Publications

isolation and partial characterization of messenger rna, from murine t cell hybrids, coding for suppressive immunoglobulin g-binding factor.	poly a rna has been isolated from a murine t cell hybridoma ( t2d4 ) that spontaneously secretes suppressive immunoglobulin g-binding factor ( iggbf ). translation products, obtained from a rabbit reticulocyte lysate translation system and after injection into xenopus laevis oocytes, contain material with the biologic activity, the affinity, and the m.w. of murine iggbf ; it suppresses secondary in vitro igg antibody production in a dose-dependent fashion. the suppressive factor binds to igg but ...	1984	6609991
during frog ontogeny, pha and con a responsiveness of splenocytes precedes that of thymocytes.	the in-vitro proliferation of splenocytes and thymocytes from xenopus laevis-gilli (hybrid clone lg-15) to the t cell mitogens, concanavalin a (con a) and phytohaemagglutinin-p (pha), were examined at specific stages of larval development (stages 51-66 of nieuwkoop & faber, 1967) and at 2 months post-metamorphosis. the responses of splenic lymphocytes to each mitogen were significant at all stages with stimulation indices ranging from 1.9 to 50.5 and 2.6 to 45.5 for pha and con a, respectively. ...	1984	6611296
characterization of highly and moderately repetitive 500 bp eco ri fragments from xenopus laevis dna.	three different types of repetitive eco ri fragments, which comigrate within a visible band of approximately 500 bp at gel electrophoresis of xenopus laevis dna eco ri digests have been cloned and sequenced. these sequences are designated as repetitive eco ri monomers: rem 1, rem 2 and rem 3. the sequences contain direct repeats, inverted repeats and palindromic elements. genomic organization of the most abundant sequence (rem 1; 0.4% of total dna) is that of an interspersed sequence. rem 2 (0.0 ...	1984	6330690
mitogen-induced b-cell differentiation in xenopus laevis.	spleen cells from the south african clawed toad xenopus laevis proliferate vigorously upon pokeweed mitogen (pwm) stimulation, as measured by 3h-thymidine uptake. the peak response is observed after 6-8 days of culture, and both light- and electron-microscopy examinations of stimulated cells reveal the presence of a large number of lymphoblasts. beside proliferation, pwm induces the in vitro differentiation of a large proportion of lymphoblasts into immunoglobulin (ig)-producing plasmablasts, as ...	1984	6334001
[appearance of secondary melanophore reactions in the ontogeny of anuran amphibia].	the development of physiological reactions of the dermal melanophores has been studied in rana temporaria, r. ridibunda and xenopus laevis. in these species, the background (secondary) reactions of melanophores appeared at different stages of larval development but their appearance was always timed with the eye slit closure.	1984	6334263
birefringent periodicities in amphibian rod outer segments.	birefringence variations, seen as regularly spaced altering light and dark rings (bands), have been observed along the length of unfixed, freshly isolated rod outer segments (ros) of both rana pipiens and xenopus laevis. in our hands, the spatial frequency of the banding pattern is from 1.3-1.6u/band in rana pipiens and 1.8-2.2u/band in xenopus laevis ros, both corresponding closely to determinations we made in the same animals of the quantity of new ros disks added each day. to further probe th ...	1984	6334590
early development of descending pathways from the brain stem to the spinal cord in xenopus laevis.	the early development of descending pathways from the brain stem to the spinal cord has been studied in xenopus laevis tadpoles. the relatively protracted development of this permanently aquatic amphibian as well as its transparency during development make this animal particularly attractive for experimental studies. between the 5th and 10th myotome the spinal cord was crushed with a thin needle and dry horseradish peroxidase (hrp) crystals were applied. after a survival time of one day the tadp ...	1984	6335361
effect of temperature and zn2+ on isometric contractile properties and electrical phenomena of frog (rana) and xenopus skeletal muscle fibers.	effects of temperature and zn2+ on the isometric contractile properties of toe muscle fibers of rana catesbeiana and xenopus laevis were studied. the maximum twitch tension almost doubled when the temperature was lowered from 20 to 4 degrees c in rana muscles but not in xenopus muscles, although the duration of action potential in xenopus muscle was increased slightly more than that seen in the rana species. the maximum rate of rise of tension was greater in xenopus muscle than in the rana muscl ...	1984	6335672
effects of ethanol on the primitive streak stage mouse embryo.	recent studies of mouse models have suggested that malformations associated with the fetal alcohol syndrome (fas) are caused by the effects of ethanol on early embryos during gastrulation and neurulation. a study of xenopus laevis embryos showed that exposure of gastrula stage amphibian embryos to ethanol inhibits migration of the mesodermal cells, causes formation of small neural plates, and subsequently causes hypoplastic craniofacial malformations in tadpoles. we now report effects of ethanol ...	1984	6463902
in vitro thymus suppression of hemagglutinin production in xenopus laevis: location, drug and temperature sensitivity.	suppression of splenic hemagglutinin (ha) production by allothymuses in vitro was further studied in xenopus laevis, the south african clawed toad. since thymic capacity to suppress splenic ha secretion into the culture medium is retained in animals previously exposed to n-methyl-n-nitrosourea (nmu), which destroys the thymus cortex in this species, suppressor function must be located in the thymus medulla. reciprocal thymus-spleen combinations showed that normal thymus can suppress immunised sp ...	1984	6464095
transport of amino acids and nucleosides in metaphase-arrested unfertilized oocytes of xenopus laevis.	metaphase-arrested, unfertilized shed oocytes of xenopus laevis obtained after hormonal stimulation of the female are able to take up nucleosides (u, t) and amino acids (ala, gly, glu, gln, tyr). for alanine, tyrosine, and glutamic acid the transport is uphill. the transport of the amino acids studied is activated by na+, whereas the uptake of the nucleosides is independent of the na+ concentration. ouabain does not inhibit the uptake of amino acids significantly. the uptake of alanine and thymi ...	1984	6467381
[evaluation of amputation techniques for the study of limb regeneration in the newt and toad].	a comparison between forelimb amputations through the radius-ulna and the humerus was made in the adult newt, cynops pyrrhogaster pyrrhogaster and the young toad, xenopus laevis. newts regenerated their forelimbs after the amputations and the new parts resembled the old in structure and function. toads regenerated their forelimbs incompletely after the amputations. the new parts lacked joints and fingers showing a simply elongate pattern. the effect of re-amputation of exposed bone on the regene ...	1984	6468505
the thiol-disulfide balance during maturation of xenopus laevis oocytes.	we measured several of the components involved in the thiol-disulfide balance of immature and mature oocytes of xenopus laevis: total soluble native sulfhydryl, reduced and oxidized glutathione, native sulfhydryl content of soluble protein, and disulfide content of soluble protein. none of these values changed during maturation. both the immature and mature oocyte were characterized by a relatively high disulfide to sulfhydryl ratio. we also measured native sulfhydryl content of germinal vesicle ...	1984	6470653
effect of caffeine on induced damage in cells of xenopus laevis.	xenopus laevis cells were treated with mitomycin c and subsequently treated with caffeine during either the s- or g2-phase of the cell cycle. the frequency of induced chromatid exchanges was especially increased by caffeine posttreatment during the s-phase. this increase took place at the expense of the frequency of isochromatid breaks, which was reduced, both when the caffeine posttreatment was given during the s- and g2-phase.	1984	6472303
variations in transcriptional activity of rdna spacer promoters.	we have compared the dna sequences of several different examples of the duplicated polymerase i promoters that are found in rdna spacers of xenopus laevis. although different spacers exhibit different amounts of transcription in vivo, this does not seem to be due to dna sequence differences between spacer promoters. we have found that several different spacer promoters when subcloned and injected into oocytes exhibit similar promoter activities when transcription is assayed by primer extension a ...	1984	6473101
two populations of rod photoreceptors in the retina of xenopus laevis identified with 3h-fucose autoradiography.	the retina of xenopus laevis contains two populations of rod photoreceptors that differ in their utilization of l-fucose. following intraperitoneal injections with 3h-fucose, all rod and cone photoreceptors incorporate the label. one day after labeling, much of the radioactivity is associated with the photoreceptor outer segments. in rods, a band of radioactivity is initially located at the base of the outer segment. as the time interval between injection and recovery is extended, the band of ra ...	1984	6474834
assessment of mutagenic damage by monofunctional alkylating agents and gamma radiation in haploid and diploid frogs, xenopus laevis.	adult male south african clawed frogs, xenopus laevis, were mutagenized by 3-day immersion in aqueous solutions of ethyl methanesulfonate (ems), diethyl nitrosamine (den), or ethyl nitrosourea (enu), or by acute exposure to gamma radiation. they were then spawned repeatedly at 2-week intervals with untreated females, and embryonic survival of the progeny was used to assess genetic damage. recessive lethal effects were assessed from reduced survival of androgenetic haploid progeny. neither recess ...	1984	6479115
lineage segregation and developmental autonomy in expression of functional muscle acetylcholinesterase mrna in the ascidian embryo.	acetylcholinesterase is a histospecific marker of cell differentiation occurring only in the muscle and mesenchyme tissues of the ascidian embryo. the distribution of functional mrna coding for this enzyme has been investigated and it is shown here that only cells of muscle and mesenchyme lineages possess such a template. blastomeres of four cell lineage quadrants were separated microsurgically from eight-cell-stage embryos of ciona intestinalis and raised in isolation until muscle development w ...	1984	6479447
interneurones in the xenopus embryo spinal cord: sensory excitation and activity during swimming.	the dorsolateral spinal cord of embryonic xenopus laevis has previously been shown to contain two anatomical classes of interneurones with dendrites in the dorsal tract where they could be contacted by the central axons of rohon-beard cells (roberts & clarke, 1982). the activity of these neurones within the dorsolateral spinal cord has been examined using intracellular micro-electrodes. following electrical stimulation of rohon-beard neurites within the ipsilateral skin, dorsolateral neurones re ...	1984	6481637
[surface structure of the otolithic organs of the tadpole of the clawed toad xenopus laevis].	beginning from the blastula and tail bud stages, 15 larvae of the clawed toad were kept in three emkon containers at temperature 15 degrees for 8-9 days. structure of the hair cells and otolith membrane of the larval otolithic organs was examined with a light microscope, tem and sem. in contrast to previous studies, it was found that at the stages mentioned larval otolithic organs are presented not by two, but by three maculae, i.e. the utricular, saccular and lagenar ones with two otoliths. sac ...	1984	6485654
influence of ca2+ on the voltage dependent mechanosensitivity of the hair cells in the lateral line organs of xenopus laevis.	the influence of the transepithelial voltage (vt) on the degree of synchronization (dos) of afferent spikes from lateral line organs to mechanical stimulation has been examined in the isolated voltage clamped skin of xenopus laevis. with 1 mm cacl2, 5 mm mops-koh (ph = 7.1) in the apical solution and ringer's solution on the serosal side of the skin, changes in vt from -60 mv to 65 mv (inside relative to outside) lead to a nonlinear reduction in dos to a minimum value, where the afferent spikes ...	1984	6485827
in vitro inhibition of tubulin assembly by a ribonucleoprotein complex associated with the free ribosome fraction isolated from xenopus laevis oocytes: effect at the level of microtubule-associated proteins.	the 100 000 x g supernatant prepared from defolliculated xenopus laevis oocytes inhibits, in a dose-dependent manner, the in vitro polymerization of rat brain neurotubulin. the oocyte inhibitory factor is thermolabile, totally inactivated by rnase and partially by trypsin. a preliminary purification of the inhibitor showed that it is associated with the free oocyte ribosomes (80 s). the saturable binding of microtubule-associated proteins, essentially map2, to this 80 s ribonucleoprotein fractio ...	1984	6488322
variations in aldosterone and corticosterone plasma levels during metamorphosis in xenopus laevis tadpoles.	aldosterone and corticosterone plasma levels have been determined by radioimmunoassay at various stages (st) of metamorphosis in xenopus laevis tadpoles. the aldo level first showed a significant peak at the beginning of the climax (st 58), and again at the middle of the climax (st 61-62); b level increased slightly but significantly at st 59, then showed an important peak at st 62-63. the high levels of these hormones at these stages seem to be associated with the concomitant surge of interrena ...	1984	6489739
effects of radius--ulna removal on forelimb regeneration in xenopus laevis froglets.	regeneration of boneless amputated forearms of adult newts was found to progress at a rate and to a degree comparable to amputated control limbs in which stump bones were not removed. in contrast, regeneration of boneless amputated xenopus froglet forearms was significantly delayed and did not occur until two to three weeks following amputation. this is in comparison with the initiation of distal cartilage formation observed one week postamputation in control forelimbs of xenopus froglets. the r ...	1984	6491587
effect of estrogen on xenopus laevis albumin mrna levels.	accurate quantitation of concentrations of albumin mrna by hybridization to albumin cdna allows analysis of the estrogen effect on the xenopus laevis albumin mrna levels in the liver cytoplasm during the primary stimulation. administration of estradiol-17 beta to male xenopus laevis increases the amount of both total cellular rna and poly(a)-rna but has no effect on the albumin mrna level and the amount of albumin mrna per cell is constant.	1984	6493219
identification and treatment of a lethal nematode (capillaria xenopodis) infestation in the south african frog, xenopus laevis.		1984	6500144
inhibition of na-alanine cotransport in oocytes of xenopus laevis during meiotic maturation is voltage-regulated.	during progesterone-induced maturation of oocytes of xenopus laevis the fast decrease of the rate of na+-alanine cotransport is accompanied by a depolarization of the membrane potential and an increase in the intracellular na+ activity. it is demonstrated that the decrease of the na+-dependent alanine uptake is the result of the depolarization while the simultaneous increase in intracellular na+ activity has no significant effect.	1984	6504692
evolution of vitellogenin genes: comparative analysis of the nucleotide sequences downstream of the transcription initiation site of four xenopus laevis and one chicken gene.	electron microscopic analysis of heteroduplexes between the most distantly related xenopus vitellogenin genes (a genes x b genes) has revealed the distribution of homologous regions that have been preferentially conserved after the duplication events that gave rise to the multigene family in xenopus laevis. dna sequence analysis was limited to the region downstream of the transcription initiation site of the xenopus genes a1, b1 and b2 and a comparison with the xenopus a2 and the major chicken v ...	1984	6504704
sequence homologies in the region preceding the transcription initiation site of the liver estrogen-responsive vitellogenin and apo-vldlii genes.	in the liver of oviparous vertebrates vitellogenin gene expression is controlled by estrogen. the nucleotide sequence of the 5' flanking region of the xenopus laevis vitellogenin genes a1, a2, b1 and b2 has been determined. these sequences have been compared to each other and to the equivalent region of the chicken vitellogenin ii and apo-vldlii genes which are also expressed in the liver in response to estrogen. the homology between the 5' flanking region of the xenopus genes b1 and b2 is highe ...	1984	6504705
interaction between rat brain microtubule associated proteins (maps) and free ribosomes from xenopus oocyte: a possible mechanism for the in ovo distribution of maps.	the binding of microtubule associated proteins (maps) to free 80 s ribosomes isolated from xenopus laevis oocytes inhibits in vitro tubulin assembly (jessus et al., 1984). the inhibition of tubulin polymerisation was shown to be dependent upon gtp. the dose of gtp needed to induce 50% of the maximal effect was 0.5 mm. furthermore, the inhibition is enhanced by pretreatment of the ribosomes with atp-gamma-s, and partially abolished after phosphatase treatment, which strongly suggests that protein ...	1984	6509556
interrenal function during amphibian metamorphosis: in vitro biosynthesis of radioactive corticosteroids from (4(14)c)-progesterone by interrenal in xenopus laevis tadpoles.	whole kidneys of xenopus laevis tadpoles (containing interrenal cells) or the outer postero-dorsal part of adult kidney (containing a few or no interrenal cells) were incubated with (4(14)c)-progesterone. methylene chloride extractable radioactivity of tissue homogenates in their incubation medium were purified by sequential paper chromatography and identification of some isolated fractions was attempted. a significant conversion of progesterone was only observed when interrenals were present in ...	1984	6509915
regulation by estrogen receptor of vitellogenin gene transcription in xenopus hepatocyte cultures.	we have used primary cell cultures of hepatocytes from male or female xenopus laevis to study the mechanisms by which estrogen induces vitellogenin gene transcription and how primary exposure to estrogen renders cells more responsive to secondary stimulation. we have characterized the estrogen receptor in hormonally naïve cells and in hepatocytes treated with estrogen under a variety of conditions. under all conditions the receptor has a kd congruent to 4 x 10(-10) m. hormonally naïve male cells ...	1984	6510549
[glomus cell in controlling vascular tone of the carotid labyrinth (xenopus laevis)].	to clarify the physiological significance of g-s connection (intimate apposition of the glomus cell to the smooth muscle), vascular responses of the carotid labyrinth to both catecholamines and chemoreceptor stimulants were investigated using xenopus laevis. the results obtained were as follows. density of dense-cored vesicles in the glomus cell was significantly varied in three different parts of the cytoplasm (n, m, p). in the part of the cytoplasm containing the nucleus (n) the density was lo ...	1984	6520799
[dynamics of the redistribution of pigment granules in the dermal melanophores of anuran amphibians. 1. dispersion].	the dispersion of melanosomes in the dermal melanophores of the xenopus laevis larvae has been studied by time--lapse cinematography. the process began with the appearance of distally directed melanosome flows in the cell cytoplasm. during the subsequent migration of pigment granules, the flows branched forming branches of the 2nd and higher orders. the whole cytoplasm became filled with a layer of melanosomes. during the dispersion, the movement of melanosomes in a flow is replaced by their dis ...	1984	6521976
shedding is correlated with disk membrane axial position rather than disk age in xenopus laevis rod outer segments.	disk membrane synthesis and displacement rates in xenopus laevis retinal rod outer segments, as measured by light-dark dependent birefringence band periods, are proportional to incubation temperature. outer segment length, however, is approximately the same for frogs raised at different temperatures. therefore the age of disks shed from outer segment distal tips is a function of temperature. unless the rate of disk synthesis coincidentally has the same temperature dependence as putative disk mem ...	1984	6523739
transient paralysis by heat shock of hormonal regulation of gene expression.	we have investigated the effect of heat shock on primary cultures of male and female xenopus laevis hepatocytes as a function of estrogen-induced vitellogenin gene expression. coincident with the induction of heat-shock protein (hsp) synthesis, thermal stress abolishes the estrogen activated transcription and accumulation of vitellogenin mrna, at the same time causing the destabilization of vitellogenin mrna accumulated by prior treatment with the hormone. exposure of the cells to estrogen befor ...	1984	6526005
an unusual repetitive structure of caerulein mrna from the skin of xenopus laevis.	the nucleotide sequence of a 784-bp segment of cloned caerulein mrna obtained from the skin of xenopus laevis was determined. it codes for five heterogeneous procaerulein peptides interspersed with three 147-bp intercaerulein segments (ics). the icss contain six inverted repeats and five eukaryotic enhancer-like sequences. evidence for the presence of multiple forms of caerulein mrna is presented.	1984	6526274
protein synthesis in dorsal, ventral, animal and vegetal half-embryos of xenopus laevis isolated at the 8-cell stage.	dorsal, ventral, animal and vegetal half-embryos of xenopus laevis were isolated at the 8-cell stage, and their synthesis of protein examined during 12 h of culture. the kinetics of the uptake and incorporation of [35s]-methionine did not differ greatly among the four kinds of half-embryos. two-dimensional gel electrophoreses showed that there were no detectable differences in the pattern of protein synthesis for the four types of half-embryos, at least during the first 6 h of culture which cove ...	1984	6529755
effects of alterations of cell size and number on the structure and function of the xenopus laevis nervous system.		1984	6532155
common mechanisms in vertebrate axonal navigation: retinal transplants between distantly related amphibia.	embryonic eye primordia were transplanted from the anuran, xenopus laevis, to the urodele, ambystoma mexicanum, in order to assess whether retinal axons of one species could grow to appropriate central targets in a distantly related species. to trace the early retinal projections, xenopus primordia were removed, incubated for 20 min in a solution containing [3h]proline, washed, and then transplanted to host axolotl embryos. genetically eyeless hosts were used in some of the experiments so that t ...	1984	6536722
dna binding protein from ovaries of the frog, xenopus laevis which promotes concatenation of linear dna.	a soluble extract of xenopus laevis ovaries catalyzed atp-dependent concatenation of linear duplex dna molecules. dna ligase and a unique x. laevis dna binding protein were required for the formation of concatemers. a linear dna concatenation system was reconstituted using t4 dna ligase and homogeneous x. laevis dna binding protein. this system catalyzed intermolecular ligation of dna molecules into linear concatemers of up to ten or more times monomer length.	1984	6537981
studies on the mechanism of inhibition of amphibian oocyte adenylate cyclase by progesterone.	progesterone treatment induces the meiotic maturation of xenopus laevis oocytes. previous evidence indicates that this hormonal effect may be due to inhibition of oocyte adenylate cyclase. the present work studies several aspects of the mechanism of adenylate cyclase inhibition by this hormone. forskolin greatly stimulates oocyte adenylate cyclase in the absence of guanine nucleotides and this activity is not sensitive to progesterone inhibition. in addition the forskolin-activated enzyme is not ...	1984	6538078
detection of human beta-2 interferon using a radioimmunoassay.	does the human "beta 2 interferon" (huifn-beta 2) mrna of length 1.3 kb obtained from poly(i) x poly(c) and cycloheximide-induced human diploid fibroblasts (fs-4) code for an interferon per se, or for a protein which, in turn, induces ifn-beta in the cell culture assay that is usually used to detect the antiviral activity of the translation product (obtained from xenopus laevis oocytes) of this mrna? this question has been resolved by demonstrating that the ifn derived from the 1.3 kb mrna can b ...	1984	6538894
acetylcholine promotes progesterone-induced maturation of xenopus oocytes.	progesterone-induced maturation of follicle-enclosed and denuded xenopus laevis oocytes was significantly shortened by a concomitant exposure to acetylcholine. the promotion of maturation by acetylcholine was blocked by the specific muscarinic antagonist atropine. the action of acetylcholine was dose dependent, and the neurotransmitter was effective at very low concentrations. progesterone progressively reduced the electrophysiological responses of x. laevis oocytes to acetylcholine, which compl ...	1984	6539359
karyophobic proteins. a category of abundant soluble proteins which accumulate in the cytoplasm.	the cytoplasm of oocytes of xenopus laevis is enriched in several soluble proteins which are either absent from the nucleus or are present there at very low concentrations. these molecules, collectively referred to as karyophobic (from the greek verbs and which are meant here in the sense of "to be afraid of" or "to avoid") proteins represent more than 20% of the total soluble cytoplasmic proteins and include some of the most abundant soluble cellular components. they may be recovered from high- ...	1984	6539709
identification and localization of a novel nucleolar protein of high molecular weight by a monoclonal antibody.	a monoclonal murine antibody (no-114) is described which reacts specifically with a polypeptide of molecular weight (mr) 180 000 present in low-speed nuclear pellets from oocytes and somatic cells of xenopus laevis and x. borealis and in isolated amplified nucleoli. two-dimensional gel electrophoresis has revealed the acidic nature of this polypeptide (isoelectric at ph of ca 4.2 in the presence of 9.5 m urea). a relatively large proportion of the protein is extracted at elevated ionic strength ...	1984	6539710
replication, integration and expression of exogenous dna injected into fertilized eggs of xenopus laevis.	we have analyzed the fate of circular and linear dna molecules following microinjection into the cytoplasm of fertilized eggs of xenopus laevis. recombinant plasmids containing sea urchin histone genes (psp 102), drosophila adh genes (sac-1), and sv40 (sv2 cat) replicate during the development of the injected frog embryo. in contrast, pbr322 either as monomers or multimers does not appear to replicate as efficiently. generally, injected circular dnas were not detectable by the gastrula stage of ...	1984	6539719
progesterone receptor characterized by photoaffinity labelling in the plasma membrane of xenopus laevis oocytes.	r 5020 (17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione) is a synthetic analogue of progesterone, which is the physiological hormone that reinitiates germinal vesicle breakdown in xenopus laevis oocytes. u.v.-driven photoaffinity labelling experiments were conducted with [3h]r 5020 in oocyte subcellular fractions, and covalently bound radioactivity was analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. in p-10000 (the pellet sedimenting between 1000 and 10000 g and which co ...	1984	6540084
the transcriptional regulation of xenopus 5s rna genes in chromatin: the roles of active stable transcription complexes and histone h1.	the properties of active and repressed 5s rna genes in somatic cell chromatin from xenopus laevis cultured cells were studied by transcription in vitro. the somatic 5s rna genes, which are active in vivo, are packaged in chromatin as active stable transcription complexes lacking only rna polymerase iii for transcription activity. the oocyte 5s rna genes, which are inactive in somatic tissues, do not have transcription factors bound to them in purified chromatin and are prevented from binding the ...	1984	6540147
structural basis of the activation wave in the egg of xenopus laevis.	a series of changes in the surface of activated xenopus eggs was observed. within a few seconds of prick activation a light area appears near the pricking point and expands as a circular light zone (light wave). some 60 s later this is followed by a dark area expanding as a circular dark zone (dark wave). both waves travel at a rate of about 9 micron/s at 21 degrees c. in the light zone, cortical granules are breaking down, microvilli are elongating, and the egg surface is expanded. on the other ...	1984	6540794
tumor promoter pma stimulates the synthesis and secretion of mouse pro-urokinase in msv-transformed 3t3 cells: this is mediated by an increase in urokinase mrna content.	in mouse msv-3t3 cells the synthesis of the urokinase form of plasminogen activator was increased 10-fold after addition of the tumor promoter phorbol-12-myristate-13-acetate (pma). pma also stimulated the secretion of the protein into the culture medium, mostly in the form of enzymatically inactive pro-urokinase. when assayed by injecting rna into xenopus laevis oocytes, the concentration of functional urokinase mrna was found to be 6- to 10-fold higher in the pma-treated cells; a similar incre ...	1984	6541126
control of cell shape and locomotion by external calcium.	dependence of locomotion of xenopus laevis epidermal cells on calcium influx from the external medium was investigated. inhibition of ca2+ influx by 2 mm la3+ or 4 mm tb3+ in the culture medium causes an immediate stop to locomotion and a loss of motion at the outer margin of the lamella; microcolliculi disappear and the entire lamella becomes flat and very thin. the cell body region enlarges by spreading into the lamella to an extent approximately coincident with the distribution of myosin. the ...	1984	6541148
the mitochondrial cloud of xenopus oocytes: the source of germinal granule material.	the mitochondrial cloud is a prominent mass in the cytoplasm of previtellogenic oocytes of xenopus laevis. it is shown here that the cloud contains both mitochondria and electron-dense granulofibrillar material (gfm). using a combination of light microscopical, fluorescence, time-lapse filming, and electron microscopical techniques, the ontogeny of these components is reported and their fate is studied. it was found that the cloud is stationary in previtellogenic stages and fragments into island ...	1984	6541166
reactivity of lectin from xenopus laevis eggs towards tumor cells and human erythrocytes.		1984	6541530
progesterone inhibition of xenopus oocyte adenylate cyclase is not mediated via the bordetella pertussis toxin substrate.	preincubation of intact xenopus laevis oocytes with islet-activating protein (iap) stimulates plasma membrane adenylate cyclase activity measured in the presence of either gtp or 5'-guanylyl imidodiphosphate. the toxin appears to act by catalyzing the adp-ribosylation of a 41,000-d protein in the oocyte plasma membrane that is distinct from the 45,000- and 52,000-d proteins labeled by cholera toxin. preincubation of intact oocytes with iap for 2.5 hr inhibits 80% of the adp-ribosylation of oocyt ...	1984	6541752
chromosomal location of a major trna gene cluster of xenopus laevis.	in xenopus laevis, genes encoding trnaphe, trnatyr, trnamet1, trnaasn, trnaala, trnaleu, and trnalys are clustered within a 3.18-kb (kilobase) fragment of dna. this fragment is tandemly repeated some 150 times in the haploid genome and its components are found outside the repeat only to a limited extent. the fragment hybridizes in situ to a single site very near the telomere on the long arm of one of the acrocentric chromosomes of the group comprising chromosomes 13-18. all the chromosomes of th ...	1984	6542486
segregation of mutant ovalbumins and ovalbumin-globin fusion proteins in xenopus oocytes. identification of an ovalbumin signal sequence.	the intramolecular signals for chicken ovalbumin secretion were examined by producing mutant proteins in xenopus oocytes. an ovalbumin complementary dna clone was manipulated in vitro, and constructs containing altered protein-coding sequences and either the simian virus 40 (sv40) early promoter or herpes simplex thymidine kinase promoter, were microinjected into xenopus laevis oocytes. the removal of the eight extreme n-terminal amino acids of ovalbumin had no effect on the segregation of ovalb ...	1984	6543229
effect of intercalating agents on rna polymerase i promoter selection in xenopus laevis.	we have analyzed the effect of dna intercalating agents on the transcription signals from two different xenopus laevis rna polymerase i promoters. the transcription signal from the promoter for the 7.5-kilobase rrna precursor (the gene promoter) is unaffected over a large range of intercalating agent concentrations regardless of whether the template is injected plasmid dna in oocytes, the amplified endogenous nucleoli of oocytes, or the endogenous chromosomes of cultured xenopus kidney cells. th ...	1984	6543244
unequal activation by estrogen of individual xenopus vitellogenin genes during development.	using a technique of filter hybridization under very stringent conditions to hindiii fragments of complementary dna cloned in plasmids, we have measured the accumulation in hepatocytes of mrna specified by each of the four vitellogenin genes (a1, a2, b1, b2) at different stages of development of xenopus laevis. the ontogenic competence of embryonic liver to respond to the first exposure to estradiol-17 beta, in terms of activation of transcription of this multigene family, is acquired late in me ...	1984	6546552
polymorphism and absence of leu-enkephalin sequences in proenkephalin genes in xenopus laevis.	the structures of the genes coding for the opioid peptide precursors proopiomelanocortin, proenkephalin (proenkephalin a) and prodynorphin (proenkephalin b), are known for some mammalian species. to gain insight into the evolutionary history of these precursors, we have examined the proenkephalin gene in the south african clawed toad, xenopus laevis, which diverged from the principal line of vertebrate evolution some 350 myr ago. the human proenkephalin gene consists of four exons, of which the ...	1984	6547769
partial characterization of lectin binding sites of retinal photoreceptor outer segments and interphotoreceptor matrix.	we have used cytochemistry together with exoglycosidase digestion and polyacrylamide gel electrophoresis to partially characterize lectin binding sites of the interphotoreceptor matrix and of photoreceptor outer segments. in order to obtain uniform access of reagents to all regions of the preparation, we have used a procedure in which plastic sections are etched with sodium ethoxide prior to cytochemical analysis. neuraminidase pretreatment of plastic-embedded sections of xenopus laevis eyecups ...	1984	6548230
the accumulation of prominent tadpole mrnas occurs at the beginning of neurulation in xenopus laevis embryos.	cloned cdna probes have been used to measure the sizes and titers of transcripts in total rna preparations during early development in xenopus laevis. of more than 20 different sequences derived from abundant and moderately abundant rna which were present in full-grown oocytes and persisted during early development, the transcript sizes of all but 3 of these sequences were invariant. two transcripts were of a higher molecular weight in oocytes than in embryos, but their titers in oocytes were le ...	1984	6548717
identification of xenopus laevis mrnas with homology to repetitive sequences.	hybrid selection translation experiments have been carried out with genomic and cdna relatives of two repetitive sequence families. on the basis of the in vitro translation products detected, it was found that transcripts complementary to these repeats are linked to several different mature mrnas in stage 40 embryos of xenopus laevis. one repeat hybridizes to mrnas that direct the synthesis of 17 proteins. the second is present on mrnas coding for 3 proteins. by estimating the abundance of these ...	1984	6549063
two recessive mutations with maternal effect upon colour and cleavage ofxenopus l. laevis eggs.	"pale eggs" and "partial cleavage" are two mutations with a maternal effect that are found in the same family ofxenopus l. laevis. the pale eggs have animal hemispheres of a yellow to beige colour and give rise to normally pigmented tadpoles and frogs. the cells of pale embryos contain fewer melanosomes than those of controls. the partial cleavage eggs are characterized by an abnormality of cleavage visible from the eight-cell stage onwards, by abnormal yolk platelet distribution and abnormal cy ...	1984	28305590
inducing activity of subcellular fractions from amphibian embryos.	the homogenate from unfertilized eggs, gastrulae, neurulae and hatched embryos ofxenopus laevis was fractionated by differential centrifugation and subsequent repeated centrifugation on discontinuous sucrose gradients. a high archencephalic-neural inducing activity was found in rnp particles, which were released from the high-speed ("microsomal") sediment by treatment with edta, and in a fraction of heterogeneous small vesicles. the highest archencephalic inducing activity was observed in rnp pa ...	1984	28305490
the development of retinal ganglion cells in a tetraploid strain of xenopus laevis: a morphological study utilizing intracellular dye injection.	the morphological development of retinal ganglion cells was examined in a tetraploid strain of xenopus frogs. the enlarged cells of the tetraploid strain facilitate the application of intracellular techniques. using an in vitro retinal preparation and nomarski optics, intracellular recording and dye injection were carried out under visual control on ganglion cells in central retina from 2 days of development (stage 24) to metamorphosis (stage 64). we identified three phases in the morphological ...	1984	19180813
expression of alfalfa mosaic virus rna 4 cdna transcripts in vitro and in vivo.	copies of alfalfa mosaic virus (amv) rna 4 synthesized by transcription in vitro were shown to be biologically active in protoplasts when inoculated together with a mixture of amv rnas 1, 2, and 3. a 5' cap was essential for activity, whereas 15 nonviral nucleotides at the 5' end of the rna transcripts did not detectably affect activity. transcripts that terminated 65 nucleotides from the 3' end of the coding region and transcripts that lacked all or part of the 3'-noncoding region were effectiv ...	1985	18640556
fine structure of oviducal epithelium of xenopus laevis in relation to its role in secreting egg envelopes.	during passage through the oviduct, the egg of xenopus laevis acquires the following substances or envelopes: electron-dense particles in the vitelline coat, the prefertilization layer in and around the vitelline coat, and four layers of jelly. both gross anatomical observation and light and scanning or transmission electron microscopic observations of various levels of oviduct revealed that the first two are produced in the pars recta 1 and 2 portions, and that jelly layers 1-4 are added in the ...	1985	29976012
epidermal development in xenopus laevis: the definition of a monoclonal antibody to an epidermal marker.	a monoclonal antibody 2f7.c7 which identifies an epidermal antigen common to both anuran and urodele amphibia is described. this antigen has a high molecular weight and is expressed at stage 12 1/2 first inside and then on the surface of epidermal cells. it is not expressed on presumptive nervous tissue. it is expressed on all cells of the larval epidermis including ciliated and nonciliated cells and sucker. the relationship of the epidermal antigen to 'epimucin' is investigated by blocking expe ...	1985	3831211
the function and mechanism of convergent extension during gastrulation of xenopus laevis.	the processes thought to function in xenopus gastrulation include bottle cell formation, migration of cells on the roof of the blastocoel, and autonomous convergent extension of the circumblastoporal region. a review of recent and classical results shows that only the last accounts for the bulk of the tissue displacement of gastrulation, including spreading of the marginal zone toward the blastopore, involution of the marginal zone, and closure of the blastopore. microsurgical manipulation and e ...	1985	3831213
chromosome replication in early development of xenopus laevis.	eggs of xenopus laevis contain exceptionally large amounts of materials involved in chromosome replication. this maternal stockpile allows an embryo to produce about 80 000 cells in less than 24 h. the adaptations which achieve this involve the mechanisms of both dna replication and chromatin assembly.	1985	3831215
a mass spectrometric assay for novel peptides: application to xenopus laevis skin secretions.	the peptides secreted by the south african frog xenopus laevis were screened systematically using a strategy based on fast atom bombardment mass spectrometry (fab-ms). high performance liquid chromatography (hplc) of crude and sephadex g-10 chromatographed secretions showed that many more peptides were present in these secretions than those previously identified, i.e., xenopsin, caerulein, trh and pgla. fractions from the hplc were analyzed directly by fab-ms to determine the molecular weights o ...	1985	3831964
studies on the endogenous galactose-binding lectin during early development of the embryo of xenopus laevis.	embryos of the frog xenopus laevis at cleavage, blastula, gastrula and neurula stages contain a galactose-specific lectin. extracts of gastrula embryos show the highest specific activity for this lectin compared to the other stages. haemagglutinating activity of crude extracts is inhibited by lactose, alpha-galactose, beta-galactose, alpha gal(1----4) beta gal, beta gal(1----3) alpha galnac, beta gal(1----3) beta glcnac, beta gal (1----4) beta glcnac, and most effectively by the disaccharide alp ...	1985	3833862
factors guiding regenerating retinotectal fibres in the frog xenopus laevis.	i have examined the pathways of retinotectal fibres regenerating back to the contralateral tectum, and also to innervated and 'virgin' ipsilateral tecta in postmetamorphic xenopus. the fibres were visualized by hrp labelling of either the whole optic nerve, or a selected quadrant of the retina. most fibres grow into either the ipsilateral or contralateral optic tract, although a small proportion go down the outside of the contralateral optic nerve. in the tracts, many fibres grow superficially, ...	1985	3834030
cytological analyses of factors which determine the number of primordial germ cells (pgcs) in xenopus laevis.	correlation of the number of primordial germ cells (pgcs) at stage 47 with the amount of germ plasm at the 8-cell stage and with the number of the germ-plasm-containing cells (gpccs) was analysed using two different laboratory-raised colonies of xenopus laevis, hd and j groups. the average number of pgcs in j group tadpoles was significantly larger than that in hd group tadpoles. the amount of germ plasm in j group embryos was also demonstrated to be larger than in hd group embryos. the amount o ...	1985	3834031
the effect of egg rotation on the differentiation of primordial germ cells in xenopus laevis.	eggs of x. laevis were rotated (sperm entrance point downwards) either through 90 degrees (1 x 90 embryos) or 180 degrees in two 90 degrees steps (2 x 90 embryos) at approximately 25-30 min postfertilization after cooling to 13 degrees c. the embryos were kept in their off-axis orientation and cooled until the early gastrula stage. rotation resulted in relocation of egg constituents with slight changes in the distribution of outer cortical and subcortical components and major changes in inner co ...	1985	3834040
a proposed neural pathway for vocalization in south african clawed frogs, xenopus laevis.	vocalizations of south african clawed frogs are produced by contractions of laryngeal muscles innervated by motor neurons of the caudal medulla (within cranial nerve nucleus ix-x). we have traced afferents to laryngeal motor neurons in male and female frogs using retrograde axonal transport of horseradish peroxidase conjugated to wheat germ agglutinin (hrp-wga). after iontophoretic injection of hrp-wga into n. ix-x, retrogradely labelled neurons were seen in the contralateral n. ix-x, in rhomben ...	1985	3837111
stimulation of sea urchin h2b histone gene transcription by a chromatin-associated protein fraction depends on gene sequences downstream of the transcription start site.	we isolated a chromosomal protein fraction derived from chromatin of sea urchin embryos which specifically stimulated the expression of the histone h2b gene by a factor of 5- to 10-fold when the complete sea urchin histone gene repeat h22 was injected in xenopus laevis oocyte nuclei. gene manipulation experiments revealed the existence of two different target sites in the h2b gene which appear to mediate the response to injection of the stimulatory sea urchin chromatin-associated proteins; both ...	1985	3837183
coordinate estrogen induction of vitellogenin and a small serum protein mrna in xenopus laevis liver.	we have used plus-minus hybridization to identify xenopus liver cdna clones of mrnas whose levels are regulated by estrogen. one clone identified in this way was shown to be a nearly full-length cdna clone of the mrna coding for a small 22 000 dalton estrogen-inducible serum protein (eisp). quantitation of eisp mrna levels by in vitro translation and by hybridization to the cloned dna demonstrated a 7-12-fold estrogen induction of eisp mrna, both in vivo and in primary xenopus liver cultures. th ...	1985	3838520
solid-phase synthesis of pyla and isolation of its natural counterpart, pgla [pyla-(4-24)] from skin secretion of xenopus laevis.	from the nucleotide sequence of clones isolated from a cdna library constructed from skin of xenopus laevis, the existence of pyla, a peptide comprised of 24 amino acids, was predicted. this peptide was synthesized by solid-phase methods and purified to homogeneity with an overall yield of 61%. the synthetic peptide was used as reference substance to search for its natural counterpart in skin secretion of xenopus. two peptides were found which were very similar to pyla except for the absence of ...	1985	3839186
nucleotide sequence of cloned cdna for pro-opiomelanocortin in the amphibian xenopus laevis.	the function of alpha-melanocyte-stimulating hormone (alpha-msh) is not known in mammals. it is well-established in the amphibian xenopus laevis in which alpha-msh mediates the process of adaptation to a dark background. the amino acid sequence of this hormone is, however, not known in amphibians. in order to determine the primary structure of the precursor protein for alpha-msh, which in mammals has been called pro-opiomelancortin (pomc), we constructed a cdna library from xenopus pituitary mrn ...	1985	3840481
nucleotide sequence of the l1 ribosomal protein gene of xenopus laevis: remarkable sequence homology among introns.	ribosomal protein l1 is encoded by two genes in xenopus laevis. the comparison of two cdna sequences shows that the two l1 gene copies (l1a and l1b) have diverged in many silent sites and very few substitution sites; moreover a small duplication occurred at the very end of the coding region of the l1b gene which thus codes for a product five amino acids longer than that coded by l1a. quantitatively the divergence between the two l1 genes confirms that a whole genome duplication took place in xen ...	1985	3841512
biosynthesis of peptides in the skin of xenopus laevis: isolation of novel peptides predicted from the sequence of cloned cdnas.	from skin of xenopus laevis, a few peptides have been isolated which are identical or homologous to gastrointestinal hormones and/or neurotransmitters of mammalian origin. we have studied the biosynthesis of these peptides using recombinant dna techniques. from cdna librariers constructed from skin mrna, clones with inserts coding for the precursors of caerulein, thyrotropin releasing hormone and a new peptide termed pgla have been isolated and sequenced. in the case of caerulein, a small family ...	1985	3841688
biochemical research on oogenesis. aminoacyl trna turns over in the 42-s particles of xenopus laevis oocytes, but its ester bond is protected against hydrolysis.	the ester bond aminoacyl trna is protected against hydrolysis in the 42-s particles (thesaurisomes) present in xenopus laevis previtellogenic oocytes. deacylation of trna is very slow in vitro, unless atp is present. atp causes a partial turnover of aminoacyl trna in vitro, with no detectable decrease in the overall aminoacylation level of trna, which remains close to 100%. trna in the particles turns over rapidly in vivo. since the ester bond of aminoacyl trna is stabilized inside the 42-s part ...	1985	3847348
purification and characterization of an endonuclease from xenopus laevis ovaries which accurately processes the 3' terminus of human pre-trna-met(i) (3' pre-trnase).	we have previously reported that the primary transcript of the human trnameti gene undergoes accurate processing to a mature 72-nucleotide species by activities present in the high speed supernatant of xenopus laevis ovarian extracts (zasloff, m., santos, t., romeo, p., and rosenberg, m. (1982a) j. biol. chem. 257, 7857-7863). we now report the purification and characterization of the enzyme which processes the 3' terminus of the human pre-trnameti species. the activity has been purified about 5 ...	1985	3848432
trna nuclear transport: defining the critical regions of human trnaimet by point mutagenesis.	we recently described a carrier-mediated nuclear transport system for trna in xenopus laevis oocytes. a natural human trnaimet variant with a g to t transversion in position 57 is defective in transport across the nuclear membrane. in addition, processing of the primary transcript of the variant gene is much less efficient than the wild type. we now describe the nuclear transport and processing phenotypes of 30 different point mutants generated by in vitro mutagenesis of a wild-type human trnaim ...	1985	3852693
a protein kinase from xenopus eggs specific for ribosomal protein s6.	a protein kinase specific for ribosomal protein s6 has been purified from eggs of xenopus laevis. as visualized on a silver-stained polyacrylamide gel, the major protein in the preparation migrated with a mr of 90,000. incubation of the enzyme preparation with [gamma-32p]atp led to phosphorylation of this protein on serine residues. upon glycerol gradient centrifugation, the s6 kinase activity and the mr 90,000 protein both sedimented with a mr of 50,000-55,000. two-dimensional gel electrophores ...	1985	3856226
identification of a messenger ribonucleic acid fraction in human prostatic cancer cells coding for a novel osteoblast-stimulating factor.	prostatic cancer is frequently associated with new bone formation although the tumor-derived factors responsible for changes in bone cell function have not been identified. we have examined the synthesis of osteoblast-stimulating factors in a cultured human prostatic cancer cell line (pc-3) and show that conditioned medium from pc-3 cells stimulate mitogenesis and alkaline phosphatase in cells with the osteoblast phenotype (cultured rat osteosarcoma cells) and collagen synthesis in fetal rat cal ...	1985	3861313
dorsal lateral plate mesoderm influences proliferation and differentiation of hemopoietic stem cells derived from ventral lateral plate mesoderm during early development of xenopus laevis embryos.	the developmental pattern of dorsal and ventral lateral plate mesoderm was examined by explanting these regions and culturing them in serum-free conditions for 10 days. under these circumstances, ventral lateral plate mesoderm gave rise to hemopoietic cells, and dorsal lateral plate mesoderm gave rise to stromal cells. comparison of the differentiation pattern observed when dorsal and ventral mesoderm were cultured separately versus the pattern observed when dorsal and ventral mesoderm were cult ...	1985	3861753
change of karyoskeleton during spermatogenesis of xenopus: expression of lamin liv, a nuclear lamina protein specific for the male germ line.	lamins are the major constituent proteins of the nuclear lamina. in the frog, xenopus laevis, they are the products of a multigene family whose expression can be correlated to certain routes of cell differentiation. for example, lamins li (mr, 72,000) and lii (mr, 68,000) is expressed, together with li/lii, in certain highly differentiated cell types such as neurons and muscle cells and is the only lamin present in diplotene oocytes. here we report the identification by means of two monoclonal a ...	1985	3862126
differentiating effects of murine nerve growth factor in the peripheral and central nervous systems of xenopus laevis tadpoles.	the present investigation was directed toward exploration of the spectrum of action of murine nerve growth factor (m-ngf) in peripheral cells and neurons in the central nervous system (cns) of xenopus laevis tadpoles. it was found that systemic m-ngf injections elicit growth and differentiative effects not only on sensory and sympathetic nerve cells but also on several populations in the cns. the finding that aminergic and peptidergic neurons in brain centers are highly receptive to m-ngf activi ...	1985	3863142
genomic organization and nucleotide sequence of two distinct histone gene clusters from xenopus laevis. identification of novel conserved upstream sequence elements.	we have performed a detailed analysis of the genomic organization and the nucleotide sequence of two distinct xenopus laevis histone gene clusters totaling approximately 23.5 x 10(3) base-pairs. each cluster contains at least one copy of each of the five histone genes. however, these genes are present in different arrangements within each cluster and different h1a, h2a and h2b proteins (variants) are encoded by the respective genes of each cluster. southern blot analysis of genomic x. laevis dna ...	1985	3863963
germ plasm and germ cell determination in xenopus laevis as studied by cell transplantation analysis.		1985	3868485
regulation of the production of granulocyte-macrophage colony-stimulating factor by macrophage-like tumour cell lines.	macrophage tumour cell lines (pu5-1.8, p388d1) produced detectable granulocyte macrophage colony-stimulating (csf-2) activity measured using a factor-dependent cell line fdc-p1. the production of csf-2 was enhanced by endotoxin and inhibited by serum, and correlated inversely with [3h]tdr incorporation. mrna isolated from pu5-1.8 or p388d1 cells initiated csf-2 production when injected into xenopus laevis oocytes. the specific activity in this assay was unaltered in mrna isolated from endotoxin- ...	1985	3871405
transformed xenopus embryos as a transient expression system to analyze gene expression at the midblastula transition.	the onset of transcriptional activity during embryogenesis in xenopus laevis is at the 4000- to 8000-cell stage (stage 8-8.5) and is referred to as the midblastula transition (mbt). most exogenous circular dna that is microinjected into the fertilized egg also is expressed at the mbt. the transformed xenopus embryo at these early stages was used as a transient expression system in order to determine the effects of (1) promoter strength, (2) physical conformation, (3) degree of replication, and ( ...	1985	3871711
murine and human interleukin 2 can substitute for the thymus in immune responses to tnp-ficoll in xenopus laevis, the south african clawed toad.	extirpation of the thymuses of xenopus laevis abrogates the capacity to respond to trinitrophenol (tnp)-ficoll regardless of the age of the animal. this thymus requirement can be substituted for by a variety of treatments which stimulate thymus-derived (t)cell activity in the periphery, such as the rejection of allogeneic skin grafts, immunologic challenge with thymus-dependent immunogens, (e.g., heterologous erythrocytes), or plant-derived lectins (e.g., concanavalin a). here we report that int ...	1985	3873289
comparative studies on the electric nature of amphibian gonadotropin.	the isoelectric focusing (ief) profiles of pituitary gonadotropic (gth) activity in six species of adult male amphibians were examined in addition to the newt and bullfrog. the gth activity was measured by two radioreceptor assay (rra) systems; one with xenopus laevis testicular homogenate as the receptor preparation, and the other with anolis carolinensis testicular homogenate, both employing 125i-labeled rat fsh as the radioligand, or by a radioimmunoassay (ria) system for bullfrog basic gth ( ...	1985	3874809
activation of frog (xenopus laevis) eggs by inositol trisphosphate. i. characterization of ca2+ release from intracellular stores.	iontophoresis of inositol 1, 4, 5-triphosphate into frog (xenopus laevis) eggs activated early developmental events such as membrane depolarization, cortical contraction, cortical granule exocytosis, and abortive cleavage furrow formation (pseudocleavage). inositol 1, 4-bisphosphate also triggered these events, but only at doses approximately 100-fold higher, whereas no level of fructose-1, 6-bisphosphate tested activated eggs. using ca2+-selective microelectrodes, we observed that activating do ...	1985	3874873
construction of cdna coding for human von willebrand factor using antibody probes for colony-screening and mapping of the chromosomal gene.	von willebrand factor (vwf) mrna was identified in fractionated polya+ rna preparations isolated from cultured human endothelial cells. micro-injection of specific polya+ rna fractions in xenopus laevis oocytes provoked the synthesis of a vwf-like product which could be detected with an immunoradiometric assay relying on sepharose-linked monoclonal anti-vwf igg and different radiolabeled monoclonal anti-vwf iggs. a vwf-mrna-containing polya+ rna preparation served as substrate for a size-selecte ...	1985	3875078
[structure of the vestibular apparatus and ionic composition of the body of xenopus laevis larvae as affected by weightlessness].	clawed frog larvae (stages 45-46) that developed for 9 and 8 days beginning with the blastula and tail bud stages, respectively, in the weightless state were investigated. scanning microscopy of the larval labyrinths did not reveal significant qualitative changes in the receptor and supporting cells of the maculae and in the otolith membrane. determination of the electrolyte composition (na, k, ca, mg) of the larval body showed no significant changes in the relative content of these elements. th ...	1985	3875754