| protein kinase c modulates neurotransmitter responses in xenopus oocytes injected with rat brain rna. | oocytes of the frog xenopus laevis express various exogenous neurotransmitter receptors and ion channels when injected with rna from excitable tissues. the oocytes serve as a convenient model system in which modulation of neurotransmitter responses can be studied. we examined the effects of activators and an inhibitor of protein kinase c (pkc) on responses to serotonin (5-ht), acetylcholine (ach), kainate, and gamma-aminobutyric acid (gaba) in oocytes injected with rna from rat brain. the pkc ac ... | 1989 | 2471032 |
| a specific quisqualate agonist inhibits kainate responses induced in xenopus oocytes injected with rat brain rna. | electrophysiological recording was used to study non-n-methyl-d-aspartate (nmda) excitatory amino acid (eaa) receptors after injection of rat brain ribonucleic acid (rna) in xenopus laevis oocytes. quisqualate (qa) induced two types of responses, a smooth one and an oscillatory one. these responses are probably mediated by the ionotropic (qai, a cationic channel) and the metabotropic (qap, a newly discovered receptor coupled to phospholipase c) qa receptors respectively. alpha-amino-3-hydroxy-5- ... | 1989 | 2471121 |
| inhibition of in vivo and in vitro transcription by monoclonal antibodies prepared against wheat germ rna polymerase ii that react with the heptapeptide repeat of eukaryotic rna polymerase ii. | wheat germ rna polymerase ii was used to raise monoclonal antibodies (mabs) that cross-react with the largest subunit of calf thymus rna polymerase ii. most of these mabs were of the igm isotype and were shown to react with a synthetic peptide containing the consensus sequence for the c-terminal heptapeptide repeat that has been found on the largest subunit of rna polymerase ii from a variety of eukaryotic organisms. a representative mab (3wg2) was tested for its effect on transcription in both ... | 1989 | 2472398 |
| expression of cell adhesion molecule e-cadherin in xenopus embryos begins at gastrulation and predominates in the ectoderm. | the expression of the ca2+-dependent epithelial cell adhesion molecule e-cadherin (also known as uvomorulin and l-cam) in the early stages of embryonic development of xenopus laevis was examined. e-cadherin was identified in the xenopus a6 epithelial cell line by antibody cross-reactivity and several biochemical characteristics. four independent mabs were generated against purified xenopus e-cadherin. all four mabs recognized the same polypeptides in a6 cells, adult epithelial tissues, and embry ... | 1989 | 2472408 |
| receptor number determines latency and amplitude of the thyrotropin-releasing hormone response in xenopus oocytes injected with pituitary rna. | trh evokes depolarizing membrane electrical responses in xenopus laevis oocytes injected with rna from pituitary cells. we have shown previously that the amplitude of this response is directly proportional to the dose of trh and the amount of rna injected. herein we show that the number of trh receptors expressed on oocytes after injection of rat pituitary (gh3) cell rna or mouse thyrotropic (ttt) tumor rna determines the latency as well as the amplitude of the response. in oocytes injected with ... | 1989 | 2472551 |
| the yes proto-oncogene is present in amphibians and contributes to the maternal rna pool in the oocyte. | low stringency screening of a cdna library from the frog xenopus laevis with a viral yes oncogene probe resulted in the isolation of clones with restriction maps which were distinct from previously identified x. laevis src cdna clones. the polypeptide produced by in vitro translation of rna synthesized from one of the clones was slightly larger in size than x. laevis pp60src, but gave protease cleavage patterns which were nearly identical to those yielded by pp60src. determination of the dna seq ... | 1989 | 2472592 |
| dual regulation by protein kinase c of the muscarinic response in xenopus oocytes. | muscarinic stimulation of follicle-enclosed oocytes of xenopus laevis results in a complex response that involves both depolarizing and hyperpolarizing currents (dascal and landau 1980). we studied the involvement of protein kinase c (pk-c1) in the regulation of the acetylcholine-evoked rapid (d1) and of the slow (d2) depolarizing chloride (cl-) currents. in oocytes maintained at -100 mv [the reversal potential of potassium (k+) ions] under two electrode voltage clamp, the pk-c activatory 4-beta ... | 1989 | 2472599 |
| excitatory amino acids: the involvement of second messengers in the signal transduction process. | 1. excitatory amino acids (eaa) can activate second messenger systems in addition to a direct gating of ion channels. a discrete coupling between novel eaa receptor subtypes and second messenger systems has been previously proposed. 2. eaas have been suggested to activate both adenylate and guanylate cyclases and also to induce phosphoinositide (pi) turnover. the increased pi turnover was observed in both central neurons and glia, and a "quisqualate-type" receptor has been most frequently involv ... | 1989 | 2472889 |
| persistence and expression of circular dnas encoding drosophila amylase, bacterial chloramphenicol acetyltransferase, and others in xenopus laevis embryos. | we injected circular forms of several different dnas into fertilized eggs of xenopus laevis, and studied the persistence and expression of the injected dnas during early embryonic development. when we injected plasmids which contained drosophila amylase genes, the copy number of the injected dna increased only slightly during cleavage, started to decrease at the blastula stage, then became very small at the tadpole stage. in such embryos, drosophila amylase activity was detected at and after the ... | 1989 | 2472899 |
| junction between parent and daughter axons in regenerating myelinated nerve: properties of structure and rapid axonal transport. | the primary aim of this work was to investigate the properties of rapid axonal transport in regenerating myelinated axons in the sciatic nerve of xenopus laevis, with particular attention to events at the junction between the proximal, intact axon (the "parent") and the distal, newly formed axon (the "daughter"). morphological studies indicated that all myelinated axons initiated regeneration and that at least 80% of these axons regenerated at a rate of 1 mm/day or greater (20 degrees c). the ul ... | 1989 | 2473097 |
| the role of the various human peripheral blood mononuclear cells in the production of sendai virus-induced interferon: ifn mrna studies. | we have studied the relative contribution made to the production of interferon (ifn) in vitro in response to sendai virus by the cells of different types present in human peripheral blood, with particular emphasis on the amounts of poly(a) plus rna extractable from each subpopulation and its content of ifn mrna. peripheral blood cells were fractionated by conventional techniques, and the amounts of ifn made after induction with sendai virus were measured. the proportion of ifn-producing cells in ... | 1989 | 2473143 |
| thyroid hormone induces constitutive keratin gene expression during xenopus laevis development. | we have used in vitro explant cultures of xenopus laevis skin to investigate the role that the thyroid hormone triiodothyronine (t3) plays in activating the 63-kilodalton (kda) keratin genes. the activation of these genes in vivo requires two distinct steps, one independent of t3 and one dependent on t3. in this report we have shown that the same two steps are required to fully activate the 63-kda keratin genes in skin explant cultures, and we have characterized the t3-mediated step in greater d ... | 1989 | 2473388 |
| long-term cultures of neurons from adult frog brain express gaba and glutamate-activated channels. | cells from adult xenopus laevis brainstem and spinal cord were dissociated with mild enzymatic treatment and grown in long-term cell culture. these cells had specific attachment/substrate and medium/serum requirements. cells with bipolar and multipolar morphology were positively identified as neurons using immunohistochemistry with monoclonal antibodies to rat and bovine neurofilament proteins which we show here cross-react with similar amphibian proteins. patch clamp recordings demonstrated tha ... | 1989 | 2474056 |
| cytokeratin filaments and desmosomes in the epithelioid cells of the perineurial and arachnoidal sheaths of some vertebrate species. | using electron microscopy and immunohistochemistry with a large panel of antibodies to various cytoskeletal proteins we have noted that the single- or multi-layered sheaths of epithelioid cells ("neurothelia") surrounding peripheral nerves (perineurial cells) or structures of the central nervous system, including the optic nerve (arachnoid cells), show remarkable interspecies differences in their cytoskeletal complements. in two anuran amphibia examined (xenopus laevis, rana ridibunda), the cell ... | 1989 | 2474473 |
| gene-specific labeling of chromatin for electron microscopy. | in restriction enzyme digested xenopus laevis erythrocyte chromatin, the 5s oocyte genes were specifically labeled with colloidal gold so they could be identified in an electron microscopic study. nuclei were digested first with hindiii restriction endonuclease followed by t7 exonuclease to leave single-stranded 3' tails on the fragments. a biotinylated 15-mer oligonucleotide complementary to the tail on the 3' end of the 5s gene was annealed to the chromatin, and streptavidin complexed colloida ... | 1989 | 2474479 |
| an epithelium-type cytoskeleton in a glial cell: astrocytes of amphibian optic nerves contain cytokeratin filaments and are connected by desmosomes. | in higher vertebrates the cytoskeleton of glial cells, notably astrocytes, is characterized (a) by masses of intermediate filaments (ifs) that contain the hallmark protein of glial differentiation, the glial filament protein (gfp); and (b) by the absence of cytokeratin ifs and if-anchoring membrane domains of the desmosome type. here we report that in certain amphibian species (xenopus laevis, rana ridibunda, and pleurodeles waltlii) the astrocytes of the optic nerve contain a completely differe ... | 1989 | 2474553 |
| mitochondrial gene expression during xenopus laevis development: a molecular study. | mitochondrial gene expression has been analysed during embryonic development of xenopus laevis; the relative amounts of 12s and 16s ribosomal rnas and of most mitochondrial messenger rnas were determined by slot-blot and northern-blot hybridization experiments with specific mitochondrial dna probes. the rrna content per embryo remained constant during early development, confirming earlier results of chase and dawid (1972, dev. biol., 27, 504-518.); on the contrary, all mrnas decreased abruptly a ... | 1989 | 2475342 |
| effects of tha on ionic currents in myelinated axons of xenopus laevis. | in voltage-clamp experiments with the myelinated nerve fibre of xenopus laevis, 9-amino-1,2,3,4-tetrahydroacridine (tha) decreased both na+ and k+ currents and shifted the steady state inactivation potential curve in a negative direction. the effects may be described as (a) a decrease of the permeability constant pna, (b) a modified potential dependence of the inactivating system and (c) a decrease of pk. the na+ system was affected more than the k+ system. | 1989 | 2475350 |
| adenosine 5'-triphosphate activates acetylcholine receptor channels in cultured xenopus myotomal muscle cells. | 1. single-channel currents activated by extracellular adenosine 5'-triphosphate (atp-induced currents) were recorded in cultured muscle cells of xenopus laevis using the cell-attached patch clamp technique. 2. the amplitude histogram of the atp-induced currents had two distinct peaks, corresponding to 60 ps (high-conductance (gamma) channels currents) and 41 ps (low-gamma channel currents). the peak values of the currents were unaltered during 1-6 days in culture. 3. the mean open time of the tw ... | 1988 | 2475606 |
| morphological characterization of substance p-like immunoreactive amacrine cells in the anuran retina. | using substance p immunohistochemistry it was possible to demonstrate a class of morphologically homogeneous group of neurons in the inner nuclear layer (inl) of the retina of two anuran species: xenopus laevis and bufo marinus. the number of cells with substance p-like immunoreactivity (sp-li) was about 250 and 800 in juvenile and 600 and 2500 in adult xenopus and bufo, respectively, sp-li cells had a small soma with one primary dendrite having up to four slender branches, located in the vitrea ... | 1989 | 2475974 |
| angiogenesis on the optic tectum of albino xenopus laevis tadpoles. | developing blood vessels were observed directly on the dorsal surface of the optic tectum of anesthetized, transparent albino xenopus laevis tadpoles, stages 41-54. case histories of individual tadpoles indicated that pial capillaries developed by the classical mechanism of sprouting of endothelial cells from existing blood vessels. 'deep sources' appeared on the tectal surface during development. these were sites of upwelling blood cells from capillaries within the nervous tissue of the tectum ... | 1989 | 2476259 |
| rat brain glutamate receptors activate chloride channels in xenopus oocytes coupled by inositol trisphosphate and ca2+. | 1. ionic currents were studied in xenopus laevis oocytes using the patch-clamp and the whole-cell voltage-clamp techniques. 2. single-channel currents were recorded from the cell-attached patches in oocytes injected with rat brain mrna when glutamate was applied locally outside the patch. the single-channel conductance was 3.66 ps, and the extrapolated equilibrium potential was -23.0 mv, indicating that the channels were chloride selective. 3. single-channel currents with similar characteristics ... | 1989 | 2476556 |
| changes in the patterns of rna synthesis in early embryogenesis of xenopus laevis. | we analyzed the accumulation of newly-synthesized heterogeneous mrna-like rna, 4 s rna, 5 s rna, snrnas and rrna before and after the midblastula transition (mbt) in xenopus laevis embryogenesis. based on the kinetics of the labeling, we concluded that the pattern of rna synthesis in xenopus embryogenesis changes following at least three characteristically different phases. the first phase is the pre-mbt stage, which is characterized by the synthesis of heterogeneous mrna-like rna, accompanied b ... | 1989 | 2478271 |
| expression of intermediate filament proteins during development of xenopus laevis. iii. identification of mrnas encoding cytokeratins typical of complex epithelia. | a xenopus laevis mrna encoding a cytokeratin of the basic (type ii) subfamily that is expressed in postgastrulation embryos was cdna-cloned and sequenced. comparison of the deduced amino acid sequence of this polypeptide (513 residues, calculated mol. wt 55,454; mr approximately 58,000 on sds-page) with those of other cytokeratins revealed its relationship to certain type ii cytokeratins of the same and other species, but also remarkable differences. using a subclone representing the 3'-untransl ... | 1988 | 2478354 |
| cell lineage analysis reveals multipotent precursors in the ciliary margin of the frog retina. | the eyes of lower vertebrates grow throughout life by the proliferation of cells in the ciliary margin. to determine the range of cell types that descend from single cells of the ciliary margin in xenopus laevis embryos, a cell lineage study was performed. precursor cells in the periphery of the eyes were labeled by intracellular injection of rhodamine dextran, and the proliferation of these cells resulted in clones of labeled descendants. the number of cells per clone was quite variable (range, ... | 1989 | 2478403 |
| an antisense transcript from the xenopus laevis bfgf gene coding for an evolutionarily conserved 24 kd protein. | screening of a xenopus laevis oocyte cdna library with a rat basic fibroblast growth factor (bfgf) cdna led to the isolation of a 1.35 kb sequence containing exon iii of the bfgf gene. reverse complementary listing of this sequence revealed a polyadenylated transcript with an open reading frame coding for an unknown protein of mol. wt 24,292 daltons. the coding part of bfgf exon iii is located in this putative mrna in opposite direction within the 3' untranslated region. by hybridization studies ... | 1989 | 2479540 |
| anion transport in oocytes of xenopus laevis induced by expression of mouse erythroid band 3 protein--encoding crna and of a crna derivative obtained by site-directed mutagenesis at the stilbene disulfonate binding site. | a vector was constructed containing a cdna for mouse band 3 obtained from demuth et al. (1986, embo j., 5, 1205-1214), a synthetic linker (containing 5'-non-translated region, start codon and a coding region for the first 12 n-terminal amino acids), and rna polymerase promoters suitable for in vitro transcription of crna. after injection of the crna into the cytoplasm of xenopus oocytes and incubation for 16 h, expression of mouse band 3 was demonstrated by immunoprecipitation, immunohistochemic ... | 1989 | 2479548 |
| [isolation of mrna from protoplasts of spore-forming bacteria and study of its translation products]. | total rna was isolated from the protoplasts of bacillus intermedius 7p which actively produced alkaline exocellular rnase. a fraction of polyadenylated rna was isolated from this rna using chromatography on poly(u) sepharose. the total rna and poly(a) +rna were translated in xenopus laevis oocytes. bacterial exocellular rnase was identified among the products of translation by means of electrophoretic and immunological analyses. the mrna of rnase secreted by b. intermedius 7p was concluded to be ... | 1989 | 2479813 |
| functional expression of mammalian glucose transporters in xenopus laevis oocytes: evidence for cell-dependent insulin sensitivity. | we report the functional expression of two different mammalian facilitative glucose transporters in xenopus oocytes. the rnas encoding the rat brain and liver glucose transporters were transcribed in vitro and microinjected into xenopus oocytes. microinjected cells showed a marked increase in 2-deoxy-d-glucose uptake as compared with controls injected with water. 2-deoxy-d-glucose uptake increased during the 5 days after microinjection of the rnas, and the microinjected rnas were stable for at l ... | 1989 | 2479821 |
| expression of the mammalian na+-independent l system amino acid transporter in xenopus laevis oocytes. | system l is primarily responsible for the na+-independent transport of neutral amino acids, those with bulky chains such as leucine, isoleucine, phenylalanine, etc., into mammalian cells. mrna from rat kidney and human lymphoid cells, when microinjected into xenopus laevis oocytes, induced expression of this transport system. the expressed transport exhibits characteristics similar to those reported for the system l amino acid transporter from a variety of mammalian cells. injection of size-frac ... | 1989 | 2480748 |
| primary structure and developmental expression of a large cytoplasmic domain form of xenopus laevis neural cell adhesion molecule (ncam). | the neural cell adhesion molecule, (ncam), is involved in cell-cell interactions during development of the vertebrate nervous system. ncam exists in multiple protein forms and these are selectively expressed in different cells and at different times during development. here we report the complete amino acid sequence of the large cytoplasmic form of xenopus laevis ncam, derived from a full-length cdna clone. using specific probes the expression of different ncam transcripts during xenopus embryog ... | 1989 | 2481269 |
| membrane currents elicited by prostaglandins, atrial natriuretic factor and oxytocin in follicle-enclosed xenopus oocytes. | 1. membrane currents were recorded from voltage clamped xenopus laevis oocytes, still surrounded by follicular cells, theca and enveloping inner ovarian epithelia (ovarian follicles). 2. superfusing follicles with frog ringer solution containing e-series prostaglandins (pge1 or pge2) or oxytocin (0.5-2 microm) generated slow membrane currents arising from an increase in membrane conductance to k+. 3. follicles taken from different frogs varied greatly in responsiveness to pge and oxytocin. for e ... | 1989 | 2481734 |
| amphibian albumins as members of the albumin, alpha-fetoprotein, vitamin d-binding protein multigene family. | the xenopus laevis 68-kd and 74-kd albumin amino acid sequences are examined with respect to their relationship to the other known members of the albumin/alpha-fetoprotein/vitamin d-binding protein gene family. each of the three members of this family presents a unique pattern of conserved regions indicating a differential selective pressure related to specific functional characteristics. furthermore, an evolutionary tree of these genes was deduced from the divergence times calculated from direc ... | 1989 | 2481749 |
| conformation and dynamics of an rna internal loop. | the conformation and the dynamics of an rna oligonucleotide (26 nucleotides) which is a model for loop e in eukaryotic 5s rna have been investigated by one- and two-dimensional nmr. the central portion of the oligonucleotide contains two g a oppositions, a common feature of ribosomal rnas. the exchangeable proton spectrum indicates that an internal loop separates two stems of four and five base pairs. this observation is not consistent with structures for loop e containing mismatched g.a base pa ... | 1989 | 2482068 |
| mapping of transcription units on xenopus laevis lampbrush chromosomes by in situ hybridization with biotin-labeled cdna probes. | a non-radioactive in situ hybridization method is described for the localization of transcription units of defined genes to lateral loops of xenopus laevis lampbrush chromosomes. two xenopus cdna probes were used encoding the nucleolar protein no38/b23 and cytokeratin 1(8). both proteins are known to be synthesized in xenopus oocytes, and northern blot analysis revealed the presence of the corresponding mrnas in different oogenic stages. the probes were enzymatically labeled with biotin-dctp and ... | 1989 | 2482178 |
| a novel calcium-dependent chloride current in xenopus oocytes injected with brain messenger rna. | 1. membrane currents were studied in voltage-clamped xenopus laevis oocytes which had been injected with total rat brain rna. 2. when the membrane potential was stepped from -100 to +10 mv, two components of outward current were observed which were named tout1 and tout2. 3. both tout1 and tout2 were eliminated in chloride-free or calcium-free media and blocked by 9-anthroic acid, indicating that they represented calcium-dependent chloride currents. 4. both currents were dependent on extracellula ... | 1989 | 2482884 |
| biochemical research on oogenesis. rna accumulation in the oocytes of the newt pleurodeles waltl. | we have compared the accumulation of 5s rna and trna in oocytes of pleurodeles waltl with the corresponding process previously studied in xenopus laevis. 5s rna synthesis is regulated similarly in both species since different families of 5s rna genes are transcribed in oocytes and in somatic cells of p. waltl, as in those of x. laevis. previtellogenic oocytes of p. waltl contain only one prominent kind of storage particles (thesaurisomes). in contrast, x. laevis oocytes of the same size contain ... | 1989 | 2483368 |
| mesoderm-inducing properties of int-2 and kfgf: two oncogene-encoded growth factors related to fgf. | many theories of neoplasia suggest that oncogenic transformations result from aberrations in the control mechanisms which normally regulate growth and differentiation during embryonic development. it has recently become clear that many proto-oncogenes are differentially expressed during embryonic development and may thus be important embryonic regulatory molecules. we report here that the products of two transforming oncogenes int-2 and hst/ks (now called kfgf) can, with different potencies, ind ... | 1989 | 2483371 |
| [aeromonas hydrophila. infection in xenopus laevis]. | aeromonas hydrophila caused severe disease in a group of 50 xenopus leavis three weeks after being transferred from their laboratory conditions. the first clinical signs observed were marked pallor, petechiae, lethargy, anorexia, and edema. the duration of the disease was about 48 days, during which 4 animals acquired the disease and 10 died. the study of the bacteriology of the skin and skeletal muscles showed at necropsy subcutaneous edema, hemorrhage, and ascitis. aeromonas hydrophila was iso ... | 1989 | 2486216 |
| fibroblast growth factor and transforming growth factor beta in early embryonic development. | growth factors are known to have pleiotropic effects on many cell types ranging from the control of cell proliferation to inducing cell differentiation. fgf and tgf beta are members of two growth factor families which are thought to be involved in embryogenesis of the frog, xenopus laevis. these two growth factors are equivalent to the embryonic "morphogen(s)" which induce one of the first differentiation events during embryogenesis, the formation of the mesoderm. embryonic induction events are ... | 1989 | 2491256 |
| homology of the 70-kilodalton antigens from mycobacterium leprae and mycobacterium bovis with the mycobacterium tuberculosis 71-kilodalton antigen and with the conserved heat shock protein 70 of eucaryotes. | two lambda gt11 recombinant clones, jkl2 and jkl15, each containing an insert coding for part of the highly immunogenic 70-kilodalton (kda) protein antigen, were isolated from a mycobacterium leprae genomic library by immunoscreening with the monoclonal antibody l7. clone jkl2 contained the largest insert, 2.3 kilobase pairs. nonoverlapping fragments of this insert were used as probes and showed strong hybridization to a number of mycobacterium tuberculosis-lambda gt11 recombinants producing pro ... | 1989 | 2491836 |
| a "zinc-finger"-type binding domain in tobacco streak virus coat protein. | tobacco streak virus (tsv) rna and alfalfa mosaic virus (aimv) rna will replicate only if a few copies of their coat proteins are bound to the rna. to understand this phenomenon experiments were performed to find unique features of the tsv and aimv subunits. atomic absorption analysis showed that tsv and aimv contained substantial quantities of zinc in native virions (approximately one zinc atom per four protein subunits in tsv and one zinc atom per two protein subunits in aimv), while other pla ... | 1989 | 2491924 |
| structure of the ngfi-a gene and detection of upstream sequences responsible for its transcriptional induction by nerve growth factor. | the ngfi-a gene encodes a "zinc-finger" protein that is rapidly induced by nerve growth factor (ngf) in pc12 rat pheochromocytoma cells. the complete exon/intron organization and nucleotide sequence of the rat ngfi-a gene have been determined. the gene spans 3789 nucleotides (nt) and is interrupted by a single intron at nt 588. all three zinc-finger dna-binding domains are contiguously coded for within the 3' exon; this is in contrast to the structure described by others for the xenopus laevis t ... | 1989 | 2492104 |
| lipoxygenase metabolism of polyunsaturated fatty acids in oocytes of the frog xenopus laevis. | recently, oocytes or eggs of two marine invertebrates have been found to metabolize arachidonic acid to specific monohydroxy products. these studies have prompted our examination of the oocytes of higher organisms. in the present study, oocytes of an amphibian, xenopus laevis, were examined for their capacity to biosynthesize hydroxyeicosatetraenoic acids (hetes) and related hydroxy fatty acids. two hydroxyeicosanoids were formed during incubations of oocyte homogenates with [14c]arachidonic aci ... | 1989 | 2492416 |
| retinal melatonin is metabolized within the eye of xenopus laevis. | retinal synthesis of melatonin, a potent modulator of rhythmic retinal processes, is elevated at night as a result of regulation by a circadian clock. despite high nocturnal synthetic capacity, both melatonin content and release are low in the retina of the frog xenopus laevis. we report here that cultured eyecups from xenopus have the capacity for rapid metabolic breakdown of melatonin. pharmacological analysis indicates that the initial step in this degradation pathway is deacetylation of mela ... | 1989 | 2492661 |
| thyroid hormone directly induces hepatocyte competence for estrogen-dependent vitellogenin synthesis during the metamorphosis of xenopus laevis. | hepatocytes competent for estrogen-dependent vitellogenin synthesis appeared and increased in number in the liver at the metamorphic climax of xenopus laevis (a. kawahara, s. kohara, y. sugimoto, and m. amano, 1987, dev. biol. 122, 139-145). the present study was conducted to determine whether cells competent for vitellogenin synthesis could be induced by thyroid hormone in a primary culture of larval hepatocytes. the thyroid hormone, triiodothyronine (t3), directly induced the competent cells i ... | 1989 | 2492962 |
| activators of protein kinase c trigger cortical granule exocytosis, cortical contraction, and cleavage furrow formation in xenopus laevis oocytes and eggs. | prophase i oocytes, free of follicle cells, and metaphase ii eggs of the amphibian xenopus laevis were subjected to transient treatments with the protein kinase c activators, phorbol 12-myristate 13-acetate (pma), phorbol 12,13-didecanoate, and 1-olyeoyl-2-acetyl-sn-glycerol. in both oocytes and eggs, these treatments triggered early events of amphibian development: cortical granule exocytosis, cortical contraction, and cleavage furrow formation. surprisingly, activation of oocytes occurred in t ... | 1989 | 2493460 |
| molecular cloning and sequence determination of a cdna coding for the alpha-subunit of a go-type protein of xenopus laevis oocytes. | xenopus laevis oocytes are cells ideally suited to the study of signal transduction and of the g-proteins that are involved in this process. a x. laevis cdna library in lambda gt10 has been screened with a mixture of three oligonucleotide probes designed to detect sequences found in various mammalian alpha-subunits of g-proteins. one of these clones has been purified through tertiary screening and the dna insert has been sequenced. this clone was found to include the total sequence coding for a ... | 1989 | 2494063 |
| regulation of lacz mrna translatability in a cell-free system at heat shock by the last four sense codons. | under heat shock conditions translation of xenopus laevis normal mrnas in a rabbit reticulocyte cell-free system is blocked whereas hsp70 mrna is translated. mrna for e. coli beta-galactosidase containing the last four sense codons of drosophila hsp70 at its 3'-end was constructed. this mrna is efficiently translated in a rabbit reticulocyte cell-free system at 43 degrees c. | 1989 | 2497030 |
| synthesis and activity of xenopus laevis oocyte tyrosinase. | this study investigates the mechanisms that control pigment synthesis in xenopus laevis oocytes. although we find the molecular weight of oocyte tyrosinase to be similar to that of amphibian skin, we were unable to increase its activity by proteases or detergents, as has been reported for skin tyrosinase. on the other hand, by measuring the activity of polysomal-bound enzyme, we were able to correlate increased tyrosinase activity with increased levels of enzyme synthesis. we therefore suggest t ... | 1989 | 2498458 |
| [role of c-myc protein in the early embryonic development of xenopus]. | microinjections of antibodies directed against the protein encoded by the c-myc protooncogene strongly inhibit or arrest the early cell cleavage stage of xenopus laevis embryos. injections in one blastomere of a two cell stage embryo inhibit the segmentation of this blastomere. the cleavage of the uninjected blastomere behaves normally. injections of control rabbit immunoglobulins do not alter the embryonic development. | 1989 | 2499407 |
| the two xenopus laevis src genes are co-expressed and each produces functional pp60src. | the haploid genome of xenopus laevis contains two src genes, and transcripts from both genes are found in the maternal rna pool of the oocyte (steele, r. e. (1985) nucleic acids res. 13, 1747-1761). we have now isolated cdna clones which contain complete coding sequences from both src mrnas. in vitro translation of rnas transcribed in vitro from these clones produces in each case a protein with an apparent molecular mass of 57 kda. the in vitro-synthesized proteins show identical protease cleava ... | 1989 | 2499582 |
| increased levels of leukotriene c4 in retinal pigment epithelium are correlated with early events in photoreceptor shedding in xenopus laevis. | the levels of 5-lipoxygenase products of arachidonic acid, leukotriene (lt) b4 and ltc4 in retinal pigment epithelia (rpe) from xenopus laevis were measured by radioimmunoassay (ria). rpe were isolated during various stages of photoreceptor renewal to determine possible alterations in 5-lipoxygenase activity concurrent with photoreceptor detachment and phagocytosis. both ltc4 and ltb4 were released to rpe incubation media, although levels of ltb4 in unstimulated rpe were close to the limits of d ... | 1989 | 2501069 |
| induction of glucose-regulated proteins in xenopus laevis a6 cells. | we have characterized the induction of glucose-regulated proteins (grps) in xenopus laevis a6 cells, a kidney epithelial cell line. exposure of a6 cells to medium in which 2-deoxyglucose replaced galactose resulted in enhanced synthesis of two proteins at 78 and 98 kd. the 78 kd protein was determined by two-dimensional page to consist of two isoelectric variants with pls of 5.3 and 5.2 whereas the 98 kd protein resolved into a single spot with a pl of 5.1. the 78 kd protein cross-reacted with a ... | 1989 | 2501316 |
| spatial and temporal expression of phosphorylated and non-phosphorylated forms of neurofilament proteins in the developing nervous system of xenopus laevis. | immunocytochemical studies of developing xenopus laevis embryos and tadpoles (stages 12 1/2 to 46) were performed using a panel of 11 monoclonal antibodies to phosphorylated and non-phosphorylated forms of the neurofilament proteins. these included nine antibodies to the middle molecular weight neurofilament protein (xnf-m, 175 kda), and two additional antibodies to non-phosphorylated forms of the other two neurofilament proteins (xnf-l, 73 kda; xnf-h, 205 kda). the developmental expression of x ... | 1989 | 2502330 |
| impact of altered protein structures on the intracellular traffic of a mutated vasopressin precursor from brattleboro rats. | the rat vasopressin precursor, synthesized in the reticulocyte lysate system under the direction of in vitro transcribed mrna, is processed and correctly delivered to the lumen of added microsomal vesicles. translation of mrna for the mutant (brattleboro) vasopressin precursor which lacks a translational stop codon as a consequence of a frame-shift mutation, gives rise to a mutated protein (b-mutant precursor) with a c-terminal poly(lysine) sequence encoded by the poly(a) tail. upon addition of ... | 1989 | 2502393 |
| synthesis and pathway of luciola mingrelica firefly luciferase in xenopus laevis frog oocytes and in cell-free systems. | poly (a+)rna was isolated from the lanterns of adult fireflies of l. mingrelica. the poly (a+)rna was translated in a cell-free translation mixture from rabbit reticulocyte and from krebs ii mouse ascites cells and in xenopus laevis frog oocytes. the synthesis of the enzymatically active firefly luciferase was demonstrated in all systems. in the cell-free systems a maximal quantity of luciferase is synthesized during the first 1-2 h, then the decreasing activity of luciferase is observed. the op ... | 1989 | 2503063 |
| evolutionary conserved modules associated with zinc fingers in xenopus laevis. | many dna-binding proteins that are involved in the differential regulation of gene expression are composed of multiple discrete modules. association of the homeobox-encoded helix-turn-helix dna-binding motif with conserved modules, such as the paired box or the pou domain, has led to the definition of structurally and functionally related subfamilies of regulatory proteins. the zinc finger, which is the second major nucleic acid-binding motif characterized to date, defines large multigene famili ... | 1989 | 2503827 |
| biosynthesis of sulfated proteoglycans in amphibian embryonal cells. | the synthesis of sulfated proteoglycans in small explants from various parts of late blastulae from ambystoma mexicanum or xenopus laevis was investigated by incorporation of radioactive sulfate or glucosamine and galactosamine in media of low, normal or high tonicity. the explants differentiated into ciliated aggregates of fibroblast-like cells, or remained undifferentiated depending upon their origin in the embryo. high tonicity induces the explants to dissociate and prevents morphological dif ... | 1989 | 2504303 |
| lh-stimulation of the adenylyl cyclase system in follicles and oocytes of xenopus laevis. | the presence of an adenylyl cyclase sensitive to lh in xenopus laevis is studied. the assay for adenylyl cyclase in membranes and homogenates from xenopus laevis follicles and oocytes is characterized and the aim is centered on the appearance of lh-response through oogenesis. the results show a stimulation by lh in whole follicle and oocytes surrounded by the follicle cells. the oocytes become responsive to lh from stage iii onwards, suggesting an action of the gonadotropin on the monolayer of f ... | 1989 | 2505348 |
| dendritic morphology of identified retinal ganglion cells in xenopus laevis: a comparison between the results of horseradish peroxidase and cobaltic-lysine retrograde labelling. | following the application either of cobaltic-lysine complex or a 30% solution of horseradish peroxidase (hrp) in a sealed tube to the cut end of the optic nerve of young adult xenopus frogs, the dendritic morphology of large ganglion cells was studied in retinal wholemount preparations, and compared with that in animals of the same size as revealed by the short time administration of hrp crystals. in the former two groups of animals, after 24 h survival, the size of the dendritic arborization of ... | 1989 | 2505823 |
| two calcium-activated chloride conductances in xenopus laevis oocytes permeabilized with the ionophore a23187. | 1. currents evoked by elevated intracellular free ca2+ in xenopus laevis oocytes were studied using the two-electrode voltage clamp technique. the elevation in ca2+ concentration was achieved in three ways: by the use of the divalent cation ionophore a23187; by application of ca2+-mobilizing neurotransmitters serotonin and acetylcholine (ach); by the entry of ca2+ through voltage-dependent channels. 2. in most experiments, the membrane was permeabilized to ca2+ by a 15 min pretreatment with a231 ... | 1989 | 2506341 |
| cytostatic factor (csf) in the eggs of xenopus laevis. | cytostatic factor (csf) in unfertilized egg cytoplasm causes metaphase arrest when microinjected into zygotes. this was originally described in rana pipiens eggs in xenopus laevis, csf has also been demonstrated. but only when the calcium-chelating agent, egta, was injected into the egg cytoplasm. in the present study, however, csf was demonstrated in xenopus eggs when donor egg activation was prevented by treatment with co2 and mg2+ instead of by egta, and recipient blastomere degeneration was ... | 1989 | 2509228 |
| second-order repeats in xenopus laevis finger proteins. | the primary structure of 342 finger repeats encoded in 42 different cdna clones isolated from xenopus laevis oocyte and gastrula cdna libraries has been determined. comparative sequence analysis of the predicted protein sequences results in a consensus repeat sequence that has an extended conserved segment of 16 amino acid residues, including the evolutionary conserved h/c link element, connected to a highly variable segment that is located in the finger loop region. groups of tandem finger repe ... | 1989 | 2509712 |
| retino-retinal projections in three anuran species. | in juvenile and adult xenopus laevis, in adult bufo marinus and rana esculenta frogs retino-retinal projections were traced by filling the central stump of one optic nerve, cut 2-3 mm from the eye, with horse-radish peroxidase (hrp) or cobaltic-lysine complex (clc). the presence of retino-retinal projections was confirmed in all 3 species both in the juvenile and the adult. up to 12 ganglion cells per retina were found to be filled retrogradely with hrp together with optic axons filled anterogra ... | 1989 | 2510094 |
| evolution of immunoglobulin genes: vh families in the amphibian xenopus. | we have isolated multiple independent cdna clones that represent mrna sequences of immunoglobulin heavy chains from the spleen of adult xenopus laevis. these cdna clones contained constant (c) region sequences that were either cmu or a separate c region sequence believed to be cnu. in individual cdna clones the c region sequences were associated with independent heavy-chain variable region (vh) sequences that were classifiable into five distinct families. genomic southern blotting analyses with ... | 1989 | 2510156 |
| lysine 539 of human band 3 is not essential for ion transport or inhibition by stilbene disulfonates. | the anion transporter from human red blood cells, band 3, has been expressed in xenopus laevis frog oocytes microinjected with mrna prepared from the cdna clone. about 10% of the protein is present at the plasma membrane as determined by immunoprecipitation of covalently bound 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (dids) with anti-dids antibody. the expressed band 3 transport chloride at a rate comparable to that in erythrocytes. transport of chloride is inhibited by stilbene disulfo ... | 1989 | 2511191 |
| consensus peptide antibodies reveal a widespread occurrence of ca2+/lipid-binding proteins of the annexin family. | antibodies generated against synthetic peptides that correspond to highly conserved sequence motifs in the annexins reacted with a variety of annexins from different species. these include xenopus laevis and drosophila melanogaster, which contain cross-reacting polypeptides of apparent mr 34,000 and 30,000. as expected for typical annexins, the two drosophila proteins interact in a ca2+-dependent manner with phosphatidylserine liposomes. | 1989 | 2513230 |
| neurons expressing thyrotropin-releasing hormone-like messenger ribonucleic acid are widely distributed in xenopus laevis brain. | neurons containing messenger ribonucleic acid encoding thyrotropin-releasing hormone (trh) in the brain of xenopus laevis were visualized using in situ hybridization histochemistry. trh-like mrna-containing cells were detected in each coronal section tested, from the rostral tip of the telencephalon to the brainstem. in the telencephalon, labeled cells were observed in the olfactory nucleus, nucleus accumbens, striatum, diagonal band, and amygdala. many intensely labeled cells were found in the ... | 1989 | 2513244 |
| on the coupling between dna replication and mitosis. | the rapid, early cell divisions in xenopus laevis embryos are driven by an inflexible oscillator that is not influenced by the state of the dna. in contrast, mitosis in somatic cells can be prevented by blocking replication or by damaging the dna through irradiation. we have investigated the transition from the rapid, early cell cycle to the slower, more somatic-like cell cycle that occurs after division twelve in developing xenopus embryos, a stage called the mid-blastula transition (mbt). when ... | 1989 | 2517560 |
| comparative lectin-binding patterns in the epidermis and dermal glands of bufo bufo (l.) and xenopus laevis (daudin). | bouin-fixed and paraffin-embedded sections from the dorsal skin of bufo bufo and xenopus laevis were subjected to lectin histochemistry. a panel of biotinylated lectins (con-a, psa, lca, uea-i, dba, sba, sja, rca-i, bsl-i, wga, s-wga, pha-e and pha-l) and an avidin-biotin-peroxidase complex (abc) showed a species-specific compartmentalization of saccharides to certain parts of the epidermis and glandular domains. some marked histochemical differences between the two examined species adapted to f ... | 1989 | 2517585 |
| intracellular calcium and tension during fatigue in isolated single muscle fibres from xenopus laevis. | 1. single muscle fibres were dissected from xenopus lumbrical muscles and microinjected with the photoprotein aequorin in order to measure the myoplasmic free calcium concentration ([ca2+]i). fatigue was produced by repeated intermittent tetanic stimulation continued until tension had declined to approximately 50% of the initial level. fibres were then allowed to recover by giving tetani at less frequent intervals. aequorin light (a measure of [ca2+]i) and tension were measured during fatiguing ... | 1989 | 2517988 |
| the morphological characterization and distribution of displaced ganglion cells in the anuran retina. | the number, dendritic morphology, and retinal distribution of displaced ganglion cells were studied in two anuran species, xenopus laevis and bufo marinus. horseradish peroxidase or cobaltic lysine complex was applied to the cut end of the optic nerve, and the size, shape, and retinal position of retrogradely filled ganglion cells displaced into the inner nuclear layer were determined in retinal wholemount and sectioned material. approximately 1% of ganglion cells in xenopus and 0.1% in bufo wer ... | 1989 | 2518634 |
| developmental expression of the protein product of vg1, a localized maternal mrna in the frog xenopus laevis. | vg1 is a maternal mrna localized in the vegetal cortex of xenopus laevis oocytes, that encodes a protein homologous to the mammalian growth factor tgf-beta. using a polyclonal antibody to a t7-vg1 fusion protein, we have identified the native protein. we find that a single protein of mr 40 kd is immunoprecipitated following in vitro translation of oocyte poly(a)+ rna, whilst two proteins of mr 45 and 43.5 kd are immunoprecipitated from oocyte and embryo extracts. synthesis of at least the 40 kd, ... | 1989 | 2519512 |
| recombinant soluble fc epsilon receptor ii (fc epsilon rii/cd23) has ige binding activity but no b cell growth promoting activity. | we have undertaken the production of recombinant soluble fc epsilon receptor ii (fc epsilon rii) as a secretory protein, but not as a cleavage product of membrane-bound receptor. several plasmid constructs containing soluble receptor sequence were prepared. only a chimeric gene containing the sequences encoding il-6 signal peptide and the soluble moiety of fc epsilon rii could be expressed in xenopus laevis oocytes and cho cells, resulting in the secretion of soluble fc epsilon rii. the recombin ... | 1989 | 2523938 |
| in vivo photocrosslinking reveals that transcription factor binding to the mammalian atf recognition sequence is required for e1a-induced transactivation in injected xenopus laevis oocytes. | the adenovirus e1a 13s mrna product transactivates genes injected into xenopus laevis oocytes that are normally e1a-inducible in mammalian cells. however, e1a-stimulated transcription, but not basal (uninduced) transcription, was inhibited if oocytes were incubated in the presence of protein synthesis inhibitors. this suggests that a cellular protein(s) is required for e1a-induced transactivation, but that it is dispensable for basal transcription. in order to identify such a protein from xenopu ... | 1989 | 2526318 |
| aldosterone binding sites along nephron of xenopus and rabbit. | distal segment of several amphibians exhibits aldosterone-modulated ion transport properties. on the other hand, a6 cells, derived from xenopus laevis (xl) kidney, are aldosterone sensitive. we examined the distribution of aldosterone binding sites in isolated tubules of xl compared with rabbit. after incubation with 2 nm [3h]aldosterone, microdissected tubular segments from proximal (pt), distal straight segment (dst), and flask cell collecting (ct) tubules from xl and from rabbit cortical thic ... | 1989 | 2526595 |
| xenopus homolog of the mos protooncogene transforms mammalian fibroblasts and induces maturation of xenopus oocytes. | the oncogene v-mos transforms mammalian fibroblasts and encodes a serine/threonine protein kinase. expression of the c-mos protooncogene is most abundant in germ cells, suggesting a normal role for c-mos in meiosis. here we describe the isolation of cdna clones containing the complete coding region of the xenopus laevis homolog of c-mos (mosxe). the mosxe gene is transforming when introduced into murine nih 3t3 cells, and transformation is abrogated by a lysine-to-arginine mutation in the canoni ... | 1989 | 2527365 |
| histochemistry and isomyosins of tail musculature in xenopus. | the main bulk of the larval tail in xenopus laevis is composed of thick muscle fibres which are succinate dehydrogenase (sdh) negative and show strong positive atpase activity only at alkaline preincubation (ph 10.4). the thin muscle fibres (which cover the surface of the myotomes and extend to the tail tip) show positive sdh activity as well as strong positive atpase activity after both alkaline and acid preincubations (ph 10.4, 4.5, 4.4, and 4.3). the pattern of myosin isoenzymes does not chan ... | 1989 | 2527868 |
| aldosterone receptors in a6 cells: physicochemical characterization and autoradiographic study. | the a6 cell line is derived from the kidney of xenopus laevis. aldosterone increases sodium transport across a6 cell epithelia. in the present study, aldosterone binding characteristics were studied in a6 cell cytosol. both type i (mineralocorticoid) and type ii (glucocorticoid) receptors are present in the cytosolic fraction of these cells. aldosterone and corticosterone had a high affinity for type i sites (kd = 1.25 and 0.16 nm, respectively) and a lower affinity for type ii sites (kd = 39 an ... | 1989 | 2529773 |
| immunohistochemical localization of beta-endorphin-like material in the urodele and anuran amphibian tissues. | in the present study, we have localized for the first time beta-endorphin (beta-ep)-like material in the adult and larval urodele and anuran tissues using immunohistochemical techniques. in the adult notophthalmus viridescens and ambystoma mexicanum, strong immunoreactivity to beta-ep antisera was observed in the region of the intermediate lobe, the latter fluorescing as a discrete body. the fluorescence was confined to the periphery of the cells, while the nuclei and the immediately surrounding ... | 1989 | 2530130 |
| molecular characterization of the murine interferon gamma receptor cdna. | interferon gamma receptors (ifn-gamma r) exhibit remarkable species specificity. in order to understand the basis for this phenomenon, we have isolated a recombinant cdna clone corresponding to the mouse (mu) ifn-gamma r. microinjection of the mrna synthesized in vitro corresponding to the cloned cdna into xenopus laevis oocytes resulted in the synthesis of a protein that specifically binds mu-ifn-gamma. analysis of murine genomic and rna blots with the cdna probe indicates the presence of a sin ... | 1989 | 2530216 |
| ontogenetic development of s-antigen- and rod-opsin immunoreactions in retinal and pineal photoreceptors of xenopus laevis in relation to the onset of melatonin-dependent color-change mechanisms. | in xenopus laevis daud., the ontogenetic occurrence of two photoreceptor-specific proteins, s-antigen and rod-opsin, was investigated and correlated to the maturation of the neurohormonal effector system involved in melatonin-dependent color-change mechanisms. tadpoles ranging from stage 12 to 57 (nieuwkoop and faber 1956) were fixed in zamboni's or bouin's solution. frozen or paraffin sections of either total heads or dissected brains and eyes were prepared and treated with highly specific anti ... | 1989 | 2531037 |
| an abundant u6 snrnp found in germ cells and embryos of xenopus laevis. | the particle state of u snrnps was analyzed in oocytes, eggs, embryos and testes from xenopus laevis. in each case both the relative abundance and the composition of some u snrnps were found to differ from that of somatic cells. u2 and u6 snrnps were the most prominent u snrnps in germ cells and early embryos. in particular, the concentration of u6 snrna was 10-20 times higher than that of u4 snrna. most of the u6 snrna was not associated with u4 snrna and migrated on sucrose gradients as a u6 s ... | 1989 | 2531660 |
| thyroid function and immune reactivity during metamorphosis in xenopus laevis, the south african clawed toad. | high plasma titers of thyroid and adrenocorticoid hormones are present during the metamorphosis of xenopus laevis. here we examine the influence of thyroid hormones on several features of immune reactivity during this period, e.g., the capacity of thymus-derived immunocytes to reduce (immune suppression) or amplify (helper function) antibody production. further, we test whether thyroid hormone is able to modulate the expression of putative interleukin 2 (il-2) receptors on lectin-activated adult ... | 1989 | 2532164 |
| sequence-specific methylation in a downstream region of the late e2a promoter of adenovirus type 2 dna prevents protein binding. | in studies on the promoter-inhibitory effect of sequence-specific dna methylations, the late e2a promoter of human adenovirus type 2 (ad2) has been used as an experimental tool. upon the in vitro methylation of 5'-ccgg-3' (hpaii) sequences at nucleotides +24, +6 and -215 relative to nucleotide + 1, the site of transcriptional initiation, promoter inhibition or inactivation has been demonstrated in transient expression tests in xenopus laevis oocytes (langner et al., 1984), in mammalian cells (la ... | 1989 | 2532258 |
| ontogeny and tissue distribution of leukocyte-common antigen bearing cells during early development of xenopus laevis. | to analyze the ontogenic emergence of leukocytes during early development, a mouse monoclonal antibody (igg1), designated as xl-1, was produced against the peritoneal macrophages of adult xenopus laevis. the xl-1 determinant was expressed on all types of leukocytes, including lymphocytes, granulocytes, thrombocytes and macrophages, but not on erythrocytes of either larvae or adults. immunohistochemical observations of the hemopoietic organs revealed that the xl-1+ cells with granulocyte and/or m ... | 1989 | 2533066 |
| purification and characterization of a novel protein phosphatase highly specific for ribosomal protein s6. | ribosomal protein s6 is the principal phosphoprotein of the eucaryotic ribosome that becomes multiply phosphorylated on serine residues in response to a wide variety of mitogenic stimuli. in this paper the principal protein phosphatases able to dephosphorylate s6 were characterized in xenopus laevis ovary and eggs. two enzymes termed peak i and peak ii were found to account for most s6 phosphatase activity in both oocytes and eggs. the peak i enzyme had an apparent mr of 200,000 on gel filtratio ... | 1989 | 2535837 |
| supercoiled loop organization of genomic dna: a close relationship between loop domains, expression units, and replicon organization in rdna from xenopus laevis. | analysis of the organization of a specific chromosomal gene, the gene for rrna in xenopus laevis, has evidenced a close relationship between loop organization, replication organization, and expression units. the nontranscribed spacer appears to be involved in all three levels of organization. furthermore the replication origin region appears to be involved in nuclear matrix anchorage and is closely related to the 40 s transcription promoter. this organization suggests how expression domains may ... | 1989 | 2536612 |
| outer segment growth and periciliary vesicle turnover in developing photoreceptors of xenopus laevis. | it has been proposed that periciliary vesicles in the photoreceptor inner segment represent newly synthesized membrane en route to the outer segment, and that membrane is delivered to the outer segment via fusion of these vesicles with the plasma membrane at the base of the connecting cilium and sclerad flow of the ciliary membrane. the present research was undertaken to test the periciliary vesicle hypothesis and clarify the dynamics of membrane flow in vertebrate photoreceptors. light- and ele ... | 1989 | 2538237 |
| okadaic acid, a specific protein phosphatase inhibitor, induces maturation and mpf formation in xenopus laevis oocytes. | micro-injection of, or incubation with okadaic acid (oa), a specific phosphatase inhibitor, can induce formation of maturation-promoting factor (mpf) and germinal vesicle breakdown (gvbd) in xenopus laevis oocytes. comparison of the dose-response curves of oa on maturation, isolated enzymes and phosphatase activities in crude oocyte preparations suggests that inhibition of both polycation-stimulated (pcs) and atp,mg-dependent (amd) phosphatases is sufficient but requires that a critical phosphor ... | 1989 | 2538367 |
| metabolic regulation during early frog development: glycogenic flux in xenopus oocytes, eggs, and embryos. | 32p-labeled glucose 6-phosphate and phosphoenolpyruvate were injected into oocytes, fertilized eggs, and early embryos of xenopus laevis, and the 32p label was followed into glycolytic enzymes and acid-soluble metabolites. the kinetics of labeling of phosphoglucomutase and phosphoglyceromutase and the formation of specific metabolites were used to measure carbon flux through glycolytic intermediates in these cells. in full-grown stage vi oocytes, fertilized eggs, and cells of cleaving embryos, c ... | 1989 | 2538374 |
| metabolic regulation during early frog development: flow of glycolytic carbon into phospholipids in xenopus oocytes and fertilized eggs. | 32p-labeled glucose 6-phosphate, [32p]phosphoenolpyruvate, and [gamma-32p]atp were injected into oocytes and fertilized eggs of xenopus laevis, and the incorporation of the 32p label was followed into phospholipids. several classes of phospholipids incorporated 32p label from the injected glycolytic intermediates, including lysophosphatidic acid, phosphatidic acid, phosphatidylinositol, and phosphatidylinositol phosphates, inferring de novo synthesis of these lipids from dihydroxyacetone phospha ... | 1989 | 2538375 |
| a high molecular weight topoisomerase i from xenopus laevis ovaries. | dna topoisomerase i has been purified from homogenates of mature xenopus laevis ovaries. the initial stages in purification of the native enzyme employed a rapid series of three chromatographic steps, followed by gel filtration performed in the presence of sodium dodecyl sulfate. polypeptides that might represent topoisomerase i were identified by specific labeling of the topoisomerase species with radioactive dna. sodium dodecyl sulfate-polyacrylamide gel electrophoresis of topoisomerase i radi ... | 1989 | 2538454 |
| 28 s ribosomal rna in vertebrates. locations of large-scale features revealed by electron microscopy in relation to other features of the sequences. | the 28 s rrna from several vertebrate species, when examined by electron microscopy, is seen to contain regions of extensive secondary structure, as first reported for hela-cell 28 s rrna by wellauer & dawid [(1973) proc. natl. acad. sci. u.s.a. 70, 2827-2831]. here we correlate the locations of these regions, determined from the electron-microscopic data, with the primary structure of 28 s rrna from human, mouse and xenopus laevis determined by sequence analysis of rdna. the secondary-structure ... | 1989 | 2539104 |
| angiotensin ii stimulates an endogenous response in xenopus laevis ovarian follicles. | while responses to angiotensin ii have previously been induced in xenopus laevis oocytes after injection of messenger rna extracted from mammalian tissue, no endogenous responses of ovarian tissue to this hormone have been reported. here we describe such an endogenous dose-dependent response to angiotensin ii, detected by conventional electrophysiological techniques, in follicular oocytes. the ed50 of the response was estimated to be 0.15 +/- 0.07 microm (s.e.m.). maximal depolarization, obtaine ... | 1989 | 2539118 |
| the action of pyrethroids on sodium channels in myelinated nerve fibres and spinal ganglion cells of the frog. | the interaction of pyrethroids with the voltage-dependent sodium channel was studied in voltage-clamped nodes of ranvier and isolated spinal ganglion neurons of the clawed frog, xenopus laevis. in the node, pyrethroids prolonged the sodium tail current associated with a step repolarization of the membrane. it was found that the amplitude of the slow, pyrethroid-induced, sodium tail current (pit) first increased and then decreased as a function of the duration of membrane depolarization (to -5 mv ... | 1989 | 2539885 |
| factors that regulate the activity of the phosphatidylinositol kinase present in oocyte membranes of xenopus laevis. | 1. phosphatidylinositol kinase present in the membranes of xenopus laevis oocytes was characterized. 2. the enzyme requires mg2+ or mn2+ at 10 mm and exogenous phosphatidylinositol (50 microm) increases the formation of phosphatidylinositol-4-phosphate. 3. the oocyte phosphatidylinositol kinase cannot use gtp as a phosphate donor but this compound inhibits competitively the utilization of atp. 4. addition of phosphatidylserine and phosphatidylinositol-4,5-bisphosphate stimulates the phosphorylat ... | 1989 | 2539941 |
| replication of plasmid dna in fertilized xenopus eggs is sensitive to both the topology and size of the injected template. | the behavior of various plasmid templates was examined following their microinjection into fertilized eggs of the frog xenopus laevis using an assay that permits the examination of both replicated and unreplicated plasmids in single eggs. our results show that both the size and the topology of the template drastically affect the fate of the injected plasmid. only a small proportion of injected monomeric supercoiled plasmids underwent replication during 6 h of incubation, although not all injecte ... | 1989 | 2539959 |
| analysis of histamine as a hair-cell transmitter in the lateral line of xenopus laevis. | the actions of histamine and histamine antagonists on afferent nerve activity were investigated in the lateral line of xenopus laevis. histamine (0.002-2.0 mm) had no effect on spontaneous activity or excitatory responses to water motion. in contrast, pyrilamine, an h1 receptor antagonist, suppressed spontaneous activity beginning at 0.01-0.05 mm. below 0.3 mm the suppression was often preceded by a small excitatory response and responses to high (24-30 db re threshold), but not low (0-18 db) le ... | 1989 | 2540134 |