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expression of xmyod protein in early xenopus laevis embryos.a monoclonal antibody specific for xenopus myod (xmyod) has been characterized and used to describe the pattern of expression of this myogenic factor in early frog development. the antibody recognizes an epitope close to the n terminus of the products of both xmyod genes, but does not bind xmyf5 or xmrf4, the other two myogenic factors that have been described in xenopus. it reacts in embryo extracts only with xmyod, which is extensively phosphorylated in the embryo. the distribution of xmyod pr ...19921315678
mutation of a cysteine in the first transmembrane segment of na,k-atpase alpha subunit confers ouabain resistance.the cardiac glycoside ouabain inhibits na,k-atpase by binding to the alpha subunit. in a highly ouabain resistant clone from the mdck cell line, we have found two alleles of the alpha subunit in which the cysteine, present in the wild-type first transmembrane segment, is replaced by a tyrosine (y) or a phenylalanine (f). we have studied the kinetics of ouabain inhibition by measuring the current generated by the na,k-pump in xenopus oocytes injected with wild-type and mutated alpha 1 and wild-ty ...19921316269
initiation of translation of human rhinovirus rna: mapping the internal ribosome entry site.in order to map the 3' boundary of the segments needed for translation initiation at the correct site on human rhinovirus 2, deletions were made from the 3' end of the viral 5'-untranslated region. these truncated viral segments were placed immediately upstream of a reporter gene, a derivative of the influenza virus ns cdna, either as monocistronic constructs or as dicistronic constructs in which the upstream cistron was the xenopus laevis cyclin b2 cdna. in vitro transcripts of these clones wer ...19921316679
beta-subunit expression is required for camp-dependent increase of cloned cardiac and vascular calcium channel currents.in contrast to vascular smooth muscle (vsm), camp-dependent phosphorylation increases l-type voltage dependent ca(2+)-channel (l-vdcc) activity in heart. to investigate whether this difference depends on the tissue-specific alpha 1-subunit of the l-vdcc or its regulation by other subunits, we used a xenopus laevis oocyte expression system. injection of camp into oocytes expressing cardiac alpha 1 or vsm alpha 1 alone had no effect on l-vdcc activity. however, camp increased l-vdcc activity 2-fol ...19921317953
complementation of formyl peptide receptor-mediated signal transduction in xenopus laevis oocytes.formyl-methionine-containing peptides (e.g. fmet-leu-phe) stimulate a variety of neutrophil functions by interacting with specific cell surface receptors which are coupled via g-proteins to stimulation of phospholipase c. two markedly distinct cdnas coding for formyl peptide receptors have recently been isolated from a rabbit and a human cdna library respectively. to examine the hitherto unknown signal transduction properties of the formyl peptide receptor encoded by the human cdna, we have used ...19921318022
localization of binding sites for atrial natriuretic factor and angiotensin ii in the central nervous system of the clawed toad xenopus laevis.the distribution of binding sites for atrial natriuretic factor (anf) and angiotensin ii (a ii) was investigated in the central nervous system (cns) of the clawed toad xenopus laevis by means of in vitro autoradiography using [125i]-rat anf(99-126) or [125i] [val5] a ii and [125i]human a ii as labeled ligands. the highest densities of specific anf-binding were detected in the nucleus habenularis, thalamic regions, hypophyseal pars nervosa and nucleus interpeduncularis. moderate anf-binding was f ...19921318168
effect of putative melatonin receptor antagonists on melatonin-induced pigment aggregation in isolated xenopus laevis melanophores.the ability of putative melatonin receptor antagonists to antagonise melatonin-induced aggregation of pigment granules in cultured neural crest xenopus laevis melanophores was examined. neither ml 23 (n-(2,4-dinitrophenyl)-5-methoxytryptamine) nor 6-methoxy-2-benzoxazolinone showed agonist or antagonist activity. n-acetyltryptamine and n-butanoyltryptamine were partial agonists; both compounds aggregated pigment granules in some cells, but also reversed melatonin-induced pigment agreggation in a ...19921319920
angiotensin ii and acetylcholine differentially activate mobilization of inositol phosphates in xenopus laevis ovarian follicles.angiotensin ii (aii) evokes a ca(2+)-dependent cl- current in xenopus laevis ovarian follicles that appears to involve a pertussis-toxin-sensitive g protein mediating phosphoinositide hydrolysis and ca2+ mobilization from intracellular stores. follicle responses to aii closely resemble the two-component response stimulated by acetylcholine (ach) in this tissue. intraoocyte injections of phytic acid, heparin, and inositol 1,4,5-trisphosphate [ins(1,4,5)p3], acting as inhibitors of ins(1,4,5)p3-in ...19921320248
antitumor activity of magainin analogues against human lung cancer cell lines.magainin 1 and magainin 2, originally isolated from african clawed frog xenopus laevis skin, inhibit the growth of bacteria and fungi. synthetic magainin a (mag a) and magainin g (mag g) are more potent against bacteria and protozoa. in order to determine the antitumor activity of these analogues, we have tested these two analogues against six small cell lung cancer (sclc) cell lines nci-h82, nci-h526, nci-h678, nci-h735, nci-h841, and nci-h889, which were known to differ by more than 10-fold in ...19921319823
thymus ontogeny in frogs: t-cell renewal at metamorphosis.metamorphosis in amphibians presents a unique problem for the developing immune system. because tadpoles are free-living, they need an immune system to protect against potential pathogens. however, at metamorphosis, they acquire a variety of new adult-specific molecules to which the tadpole immune system must become tolerant. we hypothesized that xenopus laevis tadpoles may avoid potentially destructive antiself responses by largely discarding the larval immune system at metamorphosis and acquir ...19921320967
early appearance of and neuronal contribution to agrin-like molecules at embryonic frog nerve-muscle synapses formed in culture.antibodies against chicken and torpedo agrin were used for immunofluorescent staining in order to assess the spatial distribution and temporal appearance of agrin-like molecules at newly formed synaptic contacts in cultures of embryonic xenopus nerve and muscle cells. the antibodies stained xenopus neuromuscular junctions and removed ach receptor (achr)-aggregating activity from extracts of xenopus brain. immunofluorescence was observed at almost all nerve-induced achr aggregates, even at microa ...19921322981
modulation of cardiac ca2+ channels in xenopus oocytes by protein kinase c.l-type calcium channel was expressed in xenopus laevis oocytes injected with rnas coding for different cardiac ca2+ channel subunits, or with total heart rna. the effects of activation of protein kinase c (pkc) by the phorbol ester pma (4 beta-phorbol 12-myristate 13-acetate) were studied. currents through channels composed of the main (alpha 1) subunit alone were initially increased and then decreased by pma. a similar biphasic modulation was observed when the alpha 1 subunit was expressed in c ...19921321730
nppb block of ca(++)-activated cl- currents in xenopus oocytes.nppb (5-nitro-2-(3-phenylpropylamino)-benzoate), a member of the novel class of cl- channel blockers related to diphenylamine-2-carboxylate, was studied for its effect on the ca(++)-activated cl- current (icl(ca)) in frog (xenopus laevis) oocytes. icl(ca) was activated by bath application of 5 mm ca++ to oocytes that had been ca++ permeabilized with the ca++ ionophore a23187. in order to prevent the inactivation of icl(ca) that occurs with repetitive applications of ca++, oocytes were also treat ...19921320252
a single-stranded dna binding protein required for mitochondrial dna replication in s. cerevisiae is homologous to e. coli ssb.it has previously been shown that the mitochondrial dna (mtdna) of saccharomyces cerevisiae becomes thermosensitive due to the inactivation of the mitochondrial dna helicase gene, pif1. a suppressor of this thermosensitive phenotype was isolated from a wild-type plasmid library by transforming a pif1 null strain to growth on glycerol at the non-permissive temperature. this suppressor is a nuclear gene encoding a 135 amino acid protein that is itself essential for mtdna replication; cells lacking ...19921324172
molecular dissection of a specific nuclear domain: the chromatin region of the ribosomal gene cluster in xenopus laevis.molecular dissection of the nuclear domain corresponding to the ribosomal chromatin cluster was investigated. the experimental scheme was based on the ability of restriction enzymes to digest the whole genome without affecting this region (several megabases in length). such a strategy involved the judicious choice of restriction enzymes, which is possible in xenopus laevis, where the rdna sequence is known and the repeated units are organized into one unique cluster. sali, xhoi, and ecorv digest ...19921324846
microinjection of cloned proviral rous sarcoma virus dnas into xenopus laevis one cell embryos.plasmid patv8 carrying rous sarcoma virus (rsv) dna with one long terminal repeat (ltr) or plasmid paprc carrying complete rsv proviral dna was injected into fertilized eggs of xenopus laevis. the fate of the exogenous dnas was followed during embryogenesis. in both cases a new form of dna, comigrating with endogenous dna, began to appear shortly after the injection. this new form represented a linear dimer of the injected plasmid that had formed by ligation of linear monomers of the plasmid dna ...19921326446
stimulation of mitogen-activated protein kinase by oncogenic ras p21 in xenopus oocytes. requirement for ras p21-gtpase-activating protein interaction.p21ras plays an important role in the control of cell proliferation. the molecular mechanisms implicated are unknown. we report that the injection of oncogenic lys12 ras into xenopus laevis oocytes promoted the activation of mitogen-activated protein kinase (map kinase) after a lag of about 90 min. map kinase activity was 10-fold higher 4 h after injection of oncogenic lys12 ras than after injection of nononcogenic gly12 ras. the stimulated map kinase activity remained at a plateau for at least ...19921322893
properties of the guinea-pig lung platelet-activating factor receptor encoded by the cloned cdna.platelet-activating factor (paf) is a naturally occurring phospholipid possessing proinflammatory and shock-inducing activities. although paf exerts these functions via specific receptors, the molecular structures of the receptor has not been clarified. we have isolated a cdna coding for paf receptor through expression cloning. the paf receptor expressed in xenopus laevis oocytes and cos-7 cells showed pharmacological properties consistent with those in previous reports. sequence analysis reveal ...19921326344
isolation, characterization, and localization of the inositol 1,4,5-trisphosphate receptor protein in xenopus laevis oocytes.inositol 1,4,5-trisphosphate (ins(1,4,5)p3) induces ca2+ oscillations and waves in xenopus laevis oocytes. microsomes from oocytes exhibit high-affinity binding for ins(1,4,5)p3, and demonstrate ins(1,4,5)p3-induced ca2+ release. the ins(1,4,5)p3 receptor (insp3r) was purified from oocyte microsomes as a large tetrameric complex and shown to have a monomer molecular mass of 256 kda, compared with 273 kda for the brain insp3r. binding to the oocyte receptor is highly specific for ins(1,4,5)p3 and ...19921326534
inositol monophosphatase is a highly conserved enzyme having localized structural similarity to both glycerol 3-phosphate dehydrogenase and haemoglobin.the cdna coding for an inositol monophosphatase in the oocytes of the african clawed frog, xenopus laevis, has been isolated and sequenced. the predicted primary structure of this enzyme is markedly conserved when it is compared with its mammalian functional homologues; up to 84% of the amino acid residues are identical, and conservative substitutions increase the similarity to 95%, suggesting that this sequence represents the most parsimonious primary structure for the protein to maintain not o ...19921325777
inositol lipid hydrolysis contributes to the ca2+ wave in the activating egg of xenopus laevis.we have used fluorescence ratio-imaging of fura-2 in the activating egg of xenopus laevis to study the wave of increased intracellular free ca2+ concentration ([ca2+]i) while monitoring that of cortical granule exocytosis. naturally matured eggs were dejellied, injected with fura-2, and activated by the iontophoresis of 1-30 ncoul of inositol-1,4,5-trisphosphate which triggers an immediate increase in free [ca2+]i at the injection site. the ca2+ rise spreads throughout the egg, reaching the oppo ...19921327924
choroid plexus, ependyma and arachnoidea express receptors for vitamin d: differences between "seasonal" and "non-seasonal" breeders.autoradiographic studies with [3h]1,25-dihydroxyvitamin d3 demonstrated nuclear high affinity binding sites (receptors) in epithelial cells of choroid plexus, ependyma and arachnoid in "seasonal" breeders of various vertebrate phyla, namely xiphophorus helleri, hyla crucifer, xenopus laevis, bufo woodhousei, chrysemys scripta, anolis carolinensis, nerodia sipedon and phodopus sungorus, but vitamin d receptors were undetectable in these tissues in non-seasonal breeders, such as zebra finch, labor ...19921329147
molecular cloning and expression of cdna encoding the murine gonadotropin-releasing hormone receptor.the primary structure of the gonadotropin-releasing hormone (gnrh) receptor was determined by sequencing a functional receptor cdna isolated by expression cloning from an immortalized murine gonadotroph (alpha t3) cell line. positive clone pools from a cdna library were detected by screening expressed rna in aequorin-injected xenopus laevis oocytes, in which receptor-mediated calcium responses were monitored as light emission during stimulation by gnrh. the isolated receptor cdna encodes a 327-a ...19921328228
regulation mechanisms of intracellular ph of xenopus laevis oocyte.intracellular ph values (phi) of xenopus oocytes were optically measured using a fluorescent dye, 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (bcecf). the oocytes were loaded with dye by incubation with a membrane-permeable form (bcecf-am). mean phi of the oocytes in ph 7.6 solution was 7.69. increasing ambient pco2 rapidly decreased phi and estimated buffering power was 23.8 mm/ph unit. changing ambient hco3- from 5 to 30 mm did not alter phi. after incubation in a na(+)-free solution, n ...19921327152
analysis of autofeedback mechanisms in the secretion of pro-opiomelanocortin-derived peptides by melanotrope cells of xenopus laevis.the secretion of most pituitary hormones is under the control of feedback mechanisms. the feedback control of alpha-melanophore-stimulating hormone (alpha-msh) from melanotrope cells is controversial. the possible existence of an autofeedback exerted by alpha-msh or other pomc-derived peptides on melanotrope cells of the amphibian xenopus laevis has been investigated. alpha-msh or its potent agonist 4-norleucine,7-d-phenylalanine-alpha-msh has no effect on the release of radiolabeled pomc-derive ...19921330808
l-glutamate transporter derived from mrnas of primary glial cultures: expression in xenopus laevis oocytes.a high-affinity sodium-dependent l-glutamate transporter was expressed in xenopus oocytes after microinjection of poly(a)+ rna from primary astrocyte cultures from rat brain cortex. mrna-induced l-glutamate transport was saturable by substrate and shows kinetic features similar to those found in intact glial cell preparations. l-glutamate accumulation was prevented by rising the external k+ concentration or by coincubation with l-, d-aspartate or d-glutamate. after fractionation by sucrose densi ...19921331663
the protein-phosphatase inhibitor okadaic acid mimics msh-induced and melatonin-reversible melanosome dispersion in xenopus laevis melanophores.the present study describes the ability of 315 nm okadaic acid to induce melanosome dispersion in cultured xenopus laevis melanophores. this effect of okadaic acid is similar to that of a-melanocyte stimulating hormone (msh) and can be reversed by melatonin treatment; it indicates that a member of the protein-phosphatase 1 or 2a families must be active for maintenance of the aggregated state. higher concentrations of okadaic acid (1 microm) attenuate the response of xenopus melanophores to melat ...19921329076
cl- channels in basolateral renal medullary membranes, vi. cl- conductance expression in xenopus oocytes.cl- channels from basolateral membranes of the mammalian thick ascending limb of henle differ significantly, in certain of their functional characteristics, from cl- channels in apical membranes of secretory epithelia such as trachea or small intestine and from certain cl- channels in the central nervous system. yet there is no sequence information available about basolateral thick ascending limb cl- channels. as an initial step in the isolation of a cl- channel from the thick ascending limb of ...19921332508
a method for evaluating the effects of ligands upon gs protein-coupled receptors using a recombinant melanophore-based bioassay.as an increasing number of medically important receptors that couple to stimulatory guanine nucleotide (gs) proteins are isolated and cloned, there is an equally escalating need for methods to rapidly and reproducibly evaluate potential ligands for their properties as agonists or antagonists. recently, a bioassay that can quickly and accurately determine the effects of numerous chemicals on a beta 1-like adrenergic receptor (ar) endogenous to melanophores derived from xenopus laevis was develope ...19921332547
purification and characterization of joining peptide and n-terminal peptide of proopiomelanocortin from the pars distalis of the bullfrog pituitary.the joining peptide (jp) and the n-terminal peptide of proopiomelanocortin (npp) were isolated from an acid-acetone extract of the distal lobe of the pituitary of the bullfrog, rana catesbeiana, and purified by gel filtration and reverse-phase high performance liquid chromatography. the amino acid sequence of the bullfrog jp resembled the sequences of the jps of rana ridibunda (86% similarity) and xenopus laevis (54% similarity), as deduced from the nucleotide sequences of their cdnas. the amino ...19921331997
immunoblotting technique to study release of melanophore-stimulating hormone from individual melanotrope cells of the intermediate lobe of xenopus laevis.the melanotrope cells in the pars intermedia in the pituitary of xenopus laevis synthesize and release the melanophore-stimulating hormone (alpha msh), a small peptide that causes skin darkening during the process of background adaptation. evidence has been found for a heterogeneity in biosynthetic activity of the melanotrope cells. in the present study two questions were addressed: (1) does the melanotrope cell population also show heterogeneous alpha msh-release, and (2) can this heterogeneity ...19921333944
p120, a novel substrate of protein tyrosine kinase receptors and of p60v-src, is related to cadherin-binding factors beta-catenin, plakoglobin and armadillo.a novel protein tyrosine kinase (ptk) substrate, p120, has been previously implicated in ligand-induced signaling through the epidermal growth factor, platelet-derived growth factor and colony-stimulating factor 1 receptors, and in cell transformation by p60v-src. we have isolated a near full-length cdna encoding murine p120. the encoded protein lacks significant homology with any reported protein, but it contains four copies of an imperfect 42 amino acid repeat that occurs 12.5 times in the pro ...19921334250
protein kinase c activation antagonizes melatonin-induced pigment aggregation in xenopus laevis melanophores.the pineal hormone, melatonin (5-methoxy n-acetyltryptamine) induces a rapid aggregation of melanin-containing pigment granules in isolated melanophores of xenopus laevis. treatment of melanophores with activators of protein kinase c (pkc), including phorbol esters, mezerein and a synthetic diacylglycerol, did not affect pigment granule distribution but did prevent and reverse melatonin-induced pigment aggregation. this effect was blocked by an inhibitor of pkc, ro 31-8220. the inhibitory effect ...19921334961
locations of contacts between individual zinc fingers of xenopus laevis transcription factor iiia and the internal control region of a 5s rna gene.a set of mutants of transcription factor iiia (tfiiia) have been prepared in which successive zinc-finger domains have been deleted from the carboxyl terminus of the protein. these have been analyzed by hydroxyl radical footprinting to map the location of contacts to dna by individual zinc-finger domains of tfiiia. the results suggest that the nine zinc fingers of tfiiia are organized into three dna-binding domains of three fingers each. the spatial relationship between zinc-finger contacts to 5 ...19921332765
two isoforms of the thyrotropin-releasing hormone receptor generated by alternative splicing have indistinguishable functional properties.two cdna clones encoding two different isoforms of the thyrotropin-releasing hormone receptor (trh-r) from gh3 rat anterior pituitary cells have been isolated. one isoform corresponds to the trh-r(412) receptor previously described (de la peña, p., delgado, l. m., del camino, d., and barros, f. (1992) biochem. j. 284, 891-899). the second one, named trh-r(387), contains a 52-base pair deletion, which yields a new variant of the receptor protein 25 amino acid shorter and which contains 12 new res ...19921334485
primary structure of an apical protein from xenopus laevis that participates in amiloride-sensitive sodium channel activity.high resistance epithelia express on their apical side an amiloride-sensitive sodium channel that controls sodium reabsorption. a cdna was found to encode a 1,420-amino acid long polypeptide with no signal sequence, a putative transmembrane segment, and three predicted amphipathic alpha helices. a corresponding 5.2-kb mrna was detected in xenopus laevis kidney, intestine, and oocytes, with weak expression in stomach and eyes. an antibody directed against a fusion protein containing a cooh-termin ...19921334959
the processing of beta-endorphin and alpha-melanotrophin in the pars intermedia of xenopus laevis is influenced by background adaptation.beta-endorphin- and alpha-melanotrophin (alpha-msh)-related peptides were extracted from the pars intermedia of xenopus laevis maintained for 2, 4 or 6 weeks on a white background and for the same periods on a black background. the peptides were resolved under dissociating conditions by gel exclusion chromatography on sephadex g-50 and they were detected by radioimmunoassay with antibodies to beta-endorphin, alpha,n-acetyl beta-endorphin and alpha-msh. the beta-endorphin-related peptides separat ...19921336791
a rapid quantitative bioassay for evaluating the effects of ligands upon receptors that modulate camp levels in a melanophore cell line.a new method for rapidly evaluating the effects of drugs on receptors that regulate intracellular camp in a cell line derived from xenopus laevis melanophores has been developed. melanophores were plated into sterile 96 well microtiter plates, and 3 days later the cells were treated with melatonin for 30 min to induce melanosome aggregation. subsequent exposure to msh or adrenergic agonists caused dose dependent pigment dispersion that peaked within 30 min. the cumulative pigment displacement fr ...19921337205
[the expression of kainate and gaba receptors in oocytes of bufo bufo gargarizans].oocytes of bufo bufo gargarizans were used as an expression system for analyzing structure of exogenous membrane protein and their functions. poly (a)+ mrna isolated from rat brain was injected into toad (bufo bufo gargarizans) oocytes (50 ng/oocyte). rat brain kainic acid and gamma-aminobutyric acid(gaba) receptors expressed by the injected mrna were integrated in the oocyte membrane 48 h after the injection at 19 degrees c. membrane currents induced by kainic acid (5 x 10(-5) mol/l) and gaba ( ...19921338132
expression and characterization of a canine hippocampal inwardly rectifying k+ current in xenopus oocytes.1. an inwardly rectifying potassium current expressed in xenopus laevis oocytes injected with canine hippocampal poly(a)+ rna was investigated with the two-microelectrode voltage clamp technique. 2. xenopus oocytes injected with canine hippocampal poly(a)+ rna expressed a current activated by hyperpolarization. this current contained an instantaneous and a time-dependent component. both components were inwardly rectifying and could be blocked by extracellular cs+ or ba2+. 3. the expressed curren ...19921338458
the beta subunit modulates potassium activation of the na-k pump.we recently cloned the alpha 1 and the beta 1 and beta 3 subunits of the na,k-atpase of the toad bufo marinus. to investigate possible functional differences between beta 1 and beta 3, we studied the potassium activation of na-k pumps expressed in the oocyte of xenopus laevis. na-k pump activity was measured as k(+)-induced current in voltage-clamped oocytes. we could take advantage of the relative resistance to ouabain conferred by the bufo alpha subunit to study specifically the exogenously ex ...19921337667
the lim domain-containing homeo box gene xlim-1 is expressed specifically in the organizer region of xenopus gastrula embryos.a novel cysteine-rich motif, named lim, has been identified in the homeo box genes lin-11, isl-1, and mec-3; the mec-3 and lin-11 genes determine cell lineages in caenorhabditis elegans. we isolated lim class homeo box genes from xenopus laevis that are closely related to lin-11 and mec-3 in the lim and homeo domains. this paper deals with one of these genes, xlim-1. xlim-1 mrna is found at low abundance in the unfertilized egg, has a major expression phase at the gastrula stage, decreases, and ...19921347750
cell adhesion molecules as targets for hox genes: neural cell adhesion molecule promoter activity is modulated by cotransfection with hox-2.5 and -2.4.in an effort to determine whether homeobox genes modulate the activity of the promoter of the mouse neural cell adhesion molecule (n-cam) gene, we have carried out a series of cotransfection experiments using nih 3t3 cells. plasmids were constructed containing xenopus laevis hox-2.5 and -2.4 coding sequences linked to a human cytomegalovirus promoter (cmv-hox-2.5 and cmv-hox-2.4). a 4.9-kilobase dna fragment containing 5' flanking and first exon sequences of the mouse n-cam gene was linked to a ...19921347944
[electrophysiologic parameters of ion transport systems in early developmental stages of fish and amphibia].it is shown that the membrane potential level, ionic current and membrane conductance depend on the cell cycle stage both in misgurnus fossilis l. embryos and in xenopus laevis daudin embryos by the microelectrode technics. allowing for the role of the adenylate cyclase system in the membrane potential oscillations and ion conductance of membranes, some series of experiments for analysis of the inhibitor have been carried out.19921340443
periodicities and transient shifts in anuran (xenopus laevis, rana clamitans) oxygen consumption revealed with flow-through respirometry.1. a custom-designed, computer-controlled, flow-through respirometry system was used to monitor oxygen consumption in aquatic anurans: xenopus laevis metamorphs and larval rana clamitans. 2. there was no evidence that animals were stressed in the flow-through respirometer; oxygen consumption rates in static vs open mode fell within the same range and animals were quiescent in the chambers. 3. diurnal periodicity was pronounced in x. laevis: both mean rates and variability of oxygen consumption w ...19921348672
retinoic acid induces changes in the localization of homeobox proteins in the antero-posterior axis of xenopus laevis embryos.we have studied the localization of the proteins of xeb1 and xeb2, two homeobox (hbx)-containing genes that are expressed during the early development of xenopus laevis. both proteins are expressed in juxtaposed and partially overlapping domains along the antero-posterior axis of xenopus laevis embryos, with clearly defined anterior boundaries. xeb2 is predominantly expressed in the caudal region of the hindbrain, whereas the xeb1 protein is located in the most rostral region of the spinal cord. ...19921349239
does lineage determine the dopamine phenotype in the tadpole hypothalamus?: a quantitative analysis.the ancestry of dopaminergic (da) neurons in the xenopus laevis hypothalamus was investigated by combining intracellular lineage dye injections of 16- and 32-cell blastomeres with the immunofluorescent detection of tyrosine hydroxylase at tadpole stages. at these stages, da neurons in the hypothalamus comprise a discrete nucleus that contains from 22 to 45 cells on each side [mean = 32.6 +/- 6.6 (sd)]. the da nucleus descends from only four of the 16-cell blastomeres. the two dorsal midline blas ...19921348272
coupling between the intracellular ph and the active transport of sodium in an epithelial cell line from xenopus laevis.1. the relationship between the rate of active na+ transport and intracellular ph (phi, measured as the bcecf fluorescence) was studied in a6 monolayers in the presence of co2. the total buffering power (beta total) and its components (beta i and beta co2) were assessed at various phi. 2. the activity of na+/h+ and cl-/hco3- exchangers were expressed in a6 cells; both antiports were found to participate in phi homeostasis under standard conditions. 3. alterations in the rate of na+ transport ind ...19921351827
the role of growth factors in embryonic induction in xenopus laevis.establishment of the body pattern in all animals, and especially in vertebrate embryos, depends on cell interactions. during the cleavage and blastula stages in amphibians, signal(s) from the vegetal region induce the equatorial region to become mesoderm. two types of peptide growth factors have been shown by explant culture experiments to be active in mesoderm induction. first, there are several isoforms of fibroblast growth factor (fgf), including afgf, bfgf, and hst/kfgf. fgf induces ventral, ...19921353352
response of xenopus laevis to cadmium administration.1. levels of copper, zinc and cadmium have been determined in the plasma, liver and kidneys of xenopus laevis. 2. administration of cadmium by subcutaneous injection induces metallothionein synthesis in the liver of xenopus laevis. cadmium is found to accumulate in both liver and kidneys following injection. 3. cadmium uptake, following injection, is biphasic, suggesting a saturable first-phase uptake mechanism, followed by a linear second phase. 4. zinc is displaced from the liver by administra ...19921350955
nuclear distribution of pcna during embryonic development in xenopus laevis: a reinvestigation of early cell cycles.the immunocytological distribution of the proliferating cell nuclear antigen (pcna), a protein involved in dna replication, has been examined during the early development of xenopus laevis. the protein is uniformly detected in nuclei during early stages up to the neurula stage. pcna is detected by its distinctive cyclical pattern during early development, remaining detectable only during the period of s phase of each cell cycle. immunological detection of pcna is therefore a useful and specific ...19921354219
conjugated bile acid uptake by xenopus laevis oocytes induced by microinjection with ileal poly a+ mrna.apical membranes of ileal enterocytes contain the major na+/bile acid cotransporter activity in mammals. microinjection of guinea pig ileal mucosal poly a+ mrna (25 ng) into xenopus oocytes resulted in 22,23-3h-cholyltaurine uptake at day 3 after injection (453 fmol/oocyte-hr), while control viral mrna (25 ng) gave an uptake rate of 133 fmol/oocyte-hr. the transport rate increased in direct relationship to the concentration of injected mrna, cholyltaurine, or na+ in the incubation media. uptake ...19921354958
the establishment of polarized membrane traffic in xenopus laevis embryos.delineation of apical and basolateral membrane domains is a critical step in the epithelialization of the outer layer of cells in the embryo. we have examined the initiation of polarized membrane traffic in xenopus and show that membrane traffic is not polarized in oocytes but polarized membrane domains appear at first cleavage. the following proteins encoded by injected rna transcripts were used as markers to monitor membrane traffic: (a) vsv g, a transmembrane glycoprotein preferentially inser ...19921355772
a novel homeobox gene expressed in the anterior neural plate of the xenopus embryo.to obtain gene sequences controlling the early steps of amphibian neurogenesis, we have performed differential screening of a subtractive cdna library prepared by a novel pcr-based method from a single presumptive neural plate of a xenopus laevis late-gastrula embryo. as a result we have isolated a fragment of a novel homeobox gene (named xanf-1, for xenopus anterior neural folds). this gene is expressed predominantly in the anterior part of the developing nervous system. such preferential local ...19921353734
reconstitution of the photoreceptor-pigment epithelium interface: l-glutamate stimulation of adhesive interactions and rod disc shedding after recombination of dissociated xenopus laevis eyecups.in order to investigate adhesive interactions between photoreceptor and pigment epithelial cells, we have mechanically separated neural retinas from xenopus laevis eyecups and then recombined the tissues in vitro. when tissue pairs are incubated in a defined medium, cell-cell contact is achieved within 3 hr. however, the average proportion of reassembled eyecups in which photoreceptor outer segments interdigitate with epithelial microvilli is limited. furthermore, rod disc shedding does not take ...19921355741
maturation of xenopus laevis oocyte by progesterone requires poly(a) tail elongation of mrna.meiotic maturation of xenopus laevis oocytes by progesterone requires translation of stored maternal mrnas. we investigated the role of poly(a) tail elongation of mrnas during this process using cordycepin, which inhibits poly(a) tail elongation of mrnas. when oocytes were treated with the buffer containing 10 mm cordycepin for 12 h, concentration of 3'-datp in cytosol of oocytes increased to 0.7 mm, while that of atp remained constant at around 1.2 mm. incorporation of [32p]amp into poly(a) mrn ...19921355048
the post-embryonic development of cell properties and synaptic drive underlying locomotor rhythm generation in xenopus larvae.in the first 24 h of post-embryonic development, the motor rhythm underlying swimming in xenopus laevis tadpoles changes from brief (ca. 7 ms) ventral root discharge in each cycle to bursts of activity lasting around 20 ms (sillar et al. 1991). because individual motoneurons in the spinal cord of newly hatched embryos normally fire only a single impulse per cycle, two possible changes underly the transition to motor bursts seen in larval ventral roots; desynchronization of neurons in a given ven ...19921359549
activin a induced expression of a fork head related gene in posterior chordamesoderm (notochord) of xenopus laevis embryos.a gene family encoding the fork head/hnf-3 domain has been identified in the south african clawed frog, xenopus laevis. screening of genomic dna and gastrula stage derived cdna libraries with a dna fragment encoding the drosophila fork head domain led to the isolation of a number of different clones encoding this motif. while one of the xenopus fork head sequences, xfd-3, represents the xenopus counterpart to rat hnf-3 beta, all other sequences encode novel types of fork head related proteins. h ...19921358174
bioactive substances in nerve-cord extracts from an echiuroid, urechis unicinctus--ii. peptidic substances.1. two peptides that showed an inhibitory effect on twitch contraction of the inner circular body-wall muscle of the echiuroid urechis unicinctus were purified from extracts of the ventral nerve cords of the worms. 2. on the basis of the results of amino acid analysis, amino acid sequence analysis and fab-ms measurement, the primary structures of the peptides were proposed to be h-phe-arg-val-phe-oh (frvf) and h-phe-arg-phe-oh (frf). 3. frvf and frf were synthesized, and their behavior on hplc a ...19921358528
chinese hamster ovary mrna-dependent, na(+)-independent l-leucine transport in xenopus laevis oocytes.in freshly prepared uninjected folliculated oocytes, na(+)-independent leucine uptake is mediated predominantly by a system l-like transport system. removal of follicular cells, however, results in an irreversible loss of this transport activity. when total poly(a)+ mrna derived from chinese hamster ovary (cho) cells was injected into prophase-arrested stage v or vi xenopus laevis oocytes, enhanced expression of na(+)-independent leucine transport was observed. the injected mrnas associated with ...19921360143
homeoboxes in flatworms.a search for homeobox-containing genes was done in the genome of a primitive metazoan, the parasitic tapeworm echinococcus granulosus. five different homeoboxes were isolated, none of them belonging to the classical antennapedia-type. three of the homeodomains are similar to those from the drosophila melanogaster nk-type genes. the fourth homeodomain shares extensive identity with that of the recently reported homeobox-containing gene goosecoid from xenopus laevis. the third helix (the recogniti ...19921359988
modulation of swimming rhythmicity by 5-hydroxytryptamine during post-embryonic development in xenopus laevis.during the first 24 h of post-embryonic development in xenopus laevis, a rapid change in the neural activity underlying swimming occurs in which the duration of ventral root discharge on each cycle increases from a single compound impulse to discrete bursts of activity. moreover, this change in motor output progresses rostrocaudally, suggesting that it could result from the influence of a descending neural pathway upon the spinal rhythm-generating circuitry during early post-embryonic developmen ...19921361984
electrophysiological characterization of a ttx-sensitive sodium current in native xenopus oocytes.we have studied a fast inward current expressed in oocytes from one xenopus laevis. this current was characterized as a sodium current. it was activated by depolarizations to -50 mv or higher, peaked within 3-5 ms, and then decayed following a mono-exponential timecourse. when clamped at different holding potentials, the current displayed voltage-dependent inactivation with a v0.5 of -51 mv. the channel responsible for this na+ entry was blocked by tetrodotoxin with a k0.5 of 8 nm, and was resis ...19921361986
nerve-dependent expression of c-myc protein during forelimb regeneration of xenopus laevis froglets.the consequences of denervation on the expression of c-myc protein have been analyzed on the regenerating forelimb of young froglets of xenopus laevis. the level of c-myc expression, low in control limbs and enhanced in the regenerate, is transiently increased after a three-hour total denervation. for this protein, the level of expression is not a function of the quantity of nerve in the regenerate. four days after denervation, c-myc signal is back to its base level observed in the regenerate. a ...19921363522
xenopus hox-2 genes are expressed sequentially after the onset of gastrulation and are differentially inducible by retinoic acid.in this paper, we review experiments to characterise the developmental expression and the responses to all-trans retinoic acid (ra) of six members of the hox-2 complex of homeobox-containing genes, during the early development of xenopus laevis. we showed that the six genes are expressed in a spatial sequence which is colinear with their putative 3' to 5' chromosomal sequence and that five of them are also expressed rapidly after the beginning of gastrulation, in a 3' to 5' colinear temporal seq ...19921363722
induction of anteroposterior neural pattern in xenopus by planar signals.neural pattern in vertebrates has been thought to be induced in dorsal ectoderm by 'vertical' signals from underlying, patterned dorsal mesoderm. in the frog xenopus laevis, it has recently been found that general neural differentiation and some pattern can be induced by 'planar' signals, i.e. those passing through the single plane formed by dorsal mesoderm and ectoderm, without the need for vertical interactions. results in this paper, using the frog xenopus laevis, indicate that four position- ...19921363721
valproic acid induced abnormal development of the central nervous system of three species of amphibians: implications for neural tube defects and alternative experimental systems.embryos of ambystoma mexicanum, xenopus laevis, and hyperolius viridiflavus taeniatus were exposed to various concentrations of valproic acid (vpa: 0.1, 1.5, 10 mm) from blastula stage (s) 9 on up to advanced gastrulation of control embryos (s 11 1/2-12). at 10 and 5 mm vpa early development was affected in all species tested. however, the most pronounced effects occurred in ambystoma: the neural folds appeared delayed and showed a flattened and wavy shape; the neural tube was not formed and emb ...19921363963
neuroendocrine regulation of immunity: the effects of noradrenaline in xenopus laevis, the south african clawed toad.a functional association between the peripheral nervous and the immune system in xenopus laevis, the south african clawed toad, is demonstrated. this association involves the neurotransmitter noradrenaline (na), produced and released by the sympathetic nerves of the spleen. chemical sympathectomy prior to immunization reduces splenic na, and decreases thymus-dependent (td), but increases thymus-independent (ti), antibody responses. immune challenge with representatives of the three antigen class ...19921364139
mesoderm induction and axis determination in xenopus laevis.in xenopus, as in all amphibians and possibly in vertebrate embryos in general, mesoderm formation and the establishment of the dorsoventral axis depend on inductive cell interactions. molecules involved in mesoderm induction include fgf which acts predominantly as a ventrolateral inducer, the tgf-beta homolog activin which can induce all types of mesoderm, and members of the wnt family which have powerful dorsalizing effects. early effects of inducer action include the activation of regulatory ...19921365880
high level expression of a frog alpha-amidating enzyme, ae-ii, in cultured cells and silkworm larvae using a bombyx mori nuclear polyhedrosis virus expression vector.a xenopus laevis peptidyl c-terminal alpha-amidating enzyme (ae-ii) gene, modified by deletion of a region encoding the putative membrane-spanning domain and the putative c-terminal cytosolic tail, was expressed in bomo-15 aiic insect cells and silkworm larvae using a bombyx mori baculovirus expression vector system. the expressed enzyme was identified predominantly in the culture medium and the hemolymph of silkworm larvae, indicating successful secretion of the expressed ae-ii. the level of re ...19921368810
cftr protein expression in primary and cultured epithelia.the gene responsible for the lethal disorder cystic fibrosis encodes a 1480-amino acid glycoprotein, cftr. using polyclonal antibodies directed against separate phosphorylation sites in the pre-nucleotide-binding fold (exon 9) and the r domain (exon 13), we have identified a 165-kda protein in xenopus laevis oocytes injected with recombinant cftr crna transcribed from the full-length cftr plasmid pbq4.7. a protein of the same mobility was also detected with western blotting techniques in whole c ...19921370353
molecular cloning of the murine substance k and substance p receptor genes.the peptides substance k and substance p evoke a variety of biological responses via distinct, guanosine-nucleotide-binding-regulatory-protein-coupled receptors. we have screened a murine genomic cosmid library using oligonucleotide probes and have isolated, cloned and characterized the substance k receptor and the substance p receptor genes. the coding portion of the substance k receptor gene consists of five exons distributed over 13 kbp. the substance p receptor gene is considerably larger th ...19921370937
functional expression of human myometrial endothelin receptors in xenopus laevis oocytes.we demonstrate the existence of functional endothelin receptors in human uterine myometrium using the xenopus oocyte expression system. fifty nanograms of poly(a)+rna from myometrium was injected into xenopus laevis oocytes and incubated for 70-80 h. the membrane potential of the oocyte was clamped at -60 mv and membrane current was measured during and after endothelin stimulation. endothelin-1 elicited a large inward membrane current in the oocytes injected with poly(a)+rna; endothelin-2 elicit ...19921371032
native-type dhp-sensitive calcium channel currents are produced by cloned rat aortic smooth muscle and cardiac alpha 1 subunits expressed in xenopus laevis oocytes and are regulated by alpha 2- and beta-subunits.native tissue-like l-type voltage-dependent calcium channels (l-vdcc's) were expressed by in vitro transcribed crna injection of rat aorta or rabbit cardiac alpha 1 subunit into xenopus laevis oocytes. co-injection of vsm-alpha 1 with the cloned skeletal muscle beta-subunit (sk-beta) of the l-type vdcc significantly increased the expressed peak current amplitude without significant changes in kinetics. similar results were obtained by co-injection of cardiac alpha 1 (dsht-alpha 1) the cloned ske ...19921371969
in vitro chromatin assembly promoted by the xenopus laevis s-150 cell-free extract is enhanced by treatment with rnase a.cell-free extracts employed as chromatin assembly systems contain a myriad of proteins, polyanions and nucleic acids. the roles of atp, mgcl2 and other cofactors in the catalysis of nucleosome formation by the xenopus laevis oocyte s-150 have yet to be established unequivocally. in this study we examine the influence of rna in the assembly process. under reaction conditions that inhibit nucleosome formation (+ edta), pretreatment of the extract with rnase a revives the chromatin assembly machine ...19921371870
expression of size-selected rna encoding brain serotonin transporter in xenopus laevis oocytes.the mrna that encodes a serotonin transporter was expressed using the xenopus laevis oocyte expression system. poly(a)+ rna isolated from mouse brainstem was injected into xenopus laevis oocytes, and the ability of oocytes to take up serotonin was measured 3 days postinjection. rna-dependent serotonin uptake was sensitive to citalopram, a specific inhibitor of serotonin uptake, whereas background levels of serotonin uptake were not citalopram sensitive. two rna size fractions, 4.0 and 4.5 kb, we ...19921371147
cyclic amp-dependent modulation of cardiac ca channels expressed in xenopus laevis oocytes.cyclic amp-dependent modulation of cardiac l-type voltage-dependent ca channel (vdcc) has been probed in xenopus laevis oocytes injected with poly(a+) rna from rat heart. a 2 to 3 fold increase of the ba current amplitude was routinely obtained upon microinjection of camp (50-500 microm). inhibition of protein kinase a (pka) dramatically reduced the ba current amplitude, indicating that camp-dependent modulation plays an important role in maintaining the basal activity of expressed ca channels. ...19921371671
appearance of water channels in xenopus oocytes expressing red cell chip28 protein.water rapidly crosses the plasma membrane of red blood cells (rbcs) and renal tubules through specialized channels. although selective for water, the molecular structure of these channels is unknown. the chip28 protein is an abundant integral membrane protein in mammalian rbcs and renal proximal tubules and belongs to a family of membrane proteins with unknown functions. oocytes from xenopus laevis microinjected with in vitro-transcribed chip28 rna exhibited increased osmotic water permeability; ...19921373524
pathways of nh3/nh4+ permeation across xenopus laevis oocyte cell membrane.while acid loading with extracellular nh4cl solutions usually first alkalinizes the cells through nh3 influx, and acidifies only when nh4cl is removed, xenopus oocytes became immediately acidic upon nh4cl addition and the cells did not acidify further upon its removal. since nh4cl solutions also collapsed the membrane potential (vm) and resistance (rm), we conclude that primarily nh4+ entered the cells where it liberated h+, with nh3 being trapped in intracellular lipid stores. to identify the n ...19921372714
influenza virus m2 protein has ion channel activity.the influenza virus m2 protein was expressed in xenopus laevis oocytes and shown to have an associated ion channel activity selective for monovalent ions. the anti-influenza virus drug amantadine hydrochloride significantly attenuated the inward current induced by hyperpolarization of oocyte membranes. mutations in the m2 membrane-spanning domain that confer viral resistance to amantadine produced currents that were resistant to the drug. analysis of the currents of these altered m2 proteins sug ...19921374685
expression of renal organic cation transporter in xenopus laevis oocytes.the expression of the organic cation transport system of rat renal proximal tubules has been studied in xenopus laevis oocytes injected with poly(a)+ rna from the rat renal cortex. the effectiveness of the technique was confirmed by examining expression of the na+/d-glucose co-transporter. compared with water-injected and non-injected oocytes, the injection of total poly(a)+ rna resulted in about a 3-fold increase in tetraethylammonium (tea) uptake activity. tea uptake by poly(a)(+)-rna-injected ...19921374230
an improved elisa with linear sweep voltammetry detection.an improved elisa combined with linear sweep voltammetry detection of p-nitrophenol generated by an enzyme has been investigated in this study. p-nitrophenol, produced from alkaline phosphatase catalysing p-nitrophenyl phosphate, yielded an oxidative peak at 1.06 v (vs. ag/agcl) with a wax-impregnated tubular graphite anode. without separation, the small three-electrode system was directly inserted in the well of an elisa plate for detection. the detection limit for p-nitrophenol was 1 x 10(-6) ...19921374775
analysis of a gene cluster coding for the xenopus laevis u7 snrna.a cluster of xenopus laevis u7 snrna genes has been isolated and sequenced. the gene structure is more compact than, but otherwise comparable to, the major u snrna genes since the distal sequence element (dse) is located only 4 nt upstream of the pse. the corresponding rna is present in the oocyte and accumulates early in oogenesis.19921374647
hormonal regulation of adult type keratin gene expression in larval epidermal cells of the frog xenopus laevis.triiodothyronin (t3) is known to induce amphibian metamorphosis but other hormones such as glucocorticoids accelerate t3 action. the increase in plasma concentration of both t3 and glucocorticoids during metamorphic climax is correlated with the transformation of the epidermis from larval type (uncornified) to adult type (cornified). previously we have shown that t3 induced adult-type 63 kd keratin gene expression and cornification of the larval epidermis. in this study, we have examined the eff ...19921375919
identification and early activation of a xenopus laevis p70s6k following progesterone-induced meiotic maturation.employing oligonucleotide primers derived from the dna sequence of rat p70s6k a homologous sequence was shown by polymerase chain reaction (pcr) to be present as a maternal transcript in stage iv-vi xenopus laevis oocytes. the sequence covered 665 bp of p70s6k and was 97% identical at the amino acid level. when used to probe a northern blot of the poly(a)+ mrna from stage vi oocytes, this sequence recognized four transcripts of 1.9, 2.5, 3.2 and 5.2 kb. specific rat p70s6k antibodies immunopreci ...19921374712
spatial, temporal, and hormonal regulation of epidermal keratin expression during development of the frog, xenopus laevis.to study the mechanism of hormone-induced keratin expression in the epidermis during xenopus metamorphosis, a monospecific antibody was raised against a unique carboxy-terminal peptide of the 63-kda keratin. immunohistological analysis demonstrated that the onset of 63-kda keratin expression showed distinct regional and temporal differences. the expression started at stage 54 in the hindlimb epidermis, at stage 57 in the head, and over 1 month later at stage 63 in the tail. the amount of 63-kda ...19921374352
expression cloning of a cdna from rabbit kidney cortex that induces a single transport system for cystine and dibasic and neutral amino acids.we have isolated a cdna clone by screening a rabbit kidney cortex cdna library for expression of sodium-independent transport of l-arginine and l-alanine in xenopus laevis oocytes. expressed uptake relates to a single component of sodium-independent transport for dibasic and neutral amino acids. this transport activity resembles the functionally defined system b0,+ and carries cystine and dibasic amino acids with high affinity. the rbat (b0,+ amino acid transporter-related) mrna is found mainly ...19921376925
stimulation of system y(+)-like amino acid transport by the heavy chain of human 4f2 surface antigen in xenopus laevis oocytes.a kidney cortex cdna clone (rbat) has recently been isolated, which upon in vitro transcription and capping complementary rna (crna) and injection into xenopus laevis oocytes induces a system b0,(+)-like amino acid transport activity. this cdna encodes a type ii membrane glycoprotein that shows significant homology to another type ii membrane glycoprotein, the heavy chain of the human and mouse 4f2 surface antigen (4f2hc). here we demonstrate that injection of human 4f2hc crna into oocytes resul ...19921376926
mouse thromboxane a2 receptor: cdna cloning, expression and northern blot analysis.a cdna clone for the mouse thromboxane a2 receptor was isolated from mouse lung cdna library. the cdna has a 1,023 base pair open reading frame which encodes a protein of 341 amino acid residues. sta2 and u-46619 induced inward current in xenopus laevis oocytes injected with the transcript of the clone. specific binding of [3h]s-145 was found in membranes of cos-1 cells transfected with the cdna (kd = 3.3 nm) and was displaced with unlabeled prostaglandins and thromboxane analogues in the order ...19921375456
cloning and expression of the thyrotropin-releasing hormone receptor from gh3 rat anterior pituitary cells.functional thyrotropin-releasing hormone (trh) receptors have been expressed in xenopus laevis oocytes following the microinjection of total and poly(a)+ rna from gh3 rat anterior pituitary tumour cells. under voltage-clamp conditions, application of the peptide induced a biphasic ca(2+)-dependent chloride current. the amplitude of the initial, fast, component of the response was dependent on the concentration of the hormone and on the amount of mrna injected. size fractionation of poly(a)+ rna ...19921377915
poly(a)+ rna from rabbit intestinal mucosa induces b0,+ and y+ amino acid transport activities in xenopus laevis oocytes.injection of poly(a)+ rna (mrna) isolated from rabbit intestinal mucosa into xenopus laevis oocytes results in an increase in sodium-independent uptake of l-[3h]leucine, l-[35s]cystine, and l-[3h]arginine. this uptake activity is related to an mrna species corresponding to the recently isolated rabbit kidney cortex cdna clone rbat (related to b0,+ amino acid transporter; bertran, j., werner, a., stange, g., markovich, d., moore, m. l., biber, j., testar, x., zorzano, a., palacin, m., and murer, ...19921379228
identification and developmental expression of src+ mrnas in xenopus laevis.alternative splicing of src mrna has been demonstrated in several vertebrate species to yield a neuron-specific form of src protein termed pp60+. the function of pp60+ is unknown. the early developmental expression pattern of src+ rna has not been previously examined. we have identified and characterized src+ transcripts corresponding to the two src genes in xenopus laevis using a reverse transcription/polymerase chain reaction (rt/pcr) method. both xenopus pp60+ proteins have a 5-amino-acid ins ...19921378412
the multiple beta-tubulin genes of xenopus: isolation and developmental expression of a germ-cell isotype beta-tubulin gene.in this report, we demonstrate the presence of multiple beta-tubulin genes in xenopus and begin to explore the regulation of isotypes within the beta-tubulin family by focusing on the characterization of a specific beta-tubulin cdna derived from a xenopus oocyte library. this clone (xlot: xenopus laevis oocyte beta-tubulin) contains the entire protein coding and 3'-untranslated regions of the gene, and is only missing approximately eleven nucleotides from the start of transcription. the xlot tra ...19921379202
regulation of alpha 1-beta 3-na(+)-k(+)-atpase isozyme during meiotic maturation of xenopus laevis oocytes.during progesterone-induced maturation of xenopus oocytes, the transport and ouabain binding capacity of na(+)-k(+)-atpase at the plasma membrane is completely downregulated. to elucidate the mechanism and the physiological significance of this process, we have followed the fate of oocyte alpha-beta 3-na(+)-k(+)-atpase complexes during meiotic maturation and early embryonic development. an immunocytochemical follow-up of the catalytic alpha-subunit, ouabain binding studies, cell surface iodinati ...19921377448
rapid adaptation of single mechanosensitive channels in xenopus oocytes.mechanosensitive (ms) channels are expressed in a wide range of cell types and have been implicated in diverse functions, including osmoregulation and mechanoreception. the majority of previous studies on single ms channels have been carried out on nonsensory cells and have dealt with the steady-state properties of the channel. here we measure the dynamic or nonstationary properties of the ms channel in xenopus laevis oocytes. ms channels open transiently in response to a step change in suction ...19921380158
phosphatidic acid and lysophosphatidic acid stimulate receptor-regulated membrane currents in the xenopus laevis oocyte.external application of dioleoyl-phosphatidic acid and oleoyl-lysophosphatidic acid stimulated ca(2+)-dependent chloride currents in voltage-clamped xenopus laevis oocytes. the responses were observed in oocytes from which follicular cells had been removed, indicating they were intrinsic to the oocyte itself. the lipid-induced ca(2+)-dependent chloride currents were observed in the absence of extracellular calcium, were blocked by intracellular injection of the calcium chelator, bis(o-aminopheno ...19921379791
folylpolyglutamate analogs can inhibit casein kinase ii from xenopus laevis.polyglutamate analogs of folate and related compounds were tested as inhibitors of casein kinase ii (ck ii) obtained from xenopus laevis. the inhibitory capacity of the pteroyl, 4-amino-10-methyl pteroyl (the methotrexate aromatic moiety), and p-aminobenzoil derivatives increased as the number of gamma-glutamates attached went from 2 to 7. the nature of the aromatic head, group was also important since hexa-gamma-glutamatic acid had no inhibitory activity while the folylhexaglutamate derivatives ...19921379942
comparison of ethanol sensitivity of rat brain kainate, dl-alpha-amino-3-hydroxy-5-methyl-4-isoxalone proprionic acid and n-methyl-d-aspartate receptors expressed in xenopus oocytes.the effect of ethanol (etoh) on kainate (ka), dl-alpha-amino-3-hydroxy-5-methyl-4-isoxalone proprionic acid and n-methyl-d-aspartate (nmda) receptor-operated channels was examined electrophysiologically in xenopus laevis oocytes expressing mrna from rat hippocampus and cerebellum. etoh (50, 100 mm) inhibited ka-induced currents but did not alter the ec50 for ka (approximately 78 microm). for a series of n-alcohols, potency for inhibition of ka responses was related to chain length. 6,7-dinitroqu ...19921380078
structure and expression of the drosophila ubiquitin-52-amino-acid fusion-protein gene.ubiquitin belongs to a multigene family. in drosophila two members of this family have been previously described. we report here the organization and expression of a third member, the dub52 gene, isolated by screening a drosophila melanogaster genomic library. this gene encodes an ubiquitin monomer fused to a 52-amino acid extension protein. there are no introns interrupting the coding sequence. recently, it has been described that this extension encodes a ribosomal protein in saccharomyces, dic ...19921381584
mechanisms of propofol action on ion currents in the myelinated axon of xenopus laevis.the effect of the intravenous anaesthetic, propofol (2,6-diisopropylphenol), was investigated on frog myelinated axons under voltage-clamp conditions. the effect, in the concentration range 60 microm to 10 mm, was a combination of (i) a negative shift of the steady state activation and inactivation curves for both na+ and k+ currents (ina,ik), (ii) a voltage-independent block of ina, but not of ik, and (iii) a slowed time course of ik activation. the shift was dose-dependent and, at 1 mm, about ...19921383009
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