Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| metaphase protein phosphorylation in xenopus laevis eggs. | cytoplasmic extracts of metaphase (m-phase)-arrested xenopus laevis eggs support nuclear envelope breakdown and chromosome condensation in vitro. induction of nuclear breakdown is inhibited by ampp(nh)p, a nonhydrolyzable atp analog, but not by atp or gamma-s-atp, a hydrolyzable atp analog, suggesting that protein phosphorylation may be required for m-phase nuclear events in vitro. by addition of [gamma-32p]atp, we have identified in cytoplasmic extracts and in intact eggs at least six phosphopr ... | 1987 | 3821728 |
| examination of heat shock protein mrna accumulation in early xenopus laevis embryos. | elevation of the incubation temperature of xenopus laevis neurulae from 22 to 33-35 degrees c induced the accumulation of heat shock protein (hsp) 70 mrna (2.7 kilobases (kb)) and a putative hsp 87 mrna (3.2 kb). while constitutive levels of both hsp mrnas were detectable in unfertilized eggs and cleavage-stage embryos, heat-induced accumulation was not observed until after the mid-blastula stage. exposure of xenopus laevis embryos to other stressors, such as sodium arsenite or ethanol, also ind ... | 1987 | 3828114 |
| relation between force and calcium ion concentration in different fibre types of the iliofibularis muscle of xenopus laevis. | calcium activated isometric force was measured in segments of single muscle fibres of the iliofibularis muscle of xenopus laevis skinned by freeze-drying. a subdivision in five different fibre types was made, based on the location of the fibres inside the muscle, fibre diameter and a quantitative histochemical assay for succinate dehydrogenase activity. the ca2+ sensitivity was characterized by fitting a hill curve to the force levels reached at different ca2+ concentrations. the parameter n of ... | 1987 | 3822771 |
| the nucleotide sequence of the ribosomal protein l14 gene of xenopus laevis. | 1987 | 3822843 | |
| prolactin binding sites in xenopus laevis tissues: comparison between normal and dehydrated animals. | the binding of 125i-labeled ovine prolactin (125i-oprl) to membranes from the kidney, epidermis, liver, and testis of xenopus laevis adult specimens either kept in an aquatic environment or exposed for 2 weeks to dehydrating conditions was studied. prolactin binding specificity was assayed through competition with several unlabeled hormones (oprl, hgh, rgh, rlh, and porcine insulin). in the animal exposed to dehydrating conditions a statistically highly significant reduction in prolactin binding ... | 1987 | 3803901 |
| [mosaic formation of neurons in the neurogenesis zone in the xenopus laevis tectum]. | 1987 | 3829896 | |
| structure and transcription termination of a lysine trna gene from xenopus laevis. | termination of rna polymerase iii transcripts commonly occurs at clusters of t residues. a t4 tract located 72 base-pairs beyond a lysine trna gene from xenopus laevis serves as an efficient termination site for the trna(lys) precursors synthesized from this gene in homologous cell-free extracts. nucleotides following this t tract influence the extent of read-through transcription in vitro, but in a way that differs from xenopus 5 s rna termination. only approximately 50% of the transcripts init ... | 1987 | 2443712 |
| isolation of mrna from membrane-bound polysomes synthesizing sepia officinalis haemocyanin in xenopus laevis oocytes. | isolation and translation in xenopus laevis oocytes of the mrnas from the nuclear pellet and the cytoplasmic supernatant of the branchial glands from sepia officinalis, homogenized in the presence of vanadyl-ribonucleoside complexes, revealed that the membrane-bound polysomes for haemocyanin sedimented together with the nuclei. centrifugation on a 15-50% sucrose gradient of these polysomes, released by treatment with triton x-100, yielded a major peak of heavy ones. the messenger fraction, isola ... | 1987 | 2436622 |
| gaba receptors induced in xenopus oocytes by chick brain mrna: evaluation of tbps as a use-dependent channel-blocker. | sensitivity to gaba was induced in xenopus laevis oocytes by injection of poly(a)+ mrna extracted from 19-day chick embryo brain. the effect of the convulsant drug t-butylbicyclophosphorothionate (tbps) was studied on the responses to bath-applied gaba using voltage-clamp techniques. tbps reversibly inhibited the gaba-evoked current (igaba) in a dose-dependent manner; however, the chloride currents evoked by carbachol or serotonin, or the spontaneous chloride fluctuations, were unaffected. the o ... | 1987 | 2437999 |
| activation of cryptic promoters of human c-myc genes in microinjected xenopus laevis oocytes. | the human cellular oncogene c-myc contains two promoters at the 5' end of its first non-coding exon. cryptic promoters located within the first intron are also activated to synthesize aberrant c-myc mrnas in some burkitt lymphomas with a t(8: 14) chromosome translocation in which a part of the gene structure, often the 5' non-coding exon, is truncated. we have shown elsewhere that microinjected plasmid dna carrying a normal, intact human c-myc gene directs efficient faithful transcription from i ... | 1987 | 2438422 |
| neurotensin and acetylcholine evoke common responses in frog oocytes injected with rat brain messenger ribonucleic acid. | 1. the intracellular reaction mechanism underlying electrophysiological responses evoked by neurotensin (nt) was studied using xenopus laevis oocytes injected with poly (a)+ messenger ribonucleic acid (mrna) isolated from rat brains. 2. a few days after the injection of mrna, oocytes were found to acquire sensitivity to nt and substance p. 3. under voltage-clamp conditions (-60 mv), application of nt to mrna-injected oocytes produced transient and oscillatory inward currents which began after a ... | 1987 | 2442367 |
| dna-binding fingers encoded by a trypanosome retroposon. | a trypanosoma brucei repeated dna element (trs-1, for trypanosome repeated sequence), which seems transposable, may encode a 1651 amino acid polypeptide showing homology with reverse transcriptase. this polypeptide would also carry a dna-binding domain, as suggested by the presence of five dna-binding "fingers" homologous to those of the transcription factor tfiiia of xenopus laevis and retroviral dna-binding proteins. | 1987 | 2445994 |
| hormonal activation of ionic currents in follicle-enclosed xenopus oocytes. | membrane currents were recorded, using the voltage clamp technique, from xenopus laevis oocytes still surrounded by their enveloping follicular and epithelial cells. exposure of the follicles to mammalian gonadotropins elicited a current generated largely by an increase in membrane k+ conductance. the gonadotropin response resembled responses elicited by adenosine and catecholamines in the same follicle, but was not blocked by purinergic or catecholaminergic antagonists. the gonadotropin-induced ... | 1987 | 2438692 |
| membrane turnover in rod photoreceptors: ensheathment and phagocytosis of outer segment distal tips by pseudopodia of the retinal pigment epithelium. | we have documented the ultrastructural changes that occur within the photoreceptor outer segment and the retinal pigment epithelium (rpe) during photosensitive membrane turnover. we employed an in vitro eyecup preparation from xenopus laevis in which a large shedding event was induced by adding the excitatory amino acid l-aspartate (greenberger & besharse 1985; j. comp. neurol. 239, 361-372). we found that during l-aspartate-induced shedding the rpe cells formed, on their apical domains, previou ... | 1987 | 2438704 |
| both barium and calcium activate neuronal potassium currents. | amphibian spinal neurons in culture possess both rapidly inactivating and sustained calcium-dependent potassium current components, similar to those described for other cells. divalent cation-dependent whole-cell outward currents were isolated by subtracting the voltage-dependent potassium currents recorded from xenopus laevis neurons in the presence of impermeant cadmium (100-500 microm) from the currents produced without cadmium but in the presence of permeant divalent cations (50-100 microm). ... | 1987 | 2442762 |
| inositol trisphosphate activates a voltage-dependent calcium influx in xenopus oocytes. | injection of inositol trisphosphate (ip3) into oocytes of xenopus laevis induces the appearance of a transient inward (tin) current on hyperpolarization of the membrane. this current is carried largely by chloride ions, but is shown to depend on extracellular calcium, because it is abolished by removal of calcium in the bathing fluid or by addition of manganese. recordings with aequorin as an intracellular calcium indicator show that a calcium influx is activated by hyperpolarization after intra ... | 1987 | 2442764 |
| expression of xenopus n-cam rna in ectoderm is an early response to neural induction. | we have isolated xenopus laevis n-cam cdna clones and used these to study the expression of n-cam rna during neural induction. the results show that the first marked increase in n-cam rna levels occurs during gastrulation when mesoderm comes in contact with ectoderm and induces neural development. in situ hybridization results show that the early expression of n-cam rna is localized to the neural plate and its later expression is confined to the neural tube. induction experiments with explanted ... | 1987 | 2443340 |
| distribution, expression and germ line transmission of exogenous dna sequences following microinjection into xenopus laevis eggs. | we analysed the fate, expression and germ line transmission of exogenous dna which was microinjected into fertilized eggs of xenopus laevis. dna was injected into fertilized eggs within 1 h following fertilization. the injected dna was dispersed around the site of injection and became localized to cleavage nuclei by stage 6. injected dna persisted in the tissues of 6- to 8-month-old frogs and exhibited a mosaic pattern of distribution with regard to the presence or absence and copy number betwee ... | 1987 | 2443337 |
| synthesis of heterogeneous mrna-like rna and low-molecular-weight rna before the midblastula transition in embryos of xenopus laevis. | it has been proposed and is now widely accepted that in xenopus laevis embryogenesis rna synthesis starts only at and after 12 rounds of cleavage, at the time of the midblastula transition (mbt). in this report, however, we provide evidence that rna synthesis takes place prior to the mbt stage in normally developing xenopus embryos. in the present experiments, we cultured fertilized eggs in 80 mm phosphate buffer and loosened the adhesion between blastomeres, so that [3h]uridine could be incorpo ... | 1987 | 2443406 |
| injection of inositol 1,3,4,5-tetrakisphosphate into xenopus oocytes generates a chloride current dependent upon intracellular calcium. | injection of inositol 1,3,4,5-tetrakisphosphate (ins(1,3,4,5)p4) into voltage-clamped oocytes of xenopus laevis elicited an oscillatory chloride membrane current. this response did not depend upon extracellular calcium, because it could be produced in calcium-free solution and after addition of cobalt to block calcium channels in the surface membrane. however, it was abolished after intracellular loading with the calcium chelating agent egta, indicating a dependence upon intracellular calcium. t ... | 1987 | 2446333 |
| reversible inhibition of protein import into the nucleus by wheat germ agglutinin injected into cultured cells. | the importance of glycoproteins located in the nuclear envelope in nuclear transport was tested by microinjection of karyophilic proteins into the cytoplasm of cultured human cells together with various lectins. wheat germ agglutinin (wga) blocked the nuclear transport of nucleoplasmin, a nuclear protein of xenopus laevis oocytes, and of nonnuclear proteins conjugated with a synthetic peptide containing the nuclear localization signal sequence for simian virus 40 (sv40) large t antigen. its inhi ... | 1987 | 2446896 |
| the accumulation of mature rna for the xenopus laevis ribosomal protein l1 is controlled at the level of splicing and turnover of the precursor rna. | a specific control regulates, at the level of rna splicing, the expression of the l1 ribosomal protein gene in xenopus laevis. under particular conditions, which can be summarized as an excess of free l1 protein, a precursor rna which still contains two of the nine introns of the l1 gene accumulates. in addition to the splicing block the two intron regions undergo specific endonucleolytic cleavages which produce abortive truncated molecules. the accumulation of mature l1 rna therefore results fr ... | 1987 | 2448138 |
| thyroid hormone induction of keratin genes: a two-step activation of gene expression during development. | to determine the mechanism of action of the thyroid hormone triiodothyronine (t3) during metamorphosis of the amphibian epidermis, we have investigated the developmental activation of the 63-kd keratin genes in the frog xenopus laevis. these genes code for three closely related keratins that first appear in the larval epidermis and accumulate during metamorphosis to become the most abundant proteins in the adult epidermis. we report here that the 63-kd keratins and their mrnas first appear at st ... | 1987 | 2448186 |
| expression of single calcium channels in xenopus oocytes after injection of mrna from rat heart. | oocytes of xenopus laevis, after microinjection with mrna from rat heart, display typical high-threshold calcium (ca) whole cell currents. to prepare to study structure-function relationships of the cardiac ca channel molecule, we examined the fidelity of expression of biophysical and pharmacological properties at the molecular level. cell-attached gigaseal recordings in five k-depolarized oocytes injected with adult rat heart mrna showed single channel ba currents with mean amplitude 1.3-1.5 pa ... | 1987 | 2444117 |
| analysis of cytokeratin domains by cloning and expression of intact and deleted polypeptides in escherichia coli. | using recombination of an appropriate expression vector system (pindu) with a complete cdna encoding a basic (type ii) cytokeratin, i.e. cytokeratin 8 (1) of xenopus laevis, we transformed escherichia coli cells to synthesize considerable amounts of an insoluble eukaryotic cytoskeletal protein. the cytokeratin was deposited in large 'inclusion bodies' in the bacterial cytoplasm but did not form detectable filamentous structures. however, when the e. coli-expressed cytokeratin was purified and co ... | 1987 | 2445561 |
| properties of single sodium channels translated by xenopus oocytes after injection with messenger ribonucleic acid. | 1. the properties of fast transient na channels induced in the xenopus laevis oocyte plasma membrane after injection of the oocyte with foreign messenger ribonucleic acid (mrna) were investigated with the whole-cell voltage clamp and with the patch-clamp technique. 2. the time course of expression and the effect of the metabolic inhibitors actinomycin d and tunicamycin were studied. the rate of channel insertion reached a maximum only about 3 days after injection with mrna and corresponded to th ... | 1987 | 2445971 |
| chloride-thiocyanate interactions in frog muscle anion-conducting channels at ph 5. | bi-ionic membrane potential measurements and three-microelectrode voltage clamp experiments have been performed on surface fibres of xenopus laevis sartorius muscle at various mole fractions of scn- in cl- in the perfusate, at ph 5. potassium was replaced in the test solutions by rubidium and/or tetraethylammonium and when the mole fraction of anions was changed the measured membrane potential changed to a new constant (i.e. time-independent) value. over a mole fraction range of 0.05-0.95 the pe ... | 1987 | 2446245 |
| expression of an omega-conotoxin-sensitive calcium channel in xenopus oocytes injected with mrna from torpedo electric lobe. | xenopus laevis oocytes were injected with poly(a)+ rna isolated from the electric lobe of torpedo californica. six to nine days after mrna injection of the oocytes a cadmium-sensitive inward current could be detected in oocytes bathed in a calcium- and chloride-free solution containing 40 mm barium. this inward current could be distinguished from the native barium current of control oocytes by its high sensitivity to blockade by cadmium ions and its inhibition by omega-conotoxin, a peptide neuro ... | 1987 | 2440049 |
| patch clamp characterization of sodium channels expressed from rat brain cdna. | sodium currents, ina, were recorded from xenopus laevis oocytes which had been injected with mrna synthesized by in vitro transcription of the rat brain sodium channel ii cdna (noda et al. 1986 a, b). patch pipettes were used to apply depolarizing voltage steps and to record macroscopic sodium currents of between 50 and 750 pa from cell-attached patches of the oocyte membrane. with a combination of whole-cell and patch clamp recording, the properties of the implanted sodium channels could be stu ... | 1987 | 2435540 |
| cell-type-specific expression of epidermal cytokeratin genes during gastrulation of xenopus laevis. | analysis of the spatial pattern of expression of embryo-specific epidermal cytokeratin genes in xenopus laevis shows earliest activity in the animal pole cells of stage-9 blastulae. these genes are transcribed predominantly in the epithelial or outer ectoderm, to a lesser extent in the sensorial or inner ectoderm, and at low levels if at all in other regions of the embryo. in the early gastrula the entire ectoderm, including preneural and preepidermal regions, expresses cytokeratin mrnas; accumu ... | 1987 | 2445625 |
| differential transcription of xenopus oocyte and somatic-type 5 s genes in a xenopus oocyte extract. | we have measured the transcription of xenopus laevis oocyte and somatic-type 5 s rna genes in s-150 extracts prepared from ovaries of mature x. laevis females (glikin, g. c., ruberti, i., and worcel, a. (1984) cell 37, 33-41). we find that somatic-type 5 s genes are transcribed at least 40-fold more efficiently than oocyte-type 5 s genes. since adenovirus va, xenopus oax, and xenopus trnamet genes are all transcribed at levels similar to that of the somatic-type 5 s gene, this difference reflect ... | 1987 | 2445754 |
| effects of veratridine on single neuronal sodium channels expressed in xenopus oocytes. | (1) chick neuronal na+ channels were expressed in xenopus laevis oocytes after injection with total messenger ribonucleic acid (mrna) isolated from chick brain. the currents were investigated with the whole cell voltage clamp and with the patch clamp technique. activation and inactivation of the induced current, and its sensitivity towards tetrodotoxin (ttx) and veratridine were reminiscent of vertebrate neuronal na+ channels. (2) in the presence of veratridine normal single channel openings oft ... | 1987 | 2446243 |
| further characterization of the slow muscarinic responses in xenopus oocytes. | in immature follicular oocytes of the frog xenopus laevis, application of muscarinic agonists evokes a complex response consisting of a fast and a slow cl currents (the dominant responses), cl current fluctuations, and a less prominent slow k current. the characteristics of the slow ach-evoked potassium current were studied using the two-electrode voltage clamp method, and compared to those of the ach-evoked cl currents. in experiments designed to study the k current response separately, without ... | 1987 | 2442712 |
| rate of degradation of [alpha]- and [beta]-oligodeoxynucleotides in xenopus oocytes. implications for anti-messenger strategies. | end-labelled oligodeoxynucleotides were injected into xenopus laevis oocytes and their degradation products were analysed by high-performance ion-exchange liquid chromatography after various times of incubation. the oligonucleotides were synthesised with either the natural [beta] anomers or the synthetic [alpha] anomers of deoxynucleotide units. oligo-[beta] deoxynucleotides are short-lived inside oocytes (half-life approximately equal to 10 min). covalent attachment of an intercalating agent to ... | 1987 | 2447563 |
| changes in axonal transport and glial proteins during optic nerve regeneration in xenopus laevis. | 1987 | 2443306 | |
| polar asymmetry in the organization of the cortical cytokeratin system of xenopus laevis oocytes and embryos. | we have used whole-mount immunofluorescence microscopy of late-stage xenopus laevis oocytes and early embryos to examine the organization of their cortical cytokeratin systems. in both mature oocytes and early embryos, there is a distinct animal-vegetal polarity in cytokeratin organization. in mature (stage-vi) oocytes, the cytokeratin filaments of the vegetal region form a unique, almost geodesic network; in the animal region, cytokeratin organization appears much more variable and irregular. i ... | 1987 | 2443336 |
| expression of rat brain excitatory amino acid receptors in xenopus oocytes. | xenopus laevis oocytes when injected with rat brain mrna synthesize neuronal receptors that can be analyzed electrophysiologically. after a post-injection incubation period of 24-72 hours, l-glutamic acid, kainic acid and quisqualic acid caused a dose dependent (10-100 microm) depolarization of the oocyte membrane. the voltage and conductance changes associated with kainate activation were distinguishable from those seen for l-glutamate or quisqualate. there was no response to l-aspartate applic ... | 1987 | 2449049 |
| the use of xenopus oocytes for the study of ion channels. | recently, in addition to the "traditional" research on meiotic reinitiation and fertilization mechanisms, the oocytes of the african frog xenopus laevis have been exploited for the study of numerous aspects of ion channel function and regulation, such as the properties of several endogenous voltage-dependent channels and the involvement of second messengers in mediation of neurotransmitter-evoked membrane responses. in addition, injection of these cells with exogenous messenger rna results in pr ... | 1987 | 2449311 |
| dopamine mediates the light-evoked suppression of serotonin n-acetyltransferase activity in retina. | the possible role of dopamine in the light-induced suppression of serotonin n-acetyltransferase (nat) activity in retinas of the african clawed frog (xenopus laevis) was investigated using an in vitro eye cup preparation. the nocturnal increase of retinal nat activity was significantly inhibited by either light exposure or exogenous dopamine. spiperone, a dopamine receptor blocker, antagonized this inhibitory effect of light on nat activity, but had no effect in darkness. the effect of spiperone ... | 1987 | 2445415 |
| tetrodotoxin-sensitive sodium current in native xenopus oocytes. | depolarization of oocytes of xenopus laevis usually elicits mainly passive currents, and a calcium-dependent chloride current. however, oocytes obtained from some donors show, in addition, a transient inward current on depolarization to potentials beyond ca. -40 mv. this current is abolished by tetrodotoxin at submicromolar concentrations, and is prolonged by veratrine; thus, it probably arises through sodium channels of a type similar to those found in nerve and muscle cells. however, the kinet ... | 1987 | 2449697 |
| membrane currents elicited by porcine vasoactive intestinal peptide (vip) in follicle-enclosed xenopus oocytes. | membrane currents were recorded from voltage-clamped xenopus laevis oocytes, surrounded by their enveloping follicular and epithelial cells. porcine vasoactive intestinal peptide (vip) generated a membrane current due to an increase in membrane conductance to k+. the vip current was mimicked by the adenylate cyclase activator forskolin and was potentiated by phosphodiesterase inhibitors, suggesting that adenosine 3',5'-cyclic monophosphate (cyclic amp) plays a role in mediating the response. tho ... | 1987 | 2447588 |
| soluble cytokeratins in xenopus laevis oocytes and eggs. | xenopus oocytes contain a radial network of cytokeratins which seems to fragment during meiosis reinitiation (maturation). the mature egg contains only a cortical network of cytokeratins. we have looked for the presence of soluble cytokeratins in oocytes and unfertilized eggs and have found them in both cases. however, the proportion of soluble to insoluble cytokeratins is slightly higher in the egg than in the oocyte. soluble cytokeratins incorporate 35s-methionine at a high rate in the oocyte ... | 1987 | 2451957 |
| cytokeratins in certain endothelial and smooth muscle cells of two taxonomically distant vertebrate species, xenopus laevis and man. | using immunolocalization techniques, electron microscopy, and gel electrophoresis combined with immunoblotting, we have noted remarkable interspecies differences in the expression of cytokeratins in certain nonepithelial cells. in the present study we describe, in two taxonomically distant vertebrate species, the african clawed toad xenopus laevis and man, endothelial and smooth muscle cells which express cytokeratin intermediate filaments (ifs), in addition to vimentin and/or desmin ifs. in xen ... | 1987 | 2452760 |
| cloning and characterization of a cdna from xenopus laevis coding for a protein homologous to human and murine p53. | a xenopus laevis oocyte cdna library was screened with a murine p53 cdna probe for the presence of p53-related clones. several such clones were isolated and analysed. the nucleotide sequence of the largest cdna clone (2.2 kb) showed a high degree of homology with the human (68%) and murine (70%) p53 coding sequences. this clone contains a single large open-reading frame, coding for a protein of 363 amino acids, which is 51% homologous to human p53 and 57% homologous to murine p53. furthermore, f ... | 1987 | 2830576 |
| coupling of inositol phospholipid hydrolysis to peptide hormone receptors expressed from adrenal and pituitary mrna in xenopus laevis oocytes. | the expression of several neurotransmitter and drug receptors from injected exogenous mrna in xenopus laevis oocytes has been demonstrated by electrophysiological measurements of ion channel activation. the expression of specific receptors for peptide hormones in such a translation system would facilitate studies on the structure and regulation of cell-surface receptors as well as their coupling to membrane transduction mechanisms. the expression of receptors for calcium-mobilizing hormones in x ... | 1987 | 2827166 |
| rapid stimulation of diacylglycerol production in xenopus oocytes by microinjection of h-ras p21. | the p21 products of ras proto-oncogenes are thought to be important components in pathways regulating normal cell proliferation and differentiation. these proteins acquire transforming properties as a result of activating lesions that convert ras genes to oncogenes in a wide array of malignancies. in xenopus laevis oocytes, microinjection of transforming ras p21 is a potent inducer of maturation, whereas microinjection of a monoclonal antibody to ras p21 inhibits normal maturation induced by hor ... | 1987 | 2821623 |
| [regulation of transcription of immunoglobulin kappa genes in xenopus laevis oocytes]. | recombinant plasmids containing the immunoglobulin kappa gene with deletions in the 5' and 3' regions of the gene having different position and orientation of the enhancer element were constructed. the plasmids were incubated with cell-free extracts prepared from lymphoid and non-lymphoid cells, and then injected into the nuclei of xenopus laevis oocytes. tissue-specific transcription of the v kappa gene was shown to be under control of factor(s) existing in lymphoid cells. the data reported in ... | 1987 | 2822537 |
| dna sequences in the first intron of the human pro-alpha 1(i) collagen gene enhance transcription. | a chimeric gene was constructed in which sequences between 253 base pairs (bp) upstream of the start of transcription of the human pro-alpha 1(i) collagen gene and 117 bp downstream of that site were fused to the human alpha 1-globin gene, at a site immediately upstream of the globin initiation codon. expression of this and subsequent chimeric gene constructions was investigated in microinjected xenopus laevis oocytes. presence of 253 bp of pro-alpha 1(i) collagen gene promoter sequences, contai ... | 1987 | 2822714 |
| n-terminal acetylation of melanophore-stimulating hormone in the pars intermedia of xenopus laevis is a physiologically regulated process. | the n-terminal acetylation of melanophore-stimulating hormone (msh) increases the melanotropic potency of the peptide. this modification may be important in amphibians, where msh causes skin darkening during adaptation to black background. this study examines the acetylation status of the peptide in the toad xenopus laevis under different conditions of background adaptation. acetylated and nonacetylated alpha-msh were analyzed by high-performance liquid chromatography and quantified by radioimmu ... | 1987 | 2823159 |
| expression of rat mrna coding for hormone-stimulated adenylate cyclase in xenopus oocytes. | beta-adrenergic agonist-stimulated hyperpolarization, whole-cell camp accumulation, and activity of isoproterenol-stimulated membrane-bound adenylate cyclase (ec 4.6.1.1) in xenopus laevis ovarian oocytes are entirely dependent on the presence of nascent follicle cells. a method was developed to remove rapidly and completely all extra-oocyte cell types to yield defolliculated oocytes that exhibited normal viability and resting membrane potentials yet lacked beta-adrenergic receptor (beta ar)-sti ... | 1987 | 2824269 |
| the telomeres of tetrahymena ribosomal dna are not sufficient for stabilizing linear dna in xenopus oocytes. | restriction fragments that include the telomeres of ribosomal dna from tetrahymena thermophila (ttrdna) were ligated to the ends of linearized simian virus 40 (sv40) dna. the linear sv40 dna with ttrdna ends, circular sv40 dna, linear sv40 dna, and intact ttrdna were injected into the nuclei of xenopus laevis oocytes and assayed for stability. the intact linear 21-kb ttrdna and circular sv40 dna were maintained stably for at least 72 h after injection while the linearized sv40 dna, either with o ... | 1987 | 2824294 |
| functional activity and regulation of human beta 2-adrenergic receptors expressed in xenopus oocytes. | the recently cloned human beta-adrenergic cdna and several mutated forms have been expressed in xenopus laevis oocytes by injection of rna made from the cdna under the control of the bacteriophage sp6 promoter. the cdna and gene of the beta 2-adrenergic receptor possess the unusual feature of having a second upstream atg (-101 base pairs) and a 19-codon open reading frame 5' to the initiator methionine codon of the receptor (kobilka, b. k., dixon, r. a. f., frielle, t., dohlman, h. g., bolanowsk ... | 1987 | 2824467 |
| metabolic regulation during early frog development. identification of proteins labeled by 32p-glycolytic intermediates. | when 32p-labeled phosphoenolpyruvate is injected into xenopus laevis oocytes, a 50-60-kda protein of subunit size mr 29,000 is rapidly labeled, followed by a second (monomeric) protein of 66 kda concomitant with the loss of label from the first protein. we have identified these proteins as, respectively, the glycolytic enzymes phosphoglyceromutase and phosphoglucomutase. the phosphoglyceromutase is labeled at a histidine and the phosphoglucomutase at a serine, presumably at their active sites du ... | 1987 | 2824510 |
| monohydroxyeicosatetraenoic acid and leukotriene production by the inflammatory cells of xenopus laevis. | ten frogs (xenopus laevis) were injected with mixed bacteria to produce a septic peritonitis. peritoneal inflammatory cells of eight animals were studied for monohydroxyeicosanoid and leukotriene production from exogenous arachidonic acid. large amounts of 12-hydroxyeicosatetraenoic acid were produced; smaller amounts of 5- and 15-hydroxyeicosatetraenoic and leukotriene b4 were produced. identifications were confirmed by retention times on hplc, ultraviolet spectroscopy on all products, and gas ... | 1987 | 2821155 |
| oscillatory chloride current evoked by temperature jumps during muscarinic and serotonergic activation in xenopus oocyte. | 1. membrane currents were recorded from voltage-clamped oocytes of xenopus laevis, during temperature jumps imposed by a heating light. resting oocytes usually showed little response, but large oscillatory membrane currents developed in response to cooling steps applied during activation of 'native' muscarinic receptors. 2. similar temperature jump (tjump) currents were seen during activation of oscillatory chloride currents mediated by muscarinic acetylcholine (ach), serotonin, glutamate and no ... | 1987 | 2821235 |
| cloning, sequencing, and expression of the gene coding for the human platelet alpha 2-adrenergic receptor. | the gene for the human platelet alpha 2-adrenergic receptor has been cloned with oligonucleotides corresponding to the partial amino acid sequence of the purified receptor. the identity of this gene has been confirmed by the binding of alpha 2-adrenergic ligands to the cloned receptor expressed in xenopus laevis oocytes. the deduced amino acid sequence is most similar to the recently cloned human beta 2- and beta 1-adrenergic receptors; however, similarities to the muscarinic cholinergic recepto ... | 1987 | 2823383 |
| fixation of the unmethylated or the 5'-ccgg-3' methylated adenovirus late e2a promoter-cat gene construct in the genome of hamster cells: gene expression and stability of methylation patterns. | the late e2a promoter of adenovirus type 2 (ad2) dna can be inactivated by in vitro methylation of three 5'-ccgg-3' sequences at positions +23, +5, and -215 relative to the cap site in this promoter. this inactivation has been documented in transient expression experiments both in xenopus laevis oocytes and in mammalian cells (k.-d. langner, l. vardimon, d. renz, and w. doerfler, proc. natl. acad. sci. usa 81:2950-2954, 1984; k.-d. langner, u. weyer, and w. doerfler, proc. natl. acad. sci. usa 8 ... | 1987 | 2824809 |
| a comparison of eukaryotic viral 5'-leader sequences as enhancers of mrna expression in vivo. | the 5'-untranslated leader sequences of several plant rna viruses, and a portion of the 5'-leader of an animal retrovirus, were tested for their ability to enhance expression of contiguous open reading frames for chloramphenicol acetyltransferase (cat) or beta-glucuronidase (gus) in tobacco mesophyll protoplasts, escherichia coli and oocytes of xenopus laevis. translation of capped or uncapped transcripts was substantially enhanced in almost all systems by the leader sequence of either the u1 or ... | 1987 | 2825117 |
| sequence organization and developmentally regulated transcription of a family of repetitive dna sequences of xenopus laevis. | members of a family of dna sequences of xenopus laevis have been cloned and sequenced. molecular analyses revealed that these sequences are moderately repetitive and dispersed throughout the genome. the sequences of seven clones were compared. two of the clones lie in the globin gene cluster; one 5' to the adult alpha 1 gene, and the other in the first intron of the tadpole alpha 1 gene. in all clones, the homologous region begins at the same site, but the lengths of the common regions vary from ... | 1987 | 2825138 |
| regulation of msh release from the neurointermediate lobe of xenopus laevis by crf-like peptides. | immunocytochemical studies showed the presence of a fiber system containing a crf-like peptide in the median eminence and in the neural lobe of the pituitary gland of xenopus laevis. during in vitro superfusion of neurointermediate lobe tissue, crf, sauvagine and urotensin i induced a rapid and dose-dependent stimulation of secretion of msh and endorphin. tissue of white-background adapted animals displayed a remarkably higher sensitivity to crf and sauvagine than tissue from animals that were a ... | 1987 | 2831518 |
| xfin: an embryonic gene encoding a multifingered protein in xenopus. | the xenopus laevis genome was screened for putative dna-binding gene products by using the 'finger' region of the drosophila gene krüppel as a probe. the one gene detected, named xfin, codes for a protein with 37 finger domains that comprise nearly 90% of the protein. in the light of studies by rhodes and klug (cell, 46, 123-132, 1986), these data suggest that the xfin protein has the capacity to bind an unusually large stretch (185 bases) of dna. the xfin gene is expressed as a maternal and zyg ... | 1987 | 2826129 |
| isolation and characterization of conditional lethal amber nonsense mutants of vesicular stomatitis virus. | we describe the isolation and characterization of conditional lethal amber nonsense mutants of vesicular stomatitis virus (vsv), indiana serotype. the mutants were isolated from a chemically mutagenized stock of wild-type virus by their ability to grow on genetically engineered cells which express a xenopus laevis amber suppressor tyrosine trna gene (su+ cells) but not on the non-suppressor parental cells (su- cells). five mutations were assigned to complementation group i (the l gene) and one t ... | 1987 | 2826648 |
| repair of uv-induced lesions in xenopus laevis oocytes. | we characterized a dna repair system in frog oocytes by comicroinjection of uv-irradiated pbr322 dna and radiolabeled nucleotides. repair synthesis was monitored by incorporation of label into recovered pbr322 dna and by a novel method in which the removal of uv photoproducts was determined from the shift of dna topoisomers that occurs during gel electrophoresis upon repair of these lesions. we investigated the effects of several drugs in the oocyte system and found that although novobiocin, an ... | 1987 | 2830488 |
| expression of c-myc proto-oncogene during the early development of xenopus laevis. | c-myc proto-oncogene expression in xenopus laevis oocytes and developing embryos has been investigated. stage vi oocytes as well as unfertilized eggs contain a high level of xenopus c-myc mrna (1-2.5 x 10(7) copies). however, this high level of maternal c-myc mrna declines gradually during the time of rapid and synchronous cell cleavage and becomes almost undetectable after the mid-blastula transition. the zygotic genes then become activated for the first time, whereupon the amount of newly synt ... | 1987 | 2835732 |
| an npy-like peptide may function as msh-release inhibiting factor in xenopus laevis. | this study demonstrates the presence of a rich plexus of neuropeptide y (npy) immunoreactive fibers in the hypothalamus and in the intermediate lobe of the pituitary of xenopus laevis. during superfusion of neurointermediate lobe tissue, synthetic npy induces a rapid, powerful and dose-dependent inhibition of in vitro release of msh, endorphin and other proopiomelanocortin (pomc) derived peptides. therefore, npy undoubtedly is one of the growing number of neuropeptides that are likely involved i ... | 1987 | 2883634 |
| cloning of the cdna for the human beta 1-adrenergic receptor. | screening of a human placenta lambda gt11 library has led to the isolation of the cdna for the human beta 1-adrenergic receptor (beta 1ar). used as the probe was the human genomic clone termed g-21. this clone, which contains an intronless gene for a putative receptor, was previously isolated by virtue of its cross hybridization with the human beta 2-adrenergic receptor (beta 2ar). the 2.4-kilobase cdna for the human beta 1ar encodes a protein of 477 amino acid residues that is 69% homologous wi ... | 1987 | 2825170 |
| mechanism of membrane electrical response to thyrotropin-releasing hormone in xenopus oocytes injected with gh3 pituitary cell messenger ribonucleic acid. | trh evoked a complex electrical membrane response in xenopus laevis oocytes injected with either total cytosolic or poly(a)(+)-enriched rna from gh3 pituitary cells but not in uninjected oocytes. a typical response consisted of a transient, rapid depolarizing current followed by a prolonged depolarizing current with superimposed current fluctuations. the reversal potentials of the rapid and the slow components of the response were -23.0 and -22.6 mv, respectively, and were markedly affected by c ... | 1987 | 2856406 |
| characterization of cyclic nucleotide phosphodiesterases in xenopus laevis ovary. | a cgmp-stimulated cyclic nucleotide phosphodiesterase present in cytosol of xenopus laevis ovary has been purified and characterized. a camp-specific phosphodiesterase which is not activated by either cgmp or calmodulin, has also been characterized. brief exposure of intact oocytes to 10 micro m progesterone results in an increase in activity of the camp-specific enzyme. the cgmp-stimulated and the calmodulin-activated phosphodiesterases are not altered. changes in cyclic nucleotide levels durin ... | 1987 | 2827950 |
| calcium and magnesium dependence of spontaneous and evoked afferent neural activity in the lateral-line organ of xenopus laevis. | 1. rates of spontaneous and mechanically evoked neural impulses from the xenopus laevis lateral line were compared in the presence of calcium and/or magnesium or in the absence of either divalent cation, bath-applied to the synaptic side of the mechanoreceptors. 2. spontaneous activity and total activity during mechanical stimulation decreased with increasing calcium or magnesium concentration. 3. activity during stimulation minus spontaneous activity increased with increasing calcium concentrat ... | 1987 | 2886271 |
| immunocytochemical localization and spatial relation to the adenohypophysis of a somatostatin-like and a corticotropin-releasing factor-like peptide in the brain of four amphibian species. | the distribution of somatostatin (srif) - and corticotropin-releasing factor (crf)-like - immunoreactive material was studied in the brain of four amphibian species (ambystoma mexicanum, pleurodeles waltlii, xenopus laevis, rana ridibunda) by use of immunocytochemistry. a wide network of srif-immunoreactive fibers and numerous perikarya were observed in all amphibians examined, with a dense accumulation of nerve endings in the external layer of the median eminence (elme). in the representatives ... | 1987 | 2880668 |
| neuroactive substances in inner ear extracts. | to identify the neurotransmitter released by sensory hair cells, as well as to find other substances that might influence neural function of the inner ear, we have prepared extracts from inner ears of fishes (which have large numbers of hair cells), fractionated the extracts, and studied the effects of the fractionated extracts on the discharge rate of afferent fibers innervating hair cells in the lateral line organ of the african clawed frog xenopus laevis. the extracts contain active substance ... | 1987 | 2886566 |
| accumulation of free amino acids in growing xenopus laevis oocytes. | the sizes of amino acid pools in growing xenopus laevis oocytes have been measured. the total free amino acid content per oocyte increases nearly 25-fold during oocyte growth. together, glutamic acid and aspartic acid account for approximately 59-75% of the total amino acid pool in xenopus oocytes. on the other hand, methionine and cysteine are the least abundant of the amino acids detected, each accounting for less than 0.7% of the total pool in developing oocytes. it is argued that the acid-ex ... | 1987 | 2889640 |
| a possible neurotransmitter role for cgrp in a hair-cell sensory organ. | we report that calcitonin gene-related peptide (cgrp) increases the discharge rate of afferent fibers innervating hair cells in the lateral line organ of xenopus laevis. we have localized cgrp-like immunoreactivity in small, presumably efferent, fibers innervating the lateral line organ. in addition to providing evidence for a neurotransmitter role for cgrp in a sensory system, these results may help explain the non-cholinergic excitatory effect seen with efferent stimulation in this and other h ... | 1987 | 2890408 |
| effect of osmolality on the initiation of sperm motility in xenopus laevis. | 1. seminal plasma of the south african clawed toad xenopus laevis exhibited osmolality around 250 mosmol/kg isotonic to blood plasma. 2. spermatozoa remained immotile when the semen was diluted in solutions of 100 mm nacl, 100 mm kcl or 200 mm glucose containing 20 mm hepes-naoh buffer which exhibited almost the same osmolalities (approximately 240 mosmol/kg) as seminal plasma. 3. the spermatozoa became motile in these three solutions if the osmolalities were decreased. 4. these suggest that mot ... | 1987 | 2892629 |
| a xenopus laevis gene encodes both homeobox-containing and homeobox-less transcripts. | a cdna clone (p52) that contains all the protein-coding region from the maternally expressed xlhbox 2 locus of the frog xenopus laevis has been isolated and sequenced. a probe containing the exon preceding the homeobox detected transcripts which arise from a splicing event in which the homeobox-containing exon is replaced by another exon lying 5' to it in the genome. both the homeobox-containing and homeobox-less splicing event occur in the same tissues, with the homeobox-less rna representing t ... | 1987 | 2894983 |
| amino acids, including neurotransmitter candidates, in a hair cell-enriched fraction from the lateral line of xenopus laevis. | a hair cell-enriched neuromast fraction from the lateral line of xenopus laevis was compared with adjacent tactile organ and epidermis for content of primary amine-containing components. of 32 components quantitated by cation-exchange hplc with fluorescence detection of orthophthalaldehyde adducts, l-alpha-amino adipic acid, o-phosphoethanolamine, l-alpha-glycerophosphorylethanolamine, o-phospho-l-serine, and l-lysine were elevated in concentration in the neuromast relative to the tactile organ ... | 1987 | 2881697 |
| in vitro formation of neuromuscular junctions between adult rana muscle fibres and embryonic xenopus neurons. | adult muscle fibres of the frog rana temporaria were cultured with neurons from embryos of the frog xenopus laevis. electron microscopical and electro-physiological examination of the cultures showed that hetero-specific (xenopus-rana) neuromuscular junctions were formed in vitro. nerve processes, without any schwann cell covering, made contacts anywhere along a muscle fibre, and the junctions resembled those seen during early regeneration of neuromuscular synapses in situ. functional contacts, ... | 1987 | 2885850 |
| biosynthesis of the neurofilament heavy subunit in xenopus oocytes microinjected with rat brain poly(a)+ rna. | in order to study the expression of the major subunit of neurofilaments (nfs), rat brain poly(a)+ rna was purified by three different procedures and was injected in xenopus laevis oocytes. this system was able to translate efficiently the 200 kda nf subunit as shown by a dot-blot immunoassay and by immunoprecipitation of labeled nf polypeptides. | 1987 | 2893252 |
| chromosome replication in cell-free systems from xenopus eggs. | cell-free systems from eggs of the frog xenopus laevis are able to perform most of the acts of eukaryotic chromosome replication in vitro. this now includes the crucial regulatory step of initiation, which had only been achieved for viral systems previously. purified dna or nuclei are able to initiate and complete semi-conservation replication in egg extracts in vitro (blow & laskey, cell 47, 557-587 (1986). replication does not require specialized dna sequences either in vitro or in microinject ... | 1987 | 2894683 |
| isolation of immunoreactive beta-endorphin-related and met-enkephalin-related peptides from the posterior pituitary of the amphibian, xenopus laevis. | acid extracts of the posterior pituitary of the amphibian, xenopus laevis, were analyzed with two heterologous region specific beta-endorphin rias. following gel filtration chromatography and cation exchange chromatography four peaks of immunoreactivity were detected. all four peaks were detected with a n-acetyl specific beta-endorphin ria. peak i represented 92% of the total immunoreactivity isolated following cation exchange chromatography. this peak had a net positive charge at ph 2.5 of +1 a ... | 1987 | 2964591 |
| co-evolution of base composition and codon usage in xenopus laevis and human globin genes with long-range dna organization of their genome. | eucaryotic dna is punctuated by many a+t-rich segments that we named a+t-rich linkers. two types of these a+t-rich linkers can be distinguished: (i) isolated a+t-rich linkers, and (ii) a+t-rich linkers crowded in clusters. we have analysed the distribution of a+t-rich linker across the alpha- and beta-globin gene domain in xenopus laevis and human genomes using isodenaturation and electron microscopy. comparison of our data with those previously obtained for the avian globin genes leads us to co ... | 1987 | 2957230 |
| analysis of allotolerance in thymectomized xenopus restored with semiallogeneic thymus grafts. | the triploid j strain xenopus laevis (mhc haplotype, j/j/j) were thymectomized as early larvae, and in the adult stage each animal was given a pair of thymuses or lymphocytes from semiallogeneic diploid donor frogs (j/k). the alloreactivity of host frogs was restored to third-party donors in terms of skin graft rejection and mixed leukocyte reaction, but there was specific unresponsiveness against the k haplotype. grafting of heavily irradiated (10,000 rads) thymuses also restored host reactivit ... | 1987 | 2957832 |
| prostaglandin regulation of reproductive behaviors in female xenopus laevis: sources and target sites. | 1987 | 2960159 | |
| segregation of mitochondria in the cytoplasm of xenopus vitellogenic oocytes. | in actively growing vitellogenic oocytes of xenopus laevis mitochondria segregate into 2 populations. one stays around the nucleus, actively replicates mitochondrial dna (mtdna), and builds up most of the stock of the mitochondria in the full-grown oocyte. the other moves toward the vegetal pole and stops replicating mtdna early in vitellogenesis. organelles of this population are components of the germ plasm of the cell. | 1987 | 2961387 |
| atpase activity of intact single muscle fibres of xenopus laevis is related to the rate of force redevelopment after rapid shortening. | five different fibre types have been recognized in the iliofibularis muscle of xenopus laevis. the force-velocity and histochemical characteristics of these fibres vary considerably and differences are also found in their myosin composition. in this study a comparison was made between the rate of atp hydrolysis estimated from the stable maintenance heat rate and the mechanical performance of fibres of type 1, 2 and 3. in the experiments, firstly the force-velocity relation of a fibre was determi ... | 1987 | 2959253 |
| t cell receptor-homologous mrna from a suppressor t cell clone directs the synthesis of antigen-specific suppressive products. | the lh8-105 t cell clone, obtained by radiation leukemia virus-induced transformation of hen egg-white lysozyme (hel)-specific mouse suppressor t lymphocytes, constitutively releases in the culture supernatant products able to induce specific suppression of the immune response to hel. lh8-105 cells rearrange and express the genes encoding the alpha and beta chains of the antigen-specific t cell receptor and display membrane t cell receptor structures. lh8-105 mrna specific for the alpha and beta ... | 1987 | 2952515 |
| electron microscopic studies of giant nucleus-like structure formed by lambda dna introduced into the cytoplasm of xenopus laevis fertilized eggs and embryos. | when bacteriophage lambda dna was injected into the cytoplasm of the fertilized egg of xenopus laevis, giant nucleus-like structures were assembled around the injected dna. these nucleus-like structures survived during cleavage and were partitioned into blastomeres at the blastula stage. the nucleus-like structures formed in the uncleaved fertilized eggs and the blastula cells were both surrounded by a bilayer nuclear membrane with nuclear pore complexes. the ultrastructural features of the lamb ... | 1987 | 2953439 |
| 46 kd mannose 6-phosphate receptor: cloning, expression, and homology to the 215 kd mannose 6-phosphate receptor. | we have isolated cdna clones encoding the entire sequence of the bovine 46 kd cation-dependent mannose 6-phosphate (cd man-6-p) receptor. translation of cd man-6-p receptor mrna in xenopus laevis oocytes results in a protein that binds specifically to phosphomannan-sepharose, thus demonstrating that our cdna clones encode a functional receptor. the deduced 279 amino acid sequence reveals a single polypeptide chain that contains a putative signal sequence and a transmembrane domain. trypsin diges ... | 1987 | 2954652 |
| adenovirus e1a requires synthesis of a cellular protein to establish a stable transcription complex in injected xenopus laevis oocytes. | the escherichia coli-expressed adenovirus e1a 13s mrna product injected into xenopus oocytes was active, as assessed by its ability to stimulate the transcription of an injected gene which is normally responsive to e1a in mammalian cells. in the presence of the protein synthesis inhibitors pactamycin or cycloheximide, e1a was correctly posttranslationally modified (phosphorylated) and transported to the nucleus; but it failed to stimulate the transcription of an injected gene containing the huma ... | 1987 | 2959858 |
| mitogen-activated xenopus laevis lymphocytes produce a t-cell growth factor. | mitogen-free and serum-free supernatants (sns) from cultures of phytohaemagglutinin (pha)-stimulated xenopus splenocytes, co-stimulated thymocytes, induced proliferation of splenic and thymic lymphoblast and supported growth of alloreactive t-cell lines. these sns had no effect on 'resting' splenocytes, as measured by uptake of tritiated thymidine ([3h]tdr). growth-promoting activity was also detected in sns of cultures containing alloreactive t-cell lines and either pha or irradiated stimulator ... | 1987 | 2958404 |
| isolation and expression of cdna clones coding for two sequence variants of xenopus laevis histone h5. | we have cloned and characterized cdnas coding for two variants of xenopus laevis h5 histone protein (previously called h1s). cdna was synthesized from rna of immature erythrocytes in a single reaction using a modification of the method of gubler and hoffman [gene 25 (1983) 263-269], and blunt-end ligated into the hincii site of the phage vector m13mp9. immunological screening with a polyclonal antibody yielded two clones expressing h5 peptide. sequence characterization revealed that both clones ... | 1988 | 2907322 |
| development of a metabolic activation system for the frog embryo teratogenesis assay: xenopus (fetax). | fetax (frog embryo teratogenesis assay: xenopus) is a 96-hr teratogenesis screening assay using embryos of the south african clawed frog, xenopus laevis. since xenopus embryos have limited xenobiotic metabolism through 96 hr of development, we have developed an in vitro metabolic activation system employing aroclor 1254-induced rat liver microsomes. by adding an exogenous source of mixed functional oxidase (mfo) activity, we may more accurately assess the teratogenic risk of proteratogenic compo ... | 1988 | 2905834 |
| function of c-mos proto-oncogene product in meiotic maturation in xenopus oocytes. | the c-mos proto-oncogene is expressed as a maternal mrna in oocytes and early embryos of xenopus laevis, but its translation product pp39mos is detectable only during progesterone-induced oocyte maturation. microinjection of mos-specific antisense oligonucleotides into oocytes not only prevents expression of pp39mos, but also blocks germinal vesicle breakdown, indicating that it functions during reinitiation of meiotic division. | 1988 | 2971141 |
| somatostatin-like immunoreactivity and glycine high-affinity uptake colocalize to an interplexiform cell of the xenopus laevis retina. | antibodies directed against somatostatin have been used to label a population of interplexiform cells (ipcs) in the xenopus laevis retina. these cells have spherical soma which lie in the inner nuclear layer (inl), adjacent to or one cell distal to the inner plexiform layer (ipl). processes from these cells project throughout the ipl, with a fairly dense accumulation of labeled dendrites in the upper two-fifths of the ipl and a dense, narrow band of labeled dendrites adjacent to the ganglion cel ... | 1988 | 2906071 |
| expression of the murine interferon gamma receptor in xenopus laevis oocytes. | this study describes the isolation of mrna for the murine interferon gamma receptor and its expression in frog oocytes. the binding properties and apparent molecular weight of the murine interferon gamma receptor protein synthesized in frog oocytes is similar to that found on mouse cells. this is the first report of a functional receptor for a polypeptide ligand (interferon gamma) expressed in and directly assayed on frog oocytes. | 1988 | 2971040 |
| the magainins: sequence factors relevant to increased antimicrobial activity and decreased hemolytic activity. | the magainins, two antimicrobial peptides found in the skin of the frog xenopus laevis, and 50 magainin analogs were synthesized by the method of simultaneous multiple peptide synthesis (smps). this series of peptides was prepared in order to examine the effects of omitting individual amino acids on antimicrobial activity. the series consisted of 22 magainin 1 omission analogs having a c-terminal carboxyl (m1-c) and 23 magainin 2 omission analogs having a c-terminal amide (m2-a), as well as both ... | 1988 | 2980783 |
| unmyelinated cutaneous afferent neurons activate two types of excitatory amino acid receptor in the spinal cord of xenopus laevis embryos. | the trunk and tail skin of xenopus laevis embryos near the time of hatching is innervated by the mechanoreceptive free nerve endings of rohon-beard neurons, a homogeneous class of cutaneous primary afferent fibers. rohon-beard neurons have cell bodies and axons in the dorsal spinal cord, where they monosynaptically excite a population of dorsolaterally situated interneurons (clarke and roberts, 1984). epsps can be recorded in these dorsolateral interneurons following electrical stimulation of th ... | 1988 | 2895802 |
| evaluation of the developmental toxicity of nicotine and cotinine with frog embryo teratogenesis assay: xenopus. | the teratogenic potential of nicotine and a primary metabolite, cotinine, was examined with fetax (frog embryo teratogenesis assay: xenopus). early embryos of xenopus laevis were exposed for 96 hr to nicotine or cotinine in two separate static renewal tests of each compound without addition of the metabolic activation system (mas). two static renewal tests of nicotine with the mas were also conducted. addition of the mas to nicotine reduced the lc50 from an average of 136 to 20 mg/l. however, th ... | 1988 | 2905544 |
| gaba release from xenopus retina does not correlate with horizontal cell membrane potential. | the relationship between horizontal cell membrane potential and the release of gaba was explored in the retina of xenopus laevis. the intracellularly recorded membrane potential of horizontal cells was monitored while the retina was exposed to different concentrations of depolarizing agents. the dose-response curves obtained revealed a rise from 5 to 95% maximum depolarization in 0.5-1.5 log unit concentration change. the molar concentrations that elicited a 20 mv depolarization were 40 mm (pota ... | 1988 | 2897092 |
| responses to gaba, glycine and beta-alanine induced in xenopus oocytes by messenger rna from chick and rat brain. | poly (a)+ messenger rna (mrna) was extracted from rat and chick brains, and injected into oocytes of xenopus laevis. this led to the expression of receptors that evoked membrane currents in response to gamma-aminobutyric acid (gaba), glycine and beta-alanine. these currents all inverted at about the chloride equilibrium potential in the oocyte, and showed a marked rectification at negative potentials. oocytes injected with mrna from chick optic lobe gave large responses to gaba and beta-alanine, ... | 1988 | 2898147 |