| membrane currents elicited by the epileptogenic drug pentylenetetrazole in the native oocyte of xenopus laevis. | the effects of the epileptogenic agent pentylenetetrazole (ptz) on membrane currents of native oocytes of xenopus laevis were studied. ptz elicits a response that consists of two inward currents. the first one is interpreted to be due to a decrease of potassium permeability since: (1) the input resistance is increased; (2) the equilibrium potential is near that of potassium; (3) the current is decreased during administration of potassium channel blocking agents; and (4) the ptz response can be m ... | 1991 | 1718540 |
| biosynthesis, primary structure and molecular cloning of snowdrop (galanthus nivalis l.) lectin. | poly(a)-rich rna isolated from ripening ovaries of snowdrop (galanthus nivalis l.) yielded a single 17-kda lectin polypeptide upon translation in a wheat-germ cell-free system. this lectin was purified by affinity chromatography. translation of the same rna in xenopus leavis oocytes revealed a lectin polypeptide which was about 2 kda smaller than the in vitro synthesized precursor, suggesting that the oocyte system had removed a 2-kda signal peptide. a second post-translational processing step w ... | 1991 | 1718752 |
| functional expression of a human c5a receptor clone in xenopus oocytes requires additional rna. | crna from a pcr-generated c5ar clone was prepared by in vitro transcription and microinjected into xenopus laevis oocytes. ligand-induced whole cell current could be detected after co-injection of crna for the c5ar with total rna of the unstimulated u937 cell line, but not with either of the components injected alone. these data clearly demonstrate an absolute requirement of the c5ar for an additional human factor to become functionally expressed in xenopus oocytes. | 1991 | 1718782 |
| heterologous regulation of the cardiac ca2+ channel alpha 1 subunit by skeletal muscle beta and gamma subunits. implications for the structure of cardiac l-type ca2+ channels. | high threshold l-type ca2+ channels of skeletal muscle are thought to consist of a complex of alpha 1, alpha 2 delta, beta, and gamma subunits. expression of the cloned alpha 1 subunit from skeletal and cardiac muscle has established that this protein is the dihydropyridine-sensitive ion-conducting subunit. however, the kinetics of the skeletal muscle alpha 1 alone expressed in mouse l-cells were abnormally slow and were accelerated to within the normal range by coexpression with the skeletal mu ... | 1991 | 1718988 |
| distribution of galanin-like immunoreactivity in the brain of rana esculenta and xenopus laevis. | the immunocytochemical distribution of galanin-containing perikarya and nerve terminals in the brain of rana esculenta and xenopus laevis was determined with antisera directed toward either porcine or rat galanin. the pattern of galanin-like immunoreactivity appeared to be identical with antisera directed toward either target antigen. the distribution of galanin-like immunoreactivity was similar in rana esculenta and xenopus laevis except for the absence of a distinct laminar distribution of imm ... | 1991 | 1719037 |
| calcium regulation of epidermal cell differentiation in the frog xenopus laevis. | adult frogs have a stratified epidermis with a keratinized stratum corneum. since the extracellular calcium concentration is known to regulate differentiation of mammalian epidermal cells in vitro, we studied the effects of calcium on the terminal differentiation of frog epidermal cells. exposure of the epidermal cells to a high concentration of calcium (greater than 0.2 mm) induced cornification and the synthesis of a 51 kd acidic keratin. these data are very similar to the results from mammali ... | 1991 | 1719122 |
| up-regulation of sodium pump activity in xenopus laevis oocytes by expression of heterologous beta 1 subunits of the sodium pump. | recent evidence suggests that the beta subunit of the na+ pump is essential for the alpha subunit to express catalytic activity and for assembly of the holoenzyme in the plasma membrane. we report here that injection into xenopus laevis oocytes of crnas specific for beta 1 subunit isoforms of the na+ pump of four species (torpedo californica, chicken, mouse and rat) causes a time-dependent increase in the number of ouabain-binding sites, both in the plasma membrane and in internal membranes. exp ... | 1991 | 1719955 |
| expression of adult and tadpole specific globin genes from xenopus laevis in transgenic mice. | transgenic mice were generated which carried the adult alpha and beta-globin genes and the major tadpole specific beta-globin gene of xenopus laevis. the adult specific alpha and beta genes were found to express in erythroid tissues in adult mice, while the major tadpole specific beta gene (beta t1) was expressed in blood from 12.5 day embryos. the pattern of expression of the beta t1 gene during mouse development was consistent with its being regulated as an embryonic globin gene in the mouse. ... | 1991 | 1720238 |
| distribution and expression of two interactive extracellular matrix proteins, cytotactin and cytotactin-binding proteoglycan, during development of xenopus laevis. i. embryonic development. | an immunohistochemical study of the localization of cytotactin and cytotactin-binding (ctb) proteoglycan throughout embryonic development of the anuran xenopus laevis reveals that both appear in a restricted pattern related to specific morphogenetic events. ctb proteoglycan expression is first detected during gastrulation at the blastopore lip. later, it is seen in the archenteron roof around groups of cells forming the notochord, somites and neural plate. cytotactin first appears after neurulat ... | 1991 | 1720464 |
| distribution and expression of two interactive extracellular matrix proteins, cytotactin and cytotactin-binding proteoglycan, during development of xenopus laevis. ii. metamorphosis. | during metamorphosis of xenopus laevis the extracellular matrix (ecm) proteins cytotactin and cytotactin-binding (ctb) proteoglycan and the cell adhesion molecules n-cam and ng-cam, appear in highly restricted patterns determined by immunofluorescence histology. during limb development, cytotactin appears from the earliest stages in a meshwork of ecm fibrils associated with migrating mesenchymal cells forming the limb bud. cytotactin also appears in the ecm between the apical limb ectoderm and m ... | 1991 | 1720465 |
| xenopus c-raf proto-oncogene: cloning and expression during oogenesis and early development. | we have isolated and characterized a cdna which contains the entire coding sequence of xenopus laevis raf protein. raf mrna is identified as a member of the class of maternal rnas. it is already relatively abundant at the beginning of oogenesis and is stable at least until the midblastula transition. the rna is also detected later during embryogenesis in particular in gastrula, neurula, tailbud and feeding tadpole. we have also found the rna in several adult tissues (skin, testis, stomach, intes ... | 1991 | 1721855 |
| characterization of xenopus laevis proenkephalin gene. | enkephalins are opiate peptides found in a variety of tissues including brain and pituitary. in brain, they function as neurotransmitters, neuromodulators and neurohormones. recent studies show that proenkephalin mrna is expressed early in development both in mammals and the amphibian, suggesting that enkephalins may play a unique role in embryogenesis. in order to characterize factors which regulate the onset and patterning of expression of this gene in adult and developing frog embryos, the pr ... | 1991 | 1721992 |
| recording of voltage and ca(2+)-dependent currents in xenopus oocytes using an intracellular perfusion method. | we describe a method for internal perfusion of xenopus laevis oocytes that allows control of the composition of intracellular and extracellular solutions, including the possibility of sequential introduction of different substances inside and outside the cell. using this method, it was possible to record ca2+ dependent cl- current and to inhibit it by intracellular perfusion of egta-containing solution. with a high ba2+ solution at the external surface of the perfused oocyte, ba2+ currents throu ... | 1991 | 1722267 |
| completely functional double-barreled chloride channel expressed from a single torpedo cdna. | we have performed an electrophysiological analysis of the recently cloned torpedo marmorata cl- channel. functional expression of cl- channels in oocytes of xenopus laevis previously injected with crna yielded an outward-rectifying current activated by hyperpolarization. replacement of cl- with other anions significantly reduced or inhibited the current. single-channel recordings from cell-attached patches exhibited burst-like cl- channel activity with rapid fluctuations between three equally sp ... | 1991 | 1722317 |
| cloning and functional characterization of a novel mas-related gene, modulating intracellular angiotensin ii actions. | the mas oncogene codes for a gtp binding protein-coupled receptor that determines a physiological response to angiotensin when expressed in xenopus laevis oocytes or in the neuronal cell line ng115-401l. however, another gene, rat thoracic aorta gene, structurally related to mas, is devoid of any functional similarity with the angiotensin receptor(s). the relationships between the mas-related proteins and the angiotensin receptors were investigated by identifying and characterizing new members o ... | 1991 | 1723144 |
| the potassium channel mbk1 (kv1.1) is expressed in the mouse retina. | 1. the neurons of the retina have electrical properties that are different from those of most of the other neurons of the central nervous system. to identify the voltage-gated ion channels found in the retina, we screened mouse retinal cdna libraries with oligonucleotide probes homologous to the mammalian k+ channel mbk1 (kv1.1) and ligated two partial clones to produce a full-length clone with no significant differences from mbk1. 2. expression of mbk1 mrna was determined by rnase protection. m ... | 1991 | 1723658 |
| nuclear translocation of fibroblast growth factor during xenopus mesoderm induction. | mesoderm induction, the earliest inductive cell-cell interaction in vertebrate embryogenesis, is thought to be mediated by polypeptide growth factors including fibroblast growth factor (fgf). here we present an immunocytochemical analysis of fgf during mesoderm induction in xenopus laevis. antibodies to both basic and acidic fgf were immunoreactive with oocytes and early embryos. immunostaining was predominantly intracellular and was concentrated in the marginal zone and vegetal pole throughout ... | 1991 | 1723679 |
| labeling of developing vascular endothelium after injections of rhodamine-dextran into blastomeres of xenopus laevis. | the goal of this work has been to label endothelial cells with fluorescent marker and to record their behavior during angiogenesis in vivo. single blastomeres in 16-128-cell-stage embryos of pigment-deficient xenopus laevis were injected intracellularly with 5% tetramethyl-rhodamine dextran. subsequently, the embryos and tadpoles were examined with an epifluorescence microscope, a silicon-intensified target (sit) camera, and video recordings. clones that would include endothelium could be select ... | 1991 | 1723747 |
| argiotoxin636 inhibits nmda-activated ion channels expressed in xenopus oocytes. | argiotoxin636, a component of the spider venom of argiope species, was chemically synthesized together with a number of derivatives in order to analyse their blocking activity on mammalian glutamate receptors. xenopus laevis oocytes injected with rat brain mrna served as assay system. the results showed that argiotoxin636 had a higher affinity for n-methyl-d-aspartate (nmda) than for kainate receptors, blocking the corresponding ion channels in a voltage-dependent manner. modifications of the po ... | 1991 | 1723790 |
| inhibitors of phosphodiesterase iii block stimulation of xenopus laevis oocyte ribosomal s6 kinase activity by insulin-like growth factor-i. | insulin-like growth factor-i (igf-i) stimulated xenopus laevis oocyte ribosomal s6 kinase activity 5- to 10-fold, with an apparent ec50 of 0.8 +/- 0.1 nm after 90 min of hormone treatment. igf-i-stimulated enzyme activity was inhibited by treatment of oocytes with nonselective phosphodiesterase (pde) inhibitors, with apparent ic50 values of 2 +/- 1 microm papaverine, 20 +/- 2 microm isobutylmethylxanthine, and 128 +/- 16 microm theophylline. type iii pde inhibitors also inhibited igf-i-stimulate ... | 1991 | 1724288 |
| toward a more complete 3-d structure of the nuclear pore complex. | the nuclear pore complex (npc) is a large supramolecular assembly embedded in the double-membraned nuclear envelope (ne) that plays a pivotal role in the exchange of macromolecules and particles between the nucleus and the cytoplasm. applying various methods of sample preparation to xenopus laevis whole nuclei and isolated nes in combination with conventional transmission electron microscopy and digital image processing, we have characterized several distinct components of the npc, including mas ... | 1991 | 1725493 |
| histological preparation of xenopus laevis oocytes and embryos. | | 1991 | 1725801 |
| molecular aspects of the neuronal noradrenaline transporter. | the neuronal noradrenaline transporter was partially purified by means of low and high pressure liquid chromatography using anion exchange, gel filtration and lectin affinity columns. a protein characterized by a molecular weight of 50-53 kilodalton was enriched; it may represent the transporter or a component of it. in addition, a rna fraction characterized by a mean size of 2 kilobases was isolated from pc12 rat phaeochromocytoma cells and from bovine adrenal medulla; this rna fraction caused ... | 1991 | 1726219 |
| teratogenicity of ni2+ in xenopus laevis, assayed by the fetax procedure. | the teratogenicity of ni2+ was tested by the fetax (frog embryo teratogenesis assay: xenopus) procedure in the south african frog, xenopus laevis. in seven assays, beginning at 5 h postfertilization, groups of xenopus embryos were incubated for 96 h in media that contained ni2+ (added as nicl2) at concentrations ranging from 1 x 10(-7) to 3 x 10(-3) mol/l; control groups were incubated in the same medium without added nicl2. at 101 h postfertilization, surviving embryos were counted, fixed in fo ... | 1991 | 1726404 |
| analysis of the p21 ras system during development of meiotic competence in xenopus laevis oocytes. | the ability of xenopus oocytes to undergo insulin- or insulin-like growth factor 1-induced meiotic maturation develops during oogenesis, with cells 1.0 mm in diameter or larger responding in a size-dependent manner. since insulin-induced oocyte maturation was shown previously to be p21 ras-dependent, experiments were performed to test whether a deficiency in the p21 ras system might account for meiotic incompetence in small oocytes (less than or equal to 0.9 mm diameter). both small and large oo ... | 1992 | 1728580 |
| developmental regulation of alternative splicing in the mrna encoding xenopus laevis neural cell adhesion molecule (ncam). | the neural cell adhesion molecule (ncam) is thought to play a role in the formation of the vertebrate nervous system. in mammals and chicken, it is known that more than 100 different forms of the ncam protein can be generated by alternative splicing of one primary transcript and it is possible that these different forms have distinct biological functions. a large part of the diversity is generated by alternative mrna splicing in two regions, called the pi and the muscle specific domain (msd), th ... | 1992 | 1728590 |
| embryonic retinal ablation and post-metamorphic optic nerve crush: effects upon the pattern of regenerated retinotectal connections. | we examined relationships between healing observed during embryonic xenopus retinal and optic nerve regeneration and resultant visuotectal pattern formation. dorsal (d) and nasoventral (nv) 1/3 sized eye fragments were surgically created in stage 32 xenopus laevis embryos. gross anatomical healing modes of these fragments were examined 2 days post-surgery (stage 43). healing was categorized according to the degree of cell movements observed. animals were reared through metamorphosis and electrop ... | 1992 | 1729382 |
| test of the double-strand-break repair model of recombination in xenopus laevis oocytes. | a direct test was made of predictions of the double-strand-break repair (dsbr) model of recombination in xenopus laevis oocytes. the dna substrate injected into oocytes had two directly repeated copies of a 1.25-kb sequence and was cleaved within one of them. different products were expected to result from concerted, conservative events, as predicted by the dsbr model, and from nonconservative events. only very low levels of recombination products, both conservative and nonconservative, were obs ... | 1992 | 1729593 |
| chromosomal organization of xenopus laevis oocyte and somatic 5s rrna genes in vivo. | we describe the chromosomal organization of the major oocyte and somatic 5s rna genes of xenopus laevis in chromatin isolated from erythrocyte nuclei. both major oocyte and somatic 5s dna repeats are associated with nucleosomes; however, differences exist in the organization of chromatin over the oocyte and somatic 5s rna genes. the repressed oocyte 5s rna gene is protected from nuclease digestion by incorporation into a nucleosome, and the entire oocyte 5s dna repeat is assembled into a loosely ... | 1992 | 1729615 |
| sequence analysis of cytoplasmic mrna-binding proteins of xenopus oocytes identifies a family of rna-binding proteins. | storage of maternal mrnas as nontranslated ribonucleoprotein (rnp) complexes is an adaptive strategy in various vertebrate and invertebrate oocytes, for rapid translational recruitment during embryonic development. previously, we showed that xenopus laevis oocytes have a soluble cytoplasmic pool of mrna-binding proteins and particles competent for messenger rnp assembly in vitro. here we report the isolation of cdnas for the most abundant messenger rnps, the 54- and 56-kda polypeptide (p54/p56) ... | 1992 | 1729676 |
| a peptide-hormone-inactivating endopeptidase in xenopus laevis skin secretion. | an endopeptidase was isolated from xenopus laevis skin secretions. this enzyme, which has an apparent molecular mass of 100 kda, performs a selective cleavage at the xaa-phe, xaa-leu, or xaa-ile bond (xaa = ser, phe, tyr, his, or gly) of a number of peptide hormones, including atrial natriuretic factor, substance p, angiotensin ii, bradykinin, somatostatin, neuromedins b and c, and litorin. the peptidase exhibited optimal activity at ph 7.5 and a km in the micromolar range. no cleavage was produ ... | 1992 | 1729723 |
| increases in pericellular proteolysis at developing neuromuscular junctions in culture. | to determine whether localized changes in pericellular proteolysis contribute to synapse formation, we examined the degradative actions of developing xenopus laevis nerve and muscle cells on films of extracellular matrix proteins adsorbed to the glass surface of a tissue culture chamber. skeletal myocytes, growing neurites, and fibroblasts all removed fluorescent fibronectin and laminin from the culture substratum at regions of close cell-surface contact. in addition, however, motor neurites als ... | 1992 | 1730384 |
| identification and characterization of alternatively spliced fibronectin mrnas expressed in early xenopus embryos. | sequence analysis of cdna clones encoding fibronectin (fn) from xenopus laevis reveals extensive amino acid identities with other vertebrate fns, including the presence of the arg-gly-asp (rgd) cell attachment site in type iii-10 and of a second, cell-binding site (eildv) in the alternative spliced v region of the protein. these cdnas have been used to study the expression of fn mrnas during early development. overall, levels of maternal fn mrna remain constant until the mid- to late-gastrula st ... | 1992 | 1730390 |
| genomic organization and alternative promoter usage of the two thyroid hormone receptor beta genes in xenopus laevis. | each of the two xenopus laevis thyroid hormone receptor beta genes is at least 70 kilobases in length with similar intron-exon organization. there are up to eight alternatively spliced exons in the 5'-untranslated region. excluding the extreme amino terminus, each receptor is encoded by six exons spanning about 6 kilobases of the genome, in which each of the two zinc fingers that comprise the dna-binding domain is encoded by a separate exon and the hormone-binding domain is split into three exon ... | 1992 | 1730664 |
| the regulation of thyroid hormone receptor beta genes by thyroid hormone in xenopus laevis. | the mrna level of the two xenopus laevis thyroid hormone receptor beta (tr beta) genes is up-regulated in tadpoles and cultured cells by the addition of thyroid hormone (th). up-regulation of transcripts of the 5' most exon is detectable 2-3 h before that of full-length tr beta mrna, strongly suggesting that up-regulation is under transcriptional control. the th-induced up-regulation in cultured cells is inhibited by cycloheximide when measured either by a transcription initiation assay that mea ... | 1992 | 1730665 |
| bovine chromaffin granule membranes undergo ca(2+)-regulated exocytosis in frog oocytes. | we have devised a new method that permits the investigation of exogenous secretory vesicle function using frog oocytes and bovine chromaffin granules, the secretory vesicles from adrenal chromaffin cells. highly purified chromaffin granule membranes were injected into xenopus laevis oocytes. exocytosis was detected by the appearance of dopamine-beta-hydroxylase of the chromaffin granule membrane in the oocyte plasma membrane. the appearance of dopamine-beta-hydroxylase on the oocyte surface was ... | 1992 | 1730760 |
| evolutionary conservativeness of electric field in the cu,zn superoxide dismutase active site. evidence for co-ordinated mutation of charged amino acid residues. | equipotential lines were calculated, using the poisson-boltzmann equation, for six cu,zn superoxide dismutases with different protein electric charge and various degrees of sequence homology, namely those from ox, pig, sheep, yeast, and the isoenzymes a and b from the amphibian xenopus laevis. the three-dimensional structures of the porcine and ovine superoxide dismutases were obtained by molecular modelling reconstruction using the structure of the highly homologous bovine enzyme as a template. ... | 1992 | 1731078 |
| activation of a system for the joining of nonhomologous dna ends during xenopus egg maturation. | mature xenopus laevis eggs provide an elementary reaction system of illegitimate recombination which efficiently joins nonhomologous dna ends (p. pfeiffer and w. vielmetter, nucleic acids res. 16:907-924, 1988). here we show that stage vi oocytes, known to express a system for homologous recombination (d. carroll, proc. natl. acad. sci. usa 80:6902-6906, 1983), are completely devoid of this joining system. nonhomologous dna end-to-end joining, however, attains full activity only at an extremely ... | 1992 | 1732745 |
| the differential transcriptional activity of two amphibian u1 small-nuclear rna genes correlates with structural differences in the proximal sequence element. | we previously analyzed the transcription of an axolotl u1 small-nuclear rna (snrna) gene (amu1) by microinjection into xenopus laevis oocytes. in such an assay, amu1 showed a low template activity compared to that of an x. laevis u1 snrna gene (xlu1b2). swapping the proximal sequence element (pse) with that of xlu1b2 was required for amu1 to acquire a transcription level equal to that of xlu1b2. in the present work, we examine the functional importance of the nucleotides that are common or diffe ... | 1992 | 1735429 |
| molecular analysis of xenopus laevis sparc (secreted protein, acidic, rich in cysteine). a highly conserved acidic calcium-binding extracellular-matrix protein. | sparc (secreted protein, acidic, rich in cysteine) is expressed as a 1.6 kb mrna in xenopus laevis. on the basis of cdna sequence analysis, xenopus sparc has a core mr of 32643, with one potential n-glycosylation site. western analysis of sparc isolated from xenopus long bone indicates that the mature protein has an mr of 43,000. at the amino acid level, xenopus sparc has 78-79% sequence similarity to mouse, bovine and human sparc. the least-conserved region is found within the n-terminal glutam ... | 1992 | 1736898 |
| a new cell line (xty) from a tumor of xenopus laevis. | a new cell line (xty) was derived from a tumor of a female xenopus laevis. this cell line has been proliferating in standard amphibian culture medium for more than 4 years (470 generations) and has a doubling time of 75.5 h at 25 degrees c. the cells aggregate into large groups, and their stellate morphology and the expression of desmin demonstrated by immunocytochemistry suggest that their origin is not epithelial. | 1992 | 1737584 |
| expression of rat liver glutamine transporters in xenopus laevis oocytes. | as a first step in attempting to isolate the na(+)-dependent system n transporter from rat liver we have investigated the use of prophase-arrested oocytes from xenopus laevis for the functional expression of rat liver glutamine transporters. individual oocytes, defolliculated by collagenase treatment, were injected with 50 nl of a 1 mg.ml-1 solution of poly(a)+ rna (mrna) isolated from rat liver. 50 microm l-[3h]glutamine uptake was measured 1-5 days post-injection: after 48 h, poly(a)+ rna-inje ... | 1992 | 1740435 |
| development of the olfactory nerve in the clawed frog, xenopus laevis: ii. effects of hypothyroidism. | quantitative and morphological data were obtained on developing olfactory axons in normal and hypothyroid larvae of the african clawed frog xenopus laevis. hypothyroid larvae were produced by rearing the animals, beginning at stage 48, in a 0.01% solution of propylthiouracil (ptu), a treatment that blocks synthesis of thyroid hormone. these ptu-treated larvae were compared to their age-matched siblings when these siblings reached stage 52 (premetamorphic larvae; prior to synthesis of thyroid hor ... | 1992 | 1740543 |
| a new 3'-terminus for xenopus laevis 28s ribosomal rna. | | 1992 | 1741295 |
| gene activation in the amphibian mesoderm. | cell potency is progressively restricted in amphibian development by a series of cellular interactions called inductions. the mesoderm is believed to develop in response to the earliest known induction, in which vegetal cells of the blastula divert overlying animal hemisphere cells away from epidermal and towards mesodermal fates. we describe two early markers of mesodermal differentiation in xenopus laevis, both mrnas that encode dna-binding proteins of the helix-loop-helix family. one is a fro ... | 1991 | 1742502 |
| rhythmic regulation of retinal melatonin: metabolic pathways, neurochemical mechanisms, and the ocular circadian clock. | 1. current knowledge of the mechanisms of circadian and photic regulation of retinal melatonin in vertebrates is reviewed, with a focus on recent progress and unanswered questions. 2. retinal melatonin synthesis is elevated at night, as a result of acute suppression by light and rhythmic regulation by a circadian oscillator, or clock, which has been localized to the eye in some species. 3. the development of suitable in vitro retinal preparations, particularly the eyecup from the african clawed ... | 1991 | 1742771 |
| bombinin-like peptides with antimicrobial activity from skin secretions of the asian toad, bombina orientalis. | the structures and hemolytic and bactericidal activities of three bombinin-like peptides, or blp-1-3, from the skin of bombina orientalis are described. the peptides were isolated from the skin of b. orientalis and sequenced by tandem mass spectrometry and are amphipathic, cationic peptides of 25-27 amino acids in length. the sequence of the most abundant member (blp-1) is: gly-ile-gly-ala-ser-ile-leu-ser-ala-gly-lys-ser-ala-leu-lys-gly-leu- ala-lys-gly-leu-ala-glu-his-phe-ala-asn-nh2. all three ... | 1991 | 1744108 |
| purification and characterization of a germ cell-specific form of elongation factor 1 alpha (ef-1 alpha) from xenopus laevis. | elongation factor 1 alpha (ef-1 alpha) was purified to homogeneity from full-grown oocytes of xenopus laevis. this protein is encoded by a gene previously shown to be expressed in male and female germ cells, and repressed in somatic cells. the purified protein was identified with ef-1 alpha on criteria of molecular mass, cross-reaction with antibodies raised against artemia salina ef-1 alpha, affinity for guanine nucleotides, and ability to promote the mrna-dependent binding of aminoacyl trna to ... | 1991 | 1747390 |
| induction of metamorphosis by thyroid hormone in anuran small intestine cultured organotypically in vitro. | we have developed an organ culture system of the anuran small intestine to reproduce in vitro the transition from larval to adult epithelial form which occurs during spontaneous metamorphosis. tubular fragments isolated from the small intestine of xenopus laevis tadpoles were slit open and placed on membrane filters in culture dishes. in 60% leibovitz 15 medium supplemented with 10% charcoal-treated serum, the explants were maintained in good condition for at least 10 days without any morphologi ... | 1991 | 1748625 |
| purified estrogen receptor dna binding domain expressed in escherichia coli activates transcription of an estrogen-responsive promoter in cultured cells. | the region of the xenopus laevis estrogen receptor responsible for interaction with dna, the dna binding domain (dbd), has been cloned and overexpressed in escherichia coli using a t7 rna polymerase expression system. extracts from cells transformed with the dbd expression vector contain a single protein which reacts with polyclonal antibodies to estrogen receptor and exhibits sequence-specific binding to a dna fragment containing a consensus estrogen response element. the dbd protein has been p ... | 1991 | 1748680 |
| sequence requirements for embryonic transcriptional activation of a gastrula-specific actin gene in xenopus laevis. | cytoskeletal actin genes undergo developmentally timed transcriptional activation at the gastrula stage of embryonic development in the amphibian xenopus laevis. to study the regulation of this process, a molecularly marked cloned actin gene has been introduced into living embryos by microinjection, and levels of its transcripts (which are distinct from endogenous actin message) have been measured by rnase protection. in vitro mutagenesis of the marked gene, followed by microinjection and transc ... | 1991 | 1751033 |
| cytochemical evidence of an organized microtubular cytoskeleton in xenopus laevis oocytes: involvement in the segregation of mitochondrial populations. | an organized microtubular cytoskeleton was discovered in the cytoplasm of xenopus laevis oocytes. the microtubules were observed in 10- to 30-micron cryostat sections by indirect immunoperoxidase labeling using an antibody to tubulin. a gradual extraction of cells with a nonionic detergent was essential for good penetration of the antibody into the cells. in the cytoplasm of all previtellogenic oocytes, a dense network of criss-crossed long microtubules was associated in a basket-like structure ... | 1991 | 1751040 |
| cloning, sequencing, and expression of two xenopus laevis c-ets-2 protooncogenes. | in a general approach to identify genes important in the control of genetic expression during development of xenopus laevis, two complementary dnas corresponding to two different c-ets-2 genes were cloned and sequenced. one of these complementary dnas appears to be almost full length. the two variant genes differ in their overlapping sequences by 87 nucleotide substitutions, leading to 17 amino acid modifications in the proteins, 8 of them being conservative. all but one of these changes map out ... | 1991 | 1751411 |
| regenerative capacity of retinal cells and the maintenance of their differentiation. | mechanisms underlying cell type stability and the capacity of retinal cells for transdifferentiation are discussed. it is shown that cells of amphibian pigmented epithelium can be transformed into retina or lens cells depending on the inducing cell type: the influence of retina enables them to be transformed into retina, the influence of lens epithelium, to lens cells (lentoids or lenses). this led to an attempt to discover the molecular character of cell action by means of transfilter induction ... | 1991 | 1752164 |
| formation of 6 beta-hydroxydexamethasone from dexamethasone by a6 cells. | a6 cells, a continuous cell line derived from kidney of xenopus laevis, were incubated with [3h]-dexamethasone for 24 h. when radioactive compounds in media were separated by reversed phase high pressure liquid chromatography, two radioactive fractions were found. the less polar fraction which contained 91-93% of total radioactivity cochromatographed with dexamethasone, whereas the polar fraction contained 5% of total radioactivity in media. in order to rigorously identify the polar metabolite, ... | 1991 | 1752231 |
| expression of the hepatocellular chloride-dependent sulfobromophthalein uptake system in xenopus laevis oocytes. | the expression of the basolateral chloride-activated organic anion uptake system of rat hepatocytes has been studied in xenopus laevis oocytes. injection of oocytes with rat liver poly(a)+rna resulted in the functional expression of chloride-dependent sulfobromophthalein (bsp) uptake within 3-5 d. this expressed chloride-dependent bsp uptake system exhibited saturation kinetics (apparent km approximately 6.2 microm) and efficiently extracted bsp from its binding sites on bsa. furthermore, the ch ... | 1991 | 1752967 |
| a highly efficient, cell-free translation/translocation system prepared from xenopus eggs. | we describe the use of a xenopus laevis egg extract for the in vitro translation and post translational modification of membrane and secretory proteins. this extract is capable of the translation and segregation into membranes of microgram per millilitre levels of protein from added mrnas. signal sequences of segregated proteins are efficiently cleaved and appropriate n-linked glycosylation patterns are produced. the extract also supports the quantitative assembly of murine immunoglobulin heavy ... | 1991 | 1754376 |
| masses of inositol phosphates in resting and tetanically stimulated vertebrate skeletal muscles. | the masses of inositol phosphates have been determined in isolated skeletal muscles from xenopus laevis (sartorius, tibialis anterior and iliofibularis) and rat (gastrocnemius and soleus) which were quick-frozen in the resting state and at different stages of an isometric (xenopus) or isotonic (rat) tetanus. the isomeric spectrum of inositol phosphates detected was similar to that in other tissues and cell types. the total sarcoplasmic concentrations of the isomers ins-(1,4,5,6)p4/ins(3,4,5,6)p4 ... | 1991 | 1764026 |
| functional expression of transcobalamin ii cdna in xenopus laevis oocytes. | the products of in vitro transcription of human transcobalamin ii (tc ii) cdna when microinjected into xenopus laevis oocytes yielded a single secretory protein of 43 kda. the mobility of the 43 kda band did not change following digestion with peptide n-glycosidase f. [57co]cbl bound to the medium was immunoprecipitated with anti-serum to human tc ii, but not to other cbl binders. in addition, the [57co]cbl complex also bound to placental microsomes. these results suggest that tc ii mrna transcr ... | 1991 | 1764066 |
| molecular cloning of human xpac gene homologs from chicken, xenopus laevis and drosophila melanogaster. | we cloned homologs of the human xeroderma pigmentosum group a complementing (xpac) gene from chicken, xenopus laevis and drosophila melanogaster. a comparison of the amino acid sequences of these homologs with that of the human xpac protein revealed that in the nh2-terminal domain there are only two conserved regions, one of which is presumed to function as the nuclear localization signal, whereas the cooh-terminal domain is highly conserved, the frequency of identical amino acids in all four xp ... | 1991 | 1764072 |
| amino terminal sequence of the mitochondrial protein mtdbp-c: similarity with nonhistone chromosomal proteins hmg 1 and 2. | we have previously reported the characterization of a dna-binding protein isolated from xenopus laevis mitochondria (mtdbp-c). the amino terminal sequence of this protein (26 residues) has been determined by automated edman degradation and used to search for sequence similarity with the nbrf library. a segment of 17 amino acids displays 47.1% of identity with proteins hmg-1 and 2 of various vertebrate species. | 1991 | 1764507 |
| isolation and characterization of the gene encoding ef-1 alpha o, an elongation factor 1-alpha expressed during early development of xenopus laevis. | in xenopus laevis, the gene encoding the elongation factor 1-alpha variant ef-1 alpha o, where o stands for oocyte, is expressed in oocytes and early embryos. a genomic library from x. laevis was screened with a cdna probe coding for ef-1 alpha o. two recombinant phages were isolated, one of which carries an entire ef-1 alpha o gene. this clone was characterized by restriction enzyme mapping and sequencing. comparison of cdna and genomic sequences revealed that ef-1 alpha o consists of seven exo ... | 1991 | 1765266 |
| neural regulation of calmodulin in adult xenopus leg muscle. | two ca(2+)-binding proteins important in regulating muscle responses to ca2+ flux are differentially expressed following denervation of xenopus laevis gastrocnemius. levels of parvalbumin (pv) rna transcripts and proteins decrease in abundance, while calmodulin (cam) transcript and protein levels increase. our studies on pv kinetics in xenopus follow a pattern observed in other species, however, our observation of a concomitant increase in cam has not been documented in any system. molecular ana ... | 1991 | 1769061 |
| chromosome banding in amphibia. xvi. high-resolution replication banding patterns in xenopus laevis. | high-resolution replication banding patterns were induced in prometaphase and prophase chromosomes of xenopus laevis by treating kidney cell lines with 5-bromodeoxyuridine (brdu) and deoxythymidine (dt) in succession. up to 650 early and late replicating bands per haploid karyotype were demonstrated in the very long prophase chromosomes. this permits an exact identification of all chromosome pairs of x. laevis. late replicating heterochromatin was located by analysing the time sequence of replic ... | 1991 | 1769277 |
| patterns of microtubule polymerization relating to cortical rotation in xenopus laevis eggs. | following fertilization, the xenopus egg cortex rotates relative to the cytoplasm by 30 degrees about a horizontal axis. the direction of rotation, and as a result the orientation of the embryonic body axes, is normally specified by the position of sperm entry. the mechanism of rotation appears to involve an array of aligned microtubules in the vegetal cortex (elinson and rowning, 1988, devl biol. 128, 185-197). we performed anti-tubulin immunofluorescence on sections to follow the formation of ... | 1991 | 1769322 |
| inductive differentiation of two neural lineages reconstituted in a microculture system from xenopus early gastrula cells. | neural induction of ectoderm cells has been reconstituted and examined in a microculture system derived from dissociated early gastrula cells of xenopus laevis. we have used monoclonal antibodies as specific markers to monitor cellular differentiation from three distinct ectoderm lineages in culture (n1 for cns neurons from neural tube, me1 for melanophores from neural crest and e3 for skin epidermal cells from epidermal lineages). cns neurons and melanophores differentiate when deep layer cells ... | 1991 | 1769329 |
| cell rearrangement during gastrulation of xenopus: direct observation of cultured explants. | we have analyzed cell behavior in the organizer region of the xenopus laevis gastrula by making high resolution time-lapse recordings of cultured explants. the dorsal marginal zone, comprising among other tissues prospective notochord and somitic mesoderm, was cut from early gastrulae and cultured in a way that permits high resolution microscopy of the deep mesodermal cells, whose organized intercalation produces the dramatic movements of convergent extension. at first, the explants extend witho ... | 1991 | 1769334 |
| demonstration of dopamine in electron-dense synaptic vesicles in the pars intermedia of xenopus laevis, by freeze substitution and postembedding immunogold electron microscopy. | the presence of dopamine in the pituitary of the clawed toad xenopus laevis was studied by light and electron microscope immunocytochemistry, using pre- and postembedding techniques. light microscopy showed the presence of an intricate, anti-dopamine-positive fibre network throughout the pars intermedia. in preembedded stained material, dopamine appeared to occur in varicosities which make synaptic contacts with both folliculo-stellate cells and melanotrope cells. post-embedding immunogold stain ... | 1991 | 1769861 |
| isolation and characterization of a monosialosylgangliopentaosyl ceramide from xenopus laevis oocyte. | a monosialosylgangliopentaosyl ceramide was isolated from xenopus laevis oocytes. it represented 5.8% of the total acidic glycosphingolipids. from the results of sugar-composition analysis, enzymatic hydrolysis, permethylation analysis, and negative ion fast atom bombardment mass spectrometry, the structure of the ganglioside was determined to be as follows: [sequence: see text] the predominant species of fatty acids were alpha-hydroxy fatty acids, h22:0, h24:0, and h24:1. the long chain bases o ... | 1991 | 1769969 |
| non-thermal vasodilatation by radio frequency burst-type electromagnetic field radiation in the frog. | 1. when the web of the anaesthetized xenopus laevis was perfused with ringer solution maintained at 20 degrees c, radio frequency (rf) burst-type electromagnetic (em) field radiation not only dilated arterioles of the web which had been preconstricted with noradrenaline, but also dilated arterioles under non-stimulated conditions. the em field-induced vasodilatation increased slowly and reached a plateau 60 min after the onset of radiation. after the cessation of radiation, vasodilatation remain ... | 1991 | 1770439 |
| muscle differentiation in xenopus laevis is characterized by particular states of vinculin phosphorylation. | vinculin is a 130 kd cytoskeletal protein which is involved in the anchorage of actin microfilaments to the plasma membranes at sites of cell-cell and cell-matrix contacts. in this paper we prove that smooth and cardiac muscles of xenopus laevis contain a specific isoform of vinculin not present in any other tissue including skeletal muscle and epithelia and we demonstrate that this form of the molecule is characterized by a specific state of phosphorylation. these data are discussed in view of ... | 1991 | 1773358 |
| faithful in vivo transcription termination of xenopus laevis rdna. correlation of electron microscopic spread preparations with s1 transcript analysis. | dna sequencing and subsequent functional in vitro analysis of the xenopus laevis rdna transcription termination has led to the identification of three transcription termination sequence elements: t1, located at the 3' end of the 28s rdna; t2, a putative processing site 235 bp downstream of t1; t3, the principal terminator positioned 215 bp upstream of the gene promoter. as demonstrated for nuclear run-off assays, t3 was found to be the main terminator for xenopus rdna transcription. these in vit ... | 1991 | 1773661 |
| basolateral uptake and tubular metabolism of l-citrulline in the isolated-perfused non-filtering kidney of the african clawed toad (xenopus laevis). | the kidney forms arginine (arg) by using citrulline (cit) as precursor, and is the main source of arg for systemic protein synthesis. even if the filtered and reabsorbed load (in rats) is sufficient for normal arg synthesis, the following questions remain. (a) can cit be taken up across the contraluminal membrane of the tubule cells also? if so, (b) by what kind of mechanism? and (c) is this cit, entering the cell from the peritubular side, metabolized to arg and ornithine (orn)? although these ... | 1991 | 1775371 |
| on leaking into the lumen, amino acids cross the tubule cells. secretion of l-citrulline in the isolated-perfused non-filtering kidney of the african clawed toad (xenopus laevis). | in our previous studies we were able to show that l-citrulline is taken up across the contraluminal membrane into the tubule cells of the isolated perfused non-filtering kidney of the african clawed toad (xenopus laevis). we have also described the tubular metabolism of the l-citrulline taken up. the remaining question was whether peritubular l-citrulline gains access to the tubular lumen and, if so, by what kind of mechanism. the method was the same as that described in our previous study: the ... | 1991 | 1775372 |
| neuronal nicotinic acetylcholine receptors expressed in xenopus oocytes: role of the alpha subunit in agonist sensitivity and desensitization. | neuronal nicotinic acetylcholine receptors (nachrs) were expressed in xenopus laevis oocytes after nuclear injection of complementary deoxyribonucleic acid (cdna) expression vectors. the two receptor subtypes alpha 4/n alpha 1 and alpha 3/n alpha 1 were readily distinguishable from one another by ach sensitivity and desensitization. alpha 3/n alpha 1 receptors showed lower ach sensitivity and stronger desensitization than alpha 4/n alpha 1 receptors. furthermore, although the current/voltage rel ... | 1991 | 1775381 |
| nerve cells of drosophila notch mutant are differentiated inside amphibian brain: a new approach for the analysis of genetic control of nerve cell differentiation. | fragments of the neural primordium of a new notch mutant of drosophila melanogaster produced in our laboratory were transplanted into the neural tube of embryos of 4 amphibian species (caudate and ecaudate) immediately after completion of neurulation. the grafts were identified by using a light microscope, scanning electron miscroscope, and in situ hybridization with mobile genetic elements of drosophila and fluorescent dyes as markers. as has been shown, drosophila nerve cells survive and diffe ... | 1991 | 1778472 |
| embryotoxicity and teratogenicity of cadmium chloride in xenopus laevis, assayed by the fetax procedure. | the embryotoxicity and teratogenicity of cadmium chloride (cdcl2) were tested by the fetax (frog embryo teratogenesis assay: xenopus) procedure in the south african frog, xenopus laevis. in five assays, groups of xenopus embryos were grown in media that contained cdcl2 at concentrations ranging from 0.75 to 56 mumol per l; control groups were incubated in the same medium without added cdcl2. the exposures to cdcl2 were begun at the blastula stage (five hours post-fertilization) and were terminat ... | 1991 | 1781663 |
| melatonin deacetylation: retinal vertebrate class distribution and xenopus laevis tissue distribution. | deacetylation is a rapid clearance mechanism for ocular melatonin. we have studied the distribution of retinal melatonin deacetylase activity among vertebrate classes. exogenous radiolabeled melatonin is metabolized by ocular tissue prepared from the amphibian xenopus laevis, the reptile anolis carolinensis, the teleost fish carassius auratus, and the bird gallus domesticus. in contrast, we were unable to detect ocular melatonin breakdown in rat or pig. in each species exhibiting ocular melatoni ... | 1991 | 1782560 |
| vitellogenin--homologs of mammalian apolipoproteins? | 1. to determine if a relationship exists between vertebrate vitellogenins and mammalian plasma proteins the embl and nbrf computer databases were searched with two partial amino acid sequences from xenopus laevis and gallus gallus vitellogenin. 2. a significant relationship was found between vitellogenin and human apolipoprotein b-100 genes, and confirmed using homology-determination programs. 3. further analysis shows that unique multiple proline consensus regions found in apolipoprotein b-100 ... | 1991 | 1782764 |
| the nuclear-cytoplasmic distribution of the xenopus nuclear factor, xnf7, coincides with its state of phosphorylation during early development. | we describe the characterization in xenopus laevis of a nuclear protein, xnf7, which is first detected in the oocyte gv and is eventually enriched in nuclei of cells of the adult brain. previous studies have shown that this protein contains zinc-finger-like structures and acidic domains typical of transcriptional activators, and is phosphorylated in vitro by p34cdc2 protein kinase. the protein also binds to double-stranded dna. these data suggest that xnf7 may function as a transcription factor. ... | 1991 | 1782867 |
| detection of genes encoding novel members of the ligand responsive transcription factor superfamily in xenopus laevis. | | 1991 | 1783163 |
| a concentration-clamp system allowing two-electrode voltage-clamp investigations in oocytes of xenopus laevis. | a system for rapid solution exchange (concentration-clamp) was developed for xenopus laevis oocytes. the exchange time (t90) was 10 ms. the system allows two-electrode voltage-clamp investigations. | 1991 | 1784130 |
| polylysine activates membrane-bound adenylyl cyclase from xenopus laevis oocytes through the gs transducing protein. | 1. the activity of the adenylyl cyclase found in the membranes of xenopus laevis can be affected by polylysine and other polycations. 2. the activity of the catalytic subunit measured with forskolin is inhibited by polylysine and polyarginine at concentrations above 10 microm and by spermine above 3 mm. 3. the adenylyl cyclase activity stimulated by gtp-gamma-s or f- through the stimulatory g protein (gs) can be increased by polylysine, polyornithine and spermine but not by polyarginine. 4. poly ... | 1991 | 1790677 |
| relaxation from rigor by photolysis of caged-atp in different types of muscle fibres from xenopus laevis. | using chemically skinned fast and slow fibres from the iliofibularis muscle of xenopus laevis, we measured the force changes following laser pulse photolysis of caged-atp at 4 degrees c in the presence and absence of added calcium. the time course of the early force change in the absence of calcium was used to derive an apparent second order rate constant for crossbridge detachment. these values were compared with previous model-dependent estimates stemming from force-velocity experiments. for f ... | 1991 | 1791191 |
| changes in intracellular ph following egg activation and during the early cell cycle of the amphibian pleurodeles waltlii, coincide with changes in mpf activity. | previous work on xenopus laevis suggests a temporal coincidence between inactivation of the m-phase promoting factor (mpf) and intracellular ph (phi) increase during egg activation. in addition, we recently showed that during the early cell cycle of xenopus eggs, mpf activity cycling and phi oscillations were temporally and functionally related. in the present work, using eggs of another amphibian, pleurodeles waltlii, which has a natural cell cycle considerably longer than that of xenopus laevi ... | 1991 | 1794067 |
| intracellular ph and intracellular free calcium responses to protein kinase c activators and inhibitors in xenopus eggs. | cell activation during fertilization of the egg of xenopus laevis is accompanied by various metabolic changes, including a permanent increase in intracellular ph (phi) and a transient increase in intracellular free calcium activity ([ca2+]i). recently, it has been proposed that protein kinase c (pkc) is an integral component of the xenopus fertilization pathway (bement and capco, j. cell biol. 108, 885-892, 1989). indeed, activators of pkc trigger cortical granule exocytosis and cortical contrac ... | 1991 | 1794315 |
| insulin receptors on xenopus laevis oocytes: effects of injection of ob/ob mouse liver mrna. | we describe here conditions for the detection of insulin binding sites on xenopus laevis oocytes. the binding of 125i-labelled insulin displayed sigmoidal behaviour, which is characteristic of the binding relationship between insulin and its receptor. resolution of the resulting curvilinear scatchard plot into two components revealed kd values of 8.86 x 10(-10) +/- 1.9 x 10(-10) and 5.32 x 10(-9) +/- 2.4 x 10(-9) m and n values of 9.7 x 10(7) +/- 0.4 x 10(7) and 3.3 x 10(8) +/- 0.5 x 10(8) bindi ... | 1991 | 1795023 |
| carnosine in the brain and olfactory system of amphibia and reptilia: a comparative study using immunocytochemical and biochemical methods. | the pattern of distribution of carnosine-like immunoreactivity and its relation to glial fibrillary acidic protein immunoreactivity have been studied in two lizards (gallotia galloti and tarentola delalandii) and in two anuran amphibians (rana esculenta and xenopus laevis) using immunocytochemical techniques. biochemical data obtained by paper electrophoresis show that the dipeptides carnosine and homocarnosine are both present in the brain of all the species examined. in the central nervous sys ... | 1991 | 1795878 |
| development of the olfactory bulb in the clawed frog, xenopus laevis: a morphological and quantitative analysis. | the relationship between olfactory axons and the cells of the olfactory bulb during normal development was analyzed to determine whether olfactory afferent axons could play a role in the induction of olfactory bulb formation. the morphology of the olfactory bulb in xenopus larvae from stages 26 to 58 and in adult frogs was analyzed with light and electron microscopy. axons were first observed beneath the basal lamina of the neural tube at stages 30 and 32; at stage 32, neurons in this area of th ... | 1991 | 1797876 |
| localization of a nervous system-specific class ii beta-tubulin gene in xenopus laevis embryos by whole-mount in situ hybridization. | a neural-specific beta-tubulin mrna is expressed in the developing central nervous system shown by whole-mount in situ hybridization experiments. of special interest is the fact that from the late blastula (stage 9; nieuwkoop and faber, 1967; hausen and ribesell, 1991) until the early neurula (stage 13) the signal can be found not only in the presumptive neural plate but also in the presumptive epidermis. later in development (from stage 13) the specific mrna becomes restricted to the presumptiv ... | 1991 | 1801865 |
| dose and time-dependent mesoderm induction and outgrowth formation by activin a in xenopus laevis. | we examined the quality of mesoderm induced by the action of activin a on the xenopus presumptive ectoderm when various concentrations and treatment times were employed. the minimum concentration of activin a to induce mesodermal tissues was inversely proportional to its treatment time. the explants differentiated into different types of mesodermal tissues, from ventral-type to dorsal-type depending on the concentration of activin a and its treatment time. to confirm whether activin a has a role ... | 1991 | 1801866 |
| development of the left-right axis in amphibians. | the heart and viscera of vertebrates are formed from primordia that are apparently bilaterally symmetrical. this symmetry is broken during development, yielding organs that develop characteristic asymmetries along the left-right axis. results from three lines of experimentation on embryos of the amphibian xenopus laevis indicate that left-right asymmetries are established early in development and that cellular interactions transmit left-right information from one primordium to another. first, a ... | 1991 | 1802642 |
| gene structure and chromosomal localization of the murine lamin b2 gene. | the structure of the murine lamin b2 gene has been analyzed by cloning, sequencing and hybridization techniques, including in situ hybridization. the gene exists in single copy on the distal arm of chromosome 10 and comprises at least 15 kb, containing 12 exons and 11 introns. the transcriptional start point, as determined by primer extension analysis and rnase protection, was mapped to the region -264 to -254 upstream the atg start codon. the 5' upstream region does not reveal any classical tat ... | 1991 | 1802718 |
| ultrastructure of the approximately 26s complex containing the approximately 20s cylinder particle (multicatalytic proteinase/proteasome). | we have isolated a large protein complex of approximately 26s from xenopus laevis oocytes and eggs which is composed of the approximately 20s cylinder particle (multicatalytic proteinase/proteasome) and additional proteinaceous components. in its polypeptide composition and sedimentation coefficient this approximately 26s complex closely resembles the 26s ubiquitin-dependent protease, a high molecular weight multienzyme complex recently described in the literature. specific antibodies directed a ... | 1991 | 1802724 |
| differential expression of two distinct myod genes in xenopus. | we previously reported the isolation of several complementary dnas from xenopus laevis that encode distinct myod proteins. two of these genes, xlmf1 and xlmf25, appear to represent a gene duplication as a consequence of the polyploid xenopus genome. although both myod genes are expressed exclusively in skeletal muscle in adult animals, they have very different temporal patterns of expression in early development. in the present work, we show that xlmf1 transcripts rapidly accumulated to high lev ... | 1991 | 1809374 |
| xenopus laevis: practical uses in cell and molecular biology. | | 1991 | 1811129 |
| use of oligonucleotides for antisense experiments in xenopus laevis oocytes. | | 1991 | 1811133 |
| genetics of xenopus laevis. | | 1991 | 1811134 |
| isolation of extracellular matrix structures from xenopus laevis oocytes, eggs, and embryos. | | 1991 | 1811136 |
| experimentally induced homozygosity in xenopus laevis. | | 1991 | 1811144 |