Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| primary structure of the histone h2a and h2b genes and their flanking sequences in a minor histone gene cluster of xenopus laevis. | 1982 | 7117538 | |
| subcellular localization of the trna processing enzyme, trna nucleotidyltransferase, in xenopus laevis oocytes and in somatic cells. | earlier studies of the trna processing enzyme, trna nucleotidyltransferase, in rat liver cells suggested that the enzyme was absent from nuclei, whereas more recent studies with trna transcription-processing systems from xenopus laevis oocytes indicated that the enzyme was present in germinal vesicles of these cells. in order to resolve this apparent discrepancy, the subcellular localization of trna nucleotidyltransferase in oocytes was directly determined, and its distribution in somatic cells ... | 1982 | 7122242 |
| biosynthesis of two structurally different pro-opiomelanocortins in the pars intermedia of the amphibian pituitary gland. | this study reports the biosynthesis of two forms of pro-opiomelanocortin in the pars intermedia of the pituitary gland of the african clawed toad xenopus laevis. the two forms could be resolved by dodecyl sulphate gel electrophoresis on a 9-16% acrylamide gradient and their molecular weights were 38200 and 37300. incubation of neurointermediate lobes with [3h]glucosamine followed by tryptic digestion of the newly synthesized glycoproteins, revealed that both prohormones have only one glycosylate ... | 1982 | 7128582 |
| biosynthesis of a gamma 3-melanotropin-like peptide in the pars intermedia of the amphibian pituitary gland. | this study reveals the biosynthesis of a gamma 3-melanotropin-like peptide in the pars intermedia of the pituitary gland of the aquatic toad xenopus laevis. pulse-chase experiments in vitro showed that this product is synthesized through processing of a prohormone, pro-opiomelanocortin, and that it is released into the incubation medium. the peptide immunoprecipitated with antiserum to gamma 3-melanotropin, appeared to be a glycopeptide and displayed melanotropic activity. this last observation ... | 1982 | 7128584 |
| multiple factors involved in the transcription of class iii genes in xenopus laevis. | cell-free extracts from xenopus laevis oocytes (ovarian tissue), unfertilized eggs, embryos, and cultured kidney cells direct accurate transcription of cloned 5 s rna and trna genes. fractionation of these extracts by conventional ion exchange chromatography shows that multiple components are essential for the transcription of each of these genes by rna polymerase iii. two chromatographically distinct fractions from ovary, egg, embryo, and kidney cell extracts are necessary and sufficient, in th ... | 1982 | 7130190 |
| the neuromuscular basis of swimming movements in embryos of the amphibian xenopus laevis. | when removed from their egg membranes, xenopus embryos can swim. high-speed cinematography shows that, in swimming, lateral undulations pass rostro-caudally down the body. the swimming rhythm period is 40-100 ms. in swimming, electrical activity in myotomal muscles alternates on opposite sides of a segment and sweeps rostro-caudally in ipsilateral myotomes. myotome muscle physiology was examined. muscle fibres are electrically coupled to each other, and the fibres are able to spike. the possible ... | 1982 | 7130896 |
| the central nervous origin of the swimming motor pattern in embryos of xenopus laevis. | rhythmic motor nerve activity was recorded in stage 37/38 xenopus embryos paralysed with curare. the activity was similar to the swimming motor pattern in the following ways: cycle period (40-125 ms), alternation of activity on either side of a segment, rostro-caudal phase lag. episodes of rhythmic motor activity could be evoked by stimuli that evoke swimming and inhibited by stimuli that normally inhibit swimming. on this basis we conclude that the swimming motor pattern is generated by a centr ... | 1982 | 7130897 |
| the neuromuscular basis of rhythmic struggling movements in embryos of xenopus laevis. | xenopus embryos struggle when restrained. struggling involves rhythmic movements of large amplitude, in which waves of bending propagate from the tail to the head. underlying this, electrical activity in myotomal muscles occurs in rhythmic bursts that alternate on either side of a segment. bursts in ipsilateral segments occur in a caudo-rostral sequence. curarized embryos can generate motor nerve activity in a struggling pattern in the absence of rhythmic sensory stimulation; the pattern is ther ... | 1982 | 7130898 |
| purification and physical properties of arginase from xenopus laevis. | arginase from the liver of xenopus laevis has been purified to homogeneity by heat treatment, acetone fractionation, and isoelectric focussing. the main component had an isoelectric point (i.e.p.) of 7.3; there is a minor component of i.e.p. 7.8. the molecular weight of the enzyme, as determined by gel filtration on sephadex g200, is 76,000 daltons, substantially less than that of rat liver arginase studied concurrently. the molecular weight of the subunits, as determined by electrophoresis in s ... | 1982 | 7130924 |
| characterization of spermatid/sperm basic chromosomal proteins in the genus xenopus (anura, pipidae). | spermatid/sperm basic chromosomal proteins from 17 species and subspecies of the genus xenopus (anura, pipidae) were compared. electrophoresis on acetic acid/urea/triton x-100 polyacrylamide gels revealed that each xenopus species with a diploid chromosome number of 36, 72, or 108 showed multiple, diverse spermatid/sperm-specific basic chromatin proteins with mobilities greater than the somatic histones. the numbers and mobilities of these proteins were characteristic of each xenopus species and ... | 1982 | 7130928 |
| schooling behavior of tadpoles: a potential indicator of ototoxicity. | fish and tadpoles in schools use hair cells of their lateral line system to assess their position in relation to neighbors. this suggests that pharmaceutical agents that damage hair cells in the mammalian inner ear may also alter geometry in fish and tadpole schools. we used a computer-based image analysis system to examine the effect of the ototoxic aminoglycoside antibiotic, streptomycin, on school geometry for tadpoles of the african clawed frog xenopus laevis. tadpoles exposed to streptomyci ... | 1982 | 7134246 |
| contractile properties of two varieties of twitch muscle fibres in xenopus laevis. | the contractile properties of twitch muscle fibres in the iliofibularis muscle of xenopus laevis with characteristic differences in light-microscopical appearance have been studied under isometric and isotonic conditions. type 1 fibres (large, pale) have a short contraction time (tc), a shoulder in the relaxation phase, and a high twitch-tetanus ratio. in type 2 fibres (medium-to-large with abundant mitochondria and lipid droplets) tc is longer, half-relaxation time equals tc, and the twitch-tet ... | 1982 | 7136781 |
| on the development of the spinal cord of the clawed frog, xenopus laevis. i. morphogenesis and histogenesis. | the morphogenesis and histogenesis of the spinal cord of xenopus were examined. the study encompasses the developmental period between stage 41 and stage 66 (stages according to nieuwkoop and faber 1967). this period can roughly be divided into three phases. from stage 50 up to stage 53 strong proliferation and rapid growth are the most striking features. this developmental phase is preceded and followed by less dynamic periods. from stage 41 up to stage 50 the rate of proliferation is relativel ... | 1982 | 7137589 |
| on the development of the spinal cord of the clawed frog, xenopus laevis. ii. experimental analysis of differentiation and migration. | in order to determine the time and site of origin and the final location of various cell groups in the spinal cord, tadpoles of xenopus laevis, ranging from stage 48 to stage 56 were treated with tritiated thymidine and sacrificed at various stages from 49 to 66 (stages according to nieuwkoop and faber (1967). from the poorly developed matrix at stage 48-49 not only ventral horn cells, but also neuroblasts of the intermediate zone and the dorsal horn arise. both the matrix and the ventricle expa ... | 1982 | 7137590 |
| mapping the auditory central nervous system of xenopus laevis with 2-deoxyglucose autoradiography. | 1982 | 7139290 | |
| transcription of cloned xenopus laevis ribosomal dna microinjected into xenopus oocytes, and the identification of an rna polymerase i promoter. | transcription of a cloned xenopus laevis ribosomal dna (rdna) fragment, microinjected into xenopus oocytes, is initiated at the in vivo 40s pre-ribosomal rna (pre-rrna) site (+/- 2 bp) by rna polymerase i. an x. laevis rna polymerase i promoter has been mapped by studying the transcription of in vitro rdna mutants in the oocyte system. the active promoter lies within the dna segment beginning 145 bp upstream, and most probably ending 16 bp downstream, from the 40s pre-rrna initiation site (-145 ... | 1982 | 7139716 |
| changes in the activities of mitochondrial carriers during the development of xenopus laevis. | 1982 | 7140847 | |
| the influence of miedzian 50, a cupric pesticide, on the internal organs of adult xenopus laevis. i. liver and intestine. | 1982 | 7141044 | |
| transcription of xenopus borealis rrna genes in nuclei of xenopus laevis oocytes. | 1982 | 7141111 | |
| transcription of xenopus ribosomal rna genes by rna polymerase i in vitro. | we have developed an in vitro system in which rna polymerase i accurately transcribes xenopus ribosomal rna (rrna) genes. cloned xenopus laevis ribosomal dna (rdna) is incubated in a homogenate of manually isolated xenopus borealis oocyte nuclei. the resultant rna is analyzed by an s1 nuclease mapping procedure specific for the initiation region of x. laevis rrna. we show that transcription initiates in vitro on the cloned x. laevis rdna at the in vivo initiation site. in addition, the dinucleot ... | 1982 | 7142215 |
| the development of the peripheral trigeminal innervation in xenopus embryos. | the development of the ophthalmic, maxillary and mandibular nerves has been followed in xenopus laevis embryos from the first emergence of growth cones from the trigeminal ganglia until the establishment of functional innervation of the skin or cement gland. the course of each main nerve is highly predictable and follows pre-existing openings between blocks of other tissues. the development of the mandibulary nerve was observed most easily. like that of the other trigeminal nerves it falls into ... | 1982 | 7142898 |
| regeneration and functional reconnection of an identified vertebrate central neuron. | i have examined the axonal regeneration of a pair of identified central neurons, the mauthner (m) neurons, in xenopus laevis tadpoles. lucifer yellow injections reveal regenerative sprouts arising from the proximal stumps of the m axons within a few days after axotomy; some of these can cross the lesion within 1 week. many specimens examined at later times (up to 21 weeks) have processes that extend more than 2 mm (equivalent to 5 to 10 spinal segments) beyond the lesion. m axons which have rege ... | 1982 | 7143053 |
| [translation of the genomic and subgenomic rnas of cucumber virus 3 in a cell free system from wheat embryos and in xenopus laevis oocytes]. | the purified preparation of cucumber virus 3 (cv3) (one of the member of tobamovirus group) contains, besides full-length (2.0 x 10(6)) genomic rna, a short (0.24 x 10(6)) subgenomic rna coding for coat protein in xenopus laevis oocytes as well as in the cell-free protein synthesizing system from wheat embryos. the similarity of the polypeptide coded by short cv3 rna in vitro to natural cv3 coat protein is proved by the similarity of their molecular weights, antigenic specificity and by the simi ... | 1982 | 7144749 |
| dorsal root projections in the clawed toad (xenopus laevis) as demonstrated by anterograde labeling with horseradish peroxidase. | horseradish peroxidase was applied to the proximal stumps of severed cervical, thoracic and lumbar dorsal roots in the clawed toad, xenopus laevis, in order to study the course, distribution and site of termination of dorsal root fibers in the spinal cord and brain stem. the anterograde transport of horseradish peroxidase as applied in the present study proved to be a useful and reliable technique. results show that on entering the spinal cord, dorsal root fibers segregate into a medially placed ... | 1982 | 7145089 |
| circular single stranded phage m13-dna as a template for dna synthesis in protein extracts from xenopus laevis eggs: evidence for a eukaryotic dna priming activity. | unfractionated protein extracts from activated xenopus laevis eggs contain all functions required for the chain elongation reactions in replicative dna synthesis (a.richter, b. otto and r.knippers, 1981, nucl.ac.res. 9, 3793-3807). in order to further explore the dna synthesizing capacity of this in vitro system and to obtain information on the dna priming activity in these extracts single stranded phage m13-dna was used as template for in vitro dna synthesis. the main results of this investigat ... | 1982 | 7145711 |
| oocyte growth in the sheepshead minnow: uptake of exogenous proteins by vitellogenic oocytes. | the structure of the vitellogenic follicles of the sheepshead minnow, cyprinodon variegatus, is described. follicles enlarge primarily by protein yolk accumulation (vitellogenesis) and subsequently increase in size by hydration. this study uses the electron-dense tracer, horseradish peroxidase, and a larger heterologous protein, xenopus laevis [3h]vitellogenin, to follow the fate of exogenous proteins from the maternal circulation to yolk spheres of the growing oocyte. materials appear to leave ... | 1982 | 7147228 |
| formation of gap junctions by stem cells in the developing retina of the clawed frog (xenopus laevis). | to ascertain whether gap junctions are preferentially formed by proliferated retinal stem cells, an analysis by electron microscopic autoradiography was made on the retina of the xenopus embryo at stages 26, 29 and 31, after pulse labelling with 3h-thymidine. when the administration of the isotope was carried out for 0.5 or 3 h, retinal cells in s phase or s to m phase in the cell cycle were marked with the isotope, respectively. in these specimens, most gap junctions were found on the isotope-l ... | 1982 | 7149274 |
| chromatin structure of xenopus rdna transcription termination sites. evidence for a two-step process of transcription termination. | the ultrastructure of xenopus laevis (x.l.) 40s pre-rrna transcription termination sites was investigated by electron microscopy. amplified nucleolar chromatin was rapidly dispersed and processed for chromatin spread preparations. this type of preparation revealed that many rdna termination sites appeared as 50 nm long segments of chromatin axis covered by a complex of three closely spaced rna polymerase particles. particle (ptl) was characterized by the association with the terminal full-length ... | 1982 | 7151544 |
| visuotectal projections following temporary transplantation of embryonic eyes to the body in xenopus laevis. | eye anlagen of xenopus laevis at stages 22-26 were transplanted, 180 degrees rotated, into the flank of similarly staged embryos and 24-36 h later were placed into the orbits of final hosts at stages 32-36. after metamorphosis visuotectal projections were mapped electrophysiologically. in one series, eyes were normally oriented in the final host and visuotectal projections were found to be normal. a second series, in which eyes were placed in a rotated orientation in the final host, had develope ... | 1982 | 7153700 |
| trifluoperazine-induced meiotic maturation in xenopus laevis. | xenopus oocytes were exposed to trifluoperazine, a drug that binds to the calcium-regulating protein, calmodulin. the drug induced meiotic maturation even in the absence of progesterone. when trifluoperazine was microinjected directly into oocytes the maturation of the cells was partially inhibited in that the white spot, indicative of germinal vesicle breakdown, did not appear even though the germinal itself was absent in dissected oocytes. | 1982 | 7153737 |
| the development of connections between the isthmic nucleus and the tectum in xenopus and limnodynastes tadpoles. | in adult anura reciprocal connections exist between the isthmic nucleus and ipsilateral tectum. these pathways, with a projection from the isthmic nucleus to the opposite tectum, constitute the binocular visual connections. isthmic nuclei were examined histologically after injection of horseradish peroxidase into the tectum of xenopus laevis and limnodynastes dorsalis from midlarval stages to the completion of metamorphosis and in adults. the isthmic nuclei were present throughout, their cell nu ... | 1982 | 7155452 |
| [development of the structure and stability of mauthner's neurons in xenopus laevis tadpoles on the implantation of additional auditory vesicles]. | the ultrastructure and functional changes of the mauthner cells were studied in the x. laevis tadpoles under the conditions of the experimentally doubled source of their afferentation, an additional pair of ear vesicles. additional afferent fibers grow from the receptors to the brain and form additional synapses on the soma of the mauthner cells, indistinguishable by their morphology from the terminals of their own acoustic nerves. the altered interneuronal interactions lead, on one hand, to the ... | 1982 | 7155508 |
| spontaneous and experimental infections of xenopus laevis with chlamydia psittaci. | chlamydial infection was suspected when widespread pyogranulomatous inflammation and large basophilic intracytoplasmic inclusion bodies were evident histopathologically in african clawed frogs (xenopus laevis) dying of a spontaneous disease of high morbidity and mortality. organism morphology was determined by electron microscopy of infected hepatic sinusoidal lining cells, and it was characteristic of the unique developmental cycle of a chlamydial agent. isolation and speciation of the organism ... | 1982 | 7162133 |
| activation of vitellogenin gene transcription is a direct response to estrogen in xenopus laevis liver. | estrogen induces the synthesis of vitellogenin mrna by activating transcription of the vitellogenin genes. quantitative inhibition of liver protein synthesis by cycloheximide does not prevent activation of vitellogenin gene transcription. the relative transcription rate of the vitellogenin genes in estrogen stimulated liver is similar in control and cycloheximide treated animals (800-1000 ppm). selective estrogen activation of vitellogenin gene transcription therefore represents a direct effect ... | 1982 | 7162991 |
| difference in the mechanism of the action of caffeine and thymol on the calcium sequestering property of sarcoplasmic reticulum of frog skinned muscle fibers. | the effects of caffeine and thymol on the release of calcium from sarcoplasmic reticulum (sr) of mechanically skinned fibers isolated from semitendinosus muscle of frog, xenopus laevis, are studied. calcium release caused by caffeine is composed of two processes, a fast and a slow ones. the fast process is observable only when the amount of calcium stored in sr is above a "threshold" value while the slow one detectable only below the threshold value. the rate of these two processes does not depe ... | 1982 | 7166721 |
| the role of neural retina in lens regeneration from cornea in larval xenopus laevis. | 1982 | 7170907 | |
| use of xenopus laevis larvae in 96-hour, flow-through toxicity tests with naphthalene. | 1982 | 7171848 | |
| cell locomotion in vitro by xenopus laevis gastrula mesodermal cells. | prospective mesodermal cells of xenopus laevis gastrulae showed substantial locomotion in vitro, averaging 4.3 microns/min, when dissociated and cultured on a glass surface coated with collagen and fetal bovine serum. the cells translocate by making lamellipodia and filopodia whereas the main cell body remains rounded. when two mesodermal cells made contact with each other, they showed contact paralysis of lamellipodial activity. in contrast, when mesodermal cells contact ectodermal cells, conta ... | 1982 | 7172219 |
| lactate dehydrogenase of xenopus laevis laevis and xenopus borealis depends on a multiple gene system. | lactate dehydrogenase isozymes have been reinvestigated in xenopus laevis laevis and xenopus borealis. high resolution zymograms of various organs demonstrate that in both species the ldh isozymes are governed basically by a three-gene system: ldh-a coding for positively charged polypeptide, and ldh-b and ldh-c for negatively charged polypeptides (at ph 8.9). these three ldh subunits when assembled in tetramers show differential sensitivity to heat inactivation; the c4 homotetramer is the most l ... | 1982 | 7175448 |
| the regional distribution of poly (a) and total rna concentrations during early xenopus development. | xenopus laevis embryos were oriented and sectioned into six regions along one of three axes: animal-vegetal, dorsal-ventral, or right-left. total rna (predominantly ribosomal rna) and poly riboadenylate [poly (a)] were measured for each region during early embryogenesis. the concentrations of both total rna and poly(a) are nonuniformly distributed during early development. total rna is approximately four-fold more concentrated in the more animal portions than the more vegetal portions of the emb ... | 1982 | 7175452 |
| voltage- and stage-dependent uncoupling of rohon-beard neurones during embryonic development of xenopus tadpoles. | 1. electrical coupling of rohon-beard neurones in the spinal cord of xenopus laevis has been studied from the time of closure of the neural tube (stage 20, 22h after fertilization of the egg) to the free swimming tadpole (stage 49, 12d old). pairs of cells were examined by impaling both simultaneously with single micro-electrodes having current-passing and voltage-recording capabilities.2. at the earliest time studied (stage 20), before ca(2+) action potentials are detected, cells are electrical ... | 1982 | 7175739 |
| [modeling a persistent infection by tick-borne encephalitis virus strains in a cell culture of the clawed toad]. | differences in the ability of 12 tick-borne encephalitis virus strains to induce persistent infection in the culture of clawed frog cells incubated at 26-32 degrees c were shown. in 8 strains the process of persistence was accompanied by the stable preservation of the infectious virus in the culture medium during 10 passages, while in 4 strains the virus disappeared already in passages 3-8. | 1982 | 7180255 |
| comparative study of ultrastructures of the lateral-line organs and the palatal taste organs in the african clawed toad, xenopus laevis. | the fine structure of the lateral-line organ and the palatal taste organ in the african clawed toad, xenopus laevis, was examined by means of electron microscopy. the lateral-line organ consisted of hair and accessory cells. the apical surface of a hair cell was studded with one kinocilium and 20 to 40 stereocilia. synaptic bodies and subsynaptic cisternae were found in the cytoplasm of a hair cell adjacent to the synaptic contacts with the afferent and the efferent nerve endings, respectively. ... | 1982 | 7181143 |
| development of the optic nerve in xenopus laevis. i. early development and organization. | development of the xenopus laevis optic nerve was studied by light and electron microscopy from embryonic stage 26, before the retina has formed, to juveniles, 8 months postmetamorphic. low-power em photographs of sections through the retinal optic nerve (ron), middle optic nerve (mon) and chiasmatic optic nerve (con) were prepared at different stages and the areas containing large axons (0.5 micron) were traced in optic nerve reconstructions. ordering of fibre size along a dorsoventral axis was ... | 1982 | 7183741 |
| development of the optic nerve in xenopus laevis. ii. gliogenesis, myelination and metamorphic remodelling. | we studied the time of origin, development and location of glial elements in the developing optic nerve of xenopus with light and electron microscopy. the first cells acting as a primitive glia are ependymal cells lying dorsal to the chiasmatic optic nerve (con) at nieuwkoop & faber (1956) nf stage 39. later (stage 47/48), immature astrocyte cell bodies migrate from the periphery of the middle optic nerve (mon) into the central fibre mass along cytoplasmic processes extending from the outer glia ... | 1982 | 7183742 |
| increased adhesiveness at sites of high acetylcholine receptor density on embryonic amphibian muscle cells cultured without nerve. | in culture, myotomal muscle cells from xenopus laevis embryos develop discrete patches of high acetylcholine receptor (achr) density. to examine the relative adhesiveness of these sites, muscle cells having achr patches on their lower surface (apposed to the culture dish) were identified and were then treated with dibucaine or potassium-ringer in order to cause the cells to round up. more than 90% of these cells remained attached at an achr patch after rounding up, and this was the case even whe ... | 1982 | 7183745 |
| 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 |
| 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 | |
| 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 |
| 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 |
| cellular commitment for post-gastrular increase in alkaline phosphatase activity in xenopus laevis development. | xenopus embryos were dissociated into cells and cultured in ca2+-free medium to study the relationship between the cell-to-cell interaction and macromolecular synthesis. under the conditions, cells did not aggregate at all, and remained isolated even while they were dividing actively. synthesis of dna and protein as studied by the incorporation of (3h) thymidine and (3h) leucin proceeded as in the aggregating cells. also, the activity to synthesize rrna, 5s rna, and heterogeneous rna as determin ... | 1982 | 6175549 |
| argyrophilic nuclear and nucleolar proteins of xenopus laevis oocytes identified by gel electrophoresis. | 1982 | 6173244 | |
| forskolin increases camp and inhibits progesterone induced meiosis reinitiation in xenopus laevis oocytes. | the diterpene, forskolin, is a potent and reversible inhibitor of progesterone-induced meiosis in xenopus laevis oocytes (ed50 of inhibition approximately 3 microm). forskolin alone increases camp concentration in oocytes, but, unlike with cholera toxin treatment, there is no lag phase, and reversibility is obtained by washing the cells. progesterone decreases the forskolin effect on camp accumulation, but camp concentration remains above the level observed in oocytes treated with progesterone a ... | 1982 | 6180891 |
| medusoid fibril bodies: a novel type of nuclear filament of diameter 8 to 12 nm with periodic ultrastructure demonstrated in oocytes of xenopus laevis. | 1982 | 6180897 | |
| mouse interferon messenger rna: characterization of the xenopus laevis oocyte translation product. | 1982 | 6181741 | |
| isolation and characterization of ifn-gamma mrna derived from mitogen-induced human splenocytes. | human splenocytes from large cultures (5 1) were stimulated with staphylococcus enterotoxin a (sea). after 2.5 d of conditioning, poly a+rna was isolated from these cultures and its in-vitro translational capacity was evaluated in a wheat germ extract. injection of the rna into xenopus laevis oocytes yielded a low but reproducible amount of ifn activity, which was neutralizable only by an antiserum to gamma interferon (ifn-gamma) and not by antisera to alpha interferon (ifn-alpha) and/or beta in ... | 1982 | 6182256 |
| a study of the motion of organelles which undergo retrograde and anterograde rapid axonal transport in xenopus. | 1. axonally transported organelles were detected optically in myelinated axons from xenopus laevis at room temperature (21-23 degrees c). details of the motion of organelles which were transported in the retrograde and anterograde directions were studied using filmed records.2. a group of 133 organelles with a mean retrograde velocity of 0.91 mum/sec was compared with a group of thirty-nine organelles with a mean anterograde velocity of 0.93 mum/sec.3. averaged power spectra of the positional de ... | 1982 | 6182282 |
| translation in vitro of rna from the human malarial parasite plasmodium falciparum. | rna has been isolated from the human malarial parasite, plasmodium falciparum, and translated in vitro using two systems: rabbit-reticulocyte lysate and xenopus laevis oocytes. polypeptides are synthesized that are characteristic of the parasite isolate and the developmental stage from which the rna was purified. many of these polypeptides are precipitated by antibody from an immune monkey. analysis of the primary structure of these polypeptides should give the information necessary to produce a ... | 1982 | 6182932 |
| regulation of protein synthesis and accumulation during oogenesis in xenopus laevis. | 1982 | 6183158 | |
| divergence of the two albumins of x. laevis. evidence for the glycosylation of the major 74k albumin. | the mrnas coding for the 68,000 and 74,000 dalton serum albumins of xenopus laevis were purified by hybridisation to their corresponding cloned cdna and translated using the reticulocyte lysate. the primary translational product of the 68,000 dalton albumin has a molecular weight of 70,000 daltons suggesting that it is synthesised with a signal peptide which is cleaved during secretion. in contrast, the primary translational product of the 74,000 dalton albumin has a molecular weight of 72,000 d ... | 1982 | 6184256 |
| biosynthesis of pairs of peptides related to melanotropin, corticotropin and endorphin in the pars intermedia of the amphibian pituitary gland. | this study concerns the biosynthesis of a number of peptides in the neurointermediate lobe of the pituitary gland of the aquatic toad, xenopus laevis. using pulse-chase incubations in vitro and high-performance liquid chromatographic analysis, it could be shown that these peptides are synthesized through processing of a prohormone, pro-opiomelanocortin; all peptides were released into the incubation medium. on the basis of electrophoretic analysis, selective amino acid incorporation and immunopr ... | 1982 | 6277629 |
| mrna- and dna-directed synthesis of herpes simplex virus-coded exonuclease in xenopus laevis oocytes. | microinjection of herpes simplex virus (hsv)-infected cell mrna into xenopus laevis oocytes resulted in the production of a new exonuclease activity. this enzyme strongly resembled the hsv alkaline exonuclease in many biochemical properties, and hybrid-arrested translation studies showed that it was virus coded, mapping at 0.080 to 0.185 genome map units. exonuclease mrna had a size and genome location equivalent to the mrna encoding v185 in reticulocyte lysates, suggesting that v185 is the exon ... | 1982 | 6287023 |
| chromosome-bound mitotic factors: release by endonucleases. | additional evidence is presented to support our recently reported conclusion that the mitotic factors of mammalian cells, which induce germinal vesicle breakdown and chromosome condensation when injected into fully grown xenopus laevis oocytes, are localized on metaphase chromosomes. chromosomes isolated from mitotic hela cells were further purified on sucrose gradients and digested for varying periods with either the micrococcal nuclease or dnase ii. at each time point of digestion the amount o ... | 1982 | 6287433 |
| immunohistochemical demonstration of tsh-, lh- and acth-cells in the hypophysis of tadpoles of xenopus laevis d. | by use of the immunofluorescence technique tsh-, lh- and acth-cells were localized in the hypophysis of tadpoles of xenopus laevis. the first signs of the activity of these cells were observed in early stages of the development, i.e., stage 39 for acth, and stage 42 for tsh and lh. | 1982 | 6288250 |
| cloning in a cosmid vector of complete 37 kb and 25 kb ribosomal dna repeat units from the chicken. | dna fragments of up to 40 kb containing rrna-coding sequences have been isolated from a chicken liver dna library prepared in the cosmid phc79. characterization of the cloned dna by r-loop and restriction mapping has shown that there are two size classes of repeat unit, one of 37 kb and one of 25 kb, the larger of which is a family of units which vary slightly in size. these two classes were shown to be present in the dna of a single chicken. the size of the internal transcribed spacer in the ch ... | 1982 | 6289899 |
| a restriction map of xenopus laevis mitochondrial dna. | the mitochondrial dna from xenopus laevis is a 17.4 x 10(3)-base-pair circular dna molecule. the mapping of this dna, using 19 different restriction endonucleases is reported here. the sites are as follows: 1 for bamhi, psti, saci, sali, bali; 2 for bglii, sacii, ecori, clai, 3 for xhoi, 4 for avai, xbai, pvuii, 5 for hindiii, 6 for hhai, bcli, hpai, 10 for avaii and 11 for hincii. the same sites (except for one of the two clai sites) are observed in the molecule cloned in pbr322 dna. the fragme ... | 1982 | 6290211 |
| adenylate cyclase in xenopus laevis oocytes: characterization of the progesterone-sensitive, membrane-bound form. | progesterone-induced reinitiation of meiosis in xenopus laevis oocytes involves a decrease in camp level. in these cells, adenylate cyclase is compartmentalized, with 25-30% in the plasma membrane fraction p-10000 (sedimenting at 10000 x g) and greater than 50% in the cytosol. soluble adenylate cyclase appears not to be regulated via a gtp-binding regulatory protein (g/f) and is insensitive to progesterone. in contrast, membrane-bound adenylate cyclase seems to be linked to g/f, since it is stim ... | 1982 | 6290296 |
| methylation of simian virus 40 hpa ii site affects late, but not early, viral gene expression. | dna methylation has been correlated with reduced gene expression in a number of studies, although evidence for a casual link between the two events has been lacking. because microinjection of simian virus 40 (sv40) dna into the nucleus of xenopus laevis oocytes results in the synthesis of both early and late viral gene products, it was possible to test whether a specific methylation event can affect gene expression. the single sv40 hpa ii site at 0.72 sv40 map units was specifically methylated w ... | 1982 | 6291026 |
| microinjected progesterone reinitiates meiotic maturation of xenopus laevis oocytes. | microinjection of progesterone dissolved in paraffin oil induces the reinitiation of meiotic maturation in the xenopus oocyte; 50% maturation is obtained when 50 nl of a 50 microm solution is microinjected into the oocyte. the kinetics of the response to microinjected progesterone are similar to the kinetics of response to externally applied hormone. when an aqueous solution of progesterone is microinjected instead of an oil solution, maturation is never observed, a result which confirms previou ... | 1982 | 6291050 |
| initiation of replication at specific origins in dna molecules microinjected into unfertilized eggs of the frog xenopus laevis. | initiation of dna replication at specific origins was observed by electron microscopy after microinjection of pxlr11, pxlr14 or col e1 plasmid dna molecules into unfertilized eggs of the frog, xenopus laevis. these results are in apparent contradiction with published reports (harland and laskey, cell 21, 761-771, 1980; laskey and harland, cell 24, 283-284, 1981) that specific origin sites were not used in xenopus laevis eggs. we suggest that eucaryotic origins exist that both increase the probab ... | 1982 | 6291769 |
| interaction of steroids and growth factors with the plasma membrane in the induction of oocyte maturation in xenopus laevis. | 1982 | 6292941 | |
| nad-glycohydrolase activity in xenopus laevis oocytes and early embryos. | 1982 | 6293487 | |
| simple, efficient in vitro synthesis of capped rna useful for direct expression of cloned eukaryotic genes. | a simple and efficient method for direct in vitro synthesis of capped transcripts of cloned eukaryotic genes is described. as an example capped transcripts were made from a plasmid containing the human fibroblast interferon gene cloned under the control of a prokaryotic promoter. these transcripts were translated in vivo in xenopus laevis oocytes and in vitro in reticulocyte and in wheat germ cell-free protein synthesizing systems. | 1982 | 6294601 |
| vitellogenin genes a1 and b1 are linked in the xenopus laevis genome. | genomic clones containing the xenopus laevis vitellogenin gene b1 have been isolated from dna libraries and characterized by heteroduplex mapping in the electron microscope, restriction endonuclease analysis, and in vitro transcription in a hela whole-cell extract. sequences from the 3'-flanking region of the previously isolated a1 vitellogenin gene were found in the 5'-flanking region of this b1 gene. thus, the two genes are linked, with 15.5 kilobase pairs of dna between them. their length is ... | 1982 | 6294657 |
| isolation and structural analysis of ribosomal protein genes in xenopus laevis. homology between sequences present in the gene and in several different messenger rnas. | 1982 | 6296397 | |
| characterization of histone genes isolated from xenopus laevis and xenopus tropicalis genomic libraries. | using a cdna clone for the histone h3 we have isolated, from two genomic libraries of xenopus laevis and xenopus tropicalis, clones containing four different histone gene clusters. the structural organization of x. laevis histone genes has been determined by restriction mapping, southern blot hybridization and translation of the mrnas which hybridize to the various restriction fragments. the arrangement of the histone genes in x. tropicalis has been determined by southern analysis using x. laevi ... | 1982 | 6296782 |
| organization and expression of cloned histone gene clusters from xenopus laevis and x. borealis. | we have isolated several clones containing xenopus histone genes from genomic libraries of x. laevis and x. borealis dna. each genomic clone has been mapped and the positions of 26 histone genes in seven laevis clones and 5 histone genes in one borealis clone have been determined. in laevis, the histone gene clusters show considerable variation in gene order within a single individual. when the cloned dnas were microinjected into the nucleus of xenopus oocytes, expression of cloned genes at the ... | 1982 | 6296783 |