| prostaglandin regulation of reproductive behaviors in female xenopus laevis: sources and target sites. | | 1987 | 2960159 |
| segregation of mitochondria in the cytoplasm of xenopus vitellogenic oocytes. | in actively growing vitellogenic oocytes of xenopus laevis mitochondria segregate into 2 populations. one stays around the nucleus, actively replicates mitochondrial dna (mtdna), and builds up most of the stock of the mitochondria in the full-grown oocyte. the other moves toward the vegetal pole and stops replicating mtdna early in vitellogenesis. organelles of this population are components of the germ plasm of the cell. | 1987 | 2961387 |
| isolation of immunoreactive beta-endorphin-related and met-enkephalin-related peptides from the posterior pituitary of the amphibian, xenopus laevis. | acid extracts of the posterior pituitary of the amphibian, xenopus laevis, were analyzed with two heterologous region specific beta-endorphin rias. following gel filtration chromatography and cation exchange chromatography four peaks of immunoreactivity were detected. all four peaks were detected with a n-acetyl specific beta-endorphin ria. peak i represented 92% of the total immunoreactivity isolated following cation exchange chromatography. this peak had a net positive charge at ph 2.5 of +1 a ... | 1987 | 2964591 |
| tolerance induced by grafting semi-allogeneic adult skin to larval xenopus laevis: possible involvement of specific suppressor cell activity. | major histocompatibility complex (mhc)-homozygous xenopus laevis were rendered tolerant to semi-allogeneic antigens by grafting skins of adult frogs during larval stages (larvally induced tolerance), and this tolerant state was compared with the tolerance induced in early thymectomized frogs by the grafting of semi-allogeneic nonlymphoid thymuses (thymus-reconstituted tolerance). in contrast to a total inability of thymus-reconstituted frogs both to reject skins and to exhibit a mixed leukocyte ... | 1987 | 2965044 |
| ultrastructural identification of the primitive muscle spindle in the xenopus laevis larvae. | the initial formation of muscle spindles was studied with electron microscopy using the toe muscle of xenopus laevis. at the larval stage 57 (nieuwkoop and faber 1967), muscle spindles were first identified primarily by the presence of sensory endings associated with a thin bundle of myotubes, e.g. intrafusal (if) myotubes which were partly invested by a single cellular layer. the number of if myotubes per spindle was 5 to 6; the adult complement. if- and extrafusal (ef) myotubes were almost ide ... | 1988 | 2966597 |
| assembly of functional u1 and u2 human-amphibian hybrid snrnps in xenopus laevis oocytes. | oligonucleotides complementary to regions of u1 and u2 small nuclear rnas (snrnas), when injected into xenopus laevis oocytes, rapidly induced the specific degradation of u1 and u2 snrnas, respectively, and then themselves were degraded. after such treatment, splicing of simian virus 40 (sv40) late pre-mrna transcribed from microinjected viral dna was blocked in oocytes. if before introduction of sv40 dna into oocytes hela cell u1 or u2 snrnas were injected and allowed to assemble into small nuc ... | 1988 | 2970672 |
| expression of the murine interferon gamma receptor in xenopus laevis oocytes. | this study describes the isolation of mrna for the murine interferon gamma receptor and its expression in frog oocytes. the binding properties and apparent molecular weight of the murine interferon gamma receptor protein synthesized in frog oocytes is similar to that found on mouse cells. this is the first report of a functional receptor for a polypeptide ligand (interferon gamma) expressed in and directly assayed on frog oocytes. | 1988 | 2971040 |
| function of c-mos proto-oncogene product in meiotic maturation in xenopus oocytes. | the c-mos proto-oncogene is expressed as a maternal mrna in oocytes and early embryos of xenopus laevis, but its translation product pp39mos is detectable only during progesterone-induced oocyte maturation. microinjection of mos-specific antisense oligonucleotides into oocytes not only prevents expression of pp39mos, but also blocks germinal vesicle breakdown, indicating that it functions during reinitiation of meiotic division. | 1988 | 2971141 |
| reactivation of the methylation-inactivated late e2a promoter of adenovirus type 2 by e1a (13 s) functions. | the inactivating effect of sequence-specific promoter methylations was extensively studied by using the late e2a promoter of adenovirus type 2 (ad2) dna. the modification of the three 5' ccgg 3' sequences at nucleotides +24, +6 and -215, relative to the cap site in this promoter, sufficed to silence the gene in transient expression either in xenopus laevis oocytes or in mammalian cells, and after the fixation of the e2a promoter-chloramphenicol-acetyltransferase (cat) gene construct in the genom ... | 1988 | 2971812 |
| [changes in corticosterone and aldosterone concentrations in various tissues of xenopus laevis tadpoles during the metamorphosis]. | during the metamorphosis of xenopus laevis tadpoles, tissue concentrations of corticosterone and aldosterone did not change significantly in forelegs and hindlegs; they increased in tail, liver, skin and intestine. the rise of corticosteroid concentrations appeared in tissues which were deeply transformed during the first part of the climax, when plasma levels of corticosteroids also increased. highest tissue levels, attained at the mid-climax, were maintained at least until the end of metamorph ... | 1988 | 2977958 |
| the magainins: sequence factors relevant to increased antimicrobial activity and decreased hemolytic activity. | the magainins, two antimicrobial peptides found in the skin of the frog xenopus laevis, and 50 magainin analogs were synthesized by the method of simultaneous multiple peptide synthesis (smps). this series of peptides was prepared in order to examine the effects of omitting individual amino acids on antimicrobial activity. the series consisted of 22 magainin 1 omission analogs having a c-terminal carboxyl (m1-c) and 23 magainin 2 omission analogs having a c-terminal amide (m2-a), as well as both ... | 1988 | 2980783 |
| inositol trisphosphate isomers, but not inositol 1,3,4,5-tetrakisphosphate, induce calcium influx in xenopus laevis oocytes. | to investigate the mechanisms by which inositol phosphates regulate cytosolic free ca2+ concentration ([ca2+]c), we injected xenopus oocytes with inositol phosphates and measured ca2+-activated cl- currents as an assay of [ca2+]c. inositol 1,4,5-trisphosphate (ins(1,4,5)p3) injection (0.1-10.0 pmol) induced an initial transient cl- current (i1) followed by a second more prolonged cl- current (i2). both currents were ca2+-dependent, but the source of ca2+ was different. release of intracellular c ... | 1988 | 2981051 |
| specific binding sites for ovine prolactin in three amphibian cell lines. | established cell lines (tb-6c and tb-m) obtained by continuous culture of epithelial cells from toad bufo marinus urinary bladder, which, in culture, maintained a high degree of functional differentiation, exhibited a significant number of high-affinity (ka = 1-2 x 10(10) m-1) binding sites detected both with radioiodinated (125i) ovine prolactin (oprl) and human growth hormone (hgh). binding capacity was higher in the case of tb-6c cells (7,573 +/- 581 sites/cell) than with the tb-m cells (1,16 ... | 1985 | 2981477 |
| co-existence of two different types of soluble histone complexes in nuclei of xenopus laevis oocytes. | the nuclear pool of soluble histones in xenopus laevis oocytes is organized into two major types of acidic histone complexes separable by sucrose density gradient centrifugation. one type of complex sediments at 5 s (mr approximately 120,000), is isoelectric at ph 4.6, and contains histones h3 and/or h4 tightly bound to one polypeptide of a pair of very acidic polypeptides, designated n1 and n2 (kleinschmidt, j. a., and franke, w. w. (1982) cell 29, 799-809). this complex can be selectively immu ... | 1985 | 2981836 |
| cyclic amp levels during the maturation of xenopus oocytes. | while several studies have suggested that the induction of oocyte maturation results from a transient decrease in camp levels, attempts to demonstrate such a change have led to inconsistent results with respect to whether or not a decrease occurs as well as timing of the decrease. in this report the results of experiments designed to demonstrate small changes in camp content in xenopus laevis oocytes are presented and a statistically significant 20% decrease in camp content from between 2 and 50 ... | 1985 | 2982679 |
| progesterone-inhibited phosphorylation of an unique mr 48,000 protein in the plasma membrane of xenopus laevis oocytes. | the meiotic maturation of xenopus laevis oocytes is induced in vitro by progesterone which interacts at the cell surface level. a cell-free membrane preparation (p-10,000) incorporated 32p from [gamma-32p]atp, mostly into two proteins, mr approximately 56,000 and approximately 48,000 (as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis). progesterone, added in vitro, specifically inhibited the phosphorylation of the mr approximately 48,000 protein (named p48). half-maximal ... | 1985 | 2982868 |
| development of the ipsilateral retinothalamic projection in the frog xenopus laevis. i. retinal distribution of ipsilaterally projecting cells in normal and experimentally manipulated frogs. | the distribution of ipsilaterally and contralaterally projecting cells within the retina in xenopus laevis was studied by injection of horseradish peroxidase into the thalamus on one side of the brain and subsequent determination of the locations of retrogradely labeled cells in both retinas. in normal animals, contralaterally projecting cells were found throughout the retina. ipsilaterally projecting cells, in contrast, were most frequent in temporoventral retina and largely absent from dorsona ... | 1985 | 2984358 |
| development of the ipsilateral retinothalamic projection in the frog xenopus laevis. ii. ingrowth of optic nerve fibers and production of ipsilaterally projecting retinal ganglion cells. | we have studied the development of the ipsilateral retinothalamic projection in the frog xenopus laevis by analyzing patterns of histochemical reaction product resulting from anterograde transport of horseradish peroxidase (hrp) applied to cut optic nerves in animals of various ages. we have also determined the stages during which ipsilaterally projecting ganglion cells are born using a combination of [3h] thymidine autoradiography and retrograde marking of ganglion cells following injection of ... | 1985 | 2984359 |
| development of the ipsilateral retinothalamic projection in the frog xenopus laevis. iii. the role of thyroxine. | the ipsilateral retinothalamic projection in xenopus laevis normally first appears at about stage 54, at a time when a number of other changes known to be dependent on a rise in circulating levels of thyroxine begin to occur. we have investigated the role of thyroxine in the development of the ipsilateral retinothalamic projection by studying retinal projections and patterns of retinal histogenesis in tadpoles whose ability to produce thyroxine was blocked by treatment with propylthiouracil (ptu ... | 1985 | 2984360 |
| two divergent cellular src genes are expressed in xenopus laevis. | genomic and cdna clones of the x. laevis src gene have been isolated and characterized by hybridization and dna sequence analyses. the haploid genome of x. laevis contains two src genes, which can be distinguished from one another by virtue of sequence divergence in the 3' untranslated regions. both of the genes are functional as indicated by the fact that oocytes contain rnas transcribed from each of the genes. the two genes each encode an rna which is 3.3 kb in length, or twice the length requ ... | 1985 | 2987836 |
| torsional stress induces an s1 nuclease-hypersensitive site within the promoter of the xenopus laevis oocyte-type 5s rna gene. | the internal promoter of the xenopus laevis oocyte-type 5s rna gene is preferentially cleaved by s1 and bal-31 nucleases in plasmid dna. s1 nuclease sensitivity is largely dependent on supercoiling; however, bal-31 cleaves within the 5s rna gene in linear as well as in supercoiled dna. the s1 nuclease-hypersensitive site is centered at position +48-52 of the gene at the 5' boundary of the promoter. a dnaase i-hypersensitive site is induced at this position upon binding of the transcription facto ... | 1985 | 2987960 |
| queuosine modification of the wobble base in trnahis influences 'in vivo' decoding properties. | the 'in vivo' decoding properties of four trnahis isoacceptors, two from drosophila melanogaster and two from brewer's yeast, were studied after their microinjection, along with turnip yellow mosaic virus (tymv) coat protein mrna, into xenopus laevis oocytes. the two drosophila isoacceptors are identical besides containing either a guanosine (g) or the hypermodified nucleoside queuosine (q) in the wobble position. the brewer's yeast isoacceptors differ by four bases in the anticodon stem, and by ... | 1985 | 2988936 |
| parthenogenetic activation decreases the polyphosphoinositide content of frog eggs. | polyphosphoinositides were quantified in metaphase ii-arrested eggs of the amphibian xenopus laevis and 8-10 min later in eggs activated by pricking. the content of phosphatidylinositol 4,5-biphosphate (pip2) was remarkably high in metaphase ii-arrested eggs with respect to that of phosphatidylinositol 4-phosphate (pip). it was found to drop dramatically at activation. in contrast pip content did not change significantly. | 1985 | 2991011 |
| constancy of dna organization of polymorphic and nonpolymorphic genes during development in xenopus. | a study was undertaken to test for the occurrence of dna rearrangements or amplifications during embryonic development in xenopus laevis. dna isolated from testes and liver was digested with four restriction enzymes, separated on agarose gels, transferred to nitrocellulose, and hybridized with over 50 cloned cdna probes generated from embryonic poly (a)+ rna. no qualitative or quantitative differences were detectable in the dna hybridization patterns of testes and liver dna, suggesting that, at ... | 1985 | 2991055 |
| identification by immunofluorescence of acth-producing cells in the pituitary gland of the tree frog hyla arborea. | the indirect immunofluorescence procedure was used to localize acth-producing cells in the pituitary distal lobe from hyla arborea adult specimens; the antiserum employed was rabbit anti-synthetic acth (1-24) conjugated with bsa. immunohistochemical staining was suppressed by solid-phase absorption of the anti-acth with the specific antigen. in the distal lobe one cell population is immunoreactive; these cells are predominantly localized in the anterior half, both ventrally and dorsally; they ex ... | 1985 | 2991078 |
| regulation of pro-opiomelanocortin synthesis by dopamine and camp in the amphibian pituitary intermediate lobe. | the modulation of pro-opiomelanocortin (pomc) synthesis in xenopus laevis pituitary intermediate lobe (il) during background adaptation and the role of dopamine and camp in mediating this effect were examined. neurointermediate lobes (nils) were pulselabeled in vitro with [3h]arginine and analyzed for pomc synthesis by acid-urea gel electrophoresis. after black background adaptation of the animal (7 days), pomc synthesis increased 5-6-fold, while after white background adaptation (7 days), pomc ... | 1985 | 2991229 |
| adenosine-induced k+ current in xenopus oocyte and the role of adenosine 3',5'-monophosphate. | voltage clamp technique was used in xenopus laevis oocytes in order to study and compare membrane currents evoked by extracellularly applied adenosine (0.1-10 microm) and intracellularly injected cyclic amp (0.15-10 microm). the adenosine response is a late long-lasting outward k+ current ("h" current), mediated by the ra purine receptor subtype. the h current amplitude is directly proportional to (occupancy)3; the kd for adenosine is 3.34 microm. the h current is inhibited by the intracellular ... | 1985 | 2991737 |
| a protein inhibitor of calmodulin-regulated cyclic nucleotide phosphodiesterase in amphibian ovaries. | the cytosol fraction of an extract of xenopus laevis ovaries contains a protein inhibitor that can specifically block the activation of calmodulin-sensitive cyclic nucleotide phosphodiesterase (pde i) found in that tissue. this inhibitor was purified by deae-cellulose chromatography, gel filtration on sephacryl s-200, and affinity chromatography on calmodulin-sepharose. it has a molecular weight of approximately 90,000, and is heat-labile and susceptible to inactivation by chymotrypsin. the inhi ... | 1985 | 2992390 |
| high level human interleukin 1 production by a hepatoma cell line. | the human hepatic adenocarcinoma cell line, sk-hep-1, was found to constitutively produce interleukin 1. addition of the ionophore a23187 and lipopolysaccharide resulted in a 30-fold enhancement in the release of biological activity. serum supplementation did not affect the level of production. interleukin 1 from these cells had a molecular weight of 10-20,000 daltons on gel exclusion chromatography. polyadenylated rna, when fractionated on sucrose density gradients and injected into xenopus lae ... | 1985 | 2992486 |
| point mutational analysis of the xenopus laevis 5s gene promoter. | we have introduced c to t transitions into gc and cg base pairs of the xenopus laevis somatic 5s gene coding region and its 5' flank in order to analyse their effects on transcription activity and regulation. these studies allow us to differentiate between the two promoter elements and their spacer, within the internal control region. mutations within the 5' element which dissent from the corresponding trna consensus sequence reduce transcription activity substantially without significantly affe ... | 1985 | 2992947 |
| homologous desensitization of the beta-adrenergic receptor. functional integrity of the desensitized receptor from mammalian lung. | previous work has demonstrated that injection of rats with isoproterenol is rapidly (10 min) followed by the development of a homologous form of desensitization of the beta-agonist-coupled adenylate cyclase in lung membranes. half the receptor pool becomes sequestered in a light membrane fraction while the other half remains in the plasma membranes but becomes functionally uncoupled. in the present work we sought to assess whether "local sequestration" of the functionally intact receptor away fr ... | 1985 | 2993846 |
| the pattern of expression of the xenopus laevis tadpole alpha-globin genes and the amino acid sequence of the three major tadpole alpha-globin polypeptides. | we have isolated cdna clones derived from three tadpole alpha-globin mrnas of xenopus laevis. the entire nucleotide sequence of the three mrnas has been determined from the cdna clones and is presented together with the deduced amino acid sequence of the encoded polypeptides. two of the three polypeptide sequences are 96% homologous whilst the third sequence is highly diverged, with only a 72% homology. the three tadpole alpha-globin genes are all similarly diverged from the two x. laevis adult ... | 1985 | 2993998 |
| acetylcholine and phorbol esters inhibit potassium currents evoked by adenosine and camp in xenopus oocytes. | in xenopus laevis oocytes, adenosine and other purinergic agonists induce a k+-conductance increase that is fully mimicked by intracellular application of camp. acetylcholine suppresses the k+-conductance increase caused by adenosine, by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, or by intracellular injection of camp. this effect of acetylcholine is not mimicked by intracellular injection of ca2+ or of the ca-mobilizing agent inositol 1,4,5-trisphosphate. however, adenosine and ... | 1985 | 2994058 |
| adenosine stimulates sodium transport in kidney a6 epithelia in culture. | the effects of adenosine receptor agonists and antagonists were examined in epithelia formed in culture by a6 cells, a continuous cell line derived from xenopus laevis kidney. a6 epithelia have a high electrical resistance and a short-circuit current that is equal to net sodium flux from mucosal to serosal surface. adenosine, 2-chloroadenosine, 5'-(n-ethyl)carboxamidoadenosine, and n6-(l-2-phenylisopropyl) adenosine produced concentration-dependent increases in short-circuit current. stimulation ... | 1985 | 2994488 |
| circadian regulation of retinomotor movements. i. interaction of melatonin and dopamine in the control of cone length. | in lower vertebrates, cone retinomotor movements occur in response to changes in lighting conditions and to an endogenous circadian clock. in the light, cone myoids contract, while in the dark, they elongate. in order to test the hypothesis that melatonin and dopamine may be involved in the regulation of cone movement, we have used an in vitro eyecup preparation from xenopus laevis that sustains light- and dark-adaptive cone retinomotor movement. melatonin mimics darkness by causing cone elongat ... | 1985 | 2999294 |
| comparative nucleotide sequence analysis of two types of larval beta-globin mrnas of xenopus laevis. | the complete nucleotide sequence of the cdna insert of the clone pxgl25 derived from the larval beta ii-globin mrna of xenopus laevis has been determined. the sequence of 593 nucleotides represents part of the 5'nontranslated region, the coding region for 146 amino acids and the entire 3'nontranslated region. it diverges from the related larval beta i-sequence by 24.9% in the coding region. alignment of the 5' and 3'nontranslated regions of the two related larval beta-sequences to maximum matchi ... | 1985 | 2999708 |
| functional activity and chromatin configuration of sv40 enhancer injected in xenopus laevis oocytes. | the sv40 enhancer microinjected into the nuclei of x. laevis oocytes is able to activate transcription about 100-fold when cloned upstream of the sv40 early promoter region or about 10-fold regardless of its orientation when located at a long distance from a test gene (bacterial chloramphenicol acetyl transferase). this effect is qualitatively and quantitatively similar to that observed when analogous constructions were transfected into mammalian cells. making use of a direct labelling technique ... | 1985 | 2999713 |
| gabaergic regulation of melanocyte-stimulating hormone secretion from the pars intermedia of xenopus laevis: immunocytochemical and physiological evidence. | alpha-msh secretion from the amphibian pars intermedia is under inhibitory hypothalamic control, and the catecholamine dopamine is thought to be the physiological msh release-inhibiting factor. in the present study we evaluated the possible role of the neurotransmitter gamma-aminobutyric acid (gaba) in the regulation of the pars intermedia of xenopus laevis. immunocytochemical staining with antibodies to glutamic acid decarboxylase showed the presence of a rich gabaergic network in the intermedi ... | 1986 | 3000738 |
| visualization of rna polymerase ii ternary transcription complexes formed in vitro on a xenopus laevis vitellogenin gene. | stable ternary transcription complexes assembled in vitro, using a hela whole-cell extract, have been isolated and visualized by electron microscopy. the formation of these stable complexes on the dna fragment used as template, the 5' end region of the xenopus laevis vitellogenin gene b2, depends on factors present in the whole-cell extract, rna polymerase ii and at least two nucleotides. interestingly, bending in the dna fragment was frequently observed at the binding site of rna polymerase ii. ... | 1985 | 3000768 |
| simian virus 40-mediated cis induction of the xenopus beta-globin dnase i hypersensitive site. | regions in chromatin which are hypersensitive to the action of dnase i appear to be associated with sites of genetic activity; the association between dnase i hypersensitivity and transcriptional activation is well known. in the case of the chicken beta-globin gene the establishment of a dnase i hypersensitive site is dependent on tissue-specific trans-acting factors. such factors have also been implicated in the action of viral and cellular enhancers, which are themselves hypersensitive to dnas ... | 1985 | 3001531 |
| conserved restriction sites within the ribosomal rna genes of vertebrates. | we have mapped the cleavage sites of four restriction enzymes which recognize six-base sequences within the nuclear ribosomal (rrna) genes of twelve vertebrates, including several placental mammals (homo sapiens, man; bos taurus, cow; equus caballus, horse; sus scofra, pig; ovis aries, sheep; rattus rattus, rat), a marsupial (didelphis marsupialis, opossum), a bird (gallus domesticus, chicken), an amphibian (xenopus laevis), a reptile (alligator mississipiensis), a bony fish (cynoscion nebulosus ... | 1986 | 3004584 |
| functional domains of the xenopus laevis 5s gene promoter. | to study the fine structure of the xenopus laevis somatic 5s gene internal control region, we have created 15 different transversions using mutagenic oligonucleotide primers. the effects of these mutations on 5s dna transcription in vitro as well as on stable complex formation with transcription factor tf iii a and tf iii c in crude nuclear extracts were analyzed. mutations in the common class iii 5' promoter element (nucleotides 50-61 in the 5s gene) interfere with transcription activity and st ... | 1985 | 3004969 |
| nerve-induced remodeling of muscle basal lamina during synaptogenesis. | to identify mechanisms that regulate the deposition of the junctional basal lamina during synaptogenesis, immunocytochemical experiments were carried out on cultured nerve and muscle cells derived from xenopus laevis embryos. in some experiments successive observations were made on individual muscle cells after pulse-labeling with a fluorescent monoclonal antibody specific for a basal lamina proteoglycan. in others, old and new proteoglycan molecules were differentially labeled with antibody con ... | 1986 | 3005339 |
| the vi element. a transposon-like repeated dna sequence interspersed in the vitellogenin locus of xenopus laevis. | a repeated dna element in xenopus laevis is described that is present in about 7500 copies dispersed throughout the genome. it was first identified in the 5' flanking region of one vitellogenin gene and was therefore named the vi element. seven copies are present within the vitellogenin gene region, three of them within introns of the genes a1, a2 and b2, and the other four copies in the gene flanking regions. four of these copies have been sequenced. the vi element is bounded by a well-conserve ... | 1985 | 3005589 |
| expression of ribosomal insertion in drosophila: sensitivity to intercalating drugs. | ribosomal insertions in drosophila are transcribed at very low levels. the abundance of the most prominent 0.8 kb type 1 insertion transcript increased up to 60-fold when cultured cells were exposed to the dna intercalating drug chloroquine. after injection of insertion-containing rdna in circular form into xenopus laevis oocytes an apparently identical 0.8 kb insertion transcript was synthesized, and its accumulation was stimulated several fold by coinjection of chloroquine or ethidium bromide. ... | 1986 | 3005969 |
| nucleotide sequence of the chicken 5-aminolevulinate synthase gene. | 5-aminolevulinate synthase, the first and rate-controlling enzyme of heme biosynthesis, is regulated in the liver by the end-product heme. to study this negative control mechanism, we have isolated the chicken gene for ala-synthase and determined the nucleotide sequence. the structural gene is 6.9 kb long and contains 10 exons. the transcriptional start site for ala-synthase was determined by primer extension analysis. a fragment of 291 bp from the 5' flanking region including 34 bp of the first ... | 1986 | 3005973 |
| localized maternal mrnas in xenopus laevis eggs. | | 1985 | 3006987 |
| in vitro transcription by xenopus oocytes rna polymerase iii requires a dna topoisomerase ii activity. | extracts of xenopus laevis oocytes are able to assemble minichromosomes in vitro when they are supplemented with atp and mg2+. we have followed the time course of in vitro dna supercoiling and transcription of polyoma virus closed circular dna. the transcriptional activity increased with the assembly time of chromatin in the presence of both atp and mg2+, but only residual activity was detected in the absence of either of them. we also found that polyoma dna as well as 5s rna gene transcription ... | 1986 | 3007112 |
| circadian rhythm of interrenal activity in xenopus laevis. | young specimens of xenopus laevis were kept under constant environmental conditions (artifical light from 600 to 1800 hr, feeding between 800 and 900 hr) and the concentrations of aldosterone and corticosterone in the serum were measured every 3 hr. furthermore, the kidneys containing the interrenals were removed and their corticosteroid release under stimulation by the pars distalis and mammalian acth was determined. under these conditions, the corticosteroid levels in the serum were maximal fr ... | 1986 | 3007269 |
| information transfer during embryonic induction in amphibians. | neural induction and differentiation has been studied using concanavalin a, cyclic amp, tunicamycin and calcium ionophore a 23187. competent ectoderm of xenopus laevis treated with concanavalin a differentiates into neural (archencephalic) structures. binding studies with gold-labelled cona indicate that the superficial ectodermal layer contains fewer cona-sensitive sites (alpha-d-mannoside and alpha-d-glucoside residues of glycoproteins) than the inner ectodermal layer. the small number of cona ... | 1985 | 3007651 |
| isolation and characterization of sarcomeric actin genes expressed in xenopus laevis embryos. | a xenopus laevis complementary dna (cdna) library prepared from messenger rnas extracted from embryos has been screened for actin-coding sequences. two cdna clones corresponding to an alpha cardiac and an alpha skeletal muscle actin mrna have been identified and characterized. from a genomic library, we have furthermore isolated the genes that correspond to the characterized cdnas. in addition we have identified an actin processed gene which seems to be derived from a second type of skeletal mus ... | 1986 | 3009830 |
| comparison of structural requirements of alpha-msh and acth for inducing excessive grooming and pigment dispersion. | alpha-msh and acth-like peptides are known to play an important role in the adaptation of many vertebrates to a new environment. these peptides induce pigment dispersion in amphibian melanophores through a receptor-mediated mechanism. in this study we compared the structural requirements of these peptides for melanotropic activity on xenopus laevis melanophores with those for inducing excessive grooming in the rat. with the exception of acth1-24 there is a close resemblance in structure-activity ... | 1985 | 3010259 |
| dexamethasone and estrogen regulate xenopus laevis albumin mrna levels. | the regulation of albumin mrna levels by steroid hormones was examined in a primary xenopus liver culture system. in the absence of exogenous steroid hormone, albumin mrna levels declined rapidly in culture. dexamethasone is required for preservation of albumin mrna levels in culture and effects a greater than 10 fold induction of albumin mrna in cultures maintained in steroid hormone-free medium. estrogen can override the effect of dexamethasone and elicits a decline of greater than 80% in albu ... | 1986 | 3010979 |
| cyclic amp and cell differentiation in amphibian embryonic explants. | conflicting results have been published concerning the effects of cyclic nucleotides on amphibian cell differentiation. here we report the effects of cyclic adenosine monophosphate (camp) and dibutyryl-cyclic adenosine monophosphate (db-camp) on isolated explants from late blastulae of ambystoma mexicanum and xenopus laevis. both camp and db-camp (10(-4)-10(-9) m) promote 'neuralizing' differentiation in ambystoma explants. xenopus explants treated with the nucleotides (10(-4), 10(-6), 10(-8) m) ... | 1986 | 3011532 |
| cnpase activity in the vertebrate retina, retinal pigmented epithelium, and choroid. | the activity of the enzyme 2',3'-cyclic nucleotide 3'-phosphohydrolase (cnpase, e.c.3.1.4.37) has been studied in the retina of three vertebrate species. activity was highest in the goldfish, followed by xenopus laevis and rana pipiens. also, high activity levels were found in goldfish retinal pigment epithelium and choroid, but not in the other two species. when added to in vitro culture systems, 2',3'-cyclic nucleotides were found to have no effect on goldfish cone retinomotor movement, but ca ... | 1986 | 3011952 |
| some primary olfactory axons project to the contralateral olfactory bulb in xenopus laevis. | cobaltous lysine and horseradish peroxidase (hrp) were used to trace primary olfactory axons to their terminations. the tracers were taken up in the olfactory mucosa and transported to the olfactory bulb. the results suggest that either hrp or cobaltous-lysine methods are useful and simple tools for studying such connections. in addition to the ipsilateral projection, we report here for the first time a projection to the medial part of the contralateral olfactory bulb. the overlaps of ipsi- and ... | 1986 | 3012418 |
| recbc, sbcb independent, (at)n-mediated deletion of sequences flanking a xenopus laevis beta globin gene on propagation in e. coli. | plasmids containing sequences 3' of the adult beta 1 globin gene of xenopus laevis are unstable on propagation in a range of e. coli host strains. up to 300 bp of xenopus dna are lost by rec a independent recombination between (at)37 and (at)17 sequences. additionally, smaller deletions occurring in or around the (at)37 sequence are observed. deletion of these potential cruciform structures occurs in the absence of exonuclease i, exonuclease v and exonuclease viii as the same pattern of deletion ... | 1986 | 3012463 |
| identification of initiation sites for transcription of xenopus laevis mitochondrial dna. | the sites of transcription initiation for xenopus laevis mtdna have been mapped using in vitro capping and primer extension analysis of rna isolated from oocytes. transcription of the heavy strand initiates predominantly at a site 33 nucleotides upstream of the trnaphe gene. this promoter is bidirectional, with transcription of the light strand initiating only one base pair away. a second, more predominant light strand promoter is located 70 nucleotides away from the major heavy strand promoter. ... | 1986 | 3013854 |
| conserved sequences and cell-specific dnase i hypersensitive sites upstream from the co-ordinately expressed alpha i- and alpha ii-globin genes of xenopus laevis. | the globin gene family of xenopus laevis comprises pairs of closely related genes that are arranged in two clusters, each pair of genes being co-ordinately and stage-specifically expressed. to get information on putative regulatory elements, we compared the dna sequences and the chromatin conformation 5' to the co-ordinately expressed adult alpha-globin genes. sequence analysis revealed a relatively conserved region from the cap site up to position -289, and further upstream seven distinct boxes ... | 1986 | 3014154 |
| neurohypophysial peptide potencies in cultured anuran epithelia (a6). | to characterize the v2 receptor (for antidiuretic hormone), we have studied the effect of a number of neurohypophysial hormone analogues on cyclic amp (camp) accumulation and short-circuit current in cultured epithelia formed by a6 cells. a6 is the designation of a continuous cell line derived from the kidney of xenopus laevis. the order of potency for stimulating camp accumulation and short-circuit current in a6 epithelia is like that for stimulating water permeability in toad urinary bladder. ... | 1986 | 3014910 |
| synaptic organization of dorsal root projections to lumbar motoneurons in the clawed toad (xenopus laevis). | synaptic connexions between dorsal root primary afferents and lumbar motoneurons have been investigated in the isolated spinal cord of the clawed toad. the study of monosynaptic actions evoked in motoneurons by 9th or 10th dorsal root stimulation or by impulses in single primary afferents provided evidence for both electrical and chemical junctional transmission at the sensory-motor synapses. the anterograde filling of the 9th and 10th dorsal roots with horseradish peroxidase (hrp) shows that af ... | 1986 | 3015652 |
| major transitions in histone gene expression do not occur during development in xenopus laevis. | in light of the parallels that exist in the structure of histone genes in sea urchins and in the frog, xenopus laevis, and in the early development of these animals, it has been thought that xenopus histone gene expression might be subject to the type of developmental regulation observed in sea urchins. we have examined the patterns of histone mrna accumulation in xenopus oocytes and embryos by primer extension and s1 nuclease protection techniques. the data demonstrate that histone genes which ... | 1986 | 3015703 |
| cloning and sequencing of mrnas coding for two adult alpha globin chains of the salamander pleurodeles waltlii. | a cdna library of erythrocyte mrnas was established from immature red blood cells of the adult amphibian, pleurodeles waltlii (urodele; salamander). the cdna clones corresponding to the four adult globin chains were first identified and characterized by positive selection and the cdnas derived from the two (major and minor) alpha-globin chains sequenced. the sequences presented contain both the complete 3'-noncoding region and the coding region of both chains, with the exception of the first nin ... | 1986 | 3015729 |
| voltage dependence of the rheogenic na+/k+ atpase in the membrane of oocytes of xenopus laevis. | electrophysiological experiments were performed to analyze the na+/k+-atpase in full-grown prophase-arrested oocytes of xenopus laevis. if the na+/k+-atpase is inhibited by dihydroouabain (dho), the resting potential of the membrane of na+-loaded oocytes may depolarize by nearly 50 mv. this hyperpolarizing contribution to the resting potential depends on the degree of activation of the na+/k+-atpase and varies with intracellular na+ activity (aina) and extracellular k+ (k+o). it is concluded tha ... | 1986 | 3016280 |
| comparative development of end-plate currents in two muscles of xenopus laevis. | the development of miniature end-plate currents (m.e.p.c.s) was studied in the superior oblique and interhyoideus muscles of xenopus laevis. an analysis of m.e.p.c. decays shows that each muscle possesses its own characteristic programme of end-plate current development. in the superior oblique, the exponential decay constants of m.e.p.c.s were initially about 3 ms; they declined within half a day to 1 ms and remained at that value for six weeks. they then gradually became longer, reaching a mea ... | 1986 | 3018234 |
| regulation of simian virus 40 gene expression in xenopus laevis oocytes. | expression of the simian virus 40 (sv40) early and late regions was examined in xenopus laevis oocytes microinjected with viral dna. in contrast to the situation in monkey cells, both late-strand-specific (l-strand) rna and early-strand-specific (e-strand) rna could be detected as early as 2 h after injection. at all time points tested thereafter, l-strand rna was synthesized in excess over e-strand rna. significantly greater quantities of l-strand, relative to e-strand, rna were detected over a ... | 1985 | 3018545 |
| the ribosomal spacer in xenopus laevis is transcribed as part of the primary ribosomal rna. | s1 mapping of xenopus laevis ribosomal rna transcripts, both in oocyte microinjection experiments and in vivo, shows that all but 212 bp of the so-called "non-transcribed" spacer (nts) of the ribosomal dna repeat is transcribed as part of the primary ribosomal transcript. the 40s pre-ribosomal rna (pre-rrna) is therefore a processing intermediate. the primary ribosomal transcript co-terminates with the previously described spacer transcripts [moss], at a site 213 bp upstream of the 40s pre-rrna ... | 1986 | 3018668 |
| sequence analysis of the larval beta ii-globin gene of xenopus laevis. | the 1822 bp sequence of the larval xenopus laevis beta ii-globin gene is reported together with 240 bp upstream of the gene and 190 bp beyond the site of polyadenylation. the mrna start point was determined by primer extension as well as nuclease s1 mapping and the polyadenylation site by comparison of the gene sequence to the mrna sequence derived from a corresponding cdna clone. like other vertebrate globin genes, this gene comprises three exons interrupted by two intervening sequences (ivs). ... | 1986 | 3020391 |
| induction of taurine responsiveness in xenopus oocytes by messenger rna from mouse brain. | a taurine response was induced in the surface membrane of the oocytes of xenopus laevis by injection of the mrna from the neonatal mouse brain, and the response was studied electrophysiologically. the permeability of mrna-injected oocytes to chloride ions was increased by the application of taurine in a dose-dependent manner. the same oocyte also responded to gaba, but bicuculline suppressed only the gaba response. these results suggest a possibility that taurine could be a neurotransmitter of c ... | 1986 | 3020479 |
| dna replication in vitro erases a xenopus 5s rna gene transcription complex. | replication of the xenopus laevis 5s rna gene in vitro is unimpeded by the presence of a complete transcription complex assembled on the internal control region of the gene. the transcription complex is disrupted by passage of the replication fork, specific transcription factors are displaced, and the daughter 5s rna genes are inactivated. we have been unable to demonstrate that any "memory" of the preexisting transcription complex is transmitted to the daughter dna duplexes following replicatio ... | 1986 | 3021334 |
| tx1: a transposable element from xenopus laevis with some unusual properties. | a family of transposable genetic elements in the genome of the frog, xenopus laevis, is described. they are designated tx1. transposability of the elements was deduced by characterization of a chromosomal locus which is polymorphic for the presence or absence of a tx1 element. nucleotide sequence analysis suggested that tx1 elements show target site specificity, as they are inserted at the pentanucleotide tttaa in all four cases that were examined. the elements appear to have 19-base-pair (bp) i ... | 1986 | 3022140 |
| structural analysis of ribosomal dna homologues in nucleolus-less mutant of xenopus laevis. | sequences homologous to the ribosomal dna (rdna) in a xenopus anucleolate (nucleolus-less) mutant were analyzed by southern blot analysis. the mutant was found to possess a variety of sequences homologous to non-transcribed spacer (nts) and/or coding region of rdna. 65 rdna-homologous clones were isolated from a genomic dna library of the mutant. all the clones showed only partial homology to the normal rdna unit and their restriction maps differed from that of the normal rdna unit. based on the ... | 1986 | 3023192 |
| accurate in vitro transcription of xenopus laevis mitochondrial dna from two bidirectional promoters. | the mitochondrial rna polymerase from xenopus laevis oocytes was partially purified by heparin-sepharose chromatography and phosphocellulose chromatography. this rna polymerase preparation specifically initiated the transcription of x. laevis mitochondrial dna (mtdna) from two bidirectional promoters contained within a 123-base-pair segment of the mtdna between the heavy-strand replication origin and the rrna cistrons. transcription in vitro initiated from precisely the same start sites previous ... | 1986 | 3023938 |
| conserved sequence motifs upstream from the co-ordinately expressed vitellogenin and apovldlii genes of chicken. | the vitellogenin and apovldlii yolk protein genes of chicken are transcribed in the liver upon estrogenization. to get information on putative regulatory elements, we compared more than 2 kb of their 5' flanking dna sequences. common sequence motifs were found in regions exhibiting estrogen-induced changes in chromatin structure. stretches of alternating pyrimidines and purines of about 30-nucleotides long are present at roughly similar positions. a distinct box of sequence homology in the chick ... | 1986 | 3024115 |
| formation of the 3' end on u snrnas requires at least three sequence elements. | the structural requirements for 3' end formation on the xenopus laevis u1b snrna gene have been studied. three sequence elements are shown to be required. the first is a conserved sequence element found immediately 3' of all vertebrate u snrna genes studied so far. the second is a gene internal sequence potentially capable of forming a stem-loop structure close to the 3' end of the rna. the third element lies upstream of these, and may be part of the gene promoter. experiments designed to invest ... | 1986 | 3024969 |
| the pituitary adrenocorticotropes originate from neural ridge tissue in xenopus laevis. | a series of grafting experiments was conducted to determine pituitary origins prior to brain tube closure in xenopus laevis. extirpation experiments indicated that the ventral neural ridge (vnr) tissue of stage-18+ embryos was essential for pituitary development. bolton-hunter reagent was used to label stage-18+ vnr tissue with 125i, and this tissue was then returned to the donor and its subsequent ontogenesis followed. labelled tissue was ultimately found in the ventral hypothalamus, the ventra ... | 1986 | 3025328 |
| structural and functional analysis of chicken u4 small nuclear rna genes. | two distinct chicken u4 rna genes have been cloned and characterized. they are closely linked within 465 base pairs of each other and have the same transcriptional orientation. the downstream u4 homology is a true gene, based on the criteria that it is colinear with chicken u4b rna and is expressed when injected into xenopus laevis oocytes. the upstream u4 homology, however, contains seven base substitutions relative to u4b rna. this sequence may be a nonexpressed pseudogene, but the pattern of ... | 1986 | 3025618 |
| sequences involved in accurate and efficient transcription of human c-myc genes microinjected into frog oocytes. | by microinjecting a series of deletion mutant constructs into xenopus laevis oocytes, transcriptional control regions, two promoters, of the human c-myc gene were defined. in the case of the first promoter, sequences between -60 and -37 relative to the transcription start site contained an element essential for promoter activity. in the case of the second promoter, sequences between -66 and -56 relative to the initiation site appeared to be involved in accurate and efficient transcription. in bo ... | 1986 | 3025632 |
| [transcription, in frog oocytes and transgenic mice, of recombinant plasmids with long terminal repeats of retrovirus proviruses]. | rna-dna hybridization was used to study the transcription efficiency of the genes controlled by the long terminal repeats (ltr) from two different retroviral proviruses (exogenous provirus of the chicken rous sarcoma virus and endogenous xenotropic provirus of the mouse). the oocyte nuclei of xenopus laevis and the liver of transgenic mice were used as the transcription systems. the transcription efficiency of genes with the above mentioned promoters was shown to be roughly the same for both sys ... | 1986 | 3025678 |
| polylysine-containing peptides, including the carboxyl-terminal segment of the human c-ki-ras 2 protein, affect the activity of some key membrane enzymes. | polylysine-containing peptides are found to affect membrane protein kinases, phosphatidylinositol kinases, and adenylate cyclase. poly(l-lysine), poly(d-lysine), random copolymers of lysine and serine or lysine and alanine, and poly(l-ornithine) produced large increases in the in vitro phosphorylation of some membrane proteins present in xenopus laevis oocyte membranes. poly(l-arginine) did not cause a similar stimulation. in these membranes the phosphorylation of polydisperse protein of approxi ... | 1987 | 3025867 |
| characterization of gamma-aminobutyric acid receptors in the neurointermediate lobe of the amphibian xenopus laevis. | the neurotransmitter gamma-aminobutyric acid (gaba) is involved in the regulation of secretion of msh from the intermediate lobe of xenopus laevis. the purpose of this study was to identify the gaba receptor(s) involved by determination of the effect of specific receptor agonists and antagonists on the release of immunoreactive msh from superfused neurointermediate lobes of xenopus. exogenous gaba induces a rapid inhibition of msh secretion. there was no evidence for a transitory stimulatory eff ... | 1987 | 3026779 |
| a transcription factor which binds to the enhancers of sv40, immunoglobulin heavy chain and u2 snrna genes. | in eukaryotes the transcriptional control of rna polymerase ii-mediated gene expression is exerted by cis-acting regulatory dna elements classified as promoter and enhancer sequences. these elements are composed of a number of different protein binding sites. the regulatory factors that recognize such 'modules' may be ubiquitous, tissue- or stage-specific, and positively or negatively acting. according to this model the transcriptional activity of a given gene is programmed by a combination of d ... | 1987 | 3027566 |
| a dna binding protein showing sequence specificity for a region containing the replication origin of xenopus laevis mitochondrial dna. | in xenopus laevis mitochondria up to 14 different polypeptides with affinity for the dna, have been identified by the protein blotting technique. under stringent binding conditions only one polypeptide displayed specific affinity for a restriction fragment containing the h strand origin of replication of the xenopus laevis mt chromosome. the proteins were fractionated by double stranded dna cellulose chromatography. under conditions which favor high affinity interactions between proteins and dna ... | 1987 | 3029684 |
| pbr322 dna inhibits simian virus 40 gene expression in xenopus laevis oocytes. | sv40 dna form i is expressed efficiently after its injection into the nuclei of xenopus laevis oocytes, resulting in the synthesis of rna and protein products of both viral late and early transcription units. however it was observed that injection of sv40 genes cloned into pbr322 or related plasmids yielded vastly reduced quantities of viral dna and proteins. if sv40 dna was cleaved from the plasmid, and then recircularized prior to microinjection, viral expression was regained. the inhibition b ... | 1987 | 3029720 |
| differential induction of hepatic estrogen receptor and vitellogenin gene transcription in xenopus laevis. | low levels of estrogen receptor (200-500 per cell) are present in the liver of hormonally naive male xenopus. however, administration of estradiol results in a rapid 2- to 5-fold increase in cellular estrogen receptor content concurrent with the de novo transcriptional activation of the genes for the yolk protein precursor vitellogenin. studies on xenopus embryogenesis suggest that estrogen receptor induction is required for the activation of vitellogenin transcription. the purpose of the presen ... | 1987 | 3030694 |
| mrna-directed synthesis and insertion of functional amino acid receptors in xenopus laevis oocytes. | | 1987 | 3030837 |
| infection of a poikilothermic cell line (xl-2) with eastern equine encephalitis and western equine encephalitis viruses. | eastern equine encephalitis (eee) was in cuba before the 1940s; the virus has been isolated from horses, birds, and rodents during epizootic as well as interepizootic periods. the only isolation of western equine encephalitis (wee) virus was from a sick pigeon found in the vicinity of havana university. both viruses can cause human disease; the isolation of wee virus from the centre of an urban area emphasises the need for the prompt isolation and rapid identification of these agents. the object ... | 1987 | 3031203 |
| in vivo aminoacylation of human and xenopus suppressor trnas constructed by site-specific mutagenesis. | amber suppressor trna genes were constructed by site-specific mutagenesis of the anticodons of human lysine-inserting trna (trna(lys)) and glutamine-inserting trna (trna(gln)) genes, and a xenopus laevis tyrosine-inserting trna (trna(tyr)) gene. as previous in vitro studies in prokaryotes have shown that substitution of nucleotides in the anticodon region can profoundly affect trna aminoacylation, it is important to determine whether the mutation affects aminoacylation of these eukaryotic trnas. ... | 1987 | 3031670 |
| a rise in cytosolic calcium is not necessary for maturation of xenopus laevis oocytes. | cytoplasmic free calcium levels during progesterone-induced meiotic maturation in xenopus laevis oocytes were measured using the photoprotein aequorin. the resting level of [ca2+]i was 92.6 +/- 30 nm. no significant changes were observed after progesterone addition, although a large pulse of [ca2+]i was observed upon activation of matured oocytes. these findings are discussed in terms of the role of calcium in maturation and it is concluded that calcium is not the second messenger for progestero ... | 1987 | 3032713 |
| regulation by aldosterone of na+,k+-atpase mrnas, protein synthesis, and sodium transport in cultured kidney cells. | transepithelial na+ reabsorption across tight epithelia is regulated by aldosterone. mineralocorticoids modulate the expression of a number of proteins. na+,k+-atpase has been identified as an aldosterone-induced protein (geering, k., m. girardet, c. bron, j. p. kraehenbuhl, and b. c. rossier, 1982, j. biol. chem., 257:10338-10343). using a6 cells (kidney of xenopus laevis) grown on filters we demonstrated by northern blot analysis that the induction of na+,k+-atpase was mainly mediated by a two ... | 1987 | 3032984 |
| regulation of cyclic-amp synthesis in amphibian melanotrope cells through catecholamine and gaba receptors. | catecholamines and gaba are neurotransmitters involved in the regulation of release of pro-opiomelanocortin (pomc) derived peptides from the neurointermediate lobe of xenopus laevis. the present study concerns the relation of these neurotransmitters to the adenylate cyclase system of the melanotrope cell. during in vitro incubation of isolated melanotrope cells it was found that dopamine, adrenaline and ly 171555 induced inhibition of forskolin-stimulated camp production and concomitantly inhibi ... | 1987 | 3033416 |
| neurotensin receptors on the rat liver plasma membranes. | neurotensin (nt) is now classified as a brain-gut peptide in the central nervous system and gastrointestinal tract. in the present study, we characterized the nt receptors on the rat liver plasma membranes. the specific binding of [3h]nt was time dependent, reversible, and saturable. scatchard analysis of the specific binding data yielded two classes of binding sites, a high affinity site and a low affinity site. the average maximum number of binding sites (bmax) amounted to 13.3 +/- 1.1 fmol/mg ... | 1987 | 3038090 |
| sodium-dependent and sodium-independent phosphate uptake by full-grown, prophase-arrested oocytes of xenopus laevis before and after progesterone-induced maturation. | the uptake of inorganic phosphate by full-grown, prophase-arrested oocytes occurs by two essentially independent transport systems, which accomplish the delivery of extracellular phosphate into two different cellular compartments. one transport system is sodium-dependent, the other is sodium-independent. both systems can be inhibited by sulfhydryl reagents and the sodium-dependent system becomes inhibited during progesterone-induced oocyte maturation. | 1987 | 3038342 |
| nucleotide sequence and comparative analysis of the human papillomavirus type 18 genome. phylogeny of papillomaviruses and repeated structure of the e6 and e7 gene products. | the complete nucleotide sequence and genomic organization of human papillomavirus type 18, associated with cervical cancer, has been established. a detailed comparative analysis was undertaken leading to the identification of a number of features specific for genital papillomaviruses and the construction of a phylogenetic tree. genital papillomaviruses differ from other human and animal papillomaviruses as they possess a longer e1 open reading frame (orf) and have a characteristic control region ... | 1987 | 3039146 |
| establishment of a human t-cell hybridoma that produces human macrophage activating factor for superoxide production and translation of messenger rna of the factor in xenopus laevis oocyte. | human monoblast-like histiocytic lymphoma cell line u937 was induced by a macrophage activating factor for o2- production (maf-o) to produce o2- in response to phorbol myristate acetate stimulation. a maf-o-producing human t-cell hybridoma, f4-29-4, was established which was also found to produce macrophage activating factor for glucose consumption (maf-g) and colony stimulating factor (csf) when assayed against mouse bone marrow cells. maf-o could be successfully separated from csf but not from ... | 1987 | 3039355 |
| 72-bp element contains a critical control region for sv40 late expression in xenopus laevis oocytes. | the sv40 late promoter is transcribed at least 10-fold more efficiently than the sv40 early promoter when sv40 dna is injected into the germinal vesicle of xenopus laevis oocytes. late expression in the oocyte is independent of t antigen and does not require dna replication. to identify dna sequences required for sv40 late gene expression, 12 mutants spanning nucleotide position (np) 5187 to np 304 were injected into the germinal vesicles of x. laevis oocytes, and rna was extracted 18 to 24 hr l ... | 1987 | 3039731 |
| hormonal regulation of hepatic glycogenolysis in the toad, xenopus laevis, is mediated by cyclic amp and not ca2+. | hepatic glycogenolysis and glycogen phosphorylase a activity were stimulated by arginine vasotocin (avt) in liver pieces from xenopus laevis cultured in vitro. in each case, the ec50 was about l nm. the increased rate of glycogenolysis brought about by either avt or adrenaline was maintained for at least 6 hr and was unchanged when ca2+ salts were omitted from the medium or when 2.5 mm egta was added. neither the ca2+ ionophore, a23187, nor the ca2+ channel blocker, verapamil, had any effect on ... | 1987 | 3040519 |
| changes in the expression of alpha-fodrin during embryonic development of xenopus laevis. | fodrin (nonerythroid spectrin) and its associated proteins have been previously implicated in the establishment of specialized membrane-cytoskeletal domains in differentiating cells. using antiserum which is monospecific for the alpha-subunit of fodrin, we demonstrate that alpha-fodrin is present in oocytes and adult tissues of xenopus laevis. analyses of the de novo synthesis of alpha-fodrin during embryonic development reveal that alpha-fodrin is synthesized in oocytes, but not during early de ... | 1987 | 3040772 |
| the amino-terminal sequence of the xenopus laevis mitochondrial ssb is homologous to that of the escherichia coli protein. | two closely related forms of the single-stranded dna binding protein purified from xenopus laevis oocytes mitochondria have been identified. their amino terminal sequences exhibit homology with the escherichia coli ssb protein. | 1988 | 3042458 |
| alterations in the xenopus retinotectal projection by antibodies to xenopus n-cam. | the patterned neural projection from the eye to the optic tectum of lower vertebrates (the retinotectal projection) has been proposed to be ordered by interactions between the optic nerve fibers and their surrounding tissues. to investigate the role of one such defined cell interaction, agarose implants containing antibodies to the neural cell adhesion molecule, n-cam, were inserted into the tectum of the african clawed frog, xenopus laevis. both monoclonal and polyclonal antibodies against n-ca ... | 1988 | 3044878 |