Effects of solar UV radiation on morphology and photosynthesis of filamentous cyanobacterium Arthrospira platensis

To study the impact of solar UV radiation (UVR) (280 to 400 nm) on the filamentous cyanobacterium Arthrospira (Spirulina) platensis, we examined the morphological changes and photosynthetic performance using an indoor-grown strain (which had not been exposed to sunlight for decades) and an outdoor-grown strain (which had been grown under sunlight for decades) while they were cultured with three solar radiation treatments: PAB (photosynthetically active radiation [PAR] plus UVR; 280 to 700 nm), PA (PAR plus UV-A; 320 to 700 nm), and P (PAR only; 400 to 700 nm). Solar UVR broke the spiral filaments of A. platensis exposed to full solar radiation in short-term low-cell-density cultures. This breakage was observed after 2 h for the indoor strain but after 4 to 6 h for the outdoor strain. Filament breakage also occurred in the cultures exposed to PAR alone; however, the extent of breakage was less than that observed for filaments exposed to full solar radiation. The spiral filaments broke and compressed when high-cell-density cultures were exposed to full solar radiation during long-term experiments. When UV-B was screened off, the filaments initially broke, but they elongated and became loosely arranged later (i.e., there were fewer spirals per unit of filament length). When UVR was filtered out, the spiral structure hardly broke or became looser. Photosynthetic 0, evolution in the presence of UVR was significantly suppressed in the indoor strain compared to the outdoor strain. UVR-induced inhibition increased with exposure time, and it was significantly lower in the outdoor strain. The concentration of UV-absorbing compounds was low in both strains, and there was no significant change in the amount regardless of the radiation treatment, suggesting that these compounds were not effectively used as protection against solar UVR. Self-shading, on the other hand, produced by compression of the spirals over adaptive time scales, seems to play an important role in protecting this species against deleterious UVR. Our findings suggest that the increase in UV-B irradiance due to ozone depletion not only might affect photosynthesis but also might alter the morphological development of filamentous cyanobacteria during acclimation or over adaptive time scales.

荞麦(Fagopyrum tataricum Gaertn.和F. esculentum Moench.)对紫外线B辐射的响应研究

近二十多年来，基于对臭氧层衰减、紫外线B（UV-B）增强的担心，研究者希望了解到紫外线辐射对不同作物的影响情况，增强UV-B辐射条件下是否对作物的生长发育、产量质量构成威胁。在本试验中，我们首先探讨了双子叶作物黄瓜（Cucumis sativus）和大豆（Glycine max）对不同紫外波段的生物效应[分别为B-UVA（315-400 nm），N-UVA（315-340 nm），B-UVB（275-400 nm）和N-UVB（290-340 nm），UV-（>400nm）作对照]。我们观察到所有的UV波段处理都使黄瓜和大豆的生长受到抑制，并且细胞受到不同程度的氧化伤害；UV波段处理的作用效果与不同波段的紫外有效生物辐射剂量有关。处理差异在UV-B波段内部和UV-A波段内部同样存在。植物生长UV辐射公式（BSWF）能很好的预测本试验UV-B波段内的平均植物效应，但不能预测UV-A波段的植物效应。短波UV-A的生物作用强于长波UV-A。光合色素的变化与UV波谱差异和种间差异有关。在高的紫外/可见光背景下，UV-A处理同UV-B同样导致光合色素的降低，但黄瓜类胡萝卜素/叶绿素比例升高。与其他研究者的试验结果比较后，我们认为紫外线B辐射的生物效应一致性很高，但紫外线A波段的生物学效应存在较大争议。因此我们在本试验的基础上仅进行荞麦[苦荞(Fagopyrum tataricum Gaertn.)和甜荞(Fagopyrum esculentum Moench.)]对紫外线B波段的响应研究。 我们对苦荞品种-圆籽荞进行了连续两个生长季节的大田半控制试验以观察UV-B辐射对苦荞生长、发育、产量及叶片色素的影响；试验小区进行降低UV-B、近充足UV-B和增强UV-B辐射处理。我们的试验表明在不同强度UV-B辐射下苦荞的生长、地上部生物量积累及最终产量都有所下降，但苦荞的发育加快；当前条件下的日光紫外线B辐射对植物生长和产量也造成负面影响。植物光合色素被日光及增强UV-B辐射降低；UV化合物及卢丁含量在中低剂量的UV-B辐射强度下显著升高，但在高剂量的增强UV-B辐射下短期升高后迅速下降。我们的试验表明苦荞是一个对UV-B高度敏感的作物。苦荞对UV-B的敏感性与UV-B剂量、外界环境因素及生长季节有关。 单个苦荞品种的试验结果使我们认识到外界UV-B辐射已经对苦荞生长发育构成逆境条件，未来全球气候变化条件下增强紫外线B辐射可能使其处于更不利的生长环境中。因此我们有进行了多个种群进行UV-B响应观察并筛选耐性种群。我们对15个苦荞种群进行增强UV-B辐射处理（6.30 kJ m2 UV-BBE，模拟当地25%的臭氧衰减），我们观察苦荞UV-B辐射效应存在显著的种内差异，UV-B辐射对多数种群具有抑制作用，但对一些种群还有刺激作用。我们采用主成分分析方法与作物UV-B响应指数（RI）来评价苦荞作物UV-B辐射耐性。我们发现作物的UV-B耐性不仅与其原产地背景UV-B强度有关，而且与作物相对生长效率、次生代谢产物含量（如卢丁）及其他因素有关。我们观察到苦荞伸展叶总叶绿素变化与UV-B耐性成正相关；室内苦荞幼苗的UV-B辐射致死试验表明：苦荞种群死亡率与其UV-B耐性成负相关。 此外，我们对甜荞的UV-B辐射响应也进行了初步研究。选取美姑甜荞、巧家甜荞和云龙甜荞进行5个梯度的增强UV-B辐射室外模拟试验。我们观察到UV-B辐射显著降低了甜荞的生长、生物量及产量；并严重影响了甜荞的生殖生长，降低了花序数、种子数和结实率；并且UV-B辐射对甜荞的抑制作用存在显著的剂量效应。三种甜荞品种存在显著的种内差异，其中美姑品种UV-B耐性最强，且膜脂受UV-B辐射氧化伤害最小，这与该品种UV-B辐射下较高的GR酶活性、APX酶活性和PPO酶活性、以及含量更高的抗坏血酸有关。甜荞的次生代谢也受到增强UV-B辐射的影响，其香豆酰类化合物在UV-B辐射下升高显著，而槲皮素含量也在高剂量UV-B辐射下有所增加；卢丁含量依赖UV-B辐射剂量而变化，中低剂量UV-B辐射下其卢丁含量逐渐升高，但在高剂量辐射下逐渐下降。 通过对生长在高海拔地区的荞麦作物(苦荞和甜荞)进行的室外研究，我们认识到作物不同品种存在很大的耐性差异，这就为UV-B耐性育种创造了有利条件。进一步加大荞麦种质资源筛选力度并深入认识荞麦抗性机理，在此基础上通过杂交或其他基因融合手段培育抗性品种，对高剂量UV-B辐射地区的荞麦产量的提高将起到重要推动作用，并使荞麦生产能有效应对未来全球气候变化条件下UV-B辐射可能升高的威胁。 During last few decades, due to concern of ozone layer depletion and enhancement of ultraviolet B radiation（UV-B, 280-315 nm), the agronomist want to know the responses of different crop species to UV-B. In the first experiment of our study, the effect of different UV band [B-UVA（315-400 nm), N-UVA（315-340 nm), B-UVB（275-400 nm), N-UVB（290-340 nm）and UV-（>400nm, as control)] on the cucumber（Cucumis sativus）and soybean（Glycine max）were investigated in growth room. Spectra-dependent differences in growth and oxidation indices existed within UV-A bands as well as UV-B bands. The general biological effects of different band were UV- ＜ B-UVA＜ N-UVA＜N-UVB＜B-UVB. The plant growth biologically spectra weighting function（BSWF）matched well with average plant response in UV-B region, but not in UV-A region. Shorter UV-A wavelength imposed more negative impact than longer UV-A wavelength did in both species. The effect on photosynthetic pigment was related to different UV bands and different species. The photosynthetic pigment content was decreased by UV-A spectra as well as UV-B spectra. In comparison with the results of previous studies, we found that the wavelength-dependent biological effect of ultraviolet B radiation has high consistency, but the biological effect of ultraviolet-A radiation was inconsistent. We narrow our following study on the effect of ultraviolet B radiation on the buckwheat（tartary buckwheat and common buckwheat). The tartary buckwheat（Fagopyrum tataricum Gaertn.）cultivars Yuanziqiao was grown in the sheltered field plots for two consecutive seasons under reduced, near-ambient and two supplemental levels of UV-B radiation. The crop growth, photosynthetic pigments, total biomass, final seed yield and thousand-grain weight were decreased by near-ambient and enhanced UV-B radiation, while crop development was promoted by enhanced UV-B radiation. Leaf rutin concentration and UV-B absorbing compound was generally increased by UV-B with the exception of 8.50 kJ m-2 day-1 supplemental levels. Our results showed that tartary buckwheat is a potentially UV-B sensitive species. Study on one cultivars showed that ambient solar radiation had present a stress to tartary buckwheat. This makes it necessary to observe the UV-B response of many cultivars and screen tolerant cultivars. Fifteen populations of tartary buckwheat were experienced enhanced UV-B radiation simulating 25% depletion of the stratospheric ozone layer in Kunming region, and plant responses in growth, morphology and productivity were observed. Principal components analysis（PCA）was used to evaluate overall sensitivity of plant response to UV-B as well as response index. The different populations exhibited significant differences in responses to UV-B. The photosynthetic pigments of young seedlings were also affected significantly under field condition. On the other hand, the healthy seedlings of different populations were exposed to the high level of UV-B radiation in growth chambers to determine the plant lethality rate. The plant tolerance evaluated by multivariate analysis was positively related to total plant chlorophyll change, but negatively related to lethality rate. In other hand, the UV-B responses of the other important cultivated buckwheat species, common buckwheat（Fagopyrum esculentum Moench.), were also studied preliminarily. Three widespread cultivated variety（Meigu, Qiaojia and Yunlong cultivars）were provided with five level of enhanced UV-B radiation outdoors. We observed that the crop growth, development and production were significantly decreased, and reproductive production, like anthotaxy number, seed number and seed setting ratio, was also decreased. Dose-dependent inhibition effect caused by enhanced UV-B radiation also existed in common buckwheat. Significant intraspecific difference existed in those three cultivars. The Meigu cultivars with dwarfed growth and lower production have highest UV-B tolerance as well as lowest damage in cell membrane, this could be associated with profound enhancements of glutathione reductase（GR）activity, ascorbate peroxidase activity and polyphenol oxidase activity as well as higher ascorbic acid concentration. The secondary metabolism was also affected by UV-B radiation, with profound elevation of coumarin compound and moderate increase of quercetin concentration. Rutin concentration was peaked in 5kJ m-2 UV-B. The contrasting effect of UV-B radiation on different populations indicated that there existed abundant genetic resources for selecting tolerant populations of common and tartary buckwheat. Much effort needed be pose on screening of buckwheat germplasm and clarification of mechanism of buckwheat tolerance to UV-B. On this base the tolerant cultivars could be bred by hybridization and other gene transfusion method, this would help increase buckwheat yield in high ambient UV-B region and counteract the effect of possible enhanced UV-B radiation in future.

沙棘(Hippophae rhamnoides L.)在低温和增强UV-B胁迫下的生态生理反应

植物生长和生产力受到自然界各种形式的生物和非生物胁迫因子的影响。这些胁迫包括低温、高温、盐碱、干旱、洪水、重金属、虫害、病害和紫外线辐射等等。而人类活动大大加剧了这些胁迫所带来的影响。由于人类污染而导致臭氧层衰减以及由此产生的地球表面紫外辐射增强已经成为全球气候变化的一个主要方面。UV-B胁迫，甚至当前的辐射水平，所带来的影响已经引起科学工作者的广泛关注。 为了生存和繁殖，植物不得不面临环境中各种潜在胁迫所带来的负面影响。然而，植物生活型的不可移动性决定了其逃避胁迫的局限性。因此，绝大多数植物都是通过对胁迫作出反应，通过修复或者更新组织来降低伤害。而植物应对环境变化的能力则是由其生长模式的种属特异性和本身的遗传组成所决定。在自然界，植物常常同时面临多种胁迫，这些胁迫所引发的植物反应可能具有叠加、协同或者拮抗作用。沙棘是一种具刺、具有固氮功能的多年生雌雄异株灌木，广泛分布于亚欧大陆的温带地区和亚洲亚热带的高海拔地区。在中国，沙棘常常被用作植被恢复中的先锋树种而大量栽培。本文采用沙棘作为模式植物，试图探索木本植物对低温，UV-B辐射增强以及其与干旱的复合胁迫的响应以及沙棘对这些胁迫响应是否具有种群差异性。 对来自南北两个种群的沙棘进行短日照和低温处理，检测了其在抗寒锻炼和抗寒性发育过程中存在的性别差异。结果表明，短日照和低温都分别能够诱导抗寒锻炼的发生，而两者同时存在对所有实验植株抗寒性的大小具有叠加效应。然而，短日照和低温所诱导的抗寒性在两个种群中都具有性别差异性，雄性植株比雌雄植株对短日照和低温更为敏感。同时，南北种群间也存在差异性，北方种群的植物比南方种群的植物对短日照和低温敏感，从而在短日照下抗寒锻炼的发生时间更早，低温诱导的抗寒性更大。短日照和低温诱导植物增加抗寒性的同时伴随着脱落酸的变化。脱落酸的变化因处理，种群和性别的不同而不同。这些生理反应表明不同的沙棘种群，不同的植株性别对同一环境胁迫可能存在不同的生存策略。 比较了来自高低两个海拔的沙棘种群对于干旱和UV-B辐射增强以及两者复合胁迫条件下的生理生态反应。干旱使两个种群中植株总的生物量，总叶面积，比叶面积，叶片含碳量，含磷量，木质素含量和碳氮比显著降低，使根冠比，粗根细根比和叶片脱落酸含量显著增加。干旱而非UV-B使得δ13C 值显著增加。但是，比较而言，来自高海拔的种群对干旱反应更为强烈，而来自低海拔的种群对UV-B更敏感。在UV-B辐射增强的处理下，干旱所诱导的脱落酸的积累被显著抑制。而且我们检测到在一些指标上存在显著的干旱×UV-B交互作用，如两个种群中在总生物量上，低海拔种群中在总叶面积，粗根细根比上，高海拔种群中在比叶面积，δ13C值，木质素含量上都存在明显的交互作用。这些结果表明这两个种群对胁迫具有不同的适应性反应，来自高海拔的种群比来自低海拔的种群更能够抵御干旱和UV-B胁迫。 室外实验表明，UV-B 去除/增补对沙棘高低两个海拔种群的影响都不大。对生物量的积累，植株高度以及一些常见的胁迫反应生理指标比如丙二醛、ABA 和游离脯氨酸都没有显著影响。UV-B 的效应比UV-A 大，植物反应在无UV 和仅有UV-A 的处理间没有什么区别。然而，UV-B 去除的两个处理和UV-B 存在的两个处理间存在显著区别。UV-B 使得两个种群都显著降低了比叶面积(SLA)，但却使长期用水效率增加。但UV-B对光合色素和光合系统II 的影响不大。总体看来，来自低海拔的种群对UV-B 更为敏感。 Plant is adversely affected by various abiotic and biotic stress factors. These stressors includelow temperature, heat, salt, drought, flooding, heavy metal toxicity, wounding by herbivores,infecting by pathogenic microorganisms, ultraviolet (UV) radiation and so on. Variousanthropogenic activities have accentuated the existing stress factors. One of the mostimportant aspects of global change is that of stratospheric ozone depletion caused by seriousanthropogenic pollution and the resulting increase in UV radiation reaching the surface of theEarth. Scientists have become concerned about the effects that considerable UV-B stress, evenat current levels. In order to survive and reproduce, plants have to be able to cope with lots of potentiallyharmful stress factors that are almost constantly present in their environment. Most plants’responses under stress are to neutralize the stress, repairing the damage or regrowing newtissue rather than to avoid it due to their sessile life style. The plant defense capacity dependson plant-specific modular growth patterns and genetic make-up that allows for flexibleresponses to changing environments. Plants usually encounter several stresses simultaneouslyunder field conditions, and the stresses may cause a variety of plant responses, which can beadditive, synergistic or antagonistic. Sea buckthorn (Hippophae rhamnoides L.), a thorny nitrogen fixing deciduously perennialshrub, which is widely distributed throughout the temperate zones of Asia and Europe and thesubtropical zones of Asia at high altitudes. It has been widely used in forest restoration as thepioneer species in China. In this paper, we used sea buckthorn as a model, tried to get some understand of how plants fight low temperature, enhanced UV-B radiation level and thatcombination of drought. And also, want to know whether does there exist some populationspecific responses to such stressors. Sexual differences in cold acclimation and freezing tolerance development of two contrastingsea buckthorn (Hippophae rhamnoides L.) ecotypes from northern and southern regions inChina were recorded after exposure to short day photoperiod (SD) and low temperature (LT).The results demonstrated that cold acclimation could be triggered by exposing the plants toSD or LT alone, and that a combination of both treatments had an additive effect on freezingtolerance in all plants tested. However, development of freezing tolerance was dependent onthe sex of plants under SD and LT, the males were clearly more responsive to SD and LT thanthe females in both ecotypes studied. On the other hand, development of freezing tolerancewas also ecotype-dependent, the northern ecotype was more responsive to SD and LT than thesouthern ecotype, resulting in earlier cold acclimation under SD and higher freezing toleranceunder LT. Moreover, development of freezing tolerance induced by SD and LT wasaccompanied by changes in ABA levels. These alterations in ABA levels were different indifferent treatments, ecotypes and sexes. Therefore, the differences in SD and LT-inducedphysiological responses showed that the different ecotypes and the different sexes mightemploy different survival strategies under environmental stress. Two contrasting populations from the low and high altitudinal regions were employed toinvestigate the effects of drought, UV-B and their combination on sea buckthorn. Droughtsignificantly decreased total biomass, total leaf area, specific leaf area，leaf carbon (C),phophous (P), lignin content and the ratio of C: N in both populations, and increasedroot/shoot ratio, fine root/coarse root ratio and abscisic acid content (ABA), in bothpopulations. Drought but not UV-B resulted in significantly greater carbon isotopecomposition (δ13C) values in both populations. However, the high altitudinal population wasmore responsive to drought than the low altitudinal population. The drought-inducedenhancement of ABA in the high altitudinal population was significantly suppressed in thecombination of drought and elevated UV-B. Moreover, significant drought × UV-B interactionwas detected on total biomass in both populations, total leaf area and fine root/coarse root inthe low altitudinal population, specific leaf area, δ13C value and leaf lignin content in the high altitudinal population. These results demonstrated that there were different adaptive responsesbetween two contrasting populations, the high altitudinal population exhibited highertolerance to drought and UV-B than the low altitudinal population. A field experiment was conducted to investigate effects of UV-B exclusion/supplementationon two altitudinal populations of sea buckthorn. UV-B exclusion or supplementation had littleeffects on both populations investigated. For instance, the total biomass, plant height andsome physiological index such as Malondialdehyde (MDA), ABA and free proline were notchanged significantly. The UV-B effects are more significant than that of UV-A, nodifferences were found between treatments of excluded UV and excluded UV-B. However,compared with treatments of UV-B exclusion (including absent of UV-B and all UV band),the present of UV-B (including near ambient environment and enhanced UV-B) significantdecreased specific leaf area, and increased long time water use efficiency as evaluated by δ13Cvalue. UV-B had little effects on photosynthetic pigments and Photosystem II (PSII). The lowaltitude population is more sensitive to UV-B than that of the high altitude population.

Influence of low doses microwave radiation on activities of antioxidative enzymes of Isatis indigotica seedlings exposed to enhanced UV-B radiation

IEECAS SKLLQG

A narrow-band ultraviolet B course improves vitamin D balance and alters cutaneous CYP27A1 and CYP27B1 mRNA expression levels in haemodialysis patients supplemented with oral vitamin D

Background: Chronic kidney disease (CKD) patients on dialysis are prone to vitamin D insufficiency despite oral vitamin D supplementation. Here, we studied whether narrow-band ultraviolet B (NB-UVB) exposures improve vitamin D balance.<br/><br/>Methods: 14 haemodialysis patients and 15 healthy subjects receiving oral cholecalciferol 20 µg daily got nine NB-UVB exposures on the entire body. Serum 25-hydroxyvitamin D (25(OH)D) was measured by radioimmunoassay. Cutaneous mRNA expression levels of CYP27A1 and CYP27B1, two enzymes required for hydroxylation of vitamin D into its active metabolite, were also measured. <br/><br/>Results: The baseline serum 25(OH)D concentration was 57.6 ± 18.2 nmol/l in the CKD patients and 74.3 ± 14.8 nmol/l in the healthy subjects. The NB-UVB course increased serum 25(OH)D by 14.0 nmol/l (95% CI 8.7-19.5) and 17.0 nmol/l (CI 13.7-20.2), respectively. At baseline the CKD patients showed significantly increased CYP27B1 levels compared to the healthy subjects. <br/><br/>Conclusions: A short NB-UVB course is an efficient way to improve vitamin D balance in CKD patients on dialysis who are receiving oral vitamin D supplementation. The increased cutaneous CYP27B1 levels in the CKD patients suggest that the loss of renal activity of this enzyme is at least partially compensated for by the skin.<br/>

Narrow-band ultraviolet B treatment boosts serum 25-hydroxyvitamin D in patients with psoriasis on oral vitamin D supplementation

A course of treatment with narrow-band ultraviolet B (NB-UVB) improves psoriasis and increases serum 25-hydroxyvitamin D (25(OH)D). In this study 12 patients with psoriasis who were supplemented with oral cholecalciferol, 20 µg daily, were given a course of NB-UVB and their response measured. At baseline, serum 25(OH)D was 74.14 ± 22.9 nmol/l. At the 9th exposure to NB-UVB 25(OH)D had increased by 13.2 nmol/l (95% confidence interval (95% CI) 7.2–18.4) and at the 18th exposure by 49.4 nmol/l (95% CI 35.9–64.6) above baseline. Psoriasis Area Severity Index score improved from 8.7 ± 3.5 to 4.5 ± 2.0 (p < 0.001). At baseline, psoriasis lesions showed low vitamin D metabolizing enzyme (CYP27A1, CYP27B1) and high human β-defensin-2 mRNA expression levels compared with those of the healthy subjects. In conclusion, NB-UVB treatment significantly increases serum 25(OH)D in patients with psoriasis who are taking oral vitamin D supplementation, and the concentrations remain far from the toxicity level. Healing psoriasis lesions show similar mRNA expression of vitamin D metabolizing enzymes, but higher antimicrobial peptide levels than NB-UVB-treated skin in healthy subjects.

Narrow-band ultraviolet B exposure increases serum vitamin D levels in haemodialysis patients

Chronic kidney disease (CKD) patients are especially prone to vitamin D insufficiency. Narrow-band ultraviolet B (NB-UVB) treatment increases serum 25-hydroxyvitamin D [25(OH)D] in dermatological patients, and we studied whether it also improves vitamin D balance in CKD patients on haemodialysis.

Influence of ultraviolet-B irradiation on engraftment, graft-versus-host disease and graft-versus-leukemia effect in a rat model for allogeneic bone marrow transplantation

Ultraviolet-B (UVB) irradiation is known to inhibit lymphocyte activity and consequently to reduce the incidence of graft-versus-host disease (GVHD) in experimental models for allogeneic bone marrow transplantation (BMT). GVHD is frequently associated with morbidity and mortality, but also with the beneficial graft-versus-leukemia (GVL) effect, demonstrated by a reduction in the incidence of leukemia relapse. In this study, we investigated whether UVB treatment of allogeneic T cells could prevent GVHD while sparing the beneficial GVL effect following allogeneic BMT in the Brown Norway myelocytic leukemia (BNML) rat model analogous to human acute myelocytic leukemia (AML). The dose of UVB required to abolish lethal GVHD in the rat allogeneic BMT model (WAG/Rij donors into BN recipients) was 4000 J/m2. However, this UVB dose simultaneously abrogated all GVL activity mediated by the T cells in the graft, while the radio-protective capacity of rat BM cells was strongly reduced. The number of allogeneic BM cells required to protect lethally irradiated BN rats was increased 50 to 100-fold. It is concluded that UVB acts as a non-selective form of T cell inactivation, and that UVB pretreatment of an allogeneic marrow graft is unlikely to be useful clinically as a preventive measure for GVHD, since other means of reduction of the number of functional T cells are less damaging to bone marrow stem cells.

Effect of ultraviolet-B light on lymphocyte activity at doses at which normal bone marrow stem cells are preserved

Ultraviolet B (UVB) light is known to be immunosuppressive, but, probably because of a small UVC component in the emission spectra of some of the UVB lamps used, reports vary on effective dose levels. To prevent potentially lethal graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation, alloreactive donor T-cell activity must be suppressed. In this study, a narrow wavelength UVB lamp (TL01, 312 nm peak emission) was used to determine what doses of UVB were required to abolish rat lymphocyte proliferation while simultaneously preserving rat bone marrow progenitor cell and primitive hematopoietic stem cell viability. Lymphocyte proliferation, as measured by 3H-Thymidine incorporation, in response to lectin stimulation was abolished below detection at doses greater than 3,500 J/m2. When T-cell clonogenicity was measured in a limiting dilution assay, a small fraction (0.6%) was maintained at doses up to 4,000 J/m2. Cytotoxic T-lymphocyte (CTL) activity was reduced after treatment with 4,000 J/m2, but a significant level of cytotoxicity was still maintained. Natural killer cell cytolytic activity was not affected by doses up to 4,000 J/m2. At 4,000 J+m2 there was a 10% survival of colony-forming units-granulocyte-macrophage; a 1% and 4% survival of day-8 and day-12 colony-forming units-spleen, respectively; and 11% survival of marrow repopulating ability cells. Up to 25% of late cobblestone area forming cells (4 to 5 weeks), reflecting the more immature hematopoietic stem cells, were preserved in bone marrow treated with 4,000 J/m2, indicating that early stem cells are less sensitive to UVB damage than are more committed progenitor cells. Thus, a potential therapeutic window was established at approximately 4,000 J/m2 using this light source, whereby the potentially GVHD-inducing T cells were suppressed, but a sufficient proportion of the cells responsible for engraftment was maintained.

Inhibition of 125I-epidermal growth factor binding to murine fibroblasts and keratinocytes by irradiation with ultraviolet-B light

Treatment of murine Swiss 3T3 fibroblasts and XB/2 keratinocytes with UV-B light (302 nm) resulted in a dose-dependent inhibition of [125I] epidermal growth factor (EGF) binding. The light dose required to achieve 50% inhibition of binding in both cell types was 80–85 J/m2 Decreased [125I] platelet-derived growth factor binding was not evoked even by light doses of up to 280 J/m2 UV-B irradiation did not stimultate phosphorylation of the 80 kd protein substrate for protein kinase C. Furthermore, its effect on [125I]EGF binding was not altered as a consequence of protein kinase C down-regulation following prolonged exposure of cells to phorbol esters. These results indicate that UV-B-induced transmodulation of the epidermal growth factor receptor is a specific event mediated through a protein kinase C-indepen dent pathway. Transfer of culture medium from irradiated cells to untreated control cells showed this effect was not induced as a result of transforming growth factor α release and subsequent binding to the EGF receptor in these cells.