| activation of frog (xenopus laevis) eggs by inositol trisphosphate. i. characterization of ca2+ release from intracellular stores. | iontophoresis of inositol 1, 4, 5-triphosphate into frog (xenopus laevis) eggs activated early developmental events such as membrane depolarization, cortical contraction, cortical granule exocytosis, and abortive cleavage furrow formation (pseudocleavage). inositol 1, 4-bisphosphate also triggered these events, but only at doses approximately 100-fold higher, whereas no level of fructose-1, 6-bisphosphate tested activated eggs. using ca2+-selective microelectrodes, we observed that activating do ... | 1985 | 3874873 |
| construction of cdna coding for human von willebrand factor using antibody probes for colony-screening and mapping of the chromosomal gene. | von willebrand factor (vwf) mrna was identified in fractionated polya+ rna preparations isolated from cultured human endothelial cells. micro-injection of specific polya+ rna fractions in xenopus laevis oocytes provoked the synthesis of a vwf-like product which could be detected with an immunoradiometric assay relying on sepharose-linked monoclonal anti-vwf igg and different radiolabeled monoclonal anti-vwf iggs. a vwf-mrna-containing polya+ rna preparation served as substrate for a size-selecte ... | 1985 | 3875078 |
| [structure of the vestibular apparatus and ionic composition of the body of xenopus laevis larvae as affected by weightlessness]. | clawed frog larvae (stages 45-46) that developed for 9 and 8 days beginning with the blastula and tail bud stages, respectively, in the weightless state were investigated. scanning microscopy of the larval labyrinths did not reveal significant qualitative changes in the receptor and supporting cells of the maculae and in the otolith membrane. determination of the electrolyte composition (na, k, ca, mg) of the larval body showed no significant changes in the relative content of these elements. th ... | 1985 | 3875754 |
| lectin effects on thymic suppression of hemagglutinin production in vitro by spleen fragments from xenopus laevis, the south african clawed toad. | suppression of hemagglutinin (ha) production was studied in co-cultures of thymus and spleen fragments from the south african clawed toad, xenopus laevis. concanavalin (con)a and peanut (pna) and wheatgerm (wga)agglutinins were tested in conjunction with, or as a substitute for antigenic induction of thymus suppression. while thymuses from animals injected with pna or wga and antigen expressed suppressor function, those treated with con a and antigen did not. spleen fragments from animals challe ... | 1985 | 3875915 |
| specificity of motoneuron projection patterns during development of the bullfrog tadpole (rana catesbeiana). | the pattern of connectivity between motoneurons of the lumbar lateral motor column (lmc) and hindlimb regions was examined in bullfrog tadpoles (rana catesbeiana) over the course of larval development. the purpose of this study was to determine if a period of relatively imprecise connectivity, such has been found in the toad xenopus laevis (lamb, '76), could be identified. patterns of connectivity were assessed by placing small amounts of the retrogradely transported enzyme horseradish peroxidas ... | 1985 | 3876358 |
| a species difference between rana and xenopus in the occurrence of intertectal neuronal plasticity. | in anuran amphibians, a system of neuronal connections links the two optic tecta and is involved in projections of the binocular visual field to the optic tecta. electrophysiological studies have shown that in the frog, xenopus laevis, the pattern of connections may be modified by procedures such as larval rotation of one eye. this modification appears to be effected by visual experience. workers in other laboratories, however, found no evidence of such a modification in the related frog rana pi ... | 1985 | 3876526 |
| lethal graft-versus-host reaction induced by parental cells in the clawed frog, xenopus laevis. | (j x k)f1 hybrid frogs, xenopus laevis, were produced by mating between the mhc-homozygous but distinct "j" and "k" group frogs. when the spleen or splenocytes from parental j were transplanted into the f1 frogs, a typical graft-versus-host reaction (gvhr) was induced that included wasting and death, accompanied by a prominent spleen enlargement and other histological changes in skin and lymphoid organs. to induce the reaction, sensitization against f1 cells prior to transfer of spleen was neces ... | 1985 | 3876634 |
| prostaglandin e2 induces receptive behaviors in female xenopus laevis. | the object of this study was to examine the effects of exogenous and endogenous prostaglandin e2 (pge2) on the sexual behavior of female south african clawed frogs, xenopus laevis. ticking and leg extension, which communicate sexual unreceptivity to males, were studied in intact, ovariectomized, and ovariectomized-oviductectomized females. the onset of the pge2 behavioral effect occurs within 30 sec to 3 min of injection for intact and ovariectomized females; for ovariectomized-oviductectomized ... | 1985 | 3878825 |
| anti-immunoglobulin m induces both b-lymphocyte proliferation and differentiation in xenopus laevis. | anti-igm induced the proliferation of spleen lymphocytes of the amphibian xenopus laevis as determined by 3h-thymidine uptake. the responding cells were b lymphocytes, since lymphocyte populations enriched in surface-ig-positive cells exhibited an increased proliferative response, and spleen cells from larvally thymectomized animals still responded to anti-igm. immunofluorescence analysis and gel electrophoresis of biosynthetically labeled ig polypeptides revealed that lymphoblasts induced by an ... | 1985 | 3879229 |
| [use of colloidal gold in ultrastructural cytochemistry]. | colloid gold stabilized by macromolecules with various binding characteristics proved to be usable in transmission electron microscopy: nucleic acids localization was studied in tissue cultures after embedding by techniques autoimmune serum-protein a--gold and rnase--gold. technique with serum autoantibodies against double-stranded dna resulted in marking condensed chromatin. further experiments with ultrastructural localization of other autoimmune components seemed to be perspective and of diag ... | 1985 | 3882253 |
| immunological relationship between oocyte nuclear proteins of xenopus laevis and x. borealis. | monoclonal antibodies (mabs) have been raised against oocyte nuclear proteins of xenopus laevis and x. borealis and have been screened for species specificity. although about 40% of all germinal vesicle polypeptides differ between the two species as judged by two-dimensional gel analysis, most mabs react with polypeptides of both species. biochemical analysis of the antigens by immunoblotting revealed that a homologue of each antigen of one species could be detected in the other species, despite ... | 1985 | 3882485 |
| testosterone-induced meiotic maturation of xenopus laevis oocytes: evidence for an early effect in the synergistic action of insulin. | meiosis reinitiation in oocytes (stage 5-6 of dumont) isolated free of follicle cells by collagenase treatment from ovarian pieces of xenopus laevis, was studied in observing the germinal vesicle breakdown (gvbd) provoked by progesterone and testosterone (0.1 nm-1 microm), alone or in association with insulin (30 micrograms/ml). testosterone, was more active than progesterone to elicit gvbd in vitro, raising the question of the relative roles of both steroids in the physiological maturation proc ... | 1985 | 3886456 |
| active maturation-promoting factor is present in mature mouse oocytes. | cytoplasmic extracts of meiotically mature mouse oocytes were injected into immature xenopus laevis oocytes, which underwent germinal vesicle breakdown within 2 h. germinal vesicle breakdown was not inhibited by incubation of the xenopus oocytes in cycloheximide (20 micrograms/ml). identically prepared extracts of meiotically immature mouse oocytes, arrested at the germinal vesicle stage by dibutyryl cyclic amp (100 micrograms/ml), did not induce germinal vesicle breakdown in xenopus oocytes. th ... | 1985 | 3886670 |
| association of the postsynaptic 43k protein with newly formed acetylcholine receptor clusters in cultured muscle cells. | the postsynaptic membrane from torpedo electric organ contains, in addition to the acetylcholine receptor (achr), a major peripheral membrane protein of approximately 43,000 mol wt (43k protein). previous studies have shown that this protein is closely associated with achr and may be involved in anchoring receptors to the postsynaptic membrane. in this study, binding sites for monoclonal antibodies (mabs) to the 43k protein have been compared to the distribution of achr in xenopus laevis muscle ... | 1985 | 3886673 |
| cell type-specific expression of nuclear lamina proteins during development of xenopus laevis. | the cell type-specific expression of the major nuclear lamina polypeptides ("lamins") during development of xenopus was studied using two monoclonal antibodies (l(0)46f7: specific for liii, the single lamin of oocytes; pkb8: specific for li and lii of some somatic cells). in the oocyte, liii localizes in the nuclear polymer, but upon nuclear envelope breakdown it is solubilized to a form sedimenting at 9 s. in early embryos, liii contributes to nuclear lamina formation until its depletion. corre ... | 1985 | 3888407 |
| immunological identification of the karyophilic, histone-binding proteins n1 and n2 in somatic cells and oocytes of diverse amphibia. | a polypeptide pair designated n1/n2 (mr 100 000 and 110 000) is an exceptionally acidic and abundant nuclear protein of oocytes of the toad, xenopus laevis, and is characterized by a pronounced karyophilia. these proteins have been shown to form specific complexes with free, i.e., non-chromatin-bound histones h3 and h4 (kleinschmidt & franke, cell 29 (1982) 799) [3]. in order to study these proteins and their possible counterparts in other species, antibodies were produced in guinea pigs against ... | 1985 | 3888645 |
| immunohistochemical distribution of the histone h1(0)/h5 variant in various tissues of adult xenopus laevis. | the cellular distribution of the histone h1(0)/h5 variant has been examined immunohistochemically in various tissues of adult xenopus laevis, using monoclonal antibodies against this variant that was isolated from erythrocyte nuclei. the h1(0)/h5 variant appears not to be erythrocyte-specific and appears to be present in all cell types of liver, stomach, and skin. in contrast, in oocyte nuclei the h1(0)/h5 variant cannot be detected, whereas they do contain h1; the nuclei of spermatogenic cells ... | 1985 | 3891099 |
| translation of human macrophage activating factor (for glucose consumption) mrna in xenopus laevis oocytes. | total messenger rna was extracted from a human t cell hybridoma, clone h-e4-9, which strongly produced macrophage activating factor for glucose consumption (maf-g). this messenger rna gave rise to functional maf-g when translated in xenopus laevis oocytes. isoelectric focusing of culture supernatants of the mrna-microinjected oocytes and the h-e4-9 cells revealed that the former contained maf-gs with isoelectric points of ph 5.0 and 3.0 while the latter contained maf-gs with isoelectric points o ... | 1985 | 3891606 |
| the role of visual experience in the formation of binocular projections in frogs. | many parts of the visual system contain topographic maps of the visual field. in such structures, the binocular portion of the visual field is generally represented by overlapping, matching projections relayed from the two eyes. one of the developmental factors which helps to bring the maps from the two eyes into register is visual input. the role of visual input is especially dramatic in the frog, xenopus laevis. in tadpoles of this species, the eyes initially face laterally and have essentiall ... | 1985 | 3896495 |
| in vitro growth of adult amphibian (xenopus laevis) hepatocytes and characterization of hepatocyte-proliferating activity in homologous serum. | adult frog (xenopus laevis) hepatocytes were found to proliferate in a culture medium containing adult homologous serum. insulin and dexamethasone were required for a net proliferation of hepatocytes. dose-response analysis showed that a low concentration of serum (greater than or equal to 0.5%) was enough to induce dna synthesis and mitosis, but a higher concentration (5%) caused certain necrotic changes. under optimal conditions, there was a two- to threefold increase in nuclei per culture 10 ... | 1985 | 3896827 |
| dynamics of tubulin structures in xenopus laevis oogenesis. | the distribution of tubulin and/or tubulin-containing structures was examined in separate classes of xenopus laevis oocytes and in germinal vesicles isolated from them. although a monoclonal antibody has been used, the technique applied on paraffin sections does not allow clear-cut definition of the state of tubulin present (monomeric, dimeric or polymerized form); however, the probable existence of assembled microtubules is indicated by supplementary techniques, i.e. histology and immunoperoxid ... | 1985 | 3897442 |
| specific recognition of altered polypeptides by widely distributed methyltransferases. | protein carboxyl methyltransferase activity has been detected in extracts prepared from bacterial cells (salmonella typhimurium), amphibian (xenopus laevis) oocytes, and transformed mammalian cell lines. this activity appears to specifically recognize altered aspartyl residues based on the observation that the synthetic peptide l-val-l-tyr-l-pro-l-isoasp-gly-l-ala is a good methyl-accepting substrate for the methyltransferase activity, but that the corresponding peptide containing a normal l-asp ... | 1985 | 3907631 |
| m-phase promoting factors from eggs of xenopus laevis. | when an m-phase promoting factor (mpf) is injected into xenopus oocytes, which are naturally arrested at the g2/prophase boundary, it induces rapid entry of the cells into m-phase. mpf is present in late g2 and in m-phase of a variety of cell types, such as xenopus eggs (naturally arrested in m), cleaving embryos, yeast, hela, and cho cultures. mpf has been purified approximately 50-fold from eggs. it is stabilized by gamma-thio-atp and by phosphoprotein phosphatase inhibitors. it runs as a prot ... | 1985 | 3908000 |
| identification of cells immunoreactive to antisera against porcine pancreatic glucagon in the gastro-intestinal tract of xenopus laevis. | | 1985 | 3909679 |
| mitogenic effects of phorbol myristate acetate (pma) on amphibian cells. | tumour promoter phorbol myristate acetate (pma) stimulates and causes proliferation of cells from the spleen, thymus and peripheral blood of xenopus laevis, the clawed toad. phagocytic cells become activated and from foci of clustered cells. b cells blast and change membrane immunoglobulin (ig) expression; a small portion go on to secrete ig. the surface ig-negative splenocyte population, which contains t cells, responds to pma by active proliferation. splenocytes, once stimulated by pma, become ... | 1985 | 3909928 |
| in vitro induction of anti-srbc response in dissociated spleen cells of xenopus laevis. | | 1985 | 3910486 |
| recombinant interleukin 2 induces immunoglobulin secretion in staphylococcus aureus cowan strain i activated human b-cells. | human b-cells, exhaustively depleted for t-cells, were activated with staphylococcus aureus cowan strain i (sac) and responded to recombinant human interleukin 2 (ril2) by secretion of immunoglobulin (ig), as measured by a protein a hemolytic plaque assay. the ril2, however, had to be present early, since addition later than 24 h after sac-activation of the b-cells reduced the response to background levels. no clear dose response was observed and ig-secreting cells (isc) could be induced even wi ... | 1985 | 3910564 |
| mesoderm induction in xenopus laevis: a quantitative study using a cell lineage label and tissue-specific antibodies. | we have compared the development of the animal pole (ap) region of early xenopus embryos in normal development, in isolation, and in combination with explants of tissue from the vegetal pole (vp) region. for the grafts and the combinations the animal pole tissue was lineage labelled with fldx in order to ascertain the provenance of the structures formed. the normal fate of the ap region was determined by orthotopic grafts at stages 7 1/2 (early blastula), 8 (mid blastula) and 10 (early gastrula) ... | 1985 | 3912458 |
| a cdna clone for a polyadenylated rna-binding protein of xenopus laevis oocytes hybridizes to four developmentally regulated mrnas. | xenopus laevis oocytes contain a unique group of proteins which decrease during oogenesis, bind poly(a) rna, and possibly play a role in the regulation of translation. a monoclonal antibody generated against one of these proteins was used to screen an expression vector cdna library. a cdna clone was isolated and confirmed to code for the binding protein by in vitro translation of hybrid-selected rna followed by immunoprecipitation. this cdna, when used in rna gel blots, hybridized to four transc ... | 1985 | 3915533 |
| u snrna gene families in xenopus laevis. | | 1985 | 3916925 |
| isolation of tyrosinase-mrna by affinity chromatography of polysomes. | we present a method whereby some mrnas which code for enzymes can be isolated by affinity chromatography of newly synthesized polypeptides bound to their polysome complexes. using this method we have isolated tyrosinase-mrna from xenopus laevis oocytes and have analysed the translation products from the rnas thus obtained. in vitro translation reveals the presence of two mrnas coding for polypeptides of molecular weights of 20 000 and 32 000, respectively. the larger molecule corresponds to the ... | 1985 | 3917685 |
| inositol 1,4,5-triphosphate microinjection triggers activation, but not meiotic maturation in amphibian and starfish oocytes. | inositol 3,4,5-triphosphate (insp3) brought about cortical granule exocytosis and elevation of a fertilization membrane, due to a rapid increase of free calcium in cytoplasm, when injected into oocytes of the amphibian xenopus laevis arrested at second meiotic metaphase. the same result was observed when injection was performed into oocytes of the starfish marthasterias glacialis arrested either at the first meiotic prophase or after completion of meiosis. although meiotic maturation was induced ... | 1985 | 3920074 |
| ionic control of locomotion and shape of epithelial cells: i. role of calcium influx. | the role of calcium in the induction of locomotion, control of direction of locomotion, and modulation of shape of epithelial cells derived from xenopus laevis tadpole epidermis is investigated. local influx of calcium is achieved by electrophoretic release of small amounts of calcium from a micropipette (tip diameter 0.1-0.5 micron) closely apposed to the cell body or lamella. the cells are made permeable for calcium by calcium ionophore a23187, and they are kept in ca++-free, mg++-rich egta ri ... | 1985 | 3921256 |
| intertectal neuronal plasticity in xenopus laevis: persistence despite catecholamine depletion. | in normal xenopus, the tectum receives a direct projection from the contralateral retina and an indirect projection, via the intertectal system, from the ipsilateral eye. the two maps of binocular visual space, at each tectum, are in register. if one eye is rotated during larval development, the ipsilateral visuotectal projection compensates by changing its orientation. rearrangement of the intertectal system brings the ipsilateral map back into register with the contralateral map. we sought to ... | 1985 | 3922567 |
| treatment of oocyte membranes with the 2',3'-dialdehyde of guanosine triphosphate reduces progesterone inhibition of adenylyl cyclase. | treatment of xenopus laevis membranes with the 2',3'-dialdehyde of gtp (dial gtp) drastically inhibits their adenylyl cyclase activity. optimal inhibition is obtained by treatment with 1 mm dial gtp for 1h at 32 degrees c. using guanyl-5'-yl imidodiphosphate, f-, forskolin and mn2+ as activators of the enzyme it can be concluded that dial gtp preferentially reacts with the stimulatory subunit (ns) and slightly with the catalytic subunit. dial gtp treatment greatly reduces the inhibition of adeny ... | 1985 | 3922793 |
| differential effects of protease digestion on photoreceptor lectin binding sites. | the use of lectin cytochemistry together with proteolytic digestion techniques to partially characterize lectin binding sites of several intracellular compartments in frog photoreceptors was studied. uniform access of reagents to all intracellular compartments was obtained by performing the experiments directly on semithin sections of retinal tissue embedded in a hydrophilic plastic resin. protease pretreatment of sections of xenopus laevis eyecup leads to a loss of wheat germ agglutinin (wga) b ... | 1985 | 3924992 |
| evolutionary conservation of ribosomal protein mrna sequences: application for expansion of corresponding cdna and gene libraries. | cloned cdnas, containing ribosomal protein sequences from mouse (five cdnas) or xenopus laevis (six cdnas), were used to estimate the evolutionary conservation, from insects to mammals, of the corresponding mrna sequences. northern blot analysis reveals a variable degree of homology between these sequences in different eukaryotes. thus, among the ribosomal protein cdna clones utilized, some exhibit complete, others partial, and a few no interphyla cross-hybridization. melting profile analysis wa ... | 1985 | 3925998 |
| induction of nuclear envelope breakdown, chromosome condensation, and spindle formation in cell-free extracts. | incubation of demembranated sperm chromatin in cytoplasmic extracts of unfertilized xenopus laevis eggs resulted in nuclear envelope assembly, chromosome decondensation, and sperm pronuclear formation. in contrast, egg extracts made with egta-containing buffers induced the sperm chromatin to form chromosomes or irregularly shaped clumps of chromatin that were incorporated into bipolar or multipolar spindles. the 150,000 g supernatants of the egta extracts could not alone support these changes in ... | 1985 | 3926780 |
| a third immunoglobulin class in amphibians. | a new class of immunoglobulin (igx) has been found in the south african frog, xenopus laevis, and other related species. igx can be immunoprecipitated by monoclonal antibodies directed against determinants found on xenopus light chain, or on variable regions of heavy chains. reagents specific for the heavy chain of igm or the amphibian igg equivalent, igy, failed to react with igx. igx, which exists in serum as a polymer, is composed of subunits of disulfide-bonded heavy chains of 80,000 daltons ... | 1985 | 3926893 |
| cytochemical analysis of oligosaccharide processing in frog photoreceptors. | lectin cytochemistry, together with exoglycosidase enzyme digestion, has been used to characterize partially glycoconjugates of several intracellular compartments in frog photoreceptors. in order to obtain uniform access of reagents to all intracellular compartments, the experiments were performed directly on semi-thin sections of xenopus laevis retinal tissue embedded in a hydrophilic plastic resin. in the rod, the major photoreceptor intracellular binding sites for wheat germ agglutinin (wga) ... | 1985 | 3928534 |
| a detergent-activated tyrosinase from xenopus laevis. i. purification and partial characterization. | a tyrosinase has been purified from the skin of the frog xenopus laevis. dihydroxyphenylalanine oxidase and tyrosine hydroxylase activities co-purify throughout the procedure. the enzyme is isolated in an inactive form, but both enzymatic activities are activated by a variety of anionic detergents. of these, sodium dodecyl sulfate (nadodso4) is the most effective. the enzyme activation occurs at nadodso4 concentrations well below the critical micelle concentration and it remains active at concen ... | 1985 | 3930497 |
| a detergent-activated tyrosinase from xenopus laevis. ii. detergent activation and binding. | tyrosinase purified from xenopus is enzymatically inactive in aqueous buffers but is activated for both of its substrates by exposure to a variety of anionic detergents. cationic and nonionic detergents, as well as a variety of other agents are ineffective. this stimulation by detergents is observed at all stages of the purification (wittenberg, c., and triplett, e. l. (1985) j. biol. chem. 260, 12535-12541). sodium dodecyl sulfate (nadodso4) is the most effective activator, and it was chosen fo ... | 1985 | 3930498 |
| molecular cloning and expression of human tumor necrosis factor and comparison with mouse tumor necrosis factor. | u-937 cells, a monocytic line derived from a human histiocytic lymphoma, were induced for human tumor necrosis factor (tnf) secretion into the medium and were used for the preparation of tnf mrna. biological activity of the latter was quantified in a xenopus laevis oocyte injection system. tnf mrna was enriched by gradient centrifugation and this size-fractionated mrna was used for synthesis of cdna and inserted into the unique psti site of pat153. a recombinant plasmid containing human tnf cdna ... | 1985 | 3932069 |
| phylogenetic relationships among eukaryotic kingdoms inferred from ribosomal rna sequences. | phylogenetic trees among eukaryotic kingdoms were inferred for large- and small-subunit rrnas by using a maximum-likelihood method developed by felsenstein. although felsenstein's method assumes equal evolutionary rates for transitions and transversions, this is apparently not the case for these data. therefore, only transversion-type substitutions were taken into account. the molecules used were large-subunit rrnas from xenopus laevis (animalia), rice (plantae), saccharomyces cerevisiae (fungi) ... | 1985 | 3932662 |
| structural alterations in mutant precursors of the yeast trnaleu3 gene which behave as defective substrates for a highly purified splicing endoribonuclease. | we have produced a highly purified preparation of the xenopus laevis splicing endonuclease (xlai rnase). the purified enzyme correctly cleaves trna precursors, creating substrates for subsequent ligation. the 5'-half molecules have a 2',3' cyclic phosphate at their 3' termini. assuming that splicing enzymes recognize primarily structural elements in the 'mature domain', we have been studying the conformation of three splicing-defective precursors made from mutants of the yeast trnaleu3 gene. the ... | 1985 | 3937725 |
| phosphorylation and protein synthetic events in xenopus laevis oocytes microinjected with pp60v-src. | microinjection of purified pp60v-src, the transforming protein of rous sarcoma virus, into xenopus laevis oocytes accelerated the rate of progesterone- or insulin-induced meiotic maturation. this acceleration was abolished by incubating the oocytes with cycloheximide or puromycin during a 2-h interval between pp60v-src microinjection and progesterone addition. in contrast, exposure to actinomycin d did not alter the acceleration of maturation by microinjected pp60v-src. associated with progester ... | 1985 | 3939323 |
| membrane potential measurements of unfertilized and fertilized xenopus laevis eggs are affected by damage caused by the electrode. | upon penetration in an unfertilized xenopus egg bathed in 1/10 ringer, the voltage recorded by a microelectrode shows an abrupt jump to a negative voltage (ep) followed by a rapid depolarization to a steady value (er) (ep = -39.4 +/- 1.9 mv and er = -11.5 +/- 0.5 se, 54 eggs from 9 females). the same is true for fertilized eggs impaled 16-35 min after insemination (ep = -29.5 +/- 2.1 mv, er = -11.5 +/- 0.9 mv, se, 18 eggs from 3 females). the voltage recorded by a second microelectrode inserted ... | 1986 | 3940227 |
| estrogen-induced progestin receptors in the brain and pituitary of the south african clawed frog, xenopus laevis. | high-affinity progestin binding sites were found in the brain and pituitary of the female south african clawed frog, xenopus laevis. cytosol progestin receptors in the hypothalamus-preoptic area and pituitary were increased in number by estradiol treatment in ovariectomized frogs. the telencephalon also contained high-affinity binding sites, but the concentration was not affected by estrogen priming. autoradiographic analysis of the distribution of the synthetic progestin 3h-r5020 revealed some ... | 1986 | 3941759 |
| androgen-induced myogenesis and chondrogenesis in the larynx of xenopus laevis. | we investigated a possible role for testosterone-induced cell proliferation in the development of sexual dimorphism in the larynx of south african clawed frogs, xenopus laevis. androgen-induced cell proliferation was studied using [3h]thymidine autoradiography. nuclei of cartilage, perichondrium, and muscle were labeled in the larynx of sexually immature frogs of both sexes but not in adults. cell proliferation did not occur with estradiol treatment nor was it seen in nonlaryngeal muscle or cart ... | 1986 | 3943661 |
| differential induction of vitellogenin gene transcription and total transcriptional activity by estrogen in xenopus laevis liver. | the effects of estrogen on liver gene expression in xenopus laevis were examined using a nuclear transcription "run-on" assay. vitellogenin transcription was detected 2 h after a single dose of estradiol and reached a maximum on day 4. by 12 days after hormone treatment vitellogenin transcription declined to low levels. within 3 h after estrogen, total transcriptional activity increased 9-fold relative to control values, reaching a maximum level of 40-fold by 12 h. total transcription remained e ... | 1986 | 3944139 |
| expression of an epidermal antigen used to study tissue induction in the early xenopus laevis embryo. | a monoclonal antibody (epi 1) has been produced that recognizes an antigen expressed in epidermal cells of xenopus laevis embryos. the epi 1 antigen appears in embryonic epidermis at the end of gastrulation and is not expressed in nonepidermal structures derived from ectoderm (for example, neural tube or cement gland). the capacity to express the epi 1 antigen is restricted to cells of the animal hemisphere prior to the midblastula stage of development (stage 8), and tissue interactions during g ... | 1986 | 3945801 |
| the time course of the changes in axon number of both oculomotor nerves in normal and unilaterally enucleated xenopus laevis. | in this paper we analyze long-term changes, extending into adulthood, of the number of axons in the oculomotor nerve of xenopus laevis. we counted the number of axons in that nerve in normal control (nor) animals, and on the operated (ipsilateral, ip) and contralateral (co) sides of enucleated animals at premetamorphosis, metamorphic climax, juvenile (3 and 7 months) and adult (16.5 months) stages. the experimental animals had had one of their ocular primordia removed at hatching. in the nor-ner ... | 1986 | 3948006 |
| relation of actin fibrils to energy metabolism of endothelial cells. | the physiological significance of the association of glycolytic enzymes with actin fibrils was investigated in cell culture. cytochalasin d (cd) was used to induce the known actin-based sequence of events in a culture of an endothelial-cell line (xth-2) derived from hearts from tadpoles of xenopus laevis. 1 min following addition of cd, ruptures in the cortical fibrillar meshwork and in stress fibres are seen. at the same time the cellular atp level decreases by ca. 25%. this and the following r ... | 1986 | 3955635 |
| effects of various ammonium salts, amines, polyamines and alpha-methylornithine on rrna synthesis in neurula cells of xenopus laevis and xenopus borealis. | xenopus neurula cells were cultured in a medium that contained ammonium salts, amines, polyamines or alpha-methylornithine, and their rrna synthesis was examined. all the ammonium salts and amines, but not polyamines, were strong and selective inhibitors of rrna synthesis at 1.25-5.0 mm. alpha-methylornithine did not inhibit rrna synthesis, although it inhibited ornithine decarboxylase, an enzyme claimed to be a direct stimulator of rrna synthesis. during the treatment ammonium ions and monometh ... | 1986 | 3955659 |
| cell interactions and the control of gene activity during early development of xenopus laevis. | during embryonic development, regulation of the zygotic genome may be mediated by inductive interactions and by cell-autonomous inheritance of informational material from the egg; we have studied certain aspects of such regulatory events in xenopus laevis. embryos cultured in ca2+/mg2+-free medium can be dissociated and dispersed, eliminating cell-cell contact and thus precluding inductive interactions. such manipulations revealed that activation of the muscle-specific alpha-actin genes is absol ... | 1986 | 3956863 |
| dynamic aspects of retinotectal map formation revealed by a vital-dye fiber-tracing technique. | in the visual system of xenopus laevis, the axons from the retinal ganglion cells of the eye form a topographic projection onto the optic tectum. many studies have focused on revealing the mechanisms responsible for this precise and regular projection pattern. in contrast to the static view of the system that one might expect from examining the regularity of the projection, recent work on its regeneration and its changes during larval development indicate that part of the patterning process invo ... | 1986 | 3956868 |
| novel peptide fragments originating from pgla and the caerulein and xenopsin precursors from xenopus laevis. | skin secretions from the south african frog xenopus laevis have been chromatographed by high performance liquid chromatography (hplc), fractionated, and analyzed by fast atom bombardment-mass spectrometry (fab-ms). the hplc chromatograms showed the secretion to be a complex mixture with over 30 components at similar levels to the four peptides previously isolated from x. laevis skin, i.e. xenopsin, caerulein, thyrotropin-releasing hormone, and pgla. fab-ms analysis of the hplc fractions gave num ... | 1986 | 3957928 |
| origin and identification of fibers in the cranial nerve ix-x complex of xenopus laevis: lucifer yellow backfills in vitro. | the central projections of individual components of the ix-x nerve complex in the south african clawed frog, xenopus laevis, were mapped by dye diffusion with lucifer yellow in an isolated brain preparation. the method reliably revealed fiber tracts, termination zones, and detailed cell morphology. in addition, motor neurons could be doubly labelled by retrograde transport of horseradish peroxidase from muscle targets followed by backfilling the appropriate nerves with lucifer yellow. the most a ... | 1986 | 3958236 |
| atp-evoked membrane responses in xenopus oocytes. | voltage-clamp technique and intracellular injections of drugs were used to study the adenosine triphosphate (atp)-evoked depolarizing current response in the xenopus laevis oocytes. the depolarizing current was comprised of a fast transient component (d1) followed by a late long-lasting component (d2). it was carried mainly by cl- ions. the depolarizing current was better elicited by atp and adp than by amp or adenosine and was not blocked either by theophylline (0.2 mm) or by quinidine sulphate ... | 1986 | 3960699 |
| effects of denervation and delayed amputation on forelimb regeneration in xenopus laevis froglets. | left forelimbs of postmetamorphic xenopus laevis froglets were repeatedly denervated prior to and following amputation. amputations were performed 14, 21, 28, or 42 days after the original denervation. a tissue-regenerative response resulting in the formation of a spike-shaped, heteromorphic outgrowth was found in the sham-denervated and control animals, but dedifferentiation of the stump tissues was not apparent. tissue-regenerative outgrowths were not observed in the denervated cases; instead, ... | 1986 | 3963424 |
| fibronectin visualized by scanning electron microscopy immunocytochemistry on the substratum for cell migration in xenopus laevis gastrulae. | in amphibian gastrulae, scanning electron microscopy (sem) has shown the presence of a network of extracellular fibrils on the inner aspect of the ectoderm layer, which serves as the substratum for migration by the presumptive mesoderm cells. in vitro experiments have shown that the fibril network promotes attachment and migration by mesoderm cells, and probably guides the migration by contact guidance. filopodia of the migrating cells showed preferential attachment to the fibrils. use of a coll ... | 1985 | 3965325 |
| characterisation of a dictyostelium discoideum dna fragment coding for a putative trnavalguu gene. evidence for a single transcription unit consisting of two overlapping class iii genes. | a genomic dna fragment from dictyostelium discoideum was characterized. this dna, although 74% d(a + t)-rich, codes for a putative trnavalguu. the trnaval gene overlaps at its 5' half with another rna polymerase iii transcription unit. this rna polymerase iii transcription unit can be folded into a trna-like shape and is comprised of significant amounts of invariant and semi-invariant nucleotides present in all eukaryotic trnas. this unit contains the two promoter blocks defined for rna polymera ... | 1985 | 3967666 |
| stockpiling of dna polymerases during oogenesis and embryogenesis in the frog, xenopus laevis. | the amounts of the various forms of dna polymerase (alpha 1, alpha 2, beta, and gamma) have been determined in oocytes, eggs, and embryos of the frog, xenopus laevis. during oogenesis the relative proportions and absolute levels of all forms changed dramatically. in stage i (early) oocytes, dna polymerase-gamma, the "mitochondrial" polymerase, was the predominant form. during oocyte growth, dna polymerase-alpha 1 and -alpha 2 increased by more than 100-fold, dna polymerase-beta by 15-fold, and d ... | 1985 | 3968072 |
| development of early brainstem projections to the tail spinal cord of xenopus. | horseradish peroxidase (hrp) was used to determine the sequence in which axons from different brain neurons reach the tail spinal cord during embryonic and early larval development of xenopus laevis. brainstem cells of several classes project to the tail at these stages: mesencephalic reticulospinal neurons of the nucleus of the medial longitudinal fasciculus, a variety of other reticulospinal neurons, vestibulospinal neurons, and a group of median basal cells which may be raphe neurons. among t ... | 1985 | 3968253 |
| pharmacological modification of the light-induced responses of müller (glial) cells in the amphibian retina. | the light-evoked responses of müller (glial) cells were monitored by intracellular recording in the isolated, superfused retina of xenopus laevis. müller cells had dark resting potentials of -88.5 +/- 6.9 mv and small 1-2 mv light responses of variable waveform in normal ringer's solution. exposure to picrotoxin (0.5-1.0 mm) greatly enhanced the light response which then consisted of depolarizing transients (vmax 5-15 mv) at stimulus onset and offset. gaba (5-10 mm) antagonized the picrotoxin ef ... | 1985 | 3971168 |
| deinduction of transcription of xenopus 74-kda albumin genes and destabilization of mrna by estrogen in vivo and in hepatocyte cultures. | the goal of this study is to explain the molecular basis of the marked deinduction of xenopus albumin synthesis and secretion accompanying the activation of vitellogenin genes by estrogen. we have characterized by restriction analysis, dna sequencing and hybrid-selected translation of mrna, a cloned cdna specifying the two 74-kda albumins which constitute the predominant circulating form of albumin in xenopus laevis. using this recombinant dna plasmid as a hybridization probe, we have determined ... | 1985 | 3971963 |
| characterization of dna-protein complexes from the mitochondria of xenopus laevis oocytes. | mitochondrial dna (mtdna)-protein complexes (nucleoids) from xenopus laevis oocytes were purified either on rate-zonal sucrose or isopyknic metrizamide gradients. from electron microscopic studies and staphylococcal nuclease digestion experiments mtdna appears to be packaged into regular beaded structures. protein electrophoretic analysis and m banding results show that mtdna is associated with the membrane structures and also with few specific proteins including one acid-soluble polypeptide of ... | 1985 | 3972011 |
| ribosomal-protein synthesis is not autogenously regulated at the translational level in xenopus laevis. | whether ribosomal-protein synthesis in xenopus laevis is autogenously controlled at the translational level as is known to occur in prokaryotes has been studied. for this purpose ribosomal (r) proteins were prepared from x. laevis ribosomal subunits and group fractionated by ion-exchange chromatography. they were then added to an in vitro translation system directed by an oocyte mrna fraction which contains template activity for r proteins. the synthesized radioactive products were analyzed by 2 ... | 1985 | 3972154 |
| fertilization potential and electrical properties of the xenopus laevis egg. | the membrane potential of xenopus eggs was monitored continuously from prior to fertilization until early cleavage. a rapid decay of the initial potential of -33.1 +/- 8.1 (sd) mv (n = 14) upon impalement to a value of -19.3 +/- 4.2 (sd) mv (n = 68) suggested that insertion of the first electrode caused depolarization. outward and inward rectification were observed when the resting potential was made more positive than about 5 mv or more negative than about -30 mv. eggs were not activated by thi ... | 1985 | 3972161 |
| acquisition of the heat-shock response and thermotolerance during early development of xenopus laevis. | the ability to synthesize a 68,000- to 70,000-da protein (hsp) in heat-shocked early xenopus laevis embryos is dependent on the stage of development. whereas late blastula and later stage embryos synthesize hsp68-70 after heat shock, cleavage stages are incompetent with respect to hsp synthesis. in vitro translation experiments and rna blot analyses demonstrate that enhanced synthesis of hsp68-70 is associated with an accumulation of hsp68-70 mrna. examination of the effect of heat shock on pree ... | 1985 | 3972166 |
| occurrence of a species-specific nuclear antigen in the germ line of xenopus and its expression from paternal genes in hybrid frogs. | an abundant acidic germinal vesicle protein of 100,000 da has been previously described in xenopus laevis and termed n1. it is supposed to bind stored histones in the oocyte. species-specific monoclonal antibodies (mabs) have been raised against the oocyte nuclear protein of x. borealis b3, that is equivalent to protein n1 of x. laevis. these mabs have been used to monitor paternal gene expression of b3 in hybrids between x. laevis and x. borealis. protein b3 is accumulated in oocyte nuclei, she ... | 1985 | 3972177 |
| the development of the nucleus isthmi in xenopus laevis. i. cell genesis and the formation of connections with the tectum. | the nucleus isthmi (ni) of the amphibian relays visual input from one tectum to the other tectum and thus brings a visual map from the eye to the ipsilateral tectum. this isthmotectal visual map develops slowly; it is first detected electrophysiologically at stages 60-62, the age at which the eyes begin their dorsalward migration and the region of binocular overlap beings to increase in extent. during this critical period of life, normal binocular visual input is required for establishment of no ... | 1985 | 3973081 |
| regulation of neuron numbers in xenopus laevis: effects of hormonal manipulation altering size at metamorphosis. | xenopus laevis tadpoles reared in a 0.01% solution of 6-n-propyl-2-thiouracil (ptu) are blocked in their development at larval stage 54 but continue to increase in size. when released from the effects of ptu they metamorphose into frogs of sizes significantly larger than those of their untreated siblings. using this size difference to examine the hypothesis that neuron numbers are matched to the size of their postsynaptic targets during neuronal cell death, we measured the following on stage 66 ... | 1985 | 3973094 |
| developmental mutants isolated from wild-caught xenopus laevis by gynogenesis and inbreeding. | xenopus laevis obtained from indigenous african populations are a rich source of mutants affecting development. gynogenesis and inbreeding were used to isolate mutants affecting development from wild-caught xenopus laevis females. fourteen mutants were recovered from eight females tested. one mutant was recovered from each of two females. this load of 1.875 developmental mutants per female is similar to that found in the axolotl (ambystoma mexicanum), a urodele amphibian, and is only slightly le ... | 1985 | 3973558 |
| synthesis of bunyavirus-specific proteins in a continuous cell line (xtc-2) derived from xenopus laevis. | the xtc-2 cell line, derived from xenopus laevis, supported the replication of representative viruses from each of the four genera in the family bunyaviridae. generally, viral titres were higher in xtc-2 cells than in other susceptible cell lines, and for some viruses plaques were detected earlier in xtc-2 cells. the xtc-2 cell line permitted comparative analyses of bunyavirus-specific protein synthesis. the patterns of synthesis of viral proteins, characteristic of each of the genera, were obse ... | 1985 | 3973561 |
| effects of hypophysectomy and substitution with growth hormone, prolactin, and thyroxine on growth and deposition in juvenile frogs, xenopus laevis. | growth was studied in young metamorphosed frogs, xenopus laevis, following hypophysectomy and substitution with mammalian growth hormone (bgh or pgh), mammalian prolactin (oprl), and thyroxine. hypophysectomy reduced growth (weight and length increase). gh and prl proved equally efficient in restoring growth and in mobilizing energy stores (fat bodies and liver glycogen). no synergistic effects between gh and prl could be observed. gh exerted its growth-promoting effects by increasing gross food ... | 1985 | 3979807 |
| an elevated free cytosolic ca2+ wave follows fertilization in eggs of the frog, xenopus laevis. | the eggs of most or all animals are thought to be activated after fertilization by a transient increase in free cytosolic ca2+ concentration ([ca2+]i). we have applied ca2+-selective microelectrodes to detect such an increase in fertilized eggs of the frog, xenopus laevis. as observed with an electrode in the animal hemisphere, [ca2+]i increased from 0.4 to 1.2 microm over the course of 2 min after fertilization, and returned to its original value during the next 10 min. no further changes in [c ... | 1985 | 3980584 |
| growth and death of cells of the mesencephalic fifth nucleus in xenopus laevis larvae. | positions, numbers, and cell and nuclear sizes of mesencephalic fifth nucleus (m-v) cells were determined in xenopus laevis larvae in stages 47 through the end of metamorphosis at stage 66. m-v cells may be found at every tectal level, from the rostralmost section almost to the caudal pole, and in the anterior medullary velum. a large majority of the cells lie between 15 and 65% caudad of the rostral tip of the tectum. at anterior and middle tectal levels the cells lie lateral to but mainly abov ... | 1985 | 3980781 |
| xenopus mhc class ii molecules. ii. polymorphism as determined by two-dimensional gel electrophoresis. | the class ii antigens from four inbred strains of xenopus laevis (r, f, g, and j haplotypes) and six gynogenetic lg clones (two xenopus laevis, two xenopus gilli haplotypes) with functionally well-defined mhc types have been immunoprecipitated with the rabbit anti-human class ii beta-chain serum anti-p29boost and analyzed by two-dimensional gel electrophoresis. the glycosylated material from 15-hr biosynthetically labeled cells runs as a broad fuzzy band around 33kd that, upon removal of n-linke ... | 1985 | 3980992 |
| tadpole xenopus laevis hemoglobin. correlation between structure and functional properties. | perutz & brunori (1982) proposed that the cooh-terminal his and ser f9 of the beta-chains of fish and amphibian hemoglobins are responsible for their root effect and part of their alkaline bohr effect. analysis of the kinetics of carbon monoxide binding by hemoglobin from the tadpole of xenopus laevis supports that model and suggests an explanation for the absence of an alkaline bohr effect in many aquatic anura and urodela. | 1985 | 3981639 |
| innervation pattern of muscles of one-legged xenopus laevis supplied by motoneurons from both sides of the spinal cord. | in xenopus tadpoles one limb bud was removed before innervation and motoneurons from both sides of the spinal cord were induced to innervate the remaining limb. when examined after metamorphosis the motor innervation of the limb had the following characteristics. in agreement with previous findings a large proportion of contralateral motoneurons survived (51-82% of the ipsilateral numbers) and sent axons to the limb. by acetylcholinesterase staining and intracellular recording from muscle fibers ... | 1985 | 3986602 |
| ribocharin: a nuclear mr 40,000 protein specific to precursor particles of the large ribosomal subunit. | using a monoclonal antibody (no-194) we have identified, in xenopus laevis and other amphibia, an acidic protein of mr 40,000 (ribocharin) which is specifically associated with the granular component of the nucleolus and nucleoplasmic 65s particles. these particles contain the nuclear 28s rrna and apparently represent the precursor to the large ribosomal subunit in nucleocytoplasmic transit. by immunoelectron microscopy ribocharin has been localized in the granular component of the nucleolus and ... | 1985 | 3986912 |
| changes in levels of polymeric tubulin associated with activation and dorsoventral polarization of the frog egg. | the level of polymeric tubulin was measured during the first cell cycle of the electrically activated and the fertilized egg of xenopus laevis. eggs were homogenized in a microtubule-stabilizing medium, and the amount of tubulin pelleted by centrifugation was determined by quantitative western blots. the pelleted tubulin (polymer) was in the form of microtubules based on the presence of microtubules in the pellet and on the effects of cold, nocodazole, and d2o. unactivated eggs had a high level ... | 1985 | 3987962 |
| gonadotropins and the timing of progesterone-induced meiotic maturation of xenopus laevis oocytes. | isolated oocytes from 30 unstimulated xenopus laevis females required from 2.50 +/- 0.13 to 14.59 +/- 0.77 hr after progesterone exposure for the first 50% of each group to complete meiotic maturation. injecting 8 females with an amount of hcg not causing ovulation (25 micrograms, 96 iu) lowered oocyte maturation times by 45-83%. an enzyme-linked immunosorbent assay (elisa) of the blood of 18 unstimulated animals found a constituent which bound to anti-hcg in amounts (equivalent to 0-1.03 microg ... | 1985 | 3987966 |
| tunicamycin-induced alterations of the gastrulation process in xenopus laevis embryos. | | 1985 | 3988178 |
| regulation in the neural plate of xenopus laevis demonstrated by genetic markers. | to follow the subsequent history of grafted tissue in experiments designed to study regulation and commitment in the amphibian neural plate, previous workers have relied on graft scars, vital dyes applied externally to cells, or xenoplastic grafts. each of these methods has been criticized on the grounds that they do not indicate unambiguously the origins of individual cells within the operated host. to overcome these difficulties, homoplastic, genetically marked embryonic grafts were taken from ... | 1985 | 3989493 |
| fine structure of the forelimb regenerate of the african clawed toad, xenopus laevis. | forelimb regenerates from postmetamorphic xenopus froglets were examined at various stages postamputation by light microscopy and scanning and transmission electron microscopy. the outside surface of the wound epithelium was found to exhibit progressive changes following amputation with a distinct difference in appearance between stump epidermis and wound epithelium at all stages examined. the internal structure of the wound epithelium is characterized by loosely arranged cells with numerous cel ... | 1985 | 3993994 |
| the expression of creatine kinase isozymes in xenopus tropicalis, xenopus laevis laevis, and their viable hybrid. | starch gel electrophoresis of creatine kinase (ck) isozymes of xenopus tropicalis shows that at least two different genes code for ck in this diploid (2n = 20) species. these genes seen to be orthologous to the ck-a and ck-c genes of extant crossopterygian fish. additional isozymes may be interpreted either as products of duplicate genes or, more probably, as epigenetically modified forms of the homodimers atat and ctct, respectively. the originally tetraploid species x. laevis laevis (2n = 36), ... | 1985 | 3994660 |
| changes in the nuclear lamina composition during early development of xenopus laevis. | changes in protein composition of the nuclear lamina were monitored during early development in xenopus. lamin liii, the only lamin present in oocyte nuclei, serves as a lamin pool for the formation of pronuclei and early cleavage nuclei. it is present in embryos up to the tail bud stages. lamins li and lii, the lamins originally found in adult cell nuclei, appear at characteristic times in development. li first appears at the midblastula transition (mbt), and lii at the gastrula. tryptic peptid ... | 1985 | 3995581 |
| maturation of xenopus oocytes is not accompanied by electrode-detectable calcium changes. | ca2+-sensitive microelectrodes were used to study changes in cytoplasmic free calcium during progesterone-induced meiotic maturation in xenopus laevis oocytes. in contrast to previous reports, no changes were detected during the maturation process, although a large activation pulse of ca2+ was seen when in vitro matured eggs were parthenogenetically activated. the resting level of ca2+ in the oocytes was 0.14 microm +/- 0.05. | 1985 | 3996760 |
| complete nucleotide sequence of mrna for caerulein precursor from xenopus skin: the mrna contains an unusual repetitive structure. | the complete nucleotide sequence of mrna for caerulein precursor in the skin of xenopus laevis was determined. the sequence was composed of 705 bp of coding region, accounting for 234 amino acids, 58 bp of 5'-untranslated region and 158 bp of 3'-untranslated region containing two putative poly(a) signals. it coded for four caerulein peptides interspersed with three 147 bp segments (intercaerulein segment; ics). analyses of several caerulein encoding cdnas revealed some interesting features of ca ... | 1985 | 4000945 |
| the number of mitochondria in xenopus laevis ovulated oocytes. | an attempt was made to estimate the total number of mitochondria in xenopus laevis ovulated oocytes. for this purpose the necessary basic parameters were calculated employing planimetry and simple mathematical formulas. it was found that the number of mitochondria in the ovulated oocyte of xenopus is of the order of 10(7). the significance of this finding is discussed. | 1985 | 4005954 |
| effect of concanavalin a and vegetalizing factor on the outer and inner ectoderm layers of early gastrulae of xenopus laevis after treatment with cytochalasin b. | neural (archencephalic) structures have been evoked in the competent ectoderm (consisting of both ectodermal layers) of xenopus laevis by treatment with concanavalin a (con a), which probably acts on the plasma membrane. the size of the neural structures is increased when the ectoderm is incubated in cytochalasin b prior to the con a treatment. the results indicate that cytochalasin b could have an influence on the binding of con a to receptors on the plasma membrane. on the other hand, cytochal ... | 1985 | 4005955 |
| the primary structure of transcription factor tfiiia has 12 consecutive repeats. | analysis of the amino acid sequence of transcription factor tfiiia from xenopus laevis reveals the presence of 12 repeating structures, each about 30 residues in length. these segments have been aligned and their secondary structure predicted. the repeats each contain two invariant cysteines and two invariant histidines, perhaps to coordinate a zinc cation. possible nucleic acid interaction modes are discussed. | 1985 | 4007166 |
| quantitative changes in protein synthesis during oogenesis in xenopus laevis. | protein synthesis rates in xenopus laevis oocytes from stage 1 through stage 6 were measured. in addition, the translational efficiencies, total rna contents, and percentages of ribosomes in polysomes in growing oocytes at several stages were determined. stage 1 oocytes synthesize protein at a mean rate of 0.18 ng hr-1 while stage 6 oocytes make protein at a rate of 22.8 ng hr-1. polysomes from growing and full-grown oocytes sedimented in a sucrose gradient with a peak value of 300 s, correspond ... | 1985 | 4007263 |
| meiotic maturation in xenopus oocytes: a link between the cessation of protein secretion and the polarized disappearance of golgi apparati. | we have studied the relationship between the timing of the late meiotic events that occur during progesterone-induced oocyte maturation, and intracellular protein transport. we have monitored the secretion of chick oviduct proteins from xenopus laevis oocytes microinjected with polyadenylated mrna and found that chick ovalbumin and lysozyme are not secreted during the second meiotic metaphase, in contrast to the earlier prophase stage. maturation had no detectable effect on the glycosylation of ... | 1985 | 4008532 |
| translation of schistosoma mansoni antigens in xenopus oocytes microinjected with mrna from adult worms. | oocytes from xenopus laevis microinjected with rna isolated from schistosoma mansoni adult worms translated antigens recognized by sera from infected rats, humans, and from immunized rabbits. the pattern of immunoprecipitated proteins analysed by sds-polyacrylamide gel electrophoresis was species specific in rats. serum from infected fischer rats recognized antigens of 20, 27 and several bands in the 50-60 kda range whereas serum from infected brown norway rats also immunoprecipitated major band ... | 1985 | 4010705 |
| differential participation of ventral and dorsolateral mesoderms in the hemopoiesis of xenopus, as revealed in diploid-triploid or interspecific chimeras. | the thymocytes in the early larvae of xenopus laevis have been shown to be derived from precursor cells immigrating interstitially through the mesenchyme into the organ rudiments at 3-4 days of age (nieuwkoop and faber stages 42-45). orthotopic grafting of diploid tissues onto triploid stage 22 embryos followed by ploidy analyses of their hemopoietic cells revealed that both thymocytes and erythrocytes in early larvae are derived from the ventral blood islands (vbi), whereas those in late larvae ... | 1985 | 4018411 |
| the complete nucleotide sequence of the xenopus laevis mitochondrial genome. | the complete sequence of the 17,553-nucleotide xenopus laevis mitochondrial genome has been determined. a comparison of this amphibian mitochondrial genomic sequence with those of the mammalian mitochondrial genomes reveals a similar gene order and compact genomic organization. the encoded genes for 22 trnas, two ribosomal rnas, and 13 proteins (coi, coii, coiii, atpase 6, cytochrome b, and eight additional unidentified reading frames) in the amphibian mitochondria are highly homologous to their ... | 1985 | 4019494 |
| abrogation of cell surface expression of human class i transplantation antigens by an adenovirus protein in xenopus laevis oocytes. | class i transplantation antigens form complexes with a virus protein encoded in the early region e3 of the adenovirus-2 genome. the interaction between this viral glycoprotein, e19, and nascent human class i antigens has been examined by microinjecting purified mrna into xenopus laevis oocytes. both e19 and the two class i antigen subunits, the heavy chain and beta 2-microglobulin (beta 2m), were efficiently translated. the heavy chains did not become terminally glycosylated, as monitored by end ... | 1985 | 4019582 |