisplatin at approximately 1000:1 molar ratio. Cisplatin serves to stabilize GSSG but does not assert any therapeutic effect. The objective of this study is to evaluate the impact of NOV-002 on hematological suppression, excessive free radical damage and DNA fragmentation in splenocytes, and metabolite disorders in whole-body γ-irradiated rats. The obtained data revealed that rats treated with 25 mg kg(-1) NOV-002 injected intraperitoneally (i.p.) for 5 days after whole-body γ-irradiation (IR) at 6.5 Gy attenuated the decrease of red blood cells, platelets, total white blood cells, absolute lymphocytes and neutrophils counts, hematocrit value, and hemoglobin content. NOV-002 treatment inhibits serum advanced oxidation protein products, malondialdehyde concentrations as well as cholesterol, triglycerides, urea, and creatinine levels, while enhances glutathione content and superoxide dismutase activity and improves DNA fragmentation in splenocytes. These findings provide a better understanding of the NOV-002 modulating impact in whole-body γ-rays-induced hematological toxicities, oxidative stress, and biological disturbances in γ-irradiated rats and could enhance the tolerance to high doses of ionizing IR utilized in radiotherapy.

Radiosensitivity of human ovarian carcinoma and melanoma cells to γ-rays and protons

INTRODUCTION

Proton radiation offers physical advantages over conventional radiation. Radiosensitivity of human 59M ovarian cancer and HTB140 melanoma cells was investigated after exposure to γ-rays and protons.

MATERIAL AND METHODS

Irradiations were performed in the middle of a 62 MeV therapeutic proton spread out Bragg peak with doses ranging from 2 to 16 Gy. The mean energy of protons was 34.88 ±2.15 MeV, corresponding to the linear energy transfer of 4.7 ±0.2 keV/µm. Irradiations with γ-rays were performed using the same doses. Viability, proliferation and survival were assessed 7 days after both types of irradiation while analyses of cell cycle and apoptosis were performed 48 h after irradiation.

RESULTS

Results showed that γ-rays and protons reduced the number of viable cells for both cell lines, with stronger inactivation achieved after irradiation with protons. Surviving fractions for 59M were 0.91 ±0.01 for γ-rays and 0.81 ±0.01 for protons, while those for HTB140 cells were 0.93 ±0.01 for γ-rays and 0.86 ±0.01 for protons. Relative biological effectiveness of protons, being 2.47 ±0.22 for 59M and 2.08 ±0.36 for HTB140, indicated that protons provoked better cell elimination than γ-rays. After proton irradiation proliferation capacity of the two cell lines was slightly higher as compared to γ-rays. Proliferation was higher for 59M than for HTB140 cells after both types of irradiation. Induction of apoptosis and G2 arrest detected after proton irradiation were more prominent in 59M cells.

CONCLUSIONS

The obtained results suggest that protons exert better antitumour effects on ovarian carcinoma and melanoma cells than γ-rays. The dissimilar response of these cells to radiation is related to their different features.

Study of damage to red blood cells exposed to different doses of γ-ray irradiation

BACKGROUND

The aims of this research were to study alterations in the ultrastructure of red blood cells, the changes in concentrations of plasma electrolytes and the killing effect of lymphocytes in samples of blood exposed to different doses of γ-ray irradiation.

MATERIALS AND METHODS

Blood samples were treated with different doses of γ-ray irradiation and then preserved for different periods. Specimens were prepared for standard electron microscopy and transmission electron microscopy. At the same time, changes in the concentrations of Na(+), K(+) and Cl(-) and pH values in the plasma as well as Fas and FasL expression of lymphocytes before and after irradiation were determined.

RESULTS

The proportions of reversibly and irreversibly transformed cells, for example, echinocytes, sphero-echinocytes, and degenerated forms, increased with increasing doses of irradiation and storage period, while the number of discocyte shaped red blood cells decreased. The change in K(+) concentration was greater than that of Na+ or Cl(-) after irradiation and was dosage-dependent. Plasma pH was influenced by different doses of radiation and storage time. After exposure to (137)Cs γ-irradiation, the expression of both Fas and FasL in lymphocytes differed significantly from that in the control group: the expression was positively correlated with irradiation dose (r=0.95, 0.96), but no significant difference in the Fas/FasL ratio was observed (P>0.05).

DISCUSSION

We conclude that the ultrastructure of red blood cells is not changed obviously by irradiation with some doses of γ-rays and various periods of storage. However, irradiation does have some dose-dependent and time-dependent adverse effects on the erythrocytes.

Molecular genetic analysis of pollen irradiation mutagenesis in Arabidopsis

•  Pollen γ-irradiation mutagenesis was systematically investigated to generate targeted mutations in Arabidopsis. •  Irradiation effects on viability, germination and frequency of loci deletions were evaluated. •  Mutation frequency increased with irradiation dose and varied depending upon pollen developmental stage. Meiosis was the most irradiation-sensitive stage, however, it did not equate to the highest mutation frequency. High frequencies of targeted mutations were obtained by irradiation from the second mitosis to mature pollen stages, using 400-600 Gy. Targeted mutations could also be obtained using lower doses of γ-rays (e.g. 200 Gy) provided that pollen was irradiated at an earlier developmental stage. ms1ttg marker locus pseudo-dominants were used to verify the presence and size of the resultant deletions. •  The results demonstrate that γ-irradiation of pollen is an efficient approach for generating deletions in the Arabidopsis genome. Pollen mutagenesis offers the possibility of combining single-cell selection procedures with the advantages of haploid systems, including the ability to treat large numbers of pollen grains, the absence of chimerism and direct expression of targeted alleles in the M₁ generation.

Requirement of poly(ADP-ribose) polymerase in recovery from DNA damage in mice and in cells

Poly(ADP-ribose) polymerase [PARP; NAD+ ADP-ribosyltransferase; NAD+: poly(adenosine-diphosphate-D-ribosyl)-acceptor ADP-D-ribosyltransferase, EC 2.4.2.30] is a zinc-finger DNA-binding protein that detects specifically DNA strand breaks generated by genotoxic agents. To determine its biological function, we have inactivated both alleles by gene targeting in mice. Treatment of PARP-/- mice either by the alkylating agent N-methyl-N-nitrosourea (MNU) or by gamma-irradiation revealed an extreme sensitivity and a high genomic instability to both agents. Following whole body gamma-irradiation (8 Gy) mutant mice died rapidly from acute radiation toxicity to the small intestine. Mice-derived PARP-/- cells displayed a high sensitivity to MNU exposure: a G2/M arrest in mouse embryonic fibroblasts and a rapid apoptotic response and a p53 accumulation were observed in splenocytes. Altogether these results demonstrate that PARP is a survival factor playing an essential and positive role during DNA damage recovery.