structure-activity relations of amiloride and its analogues in blocking the mechanosensitive channel in xenopus oocytes.1. patch clamp recording techniques have been used to compare the block caused by amiloride and some of its structural analogues of the mechanosensitive (ms) cation selective channel in frog (xenopus laevis) oocytes. 2. like amiloride, the amiloride analogues dimethylamiloride (dma), benzamil and bromohexamethyleneamiloride (brhma) block the ms channel in a highly voltage-dependent manner. 3. all analogues tested were more potent blockers than amiloride with ic50's of 500 microm (amiloride), 370 ...19921382778
evolution of vertebrate igm: complete amino acid sequence of the constant region of ambystoma mexicanum mu chain deduced from cdna sequence.cdna clones coding for the constant region of the mexican axolotl (ambystoma mexicanum) mu heavy immunoglobulin chain were selected from total spleen rna, using a cdna polymerase chain reaction technique. the specific 5'-end primer was an oligonucleotide homologous to the jh segment of xenopus laevis mu chain. one of the clones, jha/3, corresponded to the complete constant region of the axolotl mu chain, consisting of a 1362-nucleotide sequence coding for a polypeptide of 454 amino acids followe ...19921382992
mechanisms of propofol action on ion currents in the myelinated axon of xenopus laevis.the effect of the intravenous anaesthetic, propofol (2,6-diisopropylphenol), was investigated on frog myelinated axons under voltage-clamp conditions. the effect, in the concentration range 60 microm to 10 mm, was a combination of (i) a negative shift of the steady state activation and inactivation curves for both na+ and k+ currents (ina,ik), (ii) a voltage-independent block of ina, but not of ik, and (iii) a slowed time course of ik activation. the shift was dose-dependent and, at 1 mm, about ...19921383009
characterization of a xenopus laevis ribonucleoprotein endoribonuclease. isolation of the rna component and its expression during order to facilitate studies of the assembly and transport of the site-specific rnase mitochondrial rna processing (mrp) ribonucleoprotein, we have characterized it from xenopus laevis cells. x. laevis rnase mrp displayed a similar spectrum of cleavage activity to that produced by previously isolated mammalian nuclear enzymes. a 277-nucleotide rna component of the ribonucleoprotein was identified; the gene for the rna was isolated, sequenced, and found to be 66 and 63% similar to mouse and hum ...19921383227
properties of endogenous voltage-dependent sodium currents in xenopus laevis oocytes.endogenous voltage-dependent sodium currents were recorded using standard 2-microelectrode techniques in xenopus laevis oocytes. maximal inward current occurred at -10 mv with an average amplitude of -279 +/- 17 na and steady-state inactivation was half-maximal at a voltage of -38 +/- 0.5 mv. currents were blocked by low concentrations of tetrodotoxin (ttx) with an ic50 value of 6 nm. these properties make the endogenous sodium current in xenopus oocytes similar to sodium currents expressed foll ...19921383646
niflumic and flufenamic acids are potent inhibitors of chloride secretion in mammalian airway.effects of niflumic acid (nfa) and flufenamic acid (ffa), the two nonsteroid anti-inflammatory agents recently reported to inhibit cl- current in xenopus oocytes, were examined in cultured monolayers of dog and cow trachea. both agents showed potent inhibition to the short-circuit current (isc), an index of magnitude of transepithelial cl- secretion, with values of ki of 0.02 (for nfa) and 0.06 (for ffa) mm, respectively. the sensitivity sequence of isc to the cl- channel inhibitors tested was n ...19921383667
expression of amiloride-sensitive na+ channels of hen lower intestine in xenopus oocytes: electrophysiological studies on the dependence of varying nacl intake.epithelial na+ channels were incorporated into the plasma membrane of xenopus laevis oocytes after micro-injection of rna from hen lower intestinal epithelium (colon and coprodeum). the animals were fed either a normal poultry food which contained nacl (hs), or a similar food devoid of nacl (ls). oocytes were monitored for the expression of amiloride-sensitive sodium channels by measuring membrane potentials and currents. oocytes injected with poly(a)+rna prepared from hs animals or non-injected ...19921384704
effects of lithium chloride and retinoic acid on the expression of genes from the xenopus laevis hox 2 complex.we show that xenopus laevis has a hox 2 complex, and that this complex is strongly conserved with the mammalian one, both in structure and in the rules of spatial and temporal sequential expression of its genes during the early stages of development. lithium chloride and retinoic acid, two reagents known to alter axial patterning of the body when applied to xenopus embryos, produce, respectively, embryos with reduced posterior but exaggerated anterior structures and embryos with truncation of an ...19921384809
serotonin synthesis and accumulation by neurons of the anuran retina.serotonin-synthesizing and serotonin-accumulating neurons were studied in the retinas of xenopus laevis and bufo marinus. all previously identified cell types exhibiting serotonin-like immunoreactivity (sli) were labeled by intravitreal injection of 5,7-dihydroxytryptamine (5,7-dht). they included two amacrine cell types (large and small) in both species, and one bipolar cell type in xenopus. incubation of retinas in culture medium in the ambient light reduced sli in amacrine cells and enhanced ...19921390395
mechanism of magainin 2a induced permeabilization of phospholipid vesicles.the magainins, peptide antibiotics secreted by the frog xenopus laevis, have previously been shown to permeabilize phospholipid vesicles. to elucidate the mechanism of permeabilization, we have conducted detailed kinetic studies of magainin 2 amide (mgn2a)-induced release of 6-carboxyfluorescein from vesicles of phosphatidylserine. the results show that dye release occurs in (at least) two stages--an initial rapid phase, with t1/2 approximately 3 s, followed by a much slower phase that approache ...19921390773
isolation of plasma membranes, golgi bodies and mitochondria of xenopus laevis morulae. identification of plasma membrane proteins.homogenates of xenopus morulae at the 16-32 cell stage were centrifuged on discontinuous sucrose gradients. isolated fractions were identified by electron microscopy (em) as mitochondria, a fraction enriched in golgi vesicles, and plasma membranes. a special effort was made to prepare plasma membranes free of cytoplasmic contaminants. the resulting purified plasma membranes appeared morphologically identical to plasma membranes in situ. the external surface is covered with a fibrillar coat while ...19921394088
the effect of phloretin on single potassium channels in myelinated nerve.the effect of phloretin, a dipolar organic compound, on single potassium channel currents of myelinated nerve fibres of xenopus laevis has been investigated, using inside-out patches prepared by the method of jonas et al. (1989). the i channel, a potential dependent k channel with intermediate deactivation kinetics, was reversibly blocked by 20 microm phloretin applied on the inside; the block was strongest at negative membrane potentials and less pronounced at positive potentials. phloretin shi ...19921396407
efficiency of the 5'-terminal sequence (omega) of tobacco mosaic virus rna for the initiation of eukaryotic gene translation in escherichia coli.recent studies have demonstrated that the 5' leader (omega sequence) of tobacco mosaic virus rna has a certain enhancing capacity for translation of mrna in both prokaryotes and eukaryotes. in order to estimate the efficiency of omega to initiate translation of mrna in escherichia coli, in comparison to the shine-dalgarno (s/d) sequence, we have inserted eight different eukaryotic genes into two types of e. coli expression vectors containing one constitutive promoter (p1) but different translati ...19921396694
characterization of a xenopus laevis skin peptidylglycine alpha-hydroxylating monooxygenase expressed in insect-cell culture.the c-terminal amide structure of peptide hormones and neurotransmitters is synthesized via a two-step reaction catalyzed by peptidylglycine alpha-hydroxylating monooxygenase (phm) and peptidylhydroxyglycine n-c lyase. a xenopus laevis phm expressed in insect-cell culture by the baculovirus-expression-vector system was purified to homogeneity and characterized. using a newly established assay system for phm, the kinetic features of this enzyme were investigated. as expected, the enzyme required ...19921396699
protein kinase c mutants in the auto-inhibitory region exhibit two distinct define the role of the auto-inhibitory region of protein kinase c (pkc), arg22-lys23-gly24-ala25-leu26-arg27, site-directed mutations were introduced into the basic residues. three mutants, pkcala22,23, pkcala27, and pkcala22,23,27, apparently fell into two distinct types with regard to their biochemical properties and biological activities, as judged by the enhancement of a c-fos promoter in jurkat cells and by the initiation of germinal vesicle breakdown (gvbd) in xenopus laevis oocytes. (i ...19921397296
the armadillo homologs beta-catenin and plakoglobin are differentially expressed during early development of xenopus laevis.plakoglobin and beta-catenin are cytoplasmic proteins associated with the intracellular plaques of cell adhesive junctions. while plakoglobin is present in both adherens junctions and desmosomes, beta-catenin is associated with the cadherins that accumulate only in adherens junctions. both beta-catenin and plakoglobin are homologs of armadillo, a drosophila segment polarity gene that is considered to be in the wingless signaling pathway. we have characterized the expression and distribution of b ...19921397690
multiple domains of the rna polymerase i activator hubf interact with the tata-binding protein complex hsl1 to mediate transcription.recent evidence suggests that transcription initiation by all three eukaryotic rna polymerases involves a complex of the tata-binding protein (tbp) and multiple tbp-associated factors (tafs). here, we map the functional domains of the nucleolar hmg box protein hubf, which binds to the human rrna promoter and stimulates transcription by rna polymerase i through cooperative interactions with a distinct tbp-taf complex, hsl1. dnase i footprint analysis of mutant hubf proteins and of a synthetic pep ...19921398072
the structure and complete sequence of the gene encoding chicken ribosomal protein l5.the nucleotide (nt) sequence of the gene encoding chicken ribosomal protein l5, which associates with 5s rrna, was determined. the gene contains eight exons and seven introns which spread over 7252 bp. the transcription start point (tsp) is a c residue in a tract of 13 pyrimidines, and its 5'-flanking region lacks canonical tata and caat boxes. the g+c content of the region around the tsp is calculated as high as 78%, and nine gc boxes exist within the 5'-flanking region and the first intron. th ...19921398102
the pyrimidine sequence encompassing the transcription start point of xenopus laevis ribosomal-protein-encoding genes is not obligatory for activity in oocytes.the genes coding for ribosomal proteins (r-proteins) in xenopus laevis have a stretch of about 20 pyrimidines (y) at their 5' end, in the middle of which is localized the main transcription start point (tsp). to obtain information about its possible functional significance, we have introduced by site-directed mutagenesis one or more purines at various positions within the oligo(y) tract present at the 5' end of the gene coding for r-protein s19 of x. laevis. the effect of these mutations on tran ...19921398110
comparison of the sequence and structure of transcription factor iiia from bufo americanus and rana pipiens.amino acid (aa) sequences of transcription factor iiia (tfiiia) from the toad, bufo americanus, and the grass frog, rana pipiens, were determined by cdna cloning and dna sequencing. the 3'-untranslated regions of the cdnas reveal that the tfiiia gene polyadenylation signal is attaaa, rather than the conventional aataaa. the b. americanus and r. pipiens proteins share about 60% aa sequence homology with each other and with xenopus laevis tfiiia. although these results indicate that tfiiia has mor ...19921398134
isthmotectal axons make ectopic synapses in monocular regions of the tectum in developing xenopus laevis frogs.during the development of binocular maps in the tectum of xenopus laevis, axons that relay input from the ipsilateral eye via the nucleus isthmi undergo a prolonged period of shifting connections. this shifting accompanies the dramatic change in eye position that takes place as the laterally placed eyes of the tadpole move dorsofrontally. there is a concomitant expansion of the proportion of tectum that receives contralateral retinotectal input corresponding to the binocular portion of the visua ...19921401245
synaptonemal complexes of xenopus laevis.synaptonemal complexes (scs) have been analyzed in spread xenopus spermatocytes and oocytes. they showed all the usual features of animal scs in addition to a high incidence of centromere mismatching. a centriole pair is visible throughout zygotene and pachytene. at zygotene the ends of scs are markedly thickened and are clustered at the nuclear periphery.19921401877
the stopping response of xenopus laevis embryos: pharmacology and intracellular physiology of rhythmic spinal neurones and hindbrain neurones.1. xenopus laevis embryos stop swimming in response to pressure on the cement gland. this behaviour and 'fictive' stopping are blocked by bicuculline (10 mumol 1(-1)), tubocurarine (110 mumol 1(-1)) and kynurenic acid (0.5 mmol 1(-1)). 2. intracellular recordings from spinal neurones active during swimming have shown that pressure on the cement gland evokes compound, chloride-dependent inhibitory postsynaptic potentials (ipsps). these are blocked by bicuculline, tubocurarine and kynurenic acid, ...19921402608
glomerular development and growth of the renal blood vascular system in xenopus laevis (amphibia: anura: pipidae) during metamorphic climax.microcorrosion casts of the renal vascular system of tadpoles of the clawed frog, xenopus laevis, were observed by scanning electron microscopy. glomerular differentiation was studied qualitatively and quantitatively during developmental stages 56-66 (metamorphic climax). the general structure of the renal vascular system corresponds to the pattern commonly found in anurans; however, the arterial supply has conspicuous connecting vessels that supply groups of glomeruli. in the dorsal part of the ...19921404405
different chromatin structures along the spacers flanking active and inactive xenopus rrna genes.the accessibility of dna in chromatin to psoralen was assayed to compare the chromatin structure of the rrna coding and spacer regions of the two related frog species xenopus laevis and xenopus borealis. isolated nuclei from tissue culture cells were photoreacted with psoralen, and the extent of cross-linking in the different rdna regions was analyzed by using a gel retardation assay. in both species, restriction fragments from the coding regions showed two distinct extents of cross-linking, ind ...19921406621
cooperative binding of the xenopus rna polymerase i transcription factor xubf to repetitive ribosomal gene enhancers.upstream binding factor (ubf) is a dna-binding transcription factor implicated in ribosomal gene promoter and enhancer function in vertebrates. ubf is unusual in that it has multiple dna-binding domains with homology to high-mobility-group (hmg) nonhistone chromosomal proteins 1 and 2. however, a recognizable dna consensus sequence for ubf binding is lacking. in this study, we have used gel retardation and dnase i footprinting to examine xenopus ubf (xubf) binding to xenopus laevis ribosomal gen ...19921406673
müller (glial) cells in the retina of urodeles and anurans reveal different morphology by means of freeze-fracturing.müller (glial) cells of the retina of various species of amphibia (urodeles and anurans) were investigated by means of the freeze-fracture technique. this was done because müller cells in anamniotes were believed to differ from those in mammals in that they should lack the so-called orthogonal arrays of particles (oap) which are a characteristic feature of müller cells in mammalian retina. however, as we could demonstrate previously (berg-von der emde and wolburg, glia, 2 (1989) 458), fish retin ...19921407671
cloning and developmental expression in xenopus laevis of seven additional members of the wnt family.degenerate oligonucleotide primers encoding highly conserved regions of wnt-related proteins were used with the polymerase chain reaction (pcr) to amplify cdna derived from xenopus laevis embryos. cdna sequences partially encoding seven additional members of the xwnt gene family were isolated using this strategy. these cdnas have been given the designation xwnt-2, xwnt-6, xwnt-7a, xwnt-7b, xwnt-7c, xwnt-8b and xwnt-10 based on their amino acid identity with previously described wnts. with regard ...19921408135
isolation and sequence of a cdna encoding the precursor of a bombesinlike peptide from brain and early embryos of xenopus laevis.a cdna encoding the precursor of a bombesinlike peptide was isolated from brain of xenopus laevis. the predicted end product resembles neuromedin b, which was originally isolated from mammalian spinal cord. the mrna for this precursor was also present in gastrointestinal tract and in ovaries. moreover, it could be detected in early embryos (stage 2 and stage 10) of x. laevis. these findings suggest novel roles for peptides of the bombesin family in oocyte maturation and early amphibian developme ...19921409705
dna polymerase beta and dna synthesis in xenopus oocytes and in a nuclear extract.the identities of the dna polymerases required for conversion of single-strand (ss) m13 dna to double-strand (ds) m13 dna were examined both in injected xenopus laevis oocytes and in an oocyte nuclear extract. inhibitors and antibodies specific to dna polymerases alpha and beta were used. in nuclear extracts, inhibition by the antibody to polymerase beta could be reversed by purified polymerase beta. the polymerase beta inhibitors, dideoxythymidine triphosphate (ddttp) and dideoxycytidine tripho ...19921411545
[immunohistochemical studies on the tgf beta-related protein in the early development of xenopus laevis].by the method of immunocytochemistry, using the polyclonal antibodies raised against the 1-29 n-terminal residues of tgf beta-1, we found that the protein could bind to the antibodies was present in the early embryos of xenopus. the protein was named tgf beta-related protein. it was distributed mainly in the endoderm from blastula (stg. 7) to late neurula. in the blastula (stg. 8), the protein was localized in the vegetal hemisphere near the floor of the blastocoel [plate i, fig. 1]. in the earl ...19921414123
[the effect of microinjection of anti-tgf beta-1 antibodies on the early development of xenopus laevis].in order to testify the function of the tgf beta related protein, we microinjected the antibodies against the tgf beta-1 to one blastomere of two-cell stage embryos. dosages of antibodies injected were 24-36 ng, 12 -18 ng, 6-9 ng and 1.5-2.25 ng. malformed embryos with exposed yolk mass were produced. they were designated as ye-1, ye-2 and ye-3 according to the degree of malformation which was found to be related to the dosage of antibodies injected to the blastomere. these malformed embryos cou ...19921414124
cloning and expression of a human endothelin receptor: subtype a.the polymerase chain reaction, employing degenerate primers specific for the intramembrane domains iii and vi of g-coupled receptors, was used to generate partial clones encoding those receptors carried by cultured rat aorta smooth muscle cells. one clone, spanning the intramembrane domains iv-vi of a receptor specific for endothelin-1 (et-r[a]), was used as a probe to screen a human placental cdna library. the clone pl4-3, encoding a selective type of human endothelin receptor (et-r[a]), has an ...19921415318
lysophosphatidic acid induces a pertussis toxin-sensitive ca(2+)-activated cl- current in xenopus laevis oocytes.lysophosphatidic acid (lpa) induces a ca(2+)-activated cl- current in defolliculated xenopus laevis oocytes. the response appears mediated by a specific membrane receptor, because no current is induced when related compounds [phosphatidic acid (pa), lysophosphatidylcholine (lpc), and lysophosphatidylserine (lps)] are applied extracellularly or when lpa is injected intracellularly. incubation in pertussis toxin prevents the response. the response is mediated by a ca(2+)-activated cl- current beca ...19921415674
cloning and expression of the bovine cardiac sodium-calcium exchanger.two clones (p17 and p13), each containing the complete coding sequence for the bovine cardiac na+/ca2+ exchanger, were obtained from a lambda gt10 cdna library by screening with cdna probes from the canine exchanger. the coding sequence of clone p17 was 92 and 98% identical to the canine cdna at the nucleotide and amino acid levels, respectively. nine of the 21 amino acid differences between the two exchangers were found within the 32-amino acid signal sequence. the sequenced portions of the 3' ...19921416984
suramin changes the fate of spemann's organizer and prevents neural induction in xenopus laevis.suramin, a polyanionic compound, which has previously shown to dissociate platelet derived growth factor (pdgf) from its receptor, prevents the differentiation of neural (brain) structures of recombinants of dorsal blastopore lip (spemann's organizer) and competent neuroectoderm. furthermore, the suramin treatment changes the prospective differentiation pattern of isolated blastopore lip. while untreated dorsal blastopore lip will differentiate into dorsal mesodermal structures (notochord and so ...19921419849
peripheral origin of olfactory nerve fibers by-passing the olfactory bulb in xenopus laevis.after dii injections into the diencephalon of xenopus, two types of retrogradely labelled cells were found in the nasal area: (i) receptor cells in the olfactory epithelium and (ii) a small cell group located between the main olfactory epithelium and the vomeronasal system. these results reveal an extensive extrabulbar olfactory projection of olfactory receptor cells. fibers of these cells do not terminate in the olfactory bulb but innervate targets in the diencephalon directly. the other type o ...19921422816
metasim: object-oriented modelling of cell regulation.enzymatic processes and substances are modelled as distinct objects, belonging to a limited number of classes. a set of class definitions in c++ is presented that constitutes an object-oriented programming platform. the latter supports 'biological' data types and functions and facilitates simulation of metabolic and regulatory pathways in living cells. to compute the time-evolution, euler or runge-kutta methods are used, though the latter method compromises a strict object-oriented philosophy. a ...19921422877
bromodeoxyuridine-immunohistochemistry on cellular differentiation and migration in the fundic gland of xenopus laevis during development.cellular differentiation and migration in the fundic glands of adult and larval xenopus laevis have been examined using bromodeoxyuridine-immunohistochemistry. in the adult fundic gland, cumulative labeling with bromodeoxyuridine revealed a proliferative cell zone between the surface mucous cells and mucous neck cells, in what is referred to as the neck portion of the gland. the labeling-index of mucous neck cells had rapidly increased by week-5. the labeling-index of oxynticopeptic cells showed ...19921423489
large serotonin-like immunoreactive amacrine cells in the retina of developing xenopus laevis.the earliest appearance of serotonin-like immunoreactivity (sli) in different cell types and the development of large sli amacrine cells were studied in the retina of xenopus laevis from stage 33/34 to adult. intense sli was first found in the somas of large amacrine cells at stage 39. the somas of small amacrine cells showed weak sli at stage 41, followed by bipolar cells at stage 43. the number of large sli amacrine cells in the inner nuclear layer of the retina increased from 57 at stage 40 t ...19921424082
presence of d-aspartate oxidase and free d-aspartate in amphibian (xenopus laevis, cynops pyrrhogaster) tissues.1. this paper is the first report on the presence of d-aspartate oxidase activity and free d-aspartate in the amphibian tissues. 2. the presence of d-aspartate oxidase activity in tissues of clawed toad (xenopus laevis) and japanese newt (cynops pyrrhogaster) was demonstrated by requirements for enzyme activity, selective inhibition with meso-tartrate and substrate specificity. 3. in each animal, the highest activity was found in kidney, followed by liver and brain, and no gender difference in t ...19921424565
[ultrastructure of dermal melanophores of xenopus laevis larvae in mitosis]. 19921425181
analysis of xwnt-4 in embryos of xenopus laevis: a wnt family member expressed in the brain and floor plate.this study characterizes the temporal and spatial expression during early xenopus development of xwnt-4, a member of the wnt gene family. the xwnt-4 protein contains all of the sequence motifs that are hallmarks of the wnt gene family and is 84% identical to the mouse homolog, wnt-4. the highest level of xwnt-4 expression occurs during the early neurula stage of development although its expression persists throughout embryogenesis and can be found in the adult testis, brain and epithelium. consi ...19921425335
bone morphogenetic protein 4: a ventralizing factor in early xenopus development.the mesoderm of amphibian embryos such as xenopus laevis arises through an inductive interaction in which cells of the vegetal hemisphere of the embryo act on overlying equatorial and animal pole cells. three classes of 'mesoderm-inducing factor' (mif) that might be responsible for this interaction in vivo have been discovered. these are members of the transforming growth factor type beta (tgf-beta), fibroblast growth factor (fgf) and wnt families. among the most potent mifs are the activins, me ...19921425340
a maternal factor, oz-1, activates embryonic transcription of the xenopus laevis gs17 gene.we describe the identification of an enhancer sequence and a sequence-specific dna-binding protein required for developmental expression of the xenopus laevis gs17 gene. using microinjection of recombinant plasmids into fertilized frog eggs, we have shown that a 14 base pair ct-rich sequence element, normally located about 700 bases upstream of the gs17 promoter, is sufficient to activate transcription of a heterologous reporter gene in gastrula stage embryos. this regulatory element has been ca ...19921425344
assembly of a tail-less mutant of the intermediate filament protein, vimentin, in vitro and in vivo.recent reports on the possible contribution of the non-alpha-helical carboxy-terminal domain ("tail") of type iii intermediate filament (if) proteins to if assembly have been controversial. to examine the importance and role of this domain, we have therefore engineered a xenopus laevis vimentin cdna to code for a tail-less polypeptide and have used it in combination with prokaryotic and eukaryotic expression systems. here we show that tail-less vimentin, isolated from transfected bacteria (esche ...19921425769
developmental sequence of expression of voltage-dependent currents in embryonic xenopus laevis myocytes.although the development of several of the voltage-dependent currents in embryonic amphibian myocytes has been described, the overall muscle electrical development, particularly the relative times of expression of different voltage-dependent currents, has not been addressed in a single study under one set of conditions. we have found that, in mesoderm isolated and cultured from neurula stage embryos, myocytes are identifiable before they express voltage-gated currents. these ionic currents are a ...19921426620
the rapid transient decrease of sn-1,2-diacylglycerol in progesterone-stimulated xenopus laevis oocytes is the result of an ethanol artifact.full-grown xenopus laevis oocytes resume meiosis (meiotic maturation) in response to progesterone stimulation. three studies have shown that sn-1,2-diacylglycerol (dag), the intracellular activator of protein kinase c, may be involved in this process (wasserman et al., j. exp. zool. 255, 63-71, 1990; varnold and smith, development 109, 597-604, 1990; stith et al., j. cell physiol. 149, 252-259, 1991). two of these studies (varnold and smith, 1990; stith et al., 1991) found a rapid, but transient ...19921426629
sexually dimorphic expression of a laryngeal-specific, androgen-regulated myosin heavy chain gene during xenopus laevis development.masculinization of the larynx in xenopus laevis frogs is essential for the performance of male courtship song. during postmetamorphic (pm) development, the initially female-like phenotype of laryngeal muscle (slow and fast twitch fibers) is converted to the masculine form (entirely fast twitch) under the influence of androgenic steroids. to explore the molecular basis of androgen-directed masculinization, we have isolated cdna clones encoding portions of a new xenopus myosin heavy chain (mhc) ge ...19921426643
localization of a chymotrypsin-like protease to the perivitelline space of xenopus laevis eggs.a chymotrypsin-like protease is released from xenopus laevis eggs at activation and is involved in conversion of the vitelline envelope to the fertilization envelope. to localize this enzyme in unactivated and activated eggs, we used the synthetic peptide substrate succinylalanylalanylprolylphenylalanyl-4-methoxy-2-naphthylamide whose product can be visualized using transmission electron microscopy. protease product was localized within the perivitelline space of unactivated eggs, appearing as s ...19921426648
genetic and experimental studies on a new pigment mutant in xenopus laevis.white lethal (wl) is a recessive mutation affecting the differentiation of the three types of chromatophores in xenopus laevis and eventually leading to the death of the mutants around stage 50. melanophores appear at st. 33 but differentiate abnormally, remaining pale grey, and do not proliferate after st. 41. the rare xanthophores present contain only a few differentiated pterinosomes, and the iridophores consist of noniridescent white dots. when the albino gene (ap) is combined with wl, melan ...19921431781
assembly and disassembly of axonal microtubules of the toad xenopus laevis under the effect of toads xenopus laevis living at 11 degrees (winter), the microtubular density of 4-microns myelinated axons of lumbosacral nerves was assessed with the electron microscope. in controls, the density was 11.2 microtubules/microns2. in nerves incubated at 0 degrees, microtubules decreased following a simple exponential curve with a half time of 4.7 min (k = 0.149 min-1); residual microtubules were 4.5%. after rewarming, the full complement of microtubules reappeared within 60 min. in steady state ...19921431786
kinetic control of 5 s rna gene transcription.we have determined that the differential transcription of somatic and oocyte-type 5 s rna genes in a xenopus laevis oocyte extract is a consequence of vastly different rates of stable complex assembly. somatic-type 5 s rna genes sequester a limiting transcription factor much more rapidly than oocyte-type 5 s rna genes. once formed, however, transcription complexes on both types of genes are stable, and are transcribed at nearly equivalent rates. the relative rates of stable transcription complex ...19921433283
skeletal development in xenopus laevis (anura: pipidae).postembryonic skeletal development of the pipid frog xenopus laevis is described from cleared-and-stained whole-mount specimens and sectioned material representing nieuwkoop and faber developmental stages 46-65, plus postmetamorphic individuals up to 6 months old. an assessment of variation of skeletogenesis within a single population of larvae and comparison with earlier studies revealed that the timing, but not the sequence, of skeletal development in x. laevis is more variable than previously ...19921433306
[function, molecular structure and gene expression of fibroblast growth factor (fgf/hbgf)].the structure and function of members of the fibroblast growth factor (fgf) gene family and their receptors are reviewed. all the member of this gene family bind heparin, and therefore, are also called the as heparin-binding growth factor (hbgf). in this review, the structural features of fgf/hbgf are summarized first, and general features of the structure and function of their receptors are then described briefly. after biological effects of fgf/hbgf on adult-type tissues and cultured cells are ...19921433981
structural organization of a src gene from xenopus sequence analysis of genomic clones, the exon-intron structure of one of the two src genes from xenopus laevis has been determined. the coding region of the gene is interrupted by 10 introns whose locations are identical to the introns in the coding regions of the src genes of human and chicken. the 5' untranslated region is contained on a separate exon with no sequence conservation relative to the corresponding region of the chicken gene. the 5' untranslated region of the xenopus gene contai ...19921437158
a possible role for c-myc oncoproteins in post-transcriptional regulation of ribosomal rna.overexpression of members of the myc family of oncogenes contributes to the development of many vertebrate malignancies. although several functions for myc gene products have been proposed, the targets for myc activity during oncogenesis or normal development remain to be identified. oocytes of xenopus laevis, which are non-dividing cells that accumulate abundant c-myc protein, provide an unusual opportunity to examine c-myc function. we have investigated whether the accumulation of massive amou ...19921437160
sequence differences between histones of procyclic trypanosoma brucei brucei and higher eukaryotes.four histones, a, b, c, d from procyclic trypanosoma brucei brucei, which show similarities with the amino acid composition of the core histones h3, h2a, h2b and h4, were isolated and cleaved with endoproteinase glu-c. the fragments were separated by fplc reversed phase chromatography and a subset of the fragments (a5, a9, b6, c8, d3, d9, d11) was subjected to sequence analysis. a 54-71% identity was found in the sequences of the fragment c8 and the c-terminal half of h2b and of three fragments ...19921437281
genes for xenopus laevis u3 small nuclear rna.genomic southern blots showed there are only 14 to 20 copies of u3 snrna genes per somatic genome in xenopus laevis, unlike the highly repetitive, tandem arrangement of other snrna genes in this organism. sequencing of two u3 snrna genes from lambda clones of a genomic library revealed striking similarity upstream, but much more divergence downstream. consensus motifs common to other u snrna genes were also found: a distal sequence element (dse, octamer motif at -222 to -215), a proximal sequenc ...19921437561
distribution of mrna of a na(+)-independent neutral amino acid transporter cloned from rat kidney and its expression in mammalian tissues and xenopus laevis oocytes.the na(+)-independent neutral amino acid transporter (naa-tr) that we had previously cloned from rat kidney has been investigated with respect to its distribution in mammalian tissues and cells. by northern blot analysis and rnase protection assay, a 2.4-kilobase (kb) mrna in rat intestine was found to be identical to that in rat kidney. of the other rat tissues examined, only brain and heart were found to contain mrnas related to kidney naa-tr by northern assay. however, these were larger (appr ...19921438248
calcium-binding proteins in chemoreceptors of xenopus laevis.calcium-binding proteins were investigated immunohistochemically in chemo-receptors of the olfactory epithelium and taste buds of the clawed frog, xenopus laevis. calmodulin-, s-100- and calbindin-immunoreactive material were found in sensory cells of the olfactory epithelium; however, parvalbumin-like material was absent in these cells. taste buds of the palate showed calmodulin-, s-100- and parvalbumin-immunoreactive material in sensory cells, while calbindin-immunoreactive material in support ...19921440589
a method for [3h]mannose labeling of asn-linked oligosaccharides on recombinant glycoproteins synthesized in xenopus oocytes.we have developed an efficient method for labeling the asn-linked oligosaccharides of recombinant glycoproteins synthesized in xenopus laevis oocytes. by coinjecting gdp-[3,4-(3)h]mannose with mrna for human cathepsin d, it was possible to incorporate as much as 1800 cpm per oocyte into each of the two asn-linked oligosaccharides of this glycoprotein. overall, about 50% of the microinjected gdp-[3,4-(3)h]mannose was incorporated into asn-linked oligosaccharides, a 10-fold greater value than that ...19921443567
identification of calreticulin isoforms in the central nervous the present paper we report the cloning and sequencing of the cdna encoding two calreticulin isoforms from xenopus laevis central nervous system. the two isoforms display 93% identity at the amino acid level. the predicted amino acid sequences of the amphibian calreticulins are very similar (76%) to those of mammalian liver and skeletal muscle. xenopus laevis calreticulins are characterized by a very acidic c-terminal domain endowed with the endoplasmic-reticulum retention signal kdel. the cd ...19921445218
identification of nuclear factors which interact with the 5' flanking region of the ef-1 alpha o gene in xenopus laevis.the ef-1 alpha o gene of xenopus laevis is a stage-specific gene, being transcribed in oogonia and oocytes, but not in postmeiotic germ cells and terminally differentiated cells. we found that two trans-acting factors from oocyte nuclear extract are able to interact with a dna sequence in the 5'-upstream region of the ef-1 alpha o gene. methylation interference experiments suggested that the two factors recognised the same dna element. gel retardation assays indicated that part of the protein bi ...19921446735
xenopus laevis oocyte g alpha subunits mrnas. detection and quantitation during oogenesis and early embryogenesis by competitive reverse pcr.the expression of mrnas coding for different xenopus laevis oocyte g alpha subunits was analyzed by the pcr technique. using the nucleotide sequences of five previously cloned cdnas for oocyte g alpha subunits [febs lett. 244, 188-192, 1989; febs lett. 268, 27-31, 1990] and the highly sensitive reverse pcr reaction we found that g alpha o, g alpha i-1, g alpha i-3 and g alpha s species are present in oocyte stage vi, g alpha o mrna being the most abundant transcript. g alpha o mrna was further q ...19921446737
p-domains as shuffled cysteine-rich modules in integumentary mucin c.1 (fim-c.1) from xenopus laevis. polydispersity and genetic polymorphism.a new frog integumentary mucin (fim-c.1) has been discovered by molecular cloning. this mucin contains at least six typical p-domains as cysteine-rich modules. shuffled p-domains have previously been detected in fim-a.1, and they also form the basis of various p-domain peptides, which presumably have growth-modulating activities. furthermore, fim-c.1 contains at least three threonine-rich clusters, which consist of semi-repetitive cassettes. various polydisperse transcripts have been characteriz ...19921447205
testicular masculinization of vocal behavior in juvenile female xenopus laevis reveals sensitive periods for song duration, rate, and frequency xenopus laevis, adult males but not females produce courtship songs comprised of rapid trills. two experiments were conducted to determine whether male-typical singing could be induced in females. at 6 different juvenile stages, male and female frogs were gonadectomized and implanted with testes, grown to sexual maturity, and tested for vocal behavior. all frogs with functional testicular implants sang; females sang as much as males. the frequency spectra of the clicks within trills were full ...19921447723
effect of terminal nonhomologies on homologous recombination in xenopus laevis oocytes.homologous recombination of linear dna molecules in xenopus laevis oocytes is very efficient. the predictions of molecular models for this recombination process were tested with substrates with terminal nonhomologies (nonhomologous sequences). it was found that nonhomologies on one or both ends of an otherwise efficient substrate substantially reduced the yield of recombination products. in the case of a single nonhomology, inhibition was observed for all lengths of nonhomology, from 60 to 1,690 ...19921448075
characterization of the genomic corticotropin-releasing factor (crf) gene from xenopus laevis: two members of the crf family exist in mammals, the release of pituitary acth is stimulated by crf. two related peptides exist in nonmammalian vertebrates, sauvagine from frog skin and urotensin-i from the urophysis of teleost fish. their related structures (approximately 50%) and capacity to stimulate the release of acth from mammalian and fish pituitaries has led to the proposal that sauvagine and urotensin-i are homologs of mammalian crf. however, sauvagine does not appear to stimulate acth release in amphibians, although mamma ...19921448118
[study in the anuran amphibian xenopus laevis, some blood characteristics and nitrogen excretion based on changes in the water osmolarity].the ph, the osmolality and the urea and ammonia concentrations in blood, as well as the net urea and ammonia excretions, were studied in the amphibian xenopus laevis exposed for several weeks to increased osmotic pressure (op) of the ambient water, as a result of the addition of either nacl or mannitol to the water. the ph and the ammonia concentration of the blood were independent of the variations of the ambient osmolarity. on the contrary, the blood osmolality and its urea concentration incre ...19921450981
localization of xenopsin and xenopsin precursor fragment immunoreactivities in the skin and gastrointestinal tract of xenopus laevis.xenopsin (xp) and xenopsin precursor fragment (xpf) are bioactive peptides derived from a single precursor molecule; both were isolated previously from extracts of xenopus laevis skin. the present immunohistochemical study was undertaken to determine the specific cellular localization of these two peptides in the skin and also in the gastrointestinal tract of adult xenopus. we report here that xp-like and xpf-like immunoreactivities co-exist in the granular glands of the skin and specific granul ...19921451171
ventrolateral regionalization of xenopus laevis mesoderm is characterized by the expression of alpha-smooth muscle actin.mesodermal patterning in the amphibian embryo has been extensively studied in its dorsal aspects, whereas little is known regarding its ventrolateral regionalization due to a lack of specific molecular markers for derivatives of this type of mesoderm. since smooth muscles (sm) are thought to arise from lateral plate mesoderm, we have analyzed the expression of an alpha-actin isoform specific for sm with regard to mesoderm patterning. using an antibody directed against alpha-sm actin that recogni ...19921451663
[the distribution and relation to the cytoskeleton of specific prosomal proteins in the oogenesis of the clawed toad].using immunoblotting and immunofluorescent microscopy, we showed the presence in xenopus laevis oocytes of two prosomal proteins (27 and 31-33 kda) and studied their distribution during oogenesis. in the ooplasm, both proteins are detected in prosomal clusters of various size. during previtellogenesis, prosomal proteins are diffusely distributed in the nucleoplasm and form evenly distributed clusters in the cytoplasm. during oocyte growth, prosomal proteins disappear from the nucleus and form an ...19921454294
fission yeast cdc21+ belongs to a family of proteins involved in an early step of chromosome replication.the cdc21+ gene of schizosaccharomyces pombe was originally identified in a screen for cdc mutants affecting s phase and nuclear division. here we show that the cdc21+ gene product belongs to a family of proteins implicated in dna replication. these include the saccharomyces cerevisiae mcm2 and mcm3 proteins, which are needed for the efficient function of certain replication origins, and s.cerevisiae cdc46, which is required for the initiation of chromosome replication. the cdc21 mutant is defec ...19921454522
[the structure of the reticulum of mauthner's neurons in tadpoles of the clawed toad grown under increased gravitational force].the ultrastructure of the mauthner cells (m-cells) and the behaviour of xenopus laevis tadpoles, reared from eggs under increased gravity (2.9 g) which changes the activity of an afferent vestibular input, were investigated. besides, a study was made of tadpoles after the hindbrain ablation at earlier embryonal stages which significantly altered the microenvironment of m-cells. it is shown that experimental treatments enhance the proliferation of endoplasmic reticulum and its derivatives, so cal ...19921455551
identification of bone morphogenetic protein-2 in early xenopus laevis embryos.polyclonal antibodies capable of reacting with amphibian bone morphogenetic protein (bmp-2 and -4) were raised in rabbits by immunization with a synthetic 21 amino acid peptide which corresponds to a sequence residing in the mature protein of xenopus bmp-2 (xbmp-2). the antibodies recognized an embryonic bmp as well as mammalian and bacteria expressed recombinant xbmps. the antibodies detected, under reducing conditions, a 30 kda protein in the extract of oocytes and embryos during early develop ...19921457128
evaluation of acetaminophen-induced developmental toxicity using fetax.potential mechanisms of acetaminophen-induced developmental toxicity were evaluated using fetax (frog embryo teratogenesis assay-xenopus). early xenopus laevis embryos were exposed to acetaminophen for 96-h in two definitive concentrations-response assays with and without an exogenous metabolic activation system (mas). two static renewal tests of acetaminophen and the mas treated with carbon monoxide, cimetidine, ellipticine, diethyl maleate, and supplemented with glutathione were also performed ...19921459044
identification of plakoglobin in oocytes and early embryos of xenopus laevis: maternal expression of a gene encoding a junctional plaque protein.we have isolated a cdna encoding the junctional plaque protein plakoglobin of xenopus laevis and determined its amino acid sequence. comparisons with sequences of related proteins of the same and other species revealed that in xenopus plakoglobin and beta-catenin are two different proteins, encoded by separate genes, that both genes are expressed in embryogenesis, and that the amphibian plakoglobin is more closely related to the human plakoglobin than to beta-catenin of the same species. using t ...19921459359
neuron-specific enolase-like immunoreactivity in the vertebrate retina: selective labelling of müller cells in anura.neuron-specific enolase (nse) immunocytochemistry was carried out in retinae of goldfish, axolotl, clawed frog, cane toad, lizard, chick, guinea-pig, rabbit, rat, cat and human. with the exception of anura, strong immunoreactivity was seen in the large ganglion, amacrine cells and horizontal cells of the retina in all of the other species. photoreceptors were found to be labelled in the rat and human retina and only one cone type in rabbit. photoreceptor pedicles and ellipsoids were stained in t ...19921459864
genes encoding xenopus laevis ig l chains. implications for the evolution of kappa and lambda chains.xenopus laevis ig contain two distinct types of l chains, designated rho or l1 and sigma or l2. we have analyzed xenopus genomic dna by southern blotting with cdna probes specific for l1 v and c regions. many fragments hybridized to the v probe, but only one or two fragments hybridized to the c probe. corresponding c, j, and v gene segments were identified on clones isolated from a genomic library prepared from the same dna. one clone contains a c gene segment separated from a j gene segment by ...19921460285
[the nuclei of follicular cells do not control oocyte maturation in amphibians induced by gonadotropic hormones in vitro].the inhibitory effect of actinomycin d (5 micrograms/ml) on maturation of the follicle-enclosed oocytes of rana temporaria and xenopus laevis induced in vitro by pituitary suspension and human chorionic gonadotropin, respectively, is not observed at low concentrations of the hormones. these data suggest that nuclei of the follicle cells are not involved in the control of the pituitary-dependent oocyte maturation in amphibians.19921461634
thyroid hormone-induced gene expression changes in the developing frog limb.greater than 120 genes are up-regulated in xenopus laevis limb buds within the first 24 h after induction of metamorphosis by thyroid hormone. fourteen of these have been isolated and characterized. four encode heat shock proteins. the identified regulated genes have in common a relatedness with cell growth as exemplified by the serum response of quiescent fibroblasts. some of the genes respond directly to hormone. however, the majority appear to be secondary response genes judging from their de ...19921464592
presynaptic localization of sodium/calcium exchangers in neuromuscular preparations.calcium ions play a critical role in neurotransmitter release. the cytosolic ca2+ concentration ([ca2+]cyt) at nerve terminals must therefore be carefully controlled. several different mechanisms, including a plasmalemmal na/ca exchanger, are involved in regulating [ca2+]cyt. we employed immunofluorescence microscopy with polyclonal antiserum raised against dog cardiac sarcolemmal na/ca exchanger to determine the distribution of the exchanger in vertebrate neuromuscular preparations. our data in ...19921464773
a 69-kda rna-binding protein from xenopus oocytes recognizes a common motif in two vegetally localized maternal mrnas.vg1 mrna, a maternal message encoding a member of the transforming growth factor beta superfamily, undergoes localization to the vegetal cortex of xenopus laevis oocytes during a narrow period of oogenesis. a 340-nucleotide sequence has been identified in vg1 rna that directs its vegetal localization [mowry, k. l. & melton, d. a. (1992) science 255, 991-994]. to understand how cis- and trans-acting factors are involved in vg1 mrna localization, we have looked for specific interactions in vitro b ...19921465415
range of messenger action of calcium ion and inositol 1,4,5-trisphosphate.the range of messenger action of a point source of ca2+ or inositol 1,4,5-trisphosphate (ip3) was determined from measurements of their diffusion coefficients in a cytosolic extract from xenopus laevis oocytes. the diffusion coefficient (d) of [3h]ip3 injected into an extract was 283 microns 2/s. d for ca2+ increased from 13 to 65 microns 2/s when the free calcium concentration was raised from about 90 nm to 1 microm. the slow diffusion of ca2+ in the physiologic concentration range results from ...19921465619
developmentally regulated expression of a mitogen-activated protein kinase in xenopus laevis.mitogen-activated protein (map) kinases are activated in somatic cells in response to many extracellular stimuli and in oocytes during meiotic maturation. we have examined the tissue specificity of expression of a map kinase (xp42) in adult and larval xenopus laevis. map kinase rna and protein were abundant in the nervous system and lymphoid tissues and were readily detected in most other organs. a remarkably high level of rna was detected in ovary. fractionation of oocytes showed that map kinas ...19921467305
recoverin in pineal organs and retinae of various vertebrate species including man.recoverin is a recently discovered 26 kda calcium-binding protein, which activates guanylate cyclase in retinal photoreceptors when the intracellular concentration of free calcium drops upon photoexcitation. in this study we examined the distribution of recoverin in retinae and pineal organs of xenopus laevis larvae, 1-day-old chicken, adult pigeon, albino rat, sheep and man by means of immunocytochemistry. recoverin immunoreaction was found in all species investigated except for the chicken. in ...19921467959
nucleotide sequence of the genes for ribosomal proteins hs15 and hsh from haloarcula marismortui: an archaeon-specific gene cluster.the nucleotide sequences of the genes for two ribosomal proteins, hs15 and hsh, from the archaeon haloarcula marismortui, have been determined. the genes were found in a cluster together with another open reading frame with a probable regulatory function. hs15 and hsh have counterparts in eucarya. hs15 is significantly homologous to s19 from frog (xenopus laevis). hsh is related to s37 from yeast (saccharomyces cerevisiae) and s27 from fly (drosophila melanogaster), as well as to other members o ...19921468549
characterization of two types of ribosomal gene transcription in xenopus laevis oocytes.when the germinal vesicle of xenopus laevis oocytes is translocated into the vegetal hemisphere by centrifugation, the normally silent ribosomal spacer promoters are strongly induced. this induction correlates with the permeability of the nuclear envelope to dextran of molecular weight 70 kda, thus raising the possibility that the transcriptional changes are due to mixing of nuclear and cytoplasmic components. this basic observation prompted a thorough investigation of ribosomal gene transcripti ...19921472871
expression of carnosine-like immunoreactivity during retinal development in the clawed frog (xenopus laevis).the development of neurons immunoreactive to carnosine (beta-alanyl-l-histidine) was studied in the retina of xenopus laevis during the premetamorphic period. carnosine-like immunoreactivity was detected in photoreceptors from stage 39/40 (according to nieuwkoop and faber [normal tables of xenopus laevis (daudin), elsevier, amsterdam, 1956]) and in bipolar cells and their processes in the inner plexiform layer from stage 44/45. at all the developmental stages studied, neuroepithelial cells at th ...19921473272
immune system activation associated with a naturally occurring infection in xenopus laevis.immune system activation correlated with a naturally occurring infection has been found in the south african clawed frog xenopus laevis. the microorganism thought to be the cause of this infection is coccobacilloid and approximately 1 micron in diameter. since this microorganism does not grow on conventional bacterial media and it has been observed intracellularly, it may be an obligate intracellular bacterium. it has been found in xenopus peripheral blood and in highly vascularized organs such ...19921473595
distribution of vasotocin- and mesotocin-like immunoreactivities in the brain of the south african clawed frog order to obtain more insight into primitive and derived conditions of neuropeptidergic systems in vertebrates, in particular amphibians, we have studied immunohistochemically the distribution of vasotocin (avt) and mesotocin (mst) neuronal elements in the brain of the south african clawed frog xenopus laevis. apart from a well-developed hypothalamohypophysial system, the antibodies revealed the existence of extrahypothalamic avt- and mst-immunoreactive cell groups as well as extensive extrahy ...19921476666
amphibian intestinal villin: isolation and expression during embryonic and larval actin-binding protein of m(r) 105,000 has been isolated from anuran amphibian intestinal mucosa. polyclonal antibodies directed against chicken and pig intestinal villins and anti-porcine villin headpiece monoclonal antibody crossreact with the amphibian m(r) 105,000 protein. furthermore, the latter possesses an nh2-terminal sequence that is very homologous to those of avian and mammalian villins. in addition, polyclonal antibodies directed against amphibian intestinal m(r) 105,000 protein cr ...19921478966
identity elements for n2-dimethylation of guanosine-26 in yeast trnas.n2,n2-dimethylguanosine (m2(2)g) is a characteristic nucleoside that is found in the bend between the dihydro-uridine (d) stem and the anticodon (ac) stem in over 80% of the eukaryotic trna species having guanosine at position 26 (g26). however, since a few eukaryotic trnas have an unmodified g in that position, g26 is a necessary but not a sufficient condition for dimethylation. in yeast trna(asp) g26 is unmodified. we have successively changed the near surroundings of g26 in this trna until g2 ...19921480477
expression and potential functions of g-protein alpha subunits in embryos of xenopus laevis.during early embryonic development, many inductive interactions between tissues depend on signal transduction processes. we began to test the possibility that g-proteins participate in the signal transduction pathways that mediate neural induction. the expression during xenopus development of three g alpha subunits, g alpha 0, g alpha i-1 and g alpha s-1, was characterized. the three maternally expressed genes showed different expression patterns during early development. whole-mount in situ hyb ...19921483383
the primary structure of piscine (oncorhynchus mykiss) retinol-binding protein and a comparison with the three-dimensional structure of mammalian retinol-binding protein.1. the primary structures of two variants of rainbow trout (oncorhynchus mykiss) plasma retinol-binding protein (rbp) were determined and found to be approximately 60% identical with those of both human and xenopus laevis rbps. the comparable sequence similarities that we have found agree with the estimate of similar divergence times between bony fishes and mammals and between bony fishes and amphibians. the two piscine rbp variants differ by six amino acid substitutions at positions that are no ...19921483476
effect of rabbit duodenal mrna on phosphate transport in xenopus laevis oocytes: dependence on 1,25-dihydroxy-vitamin-d3.expression of na(+)-dependent transport of phosphate (pi) was analysed in xenopus laevis oocytes after injection of poly(a)-rich rna isolated from the duodenal mucosa of rabbits with increased levels of 1,25-(oh)2-vitd3 (injection of vitamin d3 or low-pi diet) or from control animals. in parallel, the effect of elevated levels of vitamin d3 was studied in isolated duodenal brush-border membrane vesicles. in brush-border membrane vesicles, the rate of na(+)-pi cotransport was found to be doubled ...19921488278
identification and developmental expression of a novel low molecular weight neuronal intermediate filament protein expressed in xenopus laevis.xenopus laevis is a valuable model system for the study of vertebrate neuroembryogenesis. however, very few well-characterized nervous system-specific molecular markers are available for studies in this organism. we screened a x. laevis adult brain cdna library using a cdna probe for mouse low molecular weight neurofilament protein (nf-l) in order to identify neuron-specific intermediate filament proteins. clones for two distinct neuron-specific intermediate filament proteins were isolated and s ...19921494944
individual variability in the translational regulation of ribosomal protein synthesis in xenopus laevis.ribosomal protein synthesis is regulated by controlling the fraction of mrna associated with polysomes. it is known that this value changes in different developmental stages during xenopus embryogenesis or, more generally, with changing cell growth conditions. we present here an analysis of the proportion of mrna loaded on polysomes, carried out with probes for five different ribosomal proteins on several batches of xenopus embryos obtained from different individuals. the results obtained indica ...19921495485
characterization of the ileal na+/bile salt co-transporter in brush border membrane vesicles and functional expression in xenopus laevis oocytes.the na+/bile salt co-transporter of the pig ileal brush border membrane has been expressed in xenopus laevis oocytes. injection of pig ileal poly (a)+ rna into oocytes resulted in the functional expression of an na(+)-gradient-stimulated taurocholate uptake within 2-5 days. the expressed na(+)-dependent taurocholate uptake exhibited saturation kinetics (apparent km of 48 microm), and displayed similar competitive substrate inhibition by taurodeoxycholate as the native brush border na+/bile salt ...19921497617
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