The influence of ionizing radiation on spore germination and emergent hyphal growth response reactions of microfungi

The accident at the Chernobyl Atomic Energy Station resulted in radiation contamination of large tracts of land and particularly the reactor building itself. Sustained exposure of microfungi to radiation appears to have resulted in formerly unknown adaptive features, such as directed growth of fungi to sources of ionizing radiation. We evaluate here spore germination and subsequent emergent hyphal growth of microfungi in the presence of pure gamma or mixed beta and gamma radiation of fungi isolated from a range of long term background radiation levels. Conidiospore suspensions were exposed to collimated beams of radiation and percent spore germination and length of emergent hyphae were measured. All fungal species isolated from background radiation showed inhibition or no response in germination when irradiated. Isolates from sites with elevated radiation showed a stimulation in spore germination (69% mixed radiation and 46% for gamma irradiation). Most isolates from low background radiation sites showed a significant reduced or no response to exposure to either source of radiation, whereas the stimulatory effect of experimental exposure to radiation appeared to increase in magnitude as prior exposure to radiation increased. We propose that the enhanced spore germination and hyphal growth seen in the exposure trials is induced by prior long term exposure to radiation and these factors could be important in controlling the decomposition of radionuclide-bearing resources in the environment.     

暖温带落叶阔叶林辐射能量环境初步研究

本文对暖温带落叶阔叶林辐射能量环境进行了初步探讨,文中对林、灌、草各层次的总、反、净、光台有效及吸收、透射等辐时因子的变化分别进行了系统分析。主要结论如下：（１）在生长季（５─１０日）期间,抵达林冠的太阳总辐射为３０９５．４５ＭＪ·ｍ￣（－２）,抵达灌草层的为３８８．３４ＭＪ·ｍ￣（－２）。峰值出现在５月,谷值在８月。（２）生氏季内,抵达群落的太阳总辐射主要集中于５、６两月,占整个生长季的４０．９９％。（３）生长季内,林冠上方净辐射总值为１６５８．７４ＭＪ·ｍ￣（－２）。（４）林冠反射主要受入射光的光谱特性及群落发育状况共同影响,反射率的变化主要与群落发育状况相关;灌草层的反射及后射率主要受群落发育状况的影响。（５）整个生长季,林冠所接收的光台有效辐时为１３０８．３ＭＪ·ｍ￣（－２）,灌草层为１９４．２１ＭＪ·ｍ￣（－２）。（６）净辐射日进程受气候因素影响十分强烈。（７）群落内光能资源的时空分布存在很大差异。     

Effect of incident radiation integral on cauliflower growth and development after curd initiation

Two field experiments were conducted to assess the response of cauliflower cv. “Nautilus F1” to different radiation integrals after curd initiation by covering the plants with different levels (0, 38, 50 and 68%) of neutral shading materials during the autumn 1998 and summer 2000. Cauliflower growth and development declined with increasing shade levels after curd initiation. Total above ground dry matter increased linearly with accumulated incident radiation integral after curd initiation, however, under lower radiation conditions, the rate of increase per unit incident radiation integral was greater than under higher radiation conditions. Moreover, radiation conversion coefficient declined linearly with increasing incident radiation integrals up to approximately 6.1 MJ m⁻² d⁻¹ and thereafter, declined more slowly with further increase in incident radiation integrals. Therefore, dry matter accumulation was potentially more efficient under lower incident radiation than higher incident radiation levels. Radiation conversion coefficients for plants under low incident radiation levels were greater than under high incident radiation levels. Curd growth also increased linearly with increasing accumulated incident radiation integral with greater mean relative curd dry matter increase per MJ under lower incident radiation conditions than higher incident radiation levels.     

Effects of Ultraviolet-B Irradiances on Soybean: II. INTERACTION BETWEEN ULTRAVIOLET-B AND PHOTOSYNTHETICALLY ACTIVE RADIATION ON NET PHOTOSYNTHESIS, DARK RESPIRATION, AND TRANSPIRATION

Soybean plants (cv. Hardee) were grown from seed under four ultraviolet-B radiation flux densities and four photosynthetically active radiation levels in a factorial design. Net photosynthesis, dark respiration, and transpiration were measured after 2 and 6 weeks of exposure. Effects of ultraviolet-B radiation were dependent upon photosynthetically active radiation levels. Ultraviolet-B radiation adversely affected net photosynthesis at low photosynthetically active radiation levels, but had little consequence at levels normally saturating photosynthesis in the field. Ultraviolet-B radiation affected both stomatal and nonstomatal resistances to carbon dioxide under low levels of photosynthetically active radiation. The present study demonstrates interactions between ultraviolet-B and photosynthetically active radiation.     

X-ray and UV-radiation sensitivity of circulating lymphocytes in multiple epidermal cancer in relation to previous radiation exposure

The cellular sensitivity to X rays (200 kV, 16 mA) and UV radiation (254 nm) was examined in lymphocytes from three groups of patients with multiple epidermal malignant tumors, selected by their clinical history of carcinogenesis. Eight patients previously exposed to low energy ionizing radiation (less than or equal to 12 kV) had an increased cellular sensitivity to UV radiation as well as X rays compared with 24 age and sex matched controls. This indicates the existence of a cellular cross-sensitivity to UV radiation and ionizing radiation not previously established for human cells. In contrast six patients previously exposed to high energy ionizing radiation (between 25 and 170 kV) had normal cellular response to both UV radiation and X rays, indicating a different biologic effect of low and high energy ionizing radiation. In the third group of patients, previously exposed to therapeutic UV radiation/excess sunlight, the lymphocytes had a normal response to X rays, but an increased sensitivity to UV radiation. The possibility of evaluating the individual risk at radiation exposure is suggested.     

Selection of Autographa californica nuclear polyhedrosis virus for resistance to inactivation by near ultraviolet,far ultraviolet,and thermal radiation

Experiments were performed to isolate strains of Autographa californica nuclear polyhedrosis virus (Baculovirus) with inherent resistance to inactivation by far ultraviolet radiation, near ultraviolet radiation, and thermal radiation. Virus with apparently increased resistance to inactivation by near ultraviolet radiation was isolated. Virus with increased resistance to far ultraviolet radiation was not obtained. No significant differences in response to thermal radiation were observed between wild virus and virus selected for increased resistance to inactivation by this agent. Repeated selection treatment with far ultraviolet radiation and with near ultraviolet radiation resulted in the production of virus with significantly reduced virulence in comparison with wild virus. The virulence of heat-selected virus did not differ from wild virus.     

Natural background radiation: problem of radionuclide migration and biological effects

Natural radiation background is the main contributor to radiation dose delivered to plants, animals, and man. That is why its effects are of increasing interest in radiobiology, radioecology, and radiation hygiene. The following problems are discussed: migration of main natural radionuclides in biosphere, dose formation, biological role of natural radiation background on the Earth, standards for natural radiation background, and problems of natural radiation background and biosphere evolution. The tasks of further radiobiological research in evaluating the role of natural radiation background are outlined.     

Protective mechanisms and acclimation to solar ultraviolet-B radiation in Oenothera stricta

Abstract Mechanisms of plant protection and acclimation to potentially damaging solar ultraviolet-B (UV-B, 280–320 nm) radiation incident on the Earth's surface were examined in Oenothera stricta. Attenuation of this radiation in the upper leaf epidermis reduces the penetration of UV-B radiation to the mesophyll where damage to physiologically sensitive targets can occur. The epidermis is a highly selective radiation filter that can attenuate up to 95% of the incident UV-B radiation and yet transmit between 70% and 80% of the visible radiation. Exposure to UV-B radiation significantly reduced the degree of epidermal UV-B transmittance by as much as 33%. No significant reduction in epidermal transmittance of visible radiation was observed as a result of UV-B exposure. The plasticity in epidermal UV-B transmittance results from production of flavonoid and related phenolic compounds in the tissue. Absorbance of UV-B radiation in llavonoid extract solutions from epidermal and mesophyll tissues significantly increased by as much as 100% and 35%, respectively, after exposure to UV-B radiation. Photosynthetic rates of leaves exposed to UV-B radiation were not significantly reduced at dose rates representative of the radiation flux found in the habitat of this species, but significant photosynthetic depression was observed at dose rates that exceed the field UV-B flux. The phenotypic plasticity in epidermal UV-B transmittance resulting in decreased penetration of damaging UV-B radiation to the mesophyll may reduce the rate of damage to a level where repair mechanisms can keep pace with reduced injury.     

Manifestation of radiation effects in cold environment: data review and modeling

The peculiarities of radiation response in animals at low environmental temperatures are analyzed in the context of radiation safety of the Arctic/Northern wildlife. The paper includes a data review on radiation effects in cold environments based on international and Russian publications since 1948, which forms a supplement to the EPIC and FREDERICA data collections. In homoiothermic and heterothermic animals, imbalances in thermoregulation caused by ionizing radiation are discussed, which increase energy loss of animals, and decrease their fitness to the Arctic/Northern climate. In poikilothermic animals, both radiation damage and recovery are temperature dependant, their rates being slow in the cold environment. At low temperatures, radiation damage of biological tissues is conserved in hidden form; when the temperature of poikilothermic animal rises to a normal level, radiation injury is developed rapidly similar to acute dose response. Additionally, a mathematical model is described, demonstrating the combined effects of chronic radiation exposures and seasonal temperature variations on a fish population. Computer simulations show that at the same level of irradiation, the overall radiation damage to Arctic/Northern poikilothermic fish is higher than that to the fish from warm climate. Considering the peculiarities of radiation effects in the cold climate, the Arctic/Northern fauna might be expected to be more vulnerable to chronic radiation stress compared to temperate fauna. In the case of acute radiation exposure during winter periods, hibernation of heterothermic and cooling of poikilothermic animals may provide temporary protection from acute radiation effects.     

Effects of artificial and solar UV-B radiation on the gravitactic orientation of the dinoflagellate, Peridinium gatunense

Abstract The effects of artificial and solar UV-B radiation on the gravitactic (formerly called geotactic) orientation of the freshwater dinoflagellate Peridinium gatunense were measured under artificial UV-B radiation and in a temperature-controlled growth chamber under solar radiation in Portugal. Circular histograms of gravitaxis show the impairement of orientation after UV irradiation. The degree of orientation, quantified using the Rayleigh test and top quadrant summation, decreased as the exposure time to the radiation prolonged. The effects of artifical UV-B radiation on orientation are stronger than those of solar radiation, probably because the radiation source emits higher fluence rates below 300 nm than found in solar radiation. After UV radiation, the gravitactic orientation under artificially increased acceleration at 2 g was drastically affected.     

鸦胆子油乳联合放疗治疗鼻咽癌的临床疗效观察

目的:探讨鸦胆子油乳联合放疗治疗鼻咽癌的临床疗效及安全性。方法:将在我科就诊的154例鼻咽癌患者随机分为对照组和治疗组,治疗组患者在常规放射治疗的基础上联合鸦胆子油乳治疗,而对照组患者单纯接受常规放射治疗。待治疗结束后,观察并比较两组患者的临床疗效、血液学指标及不良反应的发生情况。结果:对照组和治疗组的临床有效率分别为63.16%、82.05%,治疗组的临床有效率明显高于对照组,两组间比较有统计学差异(P0.05)。治疗后,治疗组患者的血液学指标如白细胞计数、红细胞计数、血红蛋白水平、CD4+/CD8+等均显著高于对照组,不良反应如恶心呕吐、张口困难、吞咽困难、声音嘶哑、口腔炎均明显低于对照组,差异具有统计学意义(P0.05)。结论:鸦胆子油乳联合放射治疗能够有效提高鼻咽癌患者的临床疗效,并且降低放疗所致的各种不良反应,值得临床推广应用。     

Optimizing solar UV-radiation exposures for vitamin D3: comparing global and diffuse spectral UV radiation

Currently, there is a major gap in the knowledge that is needed to optimize the beneficial effects related to ultraviolet (UV) radiation at wavelengths that induce vitamin D(3) synthesis (UV(D3)) compared to reducing the biologically damaging overexposure to UV radiation. The aim of this study was to investigate the use of diffuse (radiation that is scattered from all directions) UV radiation to optimize exposures to UV(D3) radiation and maximize the reduction of exposure to UVA radiation. Data on global and diffuse solar UV-radiation spectra were collected at 10-min intervals in the Southern Hemisphere in the late spring and summer from 1 November 2006 to 28 February 2007. For a solar zenith angle (SZA) of approximately 5 degrees , the observed maximum UV(D3) irradiances were 0.80 W/m(2) and 0.46 W/m(2) for global and diffuse UV radiation, respectively. The observed maximum UVA irradiances were 79.0 W/m(2) and 36.2 W/m(2) for global and diffuse UV radiation, respectively. For diffuse UV radiation, the maximum ratio of vitamin D(3) to UVA radiation was 1.75% at a SZA of approximately 10 degrees , whereas the maximum ratio for global UV was 1.27% at 10 degrees . For SZAs of 25 degrees and less, more UV radiation is in the wavelength region contributing to vitamin D(3) synthesis (UV(D3)) than in the UVA region for diffuse UV radiation than for global UV radiation.     

Emphasis of biological research for space radiation]

The paper summarized issues, current status and the recent topics in biological research of space radiation. Researches to estimate a risk associated with space radiation exposure during a long-term manned space flight, such as in the International Space Station, is emphasized because of the large uncertainty of biological effects and a complexity of the radiation environment in space. The Issues addressed are; 1) biological effects and end points in low dose radiation, 2) biological effects under low dose rate and long-term radiation exposure, 3) modification of biological responses to radiation under space environments, 4) various aspects of biological end points vs. cellular and molecular mechanisms, 5) estimation of human risk associated with radiation exposure in space flight, 6) regulations for radiation exposure limits for space workers. The paper also summarized and introduced recent progress in space related radiation researches with various biological systems.     

Selective light transmittance of translucent bracts in the Himalayan giant glasshouse plant Rheum nobile Hook. f. & Thomson (Polygonaceae)

Translucent bract transmittance of ultraviolet (UV) to infrared (IR) radiation (between 320 and 800 nm) and leaf anatomy were examined in a glasshouse plant, Rheum nobile Hook. f. & Thomson (Polygonaceae) to assess the function of avoiding injury by UV radiation while keeping the inflorescence warm by photosynthetically active (PA) and IR radiation. Although the translucent bracts and rosulate leaves transmitted little UV radiation, the former always transmit more PA and IR radiation. Additionally, the bracts transmit much more scattered solar radiation than direct radiation. The bracts are also anatomically different from the rosulate leaves. They have two or three layers of mesophyll cells with neither palisade nor spongy parenchymatous cells; in addition, the uppermost layer of mesophyll and the epidermis stain easily, and both are thought to play a role in attenuating UV radiation. The leaf epidermis of many land plants has UV absorbing pigments such as flavonoids, which absorb almost all UV radiation. Thus the role of the bracts of R. nobile is to protect the reproductive organs by absorbing UV radiation and to keep them warm by transmitting PA and IR radiation. The bracts are believed to have adapted function and form to the environment, in particular, to the weather conditions of the eastern Himalaya.     

人工同龄纯林冠层辐射场模拟模型 II.应用与验证

应用建立的人工同龄林辐射场模型对杉木 (Cunninghamialanceolata)人工林冠层辐射场进行了模拟 ,以实测的冠层辐射数据对模型进行了验证 ,对模型的不确定性以及叶面积密度和叶片散射的影响进行了计算和分析。结果表明 ,模拟和实测辐射场及日总量无显著差异 ,所建模型适于对杉木人工林冠层辐射的模拟。模型可能的误差来源包括树冠形状的不规则性、树冠大小和高低的不一致性、叶片在小范围内的簇生性等。考虑二维叶面积密度 (LAD)分布的模拟结果优于平均LAD。叶片的散射辐射约占总辐射的 3%～ 11%,且越靠近树冠里层和下部 ,散射作用越大。     

Internal filters: Prospects for UV-acclimation in higher plants

Wavelength-selective absorption of solar radiation within plant leaves allows penetration of visible radiation (400–700 nm) to the chloroplasts, while removing much of the damaging ultraviolet-B (UV-B, 280–320 nm) radiation. Flavonoids are important in this wavelength-selective absorption. Induction of flavonoid synthesis by solar radiation, and specifically by UV-B radiation, is discussed as this relates to the potential acclimation of plants to enhanced solar UV-B radiation that would result from stratospheric ozone reduction.     

热带季节雨林林窗辐射特征研究

利用不同季节热带季节雨林林窗、林内及旷地不同波长太阳辐射的实测资料,探讨了热带季节雨林林窗不同波长辐射特征。结果表明,热带季节雨林林窗中央和北侧林冠下的不同波长太阳辐射存在“突跃现象”,中午前后各辐射量值迅速达到最大后又急速下降;林窗内不同波长太阳辐射日总量值均大于林内,却小于旷地;林窗中央和北侧林冠下比较可见,在干热季、雨季和雨季后期,林窗中央的各辐射要素总量值高于北侧林冠下,但雾凉季时受浓雾和太阳高度以及方位的影响,各辐射要素总量值较北侧林冠下低;林窗中央的总辐射日总量在雨季太阳高度角最大时最高,雨季后期和干热季其次,雾凉季时最小;林窗中央和北侧林冠下的红外辐射及可见光在总辐射中所占份额随季节的变化而不同,充分显示了林窗辐射环境的异质性;与旷地和林内相比,林窗内各测点的红外辐射在总辐射中所占份额介于旷地和林内之间．高于旷地却低于林内;而可见光占总辐射的比值情况正好相反．另外,林窗可见光分配率的季节变化都大于红外辐射;热带季节雨林林窗育增加红外辐射、减少可见光的特征．     

Heat potentiation of radiation damage versus radiation potentiation of heat damage

The enhanced lethality of mammalian cells after combined treatment with hyperthermia and radiation is usually attributed to heat potentiation of radiation damage. However, it has been suggested that the situation may be reversed and that radiation may act as a modifier for heat damage. To test this hypothesis, BP-8 murine sarcoma cells were subjected to sequential radiation and heat treatments and the kinetics and extent of cell death were evaluated with the [125I]-iododeoxyuridine prelabeling assay. Cell death after heating was rapid and essentially complete within 2 days after heat exposure, whereas radiation death was slow and became apparent only after a delay period of 3 days. Combined exposure of cells to radiation and heat caused a pronounced increase in the delayed component of cell death, that is, the radiation component of death. Irradiation of cells before heating did not change the early heat component of cell death even in cells that were exposed to massive radiation doses of up to 300 Gy prior to heating. These results indicate that the increased cell death observed in hyperthermia/radiation-treated cells results from heat potentiation of radiation damage, not radiation potentiation of heat damage.     

Modelling the effects of changes in solar radiation on gross primary production in subtropical evergreen needle-leaf plantations

太阳辐射是陆地生态系统碳水循环的能量来源。太阳辐射的变化对植被吸收大气CO₂具有重要影响。该文通过辐射观测数据建立散射辐射比例与晴空指数的关系, 结合生态过程模型(BEPS)和通量观测数据, 模拟分析了太阳辐射变化对千烟洲常绿针叶林总初级生产力(GPP)的影响。研究结果表明: 千烟洲森林生态系统的阴叶对年GPP总量的贡献达67%, 太阳辐射变化对阴叶光合作用的影响决定了冠层GPP的变化; 太阳辐射强度和分布的年际差异导致年GPP对太阳辐射变化的响应不同, 2003、2004和2005年太阳辐射分别变化-5.44%、-1.83%和6.26%, 可使千烟洲生态系统当年GPP总量达到最大值; 在季节上, 太阳辐射的增加会导致5-6月GPP上升, 7-9月GPP下降, 使年GPP变化程度降低; 在天尺度上, 晴空指数在0.43时, 太阳辐射变化对GPP的影响最小。     

VARIATION IN UV-B SENSITIVITY IN PLANTS FROM A 3,000-m ELEVATIONAL GRADIENT IN HAWAII

Interest in the potential consequences of stratospheric ozone depletion has led to numerous studies that have evaluated the effects of ultraviolet-B (UV-B) radiation on plant growth and productivity. However, few studies have been conducted on plants from natural ecosystems. Differences in solar UV-B radiation along latitudinal or elevational gradients may have resulted in plants from diverse habitats developing contrasting sensitivities to UV-B radiation. In this study, seeds were collected along a 3,000-m elevational gradient in Hawaii and then germinated and grown in an unshaded greenhouse with either no UV-B radiation or one of two daily UV-B irradiances, 15.5 or 23.1 kj m². Seedlings were grown for 12 weeks and harvested to determine whether UV-B radiation altered plant biomass. The responses to UV-B radiation varied among species, but, in general, sensitivity to UV-B radiation was reduced as the elevation of seed collection increased. Of the 33 species tested, UV-B radiation significantly reduced plant height in 14 species and biomass in eight species. Biomass increased in four species grown under UV-B radiation. This study provides clear evidence that natural plant populations exhibit wide variation in UV-B radiation sensitivity and that this variation is related to the natural (ambient) UV-B radiation environment in which these plants grow.