Publications
| Title | Abstract | Year Filter | PMID(sorted descending) Filter |
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| 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 ... | 1992 | 1537407 |
| 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 ... | 1992 | 1536650 |
| 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 ... | 1992 | 1535684 |
| 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 ... | 1992 | 1534778 |
| 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 ... | 1992 | 1532947 |
| expression of rat renal sodium/phosphate cotransporter in xenopus laevis oocytes. | in 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 ... | 1992 | 1532329 |
| 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 laevis. | in 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 ... | 1992 | 1532231 |
| 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 ... | 1992 | 1531366 |
| 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 ... | 1992 | 1531011 |
| maintenance of xenopus laevis and oocyte injection. | 1992 | 1528120 | |
| 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 ... | 1992 | 1528091 |
| 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 ... | 1992 | 1525016 |
| 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 ... | 1992 | 1525011 |
| 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 ... | 1992 | 1522141 |
| plasticity of binocular visual connections in the frog, xenopus laevis: reversibility of effects of early visual deprivation. | in 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 ... | 1992 | 1521600 |
| 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 ... | 1992 | 1521564 |
| 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 ... | 1992 | 1521522 |
| 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 ... | 1992 | 1521501 |
| [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 ... | 1992 | 1521175 |
| 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 ... | 1992 | 1518071 |
| 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 ... | 1992 | 1517247 |
| 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 ... | 1992 | 1516776 |
| 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 ... | 1992 | 1516744 |
| 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 ... | 1992 | 1511893 |
| 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 ... | 1992 | 1511699 |
| 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 ... | 1992 | 1510932 |
| 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 ... | 1992 | 1510665 |
| 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 ... | 1992 | 1509782 |
| 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 ... | 1992 | 1508183 |
| 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 ... | 1992 | 1507234 |
| 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 ... | 1992 | 1501883 |
| 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 ... | 1992 | 1501246 |
| 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. | 1992 | 1500885 |
| 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 ... | 1992 | 1499114 |
| 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 ... | 1992 | 1498041 |
| 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 ... | 1992 | 1497868 |
| 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 ... | 1992 | 1497861 |
| readthrough enhancement and promoter occlusion on the ribosomal genes of xenopus laevis. | an 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 ... | 1992 | 1497859 |
| characterization of the ileal na+/bile salt co-transporter in brush border membrane vesicles and functional expression in xenopus laevis oocytes. | the na+/bile salt co-transporter of the pig ileal brush border membrane has been expressed in xenopus laevis oocytes. injection of pig ileal poly (a)+ rna into oocytes resulted in the functional expression of an na(+)-gradient-stimulated taurocholate uptake within 2-5 days. the expressed na(+)-dependent taurocholate uptake exhibited saturation kinetics (apparent km of 48 microm), and displayed similar competitive substrate inhibition by taurodeoxycholate as the native brush border na+/bile salt ... | 1992 | 1497617 |
| individual variability in the translational regulation of ribosomal protein synthesis in xenopus laevis. | ribosomal protein synthesis is regulated by controlling the fraction of mrna associated with polysomes. it is known that this value changes in different developmental stages during xenopus embryogenesis or, more generally, with changing cell growth conditions. we present here an analysis of the proportion of mrna loaded on polysomes, carried out with probes for five different ribosomal proteins on several batches of xenopus embryos obtained from different individuals. the results obtained indica ... | 1992 | 1495485 |
| identification and developmental expression of a novel low molecular weight neuronal intermediate filament protein expressed in xenopus laevis. | xenopus laevis is a valuable model system for the study of vertebrate neuroembryogenesis. however, very few well-characterized nervous system-specific molecular markers are available for studies in this organism. we screened a x. laevis adult brain cdna library using a cdna probe for mouse low molecular weight neurofilament protein (nf-l) in order to identify neuron-specific intermediate filament proteins. clones for two distinct neuron-specific intermediate filament proteins were isolated and s ... | 1992 | 1494944 |
| effect of rabbit duodenal mrna on phosphate transport in xenopus laevis oocytes: dependence on 1,25-dihydroxy-vitamin-d3. | expression of na(+)-dependent transport of phosphate (pi) was analysed in xenopus laevis oocytes after injection of poly(a)-rich rna isolated from the duodenal mucosa of rabbits with increased levels of 1,25-(oh)2-vitd3 (injection of vitamin d3 or low-pi diet) or from control animals. in parallel, the effect of elevated levels of vitamin d3 was studied in isolated duodenal brush-border membrane vesicles. in brush-border membrane vesicles, the rate of na(+)-pi cotransport was found to be doubled ... | 1992 | 1488278 |
| the primary structure of piscine (oncorhynchus mykiss) retinol-binding protein and a comparison with the three-dimensional structure of mammalian retinol-binding protein. | 1. the primary structures of two variants of rainbow trout (oncorhynchus mykiss) plasma retinol-binding protein (rbp) were determined and found to be approximately 60% identical with those of both human and xenopus laevis rbps. the comparable sequence similarities that we have found agree with the estimate of similar divergence times between bony fishes and mammals and between bony fishes and amphibians. the two piscine rbp variants differ by six amino acid substitutions at positions that are no ... | 1992 | 1483476 |
| expression and potential functions of g-protein alpha subunits in embryos of xenopus laevis. | during early embryonic development, many inductive interactions between tissues depend on signal transduction processes. we began to test the possibility that g-proteins participate in the signal transduction pathways that mediate neural induction. the expression during xenopus development of three g alpha subunits, g alpha 0, g alpha i-1 and g alpha s-1, was characterized. the three maternally expressed genes showed different expression patterns during early development. whole-mount in situ hyb ... | 1992 | 1483383 |
| identity elements for n2-dimethylation of guanosine-26 in yeast trnas. | n2,n2-dimethylguanosine (m2(2)g) is a characteristic nucleoside that is found in the bend between the dihydro-uridine (d) stem and the anticodon (ac) stem in over 80% of the eukaryotic trna species having guanosine at position 26 (g26). however, since a few eukaryotic trnas have an unmodified g in that position, g26 is a necessary but not a sufficient condition for dimethylation. in yeast trna(asp) g26 is unmodified. we have successively changed the near surroundings of g26 in this trna until g2 ... | 1992 | 1480477 |
| amphibian intestinal villin: isolation and expression during embryonic and larval development. | an actin-binding protein of m(r) 105,000 has been isolated from anuran amphibian intestinal mucosa. polyclonal antibodies directed against chicken and pig intestinal villins and anti-porcine villin headpiece monoclonal antibody crossreact with the amphibian m(r) 105,000 protein. furthermore, the latter possesses an nh2-terminal sequence that is very homologous to those of avian and mammalian villins. in addition, polyclonal antibodies directed against amphibian intestinal m(r) 105,000 protein cr ... | 1992 | 1478966 |
| distribution of vasotocin- and mesotocin-like immunoreactivities in the brain of the south african clawed frog xenopus-laevis. | in order to obtain more insight into primitive and derived conditions of neuropeptidergic systems in vertebrates, in particular amphibians, we have studied immunohistochemically the distribution of vasotocin (avt) and mesotocin (mst) neuronal elements in the brain of the south african clawed frog xenopus laevis. apart from a well-developed hypothalamohypophysial system, the antibodies revealed the existence of extrahypothalamic avt- and mst-immunoreactive cell groups as well as extensive extrahy ... | 1992 | 1476666 |
| immune system activation associated with a naturally occurring infection in xenopus laevis. | immune system activation correlated with a naturally occurring infection has been found in the south african clawed frog xenopus laevis. the microorganism thought to be the cause of this infection is coccobacilloid and approximately 1 micron in diameter. since this microorganism does not grow on conventional bacterial media and it has been observed intracellularly, it may be an obligate intracellular bacterium. it has been found in xenopus peripheral blood and in highly vascularized organs such ... | 1992 | 1473595 |
| expression of carnosine-like immunoreactivity during retinal development in the clawed frog (xenopus laevis). | the development of neurons immunoreactive to carnosine (beta-alanyl-l-histidine) was studied in the retina of xenopus laevis during the premetamorphic period. carnosine-like immunoreactivity was detected in photoreceptors from stage 39/40 (according to nieuwkoop and faber [normal tables of xenopus laevis (daudin), elsevier, amsterdam, 1956]) and in bipolar cells and their processes in the inner plexiform layer from stage 44/45. at all the developmental stages studied, neuroepithelial cells at th ... | 1992 | 1473272 |
| characterization of two types of ribosomal gene transcription in xenopus laevis oocytes. | when the germinal vesicle of xenopus laevis oocytes is translocated into the vegetal hemisphere by centrifugation, the normally silent ribosomal spacer promoters are strongly induced. this induction correlates with the permeability of the nuclear envelope to dextran of molecular weight 70 kda, thus raising the possibility that the transcriptional changes are due to mixing of nuclear and cytoplasmic components. this basic observation prompted a thorough investigation of ribosomal gene transcripti ... | 1992 | 1472871 |
| nucleotide sequence of the genes for ribosomal proteins hs15 and hsh from haloarcula marismortui: an archaeon-specific gene cluster. | the nucleotide sequences of the genes for two ribosomal proteins, hs15 and hsh, from the archaeon haloarcula marismortui, have been determined. the genes were found in a cluster together with another open reading frame with a probable regulatory function. hs15 and hsh have counterparts in eucarya. hs15 is significantly homologous to s19 from frog (xenopus laevis). hsh is related to s37 from yeast (saccharomyces cerevisiae) and s27 from fly (drosophila melanogaster), as well as to other members o ... | 1992 | 1468549 |
| recoverin in pineal organs and retinae of various vertebrate species including man. | recoverin is a recently discovered 26 kda calcium-binding protein, which activates guanylate cyclase in retinal photoreceptors when the intracellular concentration of free calcium drops upon photoexcitation. in this study we examined the distribution of recoverin in retinae and pineal organs of xenopus laevis larvae, 1-day-old chicken, adult pigeon, albino rat, sheep and man by means of immunocytochemistry. recoverin immunoreaction was found in all species investigated except for the chicken. in ... | 1992 | 1467959 |
| developmentally regulated expression of a mitogen-activated protein kinase in xenopus laevis. | mitogen-activated protein (map) kinases are activated in somatic cells in response to many extracellular stimuli and in oocytes during meiotic maturation. we have examined the tissue specificity of expression of a map kinase (xp42) in adult and larval xenopus laevis. map kinase rna and protein were abundant in the nervous system and lymphoid tissues and were readily detected in most other organs. a remarkably high level of rna was detected in ovary. fractionation of oocytes showed that map kinas ... | 1992 | 1467305 |
| range of messenger action of calcium ion and inositol 1,4,5-trisphosphate. | the range of messenger action of a point source of ca2+ or inositol 1,4,5-trisphosphate (ip3) was determined from measurements of their diffusion coefficients in a cytosolic extract from xenopus laevis oocytes. the diffusion coefficient (d) of [3h]ip3 injected into an extract was 283 microns 2/s. d for ca2+ increased from 13 to 65 microns 2/s when the free calcium concentration was raised from about 90 nm to 1 microm. the slow diffusion of ca2+ in the physiologic concentration range results from ... | 1992 | 1465619 |
| a 69-kda rna-binding protein from xenopus oocytes recognizes a common motif in two vegetally localized maternal mrnas. | vg1 mrna, a maternal message encoding a member of the transforming growth factor beta superfamily, undergoes localization to the vegetal cortex of xenopus laevis oocytes during a narrow period of oogenesis. a 340-nucleotide sequence has been identified in vg1 rna that directs its vegetal localization [mowry, k. l. & melton, d. a. (1992) science 255, 991-994]. to understand how cis- and trans-acting factors are involved in vg1 mrna localization, we have looked for specific interactions in vitro b ... | 1992 | 1465415 |
| presynaptic localization of sodium/calcium exchangers in neuromuscular preparations. | calcium ions play a critical role in neurotransmitter release. the cytosolic ca2+ concentration ([ca2+]cyt) at nerve terminals must therefore be carefully controlled. several different mechanisms, including a plasmalemmal na/ca exchanger, are involved in regulating [ca2+]cyt. we employed immunofluorescence microscopy with polyclonal antiserum raised against dog cardiac sarcolemmal na/ca exchanger to determine the distribution of the exchanger in vertebrate neuromuscular preparations. our data in ... | 1992 | 1464773 |
| thyroid hormone-induced gene expression changes in the developing frog limb. | greater than 120 genes are up-regulated in xenopus laevis limb buds within the first 24 h after induction of metamorphosis by thyroid hormone. fourteen of these have been isolated and characterized. four encode heat shock proteins. the identified regulated genes have in common a relatedness with cell growth as exemplified by the serum response of quiescent fibroblasts. some of the genes respond directly to hormone. however, the majority appear to be secondary response genes judging from their de ... | 1992 | 1464592 |
| [the nuclei of follicular cells do not control oocyte maturation in amphibians induced by gonadotropic hormones in vitro]. | the inhibitory effect of actinomycin d (5 micrograms/ml) on maturation of the follicle-enclosed oocytes of rana temporaria and xenopus laevis induced in vitro by pituitary suspension and human chorionic gonadotropin, respectively, is not observed at low concentrations of the hormones. these data suggest that nuclei of the follicle cells are not involved in the control of the pituitary-dependent oocyte maturation in amphibians. | 1992 | 1461634 |
| genes encoding xenopus laevis ig l chains. implications for the evolution of kappa and lambda chains. | xenopus laevis ig contain two distinct types of l chains, designated rho or l1 and sigma or l2. we have analyzed xenopus genomic dna by southern blotting with cdna probes specific for l1 v and c regions. many fragments hybridized to the v probe, but only one or two fragments hybridized to the c probe. corresponding c, j, and v gene segments were identified on clones isolated from a genomic library prepared from the same dna. one clone contains a c gene segment separated from a j gene segment by ... | 1992 | 1460285 |
| neuron-specific enolase-like immunoreactivity in the vertebrate retina: selective labelling of müller cells in anura. | neuron-specific enolase (nse) immunocytochemistry was carried out in retinae of goldfish, axolotl, clawed frog, cane toad, lizard, chick, guinea-pig, rabbit, rat, cat and human. with the exception of anura, strong immunoreactivity was seen in the large ganglion, amacrine cells and horizontal cells of the retina in all of the other species. photoreceptors were found to be labelled in the rat and human retina and only one cone type in rabbit. photoreceptor pedicles and ellipsoids were stained in t ... | 1992 | 1459864 |
| identification of plakoglobin in oocytes and early embryos of xenopus laevis: maternal expression of a gene encoding a junctional plaque protein. | we have isolated a cdna encoding the junctional plaque protein plakoglobin of xenopus laevis and determined its amino acid sequence. comparisons with sequences of related proteins of the same and other species revealed that in xenopus plakoglobin and beta-catenin are two different proteins, encoded by separate genes, that both genes are expressed in embryogenesis, and that the amphibian plakoglobin is more closely related to the human plakoglobin than to beta-catenin of the same species. using t ... | 1992 | 1459359 |
| evaluation of acetaminophen-induced developmental toxicity using fetax. | potential mechanisms of acetaminophen-induced developmental toxicity were evaluated using fetax (frog embryo teratogenesis assay-xenopus). early xenopus laevis embryos were exposed to acetaminophen for 96-h in two definitive concentrations-response assays with and without an exogenous metabolic activation system (mas). two static renewal tests of acetaminophen and the mas treated with carbon monoxide, cimetidine, ellipticine, diethyl maleate, and supplemented with glutathione were also performed ... | 1992 | 1459044 |
| identification of bone morphogenetic protein-2 in early xenopus laevis embryos. | polyclonal antibodies capable of reacting with amphibian bone morphogenetic protein (bmp-2 and -4) were raised in rabbits by immunization with a synthetic 21 amino acid peptide which corresponds to a sequence residing in the mature protein of xenopus bmp-2 (xbmp-2). the antibodies recognized an embryonic bmp as well as mammalian and bacteria expressed recombinant xbmps. the antibodies detected, under reducing conditions, a 30 kda protein in the extract of oocytes and embryos during early develop ... | 1992 | 1457128 |
| [the structure of the reticulum of mauthner's neurons in tadpoles of the clawed toad grown under increased gravitational force]. | the ultrastructure of the mauthner cells (m-cells) and the behaviour of xenopus laevis tadpoles, reared from eggs under increased gravity (2.9 g) which changes the activity of an afferent vestibular input, were investigated. besides, a study was made of tadpoles after the hindbrain ablation at earlier embryonal stages which significantly altered the microenvironment of m-cells. it is shown that experimental treatments enhance the proliferation of endoplasmic reticulum and its derivatives, so cal ... | 1992 | 1455551 |
| fission yeast cdc21+ belongs to a family of proteins involved in an early step of chromosome replication. | the cdc21+ gene of schizosaccharomyces pombe was originally identified in a screen for cdc mutants affecting s phase and nuclear division. here we show that the cdc21+ gene product belongs to a family of proteins implicated in dna replication. these include the saccharomyces cerevisiae mcm2 and mcm3 proteins, which are needed for the efficient function of certain replication origins, and s.cerevisiae cdc46, which is required for the initiation of chromosome replication. the cdc21 mutant is defec ... | 1992 | 1454522 |
| [the distribution and relation to the cytoskeleton of specific prosomal proteins in the oogenesis of the clawed toad]. | using immunoblotting and immunofluorescent microscopy, we showed the presence in xenopus laevis oocytes of two prosomal proteins (27 and 31-33 kda) and studied their distribution during oogenesis. in the ooplasm, both proteins are detected in prosomal clusters of various size. during previtellogenesis, prosomal proteins are diffusely distributed in the nucleoplasm and form evenly distributed clusters in the cytoplasm. during oocyte growth, prosomal proteins disappear from the nucleus and form an ... | 1992 | 1454294 |
| ventrolateral regionalization of xenopus laevis mesoderm is characterized by the expression of alpha-smooth muscle actin. | mesodermal patterning in the amphibian embryo has been extensively studied in its dorsal aspects, whereas little is known regarding its ventrolateral regionalization due to a lack of specific molecular markers for derivatives of this type of mesoderm. since smooth muscles (sm) are thought to arise from lateral plate mesoderm, we have analyzed the expression of an alpha-actin isoform specific for sm with regard to mesoderm patterning. using an antibody directed against alpha-sm actin that recogni ... | 1992 | 1451663 |
| localization of xenopsin and xenopsin precursor fragment immunoreactivities in the skin and gastrointestinal tract of xenopus laevis. | xenopsin (xp) and xenopsin precursor fragment (xpf) are bioactive peptides derived from a single precursor molecule; both were isolated previously from extracts of xenopus laevis skin. the present immunohistochemical study was undertaken to determine the specific cellular localization of these two peptides in the skin and also in the gastrointestinal tract of adult xenopus. we report here that xp-like and xpf-like immunoreactivities co-exist in the granular glands of the skin and specific granul ... | 1992 | 1451171 |
| [study in the anuran amphibian xenopus laevis, some blood characteristics and nitrogen excretion based on changes in the water osmolarity]. | the ph, the osmolality and the urea and ammonia concentrations in blood, as well as the net urea and ammonia excretions, were studied in the amphibian xenopus laevis exposed for several weeks to increased osmotic pressure (op) of the ambient water, as a result of the addition of either nacl or mannitol to the water. the ph and the ammonia concentration of the blood were independent of the variations of the ambient osmolarity. on the contrary, the blood osmolality and its urea concentration incre ... | 1992 | 1450981 |
| characterization of the genomic corticotropin-releasing factor (crf) gene from xenopus laevis: two members of the crf family exist in amphibians. | in mammals, the release of pituitary acth is stimulated by crf. two related peptides exist in nonmammalian vertebrates, sauvagine from frog skin and urotensin-i from the urophysis of teleost fish. their related structures (approximately 50%) and capacity to stimulate the release of acth from mammalian and fish pituitaries has led to the proposal that sauvagine and urotensin-i are homologs of mammalian crf. however, sauvagine does not appear to stimulate acth release in amphibians, although mamma ... | 1992 | 1448118 |
| effect of terminal nonhomologies on homologous recombination in xenopus laevis oocytes. | homologous recombination of linear dna molecules in xenopus laevis oocytes is very efficient. the predictions of molecular models for this recombination process were tested with substrates with terminal nonhomologies (nonhomologous sequences). it was found that nonhomologies on one or both ends of an otherwise efficient substrate substantially reduced the yield of recombination products. in the case of a single nonhomology, inhibition was observed for all lengths of nonhomology, from 60 to 1,690 ... | 1992 | 1448075 |
| testicular masculinization of vocal behavior in juvenile female xenopus laevis reveals sensitive periods for song duration, rate, and frequency spectra. | in xenopus laevis, adult males but not females produce courtship songs comprised of rapid trills. two experiments were conducted to determine whether male-typical singing could be induced in females. at 6 different juvenile stages, male and female frogs were gonadectomized and implanted with testes, grown to sexual maturity, and tested for vocal behavior. all frogs with functional testicular implants sang; females sang as much as males. the frequency spectra of the clicks within trills were full ... | 1992 | 1447723 |
| p-domains as shuffled cysteine-rich modules in integumentary mucin c.1 (fim-c.1) from xenopus laevis. polydispersity and genetic polymorphism. | a new frog integumentary mucin (fim-c.1) has been discovered by molecular cloning. this mucin contains at least six typical p-domains as cysteine-rich modules. shuffled p-domains have previously been detected in fim-a.1, and they also form the basis of various p-domain peptides, which presumably have growth-modulating activities. furthermore, fim-c.1 contains at least three threonine-rich clusters, which consist of semi-repetitive cassettes. various polydisperse transcripts have been characteriz ... | 1992 | 1447205 |
| xenopus laevis oocyte g alpha subunits mrnas. detection and quantitation during oogenesis and early embryogenesis by competitive reverse pcr. | the expression of mrnas coding for different xenopus laevis oocyte g alpha subunits was analyzed by the pcr technique. using the nucleotide sequences of five previously cloned cdnas for oocyte g alpha subunits [febs lett. 244, 188-192, 1989; febs lett. 268, 27-31, 1990] and the highly sensitive reverse pcr reaction we found that g alpha o, g alpha i-1, g alpha i-3 and g alpha s species are present in oocyte stage vi, g alpha o mrna being the most abundant transcript. g alpha o mrna was further q ... | 1992 | 1446737 |
| identification of nuclear factors which interact with the 5' flanking region of the ef-1 alpha o gene in xenopus laevis. | the ef-1 alpha o gene of xenopus laevis is a stage-specific gene, being transcribed in oogonia and oocytes, but not in postmeiotic germ cells and terminally differentiated cells. we found that two trans-acting factors from oocyte nuclear extract are able to interact with a dna sequence in the 5'-upstream region of the ef-1 alpha o gene. methylation interference experiments suggested that the two factors recognised the same dna element. gel retardation assays indicated that part of the protein bi ... | 1992 | 1446735 |
| identification of calreticulin isoforms in the central nervous system. | in the present paper we report the cloning and sequencing of the cdna encoding two calreticulin isoforms from xenopus laevis central nervous system. the two isoforms display 93% identity at the amino acid level. the predicted amino acid sequences of the amphibian calreticulins are very similar (76%) to those of mammalian liver and skeletal muscle. xenopus laevis calreticulins are characterized by a very acidic c-terminal domain endowed with the endoplasmic-reticulum retention signal kdel. the cd ... | 1992 | 1445218 |
| a method for [3h]mannose labeling of asn-linked oligosaccharides on recombinant glycoproteins synthesized in xenopus oocytes. | we have developed an efficient method for labeling the asn-linked oligosaccharides of recombinant glycoproteins synthesized in xenopus laevis oocytes. by coinjecting gdp-[3,4-(3)h]mannose with mrna for human cathepsin d, it was possible to incorporate as much as 1800 cpm per oocyte into each of the two asn-linked oligosaccharides of this glycoprotein. overall, about 50% of the microinjected gdp-[3,4-(3)h]mannose was incorporated into asn-linked oligosaccharides, a 10-fold greater value than that ... | 1992 | 1443567 |
| calcium-binding proteins in chemoreceptors of xenopus laevis. | calcium-binding proteins were investigated immunohistochemically in chemo-receptors of the olfactory epithelium and taste buds of the clawed frog, xenopus laevis. calmodulin-, s-100- and calbindin-immunoreactive material were found in sensory cells of the olfactory epithelium; however, parvalbumin-like material was absent in these cells. taste buds of the palate showed calmodulin-, s-100- and parvalbumin-immunoreactive material in sensory cells, while calbindin-immunoreactive material in support ... | 1992 | 1440589 |
| distribution of mrna of a na(+)-independent neutral amino acid transporter cloned from rat kidney and its expression in mammalian tissues and xenopus laevis oocytes. | the na(+)-independent neutral amino acid transporter (naa-tr) that we had previously cloned from rat kidney has been investigated with respect to its distribution in mammalian tissues and cells. by northern blot analysis and rnase protection assay, a 2.4-kilobase (kb) mrna in rat intestine was found to be identical to that in rat kidney. of the other rat tissues examined, only brain and heart were found to contain mrnas related to kidney naa-tr by northern assay. however, these were larger (appr ... | 1992 | 1438248 |
| genes for xenopus laevis u3 small nuclear rna. | genomic southern blots showed there are only 14 to 20 copies of u3 snrna genes per somatic genome in xenopus laevis, unlike the highly repetitive, tandem arrangement of other snrna genes in this organism. sequencing of two u3 snrna genes from lambda clones of a genomic library revealed striking similarity upstream, but much more divergence downstream. consensus motifs common to other u snrna genes were also found: a distal sequence element (dse, octamer motif at -222 to -215), a proximal sequenc ... | 1992 | 1437561 |
| sequence differences between histones of procyclic trypanosoma brucei brucei and higher eukaryotes. | four histones, a, b, c, d from procyclic trypanosoma brucei brucei, which show similarities with the amino acid composition of the core histones h3, h2a, h2b and h4, were isolated and cleaved with endoproteinase glu-c. the fragments were separated by fplc reversed phase chromatography and a subset of the fragments (a5, a9, b6, c8, d3, d9, d11) was subjected to sequence analysis. a 54-71% identity was found in the sequences of the fragment c8 and the c-terminal half of h2b and of three fragments ... | 1992 | 1437281 |
| a possible role for c-myc oncoproteins in post-transcriptional regulation of ribosomal rna. | overexpression of members of the myc family of oncogenes contributes to the development of many vertebrate malignancies. although several functions for myc gene products have been proposed, the targets for myc activity during oncogenesis or normal development remain to be identified. oocytes of xenopus laevis, which are non-dividing cells that accumulate abundant c-myc protein, provide an unusual opportunity to examine c-myc function. we have investigated whether the accumulation of massive amou ... | 1992 | 1437160 |
| structural organization of a src gene from xenopus laevis. | by sequence analysis of genomic clones, the exon-intron structure of one of the two src genes from xenopus laevis has been determined. the coding region of the gene is interrupted by 10 introns whose locations are identical to the introns in the coding regions of the src genes of human and chicken. the 5' untranslated region is contained on a separate exon with no sequence conservation relative to the corresponding region of the chicken gene. the 5' untranslated region of the xenopus gene contai ... | 1992 | 1437158 |
| [function, molecular structure and gene expression of fibroblast growth factor (fgf/hbgf)]. | the structure and function of members of the fibroblast growth factor (fgf) gene family and their receptors are reviewed. all the member of this gene family bind heparin, and therefore, are also called the as heparin-binding growth factor (hbgf). in this review, the structural features of fgf/hbgf are summarized first, and general features of the structure and function of their receptors are then described briefly. after biological effects of fgf/hbgf on adult-type tissues and cultured cells are ... | 1992 | 1433981 |
| skeletal development in xenopus laevis (anura: pipidae). | postembryonic skeletal development of the pipid frog xenopus laevis is described from cleared-and-stained whole-mount specimens and sectioned material representing nieuwkoop and faber developmental stages 46-65, plus postmetamorphic individuals up to 6 months old. an assessment of variation of skeletogenesis within a single population of larvae and comparison with earlier studies revealed that the timing, but not the sequence, of skeletal development in x. laevis is more variable than previously ... | 1992 | 1433306 |
| kinetic control of 5 s rna gene transcription. | we have determined that the differential transcription of somatic and oocyte-type 5 s rna genes in a xenopus laevis oocyte extract is a consequence of vastly different rates of stable complex assembly. somatic-type 5 s rna genes sequester a limiting transcription factor much more rapidly than oocyte-type 5 s rna genes. once formed, however, transcription complexes on both types of genes are stable, and are transcribed at nearly equivalent rates. the relative rates of stable transcription complex ... | 1992 | 1433283 |
| assembly and disassembly of axonal microtubules of the toad xenopus laevis under the effect of temperature. | in toads xenopus laevis living at 11 degrees (winter), the microtubular density of 4-microns myelinated axons of lumbosacral nerves was assessed with the electron microscope. in controls, the density was 11.2 microtubules/microns2. in nerves incubated at 0 degrees, microtubules decreased following a simple exponential curve with a half time of 4.7 min (k = 0.149 min-1); residual microtubules were 4.5%. after rewarming, the full complement of microtubules reappeared within 60 min. in steady state ... | 1992 | 1431786 |
| genetic and experimental studies on a new pigment mutant in xenopus laevis. | white lethal (wl) is a recessive mutation affecting the differentiation of the three types of chromatophores in xenopus laevis and eventually leading to the death of the mutants around stage 50. melanophores appear at st. 33 but differentiate abnormally, remaining pale grey, and do not proliferate after st. 41. the rare xanthophores present contain only a few differentiated pterinosomes, and the iridophores consist of noniridescent white dots. when the albino gene (ap) is combined with wl, melan ... | 1992 | 1431781 |
| localization of a chymotrypsin-like protease to the perivitelline space of xenopus laevis eggs. | a chymotrypsin-like protease is released from xenopus laevis eggs at activation and is involved in conversion of the vitelline envelope to the fertilization envelope. to localize this enzyme in unactivated and activated eggs, we used the synthetic peptide substrate succinylalanylalanylprolylphenylalanyl-4-methoxy-2-naphthylamide whose product can be visualized using transmission electron microscopy. protease product was localized within the perivitelline space of unactivated eggs, appearing as s ... | 1992 | 1426648 |
| sexually dimorphic expression of a laryngeal-specific, androgen-regulated myosin heavy chain gene during xenopus laevis development. | masculinization of the larynx in xenopus laevis frogs is essential for the performance of male courtship song. during postmetamorphic (pm) development, the initially female-like phenotype of laryngeal muscle (slow and fast twitch fibers) is converted to the masculine form (entirely fast twitch) under the influence of androgenic steroids. to explore the molecular basis of androgen-directed masculinization, we have isolated cdna clones encoding portions of a new xenopus myosin heavy chain (mhc) ge ... | 1992 | 1426643 |
| the rapid transient decrease of sn-1,2-diacylglycerol in progesterone-stimulated xenopus laevis oocytes is the result of an ethanol artifact. | full-grown xenopus laevis oocytes resume meiosis (meiotic maturation) in response to progesterone stimulation. three studies have shown that sn-1,2-diacylglycerol (dag), the intracellular activator of protein kinase c, may be involved in this process (wasserman et al., j. exp. zool. 255, 63-71, 1990; varnold and smith, development 109, 597-604, 1990; stith et al., j. cell physiol. 149, 252-259, 1991). two of these studies (varnold and smith, 1990; stith et al., 1991) found a rapid, but transient ... | 1992 | 1426629 |
| developmental sequence of expression of voltage-dependent currents in embryonic xenopus laevis myocytes. | although the development of several of the voltage-dependent currents in embryonic amphibian myocytes has been described, the overall muscle electrical development, particularly the relative times of expression of different voltage-dependent currents, has not been addressed in a single study under one set of conditions. we have found that, in mesoderm isolated and cultured from neurula stage embryos, myocytes are identifiable before they express voltage-gated currents. these ionic currents are a ... | 1992 | 1426620 |
| assembly of a tail-less mutant of the intermediate filament protein, vimentin, in vitro and in vivo. | recent reports on the possible contribution of the non-alpha-helical carboxy-terminal domain ("tail") of type iii intermediate filament (if) proteins to if assembly have been controversial. to examine the importance and role of this domain, we have therefore engineered a xenopus laevis vimentin cdna to code for a tail-less polypeptide and have used it in combination with prokaryotic and eukaryotic expression systems. here we show that tail-less vimentin, isolated from transfected bacteria (esche ... | 1992 | 1425769 |
| a maternal factor, oz-1, activates embryonic transcription of the xenopus laevis gs17 gene. | we describe the identification of an enhancer sequence and a sequence-specific dna-binding protein required for developmental expression of the xenopus laevis gs17 gene. using microinjection of recombinant plasmids into fertilized frog eggs, we have shown that a 14 base pair ct-rich sequence element, normally located about 700 bases upstream of the gs17 promoter, is sufficient to activate transcription of a heterologous reporter gene in gastrula stage embryos. this regulatory element has been ca ... | 1992 | 1425344 |
| bone morphogenetic protein 4: a ventralizing factor in early xenopus development. | the mesoderm of amphibian embryos such as xenopus laevis arises through an inductive interaction in which cells of the vegetal hemisphere of the embryo act on overlying equatorial and animal pole cells. three classes of 'mesoderm-inducing factor' (mif) that might be responsible for this interaction in vivo have been discovered. these are members of the transforming growth factor type beta (tgf-beta), fibroblast growth factor (fgf) and wnt families. among the most potent mifs are the activins, me ... | 1992 | 1425340 |
| analysis of xwnt-4 in embryos of xenopus laevis: a wnt family member expressed in the brain and floor plate. | this study characterizes the temporal and spatial expression during early xenopus development of xwnt-4, a member of the wnt gene family. the xwnt-4 protein contains all of the sequence motifs that are hallmarks of the wnt gene family and is 84% identical to the mouse homolog, wnt-4. the highest level of xwnt-4 expression occurs during the early neurula stage of development although its expression persists throughout embryogenesis and can be found in the adult testis, brain and epithelium. consi ... | 1992 | 1425335 |
| [ultrastructure of dermal melanophores of xenopus laevis larvae in mitosis]. | 1992 | 1425181 | |
| presence of d-aspartate oxidase and free d-aspartate in amphibian (xenopus laevis, cynops pyrrhogaster) tissues. | 1. this paper is the first report on the presence of d-aspartate oxidase activity and free d-aspartate in the amphibian tissues. 2. the presence of d-aspartate oxidase activity in tissues of clawed toad (xenopus laevis) and japanese newt (cynops pyrrhogaster) was demonstrated by requirements for enzyme activity, selective inhibition with meso-tartrate and substrate specificity. 3. in each animal, the highest activity was found in kidney, followed by liver and brain, and no gender difference in t ... | 1992 | 1424565 |
| large serotonin-like immunoreactive amacrine cells in the retina of developing xenopus laevis. | the earliest appearance of serotonin-like immunoreactivity (sli) in different cell types and the development of large sli amacrine cells were studied in the retina of xenopus laevis from stage 33/34 to adult. intense sli was first found in the somas of large amacrine cells at stage 39. the somas of small amacrine cells showed weak sli at stage 41, followed by bipolar cells at stage 43. the number of large sli amacrine cells in the inner nuclear layer of the retina increased from 57 at stage 40 t ... | 1992 | 1424082 |
| bromodeoxyuridine-immunohistochemistry on cellular differentiation and migration in the fundic gland of xenopus laevis during development. | cellular differentiation and migration in the fundic glands of adult and larval xenopus laevis have been examined using bromodeoxyuridine-immunohistochemistry. in the adult fundic gland, cumulative labeling with bromodeoxyuridine revealed a proliferative cell zone between the surface mucous cells and mucous neck cells, in what is referred to as the neck portion of the gland. the labeling-index of mucous neck cells had rapidly increased by week-5. the labeling-index of oxynticopeptic cells showed ... | 1992 | 1423489 |