Developmental lead exposure causes startle response deficits in zebrafish

Lead (Pb(2+)) exposure continues to be an important concern for fish populations. Research is required to assess the long-term behavioral effects of low-level concentrations of Pb(2+) and the physiological mechanisms that control those behaviors. Newly fertilized zebrafish embryos (<2h post fertilization; hpf) were exposed to one of three concentrations of lead (as PbCl(2)): 0, 10, or 30 nM until 24 hpf. (1) Response to a mechanosensory stimulus: Individual larvae (168 hpf) were tested for response to a directional, mechanical stimulus. The tap frequency was adjusted to either 1 or 4 taps/s. Startle response was recorded at 1000 fps. Larvae responded in a concentration-dependent pattern for latency to reaction, maximum turn velocity, time to reach V(max) and escape time. With increasing exposure concentrations, a larger number of larvae failed to respond to even the initial tap and, for those that did respond, ceased responding earlier than control larvae. These differences were more pronounced at a frequency of 4 taps/s. (2) Response to a visual stimulus: Fish, exposed as embryos (2-24 hpf) to Pb(2+) (0-10 μM) were tested as adults under low light conditions (≈ 60 μW/m(2)) for visual responses to a rotating black bar. Visual responses were significantly degraded at Pb(2+) concentrations of 30 nM. These data suggest that zebrafish are viable models for short- and long-term sensorimotor deficits induced by acute, low-level developmental Pb(2+) exposures.     

Developmental lead exposure induces depressive-like behavior in female rats

The involvement of neurotoxicants in the etiology of emotional pathologies is becoming an issue in neurotoxicology. Lead (Pb) exposure during childhood has been associated with increased impulsivity, aggressivity, and delinquency. Considering the paucity of experimental studies investigating the involvement of developmental Pb exposure in emotional disorders, our objective was to investigate whether Pb exposure during pregnancy and/or lactation could be related to depressive symptoms in adult male and female rats. Wistar dams received 10 mg of Pb, as Pb acetate, or 13.4 mg of Na acetate, by gavage, daily, during pregnancy and lactation. By cross-fostering at the time of birth, pups were either exposed to Pb or Na acetate during pregnancy only, lactation only, or during both pregnancy and lactation. At 70 days of age, animals were submitted to the open-field test followed by the forced swimming test. Pb levels were measured in the blood of dams (weaning) and pups (after behavioral evaluation). The results demonstrated that exposure to Pb during both pregnancy and lactation induced, in males, an increased emotionality state detected in the open-field test, and in females, depressive-like behavior detected in the forced swimming test. These alterations were observed at residual blood Pb levels (i.e., around 5 microg/dL).     

Developmental toxicity of auranofin in zebrafish embryos

Auranofin (AF) is used in clinic for the treatment of rheumatoid arthritis, repurposing of AF as an anticancer drug has just finished a phase I/II clinical trial, but the developmental toxicity of AF remains obscure. This study focused on its developmental toxicity by using zebrafish embryos. Zebrafish embryos were exposed to different concentrations (1, 2.5, 5, 10 μm ) of AF from 2 h post‐fertilization (hpf) to 72 hpf. At 72 hpf, two major developmental defects caused by AF were found, namely severe pericardial edema and hypopigmentation, when embryos were exposed to concentrations higher than 2.5 μm . Biochemical detection of oxidative stress enzyme combined with expressions of a series of genes related to oxidative stress, cardiac, metal stress and pigment formation were subsequently tested. The superoxide dismutase activity was decreased while malondialdehyde content was accumulated by AF treatment. The expression of oxidative stress‐related genes (sod1 , gpx1a , gst ), pigment‐related genes (mitfb , trp‐1a ) and one metal stress‐related gene ctr1 were all decreased by AF exposure. The expressions of cardiac‐related genes (amhc , vmhc ) and one metal‐related gene hsp70 were found to be significantly upregulated by AF exposure. These findings indicated the potential developmental toxicity of AF on zebrafish early development. Copyright © 2016 John Wiley & Sons, Ltd.     

Early embryonic ethanol exposure impairs shoaling and the dopaminergic and serotoninergic systems in adult zebrafish

Fetal alcohol syndrome (FAS) is a devastating disorder accompanied by numerous morphological and behavioral abnormalities. Human FAS has been modeled in laboratory animals including the zebrafish. Recently, embryonic exposure to low doses of ethanol has been shown to impair behavior without any gross morphological alterations in zebrafish. The exposed zebrafish showed reduced responses to animated conspecific images. The effect of embryonic ethanol exposure, however, has not been investigated in a real shoal and the potential mechanisms underlying the behavioral impairment are also unknown. Here we show that a 2 h long immersion in 0.25% and 0.50% (vol/vol) alcohol at 24 h post fertilization significantly increases the distance among members of freely swimming groups of zebrafish when measured at 70 days post fertilization. We also show that this impaired behavior is accompanied by reduced levels of dopamine, DOPAC, serotonin and 5HIAA as quantified by HPLC from whole brain extracts. Our results demonstrate that even very low concentrations of alcohol applied for a short period of time during the development of zebrafish can impair behavior and brain function. We argue that the observed behavioral impairment is not likely to be due to altered performance capabilities, e.g. motor function or perception, but possibly to social behavior itself. We also argue that our neurochemical data represent the first step towards understanding the mechanisms of this abnormality in zebrafish, which may lead to better modeling of, and ultimately perhaps better therapies for human FAS.     

Brief embryonic strychnine exposure in zebrafish causes long-term adult behavioral impairment with indications of embryonic synaptic changes

Zebrafish provide a powerful model of the impacts of embryonic toxicant exposure on neural development that may result in long-term behavioral dysfunction. In this study, zebrafish embryos were treated with 1.5 mM strychnine for short embryonic time windows to induce transient changes in inhibitory neural signaling, and were subsequently raised in untreated water until adulthood. PCR analysis showed indications that strychnine exposure altered expression of some genes related to glycinergic, GABAergic and glutamatergic neuronal synapses during embryonic development. In adulthood, treated fish showed significant changes in swimming speed and tank diving behavior compared to controls. Taken together, these data show that a short embryonic exposure to a neurotoxicant can alter development of neural synapses and lead to changes in adult behavior.     

佐匹克隆及其杂质对斑马鱼胚胎发育毒性的比较研究

目的 对佐匹克隆及其主要杂质的斑马鱼胚胎发育毒性进行比较研究.方法 以斑马鱼胚胎为实验对象,在体视光学显微镜下观察佐匹克隆及其主要杂质(杂质A、B、C和2-氨基-5-氯吡啶)在不同暴露浓度时对斑马鱼胚胎发育情况的影响,包括胚胎致畸、致死情况的检测与统计.结果 佐匹克隆及其4个杂质对斑马鱼胚胎发育的毒性表型类似;毒性作用...     

Developmental toxicity of low generation PAMAM dendrimers in zebrafish

Biological molecules and intracellular structures operate at the nanoscale; therefore, development of nanomedicines shows great promise for the treatment of disease by using targeted drug delivery and gene therapies. PAMAM dendrimers, which are highly branched polymers with low polydispersity and high functionality, provide an ideal architecture for construction of effective drug carriers, gene transfer devices and imaging of biological systems. For example, dendrimers bioconjugated with selective ligands such as Arg-Gly-Asp (RGD) would theoretically target cells that contain integrin receptors and show potential for use as drug delivery devices. While RGD-conjugated dendrimers are generally considered not to be cytotoxic, there currently exists little information on the risks that such materials pose to human health. In an effort to compliment and extend the knowledge gleaned from cell culture assays, we have used the zebrafish embryo as a rapid, medium throughput, cost-effective whole-animal model to provide a more comprehensive and predictive developmental toxicity screen for nanomaterials such as PAMAM dendrimers. Using the zebrafish embryo, we have assessed the developmental toxicity of low generation (G3.5 and G4) PAMAM dendrimers, as well as RGD-conjugated forms for comparison. Our results demonstrate that G4 dendrimers, which have amino functional groups, are toxic and attenuate growth and development of zebrafish embryos at sublethal concentrations; however, G3.5 dendrimers, with carboxylic acid terminal functional groups, are not toxic to zebrafish embryos. Furthermore, RGD-conjugated G4 dendrimers are less potent in causing embryo toxicity than G4 dendrimers. RGD-conjugated G3.5 dendrimers do not elicit toxicity at the highest concentrations tested and warrant further study for use as a drug delivery device.     

β-氯氰菊酯对斑马鱼胚胎的发育毒性

目的以斑马鱼胚胎为模型,探讨一种高效氯氰菊酯β-氯氰菊酯对胚胎发育的影响。方法 丙酮为助溶剂,配制β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1,采用换水式每12 h更换一半β-氯氰菊酯溶液,对斑马鱼胚胎进行96 h暴露处理,采用显微镜观察β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1对斑马鱼胚胎发育形态,测定受精后24 h(24 hpf)自主抽动次数、48 hpf心率及孵化率、72和96 hpf体轴弯曲个体比例等。结果 与正常对照组比较,β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1组斑马鱼胚胎在24 hpf前形态上未出现明显异常,48 hpf以后表现出体轴弯曲、心包囊肿等不同程度的毒性反应症状,β-氯氰菊酯0.2 mg.L-1组幼鱼胸鳍发育即受到严重抑制且黑色素减少体色偏黄;随着β-氯氰菊酯浓度的增加,斑马鱼胚胎在24 hpf时每分钟自主抽动次数由正常对照组的(0.72±0.19)次增加至(3.83±1.07)次(P<0.05);48 hpf孵化率由对照组的(15.5±4.3)%升高至(98.9±1.2)%(P<0.05)。β-氯氰菊酯0.05 mg.L-1组72 hpf和96 hpf体轴弯曲个体比例分别为6.6%和10%,β-氯氰菊酯1 mg.L-1组分别为97.8%和100%。结论 β-氯氰菊酯对斑马鱼胚胎的神经及形态发育均有明显抑制作用,并且呈现一定的时间剂量依赖性。     

Retention of lead acetate in weanling and adult rats

The relative toxicity of lead acetate provided at uniform dosages (mg/kg body weight/week) in drinking water or by a single weekly po administration was studied in weanling and adult Sprague-Dawley rats. Free erythrocyte protoporphyrins, urinary δ-aminolevulinic acid, and lead levels in blood, brain, kidney, and femur were measured. Effects of age and schedule of administration were evaluated by calculating the percentage of ingested lead retained in brain, kidney, and femur. No effects of age on levels of lead in blood or in brain tissue were observed within the same dosage schedule group when dosing was equivalent on the basis of body weight. Weanling rats had lower levels of lead in kidney and higher levels in femur than did equivalently dosed adult rats. Concentrations of lead in blood, kidney, and femur were significantly higher in weanling rats exposed to lead daily in drinking water than in weanling animals receiving an equivalent dose of lead once per week. Brain lead levels were significantly higher in adult rats receiving lead in drinking water than in intermittently exposed adult animals. Weanling rats retained significantly higher fractions of ingested lead in brain tissue and in femur than did equivalently dosed adult rats under both schedules of lead administration. Under conditions of intermittent exposure to equivalent doses of lead, adult rats retained a higher percentage of lead in kidney tissue than did weanling animals. Lead retention in kidney tissue of weanling rats was significantly higher when lead was provided daily than when equivalent doses were administered at weekly intervals.     

Trimethyltin chloride (TMT) neurobehavioral toxicity in embryonic zebrafish

Trimethyltin chloride (TMT) is a neurotoxicant that is widely present in the aquatic environment, primarily from the manufacture of PVC plastic, but few studies have evaluated aquatic neurotoxicity. We have examined TMT dose-dependent malformation and neurobehavioral toxicity in the embryonic zebrafish model. Exposure of embryos to TMT (0-10 μM) from 48 to 72 hours post fertilization (hpf) elicited a concentration-related increase (0-100%) in malformation incidence with an EC(25) of 5.55 μM. TMT also significantly modulated the frequency of tail flexion, the earliest motor behavior observed in developing zebrafish, and the ability to respond to a mechanical tail touch. Exposure to 5 μM TMT from 48 to 72 hpf modulated the photomotor response at 4 and 5 days post fertilization and significantly promoted apoptosis in the tail. Our study demonstrates the morphological and behavioral sensitivity of the developing zebrafish to TMT and establishes a platform for future identification of the affected pathways and chemical modulators of TMT toxicity.     

三氯异氰尿酸对斑马鱼胚胎及幼鱼的发育毒性

目的探讨新型消毒剂三氯异氰尿酸(TCCA)对斑马鱼胚胎及幼鱼的发育毒性。方法选择受精后2 h的斑马鱼胚胎进行染毒:①将胚胎置于含有TCCA 50,100,150,200,250和300 mg·L~(-1)的培养液中暴露48 h,检测半数致死浓度(LC_(50))。②将胚胎置于含有TCCA 0,10.4,20.8和41.7 mg·L~(-1)的培养液中暴露96 h,分别于暴露后48,72和96 h检测胚胎死亡率、畸形率和心率,采用羟胺法于暴露后2,4和6 h检测胚胎组织超氧化物歧化酶(SOD)的活性,HE染色观察暴露后7 d幼鱼头部组织病理结构。结果 TCCA暴露48 h,斑马鱼胚胎LC_(50)为166.9 mg·L~(-1)。与正常对照组相比,暴露后96 h,TCCA 41.7 mg·L~(-1)组斑马鱼胚胎死亡率和畸形率显著升高(P<0.05),TCCA各剂量组心率显著下降(P<0.05);暴露后72h,TCCA41.7mg·L~(-1)组死亡率显著升高(P<0.05),20.8和41.7mg·L~(-1)组畸形率显著升高(P<0.05),心率显著下降(P<0.05);暴露后48 h,TCCA 41.7 mg·L~(-1)组畸形率显著升高(P<0.05)、心率显著下降(P<0.05)。TCCA暴露4和6 h,20.8和41.7 mg·L~(-1)组SOD活性较正常对照组显著下降(P<0.05)。TCCA暴露7 d后,与正常对照组相比,各浓度组斑马鱼幼鱼均出现脑和眼部间隙变大及眼部视网膜分层不明显的病理改变。结论 TCCA对斑马鱼胚胎发育有毒性作用,能引起胚胎发育早期SOD活性下降,造成幼鱼视网膜组织结构损伤。     

Developmental estrogenic exposure in zebrafish (Danio rerio): II. Histological evaluation of gametogenesis and organ toxicity

Aquatic species can be exposed to endocrine disrupting chemicals (EDCs) in wastewater that often includes the weak estrogen, 4-nonylphenol (NP) and the potent estrogen, 17alpha-ethinylestradiol (EE). The goal of the present study was to determine concentration-dependent effects of developmental exposure to NP and EE on gametogenesis, as well as gonad, kidney and liver pathology using quantitative histological evaluation of hematoxylin/eosin-stained saggital sections of zebrafish (Danio rerio). The major finding of the present study was that exposure to NP (>/=100 microg/l nominal) and EE (>/=1 ng/l nominal) from 2 to 60 days post-hatch (dph) caused concentration-dependent suppression of gametogenesis in both male and female zebrafish. Severe kidney pathology was observed in 60 dph zebrafish, specifically glomerular dilation or degeneration, fibrosis, tubule enlargement and tubule necrosis, at a threshold of 10 ng/l EE. However, minor kidney histopathology indicated by increased pyknotic nuclei in kidney tubule and interstitial (hematopoietic) cells was detected at lower estrogenic exposures (>/=10 microg/l NP nominal) than delayed gametogenesis. Considering all histological parameters in the current study, the rank order of potency for pathological effects in 60 dph zebrafish was 10 ng/l EE>1 ng/l EE=100 microg/l NP>30 microg/l NP>10 microg/l NP10 (nominal concentrations). Zebrafish from the same cohort examined in the current study that had been placed in clean water from 60 to 300 dph had histologically normal testes and no kidney or liver histopathology. However, increased ovarian follicle atresia was detected at 300 dph in zebrafish exposed developmentally to 100 microg/l NP. Therefore, we conclude that functional rather than morphological changes may be more important for future evaluations of developmental exposure to estrogens in fish, and that negative effects in female rather than male gonads may contribute to prolonged breeding impairment.     

Gender-dependent behavioural impairment and brain metabolites in young adult rats after short term exposure to lead acetate

We investigated the behavioural effects of short-term lead (Pb) exposure in adult rats producing blood Pb concentration (<10 μg/dL) below those associated with neurological impairment in occupationally exposed individuals. In order to assess gender differences, we performed parallel behavioural experiments in male and female rats. Exposure to Pb acetate (50 mg/L in drinking water) for 30-45 days induced behavioural alterations consisting in hyperactivity in a novel environment and impairment of spatial memory. These effects were observed only in male rats. Object recognition, motor coordination were unaffected by Pb exposure. Magnetic resonance spectroscopy allows in vivo assessment of main brain metabolites (glutamate/glutamine, creatine, myoinositol, N-acetylaspartate and choline) whose changes have been demonstrated in several central nervous system pathologies. Exposure to Pb did not affect metabolite profile in the striatum and increase myoinositol signal in the hippocampus of male rats. The increase in myoinositol in hippocampus suggests early Pb-induced alteration in glial metabolism in this brain region and may represent a potential marker of early brain dysfunction during Pb exposure.     

Low-level lifetime lead exposure produces behavioral toxicity (spatial discrimination reversal) in adult monkeys

Cynomolgus monkeys (Macaca fascicularis) were dosed from birth with 0, 50, or 100 micrograms/kg/day of lead. This regimen resulted in blood lead concentrations of 3, 15, or 25 micrograms/dl, respectively, before withdrawal of infant formula at 200 days of age. Blood lead concentration declined thereafter over the next 100 to 150 days to steady-state concentrations of 3, 11, or 13 micrograms/dl. At 9 to 10 years of age, these monkeys were tested on a series of spatial discrimination reversal problems. The monkey was required to respond on the right-most of two push buttons in order to receive a fruit-juice reward. When the task was learned, the left-most button became correct for a total of 15 such reversals on each of three tasks. The stimuli for the first task included no irrelevant cues, the second task included irrelevant form cues, and the third task included irrelevant form and color cues. Treated monkeys were impaired relative to controls in the presence but not in the absence of irrelevant cues. Moreover, the lower dose group was impaired only during the first task after the introduction of irrelevant stimuli, but not after irrelevant stimuli were familiar. These findings represent behavioral impairment in adult monkeys as a result of lifetime lead exposure resulting in blood lead concentrations that are typical for humans in industrialized environments.     

妊娠中期可卡因对小鼠的发育毒性

目的:探讨可卡因对小鼠妊娠中期的发育毒性,尤其是对脑发育的影响.方法:建立妊娠中期给药的小鼠动物模型,体重相近的妊娠母鼠被分为三组:(1)可卡因注射自由饮食组(COC);(2)盐水注射伴有饮食对照组(SPF),饮食参考体重相近、妊娠时间相同的COC组母鼠;(3)盐水注射自由饮食组(SAL).从妊娠第8天(E8)至第12天(E12)给药,记录母鼠、胎鼠和仔鼠的各项生理指标,并用HPLC分析各组胎鼠纹状体中多巴胺、5-HT含量的变化.结果:尽管COC和 SPF组母鼠与 SAL组母鼠相比摄食量少,体重增加量少,但E17 天取材时,仅COC组胎鼠表现为脑和纹状体重量低;COC组仔鼠生后第 1天(P1)双顶径(BPD)也小于其它两组仔鼠.此外,COC组胎鼠表现出脑/体重比的降低,说明宫内暴露可卡因引起的胎鼠的发育迟缓是一个不平衡过程,脑组织的受累比其它组织严重.神经递质分析和组织学分析表明 COC组胎鼠脑内多巴胺和5-羟色胺的水平增高,肝脏呈现出形态学改变.结论:妊娠中期暴露可卡因可引起胎鼠宫内发育迟缓,尤其是脑发育迟缓.单纯母体营养不良在宫内暴露可卡因引起的后代发育迟缓过程中不能起决定性作用,而可能是药物直接作用的结果.     

Persistent behavioral impairment caused by embryonic methylphenidate exposure in zebrafish

As more adults take the stimulant medication methylphenidate to treat attention deficit hyperactivity disorder (ADHD) residual type, the risk arises with regard to exposure during early development if people taking the medication become pregnant. We studied the neurobehavioral effects of methylphenidate in zebrafish. Zebrafish offer cellular reporter systems, continuous visual access and molecular interventions such as morpholinos to help determine critical mechanisms underlying neurobehavioral teratogenicity. Previously, we had seen that persisting neurobehavioral impairment in zebrafish with developmental chlorpyrifos exposure was associated with disturbed dopamine systems. Because methylphenidate is an indirect dopamine agonist, it was thought that it might also cause persistent behavioral impairment after developmental exposure. Zebrafish embryos were exposed to the ADHD stimulant medication methylphenidate 0-5 days post fertilization (12.5-50 mg/l). They were tested for long-term behavioral effects as adults. Methylphenidate exposure (50 mg/l) caused significant increases in dopamine, norepinepherine and serotonin on day 6 but not day 30 after fertilization. In the novel tank diving test of predatory avoidance developmental methylphenidate (50 mg/l) caused a significant reduction in the normal diving response. In the three-chamber spatial learning task early developmental methylphenidate (50 mg/l) caused a significant impairment in choice accuracy. These data show that early developmental exposure of zebrafish to methylphenidate causes a long-term impairment in neurobehavioral plasticity. The identification of these functional deficits in zebrafish enables further studies with this model to determine how molecular and cellular mechanisms are disturbed to arrive at this compromised state.     

Developmental toxicity of albendazole and its three main metabolites in zebrafish embryos

Albendazole (ABZ) is used as an anthelmintic drug in humans and animals. ABZ has been shown to cause developmental toxicity in experimental animals, however it is not clear if this is caused by the parent compound or a metabolite. Zebrafish embryos were exposed from 1 to 144 hpf (hours post fertilization) to investigate the developmental toxicity of ABZ, the first metabolite albendazole sulphoxide and the subsequent metabolites albendazole sulphone (ABZSO₂) and albendazole-2-aminosulphone (ABZSO₂NH₂). The results showed that ABZ caused malformations of head and tail and embryonic lethality from 0.3 μM. In contrast, the metabolites did not display developmental toxicity at any tested concentration. Dechorionation did not influence the developmental toxic potential of ABZ and ABZSO, indicating that bioavailability was not a limiting factor. Chemical analysis showed that at sublethal concentrations, most of ABZ was metabolized to ABZSO. The results demonstrate that in zebrafish embryos ABZ rather than ABZSO displays developmental toxicity.     

Developmental toxicity of prenatal exposure to toluene

Organic solvents have become ubiquitous in our environment and are essential for industry. Many women of reproductive age are increasingly exposed to solvents such as toluene in occupational settings (ie, long-term, low-concentration exposures) or through inhalant abuse (eg, episodic, binge exposures to high concentrations). The risk for teratogenic outcome is much less with low to moderate occupational solvent exposure compared with the greater potential for adverse pregnancy outcomes, developmental delays, and neurobehavioral problems in children born to women exposed to high concentrations of abused organic solvents such as toluene, 1,1,1-trichloroethane, xylenes, and nitrous oxide. Yet the teratogenic effects of abuse patterns of exposure to toluene and other inhalants remain understudied. We briefly review how animal models can aid substantially in clarifying the developmental risk of exposure to solvents for adverse biobehavioral outcomes following abuse patterns of use and in the absence of associated health problems and co-drug abuse (eg, alcohol). Our studies also begin to establish the importance of dose (concentration) and critical perinatal periods of exposure to specific outcomes. The present results with our clinically relevant animal model of repeated, brief, high-concentration binge prenatal toluene exposure demonstrate the dose-dependent effect of toluene on prenatal development, early postnatal maturation, spontaneous exploration, and amphetamine-induced locomotor activity. The results imply that abuse patterns of toluene exposure may be more deleterious than typical occupational exposure on fetal development and suggest that animal models are effective in studying the mechanisms and risk factors of organic solvent teratogenicity.