Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| the ultrastructure of the dorsal yolk-free cytoplasm and the immediately surrounding cytoplasm in the symmetrized egg of xenopus laevis. | cytoplasmic segregation and subsequent dorsad displacement of the segregated cytoplasm lead to symmetrization of the egg of xenopus laevis. at 60 min post-fertilization (p.f.) the 'dorsal yolk-free cytoplasm' (dyfc) is located in the dorso-animal part of the egg. its ultrastructure and that of the immediately surrounding cytoplasm have been studied with transmission electron microscopy (tem). the endoplasmic reticulum (er) within the dyfc consists of single or paired cisternae and many small ves ... | 1979 | 479742 |
| cell number in relation to primary pattern formation in the embryo of xenopus laevis. i. the cell cycle during new pattern formation in response to implanted organizers. | results are presented which offer strong evidence that extensive alteration of the fates of embryonic xenopus cells occurs independently of the schedule of cell division, after operations which lead to a doubling of the axial pattern of mesodermal differentiation in the gastrula. the experimental strategy was to make estimates of total mesodermal cell numbers and mitotic index in closely matched sets, each of three synchronous sibling embryos, fixed during the ten hours following the close of ga ... | 1979 | 479743 |
| the activity of cholinesterases during the development of xenopus laevis. | the activity of cholinesterases during the early development of xenopus laevis has been examined, and the activity of acetylcholinesterase in particular has been distinguished from other cholinesterases. in contrast to some earlier findings, the activity of acetylcholinesterase is low at early stages and gradually increases during development. possible reasons for the differences between the earlier results and those reported here are discussed. | 1979 | 479745 |
| structural changes in single muscle fibers after stimulation at a low frequency. | direct stimulation of single muscle fibers from xenopus laevis at a frequency of 1 hz results in a decline of the peak isometric twitch tension after about 200 twitches. fibers were chemically fixed in glutaraldehyde after a varying number of twitches and at several fatigue levels, and the ultrastructural appearance was compared with that of resting fibers treated by identical fixation methods. no gross structural abnormalities were observed but subtle changes occurred. the mitochondria of stimu ... | 1979 | 479818 |
| [cell proliferation and migration in the roof of the mesencephalon (tectum) in xenopus laevis tadpoles and adult frogs normally and in brain injury. ii. cell proliferation and differentiation of the tectum in frogs]. | the proliferation and directions of cell differentiation in tectum opticum were studied in the young frogs under the conditions of normal development and upon brain trauma by means of 3h-thymidine autoradiography. the same types of cells were shown to be able of proliferation in both the cases: cells of the ventricle zone and glioblasts (gliocytes) in all other tectum layers. a study of directions of the tectum proliferating cells' differentiation in the frogs has shown that the proliferating ce ... | 1979 | 481850 |
| contrasting denaturation maps of xenopus laevis and xenopus borealis mitochondrial dnas. | denaturation maps of mitochondrial dnas of xenopus laevis and xenopus borealis are radically different from each other. this is in striking contrast to the invariant denaturation patterns previously recognized among mtdnas of various drosophila species, particularly, since the two toads may be even more closely related to each other than the drosophila species. | 1979 | 486484 |
| quantitative determination of amplified rdna and its distribution during oogenesis in xenopus laevis. | the number of extra-chromosomal nucleoli and their rdna content were determined during oogenesis in xenopus laevis. the highly variable number of nucleoli (500 to 2,500) in oocytes of the same stage and from the same female or of different stages or from different females is not a measure of the extent of amplification. in all oocytes examined, a inversely proportional relation was found between the number of nucleoli in an oocyte and their mean rdna content. these results indicate that there is ... | 1979 | 487908 |
| enrichment and characterization of the dna coding for vitellogenin in xenopus laevis. | purified vitellogenin mrna of xenopus laevis was incubated with mechanically sheared dna in high concentrations of formamide and the resulting r-loops (i.e. rna . dna hybrid fragments) separated from the bulk dna by caesium chloride buoyant density centrifugation. hybridization with 125i-labeled vitellogenin mrna revealed a 15--30-fold enrichment of the dna coding for vitellogenin. restriction analysis of the r-loop-enriched dna demonstrated that all known endonuclease hindiii fragments coding f ... | 1979 | 488117 |
| alpha-melanotropin-like substances in the pituitary and plasma of xenopus laevis in relation to colour change responses. | 1979 | 488671 | |
| trochlear-oculomotor nerve interactions in xenopus laevis tadpoles: a temporal study. | when the trochlear nerve (niv), which innervates the superior oblique muscle (som), is crushed or cut at stages 48-49 in xenopus tadpoles, fibers from the oculomotor nerve (niii) sprout and invade the som. the maximal percentage of specimens having at least one oculomotor nerve fiber on the som on a given day increased from 9.1% following a single crushing of niv to 84.2% following three successive severings of niv and the average number of silver-impregnated niii fibers per specimen increased f ... | 1979 | 490132 |
| x-ray effect on the development of xenopus laevis embryos--with special reference to primordial germ cells. | 1979 | 490458 | |
| toxicity of selenium to developing xenopus laevis embryos. | se in the form of sodium selenite is toxic to xenopus laevis embryos and tadpoles continuously exposed to concentrations above 1 ppm. concentrations of 2 ppm and above result in severe developmental abnormalities and increased mortality. uptake and loss of radioactive se from water are rapid, but depuration is not complete indicating that some se can remain bound by the organism. the facts that se is toxic at low levels to xenopus embryos and tadpoles, can cause developmental abnormalities, and ... | 1979 | 490681 |
| the putative promoter of a xenopus laevis ribosomal gene is reduplicated. | with the aid of a novel poly-da tailing-partial restriction technique and s1-protection mapping, the 5' terminal coding sequence for the 40s precursor ribosomal rna of xenopus laevis has been exactly identified. since the promoter sequence for the 40s rna should lie close to its 5' terminal coding sequence, we are able to conclude that the "bam-island" sequence reduplication (1) almost certainly represents a promoter reduplication. | 1979 | 493120 |
| expression of the mitochondrial genome in xenopus laevis: a map of transcripts. | the twelve most abundant transcripts in x. laevis mitochondria were characterized, and their coding regions were mapped on the mitochondrial dna (mtdna) by r loop mapping in the electron microscope and by rna gel transfer hybridization. the transcripts map in nonoverlapping positions with one exception, and they account for about 80% of the coding capacity of mtdna. ten of the twelve rna molecules contain poly(a): the two poly(a)-lacking transcripts are the rrnas. analysis withe single-strand-sp ... | 1979 | 498281 |
| turnover and processing of poly(a) in full-grown oocytes and during progesterone-induced oocyte maturation in xenopus laevis. | 1979 | 499663 | |
| the time scale of tooth development and replacement in xenopus laevis (daudin). | one hundred and seventy two larval specimens of xenopus laevis were reared in such a way that their rates of development (as measured by external criteria) were similar, and so the course of dental development could be examined histologically in a cross sectional study. in this way the events of tooth development were observed, and a time scale constructed for these events. the teeth took an average time of 26 days to develop, erupt and become ankylosed to the bony pedestal, after which each too ... | 1979 | 500489 |
| transcription initiation of xenopus 5s ribosomal rna genes in vitro. | we have studied initiation of transcription of 5s rna genes in extracts of xenopus laevis oocyte nuclei. to aid in this study we developed a general assay for specificity of transcription initiation that does not require accurate termination of transcription. following in vitro transcription with gamma-32p-labeled nucleoside triphosphages, the rna is digested with pancreatic rnaase and fingerprinted by two dimensional chromatography. a 5s rna gene with a variant sequence, in which the g residue ... | 1979 | 503853 |
| [determination of the decrease in the regenerative power of the optic tectum of xenopus laevis (daudin) during the tadpole stage]. | 1979 | 506629 | |
| unusual particle trajectories and structural arrangements in myelinated nerve fibers. | others have reported that axonally transported particles, which usually travel in a direction roughly parallel to the axis of the nerve fiber, may suddenly shift sideways as though changing tracks. examples of this rare type of movement are shown for particles undergoing transport in myelinated axons of xenopus laevis. an examination of the structure of axons from xenopus showed that some microtubules, neurofilaments, and elements of endoplasmic reticulum may also exhibit marked deviations from ... | 1979 | 509371 |
| utilization of stored mrna in xenopus embryos and its replacement by newly synthesized transcripts: histone h1 synthesis using interspecies hybrids. | we studied h1 gene expression in hybrids of xenopus laevis (female) x xenopus borealis (male) and saw paternal h1 synthesis in mid-blastulae, which indicates that the h1 genes are active by this stage. the behavior of the maternal store of h1 histone mrna was studied in androgenetic haploids. in which all stored mrna is of the laevis type and all new transcripts are borealis. this showed that the initial activation of h1 synthesis occurs entirely by mobilizing maternal transcripts and that these ... | 1979 | 509520 |
| phylogeny of immunocompetent cells: iii. mitogen response characteristics of lymphocyte subpopulations from normal and thymectomized frogs (xenopus laevis). | 1979 | 509538 | |
| the activity and properties of poly(adenosine diphosphate ribose) polymerase in vitro during the embryonic development of the south african clawed toad xenopus laevis. | 1979 | 510788 | |
| analysis of xenopus laevis globins during development and erythroid cell maturation and the construction of recombinant plasmids containing sequences derived from adult globin mrna. | 1979 | 510792 | |
| post-translational modification of rat immunoglobulins synthesized in the xenopus oocyte translation system. | the post-translational modification of rat immunoglobulin synthesised in xenopus laevis oocytes was studied. the major products of translation of rat spleen poly-(a) containing mrna were found to be assembled 7s immunoglobulin molecules indicating extensive modification of primary translation products. the possibility that these immunoglobulin molecules might include antibodies of defined specificity was investigated using spleen mrna from rats hyperimmunized with ferritin and keyhole limpet hae ... | 1979 | 511214 |
| relationships between eye factors and lens-forming transformations in the cornea and pericorneal epidermis of larval xenopus laevis. | larval xenopus laevis at stage 56 (nieuwkoop and faber, '56) were subjected to various types of lentectomy: (1) simple lentectomy, from the pupillary space after incision of outer and inner cornea; (2) lentectomy from the dorsal region of the eye; (3) lentectomy from the dorsal region of the eye and simultaneous incision of the outer cornea; (4) lentectomy from the dorsal region of the eye and simultaneous incision of the outer and inner cornea. the results obtained show that the outer cornea un ... | 1979 | 512595 |
| [elongated mitotic cells in the neuroepithelium of xenopus laevis and notophtalmus viridescens]. | most neuroepithelial cells in the embryos of xenopus laevis and notophtalmus viridescens become round upon entering into mitosis. however, many maintain their elongated form, or show long cytoplasmic processes, during mitosis. it therefore seems possible that, in these species, two groups of microtubules are present during mitosis: cytoplasmic microtubules and mitotic microtubules. | 1979 | 515478 |
| aerobic and anaerobic contributions to sustained activity in xenopus laevis. | in conditions of declining water po2, xenopus obtains the majority of resting oxygen needs from lung breathing at 15 degrees and 25 degrees c. the critical oxygen tension was 120 +/- 9 mm hg at 15 degrees c, and 90 +/- 10 mm hg at 25 degrees c. during 30 min stimulation of activity to complete exhaustion at 15 degrees c, frogs exhibited an aerobic capacity of 1.7 microliter o2.g-1.h-1 and accumulated 2.22 mg lactate . g-1. following activity these animals exhibited an oxygen debt of 49.2 microli ... | 1979 | 515565 |
| sequestration and turnover of guinea-pig milk proteins and chicken ovalbumin in xenopus oocytes. | the stability and distribution of proteins within the living cell can be studied using xenopus laevis oocytes. microinjection of messenger rnas and secretory proteins, followed by cell fractionation, shows that transfer of ovalbumin and milk proteins across intracellular membranes of the oocyte only occurs during their synthesis. thus milk protein primary translation products, made in the wheat germ cell-free system, when injected into oocytes remain in the cytosol and are not recovered within m ... | 1979 | 520309 |
| influence of ci-628 (cn-55, 945-27) on estrogen-induced vitellogenin synthesis and on the ultrastructure of hepatocytes in male xenopus laevis. | 1979 | 520332 | |
| elimination and metabolism of dimethylnitrosamine (dmn) by xenopus laevis and other amphibians. | the elimination of (14c)-dmn after i.p. injection into xenopus was measured, as was the metabolism in vitro of (14c)-dmn by liver from xenopus and 9 other amphibian species. in view of its rapid elimination from the body and low rate of metabolism by xenopus liver in vitro, dmn is unlikely to be toxic or carcinogenic in xenopus. | 1979 | 520492 |
| the localisation of lead in the skin of light- and dark-adapted xenopus laevis. | toads pretreated for 2 months on either a dark or a light background were then exposed to lead nitrate at 50 ppm lead for 21 days, the illumination regimes being maintained. metal analysis of dorsal skin showed significantly higher lead levels (p less than 0.01) in dark-adapted toads. no precipitated lead deposits were observed at the ultrastructural level, necessitating x-ray microanalysis of sections containing melanophores, gland cells and general (non-melanophore) cytoplasm. analysis showed ... | 1979 | 521319 |
| the emergence, localization and maturation of neurotransmitter systems during development of the retina in xenopus laevis. i. gamma aminobutyric acid. | the high-affinity uptake, biosynthesis and release of gaba have been studied in the retina of xenopus laevis. in the mature retina, [3h]-gaba is accumulated predominantly by horizontal cells. a second population of cells located in the inner nuclear layer (possibly a type of amacrine cell) also showed a specific gaba uptake. in addition, this retina contains significant activities of l-glutamic acid decarboxylase and also releases [3h]-gaba in response to increasing k+ concentrations in the medi ... | 1979 | 521507 |
| the use of radioiodinated protein substrates for the assay of trypsin and the hatching enzyme from the amphibian xenopus laevis. | 1979 | 525784 | |
| use of different carriers to demonstrate thymic-dependent and thymic-independent anti-trinitrophenyl reactivity in the ambhibian xenopus laevis. | 1979 | 527747 | |
| structure and formation of ankylosis in xenopus laevis. | the structure of ankylotic teeth in xenopus laevis was studied by light, transmission, and scanning electron microscopy as well as by microradiography in decalcified and undecalcified specimens. the mature teeth of xenopus laevis are calcified from the crown to the base, fused to the jaw bone, and have no uncalcified area, such as a fibrous ring separating the tooth into the crown and pedicle. microradiography shows that the mature tooth and jaw bone appear as an x-ray opaque area, except for th ... | 1979 | 529293 |
| metabolic state dependent preservation of cells by fixatives for electron microscopy. | the preservation of mitochondria, cytoplasmic vacuoles and cytoplasm by various fixatives after various pretreatments of ethothelial heart cells from xenopus laevis tadpoles in tissue culture was investigated. the study was based on phase contrast cinemicrographic recordings and on qualitative and quantitative observations with the electron microscope. three fixatives were used: 3% glutaraldehyde in phosphate buffer, followed by 1% osmium tetroxide postfixation, fixation only with 1% osmium tetr ... | 1979 | 530094 |
| neurite complexes with merkel cells in larval tentacles of xenopus laevis. | 1979 | 535028 | |
| a quantitative electron-microscope analysis of chromatin from xenopus laevis lampbrush chromosomes. | the morphology of the dnp axis and rnp transcripts from xenopus laevis lampbrush chromosomes has been analysed using a modified miller spreading technique. two basictypes of chromatin have been distinguished. (1) discrete portions of dnp exhibiting high levels of transcriptive activity, with clear initiation and termination points (transcription units). interspersed with the units are sequences with little or no transcriptive activity (spacer dnp). the combination of transcription unit plus spac ... | 1979 | 536383 |
| cell number in relation to primary pattern formation in the embryo of xenopus laevis. ii. sequential cell recruitment, and control of the cell cycle, during mesoderm formation. | morphological evidence is presented that definitive mesoderm formation in xenopus is best understood as extending to the end of the neurula phase of development. a process of recruitment of cells from the deep neurectoderm layers into mesodermal position and behaviour, strictly comparable with that already agreed to occur around the internal blastoporal 'lip' during gastrula stage 20 (earliest tail bud). spatial patterns of incidence of mitosis are described for the fifteen hours of development ... | 1979 | 536690 |
| calcium-induced dehiscence of cortical granules in xenopus laevis oocytes. | microinjection of 0.1 microgram of ca++ into xenopus laevis oocytes induces breakdown of the cortical granules. the cortical granules disappeared in both full grown (stage vi) and small growing (stage iv) oocytes. microinjection of mg++, k+, or na+ had no effect on cortical granules in either stage iv or stage vi oocytes. small quantities (0.03 microgram) of ca++ induced dehiscence of the cortical granules only in proximity to the injection site. | 1979 | 536708 |
| expression of sea urchin histone genes in the oocyte of xenopus laevis. | 1979 | 537089 | |
| a trna gene of xenopus laevis contains at least two sites promoting transcription. | a small cloned dna segment previously shown to contain all genetic information for the expression of the trna1met gene of xenopus laevis was cleaved into an anterior and posterior portion by hae iii restriction. both restriction fragments were cloned in pcr1 using ecori linkers. starting from these tdna subclones, a series of new recombinants were constructed. the transcriptional activity of the cloned dna's was tested both in an in vitro transcriptional system and by means of the oocyte injecti ... | 1979 | 537910 |
| a new method for local artificial insemination of xenopus laevis eggs. | 1979 | 545168 | |
| expression of regenerative capacity of caudal spinal cord during the larval development of xenopus laevis. | 1979 | 547620 | |
| indirect identification of prolactin-producing cells in the pituitary gland of xenopus laevis daudin. | 1979 | 550867 | |
| axonal-ependymal associations during early regeneration of the transected spinal cord in xenopus laevis tadpoles. | the nature and organization of the cellular substrate supporting axonal outgrowth during early regeneration of the spinal cord following transection and/or segment removal were examined in xenopus tadpoles. longitudinal axonal compartments, formed by radial ependymal processes in unoperated spinal cords, were maintained within the rostral and caudal stumps throughout the early post-operative period. the first neuritic sprouts to appear near the cut ends of the cord were frequently associated wit ... | 1979 | 553146 |
| patterns of cell proliferation in the retina of the clawed frog during development. | quantitative assays of the spatial pattern of cell production in the developing retina of xenopus have been made using 3h-thymidine labelling and colcemid blockade of mitosis. reconstructions were made from serial sections showing the position of every mitotic figure in the retina. after stage 54 the number of mitotic figures decreases at the dorsal margin of the retina and increases at the ventral margin. the ventral:dorsal ratio of mitoses reaches 10:1 by metamorphosis. density of mitotic figu ... | 1979 | 759449 |
| influences of thyroxine on cell proliferation in the retina of the clawed frog at different ages. | the change in spatial pattern of retinal cell production that occurs after midlarvae stages in xenopus is shown to occur because of a greater proliferative response to thyroxine in the ventral than in the dorsal margin of the retina. the asymmetry of retinal cell production is not caused by a dorsoventral difference in the duration of the mitotic cycle. it is concluded that the asymmetry is due to differences in the number of proliferative cells in different parts of the retinal margin. | 1979 | 759450 |
| patterns of cell proliferation in the developing retina of the clawed frog in relation to blood supply and position of the choroidal fissure. | the pattern of retinal vasculative is described and the position at which cell proliferation at the ventral retinal margin is maximal was shown to be at the point of entry of the ventral blood vessels. to test whether there is a causal relation between retinal blood supply and retinal cell production, surgical inversion of the eye, transplantations and excisions of retina were done to change the pattern of retinal vasculature. the growth pattern of inverted eyes was normal with respect to the in ... | 1979 | 759451 |
| photoreceptor outer segment development: light and dark regulate the rate of membrane addition and loss. | the rate of membrane addition during outer segment development and the onset of membrane loss through shedding was evaluated for xenopus laevis embryos reared at 23 degrees c in constant light (ll), constant darkness (dd), and cyclic light (12 hr l/12 hr d; ld). embryos were placed under these lighting conditions 1 day following fertilization at open neural plate stages and were sampled each day for 9 days. rod and cone outer segments were present in each treatment group on day 3 of development. ... | 1979 | 761968 |
| ultrastructural development of rohon-beard neurons: loss of intramitochondrial granules parallels loss of calcium action potentials. | we have examined the ultrastructure of the cell body of a vertebrate spinal neuron, the rohon-beard cell of xenopus laevis, at four stages during its development (nieuwkoop and faber stages: 22, 29/30, 37/38 and 42). at this time it has attained its electrical excitability and the action potential mechanism in the cell body is maturing through a sequence of stages in which the inward current is carried by ca++ (stages 20-25), later by ca++ and na+ (stages 25-40), and finally by na+ (stages 40-51 ... | 1979 | 762270 |
| remodelling of optic nerve myelin sheaths and axons during metamorphosis in xenopus laevis. | whole mounts and transverse sections of xenopus optic nerves were examined with the light and electron microscopes before, during, and after metamorphosis. in stage 52--58 tadpoles, almost all myelin sheaths were circular in transverse sections. early in metamorphosis (stages 60--61) large redundant myelin loops surrounded many large axons in central regions of the nerve. the loops subsequently were broken down into ovoids and lamellar segments that remained mostly within oligodendrocytes. these ... | 1979 | 762287 |
| thyroid hormone induces competence for oestrogen-dependent vitellogenin synthesis in developing xenopus laevis liver. | 1979 | 763351 | |
| mitochondria dna synthesis in oocytes of xenopus laevis. | 1979 | 570931 | |
| effects of injected inhibitors of microfilament and microtubule function on the gastrulation movement in xenopus laevis. | 1979 | 571368 | |
| the modification of stored histones h3 and h4 during the oogenesis and early development of xenopus laevis. | 1979 | 571369 | |
| ultraviolet effects on presumptive primordial germ cells (ppgcs) in xenopus laevis after the cleavage stage. | 1979 | 571826 | |
| modulations of histone messenger rna during the early development of xenopus laevis. | 1979 | 572787 | |
| an ultrastructural study of the effects of wheat germ agglutinin (wga) on cell cortex organization during the first cleavage of xenopus laevis eggs. i. inhibition of furrow formation. | xenopus laevis fertilized eggs have been treated with wheat germ agglutinin (wga) before the onset of the first cleavage, at the stripe stage and during groove deepening. the ultrastructure of the animal cortex of the arrested embryos has been compared with that of the same region of control embryos at different stages of first furrow formation and of cytochalasin b-treated embryos. the outer side of the plasma membrane of wga-treated embryos is covered with a coat which is different from the di ... | 1979 | 573274 |
| an ultrastructural study of the effects of wheat germ agglutinin (wga) on cell cortex organization during the first cleavage of xenopus laevis eggs. ii. cortical wound healing. | uncleaved fertilized eggs of xenopus laevis treated with wheat germ agglutinin (wga) have been pricked at the animal pole both inside and outside the regressed furrow region. the wounded cortex of both regions has been studied with the electron microscope and compared with the same region of wounded, untreated eggs. in all 3 cases, filaments are organized in an annular zone in the damaged cortex. when the surface is pricked outside the regressed furrow of wga-treated embryos, bundles of microfil ... | 1979 | 573275 |
| changes in protein synthesis during the development of xenopus laevis. | patterns of protein synthesis during the development of xenopus were studied by two-dimensional gel electrophoresis. up to the end of the blastula stage we find no newly synthesized proteins which are not already made in the oocyte. the first new proteins are seen during gastrulation, and they increase in number during neurulation. some of these are restricted to the 'ectodermal' region, and some to the 'endodermal' region of embryos divided into two parts. these new, region-specific proteins in ... | 1979 | 573306 |
| synthesis and processing of maize storage proteins in xenopus laevis oocytes. | xenopus oocytes injected with zein mrnas efficiently synthesized maize storage proteins for prolonged periods. under optimal conditions, zein was synthesized at 3 ng/hr and represented approximately 10% of the total protein synthesized in the oocyte. the mrna from the normal maize inbred line directed synthesis of all the major zein components; however, products of mrna from the opaque-2 mutant did not contain the largest zein component. zein proteins synthesized in the oocyte were 2000 daltons ... | 1979 | 16592743 |
| the role of lactic acid accumulation in muscle fatigue of two species of anurans, xenopus laevis and rana pipiens. | fatigue produced a marked increase in the lactic acid content of hind-limb muscles, the blood, and the whole animal. after 15 min of rest there was little decline of lactic acid levels but the animals could be stimulated into about 3 min of intense activity. this re-fatigue produced a further increase in lactic acid levels. gastrocnemius muscles removed from fatigued frogs and stimulated in vitro were able to generate initial tensions similar to those in control muscles; total tension was about ... | 1979 | 11799691 |
| development of the urostyle during metamorphosis in five species of anurans. | normal development of the urostyle is described during late stages of metamorphosis in five species of anurans: xenopus laevis (daudin), bufo americanus holbrook, pseudacris triseriata (wied), hyla chrysoscelis cope, and rana pipiens schreber. the developing urostyle of all five species is composed of essentially the same cartilaginous elements: one pair of basidorsals above the notochord and the subtended hypochord. among the five species there is variation in such details as the number of spin ... | 1979 | 30200677 |
| quantitative aspects of rna synthesis in normal and lithium-treated embryos ofxenopus laevis. | the treatment ofxenopus early embryos with lithium chloride produces exogastruale - embryos which fail to gastrulate normally and in which the rates of cell division are reduced. in the present study estimations of incorporations of (5-3h) uridine and the specific activities of the 5'-ribonucleotide precursor pools showed that exogastrulae have higher rates of rna synthesis per cell than control neurulae. sub-cellular fractionations showed that a greater proportion of labelled rna was retained i ... | 1979 | 28305001 |
| suspension feeding dynamics of anuran larvae related to their functional morphology. | the tadpoles of two anuran species, rana sylvatica and xenopus laevis, were fed various concentrations of two algae, anabaena sphaerica (large filaments) and chlorella pyrenoidosa (small unicells). filtering rates were measured indirectly with a coulter counter system; buccal pumping rates were observed directly.experimental measurements of buccal volume (volume cleared with each pump stroke) agreed closely with independent predictions from a descriptive model based on tadpole morphology. the xe ... | 1979 | 28309170 |
| new model cell systems (pk and xtc-2) for studying acute and persistent infections with herpes simplex and pseudorabies viruses. | herpes simplex virus type 1 (hsv-1) showed limited replication in pk (pig kidney) and xtc-2 (xenopus laevis frog) cell lines. virus replication depended on the multiplicity of infection (moi). at a high moi, hsv-1 caused a typical cytopathic effect (cpe) in xtc-2 cells but a little marked cpe in pk cells. pseudorabies virus (prv) replicated intensively in pk cells (permissive system) but not in xtc-2 cells (nonpermissive system). both viruses were adsorbed on to pk and xtc-2 cells. in infected p ... | 1980 | 6106375 |
| stimulus-induced release of endogenous amino acids from skins containing the lateral-line organ in xenopus laevis. | the release of endogenous amino acids from skins of xenopus laevis was studied by comparing the effects of pulsatile water motion on the efflux of glutamate and aspartate from isolated skins with and without lateral-line stitches. the stimulated efflux of glutamate from stitch skins was significantly greater than its stimulated efflux from non-stitch skins (p < 0.01). the results for aspartate were less clear cut. although the source and mechanisms underlying the greater stimulated efflux from s ... | 1980 | 6106556 |
| the effect of taxol on living eggs of xenopus laevis. | 1980 | 6108885 | |
| dominant lethality in xenopus laevis induced with triethylenemelamine (tem). | adult male south african clawed toads, xenopus laevis, were injected intraperitoneally with triethylenemelamine (tem) dissolved in water over a dose range of 13-1,300 micrograms/kg or with water (controls). mating of the treated males with untreated females was induced seven days later by injection of human chorionic gonadotropic hormone (hcg). accumulated lethality one week after fertilization among progeny was dose related. morphological abnormalities among embryos that survived to hatching we ... | 1980 | 6119818 |
| glutamate mimics the afferent transmitter in the xenopus laevis lateral line. | 1980 | 6113014 | |
| protein factor(s) from mitotic cho cells induce meiotic maturation in xenopus laevis oocytes. | 1980 | 6153367 | |
| the synthesis of authentic sea urchin transcriptional and translational products by sea urchin histone genes injected into xenopus laevis oocytes. | 1980 | 6154619 | |
| effects of rubidium, caesium, strontium, barium and lanthanum on ionic currents in myelinated nerve fibres from xenopus laevis. | a comparative analysis of the effects of externally applied rb+, cs+, ba2+ and la3+ on myelinated fibres under potential clamp conditions was made. the ions cs+, ba2+ and la3+ (belonging to groups 1a, 2a and 3a of period 6 in the periodic system) were found to affect the k system in specific ways. ba2+ and la3+ reduced the outward k+ current associated with positive potential steps; the effect of la3+ being larger than that of ba2+. the effect of ba2+ depended on the k+ concentration. cs+, ba2+ ... | 1980 | 6155047 |
| changes in "template-bound" and "free" rna polymerase activities in isolated nuclei from xenopus laevis embryos. | 1980 | 6155281 | |
| [synthesis of an interferon-specific translation inhibitor in xenopus laevis oocytes and its functional identification]. | 1980 | 6156812 | |
| isofocusing and immunoelectrophoretic studies of soluble eye lens proteins from regenerated and normally developed xenopus laevis. | 1980 | 6156856 | |
| a study on the steady-state population of poly(a)+rna during early development of xenopus laevis. | 1980 | 6156874 | |
| rapid orthograde transport of 32p-labelled material in amphibian sensory axons: a multiwire proportional chamber study. | a multiwire proportional chamber was used to follow the axonal transport of material labelled with [32p]orthophosphate in dorsal root ganglion (drg)--sciatic nerve preparations of xenopus laevis and rana catesbiana. the drg were exposed to label for a period of 4 h following which there was a period of continued delivery of labelled material to the nerve for up to 18 h. the front of the labelled material in the nerve moved at a velocity of 160--170 mm/24 h at room temperature (22.5--23.5 degrees ... | 1980 | 6158368 |
| characterization of cloned cdna sequences derived from xenopus laevis poly a(+) oocyte rna. | double-stranded cdna sequences were prepared from xenopus laevis ovary poly a(+) rna with amv reverse transcriptase and nuclease s1. they were inserted into the plasmid pbr 322 after ligation with a hind iii linker and were cloned in e. coli strain x1776. plasmid pools containing a cdna insert were identified by hind ii restriction and hybridization of the dna fragments with radiolabelled pbr 322 dna. hybridization of the positive pools with ovary rna labelled in vitro led to the identification ... | 1980 | 6159593 |
| le interferon mrna from human fibroblasts. | human f and le interferon can be clearly distinguished on the basis of different antigenic properties and host range. after inoculation with newcastle disease virus (ndv), gm-258 fibroblasts produced le as well as f interferon; in contrast, only f interferon was detectable after stimulation with poly(i) . poly(c). polyadenylylated mrna isolated from fibroblasts induced with poly(i) . poly(c) or ndv was injected into xenopus laevis oocytes and the interferon activities thus produced were analyzed ... | 1980 | 6159644 |
| appearance of rna with a specific size class of poly(a) in oocytes and eggs in hcg-stimulated xenopus laevis females. | using a 3h-poly(u) binding technique, poly(a) content has been measured in xenopus laevis eggs consisting of two groups: one was obtained from females 12 to 16 hr after a single injection of human chorionic gonadotropin (hcg) (designated "unstimulated" eggs), and the other was obtained one week later from the same females by the second injection of the hormone ("stimulated" eggs). the stimulated egg contained about a 1.2-fold larger amount of poly(a) than the unstimulated one. gel electrophoresi ... | 1980 | 6161208 |
| the nucleotide sequence of the putative transcription initiation site of a cloned ribosomal rna gene of the mouse. | approximately one kilobase pairs surrounding and upstream the transcription initiation site of a cloned ribosomal dna (rdna) of the mouse were sequenced. the putative transcription initiation site was determined by two independent methods: one nuclease s1 protection and the other reverse transcriptase elongation mapping using isolated 45s ribosomal rna precursor (45s rna) and appropriate restriction fragments of rdna. both methods gave an identical result; 45s rna had a structure starting from a ... | 1980 | 6162156 |
| differential effect of spermine on nuclear and cytoplasmic transfer rna methyl transferases from xenopus laevis oocytes. | x laevis ovarian tissue or isolated oocytes contain two major trna methyl transferase activities capable of methylating total e. coli trna using s-adenosyl methionine as a methyl donor. these enzymes can be resolved by chromatography on deae-cellulose or by gel filtration on sephadex g-200 into fractions i and ii. the trna methyl transferase i which is present mainly in the oocyte nuclei, has a molecular weight of 190,000 and an apparent km for s-adenosyl methionine of 1.5 microm. the activity o ... | 1980 | 6167207 |
| the short term accumulation of axonally transported organelles in the region of localized lesions of single myelinated axons. | myelinated axons were isolated from the sciatic nerve of xenopus laevis and were subjected to localized (less than 30 microns wide) lesions. in axons which were bathed in a 0.12 m potassium glutamate solution there was very little local reaction to the lesion and optically-detectable particles undergoing axoplasmic transport accumulated immediately adjacent to, and mostly distal to, the lesion. preparations fixed for electron microscopy at times up to 3 h following the lesion showed that the axo ... | 1980 | 6162922 |
| growth of anuran oocytes in serum-supplemented medium. | appropriately-sized oocytes from xenopus laevis can be grown in vitro in vitellogenin-containing serum for up to 2 weeks. the source of serum appears to be unimportant. rates of oocyte growth are somewhat better than those achieved in the presence of vitellogenin alone. rana pipiens oocytes grow about twice as fast as x. laevis oocytes under identical conditions. the oocyte culture conditions described appear to be applicable to amphibian oocytes in general. | 1980 | 6984201 |
| [vestibular apparatus study of the toad, xenopus laevis, and rats under prolonged weightlessness]. | fertilized eggs of the clawed toad xenopus laevis were placed aboard of orbital laboratory of "salut-6" spacecraft where they developed for 20 days at temperature 15 degrees c. the larvae were fixed in weightlessness. light and electronmicroscopic studies revealed undisturbed structure on the saccular and utricular maculae and otolith membranes. some ultrastructural abnormalities were found in the inner ear of adult rats after 20 days of weightlessness ("kosmos-936"). | 1980 | 6970471 |
| a hormonal component in central vestibular compensation. | in developing clawed toads xenopus laevis, the compensation mechanism of behavioural defects caused by unilateral labyrinthectomy consists of two components, a vestibular one and a hormonal one. thyroxine accelerates this compensation. | 1980 | 6971023 |
| an atlas of notochord and somite morphogenesis in several anuran and urodelean amphibians. | a scanning electron microscopic, comparative survey of notochord and somite formation including some details of change in cell morphology and arrangement, was made of selected stages of two species of anuran amphibians (xenopus laevis and rana pipiens) and two species of urodeles (ambystoma mexicanum and pleurodeles waltlii). the ectoderm or neural plate was removed from fixed embryos and the dorsal aspect of the developing notochord and somite mesoderm was photographed. micrographs of comparabl ... | 1980 | 6971322 |
| the spatio-temporal framework of melanogenic induction in pigmented retinal cells of xenopus laevis. | using methods involving transplantation of neuroectoderm and eye rudiments between ap/ap mutants and +/+ embryos of xenopus laevis, new aspects of melanogenic induction have been ascertained. the possibility of separate induction of a melanocyte cell type and of the product of terminal differentiation in it-melanosomes, has been demonstrated. melanogenic induction starts at the late gastrula stage. it has an irreversible character which has been shown using the technique of double transplantatio ... | 1980 | 6975795 |
| immunological identification and localization of the predominant nuclear protein of the amphibian oocyte nucleus. | nuclei of vitellogenic oocytes of the frog, xenopus laevis, contain a prominent protein, representing about 10% of nuclear protein, which is characterized by a polypeptide of m(r) 30,000. this protein is highly phosphorylated and acidic, displays several isoelectric variants with pi values ranging from 4.7 to 5.3, shows a high thermostability, is not stably complexed with other proteins, and is readily extracted in buffer solutions. guinea pig antibodies against this protein have allowed its spe ... | 1980 | 6987661 |
| development of the mitochondrial mass and accumulation of mtdna in previtellogenic stages of xenopus laevis oocytes. | the development of the mitochondrial mass of the previtellogenic oocytes of xenopus laevis has been analysed by a morphometric method and it has been correlated with the growth of the occyte itself. the study which was performed with oocytes from females of very different ages shows that the relative size of the mitochondrial mass in the smallest oocytes decreases gradually with the age of the females. cytophotometric analysis of the feulgen-stained mitochondrial mass enabled the mtdna content o ... | 1980 | 6988447 |
| effects of n-methyl-n-nitrosourea on the lymphoid tissues and skin allograft response of xenopus laevis. | 1980 | 6995191 | |
| initiation of ribosomal rna chains in homogenates of oocyte nuclei. | we have studied rna synthesis in homogenates of nuclei manually isolated from mature oocytes of xenopus laevis. transcription of the endogenous template is completely resistant to alpha-amanitin and represents primarily transcription of the amplified ribosomal genes. three lines of evidence demonstrate that rna polymerase i is reinitiating rna chains in this system. first, transcription continues in the homogenates for at least 8 h. during this time, 50 to 100 rna copies are synthesized per gene ... | 1980 | 6995456 |
| xenopus laevis larval thymocytes do not express surface immunoglobulin. | 1980 | 6996841 | |
| partial purification and characterization of the maturation-promoting factor from eggs of xenopus laevis. | 1980 | 7000582 | |
| molecular cloning of cdna sequences coding for the major alpha- and beta-globin polypeptides of adult xenopus laevis. | this report describes the synthesis and cloning of almost complete dna copies of the mrnas encoding the major alpha-globin and major beta-globin of x. laevis. double-stranded globin cdna was inserted into the psti site of the plasmid pbr322 and two cloned recombinants (designated pxg6c1 and pxg8d2) were selected. these were shown to contain almost complete copies of x. laevis globin mrna. restriction enzyme maps were determined for each cdna sequence using the established method of partial diges ... | 1980 | 7001356 |
| the role of zinc and follicle cells in insulin-initiated meiotic maturation of xenopus laevis oocytes. | 1980 | 7001631 | |
| more ribosomal spacer sequences from xenopus laevis. | the base sequence analysis of a xenopus laevis ribosomal dna repeat (7) has been extended to cover almost the entire non-transcribed and external transcribed spacer. a compilation of these sequences is presented. all the repetitive and non-repetitive sequence elements of the spacer are identified and their evolution discussed. comparison of the x.laevis and s.cerevisiae (25,26) ribosomal dnas shows about 80% sequence conservation in the 18s gene but no sequence conservation, from the available d ... | 1980 | 7003549 |
| rental projections in the adult xenopus laevis: a study with cobalt filling technique. | cobaltic-lysine complex was used to show retinal projections in adult xenopus laevis. retinal fibres partially decussate in the chiasma, and terminate on both sides in the nucleus ovoidalis, lateral geniculate complex, pretectal area, optic tectum, and in the basal optic nucleus. cobalt filled fibres were found in the preoptic area, dorsal hypothalamic area, and in the periventricular region close to the wall of the third ventricle. | 1980 | 7008512 |