readthrough enhancement and promoter occlusion on the ribosomal genes of xenopus rna polymerase i termination site is found just upstream of the ribosomal gene promoter in mammals and amphibia. it has been suggested that this termination site may actively enhance ribosomal transcription in a process known as readthrough enhancement or that it may simply prevent the disruption of initiation complexes or promoter occlusion. there is, however, a consensus of opinion that the terminator is important for efficient ribosomal transcription. here we have quantitatively investigat ...19921497859
compensatory effect of distal promoter sequences on the basal expression of a microinjected 70-kilodalton heat shock protein gene after the midblastula transition of xenopus laevis embryogenesis.the promoter sequences involved in the basal expression of a human 70-kilodalton heat shock protein (hsp70) gene during xenopus embryogenesis were analyzed by microinjection of mutant promoters of a hsp70--chloramphenicol acetyltransferase fusion gene into fertilized eggs and following their expression during early development. while deletion of the hsp70 gene promoter to--100 base pairs (bp) did not affect basal transcription in postmidblastula stage embryos, linker-scanner mutations in the cca ...19921497861
localization of ras proto-oncogene expression during development in xenopus laevis.the expression of the ras protooncogene was investigated in xenopus laevis, throughout development, by in situ hybridization using a 35s-labelled antisense rna probe. during oogenesis, the ras rna was strongly expressed in the cytoplasm of previtellogenic oocytes and further diluted between yolk platelets; no specific localization of transcripts was observed. the signal density was particularly weak over embryo sections until the tailbud stage. on the other hand, a high level of ras rna expressi ...19921497868
impaired t cell functions during amphibian metamorphosis: il-2 receptor expression and endogenous ligand production.t cell functions are impaired during defined developmental stages of amphibian metamorphosis (marx et al., 1987). here we show, using a fluorescent anti-human il-2 receptor antibody and flow cytometry, that during these stages, the splenocytes of xenopus laevis, the south african clawed toad, have a progressively diminished capacity to express il-2 receptors (il-2r), after in vitro lectin stimulation. preincubation with human ril-2 specifically blocks binding of the anti-il-2r antibody. separati ...19921498041
functional expression of an inactivating potassium channel cloned from human heart.recently a putative k+ channel with homology to the shaker family of potassium channels has been cloned from human ventricular myocardium. however, proof that the cdna encodes a k+ channel requires appropriate translation and expression of a functional ion-selective channel. therefore, expression of this putative human k+ channel dna was attempted by cytoplasmic injections of in vitro transcribed crna into xenopus laevis oocytes and screening by two-electrode voltage-clamp methods. this resulted ...19921499114
xenopus laevis sperm proteins, previously identified as surface proteins with egg coat binding capability, are indeed histone h4, histone h3, and sperm specific protein sp2.recently, four xenopus sperm proteins thought to be involved in binding to the egg envelope were identified (lindsay and hedrick, j. exp. zool., 245:286-293, '88). we have studied the three more abundant ones of apparent molecular weight of 14, 19, and 25 kd in sds-page. we have shown that these proteins are indeed nuclear basic proteins: the 14 kd is the histone h4, the 19 kd is the histone h3, and the 25 kd is the sperm-specific protein sp2.19921500885
transport and membrane binding of the glutamine analogue 6-diazo-5-oxo-l-norleucine (don) in xenopus laevis oocytes.we have examined transport and membrane binding of 6-diazo-5-oxo-l-norleucine (don, a photoactive diazo-analogue of glutamine) and their relationships to glutamine transport in xenopus laevis oocytes. don uptake was stereospecific and saturable (vmax of 0.44 pmol/oocyte.min and a km of 0.065 mm). don uptake was largely na+ dependent (80% at 50 microm don) and inhibited (greater than 75%) by glutamine and arginine (substrates of the system b0,+ transporter) at 1 mm. glutamine and don show mutual ...19921501246
genomic dispersal of the ets gene family during metazoan evolution.evolutionary homologs of the ets proto-oncogene have been discovered in the genomes of widely divergent eucaryote species from drosophila to sea urchin to vertebrates. the prototype mammalian ets-1 and ets-2 genes are divided into three coding domains that differ in their rate of accumulation of sequence divergence. an analysis of sequence divergence of ets gene homologs in various species has produced a phylogenetic history of the ets gene family in the context of metazoan evolutionary radiatio ...19921501883
sequence of lamprey vitellogenin. implications for the lipovitellin crystal structure.the amino acid sequence of lamprey vitellogenin has been predicted from the nucleotide sequence of cloned cdna. the sites of proteolytic cleavage that produce the lipovitellin complex from the vitellogenin have been located by comparing the n-terminal sequences of two lamprey lipovitellin polypeptides with the predicted sequence. these results also confirm that the vitellogenin sequence derived here corresponds to the lipovitellin complex for which the crystal structure has been solved previousl ...19921507234
evidence for a role of protein kinase c zeta subspecies in maturation of xenopus laevis oocytes.a number of studies have demonstrated the activation of phospholipase c-mediated hydrolysis of phosphatidylcholine (pc-plc) both by growth factors and by the product of the ras oncogene, p21ras. evidence has been presented indicating that the stimulation of this phospholipid degradative pathway is sufficient to activate mitogenesis in fibroblasts as well as that it is sufficient and necessary for induction of maturation in xenopus laevis oocytes. however, the mechanism whereby pc-plc transduces ...19921508183
use of xenopus laevis frog egg extract in diagnosing human male unexplained infertility.approximately one in six married couples find themselves involuntarily infertile. this ratio translates to between two and four million u.s. couples. although numerous tests are available for diagnosing infertility problems, 5-10 percent of all couples who seek medical treatment are diagnosed with unexplained infertility. several tests are presently available for diagnosing male infertility; however, none of the present procedures test for activation of the sperm nucleus following entry into the ...19921509782
temperature-dependent protein folding in vivo--lower growth temperature increases yield of two genetic variants of xenopus laevis cu,zn superoxide dismutase in escherichia coli.two genetic variants of xenopus laevis cu,zn superoxide dismutase, xsoda and xsodb, have been expressed in escherichia coli by recombinant dna techniques. production of both proteins was obtained, although with different yields, xsodb being more abundant than xsoda in all the conditions tested. lowering the temperature of growth was found to be a specific factor, decisive in obtaining quantitatively abundant, active xenopus enzymes. impaired folding of these proteins in the e.coli cytoplasm was ...19921510665
reconstitution of functional water channels in liposomes containing purified red cell chip28 protein.water rapidly crosses the plasma membranes of red blood cells (rbcs) and renal tubules through highly specialized channels. chip28 is an abundant integral membrane protein in rbcs and renal tubules, and xenopus laevis oocytes injected with chip28 rna exhibit high osmotic water permeability, pf [preston et al. (1992) science 256, 385-387]. purified chip28 from human rbcs was reconstituted into proteoliposomes in order to establish if chip28 is itself the functional unit of water channels and to c ...19921510932
study of the function and regulation of liver n-cam in xenopus laevis.the liver of xenopus laevis is a unique exception in terms of the cell adhesion molecules (cam) which it expresses. in most species, hepatocytes are characterized by the expression of the epithelial ca(2+)-dependent cam e-cadherin or of closely related variants of this molecule (e.g., l-cam); in xenopus liver, however, the levels of expression of epithelial cadherins is very low while a thyroxine-inducible isoform of n-cam is expressed in postmetamorphic hepatocytes. since xenopus liver n-cam is ...19921511699
rainbow trout mitochondrial dna: sequence and structural characteristics of the non-coding control region and flanking trna genes.we have determined the sequence of the 1003-bp control region (also referred to as the 'displacement-loop region') and flanking trna genes in the mitochondrial dna (mtdna) of the rainbow trout, oncorhynchus mykiss. this region has the same overall structure (i.e., trnt-trnp-control region-trnf) as in mammalian and amphibian (xenopus laevis) mitochondrial (mt)dnas. the trout control region contains apparent homologues of the conserved sequence blocks (csb) and termination-associated sequences ide ...19921511893
characterization of rna polymerase ii-dependent transcription in xenopus extracts.we examine the rna polymerase ii-dependent transcription directed by several promoters in extracts prepared from distinct developmental stages of xenopus laevis. rna polymerase ii accurately initiates transcription from the cytomegalovirus, herpes simplex virus thymidine kinase, and xenopus heat-shock protein (hsp) 70 promoters. the efficiency of transcription of these different promoters is dependent on whether extracts from oocytes, eggs, or somatic cells are used and on the temperature of inc ...19921516744
joint actions of developmental toxicants in xenopus embryos: binary mixtures of dna synthesis inhibitors.the joint toxic action for each of three binary combinations of dna synthesis inhibitors was examined at concentrations that induce malformations in xenopus laevis embryos. the three compounds, hydroxyurea, cytosine arabinoside, and 5-fluorouracil, which each inhibit a different enzyme involved in dna synthesis, were selected for joint action testing to help determine whether joint action types are related to general modes of action (e.g., inhibit dna synthesis) or to specific biochemical/molecu ...19921516776
interaction of xenopus tfiiic with the tfiiia.5 s rna gene complex.the general transcription factor tfiiic is necessary for transcription initiation by rna polymerase iii. tfiiic binds predominantly to the b-block promoter element, which is present in trna genes, several viral rna genes and repetitive dna elements, and to the tfiiia.dna complex on 5 s rna genes. here we report a characterization of xenopus laevis tfiiic and its interaction with the tfiiia.5 s rna gene complex. a polypeptide with apparent molecular mass of 85 kda was specifically cross-linked to ...19921517247
programmed cell death and heterolysis of larval epithelial cells by macrophage-like cells in the anuran small intestine in vivo and in vitro.the degenerative processes in the larval small intestine of xenopus laevis tadpoles during spontaneous metamorphosis and during thyroid hormone-induced metamorphosis in vitro were examined by electron microscopy. around the beginning of spontaneous metamorphic climax (stages 59-61), both apoptotic bodies derived from larval epithelial cells and intraepithelial macrophage-like cells suddenly increase in number. the macrophage-like cells become rounded and enlarged because of numerous vacuoles con ...19921518071
[excretion of urea and ammonia and its effect on the acid-base balance of water in the habitat of the anuran amphibian xenopus laevis. action of metabolic alkalosis].we studied in xenopus laevis the effect of changing the salinity and the acid-base status of the ambient water on the total nitrogen catabolism and the nature of the nitrogen end products, urea and ammonia. increase of the ambient osmolarity by addition of nacl led to a rise in protein catabolism and to a predominant ureotelism which can approach 95% of the excreted nitrogen. the osmolarity can reach 500 mosmol. l-1 without obvious harmful effects. nacl can then be replaced by nahco3 without inj ...19921521175
the gene structure of xenopus nuclear lamin a: a model for the evolution of a-type from b-type lamins by exon shuffling.nuclear lamins are intermediate filament (if) type proteins that form a fibrillar network underlying the inner nuclear membrane. the existence of multiple subtypes of lamins in vertebrates has been interpreted in terms of functional specialization during cell division and differentiation. the structure of a gene encoding an a-type lamin of xenopus laevis was analysed. comparison with that of a b-type lamin of the same species shows remarkable conservation of the exon/intron pattern. in both gene ...19921521501
regulation of expression of a xenopus borealis embryonic/larval alpha 3 skeletal-actin gene.we have isolated a genomic clone, related in sequence to the skeletal-actin gene sub-family. it is expressed in the skeletal muscle of embryos from the neurula stage onwards and in tadpoles, but not in adults. the equivalent xenopus laevis gene is expressed as a major transcript in adult muscle, as well as at earlier stages. the intron/exon structure is typical of vertebrate skeletal-actin genes, as is the possession of multiple copies of three serum-response elements in the promoter of this gen ...19921521522
lysophosphatidic acid induces inward currents in xenopus laevis oocytes; evidence for an extracellular site of action.lysophosphatidic acid (lpa) is a naturally occurring phospholipid that can elicit platelet aggregation, smooth muscle contraction and, in fibroblasts, cell proliferation. we now report that lpa in nanomolar concentrations evokes an inward current in native, defolliculated xenopus laevis oocytes. extracellular application of lpa from a pressure pipette to the surface of the oocyte induced an immediate response. in contrast, intracellular injection of the same amount of lpa failed to elicit a resp ...19921521564
plasticity of binocular visual connections in the frog, xenopus laevis: reversibility of effects of early visual frogs, each lobe of the midbrain optic tectum receives two spatially aligned maps of binocular visual space, one through each eye. the map from the contralateral eye is the product of direct retinal input to the tectum, while that from the ipsilateral eye is mediated by a commissural system of connections that relays binocular visual information from one tectal lobe to the other. in xenopus laevis, dark-reared from early life, the visuotectal map through the ipsilateral eye exhibits significa ...19921521600
patterns of dna replication in drosophila polytene nuclei replicating in xenopus egg and oocyte extracts.we have used xenopus laevis cell-free extracts to study patterns of dna replication in polytene nuclei isolated from salivary glands of drosophila melanogaster 3rd instar larvae. replication was visualized by supplementation with biotin-dutp so that nascent dna became labelled, thus allowing detection with fluorescein or texas-red-conjugated streptavidin. biotin incorporation was dependent on incubation in extracts. transverse bands were labelled in high-speed supernatants of eggs or oocytes in ...19921522141
expression of neurotrophin-4 mrna during oogenesis in xenopus laevis.neurotrophin-4 (nt-4), a recently discovered novel member of the family of neurotrophic factors structurally related to nerve growth factor (ngf), is abundantly expressed in the xenopus laevis ovary. in this study we have localized nt-4 mrna expressing cells in the xenopus ovary by in situ hybridization and have used this technique together with northern blot analyses to quantify nt-4 mrna expression during oogenesis in xenopus. in situ hybridization of sections through the xenopus ovary using a ...19921525011
somitogenesis in the marsupial frog gastrotheca riobambae.this paper reports the first description of somitogenesis in a non-aquatic-developing amphibian, the andean marsupial frog, gastrotheca riobambae. this frog develops from an embryonic disk located on top of a large yolky egg, bearing some resemblance to the embryo of the chick. besides the histological characterization of somite formation, we quantified cell number in the developing somites of gastrotheca, xenopus laevis and the chick. gastrotheca was found to have a mode of somitogenesis which ...19921525016
preliminary biological characterization of a melanization stimulating factor (msf) from the dorsal skin of the channel catfish, ictalurus punctatus.a two step fractionation of conditioned media made from the darkly pigmented dorsal skin of the channel catfish, ictalurus punctatus, has produced fractions that contain a melanization stimulating factor (msf). isolated neural tubes of xenopus laevis embryos exposed to conditioned media and to specific fractions exhibit greater melanization (increased numbers of melanized cells and elevated percentages of melanized cells), a greater number of dendrites per melanized cell, and a greater number of ...19921528091
maintenance of xenopus laevis and oocyte injection. 19921528120
a new metallo- endopeptidase from human neuroblastoma nb-ok-1 cells which inactivates atrial natriuretic peptide by selective cleavage at the ser123-phe124 bond.a novel metallo-endopeptidase from human neuroblastoma nb-ok-1 cells was partially purified and characterized. this enzyme activity was detected in the culture medium and could be detached from intact cells by gentle washing, suggesting a peripheral localization of the enzyme. this endopeptidase inactivated atrial natriuretic peptide (anp) by a unique and selective cleavage of the ser123-phe124 bond. it also produced hydrolysis at the xaa-phe, xaa-leu, or xaa-ile bonds of other peptide hormones ...19921531011
ubiquitous soluble mg(2+)-atpase complex. a structural study.we have performed a detailed structural analysis of the soluble mg(2+)-atpase complex purified from xenopus laevis ovary, which is an abundant and ubiquitous homo-oligomeric protein complex located in the nucleus and in the cytoplasm, belonging to a novel multigene-family of putative mg(2+)-atpases. enzyme activity staining after non-denaturing polyacrylamide gel electrophoresis revealed that mg(2+)-atpase activity of the native protein is dependent on oligomerization and could not be detected i ...19921531366
csd2, csd3, and csd4, genes required for chitin synthesis in saccharomyces cerevisiae: the csd2 gene product is related to chitin synthases and to developmentally regulated proteins in rhizobium species and xenopus saccharomyces cerevisiae, chitin forms the primary division septum and the bud scar in the walls of vegetative cells. three chitin synthetic activities have been detected. two of them, chitin synthase i and chitin synthase ii, are not required for synthesis of most of the chitin present in vivo. using a novel screen, i have identified three mutations, designated csd2, csd3, and csd4, that reduce levels of chitin in vivo by as much as 10-fold without causing any obvious perturbation of cell di ...19921532231
expression of rat renal sodium/phosphate cotransporter in xenopus laevis an attempt to identify the renal na+/pi cotransporter, xenopus laevis oocytes were used to express mrna isolated from the renal cortex of rat kidney. na(+)-dependent uptake of pi in oocytes, injected with mrna, resulted in an increase of 2-4-fold as compared to oocytes injected with water. both the new expressed and endogenous na(+)-dependent pi uptake activity were inhibited with 2 mm phosphonoformic acid (pfa). expression of pi uptake into oocytes was dose-dependent with the amount of mrna ...19921532329
localization and quantification of atrial natriuretic factor binding sites in the kidney of xenopus laevis.atrial natriuretic factor (anf) binding sites in the skin, the bladder, and the kidney of the anuran amphibian xenopus laevis were localized and quantified using quantitative in vitro autoradiography. specific binding of 125i-ranf occurred only in the glomeruli and in the adrenal tissue of the kidney. the association of 125i-ranf binding was much higher than the dissociation and there was no steady state between the ligand and the binding sites. scatchard and hill's analyses of saturation experi ...19921532947
effects of atrial natriuretic factor on corticosteroid and catecholamine secretion by the adrenals of xenopus laevis.the effects of atrial natriuretic factor (anf) on the adreno-corticosteroid and catecholamine secretion of xenopus laevis were studied in vitro and in vivo. in vitro, the effects of ranf(99-126), from 0.1 to 50 nm, on corticosteroid secretion was investigated using a perifusion system. the basal secretion of aldosterone but not corticosterone was dose dependently decreased. a prolonged perifusion with 1 nm ranf(99-126) alternated acth(1-28) stimulation of secretion of both corticosteroids. only ...19921534778
3'-end-dependent formation of u6 small nuclear ribonucleoprotein particles in xenopus laevis oocyte nuclei.we have identified and characterized a u6 small nuclear (sn) ribonucleoprotein particle (rnp) present in the nuclei of xenopus laevis oocytes. the structure of this u6 snrnp was investigated by native gel shift analysis and a combination of rna-protein uv cross-linking, rnase t1 fingerprinting, and immunoprecipitation assays. these analyses demonstrate that certain forms of u6 snrna associate with the 50-kda nuclear antigen la both in vivo and in vitro. the la protein binds the stretch of uridyl ...19921535684
expression of na(+)-independent amino acid transport in xenopus laevis oocytes by injection of rabbit kidney cortex mrna.poly(a)+ mrna was isolated from rabbit kidney cortex and injected into xenopus laevis oocytes. injection of mrna resulted in a time- and dose-dependent increase in na(+)-independent uptake of l-[3h]alanine and l-[3h]arginine. l-alanine uptake was stimulated about 3-fold and l-arginine uptake was stimulated about 8-fold after injection of mrna (25-50 ng, after 3-6 days) as compared with water-injected oocytes. t.i.c. of oocyte extracts suggested that the increased uptake actually represented an i ...19921536650
a cdna from brain of xenopus laevis coding for a new precursor of thyrotropin-releasing hormone.thyrotropin-releasing hormone (trh) is found in large amounts in the skin of xenopus laevis. in this tissue, 3 trh precursor mrnas can be detected of which the 2 more expressed encode almost identical proteins. however, northern blot analysis of trh precursor mrnas in the brain of x. laevis revealed the existence of a new mrna of about 1200 nucleotides which was present along with the larger trh precursor mrna identified in the skin. a cloned cdna of a trh precursor, corresponding in size to thi ...19921537407
xlcaax-1 is localized to the basolateral membrane of kidney tubule and other polarized epithelia during xenopus development.xlcaax-1 is a novel, maternally expressed, 110-kda, caax box containing protein that undergoes isoprenylation and palmitoylation through which it associates with the plasma membrane. we report here the cellular and subcellular localization of the xlcaax-1 protein during development of xenopus laevis. whole-mount immunocytochemistry and immunoperoxidase staining of tissue sections show that during development the xlcaax-1 protein accumulation is coincident with the differentiation of the epidermi ...19921537427
comparison of regulatory and structural regions of the xenopus laevis small heat-shock protein-encoding gene family.we have isolated several unique xenopus laevis hsp30 (encoding heat-shock protein 30) genomic clones, one of which contains two complete hsp30 genes (hsp30c and hsp30d), as well as the promoter and n-terminal coding region of a third gene (hsp30e). nucleotide sequence and restriction enzyme analysis revealed that this gene cluster is different from a cluster isolated previously. the hsp30c and hsp30d genes encode proteins of approx. 24 kda. in all, the hsp30 gene family contains a minimum of sev ...19921537552
the "on"-bipolar agonist, l-2-amino-4-phosphonobutyrate, blocks light-evoked cone contraction in xenopus eye cups.rhythmic photoreceptor metabolism in relationship to light-dark cycles is now thought to be regulated through a retinal feed-back mechanism with dopamine serving as a principal signal initiating light-evoked events. in order to test the hypothesis that depolarizing "on"-bipolar neurons participate in the retinal signalling pathway, we determined the effects of l-2-amino-4-phosphonobutyrate (l-apb) on light-evoked cone contraction in eye cups from xenopus laevis. l-apb blocked the response stereo ...19921538827
5s rrna-encoding genes of the marsupial frog gastrotheca riobambae.the major 5s rrna gene repeat of the marsupial frog, gastrotheca riobambae, is 1052 bp in length. it contains a 5s rrna gene similar to the xenopus laevis somatic gene, two spacer regions, and a pseudogene. the g. riobambae haploid genome contains about 500 copies of this predominant repeat. this relatively low number of 5s rrna genes is associated with a limited amplification of the 18s, 5.8s and 28s rrna genes in oocytes and with a slow rate of early development.19921541401
electrogenic properties of the cloned na+/glucose cotransporter: i. voltage-clamp studies.the cloned rabbit intestinal na+/glucose cotransporter was expressed in xenopus laevis oocytes. presteady-state and steady-state currents associated with cotransporter activity were measured with the two-electrode voltage-clamp technique. steady-state sugar-dependent currents were measured between -150 and +90 mv as a function of external na+ ([na]o) and alpha-methyl-d-glucopyranoside concentrations ([alpha mdg]o). k alpha mdg0.5 was found to be dependent upon [na]o and the membrane potential. a ...19921542106
identification of a nonapeptide motif in the vimentin head domain involved in intermediate filament assembly.the assembly of soluble vimentin subunits into intermediate filaments (ifs) is dependent on information located in the amino-terminal domain. using site-directed mutagenesis of a xenopus laevis vimentin cdna and an escherichia coli production system to obtain pure mutated protein, we have identified, in the head domain, a nine amino acid motif (ssyrrifgg), evolutionarily conserved from amphibia to man, which plays an important role in the orderly formation of ifs. exchanges in the central di-arg ...19921542111
promoter-cdna-directed heterologous protein expression in xenopus laevis oocytes.heterologous proteins can be expressed in xenopus laevis oocytes by cytoplasmic microinjection of mrna. to circumvent limitations inherent in this approach we investigate direct nuclear injection of strong viral expression vectors to drive transcription and subsequent translation of cdnas encoding cytoplasmic, secreted, and plasma membrane proteins. after several viral promoters had been tested, the pmt2 vector was found to be a superior expression vector for x. laevis oocytes capable of directi ...19921542676
evidence that the ras oncogene-encoded p21 protein induces oocyte maturation via activation of protein kinase c.the ras oncogene-encoded p21 protein is known to induce cell maturation of xenopus laevis oocytes and malignant transformation of nih 3t3 mouse fibroblasts. the pathways involved in oocytes and nih 3t3 cells appear to be similar to one another. for example, in both cases, the ras p21-induced cellular events involve increased intracellular levels of the second messengers diacylglycerol and inositol phosphates, the former of which activates protein kinase c (pkc). to investigate the pathway of ras ...19921542698
the cdnas coding for the alpha- and beta-subunits of xenopus laevis casein kinase ii.using a lambda gt10 cdna library obtained from xenopus laevis oocytes and probes derived from the known sequences of the human and drosophila genes, a cdna coding for the alpha-subunit of the x. laevis casein kinase ii was isolated. the coding sequence of this clone determines a polypeptide of 350 amino acids. the x. laevis sequence is 98% identical to the human and rat proteins in the first 323 amino acids. using the polymerase chain reaction to generate a 370-nucleotide-long probe, it was poss ...19921544409
comparative aspects of spermatogenic cell metabolism and sertoli cell function in xenopus laevis and mammals.due to the relative dearth of data regarding somatic cell-germ cell interactions in the testes of non-mammalian chordates, functional homologies between sertoli cells from diverse organisms have been difficult to assess. however, recent developments in non-mammalian testis cell and organ culture techniques have provided experimental approaches to compare sertoli cell-germ cell interactions in different vertebrates. data from in vitro analyses of sertoli cell-germ cell interactions are presented ...19921545192
identification of the sequences responsible for the splicing phenotype of the regulatory intron of the l1 ribosomal protein gene of xenopus laevis.splicing of the regulated third intron of the l1 ribosomal protein gene of xenopus laevis has been studied in vivo by oocyte microinjection of wild-type and mutant sp6 precursor rnas and in vitro in the heterologous hela nuclear extract. we show that two different phenomena combine to produce the peculiar splicing phenotype of this intron. one, which can be defined constitutive, shows the same features in the two systems and leads to the accumulation of spliced mrna, but in very small amounts. t ...19921545793
the influence of the olfactory placode on the development of the telencephalon in xenopus laevis.removal of the sensory plate in xenopus laevis embryos was performed to study the influence of the olfactory anlage on the development of the forebrain. embryos, which at stage 22-23 underwent removal of the olfactory anlagen, were killed from stage 47 to 60. in 79% of the animals, two olfactory organs reformed and gave origin to two olfactory nerves which contacted the forebrain. in this instance, the telencephalic hemispheres developed normally. in 14% of the animals, one olfactory organ refor ...19921545913
light-evoked contraction of red absorbing cones in the xenopus retina is maximally sensitive to green test the hypothesis that light-evoked cone contraction in eye cups from xenopus laevis is controlled through a direct mechanism initiated by the cone's own photopigment, we conducted spectral-sensitivity experiments. we estimate that initiation of contraction of red absorbing cones (611 nm) is 1.5 log units more sensitive to green (533 nm) than red (650 nm) light stimuli. the difference is comparable to that predicted from the spectral-sensitivity function of the green absorbing, principal ro ...19921547160
two-dimensional model of calcium waves reproduces the patterns observed in xenopus oocytes.biological excitability enables the rapid transmission of physiological signals over distance. using confocal fluorescence microscopy, we previously reported circular, planar, and spiral waves of ca2+ in xenopus laevis oocytes that annihilated one another upon collision. we present experimental evidence that the excitable process underlying wave propagation depends on ca2+ diffusion and does not require oscillations in inositol (1,4,5)trisphosphate (ip3) concentration. extending an existing ordi ...19921547335
nuclear processing of the 3'-terminal nucleotides of pre-u1 rna in xenopus laevis oocytes.u1 small nuclear rna is synthesized as a precursor with several extra nucleotides at its 3' end. we show that in xenopus laevis oocytes, removal of the terminal two nucleotides occurs after the rna has transited through the cytoplasm and returned to the nucleus. the activity is controlled by an inhibitor of processing, which we call tpi, for 3'-terminal processing inhibitor. this inhibitor is sensitive to both micrococcal nuclease and trypsin treatment, indicating that it is a nucleoprotein. tpi ...19921549111
binding of histones to xenopus laevis ribosomal genes with different levels of expression.the association of ribosomal rna genes with histones as a function of their expression has been studied in xenopus laevis erythrocytes, where the genes are silent, and tadpoles at stage 40, where these genes are actively transcribed. isolated nuclei were either treated with formaldehyde or irradiated with an ultraviolet laser to cross-link proteins to dna. the covalently linked protein-dna complexes were purified by centrifugation through cscl and immunoprecipitated with antibodies against h1, h ...19921551397
a major estrogen-regulated protein secreted from the liver of xenopus laevis is a member of the serpin superfamily. nucleotide sequence of cdna and hormonal induction of mrna.estrogen treatment of xenopus frogs causes four mrnas to become highly abundant in the liver. three of these mrnas have been previously identified as coding for vitellogenin, ferritin, and serum retinol binding protein. we show here that the fourth abundant liver messenger rna comprises about 1500 nucleotides and codes for a 45-kda secreted protein, designated ep45. a clone complementary to ep45 mrna was isolated, and its identity was confirmed by hybridization selection of mrna that translated ...19921551912
a novel peptide-producing cell in xenopus: multinucleated gastric mucosal cell strikingly similar to the granular gland of the skin.we have characterized a novel peptide-containing cell within the gastric mucosa of xenopus laevis. the cell is a spherical, multinucleated syncytial structure containing a cytoplasmic space filled with dense rice-shaped granules, and is strikingly similar in morphology to the well-studied granular gland of the amphibian skin. immunohistochemical and immunogold methods were used to demonstrate that several peptides previously isolated from the granular glands of the skin, including the antimicrob ...19921552176
the polymorphic integumentary mucin b.1 from xenopus laevis contains the short consensus repeat.the frog integumentary mucin b.1 (fim-b.1), discovered by molecular cloning, contains a cysteine-rich c-terminal domain which is homologous with von willebrand factor. with the help of the polymerase chain reaction, we now characterize a contiguous region 5' to the von willebrand factor domain containing the short consensus repeat typical of many proteins from the complement system. multiple transcripts have been cloned, which originate from a single animal and differ by a variable number of tan ...19921556137
intercellular communication between follicular angiotensin receptors and xenopus laevis oocytes: medication by an inositol 1,4,5-trisphosphate-dependent xenopus laevis oocytes, activation of angiotensin ii (aii) receptors on the surrounding follicular cells sends a signal through gap junctions to elevate cytoplasmic calcium concentration ([ca2+]i) within the oocyte. the two major candidates for signal transfer through gap junctions into the oocyte during aii receptor stimulation are ins(1,4,5)p3 and ca2+. in [3h]inositol-injected follicular oocytes, aii stimulated two- to fourfold increases in phosphoinositide hydrolysis and production of ino ...19921556150
a novel, activin-inducible, blastopore lip-specific gene of xenopus laevis contains a fork head dna-binding domain.the organizer region, or dorsal blastopore lip, plays a central role in the initiation of gastrulation and the formation of the body axis during xenopus development. a similar process can also be induced in ectodermal explants by activin or by injection of activin mrna into embryos. we have searched early embryo-specific cdna libraries for genes containing the fork head box sequence that encodes a dna-binding domain similar to that of the drosophila homeotic gene fork head and rat hepatocyte nuc ...19921559610
the identification and characterization of krab-domain-containing zinc finger proteins.the zinc finger motif is a highly conserved tandemly repeated sequence of 28-30 amino acids that was first identified in transcription factor tfiiia from xenopus laevis. subsequently, similar motifs were found and characterized in many genes from mammalian genomes and the genomes of lower eukaryotes such as drosophila and yeast, thereby defining a large superfamily of genes. non-finger-coding modules conserved among members of subfamilies of zinc finger genes have been described in the murine ge ...19921559709
amino acid substitutions at tryptophan 388 and tryptophan 412 of the hepg2 (glut1) glucose transporter inhibit transport activity and targeting to the plasma membrane in xenopus oocytes.all 6 tryptophan residues in the human hepg2-type glucose transporter (glut1) were individually altered by site-directed mutagenesis to investigate the role of these residues in transport function. tryptophan residues in positions 48, 65, 186, 363, 388, and 412 of glut1 were changed to either a glycine or leucine residue. mutant mrnas were synthesized and injected into xenopus laevis oocytes. transporter function as assessed by uptake of 2-deoxy-d-[3h]glucose or transport of 3-o-[3h]methylglucos ...19921560011
sequence of the sup61-rad18 region on chromosome iii of saccharomyces cerevisiae.a 7965 bp dna segment from the right arm of chromosome iii of saccharomyces cerevisiae, encompassing the sup61 and rad18 genes, was sequenced. four new open reading frames were found in this dna fragment. one of them, ycr103, is 51% homologous with the g10 gene product of xenopus laevis.19921561837
the main adenosine triphosphate-binding component of amphibian oocytes is ferritin.after fractionation of mitochondrion-free extracts of xenopus laevis and rana temporaria oocytes in sucrose gradients, a distinct peak of adenosine triphosphate (atp)/guanosine triphosphate (gtp)-binding activity in the 50-70 s range has been detected. this substance has a boyant density in cs2so4 of 1.45 g/cm3. the nucleotide-binding substance has been purified to apparent homogenety. by means of electron microscopy, sodium dodecyl sulfate-electrophoresis and other methods it has been identifie ...19921562327
a cdna from brain of xenopus laevis coding for a new precursor of thyrotropin-releasing hormone. 19921563521
localization and quantification of nonapeptide binding sites in the kidney of xenopus laevis: evidence for the existence of two different nonapeptide receptors.the distribution and properties of nonapeptide binding sites in the kidney of the anuran xenopus laevis were investigated using quantitative in vitro autoradiography. the binding studies were performed with [3h]arginine vasopressin (avp) as ligand because [125i]arginine vasotocin (avt) lacks biological activity. specific binding sites for [3h]avp are located in the glomeruli of the kidney. [3h]avp binding results in a steady state of association and dissociation between ligand and binding sites. ...19921563620
teratogenic assessment of four solvents using the frog embryo teratogenesis assay--xenopus (fetax).the frog embryo teratogenesis assay--xenopus (fetax) was used to assess the teratogenic potential of four solvents. embryos of the south african clawed frog, xenopus laevis, were exposed for 96 h to ethanol, dimethyl sulfoxide (dmso), formamide or glycerol formal. exposure groups were maintained using a static renewal system in which the exposure media were changed at 24-h intervals. survival was monitored at 24-h intervals. length, as an indicator of growth effects, and developmental malformati ...19921564253
cloning and characterization of a human angiotensin ii type 1 receptor.a human liver cdna library was screened using a rat type 1 angiotensin ii receptor cdna coding sequence as a probe. cdna clones were isolated which encoded a protein of 359 amino acids that shared 94.4% and 95.3% identify to rat and bovine type 1 angiotensin ii receptors, respectively. ligand binding studies of the cloned receptor expressed in cos cells suggested that it is pharmacologically a type 1 angiotensin ii receptor subtype. electrophysiological studies of the receptor expressed in xenop ...19921567413
expression of thymosin beta 4 gene during xenopus laevis order to investigate the molecular events which take place during gastrulation, extracts from developing xenopus embryos were analyzed for temporal peptide distribution by high performance liquid chromatography. one peptide peak which became increasingly dominant after gastrulation was purified and partially characterized. the amino acid sequence of enzymic digests showed the peptide is extremely similar to mammalian thymosin beta 4. the peptide was capable of binding actin monomers like mamm ...19921567461
epimorphic vs. tissue regeneration in xenopus forelimbs.postmetamorphic froglets of xenopus laevis regenerate hypomorphic unbranched spikes from amputated arm stumps. these are composed primarily of cartilage, produced from blastemalike structures sparsely populated with cells and rich in connective tissue. some consider these outgrowths to be an example of epimorphic regeneration produced from blastemas, albeit deficient ones. others interpret them as a case of tissue regeneration derived from fibroblastemas augmented by chondrocytes and periosteal ...19921569412
binding of the estrogen receptor dna-binding domain to the estrogen response element induces dna bending.we have used circular permutation analysis to determine whether binding of purified xenopus laevis estrogen receptor dna-binding domain (dbd) to a dna fragment containing an estrogen response element (ere) causes the dna to bend. gel mobility shift assays showed that dbd-dna complexes formed with fragments containing more centrally located eres migrated more slowly than complexes formed with fragments containing eres near the ends of the dna. dna bending standards were used to determine that the ...19921569939
the drosophila gene escargot encodes a zinc finger motif found in snail-related genes.two independent p-element enhancer detection lines were obtained that express lacz in a pattern of longitudinal stripes early in germband elongation. in this paper, molecular and genetic characterization of a gene located near these transposons is presented. sequence analysis of a cdna clone from the region reveals that this gene has a high degree of similarity with the drosophila snail gene (boulay et al., 1987). the sequence similarity extends over 400 nucleotides, and includes a region encodi ...19921571289
differential stem cell contributions to thymocyte succession during development of xenopus laevis.the contribution of two embryonic stem cell compartments to the developing thymus in the amphibian xenopus was examined throughout the larval, postmetamorphic, and adult periods. hematopoietic chimeras were produced by transplanting either the ventral blood islands (vbi) or the dorsal stem cell compartment (dsc) from diploid donors onto triploid hosts. the dna content of isolated nuclei harvested from the thymus and circulating e populations was analyzed using propidium iodide staining and flow ...19921578125
cloning and expression of the canine interferon-gamma gene.the canine interferon-gamma (cifn-gamma) chromosomal gene was isolated from a recombinant library, containing the entire dog genome, by screening with a rat ifn-gamma genomic probe. the structural organization of the cifn-gamma gene closely resembles that of the human, murine, and rat ifn-gamma genes. it contains three intervening sequences and encodes a signal sequence of 23 amino acids followed by a mature protein of 143 amino acids. two potential n-glycosylation sites are located at positions ...19921578190
the role of premotor interneurons in phase-dependent modulation of a cutaneous reflex during swimming in xenopus laevis embryos.phase-dependent reflex modulation during fictive "swimming" in xenopus laevis embryos has been examined with intracellular recordings from rhythmically active spinal neurons. (1) at rest, cutaneous trunk or tail skin stimulation evokes epsps in motoneurons and premotor excitatory and inhibitory interneurons of the opposite motor system. during swimming, these epsps can only be evoked during the depolarized phase of activity and can then produce extra action potentials that lead to phase-dependen ...19921578259
regulation of vertebrate left-right asymmetries by extracellular matrix.the vertebrate body is organized along three geometric axes: anterior-posterior, dorsal-ventral and left-right. left-right axis formation, displayed in heart and gut development, is the least understood, even though it has been studied for many years. in xenopus laevis gastrulae, a fibronectin-rich extracellular matrix is deposited on the basal surface of ectoderm cells over which cardiac and visceral primordia move during development. here i report experiments in which localized perturbation of ...19921579165
nucleotide sequence of xlpou3 cdna, a member of the pou domain gene family expressed in xenopus laevis embryos. 19921579504
oviductin. purification and properties of the oviductal protease that processes the molecular weight 43,000 glycoprotein of the xenopus laevis egg envelope.the xenopus laevis egg envelope is modified during egg transit through the pars recta oviduct. the physicochemical properties and ultrastructure of the envelope change, and the m(r) 43,000 envelope glycoprotein (gp43) is processed to m(r) 41,000. we purified a gp43 processing protease from oviductal secretory granules and studied its effects on the egg envelope. the m(r) 66,000 protease, designated oviductin, hydrolyzed the arginyl-x bond of n alpha-tert-butoxycarbonylphenylalanylserylarginyl-7- ...19921581303
mediation of inorganic anion transport by the hydrophobic domain of mouse erythroid band 3 protein expressed in oocytes of xenopus laevis.a cdna clone of the mouse erythroid band 3 protein encoding the 556 amino acid residues of the hydrophobic domain from thr-374 to the c-terminal val-929 is shown by immunoprecipitation to be expressed in xenopus oocytes. measurements of 36cl- efflux indicate that the translation product mediates cl- transport, which is inhibitable reversibly by dnds or h2dids, specific inhibitors of band 3-mediated transport. the apparent ki values are 3.6 microm and 0.094 microm, respectively, and hence similar ...19921581325
effects of heat shock on the pattern of fibronectin and laminin during somitogenesis in xenopus laevis.heat shock causes partial disruption of the segmentation pattern during somitogenesis in xenopus as well as in other vertebrates. however, xenopus undergoes a different type of somite formation than that of most vertebrates: somites are formed by rotation of cell blocks out of the paraxial mesoderm. we attempted to determine whether or not the segmentation disorder following heat shock is caused by an altered pattern of fibronectin and/or laminin, that could then effect the rotation of cell bloc ...19921581602
difference in the response to pif/activin between animal caps excised from mid- or late blastula stages of xenopus laevis.animal caps from xenopus embryos at stage 7/8 cultured in salt solution, were capable of elongating, and formed various embryonic tissues including axial mesoderm, nervous tissues and pigmented retina. in contrast, animal caps from stage 9 only developed into permanent blastulae. following exposure to pif/activin, however, such animal caps displayed morphogenetic movements. they formed tube-shaped embryoids that frequently had one or more tails but no head. we conclude that animal caps from stag ...19921582499
the marginal zone of the 32-cell amphibian embryo contains all the information required for chordamesoderm development.the formation of the amphibian organizer is evidenced by the ability of cells of the dorsal marginal zone (dmz) to self-differentiate to form notochord and to induce the formation of other axial structures from neighboring regions of the embryo. we have attempted to determine when these abilities are acquired in the urodele, ambystoma mexicanum (axolotl), and in the anuran, xenopus laevis, by removing the mesodermalizing influence of the vegetal hemisphere at different stages of development and ...19921583451
the stopping response of xenopus laevis embryos: behaviour, development and physiology.1. when xenopus laevis embryos swim into an obstruction they usually stop. this stopping response to stimulation on the head is present from stage 28 to 45. at stage 37/38 it is more reliable in restrained than in free-swimming animals, and to stimuli to the cement gland than to the head skin. 'fictive' swimming also stops reliably after the same stimuli but struggling and 'fictive' struggling do not. 2. discharge of deformation-sensitive trigeminal sensory neurons in response to pressure on the ...19921583603
comparative structural analysis of the transcriptionally active proopiomelanocortin genes a and b of xenopus the intermediate lobe of the pituitary gland, the prohormone proopiomelanocortin (pomc) is processed to, among other peptides, melanocyte-stimulating hormone (alpha-msh). in the toad xenopus laevis alpha-msh controls skin darkening during background adaptation, and the level of pomc gene transcription in the intermediate lobe depends on the color of the background. in the lobe, two structurally different pomc proteins are produced from two mrnas that are transcribed to approximately the same ...19921584015
the role of estrogen response elements in expression of the xenopus laevis vitellogenin b1 gene.we have used site-directed mutagenesis and a homologous transient transfection system to investigate the role of the two imperfect estrogen response elements (eres) located at -302/-334 in the 5'-flanking region of the estrogen-regulated xenopus laevis vitellogenin b1 gene. deletion of either ere effectively abolishes estrogen-dependent transcription of the vitellogenin promoter. neither replacement of the two imperfect eres with a single consensus ere at -334, nor insertion of one or two consen ...19921584211
stp1, a gene involved in pre-trna processing, encodes a nuclear protein containing zinc finger motifs.stp1 is an unessential yeast gene involved in the removal of intervening sequences from some, but not all, families of intervening sequence-containing pre-trnas. previously, we proposed that stp1 might encode a product that generates pre-trna conformations efficiently recognized by trna-splicing endonuclease. to test the predictions of this model, we have undertaken a molecular analysis of the stp1 gene and its products. the stp1 locus is located on chromosome iv close to at least two other gene ...19921588961
control of 4-8s rna transcription at the midblastula transition in xenopus laevis embryos.transcription of xenopus laevis u1 snrna genes is subject to a precise program with respect both to the timing of activation at the midblastula transition (mbt) and to the relative levels of the two embryonic u1 rnas (xu1b1 and b2) that are made. here, we demonstrate that exogenous xu1b genes injected into developing x. laevis embryos come under the same controls as the endogenous genes. injected u1 genes, unlike exogenous rna polymerase iii genes, remain quiescent until mbt and their activation ...19921592258
metabolic changes with fatigue in different types of single muscle fibres of xenopus laevis.1. peak isometric force of single fast (type 1) and slow (type 3) muscle fibres of xenopus decreased when fibres were stimulated intermittently above their predicted sustainable duty cycle at 20 degrees c. type 1 fibres could be fatigued to zero force. in most type 3 fibres force did not decrease below 50% of the original (p0) before activation failure, as indicated by irregular contractions. 2. fibres were rapidly frozen at different force levels and analysed by high-performance liquid chromato ...19921593475
the boll weevil vitellogenin gene: nucleotide sequence, structure, and evolutionary relationship to nematode and vertebrate vitellogenin genes.boll weevil (anthonomus grandis) eggs contain two yolk proteins, yp47 and yp160. using anti-yp160 antiserum as probe, a partial-length complementary dna (cdna) was isolated from a lambda gt11 adult female cdna library. a second partial-length cdna was isolated from a lambda gt10 adult female cdna library by differential screening with male vs. female cdnas. northern blot analysis showed that each cloned cdna hybridized to a 6-kb female-specific transcript. these cdnas were used to probe a genomi ...19921593641
transcriptional and posttranscriptional regulation of the proopiomelanocortin gene in the pars intermedia of the pituitary gland of xenopus the melanotrope cells of the intermediate pituitary gland of the amphibian xenopus laevis, expression of the pomc gene is under physiological control, i.e. it is 20- to 30-fold higher in animals adapted to a black background compared to animals adapted to a white background. to investigate whether changes in pomc messenger rna stability contribute to this difference in expression, a steady state kinetic model for mrna degradation was used to determine the half-life of pomc mrna during the ind ...19921597153
high resolution studies of the xenopus laevis ribosomal gene promoter in vivo and in vitro.the first high resolution maps of the xenopus laevis ribosomal promoter and its flanking regions (-179 to +14) have been created by assaying point mutants both in oocyte and in vitro. within the promoter boundaries (-141(-145) to +3(+4)), domains analogous to the core promoter and "upstream control element" (uce) were clearly detected. the base pairs at -133, within the uce, and -20, -10, -7, and +3, within the core, were all shown to be especially important for promotion. between the core and u ...19921597438
the cellular basis of the convergence and extension of the xenopus neural plate.there is great interest in the patterning and morphogenesis of the vertebrate nervous system, but the morphogenetic movements involved in early neural development and their underlying cellular mechanisms are poorly understood. this paper describes the cellular basis of the early neural morphogenesis of xenopus laevis. the results have important implications for neural induction. mapping the fate map of the midneurula (eagleson and harris: j. neurobiol. 21:427-440, 1990) back to the early gastrul ...19921600240
planar induction of convergence and extension of the neural plate by the organizer of xenopus.this paper demonstrates that convergence and extension within the neural plate of xenopus laevis are regulated by planar inductive interactions with the adjacent spemann organizer. the companion article (keller et al.: developmental dynamics 193:199-217, 1992) showed that the prospective hindbrain and spinal cord occupy a very short and very wide area just above the spemann organizer in the early gastrula and that these regions converge and extend greatly during gastrulation and neurulation, usi ...19921600241
modulation of nicotinic acetylcholine receptor channel by ph: a difference in ph sensitivity of torpedo and mouse receptors expressed in xenopus oocytes.1. in this study, effects of ph on the ion channel function of nicotinic acetylcholine receptor (nachr) from torpedo californica electroplax and mouse muscle bc3h-1 cells were investigated using xenopus laevis oocytes injected with in vitro synthesized rna transcripts. the acetylcholine (ach)-induced whole-cell peak current responses and slow desensitization rates were measured by voltage-clamp. 2. the ach-induced peak currents of torpedo nachrs were reversibly diminished when extracellular ph w ...19921600556
localization and quantification of angiotensin ii (a ii) binding sites in the kidney of xenopus laevis--lack of a ii receptors in the adrenal tissue.the distribution and properties of angiotensin binding sites in the kidney of the clawed toad xenopus laevis were studied using quantitative in vitro autoradiography. specific binding sites for [125i]-[val5]-angiotensin ii (a ii) were located in the glomeruli of the kidney but not in the adrenal tissue. [125i]-[val5]-a ii binding was equilibrated after 45 min. scatchard and hill analyses of saturation experiments showed that [125i]-[val5]-a ii binds to a single class of binding sites with a diss ...19921601265
a nonsteroidal follicular factor is involved in maturation process of xenopus laevis oocytes.xenopus laevis postvitellogenic ovarian follicles release into conditioned medium nonsteroidal factor(s) that potentiate progesterone-induced oocyte maturation. the molecular weight of this factor is between 1000 and 10,000 da. the potentiating activity is suppressed when follicles are incubated with cyanoketone to inhibit steroidogenesis, suggesting that the secretion of the potentiating factor can be modulated in vitro. these results indicate that the steroid-independent pathway in vitro, prev ...19921601280
physical and genetic mapping of cloned ribosomal dna from toxoplasma gondii: primary and secondary structure of the 5s gene.the ribosomal dna (rdna encoding rrna) of the obligately intracellular protozoan parasite, toxoplasma gondii, was identified, cloned, physically mapped, its copy number determined, and the 5s gene sequenced. using total rna as a probe, a collection of recombinant lambda phages containing copies of rdna were isolated from a lambda 2001 tachyzoite genomic library. northern gel hybridization confirmed specific homology of the 7.5-kb rdna unit, subcloned into ptz18r, to t. gondii rrna. the mapped rd ...19921601300
molecular cloning, expression and in vitro functional characterization of myb-related proteins in xenopus.two cdnas encoding myb-related proteins have been cloned from xenopus laevis and they have been termed xmyb1 and xmyb2. the xmyb1 cdna clone codes for an open reading frame of 733 amino acids and exhibits a high degree of similarity over the entire predicted protein sequence with the human b-myb protein. xmyb2 is a partial cdna clone encoding three copies of amino-terminal tandem repeat elements typical for the myb dna-binding domain. the predicted protein sequence is most closely related to the ...19921606020
purification, primary structure, bacterial expression and subcellular distribution of an oocyte-specific protein in xenopus.this study defines a novel xenopus laevis protein (p100) that has recently been shown to be recognized by scleroderma patient sera. using a combination of differential solubility in detergents, hydroxyapatite chromatography and one-dimensional page, p100 was purified to apparent homogeneity and the amino acid sequence was obtained. an oligonucleotide derived from this sequence was used to clone p100 cdna through a polymerase-chain-reaction cloning strategy. the entire p100 cdna sequence was dete ...19921606954
expression of xenopus laevis histone h5 gene in an approach to assess linker histone function, we engineered a cdna encoding xenopus laevis histone h5 (xlh5), into the yeast saccharomyces cerevisiae, which lacks any known proteins homologous to linker histones. xlh5 cdna when fused to the yeast gal10 promoter and 5' untranslated region (utr) was shown to be accurately transcribed at relatively high levels in cells harvested at mid to late log after exposure to at least 22 mm galactose. the resultant 0.95 kb xlh5 transcript reached steady s ...19921610895
isolation and characterization of cdna clones encoding the skeletal and smooth muscle xenopus laevis beta tropomyosin isoforms.cdnas clones corresponding to the skeletal and smooth muscle beta tropomyosins isoforms were isolated from a xenopus laevis embryo cdna library. sequence analysis indicated that the two isoforms are coded by a single gene that uses two couples of alternative exons. the expression of the x. laevis beta tropomyosin gene closely resembles that of the mammalian gene but differs from the avian gene.19921610908
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