基于人体健康的3种城市森林夏季林内紫外线辐射环境特征比较研究

以中波紫外线为主的紫外辐射对人体健康具有多种生物学影响,城市森林能够为居民提供温和的紫外辐射环境。为了解林下紫外线辐射环境特征是否存在树种间差异,对北京市3种常见遮荫树种的夏季林下紫外辐射(UV)强度、林内与林外UV辐射的比值(SR)、UV-B在总UV辐射中占比(UV-B/UV),以及VD合成和红斑效应两种人体作用有效辐射强度(UV_VD、UV_er)进行了测算。结果表明：(1)三种林分林内紫外辐射总量是林外的3%—10%,不同林分的林内UV强度具有显著差异,元宝枫林对UV屏蔽能力最强,其次是栾树林和国槐林;(2)三种林分林冠对不同波长上紫外辐射能量的屏蔽能力具有明显的一致性,林冠对UV-B的屏蔽能力没有在UVA波段强和稳定,林内UV-B/UV普遍高于林外,其中元宝枫林最高,其次为栾树林,国槐林最低;(3)林冠明显改变了日光UV_VD和UV_er两种人体作用光谱曲线的形态,三种林分内的人体作用光谱曲线形态相似,强度上,林内外UV_VD/UV_er值均接近1,不同林分间...     

Wavelength-dependent xanthophyll cycle activity in marine microalgae exposed to natural ultraviolet radiation

The wavelength dependency of xanthophyll cycling in two marine microalgae (Thalassiosira weissflogii and Dunaliella tertiolecta) was studied by establishing biological weighting functions (BWFs) during exposure to natural ultraviolet radiation. High-(HL) and low-(LL) light-acclimated cultures of both species were exposed outdoors for up to 60 min under a series of UVR (280–400 nm) cut-off filters, after which the de-epoxidation state of xanthophyll cycle pigments, radiocarbon assimilation and photochemical quantum yield were measured. Exposures were repeated 4–8 times during the daily cycle to create exposure–response curves for each wavelength condition. UVR affected the three target processes significantly in both species and biological weights increased with decreasing wavelength, particularly in the UVBR region (280–315 nm). Minor wavelength dependency was observed between 315 and 360 nm. After BWF normalization to 300 nm, the LL cultures showed highly similar responses when comparing the three target processes, while the BWFs for the HL cultures differed significantly. The observed enhanced xanthophyll cycling activity in the UVR region implied that xanthophylls had an active role in diminishing UVR stress. However, this enhancement seems to be an indirect effect of damage within the dark reactions of photosynthesis. Hence, another vital target process further downstream in the photosynthetic process, possibly involved in the dark reactions, seems to be responsible for the high similarity in BWFs.     

Responses of Antarctic Iridaea cordata (Rhodophyta) tetraspores exposed to ultraviolet radiation

In Antarctica ozone depletion is highest during spring, coinciding with the reproduction of many seaweed species. Propagules are the life-stage of an alga most susceptible to environmental perturbations. Therefore, fertile thalli of Iridaea cordata (Turner) Bory (Rhodophyta) were collected in the eulittoral of King George Island (Antarctica) to examine spore susceptibility to ultraviolet radiation (UVR). In the laboratory, freshly released tetraspores were exposed to photosynthetically active radiation (PAR) (400–700 nm), PAR+UV-A (320–700 nm) or PAR+UV-A+UV-B (280–700 nm). Photosynthetic efficiency was measured during 1–8 h of exposure and after 48 h of recovery. Additionally, mycosporine-like amino acids (MAAs) and DNA damage were determined. Saturating irradiance of photosynthesis of freshly released tetraspores was 57 µmol photons m⁻² s⁻¹. Exposure to increasing fluence of PAR reduced photosynthetic efficiency. UVR further decreased the photosynthetic efficiencies of the tetraspores but spores were able to recover completely after UVR exposure and 2 days post-cultivation under low PAR. DNA damage was minimal and lesions were effectively repaired under photoreactivating light. Concentrations of the MAAs shinorine and palythine were higher in tetraspores treated with UVR than in spores only exposed to PAR. Generally, the tetraspores show a good UV tolerance. This flexible response of the tetraspores of this species to changing radiation conditions enables the alga to grow along a considerable depth gradient from the sublittoral to the eulittoral where they can be exposed to enhanced UVBR under conditions of stratospheric ozone depletion.     

Patch size and base composition of ultraviolet light-induced repair synthesis in toluenized Escherichia coli.

Small patch repair in ultraviolet-irradiated Escherichia coli is saturated at deoxyrmcleoside triphosphate concentrations (～ 2 μm of each dNTP) that are severely limiting for DNA replication. The low requirement of the repair process for dNTPs permits direct demonstration of u.v.-induced DNA synthesis by incorporation of labeled dNTP and determination of its extent, base composition and patch size.It is concluded that DNA polymeraso 1 is involved in small patch repair and that an average of 13 to 16 nucleotides are re-inserted per pyrimidine dimer excised. The average base composition of the repaired stretches adjacent to the dimers is similar to that of total E. coli DNA.An assay utilizing endogenous u.v.-specific endonuclease to determine dimer excision is described.     

Studies on the resistance/reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts exposed to medium-pressure ultraviolet radiation

The ex vivo and in vivo reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts after exposure to different doses of ultraviolet (UV) radiation was determined using animal infectivity. The infectivity of UV-treated parasites stored for 1-4 days (G. muris) or 1-17 days (C. parvum) at room temperature in the dark was similar to that of organisms administered immediately after UV treatment, indicating that the parasites did not reactivate ex vivo. In contrast, we observed in vivo reactivation of G. muris in three of seven independent animal infectivity experiments, when parasites were treated with relatively low doses of medium-pressure UV (<25 mJ/cm(2)). Our observations indicate that G. muris cysts and C. parvum oocysts exposed to medium-pressure UV doses of 60 mJ/cm(2) or higher did not exhibit resistance to and/or reactivation following treatment. This suggests that when appropriate doses of UV are used, significant and permanent inactivation of these parasites may be achieved.     

The effects of ultraviolet-B radiation on loblolly pine. I. Growth, photosynthesis and pigment production in greenhouse-grown seedlings

One-year old loblolly pine ( Pinus taeda L.) seedlings were grown in an unshaded greenhouse for 7 months under 4 levels of ultraviolet-B (UV-B) radiation simulating stratospheric ozone reductions of 16, 25 and 40% and included a control with no UV-B radiation. Periodic measurements were made of growth and gas exchange characteristics and needle chlorophyll and UV-B-absorbing-compound concentrations. The effectiveness of UV-B radiation on seedling growth and physiology varied with the UV-B irradiance level. Seedlings receiving the lowest supplemental UV-B irradiance showed reductions in growth and photosynthetic capacity after only 1 month of irradiation. These reductions persisted and resulted in lower biomass production, while no increases in UV-B-absorbing compounds in needles were observed. Seedlings receiving UV-B radiation which simulated a 25% stratospheric ozone reduction showed an increase in UV-B-absorbing-compound concentrations after 6 months, which paralleled a recovery in photosynthesis and growth after an initial decrease in these characteristics. The seedlings grown at the highest UV-B irradiance (40% stratospheric ozone reduction) showed a more rapid increase in the concentration of UV-B-absorbing compounds and no effects of UV-B radiation on growth or photosynthetic capacity until after 4 months at this irradiance. Changes in photosynthetic capacity were probably the result of direct effects on light-dependent processes, since no effects were observed on either needle chlorophyll concentrations or stomatal conductance. Further studies are necessary to determine whether these responses persist and accumulate over subsequent years.     

Relaxation of the non-photochemical chlorophyll fluorescence quenching in diatoms: kinetics,components and mechanisms

Diatoms are especially important microorganisms because they constitute the larger group of microalgae. To survive the constant variations of the light environment, diatoms have developed mechanisms aiming at the dissipation of excess energy, such as the xanthophyll cycle and the non-photochemical chlorophyll (Chl) fluorescence quenching. This contribution is dedicated to the relaxation of the latter process when the adverse conditions cease. An original nonlinear regression analysis of the relaxation of non-photochemical Chl fluorescence quenching, qN, in diatoms is presented. It was used to obtain experimental evidence for the existence of three time-resolved components in the diatom Phaeodactylum tricornutum: qNf, qNi and qNs. qNf (s time-scale) and qNs (h time-scale) are exponential in shape. By contrast, qNi (min time-scale) is of sigmoidal nature and is dominant among the three components. The application of metabolic inhibitors (dithiothreitol, ammonium chloride, cadmium and diphenyleneiodonium chloride) allowed the identification of the mechanisms on which each component mostly relies. qNi is linked to the relaxation of the ΔpH gradient and the reversal of the xanthophyll cycle. qNs quantifies the stage of photoinhibition caused by the high light exposure, qNf seems to reflect fast conformational changes within thylakoid membranes in the vicinity of the photosystem II complexes.     

Role of dissolved organic carbon in the attenuation of photosynthetically active and ultraviolet radiation in Adirondack lakes

1. We surveyed eighty-five lakes located in the Adirondack Mountain Region of New York State, U.S.A., to characterize the attenuation of photosynthetically active (PAR) and ultraviolet radiation (UVR) in relation to dissolved organic carbon (DOC) concentrations and pH. Attenuation of PAR was quantified in situ . Attenuation was also inferred by measuring the light absorption of filtered lake water samples at wavelengths (300, 340 and 440 nm) representing UV-B, UV-A and PAR.
2. Substantial variation in transparency was observed among lakes in this region. Attenuation depths ( z _1%) for PAR ranged from 0.5 to greater than 20 m, while inferred values for UV-B and UV-A ranged from a few centimetres to > 5 m. Median values of UV-A penetration (0.75 m) and UV-B penetration (0.45 m) corresponded to 11% (UV-A) and 6% (UV-B) of lake maximum depth.
3. Much of the variation in PAR and UVR attenuation was explained by differences in lake DOC. Univariate power models based solely on DOC accounted for 85% (PAR), 90% (UV-A) and 91% (UV-B) of the variation in absorption.
4. Attenuation and absorption coefficients were generally lower for recently acidified lakes compared to acidic and circumneutral lakes which have not undergone recent acidification. However, differences among these three groups of lakes were not statistically significant. Our results suggest that the effects of acidification on the optical properties of a regional population of lakes, even in an area experiencing widespread acidification, are relatively subtle in comparison with other factors contributing to inter-lake variability.
5. The presence of near-shore wetlands is probably a key factor influencing regional variability in DOC and light climate among Adirondack lakes. Temporal variability in climatic factors influencing wetland DOC production and export may mask more subtle influences on lake DOC associated with anthropogenic acidification.     

Susceptibility of spores of the microsporidian Nosema algerae to sunlight and germicidal ultraviolet radiation

Spores of the microsporidian Nosema algerae exposed to 1, 2, and 4 hr of sunlight and 121 μW/cm² of germicidal ultraviolet light were fed to first-instar Anopheles albimanus. Twenty days after feeding, the incidence and intensity of infection (spores/mosquito) were recorded from adult mosquitoes. While sunlight-treated spores showed no significant decline in incidence of infection after 1-, 2-, and 4-hr exposures, intensity of infection decreased significantly after the 2- and 4-hr exposures. Incidence of infection of mosquitoes fed bactericidal ultraviolet light-treated spores declined 48.2, 76.2, and 99.9% after 1-, 2-, and 8-min exposures, respectively. Measured by intensity of infection, activity of bactericidal light-treated spores decreased 87.2% after 1 min, 91.7% after 2 min, and 99.9% after 8 min. Levels of radiation required to inactivate spores of N. algerae fell within the range reported for other Microsporidia.     

Additional notes on requirements of captive whiptail lizards (Cnemidophorus), with emphasis on ultraviolet radiation

Since 1972 we have maintained a colony of parthenogenetic Cnemidophorus exsanguis, which has reached the seventh generation in our laboratory. This paper reports improved husbandry techniques that allow maintenance of healthy, reproducing colonies of this and additional species of Cnemidophorus. In addition, aspects of the physiology of calcium regulation and metabolic bone disease are discussed in relation to the captive rearing of lizards through many generations.     

Phenotypic persistence and external shielding ultraviolet radiation inactivation kinetic model

Aim: To develop an inactivation kinetic model to describe ultraviolet (UV) dose‐response behaviour for micro‐organisms that exhibit tailing using two commonly referenced causes for tailing: physical shielding of micro‐organisms and phenotypic persistence. Methods and Results: Dose‐response data for Escherichia coli, Mycobacterium terrae and Bacillus subtilis spores exposed to UV radiation were fit to the phenotypic persistence and external shielding (PPES) model. The fraction of persistent micro‐organisms in the original population (N_persistent/N_total) that exhibited reduced sensitivity to UV radiation was estimated by the PPES model as approx. 10^?7, 10^?5 and 10^?4 for E. coli, B. subtilis spores and Myco. terrae, respectively. Particle shielding effects were evaluated for Myco. terrae and resulted in additional reduction in UV sensitivity. Conclusions: Tailing occurred in laboratory experiments even when clumping and shielding were eliminated as major factors in UV resistance, suggesting that phenotypic persistence in addition to shielding may be important to consider when evaluating dose‐response curves for disinfection applications. Significance and Impact of the Study: The PPES model provides a mechanistically plausible tool for estimating the dose–response behaviour for micro‐organisms that exhibit tailing in dispersed and aggregated settings. Accurate dose‐response behaviour (including the tailing region) is critical to the analysis and validation of all UV disinfection systems.     

长波紫外线辐射对脊椎动物的影响

臭氧层空洞的加剧使紫外辐射不断加强,造成的环境污染已经成为广为关注的问题,但大多数都集中在中波紫外线(UVB)的生物学作用及其与两栖动物衰减关系的研究,有关长波紫外线(UVA)对生物体损伤作用的研究却甚少。本文综述了近年来UVA对脊椎动物损伤的研究概况,从细胞结构、酶活性、遗传物质、膜结构以及免疫系统等方面阐述了UVA的损伤机理,并对低剂量辐射诱导兴奋效应对紫外损伤的保护作用进行了简要概述。最后分析和总结了关于UVA损伤研究所存在的问题及两栖动物作为实验用动物模型在研究紫外线损伤中的作用。     

紫外辐射对水生生物的影响研究进展

紫外辐射对陆生植物的生物学效应已被广泛研究,对水生生物也能产生一系列影响。本文在综述国内外紫外线在水体中渗透状况及影响因素的基础上,阐述了紫外辐射对浮游细菌和微型浮游生物、浮游植物、浮游动物、大型藻类、鱼卵和幼鱼、鱼类及两栖动物的生物学效应,从直接效应和间接效应两方面介绍了紫外辐射对水生生物作用的机理。未来研究应该注重紫外辐射与气候变化、酸沉降、水污染等环境因子联合作用对水生有机体产生影响,其研究对象应扩展至沉水植物、底栖生物等大部分水生有机体,这些研究将对深入研究水生生态系统的演化、水生生态系统退化及其修复起重要作用。     

A morphological and cytological study of Petunia hybrida exposed to UV-B radiation

The aim of this study was to investigate whether the cytoskeleton, and in particular the microtubular system, is affected by enhanced levels of ultraviolet-B (280–320 nm, 9 kJ m⁻² day⁻¹ biologically effective UV-B radiation) radiation in epidermal cells of Petunia x hybrida Vilm, isolated from leaves of plants grown under UV-B radiation and visible light. In addition, morphological changes during development were monitored. In a previous study microtubules were depolymerized and delays in the different stages of the cell cycle were found when protoplasts of Petunia were irradiated with UV-B radiation (Staxén et al. 1993. Protoplasma 173: 70–76). Thus it was of interest to ascertain whether the cytoskeleton would be similarly affected in an intact system. Assuming an effect of UV-B radiation on the microtubular system, we wished to determine whether this could be correlated to concomitant changes in leaf morphology. Plants of Petunia hybrida were grown in greenhouse conditions in the presence or absence of UV-B radiation. During the course of the experiment, samples were taken from young, expanding leaves and from older, fully expanded leaves and prepared for localization and analysis of microtubules from the adaxial epidermal cells. Morphology rather than the cytoskeleton was affected by UV radiation, despite the fact that the epidermal cytoskeleton would most likely be affected, since it is located in the cells which form the first intercepting layer for incident radiation.
Morphological changes under UV-B radiation, as compared to those under control conditions, were reflected in earlier flowering and an increase in leaf number. Cell division was thus stimulated as was also evidenced from the increased leaf area. Our results indicate that the number of stomata differentiated on a leaf area basis was not altered although the number of stomata per epidermal cell was reduced.     

Cell line dependent involvement of ceramide in ultraviolet light-induced apoptosis

Ultraviolet light (UV) activates an acid sphingomyelinase (ASMase) pathway, which hydrolyzes sphingomyeline to ceramide. Ceramide has been found to be a second messenger, which activates the c-jun N-terminal kinase (JNK) that is required for apoptotic cell death. However, the role of ceramide in UV-induced JNK activation and apoptosis remains controversial. In this study, we examined the correlation among ceramide production, JNK activation and cell apoptosis after UV-irradiation in three cell lines: 293 (kidney), Jurkat (lymphocytes) and MCF-7 (breast) were used in this study. The ceramide production was analyzed using the diacylglycerol kinase assay method. The JNK activation was measured by Western blot analysis using an antibody specifically recognizing phosphorylated JNK. Cell apoptosis was determined by morphological change or flow cytometry. Our data show that UV-irradiation induces ceramide production in both 293 and Jurkat cells. Inhibition of ceramide production by desipramine (25–50 M) reduced UV-induced JNK activation in both 293 and Jurkat cells; and protects 293 cells from UV-induced apoptosis. However, inhibition of ceramide production does not prevent Jurkat cells from UV-induced apoptosis. In addition, our data demonstrates that UV-irradiation induces JNK activation and apoptosis of MCF-7 cells without production of detectable amounts of ceramide after UV-irradiation. These results suggest that UV-induced JNK activation and apoptosis can be mediated through a ceramide dependent or an independent pathway.     

Origin and evolution of the canal raphe system in diatoms

One lineage of pennate diatoms has a slit through the siliceous cell wall, called a "raphe," that functions in motility. Raphid pennate diatoms number in the perhaps tens of thousands of species, with the diversity of raphe forms potentially matching this number. Three lineages-the Bacillariales, Rhopalodiales, and Surirellales-possess a complex and presumably highly derived raphe that is physically separated from the cell interior, most often by a set of siliceous braces. Because the relationship among these three lineages is unclear, the number of origins of the canal raphe system and the homology of it and its constitutive parts among these lineages, is equally unclear. We reconstructed the phylogeny of raphid pennate diatoms and included, for the first time, members of all three canal raphid diatom lineages, and used the phylogeny to test specific hypotheses about the origin of the canal raphe. The canal raphe appears to have evolved twice, once in the common ancestor of Bacillariales and once in the common ancestor of Rhopalodiales and Surirellales, which form a monophyletic group in our analyses. These results recommend careful follow-up morphogenesis studies of the canal raphe in these two lineages to determine the underlying developmental basis for this remarkable case of parallel evolution.