Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| phosphorylation of ribosomal proteins during maturation of xenopus laevis oocytes. | 1981 | 7318832 | |
| [abnormal thyroid gland occurred in a colony of xenopus laevis maintained at gumma university (author's transl)]. | thyroid hypertrophy of unknown cause occurred in a colony of xenopus laevis maintained at the institute of endocrinology, gunma university, maebashi, japan. these animals were kept in small aquaria with well water and fed on minced pig liver. an etiologic investigation was made on the thyroid abnormality by assessing its occurrence and histopathologic features and rearing conditions of the animals in comparison with those of the colonies at tokyo and sendai. 1) the occurrence of abnormal thyroid ... | 1981 | 7318945 |
| measurement of 5 s rna accumulation in oocytes of xenopus laevis using a cdna probe. | 1981 | 7327260 | |
| interferometric studies of endothelial cells in primary culture. | a population of endothelial cells grown from xenopus laevis tadpole hearts was investigated by microinterferometry. the resulting interferograms were evaluated by an automatic image analyzer. the mean values of dry mass were 778 +/- 340 pg (10(-15) g) for whole cells, 648 +/- 309 pg for cytoplasm, 116 +/- 45 pg for nuclei, and 19 +/- 10 pg for nucleoli. two subpopulations of cells were identified, an actively growing one and a less active one. the density (dry mass per microm2) of the nuclei and ... | 1981 | 7327947 |
| [ontogenesis of the acetylcholine system in the brain of the south african clawed toad (xenopus laevis daudin)]. | 1. during the development of the acetylcholine system of the xenopus brain a distinct increase in neurotransmitter content was found which is interpreted as an expression of increased activity of cholinergic neurons. the acetylcholine content in the whole brain increases markedly from hatching to metamorphosis. during this period regional differences of transmitter distribution can be observed. 2. the chat activity of the whole brain remains constant during total larval life, whereas the ache ac ... | 1981 | 7328310 |
| cell type-specific differences in protein composition of nuclear pore complex-lamina structures in oocytes and erythrocytes of xenopus laevis. | 1981 | 7328650 | |
| cells of origin of descending pathways to the spinal cord in the clawed toad (xenopus laevis). | 1981 | 7329548 | |
| factors involved in the development of ipsilateral retinothalamic projections in xenopus laevis. | the extent, and the development, of the ipsilateral retinothalamic projection in the frog xenopus laevis have been studied using terminal degeneration and autoradiographic techniques. this ipsilateral projection derives only from those retinal areas receiving visual information from the binocular portion of the visual field. in xenopus, the ipsilateral retinothalamic projection arises from a larger area of the retina than was found to be the case in earlier studies on rana. this correlates with ... | 1981 | 7334300 |
| selective in vitro transcription of one of the two alu family repeats present in the 5' flanking region of the human epsilon-globin gene. | the sequence of 2965 nucleotides 5' of the human epsilon-globin gene has been completed. it includes two alu family repeats present in an inverted configuration. only the one located farthest from the gene was active as template for rna polymerase iii in a transcription system prepared from nuclei of xenopus laevis oocytes. this selective transcription may be explained by the lack of homology of the first 45 nucleotides of the non transcribed repeat with other members of the alu family. in fact ... | 1981 | 7335492 |
| comparison of hemoglobins from the genus xenopus (amphibia salienta). | a survey of the electrophoretic mobility of hemoglobins of 14 species and subspecies of the genus xenopus was undertaken. it was found that the variation between the different taxons considered was quite important in the number and the degree of the hemoglobin bands on polyacrylamide slab gels. the profiles of the hemoglobin electrophoretic pattern in tube gels gave corresponding results, confirming the variation between the different xenopus species. the degree of resolution obtained on polyacr ... | 1981 | 7338720 |
| "degenerative cement gland" (dcg), a lethal recessive mutation in xenopus laevis. | 1981 | 7340360 | |
| the invasion of cultured cell layers and intact epithelia. | this paper concerns the invasive behaviour of a migratory embryonic cell type, the primordial germ cell (pgc) of the anuran amphibian xenopus laevis. scanning electron microscopy of isolated pgcs shows that they invade layers of cells derived from adult xenopus mesentery, and the epithelium of the intact mesentery itself. this invasion is at least partly due to the stimulation by the pgcs of process formation in both cultured and intact epithelial cells. these broad lamellipodia move over the su ... | 1981 | 7347430 |
| germinal vesicle breakdown in the xenopus laevis oocyte: description of a transient microtubular structure. | during progesterone-induced meiotic maturation of xenopus oocytes in vitro, 7 morphological stages were defined. using cytological analysis, nuclear breakdown was divided into three stages. stage 1 corresponded to basal germinal vesicle breakdown. stage 2 was characterized by the advent and development of a fibrillar network formed by microtubules at the basal part of the nucleus. below, a lamellar microtubule organizing center (mtoc) was present. numerous vesicles of smooth endoplasmic reticulu ... | 1981 | 7349521 |
| influence of diet on the susceptibility of xenopus laevis tadpoles to thiopentone and a membrane probe. | xenopus laevis tadpoles were produced from wild-caught, laboratory-reared toads. separate sets were fed on diets of (1) liver powder; (2) nettle powder; (3) aminosol and intralipid. the tadpoles were reared for 3 weeks at 22 degrees c and then three groups of experiments performed. group i experiments showed a significant difference in the response to thiopentone between tadpoles fed on liver powder and those fed on nettle powder. group ii experiments showed a difference in response to thiopento ... | 1981 | 7248121 |
| h1 histone variants in xenopus laevis. | 1981 | 7250503 | |
| locations of androgen-concentrating cells in the brain of xenopus laevis: autoradiography with 3h-dihydrotestosterone. | the distribution of hormone-concentrating cells in the brains of south african clawed frogs, xenopus laevis, was examined autoradiographically after the administration of 3h-dihydrotestosterone. hormone-accumulating cells were found in cranial nerve nucleus ix-x and adjacent smaller cells, a presumed medullary vestibular nucleus, a presumed sensory nucleus of cranial nerve v, dorsal tegmental area of the medulla, laminar nucleus of the torus semicircularis, ventral thalamus, and anterior pituita ... | 1981 | 7251941 |
| toxic and teratogenic effects of selected aromatic amines on embryos of the amphibian xenopus laevis. | evaluations of the toxic and teratogenic effects of four aromatic amines, acridine, aniline, pyridine, and quinoline, have been made on amphibian (xenopus laevis) embryos. for toxicity testing, the embryos were divided into three groups according to stage of development: group i were mid-blastulae, group ii were tailbud embryos, and group iii were swimming larvae. of the amines tested, acridine and quinoline were the most toxic, followed by aniline and pyridine. ninety six hr lc50 values for acr ... | 1981 | 7259304 |
| the structure of vitellogenin. multiple vitellogenins in xenopus laevis give rise to multiple forms of the yolk proteins. | 1981 | 7263674 | |
| isolation of a xenopus laevis alpha-globin gene. | 1981 | 7265209 | |
| aeromonas hydrophila infection in xenopus laevis. | aeromonas hydrophila caused severe disease in a group of xenopus laevis within 3 weeks of receipt. the primary clinical signs were marked pallor of the skin, petechiation, lethargy, anorexia, and edema. the duration of the outbreak was approximately 45 days during which time 21 frogs became sick and 18 died, despite tetracycline therapy. pale skin, subcutaneous edema and hemorrhages, ascites, and pale livers were seen at necropsy. aeromonas hydrophila was isolated from skin, and the same organis ... | 1981 | 7265911 |
| oestrogen receptor levels and vitellogenin synthesis during development of xenopus laevis. | 1981 | 7266654 | |
| a simple apparatus for injection of nanoliter quantities into xenopus laevis oocytes. | 1981 | 7270884 | |
| a giant cell with dendritic cell properties in spleens of the anuran amphibian xenopus laevis. | 1981 | 7274523 | |
| development of axosomatic synapses of the xenopus spinal cord with special reference to subsurface cisterns and c-type synapses. | the relationships of highly flattened subsurface cisterns (sccs) were investigated electron microscopically in the spinal cord at various developmental stages of tadpoles and adult toads, xenopus laevis. in medial ventral motor cells (mvcs) of the adult, more than 90% of 156 sscs examined were situated postsynaptically. similarly, more than 90% of 540 sscs in lateral motor column cells (lmcs) were postsynaptic. by contrast, in early developmental stages, the sscs were initially formed by regiona ... | 1981 | 7276242 |
| development of sodium permeability inactivation in nodal membranes. | 1. the time course of inactivation of the sodium permeability was studied in myelinated nerve fibres of xenopus laevis using the voltage-clamp technique of nonner (1969). the potassium currents were blocked by 10 mm-tetraethylammonium chloride (tea). the remaining currents were corrected for leakage and capacity currents. 2. the decay of the sodium current was double-exponential confirming chiu's (1977) findings the slower time constant was observed in tea-free solutions by clamping to vk in hig ... | 1981 | 7277227 |
| dna methylase during xenopus laevis development. | the dna methylase activity present in embryos and cultured cells of xenopus laevis resembles dna methylase from mammalian tissues. little or no activity is found in mature germinal vesicles, though nuclear activity rises rapidly after fertilization. this rise may result in part from a relocation of cytoplasmic enzyme. | 1981 | 7284389 |
| isolation and characterization of xenopus laevis albumin mrna. | the messenger rna for albumin was isolated from the liver of male frogs. purification was achieved using oligo(dt)-cellulose chromatography and sucrose gradient centrifugation under denaturing conditions. as judged by translational activity in a cell-free protein-synthesizing system derived from rabbit reticulocytes, albumin mrna was enriched 259-fold as compared to the total ribonucleic acid of the liver cells. purified albumin mrna migrated after sucrose gradient centrifugation as a single sym ... | 1981 | 7285921 |
| the movement of the prospective eye vesicles from the neural plate into the neural fold in ambystoma mexicanum and xenopus laevis. | 1981 | 7286445 | |
| conservatism of the h-y/h-w receptor. | soluble h-y antigen is taken up by cells of the homogametic gonad of cattle, dog, chicken and south african clawed frog. after in vitro exposure to mouse testis supernatant or male fetal calf serum, xx ovary cells or zz testis cells, which are normally h-y-, acquire the h-y+ (h-w+) phenotype and absorb mouse h-y antibody in standard serological assays. in addition, h-y antigens of the different species can compete for attachment to target cells of a single species. in a new competitive binding r ... | 1981 | 7286993 |
| regional effects of sodium aspartate and sodium glutamate on protein synthesis in the retina. | isolated retinas from xenopus laevis tadpoles or juvenile frogs were incubated in ringer's bicarbonate-glucose medium in which sodium chloride was replaced with equimolar amounts of either sodium aspartate (naasp) or sodium glutamate (naglu). at all concentrations tested (0.1 to 50 mm), both acidic amino acids caused a dramatic decrease in the incorporation of 3h-leucine into proteins in the inner retina. higher concentrations of these acids (50 mm) caused an increase in the incorporation of the ... | 1981 | 7287345 |
| an experimental analysis of the role of bottle cells and the deep marginal zone in gastrulation of xenopus laevis. | earlier work suggested that the change in shape or the active migration of the bottle cells in the amphibian blastoporal region results in an invagination that comprises a major part of gastrulation. in the present study of gastrulation in xenopus laevis, microsurgical extirpation and rearrangement experiments, analyzed with time-lapse cinemicrography and scanning electron microscopy, show that the bottle cells have a lesser role in gastrulation. gastrulation is not a process of invagination but ... | 1981 | 7288390 |
| development of xenopus laevis embryos in a static magnetic field. | 1981 | 7295366 | |
| light stimulates the incorporation of inositol into phosphatidylinositol in the retina. | the incorporation of [3h]inositol into phosphatidylinositol in retinas of xenopus laevis tadpoles or young adults in short-term organ culture is stimulated by light, compared to retinas maintained under identical conditions in darkness. over 95% of the label incorporated into lipid was in phosphatidylinositol, and none was incorporated into retinal proteins. the stimulation of incorporation was localized by autoradiography to the outer plexiform layer, a neurophil composed primarily of horizonta ... | 1981 | 7295756 |
| replication of ribosomal dna in xenopus laevis. | the study of the localization of the replication origins of rdna in xenopus laevis has been approached by two different methods. 1. the dna of x. laevis larvae was fractionated by cscl gradient centrifugation in bulk and ribosomal dna and examined in the electron microscope. in bulk dna, clusters of microbubbles, which are related with the origins of replication, appear to be spaced along the dna molecules at intervals comparable with the size of the 'average' replicon of x. laevis. in ribosomal ... | 1981 | 7297565 |
| effect of 5'-methylthioadenosine on nucleolar morphology and rna metabolism in cultured xenopus laevis cells. | 1981 | 7308302 | |
| a middle-affinity estrogen-specific binding protein in livers of vitellogenic and nonvitellogenic xenopus laevis. | 1981 | 7308579 | |
| neural plate morphogenesis and axial stretching in "notochord-defective" xenopus laevis embryos. | 1981 | 7308580 | |
| patterns of transcriptional activity of nucleolar genes during progesterone-induced maturation of oocytes of xenopus laevis. | maturation has been induced in full grown oocytes of xenopus laevis by incubation in progesterone, and the ultrastructure of their nucleoli has been examined by electron microscopy using the chromatin spreading technique. we show that in this species numerous extrachromosomal nucleoli maintain high levels of transcription of rdna for up to 200 min after the application of the hormone, i.e., shortly before germinal vesicle breakdown. transcription has been identified as normal arrays of matrix un ... | 1981 | 7308608 |
| target dependency of developing motoneurons in xenopus laevis. | the effect of complete and partial limb bud removal on motoneuron survival was studied in xenopus laevis tadpoles. amputation of both hind limb buds at stage 49 before limb innervation begins caused the subsequent death of all motoneurons. this result confirms that there are no exceptions to the rule that developing motoneurons must contact the limb to survive. partial removals of the limb at early stages of innervation caused the subsequent death of motoneurons that normally project to the dele ... | 1981 | 7309919 |
| progesterone inhibits membrane-bound adenylate cyclase in xenopus laevis oocytes. | recent experimental evidence indicates that progesterone acts at the cell surface to trigger protein synthesis and to reinitiate the first meiotic division in xenopus laevis oocytes. the steroid hormone is physiologically released by follicle cells surrounding oocytes in the ovaries, and this naturally occurring event can be reproduced in vitro by adding progesterone to the incubation medium. recently, cyclic amp has been implicated in the mechanism of progesterone action in oocytes; there was a ... | 1981 | 7195984 |
| a reinvestigation of the role of the grey crescent in axis formation in xenopus laevis. | gravitationally induced displacements of the contents of the frog egg can predictably determine the orientation of the subsequent dorsal-ventral axis of the embryo, regardless of the original position of sperm entry or of the grey crescent. in certain conditions, these displacements in the egg can also lead to the formation of a second axis, that is, to twinning. the previously reported ability of grafts of grey crescent cortex to induce secondary axes in recipient eggs is interpreted here as an ... | 1981 | 7195987 |
| stability of non-polyadenylated viral mrnas injected into frog oocytes. | the naturally non-polyadenylated mrnas of reovirus were shown to have a half-life in excess of 3 days when injected into xenopus laevis oocytes. hybridization analysis and gel electrophoresis showed that all 10 mrna species had a similar high stability, despite being translated at widely differing rates. we have confirmed previous findings indicating a role for the 5'-terminal cap structure in determining reovirus mrna stability [furuichi et al. (1977) nature (lond.) 266, 235-239]. the significa ... | 1981 | 7196332 |
| the secretion of proteins in vitro from xenopus oocytes and their accessory cells: a biochemical and morphological study. | protein secretion by xenopus laevis oocytes and their surrounding follicular cells in vitro has been investigated using two-dimensional gel electrophoresis. viable oocytes, devoid of follicle layers, were prepared by treatment with collagenase; they retain in full their capacity to synthesize, sequester and export secretory proteins following microinjection with heterologous messenger rna. both rna-injected and normal cells export a large number of endogenous oocyte proteins and, as with heterol ... | 1981 | 7196433 |
| mitochondrial dna synthesis in xenopus laevis enucleated eggs. | 1981 | 7197198 | |
| the primary structure of oocyte and somatic 5s rrnas from the loach misgurnus fossilis. | somatic and oocyte 5s rrnas from the liver and unfertilized eggs of the loach (misgurnus fossilis have been sequenced and found to differ in six nucleotides. all the substitutions are confined to the 5'-half of the molecules; 4 of them are pyrimidine-pyrimidine substitutions, and 2 are purine-pyrimidine ones. considerable differences, both in the position and the character of substitutions, have been established when these 5s rrnas were compared with somatic and oocyte 5s rrnas from xenopus bore ... | 1981 | 7197777 |
| observations on intracellular ph during cleavage of eggs of xenopus laevis. | direct measurements of intracellular ph was made with recessed-tip ph microelectrodes in fertilized eggs of the frog, xenopus laevis, from approximately 1 h after fertilization to mid-blastula. the intracellular ph just before first cleavage was 7.65 +/- 0.04 (sd; n = 9). by stage 5 to the middle of stage 6, average intracellular ph was 7.70 +/- 0.06 (sd; n = 16). a statistically significant alkalization of 0.18 +/- 0.03 ph unit (sd; n = 5) was observed beginning in early blastula. a cycle of le ... | 1981 | 7198125 |
| 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 |
| genetic control of t helper cell function in the clawed toad xenopus laevis. | the genetic control of the collaboration between xenopus t and b cells has been analyzed in vivo using cells from five strains of major histocompatibility complex-defined xenopus. when carrier (fowl gamma-globulin)-primed t cells and hapten (dinitrophenylated keyhole limpet hemocyanin)-primed b cells differed by minor histocompatibility antigens or by only one haplotype of the major histocompatibility complex, the collaboration was efficient in the sense that large numbers of plaques, low-molecu ... | 1981 | 7011821 |
| axon regeneration by developing limb motoneurones in xenopus laevis. | newly generated motoneurones invading the limb bud were labelled with horseradish peroxidase to identify them later in development. they were then axotomized by amputating the limb bud. the limb bud was replaced immediately in some animals. after the period of normal motoneurone death, which falls a few days after the operation, many horseradish peroxidase labelled motoneurones were still alive provided the limb bud had been replaced. without a limb bud, labelled motoneurones were few or non-exi ... | 1981 | 7225797 |
| pineal complex of the clawed toad, xenopus laevis daud.: structure and function. | the morphological and physiological properties of the pineal complex of xenopus laevis were investigated in larval, juvenile and adult animals. in a representative majority of adult x. laevis, the frontal organ does not display signs of degeneration. fully differentiated frontal organs contain photoreceptors typical of the pineal complex of lower vertebrates. by means of the acetylcholinesterase (ache)-reaction approximately 30 neurons of two different types were demonstrated in the frontal orga ... | 1981 | 7226202 |
| transplantation of insect giant chromosome nuclei into amphibian oocytes. | polytene salivary gland nuclei of chironomus pallidivittatus were transplanted into oocytes of xenopus laevis which were then cultured in vitro for 18 h. the giant chromosomes and nucleoli as well as the entire nuclei enlarged considerably in volume during this time. the polyteny and specific chromomere pattern of the chromosomes were maintained, and the puffing of the salivary gland-specific balbiani rings was not noticeably changed. - polytene nuclei from differentiated insect cells transplant ... | 1981 | 7227037 |
| patterns of protein synthesis in livers of xenopus laevis during metamorphosis: effects of estrogen in normal and thyrostatic animals. | 1981 | 7227631 | |
| patterns of motor innervation in the pectoral muscle of adult xenopus laevis: evidence for possible synaptic remodelling. | 1. an anatomical and electrophysiological study was performed on the pectoral muscle of xenopus laevis. 2. silver-impregnated preparations revealed immature endings, collateral and terminal sprouting and signs of synaptic regression. 3. twenty percent of the fibres received a dual innervation from two different nerves. the synapses of 25% of these fibres are formed in close vicinity. 4. some of the singly innervated and most of the dually innervated end-plates generated only subthreshold electri ... | 1981 | 7230035 |
| modifications in oocyte protein synthesis induced by progesterone in xenopus laevis. | 1981 | 7238884 | |
| a method for the enhancement of bi- and trispermic fertilization in eggs of xenopus laevis. | 1981 | 7238954 | |
| characterization of a new cell line, xl2, obtained from xenopus laevis and determination of optimal culture conditions. | a new amphibian permanent cell line is described. it is called xl2 and was initiated from stage 35 tadpoles of xenopus laevis. the cell line has an epithelioid morphology and most cells can be classified into two populations with respective chromosome modal numbers 36 and 74. contact inhibition is low. its growth is vigorous in l15 or mem medium supplemented with fetal bovine serum. the mean doubling time is 39 hr and the saturation density is 700,000 cells/cm2 at 25 degrees c. the absolute plat ... | 1981 | 7239540 |
| experimental analysis of the lens-forming competence of the cornea, iris, and retina in xenopus laevis tadpoles. | the present research was carried out using xenopus laevis tadpoles at stage 50-51 to ascertain whether eye territories other than the outer cornea and the pericorneal epidermis have lens-forming competence, particularly the iris and/or retina. five experiments were performed: simple lentectomy; removal of lens, outer cornea, and pericorneal integument; removal of lens, outer cornea, and pericorneal integument, and simultaneous incision of retina; removal of lens, outer cornea and pericorneal int ... | 1981 | 7241066 |
| [replication of heterologous and recombinant dna in xenopus laevis oocytes]. | 1981 | 7245876 | |
| vitellogenesis and the vitellogenin gene family. | vitellogenin is synthesized under estrogen control in the liver, extensively modified, transported to the ovary, and there processed to the yolk proteins lipovitellin and phosvitin. in the frog xenopus laevis there are at least four distinct but related vitellogenin genes. the two genes a1 and a2 have a 95 percent sequence homology in their messenger rna coding regions, and contain 33 introns that interrupt the coding region (exons) at homologous positions. sequences and lengths of analogous int ... | 1981 | 7209528 |
| some observations on the behaviour of chloride current--voltage relations in xenopus muscle membrane in acid solutions. | chloride current--voltage relations in xenopus laevis muscle membrane have been investigated in phosphate-buffered solution (ph 5.2--5.4) using a three-microelectrode voltage clamp. resting chloride conductance in these conditions is about 10(-4) s/cm2, approximately 1/10th that at ph 8.8. when the membrane potential is stepped from the holding (resting) potential to a more negative voltage the current rises from the initial to the steady state. the instantaneous current--voltage relation is lin ... | 1981 | 7214211 |
| identification in xenopus laevis of a class of oocyte-specific proteins bound to messenger rna. | proteins associated with poly(a)-rich rna in xenopus laevis oocytes have been identified in immature ovary homogenates using sucrose gradient centrifugation, oligo(dt)-cellulose fractionation and analysis by sodium dodecyl sulphate/polyacrylamide gel electrophoresis and two-dimensional acid/urea/sodium dodecyl sulphate gel electrophoresis. at least eight proteins are associated with ribonucleoprotein complexes and have the following properties. 1. four major proteins, mrnp1-4, cosediment with po ... | 1981 | 7215334 |
| 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 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 |
| 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 |
| 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 |
| 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 comparison of xenopus laevis oocyte and embryo mrna. | 1981 | 6169574 | |
| 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 | |
| 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 |
| organization and sequence analysis of a cluster of repetitive dna elements from xenopus laevis. | 1981 | 6173488 | |
| translation of human interferon mrnas in xenopus laevis oocytes. | 1981 | 6173723 | |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 | |
| 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 | |
| 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 |
| 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 |
| adenylate cyclase and cyclic amp-phosphodiesterase activities during the early phase of maturation in xenopus laevis oocytes. | 1981 | 6162679 | |
| 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 |
| 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 |
| hepatic microsomal mixed-function oxidase in the frog, xenopus laevis. | 1981 | 6112107 | |
| 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 |
| evidence for the involvement of transglutaminase in the uptake of vitellogenin by xenopus laevis oocytes. | 1981 | 6112986 | |
| 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 |
| properties of acetylcholine receptors translated by cat muscle mrna in xenopus oocytes. | poly(a)+ mrna, extracted from denervated skeletal muscles of the cat, directs the synthesis of acetylcholine receptors in xenopus laevis oocytes. the receptors are inserted in the oocyte membrane where they form acetylcholine receptor-channel complexes which have properties like those of the native receptors in the muscle membrane. | 1982 | 6144542 |