Publications
| Title | Abstract | Year Filter | PMID(sorted descending) Filter |
|---|
| metasim: object-oriented modelling of cell regulation. | enzymatic processes and substances are modelled as distinct objects, belonging to a limited number of classes. a set of class definitions in c++ is presented that constitutes an object-oriented programming platform. the latter supports 'biological' data types and functions and facilitates simulation of metabolic and regulatory pathways in living cells. to compute the time-evolution, euler or runge-kutta methods are used, though the latter method compromises a strict object-oriented philosophy. a ... | 1992 | 1422877 |
| peripheral origin of olfactory nerve fibers by-passing the olfactory bulb in xenopus laevis. | after dii injections into the diencephalon of xenopus, two types of retrogradely labelled cells were found in the nasal area: (i) receptor cells in the olfactory epithelium and (ii) a small cell group located between the main olfactory epithelium and the vomeronasal system. these results reveal an extensive extrabulbar olfactory projection of olfactory receptor cells. fibers of these cells do not terminate in the olfactory bulb but innervate targets in the diencephalon directly. the other type o ... | 1992 | 1422816 |
| suramin changes the fate of spemann's organizer and prevents neural induction in xenopus laevis. | suramin, a polyanionic compound, which has previously shown to dissociate platelet derived growth factor (pdgf) from its receptor, prevents the differentiation of neural (brain) structures of recombinants of dorsal blastopore lip (spemann's organizer) and competent neuroectoderm. furthermore, the suramin treatment changes the prospective differentiation pattern of isolated blastopore lip. while untreated dorsal blastopore lip will differentiate into dorsal mesodermal structures (notochord and so ... | 1992 | 1419849 |
| cloning and expression of the bovine cardiac sodium-calcium exchanger. | two clones (p17 and p13), each containing the complete coding sequence for the bovine cardiac na+/ca2+ exchanger, were obtained from a lambda gt10 cdna library by screening with cdna probes from the canine exchanger. the coding sequence of clone p17 was 92 and 98% identical to the canine cdna at the nucleotide and amino acid levels, respectively. nine of the 21 amino acid differences between the two exchangers were found within the 32-amino acid signal sequence. the sequenced portions of the 3' ... | 1992 | 1416984 |
| lysophosphatidic acid induces a pertussis toxin-sensitive ca(2+)-activated cl- current in xenopus laevis oocytes. | lysophosphatidic acid (lpa) induces a ca(2+)-activated cl- current in defolliculated xenopus laevis oocytes. the response appears mediated by a specific membrane receptor, because no current is induced when related compounds [phosphatidic acid (pa), lysophosphatidylcholine (lpc), and lysophosphatidylserine (lps)] are applied extracellularly or when lpa is injected intracellularly. incubation in pertussis toxin prevents the response. the response is mediated by a ca(2+)-activated cl- current beca ... | 1992 | 1415674 |
| cloning and expression of a human endothelin receptor: subtype a. | the polymerase chain reaction, employing degenerate primers specific for the intramembrane domains iii and vi of g-coupled receptors, was used to generate partial clones encoding those receptors carried by cultured rat aorta smooth muscle cells. one clone, spanning the intramembrane domains iv-vi of a receptor specific for endothelin-1 (et-r[a]), was used as a probe to screen a human placental cdna library. the clone pl4-3, encoding a selective type of human endothelin receptor (et-r[a]), has an ... | 1992 | 1415318 |
| [the effect of microinjection of anti-tgf beta-1 antibodies on the early development of xenopus laevis]. | in order to testify the function of the tgf beta related protein, we microinjected the antibodies against the tgf beta-1 to one blastomere of two-cell stage embryos. dosages of antibodies injected were 24-36 ng, 12 -18 ng, 6-9 ng and 1.5-2.25 ng. malformed embryos with exposed yolk mass were produced. they were designated as ye-1, ye-2 and ye-3 according to the degree of malformation which was found to be related to the dosage of antibodies injected to the blastomere. these malformed embryos cou ... | 1992 | 1414124 |
| [immunohistochemical studies on the tgf beta-related protein in the early development of xenopus laevis]. | by the method of immunocytochemistry, using the polyclonal antibodies raised against the 1-29 n-terminal residues of tgf beta-1, we found that the protein could bind to the antibodies was present in the early embryos of xenopus. the protein was named tgf beta-related protein. it was distributed mainly in the endoderm from blastula (stg. 7) to late neurula. in the blastula (stg. 8), the protein was localized in the vegetal hemisphere near the floor of the blastocoel [plate i, fig. 1]. in the earl ... | 1992 | 1414123 |
| dna polymerase beta and dna synthesis in xenopus oocytes and in a nuclear extract. | the identities of the dna polymerases required for conversion of single-strand (ss) m13 dna to double-strand (ds) m13 dna were examined both in injected xenopus laevis oocytes and in an oocyte nuclear extract. inhibitors and antibodies specific to dna polymerases alpha and beta were used. in nuclear extracts, inhibition by the antibody to polymerase beta could be reversed by purified polymerase beta. the polymerase beta inhibitors, dideoxythymidine triphosphate (ddttp) and dideoxycytidine tripho ... | 1992 | 1411545 |
| isolation and sequence of a cdna encoding the precursor of a bombesinlike peptide from brain and early embryos of xenopus laevis. | a cdna encoding the precursor of a bombesinlike peptide was isolated from brain of xenopus laevis. the predicted end product resembles neuromedin b, which was originally isolated from mammalian spinal cord. the mrna for this precursor was also present in gastrointestinal tract and in ovaries. moreover, it could be detected in early embryos (stage 2 and stage 10) of x. laevis. these findings suggest novel roles for peptides of the bombesin family in oocyte maturation and early amphibian developme ... | 1992 | 1409705 |
| cloning and developmental expression in xenopus laevis of seven additional members of the wnt family. | degenerate oligonucleotide primers encoding highly conserved regions of wnt-related proteins were used with the polymerase chain reaction (pcr) to amplify cdna derived from xenopus laevis embryos. cdna sequences partially encoding seven additional members of the xwnt gene family were isolated using this strategy. these cdnas have been given the designation xwnt-2, xwnt-6, xwnt-7a, xwnt-7b, xwnt-7c, xwnt-8b and xwnt-10 based on their amino acid identity with previously described wnts. with regard ... | 1992 | 1408135 |
| müller (glial) cells in the retina of urodeles and anurans reveal different morphology by means of freeze-fracturing. | müller (glial) cells of the retina of various species of amphibia (urodeles and anurans) were investigated by means of the freeze-fracture technique. this was done because müller cells in anamniotes were believed to differ from those in mammals in that they should lack the so-called orthogonal arrays of particles (oap) which are a characteristic feature of müller cells in mammalian retina. however, as we could demonstrate previously (berg-von der emde and wolburg, glia, 2 (1989) 458), fish retin ... | 1992 | 1407671 |
| cooperative binding of the xenopus rna polymerase i transcription factor xubf to repetitive ribosomal gene enhancers. | upstream binding factor (ubf) is a dna-binding transcription factor implicated in ribosomal gene promoter and enhancer function in vertebrates. ubf is unusual in that it has multiple dna-binding domains with homology to high-mobility-group (hmg) nonhistone chromosomal proteins 1 and 2. however, a recognizable dna consensus sequence for ubf binding is lacking. in this study, we have used gel retardation and dnase i footprinting to examine xenopus ubf (xubf) binding to xenopus laevis ribosomal gen ... | 1992 | 1406673 |
| different chromatin structures along the spacers flanking active and inactive xenopus rrna genes. | the accessibility of dna in chromatin to psoralen was assayed to compare the chromatin structure of the rrna coding and spacer regions of the two related frog species xenopus laevis and xenopus borealis. isolated nuclei from tissue culture cells were photoreacted with psoralen, and the extent of cross-linking in the different rdna regions was analyzed by using a gel retardation assay. in both species, restriction fragments from the coding regions showed two distinct extents of cross-linking, ind ... | 1992 | 1406621 |
| glomerular development and growth of the renal blood vascular system in xenopus laevis (amphibia: anura: pipidae) during metamorphic climax. | microcorrosion casts of the renal vascular system of tadpoles of the clawed frog, xenopus laevis, were observed by scanning electron microscopy. glomerular differentiation was studied qualitatively and quantitatively during developmental stages 56-66 (metamorphic climax). the general structure of the renal vascular system corresponds to the pattern commonly found in anurans; however, the arterial supply has conspicuous connecting vessels that supply groups of glomeruli. in the dorsal part of the ... | 1992 | 1404405 |
| the stopping response of xenopus laevis embryos: pharmacology and intracellular physiology of rhythmic spinal neurones and hindbrain neurones. | 1. xenopus laevis embryos stop swimming in response to pressure on the cement gland. this behaviour and 'fictive' stopping are blocked by bicuculline (10 mumol 1(-1)), tubocurarine (110 mumol 1(-1)) and kynurenic acid (0.5 mmol 1(-1)). 2. intracellular recordings from spinal neurones active during swimming have shown that pressure on the cement gland evokes compound, chloride-dependent inhibitory postsynaptic potentials (ipsps). these are blocked by bicuculline, tubocurarine and kynurenic acid, ... | 1992 | 1402608 |
| synaptonemal complexes of xenopus laevis. | synaptonemal complexes (scs) have been analyzed in spread xenopus spermatocytes and oocytes. they showed all the usual features of animal scs in addition to a high incidence of centromere mismatching. a centriole pair is visible throughout zygotene and pachytene. at zygotene the ends of scs are markedly thickened and are clustered at the nuclear periphery. | 1992 | 1401877 |
| isthmotectal axons make ectopic synapses in monocular regions of the tectum in developing xenopus laevis frogs. | during the development of binocular maps in the tectum of xenopus laevis, axons that relay input from the ipsilateral eye via the nucleus isthmi undergo a prolonged period of shifting connections. this shifting accompanies the dramatic change in eye position that takes place as the laterally placed eyes of the tadpole move dorsofrontally. there is a concomitant expansion of the proportion of tectum that receives contralateral retinotectal input corresponding to the binocular portion of the visua ... | 1992 | 1401245 |
| comparison of the sequence and structure of transcription factor iiia from bufo americanus and rana pipiens. | amino acid (aa) sequences of transcription factor iiia (tfiiia) from the toad, bufo americanus, and the grass frog, rana pipiens, were determined by cdna cloning and dna sequencing. the 3'-untranslated regions of the cdnas reveal that the tfiiia gene polyadenylation signal is attaaa, rather than the conventional aataaa. the b. americanus and r. pipiens proteins share about 60% aa sequence homology with each other and with xenopus laevis tfiiia. although these results indicate that tfiiia has mor ... | 1992 | 1398134 |
| the pyrimidine sequence encompassing the transcription start point of xenopus laevis ribosomal-protein-encoding genes is not obligatory for activity in oocytes. | the genes coding for ribosomal proteins (r-proteins) in xenopus laevis have a stretch of about 20 pyrimidines (y) at their 5' end, in the middle of which is localized the main transcription start point (tsp). to obtain information about its possible functional significance, we have introduced by site-directed mutagenesis one or more purines at various positions within the oligo(y) tract present at the 5' end of the gene coding for r-protein s19 of x. laevis. the effect of these mutations on tran ... | 1992 | 1398110 |
| the structure and complete sequence of the gene encoding chicken ribosomal protein l5. | the nucleotide (nt) sequence of the gene encoding chicken ribosomal protein l5, which associates with 5s rrna, was determined. the gene contains eight exons and seven introns which spread over 7252 bp. the transcription start point (tsp) is a c residue in a tract of 13 pyrimidines, and its 5'-flanking region lacks canonical tata and caat boxes. the g+c content of the region around the tsp is calculated as high as 78%, and nine gc boxes exist within the 5'-flanking region and the first intron. th ... | 1992 | 1398102 |
| multiple domains of the rna polymerase i activator hubf interact with the tata-binding protein complex hsl1 to mediate transcription. | recent evidence suggests that transcription initiation by all three eukaryotic rna polymerases involves a complex of the tata-binding protein (tbp) and multiple tbp-associated factors (tafs). here, we map the functional domains of the nucleolar hmg box protein hubf, which binds to the human rrna promoter and stimulates transcription by rna polymerase i through cooperative interactions with a distinct tbp-taf complex, hsl1. dnase i footprint analysis of mutant hubf proteins and of a synthetic pep ... | 1992 | 1398072 |
| the armadillo homologs beta-catenin and plakoglobin are differentially expressed during early development of xenopus laevis. | plakoglobin and beta-catenin are cytoplasmic proteins associated with the intracellular plaques of cell adhesive junctions. while plakoglobin is present in both adherens junctions and desmosomes, beta-catenin is associated with the cadherins that accumulate only in adherens junctions. both beta-catenin and plakoglobin are homologs of armadillo, a drosophila segment polarity gene that is considered to be in the wingless signaling pathway. we have characterized the expression and distribution of b ... | 1992 | 1397690 |
| protein kinase c mutants in the auto-inhibitory region exhibit two distinct properties. | to define the role of the auto-inhibitory region of protein kinase c (pkc), arg22-lys23-gly24-ala25-leu26-arg27, site-directed mutations were introduced into the basic residues. three mutants, pkcala22,23, pkcala27, and pkcala22,23,27, apparently fell into two distinct types with regard to their biochemical properties and biological activities, as judged by the enhancement of a c-fos promoter in jurkat cells and by the initiation of germinal vesicle breakdown (gvbd) in xenopus laevis oocytes. (i ... | 1992 | 1397296 |
| characterization of a xenopus laevis skin peptidylglycine alpha-hydroxylating monooxygenase expressed in insect-cell culture. | the c-terminal amide structure of peptide hormones and neurotransmitters is synthesized via a two-step reaction catalyzed by peptidylglycine alpha-hydroxylating monooxygenase (phm) and peptidylhydroxyglycine n-c lyase. a xenopus laevis phm expressed in insect-cell culture by the baculovirus-expression-vector system was purified to homogeneity and characterized. using a newly established assay system for phm, the kinetic features of this enzyme were investigated. as expected, the enzyme required ... | 1992 | 1396699 |
| efficiency of the 5'-terminal sequence (omega) of tobacco mosaic virus rna for the initiation of eukaryotic gene translation in escherichia coli. | recent studies have demonstrated that the 5' leader (omega sequence) of tobacco mosaic virus rna has a certain enhancing capacity for translation of mrna in both prokaryotes and eukaryotes. in order to estimate the efficiency of omega to initiate translation of mrna in escherichia coli, in comparison to the shine-dalgarno (s/d) sequence, we have inserted eight different eukaryotic genes into two types of e. coli expression vectors containing one constitutive promoter (p1) but different translati ... | 1992 | 1396694 |
| the effect of phloretin on single potassium channels in myelinated nerve. | the effect of phloretin, a dipolar organic compound, on single potassium channel currents of myelinated nerve fibres of xenopus laevis has been investigated, using inside-out patches prepared by the method of jonas et al. (1989). the i channel, a potential dependent k channel with intermediate deactivation kinetics, was reversibly blocked by 20 microm phloretin applied on the inside; the block was strongest at negative membrane potentials and less pronounced at positive potentials. phloretin shi ... | 1992 | 1396407 |
| isolation of plasma membranes, golgi bodies and mitochondria of xenopus laevis morulae. identification of plasma membrane proteins. | homogenates of xenopus morulae at the 16-32 cell stage were centrifuged on discontinuous sucrose gradients. isolated fractions were identified by electron microscopy (em) as mitochondria, a fraction enriched in golgi vesicles, and plasma membranes. a special effort was made to prepare plasma membranes free of cytoplasmic contaminants. the resulting purified plasma membranes appeared morphologically identical to plasma membranes in situ. the external surface is covered with a fibrillar coat while ... | 1992 | 1394088 |
| mechanism of magainin 2a induced permeabilization of phospholipid vesicles. | the magainins, peptide antibiotics secreted by the frog xenopus laevis, have previously been shown to permeabilize phospholipid vesicles. to elucidate the mechanism of permeabilization, we have conducted detailed kinetic studies of magainin 2 amide (mgn2a)-induced release of 6-carboxyfluorescein from vesicles of phosphatidylserine. the results show that dye release occurs in (at least) two stages--an initial rapid phase, with t1/2 approximately 3 s, followed by a much slower phase that approache ... | 1992 | 1390773 |
| serotonin synthesis and accumulation by neurons of the anuran retina. | serotonin-synthesizing and serotonin-accumulating neurons were studied in the retinas of xenopus laevis and bufo marinus. all previously identified cell types exhibiting serotonin-like immunoreactivity (sli) were labeled by intravitreal injection of 5,7-dihydroxytryptamine (5,7-dht). they included two amacrine cell types (large and small) in both species, and one bipolar cell type in xenopus. incubation of retinas in culture medium in the ambient light reduced sli in amacrine cells and enhanced ... | 1992 | 1390395 |
| effects of lithium chloride and retinoic acid on the expression of genes from the xenopus laevis hox 2 complex. | we show that xenopus laevis has a hox 2 complex, and that this complex is strongly conserved with the mammalian one, both in structure and in the rules of spatial and temporal sequential expression of its genes during the early stages of development. lithium chloride and retinoic acid, two reagents known to alter axial patterning of the body when applied to xenopus embryos, produce, respectively, embryos with reduced posterior but exaggerated anterior structures and embryos with truncation of an ... | 1992 | 1384809 |
| expression of amiloride-sensitive na+ channels of hen lower intestine in xenopus oocytes: electrophysiological studies on the dependence of varying nacl intake. | epithelial na+ channels were incorporated into the plasma membrane of xenopus laevis oocytes after micro-injection of rna from hen lower intestinal epithelium (colon and coprodeum). the animals were fed either a normal poultry food which contained nacl (hs), or a similar food devoid of nacl (ls). oocytes were monitored for the expression of amiloride-sensitive sodium channels by measuring membrane potentials and currents. oocytes injected with poly(a)+rna prepared from hs animals or non-injected ... | 1992 | 1384704 |
| niflumic and flufenamic acids are potent inhibitors of chloride secretion in mammalian airway. | effects of niflumic acid (nfa) and flufenamic acid (ffa), the two nonsteroid anti-inflammatory agents recently reported to inhibit cl- current in xenopus oocytes, were examined in cultured monolayers of dog and cow trachea. both agents showed potent inhibition to the short-circuit current (isc), an index of magnitude of transepithelial cl- secretion, with values of ki of 0.02 (for nfa) and 0.06 (for ffa) mm, respectively. the sensitivity sequence of isc to the cl- channel inhibitors tested was n ... | 1992 | 1383667 |
| properties of endogenous voltage-dependent sodium currents in xenopus laevis oocytes. | endogenous voltage-dependent sodium currents were recorded using standard 2-microelectrode techniques in xenopus laevis oocytes. maximal inward current occurred at -10 mv with an average amplitude of -279 +/- 17 na and steady-state inactivation was half-maximal at a voltage of -38 +/- 0.5 mv. currents were blocked by low concentrations of tetrodotoxin (ttx) with an ic50 value of 6 nm. these properties make the endogenous sodium current in xenopus oocytes similar to sodium currents expressed foll ... | 1992 | 1383646 |
| characterization of a xenopus laevis ribonucleoprotein endoribonuclease. isolation of the rna component and its expression during development. | in order to facilitate studies of the assembly and transport of the site-specific rnase mitochondrial rna processing (mrp) ribonucleoprotein, we have characterized it from xenopus laevis cells. x. laevis rnase mrp displayed a similar spectrum of cleavage activity to that produced by previously isolated mammalian nuclear enzymes. a 277-nucleotide rna component of the ribonucleoprotein was identified; the gene for the rna was isolated, sequenced, and found to be 66 and 63% similar to mouse and hum ... | 1992 | 1383227 |
| 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 ... | 1992 | 1383009 |
| evolution of vertebrate igm: complete amino acid sequence of the constant region of ambystoma mexicanum mu chain deduced from cdna sequence. | cdna clones coding for the constant region of the mexican axolotl (ambystoma mexicanum) mu heavy immunoglobulin chain were selected from total spleen rna, using a cdna polymerase chain reaction technique. the specific 5'-end primer was an oligonucleotide homologous to the jh segment of xenopus laevis mu chain. one of the clones, jha/3, corresponded to the complete constant region of the axolotl mu chain, consisting of a 1362-nucleotide sequence coding for a polypeptide of 454 amino acids followe ... | 1992 | 1382992 |
| structure-activity relations of amiloride and its analogues in blocking the mechanosensitive channel in xenopus oocytes. | 1. patch clamp recording techniques have been used to compare the block caused by amiloride and some of its structural analogues of the mechanosensitive (ms) cation selective channel in frog (xenopus laevis) oocytes. 2. like amiloride, the amiloride analogues dimethylamiloride (dma), benzamil and bromohexamethyleneamiloride (brhma) block the ms channel in a highly voltage-dependent manner. 3. all analogues tested were more potent blockers than amiloride with ic50's of 500 microm (amiloride), 370 ... | 1992 | 1382778 |
| 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 ... | 1992 | 1381584 |
| primary sequence and functional expression of a novel ouabain-resistant na,k-atpase. the beta subunit modulates potassium activation of the na,k-pump. | in order to understand the molecular mechanism of ouabain resistance in the toad bufo marinus, na,k-atpase alpha and beta subunits have been cloned and their functional properties tested in the xenopus laevis oocyte expression system. according to sequence comparison between species, alpha 1, beta 1, and beta 3 isoforms were identified in a clonal toad urinary bladder cell line (tbm 18-23). the sequence of the alpha 1 isoform is characterized by two positively charged amino acids (arg, lys) at t ... | 1992 | 1380956 |
| 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 ... | 1992 | 1380158 |
| 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 ... | 1992 | 1380078 |
| 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 ... | 1992 | 1379942 |
| 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 ... | 1992 | 1379791 |
| 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, ... | 1992 | 1379228 |
| 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 ... | 1992 | 1379202 |
| 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 ... | 1992 | 1378412 |
| 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 ... | 1992 | 1377915 |
| 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 ... | 1992 | 1377448 |
| 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 ... | 1992 | 1376926 |
| 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 ... | 1992 | 1376925 |
| 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 ... | 1992 | 1375919 |
| 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 ... | 1992 | 1375456 |
| 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) ... | 1992 | 1374775 |
| 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 ... | 1992 | 1374712 |
| 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 ... | 1992 | 1374685 |
| 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. | 1992 | 1374647 |
| 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 ... | 1992 | 1374352 |
| 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 ... | 1992 | 1374230 |
| 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; ... | 1992 | 1373524 |
| 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 ... | 1992 | 1372714 |
| 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 ... | 1992 | 1371969 |
| 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 ... | 1992 | 1371870 |
| 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. ... | 1992 | 1371671 |
| 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 ... | 1992 | 1371147 |
| 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 ... | 1992 | 1371032 |
| 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 ... | 1992 | 1370937 |
| 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 ... | 1992 | 1370353 |
| 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 ... | 1992 | 1368810 |
| 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 ... | 1992 | 1365880 |
| 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 ... | 1992 | 1364139 |
| 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 ... | 1992 | 1363963 |
| 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 ... | 1992 | 1363722 |
| 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- ... | 1992 | 1363721 |
| 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 ... | 1992 | 1363522 |
| 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 ... | 1992 | 1361986 |
| 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 ... | 1992 | 1361984 |
| 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 ... | 1992 | 1360143 |
| 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 ... | 1992 | 1359988 |
| 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 ... | 1992 | 1359549 |
| 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 ... | 1992 | 1358528 |
| 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 ... | 1992 | 1358174 |
| 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 ... | 1992 | 1355772 |
| 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 ... | 1992 | 1355741 |
| 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 ... | 1992 | 1355048 |
| 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 ... | 1992 | 1354958 |
| 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 ... | 1992 | 1354219 |
| 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 ... | 1992 | 1353734 |
| 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, ... | 1992 | 1353352 |
| 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 ... | 1992 | 1351827 |
| 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 ... | 1992 | 1350955 |
| 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. ... | 1992 | 1349239 |
| 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 ... | 1992 | 1348672 |
| 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 ... | 1992 | 1348272 |
| 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 ... | 1992 | 1347944 |
| 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 ... | 1992 | 1347750 |
| [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. | 1992 | 1340443 |
| 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 ... | 1992 | 1338458 |
| [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 ( ... | 1992 | 1338132 |
| 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 ... | 1992 | 1337667 |