西藏尼洋河流域果树资源及其开发途径探讨

西藏尼洋河流域果树资源丰富,栽培果树有苹果、梨、桃、李、杏和葡萄等9种和90多个品种;野生果树有7科16属41种,目前利用程度低,开发潜力大。文中提出了该地区果树资源的开发途径,在尼洋河下游和雅鲁藏布江的扎绕乡至派乡之间段的河谷地上形成“Y”字型的水(干)果种植带,建设成为西藏的水(干)果生产基地,并对现有果园改造更新,充分利用野生水果资源,建立果品综合加工厂等以满足西藏市场对水果和果品的需要。     

Inhibition of ROS elevation and damage to mitochondrial function prevents lead-induced neurotoxic effects on structures and functions of AFD neurons in Caenorhabditis elegans

Here we investigated the possible roles of oxidative stress in the formation of decreased thermotaxis to cultivation temperature in lead (Pb)-exposed nematodes Caenorhabditis elagans. Exposure to Pb at the examined concentrations decreased thermotaxis behaviors, and induced severe deficits in the structural properties of AFD sensory neurons. Meanwhile, Pb exposure caused the induction of severe oxidative damage, reactive oxygen species (ROS) production, and mitochondrial dysfunction in young adults. Moreover, pre-treatment with the antioxidants dimethyl sulfoxide (DMSO), ascorbate and N-acetyl-L-cysteine (NAC), used to inhibit both the ROS elevation and the mitochondrial dysfunction caused by Pb exposure, at the L2-larval stage prevented the induction of oxidative damage and the formation of severe deficits in thermotaxis and structural properties of AFD sensory neurons in Pb-exposed young adults. Therefore, the formation of oxidative stress caused by Pb exposure may be due to both the induction of ROS elevation and damage to mitochondrial function, and oxidative stress may play a key role in inducing the neurotoxic effects on the structures and function of AFD sensory neurons in Pb-exposed nematodes.     

Dietary antioxidants, lipid peroxidation and plumage colouration in nestling blue tits Cyanistes caeruleus

Carotenoid pigments are responsible for many of the red, yellow and orange plumage and integument traits seen in birds. One idea suggests that since carotenoids can act as antioxidants, carotenoid-mediated colouration may reveal an individual's ability to resist oxidative damage. In fact, there is currently very little information on the effects of most dietary-acquired antioxidants on oxidative stress in wild birds. Here, we assessed the impacts on oxidative damage, plasma antioxidants, growth and plumage colouration after supplementing nestling blue tits Cyanistes caeruleus with one of three diets; control, carotenoid treatment or α-tocopherol treatment. Oxidative damage was assessed by HPLC analysis of plasma levels of malondialdehyde (MDA), a by-product of lipid peroxidation. Contrary to predictions, we found no differences in oxidative damage, plumage colouration or growth rate between treatment groups. Although plasma lutein concentrations were significantly raised in carotenoid-fed chicks, α-tocopherol treatment had no effect on concentrations of plasma α-tocopherol compared with controls. Interestingly, we found that faster growing chicks had higher levels of oxidative damage than slower growing birds, independent of treatment, body mass and condition at fledging. Moreover, the chromatic signal of the chest plumage of birds was positively correlated with levels of MDA but not plasma antioxidant concentrations: more colourful nestlings had higher oxidative damage than less colourful individuals. Thus, increased carotenoid-mediated plumage does not reveal resistance to oxidative damage for nestling blue tits, but may indicate costs paid, in terms of oxidative damage. Our results indicate that the trade-offs between competing physiological systems for dietary antioxidants are likely to be complex in rapidly developing birds. Moreover, interpreting the biological relevance of different biomarkers of antioxidant status represents a challenge for evolutionary ecology.     

The use of olfaction in the foraging behaviour of the golden-mantled flying fox,<Emphasis Type="Italic"> Pteropus pumilus</Emphasis>, and the greater musky fruit bat,<Emphasis Type="Italic"> Ptenochirus jagori</Emphasis> (Megachiroptera: Pteropodidae)

Double-choice experiments with three adult males of the little golden-mantled flying fox, Pteropus pumilus, and ten adult greater musky fruit bats, Ptenochirus jagori (both Megachiroptera: Pteropodidae), demonstrate that they are able to discriminate accurately between an empty dish and a dish containing fruits of one of several species by odour alone. Tests were run using fruits of six fruit species for Pteropus pumilus and five fruit species for Ptenochirus jagori. The fruit species used are known to be consumed in the wild by Ptenochirus jagori and are, with two exceptions, species of the natural rain-forest habitat. This is the first study to show that fruit bats are also able to assess the ripeness of a fruit exclusively by its odour. The bats preferred ripe over unripe fruits of the same species. Thus, both Pteropus pumilus and Ptenochirus jagori can not only locate fruits by their odour but can also discriminate between ripe and unripe fruits of the same species by olfaction. The results confirm and expand earlier findings on the role of olfactory cues in the orientation of foraging pteropodids.     

Fruit traits and temporal abundance shape plant-frugivore interaction networks in a seasonal tropical forest

Interactions between fleshy fruited plants and frugivores are crucial for the structuring and functioning of biotic communities, particularly in tropical forests where both groups are diverse and play different roles in network organization. However, it remains poorly understood how different groups of frugivore species and fruit traits contribute to network structure. We recorded interactions among 28 plant species and three groups of frugivores (birds, bats, and non-flying mammals) in a seasonal forest in Mexico to determine which species contribute more to network structure and evaluate the importance of each species. We also determined whether fruit abundance, water content, morphology traits, and fruiting phenology are related to network parameters: the number of interactions, species contribution to nestedness, and species strength. We found that plants did not depend on a single group of frugivores, but rather on one species of each group: the bird Pitangus sulphuratus, the bat Sturnira parvidens, and the non-flying mammal Procyon lotor. The abundance, size, and water content of the fruits were significantly related to the contribution to nestedness, number of interactions, and species strength index of plant species. Tree species and birds contributed mainly to the nested structure of the network. We show that the structure of plant-frugivore networks in this seasonal forest is non-random and that fruit traits (i.e., abundance, phenology, size, and water content) are important factors shaping plant-frugivore networks. Identification of the key species and their traits that maintain the complex structure of species interactions is therefore fundamental for the integral conservation of tropical forests.     

Nestling rearing is antioxidant demanding in female barn swallows (Hirundo rustica)

Reproduction is a demanding activity, since organisms must produce and, in some cases, protect and provision their progeny. Hence, a central tenet of life-history theory predicts that parents have to trade parental care against body maintenance. One physiological cost thought to be particularly important as a modulator of such trade-offs is oxidative stress. However, evidence in favour of the hypothesis of an oxidative cost of reproduction is contradictory. In this study, we manipulated the brood size of wild barn swallows Hirundo rustica soon after hatching of their nestlings to test whether an increase in nestling rearing effort translates into an increased oxidative damage and a decreased antioxidant protection at the end of the nestling rearing period. We found that, while plasma oxidative damage was unaffected by brood size enlargement, females rearing enlarged broods showed a decrease in plasma non-enzymatic antioxidants during the nestling rearing period. This was not the case among females rearing reduced broods and among males assigned to either treatment. Moreover, individuals with higher plasma oxidative damage soon after the brood size manipulation had lower plasma non-enzymatic antioxidants at the end of the nestling rearing period, suggesting that non-enzymatic antioxidants were depleted to buffer the negative effects of high oxidative damage. Our findings point to antioxidant depletion as a potential mechanism mediating the cost of reproduction among female birds.     

Enantioselective induction of oxidative stress by acetofenate in rat PC12 cells

In a non-chiral environment,the enantiomers of a racemate possessed the identical physico-chemical properties,but in the biological systems they possessed different activities.Considering that the involvement of oxidative damage has been implicated in the toxicities of various pesticides,this study investigated the possibility of enantioselective oxidative stress and cytotoxicity induction by acetofenate (AF) which contains an asymmetrical center on PC12 cells.The results of the cytotoxicity assay indicated that S-(+)-AF presented more toxic effects than R-(-)-AF and (±)-AF.It also demonstrated that S-(+)-AF possessed the strongest effects in induction of reactive oxygen species (ROS) production,decrease in superoxide dismutase (SOD) and catalase (CAT) activities,and increase in malondialdehyde (MDA) level.These results suggested that AF and its enantiomers could induce enantioselective cytotoxicity in PC12 cells mediated by oxidative stress.Therefore,the assessment in environmental safety and new chiral pesticide development should consider enantioselectivity.     

满江红花青素在镉胁迫下的抗氧化作用

为了研究镉胁迫诱导满江红体内花青素合成的生理功能,采用镉诱导和体外实验的方法评价了满江红体内花青素的抗氧化作用.测试指标包括还原力、清除超氧阴离子(O-2)、过氧化氢(H2O2)、羟自由基(·OH)的能力.结果表明,花青素的还原力和对氧自由基的清除作用随花青素提取物浓度的增加而增加.因此,镉胁迫下合成的花青素是一种清除活性氧自由基的良好抗氧化剂.镉胁迫对满江红活性氧代谢影响的试验结果表明,在0.5mg·L-1Cd胁迫下,满江红体内O-2和H2O2大量积累,造成活性氧胁迫,说明花青素只能在一定程度上保护满江红免受过氧化伤害.本实验初步证实,花青素含量的增加是满江红抗性机理之一,可缓解镉的毒害.     

Primary neuronal-astrocytic co-culture platform for neurotoxicity assessment of di-(2-ethylhexyl) phthalate

Plastics such as polyvinyl chlorides （PVC） are widely used in many indoor constructed environments; however, their unbound chemicals, such as di-（2-ethylhexyl） phthalates （DEHP）, can leach into the surrounding environment. This study focused on DEHP＇s effect on the central nervous system by determining the precise DEHP content in mice brain tissue after exposure to the chemical, to evaluate the specific exposure range. Primary neuronal-astrocyte co-culture systems were used as in vitro models for chemical hazard identification of DEHP. Oxidative stress was hypothesized as a probable mechanism involved, and therefore the total reactive oxygen species （ROS） concentration was determined as a biomarker of oxidative stress. In addition, NeuriteTracer, a neurite tracing plugin with ImageJ, was used to develop an assay for neurotoxicity to provide quantitative measurements of neurological parameters, such as neuronal number, neuron count and neurite length, all of which could indicate neurotoxic effects. The results showed that with 1 nmol/L DEHP exposure, there was a significant increase in ROS concentrations, indicating that the neuronal-astrocyte cultures were injured due to exposure to DEHP. In response, astrocyte proliferation （gliosis） was initiated, serving as a mechanism to maintain a homeostatic environment for neurons and protect neurons from toxic chemicals. There is a need to assess the cumulative effects of DEHP in animals to evaluate the possible uotake and effects on the human neuronal system from exoosure to DEHP in the indoor environment.     

Quantum dots enhance Cu2+-induced hepatic L02 cells toxicity

As a new class of xenogenous nanoparticle,quantum dots (QDs) possess the potential to co-exist with Cu2+ in human liver.The combined toxicity is thus concerned.Considering QDs and Cu2+ are known ROS (reactive oxygen species) inducer,we investigated the combined oxidative stress and corresponding protective strategy using human hepatic L02 cells.The results demonstrated that the presence of a small amount of MPA-CdTe QDs (2 μg/mL) in a Cu2+ solution (2.5-20 μg/mL) resulted in a higher toxicity with up to 8-fold cell viability decrease,which was accompanied by cell morphology changes.The combined toxicity was then confirmed as ROS associated oxidative stress with up to 300% and 35% increase of the intracellular ROS level and glutathione S-transferase (GST) activity,respectively.N-acetylcysteine (NAC) can also provide almost complete protection against the induced toxicity.Therefore,the ROS associated oxidant injury might be responsible for the QDs-Cu2+/Cu2+ induced toxicity and could be balanced through cytoprotective antioxidant enzyme GST.     

磷化氢生物净化体系及抑制作用机理

在PH₃生物净化体系中添加呼吸链电子传递抑制剂,对比分析微生物生长代谢、磷的迁移转化、活性氧（ROS）产生及氧化酶活性等变化规律.当鱼藤酮或抗霉素A分别添加至R1、R2PH₃生物反应器后,其微生物体O₂^-·含量在运行时间14~17d期间的平均值分别上升至0.68,0.96mmol/g,明显高于空白对照组R0反应器.除自由基O₂^-·外,另一类型的活性氧HO·也存在于PH₃净化系统中;受累积的活性氧影响,生物体内丙二醛（MDA）含量处于较高水平,PH₃净化效率通常不超过75%,添加抑制剂的R1与R2反应体系在15~17d期间PH₃平均去除率分别下降至65.1%、59.5%.pH值、ROS含量以及氧化酶活性等因素均明显影响PH₃生物净化效果,当Fe³⁺、Cu²⁺、Mg²⁺等金属阳离子迁移转运至微生物体内时,超氧化物歧化酶（SOD）与过氧化氢酶（CATase）活性得以不同程度的增强,可缓解活性物质O₂^-·或HO·导致的氧化胁迫作用,PH₃净化效能得以适度提升.     

Oxidative stress and DNA damages induced by cadmium accumulation

Experimental evidence shows that cadmium （Cd） could induce oxidative stress and then causes DNA damage in animal cells, however, whether such effect exists in plants is still unclear. In the present study, Vicia faba plants was exposed to 5 and 10 mg/L Cd for 4 d to investigate the distribution of Cd in plant, the metal effects on the cell lipids, antioxidative enzymes and DNA damages in leaves. Cd induced an increase in Cd concentrations in plants. An enhanced level of lipid peroxidation in leaves and an enhanced concentration of H2O2 in root tissues suggested that Cd caused oxidative stress in Vicia faba. Compared with control, Cd-induced enhancement in superoxide dismutase activity was significant at 5 mg/L than at 10 mg/kg in leaves, by contrast, catalase and peroxidaseactivities were significantly suppressed by Cd addition. DNA damage was detected by neutral/neutral, alkaline/neutral and alkaline/alkaline Comet assay. Increased levels of DNA damages induced by Cd occurred with reference to oxidative stress in leaves, therefore, oxidative stress induced by Cd accumulation in plants contributed to DNA damages and was possibly an important mechanism of Cd-phytotoxicity in Vicia faba plants.     

Characterisation of acute toxicity, genotoxicity and oxidative stress posed by textile effluent on zebrafish

Textile industries are important sources of toxic discharges and contribute enormously to water deterioration, while little attention has been paid to the toxicity of textile effluents in discharge regulation. Bioassays with zebrafish were employed to evaluate the toxicity of wastewater samples collected from different stages at a textile factory and sewage treatment plants (STPs). Physico-chemical parameters, acute toxicity, genotoxicity and oxidative stress biomarkers were analyzed. The wastewater samples from bleaching, rinsing and soaping of the textile factory exhibited high acute toxicity and genotoxicity. The coexisting components of dye compounds, as assistants and oxidants, seemed to cause some effect on the toxic response. After treatment employing the anoxic-oxic (A/O) process in STPs, the color and the chemical oxygen demand (COD) were reduced by 40% and 84%, respectively, falling within the criteria of the Chinese Sewage Discharge Standard. In contrast, increases in acute toxicity and genotoxicity were observed in the anaerobic tank, indicating the formation of toxic intermediates. The genotoxicity of the effluent of the STP was not significantly different from that of the influent, suggesting the wastewater treatment processes were not effective in removing the genotoxicity of the dye wastewater. Results indicated that the effluent contains pro-oxidants since the activities of glutathione (GSH), malondialdehyde (MDA), and total anti-oxidation capacity (T-AOC) were all elevated. In addition, decreases in superoxide dismutase (SOD) and glutathione-S transferase (GST) activities observed can be interpreted as a cytotoxicity sign due to an over-production of reactive oxygen species (ROS). The results of the present study suggest that the STPs were not capable of reducing the toxicity of wastewater sufficiently. Further treatment is needed to remove the potential risks posed by textile effluent to ecosystems and human health, and employing a toxicity index is necessary for discharge regulation.     

甲磺隆对沉水植物伊乐藻的生理生态效应研究

采用室内水培实验方法,研究不同浓度甲磺隆对伊乐藻生长的影响及其体内光合色素含量和3种抗氧化酶活性的变化.结果表明,甲磺隆可以刺激伊乐藻新芽萌发,但是对植株的生长具有明显的抑制作用.浓度≤5.mg/L的甲磺隆在实验初期可促进伊乐藻体内叶绿素含量的增加,随时间的延长,最终抑制叶绿素的合成,降低了植物体的光合作用能力.低浓度条件下, CAT及POD活性先升高后降低,而SOD活性持续升高.较高浓度和较长时间处理时,伊乐藻抗氧化酶系统活性下降.甲磺隆胁迫可以引起伊乐藻体内活性氧的产生和积累,诱导抗氧化酶活性,当胁迫超过一定强度时,抗氧化酶活性受到抑制,活性氧不能及时清除,从而对植物体形成氧化损伤,这可能是该类除草剂对水生植物的重要致毒机制之一.     

Shade tree management affects fruit abortion, insect pests and pathogens of cacao

The mortality of cacao fruits caused by early fruit abortion or insect and pathogen attacks was investigated in differently managed agroforestry systems in Central Sulawesi, Indonesia. Nine agroforestry systems shaded by three different types of tree stands were selected, which represented a decrease in structural heterogeneity: forest remnants, diverse planted trees and one or two species of planted leguminose trees. After standardized manual cross-pollination, the development of 600 fruits on 54 trees (6 trees per agroforest) was followed during 18 weeks of fruit development. In total, 432 of all fruits were lost before maturity, which seriously undermined yields. The proportion of harvested fruits per tree (overall average: 27 ± 4%) was not affected by canopy type. Although shade cover did not have a significant effect, losses due to fruit abortion were most likely under forest shade, where nitrogen-fixing leguminose shade trees were absent. Fruit losses due to pathogenic infections and insect attacks increased with the homogenization of the agroforests, supporting the hypothesis that agricultural homogenization increases risks of pest outbreaks. In conclusion, shade management may be improved to increase yields from cacao using highly diversified natural shade agroforestry systems.     

Pseudomonas putida细胞对微囊藻毒素-LR的胁迫响应

将1.0g/L的微囊藻毒素-LR(MC-LR)降解菌恶臭假单胞菌(Pseudomonas putida)置于含不同浓度MC-LR的体系中,研究了体系中菌体细胞完整性和生物量的变化,考察了MC-LR对细胞的氧化胁迫以及抗氧化酶的响应.结果表明,MC-LR能够增大P. putida细胞质膜通透性,造成膜损伤,导致胞内物质外流,使细胞完整性遭到破坏;同时,MC-LR能够引起P. putida细胞的氧化胁迫,随着毒素暴露时间的延长,活性氧自由基(ROS)和膜脂过氧化产物丙二醛(MDA)含量显著升高,具有明显的剂量效应.超氧化物歧化酶(SOD)活性在MC-LR的诱导下有一个先升后降的过程,表现为对低浓度污染物的主动响应,而高浓度(2.5 mg/L)MC-LR作用5d后,ROS积累到相当高水平,对细胞代谢功能造成破坏,使SOD活性下降,并加速细胞的死亡,P. putida生物量与对照相比,下降了将近50%.     

Ethanol concentration in food and body condition affect foraging behavior in Egyptian fruit bats (Rousettus aegyptiacus)

Ethanol occurs in fleshy fruit as a result of sugar fermentation by both microorganisms and the plant itself; its concentration [EtOH] increases as fruit ripens. At low concentrations, ethanol is a nutrient, whereas at high concentrations, it is toxic. We hypothesized that the effects of ethanol on the foraging behavior of frugivorous vertebrates depend on its concentration in food and the body condition of the forager. We predicted that ethanol stimulates food consumption when its concentration is similar to that found in ripe fruit, whereas [EtOH] below or above that of ripe fruit has either no effect, or else deters foragers, respectively. Moreover, we expected that the amount of food ingested on a particular day of feeding influences the toxic effects of ethanol on a forager, and consequently shapes its feeding decisions on the following day. We therefore predicted that for a food-restricted forager, ethanol-rich food is of lower value than ethanol-free food. We used Egyptian fruit bats (Rousettus aegyptiacus) as a model to test our hypotheses, and found that ethanol did not increase the value of food for the bats. High [EtOH] reduced the value of food for well-fed bats. However, for food-restricted bats, there was no difference between the value of ethanol-rich and ethanol-free food. Thus, microorganisms, via their production of ethanol, may affect the patterns of feeding of seed-dispersing frugivores. However, these patterns could be modified by the body condition of the animals because they might trade-off the costs of intoxication against the value of nutrients acquired.     

邻苯二甲酸二丁酯影响阿尔茨海默病大鼠学习记忆能力的分子机制研究

为探究邻苯二甲酸二丁酯（DBP）影响阿尔茨海默病（AD）大鼠学习记忆能力的分子机制,将56只SPF级5~6周龄雌性Wistar大鼠随机平均分为7组：阴性对照组、0.25 mg·kg^-1·d^-1 DBP组、2.5 mg·kg^-1·d^-1 DBP组、25 mg·kg^-1·d^-1 DBP组、250 mg·kg^-1·d^-1 DBP组、AD模型组和AD+25 mg·kg^-1·d^-1 DBP组.连续灌胃处理28 d,观察Morris水迷宫结果,检测脑海马组织中活性氧（ROS）、还原型谷胱甘肽（GSH）、丙二醛（MDA）、8-羟基脱氧鸟苷（8-OHdG）的含量;采用实时荧光定量PCR （qPCR）检测Bcl-2、Bax和Caspase-3 mRNA的转录水平;通过免疫印迹试验（Western blot）检测Bcl-2、Bax和Caspase-3的蛋白表达水平.结果表明,与阴性对照组相比,不同染毒组、DBP组大鼠的学习记忆能力下降,氧化应激水平上升,且随DBP染毒浓度升高而加剧（p<0.05,p<0.01）;AD+25 mg·kg^-1·d^-1 DBP组较AD模型组大鼠的学习记忆能力损伤加剧,氧化应激水平和Bcl-2/Bax/Caspase-3信号通路上调,差异具有统计学意义（p<0.05）.由此推测,DBP可通过氧化应激作用,上调Bcl-2/Bax/Caspase-3信号通路,加剧AD大鼠海马组织的损伤,导致学习记忆能力下降.本文通过DBP影响AD大鼠学习记忆能力的分子机制研究,揭示了氧化应激对凋亡信号通路的作用,并为进一步研究DBP的毒性提供了理论和数据依据.     

Hot bats: extreme thermal tolerance in a desert heat wave

Climate change is predicted to increase temperature extremes and thus thermal stress on organisms. Animals living in hot deserts are already exposed to high ambient temperatures (T _a) making them especially vulnerable to further warming. However, little is known about the effect of extreme heat events on small desert mammals, especially tree-roosting microbats that are not strongly protected from environmental temperature fluctuations. During a heat wave with record T _as at Sturt National Park, we quantified the thermal physiology and behaviour of a single free-ranging little broad-nosed (Scotorepens greyii, henceforth Scotorepens) and two inland freetail bats (Mormopterus species 3, henceforth Mormopterus) using temperature telemetry over 3 days. On 11 and 13 January, maximum T _a was ～45.0 °C, and all monitored bats were thermoconforming. On 12 January 2013, when T _a exceeded 48.0 °C, Scotorepens abandoned its poorly insulated roost during the daytime, whereas both Mormopterus remained in their better insulated roosts and were mostly thermoconforming. Maximum skin temperatures (T _skin) ranged from 44.0 to 44.3 °C in Scotorepens and from 40.0 to 45.8 °C in Mormopterus, and these are the highest T _skin values reported for any free-ranging bat. Our study provides the first evidence of extensive heat tolerance in free-ranging desert microbats. It shows that these bats can tolerate the most extreme T _skin range known for mammals (3.3 to 45.8 °C) and delay regulation of T _skin by thermoconforming over a wide temperature range and thus decrease the risks of dehydration and consequently death.     

ZnO-NPs对好氧反硝化细菌Zobellella sp. B307的致毒机制

本文以一株筛自胶州湾沉积物中的好氧反硝化细菌Zobellella sp.B307为研究对象，在短期暴露条件下，通过细菌的生长、脱氮能力，相关酶活以及代谢途径等指标的变化，研究纳米氧化锌（ZnO-NPs）对该菌株的毒性效应；结合锌离子溶出试验、CAT和ROS等氧化应激水平测定，探讨ZnO-NPs对该菌株的致毒机制.结果表明，200mg/L的ZnO-NPs会使菌株硝酸盐氮去除率降至57.53%，LDH升高至对照组的378%，ROS水平高达对照组的5.34倍，SOD活性比对照组升高了60.32%，NIR活性仅为对照组的14.46%；ZnO-NPs主要通过诱导菌株活性氧的生成使其膜通透性改变、相关酶活性下降，并使相关蛋白质、氨基酸的合成及基因表达等代谢通路受到影响，进而抑制该菌株的反硝化能力；游离锌离子的产生可能不是ZnO-NPs对菌株的主要致毒途径.