| the formation of multinuclear muscle fibres in xenopus laevis i. observations on dissociated myotomal cells and autoradiography. | | 1984 | 6724444 |
| intercellular junctions between the follicle cells and oocytes of xenopus laevis. | during development, the oocytes of xenopus laevis establish junctional contact with the follicle cells enveloping them. these junctions have alternatively been described as desmosomes and as gap junctions. in this paper the morphology of these junctions has been examined in gonadotropin-stimulated and unstimulated animals at all stages of development. contact between the oocyte and follicle cell plasma membranes is visible in stage i oocytes as thickenings in the membranes, separated by intercel ... | 1984 | 6726143 |
| two healing patterns correlate with different adult neural connectivity patterns in regenerating embryonic xenopus retina. | nasal and temporal one-third-sized eye fragments, formed by ablation at stage 32-33 of xenopus laevis embryos, heal and, in about 50% of the cases, survive to make eyes in the postmetamorphic animal which have mappable visuotectal projections. the majority of nasal one-third eyes have duplicate projections whereas the majority of temporal one-third eyes have unduplicated projections. most nasal one-third eye fragments and a minority of temporal eye fragments heal by the extrusion of cells from t ... | 1984 | 6726148 |
| reversible inhibition of translation by xenopus oocyte-specific proteins. | a characteristic of growing oocytes of all animal species is the synthesis and accumulation of messenger rna which is destined to be used primarily by the early embryo. the mechanism(s) which regulates the translation of this maternal mrna remains unknown. however, the inability of the oocyte to translate all of its putative mrna has been attributed to at least three limitations: (1) the rate of translation is limited by the availability of components of the translational apparatus other than mr ... | 1984 | 6727992 |
| regeneration of transected dorsal root ganglion cell axons into the spinal cord in adult frogs (xenopus laevis). | the extent of regeneration of the central axonal processes of dorsal root ganglion cells was determined using anterograde horseradish peroxidase histochemistry at 1-12 weeks after dorsal root transection in adult frogs. at 4, 8 and 12 weeks axons were found to have regenerated across the dorsal root entry zone and into the spinal cord. | 1984 | 6733463 |
| [specific inhibition of cleavage divisions in xenopus laevis in propranolol microinjection]. | | 1984 | 6734415 |
| platanna (xenopus laevis) as a test organism for determining the embryotoxic effects of environmental chemicals. | it has been successfully demonstrated that platanna (xenopus laevis) allows the artificial induction of spawning at any time during the year. the number of eggs collected from a female ranged between 500 and 2400, the fertilization rate varying between 10 and 85%. when unaffected by chemicals, the embryonic development of the larvae took between 8 and 30 weeks. di(2-ethylhexyl) phthalate (dehp), methylmercury chloride, and the thalidomide analog em 12 were used for the experiments described. deh ... | 1984 | 6734493 |
| heterogeneous distribution and replication activity of mitochondria in xenopus laevis oocytes. | in early diplotene oocytes of xenopus laevis mitochondria are not dispersed all over the cytoplasm but gathered in a well described mitochondrial mass [18]. when tracing these organelles during active vitellogenesis we observe that some of them are involved in the elaboration of a cortical layer at the vegetative hemisphere of the cell while others stay around the nucleus. the latter contribute to the transient formation of a mitochondrial crown throughout active mitochondriogenesis. autoradiogr ... | 1984 | 6734625 |
| phosphorylation of non-histone proteins associated with mitosis in hela cells. | our previous studies indicated that certain non-histone proteins (nhp) extractable with 0.2 m nacl from mitotic hela cells induce germinal vesicle breakdown and chromosome condensation in xenopus laevis oocytes. since the maturation-promoting activity of the mitotic proteins is stabilized by phosphatase inhibitors, we decided to examine whether phosphorylation of nhp plays a role in the condensation of chromosomes during mitosis. hela cells, synchronized in s phase, were labeled with 32p at the ... | 1984 | 6734751 |
| lateral mobility of plasma membrane lipids in dividing xenopus eggs. | the lateral mobility of plasma membrane lipids was analyzed during first cleavage of xenopus laevis eggs by fluorescence photobleaching recovery (fpr) measurements, using the lipid analogs 5-(n-hexadecanoyl)aminofluorescein ("hedaf") and 5-(n-tetradecanoyl)aminofluorescein ("tedaf") as probes. the preexisting plasma membrane of the animal side showed an inhomogeneous, dotted fluorescence pattern after labeling and the lateral mobility of both probes used was below the detection limits of the fpr ... | 1984 | 6734936 |
| a flow cytometric analysis of the embryonic origin of lymphocytes in diploid/triploid chimeric xenopus laevis. | quantitative flow cytometry was used to examine the embryonic origin of lymphocytes in xenopus laevis. reciprocal head/body transplants were made between diploid (2n) and triploid (3n) embryos of the same developmental stages ranging from neural plate to tail bud stages. thymuses and spleens were removed from postmetamorphic chimeras. cell suspensions were stained with the fluorescent dna stain, mithramycin, and the ploidy (relative fluorescence intensity) of the cells was then determined by flo ... | 1984 | 6734938 |
| the modifications of cortical endoplasmic reticulum during in vitro maturation of xenopus laevis oocytes and its involvement in cortical granule exocytosis. | in xenopus laevis eggs, cisternae shells which surround cortical granules (cg) are part of a cortical endoplasmic reticulum (er) network. in this paper the origin of such er shells has been studied in full-grown, progesterone-exposed xenopus oocytes. furthermore, the possible role of the cortical er in the activation process has been investigated by pricking maturing oocytes. it has been shown that in full-grown ovarian oocytes er cg shells are absent and er cisternae are extensively and randoml ... | 1984 | 6736888 |
| effects of light-deprivation on development of photopositive behavior in xenopus laevis tadpoles. | the development of amphibian sensory systems and behavior is generally considered to proceed normally without reference to sensory experience during embryonic or larval stages. most of the supporting research, however, has concentrated on the retinotectal (visual) systems of anurans and has ignored behaviors directed by other sensory systems. we demonstrate that early exposure to light is necessary for the development of photopositive behavior in xenopus laevis tadpoles, a behavior probably dire ... | 1984 | 6736894 |
| activity of commissural interneurons in spinal cord of xenopus embryos. | horseradish peroxidase- (hrp) filled microelectrodes have been used to examine the anatomy and physiology of "commissural interneurons," a morphologically defined class of spinal cord interneuron in xenopus laevis embryos. commissural interneurons have unipolar cell bodies in the dorsal half of the spinal cord. their dendrites lie in the mid to ventral parts of the lateral tracts and their axons cross the cord ventrally, t branch, and ascend and descend on the opposite side of the cord. recordin ... | 1984 | 6737030 |
| [characteristics of cardiac growth and energy metabolism in the development of the clawed toad]. | the relative content of the actomyosin complex proteins increases with respect to the total heart protein during the heart growth in xenopus laevis. the intensity of the heart sections respiration was shown to depend on the heart weight. constants were determined in an equation describing this dependence. the decrease in the intensity of the heart sections respiration is determined mainly by the decrease of the mitochondrial protein content. | 1984 | 6739034 |
| different modes of pronephric duct origin among vertebrates. | it is possible to distinguish differences in pronephric duct morphogenesis by using scanning electron microscopy to observe the results of blocking, marking and grafting experiments as well as the normal course of development. here we compare the mode of pronephric duct development in embryos representing three orders of vertebrates: birds (class, aves; order, gallus); frogs (class, amphibia; order, anura); and salamanders (class, amphibia; order, urodela). the axolotl (a urodele) pronephric duc ... | 1984 | 6740242 |
| a morphometric study of the retinal ganglion cell layer and optic nerve from metamorphosis in xenopus laevis. | the number and distribution of cells in the retinal ganglion layer have been examined in nissl-stained wholemounts during postmetamorphic life in xenopus laevis. total cell number at metamorphic climax, in the 3 and 4 month juveniles and in 5 year adults were 30,000-41,000, 45,000-51,000 and 71,000-82,000 respectively. optic axon counts of 29,000, 39,000 and 58,000 at these stages suggested that most cells counted were ganglion cells and that their number doubled during this period. cell distrib ... | 1984 | 6740963 |
| cerebellar connections in xenopus laevis. an hrp study. | in the present study the cerebellar afferents in the clawed toad xenopus laevis have been analysed with the horseradish peroxidase (hrp) technique. in addition, data on the efferent connections of the cerebellum could be gathered, based on the phenomenon of anterograde transport of hrp. cerebellar afferents in xenopus laevis appear to arise mainly in the vestibular nuclear complex, in a primordial inferior olive and in the spinal cord. both primary (arising in the ipsilateral vestibular ganglion ... | 1984 | 6742456 |
| globin evolution in some species of the genus bufo. | the globins of 10 species of toads of the genus bufo have been analysed. from the values of the reciprocal rates between their amino acid residues a 'dissimilarity matrix' was made. in this have been included the values related to discoglossus pictus and xenopus laevis. the numerical data, derived from a computer program, gave a dendrogram representing the evolution of the analysed globins. this appears correlated to the geographical distribution and to the metabolic adaptation of the correspond ... | 1984 | 6744827 |
| structure and in vitro transcription of a glycine trna gene from bombyx mori. | we report the sequences of a bombyx mori trna1gly gene, its flanking regions, and its in vitro transcription products. the 5' flanking dna contains the sequences tatac, tatttt and ttc located 30, 18 and 4 nucleotides, respectively, in front of the transcription initiation site. these resemble, in both position and composition, sequences preceding other rna polymerase iii genes of b. mori. a deletion mutant retaining these conserved sequences and an additional 8 bp of flanking dna is transcribed ... | 1984 | 6745242 |
| inhibition of eukaryotic trna transcription by potential z-dna sequences. | the effect of d(ca/tg)n dna segments on trna transcription has been examined. alternating purine-pyrimidine tracts were cloned at a long distance from, adjacent to, or within the coding sequence of a trnapro gene from caenorhabditis elegans and shown to be able to assume the a-dna conformation in vitro in physiological salt concentrations. the transcriptional level of these constructs was compared to that of normal tdnapro by micro-injection into xenopus laevis oocytes. our results show a strong ... | 1984 | 6745243 |
| studies on three kinds of lectins from xenopus laevis skin. | among skin extracts of various frogs, lectin activity was found only in fractions prepared from xenopus laevis skin. 3 skin lectins have been separated. among these, the lectin designated s2-dlc was isolated in a homogeneous state and showed a preferential agglutination of ehrlich and s-180 ascites tumor cells; other tumor cells and human erythrocytes were not agglutinated. the lectin-dependent agglutination was inhibited by d-fucose, l-arabinose, d-galactose, lactose and lactulose. the sugar sp ... | 1984 | 6745400 |
| tnp-ficoll response in xenopus laevis: substitution and reconstitution in thymectomized animals. | the capacity to respond to haptenated ficoll, though thymus-independent in mammals, is lost in xenopus laevis following thymectomy at any stage of development. this capacity can be restored to thymectomized xenopus by whole allogeneic thymus implants, by thymus implants from animals treated with n-methyl-n-nitrosourea (which have an active thymus medulla but no cortex, and which lack certain thymus-dependent immunological functions), and concanavalin a. these results are discussed in terms of th ... | 1984 | 6745996 |
| isolation and characterization of the third component of complement in the serum of the clawed frog, xenopus laevis. | the hemolytic activity against srbc in the serum of normal xenopus is dependent on specific antibody and both ca++ and mg++, whereas the activity against rrbc is dependent on mg++ alone. both of these hemolytic activities disappeared after treatment of the serum with zymosan or with the specific rabbit antiserum against one of the zymosan-binding proteins in xenopus serum. by using this antiserum as a probe, a complement component (xc) was purified as a single entity from the xenopus plasma afte ... | 1984 | 6747292 |
| characterization of the intermittent breathing pattern in xenopus laevis. | xenopus laevis exhibits an extensive repertoire of breathing patterns during voluntary diving-emergence behaviour. in experiments where animals surfaced to breathe at a blowhole fitted with a pneumotachograph, two noticeably different patterns of breathing were observed. in the first (burst breathing), long periods of diving were periodically interrupted by short visits to the surface when a discrete series of evenly spaced ventilations occurred. on other occasions, the same animal might rise to ... | 1984 | 6747538 |
| functional conflicts between feeding and gas exchange in suspension-feeding tadpoles, xenopus laevis. | air-breathing tadpoles of xenopus laevis (amphibia: anura) use buccopharyngeal surfaces for both gas exchange and capture of food particles in the water. in dense food suspensions, tadpoles decrease ventilation of the buccopharynx and increase air breathing. the lung ventilatory frequency is elevated even though the rate of oxygen consumption is at or below resting levels, suggesting that the lung hyperventilation reflects compensation for decreased buccopharyngeal respiration rather than an inc ... | 1984 | 6747542 |
| the effect of trifluoperazine on maturation of xenopus laevis oocytes. | full grown xenopus oocytes were incubated with trifluoperazine (tfp) or injected with tfp. incubation of oocytes in tfp resulted in normal-appearing meiotic maturation, as judged by the presence of the white spot and the absence of the germinal vesicle. cortical granule breakdown in tfp-incubated oocytes was not normal. abnormal cortical granule breakdown was also observed when progesterone-maturated oocytes were activated in the presence of tfp. oocytes microinjected with tfp and incubated with ... | 1984 | 6747571 |
| in vitro digestion of actomyosin by extracts from tails of metamorphosing xenopus laevis. | 1. actomyosin purified from the tails of immature tadpoles of xenopus laevis was degraded by exposure to low salt, 16,000 g supernatant extracts of involuting tadpole tails, as assayed by sds polyacrylamide gel electrophoresis. 2. the proteolytic activity of the tail extracts was inhibited by atp and leupeptin. myosin (193,000 daltons) is initially cut to produce a 161,000 dalton fragment, then in a second step yielding 95,000 dalton fragments. 3. both atp and leupeptin inhibit the formation of ... | 1982 | 6749404 |
| restoration of antibody responsiveness in early thymectomized xenopus by implantation of major histocompatibility complex-mismatched larval thymus. | the restorative potential of isogeneic and fully allogeneic thymic implants to restore in vivo antibody responsiveness to a thymus-dependent antigen has been examined in thymectomized clawed toads. isogeneic clones (xenopus laevis/gilli and x. laevis/muelleri hybrids) of known major histocompatability complex (mhc) haplotypes were thymectomized at 5-7 days, implanted with mhc-identical or -mismatched (normal or irradiated ) thymuses from 5-week-old larvae and 4 months later injected with dinitro ... | 1982 | 6749529 |
| female sex behaviors in the south african clawed frog, xenopus laevis: gonadotropin-releasing, gonadotropic, and steroid hormones. | | 1982 | 6749641 |
| splenic white pulp as a thymus-independent area in the african clawed toad, xenopus laevis. | an indirect immunofluorescence study of the frozen sections of the spleen of an anuran amphibian, xenopus laevis, showed that lymphocytes bearing a small amount of immunoglobulin (ig) were localized mostly in the white pulp of non-immunized toads. there were fewer fluorescent cells in the red pulp. in the toads hyperimmunized with human gamma globulin (hgg), cells with strong cytoplasmic fluorescence increased significantly in the outer part of the white pulp. electron microscopy of spleens from ... | 1982 | 6751550 |
| thymocyte precursors in early-thymectomized xenopus: migration into and differentiation in allogenic thymus grafts. | in an anuran amphibian, xenopus laevis, thymectomy of 4-day-old larvae abrogates t-cell dependent immune responsiveness. when such early-thymectomized (tx) diploid frogs were implanted with histocompatible triploid thymuses and grafted 8 weeks later with skin from third-party donors, the grafts were rejected relatively normally in 20-27 days. microspectrophotometric determination of ploidy 3-5 months after thymus reconstitution revealed that most thymocytes were donor-derived. in contrast, when ... | 1982 | 6751892 |
| immunological localization of a major karyoskeletal protein in nucleoli of oocytes and somatic cells of xenopus laevis. | oocyte nuclei of xenopus laevis contain two major karyoskeletal proteins characterized by their resistance to extractions in high salt buffers and the detergent triton x-100, i.e. a polypeptide of 68,000 mol wt which is located in the core complex-lamina structure and a polypeptide of 145,000 mol wt enriched in nucleolar fractions. both proteins are also different by tryptic peptide maps and immunological determinants. mouse antibodies were raised against insoluble karyoskeletal proteins from xe ... | 1982 | 6752154 |
| dissection of a replication origin of xenopus dna. | a previously cloned 503-base pair (bp) ecori segment of genomic dna from xenopus laevis selected for enhancement of replication of its vector plasmid was moved to the ecori site of pbr322. this plasmid designated pjcc31 and five other clones, which were made by cleaving the 503-bp segment in relation to a dispersed repeated sequence and subcloning, were compared with pbr322 for replication by microinjection into xenopus eggs. the replication measured by incorporation of a 32p-labeled nucleotide ... | 1982 | 6752953 |
| immunogenetic aspects of in vivo allotolerance induction during the ontogeny of xenopus laevis. | this study describes the ontogeny of allograft immunity in a partially inbred strain of frogs (xenopus laevis). at various times during the frogs' premetamorphic, perimetamorphic, and postmetamorphic life, major histocompatibility complex (mhc) homozygous strain jj xenopus (mhc haplotype j) were grafted with skin from adult donors of defined mhc homozygous (j,f) and heterozygous (j/f,f/h) haplotypes. this protocol reveals that destructive allograft reactivity to mhc alloantigens in xenopus matur ... | 1982 | 6754587 |
| establishment of mammalian cell lines containing multiple nonsense mutations and functional suppressor trna genes. | we describe the generation of mammalian cell lines carrying amber suppressor genes. nonsense mutants in the herpes simplex virus thymidine kinase (hsv tk) gene, the escherichia coli xanthine-guanine phosphoribosyl transferase (eco-gpt) gene and the aminoglycoside 3' phosphotransferase gene of the tn5 transposon (npt-ii) were isolated and characterized. each gene was engineered with the appropriate control signals to allow expression in both e. coli and mammalian cells. expression in e. coli made ... | 1982 | 6760983 |
| sequences of four trna genes from caenorhabditis elegans and the expression of c. elegans trnaleu (anticodon iag) in xenopus oocytes. | four trna genes have been identified in cloned segments of caenorhabditis elegans dna by trna hybridisation and expression after injection into xenopus laevis oocyte nuclei. from dna sequencing these are (with dna anticodon sequences) trnaasp (gtc), trnaleu (aag), trnalys (ctt) and trnapro (tgg). their flanking dna sequences are compared. two identical trnalys (ctt) genes from different regions of the genome have quite unrelated 5' flanking sequences. the trna synthesised in xenopus oocytes afte ... | 1982 | 6761649 |
| an immunocytochemical method for the visualization of tubulin-containing structures in the egg of xenopus laevis. | tubulin can be isolated and purified from xenopus laevis eggs through modification of olmstedt's (1970) tubulin isolation method, viz. by repeating the vinblastin precipitation step after resuspension of the sediment in a detergent-containing stabilizing medium. by this we overcome the deleterious influence of the yolk granules in the isolation procedure. from 11 of xenopus laevis eggs 25 mg vb-paracrystals can be obtained. the apparent molecular weight of the purified tubulin is 52,800. antiser ... | 1982 | 6762372 |
| active polypeptide fragments common to prokaryotic, eukaryotic, and mitochondrial dna polymerases. | with a procedure that allows the renaturation of the dna polymerase catalytic activity in situ after sds-polyacrylamide gel electrophoresis, we have compared the active polypeptides present in extracts from organisms covering a wide evolutionary range from prokaryotes to eukaryotes, namely: escherichia coli, oryza sativa, daucus carota , neurospora crassa, dictyostelium discoideum, saccharomyces cerevisiae, ceratitis capitata, leucophaea maderae , xenopus laevis, rat tissues and human lymphoblas ... | 1982 | 6765191 |
| 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 |
| drosophila nuclei replicate in xenopus eggs. | nuclei isolated from a permanent cell line derived from drosophila melanogaster embryos have been injected, along with a radioactive dna precursor [3h]ttp, into xenopus laevis eggs. in culture, less than 7% of the cells were in s phase. after a 90 min incubation, following injection into eggs, 99% of the nuclei were shown by autoradiography to have synthesized dna. in a similar experiment, a density label brdutp was injected into eggs along with the nuclei. subsequent analysis on caesium chlorid ... | 1980 | 6768826 |
| intracellular ph in early xenopus embryos: its effect on current flow between blastomeres. | 1. electrophysiological techniques were used to monitor the flow of electric current from one cell to the next in xenopus laevis embryos between the 4-cell and early blastula stages of development. intracellular ph and blastocoel ph were determined using ph-sensitive micro-electrodes. 2. the resting intracellular ph was 7.74+/-0.02 (s.e. of mean, n = 29); there were no systematic differences between developmental stages. blastocoel cavity ph was 8.4+/-0.06 (s.e. of mean, n = 10). the intracellul ... | 1980 | 6770084 |
| the determination of genome size in male and female germ cells of drosophila melanogaster by dna-feulgen cytophotometry. | the amounts of dna in haploid and diploid cells of drosophila melanogaster have been determined by dna-feulgen cytophotometry, using xenopus laevis erythrocyte nuclei as a reference standard. the haploid male genome is estimated to be 0.18 pg dna and the haploid female genome, 0.20 pg dna. | 1980 | 6771237 |
| the identification of messenger rna coding for immunoglobulin heavy and light chains of xenopus laevis. | total poly(a)-containing mrna isolated from xenopus spleens was translated in a rabbit reticulocyte lysate in vitro protein-synthesizing system. approx. 1% of the radioactivity incorporated into the protein was precipitated by an antibody directed against adult xenopus igm. the immunoprecipitated proteins were characterized as igm heavy and light chains by their molecular weight as determined by polyacrylamide-sodium dodecyl sulfate gel electrophoresis the sequence variability of the synthesized ... | 1980 | 6772222 |
| the role of thyroxine in the transition of vitellogenin synthesis from noninducibility to inducibility during metamorphosis in xenopus laevis. | | 1980 | 6772502 |
| increased ornithine decarboxylase activity during meiotic maturation in xenopus laevis oocytes. | | 1980 | 6776957 |
| sds-polyacrylamide gel electrophoresis of isolated cortices of xenopus laevis eggs. | outer cytoplasmic membranes of xenopus laevis eggs were isolated by manual dissection. cortices of unfertilized eggs and membranes of fertilized stages were subjected to sds-polyacrylamide gel electrophoresis. the coomassie-blue stained gels of membranes from unfertilized eggs and fertilized stages showed 21 and 17 major bands, respectively, covering a molecular weight range of 27000 - 275000 daltons. to demonstrate their purity, the preparations were examined by light and electron microscopy an ... | 1980 | 6777051 |
| isolation and characterization of the hatching enzyme from the amphibian, xenopus laevis. | | 1981 | 6784682 |
| location and release of trh and 5-ht from amphibian skin. | the occurrence and release of thyrotrophin-releasing hormone (trh) and 5-hydroxytryptamine (5-ht) from amphibian skin have been described by previous investigators. in the present study, the precise location and site of release of trh and 5-ht from the skin of rana pipiens and xenopus laevis have been examined using a combination of procedures including immunohistochemistry, hplc, and radioimmunoassay. the results indicate that trh is located specifically within the dermal glands of these specie ... | 1981 | 6784937 |
| [histochemical localization of carbonic anhydrase in flask cells of the clawfrog mesonephros (xenopus laevis daudin) (author's transl)]. | carbonic anhydrase activity was demonstrated in the flask cells of intermediate segments and collecting tubules of the clawfrog-mesonephros with the cobalt-bicarbonate method of häusler (1958) and hansson (1967). additional the luminal surface of proximal and distal convoluted tubules reacted positively. by electron microscopy the enzyme activity in the flask cells was localized mainly on the surface of microvilli like cytoplasmic processes which lined the lumen of intracellular secretion capill ... | 1981 | 6791445 |
| poor evidence for insulin/insulin-like immunoreactivity in the cns of lower vertebrates. | the localization of insulin/insulin-like immunoreactivity was studied in the brain and the pancreas of an amphibian (clawed frog [xenopus laevis daudin]) and in the cns of two teleost fishes (bream [abramis brama l.] and rudd [scardinius erythrophthalmus l.] using the indirect immunofluorescence technique. with exception of cerebellar purkinje cells no neuronal elements were found to contain insulin-like material. the frog pancreas was characterized by a strong immunofluorescence in cells produc ... | 1981 | 6795888 |
| early events in the development of the immune system of xenopus laevis: characterization of lymphocytes in two-day-old embryos. | | 1981 | 6797849 |
| a comparative ultrastructural and physiological study on melanophores of wild-type and periodic albino mutants of xenopus laevis. | pigment of tail-fin melanophores in periodic albino xenopus laevis tadpoles is dispersed in response to darkness and to alpha-msh in a manner similar to wild-type melanophores. however, periodic albino tadpoles lack the response to different background conditions and the melatonin-induced aggregation in darkness. the tyrosinase activity in cells of the latter type tadpoles is weak compared to the wild-type cells. ultrastructural examination of melanophores from periodic albino mutants and cells ... | 1982 | 6800656 |
| the amphibian epidermis: distribution of mitochondria-rich cells and the effect of oxytocin. | it is known that the ion-transporting capacity and the permeability to water of amphibian skins vary greatly both between and within species. furthermore, the extent to which different skins respond to hormonal stimulation of these parameters also shows considerable inter- and intra-specific variation. as a first step towards defining a possible morphological basis for this physiological heterogeneity, we examined different regions of skins from 3 anurans, bufo bufo, rana ridibunda and xenopus l ... | 1981 | 6801063 |
| comparative acid phosphatase distribution in the suprarenal gland of discoglossus pictus, xenopus laevis and bufo bufo (anurans, amphibia). | acid phosphatase activity was found to have a similar distribution in the suprarenal glands of discoglossus pictus, xenopus laevis and bufo bufo (anurans, amphibia) as determined by light and electron histochemical localization. the enzymatic activity is localized in the lysosomes of both the interrenal cells and the chromaffin cells. it is, moreover, positive on the granule membranes of the adrenaline cells whereas it appears only occasionally on the granule membranes of the noradrenaline cells ... | 1981 | 6802124 |
| isolation and characterization of multiple components of basic gonadotropin from bullfrog (rana catesbeiana) pituitary gland. | four gonadotropin components were purified from the basic protein fraction of bullfrog pituitary glands. all the components had high potencies not only in the ovulation assay using xenopus laevis ovaries but also in the competitive binding assay for rat follicle-stimulating hormone (fsh) using xenopus laevis testis. the isoelectric points of the four components determined by isoelectric focusing were at ph 8.8, 9.0, 9.1, and 9.3, respectively. no appreciable difference in the physical and chemic ... | 1981 | 6802808 |
| synthesis and maturation of xenopus laevis methionine trna gene transcripts in homologous cell-free extracts. | a cloned initiator methionine trna gene from xenopus laevis has been transcribed in cell-free extracts (s-100) prepared from cultured x. laevis kidney cells. rna polymerase iii produces two primary transcripts of this gene which initiate with a pppg and a pppa located seven and four nucleotides, respectively, in front of the mature trnamet1 5' end. both terminate with a dt5 tract just beyond the nucleotides encoding the mature trna. the trna precursors are readily processed in vitro to mature le ... | 1982 | 6802833 |
| development of harderian gland during metamorphosis in anurans. | development of harderian gland of larvae of rana japonica, bufo bufo japonicus, and xenopus laevis was studied. in the adult animals, well-developed harderian glands were invariably present in the orbit. in rana and bufo, the gland first appeared at late prometamorphic stage and in xenopus it appeared around climax stage. in thyroidectomized tadpoles of bufo and rana, the harderian gland was induced by thyroxine. in hypophysectomized tadpoles of bufo the gland developed when they were treated wi ... | 1982 | 6803615 |
| correlation among the changes in the levels of thyroid hormones, thyrotropin and thyrotropin-releasing hormone during the development of xenopus laevis. | the influence of thyroid hormones on neurogenesis suggested that these hormones might affect the maturation and development of neural centers which ultimately regulate thyroid function. changes in the levels of the thyroid hormones, thyrotropin and the thyrotropin-releasing hormone in 'brain' and 'thyroid' fractions were, therefore, correlated at several developmental stages. all hormones showed increases from their initial detection through metamorphosis. the thyroid hormones were observed earl ... | 1982 | 6804283 |
| carbon dioxide reversibly inhibits meiosis of xenopus laevis oocyte and the appearance of the maturation promoting factor. | | 1982 | 6804286 |
| effects of fenitrothion and carbaryl on xenopus laevis development. | when xenopus laevis embryos were treated with fenitrothion, a substantial proportion failed to survive to hatching only when the concentration approached saturation. however, after exposure to 10 ppm of fenitrothion, most were abnormal and did not survive past feeding stage. different embryonic stages were not equally sensitive to fenitrothion and the greatest sensitivity was observed at gastrulation. the most common visible abnormalities were altered body shape, including microcephaly, and edem ... | 1981 | 6805100 |
| pepsin and trypsin activity in the fore gut of metamorphosing xenopus laevis larvae. | | 1981 | 6806130 |
| changes in mitochondrial respiration during the development of xenopus laevis. | mitochondria isolated from xenopus laevis embryos at various developmental stages show a good oxidative capacity and an acceptable respiratory control provided that certain requirements are fulfilled. the rates of respiration with pyruvate and krebs' cycle intermediates, especially with citrate and isocitrate, are very low during cleavage stages and increase after gastrulation. glutamate in the presence of malate is the only substrate to be readily oxidized during early development and its rate ... | 1982 | 6811140 |
| a polypeptide domain that specifies migration of nucleoplasmin into the nucleus. | nucleoplasmin is the most abundant protein of the nucleus of xenopus laevis oocytes. it rapidly enters the nucleus after being injected into oocyte cytoplasm. partial proteolysis of the nucleoplasmin pentamer reveals two structural domains within each subunit: a relatively exposed "tail" and a protected "core." when all the "tails" have been removed from the pentamer the residual "core" remains pentameric. this pentameric core fails to enter the nucleus, remaining stably in the cytoplasm. a sing ... | 1982 | 6814762 |
| aldosterone-induced proteins in renal epithelia. | similar aldosterone-induced proteins have been demonstrated in two renal epithelia, the urinary bladder of the toad, bufo marinus, and epithelia formed by cells of the a6 line derived from the kidney of the toad, xenopus laevis. the proteins are induced along with the stimulation of na+ transport but their synthesis is not dependent on na+ transport per se. in view of the similar characteristics of the aldosterone-induced proteins in these two different epithelia, we suggest that they may have a ... | 1982 | 6816293 |
| [development of the adenylate cyclase activity of the embryonic chorda-mesoderm and endoderm during the migration of primordial germ cells in xenopus laevis (anuran amphibian)]. | in the embryo of xenopus laevis, adenylate cyclase activity is higher in the chorda-mesoderm than in the endoderm. the peak of activity in the chorda-mesoderm is observed at the beginning of the migration of the primordial germ cells (pgc). there could be a correlation between the adenylate cyclase activity of the chorda-mesoderm and the intraendodermic migration of the pgc. | 1982 | 6816405 |
| kinetic properties of arginase from xenopus laevis. | 1. arginase from the liver of xenopus laevis has a michaelis constant (km) for arginine of 42 mm, a minor component having a km of 29 mm. the km is independent of ph in the range of 7.0-11.0 and also independent of manganese ion concentration. 2. manganese is required for activation, showing an optimum at 50 mm with inhibition at higher concentrations. 3. the enzyme is inhibited by high concentrations of the substrate l-arginine and by l-lysine and l-ornithine in a competitive manner with respec ... | 1982 | 6816505 |
| the nucleotide sequence of phenylalanine trna of xenopus laevis. | the nucleotide sequence of xenopus laevis phenylalanine trna extracted from oocytes was determined to be: pgccgaaauam2gcucm1ag ddgggagagcm22 g psi psi agacmugmaaya psi c uaaagm7gdcm5ccuggt psi cgm1aucccgg guuucggcaccaoh. this result was achieved by analysing, with classical procedures [6], the oligonucleotides obtained after digestion by t1 or pancreatic ribonuclease. this sequence is identical to the mammalian sequence. it has been entirely conserved during 10(8) years, the time lapse between t ... | 1982 | 6817827 |
| biochemical studies of xenopus laevis lymphocytes surface immunoglobulins. | cell surface immunoglobulins of adult xenopus laevis splenic small lymphocytes were analysed utilizing direct immunofluorescent staining and lactoperoxidase-catalysed radioiodination followed by immunoprecipitation of ig molecules and characterization on sds-page. nearly 30% of splenic lymphocytes are surface ig positive. the hmw and lmw ig classes are present on the surface of 23% and less than 5% of the cells, respectively. the mu chains of membrane hmw ig have an apparent m.w. of 84,000 versu ... | 1982 | 6819167 |
| [demonstration of maturation promoting factor activity in saccharomyces cerevisiae]. | microinjection of a crude yeast extract into fully grown immature xenopus laevis oocytes induces the reinitiation of meiotic maturation as does xenopus laevis oocyte mpf (maturation promoting factor) by itself. using several strains of yeast exhibiting temperature sensitive cell cycle block (cdc), it was observed that yeast extract exhibits mpf activity only when obtained during the time interval from the g2 period to the metaphase. this observation stresses eucaryotic ubiquity of mpf. | 1982 | 6820313 |
| the effect of calcium ion perturbation on the morphology of cells isolated from early embryos of xenopus laevis. | | 1982 | 6821013 |
| translation and assembly of hla-dr antigens in xenopus oocytes injected with mrna from a human b-cell line. | hla-dr antigens are polymorphic cell surface glycoproteins, expressed primarily in b lymphocytes and macrophages, which are thought to play an important role in the immune response. two polypeptide chains, alpha and beta, are associated at the cell surface, and a third chain associates with alpha and beta intracellularly. rna isolated from the human b-cell line raji was injected in xenopus laevis oocytes. immunoprecipitates of translation products with several monoclonal antibodies revealed the ... | 1982 | 6821356 |
| multiple forms of dna-dependent rna polymerases in xenopus laevis. properties, purification, and subunit structure of class iii rna polymerases. | the class iii rna polymerases present in xenopus laevis tissues were solubilized and partially purified by ion exchange chromatography. single chromatographic species were detected in extracts from ovary, liver, and a kidney-derived cultured cell, whereas two chromatographic forms were detected in liver extracts. all class iii enzymes analyzed exhibited characteristic responses to ionic strength changes, synthetic polynucleotide templates, and alpha-amanitin. these chromatographic and catalytic ... | 1983 | 6822542 |
| regulation of synaptic position, size, and strength in anuran skeletal muscle. | an analysis of the physiology, morphology, and position of endplates on identified fibers in the xenopus laevis pectoralis muscle has revealed the following. 1. the percentage of fibers with one endplate is lower in large muscles, and within the same muscle, singly innervated fibers are smaller than dually innervated fibers. 2. single junctions tend to be stronger than junctions on dually innervated fibers. 3. single junctions typically are located near the middle of their fibers, while the endp ... | 1983 | 6822853 |
| order in the initial retinotectal map in xenopus: a new technique for labelling growing nerve fibres. | retinal nerve fibres form an orderly map of visual space in several centres in the vertebrate brain. such topographic maps are a common feature of central nervous system organization, yet the way in which they develop is poorly understood. early nerve projections in the fetal and neonatal mammalian brain have been found in several cases to be less restricted than those in the adult, suggesting that nerve fibres may initially form a diffuse set of connections in their target structure from which ... | 1983 | 6823290 |
| abnormal visual input leads to development of abnormal axon trajectories in frogs. | throughout the normal vertebrate brain, visual maps form the left and right eyes overlap and are in register with one another. visual input has a major role in the development of the pathways which mediate these binocular projections. a dramatic example of the developmental role of sensory input occurs in the isthmo-tectal projection, which is part of the polysynaptic relay from the eye to the ipsilateral tectum of the frog, xenopus laevis. if one eye is rotated when the animal is still a tadpol ... | 1983 | 6823306 |
| the xenopus laevis globin gene family: chromosomal arrangement and gene structure. | clones containing nine different larval and adult globin genes have been isolated from two genomic libraries of xenopus laevis. they encompass three distinct dna regions: a 70 kb region containing five genes in the order 5'-alpha lla-alpha llb-alpha al-beta al-beta lla-3', all with the same transcriptional polarity; a 40 kb region with three genes, 5'-alpha llla-alpha lllb-alpha all-3', again with the same polarity; and a 10 kb segment comprising the beta llla gene only. the beta all gene has no ... | 1983 | 6825173 |
| the phosphorylation of ribosomal protein s6 from progesterone-stimulated xenopus laevis oocytes. kinetic studies and phosphopeptide analysis. | xenopus laevis oocytes were prelabeled with [32p]orthophosphate overnight before maturation was induced by progesterone stimulation. the phosphorylation status of ribosomal protein s6 from control oocytes and the temporal changes in s6 phosphorylation after progesterone treatment were analyzed by two-dimensional gel electrophoresis. s6 protein was separated in up to five distinct s6 species, which differed in their degree of phosphorylation. 32p labeling of s6, as judged from the shift of radioa ... | 1983 | 6825671 |
| changes in d-loop frequency and superhelicity among the mitochondrial dna molecules in relation to organelle biogenesis in oocytes of xenopus laevis. | changes in mitochondrial dna (mtdna) replication activity are known to occur during oogenesis in xenopus laevis. electron microscopic and electrophoretic analyses carried out on mtdna molecules at different vitellogenic stages show that 1. the frequency of displacement loop (d-loop) forms is correlated with the intensity of mitochondrial biogenesis. 2. most of the native molecules as well as the d-loop carrying ones are superhelical. 3. four families of different superhelicity may be distinguish ... | 1983 | 6825715 |
| lens forming transformations in larval xenopus laevis induced by denatured eye-cup or its whole protein complement. | implants of lensectomized eye placed between the outer and inner cornea, denatured by ethanol treatment and implants of total protein pellets from homogenates of lensectomized eyes, induce lens-forming transformations of the outer cornea of larval xenopus laevis. | 1983 | 6825801 |
| classification of dna polymerase activities from ovaries of the frog, xenopus laevis. | four distinct dna polymerase activities were isolated from ovaries of the frog xenopus laevis. specific assays for each activity were established. the isolated activities were characterized by molecular weight, template-primer preferences, and sensitivity to specific inhibitors as xenopus laevis ovarian dna polymerases-alpha 1, -alpha 2, -beta, and -gamma. all previously described xenopus laevis dna polymerases were classified using these properties. | 1983 | 6825948 |
| a microscope perfusion respirometer for continuous respiration measurement of cultured cells during microscopic observation. | the construction of a microscope perfusion respirometer (mpr) for simultaneous recording of cellular respiration and microscopic morphology is described. all light microscope techniques for living cells (e.g. phase contrast, differential interference contrast (dic), fluorimetry) can be applied to the monolayer cells grown on a coverslip. the main constituents of the mpr are a) a precision operating perfusion pump (constant volume output), b) a modified dvorak-stotler perfusion chamber, c) a spec ... | 1983 | 6828001 |
| the degradation of urate in liver peroxisomes. association of allantoinase with allantoicase in amphibian liver but not in fish and invertebrate liver. | allantoinase and allantoicase were co-purified from frog (rana catesbeiana) liver. the ratio of the two enzyme activities remained constant during purification and was unchanged by a variety of treatments of the purified enzyme. these results suggest that allantoinase and allantoicase are located in the same protein. it was found that the two hepatic enzyme activities are also associated with the same protein in other frogs (xenopus laevis and rana nigromacultata), tadpoles (r. catesbeiana), and ... | 1983 | 6833275 |
| a transcriptional function for the repetitive ribosomal spacer in xenopus laevis. | the function of the xenopus laevis ribosomal spacer has been studied in vivo and by microinjection of in vitro mutants into xenopus oocytes. it is shown that the spacer directs specific rna transcripts which most probably terminate upstream of the ribosomal genes and that it is able to modulate transcription of these genes. the data lead to a model in which the ribosomal spacer is a loading site for rna polymerase i and spacer transcription is the driving force by which polymerase is delivered t ... | 1983 | 6835360 |
| [effect of piracetam and gamma-aminobutyric acid on defensive conditioned reflexes in xenopus laevis]. | | 1983 | 6837151 |
| endogenous electrical current leaves the limb and prelimb region of the xenopus embryo. | the electrical current pattern around the developing xenopus laevis embryo was mapped with a vibrating probe. current (taken as the movement of positive charge) was found to leave the emerging hind limb bud and to enter the gill region of the stage 47 embryo. the magnitude of the current leaving the limb was about 7 microa/cm2 and the current entering the gill was about 60 microa/cm2. other regions of smaller outward current were found between the limb and gill. at stage 43, prior to the appeara ... | 1983 | 6840399 |
| the cell masses in the brainstem of the south african clawed frog xenopus laevis: a topographical and topological analysis. | | 1983 | 6841669 |
| thiosemicarbazide-induced osteolathyrism in metamorphosing xenopus laevis. | exposure of xenopus laevis tadpoles to thiosemicarbazide (tsc), at concentrations from 10 to 75 mg/liter, causes an inhibition of metamorphosis and produces the classic manifestations of the experimental disease, osteolathyrism. concentration-dependent effects of tsc exposure are observed in growth rate and in the severity of the osteolathyrogenic effect. concentrations allowing the most rapid growth produce the more extreme osteolathyrogenic defects. osteolathyrism in these animals is identical ... | 1983 | 6842158 |
| determination of the rate of rrna synthesis in xenopus laevis triploid embryos produced by low-temperature treatment. | triploid embryos of xenopus laevis were obtained by cold-temperature shocking of the fertilized eggs, and the rate of the ribosomal rna (rrna) synthesis was determined for comparison with that in diploid embryos. for this purpose, both triploid and diploid embryos were dissociated into cells at the neurula stage, and then labeled with (3h)uridine for varying lengths of time. the rate of rrna synthesis, as estimated after determination of (3h)utp specific radioactivity and the total label incorpo ... | 1983 | 6842162 |
| clonal organization of the central nervous system of the frog. iii. clones stemming from individual blastomeres of the 128-, 256-, and 512-cell stages. | horseradish peroxidase injected into individual blastomeres of 128-, 256-, and 512-cell embyros of xenopus laevis was identified in cells of the central nervous system (cns) at early to middle larval stages. labeled cells were dispersed, mingled with unlabeled cells. four boundaries in the cns could be defined by the behavior of clones of labeled cells: in the transverse plane at the level of the isthmus; in the horizontal plane between dorsal and ventral regions extending the entire length of t ... | 1983 | 6842280 |
| some characteristics of thymus suppression of antibody production in vitro in xenopus laevis, the south african clawed toad. | organ cultures were used to test whether thymus suppression of antibody production by spleen cells of xenopus laevis is antigen inducible, antigen specific, or genetically restricted when a thymus-dependent (td) antigen, horse erythrocytes (hrbc), is injected in vivo. the capacity of mammalian thymus-independent (ti) antigens, e.g. tnp-ficoll (ti-2) and tnp-lps (ti-1) to induce thymus suppression of the anti-hrbc) response was also tested. additionally, the susceptibility of ti spleen responses ... | 1983 | 6845406 |
| the accumulation of the maternal pool of histone h1a during oogenesis in xenopus laevis. | the accumulation of the maternal pool of histone h1a in xenopus laevis oocytes was measured by the use of a semi-quantitative immunoradiographic method. this method implies the size-fractionation of total basic protein extracts from oocytes on a polyacrylamide gel, blotting of the proteins to diazotized paper and detection of histone proteins on the blots with the aid of antibodies to histone h1a and of [125i]protein a. it is shown that the maternal h1a pool that is present in fully-grown oocyte ... | 1983 | 6850837 |
| subcellular distribution in xenopus laevis oocytes of a microinjected poly(a)-binding protein from artemia salina gastrulae. | the poly(a)-binding protein p38 of non-polysomal mrnp from artemia salina gastrulae was labelled by reductive methylation and microinjected into the cytoplasm of xenopus laevis oocytes. the labelled protein has a half-life of approximately 20 h and accumulated in the nucleus of the oocyte. the kinetics of accumulation reached a plateau at about 15 h after microinjection. p38 accumulates in the nucleus to a final concentration 3.15 times higher than that reached by free diffusion. this fact sugge ... | 1983 | 6852017 |
| secretion of plant storage globulin polypeptides by xenopus laevis oocytes. | xenopus oocytes injected with poly(a)-containing rna from developing cotyledons of field beans (vicia faba l. var. minor) synthesize precursor polypeptides to the major storage globulins legumin and vicilin. these polypeptides are secreted into the medium without proteolytic cleavage of the legumin propolypeptides into the mature disulfide-linked alpha and beta chains. similarly, storage globulin polypeptides from pea (pisum sativum l.) and french bean (phaseolus vulgaris l.) were secreted from ... | 1983 | 6852043 |
| transcriptional activity in previtellogenic oocyte germinal vesicles from xenopus laevis. | we have isolated germinal vesicles from previtellogenic xenopus oocytes on a scale suitable for biochemical studies. the organelles were active in rna synthesis, mainly mediated by endogenous rna polymerase i. nascent transcripts were 5-18s in size and complementary to dna sequences present at intermediate reiteration frequency (several hundred copies per haploid genome). hybridization to cloned 5s and 40s ribosomal genes demonstrated that the in vitro transcripts contained the latter, but not t ... | 1983 | 6852126 |
| rod photoreceptor disc shedding in eye cups: relationship to bicarbonate and amino acids. | we previously demonstrated that disc shedding in eye cups from xenopus laevis depends on medium bicarbonate concentration, but also found that other unidentified medium components influenced the response. here, in order to determine which medium components influence shedding, we used high bicarbonate salt solutions supplemented with medium components in amphibian tissue culture medium. compared to the high bicarbonate salt solution alone, addition of fetal bovine serum or whole egg ultrafiltrate ... | 1983 | 6852133 |
| effects of inducers on inner and outer gastrula ectoderm layers of xenopus laevis. | gastrula ectoderm, isolated from xenopus laevis, was cultured in holtfreter solution or modified leibovitz medium (l-15) by the sandwich-method with or without inducer. the ectoderm (sd cell layers) consisted of two cell sheets, representing a superficial (s) and a deep (d) layer. in the l-15 medium rather than in holtfreter solution, the two cell layers separate out into distinct cell masses. this difference in cell affinity under certain experimental conditions could indicate that the deep lay ... | 1983 | 6852404 |
| can differences in limb regeneration ability between individuals within certain amphibian species be explained by differences in the quantity of innervation? | in some species of amphibians, the regenerative response to limb amputation is not uniform. for example, regenerative ability varies from one individual to another within the species xenopus laevis, ambystoma maculatum, and amphiuma tridactylum. in many species, limb regenerative ability declines with increasing age. the objective of this investigation was to determine if this variation in regenerative ability can be explained by variation in the quantity of innervation. in each of the above-nam ... | 1983 | 6854257 |
| regular arrangement of nucleosomes on 5s rrna genes in xenopus laevis. | the chromatin structure of the oocyte-type 5s rna genes in xenopus laevis was investigated. blot hybridization analysis of dna from micrococcal nuclease digests of erythrocyte nuclei showed that 5s dna has the same average nucleosome repeat length, 192 +/- 4 base pairs, as two xenopus satellite dnas and bulk erythrocyte chromatin. the positions of nuclease-sensitive regions in the 5s dna repeats of purified dna and chromatin from erythrocytes were mapped by using an indirect end-labeling techniq ... | 1983 | 6855773 |
| transmission of integrated sea urchin histone genes by nuclear transplantation in xenopus laevis. | sea urchin histone genes contained in a recombinant plasmid psp102 were microinjected into the cytoplasm of fertilized eggs of xenopus laevis. by the late blastula stage, plasmid dna sequences were detected comigrating with the high molecular weight cellular dna (greater than 48 kilobases). analysis of the dna from injected embryos digested with various restriction endonuclease demonstrated that the injected dna was integrated into the frog genome. clones of embryos containing the psp102 dna seq ... | 1983 | 6857265 |