Publications

the secondary structure of the protein l1 binding region of ribosomal 23s rna. homologies with putative secondary structures of the l11 mrna and of a region of mitochondrial 16s rrna.	an heterologous complex was formed between e. coli protein l1 and p. vulgaris 23s rna. we determined the primary structure of the rna region which remained associated with protein l1 after rnase digestion of this complex. we also identified the loci of this rna region which are highly susceptible to t1, s1 and naja oxiana nuclease digestions respectively. by comparison of these results with those previously obtained with the homologous regions of e. coli and b. stearothermophilus 23s rnas, we po ...	1981	7010313
highly conserved lipoprotein assembly in teleost and amphibian yolk-platelet crystals.	ohlendorf et al. have reported that yolk-platelet crystals in the frog, xenopus laevis, were orthorhombic (space group p21221) and consisted of elongated asymmetric units (approximately 5.5 x 11.5 x 25 nm). the presence of an orthorhombic lattice in amphibian yolk platelets fulfilling the symmetry requirements of crystals had been missed in earlier structural interpretations. a comparative study of teleost, urodele and anuran yolk-platelet crystals performed in our laboratory has shown the wides ...	1981	6969859
the hatching enzyme from xenopus laevis: limited proteolysis of the fertilization envelope.	hatching in the amphibian xenopus laevis involves release of an embryo-secreted hatching enzyme, a protease, which weakens the envelope surrounding the embryo. the envelope is not totally solubilized, which infers that only selected envelope components are hydrolyzed by the enzyme. the susceptibility of the glycoprotein components composing the envelope to hydrolysis by the hatching enzyme was investigated. isolated envelopes in various physical states, ie, particulate and solubilized, were trea ...	1981	6965088
31p nmr reveals increased intracellular ph after fertilization in xenopus eggs.	31p nmr spectra of mature eggs of the frog (xenopus laevis) were taken prior to and after both fertilization and activation by a ca2+/h+ ionophore (a23187). the eggs were constantly perfused with fresh well-buffered solution during the experiments, and the intracellular ph (phi) was determined from the ph-dependent chemical shift of the internal pi peak. the detection of this pi peak in the presence of overlapping yolk phosphoprotein signals was accomplished by a t2 experiment which discriminate ...	1981	6945594
a dna binding protein from xenopus laevis oocyte mitochondria.		1981	6894896
internal control regions for transcription of eukaryotic trna genes.	we have identified the region within a eukaryotic trna gene required for initiation of transcription. these results were obtained by systematically constructing deletions extending from the 5' or the 3' flanking regions into a cloned drosophila trnaarg gene by using nuclease bal 31. the ability of the newly generated deletion clones to direct the in vitro synthesis of trna precursors was measured in transcription systems from xenopus laevis oocytes, drosophila kc cells, and hela cells. two contr ...	1981	6947245
in vitro transcription of cloned 5s rna genes of the newt notophthalmus.	recombinant plasmids that carried genes coding for 5s ribosomal rna of the newt, notophthalmus viridescens, were transcribed in vitro with extracts of xenopus laevis oocyte nuclei. plasmids containing multiple repeats of the 5s gene and spacer directed accurate transcription of 5s rna (120 bases). individual repeat units were recloned by inserting sau 3a restriction fragments into the bam hi site of plasmid pbr322. because each repeat was cut by the enzyme within the coding region, the inserts h ...	1981	6945306
a mosaicism in the higher order structure of xenopus oocyte nucleolar chromatin prior to and during ribosomal gene transcription.	we report an analysis by electron microscopy of the differences in the folding of ribosomal gene and adjacent nontranscribed spacer dna of xenopus laevis oocytes into supranucleosomal chromatin structures. the chromatin structures identified in gene and spacer regions of transcriptionally active nucleoli (from stage 5 oocytes) were compared with those found in nucleoli prior to transcription (from stage 2 oocytes) to determine whether changes in the chromatin structure occur when transcription i ...	1981	6939485
modulation of the neural control of the clasp reflex in male xenopus laevis by androgens: a multidisciplinary study.	the neural control of the clasp reflex in male xenopus laevis has been studied by using anatomical, electrophysiological, and biochemical techniques. neurons in spinal segment 2 of castrated males accumulate label after injection of [3h]-dihydrotestosterone; these neurons are distributed within the rostral portions of the motoneuronal pools of the sternoradialis and flexor carpi radialis muscles. in vitro recordings from the nerve to the sternoradialis muscle in the isolated spinal cord preparat ...	1981	6946519
transformation of frog embryos with a rabbit beta-globin gene.	in order to study the fate and possible expression of foreign dna during embryogenesis of the frog xenopus laevis, we have injected a rabbit beta-globin gene into fertilized xenopus eggs. frog embryo dna was extracted at various stages of development, fractionated by agarose gel electrophoresis, transferred to nitrocellulose filters, and hybridized to labeled beta-globin recombinant plasmid dna. it was found that the injected dna replicated extrachromosomally, reaching, at gastrula stage, a leve ...	1981	6946453
methylation of adenovirus genes in transformed cells and in vitro: influence on the regulation of gene expression?	an inverse correlation has been described between the levels of dna methylation in specific segments of adenovirus dna integrated into the genomes of transformed and tumor cells and the extent to which these segments are expressed as messenger rna. in the adenovirus type 2 (ad2)-transformed hamster cell lines he2 and he3, the virus-specific dna binding protein (dbp) is not expressed, and the dna in the dbp gene is completely methylated in all 5'-ccgg-3' sites. at least part of the late promoter/ ...	1981	6895196
location and release of trh and 5-ht from amphibian skin.	the occurrence and release of thyrotrophin-releasing hormone (trh) and 5-hydroxytryptamine (5-ht) from amphibian skin have been described by previous investigators. in the present study, the precise location and site of release of trh and 5-ht from the skin of rana pipiens and xenopus laevis have been examined using a combination of procedures including immunohistochemistry, hplc, and radioimmunoassay. the results indicate that trh is located specifically within the dermal glands of these specie ...	1981	6784937
comparative acid phosphatase distribution in the suprarenal gland of discoglossus pictus, xenopus laevis and bufo bufo (anurans, amphibia).	acid phosphatase activity was found to have a similar distribution in the suprarenal glands of discoglossus pictus, xenopus laevis and bufo bufo (anurans, amphibia) as determined by light and electron histochemical localization. the enzymatic activity is localized in the lysosomes of both the interrenal cells and the chromaffin cells. it is, moreover, positive on the granule membranes of the adrenaline cells whereas it appears only occasionally on the granule membranes of the noradrenaline cells ...	1981	6802124
isolation and characterization of multiple components of basic gonadotropin from bullfrog (rana catesbeiana) pituitary gland.	four gonadotropin components were purified from the basic protein fraction of bullfrog pituitary glands. all the components had high potencies not only in the ovulation assay using xenopus laevis ovaries but also in the competitive binding assay for rat follicle-stimulating hormone (fsh) using xenopus laevis testis. the isoelectric points of the four components determined by isoelectric focusing were at ph 8.8, 9.0, 9.1, and 9.3, respectively. no appreciable difference in the physical and chemic ...	1981	6802808
poor evidence for insulin/insulin-like immunoreactivity in the cns of lower vertebrates.	the localization of insulin/insulin-like immunoreactivity was studied in the brain and the pancreas of an amphibian (clawed frog [xenopus laevis daudin]) and in the cns of two teleost fishes (bream [abramis brama l.] and rudd [scardinius erythrophthalmus l.] using the indirect immunofluorescence technique. with exception of cerebellar purkinje cells no neuronal elements were found to contain insulin-like material. the frog pancreas was characterized by a strong immunofluorescence in cells produc ...	1981	6795888
ribonuclease "xlai," an activity from xenopus laevis oocytes that excises intervening sequences from yeast transfer ribonucleic acid precursors.	a ribonuclease (rnase) activity, rnase "xlai," responsible for the excision of intervening sequences from two yeast transfer ribonucleic acid (trna) precursors, pre-trna(tyr) and pre-trna(3leu), has been purified 54-fold from nuclear extracts of xenopus laevis oocytes. the rnase preparation is essentially free of contaminating rnase. a quantitative assay for rnase xlai was developed, and the reaction products were characterized. rnase xlai cleavage sites in the yeast trna precursors were identic ...	1981	6765601
the amphibian epidermis: distribution of mitochondria-rich cells and the effect of oxytocin.	it is known that the ion-transporting capacity and the permeability to water of amphibian skins vary greatly both between and within species. furthermore, the extent to which different skins respond to hormonal stimulation of these parameters also shows considerable inter- and intra-specific variation. as a first step towards defining a possible morphological basis for this physiological heterogeneity, we examined different regions of skins from 3 anurans, bufo bufo, rana ridibunda and xenopus l ...	1981	6801063
pepsin and trypsin activity in the fore gut of metamorphosing xenopus laevis larvae.		1981	6806130
tetanus toxin: a marker of amphibian neuronal differentiation in vitro.	tetanus toxin may be used to specifically mark neurones in cultures of mammalian and chick nervous tissue. we have prepared cultures of neural ectoderm and underlying mesoderm from late neurula xenopus laevis embryos, and shown that in this amphibian species, neurones are labelled by tetanus toxin. aggregate cultures of ectoderm and mesoderm from late blastula embryos were than examined to determine whether tetanus toxin might be used to mark neuronal precursor cells. our observations suggest th ...	1981	7015184
ultrastructural identification of gastrin-like immunoreactive nerve fibres in the brain of xenopus laevis by means of colloidal gold or ferritin immunocytochemical methods.		1981	7016332
origin of replication from xenopus laevis mitochondrial dna promotes high-frequency transformation of yeast.	a specific fraction of chromosomal dna from both yeast and a wide variety of other eukaryotes, but not from escherichia coli, promotes high-frequency transformation in yeast. the plasmids containing these sequences are maintained as extra-chromosomal molecules in transformed cells. these results suggest that similar or identical sequences are used for the initiation of dna replication in eukaryotes. to test this hypothesis, several foreign eukaryotic dnas implicated directly or indirectly in the ...	1981	7019920
ph changes associated with meiotic maturation in oocytes of xenopus laevis.		1981	7021268
prolonged survival of major histocompatibility complex-disparate skin allografts transplanted to the metamorphosing frog, xenopus laevis.		1981	7022797
actin in xenopus development: indirect immunofluorescence study of actin localization.	actin was studied in xenopus unfertilized eggs and early developmental stages. immunochemical proof is given of structural differences between xenopus laevis muscle actin and nonmuscle cell actin. actin localization and changes of actin aggregation during xenopus development were observed using indirect immunofluorescence. we have also tried to explain the presence of an actin shell around the yolk platelets that appeared in our experiments.	1981	7030842
secondary lens formation from the cornea following implantation of larval tissues between the inner and outer corneas of xenopus laevis tadpoles.	secondary lens formation from the cornea of larval xenopus laevis has been used as a measure of the lens-inducing capacities of various larval xenopus tissues. the experimental design employed involved implantation of selected body tissues between the inner and outer cornea of stage-50 tadpole eyes, in such a way that the integrity of the inner cornea and eye cup was not disrupted. implantation of retina, pituitary, limb blastema or limb bud resulted in secondary lens formation from the outer co ...	1981	7031166
locomotion of xenopus epidermis cells in primary culture.	the locomotion of single epidermis cells, grown out from xenopus laevis tadpole tails has been investigated by time-lapse cinemicrography using phase-contrast and reflection-contrast optics. the cells develop a large, mostly 200-250 nm thick, lamella, which adheres homogeneously to the supporting coverglass and exceeds the projection area of the cell body. from the comparison of ric-pictures taken at high (1.06) and low (0.62) numerical aperture of illumination (i.n.a.) we deduce that at low i.n ...	1981	7037800
effects of fenitrothion and carbaryl on xenopus laevis development.	when xenopus laevis embryos were treated with fenitrothion, a substantial proportion failed to survive to hatching only when the concentration approached saturation. however, after exposure to 10 ppm of fenitrothion, most were abnormal and did not survive past feeding stage. different embryonic stages were not equally sensitive to fenitrothion and the greatest sensitivity was observed at gastrulation. the most common visible abnormalities were altered body shape, including microcephaly, and edem ...	1981	6805100
isolation and characterization of the hatching enzyme from the amphibian, xenopus laevis.		1981	6784682
[histochemical localization of carbonic anhydrase in flask cells of the clawfrog mesonephros (xenopus laevis daudin) (author's transl)].	carbonic anhydrase activity was demonstrated in the flask cells of intermediate segments and collecting tubules of the clawfrog-mesonephros with the cobalt-bicarbonate method of häusler (1958) and hansson (1967). additional the luminal surface of proximal and distal convoluted tubules reacted positively. by electron microscopy the enzyme activity in the flask cells was localized mainly on the surface of microvilli like cytoplasmic processes which lined the lumen of intracellular secretion capill ...	1981	6791445
early events in the development of the immune system of xenopus laevis: characterization of lymphocytes in two-day-old embryos.		1981	6797849
effect of skin allograft immunization on the mixed leukocyte reaction of the clawed frog, xenopus laevis.	one-way mixed leukocyte reactions (mlrs) of responder spleen cells from frogs (xenopus laevis) that had rejected skin grafts were examined. maximum and median stimulation indices (sis) of cultures that contained responder cells from the graft recipient and stimulator cells from the graft donor were significantly greater than the peak and median sis of cultures in which the responder splenocytes were from control, nonimmune animals. significant stimulation was also recorded earlier (day 2 of cult ...	1981	6460353
correlation between the cell cycle in the neurectoderm and differentiation during the early development of xenopus laevis. 2 inhibition of dna synthesis and mitosis during gastrulation.	the hypothesis that cell differentiation during primary induction may be coupled with a 'quantal' cell cycle in the presumptive neurectoderm is considered. embryos of xenopus laevis were incubated with fluorodeoxyuridine or mitomycin c during gastrulation or neurulation. embryos treated during the gastrula stage developed abnormalities of the brain but not of other tissues. this is seen as lending support to the idea that the wave of dna synthesis and mitosis in the presumptive neurectoderm duri ...	1981	6460598
monoclonal anti-igm can separate t cell from b cell proliferative responses in the frog, xenopus laevis.	the role of sigm+ lymphocytes in frog mitogen responses and mixed lymphocyte reactions was examined. a murine monoclonal antibody with specificity for xenopus laevis igm was produced. the anti-igm activity was not inhibited by glycoproteins other than xenopus igm, but could be inhibited with periodate-treated frog igm. fluorescent microsphere-coupled anti-igm was used to show that adult and larval thymocytes had few sigm+ lymphocytes, whereas spleens contained 19 to 34% sigm+ lymphocytes. the sp ...	1981	6456307
messenger rnas of mouse hepatitis virus a59: isolation and characterization, translation in xenopus laevis oocytes of rnas 3, 6 and 7, uv target sizes of the transcription templates.		1981	6278883
in vitro transcription of a cloned mouse ribosomal rna gene.	an in vitro transcription system which utilizes cloned mouse ribosomal rna gene (rdna) fragments and a mouse cell extract has been developed. rna polymerases i is apparently responsible for this transcription as evidenced by the complete resistance to a high concentration (200 micrograms/ml) of alpha-amanitin. run-off products obtained with three different truncated rdna fragments indicated that rna was transcribed from a unique site of rdna. the s1 nuclease protection mapping of the in vitro pr ...	1981	6278446
dna topoisomerase i from mitochondria of xenopus laevis oocytes.	activity of dna topoisomerase i has been characterized in extracts of mitochondria purified from xenopus laevis oocytes. several lines of evidence have been obtained for the intramitochondrial localization of the enzyme. the mitochondria-associated of dna topoisomerase i represents 1% of the activity recovered from a total ovary population of oocytes. the enzymes has been purified by deae-cellulose, phosphocellulose and double-stranded dna cellulose chromatography and its properties compared to ...	1981	6269855
the rise and fall of electrical excitability in the oocyte of xenopus laevis.	1. an electrically excited (gated) sodium selective channel has been found in the xenopus laevis oocyte, a cell membrane previously considered non-excitable. 2. the channel is produced by prolonged depolarization of the membrane and is removed by prolonged repolarization. both processes are very dependent on temperature and potential. 3. once produced, the channel can be opened and closed electrically, but does not show inactivation as is found in other sodium selective channels. 4. the sodium s ...	1981	6286961
hormone effects on transport in cultured epithelia with high electrical resistance.	three continuous lines of amphibian epithelial cells form epithelia with a high transepithelial resistance (greater than 4,000 omega . cm2) in culture. the cell lines are tb-m and tb-6c, derived from the urinary bladder of bufo marinus, and a6, derived from the kidney of xenopus laevis. short-circuit current is equivalent to net mucosa-to-serosa sodium transport in two cell lines and slightly exceeds sodium transport in epithelia formed by tb-6c cells. none of the cell lines has an adenylate cyc ...	1981	6259946
purification and characterization of xenopus laevis type i topoisomerase.	a topoisomerase activity was purified from mature ovaries and from nuclei of stage 6 oocytes of xenopus laevis. from both preparations we obtained a single polypeptide chain having an estimated molecular weight of 67,000. the enzyme purified from ovaries is active in the presence of 150 mm monovalent cation, but its activity is more than 1 order of magnitude higher in the presence of 6 mm mg2+; the enzyme purified from nuclei requires mg2+ through all the steps of purification. enucleated oocyte ...	1981	6260773
translation of three mouse hepatitis virus strain a59 subgenomic rnas in xenopus laevis oocytes.	we have purified the seven virus-specific rnas which were previously shown to be induced in sac(-) cells upon infection with mouse hepatitis virus strain a59 (w. j. m. spaan, p. j. m. rottier, m. c. horzinek, and b. a. m. van der zeijst, virology 108:424-434, 1981). the individual rnas, prepared by agarose gel electrophoresis of the polyadenylated rna fraction from infected cells, were obtained pure, except for the preparations of rnas 4, 5, and 6, which contained some contamination of rna 7. th ...	1981	6264100
calmodulin triggers the resumption of meiosis in amphibian oocytes.	the calcium-binding protein, calmodulin, has been purified from xenopus laevis oocytes. this 18,500-dalton protein, pl 4.3, has two high-affinity calcium-binding sites per mole protein having a dissociation constant of 2.8 x 10(-6) m. full-grown xenopus oocytes, arrested in late g2 of the meiotic cell cycle, resumed meiosis when microinjected with 60-80 ng (3-4 pmol) of calmodulin in the form of a calcium-calmodulin complex. the timing of the meiotic events in these recipient oocytes was the sam ...	1981	6265465
the organization of the histone genes in the genome of xenopus laevis.	we have studied the organization of the histone genes in the dna from several individuals of xenopus laevis. for that purpose, southern blots of genomic dna, that was digested with several restriction enzymes, were hybridized with radioactively labeled dna fragments from clone x1-hi-1 (14), containing genes for xenopus histones h2a, h2b, h3 and h4. in the dna of all animals that were screened we found a major repeating unit of 14 kilobasepairs, which contains genes for histones h2a, h2b, h3 and ...	1981	6265869
mitochondrial number, cytochrome oxidase and succinic dehydrogenase activity in xenopus laevis oocytes.	an estimate has been made of the numbers of mitochondria in the mitochondrial cloud (balbiani body) of xenopus laevis oocytes ranging in size from 50 to 250 micrometers. the mitochondrial number is expressed in terms of a 'standard' organelle measuring 2 micrometers in length and 0.2 micrometer in diameter and is derived by measurements on electron micrographs of sections through the cloud. it is found that the amount of mitochondrial material rises very rapidly as the oocyte grows in size. at t ...	1981	6268730
isolation and characterization of genomic clones covering the chicken vitellogenin gene.	a series of overlapping recombinant clones, which cover the vitellogenin gene, has been isolated from a phage-lambda linked chicken gene library. the dna of the overlapping clones spans 28 kb of contiguous dna sequences in the chicken genome. electron microscopic analysis of hybrids between vitellogenin mrna and the genomic clones indicates that the chicken vitellogenin gene has a length of approximately 22 kb, about 3.8 times the size of the mrna. the mrna sequence is interrupted by at least 33 ...	1981	6269078
involvement of camp in the cytoplasmic control of meiotic cell division in xenopus laevis oocytes.	1) there is a large body of evidence for an inhibitory role for camp in progesterone induced meiosis in amphibian oocytes consistent with its known inhibitory activity in mammalian oocytes (5,26). it implies that the action of steroid hormones in this particular tissue is mediated by modifications of camp levels within the cell. 2) bacterial toxins have proved to be useful reagents in the investigation of the regulatory role of cyclic nucleotides in the resumption of cell division in amphibian o ...	1981	6269393
quantitation of the accumulation of histone messenger rna during oogenesis in xenopus laevis.		1981	6269929
transcription and translation of the herpes simplex virus type 1 thymidine kinase gene after microinjection into xenopus laevis oocytes.	the hybrid plasmid ptk1 consists of the herpes simplex virus type 1 (hsv-1) bamhi p fragment, which contains the thymidine kinase (tk) gene, inserted into the vector pat 153. when ptk1 dna was microinjected into nuclei of xenopus laevis oocytes, functional hsv-1-specific tk was produced, showing that transcription and translation of the gene occurred. investigation of ptk1-specific rna by "southern' blot hybridization revealed that all regions of the hybrid plasmid were transcribed by rna polyme ...	1981	6270258
calmodulin is involved in the first step of oocyte maturation: effects of the antipsychotic drug fluphenazine and of anticalmodulin antibodies on the progesterone-induced maturation of xenopus laevis oocyte.	specific anticalmodulin antibodies were microinjected into full-grown xenopus laevis oocyte, and it is shown that in ovo blockade of the complex ca2+-calmodulin accelerates the kinetics of progesterone-induced maturation, even though the molar ratio of antibody binding sites to total calmodulin was only 0.16. addition of 200 microm fluphenazine to the oocyte incubation medium resulted in a similar acceleration of steroid-induced maturation. neither protein kinase inhibitor (pki) nor maturation p ...	1981	6274518
equilibrium properties of a voltage-dependent junctional conductance.	the conductance of junctions between amphibian blastomeres is strongly voltage dependent. isolated pairs of blastomeres from embryos of ambystoma mexicanum, xenopus laevis, and rana pipiens were voltage clamped, and junctional current was measured during transjunctional voltage steps. the steady-state junctional conductance decreases as a steep function of transjunctional voltage of either polarity. a voltage-insensitive conductance less than 5% of the maximum remains at large transjunctional vo ...	1981	6259274
specific binding of a prokaryotic ribosomal protein to a eukaryotic ribosomal rna: implications for evolution and autoregulation.	ribosomal protein l1 from the prokaryote escherichia coli has been shown to form a specific complex with 26s ribosomal rna from the eukaryote dictyostelium discoideum. the segment of dictyostelium rrna protected from ribonuclease digestion by l1 and the corresponding region in dictyostelium rdna were investigated by nucleotide sequence analysis, and an analogous section in rdna from xenopus laevis was identified. when the l1-specific segments from eukaryotic rrna were compared with those from pr ...	1981	6265904
adenosine 3' :5' monophosphate receptor sites in xenopus laevis oocytes.	adenosine 3':5' cyclic monophosphate (cyclic amp) binds to proteins present in the 100,000 g supernatant fractions of full-grown oocytes of xenopus laevis. optimal ph for the binding is 4.0. two receptor binding sites have been characterized by density gradient centrifugation as peaks with sedimentation constants of 4.6 s and 5.9 s. the apparent dissociation constants for the two cyclic amp binding sites are 7 nm and 40 nm. the total cyclic amp binding capacity of oocyte cytosol is 15.8 +/- 2.2 ...	1981	6276257
replication of heterologous dna in xenopus laevis oocytes.		1981	6262120
interaction between motor axons from two different nerves reinnervating the pectoral muscle of xenopus laevis.	1. an electrophysiological and morphological study of sprouting and regeneration of motor nerves has been performed in the dually innervated pectoral muscle of xenopus laevis. 2. section of one of the nerves induced axon sprouting in the intact nerve. synapse formation by the sprouting axons was slow since the intact nerve took more than 3 months to increase its field of innervation by 70%. the rate of axon regeneration was faster than that of axon sprouting since the cut nerve reinnervated its ...	1981	6262504
nucleotide sequence of the initiation site for ribosomal rna transcription in drosophila melanogaster: comparison of genes with and without insertions.	the sequence of 470 nucleotides surrounding the initiation site for rrna transcription in drosophila melanogaster has been determined. the precise initiation site was determined first by measuring the dna fragment protected by the rrna precursor against digestion by the single-strand specific nuclease s1 and second by direct sequence determination of the first 13 nucleotides of the rrna precursor. because greater than 80% od rrna precursor molecules have been shown previously to bear pppa or ppa ...	1981	6262809
[meiotic maturation of the ovocyte of xenopus laevis : a 4-step mechanism].	microinjection of the pure inhibitor (1) of camp dependent protein kinases (1.5 mum) into xenopus oocytes triggered 100% germinal vesicle break down (gvbd), faster than progesterone and slower than the maturation promoting factor (mpf). cholera toxin does not block (i) induced maturation; however cycloheximide inhibits (i) but not mpf induced gvbd.	1981	6263509
replication of sv40 chromatin in extracts from eggs of xenopus laevis.	simian virus 40 (sv40) nucleoprotein complexes were prepared from lytically infected cells and used as primer-templates for dna replication in protein extracts from xenopus eggs. we found that nucleoprotein containing replicating sv40 dna served as primer-template while nucleoprotein with nonreplicating sv40 dna was ineffective. in vitro dna synthesis begins with short dna fragments ("okazaki fragments") which are, in later steps, joined to give unit length sv40 dna strands, suggesting that in v ...	1981	6269093
effect of a methyl-transferase inhibitor, 5'-deoxy'5'-s-isobutyl-thioadenosine (siba) on camp level and progesterone induced meiosis reinitiation in xenopus laevis oocytes.		1981	6268063
primary structure of the histone h3 and h4 genes and their flanking sequences in a minor histone gene cluster of xenopus laevis.		1981	6274702
the emergence, localization, and maturation of neurotransmitter systems during development of the retina in xenopus laevis: ii. glycine.	the high-affinity uptake and release of glycine was studied in retinas of xenopus laevis. in the toad and tadpole retina, 3h-glycine was accumulated by a population of cells located predominantly in the inner nuclear layer. when retinas preloaded with 3h-glycine were subjected to high k+-concentrations, these retinas released large amounts of 3h-glycine by a ca++-dependent mechanism. the appearance and maturation of these putative glycinergic properties was followed during retinal development. o ...	1981	6257765
deletion of the 3' half of the yeast trna-leu3 gene does not abolish promotor function in vitro.	the promotor function of the 3' and 5' half trna sequences in the yeast trna-leu3 gene has been studied by in vitro transcription in xenopus laevis germinal vesicle (gv) extracts. truncation of the dna template within the trna intervening sequence by hpa i abolishes transcription. however, separation of the trna gene halves by insertion of a 300 bp dna fragment at the hpa i site does not affect the promoter efficiency. further, the complete sequence of the 3' half of the trna is not necessary fo ...	1981	6277504
the emergence, localization, and maturation of neurotransmitter systems during development of the retina in xenopus laevis. iii. dopamine.	the uptake, synthesis, and release of dopamine was studied in retinas of xenopus laevis. in the tadpole and adult retina, 3h-dopamine is accumulated by cells located in the inner nuclear layer. retinas preloaded with 3h-dopamine release this compound in response to high k+ concentrations in the medium. this release is probably ca++-dependent as it is inhibited by co++ in the medium. adult retinas are also capable of synthesizing 3h-dopamine from 3h-tyrosine. the appearance and maturation of thes ...	1981	6257766
a transcriptionally active pseudogene in xenopus laevis oocyte 5s dna.	dna that encodes the xenopus laevis 5s pseudogene is transcribed following microinjection into oocyte nuclei. transcription in injected oocytes is accurate, is mediated by rna polymerase iii and is initiated at the first nucleotide of the pseudogene. the level of pseudogene transcription can be as high as 85% of that of the normal 5s gene. the results suggest that the observed absence of pseudogene transcripts of defined length in vivo probably is due to inefficient termination of transcription.	1981	6166389
cellular titers and subcellular distributions of abundant polyadenylate-containing ribonucleic acid species during early development in the frog xenopus laevis.	the distribution of cytoplasmic messenger ribonucleic acids (rnas) in translationally active polysomes and inactive ribonucleoprotein particles changes during early development. cellular levels and subcellular distributions have been determined for most messenger rnas, but little is known about how individual sequences change. in this study, we used hybridization techniques with cloned sequences to measure the titers of 23 mitochondrial and non-mitochondrial polyadenylate-containing [poly(a)+]rn ...	1981	6180297
clonal organization of the central nervous system of the frog. ii. clones stemming from individual blastomeres of the 32- and 64-cell stages.	horseradish peroxidase injected into individual blastomeres of 32- and 64-cell embryos of xenopus laevis was identified in cells of the central nervous system (cns) at larval stages 31 to 39. the cns received contributions from 24 blastomeres of the 32-cell stage and 38 blastomeres of the 64-cell stage. the region of cns in which all of the labeled descendants of a single blastomere were dispersed is called a clonal domain. mingling of labeled and unlabeled cells always occurred in a clonal doma ...	1981	6167693
organization and sequence analysis of a cluster of repetitive dna elements from xenopus laevis.		1981	6173488
fate of secretory proteins trapped in oocytes of xenopus laevis by disruption of the cytoskeleton or by imbalanced subunit synthesis.	the effects of imbalanced subunit synthesis, temperature, colchicine, and cytochalasin on the secretion from xenopus laevis oocytes of a variety of avian and mammalian proteins were investigated; these proteins were encoded by microinjected messenger rna. cytochalasin and colchicine together severely reduced secretion in a temperature-independent manner, the exact reduction varying among the different proteins. in contrast cytochalasin alone had no effect, whereas colchicine alone caused a small ...	1981	6173386
a comparison of xenopus laevis oocyte and embryo mrna.		1981	6169574
partial characterization of gamma (immune) interferon mrna extracted from human lymphocytes.	gamma (immune) interferon (ifn-gamma) was induced in cultures of fresh human lymphocytes by combined treatment with a phorbol ester (12-o-tetradecanoylphorbol 13-acetate, tpa) and the t cell mitogen phytohemagglutinin (pha). compared to the ifn-gamma yields obtained with pha induction alone, the inclusion of tpa caused a significant enhancement of ifn-gamma production. poly(a)-containing mrna was isolated from mononuclear cells induced with tpa and pha. injected into xenopus laevis oocytes, this ...	1981	6167986
albumin is encoded by 2 messenger rnas in xenopus laevis.	a cdna clone library was prepared from liver poly(a) rna pf non-estrogenized xenopus laevis. albumin coding sequences were screened by hybridization to a cdna prepared from poly(a) rna enriched by sucrose density gradient centrifugation, and by a sensitive solid-phase radioimmunoassay to detect clones that contain templates for albumin antigenic determinants. nine clones were obtained by this approach, and all but one have the cdna inserted in phase with the beta-lactamase gene of pbr322. mappin ...	1981	6174943
translation of human immune interferon messenger rna in xenopus laevis oocytes.		1981	6168263
xenopus laevis serum albumins are encoded in two closely related genes.	cdna clones containing sequences complementary to xenopus laevis albumin mrna have been identified in a collection of cdna clones made from poly(a)+ rna prepared from male xenopus laevis liver. although all the albumin cdna clones crosshybridise, restriction enzyme and heteroduplex analysis show that there are 2 closely related albumin mrna sequences. the 2 albumin mrnas are only mismatched by 8% but could be isolated by positive selection using stringent hybridization conditions. oocytes inject ...	1981	6169009
a nucleolar skeleton of protein filaments demonstrated in amplified nucleoli of xenopus laevis.	the amplified, extrachromosomal nucleoli of xenopus oocytes contain a meshwork of approximately 4-nm-thick filaments, which are densely coiled into higher-order fibrils of diameter 30-40 nm and are resistant to treatment with high- and low-salt concentrations, nucleases (dnase i, pancreatic rnase, micrococcal nuclease), sulfhydryl agents, and various nonionic detergents. this filamentous "skeleton" has been prepared from manually isolated nuclear contents and nucleoli as well as from nucleoli is ...	1981	6169728
[identification of the isoadenylate synthetase in the messenger rna translation products of antiviral proteins].	a further study of conditions for induction, determinations of activity and products of mrnas translation of avp having nonspecific antiviral activity from l-929 cells treated with poly(i) . poly(c) was carried out. under conditions of superinduction of interferon the yield of avp mrna is reduced unlike that of interferon mrna. manifestations of the antiviral effect of avp mrna translation products do not seem to require the stages of transcription as dihydrorifampicin exerts no influence on thi ...	1981	6170176
nucleoprotein cytochemistry during oogenesis in a unisexual fish, poecilia formosa.	cytochemical methods and electron microscopy were used to study changes in the chemical composition of nuclear, nucleolar and perinuclear bodies during the early stages of oocyte development in poecilia formosa, an apomictic species of fish that produces only female offspring. prominent accumulations of ribonucleoprotein (rnp) occur in nucleoli and appear on either side of the nuclear envelope during diplotene. in certain planes of section, rnp material seems to be in transit across this interfa ...	1981	6170612
comparative analysis of cloned larval and adult globin cdna sequences of xenopus laevis.		1981	6171466
adenylate cyclase and cyclic amp-phosphodiesterase activities during the early phase of maturation in xenopus laevis oocytes.		1981	6162679
synthesis and insertion, both in vivo and in vitro, of rat-liver cytochrome p-450 and epoxide hydratase into xenopus laevis membranes.	we described whole cell and cell-free systems capable of inserting into membranes cytochrome p-450 and epoxide hydratase made under the direction of rat liver rna. the systems have been used to study the pathways followed by newly made secretory and integral membrane proteins. the cell-free system contains xenopus laevis embryo membranes, and demonstrates competition for a common receptor between cytochrome p-450 and epoxide hydratase, and normal secretory proteins: evidence is provided for diff ...	1981	6165584
molecular structure of maternal rna.	the presence of a stable maternal mrna population in mature oocytes of many species is well established. in this paper we show that the mature egg contains, in addition to these mature mrnas, a structurally more complex population of rna transcripts. this latter class of rna consists of polyadenylated transcripts of repetitive and nonrepetitive dna elements covalently linked into long interspersed molecules. as much as seventy percent of the polyadenylated egg rna of xenopus laevis and strongylo ...	1981	6173173
the influence of topology and glycosylation on the fate of heterologous secretory proteins made in xenopus oocytes.	secretory proteins made in xenopus laevis oocytes under the direction of heterologous messenger rna are modified, topologically segregated and exported. thus the oocyte may serve as a useful surrogate secretory system and we have studied some of the factors governing access to the export pathway. unglycosylated chicken ovalbumin, synthesized and trapped in the cytosol, is not secreted but glycosylated ovalbumin, found sequestered within vesicles, is exported from oocytes. however, ovalbumin, whi ...	1981	6162638
accumulation, spatial distribution and partial characterization of poly(a)+rna in the developing oocytes of xenopus laevis.		1981	6175714
translation of human interferon mrnas in xenopus laevis oocytes.		1981	6173723
nucleosome arrangement on trna genes of xenopus laevis.	we have examined the chromatin structure of a repeated cluster of trna genes of xenopus laevis, with particular attention to possible phase relationships between nucleosomes and the underlying tdna sequence. in transcriptionally active liver and cultured kidney cells, essentially all tdna is packaged into regularly spaced nucleosomes, but no detectable phase relationship exists between nucleosomes and dna sequence. only in transcriptionally inactive erythrocytes do nucleosomes on all tdna repeat ...	1981	6101200
xenopus laevis ribosomal protein genes: isolation of recombinant cdna clones and study of the genomic organization.	poly-a+ mrna from xenopus laevis oocytes, partially enriched for r-protein coding capacity has been used as starting material for preparing a cdna bank in plasmid pbr322. the clones containing sequences specific for r-proteins have been selected by translation of the complementary mrnas. clones for six different r-proteins have been identified and utilized as probes for studying their genomic organization. two gene copies per haploid genome were found for r-proteins l1, l14, s19, and four-five f ...	1981	6112733
comparative actions of glutamate and related substances on the xenopus laevis lateral line.		1981	6113083
microsuperfusion of neurointermediate lobes of xenopus laevis: concomitant and coordinately controlled release of newly synthesized peptides.		1981	6113093
hepatic microsomal mixed-function oxidase in the frog, xenopus laevis.		1981	6112107
trh, gh-rih, and lh-rh in metamorphosing xenopus laevis.		1981	6113189
central action of l-dopa in blood pressure regulation and effect on catecholamine content in the frog, xenopus laevis.		1981	6117402
estrogen regulation of hepatic 3-hydroxy-3-methylglutaryl coenzyme a reductase and acetyl-coa carboxylase in xenopus laevis.	administration of estradiol-17 beta to male xenopus laevis evokes the proliferation of the endoplasmic reticulum and the golgi apparatus and the synthesis and secretion by the liver of massive amounts of the egg yolk precursor phospholipoglycoprotein, vitellogenin. we have investigated the effects of estrogen on three key regulatory enzymes in lipid biosynthesis, 3-hydroxy-3-methylglutaryl (hmg)-coa reductase, the major regulatory enzyme in cholesterol and isoprenoid synthesis, and acetyl-coa ca ...	1981	6110664
evidence for the involvement of transglutaminase in the uptake of vitellogenin by xenopus laevis oocytes.		1981	6112986
synapse formation and modification between distal retinal neurons in larval and juvenile xenopus.	a serial section analysis of photoreceptor synaptic bases was undertaken in the clawed frog xenopus laevis. the developmental period from tadpole stage 48 through metamorphosis was studied. horizontal cells contacted rod and cone photoreceptors at ribbon synapses; the number of such contacts per receptor base was constant for rods, but increased for cones as a function of developmental stage. in pre-metamorphic animals bipolar cells contacted receptors only through basal junctions; their number ...	1981	6111804
primordial germ cells of xenopus embryos: the role of fibronectin in their adhesion during migration.	primordial germ cells (pgcs) of xenopus laevis are highly migratory. the last section of their migratory pathway is through the dorsal mesentery of the tadpole gut. this in vivo pathway is rich in fibronectin, a glycoprotein that promotes cell adhesion and migration in vitro. isolated pgcs are associated with cells from the mesentery and with fibronectin. treatment with trypsin removes both the mesentery cells and the fibronectin. the pgcs do not appear to resynthesize detectable fibronectin in ...	1981	6101198
contact relations and guidance of primordial germ cells on their migratory route in embryos of xenopus laevis.	this paper describes the relationship between primordial germ cells (p.g.cs) and the substrate over which they migrate in early embryos of the anuran amphibian xenopus laevis. p.g.cs migrate from the embryonic gut to the dorsal body wall along the dorsal mesentery at the earliest swimming stage. our earlier papers have described the way in which p.g.cs move in vitro. in this work we have studied the shape and cytoarchitecture of both p.g.cs and the coelomic epithelial cells (c.e.cs) over which t ...	1981	6117867
participation of deoxyribonucleic acid polymerase alpha in amplification of ribosomal deoxyribonucleic acid in xenopus laevis.	aphidicolin, a known inhibitor of eucaryotic deoxyribonucleic acid (dna) polymerase alpha, efficiently inhibited amplification of ribosomal dna during oogenesis in xenopus laevis. dna polymerase alpha, but not dna polymerase gamma, as isolated from ovaries, was sensitive to aphidicolin. dna polymerase beta was not detectable in xenopus ovary extracts. therefore, dna polymerase alpha plays a major role in ribosomal ribonucleic acid gene amplification.	1981	9279381
ultrastructure of sites of cholinesterase activity on amphibian embryonic muscle cells cultured without nerve.	muscle cells, derived from 1-day-old embryos of xenopus laevis, were cultured in the absence of nerve and then examined histochemically for cholinesterase activity. virtually all of the cells exhibited one or more discrete patches of cholinesterase activity on their surface. the patches were located not only on the lower cell surface which was apposed to the floor of the culture dish but also on the lateral and upper surfaces which were not apposed to any solid substrate. at many of the cholines ...	1981	20737872
electrical membrane properties of the xenopus laevis oocyte during progesterone-induced meiotic maturation.	the membrane input resistance (r(m)), potential (e(m)), and capacitance (c(m)) of fully grown xenopus oocytes removed from their follicles have been measured. before hormonal maturation, r(m), e(m), and c(m) were found to be: 1.86 +/- 0.63 momega, -49 +/- 17 mv, and 11.9 +/- 4.8 microf/cm2 of apparent surface area. long-term recording from oocytes in the presence of 1 microm progesterone reveal that during early gvbd (germinal vesicle breakdown) the membrane potential depolarized to about -10 mv ...	1981	20737886
full-grown oocytes from xenopus laevis resume growth when placed in culture.	when most full-grown, follicle cell-invested oocytes from xenopus laevis are placed in an appropriate culture medium, they resume growth and remain physiologically healthy for at least 2-3 weeks. rates of growth by full-grown oocytes in vitro generally approximate and can even exceed the most rapid growth rate achieved by vitellogenic oocytes in vivo. resumption of oocyte growth can be correlated with the loss of investing follicle cells, which under normal conditions appear to interfere with vi ...	1981	16593019
cloning of cdna sequences derived from poly(a)+ nuclear rna ofxenopus laevis at different developmental stages: evidence for stage specific regulation.	nuclear poly(a)+ rna was isolated from gastrula and early tadpole stages ofxenopus laevis, transcribed into cdna and integrated as double stranded cdna by the g-c joining method into the pst cleavage site of plasmid pbr 322. after cloning ine. coli strain hb 101 the clone libraries were hybridized to32p labelled cdna derived from nuclear poly(a)+ rna of the two different developmental stages. about 20% of the clones gave a positive hybridization signal thus representing rna molecules of high and ...	1981	28305358
fiber type composition and postmetamorphic growth of anuran hindlimb muscles.	fiber type composition distinguished by the level of succinic dehydrogenase, mean fiber diameter, and fiber number were determined for the gracilis major and sartorius in ontogenetic series of the anurans rana pipiens, bufo americanus, and xenopus laevis to characterize muscle composition and mode of muscle growth. a correlation can be made between the respective locomotor mode of these anurans, their activity physiology, and the fiber type composition of the propulsive muscles. r. pipiens and x ...	1981	30119589
developmentally regulated poly(a) containing rna sequences in xenopus laevis.		1982	6125943