Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| similarities of membrane structure in freeze-fractured xenopus laevis kidney collecting tubule and urinary bladder. | the collecting tubule of xenopus laevis kidney is formed of two main types of cell: the socalled flask cells (or mitochondria-rich cells) and the remaining, more cuboidal epithelial cells. it has previously been shown that the flask-cell plasma membrane contains a population of elongated intramembrane particles similar to those found in mitochondria-rich cells of the toad bladder. it is now clear that the structure of the apical membrane of the remaining epithelial cells of the collecting duct i ... | 1980 | 7440657 |
| the development of lampbrush chromosome-type transcription in the early diplotene oocytes of xenopus laevis: an electron-microscope analysis. | oocytes of xenopus laevis in pachytene and early diplotene of meiosis have been studied using the miller spreading technique. transcription first appears in germinal vesicles 25-40 micrometers in diameter, when the oocyte is in early diplotene. transcription at this stage consists of arrays of short rnp transcripts, irregularly distributed along the dnp axis. linear regression analysis has shown that many of these arrays are transcription units (type i) with the transcripts having a common point ... | 1980 | 7440660 |
| re-evaluation of the 'contralateral' effects of sodium and potassium on sodium transport through toad skin. | 1. changes in the concentration of na in the outer bathing solution, [na]o, or of k in the inner bathing solution, [k]i, alter the electrical responses of the isolated toad skin to changes in ionic concentrations in the contralateral solutions. the mechanism(s) of these apparently contralateral effects remain(s) unknown. 2. the phenomenon has been investigated here in the isolated abdominal skin of xenopus laevis. each skin was exposed to multiple levels of [na]o and [k]i, of between 5 and 112 m ... | 1980 | 7441564 |
| rabies mrna translation in xenopus laevis oocytes. | two rabies virus-specific mrna species were identified by analysis of their encoded proteins after translation of the partially purified species in xenopus laevis oocytes. one of these coded for the virion surface glycoprotein (g protein), and the other coded for the major structural protein of the virion nucleocapsid (n protein). the g-mrna sedimented in a sucrose density gradient at about 18s, and the n-mrna had a sedimentation coefficient of approximately 16s. their respective translation pro ... | 1980 | 7441819 |
| lipid metabolism during embryonic and early postembryonic development of xenopus laevis. | xenopus laevis embryos were analyzed for their lipid content from fertilization to feeding stage. the amounts of the major lipids did not change until after hatching, but at the feeding stage the amounts of phosphatidylcholine (pc), phosphatidylethanolamine (pe), and sterol esters (se) increased approximately twofold. prior to hatching, [14c]acetate label was incorporated primarily into the fatty acyl chains of pe. after hatching, increasing amounts of label were found in other phospholipids, in ... | 1980 | 7448620 |
| lens formation from cornea in the presence of the old lens in larval xenopus laevis. | three different types of experiments were carried out to investigate the role of the lens in lens-forming transformations of the outer cornea of xenopus laevis tadpoles (at stage 51, as defined by nieuwkoop and faber, '56): 1) simple lentectomy; 2) incision of outer and inner cornea in the region opposite the dorsal iris without lens removal; and 3) incision of outer and inner cornea and perforation of dorsal iris without lens removal. the results indicate that the outer cornea of xenopus laevis ... | 1980 | 7452196 |
| [tumour induction by methylnitrosourea in clawed frogs (xenopus laevis) (author's transl)]. | 15 clawed frogs were bathed 12 to 17 times in solutions of 2 mg methylnitrosourea, dissolved in 1000 ml destilled water. 7 frogs developed tumours 8 to 22 months after starting the experiments. another frog died of polycystic kidneys. the tumours were adenocarcinomas of the kidneys, sarcomas and a benign papilloma of the pelvis of the left kidney. a sarcoma of the soft tissues of the head showed an excessive granular storage of acid mucopolysaccharides in the cytoplasma of many tumour cells. tum ... | 1980 | 7458575 |
| xenopus laevis histone genes: variant h1 genes are present in different clusters. | the xenopus laevis histone genes have been isolated from a bacteriophage lambda library using a cloned cdna probe to x. laevis h4 mrna (px1ch4). their structural organization has been determined by restriction mapping, blot hybridization and hybridization selection and translation of xenopus histone mrnas. they are clustered and probably tandemly arranged but, in contrast to invertebrate histone genes (kedes, 1979), there has been extensive sequence divergence in the spacer regions of the cluste ... | 1980 | 7460012 |
| accumulation of individual pa+ rnas during oogenesis of xenopus laevis. | rna metabolism during amphibian oogenesis has been investigated by the analysis of individual cdna cloned sequences. two cdna clone libraries were constructed from the pa+ rna of xenopus ovary and of tadpole. the accumulation of rnas complementary to individual clones was examined during oogenesis by isolating rna from oocytes of different stages. there are only two patterns of accumulation during oogenesis. mitochondrial mrna sequences accumulate throughout all the stages of oogenesis, whereas ... | 1980 | 7460014 |
| effects of some heavy metal ions on the ionic currents of myelinated fibres from xenopus laevis. | 1. the effect of the heavy metal ions mn2+, co2+, ni2+, cu2+, zn2+, cd2+ and hg2+ on permeability parameters of the nerve membrane was investigated. the ions were applied externally to single myelinated fibres of xenopus laevis. the ionic currents, associated with potential steps were measured and analysed. 2. zn2+ reversibly slowed down the kinetics of the k system. the effect at large potential steps was described as an increase of tau n. 3.4 mm-zn2+ increased tau n about three times. 3. ni2+ ... | 1980 | 7463361 |
| polyneural innervation: mechanical properties of overlapping motor units in a small foot muscle of xenopus laevis. | 1. extensor digitorum longus iv of xenopus laevis was isolated together with its nerve and the 8th and 9th spinal roots. motor units were functionally isolated, by splitting and stimulating ventral root filaments. 2. motor units were stimulated separately and in pairs. between many pairs, overlap of motor innervation was found (evidence of polyneuronal innervation of muscle fibres). evidence for overlap was a deficit in the tension developed when the two units were stimulated together compared w ... | 1980 | 7463363 |
| electrical responses of muscle fibres in a small foot muscle of xenopus laevis. | 1. extensor digitorum longus iv (edl iv) of xenopus laevis was isolated together with its nerve and the 8th and 9th spinal roots. motor units were functionally isolated.2. glass micro-electrodes were used to penetrate the muscle fibres and to record their electrical responses to stimulation of single motor axons, or the total motor supply to the muscle.3. three types of electrical response were recorded from muscle fibres: an action potential in response to a single nerve stimulus (type 1), an a ... | 1980 | 7463366 |
| changes in polyribosomes and poly(a)-containing polyribosomal rna in the uterus of the ovariectomized rat in response to oestradiol-17 beta treatment. | polyribosome formation and the characteristics of polyribosomal poly(a)-containing rna from uteri of ovariectomized rats responding to a single dose of oestradiol-17 beta was investigated. the mean proportion of polyribosomes in the atrophic uterus was 65%. in response to 10 micrograms of oestradiol-17 beta/100 g body mass, the amount of polyribosomes increased to 88% 24 h after stimulation. thereafter the proportion of polyribosomes decreased to a value of 48% at 72h. the pattern of amino acid ... | 1980 | 7470028 |
| properties of motor units in a small foot muscle of xenopus laevis. | 1. extensor digitorum longus iv muscle (edl iv) of xenopus laevis was isolated together with its nerve and the 8th and 9th spinal roots. motor units were functionally isolated and their properties investigated. 2. the motor unit isometric twitch and tetanic tensions, contraction time and axon conduction time and distance were measured. axon conduction velocity and twitch:tetanus ratio were calculated. 3. the distributions of motor unit properties were continuous and showed no tendency to separat ... | 1980 | 7463359 |
| the nucleotide sequence of the major beta-globin mrna from xenopus laevis. | the nucleotide sequence of a cloned fragment containing an almost complete copy of the mrna encoding the major adult beta-globin polypeptide in xenopus laevis, the south african clawed toad, is presented. a procedure for strand separation by hybridization to complementary mrna was used to determine some of the sequence and this technique is described. the complete amino acid sequence of the polypeptide has been deduced and comparison with other vertebrate beta-globins reveals several highly cons ... | 1980 | 7433108 |
| multiple ribosomal gene sites revealed by in situ hybridization of xenopus rdna to triturus lampbrush chromosomes. | a variety of 3h-labelled ribosomal gene probes were hybridized in situ to the nascent transcripts of lampbrush chromosomes from the crested newt, triturus cristatus carnifex. the probes were from xenopus laevis and included rdna isolated by cscl gradient centrifugation, recombinant plasmids and purified restriction fragments of rdna. all the probes gave essentially the same result. about 10-15 loop pairs were distinctly labelled in each preparation, almost all of them located on the heteromorphi ... | 1980 | 7438882 |
| the lens proteins in adult and embryos of the periodic albino mutant ofxenopus laevis. | the crystallins of normal and ap mutants ofx. laevis have been studied using biochemical (electrophoresis in agar and polyacrylamide gels, isoelectric focusing) and immunochemical methods (immunoelectrophoresis, immunodiffusion, immunoabsorption, immunofluorescence, isoelectrofocusing with immunoidentification). the immunochemical analysis was carried out with rabbit antisera prepared against electrophoretic fractions of the mutant lens.crystallins of adultx. laevis (ap/ap; ++/++) are heterogeno ... | 1980 | 28305170 |
| the effects of tunicamycin and 2-deoxy-d-glucose on the development ofxenopus laevis embryos. | tunicamycin and 2-deoxy-d-glucose were applied toxenopus laevis embryos in the first cleavage furrow, blastula and early gastrula stages. no effect was observed with 2-deoxy-d-glucose up to the concentration 0.1 m. the effect of tunicamycin is dose- and stage-dependent. at the concentration of 5 μg/ml cleaving embryos are arrested at the onset of gastrulation and their cells exhibit decreased intercellular adhesivity, while embryos treated in the blastula and early gastrula stages may develop up ... | 1980 | 28305930 |
| the role of tensile fields and contact cell polarization in the morphogenesis of amphibian axial rudiments. | the role of stretching-generated tensile stresses upon the organization of axial rudiments have been studied. pieces of the dorsal wall ofxenopus laevis andrana temporaria embryos at the late gastrula stage were rotated through 90°, transplanted into the field of neurulation tensions of another embryo and replaced by ventral tissues already insensitive to inductive influences. the axial rudiments which developed from rotated and transplanted dorsal tissues oped from rotated and transplanted dors ... | 1980 | 28305148 |
| the role of zinc and follicle cells in insulin-initiated meiotic maturation of xenopus laevis oocytes. | 1980 | 17800845 | |
| retinal development: time and order of appearance of specific neuronal properties. | the high affinity uptake, biosynthesis and k(+)-stimulated release of certain neurotransmitter candidates was studied in adult and developing retinas of xenopus laevis. in the adult retina, (3)h-gaba was accumulated predominantly by horizontal cells while (3)h-glycine and (3)h-dopamine were accumulated by cells located deeper in the inner nuclear layer (possibly a type of amacrine or interplexiform cells). this retina also synthesized gaba, dopamine and acetylcholine from their precursors suppli ... | 1980 | 20487728 |
| synthesis in vitro of corticosteroid-binding globulin from rat liver messenger ribonucleic acid. | to show that corticosteroid-binding globulin (cbg), a plasma glycoprotein, is synthesized in the liver as well as to develop a tool with which to study the hormonal factors which control its synthesis, we undertook to translate rat cbg mrna in vitro. rat liver mrna was translated in the presence of [35s]methionine in both a rabbit reticulocyte lysate (cell-free) system and a xenopus laevis oocyte (whole cell) system. a monospecific antibody against highly purified rat cbg was used to precipitate ... | 1981 | 7460843 |
| germinal vesicle breakdown in the xenopus laevis oocyte: description of a transient microtubular structure. | during progesterone-induced meiotic maturation of xenopus oocytes in vitro, 7 morphological stages were defined. using cytological analysis, nuclear breakdown was divided into three stages. stage 1 corresponded to basal germinal vesicle breakdown. stage 2 was characterized by the advent and development of a fibrillar network formed by microtubules at the basal part of the nucleus. below, a lamellar microtubule organizing center (mtoc) was present. numerous vesicles of smooth endoplasmic reticulu ... | 1981 | 7349521 |
| experimental evidence for autonomous action of the periodic albinism (ap) gene within developing retinal pigment cells and melanophores of xenopus laevis. | genes which affect pigment elaboration may do so by autonomous action within the developing pigment cells or by way of tissue interactions leading to pigment cell differentiation. the site of action of the periodic albinism (ap) gene was investigated by substituting presumptive neural ectoderm of gastrulae of one genotype with uncommitted ectoderm of different genotype. retinal pigment cells and melanophores arising from such grafts were found to differentiate according to their own genotype in ... | 1981 | 7310308 |
| factors involved in the development of ipsilateral retinothalamic projections in xenopus laevis. | the extent, and the development, of the ipsilateral retinothalamic projection in the frog xenopus laevis have been studied using terminal degeneration and autoradiographic techniques. this ipsilateral projection derives only from those retinal areas receiving visual information from the binocular portion of the visual field. in xenopus, the ipsilateral retinothalamic projection arises from a larger area of the retina than was found to be the case in earlier studies on rana. this correlates with ... | 1981 | 7334300 |
| comparison of hemoglobins from the genus xenopus (amphibia salienta). | a survey of the electrophoretic mobility of hemoglobins of 14 species and subspecies of the genus xenopus was undertaken. it was found that the variation between the different taxons considered was quite important in the number and the degree of the hemoglobin bands on polyacrylamide slab gels. the profiles of the hemoglobin electrophoretic pattern in tube gels gave corresponding results, confirming the variation between the different xenopus species. the degree of resolution obtained on polyacr ... | 1981 | 7338720 |
| cells of origin of descending pathways to the spinal cord in the clawed toad (xenopus laevis). | 1981 | 7329548 | |
| measurement of 5 s rna accumulation in oocytes of xenopus laevis using a cdna probe. | 1981 | 7327260 | |
| interferometric studies of endothelial cells in primary culture. | a population of endothelial cells grown from xenopus laevis tadpole hearts was investigated by microinterferometry. the resulting interferograms were evaluated by an automatic image analyzer. the mean values of dry mass were 778 +/- 340 pg (10(-15) g) for whole cells, 648 +/- 309 pg for cytoplasm, 116 +/- 45 pg for nuclei, and 19 +/- 10 pg for nucleoli. two subpopulations of cells were identified, an actively growing one and a less active one. the density (dry mass per microm2) of the nuclei and ... | 1981 | 7327947 |
| somitogenesis in the amphibian xenopus laevis: scanning electron microscopic analysis of intrasomitic cellular arrangements during somite rotation. | the intrasomitic changes in cell arrangement which accompany somite rotation during somitogenesis in xenopus laevis were analysed with the scanning electron microscope (sem). longitudinal, horizontal fractures of whole embryos were examined at various dorsoventral levels of stage-22 to -24 embryos. observations of the gross morphological features of somitogenesis, and the cellular changes which accompany somite segmentation and somite rotation were made. several of these observations lead to mod ... | 1981 | 7310302 |
| influence of diet on the susceptibility of xenopus laevis tadpoles to thiopentone and a membrane probe. | xenopus laevis tadpoles were produced from wild-caught, laboratory-reared toads. separate sets were fed on diets of (1) liver powder; (2) nettle powder; (3) aminosol and intralipid. the tadpoles were reared for 3 weeks at 22 degrees c and then three groups of experiments performed. group i experiments showed a significant difference in the response to thiopentone between tadpoles fed on liver powder and those fed on nettle powder. group ii experiments showed a difference in response to thiopento ... | 1981 | 7248121 |
| tubulin:tyrosine ligase in oocytes and embryos of xenopus laevis. | 1981 | 7461286 | |
| h1 histone variants in xenopus laevis. | 1981 | 7250503 | |
| the formation of somites and early myotomal myogenesis in xenopus laevis, bombina variegata and pelobates fuscus. | myogenesis in xenopus laevis and in bombina variegata is similar despite differences in the structure of the nonsegmented mesoderm and in the formation of the myotomes. in x. laevis the nonsegmented mesoderm consists of two cell layers with the premyocoel between them. during somitogenesis the premyoblasts rotate covering subsequently the whole myotome length. in b. variegata the premyocoel is absent. the myotomal cells change their shape and elongate, attaining ultimately the whole myotome leng ... | 1981 | 7310306 |
| the direction of growth of differentiating neurones and myoblasts from frog embryos in an applied electric field. | 1. disaggregated single neurones and myoblasts obtained from the neural tube and somites of xenopus laevis embryos (stages 17-21) were cultured in the presence of steady small electric fields. 2. neurites grew preferentially towards the negative pole, or cathode, in field strengths of 7-190 mv/mm. many turned through considerable angles to do so. this effect disappeared below a threshold level of about 7 mv/mm. 3. greater numbers of neurones sprouted neurites in cultures exposed to an electric f ... | 1981 | 7310685 |
| patterns of transcriptional activity of nucleolar genes during progesterone-induced maturation of oocytes of xenopus laevis. | maturation has been induced in full grown oocytes of xenopus laevis by incubation in progesterone, and the ultrastructure of their nucleoli has been examined by electron microscopy using the chromatin spreading technique. we show that in this species numerous extrachromosomal nucleoli maintain high levels of transcription of rdna for up to 200 min after the application of the hormone, i.e., shortly before germinal vesicle breakdown. transcription has been identified as normal arrays of matrix un ... | 1981 | 7308608 |
| target dependency of developing motoneurons in xenopus laevis. | the effect of complete and partial limb bud removal on motoneuron survival was studied in xenopus laevis tadpoles. amputation of both hind limb buds at stage 49 before limb innervation begins caused the subsequent death of all motoneurons. this result confirms that there are no exceptions to the rule that developing motoneurons must contact the limb to survive. partial removals of the limb at early stages of innervation caused the subsequent death of motoneurons that normally project to the dele ... | 1981 | 7309919 |
| development of sodium permeability inactivation in nodal membranes. | 1. the time course of inactivation of the sodium permeability was studied in myelinated nerve fibres of xenopus laevis using the voltage-clamp technique of nonner (1969). the potassium currents were blocked by 10 mm-tetraethylammonium chloride (tea). the remaining currents were corrected for leakage and capacity currents. 2. the decay of the sodium current was double-exponential confirming chiu's (1977) findings the slower time constant was observed in tea-free solutions by clamping to vk in hig ... | 1981 | 7277227 |
| dna methylase during xenopus laevis development. | the dna methylase activity present in embryos and cultured cells of xenopus laevis resembles dna methylase from mammalian tissues. little or no activity is found in mature germinal vesicles, though nuclear activity rises rapidly after fertilization. this rise may result in part from a relocation of cytoplasmic enzyme. | 1981 | 7284389 |
| development of xenopus laevis embryos in a static magnetic field. | 1981 | 7295366 | |
| light stimulates the incorporation of inositol into phosphatidylinositol in the retina. | the incorporation of [3h]inositol into phosphatidylinositol in retinas of xenopus laevis tadpoles or young adults in short-term organ culture is stimulated by light, compared to retinas maintained under identical conditions in darkness. over 95% of the label incorporated into lipid was in phosphatidylinositol, and none was incorporated into retinal proteins. the stimulation of incorporation was localized by autoradiography to the outer plexiform layer, a neurophil composed primarily of horizonta ... | 1981 | 7295756 |
| development of axosomatic synapses of the xenopus spinal cord with special reference to subsurface cisterns and c-type synapses. | the relationships of highly flattened subsurface cisterns (sccs) were investigated electron microscopically in the spinal cord at various developmental stages of tadpoles and adult toads, xenopus laevis. in medial ventral motor cells (mvcs) of the adult, more than 90% of 156 sscs examined were situated postsynaptically. similarly, more than 90% of 540 sscs in lateral motor column cells (lmcs) were postsynaptic. by contrast, in early developmental stages, the sscs were initially formed by regiona ... | 1981 | 7276242 |
| "degenerative cement gland" (dcg), a lethal recessive mutation in xenopus laevis. | 1981 | 7340360 | |
| the invasion of cultured cell layers and intact epithelia. | this paper concerns the invasive behaviour of a migratory embryonic cell type, the primordial germ cell (pgc) of the anuran amphibian xenopus laevis. scanning electron microscopy of isolated pgcs shows that they invade layers of cells derived from adult xenopus mesentery, and the epithelium of the intact mesentery itself. this invasion is at least partly due to the stimulation by the pgcs of process formation in both cultured and intact epithelial cells. these broad lamellipodia move over the su ... | 1981 | 7347430 |
| locations of androgen-concentrating cells in the brain of xenopus laevis: autoradiography with 3h-dihydrotestosterone. | the distribution of hormone-concentrating cells in the brains of south african clawed frogs, xenopus laevis, was examined autoradiographically after the administration of 3h-dihydrotestosterone. hormone-accumulating cells were found in cranial nerve nucleus ix-x and adjacent smaller cells, a presumed medullary vestibular nucleus, a presumed sensory nucleus of cranial nerve v, dorsal tegmental area of the medulla, laminar nucleus of the torus semicircularis, ventral thalamus, and anterior pituita ... | 1981 | 7251941 |
| patterns of protein synthesis in livers of xenopus laevis during metamorphosis: effects of estrogen in normal and thyrostatic animals. | 1981 | 7227631 | |
| selective in vitro transcription of one of the two alu family repeats present in the 5' flanking region of the human epsilon-globin gene. | the sequence of 2965 nucleotides 5' of the human epsilon-globin gene has been completed. it includes two alu family repeats present in an inverted configuration. only the one located farthest from the gene was active as template for rna polymerase iii in a transcription system prepared from nuclei of xenopus laevis oocytes. this selective transcription may be explained by the lack of homology of the first 45 nucleotides of the non transcribed repeat with other members of the alu family. in fact ... | 1981 | 7335492 |
| toxic and teratogenic effects of selected aromatic amines on embryos of the amphibian xenopus laevis. | evaluations of the toxic and teratogenic effects of four aromatic amines, acridine, aniline, pyridine, and quinoline, have been made on amphibian (xenopus laevis) embryos. for toxicity testing, the embryos were divided into three groups according to stage of development: group i were mid-blastulae, group ii were tailbud embryos, and group iii were swimming larvae. of the amines tested, acridine and quinoline were the most toxic, followed by aniline and pyridine. ninety six hr lc50 values for acr ... | 1981 | 7259304 |
| the structure of vitellogenin. multiple vitellogenins in xenopus laevis give rise to multiple forms of the yolk proteins. | 1981 | 7263674 | |
| aeromonas hydrophila infection in xenopus laevis. | aeromonas hydrophila caused severe disease in a group of xenopus laevis within 3 weeks of receipt. the primary clinical signs were marked pallor of the skin, petechiation, lethargy, anorexia, and edema. the duration of the outbreak was approximately 45 days during which time 21 frogs became sick and 18 died, despite tetracycline therapy. pale skin, subcutaneous edema and hemorrhages, ascites, and pale livers were seen at necropsy. aeromonas hydrophila was isolated from skin, and the same organis ... | 1981 | 7265911 |
| [ontogenesis of the acetylcholine system in the brain of the south african clawed toad (xenopus laevis daudin)]. | 1. during the development of the acetylcholine system of the xenopus brain a distinct increase in neurotransmitter content was found which is interpreted as an expression of increased activity of cholinergic neurons. the acetylcholine content in the whole brain increases markedly from hatching to metamorphosis. during this period regional differences of transmitter distribution can be observed. 2. the chat activity of the whole brain remains constant during total larval life, whereas the ache ac ... | 1981 | 7328310 |
| cell type-specific differences in protein composition of nuclear pore complex-lamina structures in oocytes and erythrocytes of xenopus laevis. | 1981 | 7328650 | |
| axon regeneration by developing limb motoneurones in xenopus laevis. | newly generated motoneurones invading the limb bud were labelled with horseradish peroxidase to identify them later in development. they were then axotomized by amputating the limb bud. the limb bud was replaced immediately in some animals. after the period of normal motoneurone death, which falls a few days after the operation, many horseradish peroxidase labelled motoneurones were still alive provided the limb bud had been replaced. without a limb bud, labelled motoneurones were few or non-exi ... | 1981 | 7225797 |
| transplantation of insect giant chromosome nuclei into amphibian oocytes. | polytene salivary gland nuclei of chironomus pallidivittatus were transplanted into oocytes of xenopus laevis which were then cultured in vitro for 18 h. the giant chromosomes and nucleoli as well as the entire nuclei enlarged considerably in volume during this time. the polyteny and specific chromomere pattern of the chromosomes were maintained, and the puffing of the salivary gland-specific balbiani rings was not noticeably changed. - polytene nuclei from differentiated insect cells transplant ... | 1981 | 7227037 |
| patterns of motor innervation in the pectoral muscle of adult xenopus laevis: evidence for possible synaptic remodelling. | 1. an anatomical and electrophysiological study was performed on the pectoral muscle of xenopus laevis. 2. silver-impregnated preparations revealed immature endings, collateral and terminal sprouting and signs of synaptic regression. 3. twenty percent of the fibres received a dual innervation from two different nerves. the synapses of 25% of these fibres are formed in close vicinity. 4. some of the singly innervated and most of the dually innervated end-plates generated only subthreshold electri ... | 1981 | 7230035 |
| adenylate cyclase activity in xenopus laevis ovarian follicles. | 1981 | 7311973 | |
| two conserved sequence blocks within eukaryotic trna genes are major promoter elements. | the split promoter sequences of a trnaleucug gene of xenopus laevis have been mapped to nucleotides 13-20 and 51-64 of the trnaleu coding sequences. the sequences closely coincide with two conserved sequence blocks present in all eukaryotic trna genes. the two conserved sequence blocks were found to be exchangeable between trna genes as chimaeric trnamet--trnaleu genes proved transcriptionally active. furthermore, two prokaryotic trna genes exhibiting strong homologies with the two blocks yielde ... | 1981 | 7312050 |
| a microspectrophotometric study of normal and artificial visual pigments in the photoreceptors of xenopus laevis. | 1981 | 7314464 | |
| phosphorylation of ribosomal proteins during maturation of xenopus laevis oocytes. | 1981 | 7318832 | |
| [abnormal thyroid gland occurred in a colony of xenopus laevis maintained at gumma university (author's transl)]. | thyroid hypertrophy of unknown cause occurred in a colony of xenopus laevis maintained at the institute of endocrinology, gunma university, maebashi, japan. these animals were kept in small aquaria with well water and fed on minced pig liver. an etiologic investigation was made on the thyroid abnormality by assessing its occurrence and histopathologic features and rearing conditions of the animals in comparison with those of the colonies at tokyo and sendai. 1) the occurrence of abnormal thyroid ... | 1981 | 7318945 |
| experimental analysis of the lens-forming competence of the cornea, iris, and retina in xenopus laevis tadpoles. | the present research was carried out using xenopus laevis tadpoles at stage 50-51 to ascertain whether eye territories other than the outer cornea and the pericorneal epidermis have lens-forming competence, particularly the iris and/or retina. five experiments were performed: simple lentectomy; removal of lens, outer cornea, and pericorneal integument; removal of lens, outer cornea, and pericorneal integument, and simultaneous incision of retina; removal of lens, outer cornea and pericorneal int ... | 1981 | 7241066 |
| replication of ribosomal dna in xenopus laevis. | the study of the localization of the replication origins of rdna in xenopus laevis has been approached by two different methods. 1. the dna of x. laevis larvae was fractionated by cscl gradient centrifugation in bulk and ribosomal dna and examined in the electron microscope. in bulk dna, clusters of microbubbles, which are related with the origins of replication, appear to be spaced along the dna molecules at intervals comparable with the size of the 'average' replicon of x. laevis. in ribosomal ... | 1981 | 7297565 |
| effect of 5'-methylthioadenosine on nucleolar morphology and rna metabolism in cultured xenopus laevis cells. | 1981 | 7308302 | |
| a middle-affinity estrogen-specific binding protein in livers of vitellogenic and nonvitellogenic xenopus laevis. | 1981 | 7308579 | |
| neural plate morphogenesis and axial stretching in "notochord-defective" xenopus laevis embryos. | 1981 | 7308580 | |
| some observations on the behaviour of chloride current--voltage relations in xenopus muscle membrane in acid solutions. | chloride current--voltage relations in xenopus laevis muscle membrane have been investigated in phosphate-buffered solution (ph 5.2--5.4) using a three-microelectrode voltage clamp. resting chloride conductance in these conditions is about 10(-4) s/cm2, approximately 1/10th that at ph 8.8. when the membrane potential is stepped from the holding (resting) potential to a more negative voltage the current rises from the initial to the steady state. the instantaneous current--voltage relation is lin ... | 1981 | 7214211 |
| identification in xenopus laevis of a class of oocyte-specific proteins bound to messenger rna. | proteins associated with poly(a)-rich rna in xenopus laevis oocytes have been identified in immature ovary homogenates using sucrose gradient centrifugation, oligo(dt)-cellulose fractionation and analysis by sodium dodecyl sulphate/polyacrylamide gel electrophoresis and two-dimensional acid/urea/sodium dodecyl sulphate gel electrophoresis. at least eight proteins are associated with ribonucleoprotein complexes and have the following properties. 1. four major proteins, mrnp1-4, cosediment with po ... | 1981 | 7215334 |
| synthesis of androgen-dependent secretory proteins by rat seminal vesicles. | androgenic steroids control the synthesis and secretion of several proteins by the seminal vesicles of the male rat. prominent among them are 2 basic proteins, s and f, previously used as markers of androgen action. these proteins are not found among translation products of a wheat-germ protein-synthesising system supplied with mrna from seminal vesicles of normal rats. instead, higher molecular weight forms, s' and f', are formed which are nonetheless related antigenically to s and f respective ... | 1981 | 7215704 |
| intracellular phosphorylation of vitellogenin in the liver of estrogen-stimulated xenopus laevis. | a procedure was developed for the preparation of rough and smooth microsomes from small quantities of liver obtained from estrogen-stimulated xenopus laevis females. the separation involves th centrifugation of a postmitochondrial supernatant over a cscl-containing, discontinuous sucrose gradient. morphological, biochemical, and enzymatic characterization of these fractions indicates that excellent separation of rough microsomes from smooth microsomes is achieved. in addition, pulse-chase experi ... | 1981 | 7217071 |
| isolation of a xenopus laevis alpha-globin gene. | 1981 | 7265209 | |
| progesterone inhibits membrane-bound adenylate cyclase in xenopus laevis oocytes. | recent experimental evidence indicates that progesterone acts at the cell surface to trigger protein synthesis and to reinitiate the first meiotic division in xenopus laevis oocytes. the steroid hormone is physiologically released by follicle cells surrounding oocytes in the ovaries, and this naturally occurring event can be reproduced in vitro by adding progesterone to the incubation medium. recently, cyclic amp has been implicated in the mechanism of progesterone action in oocytes; there was a ... | 1981 | 7195984 |
| oestrogen receptor levels and vitellogenin synthesis during development of xenopus laevis. | 1981 | 7266654 | |
| a simple apparatus for injection of nanoliter quantities into xenopus laevis oocytes. | 1981 | 7270884 | |
| a giant cell with dendritic cell properties in spleens of the anuran amphibian xenopus laevis. | 1981 | 7274523 | |
| a reinvestigation of the role of the grey crescent in axis formation in xenopus laevis. | gravitationally induced displacements of the contents of the frog egg can predictably determine the orientation of the subsequent dorsal-ventral axis of the embryo, regardless of the original position of sperm entry or of the grey crescent. in certain conditions, these displacements in the egg can also lead to the formation of a second axis, that is, to twinning. the previously reported ability of grafts of grey crescent cortex to induce secondary axes in recipient eggs is interpreted here as an ... | 1981 | 7195987 |
| the secretion of proteins in vitro from xenopus oocytes and their accessory cells: a biochemical and morphological study. | protein secretion by xenopus laevis oocytes and their surrounding follicular cells in vitro has been investigated using two-dimensional gel electrophoresis. viable oocytes, devoid of follicle layers, were prepared by treatment with collagenase; they retain in full their capacity to synthesize, sequester and export secretory proteins following microinjection with heterologous messenger rna. both rna-injected and normal cells export a large number of endogenous oocyte proteins and, as with heterol ... | 1981 | 7196433 |
| the primary structure of oocyte and somatic 5s rrnas from the loach misgurnus fossilis. | somatic and oocyte 5s rrnas from the liver and unfertilized eggs of the loach (misgurnus fossilis have been sequenced and found to differ in six nucleotides. all the substitutions are confined to the 5'-half of the molecules; 4 of them are pyrimidine-pyrimidine substitutions, and 2 are purine-pyrimidine ones. considerable differences, both in the position and the character of substitutions, have been established when these 5s rrnas were compared with somatic and oocyte 5s rrnas from xenopus bore ... | 1981 | 7197777 |
| isolation and characterization of xenopus laevis albumin mrna. | the messenger rna for albumin was isolated from the liver of male frogs. purification was achieved using oligo(dt)-cellulose chromatography and sucrose gradient centrifugation under denaturing conditions. as judged by translational activity in a cell-free protein-synthesizing system derived from rabbit reticulocytes, albumin mrna was enriched 259-fold as compared to the total ribonucleic acid of the liver cells. purified albumin mrna migrated after sucrose gradient centrifugation as a single sym ... | 1981 | 7285921 |
| the movement of the prospective eye vesicles from the neural plate into the neural fold in ambystoma mexicanum and xenopus laevis. | 1981 | 7286445 | |
| conservatism of the h-y/h-w receptor. | soluble h-y antigen is taken up by cells of the homogametic gonad of cattle, dog, chicken and south african clawed frog. after in vitro exposure to mouse testis supernatant or male fetal calf serum, xx ovary cells or zz testis cells, which are normally h-y-, acquire the h-y+ (h-w+) phenotype and absorb mouse h-y antibody in standard serological assays. in addition, h-y antigens of the different species can compete for attachment to target cells of a single species. in a new competitive binding r ... | 1981 | 7286993 |
| regional effects of sodium aspartate and sodium glutamate on protein synthesis in the retina. | isolated retinas from xenopus laevis tadpoles or juvenile frogs were incubated in ringer's bicarbonate-glucose medium in which sodium chloride was replaced with equimolar amounts of either sodium aspartate (naasp) or sodium glutamate (naglu). at all concentrations tested (0.1 to 50 mm), both acidic amino acids caused a dramatic decrease in the incorporation of 3h-leucine into proteins in the inner retina. higher concentrations of these acids (50 mm) caused an increase in the incorporation of the ... | 1981 | 7287345 |
| an experimental analysis of the role of bottle cells and the deep marginal zone in gastrulation of xenopus laevis. | earlier work suggested that the change in shape or the active migration of the bottle cells in the amphibian blastoporal region results in an invagination that comprises a major part of gastrulation. in the present study of gastrulation in xenopus laevis, microsurgical extirpation and rearrangement experiments, analyzed with time-lapse cinemicrography and scanning electron microscopy, show that the bottle cells have a lesser role in gastrulation. gastrulation is not a process of invagination but ... | 1981 | 7288390 |
| observations on intracellular ph during cleavage of eggs of xenopus laevis. | direct measurements of intracellular ph was made with recessed-tip ph microelectrodes in fertilized eggs of the frog, xenopus laevis, from approximately 1 h after fertilization to mid-blastula. the intracellular ph just before first cleavage was 7.65 +/- 0.04 (sd; n = 9). by stage 5 to the middle of stage 6, average intracellular ph was 7.70 +/- 0.06 (sd; n = 16). a statistically significant alkalization of 0.18 +/- 0.03 ph unit (sd; n = 5) was observed beginning in early blastula. a cycle of le ... | 1981 | 7198125 |
| pineal complex of the clawed toad, xenopus laevis daud.: structure and function. | the morphological and physiological properties of the pineal complex of xenopus laevis were investigated in larval, juvenile and adult animals. in a representative majority of adult x. laevis, the frontal organ does not display signs of degeneration. fully differentiated frontal organs contain photoreceptors typical of the pineal complex of lower vertebrates. by means of the acetylcholinesterase (ache)-reaction approximately 30 neurons of two different types were demonstrated in the frontal orga ... | 1981 | 7226202 |
| modifications in oocyte protein synthesis induced by progesterone in xenopus laevis. | 1981 | 7238884 | |
| a method for the enhancement of bi- and trispermic fertilization in eggs of xenopus laevis. | 1981 | 7238954 | |
| characterization of a new cell line, xl2, obtained from xenopus laevis and determination of optimal culture conditions. | a new amphibian permanent cell line is described. it is called xl2 and was initiated from stage 35 tadpoles of xenopus laevis. the cell line has an epithelioid morphology and most cells can be classified into two populations with respective chromosome modal numbers 36 and 74. contact inhibition is low. its growth is vigorous in l15 or mem medium supplemented with fetal bovine serum. the mean doubling time is 39 hr and the saturation density is 700,000 cells/cm2 at 25 degrees c. the absolute plat ... | 1981 | 7239540 |
| vitellogenesis and the vitellogenin gene family. | vitellogenin is synthesized under estrogen control in the liver, extensively modified, transported to the ovary, and there processed to the yolk proteins lipovitellin and phosvitin. in the frog xenopus laevis there are at least four distinct but related vitellogenin genes. the two genes a1 and a2 have a 95 percent sequence homology in their messenger rna coding regions, and contain 33 introns that interrupt the coding region (exons) at homologous positions. sequences and lengths of analogous int ... | 1981 | 7209528 |
| identification and properties of terminal deoxynucleotidyltransferase from xenopus embryos prior to the development of the thymus. | the appearance of terminal deoxynucleotidyltransferase (tdt), a marker for early lymphoid cells, has been measured during the development of the south african clawed frog, xenopus laevis. the enzyme can first be detected in 2-day-old embryos, at approximately the same time as the first detectable embryonic immunoglobulin and well before the appearance of the thymus. xenopus tdt has been partially purified and some of its properties have been investigated. the partially purified enzyme is 68,000 ... | 1981 | 7217050 |
| stability of non-polyadenylated viral mrnas injected into frog oocytes. | the naturally non-polyadenylated mrnas of reovirus were shown to have a half-life in excess of 3 days when injected into xenopus laevis oocytes. hybridization analysis and gel electrophoresis showed that all 10 mrna species had a similar high stability, despite being translated at widely differing rates. we have confirmed previous findings indicating a role for the 5'-terminal cap structure in determining reovirus mrna stability [furuichi et al. (1977) nature (lond.) 266, 235-239]. the significa ... | 1981 | 7196332 |
| mitochondrial dna synthesis in xenopus laevis enucleated eggs. | 1981 | 7197198 | |
| genetic control of t helper cell function in the clawed toad xenopus laevis. | the genetic control of the collaboration between xenopus t and b cells has been analyzed in vivo using cells from five strains of major histocompatibility complex-defined xenopus. when carrier (fowl gamma-globulin)-primed t cells and hapten (dinitrophenylated keyhole limpet hemocyanin)-primed b cells differed by minor histocompatibility antigens or by only one haplotype of the major histocompatibility complex, the collaboration was efficient in the sense that large numbers of plaques, low-molecu ... | 1981 | 7011821 |
| origin of replication from xenopus laevis mitochondrial dna promotes high-frequency transformation of yeast. | a specific fraction of chromosomal dna from both yeast and a wide variety of other eukaryotes, but not from escherichia coli, promotes high-frequency transformation in yeast. the plasmids containing these sequences are maintained as extra-chromosomal molecules in transformed cells. these results suggest that similar or identical sequences are used for the initiation of dna replication in eukaryotes. to test this hypothesis, several foreign eukaryotic dnas implicated directly or indirectly in the ... | 1981 | 7019920 |
| secondary lens formation from the cornea following implantation of larval tissues between the inner and outer corneas of xenopus laevis tadpoles. | secondary lens formation from the cornea of larval xenopus laevis has been used as a measure of the lens-inducing capacities of various larval xenopus tissues. the experimental design employed involved implantation of selected body tissues between the inner and outer cornea of stage-50 tadpole eyes, in such a way that the integrity of the inner cornea and eye cup was not disrupted. implantation of retina, pituitary, limb blastema or limb bud resulted in secondary lens formation from the outer co ... | 1981 | 7031166 |
| in vitro transcription of cloned 5s rna genes of the newt notophthalmus. | recombinant plasmids that carried genes coding for 5s ribosomal rna of the newt, notophthalmus viridescens, were transcribed in vitro with extracts of xenopus laevis oocyte nuclei. plasmids containing multiple repeats of the 5s gene and spacer directed accurate transcription of 5s rna (120 bases). individual repeat units were recloned by inserting sau 3a restriction fragments into the bam hi site of plasmid pbr322. because each repeat was cut by the enzyme within the coding region, the inserts h ... | 1981 | 6945306 |
| 31p nmr reveals increased intracellular ph after fertilization in xenopus eggs. | 31p nmr spectra of mature eggs of the frog (xenopus laevis) were taken prior to and after both fertilization and activation by a ca2+/h+ ionophore (a23187). the eggs were constantly perfused with fresh well-buffered solution during the experiments, and the intracellular ph (phi) was determined from the ph-dependent chemical shift of the internal pi peak. the detection of this pi peak in the presence of overlapping yolk phosphoprotein signals was accomplished by a t2 experiment which discriminate ... | 1981 | 6945594 |
| highly conserved lipoprotein assembly in teleost and amphibian yolk-platelet crystals. | ohlendorf et al. have reported that yolk-platelet crystals in the frog, xenopus laevis, were orthorhombic (space group p21221) and consisted of elongated asymmetric units (approximately 5.5 x 11.5 x 25 nm). the presence of an orthorhombic lattice in amphibian yolk platelets fulfilling the symmetry requirements of crystals had been missed in earlier structural interpretations. a comparative study of teleost, urodele and anuran yolk-platelet crystals performed in our laboratory has shown the wides ... | 1981 | 6969859 |
| cholesterol-induced in vitro maturation of oocytes of acipenser stellatus, xenopus laevis, and rana temporaria. | 1981 | 6973502 | |
| locomotion of xenopus epidermis cells in primary culture. | the locomotion of single epidermis cells, grown out from xenopus laevis tadpole tails has been investigated by time-lapse cinemicrography using phase-contrast and reflection-contrast optics. the cells develop a large, mostly 200-250 nm thick, lamella, which adheres homogeneously to the supporting coverglass and exceeds the projection area of the cell body. from the comparison of ric-pictures taken at high (1.06) and low (0.62) numerical aperture of illumination (i.n.a.) we deduce that at low i.n ... | 1981 | 7037800 |
| internal control regions for transcription of eukaryotic trna genes. | we have identified the region within a eukaryotic trna gene required for initiation of transcription. these results were obtained by systematically constructing deletions extending from the 5' or the 3' flanking regions into a cloned drosophila trnaarg gene by using nuclease bal 31. the ability of the newly generated deletion clones to direct the in vitro synthesis of trna precursors was measured in transcription systems from xenopus laevis oocytes, drosophila kc cells, and hela cells. two contr ... | 1981 | 6947245 |