衣藻细胞的重金属结合特性及其抗性机制

衣藻(Chlamydomonas)是隶属于绿藻门团藻目衣藻属的单细胞真核藻类。因其独特的结构与功能特性,衣藻具有高效的重金属结合能力,同时也表现出很高重金属抗性。目前利用衣藻去除工业污水中有害重金属,以及开展生物冶金等方面的研究已成为热点。文章对衣藻细胞的重金属结合特性,及其耐受重金属胁迫的抗性机制进行了深入地探讨和总结。主要内容包括:衣藻吸附重金属的动力学特征、影响吸附效率的因素、固定化衣藻对重金属的吸附与解吸附,衣藻细胞内的重金属结合因子、重金属转运蛋白等。     

Djungarian hamsters (Phodopus sungorus) are not susceptible to stimulating effects of 6-methoxy-2-benzoxazolinone on reproductive organs

The secondary plant metabolite 6-methoxy-2-benzoxazolinone (6-MBOA) is abundant in vegetative parts of monocotyledons emerging in spring. This grazing protective has been shown to promote gonadal growth and, thus enable precise alignment of reproductive activity with favorable environmental conditions in a variety of seasonally breeding rodent species. Feeding and breeding ecology make the Djungarian hamster (Phodopus sungorus) a potential candidate using 6-MBOA as an acute environmental cue to optimize reproductive timing when photorefractoriness induces reproductive recrudescence. Therefore, four different experiments were designed to examine whether the hamsters’ reproductive organs are responsive to oral 6-MBOA administration under different photoperiodic conditions. Only under a long photoperiod, we found a slight increase in uterine weights. In a short photoperiod, 6-MBOA-treated hamsters showed a slight body weight gain without a change in uterine weights. However, these marginal effects are likely not to be of ecophysiological significance for reproductive timing. The results are in agreement with the common view that the annual changes in photoperiod length are not only the predominant environmental cue for Djungarian hamsters, but are also sufficient to synchronize reproductive efforts with favorable breeding conditions in highly predictable climates like the continental Asian steppes.     

Circannuale Rhythmen bei Tieren und ihre photoperiodische Synchronisation

During the last years, evidence has been accumulated indicating that the annual cycles of physiological and behavioral functions in animals are often preprogrammed as endogenous circannual rhythms. Under seasonally constant environmental conditions these rhythms persist for several cycles with periods deviating from year, whereas under natural conditions they are usually synchronized by seasonal changes in the environment, particularly that of photoperiod. Hence, the annual rhythm of photoperiod constitutes a Zeitgeber for the endogenous rhythmicity rather than providing causal stimuli that release particular activities at particular times of the year. On the basis of this new concept several peculiarities of annual biological rhythms under the influence of photoperiodic cycles with different properties can be better understood, at least at a formal level.     

A novel function for the pineal organ in the control of swim depth in the Atlantic halibut larva

The pineal organ of vertebrates is a photo-sensitive structure that conveys photoperiod information to the brain. This information influences circadian rhythm and related metabolic processes such as thermoregulation, hatching time, body growth, and the timing of reproduction. This study demonstrates extra-ocular light responses that control swim depth in the larva of the Atlantic halibut, Hyppoglosus hyppoglosus. Young larvae without a functional eye (<29 days) swim upwards after an average delay of 5 s following the onset of a downwelling light stimulus, but sink downwards a few seconds later. Older larvae (₉ days), which possess a functional eye, swim immediately downwards (microsecond delay) following the onset of the light stimulus, but proceed to swim upwards several seconds later. These two response patterns are thus opposite in polarity and have different time kinetics. Because the pineal organ of the Atlantic halibut develops during the embryonic stage, and because it is the only centre in the brain that expresses functional visual pigments (opsins) at early larval stages, it is the only photosensory organ capable of generating the extra-ocular responses observed.     

Fungal spore germination into yeast or mycelium: possible implications of dimorphism in evolution and human pathogenesis

 The ability of dimorphism in fungi is conventionally regarded as a reversible change between the two vegetative forms, yeast and mycelium, in response to environmental change. A zygomycetous isolate, Benjaminiella poitrasii, exhibited yeast-mycelium transition in response to the change in temperature (37–28  °C) and decrease in glucose concentration. For the first time the presence of dimorphic response during asexual and sexual spore germination is reported under the dimorphism-triggering conditions in B. poitrasii. The zygospores germinated into budding yeast when subjected to yeast-form supporting conditions. The mycelium-form favoring conditions gave rise to true mycelium. Similarly, the asexual spores displayed a dimorphic response during germination. Our observations suggest that dimorphism is an intrinsic ability present in the vegetative, asexual, and sexual forms of the fungus. As dimorphic fungi are intermediate to the unicellular yeast and the filamentous forms, understanding of the dimorphic character could be useful to trace the evolutionary relationships among taxonomically different fungi. Moreover, the implications of spore germination during the onset of pathogenesis and in drug development for human health care are discussed. Received: 4 November 1999 / Accepted in revised form: 28 February 2000     

Caste-fate determination primarily occurs after adult emergence in a primitively eusocial paper wasp: significance of the photoperiod during the adult stage

Independent-founding paper wasps constitute a major group of primitively eusocial insects, and when caste-fate determination occurs in temperate species of these wasps, particularly regarding whether it occurs before or after emergence, remains unclear. No critical morphological differences occur between potential queens of the next generation (often called gynes) and workers in primitively eusocial insects. The gynes of temperate species are characterized by diapausing, and the nutrients available during the larval stage have often been believed to determine caste fate. Short days usually induce diapause in temperate nonsocial insects, although few investigations of the effects of day length on caste-fate determination in paper wasps have been conducted. By exposing individuals to different combinations of short and long days during the immature and adult stages, we show for the first time that short days during the adult stage (but not during the immature stage) facilitated caste-fate determination toward gynes in a paper wasp. Moreover, the decision to diapause partly depended on changes in the photoperiod during the pupal and adult stages. The size of the adult also affected caste-fate determination, with diapause more likely to occur in large adults, but this size effect did not occur when individuals were exposed to many short days during the pupal stage. In addition, all adults except for a small proportion of smaller individuals prepared for diapause under short days. These findings suggest that the photoperiod is a higher priority cue than adult size.     

藻类对造纸废水中COD的去除效率研究

实验比较了绿藻(栅藻、小球衣藻、莱因衣藻、普通小球藻、蛋白核小球藻、实球藻、空球藻),硅藻(小环藻、舟型藻),中型裸藻,纤细裸藻,牟氏角毛藻(海洋硅藻)对造纸废水COD的去除能力。结果表明,硅藻中的舟形藻和小环藻对造纸废水COD的去除效率最高,培养18d后,其去除率分别达到87.09%和88.18%。此外,还研究了不同初始藻浓度对COD去除率的影响,发现初始藻浓度为106cells/mL的去除率最佳,上述结果为进一步研究造纸废水的藻类处理工艺奠定了基础。     

Photoperiod affects daily torpor and tissue fatty acid composition in deer mice

Photoperiod and dietary lipids both influence thermal physiology and the pattern of torpor of heterothermic mammals. The aim of the present study was to test the hypothesis that photoperiod-induced physiological changes are linked to differences in tissue fatty acid composition of deer mice, Peromyscus maniculatus (∼18-g body mass). Deer mice were acclimated for >8 weeks to one of three photoperiods (LD, light/dark): LD 8:16 (short photoperiod), LD 12:12 (equinox photoperiod), and LD 16:8 (long photoperiod). Deer mice under short and equinox photoperiods showed a greater occurrence of torpor than those under long photoperiods (71, 70, and 14%, respectively). The duration of torpor bouts was longest in deer mice under short photoperiod (9.3 ± 2.6 h), intermediate under equinox photoperiod (5.1 ± 0.3 h), and shortest under long photoperiod (3.7 ± 0.6 h). Physiological differences in torpor use were associated with significant alterations of fatty acid composition in ∼50% of the major fatty acids from leg muscle total lipids, whereas white adipose tissue fatty acid composition showed fewer changes. Our results provide the first evidence that physiological changes due to photoperiod exposure do result in changes in lipid composition in the muscle tissue of deer mice and suggest that these may play a role in survival of low body temperature and metabolic rate during torpor, thus, enhancing favourable energy balance over the course of the winter.     

气温和土壤湿度变化对3种典型荒漠植物种子发芽的影响

植物种子发芽对气温和土壤湿度变化的响应是气候变化对荒漠生态系统影响的关键. 为了分析荒漠植物种子发芽对气温和土壤湿度变化的响应趋势,选择典型荒漠植物沙拐枣(Calligonum mongolica)、泡泡刺(Nitraria sphaerocarpa)和麻黄(Ephedra przewalskii),在人工气候箱中分析在3种土壤湿度(3%,5%和15%),2种气温(16 ℃/22 ℃ 和21 ℃/27 ℃)和浸种(12 h)与不浸种处理下种子的发芽趋势. 结果显示:沙拐枣和泡泡刺种子的发芽率随土壤湿度的增加而增加,浸种下随气温的升高其发芽率增幅比不浸种下大;不浸种下气温升高麻黄种子发芽率增幅比不浸种下大,浸种下土壤湿度为3%时气温升高其发芽率增幅比土壤湿度为5%和15%时大(P<0.05). 3种植物种子发芽指数随气温的升高和土壤湿度的增加而增加,不浸种下气温升高沙拐枣和泡泡刺种子的发芽指数显著增加,浸种下其发芽指数增幅不大;不浸种下气温升高麻黄种子发芽指数增幅较小,浸种下其发芽指数增幅较大. 3种植物种子均在培养初期发芽速率增加较快. 荒漠植物种子发芽受气温和土壤湿度的共同影响,不同植物种子发芽对这些因素的变化有不同的响应.      

典型锥形结构两点响应控制试验研究

目的研究小长径比结构进行两点振动响应控制时的可行性,提升地面振动模拟真实性。方法针对一长径比约3:1的短圆锥结构,首先以圆锥表面气动载荷为振动输入载荷,通过数值仿真获得结构在自由状态下内部两点的加速度功率谱密度曲线,再采用激励杆和激励板的形式进行两点激励加载,控制要求的两点加速度响应。将真实响应的控制结果与常用梯形谱的控制结果进行对比,分析控制的有效性及结果的合理性。结果通过对比不同的两点激励加载部位,发现振动控制效果会存在明显差异,以仿真的结构响应作为振动控制谱,具有良好的振动控制效果,实际控制的功率谱密度曲线只在局部"谷"的地方和低频段出现超差,实际均方根值与要求均方根值差异较小。结论以仿真得到的结构内部响应作为振动控制谱,可以提高结构地面振动考核的真实性。当振动激励部位选择合适时,对于小长径比结构,也可以得到良好的控制效果。     

Characterization of arsenate transformation and identification of arsenate reductase in a green alga Chlamydomonas reinhardtii

Arsenic (As) is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide. Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in freshwater aquatic systems. Arsenic metabolism processes of this alga through arsenate reduction and sequent store and efflux were investigated. When supplied with 10 mol/L arsenate, arsenic speciation analysis showed that arsenite concentration increased from 5.7 to 15.7 mg/kg dry weight during a 7-day period, accounting for 18%–24% of the total As in alga. When treated with different levels of arsenate (10, 20, 30, 40, 50 mol/L) for 7 days, the arsenite concentration increased with increasing external arsenate concentrations, the proportion of arsenite was up to 23%–28% of the total As in alga. In efflux experiments, both arsenate and arsenite could be found in the efflux solutions. Additionally, the efflux of arsenate was more than that of arsenite. Furthermore, two arsenate reductase genes of C. reinhardtii (CrACR2s) were cloned and expressed in Escherichia coli strain WC3110 (ΔarsC) for the first time. The abilities of both CrACR2s genes to complement the arsenatesensitive strain were examined. CrACR2.1 restored arsenate resistance at 0.8 mmol/L. However, CrACR2.2 showed much less ability to complement. The gene products were demonstrated to reduce arsenate to arsenite in vivo. In agreement with the complementation results, CrACR2.1 showed higher reduction ability than CrACR2.2, when treated with 0.4 mmol/L arsenate for 16 hr incubation.     

苯系混合气体生物滴滤器非稳态工况性能

用以纤维附着活性炭(ACOF)和不锈钢丝网为载体材料的气体生物滴滤器(BTF)进行了净化TEX(甲苯、乙苯和二甲苯)混合气体的负荷冲击和闲置恢复运行.负荷冲击实验表明,在最大消除能力范围以内,污染负荷加倍后,起始阶段净化效率下降20%左右,但2d后就基本恢复原有效率.闲置恢复实验表明,8～12 h的停运闲置对设备的性能基本无影响;2d闲置停运后,恢复开机时性能下降20%左右,但在4～6h内便能恢复;29d的闲置对设备的性能影响较大,恢复开机时性能下降70%～80%,需10d左右的时间才能基本恢复.结果表明,采用ACOF和不锈钢丝网的BTF具较好的抗负荷变化及缓冲能力.     

饥饿诱导对蒽降解菌降解能力和存活能力影响研究

对一株蒽降解菌株进行饥饿诱导。将饥饿诱导后的蒽降解菌株作为外源降解菌中投入到蒽溶液中进行降解。经过饥饿处理2d后的菌株对蒽质量浓度100mg/L和50mg/L的降解转化率分别提高27.8%和23.7%,经过饥饿处理6d以后的菌株对蒽的降解转化率提高则不明显,对蒽质量浓度100mg/L和50mg/L的降解转化率分别提高4.3%和5.9%。经过饥饿诱导后细菌的大小以及细胞表面疏水性发生变化的同时,其存活能力也得到提高。     

异噻唑啉酮的灭藻效应及其生物毒性试验

研究了异噻唑啉酮在海水中的灭藻效应,确定了其对于代表性藻类的浓度-反应关系,并且对其进行了生物毒性试验。根据试验结果采用概率单位法进行数据处理,得出异噻唑啉酮对卤虫无节幼体96 h的半致死浓度(LC50)为10.4 mg／L,并对剂量反应方程进行x2检验,结果表明符合精度要求,计算出的96h-LC50真实可靠。该杀生剂在低浓度下对海洋单细胞藻类有较高的杀灭效应,而且生物毒性较小,是比较适合化学法处理船舶压载水的杀生剂。     

运用Spike模型分析CVM中零响应对价值评估的影响——以南京市居民对长江流域生态补偿的支付意愿为例

条件价值法调查中会有相当比例的受访者不愿意支付费用,对这部分群体如果处理不当会影响到价值评估的可靠性和有效性。以南京市居民对长江流域生态补偿的支付意愿为例,采用双边界两分式问卷调查获取1 403份有效样本。分析了忽略零响应问题的传统模型所造成的支付意愿(Willingness to Pay,WTP)估算偏差,并采用Spike模型对WTP估算进行了校正。结果显示:若直接删除零响应样本,中位数WTP在359~396元/(户·a)之间;而将零响应的实际支付用接近零的正数进行替代,得到的中位数WTP在154~208元/(户·a)之间。根据Spike模型,将真实零响应样本纳入分析后,得到的WTP估算结果在259~288元/(户·a) 之间。表明直接删除零响应会明显高估WTP,而用零或接近零的正数替代零响应又会低估WTP。未来5 a内长江南京段的生态补偿总价值至少为24.4×10⁸元。将决策过程划分为"加入决策"和"支付决策"两个阶段后,论文还发现,"加入决策"和"支付决策"是两种不同的机制,二者在影响因素上存在差异。此外,不同收入家庭的WTP存在明显异质性。     

Repeated exposure to cat urine induces complex behavioral,hormonal, and c-fos mRNA responses in Norway rats (<Emphasis Type="Italic">Rattus norvegicus</Emphasis>)

Prey species show specific adaptations that allow recognition, avoidance, and defense against predators. This study was undertaken to investigate the processing of a chronic, life-threatening stimulus to Norway rats (Rattus norvegicus). One hundred forty-four Norway rats were tested by repeated presentation of cat urine for 1 h at different days in a defensive withdrawal apparatus. Rats exposed to urine for short periods showed significantly larger defensive behavioral and medial hypothalamic c-fos messenger RNA (mRNA) responses than other groups. These defensive responses habituated shortly after the presentation of cat urine. Serum levels of adrenocorticotropic hormone and corticosterone increased significantly when animals were repeatedly exposed to cat urine. However, the hormonal responses took longer to habituate than the behavioral and molecular responses did. We conclude that the behavioral and c-fos mRNA responses are “primed” for habituation to repeated exposures to cat urine, while the hormonal responses show “resistance.” The results support our hypothesis that the strongest anti-predator responses at three levels would occur during short-term exposure to cat urine and that these responses would subsequently disappear on prolonged exposure. This study assists understanding the way in which the different levels of defensive responses are integrated and react during chronic stress.     

Uncoupling primer and releaser responses to pheromone in honey bees

Pheromones produce dramatic behavioral and physiological responses in a wide variety of species. Releaser pheromones elicit rapid responses within seconds or minutes, while primer pheromones produce long-term changes which may take days to manifest. Honeybee queen mandibular pheromone (QMP) elicits multiple distinct behavioral and physiological responses in worker bees, as both a releaser and primer, and thus produces responses on vastly different time scales. In this study, we demonstrate that releaser and primer responses to QMP can be uncoupled. First, treatment with the juvenile hormone analog methoprene leaves a releaser response (attraction to QMP) intact, but modulates QMP’s primer effects on sucrose responsiveness. Secondly, two components of QMP (9-ODA and 9-HDA) do not elicit a releaser response (attraction) but are as effective as QMP at modulating a primer response, downregulation of foraging-related brain gene expression. These results suggest that different responses to a single pheromone may be produced via distinct pathways.     

酸雨对种子萌发影响的实验研究

采用ＰＨ值２．５、３．０、３．５、４．５的酸雨处理小麦种子，观察种子的萌发率、平均萌发天数和萌发势。结果表明：酸雨对种子的萌发率和平均萌发无显著影响，但对种子萌发势有显著影响。     

石油污染土壤物化修复前后生物毒性效应

采用作物种子的发芽率作为生态指标对石油污染土壤进行毒性分析,并以蚯蚓为实验生物,研究了石油污染物的生物效应及其对土壤生态系统的影响.结果表明,不同的作物种子对石油污染表现出不同的耐受性,对照清洁土壤,大多数作物种子的萌发都明显受到石油污染的抑制,其中受石油污染影响最严重的是黄豆、蚕豆、玉米.相比之下,在不同石油污染水平下绿豆具有较高的耐受性,且种子发芽率均在90%以上.蚯蚓在受到污染胁迫时,在生理水平上会发生明显的变化,进而影响其存活和生长能力,实验观测到随着石油污染加重蚯蚓存活时间显著下降.在高污染水平石油污染的土壤中(石油污染水平>30 000 mg.kg-1),蚯蚓的耐性降低,仅可以存活5 d左右,说明石油烃对蚯蚓的毒性较大,主要是因为蚯蚓直接与石油接触导致其中毒脱水而死亡.处理后油田污染土,即使在污染水平很低(≈30 mg.kg-1)的情况下,蚯蚓存活时间依然很短(3 d左右),是因为经过石油醚处理过的土壤,其营养物质也随着石油而被处理掉,而土壤中有机质等营养物对蚯蚓的生存具有很大影响.     

短时间间隔的土地利用变化监测

传统的土地利用变化监测方法已无法完全满足当前经济的快速发展和城市急剧扩张的要求,利用光学遥感数据对地观测也受到天气和云层覆盖等诸多因素的限制。而Radarsat-1等雷达遥感数据可以在"全天候"的条件下对地表进行观测。论文以Radarsat-1图像获取的24 d时间周期为最短时间间隔,分析了24 d、48 d和72 d时间间隔下的土地利用变化监测,对短时间间隔内的土地利用变化监测的结果进行了总结。监测的结果需要在精度与时间间隔之间做出取舍。对于大部分的情况,24 d的时间间隔已可以得到60%以上精度的结果,部分月份的监测需要48 d的监测时间间隔。若需要更高的精度,则需要72 d甚至更长。