Low Dose Rate Gamma Irradiation Research Articles

The blackening of organotin catalyzed silicone adhesive via low dose rate gamma irradiation

Low dose rate gamma irradiation blackening effect of organotin catalyzed silicone adhesive is presented. When the total dose accumulated to 350 kGy at low dose rate (0.03 Gy/s), there is a significant blackening of the color changing from transparent to black by the increasing of dose, which is simultaneously deepened by the decreasing of dose rate. That is, low dose rate and accumulated dose both affect the final color of silicone adhesive. The structure changes of silicone adhesive before and after blackening are characterized by UV–vis, FTIR, and SPME-GC-MS, and the mechanism of blackening is deduced to be related to the content of SnO.

The role of pharmaceutical analysis in ensuring the safety of drug radiation sterilization

Radiation sterilization is a widely used method for ensuring the sterility of medical and pharmaceutical products. The process involves exposing the products to ionizing radiation, which destroys microorganisms such as bacteria, viruses, and fungi, rendering the products sterile. The most commonly used ionizing radiation sterilization methods are highly penetrating with low dose rate gamma-irradiation from isotopic sources and less penetrating but with high dose rate e-beam from accelerators. This review provides an overview of the principles and applications of radiation sterilization, including the types of radiation sources used, the differences between them that may affect the efficacy of the process, and the regulatory requirements for radiation sterilization of active pharmaceutical ingredients and drug dosage forms. This review focuses on the analytical methods used to evaluate the effect of irradiation on drug substances. Finally, it discusses studies on radiation sterilization of various groups of drugs, including anthracyclines, β-lactam antibiotics, chloramphenicol and its derivatives, sulphonamides, antifungal drugs, β-blockers, nonsteroidal anti-inflammatory drugs, steroids, and others, and drug dosage forms.

Influence of low dose rate gamma radiation on breakdown voltage and electrical breakdown time delay of working gas Geiger-Muller chamber

This paper presents the experimental data on the dynamic breakdown voltage and electrical breakdown time delay of commercial Geiger-Muller chamber manufactured by PHILIPS. The distributions of these data were determined. Static breakdown voltage was estimated based on the mean value of dynamic breakdown voltage as the function of voltage increase rate, for the cases when gamma radiation was not presented and in its presence. In order to separate the mechanisms that predominantly influence the initiation of breakdown for different values of relaxation time, the dependences of mean value of electrical breakdown time delay as the function of relaxation time was analyzed. It has been shown that during the relaxation times up to 3 ms positive ions plays a dominant role in initiating the breakdown while for relaxation times from 3 ms to 30 s initiation of the breakdown is caused by electrically neutral active particles. The effect of gamma radiation on electrical breakdown time delay was observed for relaxation time greater than 7 s.

Structural and optical effects of low dose rate Co-60 gamma irradiation on PbS thin films

Thin films of lead sulphide (PbS) were grown on the Si (100) and glass substrates using the simple chemical bath deposition (CBD) method. The prepared films had the cubic structure at room temperature, and the thickness was 350 nm at a 120 min deposition time. In this work, the effect of low-dose rate gamma irradiation on the structural and optical characteristics of the prepared thin films was investigated. The PbS thin films were exposed at the National SSDL (Secondary Standard Dosimetry Laboratory) using gamma beam emitted from Co-60 source, the average energy of the photon beam was 1.25 MeV. Here, four different doses (1, 2, 3 and 4 kGy) were used and the dose rate was about 380 mGy/min. The changes on the optical and structural properties of the PbS films due to the gamma irradiation were evaluated. The results showed that the intensity of photoluminescence PL and the grain size decreased with increasing the radiation dose. This could be related to the changes in the crystalline structural during the experiment. In addition, the band gap obtained by the UV transmittance spectrum was confirmed with the results of XRD. These results could indicate the potential application for PbS film in microelectronic field.

Targeting NRF2, Regulator of Antioxidant System, to Sensitize Glioblastoma Neurosphere Cells to Radiation-Induced Oxidative Stress.

The presence of glioma stem cells (GSCs), which are enriched in neurospheres, may be connected to the radioresistance of glioblastoma (GBM) due to their enhanced antioxidant defense and elevated DNA repair capacity. The aim was to evaluate the responses to different radiation qualities and to reduce radioresistance of U87MG cells, a GBM cell line. U87MG cells were cultured in a 3D model and irradiated with low (24 mGy/h) and high (0.39 Gy/min) dose rates of low LET gamma and high LET carbon ions (1-2 Gy/min). Thereafter, expression of proteins related to oxidative stress response, extracellular 8-oxo-dG, and neurospheres were determined. LD50 for carbon ions was significantly lower compared to LD50 of high and low dose rate gamma radiation. A significantly higher level of 8-oxo-dG was detected in the media of cells exposed to a low dose rate as compared to a high dose rate of gamma or carbon ions. A downregulation of oxidative stress proteins was also observed (NRF2, hMTH1, and SOD1). The NRF2 gene was knocked down by CRISPR/Cas9 in neurosphere cells, resulting in less self-renewal, more differentiated cells, and less proliferation capacity after irradiation with low and high dose rate gamma rays. Overall, U87MG glioma neurospheres presented differential responses to distinct radiation qualities and NRF2 plays an important role in cellular sensitivity to radiation.

Comparison of holes trapping and protons transport induced by low dose rate gamma radiation in oxide on different SiGe processes

Space-related electronics contain different types of oxide isolations which are the crucial factor resulting in device degradation and failure. Previous studies show that the local oxidation of silicon (LOCOS) isolation Silicon‑germanium heterojunction bipolar transistor (SiGe HBT) experience more significantly low dose rate sensitivity than that of shallow trench (STI) isolation SiGe HBTs and behave a “true” dose rate effect. In our work, the electron-hole pairs (EHPs) generation, holes trapped and protons transport inside oxide are simulated in LOCOS and STI isolation SiGe HBTs to explanation the different response t enhanced low dose rate sensitivity (ELDRS). The simulation results show that LOCOS oxide has a larger generation of EHPs than that of STI oxide leading to more surviving holes and protons release within oxide.

Genotoxic effects of high dose rate X-ray and low dose rate gamma radiation in ApcMin/+ mice.

Risk estimates for radiation‐induced cancer in humans are based on epidemiological data largely drawn from the Japanese atomic bomb survivor studies, which received an acute high dose rate (HDR) ionising radiation. Limited knowledge exists about the effects of chronic low dose rate (LDR) exposure, particularly with respect to the application of the dose and dose rate effectiveness factor. As part of a study to investigate the development of colon cancer following chronic LDR vs. acute HDR radiation, this study presents the results of genotoxic effects in blood of exposed mice. CBAB6 F1 Apc+/+ (wild type) and ApcMin/+ mice were chronically exposed to estimated whole body absorbed doses of 1.7 or 3.2 Gy 60Co‐γ‐rays at a LDR (2.2 mGy h−1) or acutely exposed to 2.6 Gy HDR X‐rays (1.3 Gy min−1). Genotoxic endpoints assessed in blood included chromosomal damage (flow cytometry based micronuclei (MN) assay), mutation analyses (Pig‐a gene mutation assay), and levels of DNA lesions (Comet assay, single‐strand breaks (ssb), alkali labile sites (als), oxidized DNA bases). Ionising radiation (ca. 3 Gy) induced genotoxic effects dependent on the dose rate. Chromosomal aberrations (MN assay) increased 3‐ and 10‐fold after chronic LDR and acute HDR, respectively. Phenotypic mutation frequencies as well as DNA lesions (ssb/als) were modulated after acute HDR but not after chronic LDR. The ApcMin/+ genotype did not influence the outcome in any of the investigated endpoints. The results herein will add to the scant data available on genotoxic effects following chronic LDR of ionising radiation. Environ. Mol. Mutagen. 58:560–569, 2017. © 2017 The Authors Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society

Mimicking the effects of spaceflight on bone: Combined effects of disuse and chronic low-dose rate radiation exposure on bone mass in mice

During spaceflight, crewmembers are subjected to biomechanical and biological challenges including microgravity and radiation. In the skeleton, spaceflight leads to bone loss, increasing the risk of fracture. Studies utilizing hindlimb suspension (HLS) as a ground-based model of spaceflight often neglect the concomitant effects of radiation exposure, and even when radiation is accounted for, it is often delivered at a high-dose rate over a very short period of time, which does not faithfully mimic spaceflight conditions. This study was designed to investigate the skeletal effects of low-dose rate gamma irradiation (8.5 cGy gamma radiation per day for 20 days, amounting to a total dose of 1.7 Gy) when administered simultaneously to disuse from HLS. The goal was to determine whether continuous, low-dose rate radiation administered during disuse would exacerbate bone loss in a murine HLS model. Four groups of 16 week old female C57BL/6 mice were studied: weight bearing + no radiation (WB+NR), HLS + NR, WB + radiation exposure (WB+RAD), and HLS+RAD. Surprisingly, although HLS led to cortical and trabecular bone loss, concurrent radiation exposure did not exacerbate these effects. Our results raise the possibility that mechanical unloading has larger effects on the bone loss that occurs during spaceflight than low-dose rate radiation.

Two Stages of Surface-Defect Formation in a MOS Structure under Low-Dose Rate Gamma Irradiation

The results of an experimental study of how surface defects are formed at the Si–SiO2 interface at γ-radiation dose rates of P = 0.1 and 1.0 rad/s are reported. It is found that the surface defects are formed in two stages. The defect-formation mechanisms are analyzed.

In vitro radiosensitization by gold nanoparticles during continuous low-dose-rate gamma irradiation with I-125 brachytherapy seeds

This communication reports the first experimental evidence of gold nanoparticle (AuNP) radiosensitization during continuous low-dose-rate (LDR) gamma irradiation with low-energy brachytherapy sources. HeLa cell cultures incubated with and without AuNP were irradiated with an I-125 seed plaque designed to produce a relatively homogeneous dose distribution in the plane of the cell culture slide. Four sets of irradiation experiments were conducted at low-dose rates ranging from 2.1 to 4.5cGy/h. Residual γH2AX was measured 24h after irradiation and used to compare radiation damage to the cells with and without AuNP. The data demonstrate that the biological effect when irradiating in the presence of 0.2mg/ml concentration of AuNP is about 70%–130% greater than without AuNP. Meanwhile, without radiation, the AuNP showed minimal effect on the cancer cells. These findings provide in vitro evidence that AuNP may be employed as radiosensitizers during continuous LDR brachytherapy. From the Clinical EditorIn this basic science paper, the application of gold nanoparticles as radiosensitizing agents for low dose rate gamma radiation therapy is discussed, demonstrating efficacy in cell culture models.

PtRu/C Electrocatalysts Prepared Using Gamma and Electron Beam Irradiation for Methanol Electrooxidation

PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles) were prepared in a single step submitting water/2-propanol mixtures containing Pt(IV) and Ru(III) ions and the carbon support to gamma and electron beam irradiation. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), and cyclic voltammetry and tested for methanol electrooxidation. PtRu/C electrocatalyst can be prepared in few minutes using high dose rate electron beam irradiation while using low dose rate gamma irradiation some hours were necessary to prepare it. The obtained materials showed the face-centered cubic (fcc) structure of Pt and Pt alloys with average nanoparticle sizes of around 3 nm. The material prepared using electron beam irradiation was more active for methanol electrooxidation than the material prepared using gamma irradiation.

Risks Associated with Low Doses and Low Dose Rates of Ionizing Radiation: Why Linearity May Be (Almost) the Best We Can Do

Deterministic and stochastic effects associated with high-dose ionizing radiation (x-ray) exposure have been known for almost as long as ionizing radiation itself (1–3). At lower doses, radiation risks are primarily stochastic effects, in particular, somatic effects (cancer) rather than the deterministic effects characteristic of higher-dose exposure (4–6). In contrast to deterministic effects, for stochastic effects, scientific committees generally assume that at sufficiently low doses there is a positive linear component to the dose response—that is, that there is no threshold (4–6). This does not preclude there being higher-order (eg, quadratic) powers of dose in the dose response that may be of importance at higher doses. It is on this basis that models linear (or linear-quadratic) in dose are often used to extrapolate the experience of the Japanese atomic bomb survivors (who were typically exposed at a high dose rate to moderate doses [average, 0.1 Sv]) to estimate risks from low doses and low dose rates (4–6). Most population-based cancer risk estimates are based primarily on the Japanese atomic bomb survivor Life Span Study (LSS) cohort data (4–6). However, evidence of excess risks comes from a large number of other studies as well. In the parallel editorial (7), evidence is presented for possible real (or at least “practical”) thresholds or “hormetic” (beneficial) effects of low doses of ionizing radiation. As we summarize here, and in contrast to the arguments of Tubiana et al (7), we judge that there is little epidemiologic or biologic evidence for these for cancer. The arguments are of three forms: (a) assessment of the degree of curvature in the cancer dose response within the Japanese atomic bomb survivors and other exposed groups (in particular, departure from linear or linear-quadratic curvature), (b) consistency of risks between the Japanese and other moderate- and low-dose cohorts, and (c) assessment of biologic data on mechanisms. Most of the information on radiation-induced cancer risk comes from (a) the Japanese atomic bomb survivors, (b) medically exposed populations, (c) occupationally exposed groups, and (d) environmentally exposed groups (6). In the higher-dose radiation therapy studies, where doses received are very much higher than in the LSS, sometimes in the range at which cell sterilization occurs, excess cancer risks per unit dose tend to be less than in comparable subsets of the LSS (8,9). However, as we show, risks in moderate- and low-dose medically and occupationally exposed groups are generally consistent with those in the LSS.

Influence of chronic low-dose rate gamma-irradiation on the life span of Drosophila inbred and outbred strains

The hormetic effect of low dose rate irradiation is well known for the longevity of Drosophila melanogaster . However the mechanism is not well understood. Since the most of Drosophila laboratory strains maintained as inbred or isogenic, it was suggested that radiation hormesis in flies may be induced by increasing of the rate of genetic heterogeneity that abolishes the inbreeding depression (Moskalev, 2007). The objective of our research was to investigate the effect of low-dose rate irradiation on the longevity and genetic instability in inbred strain of Drosophila melanogaster . We used wild type Drosophila melanogaster strain Canton-S, maintained in bottle population, and the inbred lineage initiated from it. Experimental strains were chronically irradiated in dose rate of 0.17 cGy/h during 3 generations. The rate of absorbed dose was 60 cGy per generation. The survivorship analysis for males and females was performed after 1, 2 and 3 generations of chronic irradiation. The genetic instability in somatic cells was examined by bristle defects assay. The obtained results will be discussed in presentation. References Moskalev A. A. Chronic gamma-irradiation effect on Drosophila melanogaster lifespan in generations of wild-type isogenic and heterogenic strains // Int. J. Low Radiation, 2007. – Vol. 4, # 3. – P. 169-175.

Amelioration of Type II Diabetes indb/dbMice by Continuous Low-Dose-Rate γ Irradiation

Low-dose-rate radiation modulates various biological responses including carcinogenesis, immunological responses and diabetes. We found that continuous irradiation with low-dose-rate gamma rays ameliorated type II diabetes in db/db mice, diabetic mice that lack leptin receptors. Whole-body exposure of db/db mice to low dose-rate gamma radiation improved glucose clearance without affecting the response to insulin. Histological studies suggested that degeneration of pancreatic islets was significantly suppressed by the radiation. Insulin secretion in response to glucose loading was increased significantly in the irradiated mice. These results suggest that low-dose-rate gamma radiation ameliorates type II diabetes by maintaining insulin secretion, which gradually decreases during the progression of diabetes due to degeneration of pancreatic islets. We also inferred that protection from oxidative damage is involved in the anti-diabetic effect of low-dose-rate gamma rays because expression and activity of pancreatic superoxide dismutase were significantly elevated by low-dose-rate gamma radiation.

低線量・低線量率ガンマ線の生物応答に関するメタ・ナリシス

低線量・低線量率ガンマ線の生物応答に関するメタ・ナリシス

The influence of very low dose rate gamma-radiation on genetic structures of mice: molecular and cytogenetic study

The results of investigation of molecular genetic and cytogenetic characteristics of CBA/lac male mice exposed to continuous very low dose rate gamma-radiation (0.17 cGy/day) during 40, 80, 120, and 210 days are presented in this study. Total accumulated doses were 6.8, 13.6, 20.4, 35.7 cGy, respectively. The parameters studied were levels of DNA-protein cross-links (DPCs) and DNA breaks in spleen lymphocytes (SLs), as well as percentage of bone marrow polychromatic erythrocytes with micronuclei (MNPCEs) and peripheral blood normochromatic erythrocytes with micronuclei (MNNCEs), using the DNA precipitation, the DNA alkali unwinding, the single cell gel electrophoresis (comet) assays and the micronucleus test, respectively. In addition, the induction of DNA damage in SLs after incubation with hydrogen peroxide (H2O2 at 0.1–5 mM) was studied. An increase in the sensitivity of SLs to H2O2 was revealed at 40 days of irradiation (6.7 cGy) as compared to SLs from non-irradiated control animals. However, after 120 days of exposure to radiation (20.4 cGy), SLs became more resistant to H2O2 treatment. This effect could be attributed to a development of adaptation processes triggered upon accumulation of a certain dose (in our experiments it is ∼20 cGy). Beginning from 80 days of irradiation (13.6 cGy), an increased level of DNA relaxation was observed, most likely indicating the induction of proliferation of SLs. Noteworthy is that populations of cells with markedly high level of DNA damage and apoptotic cells were registered. A level of DPCs in SLs was increased at 40 days of point only. No increase in bone marrow MNPCE or peripheral blood MNCCE in mice continuously exposed to very low-dose rate radiation was registered as compared with non-irradiated mice.

Mechanism for Amelioration of Type II Diabetes by Continuous Exposure of Low Dose Rate Gamma Radiation

Mechanism for Amelioration of Type II Diabetes by Continuous Exposure of Low Dose Rate Gamma Radiation

Effects of Low Dose-Rate Gamma Irradiation on Tumor Cell Rejection in Mice

Effects of Low Dose-Rate Gamma Irradiation on Tumor Cell Rejection in Mice

Caffeine induces a second wave of apoptosis after low dose-rate gamma radiation of HL-60 cells.

Most cell lines that lack functional p53 protein are arrested in the G(2) phase of the cell cycle due to DNA damage. It was previously found that the human promyelocyte leukemia cells HL-60 (TP53 negative) that had been exposed to ionizing radiation at doses up to 10 Gy were arrested in the G(2) phase for a period of 24 h. The radioresistance of HL-60 cells that were exposed to low dose-rate gamma irradiation of 3.9 mGy/min, which resulted in a pronounced accumulation of the cells in the G(2) phase during the exposure period, increased compared with the radioresistance of cells that were exposed to a high dose-rate gamma irradiation of 0.6 Gy/min. The D(0) value (i.e. the radiation dose leading to 37% cell survival) for low dose-rate radiation was 3.7 Gy and for high dose-rate radiation 2.2 Gy. In this study, prevention of G(2) phase arrest by caffeine (2 mM) and irradiation of cells with low dose-rate irradiation in all phases of the cell cycle proved to cause radiosensitization (D(0)=2.2 Gy). The irradiation in the presence of caffeine resulted in a second wave of apoptosis on days 5-7 post-irradiation. Caffeine-induced apoptosis occurring later than day 7 post-irradiation is postulated to be a result of unscheduled DNA replication and cell cycle progress.

Exposure to chronic, low-dose rate gamma-radiation at Chornobyl does not induce point mutations in Big Blue mice.

Empirical genetic effects resulting from low-dose rate irradiation and chronic, cumulative exposure are poorly characterized. Expected effects are based on epidemiological studies and downward, linear extrapolations from nonthreshold models derived from acute, high-dose exposures. These extrapolations and their associated risk coefficients have no experimental support, and because of their inherent uncertainty they are the subject of considerable debate. The expectation of deleterious genetic effects resulting from low-dose rate irradiation and chronic exposure is in need of empirical assessment because this type of exposure is typical of those encountered in occupational, residential, and environmental settings. Recent acute low-dose (<10 cGy) studies using cytogenetic and point mutation endpoints indicate that observed effects range from those lower than spontaneous to an increase in the frequency of point mutations. Using the Big Blue assay, we examined the ability of chronic, continuous gamma-irradiation (2.3 x 10(-3) cGy/min) in the Chornobyl environment to induce point mutations. This system has demonstrated a significant point mutation sensitivity (4.5-fold increase) to acute, high-dose (1-3 Gy) gamma-radiation. Mutant frequencies and the mutation spectra were examined in exposed and reference samples of Big Blue mice following 90 days exposure (cumulative absorbed dose = 3 Gy) to the Chornobyl environment. No significant increase in the mutant frequency or bias in the mutational spectrum was observed in exposed individuals. This finding suggests that low-dose rate gamma-irradiation at Chornobyl does not induce point mutations and that cumulative, chronically absorbed doses do not induce the same genetic effects as acute doses of the same magnitude.