Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
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| diploid gynogenesis in xenopus laevis and the localization with respect to the centromere of the gene for periodic albinism ap. | diploid gynogenetic xenopus laevis were obtained by inseminating the eggs with u.v. irradiated spermatozoa, and treating them with hydrostatic pressure to inhibit the expulsion of the second polar body. a u.v. dose of 3000 ergs/mm2 genetically inactivates the spermatozoa without loss of their ability to activate egg development. the use of a genetic marker on very large samples of eggs made it possible to verify the efficiency of the methods employed. the comparison of the development of diploid ... | 1984 | 6594425 |
| the nucleotide sequence of mannosyl-q-containing trnaasp from xenopus laevis oocytes. | the nucleotide sequence of trnaasp from x. laevis oocytes was determined as being: (sequence in text) the trna is 75 nucleotides long. this sequence is very similar (75% to 97% identity) to all other eukaryotic trnaasp sequenced so far, except for the bovine liver trnaasp (32% identity). the relation between the presence of a mannosyl group on queuosine (q) at position 34 and the nucleotide sequence of the anticodon loop is discussed. | 1984 | 6570443 |
| perpendicular orientation and directional migration of amphibian neural crest cells in dc electrical fields. | the behavior of cultured neural crest cells of ambystoma mexicanum and xenopus laevis in dc electrical fields was studied. in fields of 1-5 v/cm, isolated or confluent cells retract both their anode- and cathode-facing margins. subsequently, the cells elongate, with protrusive activity confined to their narrow ends. in larger fields (greater than or equal to 5 v/cm), protrusions form on the cathode-facing sides of the perpendicularly oriented cells. the cells then begin migrating laterally, perp ... | 1984 | 6582473 |
| xenopsin: the neurotensin-like octapeptide from xenopus skin at the carboxyl terminus of its precursor. | we have synthesized two oligodeoxyribonucleotide mixtures that contain sequences complementary to different parts of the hypothetical mrna sequence of xenopsin, a biologically active octapeptide found in skin extracts from xenopus laevis. the two primer pools were independently used to initiate reverse transcription on skin poly(a)+ rna and the resulting cdnas were then used to screen in parallel a cdna library prepared from skin poly(a)+ rna. one of the clones that hybridized with both probes w ... | 1984 | 6582494 |
| 3' editing of mrnas: sequence requirements and involvement of a 60-nucleotide rna in maturation of histone mrna precursors. | in vitro-synthesized transcripts of the sea urchin histone h2a gene with 3' extensions are efficiently and rapidly processed to h2a mrna with faithful 3' ends in xenopus laevis oocyte nuclei. processing requires the presence of a histone-specific dyad symmetry element and of h2a-proximal spacer sequences in the precursor rna. in dna injection experiments with a processing-deficient h2a mutant, the transcription products appear to terminate heterogeneously in the first 100-200 base pairs of the p ... | 1984 | 6583695 |
| alteration of the retinotectal map in xenopus by antibodies to neural cell adhesion molecules. | the neural cell adhesion molecule (n-cam) mediates neuron-neuron adhesion, is ubiquitous in the nervous system of developing and mature vertebrates, and undergoes major alterations in both amount and distribution during development. perturbation of homophilic (n-cam to n-cam) binding by univalent fragments of specific anti-n-cam antibodies has previously been found to alter neural tissue patterns in vitro. to show that significant alterations can also occur in vivo, antibodies to xenopus n-cam w ... | 1984 | 6588385 |
| coincidence of endoplasmic reticulum pattern as visualized by fitc-con a-fluorescence and electron microscopy. | fitc-con a-fluorescence and electron microscopy have been used in parallel for the visualization of rough endoplasmic reticulum in xenopus laevis tadpole heart primary tissue culture cells. rer distribution pattern as revealed by both methods is compared by superimposition of images of the same cell. coincidence of rer distribution is established. | 1984 | 6201466 |
| ultrastructural localization of nucleolar organizers during oogenesis in xenopus laevis using a silver technique. | silver staining at the electron microscopic level of the nucleolar organizers was carried out on xenopus laevis oocytes at various stages of oogenesis. the results indicate that a positive reaction takes place exclusively in the dense fibrillar component of the extrachromosomal nucleoli. this constituent undergoes morphological changes of distribution and architecture, which have been correlated with modifications of the transcriptional activity of the nucleoli. when nucleolar activity is reduce ... | 1984 | 6201496 |
| sensory physiology, anatomy and immunohistochemistry of rohon-beard neurones in embryos of xenopus laevis. | rohon-beard neurones show substance p-like immunoactivity in their somas and in their centrally projecting axons. peripherally, the morphology of their free nerve endings within the trunk skin has been shown using horseradish peroxidase staining. the excitation of rohon-beard neurones by natural and electrical stimulation of the skin has been examined using intracellular micro-electrodes in the late embryo of xenopus laevis. rohon-beard cells are sensitive to transient, local indentation of the ... | 1984 | 6201612 |
| studies on xenopus immunoglobulins using monoclonal antibodies. | monoclonal antibodies raised against xenopus ig recognize antigenic determinants on igm and low mol. wt ig (lmw ig or igy ). on sds-page two forms of mu were distinguished in the supernatant and cell lysate of tunicamycin-treated spleen cell culture. the two bands of v observed in serum appear to be the result of carbohydrate heterogeneity. the light chains resolved into two distinct bands which differed in peptide maps; the more slowly migrating band of light chain was preferentially associated ... | 1984 | 6203031 |
| xenopus laevis u1 snrna genes: characterisation of transcriptionally active genes reveals major and minor repeated gene families. | xenopus laevis u1 snrna genes are found in several different genomic arrangements. the major family of genes is organised in tandem repeats of 1.8 kb. the minor u1-family is much less abundant and is present on 1.2-kb hinfi restriction fragments. in addition there are genomic arrangements present in one or very few copies, which could represent the ends of repeating units. there is no evidence for the presence of u1 pseudogenes in xenopus. a cluster of u1 snrna genes consisting of a member of th ... | 1984 | 6203742 |
| immunological identity of proteins that bind stored 5s rna in xenopus oocytes. | in small oocytes of xenopus laevis, the three most abundant proteins are isolated as basic polypeptides with molecular weights of 48 kd (p48), 43 kd (p43) and 40 kd (p40, also known as transcription factor iiia). all three proteins share common properties in being able to bind specifically ribosomal 5s rna molecules and influence, in different ways, their rates of production and utilization. it has been shown by biochemical analysis and immunological characterization that the three proteins are ... | 1984 | 6203770 |
| early cellular interactions promote embryonic axis formation in xenopus laevis. | we have attempted to define the location and mode of action of axial determinants in the egg of xenopus laevis. to this end, we transplanted small numbers of blastomeres from normal 64-cell stage embryos into synchronous recipient embryos which had been irradiated with ultraviolet light prior to first cleavage. without transplantation, such embryos fail to develop dorsal structures of the embryonic body axis. we found that one to three blastomeres transplanted from the vegetal-most octet of cell ... | 1984 | 6203792 |
| synthesis of human u1 rna. ii. identification of two regions of the promoter essential for transcription initiation at position +1. | we have analyzed the requirements for human u1 rna transcription catalyzed by rna polymerase ii. in xenopus laevis oocytes, a human u1 rna gene with only 231 and 35 nucleotides of the 5' and 3' flanking regions, respectively (lund, e. and dahlberg, j. e. (1984) j. biol. chem. 259, 2013-2021), is able to support accumulation of human u1 rna. we show that the point in the template corresponding to the 5' end of u1 rna is a site of transcription initiation. that result rules out the possibility tha ... | 1984 | 6203910 |
| amino acid sequence of the carboxy-terminal part of an acidic type i cytokeratin of molecular weight 51 000 from xenopus laevis epidermis as predicted from the cdna sequence. | the dna sequence of a clone from a cdna library made from xenopus laevis skin is described. this sequence represents the 3'-terminal end of an mrna which codes for an epidermal cytokeratin polypeptide of mol. wt. 51 000 of the acidic (type i) subfamily as identified by hybridization-selection of mrnas, followed by gel electrophoretic identification of the polypeptides synthesized by translation in vitro. the partial amino acid sequence of the amphibian cytokeratin shows strong similarity to type ... | 1984 | 6204859 |
| the histone h5 variant in xenopus laevis. | the presumptive histone h5 of xenopus laevis has been characterized by sds and acid-urea-triton polyacrylamide gel electrophoresis and compared with chicken histone h5. chicken h5 has a lower electrophoretic mobility compared to that of xenopus h5 in both gel systems. it is shown, using a polyclonal antiserum against chicken h5, that the xenopus histone h5 is immunologically related to chicken histone h5. monoclonal antibodies have been prepared to the xenopus histone types h5 and h1a, that do n ... | 1984 | 6205766 |
| topography of the retinal ganglion cell layer of xenopus. | cell distribution in the retinal ganglion cell layer of xenopus laevis was studied by electron microscopy and the retinal wholemount method. unlike the familiar stratification of the retina, the ganglion cell perikarya and their axons were localised in the same layer, but strictly segregated in alternate rows converging in a radial pattern on the optic disc. rows of perikarya (retinal cords) were two to ten cells wide and clearly defined for a little more than half the distance between the optic ... | 1984 | 6206043 |
| altered levels of a 5 s gene-specific transcription factor (tfiiia) during oogenesis and embryonic development of xenopus laevis. | xenopus laevis oocytes contain a 38,000-da protein which serves both as a 5 s gene-specific transcription initiation factor (tfiiia) and to stabilize 5 s rna in ribonucleoprotein complexes. using an antibody to this protein we have measured the levels of tfiiia during oogenesis and embryonic development in x. laevis. the maximal steady state level (approximately 10(12) molecules/oocyte) is reached early in oogenesis but drops 10- to 20-fold in later stages and another 10- to 20-fold during ovula ... | 1984 | 6206067 |
| patterns of junctional communication in the early amphibian embryo. | it has long been recognized that cells in early embryos can communicate with each other via a direct cell-to-cell pathway, probably mediated by gap junctions. low electrical resistance pathways, detected electrophysiologically, have been identified in all species examined so far. however, studies in various embryos on the transfer of molecules larger than small ions (for example, fluorescent dyes in the molecular weight range 350-500) have given conflicting results. in all these studies the abil ... | 1984 | 6206399 |
| transcription of a long, interspersed, highly repeated dna element in xenopus laevis. | we have analyzed the transcription of 1723, a long, repeated dna element that is interspersed in the genome of xenopus laevis (b. k. kay and i. b. dawid (1983) j. mol. biol. 170, 583-596). we have detected rna homologous to 1723 in total cellular rna from ovaries, embryos, liver, and cultured kidney cells. transcripts from both strands of the element are present at similar concentrations in these different rna preparations. in oocytes, approximately 100 pairs of lampbrush chromosome loops are ac ... | 1984 | 6207063 |
| differential expression of multiple u1 small nuclear rnas in oocytes and embryos of xenopus laevis. | the small nuclear rna, u1, is a highly conserved, 165 nucleotide long rna which has been implicated in the processing of mrna precursors. we present evidence that in the amphibian x. laevis there exist at least seven species of u1 rna, which differ in sequence but not in length. strikingly, these rnas are not coordinately expressed. two of the u1 rnas are the predominant u1 species transcribed in the late blastula-early gastrula stages of xenopus embryogenesis. these two rnas, designated xu1a an ... | 1984 | 6207932 |
| small nuclear u-ribonucleoproteins in xenopus laevis development. uncoupled accumulation of the protein and rna components. | the accumulation of protein and rna components of small nuclear u-ribonucleoprotein particles is non-co-ordinate during oogenesis and early embryogenesis in xenopus laevis. northern blot hybridization of a cloned xenopus u2-rna gene to oocyte and embryo rnas demonstrates that the amount of small nuclear u2-rna per oocyte reaches a plateau early in oogenesis (at the start of yolk deposition); further accumulation is not observed in oogenesis, nor in embryogenesis until the late blastula stage. in ... | 1984 | 6208365 |
| multiple ubiquitin mrnas during xenopus laevis development contain tandem repeats of the 76 amino acid coding sequence. | a cdna clone, pxlgc20, was isolated from a library constructed from poly(a)+ rna from stage 10 x. laevis gastrulae. this sequence hybridizes with up to nine different rna species ranging in size from 1600 to 3500 nucleotides, regularly spaced at intervals of about 230 nucleotides. clone pxlgc20 contains two complete repeats of a 228 bp sequence as well as part of a third repeat, all adjacent and in the same orientation. one possible translational reading frame in pxlgc20 completely spans the rep ... | 1984 | 6209017 |
| alu sequences are processed 7sl rna genes. | 7sl rna is an abundant cytoplasmic rna which functions in protein secretion as a component of the signal recognition particle. alu sequences are the most abundant family of human and rodent middle repetitive dna sequences (reviewed in ref. 2). the primary structure of human 7sl rna consists of an alu sequence interrupted by a 155-base pair (bp) sequence that is unique to 7sl rna. in order to obtain information about the evolution of the alu domain of 7sl rna, we have determined the nucleotide se ... | 1984 | 6209580 |
| a temporal variation in nonneuronal protein synthesis in dorsal root ganglia and nerve and its significance to studies of axonal transport. | protein synthesis and fast axonal transport were studied in vitro using dorsal root ganglia (drg)-sciatic nerve preparations from the amphibian xenopus laevis. it was observed that the rate of incorporation of [3h]leucine into protein in drg and isolated segments of nerve began to increase 9 to 11 h after killing the animal, attaining at 13 to 17 h a maximum of 5- to 10-times preincrease (less than 9 h) values. at the same time as an increase in the rate of incorporation began, synthesis commenc ... | 1984 | 6199227 |
| cell lineage analysis of neural induction: origins of cells forming the induced nervous system. | horseradish peroxidase (hrp) was used as an intracellular lineage tracer in two experiments designed to reveal the sites of origin of cells that formed the duplicate embryo which developed in relation to an organizer grafted in the ventral marginal zone (vmz) of xenopus laevis embryos. in the first experiment a dorsal blastoporal lip fully labeled with hrp was grafted in the vmz of an unlabeled embryo at the beginning of gastrulation. this resulted in development of a second embryo in which labe ... | 1984 | 6199240 |
| in vitro methylation of hpaii sites in xenopus laevis rdna does not affect its transcription in oocytes. | the effect of methylation of x. laevis rdna on its transcription was tested by methylating all of the hpaii sites in a series of rdna plasmids and injecting the methylated rdna into x. borealis oocytes. analysis of rna transcribed from the injected plasmids showed that methylation of rdna in vitro does not affect transcription of x. laevis ribosomal genes. this result suggests that despite the observed correlation between demethylation of rdna and synthesis of ribosomal rna in x. laevis embryos ... | 1984 | 6199746 |
| cyclosporin a is a differential inhibitor of eukaryotic rna polymerases. | in order to investigate the molecular mechanism of biological action of the drug cyclosporin a (csa), we have studied its effect on eukaryotic rna polymerase activities in two systems: (a) in vitro transcription; (b) injection into frog oocytes. the electron microscopic transcription r-loop method [1] has been used to assay for specific transcription of an immunoglobulin gene clone in hela cell lysates. in this system, csa inhibits efficiently the transcription of immunoglobulin genes. dilution ... | 1984 | 6200340 |
| helper activity for antibody synthesis encoded by mrna extracted from human peripheral blood mononuclear cells. | translation products in xenopus laevis of mrna from human peripheral blood mononuclear cells were tested for their capacity to replace t cells in the anti-srbc response of nude spleen cells. when the starting material came from pha or fcs-stimulated lymphocytes, the translated lymphokines, displaying such a b cell helper activity were found to be encoded by mrna sedimenting at 6-7s and 13s on a sucrose density gradient. 6-7s mrna from control, non-stimulated lymphocytes was also able to code for ... | 1984 | 6201168 |
| lectins and substitution for helper function in anti-hapten responses in xenopus laevis. | substitution by lectins for the carrier-priming requirement in thymus-dependent, antigen-binding responses in xenopus laevis has been examined. concanavalin a (con a) was found to substitute for carrier priming in control, early-thymectomized and adult-thymectomized animals, but not in animals given a single, high dose of n-methyl-n-nitrosourea, which has a permanent effect on certain thymus-dependent functions in this species. lipopolysaccharide and other lectins, such as peanut agglutinin and ... | 1984 | 6235180 |
| [expression of hepatitis b virus (hbv) genome in the oocytes of two species of amphibians]. | xenopus laevis and pleurodeles waltlii oocyte nuclei are injected with a recombinant plasmid pcp 10, carrying two hepatitis b virus (hbv) genomes in a tandem arrangement. transcription occurs in oocytes of both species and production of viral rnas is demonstrated; better quantitative results are obtained with p. waltlii oocytes. two viral proteins are detected: hepatitis b surface antigen (ag hbs) and hepatitis b core antigen (ag hbc). these proteins can be shown only in oocyte homogenates, and ... | 1984 | 6235876 |
| cell surface expression of murine, rat, and human fc receptors by xenopus oocytes. | we report that xenopus laevis oocytes can efficiently translate and insert heterologous membrane receptors into the oocyte plasma membrane, where they can be detected by the binding of either monoclonal antibodies or ligands. thus, oocytes injected with mrna from the mouse j774 macrophage-like cell line, the rat rbl-1 basophilic leukemia, and the u937 promonocyte cell line, bound 2.4g2 fab, rat ige, and mouse igg2a, respectively. the increase in the high avidity fc gamma r observed after gamma-i ... | 1984 | 6236275 |
| a qualitative difference in the interleukin 2 (il-2) requirement of helper and cytotoxic t lymphocytes. | a qualitative difference in the requirement of mouse helper and cytotoxic t lymphocytes for interleukin 2 (il-2) was revealed by offering such cells il-2 synthesized in xenopus laevis oocytes that had been microinjected with messenger rna (mrna) encoding human il-2. while both helper and cytotoxic mouse t-cell lines proliferate in response to the il-2 present in medium conditioned by stimulated human lymphocytes, only helper-t-cell lines respond to human il-2 secreted from oocytes. this result d ... | 1984 | 6236885 |
| calcium sequestering activities of reticulum vesicles from xenopus laevis oocytes. | membrane vesicles isolated from xenopus laevis full-grown stage vi and mature oocytes accumulate 45ca in the presence of atp and oxalate. the ca2+-pumping activity measured in vitro does not appear to be modified during meiotic maturation; it is not affected by the complex ca2+-calmodulin. preliminary experiments have shown that the addition of na+ (30 mm) rapidly discharges accumulated 45ca into oocyte vesicles indicating that a na+/ca2+ exchange system occurs in this membrane fraction. during ... | 1984 | 6238836 |
| localization of soluble endogenous lectins and their ligands at specific extracellular sites. | soluble lectins of chicken, rat, frog, and the cellular slime mold, dictyostelium discoideum, were purified and specific antibodies raised against these proteins were used to immunohistochemically localize the lectins in and around the tissues in which they were synthesized. within cells, some of these soluble lectins (chicken-lactose-lectin-ii in intestinal goblet cells, discoidin ii in prespore cells) appear to be concentrated within vesicles whereas others (e.g., rat beta-galactoside lectin i ... | 1984 | 6240298 |
| amiloride and other blockers of electrolyte flux as inhibitors of progesterone-stimulated meiotic maturation in xenopus oocytes. | amiloride and seven of its analogues, as well as seven substances of other structural types, all of which control electrolyte transport, were tested for their effectiveness for inhibiting the progesterone-stimulated meiotic maturation cycle of oocytes from the amphibian xenopus laevis. data were also collected on the ability of the oocytes to recover from the drug's inhibitory effect and on the toxicity of each drug. the data revealed that up to a 14-fold difference exists in the inhibitory conc ... | 1984 | 6321028 |
| comparative analysis of the cdna sequences derived from the larval and the adult alpha 1-globin mrnas of xenopus laevis. | the complete nucleotide sequences of cloned cdna segments derived from the larval and the adult alpha 1-globin mrna of xenopus laevis have been determined. these sequences comprise part of the 5' noncoding region, the entire coding region and the 3' noncoding region, including the polyadenylation site. the larval sequence differs from the adult one by a much longer 3' noncoding region. the sequences diverge by 47%, but codon usage is similar. comparison of the amino acid sequences of vertebrates ... | 1984 | 6322851 |
| anucleolate frog embryos contain ribosomal dna sequences and a nucleolar antigen. | previous studies of xenopus laevis embryos homozygous for the nucleolar deletion mutation have concluded that these embryos contain few, if any, copies of the genes for the 18 s and 28 s ribosomal rnas. using hybridization to restriction endonuclease digests of dna it is found, in fact, that a small amount of ribosomal dna is still present in such embryos. the ribosomal dna in these embryos appears to include a few normal repeats together with a variety of unusual fragments containing either spa ... | 1984 | 6323234 |
| the nucleotide sequence of a rat 18 s ribosomal ribonucleic acid gene and a proposal for the secondary structure of 18 s ribosomal ribonucleic acid. | the nucleotide sequence of a rat 18 s rrna gene was determined. the 18 s rrna encoded in the gene contains 1874 nucleotides, and the molecular weight estimated from the sequence is 6.09 x 10(5). the sequences of rat and xenopus laevis 18 s rrnas are very similar; the only differences of consequence are the insertions between nucleotides 197 and 206 and between 258 and 279 of the rat nucleic acid of sequences rich in guanine and cytosine. a proposal is presented for the secondary structure of rat ... | 1984 | 6323401 |
| messenger rna from human brain induces drug- and voltage-operated channels in xenopus oocytes. | sodium channels and receptors to serotonin and kainate were 'transplanted' from human brain into frog oocytes, by isolating messenger rna from a fetal brain, and injecting it into xenopus laevis oocytes. the mrna was translated by the oocyte and induced the appearance of functional receptors and channels in its membrane. this approach renders drug- and voltage-operated channels of the human brain more amenable to detailed study. | 1984 | 6323990 |
| construction of a uga suppressor trna by modification in vitro of yeast trnacys. | in this paper we describe the construction of a yeast trnacys uga suppressor. after specific hydrolysis of the parent molecule, the first base of the anticodon gca was replaced by a uracil. the resulting molecule, harboring a uca anticodon, was injected into xenopus laevis oocytes in order to test its biological activities. the level of aminoacylation was similar to that of the parent molecule. readthrough of the uga termination codon in beta-globin mrna, coinjected with the trna, indicated supp ... | 1984 | 6363071 |
| synthesis and partial maturation of the alpha- and gamma-subunits of the mouse submaxillary gland nerve growth factor in xenopus laevis oocytes. | sera raised against the alpha-, beta- and gamma-subunits of the mouse 7 s ngf were used to characterize translation products coded by submaxillary gland mrnas microinjected into xenopus oocytes. anti-beta ngf sera did not cross-react with any material. in contrast, the precursors of the alpha- and gamma-subunits, as well as that of renin were identified. use of tunicamycin, and a comparison of the translation products obtained in oocytes or in the reticulocyte lysate indicated that oocytes achie ... | 1984 | 6363124 |
| structure and transmembrane nature of the acetylcholine receptor in amphibian skeletal muscle as revealed by cross-reacting monoclonal antibodies. | a collection of 126 monoclonal antibodies (mabs) made against acetylcholine receptors (achrs) from the electric organs of torpedo californica or electrophorus electricus was tested for cross-reactivity with achrs in cryostat sections of skeletal muscle from rana pipiens and xenopus laevis by indirect immunofluorescence. 49 mabs (39%) cross-reacted with achrs from rana, and 25 mabs (20%) cross-reacted with achrs from xenopus. mabs specific for each of the four subunits of electric organ achr (alp ... | 1984 | 6363425 |
| pronounced structural similarities between the small subunit ribosomal rna genes of wheat mitochondria and escherichia coli. | we present here the nucleotide sequence of the small subunit (18s) rrna gene from wheat mitochondria. aside from five discrete variable domains, this gene and the analogous (16s) rrna gene in escherichia coli show essentially a one-to-one correspondence in their potential secondary structures, with regions accounting for 86% of the bacterial 16s rrna having a strict secondary structure counterpart in the mitochondrial 18s rrna. primary sequence identity between the two rrnas ranges from 73% to 8 ... | 1984 | 6364144 |
| a survey of h1o-and h5-like protein structure and distribution in higher and lower eukaryotes. | a survey of h1o and h5-like proteins has been conducted through a range of higher and lower eukaryotic species. all mammals examined possessed h1o proteins, although in variable amounts, and the protein's structure was well conserved, though not invariant. the testis-specific histone hlt (from rat) did not have an h1o-like structure and it appears that h1o does not occur in spermatocytes in any form. the results also show that xenopus laevis contains h1o-like proteins, but lower, non-vertebrate ... | 1984 | 6365542 |
| electron microscopic immunolocalization of a karyoskeletal protein of molecular weight 145 000 in nucleoli and perinucleolar bodies of xenopus laevis. | amplified nucleoli of xenopus laevis oocytes contain a major karyoskeletal protein of mr 145 000 insoluble in low- and high-salt buffer as well as in non-denaturing detergents. electron microscopic localization on native and high-salt extracted nucleoli using specific murine antibodies against this polypeptide and gold-coupled antibodies for visualization reveals that the mr 145 000 protein is located in coils of filaments of ca 4 nm diameter. in addition, this protein occurs in the medusoid fil ... | 1984 | 6365576 |
| the effect of insulin on intracellular ph and ribosomal protein s6 phosphorylation in oocytes of xenopus laevis. | both insulin and progesterone are capable of stimulating germinal vesicle breakdown (gvbd) of large, stage vi oocytes of xenopus laevis. numerous studies have shown an increase in intracellular ph (phi) and ribosomal protein s6 phosphorylation prior to gvbd in oocytes treated with progesterone. in this study the effect of insulin and progesterone on phi and s6 phosphorylation was compared. both hormones increased phi and s6 phosphorylation to similar levels and the time course of phi change was ... | 1984 | 6365656 |
| induction of germinal vesicle breakdown in xenopus laevis oocytes: synergistic action of progesterone and insulin. | progesterone is the hormone that reinitiates the meiotic division of amphibian oocytes and insulin and insulin-like growth factors are also active on defolliculated oocytes in vitro. we have studied xenopus laevis oocytes (stage 5-6) of different hormonal sensitivities, obtained from unstimulated and from human chorionic gonadotrophin-stimulated females. some oocytes from unstimulated females were also precultured with a subthreshold level of progesterone. a dose-dependent potentiating effect of ... | 1984 | 6368732 |
| enzymatic conversion of adenosine to inosine in the wobble position of yeast trnaasp: the dependence on the anticodon sequence. | we have investigated the specificity of the trna modifying enzyme that transforms the adenosine at position 34 (wobble position) into inosine in the anticodon of several trnas. for this purpose, we have constructed sixteen recombinants of yeast trnaasp harboring an axy anticodon (where x or y was one of the four nucleotides a, g, c or u). this was done by enzymatic manipulations in vitro of the yeast trnaasp, involving specific hydrolysis with s1-nuclease and rnaase a, phosphorylation with t4-po ... | 1984 | 6369251 |
| ribonucleoprotein particles from xenopus eggs and embryos. neural-archencephalic-inducing activity of the protein moiety. | ribonucleoprotein particles were isolated from unfertilized eggs and gastrula stages of xenopus laevis. the particles from both stages induce in gastrula ectoderm the formation of large foreheads (neural-archencephalic-inducing activity), whereas ribosomal subunits have no inducing activity. the inducing activity of particles from both stages is largely abolished after treatment with proteolytic enzymes and to some extent with ribonuclease. the protein moiety of gastrula ribonucleoprotein partic ... | 1984 | 6370694 |
| inactivation of mitotic factors by ultraviolet irradiation of hela cells in mitosis. | extracts from mitotic hela cells, when injected into fully grown xenopus laevis oocytes, exhibit maturation-promoting activity (mpa) indicated by germinal vesicle breakdown (gvbd) and chromosome condensation. recently, we observed that the mpa of mitotic cell extracts is neutralized by the inhibitors of mitotic factors (imf) in hela cells, which are activated at telophase and remain active throughout the g1 period. the activity of the imf coincides with the process of chromosome decondensation, ... | 1984 | 6371031 |
| the identification of a tissue-restricted plasma membrane marker in xenopus laevis embryos by using a monoclonal antibody. | a library of monoclonal antibodies raised against partially purified membrane fractions from xenopus laevis oocytes has been produced. one of these antibodies has been cloned and characterized in detail. it was found to be specific for a membrane-bound antigen of apparent mr, 55,000. the distribution of the antigen has been studied by indirect immunofluorescence on sections of x. laevis embryos and has been found to be highly specific for some ectodermal and endodermal tissues. it was not presen ... | 1984 | 6373020 |
| secondary structure of mouse 28s rrna and general model for the folding of the large rrna in eukaryotes. | we present a secondary structure model for the entire sequence of mouse 28s rrna (1) which is based on an extensive comparative analysis of the available eukaryotic sequences, i.e. yeast (2, 3), physarum polycephalum (4), xenopus laevis (5) and rat (6). it has been derived with close reference to the models previously proposed for yeast 26s rrna (2) and for prokaryotic 23s rrna (7-9). examination of the recently published eukaryotic sequences confirms that all pro- and eukaryotic large rrnas sha ... | 1984 | 6374617 |
| elicitation of weak immune response in larval and adult xenopus laevis by allografted pituitary. | to test the claim that tolerance to organ-specific self antigens is established during the ontogenic development of the immune system, pituitary anlagen were removed from early tailbud embryos of xenopus laevis, and the resulting hypophysectomized tadpoles were grafted with pituitaries after the tadpoles had become immunocompetent. the result was that none of the histocompatible or allogeneic pituitary grafts was rejected throughout an observation period of 100 days. subsequent experiments revea ... | 1984 | 6382714 |
| subcellular distribution of ribosomal proteins s6 and el12. analysis by autoradiography and immunofluorescence of sections from oocytes of xenopus laevis. | the process of ribosome assembly in eukaryotes was studied by injecting tritium-labeled ribosomal proteins s6 and el12 into oocytes of xenopus laevis. the subcellular distribution of the two proteins was visualized by means of autoradiography in sections of oocytes. protein s6 but not el12 was found in the nucleus where it accumulated at the nucleoli. in the presence of actinomycin d the accumulation of s6 at the nucleoli was reduced. in-situ immunofluorescence studies indicated that s6 is locat ... | 1984 | 6383624 |
| interaction of metabolic inhibitors with actin fibrils. | the dependence of the arrangement of fibrillar actin in cultured endothelial cells on metabolic conditions was investigated with cellular elements derived from the heart of xenopus laevis tadpoles. either primary culture or an established cell line (xth-2) were used in these studies. the metabolic stage of the cells was influenced by inhibiting respiration and lactate production. the actin pattern was revealed either by indirect immunofluorescence or by tetramethylrhodaminyl (tritc)-phalloidin f ... | 1984 | 6386168 |
| collagen transition types during osteogenesis in xenopus laevis. an immunofluorescence study with heterologous antisera. | 1984 | 6386627 | |
| oocytes and early embryos of xenopus laevis contain intermediate filaments which react with anti-mammalian vimentin antibodies. | previous studies have shown that xenopus oocytes possess a cortical shell, which includes actin-containing microfilaments and cytokeratin-containing intermediate filaments. in this paper we show that oocytes of xenopus laevis also contain filaments throughout their cytoplasm which are stained by several anti-vimentin antibody preparations. we also show that dramatic changes in pattern of these filaments occur during oocyte differentiation, first during vitellogenesis, and then during maturation ... | 1984 | 6389749 |
| structural requirements for the interaction of 5s rrna with the eukaryotic transcription factor iiia. | in order to study the binding of the eukaryotic transcription factor iiia to heterologous 5s rrnas with a low degree of overall sequence conservation (less than 20%) we have utilized a transcription competition assay involving eubacterial, archaebacterial and eukaryotic 5s rrnas. all the molecules inhibit xenopus 5s rrna transcription specifically, which suggests that only a small amount of specific conserved rna sequences, if indeed any, are essential for the interaction of the transcription fa ... | 1984 | 6390342 |
| post-translational modification of exogenous proteins in xenopus laevis oocytes. | 1984 | 6397378 | |
| karyoskeletal proteins and the organization of the amphibian oocyte nucleus. | we have investigated the existence of structural components in the nucleus of the oocyte of xenopus laevis and other amphibia that are insoluble in non-denaturing detergents and buffers of low and high ionic strength. these cells are particularly suitable for such studies as they have a high frequency of extrachromosomal amplified nucleoli and pore complexes of the nuclear envelope. using biochemical and immunological techniques, we have shown these structures to contain only two major proteins. ... | 1984 | 6397470 |
| changes in antibody and complement production in xenopus laevis during postmetamorphic development revealed in a primary in vivo or in vitro antibody response. | xenopus laevis (g-line) mounts a primary plaque forming cell (pfc) response either in vivo or in vitro following challenge with foreign erythrocytes. methods are described for generating and assaying the response, which specify criteria such as antigen dose, antigen choice, response kinetics, and complement source. the results suggest that at the peak of the primary response (approximately day 6), animals of different ages produce predominantly different 'classes' of antibody which display marke ... | 1984 | 6398353 |
| restoration of the antibody response to sheep erythrocytes in thymectomized xenopus implanted with mhc-compatible or mhc-incompatible thymus. | these experiments make use of an amphibian model system for investigating the role of the thymus in t helper cell education. clawed toads (xenopus laevis), thymectomized at 7 days, are unable to mount an antibody response to thymus-dependent antigens, such as sheep red blood cells (srbc). when thymectomized larvae are implanted with larval thymuses (either irradiated or non-irradiated), incompatible at the major histocompatibility complex (mhc) or with mhc-compatible or -incompatible 'adult' thy ... | 1984 | 6398354 |
| the onset of activation responsiveness during maturation coincides with the formation of the cortical endoplasmic reticulum in oocytes of xenopus laevis. | immature, stage vi oocytes of xenopus laevis fail to activate (i.e., to propagate a cortical reaction and elevate a fertilization envelope) when pricked or exposed to a23187. we determined the times during maturation when immature oocytes treated with progesterone in vitro developed the capacity to respond to pricking and to ionophore. responsiveness to ionophore first appears at about 3.5-4.5 hr after progesterone treatment; all oocytes are activated by 8-9 hr after progesterone. the capacity t ... | 1984 | 6421640 |
| [does masui's ca-sensitive cytostatic factor exist in the cytoplasm of mature nonactivated eggs of acipenser stellatus, rana temporaria and xenopus laevis?]. | the cytoplasm of mature non-activated and cleaving eggs of a. stellatus and r. temporaria had no cytostatic effect. the cytoplasm treated with egta, being injected in one of two blastomeres of the cleaving egg of the same species, inhibits fully or partially the cleavage. the nuclei in the "arrested" blastomeres had, however, vesicular structure but were not blocked at metaphase, as could be expected if the cleavage was inhibited by a cytostatic factor described by masui (1974). the portion of p ... | 1984 | 6422374 |
| xenopus laevis 18s ribosomal rna: experimental determination of secondary structural elements, and locations of methyl groups in the secondary structure model. | 18s ribosomal rna from x. laevis was subjected to partial digestion with ribonucleases a or t1 under a variety of conditions, and base-paired fragments were isolated. sequence analysis of the fragments enabled five base-paired secondary structural elements of the 18s rna to be established. four of these elements (covering bases 221-256, 713-757, 1494-1555 and 1669-1779) confirm our previous secondary structure predictions, whereas the fifth (comprising bases 1103-1125) represents a phylogenetica ... | 1984 | 6424099 |
| biosynthesis of thyrotropin releasing hormone in the skin of xenopus laevis: partial sequence of the precursor deduced from cloned cdna. | skin of xenopus laevis contains relatively large quantities of thyrotropin releasing hormone (trh). total mrna isolated from skin was cloned in the plasmid puc8. among 1400 cdna clones, one was found with an insert of 478 nucleotides coding for the amino-terminal part of prepro-trh. this clone was detected using a mixture of two synthetic undecanucleotides for colony hybridization. the single open reading frame starts with a methionine residue and a stretch of hydrophobic amino acids, as is typi ... | 1984 | 6425056 |
| cell cycle dynamics of an m-phase-specific cytoplasmic factor in xenopus laevis oocytes and eggs. | we have examined the regulation of maturation-promoting factor (mpf) activity in the mitotic and meiotic cell cycles of xenopus laevis eggs and oocytes. to this end, we developed a method for the small scale extraction of eggs and oocytes and measured mpf activity in extracts by a dilution end point assay. we find that in oocytes, mpf activity appears before germinal vesicle breakdown and then disappears rapidly at the end of the first meiotic cycle. in the second meiotic cycle, mpf reappears be ... | 1984 | 6425302 |
| effects of ca2+ ions on the formation of metaphase chromosomes and sperm pronuclei in cell-free preparations from unactivated rana pipiens eggs. | nuclei transplanted into unactivated amphibian eggs are known to condense into metaphase chromosomes whereas those transplanted into activated eggs decondense and enlarge. we have made cell-free cytoplasmic preparations from rana pipiens eggs which can induce demembranated xenopus laevis sperm to undergo changes similar to those seen in intact eggs. sperm chromatin which is incubated for 3 hr in unactivated egg preparations made using a buffer containing 3 mm egta is induced to form metaphase ch ... | 1984 | 6427039 |
| beta 2-microglobulin induces intracellular transport of human class i transplantation antigen heavy chains in xenopus laevis oocytes. | human class i transplantation antigens are cell-surface-expressed molecules composed of one glycosylated, membrane-integrated heavy chain and one nonglycosylated, water-soluble subunit, beta 2-microglobulin (beta 2m). we have examined the intracellular transport of the two subunits by microinjecting mrna into xenopus laevis oocytes. beta 2m, translated in oocytes, was transported and secreted into the medium in the absence of heavy chains whereas heavy chains were retained in the endoplasmic ret ... | 1984 | 6429156 |
| calcium ultrastructural localization in xenopus laevis eggs following activation by pricking or by calcium ionophore a 23187. | in the egg of xenopus laevis a cortical network of smooth endoplasmic reticulum (ser) surrounds and interconnects each cortical granule (cg) (campanella and andreuccetti, '77). this network is a possible intracellular site of calcium storage to be called into action for cg exocytosis. in our experiments, xenopus eggs, unfertilized or activated by pricking or by calcium ionophore a 23187, have been fixed in osmium-pyroantimonate for calcium localization. our data show that deposits can be detecte ... | 1984 | 6429269 |
| fly and frog homoeo domains show homologies with yeast mating type regulatory proteins. | homoeotic genes in the bithorax and antennapedia complexes of drosophila melanogaster appear to specify the developmental fate of segments of the fly. some of these genes (ultrabithorax, antennapedia and fushi tarazu) share homology due to their conservation of a 'homoeo domain'1,2 consisting of 60 amino acids. cross-hybridization and cloning experiments show that the homoeo domain is conserved in a frog (xenopus laevis) gene expressed in early development and may also be present in earthworm, b ... | 1984 | 6429549 |
| increased rate of capping of concanavalin a receptors during early xenopus development is related to changes in protein and lipid mobility. | the mobility characteristics of plasma membrane constituents were studied in dissociated cells from embryos of xenopus laevis at various stages of development from early blastula until neurulation. an increased rate of fluorescein isothiocyanate-concanavalin a induced patching and capping of con a-binding proteins during this period of development was correlated with a threefold increase in the lateral mobility of the receptor molecules, as determined by the fluorescent photobleaching recovery ( ... | 1984 | 6430735 |
| the comparative distribution of xenopsin- and neurotensin-like immunoreactivity in xenopus laevis and rat tissues. | the regional distribution of xenopsin-like immunoreactivity (xpli) and of neurotensin-like immunoreactivity (ntli) was studied by radioimmunoassay in tissues of xenopus laevis and rat. in xenopus laevis, xpli showed a wide distribution throughout central and peripheral tissues with the highest concentration in the skin; ntli was found in both central and peripheral tissues with the exception of the skin. gel chromatography on sephadex g-25 was used in order to characterize the immunoreactive mat ... | 1984 | 6434152 |
| uncoupled synthesis of h1o-like histone h1s during late erythropoiesis in xenopus laevis. | this study investigated the synthesis of xenopus histones during erythropoiesis. although cessation of dna replication in the mid-stages of erythroid maturation is accompanied by arrested synthesis of histone h1 and core histones, synthesis of h1o (an h1o-like histone) was found to continue into late stages of erythropoiesis, as has been reported for avian erythrocyte histone h5. this was accompanied by a threefold increase in the relative amount of xenopus h1s, similar to the accumulation repor ... | 1984 | 6434311 |
| oocyte adenylyl cyclase contains ni, yet the guanine nucleotide-dependent inhibition by progesterone is not sensitive to pertussis toxin. | membranes were obtained from xenopus laevis oocytes after removal of follicular cells by collagenase treatment. [32p]adp-ribosylation with pertussis toxin showed them to contain a single mr = 40000 substrate for this toxin that co-migrates on sodium dodecylsufate-polyacrylamide gel electrophoresis with pure human erythrocyte ni, the inhibitory regulatory component of adenylyl cyclase. [32p]adp-ribosylation of oocyte membranes with cholera toxin also showed presence of a single substrate but of m ... | 1984 | 6434346 |
| distribution and utilization of 5 s-rna-binding proteins during the development of xenopus oocytes. | at early stages of oogenesis in xenopus laevis most of the ribosomal 5s rna is complexed with three proteins to form two types of cytoplasmic rnp storage particle. a particle sedimenting at 42s contains 5s rna and trna together with two proteins of mr 48000 (p48) and mr 43000 (p43) and a second particle sedimenting at 7s contains 5s rna plus a protein of mr 40000 (p40, also known as the transcription factor, tfiiia). in this report we use antibodies monospecific for each protein to follow the mo ... | 1984 | 6436024 |
| the structure of cytoplasm in directly frozen cultured cells. i. filamentous meshworks and the cytoplasmic ground substance. | cultured fibroblasts or epithelial cells derived from xenopus laevis embryos were directly frozen, freeze-substituted by an improved method, and then either critical-point-dried and viewed as whole mounts, or embedded and thin sectioned. in thin regions of these cells, where ice crystal artifacts are absent, the cytoplasm consisted of a dense, highly interconnected meshwork of filaments, embedded in a finely granular ground substance. the meshwork in directly frozen, intact cells was compared wi ... | 1984 | 6436253 |
| [potentiation of the effect of steroid hormones (progesterone and testosterone) inducing the reinitiation of meiosis in xenopus oocytes in vitro, by inhibitors of phosphatase activity]. | the induction of meiosis reinitiation by steroid hormones (progesterone and testosterone) in xenopus laevis oocytes was studied in vitro in presence of inhibitors of phosphatase activity such as beta-glycerophosphate, considered as a competitive inhibitor, and the two ions, zn++ and moo--4. kinetics of the germinal vesicle breakdown indicating the reinitiation of meiosis, have shown that while these phosphatase inhibitors were not active by themselves under the present experimental conditions, t ... | 1984 | 6437623 |
| fidelity of transcription of xenopus laevis globin genes injected into xenopus laevis oocytes and unfertilized eggs. | the xenopus laevis alpha 1- and beta 1-globin genes were injected into oocytes and unfertilized eggs of x. laevis. in oocytes, the injected globin genes were actively transcribed, but the majority of the transcripts were incorrectly initiated. in unfertilized eggs, the injected genes were transcribed at a low level but only from the correct start sites. in oocytes, the injected circular plasmid dna containing the cloned globin genes persisted but did not replicate. in contrast, dna injected into ... | 1984 | 6438494 |
| does the guanine nucleotide regulatory protein ni mediate progesterone inhibition of xenopus oocyte adenylate cyclase? | in xenopus laevis oocytes progesterone is able to inhibit directly the plasma membrane adenylate cyclase activity and induce reinitiation of meiotic maturation. to determine whether progesterone inhibition is mediated by the inhibitory guanine nucleotide-binding regulatory component of adenylate cyclase, ni, the effect of the bordetella pertussis toxin (iap) and limited proteolysis on progesterone action in oocytes was investigated. treatment of oocyte membranes with islet activating protein (ia ... | 1984 | 6439557 |
| evolution of the human sarcomeric-actin genes: evidence for units of selection within the 3' untranslated regions of the mrnas. | the complete 3' untranslated region (3'utr) sequence of the human skeletal-actin gene has been compared with the corresponding regions of the rat and chicken skeletal-actin genes. this comparison reveals that the skeletal-actin 3'utr is composed of conserved and nonconserved segments. by using genomic southern transfer blots and thermal stability (tm) measurements, we found that the cardiac-actin gene 3'utr also consists of conserved and nonconserved segments. comparison of human and xenopus lae ... | 1984 | 6439877 |
| persistence, methylation and expression of vitellogenin gene derivatives after injection into fertilized eggs of xenopus laevis. | we report the fate of different derivatives of the vitellogenin genes after injection into fertilized eggs of xenopus. we injected a constructed minigene as well as a 5' fragment of the a2 vitellogenin gene. the minigene survives in embryogenesis much better than the 5' a2 fragment and is retained more frequently and at a higher level in frog tissues. the mosaic distribution of the foreign dna in different frog tissues indicates that no integration occurred before the first cleavage stage. the p ... | 1984 | 6324111 |
| the methylation pattern of trna genes in xenopus laevis. | the methylation sensitive restriction enzymes hha i and hpa ii were used to analyse the methylation pattern of a trna gene cluster in germ line and somatic dna of xenopus laevis. a single tdna repeat containing 8 trna genes was studied and all copies were found to be fully modified in sperm dna. in the dna from erythroid cells, hepatocytes, kidney and brain, most tdna repeats were found to be fully modified. however, in a fraction of the repeats, specific demethylated sites can be detected, givi ... | 1984 | 6324123 |
| does timing of axon outgrowth influence initial retinotectal topography in xenopus? | the question of whether timing is involved in generating the topographic organization of the earliest embryonic projection from the retina to the tectum has been examined in xenopus laevis. first, the normal schedule of axonal outgrowth from the retina to the tectum was characterized. groups of axons originating from either dorsal or ventral extremes of the retina were labeled by in vitro incubation of sectors (one-quarter to one-third) of eye primordia in [3h]proline and their time courses of o ... | 1984 | 6325604 |
| isolation and characterization of calmodulin genes from xenopus laevis. | two cdnas derived from xenopus laevis calmodulin mrna have been cloned. both cdnas contain the complete protein-coding region and various lengths of untranslated segments. the two cdnas encode an identical protein but differ from each other by 5% nucleotide substitutions. the 5' and 3' untranslated regions, to the extent available, are highly homologous between the two cdnas. the predicted sequence of x. laevis calmodulin is identical to that of vertebrate calmodulins from mammals and chickens a ... | 1984 | 6325880 |
| organization of xenopus histone gene variants within clusters and their transcriptional expression. | using previously cloned xenopus nucleosomal core histone genes as hybridization probes, a genomic dna library of xenopus laevis was screened for histone gene clusters. from over 200 histone-gene containing clones identified, 36 were selected as possibly containing h1 histone genes by hybridization to a probe derived from a sea urchin h1 histone gene. these 36 clones were further analyzed by hybrid-selected translation for the definitive presence of h1 histone genes. the genes for three different ... | 1984 | 6326836 |
| cloning of an x. laevis gene expressed during early embryogenesis coding for a peptide region homologous to drosophila homeotic genes. | a xenopus laevis gene was cloned on the basis of cross-homology to a region conserved between several drosophila homeotic genes. it was shown to be expressed during early development, starting at late gastrulation and producing three transcripts under specific temporal control. the frog gene contains a region coding for 60 amino acids, which is extremely conserved when compared to drosophila homeotic genes in the region of the homeo domain. southern blot analysis indicates that there are at leas ... | 1984 | 6327066 |
| processing of the 3' sequence extensions upon the 5s rrna of a mutant yeast in xenopus laevis germinal vesicle extract. | a processing endonuclease acts to remove a short sequence from the 3' end of transcripts of the saccharomyces cerevisiae 5s ribosomal rna gene in generating the mature sequence of 5s rna. cells bearing the nuclear mutation rna82 .1 lack this activity and accumulate 5s forms with additional nucleotides at their 3' termini. 5s rnas labelled during short pulse- labellings of the mutant are essentially primary transcripts that mostly have the sequence u-u-a-u-u-u-c[u-u-u-u(u-u)] added to the 3' end ... | 1984 | 6327301 |
| dna methylation of three 5' c-c-g-g 3' sites in the promoter and 5' region inactivate the e2a gene of adenovirus type 2. | the e2a gene of human adenovirus type 2 (ad2) encodes the 72-kilodalton dna-binding protein. we previously described perfect inverse correlations between the methylation of all 5' c-c-g-g 3' sequences in the ad2 e2a gene in virus-transformed hamster cells containing viral dna sequences in an integrated state and the extent to which this gene is expressed. we subsequently showed that in vitro methylation of all 14 5' c-c-g-g 3' sequences in the cloned e2a gene by prokaryotic hpa ii dna methyltran ... | 1984 | 6328479 |
| properties of a cyclic nucleotide phosphodiesterase of amphibian oocytes that is activated by calmodulin and calcium, by tryptic proteolysis, and by phospholipids. | a calmodulin-ca2+-stimulated cyclic nucleotide phosphodiesterase (ec 3.1.4.17) which hydrolyzed both cgmp and camp has been purified about 2000-fold from ovaries of the amphibian xenopus laevis. gel filtration through sephadex g-200 indicated a molecular weight of 140,000. a single, major protein band of molecular weight 66,000 was observed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. in addition to the stimulation by calmodulin-ca2+, the enzyme was activated 5- to 10-fold by pr ... | 1984 | 6329099 |
| isolation of a mitochondrial dna topoisomerase from human leukemia cells. | mitochondria from human acute lymphoblastic leukemia cells contain an atp-independent dna topoisomerase which can relax negative and positive supercoils. this enzyme has been purified 200-fold by carboxymethyl-cellulose or double stranded dna-cellulose chromatography. in contrast to the molecular weights reported for mitochondrial topoisomerases in other systems, the native leukemia enzyme has a molecular weight of 132,000 daltons as determined by gel permeation chromatography in buffer containi ... | 1984 | 6329201 |
| initiation of sv40 dna replication after microinjection into xenopus eggs. | we have examined the capacity of xenopus laevis eggs to support replication of microinjected sv40 dna. as previously reported, microinjected dna undergoes semi-conservative replication. unlabeled sv40 dna was microinjected with [3h]dttp and, after a 3 h incubation period, the dna was recovered and adsorbed to bnd-cellulose. elution with an nacl gradient removes molecules that are entirely double-stranded but not those with single-stranded regions. the latter dna population is eluted with caffein ... | 1984 | 6329301 |
| microsomal monooxygenase system in frog livers. | liver microsomes prepared from four species of frog, rana catesbeiana, rana nigromaculata , bufo bufo japonicus, and xenopus laevis, contained cytochrome p-450 and showed nad(p)h-dependent monooxygenase activities to several foreign chemical compounds tested. the oxidations of the chemical compounds by frog liver microsomes showed significant variations among frog species. the oxidation of 7-ethoxycoumarin was much faster than that by rat liver microsomes. the oxidation of benzo(a)pyrene was sig ... | 1984 | 6329594 |
| roles of cytosol and cytoplasmic particles in nuclear envelope assembly and sperm pronuclear formation in cell-free preparations from amphibian eggs. | a cell-free cytoplasmic preparation from activated rana pipiens eggs could induce in demembranated xenopus laevis sperm nuclei morphological changes similar to those seen during pronuclear formation in intact eggs. the condensed sperm chromatin underwent an initial rapid, but limited, dispersion. a nuclear envelope formed around the dispersed chromatin and the nuclei enlarged. the subcellular distribution of the components required for these changes was examined by separating the preparations in ... | 1984 | 6609160 |
| phorbol ester increases the level of interleukin 2 mrna in mitogen-stimulated human lymphocytes. | tpa alone did not induce the production of il 2 in human tonsillar lymphocytes but enhanced the pha-induced il 2 production by seven-fold. that the effect of tpa was due to an increase in il 2 mrna was demonstrated by examining the amount of il 2 mrna translatable in xenopus laevis oocytes, and by northern blotting analysis using il 2 cdna as a probe. in these ways, it was shown that tpa alone did not induce any significant il 2 mrna synthesis, but when added together with pha it increased the l ... | 1984 | 6609189 |
| control of biologically active interleukin 2 messenger rna formation in induced human lymphocytes. | the regulation of human interleukin 2 (il-2) mrna production in induced normal lymphocytes was studied by following the expression of isolated mrna in microinjected oocytes of xenopus laevis. mitogenic stimulation results in the appearance of greatly increased levels of il-2 mrna activity. this process requires de novo transcription. induction is followed promptly by a shutoff of active il-2 mrna formation. this shutoff requires the synthesis of a protein repressor and can be prevented by cycloh ... | 1984 | 6609365 |
| immunologic reactivity to tnp-ficoll during development and ageing in xenopus laevis, the south african clawed toad. | the immunological response of xenopus laevis to haptenated ficoll was examined throughout development. the capacity to respond to tnp-ficoll originated with the first appearance (at stage 48, 8 days post-fertilisation) of mature thymic lymphocytes, and preceded the ability to respond to heterologous erythrocytes. during premetamorphosis the response increased, while during prometamorphosis , particularly at stages 57-58, there was a marked reduction. the response recovered during the metamorphic ... | 1984 | 6609773 |
| isolation and functional property of mrnas coding for human interleukin 2. | interleukin 2 (il 2) is a lymphokine with specific growth promoting properties for activated t cells. the isolation and purification of specific mrnas coding for this protein is reported. the analysis of total poly a + containing rna from pha stimulated t lymphocytes on agarose gels reveals the existence of at least two different il-2 mrnas. isolated rnas have been microinjected separately into xenopus laevis oocytes for translation and consecutively the synthesized proteins were tested for acti ... | 1984 | 6609779 |
| isolation and partial characterization of messenger rna, from murine t cell hybrids, coding for suppressive immunoglobulin g-binding factor. | poly a rna has been isolated from a murine t cell hybridoma ( t2d4 ) that spontaneously secretes suppressive immunoglobulin g-binding factor ( iggbf ). translation products, obtained from a rabbit reticulocyte lysate translation system and after injection into xenopus laevis oocytes, contain material with the biologic activity, the affinity, and the m.w. of murine iggbf ; it suppresses secondary in vitro igg antibody production in a dose-dependent fashion. the suppressive factor binds to igg but ... | 1984 | 6609991 |