Publications

inhibition by phenothiazine derivatives of the adenylate cyclase of amphibian oocytes.	the adenylate cyclase activity of membranes of xenopus laevis oocytes and follicle cells was affected by the presence of 2-chloro-10-(3-aminopropyl)phenothiazine (capp) and two other antipsychotic drugs, fluphenazine and penfluridol. capp, at concentrations of 10 and 100 microm, had opposite effects on the activation of the oocyte adenylate cyclase by effectors that act through the g/f regulatory subunit. under these conditions, the drug stimulated the activation by fluoride and drastically inhi ...	1983	6139113
voltage-operated channels induced by foreign messenger rna in xenopus oocytes.	poly(a)+ messenger rna (mrna) extracted from rat brains or from cat muscles was injected into xenopus laevis oocytes. this led to the incorporation of voltage-operated na+ and k+ channels into the oocyte membrane. these channels are not normally present in the oocyte and presumably result from the synthesis and processing of proteins coded by the injected mrna. tetrodotoxin blocked the na+ channels induced by mrna derived from either innervated or denervated muscle.	1983	6140681
a rapid increase in acetylcholinesterase mrna during ascidian embryogenesis as demonstrated by microinjection into xenopus laevis oocytes.	poly(a+)rna was prepared from ciona intestinalis embryos isolated from six different developmental stages. using xenopus laevis oocytes as a translation assay, we find that functional acetylcholinesterase (ache) mrna is not present in ciona embryos until shortly before the neural plate stage. these studies show that ascidian ache mrna is translated in xenopus oocytes which should prove useful as an aid for cloning this gene. the interest in this enzyme stems from the possible correlation between ...	1983	6141851
somatostatin-immunoreactive cells in the gastro-entero-pancreatic endocrine system of xenopus laevis.	somatostatin-like immunoreactivity has been demonstrated in cells of the gastro-entero-pancreatic endocrine system of xenopus laevis (amphibia) using peroxidase-anti-peroxidase immunohistochemistry. the identified cells of the gastro-intestinal tract correspond to the "open-paraneurons" of fujita (1974). somatostatin-immunoreactive cells were found in the stomach (fundic and pyloric region), the duodenum and in the anterior ileum, but not in the colon. the dimensions of these 'somatostatin-open- ...	1983	6142568
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
effects of atp and related compounds on the ca-induced ca release mechanism of the xenopus sr.	the effects of atp and related compounds on the ca2+ release mechanism of the sarcoplasmic reticulum (sr) was studied by using skinned skeletal muscle fibers of xenopus laevis. atp evoked marked ca2+ release at very low level of mg2+. beta, gamma-methylene analogue of atp was almost as effective as atp, which suggests ca2+ release evoked by atp is elicited without atp hydrolysis. adp and amp also evoked ca2+ release from the sr, but the effect of them became gradually weaker than that of atp as ...	1984	6143296
adrenergic regulation of glycogenolysis in liver of xenopus laevis in vitro.	glycogenolysis was stimulated by catecholamines in in vitro cultures of hepatic tissue of xenopus laevis. dose response curves showed that adrenaline and isoprenaline were equally effective while noradrenaline and phenylephrine were progressively less effective in eliciting glycogen breakdown. neither oxymetazoline nor methoxamine had any effect on glycogenolysis. administration of adrenaline to cultures was followed within 1 min by a rise in tissue cyclic amp concentration and within 2 min by a ...	1984	6144450
a monoclonal antibody against nuclear lamina proteins reveals cell type-specificity in xenopus laevis.	immunofluorescence microscopy shows that the monoclonal murine antibody pkb8 stains the nuclear lamina of various somatic cells from vertebrates as diverse as mammals, birds and amphibia. it also decorates the nuclear periphery of oocytes from rat and chicken but does not react with spermatocytes, spermatids and spermatozoa. immunoblotting experiments demonstrate reaction with lamina polypeptides a, b and c of rat, with lamina polypeptide a of chicken, and with lamina polypeptides li and lii of ...	1984	6198191
glutamate and kainate receptors induced by rat brain messenger rna in xenopus oocytes.	xenopus laevis oocytes injected with poly(a)+ mrna extracted from rat brain became sensitive to serotonin, glutamate, kainate, acetylcholine and gamma-aminobutyrate. application of these substances to mrna-injected oocytes elicited membrane currents. the glutamate- and acetylcholine-induced currents usually showed oscillations, while the kainate current was smooth. the current oscillations during glutamate application reversed direction at about the chloride equilibrium potential (-24 mv), but t ...	1984	6145158
effects of synthetic mammalian thyrotrophin releasing hormone, somatostatin and dopamine on the secretion of prolactin and growth hormone from amphibian and reptilian pituitary glands incubated in vitro.	pituitary glands of grassfrog (rana pipiens), bullfrog (rana catesbeiana), clawed toad (xenopus laevis) and two species of terrapin (chrysemys picta and pseudemys scripta) were incubated in medium containing hypothalamic extract (he), thyrotrophin releasing hormone (trh), somatostatin, dopamine, or combinations of these treatments. prolactin and gh concentrations in the medium were determined by densitometry after polyacrylamide-gel electrophoretic separation. hypothalamic extract stimulated sec ...	1984	6146654
the relation between soma position and fibre trajectory of neurons in the mesencephalic trigeminal nucleus of xenopus laevis.	in adult xenopus laevis the mandibular and ophthalmic branches of the trigeminal nerve were backfilled with cocl2 or cobaltous lysine and whole brains silver intensified to reveal neurons of the mesencephalic vth nucleus (mes. v). the nucleus contains about 100 cells arranged in a band extending arch-like from the ventrolateral margin of the optic tectum to the midline. many cells possess a small number of short dendritic processes that arborize in the tectal neuropil; in some cells one dendrite ...	1984	6146985
xenopus laevis 28s ribosomal rna: a secondary structure model and its evolutionary and functional implications.	based upon the three experimentally derived models of e. coli 23s rrna (1-3) and the partial model for yeast 26s rrna (4), which was deduced by homology to e. coli, we derived a secondary structure model for xenopus laevis 28s rrna. this is the first complete model presented for eukaryotic 28s rrna. compensatory base changes support the general validity of our model and offer help to resolve which of the three e. coli models is correct in regions where they are different from one another. eukary ...	1984	6147812
regional distribution of polyadenylated mrna in xenopus laevis embryos.	xenopus laevis embryos were dissected into dorsal and ventral regions in post-gastrula stages. polyadenylated and nonpolyadenylated ribonucleic acids were separated on oligo (dt) cellulose and translated in vitro. the radioactivity incorporated into the translation products directed by polyadenylated and nonpolyadenylated messenger ribonucleic acids shows that in the dorsal region most proteins are synthesized on polyadenylated messenger ribonucleic acid templates in all the stages, while in the ...	1984	6148270
myosin isoenzymes in single muscle fibres of xenopus laevis: analysis of five different functional types.	an analysis has been performed of the native myosin isoenzyme composition of isolated skeletal muscle fibres from xenopus laevis with well-defined isotonic contraction properties. fast twitch 'white' (type 1) fibres contained three isomyosins; fast twitch 'red' (type 2) fibres showed two major myosin bands with migration velocities very similar to those of the two slower bands in type 1. slow twitch (type 3) fibres yielded a single, slowly migrating band as did slow tonic (type 5) fibres, wherea ...	1984	6149559
inhibitors of metalloendoprotease activity prevent k+-stimulated neurotransmitter release from the retina of xenopus laevis.	metalloendoprotease activity was identified in retinal homogenates using a synthetic fluorogenic metalloendoprotease substrate and specific metalloendoprotease inhibitors. the requirement of metalloendoprotease activity in neurotransmitter release was examined during the depolarization-induced release of [3h]glycine from the retina of xenopus laevis. neurons with high affinity uptake and calcium-dependent, k+-stimulated release of glycine have been described previously in this retina. when isola ...	1984	6150072
translation of mrna for human lymphotoxin in microinjected xenopus oocytes.	synthesis and secretion of biologically active human lymphotoxin (lt) can be detected in xenopus laevis oocytes following their inoculation with poly(a+) rna from human stimulated peripheral blood lymphocytes, but not in oocytes inoculated with rna from unstimulated lymphocytes or from fibroblastoid cells. in size-fractionating mrna of stimulated lymphocytes most lt activity is found to be coded for by rna with an approximate sedimentation value of 19 s.	1984	6150867
analysis of embryonic induction by using cell lineage markers.	three distinct inductive interactions have been demonstrated in early embryos of xenopus laevis: mesoderm induction, dorsalization and neural induction. the experiments were done with grafts from embryos uniformly labelled with passive cell lineage markers, either fitc-lysine-dextran (fldx) or horseradish peroxidase (hrp), which allow the provenance of regions to be determined down to the single cell level. in each case the fate of the target tissue in the presence of the appropriate inductor wa ...	1984	6151705
region-specific regulation of the actin multi-gene family in early amphibian embryos.	the actin multi-gene family shows both spatial and temporal regulation during early embryogenesis in the amphibian xenopus laevis. both muscle-specific and ubiquitous cytoskeletal actin genes are activated at the end of gastrulation; transcription of the alpha-cardiac and alpha-skeletal actin genes is restricted to the somitic mesoderm and its muscle-forming derivatives providing a convenient molecular marker for this early embryonic tissue.	1984	6151706
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
effects of polyamines on the first division cycle of xenopus laevis eggs.	the involvement of polyamines in cytokinesis has been examined in eggs of the amphibian x. laevis. microinjection of spermine or spermidine into unfertilized eggs induced a shortening of the first division cycle and early formation of cleavage-like constrictions. eggs were activated by injection and developed furrows about 45 min later, whereas the first division normally occurred around 120 min after activation. in terms of concentration, spermine was slightly more effective than spermidine, bu ...	1984	6692860
pattern regulation in defect embryos of xenopus laevis.	defect embryos of 24 series were prepared by removing increasing numbers of blastomeres from an 8-cell embryo of xenopus laevis. they were cultured and their development was examined macroscopically when controls reached a tailbud stage or later. results show that most of defect embryos of 12 series develop normally, and some of them become normal frogs. each of these defect embryos contain at least two animal blastomeres, one dorsal, and one ventral blastomere of the vegetal hemisphere. this su ...	1984	6692985
biochemical and histochemical aspects of acetylcholinesterase development in the larval cns of xenopus laevis.		1984	6697348
comparison by electrophoresis of proteins characteristic of the lateral line and skin of xenopus laevis.	in experiments aimed at determining acousticolateralis marker proteins, fractions of lateral-line organs and skin of xenopus laevis were analyzed by one- and two-dimensional polyacrylamide-gel electrophoresis. a protein fraction of approximately 44k mol. wt (k = 1000 daltons) and isoelectric ph 6.3, consisting of at least two components, was enhanced in lateral-line neuromast tissue (containing hair cells) and was decreased in tactile organs and skin (lacking hair cells). this "neuromast-marker- ...	1984	6697690
isolated clusters of paired tandemly repeated sequences in the xenopus laevis genome.	there exist in the xenopus laevis genome clusters of tandemly repeated dna sequences, consisting of two types of 393-base-pair repeating unit. each such cluster contains several units of one of these paired tandem repeats (ptr-1), followed by several units of the other repeat (ptr-2). the number of repeats of each type is variable from cluster to cluster and averages about seven of each type per cluster. every cluster has ca. 1,000 base pairs of common left flanking sequence (adjacent to the ptr ...	1984	6700590
induction of the ipsilateral retinothalamic projection in xenopus laevis by thyroxine.	hormones are important in the development of behaviour and there is now abundant evidence that they also affect the morphological development of the nervous system. in principle, hormones could act by inducing new patterns of connectivity between widely separated structures in the nervous system or by influencing local connectivity. most available work documents effects of the latter sort. we present here evidence for the former. our results indicate that thyroxine, the hormone which causes meta ...	1984	6700701
genetic limits of thymic immunosuppression of anti-hapten antibody production in xenopus laevis laevis, the south african clawed toad.	thymic immunosuppression in adult xenopus laevis laevis, the south african clawed toad, is antigen-dependent and antigen-specific, but it is not genetically restricted. in this report, we show that combination in vitro with a thymus from an immunized xenopus laevis laevis can suppress antibody production to a hapten from spleen fragments, if the spleen fragments are derived from a subspecies of xenopus laevis or a species of xenopus which shares the same diploid chromosome number (2n = 36). some ...	1984	6707484
sodium-alanine cotransport in oocytes of xenopus laevis: correlation of alanine and sodium fluxes with potential and current changes.	the sodium-dependent l-alanine transport across the plasma membrane of oocytes of xenopus laevis was studied by means of [14c]-l-alanine, 22na+ and electrophysiological measurements. at fixed sodium concentrations, the dependence of alanine transport on alanine concentration follows michaelis-menten kinetics; at fixed alanine concentrations, the transport varies with sodium concentration with a hill coefficient of 2. in the presence of sodium the uptake of alanine is accompanied by a depolarizat ...	1984	6708092
compact structure of ribosomal chromatin in xenopus laevis.	micrococcal nuclease digestion was used as a tool to study the organization of the ribosomal chromatin in liver, blood and embryo cells of x. laevis. it was found that in liver and blood cells, ribosomal dna is efficiently protected from nuclease attack in comparison to bulk chromatin. although ribosomal chromatin is fragmented in a typical nucleosomal pattern, a considerable portion of ribosomal dna retains a high molecular weight even after extensive digestion. a greater accessibility of the c ...	1984	6709502
pathology of naturally occurring chlamydiosis in african clawed frogs (xenopus laevis).	chlamydiosis was diagnosed in six african clawed frogs (xenopus laevis) from a tank of laboratory-bred frogs experiencing sudden deaths. gross findings were hepatomegaly, distention of the gall bladder, and splenomegaly. hepatic lesions were present in each frog and were characterized by mononuclear cell infiltrates, necrosis of hepatocytes, kupffer's cell proliferation, and sinusoidal fibrin thrombi. cholestasis, hemosiderin-laden kupffer's cells, parenchymal infarction, and multinucleated hepa ...	1984	6710808
the ultrastructural organization of gap junctions between follicle cells and the oocyte in xenopus laevis.	the cellular contact sites between the full-grown oocyte of xenopus laevis and the surface extensions of surrounding follicles cells were analysed by electron microscopy of ultrathin sections, freeze-fracture replicas and critical point-dried specimens. evidence is given for the presence of clusters of intramembranous particles (imps) at the p-face which represent gap junctions in diverse forms. most common are maculae (phi 0.2-0.5 micron) of densely packed imps (phi 12 +/- 2 nm) which represent ...	1984	6714245
nerve disperses preexisting acetylcholine receptor clusters prior to induction of receptor accumulation in xenopus muscle cultures.	we have investigated the sequential changes of acetylcholine receptor (achr) distribution on identified xenopus laevis muscle cells in culture before and after innervation. achrs on muscle cells were stained with tetramethylrhodamine-conjugated alpha-bungarotoxin and the distribution of achr clusters was examined on a fluorescence microscope using an image intensifier. large receptor clusters were identified on muscle cells and their fate was followed afterward. in muscle cells cultured without ...	1984	6714520
in vivo development of cholinesterase at a neuromuscular junction in the absence of motor activity in xenopus laevis.	embryos of xenopus laevis were selected prior to the onset of innervation and were raised for 2 days in the anaesthetic tricaine methanesulphonate (200 micrograms/ml). the gross development of these tricaine-reared animals appeared normal despite the absence of spontaneous motor activity and the lack of motor responses to prodding with a pin. motor activity quickly appeared when the anaesthetic was withdrawn. intracellular recording from the myotomes of intact, tricaine-maintained animals failed ...	1984	6716295
differential expression of the xenopus laevis tadpole and adult beta-globin genes when injected into fertilized xenopus laevis eggs.	xenopus laevis tadpole and adult beta-globin genes were injected into fertilized x. laevis eggs. both injected genes replicated and were retained in the developing embryos with equal efficiency. transcripts of the injected adult gene were detectable at gastrulation and reached a maximum level shortly thereafter. in contrast, transcripts of the injected tadpole gene were not detected until much later stages of development. the level of expression of both the injected genes was low compared with t ...	1984	6717434
enhancer-like properties of the 60/81 bp elements in the ribosomal gene spacer of xenopus laevis.	the spacer region of the xenopus laevis ribosomal gene contains blocks of repetitive sequence elements that are 60 or 81 bp long. these 60/81 bp elements function as enhancer elements for the rna polymerase i promoter at the 5' end of the gene. an rna polymerase i promoter adjacent to a block of 60/81 bp elements is always dominant over a promoter on a second plasmid when both are coinjected into oocyte nuclei. if two promoters are placed on the same plasmid containing enhancers, both promoters ...	1984	6722873
inhibitor of ribosomal rna synthesis in xenopus laevis embryos. vii. inhibition of 40s pre-rrna synthesis in xenopus neurula cells.	a fraction containing acid-soluble materials (pca-extract) from xenopus early blastulae preferentially inhibits the incorporation of [3h]uridine into 18s and 28s rrna in xenopus neurula cells. pulse- laneling experiments revealed that whereas tubercidin, a known inhibitor of rrna processing, produced a marked accumulation of the label in 40s pre-rrna, xenopus inhibitor suppressed labeling of the pre-rrna. when tubercidin was added to cells whose activity for rrna synthesis had been lowered by th ...	1984	6722909
protein synthesis in dorsal and ventral regions of xenopus laevis embryos in relation to dorsal and ventral differentiation.	two-dimensional gel electrophoresis has been used to analyze protein synthesis in dorsal and ventral regions in embryonic stages of xenopus laevis. proteins specific either to dorsal or to ventral regions are synthesized for the first time at gastrulation, concomitant with morphological differentiation. the reliability of these proteins as markers of dorsal and ventral differentiation was tested by examining their synthesis in uv-irradiated embryos, which have severely reduced capacity for dorsa ...	1984	6724133
stimulation of dna synthesis by microinjection of diadenosine 5',5''-p1, p4-tetraphosphate (ap4a) into xenopus laevis oocytes.	ap4a stimulated dna synthesis when injected into oocytes. the stimulation was dramatically increased when an exogenous template was microinjected. aphidicolin inhibited the effect of ap4a, supporting a role of dna polymerase alpha in this process. no stimulation by ap4a was observed in microinjected eggs, nor atp was able to mimic the in vivo effect of ap4a. besides microinjected activated dna, the stimulation by ap4a of dna synthesis was also observed with poly dt and poly dt-poly da as templat ...	1984	6724135
the formation of multinuclear muscle fibres in xenopus laevis i. observations on dissociated myotomal cells and autoradiography.		1984	6724444
intercellular junctions between the follicle cells and oocytes of xenopus laevis.	during development, the oocytes of xenopus laevis establish junctional contact with the follicle cells enveloping them. these junctions have alternatively been described as desmosomes and as gap junctions. in this paper the morphology of these junctions has been examined in gonadotropin-stimulated and unstimulated animals at all stages of development. contact between the oocyte and follicle cell plasma membranes is visible in stage i oocytes as thickenings in the membranes, separated by intercel ...	1984	6726143
two healing patterns correlate with different adult neural connectivity patterns in regenerating embryonic xenopus retina.	nasal and temporal one-third-sized eye fragments, formed by ablation at stage 32-33 of xenopus laevis embryos, heal and, in about 50% of the cases, survive to make eyes in the postmetamorphic animal which have mappable visuotectal projections. the majority of nasal one-third eyes have duplicate projections whereas the majority of temporal one-third eyes have unduplicated projections. most nasal one-third eye fragments and a minority of temporal eye fragments heal by the extrusion of cells from t ...	1984	6726148
reversible inhibition of translation by xenopus oocyte-specific proteins.	a characteristic of growing oocytes of all animal species is the synthesis and accumulation of messenger rna which is destined to be used primarily by the early embryo. the mechanism(s) which regulates the translation of this maternal mrna remains unknown. however, the inability of the oocyte to translate all of its putative mrna has been attributed to at least three limitations: (1) the rate of translation is limited by the availability of components of the translational apparatus other than mr ...	1984	6727992
regeneration of transected dorsal root ganglion cell axons into the spinal cord in adult frogs (xenopus laevis).	the extent of regeneration of the central axonal processes of dorsal root ganglion cells was determined using anterograde horseradish peroxidase histochemistry at 1-12 weeks after dorsal root transection in adult frogs. at 4, 8 and 12 weeks axons were found to have regenerated across the dorsal root entry zone and into the spinal cord.	1984	6733463
[specific inhibition of cleavage divisions in xenopus laevis in propranolol microinjection].		1984	6734415
platanna (xenopus laevis) as a test organism for determining the embryotoxic effects of environmental chemicals.	it has been successfully demonstrated that platanna (xenopus laevis) allows the artificial induction of spawning at any time during the year. the number of eggs collected from a female ranged between 500 and 2400, the fertilization rate varying between 10 and 85%. when unaffected by chemicals, the embryonic development of the larvae took between 8 and 30 weeks. di(2-ethylhexyl) phthalate (dehp), methylmercury chloride, and the thalidomide analog em 12 were used for the experiments described. deh ...	1984	6734493
heterogeneous distribution and replication activity of mitochondria in xenopus laevis oocytes.	in early diplotene oocytes of xenopus laevis mitochondria are not dispersed all over the cytoplasm but gathered in a well described mitochondrial mass [18]. when tracing these organelles during active vitellogenesis we observe that some of them are involved in the elaboration of a cortical layer at the vegetative hemisphere of the cell while others stay around the nucleus. the latter contribute to the transient formation of a mitochondrial crown throughout active mitochondriogenesis. autoradiogr ...	1984	6734625
phosphorylation of non-histone proteins associated with mitosis in hela cells.	our previous studies indicated that certain non-histone proteins (nhp) extractable with 0.2 m nacl from mitotic hela cells induce germinal vesicle breakdown and chromosome condensation in xenopus laevis oocytes. since the maturation-promoting activity of the mitotic proteins is stabilized by phosphatase inhibitors, we decided to examine whether phosphorylation of nhp plays a role in the condensation of chromosomes during mitosis. hela cells, synchronized in s phase, were labeled with 32p at the ...	1984	6734751
lateral mobility of plasma membrane lipids in dividing xenopus eggs.	the lateral mobility of plasma membrane lipids was analyzed during first cleavage of xenopus laevis eggs by fluorescence photobleaching recovery (fpr) measurements, using the lipid analogs 5-(n-hexadecanoyl)aminofluorescein ("hedaf") and 5-(n-tetradecanoyl)aminofluorescein ("tedaf") as probes. the preexisting plasma membrane of the animal side showed an inhomogeneous, dotted fluorescence pattern after labeling and the lateral mobility of both probes used was below the detection limits of the fpr ...	1984	6734936
a flow cytometric analysis of the embryonic origin of lymphocytes in diploid/triploid chimeric xenopus laevis.	quantitative flow cytometry was used to examine the embryonic origin of lymphocytes in xenopus laevis. reciprocal head/body transplants were made between diploid (2n) and triploid (3n) embryos of the same developmental stages ranging from neural plate to tail bud stages. thymuses and spleens were removed from postmetamorphic chimeras. cell suspensions were stained with the fluorescent dna stain, mithramycin, and the ploidy (relative fluorescence intensity) of the cells was then determined by flo ...	1984	6734938
the modifications of cortical endoplasmic reticulum during in vitro maturation of xenopus laevis oocytes and its involvement in cortical granule exocytosis.	in xenopus laevis eggs, cisternae shells which surround cortical granules (cg) are part of a cortical endoplasmic reticulum (er) network. in this paper the origin of such er shells has been studied in full-grown, progesterone-exposed xenopus oocytes. furthermore, the possible role of the cortical er in the activation process has been investigated by pricking maturing oocytes. it has been shown that in full-grown ovarian oocytes er cg shells are absent and er cisternae are extensively and randoml ...	1984	6736888
effects of light-deprivation on development of photopositive behavior in xenopus laevis tadpoles.	the development of amphibian sensory systems and behavior is generally considered to proceed normally without reference to sensory experience during embryonic or larval stages. most of the supporting research, however, has concentrated on the retinotectal (visual) systems of anurans and has ignored behaviors directed by other sensory systems. we demonstrate that early exposure to light is necessary for the development of photopositive behavior in xenopus laevis tadpoles, a behavior probably dire ...	1984	6736894
activity of commissural interneurons in spinal cord of xenopus embryos.	horseradish peroxidase- (hrp) filled microelectrodes have been used to examine the anatomy and physiology of "commissural interneurons," a morphologically defined class of spinal cord interneuron in xenopus laevis embryos. commissural interneurons have unipolar cell bodies in the dorsal half of the spinal cord. their dendrites lie in the mid to ventral parts of the lateral tracts and their axons cross the cord ventrally, t branch, and ascend and descend on the opposite side of the cord. recordin ...	1984	6737030
[characteristics of cardiac growth and energy metabolism in the development of the clawed toad].	the relative content of the actomyosin complex proteins increases with respect to the total heart protein during the heart growth in xenopus laevis. the intensity of the heart sections respiration was shown to depend on the heart weight. constants were determined in an equation describing this dependence. the decrease in the intensity of the heart sections respiration is determined mainly by the decrease of the mitochondrial protein content.	1984	6739034
different modes of pronephric duct origin among vertebrates.	it is possible to distinguish differences in pronephric duct morphogenesis by using scanning electron microscopy to observe the results of blocking, marking and grafting experiments as well as the normal course of development. here we compare the mode of pronephric duct development in embryos representing three orders of vertebrates: birds (class, aves; order, gallus); frogs (class, amphibia; order, anura); and salamanders (class, amphibia; order, urodela). the axolotl (a urodele) pronephric duc ...	1984	6740242
a morphometric study of the retinal ganglion cell layer and optic nerve from metamorphosis in xenopus laevis.	the number and distribution of cells in the retinal ganglion layer have been examined in nissl-stained wholemounts during postmetamorphic life in xenopus laevis. total cell number at metamorphic climax, in the 3 and 4 month juveniles and in 5 year adults were 30,000-41,000, 45,000-51,000 and 71,000-82,000 respectively. optic axon counts of 29,000, 39,000 and 58,000 at these stages suggested that most cells counted were ganglion cells and that their number doubled during this period. cell distrib ...	1984	6740963
cerebellar connections in xenopus laevis. an hrp study.	in the present study the cerebellar afferents in the clawed toad xenopus laevis have been analysed with the horseradish peroxidase (hrp) technique. in addition, data on the efferent connections of the cerebellum could be gathered, based on the phenomenon of anterograde transport of hrp. cerebellar afferents in xenopus laevis appear to arise mainly in the vestibular nuclear complex, in a primordial inferior olive and in the spinal cord. both primary (arising in the ipsilateral vestibular ganglion ...	1984	6742456
globin evolution in some species of the genus bufo.	the globins of 10 species of toads of the genus bufo have been analysed. from the values of the reciprocal rates between their amino acid residues a 'dissimilarity matrix' was made. in this have been included the values related to discoglossus pictus and xenopus laevis. the numerical data, derived from a computer program, gave a dendrogram representing the evolution of the analysed globins. this appears correlated to the geographical distribution and to the metabolic adaptation of the correspond ...	1984	6744827
structure and in vitro transcription of a glycine trna gene from bombyx mori.	we report the sequences of a bombyx mori trna1gly gene, its flanking regions, and its in vitro transcription products. the 5' flanking dna contains the sequences tatac, tatttt and ttc located 30, 18 and 4 nucleotides, respectively, in front of the transcription initiation site. these resemble, in both position and composition, sequences preceding other rna polymerase iii genes of b. mori. a deletion mutant retaining these conserved sequences and an additional 8 bp of flanking dna is transcribed ...	1984	6745242
inhibition of eukaryotic trna transcription by potential z-dna sequences.	the effect of d(ca/tg)n dna segments on trna transcription has been examined. alternating purine-pyrimidine tracts were cloned at a long distance from, adjacent to, or within the coding sequence of a trnapro gene from caenorhabditis elegans and shown to be able to assume the a-dna conformation in vitro in physiological salt concentrations. the transcriptional level of these constructs was compared to that of normal tdnapro by micro-injection into xenopus laevis oocytes. our results show a strong ...	1984	6745243
studies on three kinds of lectins from xenopus laevis skin.	among skin extracts of various frogs, lectin activity was found only in fractions prepared from xenopus laevis skin. 3 skin lectins have been separated. among these, the lectin designated s2-dlc was isolated in a homogeneous state and showed a preferential agglutination of ehrlich and s-180 ascites tumor cells; other tumor cells and human erythrocytes were not agglutinated. the lectin-dependent agglutination was inhibited by d-fucose, l-arabinose, d-galactose, lactose and lactulose. the sugar sp ...	1984	6745400
tnp-ficoll response in xenopus laevis: substitution and reconstitution in thymectomized animals.	the capacity to respond to haptenated ficoll, though thymus-independent in mammals, is lost in xenopus laevis following thymectomy at any stage of development. this capacity can be restored to thymectomized xenopus by whole allogeneic thymus implants, by thymus implants from animals treated with n-methyl-n-nitrosourea (which have an active thymus medulla but no cortex, and which lack certain thymus-dependent immunological functions), and concanavalin a. these results are discussed in terms of th ...	1984	6745996
isolation and characterization of the third component of complement in the serum of the clawed frog, xenopus laevis.	the hemolytic activity against srbc in the serum of normal xenopus is dependent on specific antibody and both ca++ and mg++, whereas the activity against rrbc is dependent on mg++ alone. both of these hemolytic activities disappeared after treatment of the serum with zymosan or with the specific rabbit antiserum against one of the zymosan-binding proteins in xenopus serum. by using this antiserum as a probe, a complement component (xc) was purified as a single entity from the xenopus plasma afte ...	1984	6747292
characterization of the intermittent breathing pattern in xenopus laevis.	xenopus laevis exhibits an extensive repertoire of breathing patterns during voluntary diving-emergence behaviour. in experiments where animals surfaced to breathe at a blowhole fitted with a pneumotachograph, two noticeably different patterns of breathing were observed. in the first (burst breathing), long periods of diving were periodically interrupted by short visits to the surface when a discrete series of evenly spaced ventilations occurred. on other occasions, the same animal might rise to ...	1984	6747538
functional conflicts between feeding and gas exchange in suspension-feeding tadpoles, xenopus laevis.	air-breathing tadpoles of xenopus laevis (amphibia: anura) use buccopharyngeal surfaces for both gas exchange and capture of food particles in the water. in dense food suspensions, tadpoles decrease ventilation of the buccopharynx and increase air breathing. the lung ventilatory frequency is elevated even though the rate of oxygen consumption is at or below resting levels, suggesting that the lung hyperventilation reflects compensation for decreased buccopharyngeal respiration rather than an inc ...	1984	6747542
the effect of trifluoperazine on maturation of xenopus laevis oocytes.	full grown xenopus oocytes were incubated with trifluoperazine (tfp) or injected with tfp. incubation of oocytes in tfp resulted in normal-appearing meiotic maturation, as judged by the presence of the white spot and the absence of the germinal vesicle. cortical granule breakdown in tfp-incubated oocytes was not normal. abnormal cortical granule breakdown was also observed when progesterone-maturated oocytes were activated in the presence of tfp. oocytes microinjected with tfp and incubated with ...	1984	6747571
lactoferrin biosynthesis during granulocytopoiesis.	we examined the synthesis of lactoferrin, an iron binding protein that, among hematopoietic cells, is restricted to secondary granules of polymorphonuclear leukocytes. lactoferrin biosynthesis was absent from leukemic myeloblasts and promyelocytes but abundant in normal bone marrow and both the bone marrow and peripheral blood of patients with chronic myelogenous leukemia (cgl) if the samples contained substantial numbers of myelocytes and metamyelocytes. lactoferrin was present in the steady st ...	1984	6593100
diploid gynogenesis in xenopus laevis and the localization with respect to the centromere of the gene for periodic albinism ap.	diploid gynogenetic xenopus laevis were obtained by inseminating the eggs with u.v. irradiated spermatozoa, and treating them with hydrostatic pressure to inhibit the expulsion of the second polar body. a u.v. dose of 3000 ergs/mm2 genetically inactivates the spermatozoa without loss of their ability to activate egg development. the use of a genetic marker on very large samples of eggs made it possible to verify the efficiency of the methods employed. the comparison of the development of diploid ...	1984	6594425