神经网络用于卤代肉桂酸对羊角月牙藻毒性的预测研究

卤代肉桂酸因具有肉桂酸一样的抑菌、抗氧化和抗微生物活性作用,故被广泛应用于医药、化妆品和农药等生产行业.为了研究卤代肉桂酸对羊角月牙藻急性毒性与其分子结构之间的定量构效关系,基于分子拓扑理论,计算了14个卤代肉桂酸分子的4类分子结构参数,筛选了电性拓扑状态指数(E13)和电性距离矢量(M15)作为理论结构描述符,将其与卤代肉桂酸对羊角月牙藻急性毒性进行回归分析,并将这2种参数作为神经网络法的输入层参数,采用2-2-1的神经网络结构,构建了相关性良好的预测毒性的神经网络模型,模型的总相关系数(R总)为0.951,预测的毒性值与其相应文献实验值的相对平均误差为4.49％,吻合度较好,利用模型预测了另外12种卤代肉桂酸对羊角月牙藻急性毒性.结果表明,卤代肉桂酸对羊角月牙藻急性毒性与2种分子结构参数具有良好的非线性关系.     

基于分子对接的取代脲类除草剂对羊角月牙藻的毒性大于铜绿微囊藻的机理初探

本文以蓝藻水华优势藻种——铜绿微囊藻和典型绿藻——羊角月牙藻为受试生物,测定了4种取代脲类除草剂对两种藻的96 h急性毒性,并初步探讨了引起毒性差异的原因.结果显示,4种取代脲类除草剂对羊角月牙藻的毒性均大于铜绿微囊藻.分子对接的结果表明,取代脲类除草剂与羊角月牙藻的D1蛋白的结合能力大于铜绿微囊藻,这可能是导致羊角月牙藻对取代脲类除草剂更加敏感的原因.同时,分子对接揭示了氯离子可以增加取代脲类除草剂的疏水性,从而使化合物更易接近活性位点内部的疏水区域,更易与相应的氨基酸形成氢键.     

用分子连接指数研究氯代芳香族化合物对绿藻的毒性及QSAR分析

本文测定了一批氯代芳香族化合物对羊角月牙藻的急性毒性,运用分子连接性指数分析了化合物结构与其毒性之间的定量关系,并用逐一抽取法检验比较了模型的稳健性.     

二苯甲酮类紫外防晒剂发光菌急性毒性及QSAR研究

二苯甲酮类化合物广泛用于防晒剂、塑料添加剂、香味剂等。随着紫外防晒产品的大量使用,其环境及健康风险越来越受到人们的关注。为揭示二苯甲酮类污染物的毒性特征,选择了14种二苯甲酮类化合物作为目标化合物,测试了它们对发光细菌的急性毒性效应。分别运用二维、三维定量构效相关技术和分子对接技术探讨了目标化合物的分子结构特征对毒性效应的影响。结果表明14种二苯甲酮类化合物对发光菌急性毒性的EC50值在17.67到243.82 mg·L-1范围内,其中2-羟基-4-甲氧基-5-磺酸基二苯甲酮的急性毒性最低,2,2',4,4'-四羟基二苯甲酮的毒性最高。羟基取代的二苯甲酮化合物的急性毒性随着分子中羟基数量的增加而升高;具有相同羟基数量的二苯甲酮类化合物,羟基位于苯环4-位时毒性最高,3-位时次之,2-位时毒性最低。QSAR结果表明,运用静电场、氢键受体场和氢键供体场能很好解释这类化合物的毒性特征,若在苯环4-位引入带正电荷的官能团、在苯环2-,4-位引入氢键受体,都将导致毒性升高。上述研究结果将为科学评价该类化合物的潜在生态风险提供基础数据。     

纳米氧化锌对羊角月牙藻毒性效应及其在藻细胞内外的分布

为研究纳米氧化锌(ZnO NP)的毒性效应及其在细胞内外分布,以羊角月牙藻(Selenastrum capricornutum)为模型藻类,研究了不同浓度ZnO NP对羊角月牙藻生长、叶绿素含量、可溶性蛋白含量、超氧化物岐化酶(SOD)及过氧化物酶(POD)活性、丙二醛(MDA)含量及细胞内外ZnO NP含量变化。结果表明,ZnO NP对羊角月牙藻的生长抑制与处理浓度呈现正相关。在45 mg·L~(-1)ZnO NP暴露24 h后,其生长抑制率已达到95%。当ZnO NP处理藻细胞72 h后,羊角月牙藻细胞的叶绿素含量与处理浓度之间存在剂量-效应关系。低浓度(0.5 mg·L~(-1))ZnO NP处理后藻细胞可溶性蛋白质含量、SOD和POD活性明显下降,MDA含量升高,其产生的毒性效应高于高浓度组(5 mg·L~(-1)、45 mg·L~(-1))。细胞培养液溶出Zn2+量及藻细胞外吸附的ZnO NP量与ZnO NP处理浓度成正比,但是藻细胞内ZnO NP量与ZnO NP浓度没有相关性,胞内积累量基本维持不变。研究表明,各浓度组对藻细胞毒性的差异,不仅与细胞内Zn2+量有关,还与细胞外粘附的ZnO NP有关。     

苯砜基乙酸酯类化合物发光菌毒性效应的CoMFA研究

应用比较分子场分析方法(CoMFA)对56种苯砜基乙酸酯类化合物的发光菌急性毒性进行了研究,获得了6组分三维定量结构-活性相关模型(3D-QSAR)．模型的交叉验证相关系数(q^2)和常规相关系数(r^2)分别为0．823和0．958,说明该模型具有较高的稳定性和较好的预测能力．模型分析表明：该类化合物发光菌急性毒性效应与化合物分子的空间场和静电场具有显著相关关系．     

卤代苯及其衍生物的比较分子场研究

用比较分子场（CoMFA）方法分析了一组卤代苯及其衍生物对发光菌的毒性数据，所建立的CoMFA模型有很好的自身一致性和较强的预测能力。对系列化合物的研究结果表明：该类化合物的立体效应是描述其毒性和进行构效关系研究的重要结构参数；毒性大小与取代基体积大小有关，取代基体积愈大则毒性愈大。     

可离子化有机污染物对大型溞的毒性及QSAR研究

取代苯酚、苯胺和苯甲酸类化合物是在环境水体中具有较强生物毒性的芳香族可离子化有机化合物,它们在水体中对水生生物和水生生态系统都有较大危害。测定此类化合物在p H值为6、7.8和9的条件下对大型溞的24 h急性毒性,计算化合物在不同p H值条件下的中性态分子所占比例F0。研究毒性与F0的相关性,结果表明F0对取代苯酚和苯甲酸类化合物的毒性的影响较大而对取代苯胺毒性的影响很小。对于卤代苯甲酸类化合物,毒性与疏水性的相关性较好,但是羟基苯甲酸类化合物的毒性与疏水性参数的相关性很差,引入量子化学参数EHOMO和取代羟基个数NOH,可以改进苯甲酸类化合物的模型的质量。     

三氯生对羊角月牙藻生长及其抗氧化系统的影响

以羊角月牙藻(Selenastrum capricornutum)为实验材料,研究了三氯生(triclosan,TCS)对羊角月牙藻生长、光合作用叶绿素荧光动力学参数及抗氧化酶活性的影响。结果表明,TCS对羊角月牙藻的96h-EC50为0.112mg·L-1,属于高毒。TCS暴露对羊角月牙藻的叶绿素荧光中ABS/RC、PIabs、RC/CSo和OEC比例等参数有显著影响。随着三氯生浓度的增大,羊角月牙藻的叶绿素荧光中ABS/RC大幅上升,PIabs、RC/CSo和OEC比例下降;当三氯生浓度为0.256mg·L-1时,ABS/RC达到最大值,PIabs、RC/CSo和OEC比例下降为最小值,表明藻细胞光合作用的原初反应及电子链传递过程受到严重阻碍。同时,三氯生对羊角月牙藻体内抗氧化酶系中GST活性和MDA含量也有较大影响。在低浓度暴露下,GST活性随TCS浓度增加而增大,但当TCS浓度超过0.256mg·L-1时,GST活性出现显著下降,同时MDA含量达到最大,这种GST活性的下降同时伴随MDA含量的增加表明藻细胞膜系统受到较大损害。     

不同微藻对典型行业废水急性毒性响应的敏感性研究

研究考察了不同行业废水对4种微藻24 h和72 h的急性毒性效应。以斜生栅藻(Scenedesmus obliquus)、蛋白核小球藻(Chlorella pyrenoidosa)、海水小球藻(Chlorella spp.)以及等鞭金藻(Isochrysis galbana)为指示生物,采用COD浓度较高的焦化厂实际生产废水和制药厂实际生产废水、COD浓度较低的印染厂生化处理后出水和城市污水处理厂进出水作为受试水体,以微藻的生长抑制率为测试指标,评价微藻对不同行业废水的急性毒性效应和敏感性。结果表明,不同行业废水对4种微藻的急性毒性效应有所不同:焦化废水对等鞭金藻的生长抑制作用最强,制药废水对斜生栅藻的毒性效应最为明显,印染废水及城市污水处理厂的进出水对海水小球藻的毒性较为显著,说明不同微藻对不同行业废水毒性的敏感性存在差异。上述研究结果为废水毒性评价中受试物种的选择提供了基础数据。     

Antennal responses of four species of tree-killing bark beetles (Coleoptera: Scolytidae) to volatiles collected from beetles,and their host and nonhost conifers

Summary. Host selection in tree-killing bark beetles (Coleoptera: Scolytidae) is mediated by a complex of semiochemical cues. Using gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses, we conducted a comparative study of the electrophysiological responses of four species of tree-killing bark beetles, the Douglas-fir beetle, Dendroctonus pseudotsugae, Hopkins, the mountain pine beetle, D. ponderosae Hopkins, the spruce beetle, D. rufipennis Kirby, and the western balsam bark beetle, Dryocoetes confusus Swaine, to volatiles captured by aeration of 1) bole and foliage of four sympatric species of conifers, Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, lodgepole pine, Pinus contorta var. latifolia Engelm., interior spruce, Picea engelmannii x glauca, and interior fir, Abies lasiocarpa x bifolia, and 2) con- and heterospecific beetles at three stages of attack. We identified 13 monoterpenes in the conifers and nine compounds in the volatiles of beetles that elicited antennal responses. There was no qualitative difference in the terpene constitution of the four species of conifers and very little difference across beetle species in their antennal response to compounds from conifers or beetles. The lack of species-specific major or minor components in conifers suggests that beetles would need to detect differences in the ratios of different compounds in conifers to discriminate among them. Attraction to hosts and avoidance of nonhost conifers may be accentuated by perception of compounds emitted by con- and heterospecific beetles, respectively. The 22 compounds identified are candidate semiochemicals with potential behavioural roles in host location and discrimination.     

Diet-induced chemical phytomimesis by twig-like caterpillars of Biston robustum Butler (Lepidoptera: Geometridae)

Summary. Polyphagous caterpillars of the giant geometer Biston robustum resemble the twigs of their respective food sources in color and shape. Common predatory ants, including Lasius and Formica, were often observed to freely prowl directly on caterpillars bodies, even after antennal contact. This suggests that the cuticular chemicals of the caterpillars resemble those of the twigs of the foodplants, so we analyzed both by GC and GC-MS. The chemical compositions differed among caterpillars fed on a cherry, Prunus yedoensis, a chinquapin Castanopsis cuspidata, and a camellia Camellia japonica. The cuticular chemicals of the caterpillars resembled those of their corresponding food sources. When the caterpillar diets were switched from the cherry to camellia or chinquapin at the 4^th instars, the caterpillars cuticular chemicals changed after molting to resemble those of their respective foods. Caterpillars also changed their cuticular chemicals when they perched on cherry twigs and fed on camellia or chinquapin leaves, but not when they perched on camellia or chinquapin twigs and fed on cherry leaves. The chemical similarities between the caterpillars and the twigs were due to the digestion of host leaves, which indicates that this is a diet-induced adaptation.     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.     

Benthic macrophyte communities in the Ghar El Melh lagoon (North Tunisia)

This work deals with the biodiversity and distribution of benthic macrophytes in the Ghar El Melh lagoon, a Mediterranean coastal lagoon located in the North of Tunisia. An inventory was made of the benthic flora and submerged macrophyte communities were mapped during two successive campaigns (the summer of 1999 and the winter of 2000). The following 24 macrophyte species were identified: seven red algae, two brown algae, 11 green algae, and four marine angiosperms. The results were compared with available data from the literature. Ruppia cirrhosa is the most dominant species. It is found in all lagoon parts, except in the west sector.Ruppia beds are usually associated withCladophora forming heterogeneous communities. During summerRuppia cirrhosa shows a large distribution, covering an area of ca. 21.4 km², with dense, extensive beds covering 80–100%. In winter, severalCladophora species have a very large distribution as well, covering nearly an area of 28.5 km² with an average cover of 46%. The green algaeCaulerpa prolifera is confined to the eastern part of the lagoon which is mainly affected by seawater. In comparison with previous situations, many transformations were observed in biodiversity and spatial distribution of the dominant communities. Thus,Cymodocea nodosa andZostera beds, which dominated in the 1970s, were replaced byZostera andCaulerpa prolifera in the 1980s and are currently succeeded byRuppia cirrhosa andCladophora. Restoration of the Ghar El Melh lagoon will enable an increase in the exchange with the open sea and the circulation of water, in particular in the confined zones. This should considerably improve the water quality and would positively influence the phytobenthic communities.     

Absolute configuration of the major sex pheromone component of the satin moth, Leucoma salicis, verified by field trapping test in Hungary

Summary. Male satin moths, Leucoma (Stilpnotia) salicis L. (Lepidoptera, Lymantriidae) were attracted only to (3Z,6R,7S,9R,10S)-isomer out of the four (3Z)-cis-6,7-cis-9,10-diepoxy-3-henicosenes (leucomalure). This was demonstrated by field trapping test with a bivoltine population in a mixed poplar-willow forest along the flood area of the river Danube at Adony, Hungary.     

Increase of multi-metal tolerance of three leguminous plants by arbuscular mycorrhizal fungi colonization

A greenhouse pot experiment was conducted to investigate the effects of the colonization of arbuscular mycorrhizal fungus (AMF) Glomus mosseae on the growth and metal uptake of three leguminous plants (Sesbania rostrata, Sesbania cannabina, Medicago sativa) grown in multi-metal contaminated soil. AMF colonization increased the growth of the legumes, indicating that AMF colonization increased the plant’s resistance to heavy metals. It also significantly stimulated the formation of root nodules and increased the N and P uptake of all of the tested leguminous plants, which might be one of the tolerance mechanisms conferred by AMF. Compared with the control, colonization by G. mosseae decreased the concentration of metals, such as Cu, in the shoots of the three legumes, indicating that the decreased heavy metals uptake and growth dilution were induced by AMF treatment, thereby reducing the heavy metal toxicity to the plants. The root/shoot ratios of Cu in the three legumes and Zn in M. sativa were significantly increased (P < 0.05) with AMF colonization, indicating that heavy metals were immobilized by the mycorrhiza and the heavy metal translocations to the shoot were decreased.     

Main nutrient compounds in food bodies of Mexican <Emphasis Type="Italic">Acacia</Emphasis> ant-plants

Summary. Myrmecophytic plants use obligate ant mutualists as a constitutive indirect defence mechanism. These plants often produce cellular food bodies (FBs) to nourish their resident ants. Lipids, proteins, and even highly specialised compounds such as glycogen have been reported from FBs, but detailed chemical analyses of FB composition have so far been presented only for Southeast Asian Macaranga and Central American Piper myrmecophytes. Here we report the chemical composition of FBs of five myrmecophytic Acacia (Fabaceae) species from Mexico using HPLC (carbohydrates and proteins) and GC-MS (lipids). Feeding experiments revealed no hints on any use of external food sources by the inhabiting Pseudomyrmex ants. These ants obviously rely completely on FBs and extrafloral nectar provided by their hosts. The total content of nutrients in Acacia FBs was 15-25% of FB dry mass, being much lower than in Macaranga or Piper FBs. Proteins were dominating (8-14 % dm) in Acacia FBs and thus were present in higher amounts than in Macaranga FBs, yet in lower amounts than in Piper. Lipids contributed 1-9 % of dry mass, showing a lower proportion than in FBs of Macaranga or Piper. Carbohydrates made up 3-11 % dm, reaching in most Acacia species the same range as observed in Macaranga and in Piper FBs. Water content was 18-24 % of FB fresh mass, and structural tissue obviously made up a much higher proportion in Acacia FBs than in Macaranga or Piper FBs. Both characters might represent an adaptation to producing FBs unprotected at the leaf tips under dry conditions. Acacia FBs contain all amino acids and all fatty acids that are considered essential for insects, and their contents of lipids and proteins are higher than in the leaves from which they are ontogenetically derived. This indicates a putatively adaptive enrichment of nutritionally valuable compounds in structures functioning as ant-food.     

Toxicity assays of ladybirds using natural predators

Nestling blue titsParus caeruleus L. were given diets containing homogenized ladybirds, to assess the effects of their chemical defences. The 2spot, 10spot and water ladybirds produced no apparent toxic effects when small numbers were given at regular intervals.The pine and kidney-spot ladybirds slightly inhibit growth and may be toxic to very young nestlings. The Water ladybird is extremely distasteful to this predator, despite its lack of toxicity. The results are discussed with reference to the proposed Müllerian and Batesian mimetic relationships between the ladybird species.     

Testing a new model of aphid abundance with sedentary and non-sedentary predators

Aphid population dynamics has been thoroughly investigated, especially in tree-dwelling aphids. Among the controls of the aphid rate of increase are the negative effects of antagonists, the positive effects of mutualists, the density-dependence of the aphid dynamics, and the non-stationary quality of plant tissues. Here we present a mechanistic model of aphid growth that considers most of these governing factors using a simple formulation. What is new in this model is that it considers two kinds of antagonists. The first kind is a guild of aphid predator specialists that includes ladybirds (Coleoptera: Coccinellidae), but also species of some families of Hemiptera, Diptera, and Neuroptera. The second kind of antagonists consists of omnivores or generalist predators and in this particular setting is exemplified by the European earwig Forficula auricularia (Dermaptera: Forficulidae). The model developed here compared the effects of these two different kinds of aphid predators, the second one always at the site (sedentary predators) and the first one that arrives in important numbers only once the aphid population has already developed to some degree (non-sedentary predators). Multiple model parameter sets, representing different hypotheses about controls on aphid populations, were evaluated within the Generalised Likelihood Uncertainty Estimation (GLUE) methodology. The model correctly reproduced the experimental data obtained in an organic citrus grove showing the important effect that sedentary predators as earwigs can have on the aphid populations. Low densities of sedentary predators or even low predation rates can have a disproportionate effect on the final aphid density, as they prey on small populations, when the per capita effect on the aphid population is higher. During the main spring peak of aphids the role of non-sedentary predators is secondary, as they track the aphid density rather than control it. However, these non-sedentary predators are important within the proposed model to keep the second autumn peak of aphids at low values.     

加拿大一枝黄花和小飞蓬叶浸提液对大豆幼苗生长的复合化感效应

加拿大一枝黄花(Solidago canadensis)和小飞蓬(Conyza canadensis)常共同入侵至同一农田生态系统。探究了两者对大豆幼苗生长的复合化感作用。加拿大一枝黄花叶浸提液显著抑制大豆幼苗地上生物量。而小飞蓬叶浸提液也明显抑制大豆幼苗地上生物量(未达到显著水平)。与对照处理相比,两者复合叶浸提液处理未显著影响大豆幼苗地上生物量。两者复合叶浸提液处理下大豆幼苗地上生物量显著大于加拿大一枝黄花叶浸提液单一处理,同时也大于小飞蓬叶浸提液单一处理(未达到显著水平)。两者叶浸提液单一处理均明显降低大豆幼苗株高(未达到显著水平)。与对照处理相比,两者复合叶浸提液处理未显著影响大豆幼苗株高。两者复合叶浸提液处理下大豆幼苗株高明显大于两者叶浸提液单一处理(未达到显著水平)。因此,两者叶浸提液对大豆幼苗的生长均具有一定程度的抑制效应,且加拿大一枝黄花叶浸提液对大豆幼苗产生的化感作用(尤其是地上生物量)明显大于小飞蓬。两者复合化感作用明显低于两者单一化感作用,尤其是两者对大豆幼苗地上生物量的复合化感作用显著低于加拿大一枝黄花的单一化感作用。所以,化感效应可能在两者共同入侵(即两者复合作用)进程中所起的贡献低于在两者单一入侵进程中所起的作用。