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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 ...19911717323
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 ...19911717342
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 ...19911717472
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 ...19911717695
[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 ...19911717912
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 ...19911717977
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 ...19911718121
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 ...19911718122
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 ...19911718271
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 ...19911718317
membrane currents elicited by the epileptogenic drug pentylenetetrazole in the native oocyte of xenopus laevis.the effects of the epileptogenic agent pentylenetetrazole (ptz) on membrane currents of native oocytes of xenopus laevis were studied. ptz elicits a response that consists of two inward currents. the first one is interpreted to be due to a decrease of potassium permeability since: (1) the input resistance is increased; (2) the equilibrium potential is near that of potassium; (3) the current is decreased during administration of potassium channel blocking agents; and (4) the ptz response can be m ...19911718540
biosynthesis, primary structure and molecular cloning of snowdrop (galanthus nivalis l.) lectin.poly(a)-rich rna isolated from ripening ovaries of snowdrop (galanthus nivalis l.) yielded a single 17-kda lectin polypeptide upon translation in a wheat-germ cell-free system. this lectin was purified by affinity chromatography. translation of the same rna in xenopus leavis oocytes revealed a lectin polypeptide which was about 2 kda smaller than the in vitro synthesized precursor, suggesting that the oocyte system had removed a 2-kda signal peptide. a second post-translational processing step w ...19911718752
functional expression of a human c5a receptor clone in xenopus oocytes requires additional rna.crna from a pcr-generated c5ar clone was prepared by in vitro transcription and microinjected into xenopus laevis oocytes. ligand-induced whole cell current could be detected after co-injection of crna for the c5ar with total rna of the unstimulated u937 cell line, but not with either of the components injected alone. these data clearly demonstrate an absolute requirement of the c5ar for an additional human factor to become functionally expressed in xenopus oocytes.19911718782
heterologous regulation of the cardiac ca2+ channel alpha 1 subunit by skeletal muscle beta and gamma subunits. implications for the structure of cardiac l-type ca2+ channels.high threshold l-type ca2+ channels of skeletal muscle are thought to consist of a complex of alpha 1, alpha 2 delta, beta, and gamma subunits. expression of the cloned alpha 1 subunit from skeletal and cardiac muscle has established that this protein is the dihydropyridine-sensitive ion-conducting subunit. however, the kinetics of the skeletal muscle alpha 1 alone expressed in mouse l-cells were abnormally slow and were accelerated to within the normal range by coexpression with the skeletal mu ...19911718988
distribution of galanin-like immunoreactivity in the brain of rana esculenta and xenopus laevis.the immunocytochemical distribution of galanin-containing perikarya and nerve terminals in the brain of rana esculenta and xenopus laevis was determined with antisera directed toward either porcine or rat galanin. the pattern of galanin-like immunoreactivity appeared to be identical with antisera directed toward either target antigen. the distribution of galanin-like immunoreactivity was similar in rana esculenta and xenopus laevis except for the absence of a distinct laminar distribution of imm ...19911719037
calcium regulation of epidermal cell differentiation in the frog xenopus laevis.adult frogs have a stratified epidermis with a keratinized stratum corneum. since the extracellular calcium concentration is known to regulate differentiation of mammalian epidermal cells in vitro, we studied the effects of calcium on the terminal differentiation of frog epidermal cells. exposure of the epidermal cells to a high concentration of calcium (greater than 0.2 mm) induced cornification and the synthesis of a 51 kd acidic keratin. these data are very similar to the results from mammali ...19911719122
up-regulation of sodium pump activity in xenopus laevis oocytes by expression of heterologous beta 1 subunits of the sodium pump.recent evidence suggests that the beta subunit of the na+ pump is essential for the alpha subunit to express catalytic activity and for assembly of the holoenzyme in the plasma membrane. we report here that injection into xenopus laevis oocytes of crnas specific for beta 1 subunit isoforms of the na+ pump of four species (torpedo californica, chicken, mouse and rat) causes a time-dependent increase in the number of ouabain-binding sites, both in the plasma membrane and in internal membranes. exp ...19911719955
expression of adult and tadpole specific globin genes from xenopus laevis in transgenic mice.transgenic mice were generated which carried the adult alpha and beta-globin genes and the major tadpole specific beta-globin gene of xenopus laevis. the adult specific alpha and beta genes were found to express in erythroid tissues in adult mice, while the major tadpole specific beta gene (beta t1) was expressed in blood from 12.5 day embryos. the pattern of expression of the beta t1 gene during mouse development was consistent with its being regulated as an embryonic globin gene in the mouse. ...19911720238
distribution and expression of two interactive extracellular matrix proteins, cytotactin and cytotactin-binding proteoglycan, during development of xenopus laevis. i. embryonic development.an immunohistochemical study of the localization of cytotactin and cytotactin-binding (ctb) proteoglycan throughout embryonic development of the anuran xenopus laevis reveals that both appear in a restricted pattern related to specific morphogenetic events. ctb proteoglycan expression is first detected during gastrulation at the blastopore lip. later, it is seen in the archenteron roof around groups of cells forming the notochord, somites and neural plate. cytotactin first appears after neurulat ...19911720464
distribution and expression of two interactive extracellular matrix proteins, cytotactin and cytotactin-binding proteoglycan, during development of xenopus laevis. ii. metamorphosis.during metamorphosis of xenopus laevis the extracellular matrix (ecm) proteins cytotactin and cytotactin-binding (ctb) proteoglycan and the cell adhesion molecules n-cam and ng-cam, appear in highly restricted patterns determined by immunofluorescence histology. during limb development, cytotactin appears from the earliest stages in a meshwork of ecm fibrils associated with migrating mesenchymal cells forming the limb bud. cytotactin also appears in the ecm between the apical limb ectoderm and m ...19911720465
xenopus c-raf proto-oncogene: cloning and expression during oogenesis and early development.we have isolated and characterized a cdna which contains the entire coding sequence of xenopus laevis raf protein. raf mrna is identified as a member of the class of maternal rnas. it is already relatively abundant at the beginning of oogenesis and is stable at least until the midblastula transition. the rna is also detected later during embryogenesis in particular in gastrula, neurula, tailbud and feeding tadpole. we have also found the rna in several adult tissues (skin, testis, stomach, intes ...19911721855
characterization of xenopus laevis proenkephalin gene.enkephalins are opiate peptides found in a variety of tissues including brain and pituitary. in brain, they function as neurotransmitters, neuromodulators and neurohormones. recent studies show that proenkephalin mrna is expressed early in development both in mammals and the amphibian, suggesting that enkephalins may play a unique role in embryogenesis. in order to characterize factors which regulate the onset and patterning of expression of this gene in adult and developing frog embryos, the pr ...19911721992
recording of voltage and ca(2+)-dependent currents in xenopus oocytes using an intracellular perfusion method.we describe a method for internal perfusion of xenopus laevis oocytes that allows control of the composition of intracellular and extracellular solutions, including the possibility of sequential introduction of different substances inside and outside the cell. using this method, it was possible to record ca2+ dependent cl- current and to inhibit it by intracellular perfusion of egta-containing solution. with a high ba2+ solution at the external surface of the perfused oocyte, ba2+ currents throu ...19911722267
completely functional double-barreled chloride channel expressed from a single torpedo cdna.we have performed an electrophysiological analysis of the recently cloned torpedo marmorata cl- channel. functional expression of cl- channels in oocytes of xenopus laevis previously injected with crna yielded an outward-rectifying current activated by hyperpolarization. replacement of cl- with other anions significantly reduced or inhibited the current. single-channel recordings from cell-attached patches exhibited burst-like cl- channel activity with rapid fluctuations between three equally sp ...19911722317
cloning and functional characterization of a novel mas-related gene, modulating intracellular angiotensin ii actions.the mas oncogene codes for a gtp binding protein-coupled receptor that determines a physiological response to angiotensin when expressed in xenopus laevis oocytes or in the neuronal cell line ng115-401l. however, another gene, rat thoracic aorta gene, structurally related to mas, is devoid of any functional similarity with the angiotensin receptor(s). the relationships between the mas-related proteins and the angiotensin receptors were investigated by identifying and characterizing new members o ...19911723144
the potassium channel mbk1 (kv1.1) is expressed in the mouse retina.1. the neurons of the retina have electrical properties that are different from those of most of the other neurons of the central nervous system. to identify the voltage-gated ion channels found in the retina, we screened mouse retinal cdna libraries with oligonucleotide probes homologous to the mammalian k+ channel mbk1 (kv1.1) and ligated two partial clones to produce a full-length clone with no significant differences from mbk1. 2. expression of mbk1 mrna was determined by rnase protection. m ...19911723658
nuclear translocation of fibroblast growth factor during xenopus mesoderm induction.mesoderm induction, the earliest inductive cell-cell interaction in vertebrate embryogenesis, is thought to be mediated by polypeptide growth factors including fibroblast growth factor (fgf). here we present an immunocytochemical analysis of fgf during mesoderm induction in xenopus laevis. antibodies to both basic and acidic fgf were immunoreactive with oocytes and early embryos. immunostaining was predominantly intracellular and was concentrated in the marginal zone and vegetal pole throughout ...19911723679
labeling of developing vascular endothelium after injections of rhodamine-dextran into blastomeres of xenopus laevis.the goal of this work has been to label endothelial cells with fluorescent marker and to record their behavior during angiogenesis in vivo. single blastomeres in 16-128-cell-stage embryos of pigment-deficient xenopus laevis were injected intracellularly with 5% tetramethyl-rhodamine dextran. subsequently, the embryos and tadpoles were examined with an epifluorescence microscope, a silicon-intensified target (sit) camera, and video recordings. clones that would include endothelium could be select ...19911723747
argiotoxin636 inhibits nmda-activated ion channels expressed in xenopus oocytes.argiotoxin636, a component of the spider venom of argiope species, was chemically synthesized together with a number of derivatives in order to analyse their blocking activity on mammalian glutamate receptors. xenopus laevis oocytes injected with rat brain mrna served as assay system. the results showed that argiotoxin636 had a higher affinity for n-methyl-d-aspartate (nmda) than for kainate receptors, blocking the corresponding ion channels in a voltage-dependent manner. modifications of the po ...19911723790
inhibitors of phosphodiesterase iii block stimulation of xenopus laevis oocyte ribosomal s6 kinase activity by insulin-like growth factor-i.insulin-like growth factor-i (igf-i) stimulated xenopus laevis oocyte ribosomal s6 kinase activity 5- to 10-fold, with an apparent ec50 of 0.8 +/- 0.1 nm after 90 min of hormone treatment. igf-i-stimulated enzyme activity was inhibited by treatment of oocytes with nonselective phosphodiesterase (pde) inhibitors, with apparent ic50 values of 2 +/- 1 microm papaverine, 20 +/- 2 microm isobutylmethylxanthine, and 128 +/- 16 microm theophylline. type iii pde inhibitors also inhibited igf-i-stimulate ...19911724288
toward a more complete 3-d structure of the nuclear pore complex.the nuclear pore complex (npc) is a large supramolecular assembly embedded in the double-membraned nuclear envelope (ne) that plays a pivotal role in the exchange of macromolecules and particles between the nucleus and the cytoplasm. applying various methods of sample preparation to xenopus laevis whole nuclei and isolated nes in combination with conventional transmission electron microscopy and digital image processing, we have characterized several distinct components of the npc, including mas ...19911725493
histological preparation of xenopus laevis oocytes and embryos. 19911725801
molecular aspects of the neuronal noradrenaline transporter.the neuronal noradrenaline transporter was partially purified by means of low and high pressure liquid chromatography using anion exchange, gel filtration and lectin affinity columns. a protein characterized by a molecular weight of 50-53 kilodalton was enriched; it may represent the transporter or a component of it. in addition, a rna fraction characterized by a mean size of 2 kilobases was isolated from pc12 rat phaeochromocytoma cells and from bovine adrenal medulla; this rna fraction caused ...19911726219
teratogenicity of ni2+ in xenopus laevis, assayed by the fetax procedure.the teratogenicity of ni2+ was tested by the fetax (frog embryo teratogenesis assay: xenopus) procedure in the south african frog, xenopus laevis. in seven assays, beginning at 5 h postfertilization, groups of xenopus embryos were incubated for 96 h in media that contained ni2+ (added as nicl2) at concentrations ranging from 1 x 10(-7) to 3 x 10(-3) mol/l; control groups were incubated in the same medium without added nicl2. at 101 h postfertilization, surviving embryos were counted, fixed in fo ...19911726404
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 ...19911702514
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 ...19911702515
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 ...19911709045
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 ...19911709638
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 ...19911709733
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 ...19911709931
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 ...19911709932
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 ...19911710029
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 ...19911710214
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.19911710353
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%) ...19911710449
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 ...19911705882
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 ...19911705902
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 ...19911704128
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 ...19911704219
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 ...19911703301
gene activation in the amphibian mesoderm.cell potency is progressively restricted in amphibian development by a series of cellular interactions called inductions. the mesoderm is believed to develop in response to the earliest known induction, in which vegetal cells of the blastula divert overlying animal hemisphere cells away from epidermal and towards mesodermal fates. we describe two early markers of mesodermal differentiation in xenopus laevis, both mrnas that encode dna-binding proteins of the helix-loop-helix family. one is a fro ...19911742502
rhythmic regulation of retinal melatonin: metabolic pathways, neurochemical mechanisms, and the ocular circadian clock.1. current knowledge of the mechanisms of circadian and photic regulation of retinal melatonin in vertebrates is reviewed, with a focus on recent progress and unanswered questions. 2. retinal melatonin synthesis is elevated at night, as a result of acute suppression by light and rhythmic regulation by a circadian oscillator, or clock, which has been localized to the eye in some species. 3. the development of suitable in vitro retinal preparations, particularly the eyecup from the african clawed ...19911742771
bombinin-like peptides with antimicrobial activity from skin secretions of the asian toad, bombina orientalis.the structures and hemolytic and bactericidal activities of three bombinin-like peptides, or blp-1-3, from the skin of bombina orientalis are described. the peptides were isolated from the skin of b. orientalis and sequenced by tandem mass spectrometry and are amphipathic, cationic peptides of 25-27 amino acids in length. the sequence of the most abundant member (blp-1) is: gly-ile-gly-ala-ser-ile-leu-ser-ala-gly-lys-ser-ala-leu-lys-gly-leu- ala-lys-gly-leu-ala-glu-his-phe-ala-asn-nh2. all three ...19911744108
purification and characterization of a germ cell-specific form of elongation factor 1 alpha (ef-1 alpha) from xenopus laevis.elongation factor 1 alpha (ef-1 alpha) was purified to homogeneity from full-grown oocytes of xenopus laevis. this protein is encoded by a gene previously shown to be expressed in male and female germ cells, and repressed in somatic cells. the purified protein was identified with ef-1 alpha on criteria of molecular mass, cross-reaction with antibodies raised against artemia salina ef-1 alpha, affinity for guanine nucleotides, and ability to promote the mrna-dependent binding of aminoacyl trna to ...19911747390
induction of metamorphosis by thyroid hormone in anuran small intestine cultured organotypically in vitro.we have developed an organ culture system of the anuran small intestine to reproduce in vitro the transition from larval to adult epithelial form which occurs during spontaneous metamorphosis. tubular fragments isolated from the small intestine of xenopus laevis tadpoles were slit open and placed on membrane filters in culture dishes. in 60% leibovitz 15 medium supplemented with 10% charcoal-treated serum, the explants were maintained in good condition for at least 10 days without any morphologi ...19911748625
purified estrogen receptor dna binding domain expressed in escherichia coli activates transcription of an estrogen-responsive promoter in cultured cells.the region of the xenopus laevis estrogen receptor responsible for interaction with dna, the dna binding domain (dbd), has been cloned and overexpressed in escherichia coli using a t7 rna polymerase expression system. extracts from cells transformed with the dbd expression vector contain a single protein which reacts with polyclonal antibodies to estrogen receptor and exhibits sequence-specific binding to a dna fragment containing a consensus estrogen response element. the dbd protein has been p ...19911748680
sequence requirements for embryonic transcriptional activation of a gastrula-specific actin gene in xenopus laevis.cytoskeletal actin genes undergo developmentally timed transcriptional activation at the gastrula stage of embryonic development in the amphibian xenopus laevis. to study the regulation of this process, a molecularly marked cloned actin gene has been introduced into living embryos by microinjection, and levels of its transcripts (which are distinct from endogenous actin message) have been measured by rnase protection. in vitro mutagenesis of the marked gene, followed by microinjection and transc ...19911751033
cytochemical evidence of an organized microtubular cytoskeleton in xenopus laevis oocytes: involvement in the segregation of mitochondrial populations.an organized microtubular cytoskeleton was discovered in the cytoplasm of xenopus laevis oocytes. the microtubules were observed in 10- to 30-micron cryostat sections by indirect immunoperoxidase labeling using an antibody to tubulin. a gradual extraction of cells with a nonionic detergent was essential for good penetration of the antibody into the cells. in the cytoplasm of all previtellogenic oocytes, a dense network of criss-crossed long microtubules was associated in a basket-like structure ...19911751040
cloning, sequencing, and expression of two xenopus laevis c-ets-2 protooncogenes.in a general approach to identify genes important in the control of genetic expression during development of xenopus laevis, two complementary dnas corresponding to two different c-ets-2 genes were cloned and sequenced. one of these complementary dnas appears to be almost full length. the two variant genes differ in their overlapping sequences by 87 nucleotide substitutions, leading to 17 amino acid modifications in the proteins, 8 of them being conservative. all but one of these changes map out ...19911751411
regenerative capacity of retinal cells and the maintenance of their differentiation.mechanisms underlying cell type stability and the capacity of retinal cells for transdifferentiation are discussed. it is shown that cells of amphibian pigmented epithelium can be transformed into retina or lens cells depending on the inducing cell type: the influence of retina enables them to be transformed into retina, the influence of lens epithelium, to lens cells (lentoids or lenses). this led to an attempt to discover the molecular character of cell action by means of transfilter induction ...19911752164
formation of 6 beta-hydroxydexamethasone from dexamethasone by a6 cells.a6 cells, a continuous cell line derived from kidney of xenopus laevis, were incubated with [3h]-dexamethasone for 24 h. when radioactive compounds in media were separated by reversed phase high pressure liquid chromatography, two radioactive fractions were found. the less polar fraction which contained 91-93% of total radioactivity cochromatographed with dexamethasone, whereas the polar fraction contained 5% of total radioactivity in media. in order to rigorously identify the polar metabolite, ...19911752231
expression of the hepatocellular chloride-dependent sulfobromophthalein uptake system in xenopus laevis oocytes.the expression of the basolateral chloride-activated organic anion uptake system of rat hepatocytes has been studied in xenopus laevis oocytes. injection of oocytes with rat liver poly(a)+rna resulted in the functional expression of chloride-dependent sulfobromophthalein (bsp) uptake within 3-5 d. this expressed chloride-dependent bsp uptake system exhibited saturation kinetics (apparent km approximately 6.2 microm) and efficiently extracted bsp from its binding sites on bsa. furthermore, the ch ...19911752967
a highly efficient, cell-free translation/translocation system prepared from xenopus eggs.we describe the use of a xenopus laevis egg extract for the in vitro translation and post translational modification of membrane and secretory proteins. this extract is capable of the translation and segregation into membranes of microgram per millilitre levels of protein from added mrnas. signal sequences of segregated proteins are efficiently cleaved and appropriate n-linked glycosylation patterns are produced. the extract also supports the quantitative assembly of murine immunoglobulin heavy ...19911754376
masses of inositol phosphates in resting and tetanically stimulated vertebrate skeletal muscles.the masses of inositol phosphates have been determined in isolated skeletal muscles from xenopus laevis (sartorius, tibialis anterior and iliofibularis) and rat (gastrocnemius and soleus) which were quick-frozen in the resting state and at different stages of an isometric (xenopus) or isotonic (rat) tetanus. the isomeric spectrum of inositol phosphates detected was similar to that in other tissues and cell types. the total sarcoplasmic concentrations of the isomers ins-(1,4,5,6)p4/ins(3,4,5,6)p4 ...19911764026
functional expression of transcobalamin ii cdna in xenopus laevis oocytes.the products of in vitro transcription of human transcobalamin ii (tc ii) cdna when microinjected into xenopus laevis oocytes yielded a single secretory protein of 43 kda. the mobility of the 43 kda band did not change following digestion with peptide n-glycosidase f. [57co]cbl bound to the medium was immunoprecipitated with anti-serum to human tc ii, but not to other cbl binders. in addition, the [57co]cbl complex also bound to placental microsomes. these results suggest that tc ii mrna transcr ...19911764066
molecular cloning of human xpac gene homologs from chicken, xenopus laevis and drosophila melanogaster.we cloned homologs of the human xeroderma pigmentosum group a complementing (xpac) gene from chicken, xenopus laevis and drosophila melanogaster. a comparison of the amino acid sequences of these homologs with that of the human xpac protein revealed that in the nh2-terminal domain there are only two conserved regions, one of which is presumed to function as the nuclear localization signal, whereas the cooh-terminal domain is highly conserved, the frequency of identical amino acids in all four xp ...19911764072
amino terminal sequence of the mitochondrial protein mtdbp-c: similarity with nonhistone chromosomal proteins hmg 1 and 2.we have previously reported the characterization of a dna-binding protein isolated from xenopus laevis mitochondria (mtdbp-c). the amino terminal sequence of this protein (26 residues) has been determined by automated edman degradation and used to search for sequence similarity with the nbrf library. a segment of 17 amino acids displays 47.1% of identity with proteins hmg-1 and 2 of various vertebrate species.19911764507
isolation and characterization of the gene encoding ef-1 alpha o, an elongation factor 1-alpha expressed during early development of xenopus laevis.in xenopus laevis, the gene encoding the elongation factor 1-alpha variant ef-1 alpha o, where o stands for oocyte, is expressed in oocytes and early embryos. a genomic library from x. laevis was screened with a cdna probe coding for ef-1 alpha o. two recombinant phages were isolated, one of which carries an entire ef-1 alpha o gene. this clone was characterized by restriction enzyme mapping and sequencing. comparison of cdna and genomic sequences revealed that ef-1 alpha o consists of seven exo ...19911765266
neural regulation of calmodulin in adult xenopus leg muscle.two ca(2+)-binding proteins important in regulating muscle responses to ca2+ flux are differentially expressed following denervation of xenopus laevis gastrocnemius. levels of parvalbumin (pv) rna transcripts and proteins decrease in abundance, while calmodulin (cam) transcript and protein levels increase. our studies on pv kinetics in xenopus follow a pattern observed in other species, however, our observation of a concomitant increase in cam has not been documented in any system. molecular ana ...19911769061
chromosome banding in amphibia. xvi. high-resolution replication banding patterns in xenopus laevis.high-resolution replication banding patterns were induced in prometaphase and prophase chromosomes of xenopus laevis by treating kidney cell lines with 5-bromodeoxyuridine (brdu) and deoxythymidine (dt) in succession. up to 650 early and late replicating bands per haploid karyotype were demonstrated in the very long prophase chromosomes. this permits an exact identification of all chromosome pairs of x. laevis. late replicating heterochromatin was located by analysing the time sequence of replic ...19911769277
patterns of microtubule polymerization relating to cortical rotation in xenopus laevis eggs.following fertilization, the xenopus egg cortex rotates relative to the cytoplasm by 30 degrees about a horizontal axis. the direction of rotation, and as a result the orientation of the embryonic body axes, is normally specified by the position of sperm entry. the mechanism of rotation appears to involve an array of aligned microtubules in the vegetal cortex (elinson and rowning, 1988, devl biol. 128, 185-197). we performed anti-tubulin immunofluorescence on sections to follow the formation of ...19911769322
inductive differentiation of two neural lineages reconstituted in a microculture system from xenopus early gastrula cells.neural induction of ectoderm cells has been reconstituted and examined in a microculture system derived from dissociated early gastrula cells of xenopus laevis. we have used monoclonal antibodies as specific markers to monitor cellular differentiation from three distinct ectoderm lineages in culture (n1 for cns neurons from neural tube, me1 for melanophores from neural crest and e3 for skin epidermal cells from epidermal lineages). cns neurons and melanophores differentiate when deep layer cells ...19911769329
cell rearrangement during gastrulation of xenopus: direct observation of cultured explants.we have analyzed cell behavior in the organizer region of the xenopus laevis gastrula by making high resolution time-lapse recordings of cultured explants. the dorsal marginal zone, comprising among other tissues prospective notochord and somitic mesoderm, was cut from early gastrulae and cultured in a way that permits high resolution microscopy of the deep mesodermal cells, whose organized intercalation produces the dramatic movements of convergent extension. at first, the explants extend witho ...19911769334
demonstration of dopamine in electron-dense synaptic vesicles in the pars intermedia of xenopus laevis, by freeze substitution and postembedding immunogold electron microscopy.the presence of dopamine in the pituitary of the clawed toad xenopus laevis was studied by light and electron microscope immunocytochemistry, using pre- and postembedding techniques. light microscopy showed the presence of an intricate, anti-dopamine-positive fibre network throughout the pars intermedia. in preembedded stained material, dopamine appeared to occur in varicosities which make synaptic contacts with both folliculo-stellate cells and melanotrope cells. post-embedding immunogold stain ...19911769861
isolation and characterization of a monosialosylgangliopentaosyl ceramide from xenopus laevis oocyte.a monosialosylgangliopentaosyl ceramide was isolated from xenopus laevis oocytes. it represented 5.8% of the total acidic glycosphingolipids. from the results of sugar-composition analysis, enzymatic hydrolysis, permethylation analysis, and negative ion fast atom bombardment mass spectrometry, the structure of the ganglioside was determined to be as follows: [sequence: see text] the predominant species of fatty acids were alpha-hydroxy fatty acids, h22:0, h24:0, and h24:1. the long chain bases o ...19911769969
non-thermal vasodilatation by radio frequency burst-type electromagnetic field radiation in the frog.1. when the web of the anaesthetized xenopus laevis was perfused with ringer solution maintained at 20 degrees c, radio frequency (rf) burst-type electromagnetic (em) field radiation not only dilated arterioles of the web which had been preconstricted with noradrenaline, but also dilated arterioles under non-stimulated conditions. the em field-induced vasodilatation increased slowly and reached a plateau 60 min after the onset of radiation. after the cessation of radiation, vasodilatation remain ...19911770439
muscle differentiation in xenopus laevis is characterized by particular states of vinculin phosphorylation.vinculin is a 130 kd cytoskeletal protein which is involved in the anchorage of actin microfilaments to the plasma membranes at sites of cell-cell and cell-matrix contacts. in this paper we prove that smooth and cardiac muscles of xenopus laevis contain a specific isoform of vinculin not present in any other tissue including skeletal muscle and epithelia and we demonstrate that this form of the molecule is characterized by a specific state of phosphorylation. these data are discussed in view of ...19911773358
faithful in vivo transcription termination of xenopus laevis rdna. correlation of electron microscopic spread preparations with s1 transcript analysis.dna sequencing and subsequent functional in vitro analysis of the xenopus laevis rdna transcription termination has led to the identification of three transcription termination sequence elements: t1, located at the 3' end of the 28s rdna; t2, a putative processing site 235 bp downstream of t1; t3, the principal terminator positioned 215 bp upstream of the gene promoter. as demonstrated for nuclear run-off assays, t3 was found to be the main terminator for xenopus rdna transcription. these in vit ...19911773661
basolateral uptake and tubular metabolism of l-citrulline in the isolated-perfused non-filtering kidney of the african clawed toad (xenopus laevis).the kidney forms arginine (arg) by using citrulline (cit) as precursor, and is the main source of arg for systemic protein synthesis. even if the filtered and reabsorbed load (in rats) is sufficient for normal arg synthesis, the following questions remain. (a) can cit be taken up across the contraluminal membrane of the tubule cells also? if so, (b) by what kind of mechanism? and (c) is this cit, entering the cell from the peritubular side, metabolized to arg and ornithine (orn)? although these ...19911775371
on leaking into the lumen, amino acids cross the tubule cells. secretion of l-citrulline in the isolated-perfused non-filtering kidney of the african clawed toad (xenopus laevis).in our previous studies we were able to show that l-citrulline is taken up across the contraluminal membrane into the tubule cells of the isolated perfused non-filtering kidney of the african clawed toad (xenopus laevis). we have also described the tubular metabolism of the l-citrulline taken up. the remaining question was whether peritubular l-citrulline gains access to the tubular lumen and, if so, by what kind of mechanism. the method was the same as that described in our previous study: the ...19911775372
neuronal nicotinic acetylcholine receptors expressed in xenopus oocytes: role of the alpha subunit in agonist sensitivity and desensitization.neuronal nicotinic acetylcholine receptors (nachrs) were expressed in xenopus laevis oocytes after nuclear injection of complementary deoxyribonucleic acid (cdna) expression vectors. the two receptor subtypes alpha 4/n alpha 1 and alpha 3/n alpha 1 were readily distinguishable from one another by ach sensitivity and desensitization. alpha 3/n alpha 1 receptors showed lower ach sensitivity and stronger desensitization than alpha 4/n alpha 1 receptors. furthermore, although the current/voltage rel ...19911775381
nerve cells of drosophila notch mutant are differentiated inside amphibian brain: a new approach for the analysis of genetic control of nerve cell differentiation.fragments of the neural primordium of a new notch mutant of drosophila melanogaster produced in our laboratory were transplanted into the neural tube of embryos of 4 amphibian species (caudate and ecaudate) immediately after completion of neurulation. the grafts were identified by using a light microscope, scanning electron miscroscope, and in situ hybridization with mobile genetic elements of drosophila and fluorescent dyes as markers. as has been shown, drosophila nerve cells survive and diffe ...19911778472
embryotoxicity and teratogenicity of cadmium chloride in xenopus laevis, assayed by the fetax procedure.the embryotoxicity and teratogenicity of cadmium chloride (cdcl2) were tested by the fetax (frog embryo teratogenesis assay: xenopus) procedure in the south african frog, xenopus laevis. in five assays, groups of xenopus embryos were grown in media that contained cdcl2 at concentrations ranging from 0.75 to 56 mumol per l; control groups were incubated in the same medium without added cdcl2. the exposures to cdcl2 were begun at the blastula stage (five hours post-fertilization) and were terminat ...19911781663
melatonin deacetylation: retinal vertebrate class distribution and xenopus laevis tissue distribution.deacetylation is a rapid clearance mechanism for ocular melatonin. we have studied the distribution of retinal melatonin deacetylase activity among vertebrate classes. exogenous radiolabeled melatonin is metabolized by ocular tissue prepared from the amphibian xenopus laevis, the reptile anolis carolinensis, the teleost fish carassius auratus, and the bird gallus domesticus. in contrast, we were unable to detect ocular melatonin breakdown in rat or pig. in each species exhibiting ocular melatoni ...19911782560
vitellogenin--homologs of mammalian apolipoproteins?1. to determine if a relationship exists between vertebrate vitellogenins and mammalian plasma proteins the embl and nbrf computer databases were searched with two partial amino acid sequences from xenopus laevis and gallus gallus vitellogenin. 2. a significant relationship was found between vitellogenin and human apolipoprotein b-100 genes, and confirmed using homology-determination programs. 3. further analysis shows that unique multiple proline consensus regions found in apolipoprotein b-100 ...19911782764
the nuclear-cytoplasmic distribution of the xenopus nuclear factor, xnf7, coincides with its state of phosphorylation during early development.we describe the characterization in xenopus laevis of a nuclear protein, xnf7, which is first detected in the oocyte gv and is eventually enriched in nuclei of cells of the adult brain. previous studies have shown that this protein contains zinc-finger-like structures and acidic domains typical of transcriptional activators, and is phosphorylated in vitro by p34cdc2 protein kinase. the protein also binds to double-stranded dna. these data suggest that xnf7 may function as a transcription factor. ...19911782867
detection of genes encoding novel members of the ligand responsive transcription factor superfamily in xenopus laevis. 19911783163
a concentration-clamp system allowing two-electrode voltage-clamp investigations in oocytes of xenopus laevis.a system for rapid solution exchange (concentration-clamp) was developed for xenopus laevis oocytes. the exchange time (t90) was 10 ms. the system allows two-electrode voltage-clamp investigations.19911784130
polylysine activates membrane-bound adenylyl cyclase from xenopus laevis oocytes through the gs transducing protein.1. the activity of the adenylyl cyclase found in the membranes of xenopus laevis can be affected by polylysine and other polycations. 2. the activity of the catalytic subunit measured with forskolin is inhibited by polylysine and polyarginine at concentrations above 10 microm and by spermine above 3 mm. 3. the adenylyl cyclase activity stimulated by gtp-gamma-s or f- through the stimulatory g protein (gs) can be increased by polylysine, polyornithine and spermine but not by polyarginine. 4. poly ...19911790677
relaxation from rigor by photolysis of caged-atp in different types of muscle fibres from xenopus laevis.using chemically skinned fast and slow fibres from the iliofibularis muscle of xenopus laevis, we measured the force changes following laser pulse photolysis of caged-atp at 4 degrees c in the presence and absence of added calcium. the time course of the early force change in the absence of calcium was used to derive an apparent second order rate constant for crossbridge detachment. these values were compared with previous model-dependent estimates stemming from force-velocity experiments. for f ...19911791191
changes in intracellular ph following egg activation and during the early cell cycle of the amphibian pleurodeles waltlii, coincide with changes in mpf activity.previous work on xenopus laevis suggests a temporal coincidence between inactivation of the m-phase promoting factor (mpf) and intracellular ph (phi) increase during egg activation. in addition, we recently showed that during the early cell cycle of xenopus eggs, mpf activity cycling and phi oscillations were temporally and functionally related. in the present work, using eggs of another amphibian, pleurodeles waltlii, which has a natural cell cycle considerably longer than that of xenopus laevi ...19911794067
intracellular ph and intracellular free calcium responses to protein kinase c activators and inhibitors in xenopus eggs.cell activation during fertilization of the egg of xenopus laevis is accompanied by various metabolic changes, including a permanent increase in intracellular ph (phi) and a transient increase in intracellular free calcium activity ([ca2+]i). recently, it has been proposed that protein kinase c (pkc) is an integral component of the xenopus fertilization pathway (bement and capco, j. cell biol. 108, 885-892, 1989). indeed, activators of pkc trigger cortical granule exocytosis and cortical contrac ...19911794315
insulin receptors on xenopus laevis oocytes: effects of injection of ob/ob mouse liver mrna.we describe here conditions for the detection of insulin binding sites on xenopus laevis oocytes. the binding of 125i-labelled insulin displayed sigmoidal behaviour, which is characteristic of the binding relationship between insulin and its receptor. resolution of the resulting curvilinear scatchard plot into two components revealed kd values of 8.86 x 10(-10) +/- 1.9 x 10(-10) and 5.32 x 10(-9) +/- 2.4 x 10(-9) m and n values of 9.7 x 10(7) +/- 0.4 x 10(7) and 3.3 x 10(8) +/- 0.5 x 10(8) bindi ...19911795023
carnosine in the brain and olfactory system of amphibia and reptilia: a comparative study using immunocytochemical and biochemical methods.the pattern of distribution of carnosine-like immunoreactivity and its relation to glial fibrillary acidic protein immunoreactivity have been studied in two lizards (gallotia galloti and tarentola delalandii) and in two anuran amphibians (rana esculenta and xenopus laevis) using immunocytochemical techniques. biochemical data obtained by paper electrophoresis show that the dipeptides carnosine and homocarnosine are both present in the brain of all the species examined. in the central nervous sys ...19911795878
development of the olfactory bulb in the clawed frog, xenopus laevis: a morphological and quantitative analysis.the relationship between olfactory axons and the cells of the olfactory bulb during normal development was analyzed to determine whether olfactory afferent axons could play a role in the induction of olfactory bulb formation. the morphology of the olfactory bulb in xenopus larvae from stages 26 to 58 and in adult frogs was analyzed with light and electron microscopy. axons were first observed beneath the basal lamina of the neural tube at stages 30 and 32; at stage 32, neurons in this area of th ...19911797876
localization of a nervous system-specific class ii beta-tubulin gene in xenopus laevis embryos by whole-mount in situ hybridization.a neural-specific beta-tubulin mrna is expressed in the developing central nervous system shown by whole-mount in situ hybridization experiments. of special interest is the fact that from the late blastula (stage 9; nieuwkoop and faber, 1967; hausen and ribesell, 1991) until the early neurula (stage 13) the signal can be found not only in the presumptive neural plate but also in the presumptive epidermis. later in development (from stage 13) the specific mrna becomes restricted to the presumptiv ...19911801865
dose and time-dependent mesoderm induction and outgrowth formation by activin a in xenopus laevis.we examined the quality of mesoderm induced by the action of activin a on the xenopus presumptive ectoderm when various concentrations and treatment times were employed. the minimum concentration of activin a to induce mesodermal tissues was inversely proportional to its treatment time. the explants differentiated into different types of mesodermal tissues, from ventral-type to dorsal-type depending on the concentration of activin a and its treatment time. to confirm whether activin a has a role ...19911801866
development of the left-right axis in amphibians.the heart and viscera of vertebrates are formed from primordia that are apparently bilaterally symmetrical. this symmetry is broken during development, yielding organs that develop characteristic asymmetries along the left-right axis. results from three lines of experimentation on embryos of the amphibian xenopus laevis indicate that left-right asymmetries are established early in development and that cellular interactions transmit left-right information from one primordium to another. first, a ...19911802642
gene structure and chromosomal localization of the murine lamin b2 gene.the structure of the murine lamin b2 gene has been analyzed by cloning, sequencing and hybridization techniques, including in situ hybridization. the gene exists in single copy on the distal arm of chromosome 10 and comprises at least 15 kb, containing 12 exons and 11 introns. the transcriptional start point, as determined by primer extension analysis and rnase protection, was mapped to the region -264 to -254 upstream the atg start codon. the 5' upstream region does not reveal any classical tat ...19911802718
ultrastructure of the approximately 26s complex containing the approximately 20s cylinder particle (multicatalytic proteinase/proteasome).we have isolated a large protein complex of approximately 26s from xenopus laevis oocytes and eggs which is composed of the approximately 20s cylinder particle (multicatalytic proteinase/proteasome) and additional proteinaceous components. in its polypeptide composition and sedimentation coefficient this approximately 26s complex closely resembles the 26s ubiquitin-dependent protease, a high molecular weight multienzyme complex recently described in the literature. specific antibodies directed a ...19911802724
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