Enhancement of radiation exposure risk from β-emitter radionuclides due to Internal Bremsstrahlung effect: A Monte Carlo study of 90Y case

Employment of β-decaying radionuclides, used in many fields (industrial, clinical, research) requires a correct assessment of the operators’ radiological exposure. Usually, in the dosimetric evaluation, the contribution coming from Internal Bremsstrahlung (IB) accompanying the β-decay is not kept into account; nevertheless, this negligibility does not always appear justified, at least for high-energy β-emitters. By means of Monte Carlo (MC) simulations, we showed how the contribution from IB photons is noteworthy for the evaluation of the overall radiation absorbed dose in the case of ⁹⁰Y source. We evaluated an increase of the absorbed doses, respectively for a point source and the considered receptacles, up to + 34% and + 60% or + 15% and + 28%, depending on the adopted model of IB spectrum. These results demonstrate the relevance of IB phenomenon in radiation protection estimations and suggest extending future theoretical and experimental studies to other β-decaying radionuclides.     

A multicenter study of radiation doses to the eye lenses of medical staff performing non-vascular imaging and interventional radiology procedures in Japan

PurposeThis study aimed to measure the eye lens doses received by physicians and other medical staff participating in non-vascular imaging and interventional radiology procedures in Japan.Material and methodsFrom October 2014 to March 2017, 34 physicians and 29 other medical staff engaged in non-vascular imaging and interventional radiology procedures at 18 Japanese medical facilities. These professionals wore radioprotective lead glasses equipped with small, optically stimulated luminescence dosimeters and additional personal dosimeters at the neck during a 1-month monitoring period. The H_p(3) and the H_p(10) and H_p(0.07) were obtained from these devices, respectively. The monthly H_p(3), H_p(10), and H_p(0.07) for each physician and other medical staff member were then rescaled to a 12-month period to enable comparisons with the revised occupational equivalent dose limit for the eye lens.ResultsAmong physicians, the average annual H_p(3) values measured by the small luminescence dosimeters on radioprotective glasses were 25.5 ± 38.3 mSv/y (range: 0.4–166.8 mSv/y) and 9.3 ± 16.6 mSv/y (range: 0.3–82.4 mSv/y) on the left and right sides, respectively. The corresponding values for other medical staff were 3.7 ± 3.1 mSv/y (range: 0.4–10.4 mSv/y) and 3.2 ± 2.7 mSv/y (range: 0.5–11.5 mSv/y), respectively.ConclusionsThe eye lens doses incurred by physicians and other medical staff who engaged in non-vascular imaging and interventional radiology procedures in Japan were provided. Physicians should wear radioprotective glasses and use additional radioprotective devices to reduce the amount of eye lens doses they receive.     

Sinusoidal ELF magnetic fields affect acetylcholinesterase activity in cerebellum synaptosomal membranes

The effects of extremely low frequency magnetic fields (ELF‐MF) on acetylcholinesterase (AChE) activity of synaptosomal membranes were investigated. Sinusoidal fields with 50 Hz frequency and different amplitudes caused AChE activity to decrease about 27% with a threshold of about 0.74 mT. The decrease in enzymatic activity was independent of the time of permanence in the field and was completely reversible. Identical results were obtained with exposure to static MF of the same amplitudes. Moreover, the inhibitory effects on enzymatic activity are spread over frequency windows with different maximal values at 60, 200, 350, and 475 Hz. When synaptosomal membranes were solubilized with Triton, ELF‐MF did not affect AChE activity, suggesting the crucial role of the membrane, as well as the lipid linkage of the enzyme, in determining the conditions for inactivation. The results are discussed in order to give an interpretation at molecular level of the macroscopic effects produced by ELF‐MF on biological systems, in particular the alterations of embryo development in many organisms due to acetylcholine accumulation. Bioelectromagnetics 31:270–276, 2010. © 2009 Wiley‐Liss, Inc.     

Feeding responses of specialist herbivores to plant extracts and pure allelochemicals: effects of prolonged exposure

We investigated the possibility of decreased feeding deterrent response following prolonged exposure in three specialist herbivores, Plutella xylostella (larvae), Pseudaletia unipuncta (larvae), and Epilachna varivestis (adults) through leaf disc choice and no‐choice tests. Neonate larvae (<24 h old) of the three species were reared on their host plants sprayed with the antifeedants until tested. Our results demonstrated that Ps. unipuncta did not show a decrease in feeding deterrent response to extracts of Melia volkensii (choice and no‐choice tests) or oregano (Origanum vulgare) (choice test) following prolonged exposure. Plutella xylostella exhibited a decrease in feeding deterrent response to M. volkensii in a choice test only, but not to oregano. Although not significant, we did find a trend toward decreasing feeding deterrent response to M. volkensii by both species in no‐choice tests. However, both species exhibited a significant decrease in feeding deterrent response to pure allelochemicals (Ps. unipuncta to thymol, and P. xylostella to thymol and toosendanin) compared with the naïve groups, following prolonged exposure in leaf disc choice tests. Epilachna varivestis showed a significant decrease in feeding deterrent responses to both oregano and thymol in leaf disc choice tests. We conclude from our present and previous studies that not only are there interspecific differences between generalist and specialist species but also among specialist species.     

Cytogenetic monitoring of industrial radiographers using the micronucleus assay

Industrial radiography is the process of using either gamma-emitting radionuclide sources or X-ray machines to examine the safety of industrial materials. Industrial radiographers are among the radiation workers who receive the highest individual occupational radiation doses. To assess occupationally induced chromosomal damage, we performed the cytokinesis-block micronucleus (CBMN) assay in peripheral lymphocytes of 29 male industrial radiographers, exposed to ionizing radiation for 12.8 years±11.2, in comparison with 24 gender-, age-, and smoking habits-matched controls. The CBMN assay was combined with fluorescent in situ hybridization with a pan-centromeric DNA probe in 17 exposed subjects and 17 controls randomized from the initial populations. The mean cumulative equivalent dose, recorded by film dosimeters, was 67.2 mSv±49.8 over the past 5 years. The mean micronucleated binucleated cell rate (MCR) was significantly higher in the industrial radiographers than in the controls (10.7‰±5.2 versus 6.6‰±3.1, P=0.009); this difference was due to a significantly higher frequency of centromere-negative micronuclei (C−MN) in exposed subjects than in controls (8.5‰±4.9 versus 2.2‰±1.6, P<0.001). The two populations did not significantly differ in centromere-positive micronuclei (C+MN) frequency. These findings demonstrate a clastogenic effect in lymphocytes of industrial radiographers. MCR significantly positively correlated with age in the two groups. After correction for the age effect, MCR did not correlate with duration of occupational exposure. No correlation between radiation doses and MCR, C−MN, and C+MN frequencies was observed. In addition to physical dosimetry records, the enhanced chromosomal damage in lymphocytes of industrial radiographers emphasizes the importance of radiation safety programs.     

哈尔滨市室外空气真菌组成和分布的初步研究

采用曝皿法(孟加拉红培养基)连续12个月对哈尔滨市实验林场、东北林业大学家属区和哈尔滨市二环路、兴路区间3个地点的空气真菌进行取样,初步确定了哈尔滨市室外空气真菌的种类及其动态变化。试验共得到9 908个真菌菌落,经鉴定为22属(或群)49种。试验结果表明:室外空气真菌的优势菌属依次为枝孢属、链格孢、曲霉属、青霉属、附球菌属、木霉属和无孢菌群,分别占总菌落数的21.54%、15.16%1、4.70%、12.20%、11.35%、7.86%和7.80%;室外空气真菌的种类在一天中基本没有变化,但菌落的数量有一定变化,总菌落数从早至晚也逐渐增加;不同季节室外真菌的种类和菌落数有明显变化,秋季最多,冬季最少;不同采样地点的空气真菌的种类变化不大,但菌落数量有差异,菌落数量依次为公路林场家属区。     

Prenatal alcohol exposure reduces the proportion of newly produced neurons and glia in the dentate gyrus of the hippocampus in female rats

Prenatal alcohol exposure (PAE) alters adult neurogenesis and the neurogenic response to stress in male rats. As the effects of stress on neurogenesis are sexually dimorphic, the present study investigated the effects of PAE on adult hippocampal neurogenesis under both nonstressed and stressed conditions in female rats. Pregnant females were assigned to one of three prenatal treatments: (1) alcohol (PAE)—liquid alcohol (ethanol) diet ad libitum (36% ethanol-derived calories); (2) pair-fed—isocaloric liquid diet, with maltose–dextrin substituted for ethanol, in the amount consumed by a PAE partner (g/kg body wt/day of gestation); and (3) control—lab chow ad libitum. Female offspring were assigned to either nonstressed (undisturbed) or stressed (repeated restraint stress for 9 days) conditions. On day 10, all rats were injected with bromodeoxyuridine (BrdU) and perfused either 24 hours (cell proliferation) or 3 weeks (cell survival) later. We found that PAE did not significantly alter cell proliferation or survival, whereas females from the pair-fed condition exhibited elevated levels of cell survival compared to control females. Importantly, however, the proportion of both new neurons and new glial cells in the hippocampal dentate gyrus was reduced in PAE compared to control females. Exposure to stress did not alter neurogenesis in any of the prenatal treatment groups. In summary, compared to females from the control condition, prenatal dietary restriction enhanced the survival of new neurons, whereas PAE altered the differentiation of newly produced cells in the adult dentate gyrus. Alterations in hippocampal neurogenesis following PAE may contribute to learning and memory deficits seen in individuals with fetal alcohol spectrum disorders.     

Postnatal Methylmercury Exposure Induces Hyperlocomotor Activity and Cerebellar Oxidative Stress in Mice: Dependence on the Neurodevelopmental Period

During the early postnatal period the central nervous system (CNS) is extremely sensitive to external agents. The present study aims at the investigation of critical phases where methylmercury (MeHg) induces cerebellar toxicity during the suckling period in mice. Animals were treated with daily subcutaneous injections of MeHg (7 mg/kg of body weight) during four different periods (5 days each) at the early postnatal period: postnatal day (PND) 1–5, PND 6–10, PND 11–15, or PND 16–20. A control group was treated with daily subcutaneous injections of a 150 mM NaCl solution (10 ml/kg of body weight). Subjects exposed to MeHg at different postnatal periods were littermate. At PND 35, behavioral tests were performed to evaluate spontaneous locomotor activity in the open field and motor performance in the rotarod task. Biochemical parameters related to oxidative stress (levels of glutathione and thiobarbituric acid reactive substances, as well as glutathione peroxidase and glutathione reductase activity) were evaluated in cerebellum. Hyperlocomotor activity and high levels of cerebellar thiobarbituric acid reactive substances were observed in animals exposed to MeHg during the PND 11–15 or PND 16–20 periods. Cerebellar glutathione reductase activity decreased in MeHg-exposed animals. Cerebellar glutathione peroxidase activity was also decreased after MeHg exposure and the lowest enzymatic activity was found in animals exposed to MeHg during the later days of the suckling period. In addition, low levels of cerebellar glutathione were found in animals exposed to MeHg during the PND 16–20 period. The present results show that the postnatal exposure to MeHg during the second half of the suckling period causes hyperlocomotor activity in mice and point to this phase as a critical developmental stage where mouse cerebellum is a vulnerable target for the neurotoxic and pro-oxidative effects of MeHg.     

不同工艺阶段味精废水对作物种子发芽和根伸长的毒性效应

为了对味精废水的污染进行全面的评价,针对不同工艺阶段排放的味精废水,采用小麦、白菜和西红柿等作物种子,以污水为环境介质,进行了种子发芽和根伸长的污染暴露实验,并结合污染现场,进行了相应的定量分析.结果表明,在高浓度原味精废母液中, 小麦种子的发芽抑制率和根伸长的抑制率与废水的浓度呈显著正相关.味精废水对3种作物种子的发芽和根伸长的毒性强弱顺序为：西红柿＞白菜＞小麦西红柿对味精废水毒性响应最为敏感,可以认为是一种较为理想的生物毒性指示作物.味精生产不同工艺阶段所排放的污水对这3种作物种子的发芽半抑制浓度(IC₅₀)为22.0～32432 mg·L^-1,对根伸长的半抑制浓度(IC₅₀)为17.3～3320 mg·L^-1.