| the nucleotide sequence of a human cdna encoding the highly conserved nucleolar phosphoprotein b23. | a cdna clone containing the complete coding sequence for the human nucleolar phosphoprotein b23 was isolated from a burkitt's lymphoma cdna library by immunoscreening with human autoantibodies. the b23 clone contained a 1.3 kb cdna insert encoding a polypeptide of 294 amino acids with a predicted molecular mass of 32,539 daltons. the deduced b23 amino acid sequence contained 2 acidic domains rich in aspartic and glutamic acid, a feature shared by a number of nuclear and nucleolar proteins. the h ... | 1989 | 2775293 |
| xlgv7: a maternal gene product localized in nuclei of the central nervous system in xenopus laevis. | the xenopus oocyte nucleus (gv) is a storehouse for a large number of proteins that are used during early development. we have cloned and characterized a cdna coding for a maternal gene product that is localized in the gv and then becomes highly enriched in the nuclei of the central nervous system (cns) of tadpoles and adult frogs. this cdna (xlgv7) is 2.1 kb and hybridizes to a 2.4-kb rna species on northern blots. southern blots of genomic dna suggest that this gene is a member of a multigene ... | 1989 | 2721962 |
| primary structure from amino acid and cdna sequences of two cu,zn superoxide dismutase variants from xenopus laevis. | a mixture of two different amino acid sequences was discovered in cu,zn superoxide dismutase purified from the amphibian xenopus laevis. no n-terminal post-translational modification was found. the high number of substitutions in the sequence suggested that protein heterogeneity was a product of gene duplication. this was confirmed by isolation of two different cdna clones. nucleotide sequence analysis allowed the primary structure of the two peptide chains to be unambiguously assigned. the obse ... | 1989 | 2751312 |
| differential cyclophosphamide sensitivity of suppressor function in xenopus, the clawed toad. | thymocyte and splenocyte cultures from in vivo immunised xenopus were assayed to test their suppressive capacity. immunisation with tnp-polyvinylpyrrolidone induced suppression. suppression induced by the haptenated antigens, tnp-red blood cells, tnp-lipopolysaccharide, and tnp-ficoll affected the anti-tnp antibody response of splenocytes from tnp-pvp immunised animals. pretreatment with cyclophosphamide revealed both a sensitive and insensitive suppression capacity in xenopus laevis. | 1989 | 2776936 |
| a 3' exonuclease activity degrades the pseudogene 5s rna transcript and processes the major oocyte 5s rna transcript in xenopus oocytes. | transcription of the major oocyte 5s rna gene (o) and pseudogene (psi) of xenopus laevis yields different rnas with three different homologous systems: oocyte microinjection, whole oocyte extract, and fractionated tfiiia + tfiiib + tfiiic components. those peculiar results are caused by a 3' rna exonuclease activity, which is inhibited in the oocyte extract, that rapidly degrades the pseudogene 5s rna but does not degrade as readily the chimeric rna transcripts generated by hindiii-truncated 5s ... | 1989 | 2777074 |
| related proteins are phosphorylated at tyrosine in response to mitogenic stimuli and at meiosis. | forty-two-kilodalton proteins that contain phosphotyrosine in metaphase-arrested xenopus laevis eggs are closely related to p42, a protein that is phosphorylated at tyrosine when somatic cells are exposed to mitogenic stimuli. | 1989 | 2779558 |
| repair of a synthetic abasic site in dna in a xenopus laevis oocyte extract. | covalently closed circular dna containing a synthetic analog of an abasic site at a unique position was used as a substrate to study dna repair. incubation of this dna in xenopus laevis oocyte extracts resulted in rapid cleavage of the dna at the abasic site by a class ii apurinic-apyrimidinic endonuclease, followed by complete repair within 40 min. nicked circular dnas persisted for several minutes before repair by an atp-dependent dna synthesis reaction. the repair-related dna synthesis was lo ... | 1989 | 2779565 |
| the xenopus laevis ribosomal gene terminator contains sequences that both enhance and repress ribosomal transcription. | a dna segment approximately 200 base pairs upstream of the xenopus laevis ribosomal promoter acts both as an upstream promoter element that augments transcription and as a transcription terminator. it is, however, unclear to what extent these two activities are related. a segment of the x. laevis ribosomal dna, containing the terminator and the upstream promoter element, was subjected to point mutation, and the effects of the resulting mutations were investigated by oocyte microinjection. analys ... | 1989 | 2779566 |
| sequence and expression of chicken and mouse rsk: homologs of xenopus laevis ribosomal s6 kinase. | we have previously reported the isolation of cdnas encoding two closely related xenopus ribosomal s6 kinases, s6kii alpha and -beta (s. w. jones, e. erikson, j. blenis, j. l. maller, and r. l. erikson, proc. natl. acad. sci. usa 85:3377-3381, 1988). we report here the molecular cloning of one chicken and two mouse homologs of the xenopus laevis cdnas. as described for the xenopus proteins, these cdnas were found to predict polypeptides that contain two distinct kinase domains, of which one is mo ... | 1989 | 2779569 |
| expression of the poly(a)-binding protein during development of xenopus laevis. | we have isolated and sequenced cdna clones encoding the poly(a)-binding protein of xenopus laevis oocytes. polyclonal antiserum was raised against a fusion protein encoding 185 amino acids of the xenopus poly(a)-binding protein. this antiserum localizes the poly(a)-binding protein to subcellular sites associated with protein synthesis; in the retina, immunoreactive protein is detected in the synthetically active inner segment of the photoreceptor but not in the transductive outer segment. transc ... | 1989 | 2761544 |
| developmental patterns of peroxisomal enzymes in amphibian liver during spontaneous and triiodothyronine-induced metamorphosis. | 1. liver catalase, d-amino acid oxidase, urate oxidase of alytes obstetricans and xenopus laevis (anuran amphibians) and fatty acyl-coa oxidase of alytes were present at all post-embryonic stages. 2. catalase and d-amino acid oxidase activities increased during spontaneous metamorphosis of the two species. 3. during triiodothyronine-induced metamorphosis of alytes larvae, catalase and d-amino acid oxidase activities increased after a latent period. 4. our results suggest that expression of some ... | 1989 | 2776437 |
| methylation of ribosomal cistrons in diploid and tetraploid odontophrynus americanus (amphibia, anura). | odontophyrynus americanus (amphibia, anura) genomic dna from diploid and tetraploid specimens was treated with restriction enzymes sensitive to cytosine and adenine methylation (5 mec and 6 mea). in both diploids and tetraploids a high proportion of the total dna was not cleaved by 5 mec-sensitive enzymes as observed on agarose gels stained with ethidium bromide. the dnas were transferred to nitrocellulose filters and hybridized with cloned fragments containing sequences of xenopus laevis 28s an ... | 1989 | 2776516 |
| a protein kinase c cdna without the regulatory domain is active after transfection in vivo in the absence of phorbol ester. | we constructed mutant protein kinase c (pkc) cdnas which expressed pkc activity in vivo in the absence of phorbol ester activation. a hybrid pkc gene, pkac, was constructed by substituting the coding region for the n-terminal 253 amino acids of pkc alpha with the n-terminal 17 amino acids of the cyclic amp-dependent protein kinase catalytic subunit (pka). a truncated pkc gene, delta pkc beta, lacking the coding region for amino acid positions 6 to 159 of pkc beta was also constructed. these muta ... | 1989 | 2785241 |
| reconstitution of endoplasmic reticulum in rapidly dividing cells of early xenopus embryos. | the cytology of early blastomeres of xenopus laevis embryos was examined. particular attention was given to the organization of the nuclear envelope of karyomeres (chromosome vesicles) and the endoplasmic reticulum (er) at different stages in early cleavage cycles of frog development. nuclear envelope formation was observed to occur rapidly around individual chromosomes during early anaphase, and karyomeres fused subsequently to yield the final nucleus during telophase. endoplasmic reticulum in ... | 1989 | 2782291 |
| hydrins, hydroosmotic neurohypophysial peptides: osmoregulatory adaptation in amphibians through vasotocin precursor processing. | from neurointermediate pituitary glands of xenopus laevis and rana esculenta, previously unreported peptides termed hydrins, active on water permeability of frog urinary bladder and frog skin (brunn or "water-balance" effect), have been isolated and sequenced. these peptides seem to be derived from the pro-vasotocin-neurophysin precursor. hydrin 1, found in xenopus, has been identified as vasotocin c-terminally extended with the gly-lys-arg sequence; hydrin 2, found in rana, has been identified ... | 1989 | 2787509 |
| intracellular signals for developmental hemoglobin switching. | we have detected trans-acting factors that regulate developmental hemoglobin switching by fusing erythroid cells of different developmental programs. adult erythroid cells of one anuran species, xenopus laevis, were fused with tadpole erythroid cells of another frog, rana catesbeiana. in a second set of experiments, dimethyl sulfoxide-induced murine erythroleukemia cells, which express only adult mouse globins, were fused with rana tadpole erythroid cells, which express only embryonic and fetal- ... | 1989 | 2785064 |
| species variation in transcription factor iiia. | species variation in transcription factor iiia (tfiiia) was examined by comparing the abilities of tfiiias isolated from different xenopus and rana species to 1) bind rabbit anti-xenopus laevis tfiiia igg, 2) specifically interact with the xenopus borealis somatic 5s rna gene, and 3) promote transcription of the xenopus borealis 5s rna gene in vitro. in immunoblot assays, rana catesbeiana or rana pipiens tfiiia did not react readily with rabbit anti-xenopus laevis tfiiia igg (assayed with anti-r ... | 1989 | 2783776 |
| mitosis-specific monoclonal antibodies block cleavage in amphibian embryos. | by microinjecting monoclonal antibodies that bind specifically to mitotic and meiotic cells of a variety of species, we studied the biological activity of antigens recognized by these antibodies. the antibodies recognize a family of phosphoprotein antigens that are found throughout the cytoplasm of mitotic cells and particularly at microtubule organizing centers, including centrosomes and kinetochores. their binding is dependent on phosphorylation of the polypeptides. immunoglobulins were introd ... | 1989 | 2787211 |
| thyroid-stimulating hormone (tsh) deficiency caused by a single base substitution in the cagyc region of the beta-subunit. | congenital isolated thyroid-stimulating hormone (tsh) deficiency is an autosomal recessive disease that manifests as hypothyroidism (cretinism), causing severe mental and growth retardations. patients were found to have a single base substitution in the codon for the 29th amino acid of the tsh beta subunit gene. the alteration is in the center of the so-called cagyc region, which consists of an amino acid sequence conserved among all of the known glycoprotein hormone beta subunits. no other nucl ... | 1989 | 2792087 |
| nucleic acids can regulate the activity of casein kinase ii. | casein kinase ii purified from nuclei of xenopus laevis oocytes is inhibited by several specific nucleic acids. this kinase, the main phosphorylating activity of the oocyte nucleus, is markedly inhibited by poly u at 10 micrograms/ml, and this polymer is a competitive inhibitor of the phosphorylation of the substrate casein (kiapp 80 nm). m 13 phage ssdna and unfractionated yeast trna also inhibit between 50 and 200 micrograms/ml. poly c, poly a, poly ag, dsdna and escherichia coli rrna do not a ... | 1989 | 2792384 |
| oocyte and somatic tyrosine trna genes in xenopus laevis. | over a period of many months, xenopus oocytes stockpile large quantities of trna for use during the first few hours of embryogenesis. to test the idea that these trnas are transcribed from one set of genes and that another set is used by somatic cells, we used synthetic oligonucleotides to analyze the sequence and steady-state levels of unspliced tyrosine trna precursors in xenopus laevis oocytes, embryos, and cultured kidney cells. these analyses identify four kinds of tyrosine trna genes, two ... | 1989 | 2792760 |
| the plasma membrane of xenopus laevis spermatozoon. | xenopus laevis sperm plasma membrane ultrastructure has been studied by means of freeze-fracture, deep-etching, and lectin-gold binding. xenopus spermatozoa differ from those of other species in that their plasma membrane does not exhibit topographical domains. in fact, no geometric arrangement or characteristic array of particles is present on fractured plasma membrane. fractures rarely occur in acrosomal or nuclear membranes. wheat germ agglutinin receptors are distributed homogeneously on the ... | 1989 | 2793062 |
| transactivation of the xenopus rrna gene promoter by its enhancer. | a key question concerning the mechanism of transcriptional activation by enhancers is about the role of the dna that connects the enhancer to the promoter. the linking dna will be important if a regulatory protein(s) binds to the enhancer and then tracks or slides along the dna to the promoter, or if, on binding, the protein(s) alters the topological state of the dna. by contrast, if the linking dna loops out to allow the formation of a promoter-enhancer complex, or if the enhancer increases the ... | 1989 | 2797192 |
| the sequence of a nervous system-specific, class ii beta-tubulin gene from xenopus laevis. | | 1989 | 2798144 |
| identification and quantification in single muscle fibers of four isoforms of parvalbumin in the iliofibularis muscle of xenopus laevis. | the major parvalbumins present in the iliofibularis muscle of xenopus laevis were identified and the total parvalbumin content of different types of single fibers of this muscle was determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (sds). the criteria used in the identification of proteins as parvalbumins were: a relative molecular mass (mr) between 10,000 and 14,000, an isoelectric point (pi) between 4.0 and 5.0, and a ca2+-dependent mobility when run o ... | 1989 | 2790059 |
| use of chemical modifications and site-directed mutagenesis to probe the functional role of thiol groups on the gamma subunit of torpedo californica acetylcholine receptor. | alkylation of torpedo californica purified nicotinic acetylcholine receptor (achr) with n-phenylmaleimide (npm) under nonreducing conditions led to ion flux inhibition without affecting ligand binding properties [yee, a. s., corey, d. e. & mcnamee, m. g. (1986) biochemistry 25, 2110-2119]. the gamma subunit was shown to be preferentially labeled by [3h]npm with partial labeling of the alpha subunit at higher npm concentrations. alkylation occurs at cysteine residues as confirmed by amino acid an ... | 1989 | 2790013 |
| the nervus terminalis in larval and adult xenopus laevis. | nervus terminalis (nt) projections were studied by hrp injections into one nostril in adult xenopus and in xenopus tadpoles. central nt targets are: medial septum, preoptic nucleus, nucleus of the anterior commissure, and hypothalamus (mainly ipsilaterally). in xenopus tadpoles, additional fibers reach the ipsilateral dorsal thalamus and the mesencephalic tegmentum, bilaterally; furthermore, hypothalamic projections are bilateral. xenopus tadpole nt connections resemble those of adult urodeles m ... | 1989 | 2790468 |
| the developmental expression of the heat-shock response in xenopus laevis. | we have investigated the xenopus heat-shock response of somatic cells, oocytes and embryos. xenopus defolliculated oocytes displayed a highly variable response to heat shock depending on the culture medium. intact follicles, however, respond to heat stress by synthesizing an invariant pattern of hsps. although a subset of the hsp70/68 complex is expressed constitutively in the absence of heat shock in oocytes and embryos (hsc70), actual induction of hsps in response to stress does not occur unti ... | 1989 | 2806121 |
| expression of intermediate filament proteins during development of xenopus laevis. i. cdna clones encoding different forms of vimentin. | to provide a basis for studies of the expression of genes encoding the diverse kinds of intermediate-filament (if) proteins during embryogenesis of xenopus laevis we have isolated and characterized if protein cdna clones. here we report the identification of two types of xenopus vimentin, vim1 and vim4, with their complete amino acid sequences as deduced from the cloned cdnas, both of which are expressed during early embryogenesis. in addition, we have obtained two further vimentin cdnas (vim2 a ... | 1989 | 2806127 |
| expression of intermediate filament proteins during development of xenopus laevis. ii. identification and molecular characterization of desmin. | during embryogenesis of avian and mammalian species the formation of intermediate filaments (ifs) containing desmin is characteristic for myogenesis. in view of important differences of patterns of if protein expression in embryogenic pathways of amphibia on the one hand and birds and mammals on the other, we have decided to study the expression of desmin during early embryogenesis of xenopus laevis by cdna hybridization and antibody reactions. here we describe the isolation of a cdna clone enco ... | 1989 | 2806128 |
| association of higher molecular weight ribonucleoproteins of 7 s particle preparations with multimers of transcription factor iiia. | high molecular weight (hmw) fractions of xenopus laevis 7 s ribonucleoprotein (rnp) particle preparations were analyzed for rna and protein content. rna/protein ratios, amino acid analyses and western blots reveal that the major hmw fraction from a non-denaturing polyacrylamide gel (band b) contains two molecules of transcription factor protein iiia (tfiiia) to one 5 s rna. another hmw band appears to contain 4 molecules of tfiiia to one 5 s rna. yet another rnp band (band a) contains 5 s rna an ... | 1989 | 2806557 |
| a preliminary investigation into the effect of thyroid hormones on the metamorphic changes in meckel's cartilage in xenopus laevis. | the effects of short-term dosage with thyroid powder on the metamorphic changes in meckel's cartilage in xenopus laevis are described. the lag phase of development appears to be by-passed, and the usual sequential arrangement of the division and synthesis phases is disrupted, the processes of normal metamorphic changes being considerably accelerated. | 1989 | 2808112 |
| the conserved carboxy-terminal cysteine of nuclear lamins is essential for lamin association with the nuclear envelope. | we have analyzed the interaction of soluble nuclear lamins with the nuclear envelope by microinjection of normal and mutated lamins into the cytoplasm of xenopus laevis oocytes. our results demonstrate that the conserved cysteine of the carboxy-terminal tetrapeptide cys ala/ser ile met of lamins is essential for their association with the nuclear envelope. removal of this sequence or replacement of the cysteine by serine resulted in xenopus lamin l1 remaining in a soluble, non-envelope-associate ... | 1989 | 2808518 |
| sexual differences as adaptation to the different gender roles in the frog xenopus laevis daudin. | 1. various physiological parameters were determined in fed, adult, male and female xenopus laevis acclimated to 20 degrees c and with a light: dark cycle of 12:12. the results were compared for sex differences. 2. there were significant differences in food intake, oxygen consumption, and motor activity with lower values for each parameter in males than in females (table 1). 3. further significant differences were found in the plasma concentrations of calcium, total lipids, and aldosterone (table ... | 1989 | 2808856 |
| endogenous d-glucose transport in oocytes of xenopus laevis. | endogenous glucose uptake by the oocytes of xenopus laevis consists of two distinct components: one that is independent of extracellular na+, and the other one that represents na+-glucose cotransport. the latter shows similar characteristics as 2 na+-1 glucose cotransport of epithelial cells: the similarities include the dependencies on external concentrations of na+, glucose, and phlorizin, and on ph. as in epithelial cells, the glucose uptake in oocytes can also be stimulated by lanthanides. b ... | 1989 | 2810354 |
| enhanced development of striated myofibrils in xenopus myoblasts cultured in an applied electric field. | cultured myoblasts from xenopus laevis differentiating in a dc electric field (approximately 100 mv/mm) had more microfilaments, more striated myofibrils and an increased z-disc diameter than myoblasts in control cultures. | 1989 | 2798762 |
| large scale isolation of nuclei from oocytes of xenopus laevis. | we describe an improvement on the procedure of scalenghe et al. (f. scalenghe, m. buscaglia, c. steinheil, and m. crippa (1978) chromosoma 66, 299-308) for the large scale isolation of nuclei from xenopus laevis oocytes. the nuclear extract obtained was tested for its ability to transcribe a cloned xenopus 5 s rna gene and for the presence of nuclear factors interacting with a x. laevis ribosomal protein gene promoter. efficiency of accurate transcription and of factor binding is comparable with ... | 1989 | 2817341 |
| biplexiform ganglion cells in the retina of xenopus laevis. | a few cells were seen on retinal wholemounts of xenopus frogs whose dendrites branched in both the inner and the outer plexiform layers after the application of retrograde tracers to the cut optic nerve. the somas of these cells were displaced into the inner nuclear layer of the retina, and occasionally in orthotopic position. these observations provide convincing evidence that previously described biplexiform cells are ganglion cells and that these cells are regular components of the vertebrate ... | 1989 | 2804686 |
| the duty cycle of single muscle fibers from xenopus laevis. | | 1989 | 2798523 |
| rapid stimulation of diacylglycerol production in xenopus oocytes by microinjection of h-ras p21. | the p21 products of ras proto-oncogenes are thought to be important components in pathways regulating normal cell proliferation and differentiation. these proteins acquire transforming properties as a result of activating lesions that convert ras genes to oncogenes in a wide array of malignancies. in xenopus laevis oocytes, microinjection of transforming ras p21 is a potent inducer of maturation, whereas microinjection of a monoclonal antibody to ras p21 inhibits normal maturation induced by hor ... | 1987 | 2821623 |
| [regulation of transcription of immunoglobulin kappa genes in xenopus laevis oocytes]. | recombinant plasmids containing the immunoglobulin kappa gene with deletions in the 5' and 3' regions of the gene having different position and orientation of the enhancer element were constructed. the plasmids were incubated with cell-free extracts prepared from lymphoid and non-lymphoid cells, and then injected into the nuclei of xenopus laevis oocytes. tissue-specific transcription of the v kappa gene was shown to be under control of factor(s) existing in lymphoid cells. the data reported in ... | 1987 | 2822537 |
| dna sequences in the first intron of the human pro-alpha 1(i) collagen gene enhance transcription. | a chimeric gene was constructed in which sequences between 253 base pairs (bp) upstream of the start of transcription of the human pro-alpha 1(i) collagen gene and 117 bp downstream of that site were fused to the human alpha 1-globin gene, at a site immediately upstream of the globin initiation codon. expression of this and subsequent chimeric gene constructions was investigated in microinjected xenopus laevis oocytes. presence of 253 bp of pro-alpha 1(i) collagen gene promoter sequences, contai ... | 1987 | 2822714 |
| n-terminal acetylation of melanophore-stimulating hormone in the pars intermedia of xenopus laevis is a physiologically regulated process. | the n-terminal acetylation of melanophore-stimulating hormone (msh) increases the melanotropic potency of the peptide. this modification may be important in amphibians, where msh causes skin darkening during adaptation to black background. this study examines the acetylation status of the peptide in the toad xenopus laevis under different conditions of background adaptation. acetylated and nonacetylated alpha-msh were analyzed by high-performance liquid chromatography and quantified by radioimmu ... | 1987 | 2823159 |
| cloning, sequencing, and expression of the gene coding for the human platelet alpha 2-adrenergic receptor. | the gene for the human platelet alpha 2-adrenergic receptor has been cloned with oligonucleotides corresponding to the partial amino acid sequence of the purified receptor. the identity of this gene has been confirmed by the binding of alpha 2-adrenergic ligands to the cloned receptor expressed in xenopus laevis oocytes. the deduced amino acid sequence is most similar to the recently cloned human beta 2- and beta 1-adrenergic receptors; however, similarities to the muscarinic cholinergic recepto ... | 1987 | 2823383 |
| expression of rat mrna coding for hormone-stimulated adenylate cyclase in xenopus oocytes. | beta-adrenergic agonist-stimulated hyperpolarization, whole-cell camp accumulation, and activity of isoproterenol-stimulated membrane-bound adenylate cyclase (ec 4.6.1.1) in xenopus laevis ovarian oocytes are entirely dependent on the presence of nascent follicle cells. a method was developed to remove rapidly and completely all extra-oocyte cell types to yield defolliculated oocytes that exhibited normal viability and resting membrane potentials yet lacked beta-adrenergic receptor (beta ar)-sti ... | 1987 | 2824269 |
| the telomeres of tetrahymena ribosomal dna are not sufficient for stabilizing linear dna in xenopus oocytes. | restriction fragments that include the telomeres of ribosomal dna from tetrahymena thermophila (ttrdna) were ligated to the ends of linearized simian virus 40 (sv40) dna. the linear sv40 dna with ttrdna ends, circular sv40 dna, linear sv40 dna, and intact ttrdna were injected into the nuclei of xenopus laevis oocytes and assayed for stability. the intact linear 21-kb ttrdna and circular sv40 dna were maintained stably for at least 72 h after injection while the linearized sv40 dna, either with o ... | 1987 | 2824294 |
| functional activity and regulation of human beta 2-adrenergic receptors expressed in xenopus oocytes. | the recently cloned human beta-adrenergic cdna and several mutated forms have been expressed in xenopus laevis oocytes by injection of rna made from the cdna under the control of the bacteriophage sp6 promoter. the cdna and gene of the beta 2-adrenergic receptor possess the unusual feature of having a second upstream atg (-101 base pairs) and a 19-codon open reading frame 5' to the initiator methionine codon of the receptor (kobilka, b. k., dixon, r. a. f., frielle, t., dohlman, h. g., bolanowsk ... | 1987 | 2824467 |
| metabolic regulation during early frog development. identification of proteins labeled by 32p-glycolytic intermediates. | when 32p-labeled phosphoenolpyruvate is injected into xenopus laevis oocytes, a 50-60-kda protein of subunit size mr 29,000 is rapidly labeled, followed by a second (monomeric) protein of 66 kda concomitant with the loss of label from the first protein. we have identified these proteins as, respectively, the glycolytic enzymes phosphoglyceromutase and phosphoglucomutase. the phosphoglyceromutase is labeled at a histidine and the phosphoglucomutase at a serine, presumably at their active sites du ... | 1987 | 2824510 |
| fixation of the unmethylated or the 5'-ccgg-3' methylated adenovirus late e2a promoter-cat gene construct in the genome of hamster cells: gene expression and stability of methylation patterns. | the late e2a promoter of adenovirus type 2 (ad2) dna can be inactivated by in vitro methylation of three 5'-ccgg-3' sequences at positions +23, +5, and -215 relative to the cap site in this promoter. this inactivation has been documented in transient expression experiments both in xenopus laevis oocytes and in mammalian cells (k.-d. langner, l. vardimon, d. renz, and w. doerfler, proc. natl. acad. sci. usa 81:2950-2954, 1984; k.-d. langner, u. weyer, and w. doerfler, proc. natl. acad. sci. usa 8 ... | 1987 | 2824809 |
| a comparison of eukaryotic viral 5'-leader sequences as enhancers of mrna expression in vivo. | the 5'-untranslated leader sequences of several plant rna viruses, and a portion of the 5'-leader of an animal retrovirus, were tested for their ability to enhance expression of contiguous open reading frames for chloramphenicol acetyltransferase (cat) or beta-glucuronidase (gus) in tobacco mesophyll protoplasts, escherichia coli and oocytes of xenopus laevis. translation of capped or uncapped transcripts was substantially enhanced in almost all systems by the leader sequence of either the u1 or ... | 1987 | 2825117 |
| sequence organization and developmentally regulated transcription of a family of repetitive dna sequences of xenopus laevis. | members of a family of dna sequences of xenopus laevis have been cloned and sequenced. molecular analyses revealed that these sequences are moderately repetitive and dispersed throughout the genome. the sequences of seven clones were compared. two of the clones lie in the globin gene cluster; one 5' to the adult alpha 1 gene, and the other in the first intron of the tadpole alpha 1 gene. in all clones, the homologous region begins at the same site, but the lengths of the common regions vary from ... | 1987 | 2825138 |
| cloning of the cdna for the human beta 1-adrenergic receptor. | screening of a human placenta lambda gt11 library has led to the isolation of the cdna for the human beta 1-adrenergic receptor (beta 1ar). used as the probe was the human genomic clone termed g-21. this clone, which contains an intronless gene for a putative receptor, was previously isolated by virtue of its cross hybridization with the human beta 2-adrenergic receptor (beta 2ar). the 2.4-kilobase cdna for the human beta 1ar encodes a protein of 477 amino acid residues that is 69% homologous wi ... | 1987 | 2825170 |
| xfin: an embryonic gene encoding a multifingered protein in xenopus. | the xenopus laevis genome was screened for putative dna-binding gene products by using the 'finger' region of the drosophila gene krüppel as a probe. the one gene detected, named xfin, codes for a protein with 37 finger domains that comprise nearly 90% of the protein. in the light of studies by rhodes and klug (cell, 46, 123-132, 1986), these data suggest that the xfin protein has the capacity to bind an unusually large stretch (185 bases) of dna. the xfin gene is expressed as a maternal and zyg ... | 1987 | 2826129 |
| isolation and characterization of conditional lethal amber nonsense mutants of vesicular stomatitis virus. | we describe the isolation and characterization of conditional lethal amber nonsense mutants of vesicular stomatitis virus (vsv), indiana serotype. the mutants were isolated from a chemically mutagenized stock of wild-type virus by their ability to grow on genetically engineered cells which express a xenopus laevis amber suppressor tyrosine trna gene (su+ cells) but not on the non-suppressor parental cells (su- cells). five mutations were assigned to complementation group i (the l gene) and one t ... | 1987 | 2826648 |
| monohydroxyeicosatetraenoic acid and leukotriene production by the inflammatory cells of xenopus laevis. | ten frogs (xenopus laevis) were injected with mixed bacteria to produce a septic peritonitis. peritoneal inflammatory cells of eight animals were studied for monohydroxyeicosanoid and leukotriene production from exogenous arachidonic acid. large amounts of 12-hydroxyeicosatetraenoic acid were produced; smaller amounts of 5- and 15-hydroxyeicosatetraenoic and leukotriene b4 were produced. identifications were confirmed by retention times on hplc, ultraviolet spectroscopy on all products, and gas ... | 1987 | 2821155 |
| characterization of cyclic nucleotide phosphodiesterases in xenopus laevis ovary. | a cgmp-stimulated cyclic nucleotide phosphodiesterase present in cytosol of xenopus laevis ovary has been purified and characterized. a camp-specific phosphodiesterase which is not activated by either cgmp or calmodulin, has also been characterized. brief exposure of intact oocytes to 10 micro m progesterone results in an increase in activity of the camp-specific enzyme. the cgmp-stimulated and the calmodulin-activated phosphodiesterases are not altered. changes in cyclic nucleotide levels durin ... | 1987 | 2827950 |
| cloning of cdna encoding a new peptide c-terminal alpha-amidating enzyme having a putative membrane-spanning domain from xenopus laevis skin. | a cdna clone encoding a precursor of a peptide c-terminal alpha-amidating enzyme (ae-i) from xenopus laevis skin was recently isolated and sequenced in our laboratory. in this study, by using the restriction fragment of this clone as a hybridization probe, we have identified the cdna encoding another new peptide c-terminal alpha-amidating enzyme (tentatively named ae-ii) distinct from ae-i. the cdna encodes a polypeptide of 875 amino acid residues, which contains a region extensively homologous ... | 1988 | 2829895 |
| levitide, a neurohormone-like peptide from the skin of xenopus laevis. peptide and peptide precursor cdna sequences. | a novel peptide, levitide, less than glu-gly-met-ile-gly-thr-leu-thr-ser-lys-arg-ile-lys-gln-nh2 has been isolated from skin secretions of the south african frog xenopus laevis and sequenced by fast atom bombardment mass spectrometry. synthetic oligonucleotides were used as probes to screen a x. laevis skin cdna library for species coding for preprolevitide. two such clones were detected and their sequences are reported here. preprolevitide is 88 residues long, exhibits a putative signal sequenc ... | 1988 | 2830279 |
| repair of uv-induced lesions in xenopus laevis oocytes. | we characterized a dna repair system in frog oocytes by comicroinjection of uv-irradiated pbr322 dna and radiolabeled nucleotides. repair synthesis was monitored by incorporation of label into recovered pbr322 dna and by a novel method in which the removal of uv photoproducts was determined from the shift of dna topoisomers that occurs during gel electrophoresis upon repair of these lesions. we investigated the effects of several drugs in the oocyte system and found that although novobiocin, an ... | 1987 | 2830488 |
| cloning and characterization of a cdna from xenopus laevis coding for a protein homologous to human and murine p53. | a xenopus laevis oocyte cdna library was screened with a murine p53 cdna probe for the presence of p53-related clones. several such clones were isolated and analysed. the nucleotide sequence of the largest cdna clone (2.2 kb) showed a high degree of homology with the human (68%) and murine (70%) p53 coding sequences. this clone contains a single large open-reading frame, coding for a protein of 363 amino acids, which is 51% homologous to human p53 and 57% homologous to murine p53. furthermore, f ... | 1987 | 2830576 |
| estrogen-dependent in vitro transcription from the vitellogenin promoter in liver nuclear extracts. | one approach to analyzing the molecular mechanisms of gene expression in vivo is to reconstitute these events in cell-free systems in vitro. although there is some evidence for tissue-specific transcription in vitro, transcriptionally active extracts that mimic a steroid hormone-dependent enhancement of transcription have not been described. in the study reported here, nuclear extracts of liver from the frog xenopus laevis were capable of estrogen-dependent induction of a homologous vitellogenin ... | 1988 | 2830672 |
| regulation of msh release from the neurointermediate lobe of xenopus laevis by crf-like peptides. | immunocytochemical studies showed the presence of a fiber system containing a crf-like peptide in the median eminence and in the neural lobe of the pituitary gland of xenopus laevis. during in vitro superfusion of neurointermediate lobe tissue, crf, sauvagine and urotensin i induced a rapid and dose-dependent stimulation of secretion of msh and endorphin. tissue of white-background adapted animals displayed a remarkably higher sensitivity to crf and sauvagine than tissue from animals that were a ... | 1987 | 2831518 |
| growth of bluetongue and epizootic hemorrhagic disease of deer viruses in poikilothermic cell systems. | continuous cell lines from the ticks dermacentor variabilis, d. parumapertus, d. nitens, rhipicephalus sanguineus and r. appendiculatus, the mosquitoes aedes albopictus and culex quinquefasciatus and the african toad xenopus laevis were tested for their ability to replicate bluetongue (bt) and epizootic hemorrhagic disease of deer (ehd) viruses, and for their sensitivity as potential isolation systems. bt serotype 17 grew to peak titers of 10(4.5)-10(7.5) tcid50 ml-1 in all except one of the tic ... | 1988 | 2833002 |
| modulation of the substrate specificity of the polycation-stimulated protein phosphatase from xenopus laevis oocytes. | a polycation-stimulated (pcs) protein phosphatase was isolated in high yield (280 micrograms/100 g ovaries) from xenopus laevis oocytes through a procedure involving a tyrosine-agarose hydrophobic chromatography. the 220-kda enzyme contains a 35-kda and a 62-kda subunit. it was identified as the low-mr polycation-stimulated (pcsl) protein phosphatase. the labile p-nitrophenyl phosphatase activity, copurifying with the phosphorylase phosphatase activity, can be increased severalfold by preincubat ... | 1988 | 2833390 |
| xenopus laevis integrins. structural conservation and evolutionary divergence of integrin beta subunits. | we report the sequences of cdna clones for two different integrin beta subunits isolated from a xenopus laevis neurula cdna library. mrnas corresponding to both genes are first detected at gastrulation. we show that these two beta subunits are very highly related (98% identity in amino acid sequence) and probably arose at the time of tetraploidization of the x. laevis genome around 50 million years ago. comparison of these sequences with those of various other vertebrate integrin beta subunit es ... | 1988 | 2833505 |
| the cdna sequence coding for prepro-pgs (prepro-magainins) and aspects of the processing of this prepro-polypeptide. | amphibian skin is well known as a source of peptides homologous to bioactive peptides found in mammalian gut and brain. a systematic investigation of the skin secretions from xenopus laevis revealed several peptides not derivable from known precursors. the sequence elucidation, utilizing fast atom bombardment/mass spectrometry, of two peptides, pgs and pgs gly-10;lys-22, is reported. these have been independently characterized and named magainins and found to have antimicrobial activity. a mixed ... | 1988 | 2833514 |
| freeze-fracture investigations of membranes of flask cells in the kidney and of parietal cells in the stomach of claw-frog (xenopus laevis). | the flask cells of the nephron and the parietal cells in the stomach fundic glands of claw-frog show some structural similarities such as the existence of a canalicular system, the richness of mitochondria and numerous small cytoplasmatic vesicles. both cell types also seem to have common functional pecularities. with the freeze-fracture method the cell membranes of both cell types showed a richness of intramembrane particles (imps) and the existence of special elongated imps especially in the a ... | 1988 | 2833860 |
| is a decrease in cyclic amp a necessary and sufficient signal for maturation of amphibian oocytes? | acetylcholine rapidly lowered the intracellular levels of cyclic amp in stage 5 and 6 xenopus laevis oocytes. acetylcholine alone did not induce oocyte maturation, though it did accelerate maturation induced by progesterone. the effect of acetylcholine on oocyte maturation was independent of extracellular calcium concentration. adenosine increased cyclic amp and abolished the progesterone-induced decrease in cyclic amp levels in follicles and in denuded oocytes. this effect of adenosine was bloc ... | 1988 | 2834247 |
| ribosomal protein l2 in saccharomyces cerevisiae is homologous to ribosomal protein l1 in xenopus laevis. isolation and characterization of the genes. | by cross-hybridization with a cdna probe for the xenopus laevis ribosomal protein l1 we have been able to isolate the homologous genes from a saccharomyces cerevisiae genomic library. we have shown that these genes code for a ribosomal protein which was previously named l2. in yeast, like in x. laevis, these genes are present in two copies per haploid genome and, unlike the vertebrate counterpart, they do not contain introns. amino acid comparison of the x. laevis l1 and s. cerevisiae l2 protein ... | 1988 | 2834365 |
| aggregation of lysine-containing zeins into protein bodies in xenopus oocytes. | zeins, the storage proteins of maize, are totally lacking in the essential amino acids lysine and tryptophan. lysine codons and lysine- and tryptophan-encoding oligonucleotides were introduced at several positions into a 19-kilodalton zein complementary dna by oligonucleotide-mediated mutagenesis. a 450-base pair open reading frame from a simian virus 40 (sv40) coat protein was also engineered into the zein coding region. messenger rnas for the modified zeins were synthesized in vitro with an sp ... | 1988 | 2834822 |
| tissue and species conservation of the vertebrate and arthropod forms of the low molecular weight (16-18000) proteins of gap junctions. | gap junctions have been isolated from four murine tissues, from rat and xenopus laevis liver, and from nephrops norvegicus (norway lobster) hepatopancreas. the preparations of gap junctions from each vertebrate tissue contain a single major protein, mr 16,000, and those from nephrops hepatopancreas a protein, mr 18,000. immunocytochemical studies using affinity-purified antibodies raised against gap junctions from nephrops show the junctional origin of the 18k protein. immunological studies usin ... | 1988 | 2835165 |
| the inducible lac operator-repressor system is functional for control of expression of injected dna in xenopus oocytes. | we have investigated the use of the escherichia coli lac operator-repressor system to regulate the expression of genes introduced by microinjection into xenopus laevis oocytes. we observe that expression of an msv-cat fusion gene, in which the lac operator was inserted between the tata box and the transcription start point (tsp), or between the tsp and the start codon (atg), is completely repressed when the lac repressor protein is added to the plasmid suspension prior to injection. the lac repr ... | 1988 | 2835293 |
| gonadotropin action on androgen synthesis in short-term incubation of explants and dispersed cells of the testis of xenopus laevis. | testis cells of the toad xenopus laevis were dissociated with collagenase and the cell suspension was enriched for steroidogenic cells by percoll gradients. results suggested that cells should be preincubated during a 6-h period before stimulation with gonadotropin. our results indicate that a 2-h incubation period with gonadotropin was necessary to obtain a significant response. furthermore, the cells can be maintained in a functional state longer than mammalian testis cells. different gonadotr ... | 1988 | 2835421 |
| role for dna replication in beta-globin gene activation. | transcriptional activation of the xenopus laevis beta-globin gene requires the synergistic action of the simian virus 40 enhancer and dna replication in deae-dextran-mediated hela cell transfections. replication does not act through covalent modification of the template, since its requirement was not obviated by the prior replication of the transfected dna in eucaryotic cells. transfection of dna over a 100-fold range demonstrates that replication does not contribute to gene activation simply in ... | 1988 | 2835669 |
| expression of c-myc proto-oncogene during the early development of xenopus laevis. | c-myc proto-oncogene expression in xenopus laevis oocytes and developing embryos has been investigated. stage vi oocytes as well as unfertilized eggs contain a high level of xenopus c-myc mrna (1-2.5 x 10(7) copies). however, this high level of maternal c-myc mrna declines gradually during the time of rapid and synchronous cell cleavage and becomes almost undetectable after the mid-blastula transition. the zygotic genes then become activated for the first time, whereupon the amount of newly synt ... | 1987 | 2835732 |
| differences in receptor-evoked membrane electrical responses in native and mrna-injected xenopus oocytes. | xenopus laevis oocytes are giant cells suitable for studies of plasma membrane receptors and signal transduction pathways because of their capacity to express receptors after injection of heterologous mrna. we studied depolarizing chloride currents evoked by acetylcholine (accho) in native oocytes ("intrinsic accho response"), by thyrotropin-releasing hormone (trh) in oocytes injected with pituitary (gh3) cell rna ("acquired trh response"), and by accho in oocytes injected with rat brain rna ("a ... | 1988 | 2836859 |
| efficient processing and expression of human nerve growth factor receptors in xenopus laevis oocytes: effects on maturation. | the nerve growth factor (ngf) receptor is an integral membrane protein that is phosphorylated and heavily glycosylated. determination of the amino acid sequence by molecular cloning indicates that the receptor is a cysteine-rich protein which contains a signal peptide sequence and spans the lipid bilayer with a single transmembrane sequence. a single mrna of 3.8 kilobases was observed for the receptor, of which 1.5 kilobases is coding sequence. we have used microinjection of receptor rna in xeno ... | 1988 | 2838743 |
| regulation of xenopus laevis dna topoisomerase i activity by phosphorylation in vitro. | dna topoisomerase i has been purified to electrophoretic homogeneity from ovaries of the frog xenopus laevis. sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the most purified fraction revealed a single major band at 110 kda and less abundant minor bands centered at 62 kda. incubation of the most purified fraction with immobilized calf intestinal alkaline phosphatase abolished all dna topoisomerase enzymatic activity in a time-dependent reaction. treatment of the dephosphorylated x. ... | 1988 | 2839226 |
| complete synthesis and transcription in vitro of a gene coding for human ribosomal 5s rna. | the gene coding for the major human ribosomal 5s rna was chemically synthesized and cloned into a puc13 vector. this approach was taken, because attempts to isolate the human 5s gene have thus far yielded either pseudogenes or variant 5s genes of unknown function. the synthetic human gene was transcribed by rna polymerase iii either in a crude hela cell extract or in a system reconstituted from partially purified transcription factors. comparative studies with the xenopus laevis somatic 5s gene ... | 1988 | 2840349 |
| methylation of single cpg dinucleotides within a promoter element of the herpes simplex virus tk gene reduces its transcription in vivo. | the binding of the transcription factors sp1 and ctf immediately upstream from the tata box of the herpes simplex virus (type 1) thymidine kinase-coding gene (tk) facilitates efficient transcription of this gene in microinjected xenopus laevis oocytes. to establish whether the presence of methylated cpg dinucleotides within the binding sites of these two factors affects transcription of the tk gene in vivo, we replaced a 33-bp promoter segment, consisting solely of the sp1 and ctf binding sites, ... | 1988 | 2842233 |
| heat shock-induced accumulation of ubiquitin mrna in xenopus laevis embryos is developmentally regulated. | exposure of xenopus laevis embryos to heat shock induced the accumulation of ubiquitin mrna (size range, 1.7-3.5 kb) in a developmental stage-dependent fashion. while constitutive ubiquitin transcripts were detectable throughout development, heat shock-induced accumulation did not occur until the fine-cell blastula stage. continuous exposure of neurulae to heat shock (33 degrees c) induced a transient accumulation of ubiquitin mrna with peak levels occurring after 2 hr. finally, placement of xen ... | 1988 | 2843405 |
| isolation and nucleotide sequences of cdnas for xenopus laevis ribosomal protein s8: similarities in the 5' and 3' untranslated regions of mrnas for various r-proteins. | recombinant clones specific for ribosomal protein (r-protein) s8 have been isolated from a xenopus laevis cdna bank. sequence analysis shows that they are of two types, derived from two different gene copies originating from gene duplication. the two cdnas differ in several silent sites and code for the same s8 protein whose complete amino acid sequence has been derived. sequence comparison of s8 mrnas with those for other x. laevis r-proteins, has revealed interesting similarities in the 5' and ... | 1988 | 2843441 |
| sequence and developmental expression of mrna coding for a gap junction protein in xenopus. | cloned complementary dnas representing the complete coding sequence for an embryonic gap junction protein in the frog xenopus laevis have been isolated and sequenced. the cdnas hybridize with an rna of 1.5 kb that is first detected in gastrulating embryos and accumulates throughout gastrulation and neurulation. by the tailbud stage, the highest abundance of the transcript is found in the region containing ventroposterior endoderm and the rudiment of the liver. in the adult, transcripts are prese ... | 1988 | 2843548 |
| oscillatory chloride current evoked by temperature jumps during muscarinic and serotonergic activation in xenopus oocyte. | 1. membrane currents were recorded from voltage-clamped oocytes of xenopus laevis, during temperature jumps imposed by a heating light. resting oocytes usually showed little response, but large oscillatory membrane currents developed in response to cooling steps applied during activation of 'native' muscarinic receptors. 2. similar temperature jump (tjump) currents were seen during activation of oscillatory chloride currents mediated by muscarinic acetylcholine (ach), serotonin, glutamate and no ... | 1987 | 2821235 |
| functional activity of oligosaccharide-deficient (na,k)atpase expressed in xenopus oocytes. | (na,k)atpase from torpedo californica was expressed in xenopus laevis oocytes in the presence of tunicamycin by injecting mrnas for the alpha- and beta-subunits derived from the cloned cdnas into the oocytes. the oligosaccharide-deficient atpase thus synthesized was transported to the oocyte plasma membrane, where it exhibited virtually the same atpase activity, ouabain-binding capacity and 86rb+ transport activity as the fully glycosylated enzyme. we conclude that the oligosaccharide chains on ... | 1988 | 2844594 |
| an excised sv40 intron accumulates and is stable in xenopus laevis oocytes. | xenopus laevis oocytes injected with simian virus 40 (sv40) dna synthesize abundant quantities of viral late region rna. in a previous analysis of the 5' ends of oocyte sv40 late rnas, it was observed that, in contrast to the majority of the late rna species, an abundant class of viral late rnas, whose 5' ends mapped at or near nucleotide 294, was not polyadenylated. the structure of this rna class has now been characterized further. we have shown that this species consists of a class of small u ... | 1988 | 2844625 |
| proteins regulating actin assembly in oogenesis and early embryogenesis of xenopus laevis: gelsolin is the major cytoplasmic actin-binding protein. | oocytes, notably those of amphibia, accumulate large pools of nonfilamentous ("soluble") actin, both in the cytoplasm and in the nucleoplasm, which coexist with extensive actin filament arrays in the cytoplasmic cortex. because the regulation of oogenically accumulated actin is important in various processes of oogenesis, egg formation, fertilization and early embryogenesis, we have purified and characterized the major actin-binding proteins present in oocytes of xenopus laevis. here we report t ... | 1988 | 2844829 |
| polylysine and polyamine stimulation of the phosphatidylinositol kinases of amphibian oocyte membranes. | phosphatidylinositol kinase present in xenopus laevis oocyte membranes catalyzes the formation of phosphatidylinositol 4-phosphate using phosphatidylinositol and atp as substrates while the activity of a second enzyme, phosphatidylinositol-4-phosphate kinase, results in the synthesis of phosphatidylinositol 4,5-bisphosphate. large (mr greater than 20,000) homopolymers of l-lysine or l-ornithine can stimulate the activity of both of these enzymes by at least 2-fold at 10-20 microm concentrations. ... | 1988 | 2847738 |
| binding of adrenergic ligands to liver plasma membrane preparations from the axolotl, ambystoma mexicanum; the toad, xenopus laevis; and the australian lungfish, neoceratodus forsteri. | the beta-adrenergic ligand iodocyanopindolol (icp) bound specifically to hepatic plasma membrane preparations from the axolotl, ambystoma mexicanum (bmax, 40 fmol/mg protein (p) at free concentration above 140 pm; kd, 42 pm); the toad, xenopus laevis (bmax, 200 fmol/mg p at 1 nm; kd, 300 pm); and the australian lungfish, neoceratodus forsteri (bmax, 100 fmol/mg p at 5 nm). for the lungfish, the scatchard plot was curved showing two classes of binding site with kd's of 20 and 500 pm. neither the ... | 1988 | 2847957 |
| microtubular packing varies along the course of motor and sensory axons: possible regulation of microtubules by environmental cues. | in the toad xenopus laevis, the microtubular density of 3-microns myelinated fibres was assessed in peripheral nerves, dorsal and ventral roots, and dorsal and ventral funiculi of the spinal cord. in the roots, the axonal microtubular density was 6 microtubules/microns 2 and twice as much at the other sampling sites. this indicates that the pattern of the microtubular packing may vary along the course of the axon. we propose that axonal microtubules are regulated by local cues. | 1989 | 2812540 |
| competition between dna templates injected into xenopus laevis oocytes. | we have examined the competition between microinjected dna templates for endogenous xenopus oocyte transcription factors. the results suggest that (a) coinjected templates compete with one another for transcription factors, (b) the competitive ability of a template is not necessarily a function of the rate of transcription of the gene, (c) competition is due to the presence of specific dna sequences, and (d) preincubation of the test gene affects competition. | 1988 | 2844564 |
| coupling of inositol phospholipid hydrolysis to peptide hormone receptors expressed from adrenal and pituitary mrna in xenopus laevis oocytes. | the expression of several neurotransmitter and drug receptors from injected exogenous mrna in xenopus laevis oocytes has been demonstrated by electrophysiological measurements of ion channel activation. the expression of specific receptors for peptide hormones in such a translation system would facilitate studies on the structure and regulation of cell-surface receptors as well as their coupling to membrane transduction mechanisms. the expression of receptors for calcium-mobilizing hormones in x ... | 1987 | 2827166 |
| structural basis of beta-adrenergic receptor subtype specificity studied with chimeric beta 1/beta 2-adrenergic receptors. | the beta 1- and beta 2-adrenergic receptors are two structurally related, but pharmacologically distinguishable, receptor subtypes, both of which activate adenylyl cyclase in a catecholamine-dependent manner through the guanine nucleotide-binding regulatory protein gs. the receptors are approximately 50% identical in amino acid sequence and each is characterized by the presence of seven putative transmembrane domains. to elucidate the structural basis for the pharmacological distinctions between ... | 1988 | 2849109 |
| voltage dependence of the na-k atpase: measurements of ouabain-dependent membrane current and ouabain binding in oocytes of xenopus laevis. | ouabain- or dihydroouabain(dho)-sensitive membrane currents and binding of 3h-ouabain were investigated under voltage-clamp conditions in full-grown prophase-arrested oocytes of xenopus laevis. (1) the ouabain-sensitive current is outwardly directed and usually exhibits a maximum at about +20 mv. the occurrence of the maximum is not affected by application of blockers for passive k+ currents. in the presence of ba2+ as a k+ channel blocker, the ki value for inhibition of the na-k atpase by ouaba ... | 1988 | 2850533 |
| [adrenoreceptive structures in the early embryos of the clawed toad (xenopus laevis)]. | studies have been made on the binding of labeled ligands to beta-adrenoreceptor--3h-dihydroalprenolol (dha) and 125i-iodocyanopindolol (icp--in crude homogenate and subcellular fractions of toad embryos during cleavage divisions. specific binding of these ligands was observed which is confirmed by a decrease of the activity after addition of cold propranolol or adrenalin. the value of kd for dha is equal to 3 x 10(-9) m for icp--to 1.5 x 10(-9) m. in addition to this high-affinity pool of bindin ... | 1988 | 2851241 |
| analysis of hsp 30, hsp 70 and ubiquitin gene expression in xenopus laevis tadpoles. | heat-induced accumulation of hsp 30 mrna (1.1 kb) during early development of xenopus laevis was first detectable at the tailbud stage (stage 30-34). this contrasts with heat-induced accumulation of hsp 70 mrna (2.7 kb) and ubiquitin mrna (size range = 1.7-3.1 kb), which was first detectable at the mid- to late-blastula stage. continuous exposure of tadpoles to a 33 degrees c heat shock resulted in a coordinate, transient accumulation of hsp 30, hsp 70 and ubiquitin mrna. a coordinate, temporal ... | 1988 | 2848679 |
| calcium mobilization by angiotensin ii and neurotransmitter receptors expressed in xenopus laevis oocytes. | specific receptors for angiotensin ii (aii) were expressed in albino xenopus laevis oocytes co-injected with poly(a)+ mrna isolated from rat adrenal cortex and the calcium-specific photoprotein, aequorin. in such oocytes, aii elicited rapid, dose-dependent rises in cytosolic free calcium with light emission responses up to 100-fold above basal levels. ligand-induced light emission was also observed in oocytes injected with rat brain mrna and stimulated with acetylcholine and glutamate. these fin ... | 1988 | 2848720 |
| conversion of a phosphoseryl/threonyl phosphatase into a phosphotyrosyl phosphatase. | by use of the autophosphorylated epidermal-growth-factor receptor and the synthetic peptide rrlie-daey(p)aarg, representing an autophosphorylation site of the transforming protein of rous-sarcoma virus, it is demonstrated that the phosphotyrosyl phosphatase activity of the polycation-stimulated phosphatases is substantially increased by an enzyme-directed effect of atp or ppi. concomitant with this increase in phosphotyrosyl phosphatase activity, the phosphorylase phosphatase activity is decreas ... | 1988 | 2852001 |
| expression of the human serum apolipoprotein ai and aii genes in xenopus laevis oocytes. lipid-associated secretion of gene products. | the two major apolipoproteins of plasma high-density lipoproteins (hdl) are apolipoprotein ai (apo ai) and aii (apo aii). the apo ai and the correctly oriented apo ciii genes separated by 2.6 kb were obtained by fusion of two human lambda-genomic clones. the apo aii gene was isolated as a 3 kb clone. these apolipoprotein genes have been injected independently and together into xenopus laevis oocytes and their expression studied. both apolipoprotein genes were transcribed and translated into thei ... | 1988 | 2852015 |
| the organization of ribosomal genes in diploid and tetraploid species of the genus odontophrynus (amphibia, anura). | the organization of the repeat unit of the ribosomal genes was determined in populations of odontophrynus americanus 2n, 4n, o. occidentalis 2n and o. barrioi 2n (amphibia, anura) from south america. hindiii, ecori and bamhi restriction patterns of rdna from single individuals were probed with two rdna clones from xenopus laevis. variations in length and sequence were found among different species, populations and specimens. a general pattern could be established from the most frequent type of r ... | 1988 | 2851419 |