Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| events in the germ cell lineage after entry of the primordial germ cells into the genital ridges in normal and u.v.-irradiated xenopus laevis. | 1977 | 591877 | |
| variability among laboratories in the occurrence of functional modification in the intertectal visual projection of xenopus laevis [proceedings]. | 1977 | 592182 | |
| ultrastructural study on hepatic melanin in xenopus laevis. | the livers of xenopus laevis, grouped by chronological age (0.5, 2 and 3 yrs), were studied electron microscopically. ultrastructurally most of the melanin granules in the mature female liver showed an internal structure similar to the melanin granules of the oocytes. the hepatic melanin granules of immature females and of all males were pleomorphic and failed to show the characteristic internal structure similar to those of the oocytes. the oocyte is the probable source of most of the hepatic m ... | 1977 | 597850 |
| abnormalities in the visual system of xenopus after larval optic nerve section. | one optic nerve was cut in a series of larval xenopus laevis; in approximately half of these the corresponding eye was also rotated. the resultant primary visual projections were mapped in the adult. although in most cases the projections were retinotopically normal, some of them were not. these abnormal projections were consistently associated with a very thin optic nerve which reached the tectum via the oculomotor route. animals with rotated eyes which developed retinotopically organised prima ... | 1977 | 598434 |
| comparison of cell division and cell sizes in normal embryos and lithium-induced exogastrulae of xenopus laevis. | 1977 | 605749 | |
| electron microscopic studies of the developing amphibian thymus. | electron-microscopic studies of larval xenopus laevis thymus at three different stages of development are presented. studies of thymus from 5 and 8 day old larvae (ages when early thymectomy is performed) reveal a relatively undifferentiated rudiment composed of epithelial cells and lymphoid cell precursors. these findings are in marked contrast to ultrastructural observations of 30 day old larval thymus, where there exists a well defined corticomedullary differentiation with an abundance of sma ... | 1977 | 612468 |
| antibody-dependent cellular cytotoxicity in poikilotherms. | 51cr-chromate labelled chicken red blood cells, treated with rabbit (anti-chicken red blood cell) serum, are lysed in vitro, in the absence of complement, by spleen cells from xenopus laevis, ambystoma mexicanum or lacerta viridis. optimal conditions for lysis by xenopus spleen cells were determined. the phenomenon seems homologous with antibody-dependent cellular cytotoxicity (adcc) mediated by mammalian or avian k cells. the phylogenetic significance of the finding is discussed. | 1977 | 612470 |
| existence of ultraviolet-labile germ cell determinant in unfertilized eggs of xenopus laevis and its sensitivity. | 1977 | 832771 | |
| the effects of biogenic amines on carbohydrate metabolism in xenopus laevis daudin. | 1977 | 832822 | |
| in situ effects of s1 endonuclease (neurospora crassa) on pachytene chromatin of xenopus laevis females at metamorphosis. | 1977 | 837986 | |
| the visual pigment and vitamin a of xenopus laevis embryos, larvae and adults. | 1977 | 838004 | |
| evidence for polarizing zone in the limb buds of xenopus laevis. | 1977 | 838122 | |
| ultrastructural observations on cortical endoplasmic reticulum and on residual cortical granules in the egg of xenopus laevis. | 1977 | 838127 | |
| accumulation of mitochondrial dna during oogenesis in xenopus laevis. | 1977 | 838132 | |
| ribosomal rna synthesis in the eastern north-american newt, notophthalmus viridescens. | ribosomal rna (rrna) synthesis, the initiation of which is an early major event during the transformation of iris into lens in the newt, was characterized in the tvi cell-line derived from the eastern north-american newt notophthalmus viridescens. employing the technique of polyacrylamide gel electrophoresis, molecular-weight measurements were made on newt rrnas using xenopus laevis and e. coli rrnas as standards. the molecular weights of n. viridescens 28s and 18s rrna were found to be 1.4 x 10 ... | 1977 | 838209 |
| changes in the cell coat at the onset of gastrulation in xenopus laevis embryos. | four developmental stages of xenopus laevis embryos were fixed in standard electron microscopic fixatives with 1% lanthanum nitrate added. this treatment reveals a lanthanum staining material (lsm) on the cell surface and in extracellular spaces. morula and blastula stage cells have a small amount of lsm; in blastulae, 3 +/- 3 sd % of the cell surface is coated with lsm. in early gastrulae, 29 +/- 6 sd % of the cell periphery is covered with lsm. in late gastrulae, 82 +/- 13 sd % of the cell per ... | 1977 | 839183 |
| resolution of parameters in the equivalent electrical circuit of the sodium transport mechanism across toad skin. | in amphibian epithelia, amiloride reduces net sodium transport by hindering the entry of sodium to the active transport mechanism, that is, by increasing the series resistance (rser). theoretically, therefore, analysis of amiloride-induced changes in potential differences and short-circuit current should yield numerical estimates of all the parameters in the equivalent electrical circuit of the sodium transport mechanism. the concept has been explored by analysis of such changes in toad skins (x ... | 1977 | 839526 |
| transcription of specific genes in isolated nuclei by exogenous rna polymerases. | mouse plasmacytoma (mopc) 460 cells contain two chromatographic forms of rna polymerase iii (iiia and iiib) in addition to the major class i and ii rna polymerases. nuclei isolated from these cells actively synthesize rna. among the discrete transcription products observed are the 5s and 4.5s rnas and additional low molecular weight rna species (approximately 5.8s, 6.3s, and 6.6s in size). the 4.5s rnas appear to be trna precursors since they can be converted in vitro to 4s rnas. studies with al ... | 1977 | 844100 |
| size of ribosomal dna repeating units in xenopus laevis: limited individual heterogeneity and extensive population polymorphism. | 1977 | 845941 | |
| slow action of ca on myelinated nerve fibres of xenopus laevis. | single myelinated nerve fibres were isolated and the nodal currents were recorded with potential clamp technique. rapid solution changes were performed by use of a recording chamber so shaped that it had a minimal dead space. a volume ten times larger than the dead space flowed past the node within about 20 ms. the half-time of the change in na current (ina)amplitude associated with changes between solutions of different [na]:s was 100-150 ms, whereas the half-time of the change in ina associate ... | 1977 | 848308 |
| studies on the biosynthesis, assembly and secretion of vitellogenin, an oestrogen-induced multicomponent protein. | 1. the process by which the egg-yolk protein precursor vitellogenin is biosynthesized, assembled and secreted by xenopus laevis (south african clawed toad) liver was studied. it was previously shown in other laboratories that vitellogenin contains the two egg-yolk proteins lipovitellin (mol.wt. 140 000) and phosvitin (mol.wt. 35 000). 2. evidence is presented which shows that xenopus liver microsomal fractions synthesize precursors of vitellogenin. these precursors were solubilized from the memb ... | 1977 | 849274 |
| modifications by light of synaptic density in the inner plexiform layer of the toad, xenopus laevis. | 1977 | 849751 | |
| translation and distribution of rabbit globin mrna in separated cell types of xenopus laevis gastrulae. | 1977 | 849804 | |
| rna synthesis in isolated nuclei of xenopus laevis emproyos. | nuclei were isolated from tailbud embryos of xenopus laevis and their rna synthetic activity was studied. the activity was sensitive to actinomycin d, and required the presence of all four ribonucleotide triphosphates and a divalent cation (mg2+ or mn2+). the effect of the divalent cation varied depending on the presence of 0.4 m kcl: in its absence more rna was synthesized with mg2+ than with mn2+, but in its presence the situation was reversed. about 50% of the rna synthesized was sensitive to ... | 1977 | 856273 |
| lectin binding to dissociated cells from two species of xenopus embryos. | 1. fluorescein isothiocyanate-conjugated concanavalin a (f-cona) and soy bean agglutinin (f-sba) bind to the surface of edta-dissociated cells from blastula and gastrula stage xenopus laevis and x. mulleri embryos. 2. binding of these lectins is abolished by appropriate haptens (alpha-methyl-d-mannopyranoside for f-cona and 2-acetamido-2-deoxy-d-galactose for f-sba). 3. gastrula stage cells show a clustering or capping of lectin binding sites not shown by blastula stage cells. 4. at least for f- ... | 1977 | 856477 |
| effect of partial hepatectomy on the interrenal tissues of xenopus laevis (daudin). | partial hepatectomy was carried out on xenopus laevis to investigate its influence on the endocrine system. in addition to other endocrine effects, a marked hypertrophy and stimulation of the interrenal gland was observed. activated cells contain mitochondria with extended and irregularly coiled tubules embedded in a low electron dense matrix. hepatectomy induces two phases of proliferation [3 and 35 days postoperative (p.o.)]. after 106 days p.o. giant mitochondria possessing narrow and closely ... | 1977 | 858162 |
| progesterone-induced dna polymerase activity in full-grown oocytes of xenopus laevis (1). | dna polymerase activity increases in full-grown oocytes of xenopus laevis during in vitro progesterone-induced maturation. this increase is inhibited by cycloheximide. the presence of the oocyte's nucleus (germinal vesicle) seems essential for the induction of this increase: in previously enucleated oocytes, the level of dna polymerase activity does not change during progesterone treatment. furthermore, a new form of dna polymerase is detectable by deae chromatography in in vitro matured oocytes ... | 1977 | 859007 |
| inhibitor of ribosomal rna synthesis in xenopus laevis embryos. vi. occurrence in mature oocytes and unfertilized eggs. | 1977 | 863107 | |
| persistence of oocyte amplified rdna during early development of xenopus laevis eggs. | 1977 | 863108 | |
| histone mrna in xenopus laevis ovaries: identification of the h4 messenger. | rna extracted from ovaries of adult xenopus laevis and introduced into a wheat germ cell-free system, directs the synthesis of polypeptides co-electrophoresing with all five histones. by frationation of total ovary rna through sephadex g-200 and polyacrylamide gel, rna was isolated that is translated into histones 4 (h4) only. in addition, this rna labelled in vitro with [i125] hybridizes to a restriction fragment of cloned sea urchin dna known to contain the h4 gene. | 1977 | 866192 |
| a stereological approach to the study of neural organogenesis in xenopus laevis. | stereological methods are applied to the study of structural changes undergone, during neurulation, by the neuroepithelium of early embryos of xenopus laevis. in light microscopy, we evaluate: the section area of the neuroepithelium, the nucleocytoplasmic ratio, the volume fraction of the intercellular spaces, of the nuclei and of the cytoplasm. in electron microscopy, the volumetric density and the surface ratio of mitochondria as well as the surface density of the endoplasmic reticulum are mea ... | 1977 | 869225 |
| lengths and patterns of transcriptional units in the amplified nucleoli of oocytes of xenopus laevis. | transcriptionally active chromatin from peripheral amplified nucleoli of lampbrush-chromosome stage oocytes of xenopus laevis was dispersed and spread in various solutions of low salt concentrations (including some with additions of detergents) and examined by electron microscopy. nucleolar material from oocytes of animals with normal (2-nu) and mutant (1-nu) genetical constitution of nucleolus organizers was compared. histograms showing the distributions of the length of matrix units, apparent ... | 1977 | 870292 |
| an autoradiographic analysis of nucleic acid synthesis in the presumptive primordial germ cells of xenopus laevis. | microinjection of [3h]thymidine into xenopus laevis embryos between late blastula (stage 10) and early tadpole (stage 44) showed that the presumptive primordial germ cells synthesis dna between stages 10-33. the percentage of labelled cells was highest between stages 10 and 16, declined sharply between stages 22 and 26 and rose again between stages 26 and 33. the fluctuations in the labelling patterns together with increase in the number of presumptive primordial germ cells and direct observatio ... | 1977 | 870589 |
| some morphogenetic features of the adenohypophysical primordium of early xenopus laevis tadpoles. | the adenohypophyses of xenopus laevis tadpoles at developmental stages 20 to 46 (nieuwkoop and faber, 1956) were studied. from its first appearance at about stage 20 to 21, the adenohypophysial primordium passes through four morphogenetic phases, each characterized by internal events. the first phase (stages 20 to about 33/34) is characterized by extensive proliferation of the primordium. during the second phase (stages 33/34 to about 37/38), the growth of the primordium is arrested. this arrest ... | 1977 | 872195 |
| sequential changes in the structure and function of hepatocytes in estrogen-treated xenopus laevis males. | 1977 | 872992 | |
| very long-lived messenger rna in ovaries of xenopus laevis. | 1977 | 873053 | |
| differential accumulation of two size classes of poly(a) associated with messenger rna during oogenesis in xenopus laevis. | 1977 | 873054 | |
| grafting analysis of the periodic albino mutant of xenopus laevis. | 1977 | 873057 | |
| biochemical research on oogenesis: oocytes of xenopus laevis synthesize but do not accumulate 5s rna of somatic type. | 1977 | 873059 | |
| changes in neuromast chemosensitivity in xenopus laevis kept under various environmental conditions. | 1977 | 874416 | |
| changes in protein phosphorylation accompanying maturation of xenopus laevis oocytes. | 1977 | 885290 | |
| purification and characterization of xenopus laevis vitellogenin messenger rna. | 1977 | 885849 | |
| magnesium deficiency in embryos of xenopus laevis. | embryos of xenopus laevis reared in media with various low (less than or equal to 10(-5) m) magnesium ion concentrations will exhibit differing degrees of a potentially lethal magnesium starvation syndrome depending on the ion concentration and rearing temperature. the higher the rearing temperature or the lower the magnesium ion content of the medium the more severely the syndrome will be expressed. (normal development can be expected at temperatures 13-30 degrees c and magnesium ion concentrat ... | 1977 | 886266 |
| the effect of concanavalin-a on the reaggregation of cells dissociated from xenopus laevis early embryos. | the effects of concanavalin-a on the reaggregation and sorting of cells from xenopus laevis early embryos have been studied. the results suggest that at high concentrations, concanavalin-a can prevent reaggregation. | 1977 | 891827 |
| lens regeneration from cornea in tail ectopic eyes of xenopus laevis tadpoles. | 1977 | 891882 | |
| transport of different rna species from the nucleus to the cytoplasm in xenopus laevis neurula cells. | 1977 | 892232 | |
| the sensitivity of xenopus laevis tadpole tail tissue to the action of thyroid hormones. | 1977 | 892410 | |
| biosynthesis, processing, and control of release of melanotropic peptides in the neurointermediate lobe of xenopus laevis. | the neurointermediate lobes of dark-adapted toads xenopus laevis were incubated for 30 min in [3h]arginine and then "chased" for various time periods. by use of this pulse-chase paradigm there were detected 10 trichloroacetic acid (tca)-precipitable peptides separated on acid-urea polyacrylamide gels and one tca-soluble peptide separated by high-voltage electrophoresis (ph 4.9) with melanotropic activity. each of these peptides had a different degree of melanocyte stimulating hormone (msh) activ ... | 1977 | 894250 |
| in vivo repair of the 3'terminus of transfer rna injected into amphibian oocytes. | yeast transfer rna specific for phenylalanine has been treated chemically to remove either one or two nucleotides of its 3' terminus and has been injected into xenopus laevis oocytes to test whether this rna can be repaired in vivo. the results obtained showed that oocytes could aminoacylate and thus repair trnaphe that has lost both its terminal adenosine and 3' phosphate. a similar result was obtained with trnaphe that had undergone two full cycles of 3' terminal nucleotide removal. the oocyte ... | 1977 | 896475 |
| regeneration of the tail of x-irradiated xenopus tadpoles. | the effects of x-rays on the regeneration of the tail of xenopus laevis tadpoles have been studied. larvae of stage 52 were exposed in groups to irradiation either of the head or the body region with doses of 3,000 and 4,000 r. in both cases, the animals have regenerated the lost parts of their tails. | 1977 | 899691 |
| development of the myotomal neuromuscular junction in xenopus laevis: an electrophysiological and fine-structural study. | 1977 | 902924 | |
| slow mechanism for sodium permeability inactivation in myelinated nerve fibre of xenopus laevis. | 1. single myelinated nerve fibres were isolated and the nodal currents were recorded under potential clamp conditions. the effect of membrane potential on the na permeability (pna) mechanism was analysed. 2. the available pna increased slowly during negative polarization of the membrane. the time course of this change was about 10(3) times slower than the time course of the mechanism for the usual pna inactivation (h-system). the slow pna changes could be distinguished from changes in h because ... | 1977 | 903895 |
| treatment of skin-invading capillarid nematode in a colony of south african clawed frogs (xenopus laevis). | 1977 | 904298 | |
| the effect of tolbutamide on early embryos of xenopus laevis. | 1977 | 908419 | |
| purification of a dna-binding protein from xenopus laevis unfertilized eggs. | a dna-binding protein from xenopus laevis unfertilized eggs has been purified to apparent homogeneity. it is a heat stable, lysine-rich protein and has a molecular weight corresponding to 8,200 daltons, measured by sodium dodecyl sulphate gel electrophoresis. the protein, which is active in a monomeric form, stimulates dna polymerase alpha, and binds to single and double stranded dna. one egg contains about 4 x 10(12) molecules (minimum estimate) of the protein; since we calculate that 4 x 10(8) ... | 1977 | 909794 |
| lipid and polypeptide components of the crystalline yolk system from xenopus laevis. | the polypeptide and lipid components of the crystallinelipoprotein-phosphoprotein from the yolk system of xenopus laevis are described. this lipoprotein complex contains 17% lipid of which 75% is phospholipid. the phospholipid fraction consists of mostly phosphatidylcholine and phosphatidylethanolamine. the neutral lipid fraction contains mainly triglyceride. the phosphoprotein, phosvitin, has been separated from the lipoprotein, lipovitellin, by classical methods. three polypeptide chains can b ... | 1977 | 914850 |
| nuclear transplantation from intestinal epithelial cells of early and late xenopus laevis tadpoles. | the aim of these experiments was to test whether the developmental potential of nuclei from intestinal epithelial cells of xenopus laevis tadpoles declined during the life of the functional larval gut. the results of transplantation of nuclei from three different stages of development were compared: stages 46-48, when feeding begins and while yolk is still present but before the formation of the typhlosole; stage 57, just prior to the onset of metamorphic reorganization; and stage 54, an interme ... | 1977 | 915421 |
| retinal growth in double dorsal and double ventral eyes in xenopus. | the growth of normal and surgically produced compound dorsal and ventral retinae in xenopus laevis has been studied autoradiographically following injections of [3h] thymidine at stages 50 and 58. the animals were sacrificed 3 weeks after metamorphosis. the histogenetic pattern of the dorsal and ventral retinal halves was different at the three time points investigated, i.e. up to stage 50, between stages 50 and 58 and between stage 58 and 3 weeks after metamorphosis. asymmetrical dorsal retinal ... | 1977 | 915422 |
| toxicity of n-phenyl-alpha-naphthylamine and hydrazine to xenopus laevis embryos and larvae. | 1977 | 922193 | |
| isolation of globin messenger rna of xenopus laevis. | 1977 | 924017 | |
| kinetics of estrogen induction of xenopus laevis vitellogenin messenger rna as measured by hybridization to complementary dna. | 1977 | 925003 | |
| a method for collecting naturally fertilized eggs of xenopus laevis immediately after laying. | 1977 | 926758 | |
| researches on the development of xenopus laevis larvae fed on tubifex tubifex. i. presence of liposoluble vitamins in the lipid extract from tubifex worms. | vitamin e acetate (alpha-tocopheryl acetate) and related tocopherols, vitamin a acetate (dehydroretinyl acetate), vitamin a alcohol (retinol), and cholesterol were identified by thin-layer chromatography in the lipid extract from tubifex tubifex worms. compounds (perhaps vitamin d precursors, or seroidal substances) absorbing short wave uv light and/or reacting with antimony trichloride were also present but not identified. the results are discussed in relation to the growth, metamorphosis and p ... | 1977 | 576033 |
| changes in the cell surface coat during the development ofxenopus laevis embryos, detected by lectins. | the composition of the surface coat in embryonic cells ofxenopus laevis was examined by agglutination and fluorescent staining with lectins.cells of early and mid gastrula stages were agglutinated by lectins specific for d-mannose, d-galactose, l-fucose, n-acetyl-d-glucosamine and n-acetyl-d-galactosamine. no differences in agglutinability among ectoderm, mesoderm and endoderm cells were observed with lectins specific for d-mannose, d-galactose and n-acetyl-d-galactosamine, though agglutination ... | 1978 | 28305035 |
| melanin synthesis activation dependent on inductive influences. | gene activity in melanin-synthesising cells of albino periodic (ap) mutants ofxenopus laevis is expressed phenotypically in the framework of the following cycle: a period of complete albinism succeeds the short peak of pigmentation, and melanosomes which have formed disappear. skin and choroid coat melanophores as well as pigmented epithelium melanocytes are involved in this cycle.parabiosis experiments allowed hormonal regulation of the melanin-synthesising gene activity to be excluded. neural ... | 1978 | 28305010 |
| time-lapse cinemicrographic analysis of superficial cell behavior during and prior to gastrulation in xenopus laevis. | time-lapse cinemicrography was used to show what changes in the number, size, shape, arrangement and what movements of apices of superficial cells occur during epiboly, extension, convergence and blastopore formation in the blastula or gastrula of xenopus laevis. epiboly of the animal region occurs by apical expansion of superficial cells at a nearly constant rate from the midblastula to the midgastrula stage. egression of deep cells into the superficial layer does not occur. extension of the do ... | 1978 | 30235909 |
| anterograde and retrograde transport of horseradish peroxidase isoenzymes in the retino-tectal fibres of xenopus larvae. | commercial horseradish peroxidase (hrp) was separated into basic and acidic isoenzyme fractions. the ability of each of these two fractions to be taken up and transported by nerve vells was tested in the retino-tectal tract of xenopus laevis at midlarval stages. hrp isoenzymes were injected with a glass micropipette into the eye, while scratching the optic disc to break the axons of ganglion cells leaving the retina. both basic and acidic hrp were taken up by broken optic fibres and transported ... | 1978 | 19605265 |
| a natural heterohaemagglutinin in xenopus laevis serum. | in most adult xenopus laevis the serum contains a 'natural' factor capable of lysing the erythrocytes from a wide variety of amniote species. the factor has no effect on the erythrocytes of another amphibian, ambystoma mexicanum, nor will serum from one animal lyse red cells from another xenopus individual. no lysing factor was present in the serum of larval (tadpole) xenopus. heating of xenopus serum to 56 degrees for 30 min, absorption of the serum with zymosan or inulin, or removal of calcium ... | 1978 | 580428 |
| na+/k+-dependent adenosinetriphosphatase activity in the skin, kidney and muscle in xenopus laevis (daud.) adult specimens under different experimental conditions. | xenopus laevis adult specimens were exposed to environmental changes simulating those undergone by these animals in their natural "habitat". after keeping groups of animals under dry conditions, some of them were returned to water. in both cases some parameters were compared with those of control animals kept in water. a lower activity in the na+/k+-dependent atpase of the epidermis and striated muscle was detected in "dry" animals with respect to the control ones or those rehydrated whereas the ... | 1978 | 233463 |
| histological changes in xenopus laevis daudin adult specimens kept under dry conditions, then moved back to their natural aquatic environment. ii. skin, kidney and interrenal tissue. | some cytological and histochemical characteristics of skin, the kidney and interrenal tissue were studied in xenopus laevis adult specimens (1) kept in their natural aquatic environment; (2) gradually exposed to dry conditions under which they were kept one week; and (3) returned from the dry environment to water for 24 hr or a week. in the skin, the most relevant changes are those exhibited by epidermal "flask" cells. these cells are generally rather lean, tall and pas-positive in "dry" animals ... | 1978 | 318018 |
| surface changes during development and involution of the cement gland of xenopus laevis. | the cement gland was studied from stage 17, when the anlage is established, to stage 49, shortly before its disappearance. at early stages, the apical membrane is covered by small microvilli that are more abundant than in the surrounding epiblast cells. vesicular protrusions along the cell boundaries are also more numerous in the gland cells. when the gland reaches maturity, the apical membranes of gland cells differentiate into two regions. in the cranial, kidney-shaped region, the membranes ar ... | 1978 | 569548 |
| a nuclear extract of xenopus laevis oocytes that accurately transcribes 5s rna genes. | xenopus 5s rna genes in recombinant form with the plasmid pmb9 are transcribed accurately when added to a supernatant fraction obtained from disrupted nuclei of xenopus laevis oocytes. after an initial 30 min lag period, the rate of synthesis of 5s rna is constant for at least an hour and synthesis is still detected after 18 hr. as much as 40% of the total rna synthesized from the recombinant dna used in these experiments can be 5s rna. the coding strand of the 5s rna genes is transcribed at a r ... | 1978 | 569551 |
| effects of estradiol-17beta in the male xenopus laevis: isolation and translation of cytoplasmic messenger rna populations. | total xenopus liver cytoplasmic rna isolated following long-term estrogen administration (14 days) was fractioned using sepharose 4b chromatography. one of the sepharose 4b peaks was shown to contain rna with a molecular weight reported for vitellogenin mrna (approximately 34s). the presence of estrogen-induced vitellogenin mrna in the peak 5 rna was determined by translation of the rna in the oocyte and analysis of the oocyte translational products by immunoprecipitation with anti-vitellogenin. ... | 1978 | 569762 |
| oogenesis in xenopus laevis (daudin). v. relationships between developing oocytes and their investing follicular tissues. | 1978 | 619165 | |
| cell specialization in the small intestinal epithelium of adult xenopus laevis: functional aspects. | the functional activity of the epithelial cells of the intestinal folds of xenopus was analysed histochemically. there is a gradient of increasing absorptive, digestive and secretory activity from the trough regions to the crests of the longitudinal folds. the differences in functional activity correspond to differences in structural complexity, and confirm the existence of a more specialized population of cells at the fold crests and a less specialized population at the fold troughs, analogous ... | 1978 | 624675 |
| the permeability of the skin of the aquatic anuran xenopus laevis (pipidae). | the undirectional transcutaneous fluxes of na, cl, water and urea were measured, in vitro, in the pipoid anuran xenopus laevis. an active uptake (outside to inside) of na was observed but cl movements appeared to be passive. the effluxes of na and cl were low compared to those measured in other species of amphibians. the active na transport was less than that of more terrestrial species and, although it could be stimulated by vasotocin, aldosterone was ineffective. the permeability of the skin t ... | 1978 | 624899 |
| use of restriction enzymes to study eukaryotic dna methylation: i. the methylation pattern in ribosomal dna from xenopus laevis. | 1978 | 625056 | |
| steroid biosynthesis by ovarian follicles of xenopus laevis in vitro during oogenesis. | 1978 | 631550 | |
| cell specialization in the small intestinal epithelium of adult xenopus laevis: structural aspects. | the structure, cellular composition and organization of the small intestinal epithelium of adult xenopus laevis are described. the mucosa is thrown into a system of longitudinal folds and is composed mainly of columnar cells and goblet cells. leucocytes comprise about 28% of the mucosal cells. the degree of structural specialization of columnar cells varies according to their position in the folds. cells at the crest of the folds display the greastest degree of specialization, evidenced by the d ... | 1978 | 632211 |
| translation and characterization of the fatty acid synthetase messenger rna. | fatty acid synthetase messenger rna was obtained from rat liver polysomal rna and then injected into xenopus laevis oocytes. the radioactive fatty acid synthetase protein synthesized in the oocytes was identified by immunoprecipitation with anti-fatty acid synthetase antibody and the immunoprecipitate was then characterized by electrophoresis on sodium dodecyl sulfate-polyacrylamide gel. co-migration of authentic fatty acid synthetase and the labeled product synthesized in oocytes was observed. ... | 1978 | 632268 |
| a low molecular weight dna polymerase from ovaries of the frog xenopus laevis. dna polymerase-beta (ovarian). | 1978 | 632291 | |
| mapping of mitochondrial dna in xenopus laevis and x. borealis: the positions of ribosomal genes and d-loops. | 1978 | 633366 | |
| histone h2b variants from the erythrocytes of an amphibian, a reptile and a bird. | histones h2b have been isolated from the terminally differentiated diploid erythrocytes of three different classes, amphibia (xenopus laevis), reptilia (crocodilus niloticus) and aves (gallus domesticus). partial amino acid sequences revealed three regions of sequence variation, each variant involving a single amino acid substitution. | 1978 | 638193 |
| xenopus laevis as a model for the study of immunology. | 1978 | 640116 | |
| an ultrastructural study of the thyroid gland in the pre-metamorphic xenopus laevis (daudin) tadpole. | a simple method for obtaining the thyroid tissue of anuran tadpoles for ultrastructural study has been described. follicle and colloid formation in the thyroid gland have been observed in xenopus laevis tadpoles at an early stage. the activity of the thyroid gland of pre-metamorphic tadpoles does not seem to depend on the activity of the hypophysis cerebri and the hypothalamus. both 'light' and 'parafollicular' cells are present in the thyroid gland of premetamorphic xenopus laevis tadpoles. | 1978 | 640959 |
| oogenesis in xenopus laevis (daudin). vi. the route of injected tracer transport in the follicle and developing oocyte. | in xenopus laevis, vitellogenin (the yolk precursor) is synthesized in the liver and transported via the circulatory system to the ovary. in order to reach developing oocytes where it is sequestered, it must exit the circulatory system and traverse several follicular tissue layers including the theca, the follicle cell layer, and the vitelline envelope. this study demonstrates this pathway by means of electron-opaque tracers, and follows the fate of heterologous macromolecules after their incorp ... | 1978 | 641487 |
| fenestrae in the rough endoplasmic reticulum of xenopus laevis hepatocytes. | the rough endoplasmic reticulum (rer) of xenopus laevis hepatocytes was examined by freeze-fracture and by conventional thin section electron microscopy. much of the rer was present as stacks of cisternae at the cell periphery but, in addition, large whorls of cisternae were seen in the cytoplasm in most sections. freeze-fracture replicas revealed fenestrae in both stacked and whorled cisternae, although the fenestrae were more numerous in the whorls. the role of these fenestrae is unknown, but ... | 1978 | 646133 |
| cell specialization in the epithelium of the small intestine of feeding xenopus laevis tadpoles. | the intestinal epithelium of feeding xenopus laevis tadpoles was studied using light microscope, electron microscope and autoradiographic techniques. the wall of the small intestine differs from that of most other vertebrates studied in that it lacks villous-like folds. a single prominent longitudinal fold, the typhlosole, forms about stage 49, and a series of shallow longitudinal epithelial pleats is also present in some animals. the morphology of the epithelial cells indicates that there are n ... | 1978 | 649494 |
| nuclear surface complex as observed with the high resolution scanning electron microscope. visualization of the membrane surfaces of the neclear envelope and the nuclear cortex from xenopus laevis oocytes. | the nuclear envelope and associated structures from xenopus laevis oocytes (stage vi) have been examined with the high resolution scanning electron microscope (sem). the features of the inner and outer surfaces of the nuclear surface complex were revealed by manual isolation , whereas the membranes facing the perinuclear space (the space between the inner and outer nuclear membranes) were observed by fracturing the nuclear envelope in this plane and splaying the corresponding regions apart. pore ... | 1978 | 649659 |
| neural transduction in xenopus laevis lateral line system. | 1. the process of neural excitation in hair cell systems was studied in an in vitro preparation of the xenopus laevis (african clawed toad) lateral line organ. a specially designed stimulus chamber was used to apply accurately controlled pressure, water movement, or electrical stimuli, and to record the neural responses of the two afferent fibers innervating each organ or stitch. the objective of the study was to determine the characteristics of the neural responses to these stimuli, and thus ga ... | 1978 | 650276 |
| estradiol-binding protein in the nucleus of male xenopus laevis liver. | 1978 | 651871 | |
| mapping of the xenopus laevis 5.8s rdna by restriction and dna sequencing. | the location of the 5.88 rdna within the internal transcribed spacer has been found by restriction and sequence analysis. these analyses indicate the deletion of a dinucleotide from the known rrna sequence. regions to the 5' and 3' of the gene contain both uncommon sequences and palindromic structures which might provide potential control points. a secondary structure model is suggested for the 5.8s rrna incorporating the flanking sequences. | 1978 | 652517 |
| differently sized rdna repeating units of xenopus laevis are arranged as internally homogeneous clusters along the nucleolar organizer. | the organization of differently sized genes coding for rrna in xenophus laevis has been investigated by partial ecori or hindiii digestion. the electrophoretic patterns obtained revealed that most adjacent repeating units are equally sized. this conclusion is in agreement with a previous suggestion that the nucleolar organizer is made up of internally homogeneous blocks of rrna genes. | 1978 | 652524 |
| [transfer of behavior patterns through transplantation of systems of neuroanatomic structures in amphibian larvae. ii. xenoplastic transplantation of hind brain systems between xenopus laevis (daud.) as well as hymenochirus boettgeri (torn.) and triturus vulgaris]. | by replacing parts of the neural plate (prospective medulla oblongata) of triturus vulgaris by neural ectoderm of xenopus laevis larval chimaeras were obtained, which showed donorlike rhythmical movements of distinct parts of the visceral musculature according to the place of implantation. especially the branchial region with its external gills showed rhythmical movements and is the special object of this investigation. | 1978 | 654606 |
| effect of the nonionic detergent triton x-100 on sodium permeability of the myelinated nerve fibre of xenopus laevis. | the effect of the nonionic detergent triton x-100 (tx-100) on the na permeability (pna) properties of the nodal membrane in myelinated nerve fibres of xenopus laevis was analysed with potential clamp technique. application of tx-100 caused a rapid initial decrease in pna that was reversible at wash out as well as a slow irreversible block. both effects dependend on [tx-100] and duration of exposure. the reversible reduction of pna at the steady state was 50% at 40--60 micrometer tx-100. the slop ... | 1978 | 654934 |
| an autoradiographic analysis of the retinal projection in the frog xenopus laevis: new observations in an anuran visual projection. | 1978 | 656924 | |
| large scale isolation of nuclei and nucleoli from vitellogenic oocytes of xenopus laevis. | a new method is described which allows the purification of large quantities of nuclei (germinal vesicles) from xenopus laevis vitellogenic oocytes of different developmental stages. from the isolated nuclei, purified nucleoli were obtained. the isolated germinal vesicles are transcriptionally active showing endogenous rna polymerase activity as well as a high level of activity with an exogenously added template. | 1978 | 657930 |
| relative amounts of newly synthesized poly(a)+ and poly(a)- messenger rna during development of xenopus laevis. | 1978 | 658590 | |
| rapid accumulation of vitellogenin messenger rna during secondary estrogen stimulation of xenopus laevis. | accurate quantitation of low concentrations of vitellogenin mrna by hybridization to vitellogenin cdna allows analysis of the accumulation of new vitellogenin mrna sequences throughout secondary estrogen stimulation. administration of a secondary injection of estradiol-17 beta to male xenopus laevis which have been withdrawn from estrogen for 60 days results in synthesis of complete vitellogenin mrna molecules in as little as 1 h after restimulation. vitellogenin mrna accumulates at a rate of 13 ... | 1978 | 659432 |
| induced formation of asters and cleavage furrows in oocytes of xenopus laevis during in vitro maturation. | we have previously reported that injection of purified basal bodies or sperm into unfertilized eggs of xenopus laevis induced the formation of asters and irregular cleavage furrows. fully grown oocytes were found to be unable to form asters or cleavage furrows. in this paper we show that the oocyte acquires the ability to form asters upon basal body injection at the time of germinal vesicle breakdown during in vitro maturation. our evidence indicates that aster formation requires progesterone-st ... | 1978 | 660144 |