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visual deprivation and intertectal neuronal connexions in xenopus laevis. 19751778
surface immunoglobulins on xenopus laevis lymphocytes. 19763324
multiple forms of dna-dependent dna polymerase during early development and in somatic cells of xenopus laevis.four distinct dna-dependent dna polymerase activities (dna polymerases i, ii, iii and iv according to the order of elution from a deae column) have been separated from extracts of unfertilized xenopus laevis eggs. the same activities, on the basis of their chromatographic properties, template specificities and sedimentation coefficients, have been found in embryos at least until the gastrula stage. on the other hand, xenopus kidney cells grown in culture, as well as full grown oocytes lack dna p ...19769200
chemoreceptors of the lateral-line organs in intact, hypophysectomized, and prolactin-treated hypophysectomized xenopus laevis specimens. 19769241
translation of messenger rna specific for tyrosine aminotransferase in oocytes of xenopus laevis. 197610910
ontogeny of tyrosine aminotransferase in xenopus laevis. 197714857
histochemical and biochemical investigations on the changes of catecholamine content in the adrenal tissue of xenopus laevis--i. effect of salt-water stress. 197715773
histochemical and biochemical investigations on the changes of catecholamine content in the adrenal tissue of xenopus laevis--ii. effects of drug applications. 197715774
the time and duration of meiosis.ever since meiosis was recognized as a process there has been a continuing interest in its temporal aspects. two main types of meiotic timing experiments have been conducted: first, experiments to estimate the duration of meiosis (and sometimes its stages); second, experiments to locate the sensitive stage(s) when exposure of meiocytes to various treatments can affect meiotic chromosome behaviour (e.g. pairing or recombination). such experiments have played an important role in increasing our un ...197716285
alteration of structure and penetrability of the vitelline envelope after passage of eggs from coelom to oviduct in xenopus laevis.the vitelline envelope (ve) that surrounds an egg released from the ovary into the coelom of xenopus laevis differs markedly, in structure and penetrability, from the ve surrounding an oviposited egg. in a coelomic egg, the filaments that form the ve are arranged in distinct fascicles or bundles. the exterior surface of the ve is irregular in contour and is permeated by channels. in an oviposited egg, the filaments are evenly dispersed and lack a fasciculated arrangement; the exterior surface is ...197718549
effects of neurotransmitters upon the discharge of secretory product from the cutaneous glands of the red-spotted newt.the effects of sympathetic and parasympathetic agonists and antagonists on discharge of secretory product by the granular and mucous glands were examined in the red-spotted newt, notopthalmus viridescens viridescens. observations were made also on the south african clawed toad. xenopus laevis, the grass frog, rana pipiens, and the crested newt, triturus cristatus. in contrast to the granular glands of the south african clawed toad and the grass frog, which were stimulated by alpha-adrenergic age ...197721937
the occurrence and transmission of a pattern of dna methylation in xenopus laevis ribosomal dna. 197826077
synaptic organization of the inner plexiform layer of the retina of xenopus laevis. 197827791
steroid-induced meiotic division in xenopus laevis oocytes: surface and calcium.progesterone reinitiates meiotic maturation in xenopus oocytes. evidence is reported which indicates that the steroid acts at the level of the cell surface and suggests that an induced change of ca2+ distribution triggers in turn a cascade of cytoplasmic events including protein synthesis and germinal vesicle (nucleus) breakdown. these novel features of steroid hormone action in amphibian oocytes are discussed in relation to presently accepted views of the mechanism of action of steroid hormones ...197830046
structural studies of the xenopus 19s immunoglobulin and 7s immunoglobulin and two immunoglobulin-like proteins.xenopus laevis 19s and 7s immunoglobulins (ig) were extensively reduced and alkylated, their h and l chains spearated and their molecular weights determined. two kinds of l chains of molecular weight 25,000 and 27,000 were revealed by sds-polyacrylamide gel electrophoresis. in addition two ig-like proteins consisting of heavy chains only, of 19s h-type and with similar molecular weight, were detected in xenopus serum ans isolated. these proteins share common antigenic determinants with xenopus 1 ...197547834
influence of antigen dose on antibody production of intact and splenectomised xenopus laevis.antigen persistence and serum antibody production in intact xenopus were monitored using human gamma globulin (hgg), in adjuvant, in various immunisation schedules. retention of hgg in spleen and serum was directly related to the quantity injected. however, antibody responses to a dose range between 1 mu-g-6 mg antigen were similar in intensity. these were detected in the serum two weeks after injection and at this stage were exclusively mercapto-ethanol (me) sensitive; me-resistant antibodies h ...197548536
xenopus laevis 19s immunoglobulin. ultrastructure and j chain isolation.electron microscopy examination of the 19s immunoglobulin of xenopus laevis revealed a hexameric structure with a central core. the molecules measured 360-430 a across the span of the arms and the average diameter of the central region was 140 a. a polypeptide, homologous to human j chain, was isolated by chromatography on deae-cellulose from the reduced and alkylated x. laevis hexameric macroglobulin. this polypeptide had a fast mobility in alkaline-urea gel electrophoresis, with distinct antig ...197657921
diffusion of sodium in axoplasm of myelinated nerve fibre. potential clamp analysis.the diffusion of sodium and lithium in the axoplasm of myelinated fibres of xenopus laevis was investigated. the sodium current associated with pulse steps was measured and the internal sodium concentration was calculated from these measurements with the constant field equation. the internal sodium concentration was increased either (i) by massive pulse trains or (ii) by applying a sodium containing solution to a cut end of the fibre. the time course of the concentration change was measured. equ ...197661708
translation products of the alfalfa mosaic virus ribonuclei acids in wheat-germ cell-free system and in oocytes from xenopus laevis. 197664215
estimation of rdna content in xenopus laevis eggs during early development [proceedings]. 197666019
mean velocity of optically detected intraaxonal particles measured by a cross-correlation method.a method which uses by the cross correlation of optical signals is described for the determination of the mean velocity of somatopetally moving particles within nerve fibers. the method was validated by simulation experiments and by comparing the results with those obtained by averaging collections of velocities of individual particles. the significant contribution of the method is that it allows objective and rapid serial evaluation of mean particle velocity within individual nerve fibers with ...197666091
changes in the rate of histone synthesis during oocyte maturation and very early development of xenopus laevis. 197767977
distribution of immunoglobulin determinants on the surface of xenopus laevis splenic lymphocytes.the distribution of surface immunoglobulin (ig) determinants on xenopus laevis splenic lymphocytes after combination with divalent rabbit anti-ig coupled to ferritin was studied. the electron micrographs showed the presence of immune complexes in 67% of lymphocytes treated at 0 degrees c-4 degrees c. the complexes were located all around the membrane and uniformly distributed in a random fashion. the variation of ferritin grain counts on cell sections is such, that the existence of two major sub ...197769676
cytotoxic effect of a reverse transcriptase inhibitor, af/abdp cis, on ovaries of young xenopus laevis--ultrastructural and autoradiographic study.observations with the light and electron microscopes showed that a reverse transcriptase inhibitor, af/abdp cis which is a rifampicin derivative, had a toxic effect on ovaries of young xenopus laevis. it induced mitochondrial damage in all observed cells and marked alteration of the ultrastructure of nucleus of the pachytene oocyte. light autoradiography showed that af/abdp cis caused wide variation in nuclear labelling with [3h] thymidine from one pachytene oocyte to another. somatic cells were ...197770278
variations in differentiation in the regenerating lens of xenopus laevis. 197770371
progesterone-induced meiotic reinitation in vitro in xenopus laevis oocytes: a role for the displacement of membrane-bound calcium. 197773488
the induction of immunologic tolerance with type iii pneumococcal polysaccharide cross-linked or coupled to protein.type iii pneumococcal polysaccharide molecules were linked to one another, i. e. cross-linked. the product was essentially insoluble in saline. large pieces weighing 1-2 mg were inserted into mice. they produced immunologic paralysis or immune tolerance. when placed intraperitoneally in millipore chambers the cross-linked polysaccharide did not have any apparent effect, for the mice were not tolerized. when pneumococcal polysaccharide was linked to a protein, the amount of polysaccharide require ...197879330
synthesis of interferon in heterologous cells, cell-free extracts, and xenopus laevis oocytes. 197780829
free rna polymerase activities in isolated nuclei from xenopus laevis embryos. stimulation of endogenous template-bound rna polymerase ii activity by poly d(a-t) [proceedings]. 197881029
further studies of the prospective fates of blastomeres at the 32-cell stage of xenopus laevis embryos.each blastomere in the marginal zone of xenopus laevis embryos at the 32-cell stage was stained with nile blue sulphate. only specimens with the typical arrangement of blastomeres of morulae of this species were used, and special care was taken to prevent the dye from spreading to neighbouring cells and to determine the extent of stained areas. the prospective fate of each blastomere was studied and a new fate-map of the 32-cell embryo was drawn by tracing the movement of stain during the course ...197883458
translation of bovine leukemia virus virion rnas in heterologous protein-synthesizing systems.bovine leukemia virus 60 to 70s rna was heat denatured, the polyadenylic acid-containing species were separated by velocity sedimentation, and several size classes were translated in a micrococcal nuclease-treated cell-free system from rabbit reticulocytes. the major rna species sedimented at 38s and migrated as a single component of molecular weight 2.95 x 10(6) when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. the predominant polypeptides of the in vitro translation o ...197987518
[immunochemical study of the water-soluble lens proteins in the embryo of xenopus laevis with the mutation of periodic albinism].the crystallins of ap mutants of xenopus laevis have been studied in comparison with those of normal embryos and adults using the complex of immunochemical methods (immunoelectrophoresis, immunodiffusion, immunoadsorption, immunofluorescence, isoelectrofocusing with immunoidentification). the analysis was carried out with antisera to electrophoretic fractions of the mutant lens. 11 organ-specific antigens were found in the lens of both the normal and mutant animals. these proteins are heterogeno ...197988703
incorporation of 35s-sulfate into yolk platelets of xenopus laevis embryos. a study using electron microscope autoradiography.inorganic 35s-sulfate was injected into xenopus laevis embryos before first cleavage to study incorporation of the label into the yolk platelets in order to localize glycosaminoglycan synthesis. electron microscope autoradiography of embryonic thin sections from blastulae and gastrulae revealed that the primary site of label incorporation is at the edge of the yolk platelets, and, to a lesser extent, in their interiors. autoradiography of isolated yolk platelets, lacking unit membranes, indicate ...197989978
the intra-nucleolar localization of amplified rdna in xenopus laevis oocytes.a fluorescent feulgen-stain was adapted in order to demonstrate dna-containing structures inside the amplified nucleoli of xenopus laevis. at all stages of oogenesis this method reveals granules or complex structures of dna in each nucleolus. the micronucleoli which do not stain with this method and which do not reveal an internal structure in low molarity saline, unlike real nucleoli are considered as nucleolus-like bodies. the dna-containing structures in the nucleoli can be composed of one or ...197990588
preparation of complementary dna to 5 s ribosomal rna from xenopus laevis. 197991536
[immunohistochemical identification of specific antigens in stained and balsam-embedded eye lens sections].localization of specific proteins at preliminary stained with azan and embedded in balsam sections of amphibian eye lens (rana temporaria, xenopus laevis) was studied by indirect immunofluorescence. the analysis was performed on the lens of intact animals as well as on lens induced in amphibia gastrula ectoderm in vitro. to remove balsam the lens sections were successively washed by xylene, ethanol and saline (ph 7.1). then they were treated according to the general principles of immunohistochem ...197993003
a detergent-citric acid technique for isolating nuclear and cytoplasmic fractions containing undegraded rna from cells of xenopus laevis. 197994513
isolation and characterization of the nuclear matrix from the male xenopus laevis following estrogen administration: kinetics of [3h] uridine incorporation.at various times following estrogen administration, the nuclear matrix was isolated from the liver of male xenopus laevis by sucrose gradient centrifugation of nuclei treated with a high-salt buffer and dnase i in the presence of a proteolytic inhibitor (pmsc--phenylmethyl sulfonyl chloride). electron micrographs of the nuclear matrix demonstrate a sponge-like network attached to a well-defined inner envelope with a ribosome-free outer envelope. chemical analyses show that the hsb-dnase-treated ...197995125
[inhibition by the enterotoxin of vibrio cholerase of meiosis reinitiation of the xenopus laevis oocyte induced in vitro by progesterone].progesterone reinitiates in vitro meiosis in xenopus laevis oocytes. this action of the hormone can be abolished by the exotoxin of vibrio cholerae. the concentration of toxin which inhibits 50% of the progesterone (10 mum) action in about 2.5 pm. binding experiments using 125i labelled toxin demonstrated the existence of high affinity binding sites (kd approximately 0.2 nm) located probably on the surface of the oocytes.197895900
[histochemistry of the ball cell in larval epidermis of xenopus laevis daudin].presented investigations of chemical composition and metabolism of ball cell in larval epidermis of xenopus point to a regressive shape of cell corresponding to former light and electron microscopical findings. the lower requirements of energy of this cell are covered by glycolysis and possibly by pentose phosphate cycle. our hypothesis of pressure-elastic ball of cell as structural element of larval epidermis could been further supported.197897905
immunoglobulin evolution: chemical study of clawed toad (xenopus laevis) heavy and light chains.nh2 terminal amino acid sequence determinations of clawed toad (xenopus laevis) immunoglobulins indicate that approximately 30% of the heavy chains and less than 5% of the light chains have unblocked nh2 termini. the major amino acid sequence of the x. laevis 7s immunoglobulin heavy chains is the same as that of the 19s immunoglobulin heavy chains. thus in the synthesis of the heavy chains, the vh genes coding for unblocked heavy chains can associate with ch genes of both the 19s and 7s classes. ...1978103971
in vitro studies on the control of myoepithelial cell contraction in the granular glands of xenopus laevis skin. 1978104900
synthesis and processing of the mouse mopc-321 kappa chain in xenopus laevis oocytes. 1979107859
characteristics of immunoglobulin synthesized early in the development of xenopus laevis. 1979108156
[immunohistochemical identification, in an anuran amphibian (xenopus laevis daud.) of infundibular neurons reacting with antigastrin serum].neurons containing peptides immunocytologically related to gastrin have been revealed by immuno-cytology in the post-chiasmatic hypothalamus of xenopus laevis. their pericarya are localized in the postero-dorsal zone of the pars ventralis of the tuber cinereum; their axons end on the capillaries of the external zone of the median eminence.1979110481
[teratogenic effect of mercury bichloride on the embryonic development of the amphibian xenopus laevis daud]. 1979116463
measurement of calcium ion concentrations in the lateral line cupulae of xenopus laevis.1. ion selective microelectrodes were used to measure the distribution of ca2+ in the cupulae of xenopus laevis, and to observe the effects of the ca2+ blocker, la3+, and a ca2+ chelating agent (egta) on the endocupular potential and k+ concentration. 2. measurements of the endocupular ca2+ and potential were found to be in the range of 2-30 mum and 55-10 mv respectively, and their relationship indicates that ca2+ is passively distributed in the cupula. 3. the concentration of endocupular k+ and ...1979119824
[invariability of the h-y antigen expression in the heterogametic sex of some amphbians and evidence for sexual dimophrism of the antigen expression in pelodytes punctatus d (amphibia, anura)].the h-y antigen is studied in some amphibians whose sexual genetic constitution is known. thus, in pelurodeles waltlii, ambystoma mexicanum, xenopus laevis and rana ridibunda, the invariability of the h-y antigen expression in the heterogametic, sex is confirmed. in pelodytes punctatus the genetic sex is unknown but the existence of the h-y antigen in phenotypic males leads to the conclusion of a male heterogamety of the xy type.1979121269
'immobile' (im), a recessive lethal mutation of xenopus laevis tadpoles.'immobile' (im) is a recessive lethal mutation discovered in the f3 of a xenopus (xenopus laevis laevis) originating from a mesodermal nucleus of a neurula transplanted into an enucleated egg. the im embryos do not contract after mechanical stimulation nor do they present any spontaneous contraction from the neurula stage onwards. development proceeds normally during the first days after which deformation of the lower jaw and tail are observed. the im tadpoles die when normal controls are at the ...1975127824
[the tail of the tadpole of alytes obstetricans in organ culture with or without the addition of thyroxine. ultrastructural controls].the tail of the alytes obstetricans tadpole, isolated at different stages (end of proclimax and climax), was studied in organ culture. the addition of thyroxine at a concentration of 5.10(-7) induces an involution slower than in vivo. besides, this regression is comparatively slower in similar conditions, than in xenopus laevis. this delay could be explained by the important volume and the very developed musculature of this anuran tail. ultrastructural controls reveal the form of the muscles, th ...1976139991
[effects of alpha-amanitin on the development of xenopus (xenopus laevis daud.) heart in vitro].the differentiation of xenopus heart is studied in vitro, in the presence of alpha-amanitin. the results obtained depend on the concentration of the inhibitor, the length of treatment and the stage of primordium. the mrna pool assures the differentiation of explants, removed from young stages, for 12 hours. this time is half for the primordia removed from stages greater than 3,5 mm.1977143992
the regulation of growth in the mesonephric kidney of adult xenopus laevis by an endogenous inhibitor of proliferation. 1978151645
light and electron microscopic investigation of atpase activity in musculature during anuran tail resorption.the histochemical activity of adenosine triphosphatase (atpase) was studied at light and electron microscopic levels in larval tail musculature of rana catesbeiana and rana ornativentris during late metamorphic stages. the presence of low, moderate or dark reaction of k2-edta-preincubated ca++-atpase was correlated with the variable degree of degeneration of white fibres even at the late stage of tail resorption. the reasons for an increase in this atpase activity in degenerating white muscle fi ...1978153341
a study of the organisation of the ribosomal ribonucleic acid gene cluster of neurospora crassa by means of restriction endonuclease analysis and cloning in bacteriophage lambda.1. total neurospora crassa dna was restricted with endonucleases and fragments carrying rrna coding sequences were identified by hybridization with xenopus laevis ribosomal dna probes. 2. the repeating unit of the rrna gene cluster was found to be 8.6 kbp, arranged in a head-to-tail fashion. 3. digestion with hind iii yielded fragments of 3.4 kbp and 5.2 kbp and both were cloned. 4. digestion with eco ri yielded fragments of 2.2 kbp, 3.0 kbp and 3.4 kbp; the 3.0 kbp fragment was cloned. 5. seque ...1979158122
the mucosubstance coating the pneumonocytes in the lungs of xenopus laevis and lacerta viridis.the layer of mucosubstance that is associated with the free surface membranes of the pneumonocytes in the lungs of the toad xenopus laevis and the lizard lacerta viridis was demonstrated by electron microscopy using iron oxide stain. the form and staining reactions of the mucosubstance layer were similar in both animals. in electron micrographs the mucosubstance was represented by a band of densely stained material (25-50 nm thick) which coated the entire free surface of the pneumonocytes. it ap ...1975165163
response of large oocytes of xenopus laevis to progesterone in vitro in relation to oocyte size and time after previous hcg-induced ovulation. 1975166003
in vitro progesterone binding to xenopus laevis oocytes. 1975166010
studies on the liver of xenopus laevis. i. the ultrastructure of the parenchymal cell.the liver of xenopus laevis was examined with electron microscopy. its structure was found to be markedly different from that of mammals, particularly regarding the morphology of the hepatocytes to be classified as typical. it was established that the main function of such a cell is the storage of glycogen, and further that it possesses only scant organelles and other inclusions. since this type of cell was found most frequently in the liver of untreated animals, it was designated as normal cell ...1975167614
template specificity of the cytoplasmic dna polymerase in xenopus laevis oocytes. 1975167780
[the topographical localization of spinal motoneurons of the rat and its numerical alternation in regard to development (author's transl)].the topographical localization of spinal motoneurons innervating the forelimb muscles of the rat and its numerical alternation in regard to development was observed by hrp (horseradish peroxidase) method. hrp method is a histochemical technique to trace the cellular origin of axon terminal net work. when hrp is injected into the muscles, the enzyme is taken up by nerve endings and transported retrogradely by the axoplamic flow to the original cell body, and does not transported hematogenously an ...1979159327
[alterations in concanavalin a binding during retinal development in xenopus laevis].changes in concanavalin a binding were observed in the retina of xenopus laevis throughout development. prior to stage 37, the optic cup and nervous sysetm displayed a light, diffuse staining. abruptly at stage 37, however, intense staining reaction occurred in the ganglionic fibers, both plexiform layers and photoreceptor inner segments, remaining thus throughout larval and adult life. our results suggest that important structural modifications occur in retinal cells at the time of establishmen ...1979158407
mechanism of action of progesterone on amphibian oocytes. uptake and metabolism of progesterone by isolated oocytes of pleurodeles waltlii and xenopus laevis. 1975170033
light-induced formation of dense-core vesicles in rod photoreceptors in retina of xenopus laevis. 1975170537
[demonstration of a long depolarization in the oocytes of xenopus laevis]. 1979111840
changes in the content of cyclic amp and cyclic gmp during the development of xenopus laevis. 1975172338
partial mapping of methylated sequences in xenopus laevis ribosomal rna by preparative hybridization to cloned fragments of ribosomal dna.xenopus laevis rrna was hybridised to either of two cloned fragments of ribosomal dna. one fragment, designated x1r11, contains a short region of the 18 s rrna gene and most of the 28 s rrna gene. the other fragment, x1r14, contains a short region of the 28 s gene and most of the 18 s gene. after hybridization the non-complementary rrna was removed by digestion with t1 rnase and the hybridized rna was then eluted and examined by fingerprinting analysis. the 3' terminal sequence and the dimethyl- ...1979108668
clustered and interspersed repetitive dna sequences in four amphibian species with different genome size.we have compared the amount of clustered and interspersed repetitive sequences in the genome of four amphibia with different dna contents per haploid nucleus: two anura (xenopus laevis, 3 pg and bufo bufo, 7 pg) and two urodela (triturus cristatus, 23 pg and necturus maculosus, 52 pg). high molecular weight dna of the four species was denatured and reassociated to the same cot in order to obtain duplex sequences with a similar reiteration frequency. single-stranded dna was digested off with the ...1978101246
translation of oncogenic virus rna in xenopus laevis oocytes. 1976175294
[meiosis: role of a histone kinase in the condensation of ovarian oocyte chromosomes of xenopus laevis and ambystoma mexicanum].by injecting heterologous histone-kinase preparations into ovarian axolotl oocytes, it has been possible to speed up the progesterone-induced process of chromosome condensation. moreover, in some instances, this condensation and even complete maturation have been obtained after injection of protein kinase alone, thus in the absence of hormone stimulation. two different histone kinase preparations have been used: one was prepared from ascites cell chromatin and the other from in vitro ovulated xe ...1975177222
probing the program of gene expression utilized in early development.somatic cell nuclei injected into amphibian oocytes enlarge, exchange protein with the surrounding cytoplasm, and actively synthesize rna for weeks. the message activity of the rnas synthesized within the oocytes can be detected as new proteins made a few days after the injection of somatic nucleic. the oocyte cytoplasm seems to reprogram the injected nuclei, allowing the expression only of those genes which are normally active in oocytes (de robertis and gurdon, 1977). genes which are unexpress ...197995388
the stimulatory effect of hypothalamic and mesencephalic tissue on the interrenal of tadpoles of xenopus laevis daudin. 1976182611
cyclic amp synthesis in xenopus laevis oocytes: inhibition by progesterone.[alpha-32p]atp was microinjected into xenopus oocyte and neosynthesized cyclic amp was isolated. cholera toxin inhibited progesterone-induced maturation and stimulated after 3 h of preincubation the amount of neosynthesized cyclic amp. progesterone decreased the neosynthesis of cyclic amp during the first hour following addition of the hormone.197983880
quinacrine fluorescence of merkel cells in xenopus laevis.it has been shown by electron microscopy that, in xenopus laevis, merkel cells are usually situated near the ducts of the skin glands. cells which fluorescence in ultra-violet light after treatment of the skin with quinacrine can be identified with these merkel cells by their position, shape and size. the method indicates the presence of purine nucleotides, probably atp. this result is consistent with the view that "large opaque vesicles" are sites of atp storage.197879446
inhibition of the progesterone-dependent induction of meiosis by gammexane in xenopus laevis oocytes. 197771148
retrograde axonal transport of horseradish peroxidase for determining motor projection patterns to the developing limb in xenopus.horseradish peroxidase (hrp) injected into developing limb buds of xenopus laevis tadpoles is carried by retrograde axonal transport to the somata of motoneurones in the ventral horn. small injection of 10% hrp were found to remain well localised to specified sites in the limb bud. two types of labelled cells were found: diffusely labelled and granular labelled. diffusely labelled cells result from axonal damage in the presence of hrp. granular labelled cells result only from uptake of hrp from ...197770260
nerve-induced and spontaneous redistribution of acetylcholine receptors on cultured muscle cells.1. theree-day-old cultures of myotomal muscle, obtained from embryos of xenopus laevis, were stained with fluorescent conjugates of alpha-bungarotoxin and maintained in native toxin in order to ensure that ach receptors subsequently inserted into the sarcolemma would not be stained. neural tube cells were then added to the cultures. 2. when cultures were exmained 1-3 days later fluorescent stain was found to be associated with sites of nerve-muscle contact. in some cases the stain along the path ...197769707
assembly of sv40 chromatin in a cell-free system from xenopus eggs.a cell-free system is described which assembles chromatin from purified dna in 1 hr under physiological incubation conditions. it consists of a 145,000 x g (maximum) supernatant fraction from eggs of xenopus laevis. it converts sv40 dna to a nucleoprotein which co-sediments with naturally occurring sv40 chromatin and which can be cleaved by micrococcal nuclease to a highly ordered pattern of dna fragments resembling those from digestion of liver chromatin. it inserts superhelical turns into rela ...1977189936
effects of innervation on the distribution of acetylcholine receptors on cultured muscle cells.1. myotomal muscle cells from embryos of xenopus laevis were cultured as a monolayer either alone or together with neural tube cells from the same embryos. 2. spontaneous twitching and contractions evoked by electrical stimulation of neural perikarya were observed only in nerve-contacted muscle cells, and could be abolished by curare or alpha-bungarotoxin. 3. within 2 days in culture muscle cells not contacted by nerve developed one or more discrete patches of acetylcholine (ach) receptors as re ...197769706
inhibition of the rapid movement of optically detectable axonal particles colchicine and vinblastine.the rapid saltatory motion of intra-axonal particles detected by dark-field microscopy in myelinated axons isolated from sciatic nerves of adult xenopus laevis was inhibited by colchicine or vinblastine at a concentration of larger than or equal to 0.1 mm. both the predominant somatopetal transport and the somatofugal transport of these round particles were inhibited. the reduction in numbers of moving particles was apparent first in the juxtanodal portions of the isolated axons within about 1 h ...197768800
microfilaments in the external surface layer of the early amphibian embryo.a comparison was made by transmission electron microscopy of the microfilaments in the surface layers of the early embryos of triturus alpestris and xenopus laevis at stages of development up to neurulation. actin-like filaments which bound heavy meromyosin (hmm) were found in cell extracts of all stages, but were comparatively rare in the newly fertilized egg. ten nm microfilaments were present throughout development in xenopus, and from the mid-neurula stage in triturus. both kinds of microfil ...197550397
kynureninase-type enzymes and the evolution of the aerobic tryptophan-to-nicotinamide adenine dinucleotide pathway.kynureninase-type (l-kynurenine hydrolase, ec 3.7.1.3) activity has been found to be present in the livers of fish, amphibia, reptiles, and birds. in addition to past information concerning this enzyme activity in mammalian liver, it is now clear that all the major classes of vertebrates carry a highly specialized kynureninase-type enzyme, which we have termed a hydroxykynureninase. to compare the reactivities of these enzymes with l-kynurenine and l-3-hydroxykynurenine, ratios of tau values (km ...1977195620
utilization of yolk platelets and lipid bodies during the myogenesis of xenopus laevis (daudin).the premyoblast and differentiating mononuclear myoblasts of the metameric striated muscles of xenopus laevis were analysed for vitellolysis and lipid body utilization. in the course of myoblast differentiation the stainability of platelets stained with safranin and fast green shows essential variations. the platelets appear to lose their affinity for safranin and subsequently begin to stain with fast green. the yolk platelets were found to contain basic proteins, non-histone proteins, and phosp ...197550138
the activity of poly(adenosine diphosphate ribose) polymerase during the embryonic development of the south african clawed toad xenopus laevis [proceedings]. 1977198268
frog oocytes synthesize and completely process the precursor polypeptide to virion structural proteins after microinjection of avian myeloblastosis virus rna.after microinjection of xenopus laevis oocytes with rna from avian myeloblastosis virus, viral structural proteins p27, p19, p15, and p12 are formed by a sequence of posttranslational cleavages of a high-molecular-weight precursor polypeptide. the 60-70s rna aggregate or its 30-40s rna subunits obtained by heat or formamide treatment possess the same ability to serve as template in x. laevis oocytes. the processing pattern of virus-specific precursor polypeptides is the same in x. laevis oocytes ...1977198776
formation of branched dna structures by xenopus laevis oocyte extract. 1977201869
the activity of some intracellular oxidative enzymes in the thyroid follicular epithelium of xenopus laevis daud. in experimental long-term hypokinesia.histoenzymological methods were applied to examine the activities of previously little studied intracellular oxidative enzymes in the cells of the thyroid follicular epithelium of xenopus laevis daud. specimens kept in aquarium. succinate, lactate, alpha-glycerophosphate, glucose-6-phosphate and reduced nad and nadp dehydrogenases and cytochrome oxidase were studied. in comparison with other chordate species a very strong activity was revealed particularly by lactate dehydrogenase. the data obta ...1977202546
chromosome banding pattern conservatism in birds and nonhomology of chromosome banding patterns between birds, turtles, snakes and amphibians.the g-banded karyotypes of 4 species of birds representing the orders galliformes, columbiformes and musophagiformes were compared. banding pattern homology between orders was limited t 5o 5 major chromosome arms and the z chromosome. even in these major chromosome arms pericentric and paracentric inversions produced alteration of the banding pattern sequences. addition of constitutive heterochromatin was responsible for changes in banding patterns in the z chromosome. the chromosome banding pat ...197548453
control of msh synthesis and release in the aquatic toad, xenopus laevis. 1977207601
method for the preparation of active maturation promoting factor (mpf) from in vitro matured oocytes of xenopus laevis.a method for the large scale extraction of maturation promoting factor (mpf) from in vitro matured oocytes of xenopus laevis is described. mpf has been previously described only as a component(s) of hormone-matured cytoplasm within amphibian oocytes (or eggs) which is able to induce the reinitiation of the meiotic process from late diplotene stage until second metaphase arrest, when microinjected into diplotene arrested (fully grown) recipient oocytes. standard biochemical methods for the extrac ...1978207616
embryopathies due to spermatozoal impairment in xenopus laevis.an in vitro test system, involving gametes of xenopus laevis has been used to study the effect of antifertility agents upon spermatozoa as manifest in developing embryos. exposure to either the isomeric forms of dimethylmyleran, methyl methanesulphonate or gamma-radiation led to development of a range of embryopathies, whereas treatment with steroidal drugs or the rodent epididymal chemosterilants alpha-chlorohydrin and trimethylphosphate was compatible with production of apparently normal offsp ...1978209323
chromatin assembly and transcription in eggs and oocytes of xenopus laevis. 1978209936
high affinity of carozolol for beta-adrenoceptors coupled to the adenylyl cyclase in ventricular myocardium of kitten and xenopus laevis.catecholamine-induced stimulation of adenylyl cyclase in ventricular membranes of kitten and xenopus laevis was antagonized competitively by carazolol. apparent equilibrium constants ranging between 100-170 pm were estimated for the beta-adrenoceptor-carazolol complex.1978210404
the effects of alpha and beta adrenergic agents on spleen cell antigen binding in four amphibian species.adults of two urodele amphibian species (triturus cristatus carnifex and cynops hongkongensis) and two anuran species (rana temporaria and xenopus laevis laevis) were immunized with a 25% suspension of sheep or horse erythrocytes. after eight or 14 days, splenic lymphocytes were removed, and their specific red cell-binding capacities tested by immunocytoadherence. antigen-binding cells were classified as high-dose nonsecretory (s-) or secretory (s+), according to whether they bound a single laye ...1978211039
cytochrome oxidase activity of mitochondria in xenopus laevis previtellogenic oocytes. 1978211159
vital dye mapping of the gastrula and neurula of xenopus laevis. i. prospective areas and morphogenetic movements of the superficial layer. 197546836
cap analogues do not inhibit mrna translation in xenopus laevis oocytes. 1978212317
mitotic factors from mammalian cells: a preliminary characterization.the objective of this study was the preliminary characterization of the factors from mitotic hela cells that can induce meiotic maturation in xenopus laevis oocytes. we found that this factor is a heat-labile, ca2+-sensitive, nondialyzable protein with a sedimentation value of 4-5s. furthermore, no new protein synthesis was found to be required for this mitotic factor to induce maturation in the amphibian oocytes. these data suggest that the factors involved in the breakdown of nuclear membrane ...197944891
discussion paper: induction by progesterone and a "maturation-promoting factor" of soluble proteins in xenopus laevis oocytes in vitro.in vitro incubation of isolated x. laevis oocytes with progesterone induces the specific labeling of proteins during maturation. they are detected as several discrete peaks with a double-labeling technique that involves the injection of [3h] leucine into hormone-treated and [14c] leucine into control cells. the peaks are separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. identical proteins are obtained with two other steroids that provoke maturation and with p-chloromercurib ...1977214005
translation of type c viral rnas in xenopus laevis oocytes: evidence that the 120,000-molecular-weight polyprotein expressed in abelson leukemia virus-transformed cells is virus coded.the genomic rna of abelson leukemia virus (ablv) has been purified and translated in xenopus laevis oocytes. the primary ablv-specific protein synthesized is a polyprotein corresponding in molecular weight and immunological properties to a previously described p15 and p12 containing 110,000- to 130,000-molecular-weight polyprotein expressed in ablv-transformed cells. in contrast, translation of woolly monkey sarcoma virus genomic rna resulted in symthesis of a 55,000-molecular-weight polyprotein ...1978214586
calcium dependence of alpha-adrenoreceptor stimulation of myoepithelial cell contraction in the granular glands of xenopus laevis skin proceedings. 197825958
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