| interspecific variation in the emetic response of anurans. | 1. the emetic response of seven species (four genera) of frogs to apomorphine hydrochloride, copper sulfate, antimonyl potassium tartrate and mechanical stimulation at the esophageal orifice was surveyed. xenopus laevis and rhacophorus schlegelii were more sensitive to systemically administered apomorphine than were the other species tested. 2. the sensitivity of rana rugosa to apomorphine varied with the season. 3. all of the species showed vigorous vomiting behavior after the oral administrati ... | 1991 | 1687529 |
| molecular approach to dorsoanterior development in xenopus laevis. | rna from ventralized xenopus laevis embryos has been used to generate a subtracted library consisting of genes whose expression is dependent upon dorsoanterior development. clones were selected on the basis of two criteria: (1) at least 10-fold reduction in ventralized versus control embryo rna, and (2) absence of hybridization to rna from adult muscle. one of these clones, designated uvs.2, was characterized further. uvs.2, was found by in situ hybridization to be expressed exclusively in the a ... | 1990 | 1688538 |
| premature termination of transcription can be induced on an injected alpha-tubulin gene in xenopus oocytes. | the xenopus laevis alpha-tubulin gene x alpha t14, which is highly expressed during oogenesis, exhibits accurate and efficient transcription initiation when microinjected into x. laevis oocytes. however, we found previously in nuclease protection assays of transcripts from injected x alpha t14 that many protected fragments that were shorter than expected could be produced. we show here by exonuclease vii mapping, northern (rna) blotting, and gel fractionation of rna that these fragments were cau ... | 1990 | 1688998 |
| reconstitution of an insulin signaling pathway in xenopus laevis oocytes: coexpression of a mammalian insulin receptor and three different mammalian hexose transporters. | we report the functional expression of the mammalian muscle-adipocyte insulin-sensitive hexose transporter in xenopus laevis oocytes. oocytes microinjected with rna synthesized in vitro showed enhanced hexose transport activity compared with uninjected controls. however, like the endogenous oocyte hexose transporter, activity was stimulated only twofold by 1 microm insulin. x. laevis oocytes injected with in vitro-synthesized rna encoding the human insulin proreceptor expressed a functionally ac ... | 1990 | 1688999 |
| differential keratin gene expression during the differentiation of the cement gland of xenopus laevis. | the expression of both epidermal and nonepidermal keratins has been detected in the cement gland of xenopus laevis by antibody staining. northern blot and in situ hybridizations with gene-specific probes indicated the expression of the nonepidermal keratin, xk endo b, and the embryonic epidermal keratin, xk70, in the cement gland. furthermore, since explanted animal pole cells can be induced to differentiate into cement gland cells in vitro by incubation in nh4cl, we have demonstrated the in vit ... | 1990 | 1689262 |
| a serum factor that activates the phosphatidylinositol phosphate signaling system in xenopus oocytes. | blood sera from many vertebrate species elicit large oscillatory chloride currents in oocytes from the frog xenopus laevis. rabbit serum was active at dilutions as great as one part in 10 million. intracellularly applied serum was ineffective, and externally applied serum failed to trigger oscillatory currents when the intracellular level of ionized calcium was prevented from rising by loading the oocyte with egta. the serum also caused an increase of inositol 1,4,5-trisphosphate in the oocyte. ... | 1990 | 1689488 |
| expression of striatal d1 dopamine receptors coupled to inositol phosphate production and ca2+ mobilization in xenopus oocytes. | expression of central nervous system receptors for dopamine was examined by injection of poly(a)+ rna (mrna) from rat striatum into oocytes from xenopus laevis. electrophysiological measurements in mrna-injected oocytes indicated that addition of 100 microm dopamine induced an inward current (40-100 na) that was consistent with the activation of endogenous ca2(+)-dependent cl- channels. this current was also elicited by addition of the selective d1 agonist skf 38393 but not by the selective d2 a ... | 1990 | 1690425 |
| sequence requirements for transcriptional arrest in exon 1 of the murine adenosine deaminase gene. | we have previously shown that a transcription arrest site near the 5' end of the murine adenosine deaminase (ada) gene is significantly involved in the regulation of ada gene expression. to facilitate the analysis of this transcription arrest site, we have analyzed the transcription products from cloned ada gene fragments injected into xenopus laevis oocytes. when genomic fragments spanning the 5' end of the ada gene were injected into oocytes, a 96-nucleotide (nt) ada rna was the major transcri ... | 1990 | 1690842 |
| two distinct xenopus genes with homology to myod1 are expressed before somite formation in early embryogenesis. | the myogenic factors myod1 and myogenin contain a conserved region with similarity to the myc family of proto-oncogenes. to identify amphibian genes structurally and functionally related to these myogenic factors, we screened a xenopus laevis embryo cdna library under conditions of reduced stringency with probes corresponding to the myc-like helix-loop-helix motif of mouse myod1 and myogenin. several distinct cdnas that are highly related to each other and share extensive homology to myod1 were ... | 1990 | 1690844 |
| organization and sequence of the human gene encoding cytokeratin 8. | among the various intermediate filament (if) proteins, cytokeratin 8 (ck8) is especially remarkable as it is produced early in embryogenesis, is the only type-ii ck occurring in many simple epithelial cells, and can also be synthesized in certain non-epithelial cells. using a cdna probe specific for human ck8 we have isolated an approx. 14-kb genomic clone (in phage lambda embl3) which contains the gene encoding human ck8. the gene comprising a total of 7766 nucleotides (nt) from the transcripti ... | 1990 | 1691124 |
| vaults. ii. ribonucleoprotein structures are highly conserved among higher and lower eukaryotes. | vaults are cytoplasmic ribonucleoprotein structures that display a complex morphology reminiscent of the multiple arches which form cathedral vaults, hence their name. previous studies on rat liver vaults (kedersha, n. l., and l. h. rome. 1986. j. cell biol. 103:699-709) have established that their composition is unlike that of any known class of rna-containing particles in that they contain multiple copies of a unique small rna and more than 50 copies of a single polypeptide of 104,000 mr. we n ... | 1990 | 1691193 |
| the role of cytosolic and membrane factors in processing of the human beta-2 adrenergic receptor following translocation and glycosylation in a cell-free system. | the beta-2 adrenergic receptor has been proposed to have seven membrane-spanning domains. expression of functional beta-2 adrenergic receptor was achieved in a heterologous cell-free system composed of rabbit reticulocyte lysate and microsomal membranes from xenopus laevis oocytes. the functional state of the receptor protein can be determined by ligand-binding assays and by the ability of ligands to alter the susceptibility of the receptor to proteinase k digestion. the process by which functio ... | 1990 | 1692024 |
| a point mutation uncouples rna 3'-end formation and termination during ribosomal gene transcription in xenopus laevis. | two sites, t2 and t3, in the ribosomal gene spacer of xenopus laevis both direct rna 3'-end formation 15 bp upstream of the conserved box sequence gacttgc. site t2, which defines the 3' end of the 40s precursor, does not terminate transcription whereas site t3 at the 3' end of the spacer does. here we show that t2 can be converted into a t3-like site with termination activity by a single point mutation 2 bp downstream of the t2 box. rna 3'-end formation at t2 is unchanged by this mutation. conve ... | 1990 | 1692557 |
| enhanced c-myc gene expression during forelimb regenerative outgrowth in the young xenopus laevis. | analysis of the expression of the c-myc protooncogene has been carried out in the forelimb regenerate of the xenopus laevis froglet. northern blot hybridization analysis revealed the presence of a 2.5-kilobase c-myc transcript in the regenerate forelimb at a level at least 7-fold more than the one found in nonregenerating forelimbs or stumps of regenerating forelimbs. in situ hybridization analyses confirmed the relative abundance of c-myc rna in the regenerate forelimb and provided evidence of ... | 1990 | 1692624 |
| functional expression of murine multidrug resistance in xenopus laevis oocytes. | the development of multidrug resistance (mdr) is associated with the overproduction of a plasma membrane glycoprotein, p glycoprotein. here we report the functional expression of a member of the murine mdr family of proteins and show that xenopus oocytes injected with rna encoding the mouse mdr1b p glycoprotein develop a mdr-like phenotype. immunological analysis indicated that oocytes injected with the mdr1b rna synthesized a protein with the size and immunological characteristics of the mouse ... | 1990 | 1693776 |
| morphological evidence for a monosynaptic connection between cerebellar purkinje cells and vestibulospinal tract neurons in the larval clawed toad, xenopus laevis. | a double-labeling technique was used to trace synaptic connections between the efferent neurons of the cerebellum (purkinje cells) and vestibulospinal tract neurons in larvae of the clawed toad, xenopus laevis. the efferent cerebellar projection was labeled with horseradish peroxidase (hrp) while in the same preparations the brainstem neurons projecting to the spinal cord were labeled with cobaltous lysine. it was found that the distribution of the purkinje cell terminal boutons overlaps signifi ... | 1990 | 1694284 |
| neuropeptide y- and substance p-like immunoreactive amacrine cells in the retina of the developing xenopus laevis. | the development of neuropeptide y-like (npy-li) and substance p-like (sp-li) immunoreactive neurons was studied in retinas of xenopus laevis from young tadpole through to adult animals. in adult retina these neuropeptides are present in wide-field amacrine cells located in the inner nuclear layer and the ganglion cell layer of the retina. retinal wholemount preparations and sectioned material showed that immunoreactive cells appeared during early larval life and npy-li occurred earlier than sp-l ... | 1990 | 1694741 |
| copolymers of glutamic acid and tyrosine are potent inhibitors of oocyte casein kinase ii. | polypeptides rich in glutamic acid are strong inhibitors purified from isolated nuclei of xenopus laevis oocytes of casein kinase ii. the presence of tyrosine in these peptides greatly enhances their inhibitory capacity. using casein as a substrate, copolyglu:tyr (4:1) has an i50 value of 20 nm, 250 fold lower than that of polyglutamic acid which is 5 microm. a similar large difference is observed when a synthetic peptide is used as substrate. the inhibition of copolyglu:tyr is competitive with ... | 1990 | 1694780 |
| identification of g protein-coupled receptors by rnase h-mediated hybrid depletion using xenopus laevis oocytes as expression system. | a method has been developed for rapidly identifying putative g protein-coupled receptors isolated initially as small cdna fragments, following reverse transcription and polymerase chain reaction (pcr) amplification of mrna. the method is based upon the use of synthetic oligonucleotides deduced from the sequence of the amplified receptor fragments, to direct a rnase h-mediated specific degradation of hybrids formed between the oligonucleotides and the corresponding receptor-encoding mrna. loss of ... | 1990 | 1694786 |
| xk endo b is preferentially expressed in several induced embryonic tissues during the development of xenopus laevis. | xk endo b is a type i keratin that was originally identified by its preferential expression in the embryonic notochord of the amphibian xenopus laevis. a peptide identical to a short region of its predicted amino acid sequence was used to generate antibodies against the xk endo b protein. this paper reports an immunocytochemical study of the spatial expression pattern of xk endo b during development. the protein was observed in the notochord and endoderm as predicted from previous rna analysis. ... | 1990 | 1694800 |
| two precursors of thyrotropin-releasing hormone from skin of xenopus laevis. each contains seven copies of the end product. | from the skin of xenopus laevis, the cloned cdnas of two precursors of thyrotropin-releasing hormone have been isolated and sequenced. these encode almost identical precursor polypeptides each containing seven copies of the end product flanked by typical prohormones processing signals. northern blot analysis has corroborated the existence of two thyrotropin-releasing hormone precursor mrnas of similar size as the cloned cdna and demonstrated the existence of a third smaller species as well. two ... | 1990 | 1694847 |
| stability of maternal mrna in xenopus embryos: role of transcription and translation. | the first 12 cell divisions of xenopus laevis embryos do not require gene transcription. this means that the regulation of gene expression during this period is controlled at post transcriptional levels and makes xenopus early development a potentially interesting biological system with which to study the mechanisms involved. we describe here the stability characteristics of several maternal xenopus mrnas which are deadenylated soon after fertilisation (j. paris and m. philippe, dev. biol., in p ... | 1990 | 1695321 |
| expression of renal transport systems for inorganic phosphate and sulfate in xenopus laevis oocytes. | as a first step within an experimental strategy (expression cloning) leading to the structural identification of the two brush-border membrane transport systems for phosphate and sulfate, we have studied the expression of na(+)-dependent uptake of phosphate and sulfate in xenopus laevis oocytes injected with rabbit kidney cortex poly(a)+ rna (mrna). na(+)-dependent uptake of phosphate and sulfate was stimulated in a dose- and time-dependent manner up to 20-fold as compared to water-injected cont ... | 1990 | 1695629 |
| human facilitative glucose transporters. isolation, functional characterization, and gene localization of cdnas encoding an isoform (glut5) expressed in small intestine, kidney, muscle, and adipose tissue and an unusual glucose transporter pseudogene-like sequence (glut6). | two novel facilitative glucose transporter-like cdnas have been isolated from human small intestine and fetal skeletal muscle cdna libraries by low stringency cross-hybridization with a fragment of the human erythrocyte/glut1 facilitative glucose transporter cdna. one encodes a 501-amino acid facilitative glucose transporter, designated as the small intestine/glut5 isoform, having 41.7, 40.0, 38.7, and 41.6% identity with the previously described human erythrocyte/glut1, liver/glut2, brain/glut3 ... | 1990 | 1695905 |
| functional role of the cysteine 451 thiol group in the m4 helix of the gamma subunit of torpedo californica acetylcholine receptor. | previous chemical modification studies of the acetylcholine receptor [yee, a.s., corey, d.e., & mcnamee, m.g. (1986) biochemistry 25, 2110-2119] were extended by using fluorescent n-pyrenylmaleimide to alkylate purified torpedo californica nicotinic acetylcholine receptor (achr). peptide sequencing of the tryptic fragments of the labeled achr gamma subunit identified cysteines 416, 420, and 451 as the modified residues. the functional role of cys-451 in the m4 transmembrane domain of the achr ga ... | 1990 | 1696834 |
| identification and characterization of transcriptional arrest sites in exon 1 of the human adenosine deaminase gene. | analysis of human adenosine deaminase (ada) gene transcription in four different cell lines indicated that a high density of rna polymerase ii complexes is present at the 5' end of the gene and that the extent of transcription elongation beyond the promoter-proximal region governs gene expression. to determine the sequence requirements for a potential transcription arrest site in the promoter-proximal region, genomic clones containing the ada promoter, exon 1, and various lengths of intron 1 wer ... | 1990 | 1697031 |
| characterization and developmental expression of xenopus proliferating cell nuclear antigen (pcna). | the coding sequence of the proliferating cell nuclear antigen (pcna) was characterized in the amphibian xenopus laevis. the deduced protein sequence shares an extensive homology (89%) with the mammalian pcna coding sequences. xenopus pcna is expressed beginning in early oogenesis and reaches a level of 3 x 10(7) transcripts per mature oocyte, whereas proliferative somatic cells contain 3 x 10(2) pcna transcripts per cell. most of the pcna protein is expressed during late oogenesis and one single ... | 1990 | 1697269 |
| rabbit small intestinal trehalase. purification, cdna cloning, expression, and verification of glycosylphosphatidylinositol anchoring. | alpha,alpha-trehalase (ec 3.2.1.28), an intrinsic protein of intestinal brush-border membranes, was purified to homogeneity from rabbits. partial amino acid sequences were determined. two degenerate oligonucleotides based on the sequence of a cnbr peptide were employed in a polymerase chain reaction to amplify a 71-base pair fragment of trehalase dna with rabbit intestine cdna as a starting template. this fragment was used as a hybridization probe to isolate full length trehalase clones from a r ... | 1990 | 1697585 |
| changes in lectin-binding pattern in the digestive tract of xenopus laevis during metamorphosis. i. gastric region. | the distribution of structural and secretory glycoconjugates in the gastric region of metamorphosing xenopus laevis was studied by the avidin-biotin-peroxidase (abc) histochemical staining method using seven lectins (concanavalin a, con a; dolichos biflorus agglutinin, dba; peanut agglutinin, pna; ricinus communis agglutinin i, rca-i; soybean agglutinin, sba; ulex europeus agglutinin i, uea-i; and wheat germ agglutinin, wga). throughout the larval period to stage 60, the epithelium consisting of ... | 1990 | 1697625 |
| changes in lectin-binding pattern in the digestive tract of xenopus laevis during metamorphosis. ii. small intestine. | the binding of seven lectins (concanavalin a, con a; dolichos biflorus agglutinin, dba; peanut agglutinin, pna; ricinus communis agglutinin i, rca-i; soybean agglutinin, sba; ulex europeus agglutinin, uea-i; and wheat germ agglutinin, wga) to the small intestine in metamorphosing xenopus laevis was studied by the avidin-biotin-peroxidase (abc) method. the staining pattern of the epithelium with all lectins except for uea-i and con a changed gradually during metamorphic climax; the main component ... | 1990 | 1697626 |
| targeted degradation of mrna in xenopus oocytes and embryos directed by modified oligonucleotides: studies of an2 and cyclin in embryogenesis. | we have designed antisense oligodeoxyribonucleotides which are both highly resistant to nucleolytic degradation and also serve as substrates for ribonuclease h. using these compounds we have targeted the specific degradation of several maternal mrnas present in xenopus laevis oocytes and early embryos. several internucleoside linkages at both the 3' and 5' ends of the oligonucleotides were modified as phosphoramidates to provide complete protection against exonucleases, the predominant nucleolyt ... | 1990 | 1697675 |
| ktf-1, a transcriptional activator of xenopus embryonic keratin expression. | nuclear extracts from embryos of xenopus laevis were shown to contain a protein activity, ktf-1, which binds in vitro to the promoter of the embryonic, epidermis-specific keratin gene, xk81a1. mobility shift assays, methylation interference and footprinting analysis were used to show that the ktf-1 binding site contains an imperfect, palindromic sequence, accctgaggct. this sequence occurs once in the xk81a1 promoter, 152-162 base pairs upstream of the transcription start site. a construct of the ... | 1990 | 1698604 |
| poev: a xenopus oocyte protein expression vector. | we have constructed a xenopus laevis oocyte expression vector, poev, which allows cloned dna to be transcribed and translated directly in the oocyte. since proteins translated in oocytes are post-translationally modified according to conserved eukaryotic signals, these cells offer a convenient system for performing structural and functional analyses of cloned genes. poev can be used for direct analysis of proteins encoded by cloned cdnas without preparing mrna in vitro, simplifying existing prot ... | 1990 | 1699447 |
| expression of functional thrombin receptors in xenopus oocytes injected with human endothelial cell mrna. | human endothelial cell thrombin receptors were functionally expressed in xenopus laevis oocytes by injection of rna extracted from human umbilical vein endothelial cells. oocytes injected with endothelial cell rna responded to thrombin with a ca2(+)-dependent depolarizing current whose size depended on the amount of rna injected. in oocytes expressing thrombin receptors, thrombin caused homologous but not heterologous desensitization. both the catalytic and anion-binding exosites of thrombin wer ... | 1990 | 1699530 |
| the effect of myo-inositol 1,4,5-trisphosphorothioate on cl- current pattern and intracellular ca2+ in the xenopus laevis oocyte. | microinjection of myo-inositol 1,4,5-trisphosphate into voltage-clamped xenopus laevis oocytes or the stimulation of the phosphatidylinositol cycle elicits a complex ca2(+)-dependent cl- current pattern. microinjection of myo-inositol 1,3,4,5-tetrakisphosphate causes an immediate release of ca2+, but elicits a different cl- current pattern than myo-inositol 1,4,5-trisphosphate. we have studied the effects of myo-inositol 1,4,5-trisphosphorothioate, which can not be converted to myo-inositol 1,3, ... | 1990 | 1699536 |
| maturation-specific polyadenylation and translational control: diversity of cytoplasmic polyadenylation elements, influence of poly(a) tail size, and formation of stable polyadenylation complexes. | early embryonic development in xenopus laevis is programmed in part by maternally derived mrnas, many of which are translated at the completion of meiosis (oocyte maturation). polysomal recruitment of at least one of these mrnas, g10, is regulated by cytoplasmic poly(a) elongation which, in turn, is dependent upon the cytoplasmic polyadenylation element (cpe) uuuuuuauaaag and the hexanucleotide aauaaa (l. l. mcgrew, e. dworkin-rastl, m. b. dworkin, and j. d. richter, genes dev. 3:803-815, 1989). ... | 1990 | 1700272 |
| expression of the murine interleukin-5 receptor on xenopus laevis oocytes. | in this study we describe the use of xenopus laevis oocytes for the detection of mrna coding for a murine interleukin-5 (mi15) receptor. when injected with sucrose gradient fractionated polya+ rna derived from the murine 115-dependent pre b cell line b13, these oocytes could specifically bind 35s-methionine labeled mi15. a size of approximately 4000 nucleotides (25s) was estimated for the mrna corresponding to the mil5-binding activity. this binding was not blocked by a monoclonal antibody r52 s ... | 1990 | 1700706 |
| molecular cloning of the fmet-leu-phe receptor from neutrophils. | the bacterial chemotactic peptide fmet-leu-phe (fmlp) activates neutrophils upon binding to surface receptors. in a previous communication we reported the functional reconstitution of the fmlp receptor in xenopus laevis oocytes (coats, w. d., and navarro, j. (1990) j. biol. chem. 265, 5964-5966). in this work we report the isolation of the cdna encoding the fmlp receptor from neutrophils. a rabbit neutrophil cdna library was screened with an oligonucleotide probe deduced from the nucleotide sequ ... | 1990 | 1700779 |
| molecular cloning by hybrid arrest of translation in xenopus laevis oocytes. identification of a cdna encoding the type i iodothyronine 5'-deiodinase from rat liver. | the enzyme(s) catalyzing the 5'-monodeiodination of thyroxine and 3,3',5'-triiodothyronine has not yet been purified, and antibodies of demonstrated specificity are not available. thus, molecular cloning strategies which rely on the traditional screening techniques of using cdna probes or monospecific antibodies are problematic. we previously reported that expression of type i 5'-deiodinase can be induced in xenopus laevis oocytes by the injection of poly (a)+ rna prepared from rat liver (st. ge ... | 1990 | 1700781 |
| mapping light strand transcripts near the origin of replication of xenopus laevis mitochondrial dna. | transcription of the light strand of xenopus laevis mitochondrial dna initiates at two promoters located approximately 350 to 450 nucleotides upstream from the 5' ends of major d-loop dna strands. small rnas within this region have been mapped by blot hybridization, primer extension and s1 nuclease protection methods. the results reveal that the large majority of rnas within this region have 3' termini located at a sequence element, designated csb 2, that is conserved in sequence and position in ... | 1990 | 1700855 |
| site-specific mutagenesis of human chorionic gonadotrophin (hcg)-beta subunit: influence of mutation on hcg production. | the heterodimeric glycoprotein hormones, human chorionic gonadotrophin (hcg), lh, tsh and fsh, consist of two non-covalently linked subunits, the alpha and beta subunits. the beta subunit is specific for each hormone and is responsible for the biological specificity, but the beta subunits of different hormones show some degree of structural homology. the cagy (cysteine-alanine-glycine-tyrosine) region is one of the amino acid sequences that is homologous in different beta subunits and is highly ... | 1990 | 1701089 |
| development of the oculomotor and trochlear nuclei in the xenopus toad. | the development of the oculomotor and trochlear nuclei (niii and niv) was studied with the horseradish peroxidase (hrp) and the cobalt labelling techniques in xenopus laevis tadpoles. the earliest labelling of the oculomotor neuroblasts was observed at stage 32. the ipsi- and contralateral nuclei were found in two distinct groups on either side of the brainstem and the oculomotor commissure formed by crossing axons was present at this early stage. the fusion of the two nuclei began at the late l ... | 1990 | 1701864 |
| vectorial secretion of a kallikrein-like enzyme by cultured renal cells. i. general properties. | urinary kallikreins are proteolytic enzymes known to be secreted by distal nephron tubules. in this study, we demonstrate (using the chromogenic tripeptide substrate s 2266) that the renal cell line a6 from xenopus laevis secretes a kallikrein-like enzyme. secretion is present only when the cells are grown on filters, and enzyme is secreted only into the apical membrane bathing solution. enzyme secretion consists of two components, one soybean trypsin inhibitor (sbti) sensitive (ssbti) and the o ... | 1990 | 1701967 |
| gaba and neuropeptide y co-exist in axons innervating the neurointermediate lobe of the pituitary of xenopus laevis--an immunoelectron microscopic study. | the neural innervation of the neurointermediate lobe of the pituitary of the amphibian xenopus laevis has been studied at the light and electron microscopic level. in the pars intermedia melanotropes and stellate cells are abutted by varicosities originating from gaba- and neuropeptide y-producing neurons. the varicosities contain two types of vesicle: electron-lucent vesicles (mean diameter 50 nm) which are immunopositive for gaba and larger (80 nm) electron-dense vesicles which are immunoposit ... | 1990 | 1702192 |
| molecular basis of altered excitability in shaker mutants of drosophila melanogaster. | mutations in the shaker (sh) locus of drosophila melanogaster have differing effects on action potential duration and repolarization in neurons as well as on a-type k+ channels (ia) in muscle. the molecular basis of three exemplary sh alleles (shks133, she62 and sh5) has been identified. they are point mutations in the sh transcription unit expressing aberrant voltage-gated a-type k+ channels. replicas of each mutation have been introduced by in vitro mutagenesis into sh cdna. the expression of ... | 1990 | 1702382 |
| retrovirus-induced interference with collagen i gene expression in mov13 fibroblasts is maintained in the absence of dna methylation. | we have studied the role of dna methylation in repression of the murine alpha 1 type i collagen (col1a1) gene in mov13 fibroblasts. in mov13 mice, a retroviral provirus has inserted into the first intron of the col1a1 gene and blocks its expression at the level of transcriptional initiation. we found that regulatory sequences in the col1a1 promoter region that are involved in the tissue-specific regulation of the gene are unmethylated in collagen-expressing wild-type fibroblasts and methylated i ... | 1991 | 1702514 |
| liver-specific gene expression: a-activator-binding site, a promoter module present in vitellogenin and acute-phase genes. | the a2 vitellogenin gene of xenopus laevis, which is expressed liver specifically, contains an a-activator-binding site (aabs) that mediates high in vitro transcriptional activity in rat liver nuclear extracts. footprint experiments with dnase i and gel retardation assays revealed the binding of several proteins to aabs. using binding sites of known dna-binding proteins as competitors in the gel retardation assay, we found that the transcription factor c/ebp and/or one of its "iso-binders" as we ... | 1991 | 1702515 |
| primary structure and functional expression of the alpha-, beta-, gamma-, delta- and epsilon-subunits of the acetylcholine receptor from rat muscle. | the isolation and characterization of five clones carrying sequences of the alpha-, beta-, gamma-, delta- and epsilon-subunit precursors of the rat muscle acetylcholine receptor (achr) are described. the deduced amino acid sequences indicate that these polypeptides contain 457-519 amino acids and reveal the structural characteristics common to subunits of ligand-gated ion channels. the pattern of subunit-specific mrna levels in rat muscle shows characteristic changes during development and follo ... | 1990 | 1702709 |
| evolution of the major histocompatibility complex: molecular cloning of major histocompatibility complex class i from the amphibian xenopus. | class i major histocompatibility complex (mhc) cdna clones have been isolated from an expression library derived from mrna of an mhc homozygous xenopus laevis. the nucleotide and predicted amino acid sequences show definite similarity to mhc class i molecules of higher vertebrates. the immunoglobulin-like alpha-3 domain is more similar to the immunoglobulin-like domains of mammalian class ii beta chains than to those of mammalian class i molecules, and a tree based on nucleotide sequences of rep ... | 1991 | 1703301 |
| a monoclonal antibody that recognizes a phosphorylated epitope stains lampbrush chromosome loops and small granules in the amphibian germinal vesicle. | an mab library was produced against proteins from the germinal vesicle (gv) of the frog xenopus laevis; mab 104 was selected from this library on the basis of its immunofluorescent staining of lampbrush chromosome loops. chromosomes from several species of frogs and salamanders stained equally well. the antibody also stained the surface of numerous small granules in the gv nucleoplasm. the interior of the same granules was stained by antibodies against small nuclear ribonucleoproteins (snrnps). ... | 1990 | 1703534 |
| characterization of voltage-dependent calcium channels expressed in xenopus oocytes injected with mrna from rat heart. | 1. the properties of voltage dependent cardiac ca channels expressed in xenopus laevis oocytes after injection of mrna from rat heart were investigated using the double-microelectrode voltage-clamp technique. 2. endogenous ba current (iba,e) and expressed cardiac ba current (iba,c) were studied at various external concentrations of barium (ba2+). these two entities could be distinguished by their amplitude and their pharmacology. iba,c was more sensitive to the inorganic ca channel blocker manga ... | 1990 | 1703576 |
| further validation of fetax: evaluation of the developmental toxicity of five known mammalian teratogens and non-teratogens. | the developmental toxicity of five compounds was evaluated with the frog embryo teratogenesis assay: xenopus (fetax). late xenopus laevis blastulae were exposed to 5-azacytidine, methotrexate, pseudoephedrine, aspartame, and amaranth for 96 h. three separate static-renewal assays were conducted for each compound. based on teratogenic index [lc50/ec50 (malformation)] values, types and severity of induced malformations, and embryo growth, 5-azacytidine and methotrexate tested as having strong tera ... | 1990 | 1703942 |
| cloning by differential screening of a xenopus cdna coding for a protein highly homologous to cdc2. | fertilization of xenopus laevis eggs triggers a period of rapid cell division comprising 12 nearly synchronous mitoses. protein synthesis is required for these divisions, and new proteins appear after fertilization. others proteins however, which are synthesized in the unfertilized egg, are no longer made in the early embryo. to identify such proteins, a differential screen of an egg cdna library gave nine clones corresponding to mrnas that are deadenylylated soon after fertilization. the sequen ... | 1991 | 1704128 |
| expression of mrna for activin-binding protein (follistatin) during early embryonic development of xenopus laevis. | follistatin is a specific activin-binding protein and is supposed to control activin functions. during xenopus embryonic development, activin is thought to act as a natural mesoderm-inducing factor. we isolated here the xenopus follistatin cdna from xenopus ovary cdna library and studied the expression of xenopus follistatin gene during the course of early embryonic development. the xenopus follistatin has an 84% homology at the level of deduced amino acid sequence with human and porcine follist ... | 1991 | 1704219 |
| overexpression of wild-type and dominant negative mutant vimentin subunits in developing xenopus embryos. | vimentin belongs to the diverse multigene family of intermediate filament proteins, each member of which is expressed in a tissue-specific and developmentally regulated pattern. the existence of vimentin filaments has been documented in oocytes, eggs, and early embryos of xenopus laevis, but the role of these cytoskeletal components remains unknown. to investigate the functions of vimentin during early development in xenopus, we induced the overexpression of wild-type and deletion mutant subunit ... | 1990 | 1704253 |
| heterogeneity in spinal radial glia demonstrated by intermediate filament expression and hrp labelling. | considerable evidence indicates that radial glial cells play an active role in guiding growing neurites during development of the vertebrate cns. in this paper we describe subpopulations of radial glial in the spinal cord of the axolotl. amphibians maintain radial glia throughout life, and subpopulations are described using anatomical criteria following filling of individual cells with horseradish peroxidase and immunocytochemical staining with a range of intermediate filament antibodies. radial ... | 1990 | 1705577 |
| evolution of immunoglobulin light chain genes: analysis of xenopus igl isotypes and their contribution to antibody diversity. | the amphibian xenopus laevis expresses several types of immunoglobulin light chain (igl). cdna clones for two igl isotypes, c sigma 1 and c sigma 2, were analysed. c sigma is expressed in spleen and mitogen-stimulated b cells, like another xenopus igl type, termed c rho. c sigma shares less than 33% residues with c rho or with cl regions of shark, chicken and mammals. this suggests that c sigma diverged from a common ancestor of cl regions before or at the emergence of amphibians. two families o ... | 1991 | 1705882 |
| purification and partial characterization of xenopus laevis tenascin from the xtc cell line. | we report here the purification of tenascin, an extracellular matrix molecule involved in the control of morphogenesis, from the conditioned medium of the xenopus xtc cell line. tenascin was purified by affinity chromatography on a column of the monoclonal antibody mab tnm1; the molecule eluted from this column has a relative molecular mass of 210 kda after reduction. electrophoretic analysis under non-reducing conditions shows that the purified components are oligomeric disulfide-linked complex ... | 1991 | 1705902 |
| isolation, characterization, and in vitro culture of larval and adult epidermal cells of the frog xenopus laevis. | methods for the isolation and in vitro culture of larval and adult xenopus laevis epidermal cells have been developed. epidermal cells of stage 52-54 tadpoles and adult epidermal cells were enzymatically dissociated and purified (98%) by percoll-density centrifugation and unit-gravity sedimentation. both cell types attached on fibronectin-coated dishes and proliferated for 1 wk when the proper medium was used. there were four significant differences between larval and adult cells: a) adult cells ... | 1990 | 1706696 |
| molecular cloning and characterization of a new member of the gap junction gene family, connexin-31. | a new member of the connexin gene family has been identified and designated rat connexin-31 (cx31) based on its predicted molecular mass of 30,960 daltons. cx31 is 270 amino acids long and is coded for by a single copy gene. it is expressed as a 1.7-kilobase mrna that is detected in placenta, harderian gland, skin, and eye. cx31 is highly conserved and can be detected in species as distantly related to rat as xenopus laevis. it exhibits extensive sequence similarity to the previously identified ... | 1991 | 1706719 |
| electrolyte transport through a cation-selective ion channel in large intestinal enterocytes of xenopus laevis. | electrogenic ion transport through the colon epithelium of the african clawed toad (xenopus laevis) was investigated with electrophysiological methods in vitro. interest was focused on a previously described phenomenon, that removal of ca2+ from the mucosal ringer's solution increases electrogenic sodium absorption. our results clearly show that ca2+ removal reveals an apical ion channel that is not a specific na+ channel, but a non-selective cation channel with an 'apparent' ion selectivity of ... | 1991 | 1707944 |
| location of a threonine residue in the alpha-subunit m2 transmembrane segment that determines the ion flow through the acetylcholine receptor channel. | by the combination of cdna manipulation and functional analysis of normal and mutant acetylcholine receptor (achr) channels of torpedo expressed in xenopus laevis oocytes determinants of ion flow were localized in the bends bordering the putative m2 transmembrane segment (imoto et al. 1988). we now report that in the rat muscle achr, substitution of a threonine residue in the alpha-subunit localized in the m2 transmembrane segment increases or decreases the channel conductance, depending on the ... | 1991 | 1708143 |
| a developmentally regulated, nervous system-specific gene in xenopus encodes a putative rna-binding protein. | a gene from xenopus laevis that is expressed specifically in the nervous system beginning at the stage of neural plate formation has been isolated and several cdnas have been sequenced. the sequence of the predicted protein contains two copies of a presumed rna-binding domain, each of which includes two short conserved motifs characteristic for ribonucleoproteins (rnps), called the rnp-1 and rnp-2 consensus sequences. we name this gene xenopus nrp-1, for nervous system-specific rnp protein-1. se ... | 1990 | 1708282 |
| injection of rna from carp retina induces the formation of a membrane potassium channel in xenopus oocytes. | total rna was purified from freshly isolated retinas of adult carp and injected into oocytes of xenopus laevis (stages 5-6). two to six days after injection, depolarizing voltage-clamp steps evoked a slowly activated outward current as large as 3 microa. this current inactivated slowly with a single time constant (tau = 3.1 +/- 0.24 s.e.m., for vm = +30 mv). the current was inhibited by tetraethylammonium (3.8 mm for half-maximal inhibition). in the presence of co2+ (1 mm) or barium methanesulfo ... | 1991 | 1709045 |
| expression of madin-darby canine kidney cell na(+)-and cl(-)-dependent taurine transporter in xenopus laevis oocytes. | expression of a madin-darby canine kidney (mdck) cell taurine transporter was examined in xenopus oocytes that had been injected with poly(a)+ rna extracted from mdck cells. compared with water-injected oocytes, injection of total poly(a)+ rna resulted in an increase in na(+)-dependent taurine uptake which was directly related to the amount of rna injected. the magnitude of expression in poly(a)+ rna-injected oocytes was 5-10-fold higher than that of water-injected oocytes. since the vmax of tau ... | 1991 | 1709638 |
| expression of cardiac na channels with appropriate physiological and pharmacological properties in xenopus oocytes. | the objective of this study was to determine whether the xenopus laevis oocyte can express an exogenous cardiac na channel that retains its normal physiological and pharmacological properties. cardiac na channels were expressed in oocytes following injection of rna from guinea pig, rat, and human heart and detailed analysis was performed for guinea pig cardiac na channels. average current amplitudes were -351 +/- 37 na with peak current observed at -8 +/- 1 mv. steady-state inactivation was half ... | 1991 | 1709733 |
| the low density lipoprotein receptor in xenopus laevis. i. five domains that resemble the human receptor. | all five functional domains of the low density lipoprotein (ldl) receptor were assembled in their modern form more than 350 million years ago, as revealed from the sequence of two cloned cdnas from the frog xenopus laevis. the two cdnas appear to represent duplicated copies of the ldl receptor gene that arose when the entire genome of xenopus duplicated approximately 30 million years ago. both frog ldl receptors bound xenopus ldl with high affinity and human ldl with lower affinity when expresse ... | 1991 | 1709931 |
| the low density lipoprotein receptor in xenopus laevis. ii. feedback repression mediated by conserved sterol regulatory element. | the 5'-flanking regions of the two low density lipoprotein (ldl) receptor genes in xenopus laevis contain three repeat sequences that are virtually identical to the repeats that mediate sterol-regulated transcription of the human ldl receptor gene. like their human counterparts, xenopus repeats 1 and 3, but not repeat 2, bind the transcription factor sp1 and thus probably function as positive transcription elements. xenopus repeat 2, like human repeat 2, contains all of the nucleotides that are ... | 1991 | 1709932 |
| a liver protein fraction regulating hormone-dependent in vitro transcription from the vitellogenin genes induces their expression in xenopus oocytes. | xenopus laevis oocytes were used to assay for trans-acting factors shown previously to be involved in the liver-specific regulation of the vitellogenin genes in vitro. to this end, crude liver nuclear extracts obtained from adult estrogen-induced xenopus females were fractionated by heparin-sepharose chromatography using successive elutions with 0.1, 0.35, 0.6, and 1.0 m kcl. when these four fractions were injected into oocytes, only the 0.6-m kcl protein fraction significantly stimulated mrna s ... | 1991 | 1710029 |
| the transcription of dna in chicken mitochondria initiates from one major bidirectional promoter. | transcription start sites of chicken mitochondrial dna have been mapped in the control region by direct sequencing of in vitro capped mitochondrial rna species, by primer extension and by s1 nuclease protection analysis. transcription of the heavy strand initiates predominantly at a site 156 nucleotides upstream of the trna(phe) gene, i.e. about 135 nucleotides further upstream than the corresponding sites in amphibia and mammals. on the opposite strand, transcription starts predominantly one nu ... | 1991 | 1710214 |
| an rna molecule copurifies with rnase p activity from xenopus laevis oocytes. | utilizing a procedure for the purification of rnase p from xenopus laevis germinal vesicle (gv) extracts, according to which the contamination by a large, cytoplasmic, cylindrical structure (1) is avoided, we demonstrate that the x.laevis enzyme, like the hela rnase p, is precipitated by anti-th antibodies and an rna molecule (xl rna), 320 nucleotides long, copurifies with the activity. the sequence of xl rna is 60% homologous to hela h1 rna, therefore the two molecules seem related. | 1991 | 1710353 |
| human elongation factor 1 beta: cdna and derived amino acid sequence. | from a cdna library in lambda gt11 derived from poly (a+)rna of human ovarian granulosa cells a cdna clone lambda hgp34, containing an ecori insert of 829 bp, was identified. after subcloning of the insert into puc18, the clone phgp34 was obtained and sequenced. the derived amino acid sequence, corresponding to a protein of 225 amino acids, shows a high degree of homology to elongation factor 1 beta (ef-1 beta) of artemia salina (57%) and known peptide sequences of xenopus laevis ef-1 beta (86%) ... | 1991 | 1710449 |
| heterodimeric capping proteins constitute a highly conserved group of actin-binding proteins. | the two subunits of the heterodimeric protein cap32/34, an actin-binding protein, are encoded by separate single-copy genes. we have established the genomic structure of both genes. a sequence comparison of cap32/34 with capz from chicken skeletal muscle and two partially known sequences from saccharomyces cerevisiae and xenopus laevis show that heterodimeric capping proteins belong to a highly conserved group of actin-binding proteins. this conclusion is supported by the cross-reaction of polyc ... | 1990 | 1710551 |
| antibodies to phosphotyrosine injected in xenopus laevis oocytes modulate maturation induced by insulin/igf-i. | xenopus oocytes carry igf-i receptors, and undergo meiotic maturation in response to binding of igf-i or insulin to the igf-i receptor. maturation is initiated upon activation of the igf-i receptor tyrosine kinase and requires tyrosine dephosphorylation of p34cdc2, the kinase component of maturation promoting factor (mpf). to further evaluate the role of tyrosine phosphorylation in the signalling pathway triggered by insulin/igf-i, we have injected antibodies to phosphotyrosine into oocytes and ... | 1991 | 1711470 |
| x121: a localized maternal transcript in xenopus laevis. | we describe the cloning and characterization of a partial cdna, x121, that represents an rna, which is localized in the animal hemisphere of xenopus oocytes. this rna is also detected in an animal to vegetal gradient during early cleavage stages. the x121 rna titer decreases from fertilization through the gastrula stage, after which it is not detectable on northern blots. the amino acid composition of the x121 conceptual protein derived from cdna sequencing reveals a large number of acidic resid ... | 1991 | 1712210 |
| fluorescent imaging in vivo of developing blood vessels on the optic tectum of xenopus laevis. | the growth and development of individual living capillaries, venules, and endothelial sprouts on the pial surface of the brain were examined with video microscopy and intravascular fitc-dextran in anesthetized tadpoles of pigment-deficient xenopus laevis, stages 42-50. the fluorescent tracer, injected intracardially through glass micropipets, was well tolerated by the tadpoles and improved the visibility of vessels compared to transmitted light. case histories of vascular development on the opti ... | 1991 | 1712891 |
| ca2+ modulates an unspecific cation conductance in olfactory cilia of xenopus laevis. | olfactory neurones of xenopus laevis were studied by the patch clamp technique under voltage-clamp conditions. isolated receptor cells were obtained by dissociating the olfactory mucosa in a ca(2+)-free solution. usually some of the resulting isolated olfactory cells lost all of their cilia during the dissociation procedure. comparing the currents of cells with cilia to those of cells without cilia, a marked difference was found. when all known voltage-gated currents except the ca(2+)-current we ... | 1991 | 1713170 |
| detection of two zn-finger proteins of xenopus laevis, tfiiia, and p43, by probing western blots of ovary cytosol with 65zn2+, 63ni2+, or 109cd2+. | two zn-finger proteins, tfiiia (a constituent of 7s rnp particles) and p43 (a constituent of 42s rnp particles), were detected in ovary extracts of juvenile xenopus laevis females by in vitro binding of radiolabeled divalent metals. proteins fractionated by sds-page (sodium dodecylsulfate-polyacrylamide gel electrophoresis) were transferred by western blotting onto nitrocellulose membranes, probed with 65zn2+, 63ni2+, or 109cd2+, and visualized by autoradiography. detection limits for tfiiia wer ... | 1991 | 1713475 |
| the polarized distribution of poly(a+)-mrna-induced functional ion channels in the xenopus oocyte plasma membrane is prevented by anticytoskeletal drugs. | foreign mrna was expressed in xenopus laevis oocytes. newly expressed ion currents localized in defined plasma membrane areas were measured using the two-electrode voltage clamp technique in combination with a specially designed chamber, that exposed only part of the surface on the oocytes to channel agonists or inhibitors. newly expressed currents were found to be unequally distributed in the surface membrane of the oocyte. this asymmetry was most pronounced during the early phase of expression ... | 1991 | 1713591 |
| expression of the neuronal noradrenaline transporter in xenopus laevis oocytes. | rna isolated from both rat phaeochromocytoma (pc12) cells and bovine adrenal medulla was size-selected and injected into oocytes of xenopus laevis. expression of the neuronal noradrenaline transporter was assayed 3 days after injection by measuring the nisoxetine-sensitive noradrenaline uptake. a 2 kilobase fraction of either total rna derived from both tissues or of polyadenylated mrna obtained from bovine adrenal medulla caused na(+)-dependent transport of 3h-noradrenaline in the injected oocy ... | 1991 | 1714043 |
| evidence for the involvement of microtubules, er, and kinesin in the cortical rotation of fertilized frog eggs. | during the first cell cycle, the vegetal cortex of the fertilized frog egg is translocated over the cytoplasm. this process of cortical rotation creates regional cytoplasmic differences important in later development, and appears to involve an array of aligned microtubules that forms transiently beneath the vegetal cortex. we have investigated how these microtubules might be involved in generating movement by analyzing isolated cortices and sections of xenopus laevis and rana pipiens eggs. first ... | 1991 | 1714912 |
| expression of renal na(+)-ca2+ exchange activity in xenopus laevis oocytes. | the expression of a renal na(+)-ca2+ exchanger by xenopus oocytes has been investigated. each oocyte was injected with 50 ng of poly(a)+ rna from either rat or rabbit kidney or with an equivalent volume of water. na(+)-ca2+ exchange was determined 3 days after injection, by measuring ca2+ uptake by oocytes in the presence or absence of an outwardly directed na+ concentration gradient. to manipulate na+ concentration gradients, oocytes were first loaded with na+ in ca(2+)-free medium containing 9 ... | 1991 | 1715130 |
| inward currents elicited by stream of fluid during transmitter-induced current oscillations in rna-injected oocytes of xenopus laevis. | a stream of fluid elicited an inward current in rna-injected oocytes of xenopus laevis during transmitter-induced current oscillations (stream evoked inward current, ii,st). the ii,st showed the following characteristics: (1) amplitude and duration (half width time) ranged between 10 and 300 na and 1 and 3 s, respectively. (2) the ii,st could be evoked only during transmitter-induced current oscillations; with blockade of the oscillations the ii,st disappeared. (3) the induction of the ii,st was ... | 1991 | 1715533 |
| two nonallelic insulin genes in xenopus laevis are expressed differentially during neurulation in prepancreatic embryos. | insulin, traditionally regarded as a metabolic hormone, also can potently stimulate growth and differentiation in many cell types. to study further the potential role of insulin during early embryogenesis, we have used the amphibian xenopus laevis, a versatile model of vertebrate development. using (i) nucleotide sequences of two previously cloned cdnas that correspond to two different nonallelic xenopus insulin genes (both of which are expressed in the adult pancreas) and (ii) a modification of ... | 1991 | 1715574 |
| expression cloning of a rat b2 bradykinin receptor. | a cdna encoding a functional bradykinin receptor was isolated from a rat uterus library by a clonal selection strategy using xenopus laevis oocytes to assay for expression of bradykinin responses. the predicted protein is homologous to the seven transmembrane g protein-coupled superfamily of receptors. bradykinin and its analogs stimulate a cl- current oocytes expressing the receptor with the rank order of potency: bradykinin approximately lys-bradykinin greater than [tyr8]-bradykinin much great ... | 1991 | 1715575 |
| inositol tetrakisphosphates as second messengers induce ca(++)-dependent chloride currents in xenopus laevis oocytes. | microinjection of inositol 1,3,4,5-tetrakisphosphate or inositol 1,4,5-trisphosphate induced distinct chloride membrane currents in defolliculated xenopus laevis oocytes. to decide whether these cl(-)-currents were due to the injected compounds or their metabolic products, [3h]ins(1,3,4,5)p4 or [3h]ins(1,4,5)p3 were injected into oocytes and their metabolites were analyzed by hplc. our results indicate that ins(1,3,4,5)p4 itself or its metabolite ins(1,3,4,6)p4 is able to induce cl(-)-membrane c ... | 1991 | 1715700 |
| functional expression of urea channels in amphibian oocytes injected with frog urinary bladder mrna. | in amphibian urinary bladder epithelium, vasopressin increases passive urea permeability, concomitant with the appearance of a facilitated urea transport. amphibian oocytes from xenopus laevis and rana esculenta were microinjected with total or fractionated poly(a+) rna isolated from frog urinary bladder epithelial cells. after several (3-5) days at 18 degrees c, the urea flux was assayed by measuring the uptake and efflux of [14c]urea in water-injected and mrna-injected oocytes. a 2 to 3-fold i ... | 1991 | 1715756 |
| mpf is activated in growing immature xenopus oocytes in the absence of detectable tyrosine dephosphorylation of p34cdc2. | tyrosine-phosphorylated p34cdc2 and cyclin b2 are present and physically associated in small growing stage iv oocytes (800 microns in diameter) of xenopus laevis. microinjection of m-phase promoting factor (mpf) into stage iv oocytes induces germinal vesicle breakdown and the activation of the kinase activity of the p34cdc2/cyclin b2 complex measured on p13suc1 beads. during the in vivo activation of mpf in stage iv oocytes, p34cdc2 tyrosine dephosphorylation is not detectable, in contrast to st ... | 1991 | 1716585 |
| avermectin-sensitive chloride currents induced by caenorhabditis elegans rna in xenopus oocytes. | avermectins are a family of potent broad-spectrum anthelmintic compounds, which bind with high affinity to membranes isolated from the free-living nematode caenorhabditis elegans. binding of avermectins is thought to modulate chloride channel activity, but the exact mechanism for anthelmintic activity remains to be determined. in this report, the properties of an avermectin-sensitive membrane current were evaluated in xenopus laevis oocytes that were injected with poly(a)+ rna from c. elegans. i ... | 1991 | 1716730 |
| reversal of rapid axonal transport at a lesion: leupeptin inhibits reversed protein transport, but does not inhibit reversed organelle transport. | the hypothesis that the reversal of rapid axonal transport requires a proteolytic conversion of anterograde transport vesicles was examined using sciatic nerve preparations from xenopus laevis and leupeptin as an inhibitor of proteolysis. the transport of newly synthesized 35s-labeled proteins was studied with a position-sensitive detector of radiation. organelle transport in isolated myelinated axons was studied by video microscopy. leupeptin (0.1-0.4 mm) reduced the anterograde-to-retrograde r ... | 1991 | 1717113 |
| xlpou 1 and xlpou 2, two novel pou domain genes expressed in the dorsoanterior region of xenopus embryos. | pou domain genes have been shown to be important in tissue-specific gene regulation during development. we have cloned cdna's encoding two unique xenopus laevis pou-domain proteins, xlpou 1 and xlpou 2. sequencing revealed that the pou domain of both of these genes have greater than 90% homology with that of the pou iii class of proteins. xlpou 1 gene expression begins at the neural plate stage, while xlpou 2 gene expression is first detected at the neurula stage; both xlpou 1 and xlpou 2 transc ... | 1991 | 1717323 |
| analysis of calcium activated chloride current fluctuations in xenopus laevis oocytes. | fluctuations of calcium activated chloride currents were investigated in oocytes of xenopus laevis. the method of noise analysis and the model of chloride channels activation by calcium ions were used to estimate the chloride channels lifetime and the average frequency of current fluctuations, which depends on changes of cytoplasmic calcium concentration. this current fluctuations can be evoked by activation of cholinergic receptors or inhibition by na3vo4 of plasma membrane ca(2+)-atpase. the a ... | 1991 | 1717342 |
| antimicrobial peptides in the stomach of xenopus laevis. | antimicrobial peptides are widely distributed in nature and appear to play a role in the host defense of plants and animals. in this study we report the existence of antimicrobial peptides in the stomach of the vertebrate xenopus laevis, an animal previously shown to store high concentrations of antimicrobial peptides in its skin. antimicrobial activity was detected in extracts of x. laevis stomach tissue and nine antimicrobial peptides were then purified. a novel 24-amino acid peptide, designat ... | 1991 | 1717472 |
| three-dimensional model of escherichia coli ribosomal 5 s rna as deduced from structure probing in solution and computer modeling. | the conformation of escherichia coli 5 s rrna was investigated using chemical and enzymatic probes. the four bases were monitored at one of their watson-crick positions with dimethylsulfate (at c(n-3) and a(n-1], with a carbodiimide derivative (at g(n-1) and u(n-3] and with kethoxal (at g(n-1, n-2]. position n-7 of purine was probed with diethylpyrocarbonate (at a(n-7] and dimethylsulfate (at g(n-7]. double-stranded or stacked regions were tested with rnase v1 and unpaired guanine residues with ... | 1991 | 1717695 |
| [concanavalin-binding proteins and cytokeratins in different tissues of the early amphibian gastrula (rana temporaria, xenopus laevis)]. | concanavalin a (con a), a lectin which specifically interacts with ad-mannose and ad-glucose, has a neutralizing effect on the explants of the early gastrula ectoderm of several amphibian species. consequently, it was interesting to study con a-binding protein spectrum of the ectoderm and compare it to those of other early gastrula tissues. animal pole ectoderm (ape), dorsal blastopore lip (dbl) and vegetal pole endoderm (vpe) were dissected from early gastrulae of rana temporaria and xenopus la ... | 1991 | 1717912 |
| coexpression of alpha 1 with putative beta 3 subunits results in functional na+/k+ pumps in xenopus oocytes. | the active na+/k+ pump is composed of an alpha and a beta subunit. until now, three putative isoforms of the beta subunit have been identified that share sequence similarity. we have expressed the beta 1 and beta 3 isoforms of xenopus laevis na+/k(+)-atpase in xenopus oocytes to compare functional properties of the na+/k+ pump, including either of these two isoforms. na+/k+ pump current, estimated as k(+)-induced outward current in voltage-clamped oocytes, was doubled by coexpression of alpha 1 ... | 1991 | 1717977 |
| binding studies of gold labelled lectins on carbohydrate compounds of the flask cells in claw-frog kidney. | the carbohydrate compounds of the mucus of flask cells in the kidney of claw-frogs (xenopus laevis) were studied by gold marked lectins (wga, rca, l, lca, hpa, pna). we used a post-embedding technique. seminthin or ultrathin sections of lowieryl k h m-embedded kidney tissue were incubated. for light microscopy, a gold-silver technique was used. the mucus of the flask cells reacted strongly with wga, rca l and hpa, whereas lca and pna showed no binding. the golgi apparatus and small cytoplasmatic ... | 1991 | 1718121 |
| localization of calmodulin in epidermis and skin glands: a comparative immunohistological investigation in different vertebrate species. | the study deals with the immunolocalization of calmodulin-reactive epithelial cells in different vertebrates (tinca tinca, ambystoma mexicanum, xenopus laevis, rana ridibunda, columba domestica, sus scrofa domestica, homo sapiens sapiens). the immunoperoxidase technique was performed on acetone fixed frozen sections using monoclonal (bf8) and polyclonal (acam) anti-calmodulin antibodies. we were able to differentiate 2 major types of staining patterns: 1. a more superficial epidermal staining in ... | 1991 | 1718122 |
| identification of the cdna for xlcaax-1, a membrane associated xenopus maternal protein. | xlcaax-1 is a cdna coding for a caax box containing protein in xenopus laevis that undergoes isoprenylation and palmitoylation. here we report on the confirmation that this clone (formerly xlgv7) codes for a 110 kda membrane associated protein and not an 80 kda nuclear protein as originally believed (1). the reason for the misidentification was the presence of a common epitope on these two proteins recognized by the monoclonal antibody 37-1a9. we clarified the discrepancy by raising polyclonal a ... | 1991 | 1718271 |
| molecular cloning and expression of ferritin mrna in heavy metal-poisoned xenopus laevis cells. | in a search for genes transcriptionally regulated by metal ions, we have isolated a xenopus laevis ferritin cdna clone, xl2-17, from cadmium-poisoned xl2 cells. the large size of the corresponding ferritin mrna (1.4 kb) is due to the presence of a 629-nucleotide 5'-untranslated region. the xenopus ferritin sequence is highly isologous with other vertebrate ferritins. in particular, there is a complete sequence identity for the iron-responsive element (ire) located in the 5'-untranslated region i ... | 1991 | 1718317 |