single-molecule analysis of dna replication in xenopus egg extracts.the recent advent in single-molecule imaging and manipulation methods has made a significant impact on the understanding of molecular mechanisms underlying many essential cellular processes. single-molecule techniques such as electron microscopy and dna fiber assays have been employed to study the duplication of genome in eukaryotes. here, we describe a single-molecule assay that allows replication of dna attached to the functionalized surface of a microfluidic flow cell in a soluble xenopus lea ...201222503776
crotamine pharmacology revisited: novel insights based on the inhibition of kv channels.crotamine, a 5-kda peptide, possesses a unique biological versatility. not only has its cell-penetrating activity become of clinical interest but, moreover, its potential selective antitumor activity is of great pharmacological importance. in the past, several studies have attempted to elucidate the exact molecular target responsible for the crotamine-induced skeletal muscle spasm. the aim of this study was to investigate whether crotamine affects voltage-gated potassium (k(v)) channels in an ef ...201222498659
embryonic poly(a)-binding protein (epab) phosphorylation is required for xenopus oocyte maturation.oocyte maturation and early embryonic development require the cytoplasmic polyadenylation and concomitant translational activation of stored maternal mrnas. epab [embryonic poly(a)-binding protein, also known as epabp and pabpc1-like] is a multifunctional post-transcriptional regulator that binds to poly(a) tails. in the present study we find that epab is a dynamically modified phosphoprotein in xenopus laevis oocytes and show by mutation that phosphorylation at a four residue cluster is require ...201222497250
gabaergic transmission and chloride equilibrium potential are not modulated by pyruvate in the developing optic tectum of xenopus laevis the developing mammalian brain, gamma-aminobutyric acid (gaba) is thought to play an excitatory rather than an inhibitory role due to high levels of intracellular cl(-) in immature neurons. this idea, however, has been questioned by recent studies which suggest that glucose-based artificial cerebrospinal fluid (acsf) may be inadequate for experiments on immature and developing brains. these studies suggest that immature neurons may require alternative energy sources, such as lactate or pyruva ...201222496804
role of the transporter regulator protein (rs1) in the modulation of concentrative nucleoside transporters (cnts) in epithelia.slc28 genes encode three plasma membrane transporter proteins, human concentrative nucleoside transporter (cnt)1, cnt2, and cnt3, all of which are implicated in the uptake of natural nucleosides and a variety of nucleoside analogs used in the chemotherapy of cancer and viral and inflammatory diseases. mechanisms determining their trafficking toward the plasma membrane are not well known, although this might eventually become a target for therapeutic intervention. the transporter regulator rs1, w ...201222492015
a novel method to study the local mitochondrial fusion in myelinated axons in vivo.mitochondrial remodeling (replication, fission/fusion) is a dynamically regulated process with diverse functions in neurons. a myelinated axon is an extension from the cell soma of a fully differentiated neuron. mitochondria, once synthesized in the cell body, enter the axon displaying robust trafficking and accumulation at nodes of ranvier to match metabolic needs. this long-distance deployment of mitochondria to axons raises the issue of whether myelinated axons can function independently of t ...201222484559
thyroid hormone-disrupting effects and the amphibian metamorphosis assay.there are continued concerns about endocrine-disrupting chemical effects, and appropriate vertebrate models for assessment of risk are a high priority. frog tadpoles are very sensitive to environmental substances because of their habitat and the complex processes of metamorphosis regulated by the endocrine system, mainly thyroid hormones. during metamorphosis, marked alteration in hormonal factors occurs, as well as dramatic structural and functional changes in larval tissues. there are a variet ...201222481853
measuring resting membrane potential using the fluorescent voltage reporters dibac4(3) and cc2-dmpe.slow changes in steady-state (resting) transmembrane potential (v(mem)) of non-excitable cells often encode important instructive signals controlling differentiation, proliferation, and cell:cell communication. probing the function of such bioelectric gradients in vivo or in culture requires the ability to track v(mem), to characterize endogenous patterns of differential potential, map out isopotential cell groups (compartments or cell fields), and confirm the results of functional perturbation ...201222474652
a versatile protocol for mrna electroporation of xenopus laevis embryos.xenopus laevis is an ideal model system for investigating the mechanisms of pattern formation. the ability to express exogenous mrna or introduce morpholinos into cleavage-stage xenopus embryos has allowed gain- and loss-of-function experiments that reveal molecular-genetic control of development and regeneration. however, injection of mrnas into cleavage-stage embryos provides limited spatio-temporal control: it is difficult to limit targeting to small regions (e.g., inducing foci of expression ...201222474651
positive allosteric modulators differentially affect full versus partial agonist activation of the glycine receptor.taurine acts as a partial agonist at the glycine receptor (glyr) in some brain regions such as the hippocampus, striatum, and nucleus accumbens. ethanol, volatile anesthetics, and inhaled drugs of abuse are all known positive allosteric modulators of glyrs, but their effects on taurine-activated glyrs remain poorly understood, especially their effects on the high concentrations of taurine likely to be found after synaptic release. two-electrode voltage-clamp electrophysiology in xenopus laevis o ...201222473615
a potential role for differential contractility in early brain development and evolution.differences in brain structure between species have long fascinated evolutionary biologists. understanding how these differences arise requires knowing how they are generated in the embryo. growing evidence in the field of evolutionary developmental biology (evo-devo) suggests that morphological differences between species result largely from changes in the spatiotemporal regulation of gene expression during development. corresponding changes in functional cellular behaviors (morphogenetic mecha ...201222466353
mier1 (mesoderm induction early response 1 homolog (xenopus laevis)). 201224812577
calcium signaling in xenopus oocyte.knowledge about calcium signaling had increased thanks to the development and manipulation of various cell models. among all of these prototypes, xenopus laevis oocyte appears to be one of the most relevant. the understanding of the role of calcium during oocyte oogenesis, maturation and fertilization is facilitated by the big size of the cell but also by using imaging and electrophysiological approaches. so, this chapter presents how recordings of calcium-activated chloride channels and store-o ...201222453984
induction of cytochrome p450 family 1 mrnas and activities in a cell line from the frog xenopus laevis.cytochrome p450 family 1 (cyp1) includes four subfamilies of enzymes: cyp1a, cyp1b, cyp1c, and cyp1d. in many vertebrates, cyp1a, 1b, and 1c expression is induced by agonists of the aryl hydrocarbon receptor, including toxic contaminants such as chlorinated dioxins, coplanar chlorinated biphenyls, and polynuclear aromatic hydrocarbons. assessed at the level of mrna, protein, or enzyme activity, cyp1s (especially cyp1as) represent potent and popular biomarkers of contaminant exposure in aquatic v ...201222446828
heat-shock mediated overexpression of hnf1β mutations has differential effects on gene expression in the xenopus pronephric kidney.the transcription factor hnf1b, encoded by the tcf2 gene, plays an important role in the organogenesis of vertebrates. in humans, heterozygous mutations of hnf1b are associated with several diseases, such as pancreatic β-cell dysfunction leading to maturity-onset diabetes of the young (mody5), defective kidney development, disturbed liver function, pancreas atrophy, and malformations of the genital tract. the african claw frog xenopus laevis is an excellent model to study the processes involved ...201222438943
the metamorphosis of amphibian toxicogenomics.amphibians are important vertebrates in toxicology often representing both aquatic and terrestrial forms within the life history of the same species. of the thousands of species, only two have substantial genomics resources: the recently published genome of the pipid, xenopus (silurana) tropicalis, and transcript information (and ongoing genome sequencing project) of xenopus laevis. however, many more species representative of regional ecological niches and life strategies are used in toxicology ...201222435070
cell-autonomous alterations in dendritic arbor morphology and connectivity induced by overexpression of mecp2 in xenopus central neurons in vivo.methyl cpg binding protein-2 (mecp2) is an essential epigenetic regulator in human brain development. mutations in the mecp2 gene have been linked to rett syndrome, a severe x-linked progressive neurodevelopmental disorder, and one of the most common causes of mental retardation in females. mecp2 duplication and triplication have also been found to affect brain development, indicating that both loss of function and gain in mecp2 dosage lead to similar neurological phenotypes. here, we used the x ...201222427975
crim1 complexes with ß-catenin and cadherins, stabilizes cell-cell junctions and is critical for neural multicellular organisms, morphogenesis is a highly coordinated process that requires dynamically regulated adhesion between cells. an excellent example of cellular morphogenesis is the formation of the neural tube from the flattened epithelium of the neural plate. cysteine-rich motor neuron protein 1 (crim1) is a single-pass (type 1) transmembrane protein that is expressed in neural structures beginning at the neural plate stage. in the frog xenopus laevis, loss of function studies using crim ...201222427856
toxic effects of deltamethrin and λ-cyhalothrin on xenopus laevis tadpoles.this study evaluates the toxic effects of deltamethrin and λ-cyhalothrin on xenopus laevis tadpoles after 168 h of exposure. the lc(50) of deltamethrin and λ-cyhalothrin at 168 h was calculated as the μg of active ingredient per liter (μg ai/l). according to these values, the lc(50) was 6.26 and 3.94 μg ai/l for deltamethrin and λ-cyhalothrin, respectively. several enzymes were studied for early signs of intoxication following exposure to the pesticides for 24 h. glutathione-s-transferase,carbox ...201222424064
stabilization of actin filaments prevents germinal vesicle breakdown and affects microtubule organization in xenopus xenopus oocytes, extremely giant nuclei, termed germinal vesicles, contain a large amount of actin filaments most likely for mechanical integrity. here, we show that microinjection of phalloidin, an f-actin-stabilizing drug, prevents the germinal vesicle breakdown (gvbd) in oocytes treated with progesterone. these nuclei remained for more 12 h after control oocytes underwent gvbd. immunostaining showed significant elevation of actin in the remaining nuclei and many actin filament bundles in t ...201222422719
transgenic xenopus laevis with the ef1-α promoter as an experimental tool for amphibian retinal regeneration study.complete retinal regeneration occurs after the removal of the whole tissue in mature xenopus laevis, as well as in the newt. here, we produced f1 and f2 lines of transgenic x. laevis containing an egfp gene under a translation elongation factor 1-α (ef1-α) promoter and investigated how the gene is reactivated in retinal pigmented epithelial (rpe) cells when the neural retina (nr) is removed. the results showed that egfp expression is reduced in the adult ocular tissues of nonmanipulated transgen ...201222422643
identification of a major enzyme for the synthesis and hydrolysis of cyclic adp-ribose in amphibian cells and evolutional conservation of the enzyme from human to invertebrate.cyclic adp-ribose (cadpr), a metabolite of nad(+), is known to function as a second messenger for intracellular ca(2+) mobilization in various vertebrate and invertebrate tissues. in this study, we isolated two xenopus laevis cdnas (frog cd38 and cd157 cdnas) homologous to the one encoding the human cadpr-metabolizing enzyme cd38. frog cd38 and cd157 are 298-amino acid proteins with 35.9 and 27.2 % identity to human cd38 and cd157, respectively. transfection of expression vectors for frog cd38 a ...201222422046
wnk3-spak interaction is required for the modulation of ncc and other members of the slc12 family.the serine/threonine with no lysine kinase 3 (wnk3) modulates the activity of the electroneutral cation-coupled chloride cotransporters (ccc) to promote cl(-) influx and prevent cl(-) efflux, thus fitting the profile for a putative "cl(-)-sensing kinase". the ste20-type kinases, spak/osr1, become phosphorylated in response to reduction in intracellular chloride concentration and regulate the activity of nkcc1. several studies have now shown that wnks function upstream of spak/osr1. this study wa ...201222415098
identification and characterization of the rlip/ralbp1 interacting protein xreps1 in xenopus laevis early development.the fgf/ras/ral/rlip pathway is required for the gastrulation process during the early development of vertebrates. the ral interacting protein (rlip also known as ralbp1) interacts with gtp-bound ral proteins. rlip/ralbp1 is a modular protein capable of participating in many cellular functions.201222413001
median facial clefts in xenopus laevis: roles of retinoic acid signaling and homeobox genes.the upper lip and primary palate form an essential separation between the brain, nasal structures and the oral cavity. surprisingly little is known about the development of these structures, despite the fact that abnormalities can result in various forms of orofacial clefts. we have uncovered that retinoic acid is a critical regulator of upper lip and primary palate development in xenopus laevis. retinoic acid synthesis enzyme, raldh2, and retinoic acid receptor gamma (rarγ) are expressed in com ...201222405964
role of a conserved glycine triplet in the nss amino acid transporter kaat1.k+-coupled amino acid transporter 1 (kaat1) belongs to the nss family of solute transporters and it is expressed in the midgut and in salivary glands of manduca sexta larvae. as more than 80% of family members, kaati shows a stretch of three glycines (g85-g87) that according to the structure of the prototype transporter leut, is located close to the access of the permeation pathway. in this work the role of the triplet has been investigated by alanine and cysteine scanning methods in protein het ...201222402268
heterogeneous nuclear ribonucleoprotein k, an rna-binding protein, is required for optic axon regeneration in xenopus laevis.axotomized optic axons of xenopus laevis, in contrast to those of mammals, retain their ability to regenerate throughout life. to better understand the molecular basis for this successful regeneration, we focused on the role of an rna-binding protein, heterogeneous nuclear ribonucleoprotein (hnrnp) k, because it is required for axonogenesis during development and because several of its rna targets are under strong post-transcriptional control during regeneration. at 11 d after optic nerve crush, ...201222399778
a hindbrain-repressive wnt3a/meis3/tsh1 circuit promotes neuronal differentiation and coordinates tissue maturation.during development, early inducing programs must later be counterbalanced for coordinated tissue maturation. in xenopus laevis embryos, activation of the meis3 transcription factor by a mesodermal wnt3a signal lies at the core of the hindbrain developmental program. we now identify a hindbrain restricting circuit, surprisingly comprising the hindbrain inducers wnt3a and meis3, and tsh1 protein. functional and biochemical analyses show that upon tsh1 induction by strong wnt3a/meis3 feedback loop ...201222399680
corticosterone promotes emergence of fictive air breathing in xenopus laevis daudin tadpole brainstems.the emergence of air breathing during amphibian metamorphosis requires significant changes to the brainstem circuits that generate and regulate breathing. however, the mechanisms controlling this developmental process are unknown. because corticosterone plays an important role in the neuroendocrine regulation of amphibian metamorphosis, we tested the hypothesis that corticosterone augments fictive air breathing frequency in xenopus laevis. to do so, we compared the fictive air breathing frequenc ...201222399659
electrophysiological characterization of the polyspecific organic cation transporter plasma membrane monoamine transporter.plasma membrane monoamine transporter (pmat) is a polyspecific organic cation (oc) transporter that transports a variety of endogenous biogenic amines and xenobiotic cations. previous radiotracer uptake studies showed that pmat-mediated oc transport is sensitive to changes in membrane potential and extracellular ph, but the precise role of membrane potential and protons on pmat-mediated oc transport is unknown. here, we characterized the electrophysiological properties of pmat in xenopus laevis ...201222396231
the synthetic progestogen, levonorgestrel, but not natural progesterone, affects male mate calling behavior of xenopus laevis.worldwide, more than 100 million women use hormonal contraceptives, which act through progestogenic modes of action. these man-made hormones can enter the aquatic environment as they are excreted via feces and urine. xeno-progestins are able to interfere with the endocrine system of female aquatic vertebrates impairing oogenesis and reproduction. however, data on progestogenic effects on reproductive behavior of male aquatic vertebrates are lacking. to evaluate whether progestins affect the mati ...201222391239
super-resolution imaging visualizes the eightfold symmetry of gp210 proteins around the nuclear pore complex and resolves the central channel with nanometer of the most complex molecular machines of cells is the nuclear pore complex (npc), which controls all trafficking of molecules in and out of the nucleus. because of their importance for cellular processes such as gene expression and cytoskeleton organization, the structure of npcs has been studied extensively during the last few decades, mainly by electron microscopy. we have used super-resolution imaging by direct stochastic optical reconstruction microscopy (dstorm) to investigate the stru ...201222389396
down's-syndrome-related kinase dyrk1a modulates the p120-catenin-kaiso trajectory of the wnt signaling pathway.the wnt pathways contribute to many processes in cancer and development, with β-catenin being a key canonical component. p120-catenin, which is structurally similar to β-catenin, regulates the expression of certain wnt target genes, relieving repression conferred by the poz- and zinc-finger-domain-containing transcription factor kaiso. we have identified the kinase dyrk1a as a component of the p120-catenin-kaiso trajectory of the wnt pathway. using rescue and other approaches in xenopus laevis e ...201222389395
γ-aminobutyric acid transporter 2 mediates the hepatic uptake of guanidinoacetate, the creatine biosynthetic precursor, in rats.guanidinoacetic acid (gaa) is the biosynthetic precursor of creatine which is involved in storage and transmission of phosphate-bound energy. hepatocytes readily convert gaa to creatine, raising the possibility that the active uptake of gaa by hepatocytes is a regulatory factor. the purpose of this study is to investigate and identify the transporter responsible for gaa uptake by hepatocytes. the characteristics of [(14)c]gaa uptake by hepatocytes were elucidated using the in vivo liver uptake m ...201222384273
atp binding site mutagenesis reveals different subunit stoichiometry of functional p2x2/3 and p2x2/6 receptors.the aim of the present experiments was to clarify the subunit stoichiometry of p2x2/3 and p2x2/6 receptors, where the same subunit (p2x2) forms a receptor with two different partners (p2x3 or p2x6). for this purpose, four non-functional ala mutants of the p2x2, p2x3, and p2x6 subunits were generated by replacing single, homologous amino acids particularly important for agonist binding. co-expression of these mutants in hek293 cells to yield the p2x2 wt/p2x3 mutant or p2x2 mutant/p2x3 wt receptor ...201222378790
translation of incenp during oocyte maturation is required for embryonic development in xenopus laevis.the chromosome passenger complex (cpc) consists of aurora-b kinase and several other subunits. one of these, incenp, binds aurora-b and regulates its kinase activity. during xenopus oocyte maturation, incenp accumulates through translation, contributing to aurora-b activation. a previous study has demonstrated that inhibition of incenp translation during oocyte maturation diminishes aurora-b activation but does not interfere with oocyte maturation, characterized by normal maturation-specific cyc ...201222378760
suppression of intestinal calcium entry channel trpv6 by ocrl, a lipid phosphatase associated with lowe syndrome and dent disease.oculocerebrorenal syndrome of lowe (ocrl) gene product is a phosphatidyl inositol 4,5-bisphosphate [pi(4,5)p(2)] 5-phosphatase, and mutations of ocrl cause lowe syndrome and dent disease, both of which are frequently associated with hypercalciuria. transient receptor potential, vanilloid subfamily, subtype 6 (trpv6) is an intestinal epithelial ca(2+) channel mediating active ca(2+) absorption. hyperabsorption of ca(2+) was found in patients of dent disease with increased ca(2+) excretion. in thi ...201222378746
skeletal muscle regeneration in xenopus tadpoles and zebrafish larvae.mammals are not able to restore lost appendages, while many amphibians are. one important question about epimorphic regeneration is related to the origin of the new tissues and whether they come from mature cells via dedifferentiation and/or from stem cells. several studies in urodele amphibians (salamanders) indicate that, after limb or tail amputation, the multinucleated muscle fibres do dedifferentiate by fragmentation and proliferation, thereby contributing to the regenerate. in xenopus laev ...201222369050
tracing the emergence of a novel sex-determining gene in medaka, oryzias luzonensis.three sex-determining (sd) genes, sry (mammals), dmy (medaka), and dm-w (xenopus laevis), have been identified to date in vertebrates. however, how and why a new sex-determining gene appears remains unknown, as do the switching mechanisms of the master sex-determining gene. here, we used positional cloning to search for the sex-determining gene in oryzias luzonensis and found that gsdfy (gonadal soma derived growth factor on the y chromosome) has replaced dmy as the master sex-determining gene i ...201222367037
estrogens can disrupt amphibian mating behavior.the main component of classical contraceptives, 17α-ethinylestradiol (ee2), has high estrogenic activity even at environmentally relevant concentrations. although estrogenic endocrine disrupting compounds are assumed to contribute to the worldwide decline of amphibian populations by adverse effects on sexual differentiation, evidence for ee2 affecting amphibian mating behaviour is lacking. in this study, we demonstrate that ee2 exposure at five different concentrations (0.296 ng/l, 2.96 ng/l, 29 ...201222355410
determinants for activation of the atypical agc kinase greatwall during m phase entry.the atypical agc kinase greatwall (gwl) mediates a pathway that prevents the precocious removal of phosphorylations added to target proteins by m phase-promoting factor (mpf); gwl is thus essential for m phase entry and maintenance. gwl itself is activated by m phase-specific phosphorylations that are investigated here. many phosphorylations are nonessential, being located within a long nonconserved region, any part of which can be deleted without effect. using mass spectrometry and mutagenesis, ...201222354989
[mg(2+) inhibits atp-activated current mediated by rat p2x4 receptors expressed in xenopus oocytes].to investigate the modulation of mg(2+) on rat p2x4 receptors and its underlying mechanism, we transcribed cdna coding for wild-type and mutant p2x4 receptors to crna in vitro, injected the crna to oocytes of xenopus laevis using the microinjection technique and revealed the effect of mg(2+) on atp-activated currents (i(atp)) mediated by p2x4 receptors using the two-electrode whole-cell voltage clamp technique. the effects of extracellular mg(2+) on i(atp) were as follows: (1) in oocytes express ...201222348964
a bio-robotic platform for integrating internal and external mechanics during muscle-powered explore the interplay between muscle function and propulsor shape in swimming animals, we built a robotic foot to mimic the morphology and hind limb kinematics of xenopus laevis frogs. four foot shapes ranging from low aspect ratio (ar = 0.74) to high (ar = 5) were compared to test whether low-ar feet produce higher propulsive drag force resulting in faster swimming. using feedback loops, two complementary control modes were used to rotate the foot: force was transmitted to the foot either fr ...201222345392
from expression cloning to gene modeling: the development of xenopus gene sequence resources.the xenopus community has made concerted efforts over the last 10-12 years systematically to improve the available sequence information for this amphibian model organism ideally suited to the study of early development in vertebrates. here i review progress in the collection of both sequence data and physical clone reagents for protein coding genes. i conclude that we have cdna sequences for around 50% and full-length clones for about 35% of the genes in xenopus tropicalis, and similar numbers b ...201222344767
retracted: overexpression of αcp2, a translational repressor of gap-43, inhibited axon outgrowth during development in xenopus laevis.the 3'-untranslated regions (3'-utrs) of growth-associated protein 43 (gap-43), which is crucial for neural development and axonal regeneration, are highly conserved among vertebrates. previous studies in mammals have identified one u-rich cis element within gap-43 3'-utr and several trans factors that regulate its mrna stability. however, much less is known in lower vertebrates. the xenopus gap-43 3'-utr, despite its high similarity with those in higher vertebrates, contains unique cu-rich sequ ...201222342981
effects of environmentally relevant concentrations of the xeno-androgen, methyldihydrotestosterone, on male and female mating behavior in xenopus laevis.endocrine disrupting compounds (edcs) are well known to interfere with the hormone system of aquatic vertebrates and to affect their reproductive biology. 17α-methyldihydrotestosterone (mdht) is a widely used model compound for the assessment of androgenic edcs, because it binds with high affinity to nuclear androgen receptors. it was previously shown to affect various aspects of reproductive biology in aquatic vertebrates, however, evidence for mdht affecting mating behavior of aquatic vertebra ...201222342339
a role for the organic anion transporter oat3 in renal creatinine secretion in mice.tubular secretion of the organic cation, creatinine, limits its value as a marker of glomerular filtration rate (gfr) but the molecular determinants of this pathway are unclear. the organic anion transporters, oat1 and oat3, are expressed on the basolateral membrane of the proximal tubule and transport organic anions but also neutral compounds and cations. here, we demonstrate specific uptake of creatinine into mouse moat1- and moat3-microinjected xenopus laevis oocytes at a concentration of 10 ...201222338083
site-specific transgenesis in xenopus.transgenesis is an essential, powerful tool for investigating gene function and the activities of enhancers, promoters, and transcription factors in the chromatin environment. in xenopus, current methods generate germ-line transgenics by random insertion, often resulting in mosaicism, position-dependent variations in expression, and lab-to-lab differences in efficiency. we have developed and tested a xenopus flp-frt recombinase-mediated transgenesis (x-frmt) method. we demonstrate transgenesis o ...201222337567
cadherin-dependent differential cell adhesion in xenopus causes cell sorting in vitro but not in the embryo.adhesion differences between cell populations are in principle a source of strong morphogenetic forces promoting cell sorting, boundary formation and tissue positioning, and cadherins are main mediators of cell adhesion. however, a direct link between cadherin expression, differential adhesion and morphogenesis has not yet been determined for a specific process in vivo. to identify such a connection, we modulated the expression of c-cadherin in the xenopus laevis gastrula, and combined this with ...201222328523
mutations in slc20a2 link familial idiopathic basal ganglia calcification with phosphate homeostasis.familial idiopathic basal ganglia calcification (ibgc) is a genetic condition with a wide spectrum of neuropsychiatric symptoms, including parkinsonism and dementia. here, we identified mutations in slc20a2, encoding the type iii sodium-dependent phosphate transporter 2 (pit2), in ibgc-affected families of varied ancestry, and we observed significantly impaired phosphate transport activity for all assayed pit2 mutants in xenopus laevis oocytes. our results implicate altered phosphate homeostasis ...201222327515
atypical retinal degeneration 3 in mice is caused by defective pde6b pre-mrna splicing.mutations in the key rod phototransduction enzyme phosphodiesterase 6 (pde6) are known to cause recessive retinitis pigmentosa in humans. mouse models of mutant pde6 represent a common approach to understanding the mechanisms of visual disorders related to pde6 defects. mutation n605s in the pde6b subunit is linked to atypical retinal degeneration 3 (atrd3) in mice. we examined pde6 in atrd3 mice and an atrd3 mutant counterpart of human cone pde6c expressed in rods of transgenic xenopus laevis. ...201222326271
dysmorphic photoreceptors in a p23h mutant rhodopsin model of retinitis pigmentosa are metabolically active and capable of regenerating to reverse retinal degeneration.this study evaluated the capacity of xenopus laevis retina to regenerate photoreceptor cells after cyclic light-mediated acute rod photoreceptor degeneration in a transgenic p23h mutant rhodopsin model of retinits pigmentosa. after discontinuation of cyclic light exposure, we monitored histologic progression of retinal regeneration over a 3 week recovery period. to assess their metabolomic states, contralateral eyes were processed for computational molecular phenotyping. we found that retinal de ...201222323724
dynamics of the subcellular localization of ralbp1/rlip through the cell cycle: the role of targeting signals and of protein-protein interactions.the small g protein ras regulates many cell processes, such as gene expression, proliferation, apoptosis, and cell differentiation. its mutations are associated with one-third of all cancers. ras functions are mediated, at least in part, by ral proteins and their downstream effector the ral-binding protein 1 (ralbp1). ralbp1 is involved in endocytosis and in regulating the dynamics of the actin cytoskeleton. it also regulates early development since it is required for the completion of gastrulat ...201222319010
differential distribution of competence for panplacodal and neural crest induction to non-neural and neural is still controversial whether cranial placodes and neural crest cells arise from a common precursor at the neural plate border or whether placodes arise from non-neural ectoderm and neural crest from neural ectoderm. using tissue grafting in embryos of xenopus laevis, we show here that the competence for induction of neural plate, neural plate border and neural crest markers is confined to neural ectoderm, whereas competence for induction of panplacodal markers is confined to non-neural ecto ...201222318231
identification and functional characterization of the novel human ether-a-go-go-related gene (herg) r744p mutant associated with hereditary long qt syndrome 2.mutations of the cyclic nucleotide binding domain (cnbd) may disrupt human ether-a-go-go-related gene (herg) k(+) channel function and lead to hereditary long qt syndrome (lqts). we identified a novel missense mutation located in close proximity to the cnbd, herg r744p, in a patient presenting with recurrent syncope and aborted cardiac death triggered by sudden auditory stimuli. functional properties of wild type (wt) and mutant herg r744p subunits were studied in xenopus laevis oocytes using tw ...201222314138
mouse sglt3a generates proton-activated currents but does not transport sugar.sodium-glucose cotransporters (sglts) are secondary active transporters belonging to the slc5 gene family. sglt1, a well-characterized member of this family, electrogenically transports glucose and galactose. human sglt3 (hsglt3), despite sharing a high amino acid identity with human sglt1 (hsglt1), does not transport sugar, although functions as a sugar sensor. in contrast to humans, two different genes in mice and rats code for two different sglt3 proteins, sglt3a and sglt3b. we previously clo ...201222301059
an essential and highly conserved role for zic3 in left-right patterning, gastrulation and convergent extension morphogenesis.mutations in zic3 result in x-linked heterotaxy in humans, a syndrome consisting of left-right (l-r) patterning defects, midline abnormalities, and cardiac malformations. similarly, loss of function of zic3 in mouse results in abnormal l-r patterning and cardiac development. however, zic3 null mice also exhibit defects in gastrulation, neural tube closure, and axial patterning, suggesting the hypothesis that zic3 is necessary for proper convergent extension (c-e) morphogenesis. to further invest ...201222285814
glut1 mutations are a rare cause of familial idiopathic generalized epilepsy.the idiopathic generalized epilepsies (ige) are the most common genetically determined epilepsies. however, the underlying genes are largely unknown. we screened the slc2a1 gene, encoding the glucose transporter type 1 (glut1), for mutations in a group of 95 european patients with familial ige.201222282645
mustn1 is essential for craniofacial chondrogenesis during xenopus development.mustn1 is a vertebrate-specific protein that, in vitro, was showed to be essential for prechondrocyte function and thus it has the potential to regulate chondrogenesis during embryonic development. we use xenopus laevis as a model to examine mustn1 involvement in chondrogenesis. previous work suggests that mustn1 is necessary but not sufficient for chondrogenic proliferation and differentiation, as well as myogenic differentiation in vitro. mustn1 was quantified and localized in developing xenop ...201722281807
opposing modulatory effects of d1- and d2-like receptor activation on a spinal central pattern generator.the role of dopamine in regulating spinal cord function is receiving increasing attention, but its actions on spinal motor networks responsible for rhythmic behaviors remain poorly understood. here, we have explored the modulatory influence of dopamine on locomotory central pattern generator (cpg) circuitry in the spinal cord of premetamorphic xenopus laevis tadpoles. bath application of exogenous dopamine to isolated brain stem-spinal cords exerted divergent dose-dependent effects on spontaneou ...201222262823
thyroid hormone-dependent development in xenopus laevis: a sensitive screen of thyroid hormone signaling disruption by municipal wastewater treatment plant effluent.because thyroid hormones (ths) are conserved modulators of development and physiology, identification of compounds adversely affecting th signaling is critical to human and wildlife health. anurans are an established model for studying disruption of th signaling because metamorphosis is dependent upon the thyroid system. in order to strengthen this model and identify new gene transcript biomarkers for th disruption, we performed dna microarray analysis of xenopus laevis tadpole tail transcriptom ...201222248444
abnormal visual processing and increased seizure susceptibility result from developmental exposure to the biocide methylisothiazolinone.methylisothiazolinone (mit) is a commonly used biocide known to be neurotoxic in vitro. brief exposure of cortical neurons in culture to mit results in increased neurodegeneration, whereas chronic exposure of developing neurons in culture to low concentrations of mit has been shown to interfere with normal neurite outgrowth. however, the effects of chronic mit exposure on the developing nervous system have not been tested in vivo. here we expose xenopus laevis tadpoles to sub-lethal concentratio ...201222245758
apoptotic and survival signaling mediated through death receptor members during metamorphosis in the african clawed frog xenopus laevis.the tumor necrosis factor (tnf) superfamily includes death receptor (dr) ligands, such as tnf-α, fasl, and trail. death receptors (drs) induce intracellular signaling upon engagement of their cognate dr ligands, either leading to apoptosis, survival, or proinflammatory responses. the dr signaling is mediated by the recruitment of several death domain (dd)-containing molecules such as fas-associated death domain (fadd) and receptor-interacting protein (rip) 1. in this review, we describe dr signa ...201222245291
gaba expression and regulation by sensory experience in the developing visual system.the developing retinotectal system of the xenopus laevis tadpole is a model of choice for studying visual experience-dependent circuit maturation in the intact animal. the neurotransmitter gamma-aminobutyric acid (gaba) has been shown to play a critical role in the formation of sensory circuits in this preparation, however a comprehensive neuroanatomical study of gabaergic cell distribution in the developing tadpole has not been conducted. we report a detailed description of the spatial expressi ...201222242157
a dynamical model of oocyte maturation unveils precisely orchestrated meiotic decisions.maturation of vertebrate oocytes into haploid gametes relies on two consecutive meioses without intervening dna replication. the temporal sequence of cellular transitions driving eggs from g2 arrest to meiosis i (mi) and then to meiosis ii (mii) is controlled by the interplay between cyclin-dependent and mitogen-activated protein kinases. in this paper, we propose a dynamical model of the molecular network that orchestrates maturation of xenopus laevis oocytes. our model reproduces the core feat ...201222238511
friend of gata (fog) interacts with the nucleosome remodeling and deacetylase complex (nurd) to support primitive erythropoiesis in xenopus laevis.friend of gata (fog) plays many diverse roles in adult and embryonic hematopoiesis, however the mechanisms by which it functions and the roles of potential interaction partners are not completely understood. previous work has shown that overexpression of fog in xenopus laevis causes loss of blood suggesting that in contrast to its role in mammals, fog might normally function to repress erythropoiesis in this species. using loss-of-function analysis, we demonstrate that fog is essential to suppor ...201222235346
the signaling protein cd38 is essential for early embryonic development.cd38 is a multifunctional protein possessing adp-ribosyl cyclase activity responsible for both the synthesis and the degradation of several ca(2+)-mobilizing second messengers. although a variety of functions have been ascribed to cd38, such as immune responses, insulin secretion, and social behavior in adults, nothing is known of its role during embryonic development when ca(2+) signals feature prominently. here, we report the identification and functional expression of cd38 from xenopus laevis ...201222223651
evolution of advertisement calls in african clawed frogs.for most frogs, advertisement calls are essential for reproductive success, conveying information on species identity, male quality, sexual state and location. while the evolutionary divergence of call characters has been examined in a number of species, the relative impacts of genetic drift or natural and sexual selection remain unclear. insights into the evolutionary trajectory of vocal signals can be gained by examining how advertisement calls vary in a phylogenetic context. evolution by gene ...201124723737
about a snail, a toad, and rodents: animal models for adaptation research.neural adaptation mechanisms have many similarities throughout the animal kingdom, enabling to study fundamentals of human adaptation in selected animal models with experimental approaches that are impossible to apply in man. this will be illustrated by reviewing research on three of such animal models, viz. (1) the egg-laying behavior of a snail, lymnaea stagnalis: how one neuron type controls behavior, (2) adaptation to the ambient light condition by a toad, xenopus laevis: how a neuroendocrin ...201022649351
regulatory evolution of a duplicated heterodimer across species and tissues of allopolyploid clawed frogs (xenopus).changes in gene expression contribute to reproductive isolation of species, adaptation, and development and may impact the genetic fate of duplicated genes. african clawed frogs (genus xenopus) offer a useful model for examining regulatory evolution, particularly after gene duplication, because species in this genus are polyploid. additionally, these species can produce viable hybrids, and expression divergence between coexpressed species-specific alleles in hybrids can be attributed exclusively ...200919221685
differential effect of high pressure on nmda receptor currents in xenopus laevis oocytes.hyperbaric environments over 1.1 mpa induce in mammals and humans the high pressure neurological syndrome (hpns). hpns is characterized by cognitive and motor decrements associated with sleep disorders, eeg changes, tremor, and convulsions. previously, it was proposed that augmented responses of the glutamatergic n-methyl-d-aspartate receptor (nmdar) may be involved. recently, we have reported that, in rat hippocampus brain slices, isolated nmdar synaptic responses were augmented at high pressur ...200822692751
sca13.spinocerebellar ataxia 13 (sca13), initially described in a four-generation french family, has now also been characterized in a large filipino pedigree. ongoing investigations continue to identify additional sca13 families and individuals. recently, studies have shown that mutations in the voltage-gated potassium channel kcnc3 are causative for sca13. sequence analysis of kcnc3 revealed mutations 1554g-->a (r420h) in the filipino and 1639c-->a (f448l) in the french pedigrees. both mutations alte ...200818592334
gene expression in pre-mbt embryos and activation of maternally-inherited program of apoptosis to be executed at around mbt as a fail-safe mechanism in xenopus early embryogenesis.s-adenosylmethionine decarboxylase (samdc) is an enzyme which converts s-adenosylmethione (sam), a methyl donor, to decarboxylated sam (dcsam), an aminopropyl donor for polyamine biosynthesis. in our studies on gene expression control in xenopus early embryogenesis, we cloned the mrna for xenopus samdc, and overexpressed the enzyme by microinjecting its mrna into xenopus fertilized eggs. in the mrna-injected embryos, the level of samdc was enormously increased, the sam was exhausted, and protein ...200819787085
sex differences in the brain: plasticity and constraints. focus on "androgen-induced vocal transformation in adult female african clawed frogs". 200515985694
evolution of rag-1 in polyploid clawed frogs.possible genetic fates of a gene duplicate are silencing, redundancy, subfunctionalization, or novel function. these different fates can be realized at the dna, rna, or protein level, and their genetic determinants are poorly understood. we explored molecular evolution of duplicated rag-1 genes in african clawed frogs (xenopus and silurana) (1) to examine the fate of paralogs of this gene at the dna level in terms of recombination, positive selection, and gene degeneration and in the absence of ...200515703243
vocal communication between male xenopus laevis.this study focuses on the role of male-male vocal communication in the reproductive repertoire of the south african clawed frog, xenopus laevis. six male and two female call types were recorded from native ponds in the environs of cape town, south africa. these include all call types previously recorded in the laboratory as well as one previously unidentified male call: chirping. the amount of calling and the number of call types increased as the breeding season progressed. laboratory recordings ...200423457414
cellular and molecular targets of benzo[a]pyrene and metal toxicity in xenopus laevis embryos and in hep g2 cells.this paper describes the use of two in vitro systems (stage 35 xenopus laevis embryos and the human hepatoblastoma cell line, hep g2) to study effects of some environmental contaminants (benzo[a]pyrene, copper and zinc), which are representative of chemicals with different cell targets and mechanisms of action. the ability to activate benzo[a[pyrene and to metabolise it with the cytochrome p4501a isozyme were demonstrated in both in vitro systems by assessing the formation of water-soluble and p ...201425470671
effect of culture temperature on a recombinant cho cell line producing a c-terminal α-amidating order to seek an efficient method for producing a recombinant protein by using animal cell culture, we investigated various effects of the culture temperature on a recombinant cho cell line (3µ-1s), producing a c-terminal α-amidating enzyme (799bgliiα-ae) originating from xenopus laevis. the results revealed that a low culture temperature (below 37 °c) led to the following phenomena: [1] inhibited cell growth, [2] enhanced cellular productivity of the recombinant protein, [3] maintained high ...199822358553
surface mesoderm in xenopus: a revision of the stage 10 fate map.we have used two complementary cell labeling techniques to investigate dorsal mesoderm formation in xenopus laevis and hymenochirus boettgeri. epithelial grafts from fluorescently labeled donors into unlabeled hosts demonstrate that in xenopus, as previously shown for hymenochirus, superficial cells of the dorsal marginal zone have the ability to invade the notochord and somite and participate in their normal morphogenesis, in a stage-specific and region-specific manner. a new method for superfi ...199727747438
a retinoid-binding lipocalin, xlcpl1, relevant for embryonic pattern formation is expressed in the nervous system of xenopus laevis.the importance of retinoids in early development has been increasingly recognized during the past decade. their transport and action are mediated by extracellular, intracellular and nuclear proteins. here we describe the isolation and characterization of a cdna, xlcpl1, coding for a lipocalin that is most likely involved in the transport of retinoids in the embryonic nervous system of xenopus laevis. lipocalins generally are carriers for small hydrophobic molecules. the expression of xlcpl1 show ...199727747415
restricting oxygen supply to the prospective dorsal side does not reverse axis polarity in embryos of xenopus laevis.during the first cell cycle, the prospective dorsal side of the embryo of xenopus laevis becomes enriched in mitochondria relative to the ventral side. this differential distribution of mitochondria persists throughout early development, but it is not known if it is of functional significance, since there do not appear to be dorsal-ventral differences in metabolic rate. however, the unilateral anaerobiosis experiments of landström and løvtrup do suggest a role for energy metabolism in determinin ...199624173467
the role of ca(2+) in progesterone-induced germinal vesicle breakdown of xenopus laevis oocytes: the synergic effects of microtubule depolymerization and ca(2+).by monitoring (45)ca(2+) influx and efflux from oocytes a transient increase followed by a transient decrease in the ca(2+)-content of progesterone-treated oocytes was observed. chelation of intracellular ca(2+) with egta or bapta-type buffers inhibited progesterone-induced gvbd. buffers with a mid-range kd (∼1.5 μm) were most effective in inhibiting gvbd whereas buffers with a kd above or below this value were less effective. these observations indicate that intracellular ca(2+), probably in th ...199624173464
lens formation from cornea implanted into amputated hindlimbs of xenopus laevis larvae requires innervation or proliferating cell populations in the stump.the capacity of amputated early and late limbs of larval xenopus laevis to promote lens-forming transformations of corneal implants in the absence of a limb regeneration blastema has been tested by implanting outer cornea fragments from donor larvae at stage 48 (according to nieuwkoop and faber 1956), into limb stumps of larvae at stage 52 and 57. blastema formation has been prevented either by covering the amputation surface with the skin or by reconnecting the amputated part to the limb stump. ...199628306096
isolation of xenopus hgf gene promoter and its functional analysis in embryos and animal caps.previously, we isolated xenopus hgf (hepatocyte growth factor) cdna and showed in xenopus embryos that expression of this gene starts at the late gastrula stage mainly in the ventral mesoderm, and furthermore that the expression is induced in animal cap by activin a and bfgf (basic fibroblast growth factor). here we have cloned the xenopus hgf gene, covering a 14 kb 5'-upstream region and a 0.2 kb 5'-coding region. within about 0.5 kb of the 5'-flanking region, the xenopus hgf gene contained a t ...199628306033
heart formative factor(s) is localized in the anterior endoderm of early xenopus elucidate the mechanisms of early heart morphogenesis in xenopus laevis, we examined the effect of endoderm on heart morphogenesis in the early xenopus neurula. explants of anterior ventral (presumptive heart) mesoderm from early neurula were cultured alone or in combination with endoderm dissected from various regions. heart formation was scored by an original heart index based on morphology. these explant studies revealed that anterior ventral endoderm plays a critical role in heart morphog ...199628306031
the relationship of innervation and differentiation to regenerative capacity in the reamputated hindlimb of larval xenopus laevis.regenerated hindlimbs of larval xenopus laevis were reamputated at critical larval stages and levels, viz when amputation of the control limb at the same larval stage and level is followed by reduced regeneration. reamputations were performed at the level of (1) the original plane of amputation, (2) the early regenerate (cone/palette stage), (3) the late regenerate (digit stage). reamputation increased both the percentage rate of regeneration and the morphological complexity of the regenerates i ...199628306028
cardiac myogenesis: overexpression of xcsx2 or xmef2a in whole xenopus embryos induces the precocious expression of xmhcα gene.xcsx2, a homeobox-containing gene, is expressed in cardiac muscle during xenopus development, while the xmef2a gene is expressed in both cardiac and skeletal muscle. microinjection of either xcsx2 or xmef2a mrna into single blastomeres of two-cell stage xenopus embryos induced precocious expression of the myosin heavy-chain alpha (xmhcα) gene at the neural plate stage (stage 14). co-injection of both xcsx2 and xmef2a mrnas induced still earlier expression at the late gastrula stage (stage 12). t ...199528306081
establishment and movement of egg regions revealed by the size class of yolk platelets in xenopus laevis.sizes of yolk platelets were measured in sections of oocytes and embryos in xenopus. it was found that the average size of the largest group of platelets in cells differed between germ layers of neurulae. it was small (3 to 5 μm) in the ectoderm, medium-sized (5 to 8 µm) in the mesoderm, and large (over 8 μm) in the endoderm. platelets of these size classes formed layers in egg, the yolk gradient, by the end of oocyte maturation. the yolk gradient contained products of the mitochondrial cloud an ...199528306074
diagnostic exercise: anorexia, wasting, and death in south african clawed frogs. 19958569164
xenopus laevis tadpole limb regeneration in vivo and in vitro: thyroxine directly promotes blastemal cell proliferation and morphogenesis.regeneration in hindlimbs of xenopus laevis larvae which were amputated at stage 53 and 55 through the tarsalia region is promoted by thyroxine (t4), while propyl-thiouracil (ptu) inhibits regeneration when compared to controls. in this paper, by in vivo and in vitro experiments, we demonstrate that the promoting effect of t4 on the regenerative processes of larval x. laevis hindlimbs is a direct effect of this hormone on the blastemal cells. by contrast, the inhibitory effect of ptu on the rege ...199528306117
transcription patterns of four different fork head/hnf-3 related genes (xfd-4, 6, 9 and 10) in xenopus laevis embryos.we have isolated and sequenced four different members of the xenopus fork head domain related multigene family (xfd-4, 6, 9 and 10). these genes show a high degree of sequence conservation inside the evolutionary conserved fork head domain but they completely diverge outside this region. all four xfd genes are transcribed during embryogenesis but they are activated at different developmental stages. to investigate the localisation of transcripts we performed whole mount in situ hybridizations. w ...199528305961
different spatial distribution of mrnas for activin receptors (type iia and iib) and follistatin in developing embryos of xenopus laevis.spatial distribution of mrnas for activin receptors and follistatin was studied by northern blot hybridization using rnas from different parts of dissected xenopus embryos. mrnas of two activin receptors (type iia and iib) occurred uniformly in pre-gastrular embryos, but occurred in larger amounts in ectoderm (in gastrulae), neural plate (in neurulae) and anterior (head) regions (in tailbud embryos) than in other embryonic regions. by contrast, follistatin mrna appeared almost exclusively in the ...199528305956
identification of a heparin-binding, mesoderm-inducing peptide in the swim-bladder of the red seabream, pagrus major: a probable fish fibroblast growth factor.the brain, pituitary, liver, ovary and swim-bladder of the red seabream (pagrus major) were screened for the presence of a growth factor capable of stimulating the proliferation of bhk-21 cells, and the swimbladder extract was found to exert the most powerful activity. swim-bladder derived growth factor (sbdgf) with heparin-binding ability was isolated by heparin-affinity and size-exclusion chromatography using heparin-sepharose cl-6b and superose 12, respectively. the relative molecular mass of ...199424198214
effects of thyroxine and propyl-thiouracil on hindlimb regeneration of larvalxenopus laevis.xenopus laevis larvae at stage 53 and 55 (according to nieuwkoop and faber 1956) were subjected to amputation of one or both hindlimbs and reared either in thyroxine (t4) 2.5 to 10 μg/l or in propyl-thiouracil (ptu) 0.01%. results have shown that when the limb was amputated through a nearly undifferentiated region (tarsalia level, at stage 53) or through a differentiating region (tarsalia level, at stage 55), t4 accelerated the regenerative process and enhanced the mitotic and labelling indices ...199428305884
the possible role of mesodermal growth factors in the formation of endoderm inxenopus laevis.we have raised a monoclonal antibody, 4g6, against gut manually isolated from stage 42xenopus laevis embryos. it is specific for endoderm and recognises an epitope that is first expressed at stage 19 and which persists throughout subsequent development. the antibody maintains gut specificity through metamorphosis and into adulthood. the epitope is conserved in the mouse, where it is also found in the gut. isolated vegetal poles fromxenopus blastula stage embryos express the epitope autonomously ...199328305766
changing complexity of endogenous lectin activities during juvenile development of xenopus laevis.galactoside-binding lectin has been isolated from whole xenopus laevis embryos and tadpoles at four development stages: st. 24-26, 32, 41 and 47. the main lectin activity at st. 24-26 is β-galactoside specific, producing a 34/35.5k doublet on sds-page. later in development, lectin activities specific for a wide range of other sugars appear concommitant with the detection of a number of new protein bands on sds-page gels. the greatest variety of new lectin activities exists at st. 32 when lectins ...199328305988
functions and expression of liver conclusion we have shown that: (a) liver n-cam is a functionally active adhesion molecule, (b) its expression during the morphogenetic processes occurring during xenopus laevis metamorphosis correlates with morphological changes in the cell-to-cell interaction; (c) thyroxine is not directely involved in the activation of the expression of liver n-cam.199322358723
expression and distribution of sparc in early xenopus laevis embryos.sparc (secreted protein, acidic, rich in cysteine) is a highly conserved, calcium-binding, extracellular matrix protein. to investigate its role in early embryogenesis, we examined its tissue distribution in early xenopus embryos. sparc mrna transcripts were detectable by northern blot analysis beginning at the early neurula stage. sparc transcripts then rapidly accumulated, reaching their highest embryonic level at the tailbud stage. the levels of sparc mrna were similar in dorsalized (licl-tre ...199228305998
outgrowth dependency of forelimb regeneration on nerves in adult african clawed frog, xenopus laevis.the relationship between the size and shape of regenerative outgrowth and the quantity of innervation was studied in adult xenopus laevis. the forelimbs, of which the nerve supply was artificially altered, were amputated midway through the stylopodium and were kept for 1 year. the regenerative outgrowths that formed in normal limbs with an intact nerve supply were mainly spike-shaped and occasionally rod-shaped. however, when the nerve supply to the distal part of the forelimb was augmented by s ...199228305856
spatial and temporal localization of fgf receptors in xenopus laevis.mesoderm formation is a result of cell-cell interactions between the vegetal and animal hemisphere and is thought to be mediated by inducing peptide growth factors including members of the fgf and tgfβ superfamilies. our immunochemical study analyses the distribution of fgf receptors coded by the human flg gene during embryogenesis of xenopus laevis. immunostaining was detected in the dorsal and ventral ectoderm and also in the marginal zone of early cleavage, blastula and gastrula stages. signa ...199228305851
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