Potential therapeutic role of spermine via Rac1 in osteoporosis:Insights from zebrafish and mice

Osteoporosis(OP)is a prevalent metabolic bone disease.While drug therapy is essential to prevent bone loss in osteoporotic patients,current treatments are limited by side effects and high costs,necessitating the development of more effective and safer targeted therapies.Utilizing a zebrafish(Danio rerio)larval model of osteoporosis,we explored the influence of the metabolite spermine on bone homeostasis.Results showed that spermine exhibited dual activity in osteoporotic zebrafish larvae by increasing bone formation and decreasing bone resorption.Spermine not only demonstrated excellent biosafety but also mitigated prednisolone-induced embryonic neurotoxicity and cardiotoxicity.Notably,spermine showcased protective attributes in the nervous systems of both zebrafish embryos and larvae.At the molecular level,Rac1 was identified as playing a pivotal role in mediating the antiosteoporotic effects of spermine,with P53 potentially acting downstream of Rac1.These findings were confirmed using mouse(Mus musculus)models,in which spermine not only ameliorated osteoporosis but also promoted bone formation and mineralization under healthy conditions,suggesting strong potential as a bonestrengthening agent.This study underscores the beneficial role of spermine in osteoporotic bone homeostasis and skeletal system development,highlighting pivotal molecular mediators.Given their efficacy and safety,human endogenous metabolites like spermine are promising candidates for new anti-osteoporotic drug development and daily bone-fortifying agents.

Mechanism by which Rab5 promotes regeneration and functional recovery of zebrafish Mauthner axons

Rab5 is a GTPase protein that is involved in intracellular membrane trafficking. It functions by binding to various effector proteins and regulating cellular responses, including the formation of transport vesicles and their fusion with the cellular membrane. Rab5 has been reported to play an important role in the development of the zebrafish embryo;however, its role in axonal regeneration in the central nervous system remains unclear. In this study, we established a zebrafish Mauthner cell model of axonal injury using single-cell electroporation and two-photon axotomy techniques. We found that overexpression of Rab5 in single Mauthner cells promoted marked axonal regeneration and increased the number of intra-axonal transport vesicles. In contrast, treatment of zebrafish larvae with the Rab kinase inhibitor CID-1067700markedly inhibited axonal regeneration in Mauthner cells. We also found that Rab5 activated phosphatidylinositol 3-kinase(PI3K) during axonal repair of Mauthner cells and promoted the recovery of zebrafish locomotor function. Additionally, rapamycin, an inhibitor of the mechanistic target of rapamycin downstream of PI3K, markedly hindered axonal regeneration. These findings suggest that Rab5 promotes the axonal regeneration of injured zebrafish Mauthner cells by activating the PI3K signaling pathway.

Improvement in Tol2 transposon for efficient large-cargo capacity transgene applications in cultured cells and zebrafish(Danio rerio)

Most viruses and transposons serve as effective carriers for the introduction of foreign DNA up to 11 kb into vertebrate genomes.However,their activity markedly diminishes with payloads exceeding 11 kb.Expanding the payload capacity of transposons could facilitate more sophisticated cargo designs,improving the regulation of expression and minimizing mutagenic risks associated with molecular therapeutics,metabolic engineering,and transgenic animal production.In this study,we improved the Tol2 transposon by increasing protein expression levels using a translational enhancer(QBI SP163,ST)and enhanced the nuclear targeting ability using the nuclear localization protein H2B(SHT).The modified Tol2 and ST transposon efficiently integrated large DNA cargos into human cell cultures(H1299),comparable to the well-established super PiggyBac system.Furthermore,mRNA from ST and SHT showed a significant increase in transgene delivery efficiency of large DNA payloads(8 kb,14 kb,and 24 kb)into zebrafish(Danio rerio).This study presents a modified Tol2 transposon as an enhanced nonviral vector for the delivery of large DNA payloads in transgenic applications.

Metabolomic-based analysis reveals bile acid-mediated ovarian failure induced by low temperature in zebrafish

As ectotherms, fish are highly sensitive to temperature fluctuations, which can profoundly impact their reproductive cycles. In this study, we investigated the fertility and histological characteristics of zebrafish(Danio rerio) ovaries exposed to a temperature gradient ranging from the thermopreferendum temperature of the species,27℃, to lower temperatures of 22℃, 20℃, and 13℃ over a period of two weeks. Comparative metabolomic(six biological replicates for each temperature) and transcriptomic(four biological replicates for each temperature) analyses were conducted under the four temperature conditions. Results indicated that lower temperatures inhibited oocyte development and differential metabolites were involved in steroid hormone production,antioxidant function, and lipid and protein catabolism.Disrupted reproductive hormones, increased proteolysis,and lipid degradation significantly impeded oocyte development and egg maturation. Notably, a significant increase in bile acid content was noted in the ovaries of the cold-treated fish, indicating that bile acids play a critical role in ovarian failure. Overall, these findings provide valuable insights into the mechanisms governing the reproductive response of fish to cold stress.

c-myb is involved in CML progression and is a therapeutic target in the zebrafish CML model

Background:Despite the success of tyrosine kinase inhibitors in chronic myeloid leukemia(CML)therapy,CML still faces the challenges of drug resistance and progression to blast crisis.Twenty-five percent of patients have imatinib resistance and treatment difficulties due to heterogeneity after progression,but little is known about the mechanism.A key transcription factor in hematopoiesis,MYB,has been reported to increase abnormally in several types of aggressive blood disorders including CML.Methods:This study used a zebrafish model to explore the relationship between BCR/ABL1 and c-myb in CML progression.A CML zebrafish model was crossed with a c-myb hyperactivity transgenic line.Results:It was found that both exogenous BCR/ABL1 and c-myb could up-regulate the expression of neutrophil-related genes.More seriously,neutrophil accumulation was observed when BCR/ABL1 was combined with c-myb overexpression.Further studies showed that c-myb may be one of the downstream targets of BCR/ABL1 and the effect of BCR/ABL1 on neutrophils was c-myb dependent.Taking advantage of this inheritable in vivo model,it was shown that a combination of imatinib and flavopiridol,a cyclin-dependent kinase inhibitor targeting MYB,could more effectively alleviate the aggressive phenotype of the double transgene line.Conclusion:In summary,this study suggests that c-myb acts downstream of BCR/ABL1 and is involved in CML progression and is therefore a risk factor and a valuable target for the treatment of CML progression.The model used in the study could be helpful in high-throughput drug screening in CML transformation.

Three-dimensional morphological and fluorescent imaging of zebrafish with a continuous-rotational light-sheet microscope

Light-sheet fluorescence microscopy(LSFM)has been widely used to image the three-dimensional(3D)structures and functions of various millimeter-size bio-specimen such as zebrafish.However,the sample adsorption and scattering cause shading of the light-sheet illumination,preventing the even 3D image of thick samples.Herein,we report a continuous-rotational light-sheet microscope(CR-LSM)that enables simultaneous 3D bright-field and fluorescence imaging.With a high-accuracy rotational stage,CR-LSM records the outline projections and the fluorescent images of the sample at multiple rotation angles.Then,3D morphology and fluorescent structure were reconstructed with a developed algorithm.Using CR-LSM,zebrafish’s whole-fish contour and blood vessel structures were obtained simultaneously.

Ethyl acetate fraction of Sargassum pallidum extract attenuates particulate matter-induced oxidative stress and inflammation in keratinocytes and zebrafish

Objective:To evaluate the effect of the ethyl acetate fraction derived from Sargassum pallidum extract against particulate matter(PM)-induced oxidative stress and inflammation in HaCaT cells and zebrafish.Methods:HaCaT cells and zebrafish were used to evaluate the protective effects of the ethyl acetate fraction of Sargassum pallidum extract against PM-induced oxidative stress and inflammation.The production of nitric oxide(NO),intracellular ROS,prostaglandin E_(2)(PGE_(2)),and pro-inflammatory cytokines,and the expression levels of COX-2,iNOS,and NF-κB were evaluated in PM-induced HaCaT cells.Furthermore,the levels of ROS,NO,and lipid peroxidation were assessed in the PM-exposed zebrafish model.Results:The ethyl acetate fraction of Sargassum pallidum extract significantly decreased the production of NO,intracellular ROS,and PGE_(2) in PM-induced HaCaT cells.In addition,the fraction markedly suppressed the levels of pro-inflammatory cytokines and inhibited the expression levels of COX-2,iNOS,and NF-κB.Furthermore,it displayed remarkable protective effects against PM-induced inflammatory response and oxidative stress,represented by the reduction of NO,ROS,and lipid peroxidation in zebrafish.Conclusions:The ethyl acetate fraction of Sargassum pallidum extract exhibits a protective effect against PM-induced oxidative stress and inflammation both in vitro and in vivo and has the potential as a candidate for the development of pharmaceutical and cosmeceutical products.

P-aminobenzoic acid promotes retinal regeneration through activation of Ascl1a in zebrafish

The retina of zebrafish can regenerate completely after injury.M ultiple studies have demonstrated that metabolic alte rations occur during retinal damage;however to date no study has identified a link between metabolites and retinal regeneration of zebrafish.Here,we performed an unbiased metabolome sequencing in the N-methyl-D-aspartic acid-damaged retinas of zebrafish to demonstrate the metabolomic mechanism of retinal regeneration.Among the differentially-ex pressed metabolites,we found a significant decrease in p-aminobenzoic acid in the N-methyl-D-aspartic acid-damaged retinas of zebrafish.Then,we investigated the role of p-aminobenzoic acid in retinal regeneration in adult zebrafish.Impo rtantly,p-aminobenzoic acid activated Achaetescute complex-like 1a expression,thereby promoting Müller glia reprogramming and division,as well as Müller glia-derived progenitor cell proliferation.Finally,we eliminated folic acid and inflammation as downstream effectors of PABA and demonstrated that PABA had little effect on Müller glia distribution.Taken together,these findings show that PABA contributes to retinal regeneration through activation of Achaetescute complex-like 1a expression in the N-methyl-Daspartic acid-damaged retinas of zebrafish.

Effects of Imazethapyr-Based Herbicide Formulation in the Zebrafish (Danio rerio) Hepatocyte Cell Line (ZF-L): Cytotoxicity and Oxidative Stress

Seizures of agrochemical formulations have increased in Brazil and Rio Grande do Sul is among the Brazilian states with the highest number of seizures of these products obtained illicitly. The use of illicit formulations can cause significant harm to agricultural production, the environment, and non-target species. This study evaluated the cytotoxicity and oxidative stress of a seized formulation containing the herbicide imazethapyr (IMZT). Characterization of the herbicide included gas chromatography-mass spectrometry (GC-MS) and thermal analyses (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)). Hemolytic and cytotoxicity assays in ZF-L hepatic cells showed IC50 values of 12.75 µg/mL, 3.01 µg/mL, 2.67 µg/mL, and 1.61 µg/mL for erythrocytes, [3(4,5-dimethyl)-2 bromide-5 diphenyl tetrazolium] (MTT), neutral red (NR), and lactate dehydrogenase (LDH) assays, respectively. The median IC50 of 2.84 µg/mL was used in oxidative stress assays, revealing increased reactive oxygen species (ROS) production, reduced total sulfhydryl content, and decreased superoxide dismutase (SOD) and catalase (CAT) activity. This study is the first to report in vitro oxidative stress induced by IMZT in the ZF-L cell line, emphasizing the importance of in vitro assays for assessing the toxic effects of seized agrochemicals on human health and the environment.

Skin Toxicity of Wufang Babu Ointment to Zebrafish

[Objectives]Using wild-type AB strain of zebrafish as experimental animal,this study investigated the damaging effect of Wufang Babu Ointment on skin cells,in order to evaluate the skin toxicity of Wufang Babu Ointment.[Methods]Wild-type AB strain of zebrafish with an age of 2 d were taken and fed in different concentrations of Wufang Babu Ointment solution for 24 h.The number of deaths in each group of zebrafish was recorded,and the mortality rate was calculated.Using Origin 8.0 software,the maximum non lethal concentration(MNLC)was simulated.Zebrafish raised in different concentrations of Wufang Babu Ointment solution for 24 h were placed under an anatomical microscope for taking photos,to analyze and calculate the incidence of skin damage in zebrafish.Based on the statistical analysis results of this indicator,the skin toxicity of Wufang Babu Ointment was evaluated.[Results]The MNLC of Wufang Babu Ointment on zebrafish was 671μg/mL;Wufang Babu Ointment can induce skin damage at the concentrations of 224μg/mL(1/3 MNLC)and 671μg/mL(MNLC).[Conclusions]Wufang Babu Ointment had certain skin toxicity to zebrafish.

Depletion of stearoyl-CoA desaturase(scd) leads to fatty liver disease and defective mating behavior in zebrafish

Stearyl coenzyme A desaturase(SCD), also known as delta-9 desaturase, catalyzes the rate-limiting step in the formation of monounsaturated fatty acids.In mammals, depletion or inhibition of SCD activity generally leads to a decrease in triglycerides and cholesteryl esters. However, the endogenous role of scd in teleost fish remains unknown. Here, we generated a zebrafish scd mutant(scd-/-) to elucidate the role of scd in lipid metabolism and sexual development. Gas chromatography-mass spectrometry(GC-MS) showed that the scd-/- mutants had increased levels of saturated fatty acids C16:0 and C18:0, and decreased levels of monounsaturated fatty acids C16:1 and C18:1. The mutant fish displayed a short stature and an enlarged abdomen during development. Unlike Scd-/ -mammals, the scd-/- zebrafish showed significantly increased fat accumulation in the whole body,especially in the liver, leading to hepatic mitochondrial dysfunction and severe cell apoptosis.Mechanistically, srebf1, a gene encoding a transcriptional activator related to adipogenesis,acc1 and acaca, genes involved in fatty acid synthesis, and dgat2, a key gene involved in triglyceride synthesis, were significantly upregulated in mutant livers to activate fatty acid biosynthesis and adipogenesis. The scd-/- males exhibited defective natural mating behavior due to defective genital papillae but possessed functional mature sperm. All defects in the scd-/- mutants could be rescued by ubiquitous transgenic overexpression of scd. In conclusion, our study demonstrates that scd is indispensable for maintaining lipid homeostasis and development of secondary sexual characteristics in zebrafish.

Dusp 1 regulates thermal tolerance limits in zebrafish by maintaining mitochondrial integrity

Temperature tolerance restricts the distribution of a species. However, the molecular and cellular mechanisms that set the thermal tolerance limits of an organism are poorly understood. Here, we report on the function of dual-specificity phosphatase 1(DUSP1) in thermal tolerance regulation. Notably, we found that dusp1-/- zebrafish grew normally but survived within a narrowed temperature range. The higher susceptibility of these mutant fish to both cold and heat challenges was attributed to accelerated cell death caused by aggravated mitochondrial dysfunction and over-production of reactive oxygen species in the gills. The DUSP1-MAPK-DRP1 axis was identified as a key pathway regulating these processes in both fish and human cells. These observations suggest that DUSP1 may play a role in maintaining mitochondrial integrity and redox homeostasis. We therefore propose that maintenance of cellular redox homeostasis may be a key mechanism for coping with cellular thermal stress and that the interplay between signaling pathways regulating redox homeostasis in the most thermosensitive tissue(i.e., gills) may play an important role in setting the thermal tolerance limit of zebrafish.

Soxllb regulates the migration and fate determination of Müller glia-derived progenitors during retina regeneration in zebrafish

The transcription factor Sox11 plays important roles in retinal neurogenesis during vertebrate eye development.However,its function in retina regeneration remains elusive.Here we report that Sox11 b,a zebrafish Sox11 homolog,regulates the migration and fate determination of Müller glia-derived progenitors(MGPCs)in an adult zebrafish model of mechanical retinal injury.Following a stab injury,the expression of Sox11 b was induced in proliferating MGPCs in the retina.Sox11 b knockdown did not affect MGPC formation at 4 days post-injury,although the nuclear morphology and subsequent radial migration of MGPCs were alte red.At 7 days post-injury,Sox11 b knockdown res ulted in an increased proportion of MGPCs in the inner retina and a decreased propo rtion of MGPCs in the outer nuclear layer,compared with controls.Furthermore,Sox11 b knockdown led to reduced photoreceptor regeneration,while it increased the numbe rs of newborn amacrines and retinal ganglion cells.Finally,quantitative polymerase chain reaction analysis revealed that Sox11 b regulated the expression of Notch signaling components in the retina,and Notch inhibition partially recapitulated the Sox11 b knockdown phenotype,indicating that Notch signaling functions downstream of Sox11 b.Our findings imply that Sox11 b plays key roles in MGPC migration and fate determination during retina regeneration in zebrafish,which may have critical im plications for future explorations of retinal repair in mammals.

High-throughput sorting of two-color fluorescent-labeled zebrafish embryos

The zebrafish embryos were widely employed in genetics,development and drug discovery studies as miniatured animal models.Sorting of two-color fluorescent embryos is often required in large-scale experiments but it is challenging to manually sort with high efficiency.Here,we reported a high-throughput sorting system for two-color fluorescent zebraflsh embryos.The embryos can be automatically loaded from a sample pool and sorted based on the average fluorescent intensity.The two-color fluorescent signals were split into two lines and detected by an area array camera.The system achieves the sorting of 100 embryos in less than 10 min with an accuracy of greater than 95%.

Optic nerve injury-induced regeneration in the adult zebrafish is accompanied by spatiotemporal changes in mitochondrial dynamics

Axonal regeneration in the central nervous system is an energy-intensive process.In contrast to mammals,adult zebrafish can functionally recover from neuronal injury.This raises the question of how zebrafish can cope with this high energy demand.We previously showed that in adult zebrafish,subjected to an optic nerve crush,an antagonistic axon-dendrite interplay exists wherein the retraction of retinal ganglion cell dendrites is a prerequisite for effective axonal repair.We postulate a‘dendrites for regeneration’paradigm that might be linked to intraneuronal mitochondrial reshuffling,as ganglion cells likely have insufficient resources to maintain dendrites and restore axons simultaneously.Here,we characterized both mitochondrial distribution and mitochondrial dynamics within the different ganglion cell compartments(dendrites,somas,and axons)during the regenerative process.Optic nerve crush resulted in a reduction of mitochondria in the dendrites during dendritic retraction,whereafter enlarged mitochondria appeared in the optic nerve/tract during axonal regrowth.Upon dendritic regrowth in the retina,mitochondrial density inside the retinal dendrites returned to baseline levels.Moreover,a transient increase in mitochondrial fission and biogenesis was observed in retinal ganglion cell somas after optic nerve damage.Taken together,these findings suggest that during optic nerve injury-induced regeneration,mitochondria shift from the dendrites to the axons and back again and that temporary changes in mitochondrial dynamics support axonal and dendritic regrowth after optic nerve crush.

DUSP2 deletion with CRISPR/Cas9 promotes Mauthner cell axonal regeneration at the early stage of zebrafish

Axon regeneration of central neurons is a complex process that is tightly regulated by multiple extrinsic and intrinsic factors.The expression levels of distinct genes are changed after central neural system(CNS)injury and affect axon regeneration.A previous study identified dusp2 as an upregulated gene in zebrafish with spinal cord injury.Here,we found that dual specificity phosphatase 2(DUSP2)is a negative regulator of axon regeneration of the Mauthner cell(M-cell).DUSP2 is a phosphatase that mediates the dephosphorylation of JNK.In this study,we knocked out dusp2 by CRISPR/Cas9 and found that M-cell axons of dusp2(-/-)zebrafish had a better regeneration at the early stage after birth(within 8 days after birth),while those of dusp2^(+/-)zebrafish did not.Overexpression of DUSP2 in Tg(Tol 056)zebrafish by single-cell electroporation retarded the regeneration of M-cell axons.Western blotting results showed that DUSP2 knockout slightly increased the levels of phosphorylated JNK.These findings suggest that knocking out DUSP2 promoted the regeneration of zebrafish M-cell axons,possibly through enhancing JNK phosphorylation.

Construction of Zebrafish Mutants of CNTF Gene Using CRISPR/Cas9 Genome Editing Technology

Background: The prevalence of Parkinson’s disease (PD), a chronic and progressive neurodegenerative disorder, is projected to increase twofold by 2030. Leucine-rich repeat kinase 2 (LRRK2) is the most commonly observed gene in both familial and sporadic PD cases. Notably, there is a substantial augmentation in motor activity during both larval and adult stages of zebrafish lacking the lrrk2 gene. Nevertheless, the precise genetic abnormalities accountable for eliciting these phenotypes in zebrafish are yet to be elucidated. Methods: Real-time polymerase chain reaction (PCR) was conducted on zebrafish larvae at 6 days post fertilization (dpf) belonging to both the wild-type and lrk2(-/-) groups. Guide RNA was designed and subsequently employed in the PCR process. Electrophoresis was performed to facilitate identification. Results: The expression of CNTF mRNA was significantly diminished in lrrk2(-/-), in comparison to the wildtype zebrafish larvae. This finding implies that CNTF may have crucial implications in the regulated functioning of lrrk2, which is widely acknowledged as the predominant genetic factor contributing to hereditary PD. The primers for CNTF DNA were meticulously designed, and the electrophoresis results of the PCR product were subsequently presented. The wild type zebrafish embryos were meticulously prepared for micro-injection, and the resulting efficiency identification displayed the presence of the mutant PCR product, which exhibited the presence of several debris. Conclusions: The present study demonstrates the successful generation of CNTF mutant zebrafish using the CRISPR/Cas9 genome editing technique. Further investigations are necessary to deepen our understanding of the exogenous CNTF gene’s functionality.

Effect of Huanglian Jiedu Decoction on the Behavior of Zebrafish with Alzheimer's Disease

[Objectives]To study the effect of Huanglian Jiedu Decoction on the behavior of zebrafish with Alzheimer's disease caused by AlCl 3.[Methods]Each portion of Huanglian Jiedu Decoction was prepared according to the proportion of Coptis chinensis∶Phellodendron chinense Rupr.∶Scutellaria baicalensis Georgi∶Gardenia jasminoides Ellis=63 g∶42 g∶42 g∶63 g.After that,each portion of Huanglian Jiedu Decoction was soaked in 6.3 L water for 30 min and boiled twice at 100℃.The extracts were combined twice and filtered,then concentrated to 308 g/L and put into refrigerator for later use.Before training,zebrafishes were put into T-maze to adapt for 2 d,and then behavioral training was carried out for 7 d.After video recording,the behavior of zebrafish was analyzed by Smart 3.0,and qualified zebrafishes were selected for follow-up experiments.Then 60 successfully trained zebrafishes were randomly divided into control group,model group,positive group,low-dose group,medium-dose group and high-dose group of Huanglian Jiedu Decoction.Except for the control group,all the other groups were exposed to 100μg/L AlCl 3 for 7 d.After that,video was recorded,and behavioral analysis was carried out with behavioral record and analysis software Smart 3.0.And then the zebrafishes in the other four groups except the model group were treated with Huperzine A(4μg/L)and Huanglian Jiedu Decoction(154,308,616 mg/L)for 6 d,respectively.After that,it was recorded and the behavior of each group was analyzed.[Results]There was a significant difference in the time spent in the left area and the percentage of time in the left area between the control group and the model group(P<0.001).The time spent in the left area and the percentage of time in the left area in the model group and positive group,low,medium and high dose groups of Huanglian Jiedu Decoction decreased significantly(P<0.05,P<0.01,P<0.001).The swimming distance in the left area and the percentage of swimming distance in the left area in the model group were significantly higher than those in the control group(P<0.001).There was a significant difference in swimming distance between model group and positive group,low,medium and high dose groups of Huanglian Jiedu Decoction(P<0.01,P<0.001).In the percentage of swimming distance in the left area,there was a significant difference between the model group and the low and high dose groups of Huanglian Jiedu Decoction(P<0.01,P<0.001).[Conclusions]Huanglian Jiedu Decoction can improve the behavior of zebrafish with Alzheimer's disease.

Enantioselective separation and zebrafish embryo toxicity of insecticide beta-cypermethrin

Enantioselectivity of chiral pollutants is receiving growing concern due to the difference in toxicology and environment fate between enantiomers.In this study,enantiomers of insecticide beta-cypermethrin （beta-CP） were separated on selected chiral column by HPLC,and the toxicity of enantiomers was evaluated using the zebrafish embryo-larval assays.The enantiomers of beta-CP were baseline separated on Chiralcel OD and Chiralpak AD columns and detected by circular dichroism （CD） at 236 nm.Better separation could be achieved at lower temperature （e.g.,20°C） and with lower levels of polar modifiers.Pure enantiomers were obtained on Chiralcel OD.The CD spectra of enantiomers were recorded.By comparing the elution order with a previous similar study,the absolute configuration of beta-CP enantiomers was determined.The individual enantiomers were used in zebrafish embryo test,and the results showed that beta-CP enantioselectively induced yolk sac edema,pericardial edema and crooked body.The 1R-cis-αS and 1R-trans-αS enantiomers showed strong developmental toxicities at concentration of 0.1 mg/L,while the 1S-cis-αR and 1S-trans-αR induced no malformations at higher concentration （e.g.,0.3 mg/L）.The results suggest that the enantioselective toxicological effects of beta-CP should be considered when evaluating its ecotoxicological effects.

Toxicity of Graphene Quantum Dots in Zebrafish Embryo

Objective To evaluate the bio-safety of graphene quantum dots （GQDs）, we studied its effects on the embryonic development of zebrafish. Methods In vivo, biodistribution and the developmental toxicity of GQDs were investigated in embryonic zebrafish at exposure concentrations ranging from 12.5-200μg/mL for 4-96 h post-fertilization （hpf）. The mortality, hatch rate, malformation, heart rate, GQDs uptake, spontaneous movement, and larval behavior were examined. Results The fluorescence of GQDs was mainly localized in the intestines and heart. As the exposure concentration increased, the hatch and heart rate decreased, accompanied by an increase in mortality. Exposure to a high level of GQDs （200μg/mL） resulted in various embryonic malformations including pericardial edema, vitelline cyst, bent spine, and bent tail. The spontaneous movement significantly decreased after exposure to GQDs at concentrations of 50, 100, and 200μg/mL. The larval behavior testing （visible light test） showed that the total swimming distance and speed decreased dose-dependently. Embryos exposed to 12.5 μg/mL showed hyperactivity while exposure to higher concentrations （25, 50, 100, and 200μg/mL） caused remarkable hypoactivity in the light-dark test. Conclusion Low concentrations of GODs were relatively non-toxic. However, GQDs disrupt the progression of embryonic development at concentrations exceeding 50 μg/mL.