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changes in energy metabolism during the early development of xenopus laevis.xenopus embryos at various development stages were incubated in the presence of labelled substrates and the 14co2 production determined. from the rates of oxidation of glucose labelled in positions 1 and 6 and from that of radioactive acetate, pyruvate and glutamate, it was concluded that the embden-meyerhof pathway and the krebs cycle are functional during early embryogenesis, but that their relative participation in the metabolic processes is limited and increases from gastrulation onwards. ea ...19826124469
developmentally regulated poly(a) containing rna sequences in xenopus laevis. 19826125943
cerebrospinal fluid-contacting neurons and other somatostatin-immunoreactive perikarya in brains of tadpoles of xenopus laevis.in untreated tadpoles of xenopus laevis, stage 60 (nieuwkoop and faber 1956), somatostatin-immunoreactive perikarya and fiber networks are already discernible in the pallium and the septum, as well as in the anterior and posterior hypothalamus. in addition, somatostatin-immunoreactive cerebrospinal fluid (csf)-contacting neurons were found in the periventricular gray of the most caudal division of the ventral tuber cinereum. the results are discussed with respect to the inhibitory influence of t ...19826126275
translation of mrna from phytohemagglutinin-stimulated human lymphocytes: characterization of interferon mrnas.human lymphocytes obtained by cytapheresis were stimulated in spinner culture conditions by nonpurified pha in order to study the production of gamma interferon, and the characterization of ifn-gamma mrna. titers of interferon prepared in 0.6 to 4 1 batches, varied in 20 preparations from 8,000 to 32,000 units/ml. this interferon was unstable at ph 2: the residual antiviral activity after 20 h treatment was less than 3%. antibodies raised against gamma interferon from con a and sea-stimulated ly ...19826126511
effect of calmodulin inhibitor, stelazine, on the endocytosis of vitellogenin and transglutaminase activity in xenopus laevis oöcytes.the specific endocytosis of vitellogenin was measured in the presence of various concentrations of stelazine, a specific inhibitor of the calcium regulating protein, calmodulin. stelazine (200 microm) was found to inhibit the endocytosis of vitellogenin by 63% as determined by decreased uptake of vitellogenin into transitional yolk bodies and yolk platelets. the enzymatic activity of transglutaminase, a calcium-requiring enzyme implicated in receptor-mediated endocytosis, was not affected by the ...19826126807
a calcium-dependent transient outward current in xenopus laevis oocytes.membrane currents were investigated in xenopus laevis oocytes under voltage clamp. depolarizing pulses, given from a holding potential of about-100 mv, elicited a transient outward current when the membrane potential was made more positive than about-20 mv. as the potential was made increasingly positive the transient outward current first increased and then decreased. the amplitude of the transient current increased when the external ca2+ concentration was raised; and the current was abolished ...19826127718
effects of cold acclimation on the standard metabolic rate and osmotic fragility of erythrocytes in an aquatic anura, xenopus laevis. 19826128127
the effect of temperature on the contractile response of cardiac muscle from two frog species, rana temporaria and xenopus laevis, at two different calcium concentrations-i. at ph 7.7.1. mechanical parameters were recorded from paced ventricular cardiac muscle strips of two amphibian species. rana temporaria and xenopus laevis. 2. the strips contracted at ph 7.7 and with either 1.6 or 3.0 mm ca2+ while the temperature was changed from 5 to 30 degree c. 3. it is concluded that the cardiac muscles of the two frog species exhibited similar contractile responses upon temperature and ca2+ elevations at physiological ph, although x. laevis hearts displayed greater variation in tens ...19826128130
the effect of temperature on the contractile response of cardiac muscle from two frog species, rana temporaria and xenopus laevis, at two different calcium concentrations-ii. at ph 7.0 and ph 6.6.1. mechanical parameters were recorded from paced ventricular cardiac muscle strips of two amphibian species. rana temporaria and xenopus laevis. 2. the strips contracted at ph 6.6 and 7.0 with either 1.6 or 3.0 mm ca2+ while the temperature was changed from 5 to 30 degree c. 3. in the hearts of r. temporaria, but not in those of x. laevis, in increased ca2+ concentration at low ph could compensate for the effect of lowered ph. 4. it is concluded that during high co2 tension and/or low ph the m ...19826128131
co-existence of thyrotrophin releasing hormone and 5-hydroxytryptamine in the skin of xenopus laevis.1. the location, release and re-synthesis of thyrotrophin releasing hormone (trh) and 5-hydroxytryptamine (5-ht) in the skin of xenopus laevis (the south african clawed toad) have been determined using both morphological and analytical procedures. 2. high levels of trh and 5-ht are located specifically within the dermal granular glands of x. laevis and discharged from these glands following alpha-adrenergic stimulation. 4. the common occurrence and separate production of high levels of trh and 5 ...19826128147
polyadenylated mrnas from various developmental stages of xenopus laevis. role of 26 s mrna.in xenopus laevis embryos, the 26 s polyadenylated mrna, coding for the myosin heavy chain, shows a maximum relative concentration as measured by the 3h-poly(u)-hybridization technique, at the neural-plate stage (st. 12.5 of nieuwkoop and faber, [nf]) only in the dorsal (ectodermal and mesodermal) region, i.e. shortly before the morphological appearance of the somites. on the contrary, myosin-heavy-chain mrna cannot be observed in the ventral region with the same technique. this 26 s mrna begins ...19826128265
effects of d-alpha-aminoadipate on excitation of afferent fibers in the lateral line of xenopus laevis.the effects of d-alpha-aminoadipate (d alpha aa) on excitation of afferent nerve fibers in the xenopus laevis lateral line were studied in vitro. d alpha aa reversibly suppressed spontaneous activity and excitation induced by water motion at concentrations as low as 0.25-0.5 mm. higher concentrations (up to 10 mm) caused a greater suppression that was rapidly and fully reversible. l-alpha-aminoadipate at 0.25-1.0 mm had no suppressive effects. responses elicited by nmda (1.0-2.0 mm) were the mos ...19826129604
the central projections of lateral line and cutaneous sensory fibres (vii and x) in xenopus laevis.the central terminal fields of anterior (vii) and posterior (x) lateral line nerves, as well as the somatosensory fibres of vii and x, have been studied in xenopus laevis by cocl2 backfilling of appropriate nerves followed by timms intensification of whole brains. lateral line fibres terminate in a dorsomedial region of the medulla that extends from the auricular lobe of the cerebellum to the obex. there is great overlap in the terminal fields of lateral line fibres from nerves innervating diffe ...19826129631
synthesis of chick brain gaba receptors by frog oocytes.poly(a)-mrna, extracted from the optic lobe of chick embryos, directs the synthesis of gamma-aminobutyric acid (gaba) receptors in xenopus laevis oocytes. the receptors are inserted into the oocyte membrane, where they form receptor--channel complexes. when activated by gaba, and related agonists, the chick brain receptors open membrane channels that are permeable to chloride ions. thus, xenopus oocytes provide a novel and useful approach to the study of brain receptors.19826129641
localized protein synthesis during oogenesis of xenopus laevis: analysis by in situ translation. 19826130012
behavior of individual maternal pa+ rnas during embryogenesis of xenopus laevis. 19826130013
[somatostatin immunoreactive cells and their distribution in the gastrointestinal tract of xenopus laevis demonstrated with a microcomputer]. 19826131395
properties of acetylcholine receptors translated by cat muscle mrna in xenopus oocytes.poly(a)+ mrna, extracted from denervated skeletal muscles of the cat, directs the synthesis of acetylcholine receptors in xenopus laevis oocytes. the receptors are inserted in the oocyte membrane where they form acetylcholine receptor-channel complexes which have properties like those of the native receptors in the muscle membrane.19826144542
transient localizations of messenger rna in xenopus laevis oocytes. 19826172301
presence of ranatensin-like and bombesin-like peptides in amphibian brains.antibodies specific for the carboxyl-terminal regions of bombesin and of ranatensin were used to study the tissue distribution of substances immunochemically similar to these two peptides in three amphibian species. brain extracts of rana catesbeiana, rana pipiens, and xenopus laevis all contained considerable quantities of both types of immunoreactivity, with measured concentrations as high as several hundred pmol per g tissue. the two antibodies used in this study had very low crossreactivity ...19826172810
nature of albumin exported from the frog oocyte following microinjection of mouse liver mrna.microinjections of mouse liver mrna into xenopus laevis oocytes induced efficient export of a polypeptide with an apparent mr or 68,000 which was immunoprecipitable with anti-mouse albumin antibody. analysis of the anti-albumin precipitate of the exported protein by two-dimensional gel electrophoresis showed that the electrophoretic behavior precisely coincided with that of authentic mouse serum albumin. this result indicates that the xenopus oocyte may perform secretory processes similar or ide ...19826176576
sequence organization of the poly(a) rna synthesized and accumulated in lampbrush chromosome stage xenopus laevis oocytes. 19826176716
molecular cloning of human immune interferon cdna and its expression in eukaryotic cells.starting with mrna derived from staphylococcal enterotoxin a induced human splenocytes, dsdna was synthesized and inserted into unique bamhi site of the eukaryotic expression vector psv529 (1). a recombinant plasmid containing human immune interferon (ifn-gamma) cdna was identified by hybridization of plasmid inserted dna bound onto nitrocellulose filters with mrna derived from sea-induced splenocytes, translation of the eluted rna in xenopus laevis oocytes and assaying for ifn activity. plasmid ...19826176945
secretory proteins induced in human fibroblasts under conditions used for the production of interferon beta.human fibroblast cells treated with a combination of inhibitors of protein and rna synthesis [cycloheximide and actinomycin d as used to superinduce interferon beta (ifn-beta)] secrete two proteins with molecular masses of 22000 and 27000 kilodaltons (called 22-kdal and 27-kdal) that are precipitable with an antiserum raised against impure ifn-beta but are antigenically distinct from ifn-beta 1. translation in vitro of mrna extracted from human fibroblast cells induced for the production of ifn- ...19826178110
persistence of nonribosome bound 5 s rna in full-grown oocytes of xenopus laevis. 19826178636
parallel changes in protein synthesis and messenger rna content in growing and resting epithelial cells of xenopus laevis.the regulation of cell growth can be achieved at many levels but ultimately the regulatory factors must alter protein synthesis since growing cells always exhibit an increased rate of protein synthesis compared to resting cells. some studies using growing and nongrowing mammalian cells have shown that the rate of protein synthesis is directly dependent on mrna content. other studies have shown that growing the resting cells have similar amounts of mrna and that protein synthesis is regulated by ...19826178747
development of the marginal zone in the rhombenecephalon of xenopus laevis.the marginal zone is the most superficial component of the developing central nervous system. in this study we describe the pattern of formation of the marginal zone in xenopus laevis as seen with the light microscope and correlate its appearance with developing axon bundles seen with the electron microscope. the marginal zone was first identified at stage 26 on the ventrolateral aspects of the neural tube in restrictive foci throughout the medulla. by stage 28 this presumptive fiber area had ex ...19826179577
the determination of the instantaneous velocity of axonally transported organelles from filmed records of their motion.a computational procedure is described for obtaining reproducible, low noise estimates of the instantaneous velocity of axonally transported organelles. axonally transported organelles were detected in myelinated nerve fibers from xenopus laevis by dark-field microscopy. the motion of the organelles was recorded on motion picture film at 3 frames/s, and the position of organelles travelling in the retrograde direction was obtained as a pair of x (axial) and y (transverse) coordinates at each 0.3 ...19826179589
transcription of a gene for human u1 small nuclear rna.transcription of u1 small nuclear rna from a 592 bp fragment of human dna was analyzed in vivo and in vitro. when injected into xenopus laevis oocyte nuclei, the cloned dna is transcribed by rna polymerase ii to make human u1 snrna. thus the sequences of this fragment are sufficient for expression of the u1 snrna gene. moreover, injection of templates carrying deletions of flanking sequences demonstrates that the dna sequences required for in vivo transcription are located at least 100 nucleotid ...19826179630
cloning of xenopus laevis nuclear poly(a)-rich rna sequences. evidence for post-transcriptional control.cdna/rna hybridization experiments of polysomal and nuclear poly(a)-rich rna from early tadpole stages of xenopus laevis revealed that part of the nuclear poly(a)-rich rna sequences are not present within the polysomal polyadenylated rna. for a more detailed analysis of these sequences we have cloned double-stranded cdna derived from tadpole nuclear poly(a)-rich rna in the psti cleavage site of pbr 322. by colony screening with 32p-labelled cdna from polysomal and nuclear poly(a)-rich rna of the ...19826174330
effects of ototoxic antibiotics on sensory hair cell functioning.the isolated lateral-line organ of xenopus laevis was used to study reversible effects of low concentrations of aminoglycoside antibiotics on sensory hair cell functioning. extracellular receptor potentials and single fibre afferent nerve activity were recorded during stimulation of the lateral-line organ with sinusoidal water movements. the results show that dihydrostreptomycin in concentrations between 2.5 and 17.5 micrograms/ml caused an increase in spontaneous afferent nerve activity, probab ...19826174496
the spatial pattern of rna in fully grown oocytes of an amphibian, xenopus laevis.the possibility that maternal rna may be localized in specific oocyte regions was examined in fully grown oocytes of xenopus laevis. these oocytes were subdivided into six regions perpendicular to their animal-vegetal axis. each region was analyzed to determine the amount of total cellular rna, poly(a)+rna, and newly synthesized ribosomal rna. as would be expected from current evidence, total cellular rna was found to exist in a gradient-like fashion, highest at the animal pole and lowest at the ...19826174679
[effects of lindane, an organochlorine insecticide, on the thyroid gland of larvae of xenopus laevis daudin in premetamorphosis].the effects of 0.5 ppm of lindane were studied on the morphogenesis and the initial functioning of the thyroid gland. some disturbances were observed: the formation of the first follicles were delayed and ultrastructural changes were noted: increase in the number of mitochondria, reduction of the endoplasmic reticulum. this demonstrates a noxious effect of lindane at the beginning of the functional maturation of the thyroid gland.19826188517
the action of low-intensity pulsed ultrasound on amphibian embryonic tissues.amphibian embryos at different stages of development, and ectomesodermal explants (small pieces of embryonic tissue extirpated from lateral parts of the embryos just after neurulation), have been irradiated with continuous and pulsed ultrasound at a frequency of 0.88 mhz, spatial and temporal average intensities being within the range 0.025-0.1 w cm2. ultrasound pulse repetition frequencies were varied within 10-1000 hz, duty factor being constant and equal to 0.5. destruction of embryonic tissu ...19826984549
uptake and localization of 3h-2 deoxy-d-glucose by retinal photoreceptors.following dark incubation of isolated retinas of xenopus laevis in ringer solution supplemented with 3h-2-deoxy-d-glucose (2dg), virtually all of the uptake of the label was by the inner segments and synaptic bases of the photoreceptor cells. autoradiographs prepared from conventionally fixed tissue showed the same cellular distribution of label as those prepared from identically incubated, unfixed, freeze-dried retinas. however, fixation removed about 77% of the total counts. this fixation-labi ...19826976980
amphibian neurotensin (nt) is not xenopsin (xp): dual presence of nt-like and xp-like peptides in various amphibia.to clarify whether xenopsin (xp) is the amphibian counterpart of mammalian neurotensin (nt), extracts of skin, brain, and intestine from representative amphibians were subjected to immunochemical, chromatographic, and biological analyses. the results indicated the dual presence of nt- and xp-like peptides in extracts of tissues from xenopus laevis, rana catesbeiana, rana pipiens, bufo marinus, bufo americanus, and necturus maculosus, which were separated during gel chromatography on sephadex g-2 ...19826977439
autoradiographic study on the distribution of thymus-derived and thymus-independent lymphocytes in the spleen of xenopus laevis.non-thymectomized and early-thymectomized xenopus laevis were injected with 3h-thymidine, and labelled lymphocytes from thymus, spleen, and peripheral blood were transferred to histocompatible recipients to study their distribution by autoradiography. an extremely high proportion of labelled thymocytes was localized in the splenic red pulp of both non-thymectomized and thymectomized recipients after transfer. labelled splenic lymphocytes were localized in a significantly higher density in the sp ...19826978268
histones synthesized for use in early development of xenopus laevis are stored as a complex with antigenic properties similar to those of the octamer core of nucleosomes.serum of patients with systemic lupus erythematosus (sle) contains crossreacting autoantibodies which recognize histones in nucleosomes or when they are induced to form octamers in solution in the presence of 2 m nacl, but not when they are dissociated free in solution at physiological ionic strength. we have found that histones stored in eggs of xenopus laevis for use in rapid nuclear synthesis during early development react with this antibody. this reaction has been observed by radioimmunoassa ...19826979546
biophysics of underwater hearing in anuran amphibians.a standing wave tube apparatus was used to determine the biophysical basis of underwater hearing sensitivity in 3 species of rana and in xenopus laevis. a speaker inside the base of a vertical, water-filled 3 m steel pipe produced standing waves. pressure and particle motion were measured with a hydrophone and geophone respectively and were spatially 90 degrees out of phase along the length of the tube. microphonic responses were recorded from the inner ear of frogs lowered through pressure and ...19826980964
transport and phosphorylation of 2-deoxy-d-glucose by amphibian retina. effects of light and darkness.we studied the uptake of 2-deoxy-d-glucose (2dg) and the synthesis of its phosphorylated product 2dg-6-phosphate (2dg-6p) by the retinas of the clawed frog (xenopus laevis) and the bullfrog (rana catesbeiana). autoradiographs showed that most of the retinal 2dg uptake is by the photoreceptor layer. the 2dg accumulation by isolated xenopus retinas was time and concentration dependent. the kt for transport was 5.05 mm; vmax was 6.99 x 10(-10) mol . mg-1 tissue wet weight min-1. the km for 2dg-6p f ...19826981682
potassium permeability in thin amphibian myelinated fibres.potential clamp analysis of thin (10-12 micrometers) myelinated fibres from amphibia (xenopus laevis and rana temporaria) showed that they had a large delayed k-permeability (pk) and a pk/pna-ratio of 0.32, which is similar to the ratio in large (25-30 micrometers) frog fibres. these results agree with earlier evidence of a large delayed pk in 10-15 micrometers rana fibres; a recent description of a size-dependent difference in pk was thus not confirmed. the large pk (0.32 cm3s-1 x 10(-9) in 10- ...19826981796
development of peroxisomes in amphibians. ii. cytochemical and biochemical studies on the liver, kidney, and pancreas.the ontogeny of catalase-containing organelles was studied by cytochemical and biochemical methods in the liver, kidney, and pancreas during the development of rana catesbeiana. the biochemical differentiation of peroxisome in the liver and kidney was compared to that of xenopus laevis. catalase activity was localized after incubation in dab medium and studied biochemically by a spectrophotometric method. in rana catesbeiana the number of catalase-positive organelles per cell section is low in a ...19826982309
karyophilic proteins: polypeptides synthesized in vitro accumulate in the nucleus on microinjection into the cytoplasm of amphibian oocytes.the specific nucleocytoplasmic compartmentalization of proteins has been examined for some major soluble acidic nuclear proteins in oocytes of different amphibia. proteins synthesized and radioactively labeled by translation in vitro, by using mrna from ovaries of the frog xenopus laevis, were injected into the cytoplasm of living oocytes of xenopus or of the salamander pleurodeles waltlii. at various times after injection, nucleus and cytoplasm were manually separated and endogenous and injecte ...19826982470
in vivo distribution of proteins within a single cell.using the oocyte of xenopus laevis, we present an experimental system, involving two-dimensional gel electrophoresis, for measuring unambiguously the nucleocytoplasmic distribution of proteins within a living cell.19827200407
assembly of transcriptionally active 5s rna gene chromatin in vitro.we have studied the requirements for the in vitro assembly of transcriptionally active 5s rna gene chromatin from cloned xenopus laevis 5s plasmid dna. both plasmid dna and dna assembled into chromatin with xenopus oocyte extracts are transcribed efficiently in vitro. chromatin prepared by nacl reconstitution with purified histones in the absence of any cellular factors, however, is transcriptionally inert. a transcriptionally active template is formed if plasmid dna is incubated in an ovary ext ...19827201351
fate of amplified nucleoli in xenopus laevis embryos. 19827201429
structure of the active nucleolar chromatin of xenopus laevis oocytes.active nucleolar chromatin of xenopus laevis oocytes was prepared for electron microscopy by a step gradient method, which separates the chromatin from proteins and other constituents which might unspecifically bind at low ionic strength. between putative rna polymerases and within the non-transcribed spacer region, the chromatin appears as smooth, thin filaments, indistinguishable from pure dna adsorbed to the same specimen. these filaments are found under all conditions tested, even in the pre ...19827202203
mapping of transcription initiation and termination signals on xenopus laevis ribosomal dna.we have injected cloned derivatives of xenopus laevis ribosomal genes into x. laevis oocyte nuclei and examined the resulting transcription complexes in the electron microscope. from this work we conclude that the promoter lies somewhere within a region between -320 nucleotides upstream and +113 nucleotides downstream from the site of transcription initiation. this assignment agrees with inferences based on sequence conservation. it further suggests that the duplicated initiation region sequence ...19826948303
hybridization-selected translation of bombyx mori high-cysteine chorion proteins in xenopus laevis oocytes.xenopus laevis oocytes were injected with poly(a)+-mrna isolated from chorionating follicular epithelium of the domesticated silk moth (bombyx mori). on two-dimensional gel electrophoresis, the resultant translation products comigrated with authentic, secreted, chorion standards, demonstrating that the frog oocyte system synthesizes and correctly process virtually all major chorion components. a cdna clone has been shown to contain sequences complementary to those of mrnas encoding b mori high-c ...19826951160
expression of a cloned adenovirus gene is inhibited by in vitro methylation.in many viral and nonviral eukaryotic systems, an inverse correlation has been observed between the extent of dna methylation at 5'-c-c-g-g-3' sites and the extent of expression of specific genes as mrna. the e2a region of adenovirus serotype 2 (ad2) dna encodes the ad2-specific dna binding protein required for viral dna replication. in three lines of ad2 transformed hamster cells (he1, he2, and he3), multiple copies of the major part of the ad2 genome persist in an integrated state. cell lines ...19826951163
relationship between the two components of the split promoter of eukaryotic trna genes.plasmids containing eukaryotic trna genes are faithfully transcribed in the nucleus of xenopus laevis oocytes [cortese, r., melton, d. a., tranquilla, t. & smith, j. d. (1978) nucleic acids res. 5, 4593-4611]. it has been established that two separated regions within the coding sequence of a trna gene are essential and sufficient for promotion of transcription [hofstetter, h., kressmann, a. & birnstiel, m. l. (1981) cell 24, 573-585; ciliberto, g., castagnoli, l., melton, d. a. & cortese, r. (19 ...19826952243
in vitro replication of recombinant plasmids carrying chromosomal segments of xenopus laevis.recombinant plasmids carrying a segment of xenopus laevis chromosomal dna were constructed with plasmid pbr322 as the vector. a recombinant plasmid pxy65 carrying a 3.2-kilobase bamhi segment of the chromosome of x. laevis has been found to contain a repetitive sequence dispersed throughout the x. laevis chromosomes. this plasmid initiated replication in vitro when the supercoiled circular molecules were incubated in a replication system. the other recombinant plasmids tested and the pbr322 vect ...19826954512
dna primase activity associated with dna polymerase alpha from xenopus laevis ovaries.one of the two forms of dna polymerase alpha from ovaries of the frog xenopus laevis catalyzed ribonucleoside triphosphate-dependent dna synthesis on single-stranded circular fd phage dna templates. dna synthesis was dependent on atp and added template. ctp, gtp, and utp stimulated dna synthesis but were not required and could not substitute for atp. dna synthesis was not inhibited by alpha-amanitin. neither poly(dt) nor double-stranded dna served as template. analysis of [32p]-dtmp-labeled prod ...19826961403
the role of estrogen receptor in xenopus laevis vitellogenin gene expression.administration of estradiol 17 beta [estra-1,3,5(10)-triene-3,17-beta-diol] to male xenopus laevis induces the massive synthesis by the liver of the egg yolk precursor phospholipoglycoprotein, vitellogenin, and its cognate mrnas. restimulation of male x. laevis that have been previously induced to synthesize vitellogenin mrna but are inactive in vitellogenin mrna synthesis at the time of restimulation with estrogen results in more rapid accumulation of vitellogenin mrna and more efficient transc ...19826896404
a gradient of poly(a)+ rna sequences in xenopus laevis eggs and embryos. 19826896500
h3 and h4 histone cdna sequences from xenopus: a sequence comparison of h4 genes.ovarian poly (a) + rna from xenopus laevis and xenopus borealis was used to construct two cdna libraries which were screened for histone sequences. cdna clones to h4 mrna were obtained from both species and an h3 cdna clone from xenopus laevis. the complete dna sequences of these clones have been determined and are presented. these new sequences are compared with other h3 and h4 dna sequences both in the coding and 3' noncoding regions. we find that there is considerable non-random codon usage i ...19826896750
estrogen dramatically decreases albumin mrna levels and albumin synthesis in xenopus laevis liver.the levels of albumin mrna in xenopus laevis liver were measured at various times after injection of estradiol using two different methods involving hybridization of cloned albumin cdna to total liver rna. the absolute levels of albumin mrna fell by more than 95% during the first 4 days following estrogen treatment, then slowly returned to normal levels over the following 12 days. albumin synthesis paralleled the albumin mrna levels during the first 8 days after injection; but, 16 and 32 days af ...19826897244
structural analysis of a cdna clone from xenopus laevis containing a repetitive sequence element. 19826897540
the minimum intragenic sequences required for promotion of eukaryotic trna gene transcription.transcription of eukaryotic trna genes is controlled by two intragenic regions, the d-control region (which in the trna codes for the d-stem and -loop) and the t-control region (which in the trna codes for the t psi c loop). to determine whether these sequences alone are sufficient to promote trna gene transcription in vitro, the two control regions of a drosophila trnaarg gene were cloned separately from the context of the parental dna (these constructions are called trna minigenes). the trna m ...19826924209
assembly, glycosylation, and secretion of the oligomeric rat prostatic binding protein in xenopus oocytes.prostatic binding protein (pbp), a hormonally controlled oligomeric glycoprotein secreted by the rat ventral prostate, is composed of three different polypeptide chains, c1, c2, and c3. microinjection of prostate mrna into xenopus laevis oocytes results in the synthesis, processing, and correct assembly of these three components, and also in the export of pbp into the medium. the glycosylation of component c3--the only glycopeptide of pbp--by the oocyte enzymes does not lead to the same result a ...19826889597
expression of ribosomal-protein genes in xenopus laevis development.using probes to xenopus laevis ribosomal-protein (r-protein) mrnas, we have found that in the oocyte the accumulation of r-protein mrnas proceeds to a maximum level, which is attained at the onset of vitellogenesis and remains stable thereafter. in the embryo, r-protein mrna sequences are present at low levels in the cytoplasm during early cleavage (stages 2-5), become undetectable until gastrulation (stage 10) and accumulate progressively afterwards. normalization of the amount of mrna to cell ...19826889922
retinal protein synthesis in relationship to environmental lighting.a series of in vivo and in vitro experiments using xenopus laevis juvenile toads was conducted to probe the relationship between environmental lighting and protein synthesis in the retina. autoradiographic and biochemical analyses indicated that measurable changes in protein synthesis did not occur during a normal diurnal cycle when animals were conditioned to 12 hr light followed by 12 hr darkness each day (ld). however, when retinas from animals maintained in continuous darkness (dd) for 3 day ...19826890049
transcription of complementary repeat sequences in amphibian oocytes.repeat sequences are transcribed in the germinal vesicles of amphibian oocytes. in the hnrna population both complements of the repeats are found and can be readily detected because they form intermolecular duplex structures. the structure and formation of duplex regions have been studied in the hnrna of xenopus laevis, triturus cristatus, amphiuma means and necturus maculosus, a series of amphibians of increasing genome size (c-value). in t. cristatus, the duplex structures are mostly 600-1200 ...19826890891
soluble acidic complexes containing histones h3 and h4 in nuclei of xenopus laevis oocytes.oocyte nuclei of xenopus laevis contain nucleosomal-core histones in large amounts and in a soluble, non-chromatin-bound form. supernatant fractions (100,000 x g) from isolated nuclei are enriched in complexes containing histones h3 and h4, which are of distinct size (5.6s by sucrose gradient centrifugation, approximate molecular weight of 270,000 by gel filtration) and negatively charged (isoelectric at ph 4.4). these complexes bind to deae-sephacel and can be separated from nucleoplasmin. in d ...19826891289
the heat-shock response in xenopus oocytes is controlled at the translational level.xenopus laevis oocytes respond to high temperature (greater than 31 degrees c) by the synthesis of one major (70 kilodalton) protein and by a gradual reduction in the rate of normal protein synthesis. in contrast with most other cells, the heat-shock response of xenopus oocytes is controlled exclusively at the translational level. enucleated or alpha-amanitin-injected oocytes synthesize normal levels of heat-shock protein. thus high temperature induces the translation of preformed heat-shock mrn ...19826891290
insensitivity to cytochalasin b of surface contractions keyed to cleavage in the xenopus egg.in fertilized eggs of xenopus laevis a marked flattening of the pigmented animal hemisphere has been observed. the flattening begins 15-20 minutes before the appearance of the cleavage furrow. as the furrow develops, the pigmented surface relaxes and rounds up. the initial appearance of the furrow is thus shown to be a combination of furrow deepening and rounding up of adjacent pigmented surfaces. it is demonstrated that the flattening is not caused by gravity or osmotic mechanisms and that inte ...19826892157
immunological localization of the major architectural protein associated with the nuclear envelope of the xenopus laevis oocyte. 19827042377
is there really actin around xenopus laevis yolk platelets?our previous immunofluorescence experiments (1) on actin localization in xenopus development showed a fluorescent halo around xenopus yolk platelets. this fact suggests the presence of a sort of actin covering of the yolk platelet; we have called this structure the 'actin-shell'. in this work, by the use of a dnase i-fluorochrome complex, we were able clearly to demonstrate the presence of the actin-shell around xenopus yolk platelets. a proposal about the function of the actin-shell is made; it ...19827042383
b-lymphocyte differentiation in xenopus laevis larvae. 19827042416
localization of mitotic factors on metaphase chromosomes.the objective of this study was to determine whether the mitotic factors of hela cells, which induce meiotic maturation, i.e. germinal vesicle breakdown (gvbd) and chromosome condensation, when injected into fully grown xenopus laevis oocytes, were localized in the cytoplasm or associated with the metaphase chromosomes. cytoplasmic extracts were prepared by lysing mitotic hela cells in low-salt hypotonic buffer and separating the chromosomes by centrifugation. th mitotic factors bound to chromos ...19827042719
skin autografts as markers in the toad (xenopus laevis). 19827043079
dynamics of the cytoskeleton of epidermal cells in situ and in culture.the cytoskeleton of primary tissue-culture cells from the epidermis of xenopus laevis tadpoles was investigated by phase-contrast, immunofluorescence, and electron microscopy. the connection between the arrangement of different types of filaments and the mechanical properties of the epidermis is discussed. the bilayered epidermis attains stability from thick bundles of tonofilaments interconnecting the basal desmosomes. twisting of tonofilaments around each other can explain the occurrence of el ...19827044557
increased phosphorylation of ribosomal protein s6 during meiotic maturation of xenopus oocytes.a single ribosomal protein (mr, 32,000) becomes phosphorylated during progesterone-induced in vitro maturation of xenopus laevis oocytes. the protein is identified as 40s ribosomal protein s6. phosphorylation of s6 is monitored by incorporation of 32pi and by two-dimensional polyacrylamide gel electrophoresis. s6 is minimally phosphorylated in unstimulated oocytes. after progesterone treatment, phosphorylation of s6 precedes germinal vesicle breakdown (gvbd) and is maximal at the time when 50% o ...19827045876
nucleotide sequence of the 5'- and 3'- domains for rabbit 18s ribosomal rna.by direct rna sequence analysis we have determined the primary structures of both the 5' and 3' domains for rabbit 18s ribosomal rna. purified 18s rrna was labeled in vitro at either its 5' or 3' terminus with 32p, base-specifically fragmented enzymatically and chemically, and the resulting fragments electrophoretically fractionated by size in adjacent lanes of 140 cm long polyacrylamide sequencing gels run in 90% formamide. a phylogenetic comparison of both the mammalian 5' proximal 400 residue ...19827048256
nucleotide sequences of cloned cdna fragments specific for six xenopus laevis ribosomal proteins.we have previously constructed and selected six recombinant plasmids containing cdna sequences specific for different ribosomal proteins of xenopus laevis (bozzoni et al., 1981). dna cloned in these plasmids have been isolated and sequenced. amino acid sequences of the corresponding portions of the proteins have been derived from dna sequences; they are arginine- and lysine-rich as expected for ribosomal proteins. one of the cdna sequences has an open reading frame also on the strand complementa ...19827049839
intracellular glycosylation of vitellogenin in the liver of estrogen-stimulated xenopus laevis.pulse-chase experiments measuring the rates of incorporation of radiolabeled glucosamine and galactose into intracellular vitellogenin show that glycosylation of this multicomponent protein occurs in a golgi-enriched fraction isolated from homogenized liver slices. no apparent role of the rough endoplasmic reticulum in this process was demonstrable. kinetics of the intracellular translocation of glycosylated vitellogenin indicate that the galactosylated intermediate is secreted more rapidly than ...19827053388
the steroid ligands of estrogen binding proteins in xenopus laevis liver cytosol are primarily metabolites 17beta-estradiol.the interactions in vitro between [3h]estradiol and liver proteins from xenopus laevis have been examined to determine if the binding reaction meets criteria of steroid-receptors which may function in the induction of vitellogenesis. estrogenic hormones associated with proteins is serum and liver cytosol from xenopus laevis. however, the interactions between soluble liver proteins and estrogens apparently do not result from serum contamination of liver as specific binding was distinguishable by ...19827055614
an electrical block is required to prevent polyspermy in eggs fertilized by natural mating of xenopus laevis. 19827056442
testosterone 5 alpha-reductase in spinal cord of xenopus laevis.testosterone 5 alpha-reductase, the enzyme that converts testosterone to 5 alpha-dihydrotestosterone, is present in the spinal cord of xenopus laevis. in adult males the enzymatic activity is optimal at ph 7.4 and 27 degrees c; the apparent km is 2.0 x 10(-5) m and the vmax is 10.0 pmol/mg protein/h. enzymatic activity was assayed in segments of the spinal cord in each of four groups: control untreated males, females, castrated males, and sexually active clasping males. striking differences in b ...19827057185
structure of the active nucleolar chromatin of xenopus laevis oocytes.active nucleolar chromatin of xenopus laevis oocytes was prepared for electron microscopy by a step gradient method, which separates the chromatin from proteins and other constituents that might nonspecifically bind at low ionic strength. between putative rna polymerases and within the nontranscribed spacer region, the chromatin appears as smooth, thin filaments. for the first time, it is shown here that these filaments are indistinguishable from pure dna absorbed to the same specimen, even when ...19827060131
ribosomal protein s6 from xenopus laevis ovaries. isolation, phosphorylation in vivo and cross-reaction with heterologous anti-s6 antibodies.ribosomal protein s6 from xenopus laevis ovaries was prepared by ion-exchange chromatography on phosphocellulose and gel filtration on sephadex g-75. the protein was identified as s6 from its position on two-dimensional polyacrylamide gels and from its immunological cross-reaction with monoclonal antibody raised against chicken liver s6, and from the fact that it is the major phosphorylated protein of the small subunit. when oocytes were incubated with [32p]orthophosphate in the presence of prog ...19827060584
anomalous axonal outgrowth at the retina caused by injury to the optic nerve or tectal ablation in adult xenopus.the retina and optic nerve head have been examined by light and electron microscopy in adult xenopus laevis after injury to optic nerve fibres. intraorbital resection, transection or crush of the optic nerve all resulted in the appearance at the retina of a mass of actively growing axons which formed a ring around the intraretinal and adjacent choroidal portions of the optic nerve head. formation of this heterotopic axon population was first noted at two weeks after nerve injury and fibres persi ...19827069447
subcellular transport and ribosomal incorporation of microinjected protein s6 in oocytes from xenopus laevis.protein s6 was isolated from 40s ribosomal subunits of xenopus laevis oocytes, labeled with sodium boro[3h]hydride, and microinjected back into oocytes. in the first 4 h of incubation, the uptake of s6 into the nucleus increased to a maximum, with, however, no detectable incorporation into 40s ribosomal subunits. after this lag period, s6 was progressively integrated into the small ribosomal subunit. when rrna transcription was inhibited by actinomycin d, the uptake of s6 into the nucleus and it ...19827074038
inhibition of lens regeneration in larval xenopus laevis.the present research aims at showing the role played by the lens in inhibiting lens-forming transformations of the outer cornea of xenopus laevis tadpoles. two types of experiment were carried out: 1) lentectomy and insertion of a millipore filter disk at the side of the lens, and 2) lentectomy and insertion of a millipore disk with a central hole. results indicate that when the lens is replaced by a mechanical obstacle capable of preventing direct communication between vitreous and anterior cha ...19827077262
in vitro induction of germinal vesicle breakdown in xenopus laevis oocytes by melittin.the bee venom, melittin, is an amphipathic polypeptide comprising 26 amino acids with known sequence. it consists of a hydrophobic and a basic hydrophilic segment, possesses lipolytic activity, and stimulates na+-k+ pump activity. at 1.5 microm melittin induces 98% germinal vesicle breakdown (gvbd) in stage vi (dumont) oocytes and 96% in stage iv oocytes. progesterone (30 microm) induced 100% gvbd in stage vi oocytes and none in stage iv oocytes. gvbd occurs earlier with melittin than with proge ...19827084570
endocytosis of yolk proteins by xenopus laevis oócytes: kinetics of uptake of estrogen and gonadotropin-induced vitellogenins. 19827084664
lectin from embryos and oocytes of xenopus laevis. purification and properties.soluble extracts of xenopus laevis blastula stage embryos, oocytes, and adult liver contain lectin activities detected by agglutination of trypsinized, glutaraldehyde-fixed rabbit erythrocytes. lectin from the embryos and oocytes was purified by affinity chromatography on a column derivatized with melibiose. trace contaminants were removed either by preparative isoelectric focusing or by gel filtration. based on its behavior on sepharose 6b the purified oocyte lectin has an apparent molecular we ...19827085636
high sensitivity of xenopus gustatory receptors to amino acids and bitter substances.the gustatory nerve responses of the aquatic toad xenopus laevis to salts, acids, amino acids, and bitter substances were recorded. 1) the gustatory receptors were sensitive to amino acids and bitter substances. the thresholds were 10(-7) m for arg, 3 x 10(-9) m for strychnine, and 3 x 10(-8) m for quinine, 200-20,000 times lower than the thresholds for the respective stimuli in the bullfrog. 2) the basic and the neutral amino acids were effective whereas the acidic ones were not. relations betw ...19827091394
observations on the development of descending pathways from the brain stem to the spinal cord in the clawed toad xenopus laevis.anurans such as the clawed toad xenopus laevis offer a unique opportunity to study the ontogeny of descending pathways to the spinal cord. their transition from aquatic limbless tadpole to juvenile toad occurs over a protracted period time during which the animal is accessible for experimental studies. in xenopus laevis tadpoles the development of descending pathways has been studied from early limb-bud stage on (stage 50) with the aid of hrp slow-release gels. in stage 50, cells of origin of de ...19827091712
an improved method for the isolation of leucocytes from xenopus laevis blood. 19827095237
effects of cholera toxin and actinomycin on synthesis of [35s]methionine-labeled proteins during progesterone-induced maturation of xenopus laevis oocytes. 19827095262
urea cycle enzymes and glutamate dehydrogenase in xenopus laevis and bufo viridis adapted to high salinity.xenopus laevis was adapted stepwise to 600 m osmolar sodium chloride. after adaptation, the level of argininosuccinate lyase was raised 9-fold, carbamoylphosphate synthetase 6-fold, and ornithine carbamoyltransferase and arginase 3-fold. liver glutamate dehydrogenase was also raised 5-fold; kidney glutamate dehydrogenase was unchanged. in bufo viridis similarly adapted, there was a 5-fold increase in argininosuccinate lyase. when xenopus laevis was adapted to 600 m osmolar sucrose, there was onl ...19827097181
cholinesterase localization at sites of nerve contact on embryonic amphibian muscle cells in culture.cholinesterase (che), detected histochemically, was found to be localized at many sites of nerve-muscle contact in cultures of spinal cord and muscle cells derived from xenopus laevis embryos. such contacts were often characterized by a corresponding localization of acetylcholine receptors and by synaptic ultrastructure, including aggregates of clear vesicles in the nerve fibre and an 80-100 nm wide intercellular cleft. the che reaction product was localized in the cleft. when cultures were grow ...19827097313
[cellular proliferative potentials of the pigment and ciliated epithelium of the eye in clawed toads normally and during regeneration].it was shown by means of 3h-thymidine autoradiography that the cells of almost all layers of intact eyes had proliferative potencies both in albino and normal strains of xenopus laevis, as it is the case in the urodela. the removal of retina and lens in x. laevis, unlike in the urodela, did not result in the intensification of proliferation of the pigment epithelium cells. the cells of ciliary region represent the source of retina regeneration of x. laevis. the regenerating retina is incomplete ...19827099515
[ratio of the depressive effect of macromolecular synthetic inhibitors in the mitochondria to the concentration of gonadotropic hormones in the in vitro maturation of xenopus oocytes].the inhibitory action of ethidium bromide (ethbr) and chloramphenicol (cm) on in vitro oocyte maturation in xenopus laevis induced by different gonadotropic hormone concentrations was studied. two concentrations of hormone were used (hypophysial suspension of hcg): one yielding high but not maximal incidence of maturation and another exceeding 4 to 8 times the former. under the higher hormone concentration the inhibitory action of cm decreased and that of ethbr increased.19827099517
the influence of voltage conditioning on chloride currents in amphibian muscle membrane: the sigmoid conductance-voltage relation extended into the outward current region.sartorius muscle fibres of xenopus laevis were depolarized in solutions of high k+ content and then voltage clamped in solutions in which k+ was replaced by rb+ and(or) tetraethylammonium ion (tea+) at ph 9. a three-microelectrode clamp system was used in which the bath was held at virtual ground using an operational amplifier in a current meter configuration. the holding potential was set at zero membrane current potential (resting potential), close to -25 mv. a two-pulse paradigm was used to t ...19827104847
the glomus cell of the carotid labyrinth of xenopus laevis.the ultrastructure of the glomus cells of the carotid labyrinth was investigated in the anuran, xenopus laevis. these cells show many catecholamine containing granules. about 50 cells in groups of 3-5 are located near the sinusoids. morphologically, their organelles are similar to those previously reported in bufo vulgaris. striking features are (1) intimate appostion of the glomus cell to smooth muscle (g-s connection), (2) gap junctions between adjacent glomus cells, (3) exocytotic figures. ba ...19827105145
gap junctions and impulse propagation in embryonic epithelium of amphibia. a freeze-etching study.epithelium of amphibian embryos (cynops orientalis, xenopus laevis) was found in preceding experiments to generate and conduct impulses during a limited stage (26-37) of development . in order to elucidate the structural basis of impulse propagation, epithelial cells of four stages were examined by the freeze-etching method: (i) before and (ii) during acquisition of conductivity; (iii) when propagation was fully established, and (iv) when it was no longer present. only few gap junctions (gj) of ...19827105147
expression and organization of the globin genes in xenopus laevis. 19827111273
differential inhibition by progesterone of the adenylate cyclase of oocytes and follicle cells of xenopus laevis. 19827117515
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