| the functional development of the reticulo-endothelial system in the toad, xenopus laevis (daudin). | | 1969 | 5804917 |
| family of ribosomal genes of xenopus laevis. | | 1969 | 5806996 |
| effect of "halothane" on electrical coupling in pregasgrulation embryos of xenopus laevis. | | 1969 | 5807008 |
| the phosphorylation of thymidine by oocytes and eggs of xenopus laevis daudin. | | 1969 | 5808360 |
| [measurement of the "template" activity of ribonucleic acids of xenopus laevis eggs during development]. | | 1969 | 5812816 |
| the occurrence of enterochromaffin cells in tadpoles and juveniles of xenopus laevis, with special reference to 5-hydroxytryptamine and its possible roles in metamorphosis. | | 1969 | 5813225 |
| studies on amphibian yolk. 8. the estrogen-induced hepatic synthesis of a serum lipophosphoprotein and its selective uptake by the ovary and trasformation into yolk platelet proteins in xenopus laevis. | | 1969 | 5813945 |
| a morphological study of the telencephalon of the south african clawed frog, xenopus laevis. | | 1969 | 5816556 |
| a new transmissible disease in the south african clawed toad, xenopus laevis. | | 1969 | 5819157 |
| in vivo antagonism of melanophore-dispersing hormone by melatonin in adult xenopus laevis. | | 1969 | 5823806 |
| a spontaneously active fibrinolytic system in xenopus laevis which is further activated by human urokinase. | | 1965 | 5832870 |
| [a form of hereditary goiter in the batrachian xenopus laevis d]. | | 1965 | 5841259 |
| electron microscopic observations on the fine structure of the adenohypophysis of xenopus laevis. | | 1965 | 5843292 |
| [comparative study of the cytology and ultrastructure of the distal hypophysis in 3 species of anurous amphibia: rana temperaria l, bufo vulgaris laur, xenopus laevis d]. | | 1965 | 5848005 |
| pronephric system in haploid and diploid larvae of xenopus laevis. | | 1964 | 5856323 |
| cortical inheritance in the amphibian xenopus laevis: preliminary results. | | 1965 | 5858821 |
| cold blooded vertebrates, including xenopus laevis. | | 1965 | 5859239 |
| endbrain regeneration in adult xenopus laevis. | | 1965 | 5859613 |
| a study of ribosomes during embryonic development of xenopus laevis. | | 1965 | 5859847 |
| rapidly labelled ribonucleic acid in xenopus laevis embryonic cells. | | 1965 | 5859848 |
| development of hydroxyindole-o-methyl transferase activity in eye and brain of the amphibian, xenopus laevis. | | 1965 | 5864107 |
| the ultrastructure of gliosomes in the brains of amphibia. | small fragments of superficial neuropil and fragments of deeper layers from various regions of the brains of xenopus laevis daud. and rana esculenta l. were fixed in buffered osmium tetroxide, embedded in vestopal w or methacrylate, and studied with the electron microscope. the glial fibers and their meningeal end-feet contain numerous large mitochondrion-like dense bodies for which the term "gliosome" has been adopted. gliosomes have a specific and constant structure characterized by the presen ... | 1965 | 5865926 |
| computed action potential in nerve from xenopus laevis. | | 1965 | 5880362 |
| the effect of endbrain lesions on hypothalamic neurosecretion and the formation of cytoplasmic inclusions in the ependyma of xenopus laevis. | | 1965 | 5887329 |
| investigations on the neural control of clasping and feeding in xenopus laevis (daudin). | | 1964 | 5889159 |
| benzpyrene-induced tumours in the clawed toad, xenopus laevis. | | 1964 | 5898274 |
| changing serotonin levels in developing xenopus laevis. | | 1965 | 5899517 |
| input-output characteristics of the lateral-line sense organs of xenopus laevis. | | 1966 | 5941763 |
| the uptake of c14 5-hydroxytryptamine creatinine sulphate and c14 5-methyl-methionine by the epiphysis of xenopus laevis daudin. | | 1966 | 5947501 |
| the mitotic chromosomes in xenopus laevis (daudin): normal, sex reversed and female ww. | | 1966 | 5958869 |
| a reinvestigation of some of the tissue movements involved in the formation of the neural tube and the eye/lens system of triturus alpestris and xenopus laevis. | | 1966 | 5962694 |
| limb regeneration and nerve fiber number in rana sylvatica and xenopus laevis. | | 1966 | 5962946 |
| the development of the pituitary in xenopus laevis daudin. | | 1966 | 5963162 |
| localization of the ribosomal dna complements in the nucleolar organizer region of xenopus laevis. | | 1966 | 5963987 |
| occurrence of an inhibitory factor of ribosomal rna synthesis in embryonic cells of xenopus laevis. | | 1966 | 5964753 |
| development of xenopus laevis skin glands in organ culture. | | 1966 | 5964764 |
| a comparative study in vivo and in vitro of the ability of ribosomes from xenopus liver and ovary to incorporate l-[u-14c]leucine. | 1. a system for the incorporation in vitro of amino acids into protein is described for the south african clawed toad (xenopus laevis laevis daudin). 2. the incorporation of l-[u-(14)c]leucine by xenopus-liver microsomes is very much greater per mg. of microsomal rna than the incorporation by ovary microsomes. 3. the incorporation by xenopus-liver and -ovary polysomes is approximately the same when expressed per mg. of polysomal rna. 4. it was predicted from the above results that ovary microsom ... | 1966 | 5966272 |
| size distribution and stability of dna-like rna synthesized during development of anucleolate embryos of xenopus laevis. | | 1966 | 5969074 |
| monoamine oxidase in the eye, brain, and whole embryo of developing xenopus laevis. | | 1966 | 5971905 |
| experimentally produced ependymal inclusions in the brain of xenopus laevis. | | 1966 | 5973238 |
| the nucleolus and synthesis of ribosomal rna during oogenesis and embryogenesis of xenopus laevis. | | 1966 | 6007149 |
| [the ultrastructure of the peripheral cytoplasm of the ovarian oocytes and the mature egg of xenopus laevis (amphibia anura)]. | | 1966 | 6007185 |
| [the effect of fertilization on the ultrastructure of the peripheal cytoplasm of the egg of xenopus laevis]. | | 1966 | 6007186 |
| synthesis and accumulation of dna-like rna during embryogenesis of xenopus laevis. | | 1966 | 6008162 |
| synthesis and accumulation of low molecular weight rna during embryogenesis of xenopus laevis. | | 1966 | 6008163 |
| cultivation in vitro of normal and neoplastic cells of xenopus laevis. | | 1966 | 6012679 |
| nuclear transplantations between two subspecies of xenopus laevis, (xenopus laevis laevis and xenopus laevis petersi). | | 1966 | 6015171 |
| the release of bound corticosteroids from the muscle of the toad (xenopus laevis). | | 1967 | 6017307 |
| a comparison of the x-ray sensitivity of haploid and diploid zygotes of xenopus laevis. | | 1967 | 6019777 |
| histones in the wild-type and the anucleolate mutant of xenopus laevis. | a comparison of anucleolate mutant and wild-type tadpoles of xenopus laevis reveals striking differences in histones. in the mutant, synthesis of histone fractions i and iib is virtually absent and iia is reduced, while fractions iii and iv are significantly increased. | 1967 | 6020043 |
| retinal ganglion cells: specification of central connections in larval xenopus laevis. | in a series of xenopus larvae (stages 28 to 35), the left eye cup was dorsoventrally and anteroposteriorly inverted. after metamorphosis, the retinotectal projection was mapped by recording action potentials evoked in the tectum by a small spot of light projected on the retina. normal retinotectal projection was found following rotation of the eye cup at stage 28 to 29. rotation of the eye cup at stage 30 resulted in anteroposterior inversion of the retinotectal projection; rotation at stages 31 ... | 1967 | 6021901 |
| [synchronic replication of all chromosomes in xenopus laevis]. | | 1967 | 6031566 |
| contractures of single slow muscle fibres of xenopus laevis elicited by potassium, acetylcholine or choline. | | 1967 | 6033673 |
| the effect of calcium on the mechanical response of single twitch muscle fibres of xenopus laevis. | | 1967 | 6034295 |
| the control of cell number in the lumbar spinal ganglia during the development of xenopus laevis tadpoles. | | 1967 | 6049662 |
| amino acid metabolism and urea synthesis in naturally aestivating xenopus laevis. | | 1967 | 6049999 |
| method for estimating the number of eggs laid by xenopus laevis in response to the the injection of gonadotropin. | | 1967 | 6051872 |
| observations on the pars intermedia of xenopus laevis. | | 1967 | 6053400 |
| urea cycle enzymes and urea excretion during the development and metamorphosis of xenopus laevis. | | 1967 | 6058183 |
| [electron microscopic study of ribosomal structures of the cytoplasm in the course of segmentation of the egg of xenopus laevis]. | | 1967 | 6068433 |
| heterogeneity of lactate dehydrogenase in the developing and adult xenopus laevis daud. | | 1967 | 6069312 |
| the transmission of lymphosarcoma in xenopus laevis, the south african clawed toad. | | 1967 | 6071671 |
| the effect of water shortage on the nitrogen metabolism of xenopus laevis. | | 1967 | 6079420 |
| [transplantation of nuclei from the neural ectoderm in xenopus laevis. preliminary note]. | | 1967 | 6081343 |
| evidence for an intracellular precursor for human b-cell growth factor. | human b-cell growth factor has been described as a trypsin-sensitive protein of mr 12,000-14,000. evidence is provided herein that this relatively low molecular weight product may be released from a larger precursor molecule of mr 60,000-80,000. the precursor protein is confined to the cytosol of freshly isolated t lymphocytes, and only the mr 12,000-14,000 moiety is released upon lectin stimulation. the precursor protein was subjected to limited tryptic digestion, which demonstrated that the bi ... | 1984 | 6083564 |
| nucleotide sequence of human monocyte interleukin 1 precursor cdna. | interleukin 1 (il-1) is a protein with several biological activities regulating host defense and immune responses. we report here the isolation of human il-1 cdna. it encodes a precursor polypeptide of 269 amino acids (30,747 mr). mrna isolated by hybridization to this cdna was translated in a reticulocyte cell-free system, yielding immunoprecipitable il-1. furthermore, this hybrid-selected mrna was injected into xenopus laevis oocytes, which subsequently secreted biologically active il-1. the c ... | 1984 | 6083565 |
| 5s rna structure and interaction with transcription factor a. 1. ribonuclease probe of the structure of 5s rna from xenopus laevis oocytes. | the structure of xenopus laevis oocyte (xlo) 5s ribosomal rna has been probed with single-strand-specific ribonucleases t1, t2, and a with double-strand-specific ribonuclease v1 from cobra venom. the digestion of 5'- or 3'-labeled renatured 5s rna samples followed by gel purification of the digested samples allowed the determination of primary cleavage sites. results of these ribonuclease digestions provide support for the generalized 5s rna secondary structural model derived from comparative se ... | 1984 | 6084515 |
| 5s rna structure and interaction with transcription factor a. 2. ribonuclease probe of the 7s particle from xenopus laevis immature oocytes and rna exchange properties of the 7s particle. | the 5s rna complexed in the 7s particle of immature xenopus laevis oocytes was 32p labeled at its 3' end and then subjected in situ to partial digestion using ribonucleases t1, t2, a, and v1 in order to study the conformation of the complexed rna and its interaction with the transcription factor a (tfiiia). digested samples were gel purified to retrieve 5s rna that was still complexed with the transcription factor protein, and the cleavages in these rnas were analyzed on sequencing gels. the rna ... | 1984 | 6084516 |
| human u2 and u1 rna genes use similar transcription signals. | we have analyzed the requirements for human u2 rna transcription by injection of cloned u2/6 rna genes into nuclei of xenopus laevis oocytes. two forms of human u2 rnas accumulate, a major species corresponding to mature-sized u2 rna and a minor species corresponding to a 3'-extended precursor. this rna polymerase ii transcription requires only 258 and 94 bp of 5'- and 3'-flanking region sequences, respectively. efficient u2 rna synthesis depends on a promoter element located between positions - ... | 1984 | 6084596 |
| splicing of xenopus laevis ribosomal protein rnas is inhibited in vivo by antisera to ribonucleoproteins containing u1 small nuclear rna. | the activity of antisera against ribonucleoproteins containing u1 small nuclear rna (sm and rnp) has been analysed on pol ii transcripts in an in vivo system. xenopus laevis ribosomal protein gene transcripts are accumulated in the form of precursor rna when either of the two kinds of antisera are injected into the germinal vesicles of x. laevis oocytes before the injection of purified l1 and l14 ribosomal protein genes. no effect on the accumulation of mature histone mrna is detected when x. la ... | 1984 | 6084721 |
| expression of two xenopus laevis ribosomal protein genes in injected frog oocytes. a specific splicing block interferes with the l1 rna maturation. | the expression of two xenopus laevis ribosomal protein genes (l1 and l14) has been analysed by microinjection of the cloned genomic sequences into frog oocyte nuclei. while the injection of the l14 gene causes the accumulation of the corresponding protein in large excess with respect to that synthesized endogenously, the l1 gene does not. analysis of the rna shows that both genes are actively transcribed. the seven-intron-containing l14 transcript is completely processed to a mature form, while ... | 1984 | 6084725 |
| the two embryonic u1 small nuclear rnas of xenopus laevis are encoded by a major family of tandemly repeated genes. | we have identified a large family of u1 rna genes in xenopus laevis that encodes two distinct species of u1 rna. these genes are expressed primarily at the onset of transcription in the 4,000-cell embryo (d. j. forbes, m. w. kirschner, d. caput, j. e. dahlberg, and e. lund, cell 38:681-689, 1984). the two types of embryonic u1 rna genes are interspersed and are organized in large tandem arrays. the basic 1.9-kilobase repeating unit contains a single copy of each of the embryonic genes and is rei ... | 1984 | 6084809 |
| methylation of the sv40 hpaii site does not affect late viral gene expression in microinjected tissue culture cells. | intranuclear coinjection of the late sv40 kpni/bcli dna fragment and the early promotor/enhancer hpaii/bgli dna segment into permissive monkey and non-permissive mouse cells allows late sv40 gene expression without t-antigen synthesis and dna replication. these conditions were chosen to analyse the effect of dna methylation on v-antigen synthesis detached from the process of dna replication. we found that in vitro methylation of a single cytosine nucleotide proximal to the major late mrna cap si ... | 1984 | 6086395 |
| the development of the pars intermedia and its role in the regulation of dermal melanophores in the larvae of the amphibian xenopus laevis. | the ontogenesis of biosynthesis of pro-opiomelanocortin (pomc)-related peptides in the pars intermedia of xenopus laevis tadpoles was studied. the results were related to the capacity of the animal to adapt to background color through regulation of pigment dispersion in dermal melanophores. using immunocytochemical techniques with antisera to alpha-melanophore-stimulating hormone (alpha-msh), it was revealed that this peptide first appeared at developmental stage 37/38, just prior to the animal' ... | 1984 | 6086446 |
| inositol incorporation into phosphoinositides in retinal horizontal cells of xenopus laevis: enhancement by acetylcholine, inhibition by glycine. | the absorption of light by photoreceptor cells leads to an increased incorporation of [2-3h]inositol into phosphoinositides of horizontal cells in the retina of xenopus laevis in vitro. we have identified several retinal neurotransmitters that are involved in regulating this response. incubation with glycine, the neurotransmitter of an interplexiform cell that has direct synaptic input onto horizontal cells, abolishes the light effect. this inhibition is reversed by preincubation with strychnine ... | 1984 | 6086673 |
| properties of non-junctional acetylcholine receptor channels on innervated muscle of xenopus laevis. | patch-clamp recordings of current through acetylcholine-activated channels were made from non-junctional membrane of innervated myotomal muscle from xenopus laevis. two classes of acetylcholine (ach) receptor channels were identified on the basis of current amplitudes. both amplitude classes exhibited current-voltage relations which deviated from linearity as the extrapolated reversal potential was approached (-5 to -12 mv). over the range of greatest linearity the conductances of the two classe ... | 1984 | 6086900 |
| xenopus oocyte resting potential, muscarinic responses and the role of calcium and guanosine 3',5'-cyclic monophosphate. | resting potential (r.p.) and muscarinic response mechanisms were studied in xenopus laevis oocytes using the voltage-clamp technique. insertion of micro-electrodes into the oocyte produced a 'shunt' membrane conductance which partially sealed after a few minutes. the oocyte resting potential (measured with a single intracellular electrode) ranged from -40 to -60 mv. ouabain and low k+ solution depolarized both follicles and denuded oocytes. the electrogenic na+-k+ pump was more active in the lat ... | 1984 | 6086916 |
| digitoxigenin, a digitalis steroid, induces meiotic maturation of xenopus laevis oocytes. | digitoxigenin, a c23 digitalis steroid induces meiotic maturation of xenopus oocyte. the dose of digitoxigenin which induces half maximal response is 3.3 +/- 2.10(-5)m. in contrast the conjugated digitalis steroid, digitoxin (digitoxigenine + 3 digitoxoses) never triggered maturation at any of the doses tested. these experiments which show that only free digitoxigenin mimics progesterone action, suggest that both digitoxigenin and progesterone possess a common initial site of action which is not ... | 1984 | 6087028 |
| the complete nucleotide sequence of a rice 17s rrna gene. | the complete nucleotide sequence of a rice nuclear 17s rrna gene (rdna) has been determined. the rice rdna is 1812 bp long and its g + c content is 51.3%. this nucleotide sequence shows 79%, 80% and 80% homology to those of yeast, xenopus laevis and rat 18s rdnas, respectively. divergency of nucleotide sequences is largely attributed to five blocks of highly variable regions, where eukaryotic specific sequences can be observed. | 1984 | 6087286 |
| in contrast to other xenopus genes the estrogen-inducible vitellogenin genes are expressed when totally methylated. | the methylation-sensitive restriction enzymes hha i and hpa ii were used to analyze the methylation pattern of four xenopus laevis genes in dna of embryos, of erythrocytes, and of untreated and estrogen-treated hepatocytes. within these four genes all sites tested are fully modified in embryonic dna. however, the adult beta 1-globin gene is unmethylated in dna of erythrocytes, where it is expressed, and the 68 kd albumin gene, active only in hepatocytes, is specifically hypomethylated in hepatic ... | 1983 | 6088055 |
| in vivo effects of microinjected alkaline phosphatase and its low molecular weight substrates on the first meiotic cell division in xenopus laevis oocytes. | xenopus laevis oocytes were microinjected with low molecular weight phosphoesters such as 2-glycerophosphate, phosphotyrosine, phosphoserine, phosphothreonine, 4-nitrophenyl phosphate, and orthophosphate. these compounds were able to induce a considerable reduction in the time course of progesterone-induced maturation, with 2-glycerophosphate being the most effective. the basal level of camp and its drop during maturation were not affected by the microinjection of 2-glycerophosphate. the injecti ... | 1984 | 6089179 |
| a ca2+-activated channel from xenopus laevis oocyte membranes reconstituted into planar bilayers. | plasma membrane fractions from xenopus laevis oocytes were incorporated into planar lipid bilayers. we show the existence of numerous ca2+-activated nonspecific channels that are more permeable to anions. these channels are activated by ca2+ at micromolar concentration but not by mg2+, zn2+, or mn2+, even at millimolar concentrations. decreasing ca2+ concentration to less than 1 microm decreases the time of channel opening until channels close completely in the absence of ca2+ and in the presenc ... | 1984 | 6089180 |
| direct demonstration of impaired functionality of a purified desensitized beta-adrenergic receptor in a reconstituted system. | long-term exposure of various cell types to beta-adrenergic agonists such as isoproterenol leads to an attenuated responsiveness ("desensitization") of the adenylate cyclase system to further challenge with these agonists. the turkey erythrocyte model system was used earlier to show that a covalent modification of the receptor (phosphorylation) is associated with this process. the functionality of the "desensitized" beta-adrenergic receptor was assessed by implanting purified beta-adrenergic rec ... | 1984 | 6089331 |
| co-linear organization of xenopus laevis and mouse mitochondrial genomes. | cloned fragments of xenopus laevis mitochondrial dna and pleurodeles waltlii mitochondrial cdnas have been hybridized together and with mouse mtdna. in the three cases cross-hybridization was observed. the overall organization of the x. laevis fragments appeared to be co-linear with the mouse mtdna, most sequences being conserved except for the d-loop and the urf6 regions. the use of mouse mtdna has enabled us to identified several mitochondrial genes in x. laevis and p. waltlii. | 1984 | 6089785 |
| exonucleases participating in the 3'end turnover of trna in xenopus laevis. | nuclei and enucleated xenopus laevis oocytes were used as a source of exonucleases that hydrolyze the 3'terminus sequence of trna. the majority of the total activity was found in the cytoplasm. several forms of enzyme activity are obtained upon fractionation in s-200 column. both nuclear and cytoplasmic activities display a preferential cleavage of the terminal amp residue. similar results are obtained in vivo by microinjection of trna labelled in the cca sequence. aminoacylation of trna, on the ... | 1984 | 6089833 |
| slowly inactivating potassium channels induced in xenopus oocytes by messenger ribonucleic acid from torpedo brain. | poly(a+) messenger rna was extracted from the electric lobe and medulla of torpedo and injected into oocytes of xenopus laevis. the synthesis and processing of proteins coded by the injected messenger rna led to the incorporation of voltage-activated channels in the oocyte membrane. a large, well maintained outward current was recorded from injected oocytes in response to depolarization. non-injected oocytes did not show this current. the reversal potential of the current varied according to the ... | 1984 | 6090641 |
| induction of human interleukin 1 mrna measured by collagenase- and prostaglandin e2-stimulating activity in rheumatoid synovial cells. | human blood peripheral monocyte/macrophages release in culture a mononuclear cell factor (mcf) which stimulates the production of collagenase and prostaglandin e2 by human rheumatoid synovial cells and dermal fibroblasts. these two products play a role in connective tissue destruction. mcf has an apparent molecular weight of approximately 15 000 and is biologically and biochemically indistinguishable from interleukin 1. mcf therefore belongs to the well-documented nonimmune biological activities ... | 1984 | 6092094 |
| genetic recombination of xenopus laevis 5 s dna in bacteria. | the behavior in genetic recombination of xenopus laevis 5 s dna has been examined, with particular emphasis on the role of 15-base-pair tandem repeats in the a + t-rich spacer. fragments of 5 s dna were introduced into escherichia coli cells as inserts in the recombination vectors, lambda rva and lambda rvb. intermolecular recombinants were selected in which, because of properties of the phage vectors, the crossover event must have occurred within the 5 s dna inserts. inserts from individual rec ... | 1984 | 6092642 |
| the primary structure of the larval beta 1-globin gene of xenopus laevis and its flanking regions. | we present the complete nucleotide sequence of the larval beta i-globin gene of xenopus laevis including 240 nucleotides of the 5' flanking region and 594 nucleotides beyond the polyadenylation site. the site of transcription initiation was mapped by s1 nuclease, and the site of polyadenylation was determined by comparison with corresponding cdna clones. the larval xenopus beta i-gene shows the same internal structure as the beta-globin genes of higher vertebrates, viz. 3 exons interrupted by 2 ... | 1984 | 6093050 |
| atp and the processivity of xenopus laevis dna polymerase alpha. | we use specific restriction fragments as defined primers for dna synthesis on single-stranded circular phage fd dna. these structures are relatively poor templates for a highly purified dna polymerase alpha from xenopus laevis eggs. however, dna synthesis is stimulated about 5-fold by addition of atp to the reaction mixture. we show that the deoxynucleotide polymers, synthesized in the presence of atp, are significantly longer than those produced in the absence of atp. we also show that this eff ... | 1984 | 6093886 |
| stimulation of uridine phosphorylation in primary cultures of xenopus laevis hepatocytes by estradiol-17 beta. | the effects of estrogen on the uridine uptake into cells were examined in primary cultures of liver parenchymal cells from xenopus laevis. the total uptake of [3h]uridine into the estrogen-treated cells and its incorporation into rna were about 1.5 times higher than the values for control cells. the uptake of [3h]adenosine and its incorporation into rna were not affected by estrogen. an experiment in which liver parenchymal cells were double labeled with [3h]uridine and [3h]adenosine showed that ... | 1984 | 6094021 |
| na+/k+-atpase from xenopus laevis (daudin) kidney and epidermis: high sensitivity towards regulatory compounds. | na+/k+-atpase was prepared from xenopus laevis epidermis. purification was obtained by ultracentrifugation on sucrose discontinuous gradient. the maximum of enzyme-containing membranes was concentrated in the denser sucrose layer, exhibiting a good and long-lasting activity (specific activity about 55 mumoles of atp hydrolyzed/mg of protein/hour). the kd for the ouabain of kidney and epidermis enzymes were very low (in purified preparations respectively 16 nm for kidney enzyme and 4 nm for skin ... | 1984 | 6094094 |
| beta-endorphins (beta-ep) in amphibians: higher beta-ep levels during regenerating stages of anuran life cycle and immunocytochemical localization of beta-ep in regeneration blastemata. | plasma beta-endorphin (beta-ep) levels were measured at different stages of metamorphosis in anuran species, namely rana catesbeiana, r. pipiens, and xenopus laevis. the mean levels of beta-ep in tadpoles and postmetamorphic juveniles were significantly higher than adult levels in all three species examined. the pattern of high tadpole levels and low adult levels corresponds with the limb regeneration ability of the tadpole and restriction in the adult. we have also reported plasma beta-ep level ... | 1984 | 6094701 |
| the absence of calcium blocks impulse-evoked release of acetylcholine but not de novo formation of functional neuromuscular synaptic contacts in culture. | we have examined the role of calcium-dependent, impulse-evoked release of acetylcholine (ach) in the formation of functional neuromuscular contacts. dissociated cell cultures prepared from xenopus laevis embryos were maintained either in standard medium containing calcium or in calcium-free medium. both the number of neuron-myocyte contacts and the number of terminations of neurites on myocytes were reduced in ca-free medium. intracellular recordings from neuron-myocyte pairs during perfusion wi ... | 1984 | 6094749 |
| translation in xenopus oocytes of messenger rna from a431 cells for human epidermal growth factor receptor proteins. | translation of messenger rnas (mrnas) for human epidermal growth factor receptor (egf-r) proteins was accomplished in a xenopus oocyte translation system. translation of these mrnas in rabbit reticulocyte lysates and wheat germ extracts were unsuccessful, in accordance with the general difficulty in translating mrnas for membrane-bound glycoproteins in conventional heterologous cell-free systems. total poly(a)+rna from a human epidermoid carcinoma cell line a431 was injected into oocytes from xe ... | 1984 | 6096098 |
| synthesis of an ochre suppressor trna gene and expression in mammalian cells. | we have used site-specific mutagenesis to change the anticodon of a xenopus laevis tyrosine trna gene so that it would recognize ochre codons. this trna gene is expressed when amplified in monkey cells as part of a sv40 recombinant and efficiently suppresses termination at both the ochre codon separating the adenovirus 2 hexon gene from a 23-kd downstream gene and the ochre codon at the end of the ns1 gene of influenza virus a/tex/1/68. termination at an amber codon of a ns1 gene of another infl ... | 1984 | 6096120 |
| induction and disappearance of excitability in the oocyte of xenopus laevis: a voltage-clamp study. | electrically excitable, sodium-selective channels are induced in the membrane of the oocytes of xenopus laevis when it is submitted to prolonged positive potentials (kado, marcher & ozon, 1979; baud, kado & marcher, 1982). under a long positive voltage-clamp step, the membrane current, initially outward, becomes inward with a sigmoidal time course. the mean time to half-maximal inward current (t 1/2) is about 18 s at 16 degrees c when stepping the membrane potential to +55 mv. the rate of channe ... | 1984 | 6097673 |
| efficient expression of cloned complementary dnas for secretory proteins after injection into xenopus oocytes. | cloned complementary dnas encoding chicken ovalbumin, chicken prelysozyme and calf preprochymosin, prochymosin and chymosin were inserted downstream from various viral promoters in modified recombinant "shuttle" vectors. microinjection of the ovalbumin, prelysozyme and preprochymosin constructs into the nuclei of xenopus laevis oocytes resulted in the synthesis, segregation in membranes and secretion into the extracellular medium of ovalbumin, lysozyme and prochymosin, respectively. judging from ... | 1984 | 6098686 |
| intracellular acetylation of desacetyl alpha msh in the xenopus laevis neurointermediate lobe. | high performance liquid chromatography (hplc) followed by radioimmunoassay (ria) of the chromatographic fractions were used to separate and quantify, respectively, the alpha msh-like peptides stored in the neurointermediate lobe (nil) of the xenopus laevis (x. laevis) pituitary gland and released from the x. laevis nil, in vitro. immunoreactive (ir) material eluting with a similar hplc retention time as desacetyl alpha msh was the major ir peptide in the nil. material with a retention time simil ... | 1984 | 6099561 |
| pharmacological regulation in vitro of meiotic resumption in oocytes of xenopus laevis. | the pharmacological control in vitro of meiotic resumption in xenopus laevis oocytes was undertaken with a variety of drugs or agents which either mimic a steroidal hormone, progesterone, the physiological inducer of meiosis in vivo and in vitro, potentiate progesterone-induced meiosis (e.g. insulin) or inhibit the action of steroidal and non-steroidal inducers. most steroidal and non-steroidal inducers trigger a cascade of cellular events which seem to be initiated at the oocyte membrane. one m ... | 1984 | 6100710 |