| high molecular weight-multicatalytic proteinases in premature and mature oocytes of rana pipiens. | high molecular weight, multicatalytic proteinases (named proteasomes) have been for the first time found, on the basis of different protein patterns, in the cytoplasmic soluble fractions of both non-hormone-treated (premature) and progesterone-treated (mature) oocytes of a frog (rana pipiens). these enzymes, pooled separately as two fractions sedimenting between around 19s and the bottom (over 27s) on glycerol density gradient centrifugation, were composed of several molecular forms with apparen ... | 1991 | 2008178 |
| expression of genes encoding the transcription factor srf during early development of xenopus laevis: identification of a carg box-binding activity as srf. | cdna clones encoding the sequence-specific dna binding protein, serum response factor (srf), have been isolated from a xenopus laevis neurula library and their nucleotide sequence determined. the xenopus srf (srfx) gene produces multiple-sized transcripts, present at 10(5) copies per unfertilized egg. a similar level is detected in the embryo during early cleavage, but srfx transcripts accumulate rapidly following gastrulation. the protein they encode is similar in sequence to human srf in its c ... | 1991 | 2009862 |
| yeast tfiiia + tfiiic/tau-factor, but not yeast tfiiia alone, interacts with the xenopus 5s rrna gene. | the successful use of mixed heterologous in vitro transcription systems has suggested that the species specificity of rna polymerase iii transcription is low. to see if this extends to lower eukaryotic class iii transcription factors, we compared the interactions of the two yeast assembly factors, tfiiia and tfiiic/tau factor, with a homologous yeast 5s rrna gene and a heterologous xenopus laevis somatic 5s rrna gene. transcription assays showed that the xenopus gene was transcriptionally inacti ... | 1991 | 2011529 |
| expression of a mrna related to c-rel and dorsal in early xenopus laevis embryos. | we describe a xenopus mrna, xrel1, that is related to the avian protooncogene c-rel, the embryonic pattern gene dorsal of drosophila, and the mammalian transcription factor nk-kappa b/kbf1. the sequence of xrel1 is homologous to the other rel-related proteins in the large amino-terminal region that defines this class of transcriptional regulators, but the carboxyl-terminal part of the protein is quite different. xrel1 mrna is present throughout oogenesis and during early embryogenesis at 4 x 10( ... | 1991 | 2011580 |
| spiral calcium wave propagation and annihilation in xenopus laevis oocytes. | intracellular calcium (ca2+) is a ubiquitous second messenger. information is encoded in the magnitude, frequency, and spatial organization of changes in the concentration of cytosolic free ca2+. regenerative spiral waves of release of free ca2+ were observed by confocal microscopy in xenopus laevis oocytes expressing muscarinic acetylcholine receptor subtypes. this pattern of ca2+ activity is characteristic of an intracellular milieu that behaves as a regenerative excitable medium. the minimal ... | 1991 | 2011747 |
| comparison of a na+/d-glucose cotransporter from rat intestine expressed in oocytes of xenopus laevis with the endogenous cotransporter. | epithelial na+/d-glucose cotransport was incorporated into the plasma membrane of xenopus oocytes after microinjection of poly(a)(+)-mrna from rat intestine tissue and was detected by measurements of uptake of [14c]amg (methyl alpha-d-glucopyranoside). in mrna-injected oocytes, the rate of amg uptake exceeds the rate of endogenous na+/amg cotransport by a factor of up to 30. it is demonstrated that the additionally expressed transport differs qualitatively from the endogenous transport with resp ... | 1991 | 2015263 |
| the distribution of e-cadherin during xenopus laevis development. | a vast amount of experimental evidence suggests that cell surface molecules involved in cell-to-cell and/or cell-to-substrate interactions participate in the control of basic events in morphogenesis. e-cadherin is a cell adhesion molecule directly implicated in the control of ca2(+)-dependent interactions between epithelial cells. we report here the patterns of expression of e-cadherin in developmental stages of xenopus laevis ranging from early embryo to adult using immunofluorescence microscop ... | 1991 | 2015791 |
| expression of murine dihydrofolate reductase complementary dna in oocytes of xenopus laevis. | 1. murine dihydrofolate reductase was produced efficiently in a xenopus laevis oocyte that received microinjection of the dihydrofolate reductase mrna. 2. murine dihydrofolate reductase was produced under the direction of the plasmid padd26svpa, which contains adenovirus major late promoter and the simian virus 40 t antigen gene for transcription initiation and murine dehydrofolate reductase complementary dna fragment. 3. injection of the plasmid pdhfr26, which contains murine dihydrofolate redu ... | 1991 | 2015958 |
| requirement of phospholipase c-catalyzed hydrolysis of phosphatidylcholine for maturation of xenopus laevis oocytes in response to insulin and ras p21. | recent studies have demonstrated the activation of phospholipase c-mediated hydrolysis of phosphatidylcholine both by growth factors and by the product of ras oncogene, ras p21. also, evidence has been presented indicating that the stimulation of this phospholipid-degradative pathway is sufficient to activate mitogenesis in fibroblasts. in xenopus laevis oocytes, microinjection of transforming ras p21 is a potent inducer of maturation, whereas microinjection of a neutralizing anti-ras p21 antibo ... | 1991 | 2016297 |
| development of the olfactory nerve in the african clawed frog, xenopus laevis: i. normal development. | quantitative and morphological data were obtained on developing olfactory axons in the african clawed frog, xenopus laevis, during late premetamorphosis (stages 48-54), prometamorphosis (stages 55-57), and halfway through metamorphic climax (stages 58-62). larval axons throughout these stages of development did not change with respect to morphology or diameter and were similar in all respects to olfactory axons described in other vertebrate species. the number of axons in the olfactory nerve inc ... | 1991 | 2016408 |
| dna ligase i from xenopus laevis eggs. | we have purified the major dna ligase from xenopus laevis eggs and raised antibodies against it. estimates from sds page indicate that this dna ligase is a 180 kda protein. this enzyme is similar to the mammalian type i dna ligase which is presumed to be involved in dna replication. we have also analysed dna ligase activity during x. laevis early development. unfertilized eggs contain the highest level of activity reflecting the requirement for a large amount of dna replicative enzymes for the p ... | 1991 | 2017356 |
| xenopus laevis oct-1 does not bind to certain histone h2b gene promoter octamer motifs for which a novel octamer-binding factor has high affinity. | oct-1 and a second, previously unidentified octamer-binding protein (oct-r) have been identified in extracts of xenopus laevis oocytes and embryos. oct-1 does not bind to the octamer motif associated with certain xenopus laevis histone h2b gene promoters, whereas oct-r binds well to this motif, but only in the sequence context of the h2b gene promoter. | 1991 | 2017364 |
| presence of ornithine decarboxylase antizyme in primary cultured hepatocytes of the frog xenopus laevis. | ornithine decarboxylase (odc; ec 4.1.1.17) could be induced in primary cultured hepatocytes of the frog, xenopus laevis, by a hypotonic treatment. addition of 10 mm putrescine caused a rapid decay of preinduced odc after a lag period of 30 min. the putrescine-induced odc decay was faster than the odc decay in the presence of cycloheximide. simultaneous addition of cycloheximide blocked the putrescine-induced acceleration of odc decay, indicating an involvement of protein synthesis. addition of p ... | 1991 | 2018782 |
| sequence, organization and transcriptional analysis of a gene encoding a u1 snrna from the axolotl, ambystoma mexicanum. | amu1, a dna fragment containing a u1 small nuclear rna (snrna)-encoding gene, was isolated from the axolotl, ambystoma mexicanum. although this u1 snrna, produced in axolotl oocytes, exhibits the lowest degree of sequence conservation among vertebrates, its secondary structure is maintained by a number of compensatory base changes. the proximal sequence element (pse) is only weakly similar to that of the previously characterized xenopus laevis pse. exchanging either the entire upstream regions w ... | 1991 | 2022330 |
| partial purification of xenopus laevis egg extract factor(s) that induce swelling in permeabilized human sperm. | a combination of adsorption (protamine-agarose) and gel filtration (sephacryl s-300) chromatography was used to enrich for factor(s) in xenopus laevis frog egg extract that induce nuclear swelling-chromatin decondensation in permeabilized human sperm. it was determined that a 70-fold purification of the factor(s) that induce human sperm nuclear swelling has resulted from the purification scheme. the reduced, active factor(s) have a kav of 0.12 and an approximate molecular weight of 290,000 dalto ... | 1991 | 2022951 |
| complement components c1r/c1s, bone morphogenic protein 1 and xenopus laevis developmentally regulated protein uvs.2 share common repeats. | property patterns were constructed, based on an alignment of related domains in human complement subcomponents c1r and c1s as well as in the sea urchin protein uegf. this kind of consensus pattern was able to identify similar domains in a human bone morphogenic protein, in a xenopus laevis embryonal protein involved in dorsoanterior development and in a calcium-dependent serine protease secreted from malignant hamster embryo fibroblast cells. because of the high level of overall sequence homolog ... | 1991 | 2026272 |
| the effects of photoperiod and different dosages of melatonin on metamorphic rate and weight gain in xenopus laevis tadpoles. | this study examined the effects of photoperiod and three different dosages of melatonin on the rate of metamorphosis and weight gain in xenopus laevis. exposure of larvae to 23l:1d resulted in lower mean body weight and a retarded metamorphic rate in comparison to larvae exposed to 1l:23d. larvae reared in either photoperiod and treated with exogenous melatonin demonstrated a dose-dependent suppression of weight attained, with short photoperiod larvae showing a more dramatic effect. analysis of ... | 1991 | 2026314 |
| morphologic changes of the basal lamina in the small intestine of xenopus laevis during metamorphosis. | further investigations of the epithelial and mesothelial basal lamina of the duodenum of xenopus laevis during metamorphosis were performed by means of scanning electron microscopy (sem) and histochemical techniques using polyethyleneimine (pei) to demonstrate anionic sites as well as light- and transmission-electron-microscopic methods involving morphometric analysis. the basal lamina of the duodenal epithelial cells was smooth, and it was occasionally curved along the processes of the epitheli ... | 1991 | 2028731 |
| early development of rubrospinal and cerebellorubral projections in xenopus laevis. | in xenopus laevis hrp was applied at the spinomedullary border at various stages of development. in these experiments labeled rubrospinal neurons were observed from stage 48 on. hrp applications to the mesencephalic tegmentum showed, from stage 49 on, retrogradely labeled neurons in the cerebellar nucleus, particularly contralaterally. these data suggest that anuran cerebellorubral projections arise early, well before the rubrospinal innervation of the spinal cord is complete. | 1991 | 2029772 |
| transgenic xenopus laevis tadpoles: a transient in vivo model system for the manipulation of lens function and lens development. | rodent gamma-crystallin promoters were recognized as lens-specific promoters in micro-injected xenopus laevis tadpoles and targeted the expression of the chloramphenicol acetyl transferase (cat) reporter gene to the tadpole lens. the onset of expression coincided with lens cell formation. the level of expression continued to increase up to 9 days of development (stage 47), stayed at that level till at least day 13 and dropped by only 57% at day 21. in contrast, the level of expression of a non-t ... | 1991 | 2030944 |
| sequence of a cdna encoding rat ribosomal protein homologous to xenopus laevis ribosomal protein s8. | | 1991 | 2030949 |
| xenopus laevis ribosomal protein s1a cdna sequence. | | 1991 | 2030971 |
| cellular mechanisms in proximal tubular reabsorption of inorganic phosphate. | filtered inorganic phosphate (pi) is largely reabsorbed in the proximal tubule. na-pi cotransport, with a stoichiometry of at least 2:1, mediates uphill transport at the apical membrane; at the basolateral membrane different types of transport systems can be involved in efflux and uptake of pi from the interstitium. regulation of transcellular pi flux involves alteration of the apical na-pi cotransport; at least three different cellular control/sensing systems seem to participate in this regulat ... | 1991 | 2035618 |
| bovine inhibin immediately inhibits the electrophysiological response to chorionic gonadotrophin in ovarian follicles of xenopus laevis. | inhibin was originally isolated from ovarian tissue using, as a bioassay, its ability to diminish synthesis and secretion of gonadotrophins in pituitary cells after several days. inhibin is known also to modify responses to gonadotrophins in the ovary after stimulation times of hours or days. here we show that action for less than 4 min of purified bovine inhibin on ovarian follicles from xenopus laevis causes a specific, dose-responsive (greater than 10 u/ml) inhibition of the membrane hyperpol ... | 1991 | 2036993 |
| structural and functional properties of thesaurin a (42sp50), the major protein of the 42 s particles present in xenopus laevis previtellogenic oocytes. | thesaurin a is one of two protein components of a 42 s ribonucleoprotein particle that is very abundant in previtellogenic oocytes of xenopus laevis. the primary function of the 42 s particle is the long-term storage of 5 s rna and aminoacyl-trna. thesaurin a is homologous to eukaryotic elongation factor 1 alpha (ef-1 alpha) and to prokaryotic elongation factor tu (ef-tu). sequence comparison with ef-1 alpha and ef-tu of different species indicates that thesaurin a is rather distantly related to ... | 1991 | 2037589 |
| structural studies on site-directed mutants of domain 3 of xenopus laevis oocyte 5 s ribosomal rna. | base substitutions have been introduced into the highly conserved sequences of loops d and e within domain 3 of xenopus laevis oocyte 5 s rrna. the effects of these mutations on the solution structure of this 5 s rrna have been studied by means of probing with nucleases, and with chemical reagents under native and semi-denaturing conditions. the data obtained with these mutants support the graphic model of xenopus oocyte 5 s rrna proposed by westhof et al. in particular, our results rule out the ... | 1991 | 2038056 |
| involvement of single-stranded tails in homologous recombination of dna injected into xenopus laevis oocyte nuclei. | homologous recombination of dna molecules injected into xenopus laevis oocyte nuclei is extremely efficient when those molecules are linear and have overlapping homologous ends. it was previously shown that a 5'----3' exonuclease activity in oocytes attacks injected linear dnas and leaves them with single-stranded 3' tails. we tested the hypothesis that such tailed molecules are early intermediates on the pathway to recombination products. substrates with 3' tails were made in vitro and injected ... | 1991 | 2038330 |
| characterization of recombination intermediates from dna injected into xenopus laevis oocytes: evidence for a nonconservative mechanism of homologous recombination. | homologous recombination between dna molecules injected into xenopus laevis oocyte nuclei is extremely efficient if injected molecules have overlapping homologous ends. earlier work demonstrated that ends of linear molecules are degraded by a 5'----3' exonuclease activity, yielding 3' tails that participate in recombination. here, we have characterized intermediates further advanced along the recombination pathway. the intermediates were identified by their unique electrophoretic and kinetic pro ... | 1991 | 2038331 |
| characterization of a 54-nucleotide gap region in the 28s rrna gene of schistosoma mansoni. | we have analyzed 572 bp in the 28s rdna of the human blood fluke schistosoma mansoni which correspond to expansion segment 5 of domain iv as defined by clark et al. for the xenopus laevis 28s rrna. s1 nuclease mapping and primer extension analysis comparing this region with the mature 28s rrna indicate that there are 54 nucleotides present in the 28s rdna which are absent from the mature rrna. this defines a gap that creates two 28s rrna subunits (28s alpha and 28s beta). comparison of the s. ma ... | 1991 | 2038356 |
| regulation of the xenopus laevis transcription factor iiia gene during oogenesis and early embryogenesis: negative elements repress the o-tfiiia promoter in embryonic cells. | expression of the xenopus laevis transcription factor iiia (tfiiia) gene is developmentally regulated. in this study we have used defined nucleotide mutations to map cis-elements involved in transcriptional regulation of the promoter for oocyte-tfiiia (o-tfiiia) in stage ii-iv oocytes, stage vi oocytes, and tail bud embryos. during oogenesis o-tfiiia mrna levels decline 5- to 10-fold, and during early embryogenesis o-tfiiia mrna levels decline approximately 10(6)-fold per cell. in stage ii-iv oo ... | 1991 | 2040372 |
| localization of dystrophin relative to acetylcholine receptor domains in electric tissue and adult and cultured skeletal muscle. | two high-affinity mabs were prepared against torpedo dystrophin, an electric organ protein that is closely similar to human dystrophin, the gene product of the duchenne muscular dystrophy locus. the antibodies were used to localize dystrophin relative to acetylcholine receptors (achr) in electric organ and in skeletal muscle, and to show identity between torpedo dystrophin and the previously described 270/300-kd torpedo postsynaptic protein. dystrophin was found in both achr-rich and achr-poor r ... | 1991 | 2040646 |
| the rna polymerase i transcription factor xubf contains 5 tandemly repeated hmg homology boxes. | the rna polymerase i transcription factor ubf has been identified in human, mouse, rat and xenopus and the primary structure of the human protein has been determined. human ubf was shown to contain four tandem homologies to the folding domains of the hmg1 and 2 proteins and hence to belong to a previously unrecognised family of 'hmg-box' transcription factors. here, cdna clones encoding the xenopus laevis ubf (xubf) have been isolated and sequenced. northern and southern blots revealed that in t ... | 1991 | 2041774 |
| probing the molecular dimensions of general anaesthetic target sites in tadpoles (xenopus laevis) and model systems using cycloalcohols. | 1. the series of cycloalcohols c6, c7, c8 and c10 have been used to probe the molecular dimensions of a variety of general anaesthetic target sites. 2. the general anaesthetic ec50 concentrations of the cycloalcohols were determined for tadpoles (xenopus laevis). all of the cycloalcohols tested were found to be potent general anaesthetics (on average ec50/csat = 0.03). 3. the effects of the cycloalcohols on highly purified luciferase enzymes from fireflies (photinus pyralis) and bacteria (vibrio ... | 1991 | 2043920 |
| differential expression of creatine kinase isozymes during development of xenopus laevis: an unusual heterodimeric isozyme appears at metamorphosis. | the creatine kinase (ck) repertoire of xenopus laevis, which is more complex than that of most other vertebrates, involves at least four genomic loci, all showing developmental and tissue-specific expression. the differential expression of this multilocus ck isozyme system was investigated by immunohistology. specific monoclonal antibodies (mab) against the three cytoplasmic ck isozymes of xenopus laevis were isolated and characterized. two of these mabs, anti-ck-iv (dm16) and anti-ck-iii (jrm4) ... | 1991 | 2044860 |
| fertilization-induced changes in the vitelline envelope of echinoderm and amphibian eggs: self-assembly of an extracellular matrix. | the surface of the unfertilized sea urchin egg is covered by the vitelline layer (vl), a fibrous extracellular matrix that contains receptors for sperm. at fertilization, cortical granule exocytosis releases enzymes and structural proteins that cause the vl to elevate and become remodelled into the mechanically and chemically tough fertilization envelope. this envelope prevents further penetration of sperm and protects the embryo during early development. a thicker, more complex vitelline envelo ... | 1991 | 2045963 |
| structure and function of the extracellular matrix of anuran eggs. | the extracellular matrix (ecm) surrounding the anuran egg is composed of jelly coat layers, an envelope, and the perivitelline space, which separates the envelope from the egg plasma membrane. both the jelly coat layers and egg envelopes are required for fertilization in anurans. this paper reviews the current understanding of the structure-function relations of the ecm, with emphasis on the egg envelope. the fibrous egg envelope exists in four related forms. the envelope forms differ in their u ... | 1991 | 2045964 |
| morphogenetic and molecular correlates of teratogenesis in the amphibian embryo. | in attempting to develop a system to study molecular mechanisms of teratogenesis, examination of the effects of a teratogen (dimethyl sulfoxide) on both molecular and morphological aspects of embryonic development in the amphibian xenopus laevis has been conducted. characteristic morphological effects, which occur during the period from 7 to 16 hours after fertilization (i.e., gastrulation) are noted. delays in gastrulation are accompanied by changes in the regulation of transcription of several ... | 1991 | 2048043 |
| molecular cloning of cdna for the b beta subunit of xenopus fibrinogen, the product of a coordinately-regulated gene family. | fibrinogen, the principal blood-clotting protein, is made up of three different subunits synthesized in the liver. in vitro administration of glucocorticoids to liver cells from the frog xenopus laevis causes a dramatic increase in fibrinogen synthesis. investigations of molecular mechanisms underlying this hormonal stimulation at the mrna level require cdna clones complementary to the mrnas coding for the three fibrinogen subunits, called a alpha, b beta, and gamma. we describe here the isolati ... | 1991 | 2050271 |
| effects of insulin, insulin-like growth factor-i (igf-i) and progesterone on glucose and amino acid uptake in xenopus laevis oocytes. | in xenopus oocytes, insulin or igf-i activated glucose transport and maturation, but not amino acid transport, as measured by the uptake of alanine. glucose transporter identical or closely related to the mammalian erythroid/brain transporter (glut-1/egt) were found in oocyte membranes. the ec50 for stimulation of glucose uptake and of maturation were similar (1-5 x 10(-8) m for insulin and 2-8 x 10(-10) m for igf-i), confirming that these effects were mediated through igf-i receptors. other age ... | 1991 | 2050272 |
| cdna sequence of xenopus laevis bone morphogenetic protein 2 (bmp-2). | screening of a xenopus laevis ovary cdna library with an oligonucleotide derived from the activin a sequence led to the isolation of several clones belonging to the tgf-beta supergene family. one of these clones codes for the xenopus bone morphogenetic protein 2 (bmp-2). the deduced protein contains 398 amino acids with a predicted mr of 45,581. within the c-terminal 114 amino acids constituting the mature, biologically active protein there are only four exchanges (three of them are conservative ... | 1991 | 2054389 |
| sequence of a cdna clone encoding an atlantic salmon ribosomal protein. | we report here the nucleotide sequence of a cdna clone encoding a salmon (salmo salar) ribosomal (r) protein. the encoded protein shows 62.3% and 62% similarity with the l14 and l18 r-proteins in xenopus laevis and rat, respectively. | 1991 | 2055494 |
| xenopus laevis c-myc i and ii genes: molecular structure and developmental expression. | the structure of the two xenopus laevis c-myc i and c-myc ii genes has been investigated by isolating and sequencing genomic and cdnas clones. in oocytes, c-myc i mrnas represent 80-90% of the overall amount of c-myc transcripts. the c-myc i expression is controlled primarily by two differentially regulated tandem promoters p1 and p2 which are separated by 50 bases. during oogenesis, maternal c-myc i mrnas, are transcribed from both promoters whereas zygotic transcripts seem to initiate only fro ... | 1991 | 2057364 |
| autoradiography of progesterone and model compound entry and distribution in xenopus laevis oocytes. | xenopus laevis oocytes resume meiosis in response to progesterone. the initial interaction involves surface binding to numerous low-affinity receptor proteins. the mechanism of entry and functions of intracellular steroid are unknown. because the latter are important for understanding progesterone-induced maturation, a dry-mount autoradiographic technique for analyzing entry and intracellular distribution of radiolabeled steroids was developed and tested. the distinguishing feature of this cryo- ... | 1991 | 2057578 |
| insulin-like effects of vanadate on glucose uptake and on maturation in xenopus laevis oocytes. | vanadate, an inhibitor of phosphotyrosyl phosphatases that exerts insulin-like effects in intact cells, stimulated both maturation and glucose uptake in isolated xenopus laevis oocytes. vanadate enhanced the effects of insulin/igf-i and progesterone on maturation in a dose-dependent manner, with an effective concentration of 750 microm and a maximum at 2 mm, whereas, in the absence of hormone, activation of maturation was seen at 10 mm vanadate. further, vanadate at 2 mm increased glucose uptake ... | 1991 | 2059660 |
| ribosomal and chromosomal protein cdna clones of xenopus laevis thymus isolated with differential screening. | 1. xenopus laevis is an excellent system for the study of the evolution and ontogeny of the immune system. but since only immunoglobulin genes have been isolated from this species, we undertook to isolate other genes expressed in an immunologically important organ, the thymus. 2. we used differential screening of a thymus cdna library with cdna probes made from thymus and from erythroblasts. 3. approximately 50 clones which hybridized to the probe from thymus, but not from erythroblast, were iso ... | 1991 | 2060276 |
| amphibian myocardial angiotensin ii receptors are distinct from mammalian at1 and at2 receptor subtypes. | high-affinity receptors for angiotensin ii were identified on xenopus laevis cardiac membranes and characterized by binding-inhibition studies with peptide and non-peptide aii antagonists. scatchard analysis of the binding data identified a high-affinity site with kd1 = 1.6 nm and bmax1 = 3.7 pmol/mg protein and a low-affinity site with kd2 = 22 nm and bmax 2 = 9.5 pmol/mg protein. treatment with dithiothreitol reduced the number of binding sites by greater than 70%. the rank order of potency fo ... | 1991 | 2060651 |
| the cell cycle dependence of the secretory pathway in developing xenopus laevis. | the cell cycle during the cleavage period of the amphibian xenopus laevis is about 30 min long and oscillates between equal periods of mitosis and interphase. at the midblastula transition (mbt) the length of interphase begins to elongate and brings about corresponding changes in the activities of cell cycle-dependent processes. in this study protein secretion and golgi processing during embryonic xenopus development were examined. the elongation of interphase, either during normal development o ... | 1991 | 2060702 |
| prolactin inhibits both thyroid hormone-induced morphogenesis and cell death in cultured amphibian larval tissues. | we describe for the first time the successful organ culture, in a serum-free chemically defined medium, of hind limb buds from stage 54/55 xenopus laevis tadpoles in which 2 x 10(-9) m triiodothyronine (t3) precociously induces morphogenesis to give rise to morphologically normal limbs within 7 days. it was important to retain the mesenchymal tissue joining the two limb buds in order to obtain limb development in culture. t3 added to tail explants from the same larvae, cultured in parallel with ... | 1991 | 2060712 |
| expression of ras-like proteins in embryonic and adult cells of xenopus laevis. | a polyclonal antibody raised against v-ha-ras p21 was purified and its specificity was checked on ha-ras transformed cell lines. it was used to immunoprecipitate p21 from different xenopus laevis cell types: brain cells, blood cells, and embryonic material. by one-dimensional western blot analysis, we show that ras p21 is synthesized very early in oogenesis and accumulates throughout vitellogenesis. the ras p21 content, estimated to be 1.1 ng in the full-grown oocyte, remains constant during ooc ... | 1991 | 2064775 |
| analysis and cloning of the ethylene-forming enzyme from tomato by functional expression of its mrna in xenopus laevis oocytes. | the last step in biosynthesis of the plant hormone ethylene, oxidation of 1-aminocyclopropane-1-carboxylic acid (acc), is catalysed by the elusive ethylene-forming enzyme (efe). efe is induced by fungal elicitors in suspension-cultured tomato cells. we demonstrate that xenopus laevis oocytes injected with rna from elicitor-treated tomato cells gain the ability to convert acc to ethylene. the enzyme expressed in the oocytes under the direction of plant rna is indistinguishable from genuine plant ... | 1991 | 2065651 |
| xubf and rib 1 are both required for formation of a stable polymerase i promoter complex in x. laevis. | we show that three protein fractions are required for accurate transcription initiation at a xenopus laevis ribosomal gene promoter in vitro: rna polymerase i, rib1 and xubf. the rib1 and xubf fractions are both necessary and sufficient for formation of a stable initiation complex. the xubf fraction can be completely replaced by recombinant xubf. we also report the sequence of a cdna clone for xubf. xubf is 701 amino acids in length, contains domain which are related to a domain found in chromos ... | 1991 | 2065665 |
| effect of n-linked glycosylation on hepatic lipase activity. | hepatic lipase (hl) is a secretory protein synthesized in hepatocytes and bound to liver endothelium. previous studies have suggested that hl n-linked glycans are required for catalytic activity. to directly test this hypothesis, xenopus laevis oocytes were used to express native rat hl or hl lacking one or both n-linked glycosylation sites. the expressed and secreted native hl had an apparent molecular mass of 53 kda, consistent with purified rat liver hl. the mutant lacking both glycosylation ... | 1991 | 2066676 |
| preparation and rapid resolution of xenopus phosvitins and phosvettes by high-performance liquid chromatography. | the presence of acidic phosivitins phosvettes in xenopus laevis yolk platelets and their purification by (nh4)2so4 precipitation of associated lipovitellin were documented by polyacrylamide gel electrophoresis followed by staining with stains-all. procedures were further developed to resolve the various entities present in the crude phosvitin/phosvette fraction by size-exclusion, anion-exchange, and hydrophobic interaction chromatography, using a pharmacia fplc system, and their resolution was d ... | 1990 | 2077049 |
| the vocal motor neurons of xenopus laevis: development of sex differences in axon number. | sex differences in the number of muscle fibers in the larynx of clawed frogs (xenopus laevis) develop after metamorphosis. in order to examine possible contributions of neural innervation to this process, we prepared sections of the laryngeal nerve from tadpole stage 56, when the sexes can first be distinguished, through adulthood, and counted axons on electron micrographs. the adult number of axons is achieved by a sexually differentiated pattern of axonal addition and loss. axon numbers are hi ... | 1990 | 2077103 |
| downregulation of the translation elongation factor 2 kinase in xenopus laevis oocytes at the final stages of oogenesis. | phosphorylation of translation elongation factor 2(eef-2) by a specific ca2+/calmodulin-dependent eef-2 kinase plays an important role in the regulation of protein synthesis in mammalian cells. we show here that an eef-2 kinase similar to the mammalian enzyme is present in tissues of the amphibian xenopus laevis. we investigated changes in the activity of eef-2 kinase in extracts of xenopus oocytes at different stages of oogenesis. the eef-2 kinase activity was constant from stage i to stage iv ... | 1990 | 2078557 |
| regional neural induction in xenopus laevis. | during development of the xenopus embryo, the formation of the nervous system depends on an inductive interaction between mesoderm and ectoderm. the result is a neural tube that is regionally differentiated along the anterior-posterior axis from forebrain to spinal cord. the discovery of genes whose transcripts can be used as molecular markers for different regions of the nervous system has permitted reassessment of the existing theories of neural tissue formation. although the neural inducing m ... | 1990 | 2080914 |
| the mechanics of notochord elongation, straightening and stiffening in the embryo of xenopus laevis. | we have examined the biomechanical development of the notochord of xenopus early tail-bud embryos by: (1) quantifying morphological and mechanical changes in the embryo during stages 20-28, and (2) conducting manipulative experiments to elucidate mechanical roles of various components of the notochord. the notochord, which is composed of a stack of flat cells surrounded by a connective tissue sheath, elongates dramatically and begins straightening between stages 21 and 25. at this time the fiber ... | 1990 | 2081454 |
| histones in xenopus laevis' early development: the race against time. | using cloned histone gene variants, the expression of three types of histone gene clusters was studied at the rna level during early development in xenopus laevis. for each histone class the number of mrna molecules per embryo strongly decreased upon ovulation and steadily increased during early development, with a slight decrease at the neurula stage. variation of the stringency of hybridization revealed that none of the histone genes probed is specifically and uniquely expressed at any time po ... | 1990 | 2082927 |
| extracellular matrix components prevent neural differentiation of disaggregated xenopus ectoderm cells. | neuralization (archencephalic brain formation) takes place after dissociation and delayed reaggregation of animal caps of early gastrula without inducer (grunz, h. and l. tacke: cell differ. dev. 28, 211-218 (1989)). this autoneuralization can be prevented by the cell supernatant from dissociated ectoderm of xenopus laevis, which contains extracellular matrix components. after phenol extraction of the supernatant, the aqueous phase does no longer show inhibitory activity. it can be concluded fro ... | 1990 | 2083395 |
| tissue interactions involving cranial neural crest in cartilage formation in xenopus laevis (daudin). | deletion experiments in neurula stage embryos of xenopus laevis provide an approximate anuran fate map of the chondrogenic cranial neural crest which is similar to maps produced for other vertebrates. crest cells in the transverse (rostral) neural fold do not contribute to the skeleton; other cranial crest cells contribute to the larval cranial and visceral skeletons in a rostral to caudal sequence. grafting experiments show that contact with stomodeal (pharyngeal) endoderm is necessary to elici ... | 1990 | 2083397 |
| two types of intrinsic muscarinic responses in xenopus oocytes. ii. hemispheric asymmetry of responses and receptor distribution. | fully grown xenopus laevis oocytes display marked morphological asymmetry. the giant cell is divided into animal (pigmented) and vegetal hemispheres. we have developed methodology aimed at easy determination of hemispheric responses to the application of acetylcholine (ach) and determination of the distribution of muscarinic receptors. oocytes of common donors exhibit muscarinic responses that are similar when either the animal or the vegetal hemisphere of the cell is exposed to ach. oocytes of ... | 1990 | 2084615 |
| ferromagnetic isolation of endosomes: a novel method for subcellular fractionation of xenopus oocytes. | a novel method has been developed using ferric particles to label endosomes, and to achieve magnetic sorting of the various endocytic compartments involved in lipoprotein uptake into cells. ferric particles conjugated to a receptor-recognized ligand are bound to coated membrane pits and become internalized into the cytoplasm inside coated vesicles. after apparent fusion of the vesicles to tubular endosomes, the conjugates accumulate and finally discharge into multivesicular endosomes. pulse-chas ... | 1990 | 2085692 |
| a monoclonal antibody against the human il-2 receptor binds to paraformaldehyde-fixed but not viable frog (xenopus) splenocytes. | others have reported that a monoclonal anti-human il-2 receptor antibody (anti-cd25) specifically binds a membrane receptor on xenopus laevis pha-induced and paraformaldehyde-fixed splenic blasts. in this paper, we present evidence suggesting that this binding is an artifact of membrane damage. specifically, significant binding of anti-cd25 could only be achieved if the lymphoblasts were acid-washed and/or paraformaldehyde-fixed prior to being incubated with the fluoresceinated antibody. for exa ... | 1990 | 2086450 |
| microinjection of alpha-toxin from clostridium novyi type a promotes meiotic maturation in xenopus laevis oocytes. | microinjection of purified alpha-toxin into xenopus laevis oocytes induced meiotic maturation provided insulin was present in the medium. induction of maturation as indicated by breakdown of the germinal vesicle depended on the amount of intracellular alpha-toxin (with a detection limit of 2 ng/oocyte) and on the concentration of insulin. the hormone concentrations used were inactive when given alone and so was alpha-toxin (1 micrograms/ml) applied from the outside. the results demonstrate an in ... | 1990 | 2087699 |
| hormone-sensitive stages in the sexual differentiation of laryngeal muscle fiber number in xenopus laevis. | the number of muscle fibers in the vocal organ of the adult male african clawed frog, xenopus laevis, exceeds that of adult females. this sex difference is the result of rapid fiber addition in males between the end of metamorphosis, post-metamorphic stage 0 (pm0) and pm2. at pm0, male and female frogs have similar numbers of laryngeal muscle fibers. males then add more muscle fibers than females and achieve an adult value that is 1.7 times the female number. males castrated at pm0 have the same ... | 1990 | 2088715 |
| correlated onset and patterning of proopiomelanocortin gene expression in embryonic xenopus brain and pituitary. | to identify cellular interactions that underlie the spatially appropriate transcription of neural genes, we characterized the embryonic development of proopiomelanocortin (pomc) gene expression in xenopus laevis using in situ hybridization histochemistry. this has led to the establishment of a unique model system for studying how a neuropeptide gene program in four distinct cell groups is set up in pituitary and forebrain. the embryonic onset and patterning of pomc expression was found to be spa ... | 1990 | 2088717 |
| the pattern of early cleavage of the marsupial frog gastrotheca riobambae. | comparison of early development of the marsupial frog gastrotheca riobambae with xenopus laevis suggests that the cleavage pattern of xenopus and the tight coupling of events at the midblastula transition are features of the accelerated development of small amphibian eggs with aquatic reproduction, rather than generalized features of amphibian development. the large eggs of the marsupial frog gastrotheca riobambae not only display an atypical holoblastic pattern of cleavage and a very slow rate ... | 1990 | 2088720 |
| expression of the n-myc proto-oncogene during the early development of xenopus laevis. | the n-myc proto-oncogene is expressed in a wide range of tissues during mammalian embryogenesis. this observation, along with the oncogenic capacity of this gene, has led to the suggestion that n-myc plays an important role in early development. however, due to the complexity of the expression pattern and the difficulty of manipulating mammalian embryos, little progress has been made towards understanding the developmental function of this gene. to enable a more detailed analysis of the role of ... | 1990 | 2088727 |
| post-transcriptional regulation of ornithine decarboxylase in xenopus laevis oocytes. | the level at which ornithine decarboxylase expression is regulated in growing oocytes has been investigated. immunoprecipitation of the in vivo labelled proteins showed that ornithine decarboxylase accumulated less rapidly in stage iv oocytes than in previtellogenic stage i + ii oocytes. quantitative northern analysis showed that ornithine decarboxylase mrna is abundant in oocytes (about 8 x 10(8) transcripts/cell) and this number does not significantly change during oogenesis. polysome analysis ... | 1990 | 2088731 |
| isolation of a vegetalizing inducing factor after extraction with acid ethanol. concentration-dependent inducing capacity of the factor. | a vegetalizing factor has been isolated from chicken embryos by an improved method. the factor is extracted with acid/ethanol and finally purified by four consecutive steps of reversed phase hplc. the molecular mass is about 25 kda. the factor dissociates after reduction with dithiothreitol into two subunits of about 13 kda. the factor was tested on triturus alpestris by the implantation method, and on isolated ectoderm of xenopus laevis in solution. the factor induces as the crude fractions all ... | 1990 | 2090330 |
| ultrastructural comparison between regenerating and developing hindlimbs of xenopus laevis tadpoles. | hindlimbs of xenopus laevis tadpoles at stages 50 to 55 of embryonic development were amputated in order to study the fine structure associated with ontogenetic decline in regenerative ability of this anuran. regenerating hindlimbs were compared with their contralateral developing limb so as to determine the similarities and differences in ectodermal-mesenchymal ultrastructural relationships in these systems. prior to stage 53, mesenchymal cells in regenerating limbs, as well as mesenchyme cells ... | 1990 | 2092016 |
| protein kinase c acts downstream of calcium at entry into the first mitotic interphase of xenopus laevis. | transit into interphase of the first mitotic cell cycle in amphibian eggs is a process referred to as activation and is accompanied by an increase in intracellular free calcium [( ca2+]i), which may be transduced into cytoplasmic events characteristic of interphase by protein kinase c (pkc). to investigate the respective roles of [ca2+]i and pkc in xenopus laevis egg activation, the calcium signal was blocked by microinjection of the calcium chelator bapta, or the activity of pkc was blocked by ... | 1990 | 2100203 |
| a cytoplasmic determinant for dorsal axis formation in an early embryo of xenopus laevis. | in xenopus laevis, dorsal cells that arise at the future dorsal side of an early cleaving embryo have already acquired the ability to cause axis formation. since the distribution of cytoplasmic components is markedly heterogeneous in an egg and embryo, it has been supposed that the dorsal cells are endowed with the activity to form axial structures by inheriting a unique cytoplasmic component or components localized in the dorsal region of an egg or embryo. however, there has been no direct evid ... | 1990 | 2100253 |
| inhibition of proteoglycan synthesis eliminates left-right asymmetry in xenopus laevis cardiac looping. | the heart of any vertebrate is formed from an apparently symmetric cardiac tube that loops consistently in the same direction along the left-right axis of the embryo. in the amphibian xenopus laevis, inhibition of proteoglycan synthesis by p-nitrophenyl-beta-d-xylopyranoside during a narrow period of development from late gastrula to early neurula specifically eliminated the looping of the cardiac tube. most of the proteoglycans synthesized during this period were heparan sulfate proteoglycans. ... | 1990 | 2100995 |
| identification of a soluble precursor complex essential for nuclear pore assembly in vitro. | we analysed the soluble form in which the nuclear pore complex protein p68 is stored in xenopus laevis eggs and its involvement in pore complex assembly processes. we have shown previously that p68, which is the major wheat germ agglutinin (wga)-binding glycoprotein of nuclear pore complexes from xenopus oocytes, is located in the pore channel and participates in mediated transport of karyophilic proteins. using a monoclonal antibody directed against p68 (pi1) we removed this protein from xenopu ... | 1990 | 2101351 |
| characterization of a second highly conserved b-type lamin present in cells previously thought to contain only a single b-type lamin. | previous analyses of the nuclear lamina of mammalian cells have revealed three major protein components (lamins a, b and c) that have been identified by protein sequence homology as members of the intermediate filament (if) protein family. it has been claimed that mammalian cells contain either all three lamins or lamin b alone. using monoclonal antibodies specific for b-type lamins and cdna cloning we identified a second major mammalian b-type lamin (murine lamin b2), thus showing that lamin co ... | 1990 | 2102682 |
| cytostatic factor (csf) activity in cytosols extracted from xenopus laevis eggs. | cytostatic factor (csf), found in the cytoplasm of unfertilized eggs of amphibians, causes metaphase arrest when microinjected into cleaving blastomeres. although csf from rana pipiens eggs has been extracted and characterized, little is known about csf extracted from eggs of other species. we investigated the conditions required to preserve csf activity in cytosols extracted from xenopus laevis eggs and found that it was necessary to expose the eggs to co2 prior to extraction and that the extra ... | 1990 | 2105220 |
| talin and vinculin in the oocytes, eggs, and early embryos of xenopus laevis: a developmentally regulated change in distribution. | we have investigated the expression and distribution of talin and vinculin in the oocytes, eggs, and embryos of xenopus laevis. antibodies to the previously characterized avian proteins stain several different xenopus cell types identically by immunofluorescence: adhesion plaques of cultured kidney (a6) cells, the cell peripheries of oviduct cells, and the postsynaptic neuromuscular junctions of tadpole tail muscle fibers. these antibodies also identify cognate proteins of the appropriate sizes ... | 1990 | 2105901 |
| eleven distinct vh gene families and additional patterns of sequence variation suggest a high degree of immunoglobulin gene complexity in a lower vertebrate, xenopus laevis. | lower vertebrate species, including xenopus laevis, exhibit restricted antibody diversity relative to higher vertebrates. we have analyzed more than 180 vh gene-containing recombinant clones from an unamplified spleen cdna library by selective sequencing of jh and ch positive clones following iterative hybridization screening with family-specific vh probes, 11 unique families of vh genes, each associated with a unique genomic southern blot hybridization pattern, are described and compared. consi ... | 1990 | 2110243 |
| effects of divalent cations on the frequency of spontaneous action potentials from the lateral line organ of xenopus laevis. | the effect of superfusion of the internal surface of the skin of xenopus laevis with saline containing co2+, ca2+, mg2+, or ba2+, on the frequency of spontaneous action potentials of the lateral line nerve, was studied to investigate the role of extracellular ca2+ in spontaneous neural activity. addition of divalent cations to frog saline, either singly or as a mixture of two different ions, produced concentration-dependent suppression of spontaneous rate. the rank order of potency for suppressi ... | 1990 | 2110846 |
| structural modifications induced by the mtdbp-c protein in the replication origin of xenopus laevis mitochondrial dna. | the structure of the non-coding region of xenopus laevis mitochondrial dna has been studied by electron microscopy analysis of dna molecules end-labelled with streptavidin-ferritin. we have shown that the effect of a protein modifying the shape of the dna double-helix can be studied and precisely located by this method. it was found that the non-coding region contains curved segments and that the mitochondrial protein mtdbp-c preferentially enhances the curvature of the promoters-replication ori ... | 1990 | 2111178 |
| activin-like factor from a xenopus laevis cell line responsible for mesoderm induction. | induction of mesoderm during early amphibian embryogenesis can be mimicked in vitro by adding growth factors, including heparin-binding and type-beta transforming growth factors (tgf-beta), to isolated ectoderm explants from xenopus laevis embryos. although the mesoderm-inducing factor (mif) from x. laevis xtc cells (xtc-mif) has properties similar to tgf-beta, this factor is still unidentified. recently, we obtained a number of homogeneous cell lines from the heterogeneous xtc population, which ... | 1990 | 2113616 |
| alternating zinc-finger motifs in the human male-associated protein zfy. | zfy, a putative transcription factor encoded by the human y chromosome, contains a distinctive two-finger repeat: odd-numbered and even-numbered cc/hh metal-binding motifs exhibit systematic alternation in sequence pattern. such alternation, which is not generally observed in zinc-finger proteins, has also been described in an extensive family of kruppel-like genes in xenopus laevis and in the aids-associated human dna-binding protein hiv-ep1. the strict conservation of a two-finger repeat among ... | 1990 | 2116899 |
| repair of acetyl-aminofluorene modified pbr322 dna in xenopus laevis oocytes and eggs; effect of diadenosine tetraphosphate. | using xenopus laevis oocytes and unfertilized eggs, we have developed a system which allows the study of dna repair upon microinjection of pbr 322 dna which has been previously modified in vitro by n-acetyl-aminofluorene, under controlled conditions. in unfertilized eggs, an efficient repair of pbr-18aaf dna takes place, leading to a restoration of the transforming activity of the plasmid dna towards escherichia coli. the repaired dna is even efficiently replicated, the egg being "activated" by ... | 1990 | 2116915 |
| molecular cloning and sequence determination of four different cdna species coding for alpha-subunits of g proteins from xenopus laevis oocytes. | a cdna library prepared from xenopus laevis oocytes in lambda gt10 was screened with a mixture of three oligonucleotide probes designed to detect sequences found in different mammalian genes coding for alpha-subunits of g-proteins. in addition to a clone coding for a g alpha o-type subunit previously reported [(1989) febs lett. 244, 188-192] four additional clones have been found coding for different g alpha protein subunits. by comparison with mammalian alpha-subunits, these oocyte cdnas corres ... | 1990 | 2116977 |
| the changing distribution of neurons in the inner nuclear layer from metamorphosis to adult: a morphometric analysis of the anuran retina. | the generation and changing distribution of neurons of the inner nuclear layer (inl) in the retina of two anuran species, bufo marinus and xenopus laevis, were studied from metamorphosis to adult. morphometric studies were undertaken at six developmental stages in bufo and four in xenopus. the number and thickness of neurons in the inl were established in 29 predetermined retinal locations from serial sections of the eyes cut vertically or horizontally. the total number of neurons in the inl inc ... | 1990 | 2118741 |
| the organization of the cortical endoplasmic reticulum in xenopus eggs depends on intracellular ph: artefact of fixation or not? | the cortical endoplasmic reticulum (cer), which develops and becomes organized during oocyte maturation in xenopus laevis (anuran amphibians), has been thought to be essential for the propagation of the activating signal at the time of fertilization, possibly by regulating intracellular ca2+ (ca2+i) (charbonneau and grey, dev. biol. 102, 90-97, 1984). the present paper demonstrates that changing intracellular ph (phi) has an influence on the structure and organization of the cer in unactivated x ... | 1990 | 2119869 |
| a fluorescent analogue of hydrin 1: a new probe for vasotocin receptors. | hydrin 1 is the biosynthetic precursor of vasotocin in xenopus laevis. we have synthesized deamino and fluorescein analogues of hydrin 1 and characterized their physiological action in the urinary bladder of the toad, bufo marinus. 1-deamino-hydrin 1 (d-hydrin) was more potent than vasotocin in stimulating osmotic water flow across intact bladders and more potent than vasotocin in displacing tritium-labeled vasopressin [( 3h]avp) from cell membranes. 1-deamino-[11-lysine (fluorescein)]-hydrin 1 ... | 1990 | 2121046 |
| xenopus oocyte k+ current. i. fsh and adenosine stimulate follicle cell-dependent currents. | ovarian follicles of xenopus laevis frogs consist of a single large oocyte surrounded by follicle cells attached to the oocyte by gap junctions. adenosine has been found to activate an outward k+ current in follicles. this response is reduced by microinjection of protein kinase inhibitor (pki), suggesting that adenosine 3',5'-cyclic monophosphate (camp) mediates the response. to investigate this further, we verified previous studies that indicate that several methods of elevating camp in follicl ... | 1990 | 2122736 |
| selective carboxyl methylation of structurally altered calmodulins in xenopus oocytes. | the eucaryotic protein carboxyl methyltransferase specifically modifies atypical d-aspartyl and l-isoaspartyl residues which are generated spontaneously as proteins age. the selectivity of the enzyme for altered proteins in intact cells was explored by co-injecting xenopus laevis oocytes with s-adenosyl-l-[methyl-3h]methionine and structurally altered calmodulins generated during a 14-day preincubation in vitro. control experiments indicated that the oocyte protein carboxyl methyltransferase was ... | 1990 | 2123492 |
| localization of endogenous galactoside-binding lectin during morphogenesis of xenopus laevis. | a monoclonal antibody has been produced against xenopus laevis galactoside-binding neural-crest-stage lectin. this antibody inhibits lectin-mediated hemagglutination. using this antibody in conjunction with immunohistochemical techniques, lectin deposition has been studied in embryos and tadpoles at different stages of morphogenesis, from initial neural crest migration, up to the formation of a swimming tadpole. lectin levels change during development in different regions of the embryo and tadpo ... | 1990 | 2123609 |
| dystrophin as a focal adhesion protein. collocalization with talin and the mr 48,000 sarcolemmal protein in cultured xenopus muscle. | monoclonal antibodies against dystrophin and the postsynaptic 58 kda protein from torpedo electric organ were used to localize homologs of these proteins in cultured skeletal muscle (xenopus laevis). the xenopus homolog is an mr 48,000 protein and, like dystrophin, is a sarcolemmal protein. both proteins localized precisely to talin-positive sites, hence with each other, on the substrate-apposed sarcolemma. therefore, the first sites of appearance of dystrophin on cultured muscle cells are focal ... | 1990 | 2123804 |
| ribosomal 5s rna from xenopus laevis oocytes: conformation and interaction with transcription factor iiia. | this review describes extensive studies on 5s rrna from x laevis oocytes combining conformational analyses in solution (using a variety of chemical and enzymatic probes), computer modeling, site-directed mutagenesis, crosslinking and tfiiia binding. the proposed 3-dimensional model adopts a y-shaped structure with no tertiary interactions between the different domains of the rna. the conserved nucleotides are not crucial for the tertiary folding but they maintain an intrinsic structure in the lo ... | 1990 | 2124147 |
| developmental expression of the xenopus laevis fos protooncogene. | we have isolated the xenopus laevis homologue of the protooncogene fos. nucleotide sequence analysis of the complementary dna revealed a coding domain for a 370-amino acid protein which shares extensive sequence homology with the avian and mammalian fos protein. during xenopus development, the fos mrna is present in the oocyte and egg stages and declines to relatively low levels by the mid-blastula transition. transient expression of fos can be seen during the late neurula and again at the tadpo ... | 1990 | 2127691 |
| expression of receptor for alpha-latrotoxin in xenopus oocytes after injection of mrna from rat brain. | alpha-latrotoxin, the major toxin of black widow spider venom, was suggested to bind to the specific receptor on the membrane of presynaptic cells and to activate a nonselective cation channel. the aim of this investigation was to express the receptor to alpha-latrotoxin in the membrane of xenopus laevis oocytes. responses to alpha-latrotoxin were studied using a double microelectrode voltage-clamp technique on x. laevis oocytes previously injected with poly(a+)-rna from rat brain. alpha-latroto ... | 1990 | 2129054 |
| mesoderm-inducing factor from bovine amniotic fluid: purification and n-terminal amino acid sequence determination. | bovine amniotic fluid contains a protein capable of inducing mesoderm formation from animal cap cells isolated from xenopus laevis embryos at the late blastula stage. the procedure for purification of this protein is described and includes the following steps: cm-cellulose cation-exchange chromatography, chromatography on hydroxylapatite, reverse-phase hplc, size exclusion hplc, and a second reverse-phase hplc. a partially purified preparation of a mesoderm-inducing factor with high mesoderm-ind ... | 1990 | 2133067 |
| translational regulation of the expression of ribosomal protein genes in xenopus laevis. | the mrnas coding for ribosomal proteins (rp-mrna) are subjected to translational control during xenopus oogenesis and embryogenesis, and also during nutritional changes in xenopus cultured cells. this regulation, which appears to respond to the cellular need for new ribosomes, operates by changing the fraction of rp-mrna engaged on polysomes, each translated rp-mrna molecule always remaining fully loaded with ribosomes. all rp-mrnas analyzed up to now show this translational behavior, and also s ... | 1990 | 2133662 |
| molecular cloning of xenopus fibrillarin, a conserved u3 small nuclear ribonucleoprotein recognized by antisera from humans with autoimmune disease. | autoantibodies against u3 small nuclear ribonucleoprotein are associated with scleroderma autoimmune disease. they were shown to react with fibrillarin, a 34- to 36-kilodalton protein that has been detected in all eukaryotes tested from humans to yeasts. we isolated a 1.6-kilobase cdna encoding fibrillarin from a xenopus laevis cdna library. the protein contains a 79-residue-long gly-arg-rich domain in its n-terminal region and a putative rna-binding domain with ribonucleoprotein consensus seque ... | 1990 | 2136767 |
| expression of a human cocaine-sensitive dopamine transporter in xenopus laevis oocytes. | the human dopamine transporter was expressed in xenopus laevis oocytes following injection of mrna isolated from human brain substantia nigra. the specific accumulation of [3h]dopamine into these oocytes was time and na+ dependent. furthermore, [3h]dopamine accumulation was prevented by coincubation of oocytes with dopamine (100 microm) or with the dopamine uptake inhibitors gbr 12909 (1 microm) or cocaine (3 microm). in contrast, oocyte injection of mrna isolated from human globus pallidus, an ... | 1990 | 2137162 |
| potential for two isoforms of the a1 ribonucleoprotein in xenopus laevis. | we have identified the xenopus cognates for the rna-binding protein a1. this protein has previously been shown to be one of the components of the heterogeneous nuclear ribonucleoprotein (hnrnp) complex in rat and human cells. we have isolated several xenopus clones from oocyte, tailbud embryo, and leg muscle cdna libraries and determined their nucleotide sequences. potentially, two different a1 isoforms are expressed in xenopus; they have been termed xa1a and xa1b. besides insertions and deletio ... | 1990 | 2137612 |