			Home About us Contact

Zebrafish Embryos (zebrafish + embryo)

Distribution by Scientific Domains

Life Sciences	80%
Earth and Environmental Science	11%
Chemistry	6%

Selected Abstracts

Scalable and Concise Synthesis of Dichlorofluorescein Derivatives Displaying Tissue Permeation in Live Zebrafish Embryos

CHEMBIOCHEM, Issue 2 2008
Kazunori Koide Prof.
Don't be so negative. We have synthesized new dichlorofluorescein derivatives that are less negatively charged than fluorescein. The synthesis is concise and scalable, and the compounds are conjugation-ready. In addition, these compounds permeate zebrafish embryos; this suggests that they might be useful fluorescent probes for bioimaging. [source]

Automated image-based phenotypic analysis in zebrafish embryos

DEVELOPMENTAL DYNAMICS, Issue 3 2009
Andreas Vogt
Abstract Presently, the zebrafish is the only vertebrate model compatible with contemporary paradigms of drug discovery. Zebrafish embryos are amenable to automation necessary for high-throughput chemical screens, and optical transparency makes them potentially suited for image-based screening. However, the lack of tools for automated analysis of complex images presents an obstacle to using the zebrafish as a high-throughput screening model. We have developed an automated system for imaging and analyzing zebrafish embryos in multi-well plates regardless of embryo orientation and without user intervention. Images of fluorescent embryos were acquired on a high-content reader and analyzed using an artificial intelligence-based image analysis method termed Cognition Network Technology (CNT). CNT reliably detected transgenic fluorescent embryos (Tg(fli1:EGFP)y1) arrayed in 96-well plates and quantified intersegmental blood vessel development in embryos treated with small molecule inhibitors of anigiogenesis. The results demonstrate it is feasible to adapt image-based high-content screening methodology to measure complex whole organism phenotypes. Developmental Dynamics 238:656,663, 2009. © 2009 Wiley-Liss, Inc. [source]

Coordination of development and metabolism in the pre-midblastula transition zebrafish embryo

DEVELOPMENTAL DYNAMICS, Issue 7 2008
Bryce A. Mendelsohn
Abstract To define the mechanisms that coordinate early embryonic development and metabolism, we have examined the response of zebrafish embryos to anoxia before the midblastula transition. Our findings reveal that anoxic pre-midblastula transition embryos slow the cell cycle, arrest before the midblastula transition and can recover normally if restored to a normoxic environment. Analyses of respiratory rates reveal that pre-midblastula transition embryos are less reliant on oxidative phosphorylation than older embryos. Interestingly, arrest in anoxia occurs despite inhibition of zygotic transcription, revealing a central role for maternal factors in the response to energy limitation. Consistent with this concept, we demonstrate that the posttranslational energy-sensing AMP-activated protein kinase pathway is activated in anoxia in pre-midblastula transition embryos. Taken together, these findings demonstrate a maternal program capable of coordinating developmental rate and metabolism in the absence of transcription-based pathways or cell cycle checkpoints. Developmental Dynamics 237:1789,1798, 2008. © 2008 Wiley-Liss, Inc. [source]

Supraspinal input is dispensable to generate glycine-mediated locomotive behaviors in the zebrafish embryo

DEVELOPMENTAL NEUROBIOLOGY, Issue 5 2006
Gerald B. Downes
Abstract The anatomy of the developing zebrafish spinal cord is relatively simple but, despite this simplicity, it generates a sequence of three patterns of locomotive behaviors. The first behavior exhibited is spontaneous movement, then touch-evoked coiling, and finally swimming. Previous studies in zebrafish have suggested that spontaneous movements occur independent of supraspinal input and do not require chemical neurotransmission, while touch-evoked coiling and swimming depend on glycinergic neurotransmission as well as supraspinal input. In contrast, studies in other vertebrate preparations have shown that spontaneous movement requires glycine and other neurotransmitters and that later behaviors do not require supraspinal input. Here, we use lesion analysis combined with high-speed kinematic analysis to re-examine the role of glycine and supraspinal input in each of the three behaviors. We find that, similar to other vertebrate preparations, supraspinal input is not essential for spontaneous movement, touch-evoked coiling, or swimming behavior. Moreover, we find that blockade of glycinergic neurotransmission decreases the rate of spontaneous movement and impairs touch-evoked coiling and swimming, suggesting that glycinergic neurotransmission plays critical yet distinct roles for individual patterns of locomotive behaviors. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source]

Assessing the toxicity of TBBPA and HBCD by zebrafish embryo toxicity assay and biomarker analysis

ENVIRONMENTAL TOXICOLOGY, Issue 4 2009
Jun Hu
Abstract Tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are two of the most widely used brominated flame retardants (BFRs). The biological toxicity effect of TBBPA and HBCD was studied by means of zebrafish embryo toxicity assays in combination with three biomarkers, including superoxide dismutase (SOD), lipid peroxidation, (LPO), and heat shock protein (Hsp70). The standard zebrafish embryo assay showed that high concentrations of TBBPA (,0.75 mg/L) can cause lethality or malformation. For HBCD within the concentration range (0.002,10 mg/L), no endpoint was observed. Furthermore, SOD activities of zebrafish embryos exposed to TBBPA were increased with the increasing concentrations. SOD activities in the group treated by HBCD showed an increase followed by a decline. Regardless of TBBPA or HBCD, LPO were increased along with the increase of the concentration. The change pattern of Hsp70 levels was the same with LPO. All these results showed that TBBPA and HBCD could cause oxidative stress and Hsp70 overexpression, inducing acute toxicity to zebrafish embryo in a short-term exposure. The study also indicates that the zebrafish embryo assay in combination with the biomarkers is effective in aquatic environmental toxicology and risk assessment. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009. [source]

Developmental toxicity in zebrafish (Danio rerio) embryos after exposure to manufactured nanomaterials: Buckminsterfullerene aggregates (nC60) and fullerol

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2007
Xiaoshan Zhu
Abstract The present paper summarizes, to our knowledge, the first study regarding the developmental toxicity of stable buck-minsterfullerene aggregates suspended in water (nC60) using zebrafish (Danio rerio) as a vertebrate model. Zebrafish embryo survival, hatching rate, heartbeat, and pericardial edema were noted and described within 96 h of exposure. Fullerol (a hydroxylated C60 derivative, C60(OH)16,18) at 50 mg/L did not exert toxicity to zebrafish embryos. In contrast, nC60 at 1.5 mg/L delayed zebrafish embryo and larval development, decreased survival and hatching rates, and caused pericardial edema. Toxicity was mitigated by adding an antioxidant (glutathione), which suggests that a free radical,induced mechanism or another form of oxidative stress played a role in developmental toxicity. [source]

Structural and functional evidence for a singular repertoire of BMP receptor signal transducing proteins in the lophotrochozoan Crassostrea gigas suggests a shared ancestral BMP/activin pathway

FEBS JOURNAL, Issue 13 2005
Amaury Herpin
The transforming growth factor , (TGF-,) superfamily includes bone morphogenetic proteins, activins and TGF-,sensu stricto (s.s). These ligands, which transduce their signal through a heteromeric complex of type I and type II receptors, have been shown to play a key role in numerous biological processes including early embryonic development in both deuterostomes and ecdyzozoans. Lophochotrozoans, the third major group of bilaterian animals, have remained in the background of the molecular survey of metazoan development. We report the cloning and functional study of the central part of the BMP pathway machinery in the bivalve mollusc Crassostrea gigas (Cg- BMPR1 type I receptor and Cg- TGF,sfR2 type II receptor), showing an unusual functional mode of signal transduction for this superfamily. The use of the zebrafish embryo as a reporter organism revealed that Cg- BMPR1, Cg- TGF,sfR2, Cg- ALR I, an activin Type I receptor or their dominant negative acting truncated forms, when overexpressed during gastrulation, resulted in a range of phenotypes displaying severe disturbance of anterioposterior patterning, due to strong modulations of ventrolateral mesoderm patterning. The results suggest that Cg- BMPR1, and to a certain degree Cg- TGF,sfR2 proteins, function in C. gigas in a similar way to their zebrafish orthologues. Finally, based on phylogenetic analyses, we propose an evolutionary model within the complete TGF-, superfamily. Thus, evidence provided by this study argues for a possible conserved endomesoderm/ectomesoderm inductive mechanism in spiralians through an ancestral BMP/activin pathway in which the singular, promiscuous and probably unique Cg- TGF,sfR2 would be the shared type II receptor interface for both BMP and activin ligands. [source]

Claudin-5a in developing zebrafish brain barriers: another brick in the wall

BIOESSAYS, Issue 9 2010
Salim Abdelilah-Seyfried
Abstract Claudins serve essential roles in regulating paracellular permeability properties within occluding junctions. Recent studies have begun to elucidate developmental roles of claudins within immature tissues. This work has uncovered an involvement of several claudins in determining tight junction properties that have an effect on embryonic morphogenesis and physiology. During zebrafish brain morphogenesis, Claudin-5a determines the paracellular permeability of tight junctions within a transient neuroepithelial-ventricular barrier that maintains the hydrostatic fluid pressure required for brain ventricular lumen expansion. However, the roles of Claudins in development may well extend beyond being mere junctional components. Several post-translational modifications of Claudins have been characterized that indicate a direct regulation by developmental signals. This review focuses on the involvement of Claudin-5a in cerebral barrier formation in the zebrafish embryo and includes some speculations about possible modes of regulation. [source]

Cell adhesion in zebrafish myogenesis: Distribution of intermediate filaments, microfilaments, intracellular adhesion structures and extracellular matrix

CYTOSKELETON, Issue 10 2008
Manoel L. Costa
Abstract To overcome the limitations of in vitro studies, we have been studying myogenesis in situ in zebrafish embryos, at a sub-cellular level. While in previous works we focused on myofibrillogenesis and some aspects of adhesion structures, here we describe in more detail cell adhesion structures and interactions among cytoskeletal components, membrane and extracellular matrix during zebrafish muscle development. We studied the intermediate filaments, and we describe the full range of desmin distribution in zebrafish development, from perinuclear to striated, until its deposition around the intersomite septa of older somites. This adhesion structure, positive for desmin and actin, has not been previously observed in myogenesis in vitro. We also show that actin is initially located in the intersomite septum region whereas it is confined to the myofibrils later on. While actin localization changes during development, the adhesion complex proteins vinculin, paxillin, talin, dystrophin, laminin and fibronectin always appear exclusively at the intersomite septa, and appear to be co-distributed, even though the extracellular proteins accumulates before the intracellular ones. Contrary to the adhesion proteins, that are continuously distributed, desmin and sarcomeric actin form triangular aggregates among the septa and the cytoskeleton. We studied the cytoskeletal linker plectin as well, and we show that it has a distribution similar to desmin and not to actin. We conclude that the in situ adhesion structures differ from their in vitro counterparts, and that the actual zebrafish embryo myogenesis is quite different than that which occurs in in vitro systems. Cell Motil. Cytoskeleton 65: 801,815, 2008. © 2008 Wiley-Liss, Inc. [source]

Visualization of stochastic Ca2+ signals in the formed somites during the early segmentation period in intact, normally developing zebrafish embryos

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 7 2009
Christina F. Leung
Localized Ca2+ signals were consistently visualized in the formed somites of intact zebrafish embryos during the early segmentation period. Unlike the regular process of somitogenesis, these signals were stochastic in nature with respect to time and location. They did, however, occur predominantly at the medial and lateral boundaries within the formed somites. Embryos were treated with modulators of [Ca2+]i to explore the signal generation mechanism and possible developmental function of the stochastic transients. Blocking elements in the phosphoinositol pathway eliminated the stochastic signals but had no obvious effect, stochastic or otherwise, on the formed somites. Such treatments did, however, result in the subsequently formed somites being longer in the mediolateral dimension. Targeted uncaging of buffer (diazo-2) or Ca2+ (NP-ethyleneglycoltetraacetic acid [EGTA]) in the presomitic mesoderm, resulted in a regular mediolateral lengthening and shortening, respectively, of subsequently formed somites. These data suggest a requirement for IP3 receptor-mediated Ca2+ release during convergence cell movements in the presomitic mesoderm, which appears to have a distinct function from that of the IP3 receptor-mediated stochastic Ca2+ signaling in the formed somites. [source]

Ooplasmic segregation in the zebrafish zygote and early embryo: Pattern of ooplasmic movements and transport pathways

DEVELOPMENTAL DYNAMICS, Issue 8 2010
Ricardo Fuentes
Abstract Patterns of cytoplasmic movements and organization of transport pathways were examined in live or fixed zygotes and early zebrafish embryos using a variety of techniques. The zygote blastodisc grows by accumulation of ooplasm, transported to the animal pole from distinct sectors of ecto- and endoplasm at different speeds and developmental periods, using specific pathways or streamers. Slow transport (5 ,m/min) occurs during the first interphase along short streamers, whereas fast transport (9.6,40 ,m/min) takes place during the first cleavage division along axial and meridional streamers. Interconnections between streamers allow cargoes to change their speed and final destination. A similar sequence of events occurs during the following divisions. A complex network of microtubules and actin filaments in the endo- and ectoplasm appears to be involved in the transport of inclusions and mRNAs. Actin-dependent intermittent pulsations provoked high-speed back-and-forth movements of cytoplasm that may contribute to redistribution of organelles and maternal determinants. Developmental Dynamics 239:2172,2189, 2010. © 2010 Wiley-Liss, Inc. [source]

Promoter analysis of ventricular myosin heavy chain (vmhc) in zebrafish embryos

DEVELOPMENTAL DYNAMICS, Issue 7 2009
Daqing Jin
Abstract In zebrafish, ventricular myosin heavy chain (vmhc) gene is initially expressed at the anterior lateral mesoderm and thereafter its expression is restricted to the cardiac ventricle. The transcriptional control mechanisms in regulating chamber-specific expression of myosin heavy chains are not well defined. We isolated and analyzed zebrafish vmhc upstream region to examine the spatial and temporal regulation of vmhc using transgenic and transient expression techniques. Promoter deletion analyses defined a basal promoter region sufficient to drive vmhc expression in the ventricle and an upstream fragment necessary for repressing ectopic vmhc expression in the atrium. The transcriptional mechanism that prevents vmhc expression in the atrium is mediated through Nkx2.5 binding elements (NKE). We have further discovered that paired-related homeobox transcriptional factor 2 (Prx2/S8)-like binding elements are required for promoting vmhc expression, and Prrx1b, a Prx-related homeobox protein, participates in the regulation of vmhc expression with other transcriptional factors. Developmental Dynamics 238:1760,1767, 2009. © 2009 Wiley-Liss, Inc. [source]

Automated image-based phenotypic analysis in zebrafish embryos

The lim domain only protein 7 is important in zebrafish heart development

DEVELOPMENTAL DYNAMICS, Issue 12 2008
Elisabeth B. Ott
Abstract The LIM domain only protein 7 (LMO7), a member of the PDZ and LIM domain-containing protein family is a candidate gene with possible roles in embryonic development and breast cancer progression. LMO7 has been linked to actin cytoskeleton organization through nectin/afadin and to cell,cell adhesion by means of E-cadherin/catenin. In addition, LMO7 has been shown to regulate transcription of the nuclear membrane protein Emerin and other muscle relevant genes. In this study, we used in situ hybridization to investigate LMO7 expression during embryonic development in three widely used vertebrate model species: the zebrafish, the chicken and the mouse. Our temporal and spatial gene expression analysis revealed both common and distinct patterns between these species. In mouse and chicken embryos we found expression in the outflow tract, the inflow tract, the pro-epicardial organ and the second heart field, structures highly important in the developing heart. Furthermore, gene knockdown experiments in zebrafish embryos resulted in severe defects in heart development with effects on the conduction system and on heart localization. In summary, we present here the first developmental study of LMO7. We reveal the temporal and spatial expression patterns of this important gene during mouse, chicken and fish development and our findings suggest essential functions for LMO7 during vertebrate heart development. Developmental Dynamics 237:3940,3952, 2008. © 2008 Wiley-Liss, Inc. [source]

Coordination of development and metabolism in the pre-midblastula transition zebrafish embryo

Three types of cilia including a novel 9+4 axoneme on the notochordal plate of the rabbit embryo

DEVELOPMENTAL DYNAMICS, Issue 12 2006
Kerstin Feistel
Abstract Motile monocilia play a pivotal role in left-right axis determination in mouse and zebrafish embryos. Cilia with 9+0 axonemes localize to the distal indentation of the mouse egg cylinder ("node"), while Kupffer's vesicle cilia in zebrafish show 9+2 arrangements. Here we studied cilia in a prototype mammalian embryo, the rabbit, which develops via a flat blastodisc. Transcription of ciliary marker genes Foxj1, Rfx3, lrd, polaris, and Kif3a initiated in Hensen's node and persisted in the nascent notochord. Cilia emerged on cells leaving Hensen's node anteriorly to form the notochordal plate. Cilia lengthened to about 5 ,m and polarized from an initially central position to the posterior pole of cells. Electron-microscopic analysis revealed 9+0 and 9+2 cilia and a novel 9+4 axoneme intermingled in a salt-and-pepper-like fashion. Our data suggest that despite a highly conserved ciliogenic program, which initiates in the organizer, axonemal structures may vary widely within the vertebrates. Developmental Dynamics 235:3348,3358, 2006. © 2006 Wiley-Liss, Inc. [source]

Changes in gravitational force cause changes in gene expression in the lens of developing zebrafish

DEVELOPMENTAL DYNAMICS, Issue 10 2006
Naoko Shimada
Abstract Gravity has been a constant physical factor during the evolution and development of life on Earth. We have been studying effects of simulated microgravity on gene expression in transgenic zebrafish embryos expressing gfp under the influence of gene-specific promoters. In this study, we assessed the effect of microgravity on the expression of the heat shock protein 70 (hsp70) gene in lens during development using transgenic zebrafish embryos expressing gfp under the control of hsp70 promoter/enhancer. Hsp70:gfp expression was up-regulated (45%) compared with controls during the developmental period that included the lens differentiation stage. This increase was lens specific, because the entire embryo showed only a 4% increase in gfp expression. Northern blot and in situ hybridization analysis indicated that the hsp70:gfp expression recapitulated endogenous hsp70 mRNA expression. Hypergravity exposure also increased hsp70 expression during the same period. In situ hybridization analysis for two lens-specific crystallin genes revealed that neither micro- nor hypergravity affected the expression level of ,B1 - crystallin, a non-hsp gene used as a marker for lens differentiation. However, hypergravity changed the expression level of ,A - crystallin, a member of the small hsp gene family. Terminal deoxynucleotidyl transferase,mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) assay analysis showed that altered-gravity (,g) decreased apoptosis in lens during the same period and the decrease correlated with the up-regulation of hsp70 expression, suggesting that elimination of nuclei from differentiating lens fiber cells was suppressed probably through hsp70 up-regulation. These results support the idea that ,g influences hsp70 expression and differentiation in lens-specific and developmental period specific manners and that hsp family genes play a specific role in the response to ,g. Developmental Dynamics 235:2686,2694, 2006. © 2006 Wiley-Liss, Inc. [source]

Vascular endothelial growth factor receptor signaling is required for cardiac valve formation in zebrafish

DEVELOPMENTAL DYNAMICS, Issue 1 2006
You Mie Lee
Abstract Vascular endothelial growth factor-receptors (VEGF-Rs) are pivotal regulators of vascular development, but a specific role for these receptors in the formation of heart valves has not been identified. We took advantage of small molecule inhibitors of VEGF-R signaling and showed that blocking VEGF-R signaling with receptor selective tyrosine kinase inhibitors, PTK 787 and AAC 787, from 17,21 hr post-fertilization (hpf) in zebrafish embryos resulted in a functional and structural defect in cardiac valve development. Regurgitation of blood between the two chambers of the heart, as well as a loss of cell-restricted expression of the valve differentiation markers notch 1b and bone morphogenetic protein-4 (bmp - 4), was readily apparent in treated embryos. In addition, microangiography revealed a loss of a definitive atrioventricular constriction in treated embryos. Taken together, these data demonstrate a novel function for VEGF-Rs in the endocardial endothelium of the developing cardiac valve. Developmental Dynamics 235:29,37, 2006. © 2005 Wiley-Liss, Inc. [source]

Cell proliferation in the developing lateral line system of zebrafish embryos

DEVELOPMENTAL DYNAMICS, Issue 2 2005
Laurent Laguerre
Abstract The sensory organs of the embryonic lateral line system are deposited by migrating primordia that originate in the otic region. Here, we examine the pattern of cell proliferation in the posterior lateral line system. We conclude that three phases of cell proliferation are involved in the generation of this system, separated by two phases of mitotic quiescence. The first phase corresponds to generalized proliferation during gastrulation, followed by a first period of quiescence that may be related to the determination of the lateral line precursor cells. A second phase of proliferation takes place in the placode and migrating primordium. This region is organized in annuli that correspond to the expression of proneural/neurogenic genes. A second period of quiescence follows, corresponding to deposition and differentiation of the sensory organs. The third period of proliferation corresponds to continued renewal of hair cells by division of support cells within each sensory organ. Developmental Dynamics 233:466,472, 2005. © 2005 Wiley-Liss, Inc. [source]

Specification of the enveloping layer and lack of autoneuralization in zebrafish embryonic explants

DEVELOPMENTAL DYNAMICS, Issue 1 2005
Charles G. Sagerström
Abstract We have analyzed the roles of cell contact during determination of the outermost enveloping layer (EVL) and deeper neurectoderm in zebrafish embryos. Outer cells, but not deeper cells, are specified to express the EVL-specific marker, cyt1 by late blastula. EVL specification requires cell contact or close cell proximity, because cyt1 is not expressed after explant dissociation. The EVL may be homologous to the Xenopus epithelial layer, including the ventral larval epidermis. While Xenopus epidermal cytokeratin gene expression is activated by bone morphogenetic protein (BMP) signaling, zebrafish cyt1 is not responsive to BMPs. Zebrafish early gastrula ectodermal explants are specified to express the neural markers opl (zic1) and otx2, and this expression is prevented by BMP4. Dissociation of zebrafish explants prevents otx2 and opl expression, suggesting that neural specification in zebrafish requires cell contact or close cell proximity. This finding is in contrast to the case in Xenopus, where ectodermal dissociation leads to activation of neural gene expression, or autoneuralization. Our data suggest that distinct mechanisms direct development of homologous lineages in different vertebrates. Developmental Dynamics 232:85,97, 2005. © 2004 Wiley-Liss, Inc. [source]

Screen for genes differentially expressed during regeneration of the zebrafish caudal fin

DEVELOPMENTAL DYNAMICS, Issue 3 2004
Bhaja K. Padhi
Abstract The zebrafish caudal fin constitutes an important model for studying the molecular basis of tissue regeneration. The cascade of genes induced after amputation or injury, leading to restoration of the lost fin structures, include those responsible for wound healing, blastema formation, tissue outgrowth, and patterning. We carried out a systematic study to identify genes that are up-regulated during "initiation" (1 day) and "outgrowth and differentiation" (4 days) of fin regeneration by using two complementary methods, suppression subtraction hybridization (SSH) and differential display reverse transcriptase polymerase chain reaction (DDRT-PCR). We obtained 298 distinct genes/sequences from SSH libraries and 24 distinct genes/sequences by DDRT-PCR. We determined the expression of 54 of these genes using in situ hybridization. In parallel, gene expression analyses were done in zebrafish embryos and early larvae. The information gathered from the present study provides resources for further investigations into the molecular mechanisms of fin development and regeneration. Developmental Dynamics 231:527,541, 2004. © 2004 Wiley-Liss, Inc. [source]

Two Na,K-ATPase ,2 subunit isoforms are differentially expressed within the central nervous system and sensory organs during zebrafish embryogenesis

DEVELOPMENTAL DYNAMICS, Issue 2 2002
Johannes R. Rajarao
Abstract We have identified cDNAs encoding a second zebrafish ortholog of the human Na,K-ATPase ,2 subunit. The ,2b cDNA encodes a 292 amino acid-long polypeptide with 74% identity to the previously characterized zebrafish ,2a subunit. By using a zebrafish meiotic mapping panel, we determined that the ,2b gene (atp1b2b) was tightly linked to markers on linkage group 5, whereas the ,2a gene was located on linkage group 23. In situ hybridization analysis shows that in developing zebrafish embryos, atp1b2a and atp1b2b are predominantly expressed in the nervous system. ,2a transcripts were abundantly expressed throughout brain as well as spinal cord neurons and lateral line ganglia. In contrast, ,2b mRNA expression was primarily detected in sensory organs, including retina, otic vesicles, and lateral line neuromast cells. These results suggest that the ,2a and ,2b genes play distinct roles in developing brain and sensory organs, and raise the possibility that the functions encoded by the single mammalian ,2 gene may be partitioned between the two zebrafish ,2 orthologs. © 2002 Wiley-Liss, Inc. [source]

Morphogenetic domains in the yolk syncytial layer of axiating zebrafish embryos

DEVELOPMENTAL DYNAMICS, Issue 4 2001
Leonard A. D'Amico
Abstract The yolk syncytial layer (YSL) of the teleostean yolk cell is known to play important roles in the induction of cellular mesendoderm, as well as the patterning of dorsal tissues. To determine how this extraembryonic endodermal compartment is subdivided and morphologically transformed during early development, we have examined collective movements of vitally stained YSL nuclei in axiating zebrafish embryos by using four-dimensional confocal microscopy. During blastulation, gastrulation, and early segmentation, zebrafish YSL nuclei display several highly patterned movements, which are organized into spatially distinct morphogenetic domains along the anterior-posterior and dorsal-ventral axes. During the late blastula period, with the onset of epiboly, nuclei throughout the YSL initiate longitudinal movements that are directed along the animal-vegetal axis. As epiboly progresses, nuclei progressively recede from the advancing margin of the epibolic YSL. However, a small group of nuclei is retained at the YSL margin to form a constricting blastoporal ring. During mid-gastrulation, YSL nuclei undergo convergent-extension behavior toward the dorsal midline, with a subset of nuclei forming an axial domain that underlies the notochord. These highly patterned movements of YSL nuclei share remarkable similarities to the morphogenetic movements of deep cells in the overlying zebrafish blastoderm. The macroscopic shape changes of the zebrafish yolk cell, as well as the morphogenetic movements of its YSL nuclei, are homologous to several morphogenetic behaviors that are regionally expressed within the vegetal endodermal cell mass of gastrulating Xenopus embryos. In contrast to the cellular endoderm of Xenopus, the dynamics of zebrafish YSL show that a syncytial endodermal germ layer can express a temporal sequence of morphogenetic domains without undergoing progressive steps of cell fate restriction. © 2001 Wiley-Liss, Inc. [source]

Glutamate drives the touch response through a rostral loop in the spinal cord of zebrafish embryos

DEVELOPMENTAL NEUROBIOLOGY, Issue 12 2009
Thomas Pietri
Abstract Characterizing connectivity in the spinal cord of zebrafish embryos is not only prerequisite to understanding the development of locomotion, but is also necessary for maximizing the potential of genetic studies of circuit formation in this model system. During their first day of development, zebrafish embryos show two simple motor behaviors. First, they coil their trunks spontaneously, and a few hours later they start responding to touch with contralateral coils. These behaviors are contemporaneous until spontaneous coils become infrequent by 30 h. Glutamatergic neurons are distributed throughout the embryonic spinal cord, but their contribution to these early motor behaviors in immature zebrafish is still unclear. We demonstrate that the kinetics of spontaneous coiling and touch-evoked responses show distinct developmental time courses and that the touch response is dependent on AMPA-type glutamate receptor activation. Transection experiments suggest that the circuits required for touch-evoked responses are confined to the spinal cord and that only the most rostral part of the spinal cord is sufficient for triggering the full response. This rostral sensory connection is presumably established via CoPA interneurons, as they project to the rostral spinal cord. Electrophysiological analysis demonstrates that these neurons receive short latency AMPA-type glutamatergic inputs in response to ipsilateral tactile stimuli. We conclude that touch responses in early embryonic zebrafish arise only after glutamatergic synapses connect sensory neurons and interneurons to the contralateral motor network via a rostral loop. This helps define an elementary circuit that is modified by the addition of sensory inputs, resulting in behavioral transformation. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009 [source]

Hedgehog and Fgf signaling pathways regulate the development of tphR -expressing serotonergic raphe neurons in zebrafish embryos

DEVELOPMENTAL NEUROBIOLOGY, Issue 3 2004
H. Teraoka
Abstract Serotonin (5HT) plays major roles in the physiological regulation of many behavioral processes, including sleep, feeding, and mood, but the genetic mechanisms by which serotonergic neurons arise during development are poorly understood. In the present study, we have investigated the development of serotonergic neurons in the zebrafish. Neurons exhibiting 5HT-immunoreactivity (5HT-IR) are detected from 45 h postfertilization (hpf) in the ventral hindbrain raphe, the hypothalamus, pineal organ, and pretectal area. Tryptophan hydroxylases encode rate-limiting enzymes that function in the synthesis of 5HT. As part of this study, we cloned and analyzed a novel zebrafish tph gene named tphR. Unlike two other zebrafish tph genes (tphD1 and tphD2), tphR is expressed in serotonergic raphe neurons, similar to tph genes in mammalian species. tphR is also expressed in the pineal organ where it is likely to be involved in the pathway leading to synthesis of melatonin. To better understand the signaling pathways involved in the induction of the serotonergic phenotype, we analyzed tphR expression and 5HT-IR in embryos in which either Hh or Fgf signals are abrogated. Hindbrain 5HT neurons are severely reduced in mutants lacking activity of either Ace/Fgf8 or the transcription factor Noi/Pax2.1, which regulates expression of ace/fgf8, and probably other genes encoding signaling proteins. Similarly, serotonergic raphe neurons are absent in embryos lacking Hh activity confirming a conserved role for Hh signals in the induction of these cells. Conversely, over-activation of the Hh pathway increases the number of serotonergic neurons. As in mammals, our results are consistent with the transcription factors Nk2.2 and Gata3 acting downstream of Hh activity in the development of serotonergic raphe neurons. Our results show that the pathways involved in induction of hindbrain serotonergic neurons are likely to be conserved in all vertebrates and help establish the zebrafish as a model system to study this important neuronal class. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 275,288, 2004 [source]

Assessment of sediment quality of Yangtze River estuary using zebrafish (Danio rerio) embryos

ENVIRONMENTAL TOXICOLOGY, Issue 3 2010
Lingling Wu
Abstract Yangtze River estuary is one of the largest estuaries worldwide. In this study, the sediment quality of Yangtze River estuary was evaluated using zebrafish (Danio rerio) embryos. Freshly fertilized zebrafish eggs (2 h after fertilization) were exposed to the whole sediment and its organic phase of extract, respectively. The parameters, including survival rate, abnormality, hatching rate, and heart rate of the zebrafish embryos, were recorded during the 96-h exposure. The results demonstrated that the concentrations of heavy metals (Zn, Cu, Cd, Ni, Cr, and As) and low-molecular weight PAHs (Fluorene) in the sediment of Yangtze River estuary exceeded their corresponding effects range low values. The maximum concentrations of Zn and Fluorene in the sediment samples were 239.6 ,g/g and 45.9 ng/g, respectively. In both whole sediment test and organic extract test, the survival rate and heart rate of zebrafish embryos were reduced, as well as abnormalities and delayed hatching were induced. For example, the highest mortality of the embryos was 39% in the whole sediment exposure. Overall, the occurrence of toxic compounds in the sediment of Yangtze River estuary may have potentially teratogenic effect on biota. The sediment from the upstream of Yangtze River estuary have more observed toxic effects on zebrafish embryos than that form the downstream. Therefore, more attention should be paid to control these pollutants, especially heavy metals in the Yangtze River estuary. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010. [source]

Assessing the toxicity of TBBPA and HBCD by zebrafish embryo toxicity assay and biomarker analysis

Developmental toxicity in zebrafish (Danio rerio) embryos after exposure to manufactured nanomaterials: Buckminsterfullerene aggregates (nC60) and fullerol

Cellular and molecular basis of cadmium-induced deformities in zebrafish embryos

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2000
Shuk Han Cheng
Abstract Cadmium is known to cause developmental defects in a varietyof vertebrate species, but relatively little is known about the underlying molecular mechanisms. In this study, we used zebrafish (Danio rerio) embryos as a model system to investigate cadmium-induced toxicities. Fertilized embryos collected at 5-h after fertilization were incubated for 18 h in culture media containing 1 to 1, 000 ,M CdCl2. The median embryolethal concentration (LC50) was 168 ,M, whereas the median effect concentration (EC50) for total adverse effect (mortality and developmental defects) was 138 ,M. Six major types of deformities were observed: head and eye hypoplasia, hypopigmentation, cardiac edema, yolk sac abnormalities, altered axial curvature, and tail malformations. The frequency of malformations increased with cadmium concentration. Somites of embryos with altered axial curvature were investigated using the antimyosin antibody MF-20. This study demonstrated, to our knowledge for the first time, reduced myotome formation in cadmium-induced spinal deformity. Embryos with head and eye hypoplasia were studied using the anti-neural tissue antibody zns-2, and a poorly developed central nervous system was revealed. Head and eye hypoplasia were associated with lack of expression of the sonic hedgehog gene, which controls the patterning of the neural tube and somites. Genes involved in tail formations, such as evenskipped 1 and no tail, were ectopically expressed in embryos with tail malformations. Our data support the hypothesis that fish embryonic malformations induced by cadmium might be mediated through ectopic expression of developmental regulatory genes. [source]

Formation of copper complexes in landfill leachate and their toxicity to zebrafish embryos

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2000
Jonathon K. Fraser
Abstract Toxic metal organic complexeshavenot been found in natural waters, although someorganicacids form bioavailable lipophilic and metabolite-type metal complexes. Landfill leachates usually contain organic acids and in the urban environment these leachates, when mixed with storm waters containing Cu, could be a source of toxic Cu organic complexes in streams and estuaries. We investigated the formation of Cu complexes in the leachate from an active urban landfill and found that some of the complexes formed were toxic to zebrafish embryos. High and low nominal molecular weight (NMWT) fractions; >5,000 Da and <700 Da, of leachate both formed Cu complexes with almost identical Cu complexing characteristics but the toxicity was due solely to the low NMWT complexes formed in the <700 Da fraction. Chemical equilibrium modelling with MINTEQA2 and H and Cu complex conditional association constants and ligand concentrations obtained from pH and Cu titrations with a Cu ion-selective electrode and van den Berg,Ruzic analyses of the titration data was used to calculate the copper speciation in the embryo test solutions. This calculated speciation, which was confirmed by measurements of Cu2+ in the test solutions, enabled the toxicity due to the free Cu ion and to the Cu complexes to be distinguished. [source]