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a fungal metabolite asperparaline a strongly and selectively blocks insect nicotinic acetylcholine receptors: the first report on the mode of action.asperparalines produced by aspergillus japonicus jv-23 induce paralysis in silkworm (bombyx mori) larvae, but the target underlying insect toxicity remains unknown. in the present study, we have investigated the actions of asperparaline a on ligand-gated ion channels expressed in cultured larval brain neurons of the silkworm using patch-clamp electrophysiology. bath-application of asperparaline a (10 µm) had no effect on the membrane current, but when delivered for 1 min prior to co-application ...201121483774
"a functional scaffold of cns neurons for the vertebrates: the developing xenopus laevis spinal cord"in young and developing amphibians and fish the spinal cord is functional but remarkably simple compared to the adult. is the pattern of neurons and their connections common across at least these lower vertebrates? does this basic pattern extend into the brainstem? could the development of simple functioning neuronal networks depend on very basic rules of connectivity and act as pioneer networks providing a substrate for the development of more complex and subtle networks. in this review of the ...201121485014
cdc48/p97-ufd1-npl4 antagonizes aurora b during chromosome segregation in hela cells.during exit from mitosis in xenopus laevis egg extracts, the aaa+ atpase cdc48/p97 (also known as vcp in vertebrates) and its adapter ufd1-npl4 remove the kinase aurora b from chromatin to allow nucleus formation. here, we show that in hela cells ufd1-npl4 already antagonizes aurora b on chromosomes during earlier mitotic stages and that this is crucial for proper chromosome segregation. depletion of ufd1-npl4 by small interfering rna (sirna) caused chromosome alignment and anaphase defects resu ...201121486945
mechanistic analysis of xenopus exo1's function in 5'-strand resection at dna double-strand breaks.the processing of dna double-strand breaks (dsbs) into 3' single-stranded tails is the first step of homology-dependent dsb repair. a key player in this process is the highly conserved eukaryotic exonuclease 1 (exo1), yet its precise mechanism of action has not been rigorously determined. to address this issue, we reconstituted 5'-strand resection in cytosol derived from unfertilized interphase eggs of the frog xenopus laevis. xenopus exo1 (xexo1) was found to display strong 5'→3' dsdna exonucle ...201121490081
evolution of vertebrate transient receptor potential vanilloid 3 channels: opposite temperature sensitivity between mammals and western clawed frogs.transient receptor potential (trp) channels serve as temperature receptors in a wide variety of animals and must have played crucial roles in thermal adaptation. the trp vanilloid (trpv) subfamily contains several temperature receptors with different temperature sensitivities. the trpv3 channel is known to be highly expressed in skin, where it is activated by warm temperatures and serves as a sensor to detect ambient temperatures near the body temperature of homeothermic animals such as mammals. ...201121490957
expression of xnoa 36 in the mitochondrial cloud of xenopus laevis oocytes.summaryin xenopus laevis oocytes a mitochondrial cloud (mc) is found between the nucleus and the plasma membrane at stages i-ii of oogenesis. the mc contains rnas that are transported to the future vegetal pole at stage ii of oogenesis. in particular, germinal plasm mrnas are found in the message transport organiser (metro) region, the mc region opposite to the nucleus. at stages ii-iii, a second pathway transports vg1 and vegt mrnas to the area where the mc content merges with the vegetal corte ...201121492502
mapping gene expression in two xenopus species: evolutionary constraints and developmental flexibility.changes in gene expression are thought to be important for morphological evolution, though little is known about the nature or magnitude of the differences. here, we examine xenopus laevis and xenopus tropicalis, two amphibians with very similar development, and ask how their transcriptomes compare. despite separation for ~30-90 million years, there is strong conservation in gene expression in the vast majority of the expressed orthologs. significant changes occur in the level of gene expression ...201121497761
comparative morphology of the osteocyte lacunocanalicular system in various vertebrates.osteocytes are embedded in the bone matrix, and they communicate with adjacent osteocytes, osteoblasts, and osteoclasts through the osteocyte lacunocanalicular system. osteocytes are believed to be essential for the maintenance of bone homeostasis because they regulate mechanical sensing and mineral metabolism in mammalian bones; however, osteocyte morphology in other vertebrates has not been well documented. we conducted a comparative study on the morphology of osteocytes and the lacunocanalicu ...201121499992
phosphate transporter gene, ospht1;8, is involved in phosphate homeostasis in rice.plant phosphate transporters (pts) are active in the uptake of inorganic phosphate (pi) from the soil and it's translocation within the plant. here, we report on the biological properties and physiological roles of ospht1;8 (ospt8), one of the pts belonging to the pht1 family in rice (oryza sativa l.). expression of gus (£-glucuronidase) & gfp (green fluorescent protein) reporter gene driven by ospt8 promoter showed that ospt8 is expressed in various tissue organs from roots to seeds independent ...201121502185
the quaternary lidocaine derivative, qx-314, exerts biphasic effects on transient receptor potential vanilloid subtype 1 channels in vitro.: transient receptor potential vanilloid subfamily member 1 (trpv1) channels are important integrators of noxious stimuli with pronounced expression in nociceptive neurons. the experimental local anesthetic, qx-314, a quaternary (i.e., permanently charged) lidocaine derivative, recently has been shown to interact with and permeate these channels to produce nociceptive and sensory blockade in animals in vivo. however, little is known about the specific interactions between qx-314 and trpv1 channe ...201121502857
binding sites for bilobalide, diltiazem, ginkgolide and picrotoxinin at the 5-ht3 receptor.bilobalide (bb), ginkgolide b (gb), diltiazem (dtz) and picrotoxinin (pxn) are 5-ht(3) receptor antagonists whose principal sites of action are in the channel. to probe their exact binding locations 5-ht(3) receptors with substitutions in their pore lining residues were constructed (n-4'q, e-1'd, s2'a, t6's, l7't, l9'v, s12'a, i16'v, d20'e), expressed in xenopus oocytes, and the effects of the compounds on 5-ht-induced currents examined. ec(50)s at mutant receptors were less than 6-fold differen ...201121505038
comparison of diazinon toxicity to embryos of xenopus laevis and danio rerio; degradation of diazinon in water.the aim of this study was to determine the toxic effect of diazinon (organophosphate insecticide) to embryos of xenopus laevis and danio rerio. the 96-h lc(50) values showed higher toxicity of diazinon for x. leavis in standard solution (9.84 mg/l) compared to the pond water (12.64 mg/l). teratogenic index for diazinon was 1.3 and 1.6, respectively. the 96-h lc(50) diazinon values demonstrated similar sensitivity of embryos d. rerio (8.21-9.34 mg/l) and x. laevis in standard test solutions. our ...201121505793
transport via slc5a8 (smct1) is obligatory for 2-oxothiazolidine-4-carboxylate to enhance glutathione production in retinal pigment epithelial cells.purpose: to evaluate the role of slc5a8 in the transport of 2-oxothiazolidine-4-carboxylate (otc), and to determine whether otc augments glutathione production in rpe cells thereby providing protection against oxidative stress. methods: slc5a8-mediated transport of otc was monitored in x. laevis oocytes by electrophysiological means. saturation kinetics, na(+)-activation kinetics, and inhibition by ibuprofen were analyzed by monitoring otc-induced currents as a measure of transport activity. oxi ...201121508099
poly(a)-binding proteins are functionally distinct and have essential roles during vertebrate development.translational control of many mrnas in developing metazoan embryos is achieved by alterations in their poly(a) tail length. a family of cytoplasmic poly(a)-binding proteins (pabps) bind the poly(a) tail and can regulate mrna translation and stability. however, despite the extensive biochemical characterization of one family member (pabp1), surprisingly little is known about their in vivo roles or functional relatedness. because no information is available in vertebrates, we address their biologi ...201121518916
spatiotemporal expression profile of no29/nucleophosmin3 in the intestine of xenopus laevis during metamorphosis.a xenopus laevis homolog of nucleophosmin/nucleoplasmin3 (npm3), no29, has been previously identified as a thyroid hormone (th)-response gene during th-induced metamorphosis. x. laevis has another npm3 homolog (npm3) in the pseudo-tetraploid genome, whereas x. tropicalis possesses one ortholog in the diploid genome. to assess the possible roles of these npm3 homologs in amphibian metamorphosis, we have analyzed their expression profiles in x. laevis tadpoles. levels of no29 and npm3 mrna are rap ...201121519897
cloning and heterologous expression of new xano2 from xenopus laevis.we have successfully isolated a novel anoctamin (xano2), ca(2+)-activated chloride channel (ano1, tmem16a), from xenopus laevis. the cdna sequence was determined to belong to the anoctamin family by comparison with the xtmem16a sequence in a previous report. full length cdna synthesis was performed by repeating 5'- and 3'-rapid amplification of cdna end (race). we successfully completed the entire cdna sequence and transiently named this sequence xano2. the xano2 cdna is 3884 base pair (bp) long ...201121521635
gene expression profiling to examine the thyroid hormone-disrupting activity of hydroxylated polychlorinated biphenyls in metamorphosing amphibian tadpole.hydroxylated polychlorinated biphenyls are the metabolites produced from parent compounds by the drug-metabolizing enzyme cytochrome p450. these compounds are suspected to disrupt postembryonic neural development in the brains of mammals including humans. we studied the effects of these compounds on thyroid hormone function in the brain by using metamorphosing tadpoles of the african clawed toad (xenopus laevis) as a model for mammalian postembryonic development. the metamorphosis assay revealed ...201121523860
environmental constraints influencing survival of an african parasite in a north temperate habitat: effects of temperature on egg development.summaryfactors affecting survival of parasites introduced to new geographical regions include changes in environmental temperature. protopolystoma xenopodis is a monogenean introduced with the amphibian xenopus laevis from south africa to wales (probably in the 1960s) where low water temperatures impose major constraints on life-cycle processes. effects were quantified by maintenance of eggs from infections in wales under controlled conditions at 10, 12, 15, 18, 20 and 25°c. the threshold for eg ...201121524323
proteomics of m-phase entry: 'omen' vs. 'omre', the battle for oocyte quality and beyond.the understanding of cell cycle regulation benefited greatly from omic approaches. because the cell cycle engine relies heavily on proteins, proteomic methods play a key role in identification of cell cycle players. the proteomic approach delivers an enormous volume of data, but it often lacks comprehensiveness. to ensure the comprehensiveness of results the discovery of novel proteins must be followed by functional analysis. using xenopus laevis oocytes in two different proteomic screens, we ha ...201121526482
pex11β induces peroxisomal gene expression and alters peroxisome number during early xenopus laevis development.abstract:201121526995
interspecific comparisons of lymph volume and lymphatic fluxes: do lymph reserves and lymph mobilization capacities vary in anurans from different environments?abstract the femoral lymph sac volumes and lymph mobilization capacity were compared in three anuran species that span a range of environments, dehydration tolerance, ability to maintain blood volume with dehydration, and degrees of development of skeletal muscles putatively involved in moving lymph vertically to the posterior lymph hearts. the femoral lymph sac volume determined by evans blue injection and dilution in the femoral lymph sac varied interspecifically. the semiaquatic species, lith ...201121527817
the expression of αa- and βb1-crystallin during normal development and regeneration, and proteomic analysis for the regenerating lens in xenopus laevis.to explore the expression of the lens crystallins (αa- and βb1-crystallin) in xenopus laevis embryonic lens development and regeneration and to analyze the order of different crystallins generated in the regenerating lens.201121527991
correlation between physicochemical and ecotoxicological approaches to estimate landfill leachates toxicity.leachates from municipal solid waste (msw) landfills may contain a huge diversity of contaminants; these wastewaters should be considered as potentially hazardous complex mixtures, representing a potential environmental risk for surface and groundwater. current msw landfill wastes regulatory approaches deem exclusively on the physicochemical characterization and does not contemplate the ecotoxicological assessment of landfill leachates. however, the presence of highly toxic substances in consume ...201121530225
intersectin 2 nucleotide exchange factor regulates cdc42 activity during xenopus early development.intersectin 2 (itsn2) is an evolutionarily conserved scaffold protein involved in endocytic internalization, regulation of actin cytoskeleton and epithelial morphogenesis. recent studies of different itsn-deficient organisms revealed that this gene is essential for the functioning of the nervous system and for organism viability. here we report investigations on a possible role of the itsn2 long isoform in the early embryonic development of xenopuslaevis. in vertebrates, alternative splicing gen ...201121530493
molecular cloning, expression and functional analysis of interleukin-8 (il-8) in south african clawed frog (xenopus laevis).in this study, an il-8 homologue has been cloned and identified from south african clawed frog xenopus laevis (designated xlil-8). the open reading frame (orf) of xlil-8 consists of 312 bases encoding a protein of 103 amino acids. the chemokine cxc domain, which contained glu-leu-arg (elr) motif and four cysteine residues, was well conserved in south african clawed frog il-8. by quantitative real-time pcr, mrna transcript of xlil-8 was detectable in all the examined tissues with higher level in ...201121530580
wd repeat-containing protein 5, a ubiquitously expressed histone methltransferase adaptor protein, regulates smooth muscle cell selective gene activation through interaction with pituitary homeobox 2.wd repeat-containing protein 5 (wdr5) is a common component of mammalian mixed lineage leukemia methyltransferase family members, and is important for histone h3 lysine 4 methylation (h3k4me) which has been implicated in control of activation of cell lineage genes during embryogenesis. however, wdr5 has not been considered to play a specific regulatory role in epigenetic programming of cell lineage because it is ubiquitously expressed. previous work from our laboratory showed the appearance of h ...201121531708
posttranscriptional activation of gene expression in xenopus laevis oocytes by microrna-protein complexes (micrornps).microrna-protein complexes (micrornps) can activate translation of target reporters and specific mrnas in quiescent (i.e., g0) mammalian cell lines. induced quiescent cells, like folliculated immature oocytes, have high levels of camp that activate protein kinase aii (pkaii) to maintain g0 and immature states. we report microrna-mediated up-regulated expression of reporters in immature xenopus laevis oocytes, dependent on xenopus ago or human ago2 and on fxr1, as in mammalian cells. importantly, ...201121536868
et3/ednrb2 signaling is critically involved in regulating melanophore migration in xenopus.melanoblasts are derived from neural crest cells (nccs) and are the only nccs that migrate through the dorsolateral pathway. however, how melanoblasts evolved to migrate through a pathway different from other nccs is still unclear, because little is known about common molecular mechanisms of melanoblast migration that are conserved between species. endothelin receptor b2 (ednrb2) is required for avian melanoblasts to enter the dorsolateral pathway. here, we show that endothelin-3 (et3)/ednrb2 si ...201121538684
xenopus: an emerging model for studying congenital heart disease.congenital heart defects affect nearly 1% of all newborns and are a significant cause of infant death. clinical studies have identified a number of congenital heart syndromes associated with mutations in genes that are involved in the complex process of cardiogenesis. the african clawed frog, xenopus, has been instrumental in studies of vertebrate heart development and provides a valuable tool to investigate the molecular mechanisms underlying human congenital heart diseases. in this review, we ...201121538812
developmental downregulation of xenopus cyclin e is phosphorylation and nuclear import dependent and is mediated by ubiquitination.cyclins are regulatory subunits that bind to and activate catalytic cdks. cyclin e associates with cdk2 to mediate the g1/s transition of the cell cycle. cyclin e is overexpressed in breast, lung, skin, gastrointestinal, cervical, and ovarian cancers. its overexpression correlates with poor patient prognosis and is involved in the etiology of breast cancer. we have been studying how cyclin e is normally downregulated during development in order to determine if disruption of similar mechanisms co ...201121539834
thyroid disruption by di-n-butyl phthalate (dbp) and mono-n-butyl phthalate (mbp) in xenopus laevis.di-n-butyl phthalate (dbp), a chemical widely used in many consumer products, is estrogenic and capable of producing seriously reproductive and developmental effects in laboratory animals. however, recent in vitro studies have shown that dbp and mono-n-butyl phthalate (mbp), the major metabolite of dbp, possessed thyroid hormone receptor (tr) antagonist activity. it is therefore important to consider dbp and mbp that may interfere with thyroid hormone system.201121544203
description of a new octoploid frog species (anura: pipidae: xenopus) from the democratic republic of the congo, with a discussion of the biogeography of african clawed frogs in the albertine rift.we describe a new octoploid species of african clawed frog (xenopus) from the lendu plateau in the northern albertine rift of eastern democratic republic of the congo. this species is the sister taxon of xenopus vestitus (another octoploid), but is distinguished by a unique morphology, vocalization and molecular divergence in mitochondrial and autosomal dna. using a comprehensive genetic sample, we provide new information on the species ranges and intra-specific diversity of african clawed frogs ...201121546992
focal adhesion kinase protein regulates wnt3a gene expression to control cell fate specification in the developing neural plate.focal adhesion kinase (fak) is a cytoplasmic tyrosine kinase protein localized to regions called focal adhesions, which are contact points between cells and the extracellular matrix. fak protein acts as a scaffold to transfer adhesion dependent and growth factor signals into the cell. increased fak expression is linked to aggressive metastatic and invasive tumors, however little is known about its normal embryonic function. fak protein knock down during early xenopus laevis development anteriori ...201121551070
involvement of camp and calmodulin in endocytic yolk uptake during xenopus laevis oogenesis.summarythe aim of the present study was to show the participation and physiological role of calmodulin (cam) and camp during vitellogenin endocytic uptake in the amphibian xenopus laevis. the results showed a differential distribution of cam in the ovary follicles during oogenesis. the cam intracellular localization was not affected by gap junction's downregulation and cam inhibition did not completely abolished the endocytic activity of oocytes. we showed that camp was able to completely rescue ...201121554771
expression analysis of epb41l4a during xenopus laevis embryogenesis.epbl41l4a (erythrocyte protein band 4.1-like 4a, also named nbl4) is a member of the band 4.1/nbl4 (novel band 4.1-like protein 4) group of the ferm (4.1, ezrin, radixin, moesin) protein superfamily. proteins encoded by this gene family are involved in many cellular processes such as organization of epithelial cells and signal transduction. on a molecular level, band 4.1/nbl4 proteins have been shown to link membrane-associated proteins and lipids to the actin cytoskeleton. epbl41l4a has also re ...201121556855
peter pan functions independently of its role in ribosome biogenesis during early eye and craniofacial cartilage development in xenopus laevis.the xenopus oocyte possesses a large maternal store of ribosomes, thereby uncoupling early development from the de novo ribosome biosynthesis required for cell growth. brix domain-containing proteins, such as peter pan (ppan), are essential for eukaryotic ribosome biogenesis. in this study, we demonstrate that ppan is expressed maternally as well as in the eye and cranial neural crest cells (nccs) during early xenopus laevis development. depletion of ppan and interference with rrna processing us ...201121558383
insights on the evolution of prolyl 3-hydroxylation sites from comparative analysis of chicken and xenopus fibrillar collagens.recessive mutations that prevent 3-hydroxyproline formation in type i collagen have been shown to cause forms of osteogenesis imperfecta. in mammals, all a-clade collagen chains with a gpp sequence at the a1 site (p986), except α1(iii), have 3hyp at residue p986. available avian, amphibian and reptilian type iii collagen sequences from the genomic database (ensembl) all differ in sequence motif from mammals at the a1 site. this suggests a potential evolutionary distinction in prolyl 3-hydroxylat ...201121559283
asymmetric pi(3,4,5)p3 and akt signaling mediates chemotaxis of axonal growth cones.the action of many extracellular guidance cues on axon pathfinding requires ca(2+) influx at the growth cone (hong et al., 2000; nishiyama et al., 2003; henley and poo, 2004), but how activation of guidance cue receptors leads to opening of plasmalemmal ion channels remains largely unknown. analogous to the chemotaxis of amoeboid cells (parent et al., 1998; servant et al., 2000), we found that a gradient of chemoattractant triggered rapid asymmetric pi(3,4,5)p(3) accumulation at the growth cone' ...201121562263
galactosides in glycoconjugates of xenopus laevis testis shown by lectin histochemistry.the implication of galactosides and other glycoconjugates on spermatogenesis has been previously reported. glycans show such a complex structure that it makes them very difficult to analyze. lectin histochemistry is a helpful tool for the study of glycan composition. lectin histochemistry can be combined with deglycosylation pretreatments to explore the glycan type to which carbohydrates are linked. the aim of the present work was the localization of galactose (gal)-containing glycoconjugates in ...201121563271
positive gaba(a) receptor modulators from acorus calamus and structural analysis of (+)-dioxosarcoguaiacol by 1d and 2d nmr and molecular modeling.in a two-microelectrode voltage clamp with xenopus laevis oocytes, a petroleum ether extract of acorus calamus rhizomes enhanced the gaba-induced chloride current through gaba(a) receptors of the α(1)β(2)γ(2s) subtype by 277% ± 9.7% (100 μg/ml). β-asarone (1), (+)-dioxosarcoguaiacol (2), (+)-shyobunone (3), and (+)-preisocalamenediol (4) were subsequently identified as main active principles through hplc-based activity profiling and targeted isolation. the compounds induced maximum potentiation ...201121563811
norepinephrine depletion of antimicrobial peptides from the skin glands of xenopus laevis.the dermal granular glands of the south african clawed frog, xenopus laevis, contain antimicrobial peptides (amps) that are secreted following local nerve stimulation. these natural antibiotics are active against bacteria and fungi including batrachochytrium dendrobatidis, a fungal pathogen that causes the skin disease chytridiomycosis. granular gland secretion can be stimulated in the laboratory by norepinephrine injection. we found that two injections of 80nmol/g norepinephrine were necessary ...201122227319
the rna-binding protein xp54nrb isolated from a ca(2+)-dependent screen is expressed in neural structures during xenopus laevis development.in amphibian embryos, calcium (ca(2+)) signalling is a necessary and sufficient event to induce neural fate. transient elevations of [ca(2+)]i are recorded in neural tissue precursor cells in whole embryos during gastrulation. using a subtractive cdna library between control ectoderm (animal caps) and ectoderm induced toward a neural fate by ca(2+) release, we have isolated several ca(2+)-induced target genes. among the isolated genes, xp54nrb encodes a protein which exhibits the rrm domains cha ...201122252489
Integument structure and function in juvenile Xenopus laevis with disrupted thyroid balance.The skin is the largest organ in the body and is a barrier between the internal and external environment. The present study evaluates how PTU, a goitrogen, that is used to treat hyperthyroidism affects the structure and electrical properties of the frog (Xenopus laevis) skin. The results are considered in the context of the two-membrane model established in the seminal work of Ussing and collegues in the 1940s and 1950s. In vitro experiments with skin from Xenopus adults revealed that PTU can ac ...201121963960
Filaments assembly of ectopically expressed Caenorhabditis elegans lamin within Xenopus oocytes.Lamins are the major components of the nuclear lamina, a filamentous layer underlying the inner nuclear membrane and attached to the peripheral chromatin. Lamins are required for maintaining nuclear shape and are involved in most nuclear activities. Here, we studied the 3D organization of the nuclear lamina formed upon the expression of Caenorhabditis elegans lamin (Ce-lamin) within the nucleus of a Xenopus laevis oocyte. We show that Ce-lamin forms an intricate 3D meshwork of 5-6nm lamin protof ...201122085746
atptr4 and atptr6 are differentially expressed, tonoplast-localized members of the peptide transporter/nitrate transporter 1 (ptr/nrt1) family.members of the peptide transporter/nitrate transporter 1 (ptr/nrt1) family in plants transport a variety of substrates like nitrate, di- and tripepetides, auxin and carboxylates. we isolated two members of this family from arabidopsis, atptr4 and atptr6, which are highly homologous to the characterized di- and tripeptide transporters atptr1, atptr2 and atptr5. all known substrates of members of the ptr/nrt1 family were tested using heterologous expression in saccharomyces cerevisiae mutants and ...201121904872
fgf signaling is required for lens regeneration in xenopus laevis.in species of the frog genus xenopus, lens regeneration occurs through a process of transdifferentiation, in which cornea epithelial cells presumably undergo dedifferentiation and subsequently redifferentiate to form a new lens. experimental studies have shown that the retina provides the key signal required to trigger this process once the original lens is removed. a previous study showed that addition of an exogenous fibroblast growth factor (i.e., fgf1 protein) could initiate transdifferentia ...201121876116
tissue-specific alternative splicing of tak1 is conserved in deuterostomes.alternative splicing allows organisms to rapidly modulate protein functions to physiological changes and therefore represents a highly versatile adaptive process. we investigated the conservation of the evolutionary history of the "fox" family of rna-binding splicing factors (rbfox) as well as the conservation of regulated alternative splicing of the genes they control. we found that the rbfox proteins are conserved in all metazoans examined. in humans, fox proteins control muscle-specific alter ...201121873631
functional impairment of rat taurine transporter by activation of nitrogen oxide through superoxide.the objective of this study was to identify the nitrogen oxide form(s) involved in the functional impairment of the rat taurine transport system. taurine uptake activity in the rat renal brush border membrane vesicle (rbbmv) preparation or xenopus laevis oocytes that express the rat taurine transporter was compared after the pretreatment with nitrogen oxide donors from which nitric oxide (no) is released at different rates. the functional impairment was associated with a reduced v(max), but did ...201122166889
host-defense peptides in skin secretions of african clawed frogs (xenopodinae, pipidae).african clawed frogs of the xenopodinae (xenopus+silurana) constitute a well-defined system in which to study the evolutionary trajectory of duplicated genes and are a source of antimicrobial peptides with therapeutic potential. allopolyploidization events within the xenopodinae have given rise to tetraploid, octoploid, and dodecaploid species. the primary structures and distributions of host-defense peptides from the tetraploid frogs xenopus borealis, xenopusclivii, xenopuslaevis, xenopusmuelle ...201122036891
beyond the frog: the evolution of homology models of human ikkβ.nuclear factor κ b is implicated in tumor progression and chronic inflammatory diseases and is regulated by iκb kinase β (ikkβ). the crystal structure of ikkβ has been recently solved for xenopus laevis. homology models of human ikkβ have been developed prior to and after the crystal structure was solved. here, we compare four models of human ikkβ and evaluate their performance in both broad and focused library docking studies.201121911292
mouse sperm exhibit chemotaxis to allurin, a truncated member of the cysteine-rich secretory protein family.allurin, a 21 kda protein isolated from egg jelly of the frog xenopus laevis, has previously been demonstrated to attract frog sperm in two-chamber and microscopic assays. cdna cloning and sequencing has shown that allurin is a truncated member of the cysteine-rich secretory protein (crisp) family, whose members include mammalian sperm-binding proteins that have been postulated to play roles in spermatogenesis, sperm capacitation and sperm-egg binding in mammals. here, we show that allurin is a ...201122008793
Molecular evolution of vertebrate sex-determining genes.Y-linked Dmy (also called dmrt1bY) in the teleost fish medaka, W-linked Dm-W in the African clawed frog (Xenopus laevis), and Z-linked Dmrt1 in the chicken are all sex chromosome-linked Dmrt1 homologues required for sex determination. Dmy and Dm-W both are Dmrt1 palalogues evolved through Dmrt1 duplication, while chicken Dmrt1 is a Z-linked orthologue. The eutherian sex-determining gene, Sry, evolved from an allelic gene, Sox3. Here we analyzed the exon-intron structures of the Dmrt1 homologues ...201122167552
mir-124 acts through corest to control onset of sema3a sensitivity in navigating retinal growth cones.during axon pathfinding, growth cones commonly show changes in sensitivity to guidance cues that follow a cell-intrinsic timetable. the cellular timer mechanisms that regulate such changes are, however, poorly understood. here we have investigated micrornas (mirnas) in the timing control of sensitivity to the semaphorin sema3a in xenopus laevis retinal ganglion cell (rgc) growth cones. a developmental profiling screen identified mir-124 as a candidate timer. loss of mir-124 delayed the onset of ...201122138647
Targeting of mouse guanylate cyclase 1 (Gucy2e) to Xenopus laevis rod outer segments.Photoreceptor guanylate cyclase (GC1) is a transmembrane protein and responsible for synthesis of cGMP, the secondary messenger of phototransduction. It consists of an extracellular domain, a single transmembrane domain, and an intracellular domain. It is unknown how GC1 targets to the outer segments where it resides. To identify a putative GC1 targeting signal, we generated a series of peripheral membrane and transmembrane constructs encoding extracellular and intracellular mouse GC1 fragments ...201121945483
Ecological immunogenetics of life-history traits in a model amphibian.Major histocompatibility complex (MHC) genes determine immune repertoires and social preferences of vertebrates. Immunological regulation of microbial assemblages associated with individuals influences their sociality, and should also affect their life-history traits. We exposed Xenopus laevis tadpoles to water conditioned by adult conspecifics. Then, we analysed tadpole growth, development and survivorship as a function of MHC class I and class II peptide-binding region amino acid sequence simi ...201122114322
kcnq1 subdomains involved in kcne modulation revealed by an invertebrate kcnq1 orthologue.kcnq1 channels are voltage-gated potassium channels that are widely expressed in various non-neuronal tissues, such as the heart, pancreas, and intestine. kcne proteins are known as the auxiliary subunits for kcnq1 channels. the effects and functions of the different kcne proteins on kcnq1 modulation are various; the kcnq1-kcne1 ion channel complex produces a slowly activating potassium channel that is crucial for heartbeat regulation, while the kcne3 protein makes kcnq1 channels constitutively ...201122042987
melatonin receptors are anatomically organized to modulate transmission specifically to cone pathways in the retina of xenopus laevis.melatonin receptors have been identified in several retinal cell types, including photoreceptors, horizontal cells, amacrine cells, and ganglion cells. recent reports suggest that melatonin potentiates signaling from rods to inner retinal neurons. however, the organization of the melatonin receptors mediating this action in the outer plexiform layer (opl) is not clear. to assess melatonin receptor localization in the opl, double-label confocal immunohistochemistry for mel1a or mel1b melatonin re ...201122020534
Comparative homology modeling of pyruvate dehydrogenase kinase isozymes from Xenopus tropicalis reveals structural basis for their subfunctionalization.Structural-functional divergence is responsible for the preservation of highly homologous genes. Protein functions affected by mutagenesis in divergent sequences require investigation on an individual basis. In the present study, comparative homology modeling and predictive bioinformatics analysis were used to reveal for the first time the subfunctionalization of two pyruvate dehydrogenase kinase (PDK) isozymes in the western clawed frog Xenopus tropicalis. Three-dimensional structures of the tw ...201122069030
INOH: ontology-based highly structured database of signal transduction pathways.The Integrating Network Objects with Hierarchies (INOH) database is a highly structured, manually curated database of signal transduction pathways including Mammalia, Xenopus laevis, Drosophila melanogaster, Caenorhabditis elegans and canonical. Since most pathway knowledge resides in scientific articles, the database focuses on curating and encoding textual knowledge into a machine-processable form. We use a hierarchical pathway representation model with a compound graph, and every pathway comp ...201122120663
tbx5 overexpression favors a first heart field lineage in murine embryonic stem cells and in xenopus laevis embryos.the t-box transcription factor tbx5 is involved in several developmental processes including cardiogenesis. early steps of cardiac development are characterised by the formation of two cardiogenic lineages, the first (fhf) and the second heart field (shf) lineage, which arise from a common cardiac progenitor cell population. to further investigate the function of tbx5 during cardiogenesis, we generated a murine embryonic stem cell line constitutively overexpressing tbx5. differentiation of these ...201122072574
improved knockout methodology reveals that frog virus 3 mutants lacking either the 18k immediate-early gene or the truncated vif-2alpha gene are defective for replication and growth in vivo.to better assess the roles of frog virus 3 (fv3; genus ranavirus, family iridoviridae) genes in virulence and immune evasion, we have developed a reliable and efficient method to systematically knock out (ko) putative virulence genes by site-specific integration into the fv3 genome. our approach utilizes a dual selection marker consisting of the puromycin resistance gene fused in frame with the enhanced green fluorescent protein (egfp) reporter (puro-egfp cassette) under the control of the fv3 i ...201121865381
D184E mutation in aquaporin-4 gene impairs water permeability and links to deafness.Aquaporins (AQPs) play a physiological role in several organs and tissues, and their alteration is associated with disorders of water regulation. The identification of molecular interactions, which are crucial in determining the rate of water flux through the channel, is of pivotal role for the discovery of molecules able to target those interactions and therefore to be used for pathologies ascribable to an altered AQP-dependent water balance. In the present study, a mutational screening of huma ...201121952128
Role of the Local Anesthetic Receptor in the State-Dependent Inhibition of Voltage-Gated Sodium Channels by the Insecticide Metaflumizone.Sodium channel inhibitor (SCI) insecticides selectively target voltage-gated sodium (Na(v)) channels in the slow-inactivated state by binding at or near the local anesthetic (LA) receptor within the sodium channel pore. Metaflumizone is a new insecticide for the treatment of fleas on domesticated pets and has recently been reported to block insect sodium channels in the slow-inactivated state, thereby implying that it is also a member of the SCI class. Using the two-electrode voltage clamp techn ...201122127519
The effect of anions on the human P2X7 receptor.P2X7 receptors (P2X7Rs) are nonselective cation channels that are opened by the binding of extracellular ATP and are involved in the modulation of epithelial secretion, inflammation and nociception. Here, we investigated the effect of extracellular anions on channel gating and permeation of human P2X7Rs (hP2X7Rs) expressed in Xenopus laevis oocytes. Two-microelectrode voltage-clamp recordings showed that ATP-induced hP2X7R-mediated currents increased when extracellular chloride was substituted b ...201121872569
Origin and segregation of cranial placodes in Xenopus laevis.Cranial placodes are local thickenings of the vertebrate head ectoderm that contribute to the paired sense organs (olfactory epithelium, lens, inner ear, lateral line), cranial ganglia and the adenohypophysis. Here we use tissue grafting and dye injections to generated fate maps of the dorsal cranial part of the non-neural ectoderm for Xenopus embryos between neural plate and early tailbud stages. We show that all placodes arise from a crescent-shaped area located around the anterior neural plat ...201121989028
Direct pharmacological monitoring of the developmental switch in NMDAR subunit composition using TCN 213, a GluN2A-selective, glycine-dependent antagonist.Background and purpose. Developmental switches in NMDAR subunit expression have been inferred from studies of GluN2 expression levels, changes in kinetics of glutamatergic synaptic currents and sensitivity of NMDAR-mediated currents to selective GluN2B antagonists. Here we use TCN 213, a novel GluN2A-selective antagonist to identify the presence of this subunit in functional NMDARs in developing cortical neurones. Experimental approach. TEVC recordings were made from Xenopus laevis oocytes to ...201122022974
aβ oligomer directly modulates p/q-type calcium currents in xenopus oocytes.background and purpose:  amyloid-β (aβ) oligomers have been implicated in the early pathophysiology of alzheimer's disease. while the precise nature of the molecular target has not been fully revealed, a number of studies indicated that aβ oligomers modulate neuron-specific ion channels. we recently provided evidence that aβ oligomers suppress isolated p/q-type calcium currents in cultured nerve cells. using a heterologous expression system we aimed to prove a direct effect on the membrane chann ...201121883149
Single-channel Ca(2+) imaging implicates Aß1-42 amyloid pores in Alzheimer's disease pathology.Oligomeric forms of Aß peptides are implicated in Alzheimer's disease (AD) and disrupt membrane integrity, leading to cytosolic calcium (Ca(2+)) elevation. Proposed mechanisms by which Aß mediates its effects include lipid destabilization, activation of native membrane channels, and aggregation of Aß into Ca(2+)-permeable pores. We distinguished between these using total internal reflection fluorescence (TIRF) microscopy to image Ca(2+) influx in Xenopus laevis oocytes. Aß1-42 oligomers evoked s ...201122024165
wnk3 is a putative chloride-sensing kinase.the with-no-lysine kinase 3 (wnk3) is a serine/threonine kinase that modulates the activity of the electroneutral cation-coupled chloride cotransporters (ccc). using the xenopus laevis oocyte heterologous expression system, it has been shown that wnk3 activates the na(+)-coupled chloride cotransporters nkcc1, nkcc2, and ncc and inhibits the k(+)-coupled chloride cotransporters kcc1 through kcc4. interestingly, the effect of catalytically inactive wnk3 is opposite to that of wild type wnk3: inact ...201122179001
cortical localization of maternal embryonic leucine zipper kinase (melk) implicated in cytokinesis in early xenopus embryos.melk has been implicated in a large variety of functions. because its level is elevated in cancer tissues and it is involved in cell proliferation, melk is considered as a potential therapeutic target for cancers. in a recent, study we have shown that melk is involved in cytokinesis in early xenopus laevis embryos. melk dynamically accumulates at the cell cortex including a narrow band corresponding to the presumptive division furrow shortly before cytokinesis onset. melk co-localizes and intera ...201121966578
a novel barley yellow stripe 1-like transporter (hvysl2) localized to the root endodermis transports metal-phytosiderophore complexes.recent advances in our understanding of how graminaceous plants take up insoluble forms of iron from the rhizosphere and mobilize them in plant tissues are primarily based on the identification of various transporters that are specific to metal-phytosiderophore (ps) complexes containing mugineic acid and deoxymugineic acid. barley (hordeum vulgare l.) yellow stripe 1 (hvys1) is a metal-ps transporter that preferentially transports fe(iii)-ps compared with other metal complexes. here, we report t ...201121937676
parallel biotransformation of tetrabromobisphenol a in xenopus laevis and mammals: xenopus as a model for endocrine perturbation studies.the flame retardant tetrabromobisphenol a (tbbpa) is a high production flame retardant that interferes with thyroid hormone (th) signaling. despite its rapid metabolism in mammals, tbbpa is found in significant amounts in different tissues. such findings highlight first a need to better understand the effects of tbbpa and its metabolites and second the need to develop models to address these questions experimentally. we used xenopus laevis tadpoles to follow radiolabeled (14)c-tbbpa uptake and m ...201122086976
Pontocerebellar hypoplasia in association with de novo 19p13.11p13.12 microdeletion.The pontocerebellar hypoplasias (PCHs) are a group of clinically variable disorders characterized by abnormally small cerebellum and brainstem, generally inherited in an autosomal recessive pattern. While PCHs have been grouped into six subtypes, clinical diagnosis is equivocal until a genetic diagnosis is established. We report a patient with PCH, intrauterine growth restriction, ventricular septal defect, rib anomalies, midgut malrotation, and facial dysmorphic features. Using SNP analysis, we ...201121994138
Strong activation of ether-à-go-go-related gene 1 K+ channel isoforms by NS1643 in human embryonic kidney 293 and Chinese hamster ovary cells.Two different mechanisms leading to increased current have been described for the small-molecule human ether-à-go-go-related gene (herg) activator NS1643 [1,3-bis-(2-hydroxy-5-trifluoromethylphenyl)-urea]. On herg1a channels expressed in Xenopus laevis oocytes, it mainly acts via attenuation of inactivation and for rat (r) erg1b channels expressed in human embryonic kidney (HEK)-293 cells, it strongly shifts the activation curve to the left. We now investigated the NS1643 effects on erg1b channe ...201121856740
The TM2 6' Position of GABAA Receptors Mediates Alcohol Inhibition.Ionotropic ?-aminobutyric acid receptors (GABAARs), which mediate inhibitory neurotransmission in the central nervous system, are implicated in behavioral effects of alcohol and alcoholism. Site-directed mutagenesis studies support the presence of discrete molecular sites involved in alcohol enhancement and, more recently, inhibition of GABAARs. We used Xenopus laevis oocytes to investigate the 6' position in the second transmembrane region of GABAARs as a site influencing alcohol inhibition. We ...201122072732
Epithelial machines that shape the embryo.Embryonic form and the shape of many organs are the product of forces acting within and on epithelial sheets. Analysis of these processes requires both consideration of the mechanical operation of these multicellular machines and an understanding of how epithelial sheets are integrated with surrounding tissues. From the diverse array of epithelial morphogenetic movements seen during embryogenesis we review examples of epithelial sheet bending, Drosophila ventral furrow formation and ascidian gas ...201122130222
gaba(a) receptor modulators from chinese herbal medicines traditionally applied against insomnia and anxiety.several chinese herbal medicines (chms) are used in the treatment of insomnia, restlessness, or anxiety. however, mechanisms underlying this effect and scientific proof for their traditional use is scarce. in the present study chms were screened for their ability to modulate gaba-induced chloride currents (i(gaba)), and active principles were isolated thus providing scientific evidence for their use as sedative and/or anxiolytic agents in cm. herbal drugs were extracted successively with petrole ...201122118921
role of the pi3k-tor-s6k pathway in the onset of cell cycle elongation during xenopus early embryogenesis.in the early embryogenesis of the frog, xenopus laevis, cells proliferate by rapid and synchronous divisions, followed by cell cycle elongation and prolongation of the s phases, and then the appearance of the g2 and g1 phases after the midblastula transition (mbt). the beginning of cell cycle elongation was thought to depend on an increase in the nucleo-cytoplasmic (n/c) ratio in blastomeres and a decrease in cortical cytoplasmic factors necessary for cell cycle progression, although these facto ...201121958163
a decrease in dkk1, a wnt inhibitor, contributes to placental lipid accumulation in an obesity-prone rat model.placenta, as the sole transport mechanism between mother and fetus, links the maternal physical state and the immediate and life-long outcomes of the offspring. the present study examined the consequences of maternal obesity on placental lipid accumulation and metabolism. pregnant obesity prone (op) and obesity resistant (or) rat strains were fed a control diet throughout gestation. placentas were collected on gestational day 21 for mrna and oxidative stress analysis and frozen placental sectio ...201122133691
Prominin-1 Localizes to the Open Rims of Outer Segment Lamellae in Xenopus laevis Rod and Cone Photoreceptors.Purpose.Prominin-1 expresses in rod and cone photoreceptors. Mutations in the prominin-1 gene cause retinal degeneration in humans. In this study, we investigated the expression, subcellular localization of xlProminin-1 protein, the Xenopus laevis orthologue of prominin-1, in rod and cone photoreceptors of this frog.Methods.Antibodies specific for xlProminin-1 were generated. Immunoblotting was used to study the expression and posttranslational processing of xProminin-1 protein. Immunocytochemic ...201122076989
the iron transporter ferroportin can also function as a manganese exporter.the present study examined the hypothesis that the iron exporter ferroportin (fpn1/slc40a1) can also mediate cellular export of the essential trace element manganese, using xenopus laevis oocytes expressing human fpn1. when compared to oocytes expressing only the divalent metal transporter-1 (dmt1/nramp2), (54)mn accumulation was lower in oocytes also expressing fpn1. fpn1-expressing oocytes exported more (54)mn than control oocytes (26.6±0.6% versus 7.1±0.5%, respectively, over 4h at ph 7.4 whe ...201122178646
The development of the adult intestinal stem cells: Insights from studies on thyroid hormone-dependent amphibian metamorphosis.ABSTRACT: Adult organ-specific stem cells are essential for organ homeostasis and repair in adult vertebrates. The intestine is one of the best-studied organs in this regard. The intestinal epithelium undergoes constant self-renewal throughout adult life across vertebrates through the proliferation and subsequent differentiation of the adult stem cells. This self-renewal system is established late during development, around birth, in mammals when endogenous thyroid hormone (T3) levels are high. ...201121896185
growth-arrest-specific protein 2 inhibits cell division in xenopus embryos.growth-arrest-specific 2 gene was originally identified in murine fibroblasts under growth arrest conditions. furthermore, serum stimulation of quiescent, non-dividing cells leads to the down-regulation of gas2 and results in re-entry into the cell cycle. cytoskeleton rearrangements are critical for cell cycle progression and cell division and the gas2 protein has been shown to co-localize with actin and microtubules in interphase mammalian cells. despite these findings, direct evidence supporti ...201121931817
optimization of gene delivery methods in xenopus laevis kidney (a6) and chinese hamster ovary (cho) cell lines for heterologous expression of xenopus inner ear genes.the xenopus inner ear provides a useful model for studies of hearing and balance because it shares features with the mammalian inner ear, and because amphibians are capable of regenerating damaged mechanosensory hair cells. the structure and function of many proteins necessary for inner ear function have yet to be elucidated and require methods for analysis. to this end, we seek to characterize xenopus inner ear genes outside of the animal model through heterologous expression in cell lines. as ...201121959846
jShaw1, a low-threshold, fast-activating K(v)3 from the hydrozoan jellyfish Polyorchis penicillatus.Voltage-gated potassium (K(v)) channels work in concert with other ion channels to determine the frequency and duration of action potentials in excitable cells. Little is known about K(v)3 channels from invertebrates, but those that have been characterized generally display slow kinetics. Here, we report the cloning and characterization of jShaw1, the first K(v)3 isolated from a cnidarian, the jellyfish Polyorchis penicillatus, in comparison with mouse K(v)3.1 and K(v)3.2. Using a two-electrode ...201121865525
temporal and spatial expression patterns of cdc25 phosphatase isoforms during early xenopus development.in early animal development, cell proliferation and differentiation are tightly linked and coordinated. it is important, therefore, to know how the cell cycle is controlled during early development. cdc25 phosphatases activate cyclin-dependent kinases (cdks) and thereby promote cell-cycle progression. in xenopus laevis, three isoforms of cdc25 have been identified, viz. cdc25a, cdc25b and cdc25c. in this study, we isolated a cdna encoding a novel xenopus cdc25 phosphatase (named cdc25d). we inve ...201121948711
nitric oxide as a putative retinal axon pathfinding and target recognition cue in xenopus laevis.nitric oxide (no) is an atypical neurotransmitter synthesized by the enzyme nitric oxide synthase (nos) during many stages of the xenopus laevis life cycle. this research investigates whether the gas no is involved in axon guidance, the neurodevelopmental process in which axons travel through the brain to their appropriate target locations to form functional neural circuitry. through immunocytochemistry and direct labeling of the no gas with a fluorescent dye, we have found that nos expression c ...201121847432
characterization of two mutations, m287l and q266i, in the α1 glycine receptor subunit that modify sensitivity to alcohols.glycine receptors (glyrs) are inhibitory ligand-gated ion channels. ethanol potentiates glycine activation of the glyr, and putative binding sites for alcohol are located in the transmembrane (tm) domains between and within subunits. to alter alcohol sensitivity of glyr, we introduced two mutations in the glyr α1 subunit, m287l (tm3) and q266i (tm2). after expression in xenopus laevis oocytes, both mutants showed a reduction in glycine sensitivity and glycine-induced maximal currents. activation ...201122037201
xenopus staufen2 is required for anterior endodermal organ formation.defining the regulatory molecular networks involved in patterning the developing anterior endoderm is essential to understanding how the pancreas, liver, stomach and duodenum are discretely specified from each other. in this study, we analyzed the expression and function of the double-stranded rna-binding protein staufen2 in xenopus laevis endoderm. we found that staufen2 was broadly expressed within the developing endoderm beginning at gastrulation becoming localized to the anterior endoderm at ...201122162130
protein kinase c-dependent activation of human k(2p) 18.1 k(+) channels.background and purpose.  two-pore-domain potassium channels (k(2p) ) mediate k(+) background currents that modulate the membrane potential of excitable cells. k(2p) 18.1 (tresk, twik-related spinal cord k(+) channel) provides hyperpolarizing background currents in neurons. recently a dominant negative loss-of-function mutation in k(2p) 18.1 has been implicated in migraine, and activation of k(2p) 18.1 channels was proposed as therapeutic strategy. here we elucidate molecular mechanisms underly ...201122168364
Single cysteines in the extracellular and transmembrane regions modulate pannexin 1 channel function.Pannexins form high-conductance ion channels in the membranes of many vertebrate cells. Functionally, they have been associated with multiple functional pathways like the propagation of calcium waves, ATP release, responses to ischemic conditions and apoptosis. In contrast to accumulating details which uncovered their functions, the molecular mechanisms for pannexin channel regulation and activation are hardly understood. To further elucidate regulatory mechanisms, we substituted cysteine residu ...201121938521
transdifferentiation from cornea to lens in xenopus laevis depends on bmp signalling and involves upregulation of wnt signalling.surgical removal of the lens from larval xenopus laevis results in a rapid transdifferention of central corneal cells to form a new lens. the trigger for this process is understood to be an induction event arising from the unprecedented exposure of the cornea to the vitreous humour that occurs following lens removal. the molecular identity of this trigger is unknown.201121896182
expression of periostin during xenopus laevis embryogenesis.periostin (postn) is a secreted, extracellular matrix protein containing an emi domain as well as four fasciclin i-like (fas1) domains. postn protein functions in cell adhesion, cell mobility, cell proliferation and gene regulation. earlier studies have shown that postn is involved in different developmental processes such as somitogenesis, cardiogenesis and bone formation. intriguingly, postn seems to be a very good candidate to establish novel therapies against cancer and chronic heart defects ...201121901578
advances in the mode of action of pyrethroids.the ability to clone, express, and electrophysiologically measure currents carried by voltage-gated ion channels has allowed a detailed assessment of the action of pyrethroids on various target proteins.recently, the heterologous expression of various rat brain voltage-gated sodium channel isoforms in xenopus laevis oocytes has determined a wide range of sensitivities to the pyrethroids, with some channels virtually insensitive and others highly sensitive. furthermore, some isoforms show selecti ...201122025067
Toward an unbiased evolutionary platform for unraveling Xenopus developmental gene networks.The availability of both the Xenopus tropicalis genome and the soon to be released Xenopus laevis genome provides a solid foundation for Xenopus developmental biologists. The Xenopus community has presently amassed expression data for ~2,300 genes in the form of published images collected in the Xenbase, the principal Xenopus research database. A few of these genes have been examined in both X. tropicalis and X. laevis and the cross-species comparison has been proven invaluable for studying gene ...201121956895
Unfertilized frog eggs die by apoptosis following meiotic exit.ABSTRACT: BACKGROUND: A characteristic feature of frog reproduction is external fertilization accomplished outside the female's body. Mature fertilization-competent frog eggs are arrested at the meiotic metaphase II with high activity of the key meiotic regulators, maturation promoting factor (MPF) and cytostatic factor (CSF), awaiting fertilization. If the eggs are not fertilized within several hours of ovulation, they deteriorate and ultimately die by as yet unknown mechanism. RESULTS: Here, ...201122195698
[Molecular cloning and functional characterization of a novel gene encoding human prostaglandin carrier, hPrC].In the present study, we isolated and determined the pharmacological characteristics of a novel gene encoding the human prostaglandin carrier (hPrC). The isolated cDNA consisted of 1431 base pairs that encoded a 477-amino acid protein, and we found that isolated hPrC does not belong to any drug transporter families. RT-PCR analysis revealed that the hPrC mRNA is expressed in various human tissues ubiquitously. When expressed in Xenopus laevis oocytes, hPrC mediated the transport of [(3)H]prostag ...201121963977
transient expression of ngn3 in xenopus endoderm promotes early and ectopic development of pancreatic beta and delta cells.promoting ectopic development of pancreatic beta cells from other cell types is one of the strategies being pursued for the treatment of diabetes. to achieve this, a detailed outline of the molecular lineage that operates in pancreatic progenitor cells to generate beta cells over other endocrine cell types is necessary. here, we demonstrate that early transient expression of the endocrine progenitor bhlh protein neurogenin 3 (ngn3) favors the promotion of pancreatic beta and delta cell fates ove ...201122121111
protein arginine methyltransferase prmt5-mep50 methylates histones h2a and h4 and the histone chaperone nucleoplasmin in xenopus laevis eggs.histone proteins carry information contained in post-translational modifications. eukaryotic cells utilize this histone code to regulate the usage of the underlying dna. in the maturing oocytes and eggs of the frog xenopus laevis, histones are synthesized in bulk in preparation for deposition during the rapid early developmental cell cycles. during this key developmental time frame, embryonic pluripotent chromatin is established. in the egg, non-chromatin-bound histones are complexed with storag ...201122009756
Stereoselective inhibitory effect of flurbiprofen, ibuprofen and naproxen on human organic anion transporters hOAT1 and hOAT3.Nonsteroidal anti-inflammatory drugs (NSAIDs) delay the renal excretion of antifolate methotrexate by inhibiting human organic anion transporters hOAT1 (SLC22A6) and hOAT3 (SLC22A8). In this study, uptake experiments were performed using Xenopus laevis oocytes to assess stereoselectivity in the inhibitory characteristics of flurbiprofen, ibuprofen and naproxen against hOAT1 and hOAT3. Uptake of p-aminohippurate by hOAT1 was inhibited by each enantiomer of the three NSAIDs, and the inhibitory eff ...201122072415
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