Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| in vitro studies on the control of myoepithelial cell contraction in the granular glands of xenopus laevis skin. | 1978 | 104900 | |
| 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 ... | 1978 | 79330 |
| 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. | 1978 | 79446 |
| changes in hepatic levels of tyrosine aminotransferase messenger rna during induction by hydrocortisone. | messenger rna specific for tyrosine aminotransferase was quantitated by microinjection into oocytes of xenopus laevis. the heterologously translated enzyme was identified by specific immunoprecipitation and found to be identical with authentic aminotransferase by several criteria. the level of functional message present in rat liver increases during hydrocortisone induction, and this increase is directly proportional to the increased rate of synthesis of the enzyme. kinetic analysis of the chang ... | 1978 | 25898 |
| calcium dependence of alpha-adrenoreceptor stimulation of myoepithelial cell contraction in the granular glands of xenopus laevis skin proceedings. | 1978 | 25958 | |
| the occurrence and transmission of a pattern of dna methylation in xenopus laevis ribosomal dna. | 1978 | 26077 | |
| synaptic organization of the inner plexiform layer of the retina of xenopus laevis. | 1978 | 27791 | |
| 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 ... | 1978 | 30046 |
| histological changes in xenopus laevis daudin specimens kept under dry conditions, then moved back to their natural aquatic environment. i. pituitary, thyroid and testis. | the histofunctional picture of the hypophysis, thyroid and testis was studied in xenopus laevis specimens 1) kept in their natural aquatic environment; 2) gradually exposed to dehydration conditions under which they were kept one week; and 3) returned from the dry environment to water for 24 hr or 7 days. of particular interest are the changes displayed in the hypophysis by type ii acidophils, i.e. presumably prolactin producing cells. in the pituitary of "dry" animals and of those 24 hr after t ... | 1978 | 555326 |
| synthesis and processing of maize storage proteins in xenopus laevis oocytes. | xenopus oocytes injected with zein mrnas efficiently synthesized maize storage proteins for prolonged periods. under optimal conditions, zein was synthesized at 3 ng/hr and represented approximately 10% of the total protein synthesized in the oocyte. the mrna from the normal maize inbred line directed synthesis of all the major zein components; however, products of mrna from the opaque-2 mutant did not contain the largest zein component. zein proteins synthesized in the oocyte were 2000 daltons ... | 1979 | 16592743 |
| the role of lactic acid accumulation in muscle fatigue of two species of anurans, xenopus laevis and rana pipiens. | fatigue produced a marked increase in the lactic acid content of hind-limb muscles, the blood, and the whole animal. after 15 min of rest there was little decline of lactic acid levels but the animals could be stimulated into about 3 min of intense activity. this re-fatigue produced a further increase in lactic acid levels. gastrocnemius muscles removed from fatigued frogs and stimulated in vitro were able to generate initial tensions similar to those in control muscles; total tension was about ... | 1979 | 11799691 |
| development of the urostyle during metamorphosis in five species of anurans. | normal development of the urostyle is described during late stages of metamorphosis in five species of anurans: xenopus laevis (daudin), bufo americanus holbrook, pseudacris triseriata (wied), hyla chrysoscelis cope, and rana pipiens schreber. the developing urostyle of all five species is composed of essentially the same cartilaginous elements: one pair of basidorsals above the notochord and the subtended hypochord. among the five species there is variation in such details as the number of spin ... | 1979 | 30200677 |
| quantitative aspects of rna synthesis in normal and lithium-treated embryos ofxenopus laevis. | the treatment ofxenopus early embryos with lithium chloride produces exogastruale - embryos which fail to gastrulate normally and in which the rates of cell division are reduced. in the present study estimations of incorporations of (5-3h) uridine and the specific activities of the 5'-ribonucleotide precursor pools showed that exogastrulae have higher rates of rna synthesis per cell than control neurulae. sub-cellular fractionations showed that a greater proportion of labelled rna was retained i ... | 1979 | 28305001 |
| suspension feeding dynamics of anuran larvae related to their functional morphology. | the tadpoles of two anuran species, rana sylvatica and xenopus laevis, were fed various concentrations of two algae, anabaena sphaerica (large filaments) and chlorella pyrenoidosa (small unicells). filtering rates were measured indirectly with a coulter counter system; buccal pumping rates were observed directly.experimental measurements of buccal volume (volume cleared with each pump stroke) agreed closely with independent predictions from a descriptive model based on tadpole morphology. the xe ... | 1979 | 28309170 |
| 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 ... | 1979 | 44891 |
| synthesis and processing of the mouse mopc-321 kappa chain in xenopus laevis oocytes. | 1979 | 107859 | |
| characteristics of immunoglobulin synthesized early in the development of xenopus laevis. | 1979 | 108156 | |
| 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- ... | 1979 | 108668 |
| [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. | 1979 | 110481 |
| [demonstration of a long depolarization in the oocytes of xenopus laevis]. | 1979 | 111840 | |
| [teratogenic effect of mercury bichloride on the embryonic development of the amphibian xenopus laevis daud]. | 1979 | 116463 | |
| 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 ... | 1979 | 119824 |
| [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. | 1979 | 121269 |
| 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. | 1979 | 83880 |
| 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 ... | 1979 | 87518 |
| [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 ... | 1979 | 88703 |
| 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 ... | 1979 | 89978 |
| 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 ... | 1979 | 90588 |
| preparation of complementary dna to 5 s ribosomal rna from xenopus laevis. | 1979 | 91536 | |
| [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 ... | 1979 | 93003 |
| a detergent-citric acid technique for isolating nuclear and cytoplasmic fractions containing undegraded rna from cells of xenopus laevis. | 1979 | 94513 | |
| 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 ... | 1979 | 95125 |
| 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 ... | 1979 | 95388 |
| roles of cyclic amp and calcium in maturation of xenopus laevis oocytes. | 1979 | 226799 | |
| characterization of interferon messenger rna from human lymphoblastoid cells. | after treatment with sendai virus, namalwa cells form large amounts of interferon. rna extracted from treated whole cells or from their polysomes was injected into xenopus laevis oocytes and the interferon formed was titrated. the results show that the amount of interferon mrna was maximal by 9 h after treatment of the cells with sendai virus and then declined. sucrose gradient centrifugation of the mrna gave substantial purification and showed that its size was 12 s. | 1979 | 227993 |
| onset of neural function in the lateral line. | the development of the nervous system includes the formation of specific neuronal connections. some insight into the mechanisms by which these connections are made may be obtained by determining the order in which the elements of a developing system begin to function and examining any changes that may occur in the system shortly after it begins functioning. i have investigated the lateral line of the south african clawed frog, xenopus laevis and i have classified the afferent system into three e ... | 1979 | 228196 |
| biochemical characterization of lysosomes in unfertilized eggs of xenopus laevis. | relations between lysosomes and yolk platelets of amphibian eggs have been suggested. this work demonstrates the presence of acid hydrolases in oocytes induced to ovulate in vitro. about 40% of the acid hydrolases are found in a sedimentable fraction, and, in accordance with the lysosomal concept, they display structural latency. biochemical data did not indicate any association between lysosomal enzymes and yolk platelets. the mechanism of yolk resorption is discussed and it is suggested that t ... | 1979 | 228752 |
| translation of avian sarcoma virus rna in xenopus laevis oocytes. | 1979 | 218572 | |
| histone 1 phosphotransferase activities during the maturation of oocytes of xenopus laevis. | 1979 | 220911 | |
| follicle-stimulating-hormone receptors in the testis of the frog, xenopus laevis. | 1979 | 221307 | |
| the role of the carbohydrate in the stabilization, processing, and packaging of the glycosylated adrenocorticotropin-endorphin common precursor in toad pituitaries. | the neurointermediate lobes of dark adapted toads, xenopus laevis, were incubated for 30 min in [3h]arginine, [3h]arginine plus [14c]glucosamine, or [3h]glucosamine and then chased for various time periods ranging from 1--3 h. the labeled polypeptides synthesized and secreted by the lobes were analyzed by acid-urea polyacrylamide gel electrophoresis. a glycosylated acth-endorphin precursor (32,000 mol wt) was synthesized during the pulse and identified by immunoprecipitation by acth-(11--24) ant ... | 1979 | 222574 |
| dual innervation of end-plate sites and its consequences for neuromuscular transmission in muscles of adult xenopus laevis. | 1. electrophysiological study of dually innervated end-plate sites was carried out in xenopus laevis pectoral muscle fibres. end-plate potentials (e.p.p.s) and miniature end-plate potentials (m.e.p.p.s) have been recorded in mg-blocked preparations. 2. the mean quantal content (m) of each e.p.p. at dually innervated end-plates was significantly smaller than the corresponding values obtained at singly innervated ones. at a given doubly innervated end-plate site the values of m tended to be invers ... | 1979 | 222897 |
| mitochondrial dna polymerase from xenopus laevis oocytes. | 1979 | 223552 | |
| morphological and physiological aspects of melanophores in primary culture from tadpoles of xenopus laevis. | melanophores from tadpoles of xenopus laevis (daudin) were isolated by digestion of tail fins with acetyltrypsin and collagenase and maintained in primary culture for 6 weeks up to 3 months. within 36 to 72 h the melanophores develop one to eight dendritic processes per cell; secondary and tertiary branchings of the processes were frequently observed. the melanophores in primary culture disperse under the influence of alpha-msh or cyclic amp; upon rinsing out these substances the cells aggregate ... | 1979 | 223762 |
| eukaryotic dna replication: the first steps toward a multienzyme system from xenopus laevis. | 1979 | 225118 | |
| two cell-free systems constructed from xenopus laevis oocytes: generalized genetic recombination; dna supercoiling. | 1979 | 225119 | |
| transcription of cloned xenopus 5s rna genes by x. laevis rna polymerase iii in reconstituted systems. | when incubated with a soluble extract from large oocytes of xenopus laevis, recombinant dna plasmids containing either x. laevis oocyte 5s dna or x. borealis oocyte 5s dna direct the synthesis of discrete 5s rnas, which by size and sequence analysis are similar or identical to the corresponding 5s rnas synthesized in vivo. synthesis of the 5s rnas is mediated by a soluble endogenous rna polymerase iii (nucleosidetriphosphate:rna nucleotidyltransferase, ec 2.7.7.6), which presumably recognizes sp ... | 1979 | 284325 |
| isolation of a 7s particle from xenopus laevis oocytes: a 5s rna-protein complex. | previtellogenic oocytes of xenopus laevis contain a free 5s rna-protein complex sedimentating at 7 s. this particle consists of one molecule of 5s rna and one 45,000-dalton protein. the protein of the 7s particle and the protein that is released in association with 5s rna when the ribosome is treated with edta are unrelated. because the 5s rna accumulated by small oocytes in storage particles is incorporated into the ribosome later in oogenesis, we conclude that 5s rna is succesively associated ... | 1979 | 284338 |
| electrical currents through full-grown and maturing xenopus oocytes. | an extracellular vibrating electrode was used to map the current pattern around xenopus laevis oocytes. current was found to enter the animal hemisphere and leave the vegetal hemisphere; in fully grown oocytes from which the follicle cells had been removed, the maximal current density was about 1 microamperemeter/cm2. this current decreased to nearly zero in response to progesterone and several other maturation-producing agents. in the case of progesterone, the decline began within a few minutes ... | 1979 | 284407 |
| delimitation of a promoter for rna polymerase iii by means of a functional test. | a xenopus laevis dna segment containing the structural gene for trna1met and 22 base pairs at the 5' side of the gene is active in trna production. the dna segment was ligated to sea urchin histone dna and was also inserted into plasmid pcr1. both recombinant dnas were shown to produce mature trna1met at a high rate when injected into centrifuged xenopus oocytes. | 1979 | 288049 |
| mitotic factors from mammalian cells induce germinal vesicle breakdown and chromosome condensation in amphibian oocytes. | cytoplasmic extracts of hela cells synchronized in various phases of the cell cycle were injected into fully grown xenopus laevis oocytes to monitor the presence of factors that can induce meiotic maturation: i.e., germinal vesicle breakdown and chromosome condensation. extracts from gi and s phase cells had no activity. the maturation-inducing activity, which was found to be low during early and mid g2 phases, increased rapidly during late g2 and reached a peak in mitosis. the results of this s ... | 1979 | 288067 |
| structures of gustatory organs of xenopus laevis during metamorphosis. | 1979 | 297731 | |
| 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 ... | 1979 | 158122 |
| [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 ... | 1979 | 158407 |
| [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 ... | 1979 | 159327 |
| somitogenesis in amphibian embryos. i. experimental evidence for an interaction between two temporal factors in the specification of somite pattern. | somitogenesis is described in two species of anuran amphibians, xenopus laevis and rana temporaria, in which the cellular mechanics of somite formation are distinctly different. heat shocks are employed to demonstrate a wave of cellular change which precedes somite formation down the body axis. this prior wave is shown to be kinematic. it is not a propagated wave. it is a consequence of the temporal activities of the cells laid out in space, but there is no evidence that these activities depend ... | 1979 | 314486 |
| fine structural distribution of the surface-connected canalicular system in frog thrombocytes. | the existence of the surface-connected canalicular system (sccs) has been demonstrated in semithick sections of the frog thrombocytes by the use of a high voltage electron microscope. the sccs of the thrombocytes in rana catesbeiana and rana nigromaculata consists of numerous canaliculi and vesicles with a diameter of 250 nm, which join with one another to make a complex network throughout the cytoplasm. although the sccs of xenopus laevis fits well into the pattern described in rana catebeiana, ... | 1979 | 315820 |
| properties of a cytostatic factor from xenopus laevis eggs. | 1979 | 315899 | |
| the effect of adult thymectomy upon helper function in xenopus laevis, the south african clawed toad. | carrier-primed helper activity enhancing anti-hapten (tnp-) responses in young adult xenopus laevis reached peak levels 2-4 days after a low dose challenge (0.005% rbc) of unconjugated carrier. it fell quickly to negligible levels by 10 days. adult thymectomized (atx) animals were consistently unable to generate substantial levels of hapten-specific antigen-binding spleen cell (abc) activity. since atx does not severely reduce splenic abc responses to the high dose (10% rbc) of carrier used for ... | 1979 | 315915 |
| studies on aminoacyl trna synthetases and transfer rna in living xenopus laevis oocytes. | the microinjection of transfer rna into amphibian oocytes permits one to study under in vivo conditions the reactions that affect this important macromolecule. a comparative study has been carried out between the in vivo and in vitro specificity of the aminoacylation reacton. the results obtained show that modifications of the trna structure affect aminoacyl-trna synthetase recognition in the same fashion in both conditions. the in vivo aminoacylation was not affected by the presence of puromyci ... | 1979 | 261727 |
| in vivo studies on the incorporation of microinjected acidic proteins of the large ribosomal subunit from escherichia coli and artermia salina into oocyte ribosomes from xenopus laevis. | tritium-labeled acidic proteins from the large ribosomal subunit of artermia salina or escherichia coli were microinjected into the cytoplasm of stage iv/v oocytes from xenopus laevis. el12 from the large ribosomal subunit of a. salina but not l7/l12 or l7/l12--l10 from e. coli is specifically incorporated into 60s ribosomal subunits of oocytes. this incorporation is not significantly inhibited by actinomycin d. incorporation of el12 into the 60s subunits occurs in enucleated oocytes, suggesting ... | 1979 | 385044 |
| structure of deletion derivatives of a recombinant plasmid containing the transposable element tn9 in the spacer sequence of xenopus laevis 5s dna. | 1979 | 385229 | |
| the origin of yolk-dna in xenopus laevis. | xenopus laevis serum and plasma was found to contain an average of 25 microgram dna/ml. isolated x. laevis oocytes incubated in medium containing 25 microgram dna/ml labeled with either 125i, 32p or 14c and from three different sources (bovine, e. coli and x. laevis), incorporated the label at an average rate of 0.11 ng.mm-2.hr-1. sucrose gradient fractionation of oocytes revealed that 40-75% of the acid-precipitable label incorporated was associated with the yolk platelets. additional incubatio ... | 1979 | 385804 |
| hypothalamic luteinizing hormone-releasing hormone content in relation to the seasonal reproductive cycle of xenopus laevis. | 1979 | 387514 | |
| [immunofluorescence evidence for prolactin and somatotropic cells in the hypophysis of xenpus tadpoles (xenopus laevis d.)]. | 1979 | 387515 | |
| fine structure of ribosomal rna. ii. distribution of methylated sequences within xenopus laevis rrna. | the distribution of methyl groups in rrna from xenopus laevis was analyzed by hybridization of rrna to subfragments of either of two cloned rdna fragments, x1r11 and x1r12, which together constitute a complete rdna repeat unit. using a mixture of 3h-methyl plus 32p-labelled rrna as probe, the molar yield of methyl groups per rrna region in hybrid could be calculated. for this calculation the length of the rrna coding region in each dna subfragment is needed, which was determined for x1r11 subfra ... | 1979 | 388355 |
| immunohistochemical localization of a gastrin-like peptide in the brain of an amphibian, xenopus laevis daud. | the indirect immunofluorescence technique was used to demonstrate a substance reacting with gastrin antisera in the brain of xenopus laevis. immunoreactive material was found in two sites: (1) in the caudal hypothalamus more precisely in the nucleus infundibularis ventralis, (niv) of the pars ventralis of the tuber cinereum, (pvtc). the fluorescent axons of the reactive parikarya of the niv give rise to two symmetrical tracts which run rostro-ventrally and join, in the infundibular floor, the pr ... | 1979 | 389428 |
| oocyte-follicle cell gap junctions in xenopus laevis and the effects of gonadotropin on their permeability. | junctions between xenopus laevis oocytes and follicle cells have been identified as gap junctions by the passage of microinjected fluorescent dye from oocytes to follicle cells. the opening or assembly of these junctions, or both, appears to be regulated by gonadotropins. | 1979 | 569364 |
| production and fate of erythroid cells in anaemic xenopus laevis. | adult xenopus laevis, rendered anaemic by phenylhydrazine injection, have been studied during the recovery from such anaemia. electron microscopy of liver and spleen sections indicates that both of these organs are active in the phagocytosis and destruction of the old damaged red blood cells. may-grunwald and giemsa staining of liver and spleen cells following anaemia has been used to show that erythropoiesis also occurs in both liver and spleen, and this has been confirmed by electron-microscop ... | 1979 | 422678 |
| characterisation of bacterial clones containing dna sequences derived from xenopus laevis vitellogenin mrna. | a 1700 nucleotide dna sequence derived from xenopus vitellogenin mrna has been cloned in the bacterial plasmid pbr322. the identity of the cloned sequence was verified in two ways. firstly, the plasmid dna was shown to hybridise to an rna of the correct size (6,700 nucleotides). this was shown by in situ hybridisation to electrophoretically separated rna and also by the formation of "r-loops" with purified vitellogenin mrna. then, using a novel procedure in which plasmid dna covalently bound to ... | 1979 | 424303 |
| histones of xenopus laevis erythrocytes. purification and characterization of the lysine-rich fractions. | lysine-rich histones have been isolated from the terminally differentiated erythrocytes of xenopus laevis. three major proteins have been separated by ion-exchange chromatography. these proteins have been characterized by electrophoresis, amino acid analysis and immunochemical techniques. it is concluded that two 'typical' lysine-rich subfractions are present in xenopus erythrocytes and, in addition, a serine-rich histone, that shares no common antigenic determinants with the other lysine-rich h ... | 1979 | 427216 |
| transcription of a cloned ovalbumin ds-cdna in xenopus laevis oocytes. | 1979 | 435322 | |
| ultrastructural study of degeneration and regeneration in the amphibian tectum. | the processes of degeneration and reinnervation in the optic tectum of xenopus laevis have been detailed by quantitative ultrastructural analysis. the tecta were denervated either permanently, by removing the contralateral eye, or temporarily, by cutting the optic tract. after denervation the total number of synapses decreases rapidly within 4 days of a stable level of about 40% of the original number. vacated postsynaptic sites are subsequently removed by phagocytosis. when regenerating axons a ... | 1979 | 435978 |
| movements of supernumerary hindlimbs after innervation by single lumbar spinal nerves of xenopus laevis. | lumbar spinal nerves s8, s9, and s10, together innervating normal hindlimbs in xenopus laevis, were tested to cause coordinated movements in grafted hindlimbs. it could be shown that this ability is mainly restricted to lumbar nerve s9. | 1979 | 437035 |
| absence of dorsal-ventral differences in energy metabolism in early embryos of xenopus laevis. | 1979 | 437316 | |
| purification of xenopus laevis embryo and liver nuclei using metrizamide. | 1979 | 437322 | |
| hybrids of xenopus laevis and xenopus borealis express proteins from both parents. | 1979 | 437325 | |
| synthesis and transport of various rna species in developing embryos of xenopus laevis. | 1979 | 437337 | |
| tissue distribution of immunoreactive somatostatin in the south african clawed toad (xenopus laevis). | immunoreactive somatostatin is present in the brain, gut and pancreas of the south african clawed toad, but is absent from the skin, a rich source of many other brain-gut peptides. | 1979 | 438715 |
| an intermediate type of muscle fibre in xenopus laevis. | 1979 | 440437 | |
| poly(a)+ rna metabolism during oogenesis in xenopus laevis. | 1979 | 446893 | |
| light-triggered rod disc shedding in xenopus retina in vitro. | the present study was designed to determine whether light-induced rod outer segment disc shedding occurs when the eye is isolated from the rest of the organism. whole eye explants of xenopus laevis were maintained in vitro and either exposed to 5 min of light or kept in darkness. in both the in vitro eyes and in vivo controls exposed to the same conditions, a significant degree of disc shedding occurred within 1 hr of the light stimulus. the disc shedding response was larger in the explanted eye ... | 1979 | 447463 |
| vitellogenin in xenopus laevis is encoded in a small family of genes. | vitellogenin, the yolk protein precursor, is produced in x. laevis liver from a 6.3 kilobase (kb) mrna. sequences of this mrna have been transcribed into cdna and cloned in e. coli. some properties of 21 of these cloned dnas, ranging in size from 1 to 3.7 kb, have been reported by wahli et al. (1978b). this paper reports restriction endonuclease mapping, cross hybridization, heteroduplex mapping in the electron microscope and heteroduplex melting experiments with these dnas. we conclude that the ... | 1979 | 455441 |
| deletion mutants of xenopus laevis 5s ribosomal dna. | deletion mutants have been derived from a plasmid-cloned repeating unit of xenopus laevis oocyte 5s dna by introducing the transposable chloramphenicol-resistance element tn9 into the at-rich spacer sequence near the 5' terminus of the x. laevis 5s rrna gene in a recombinant plasmid and then selecting plasmids which had lost the transposable element. plasmids lacking the entire transposable element and various portions of the at-rich spacer sequence flanking the original site of tn9 integration ... | 1979 | 455442 |
| sequence organization of the spacer dna in a ribosomal gene unit of xenopus laevis. | a detailed restriction map was constructed for a cloned xenopus laevis rdna fragment containing the nontranscribed spacer (nts) and external transcribed spacer (ets) together with a portion of both the 18s and 28s rrna genes. the nts was found to contain at least three distinct repetitious areas. region 1 has a repeating unit of approximately 100 bp. the primary structure of this unit has been determined by dna sequencing. region 2 is very similar in organization to region 3, and both have an al ... | 1979 | 455459 |
| synthesis of albumin and malic enzyme in wheat-germ lysates and xenopus laevis oocytes programmed with chicken-liver messenger rna. | undegraded, biologically-active, polyadenylated rna was isolated from chicken liver by a rapid, simple procedure. liver cells were dispersed mechanically and then broken gently by controlled dounce homogenization in the absence of detergent or ribonuclease inhibitors. after removing lysosomes and mitochondria by centrifugation, rna was precipitated at ph 5.2. polyadenylated mrna was isolated directly from the detergent-solubilized precipitate by oligo(dt)-cellulose chromatography. the resulting ... | 1979 | 456360 |
| free cytoplasmic messenger ribonucleoprotein complexes from rabbit reticulocytes. | free cytoplasmic globin mrna containing mrnp-particles were isolated from rabbit reticulocytes by zonal sucrose gradient centrifugation and their properties were compared with mrnp particles isolated in the same way from edta-dissociated reticulocyte polyribosomes. the average poly(a)-length of 9s mrna from free cytoplasmic mrnp was 17-20 nucleotides being about two times shorter than the average poly(a)-length of polysomal 9s mrna. the protein composition of the free cytoplasmic mrnp particles ... | 1979 | 460182 |
| isolation and organization of calf ribosomal dna. | ribosomal dna (rdna) from calf was isolated by three density gradient centrifugations. the first centrifugation in cs2s04/bamd was used to obtain partially resolved dg+dc-rich fractions from total dna. the second and third centrifugations, in cs2s04/ag+, led to the isolation of an rdna fraction characterized by a symmetrical band in cscl, p = 1.724 g/cm3. this new procedure appears to be generally suitable for the isolation of rdna and other dg+dc-rich repeated genes. the organization of isolate ... | 1979 | 461183 |
| estrogen causes a rapid, large and prolonged rise in the level of nuclear estrogen receptor in xenopus laevis liver. | 1979 | 465076 | |
| chromatin structure of the 5s ribonucleic acid genes of xenopus laevis. | 1979 | 465464 | |
| toxicity and teratogenicity of aromatic amines to xenopus laevis. | 1979 | 465773 | |
| the carbohydrate content of isolated yolk platelets from early developmental stages of xenopus laevis. | 1979 | 466703 | |
| newly synthesized histones in chromatin of early embryos of xenopus laevis. | 1979 | 466704 | |
| the nucleolus organizers of plethodon and aneides located by in situ nucleic acid hybridization with xenopus 3h-ribosomal rna. | the main clusters of ribosomal genes, or nucleolus organizers, have been located by in situ nucleic acid hybridization of xenopus laevis 3h labelled ribosomal rna to mitotic chromosomes in squash preparations of intestinal epithelium from 7 species of plethodon and 3 species of aneides. the species used were chosen on account of having well known karyotypes and genome sizes. the plethodon species covered a range of genome size of 20--69.4 pg. the locations of those nucleolus organizers that coul ... | 1979 | 467168 |
| biochemical research on oogenesis. transfer rna is fully charged in the 42-s storage particles of xenopus laevis oocytes. | 1. transfer rna makes up 30-40% of total rna in previtellogenic oocytes of xenopus laevis. the bulk of trna is associated with 5-s rna and two proteins in a high-molecular-weight complex sedimenting at 42s. 2. we show here that all kinds of trna are present in the 42-s particles and all of them sediment coincidently. particle trna is fully charged in vivo. during purification of the 42-s particles trna becomes partially uncharged. when purified particles are incubated in vitro with amino acids a ... | 1979 | 467449 |
| synthesis and glycosylation of rat prostatic binding protein in xenopus laevis oocytes. | 1979 | 467658 | |
| classes of proteins synthesized in oocytes, eggs, embryos, and differentiated tissues of xenopus laevis. | two-dimensional gel electrophoresis has been used to analyse protein synthesis in embryonic stages and in three differentiated tissues of xenopus laevis. the patterns found in oocyte, unfertilized eggs, embryos shortly after fertilization and at progressively later stages of development have been characterized and compared with the patterns found in the brain, heart and liver of tadpoles. the results suggest that at least four classes of proteins can be recognized among the proteins synthesized, ... | 1979 | 467870 |
| in vitro synthesis of rna by xenopus spermatogenic cells i. evidence for polyadenylated and non-polyadenylated rna synthesis in different cell populations. | premeiotic and postmeiotic (haploid) gene expression during spermatogenesis in the anuran, xenopus laevis, was studied by analyzing the accumulation of radioactively labelled cytoplasmic polyadenylated [poly (a +)] and non-polyadenylated [poly (a -)] rnas. dissociated spermatogenic cells were labelled and maintained in an in vitro system capable of supporting cell differentiation. labelled cells were separated by density gradient centrifugation into subpopulations enriched for individual spermat ... | 1979 | 469479 |
| development of synaptic ultrastructure at neuromuscular contacts in an amphibian cell culture system. | cultures of dissociated myotomal muscle and spinal cord derived from embryos of xenopus laevis were grown in the presence of curare in order to abolish neuromuscular activity and were examined by electron microscopy. in one-day-old cultures a few of the neuromuscular contacts already displayed several synaptic specializations including 500 a vesicles clustered against the axolemma, increased axolemmal densities, basal lamina in the cleft, an increased sarcolemmal density and subsarcolemmal filam ... | 1979 | 469576 |
| meiotic maturation in xenopus laevis oocytes initiated by insulin. | insulin can induce meiotic division in xenopus laevis oocytes. this effect shows the specificity expected of a receptor-mediated mechanism. it is potentiated by ethynylestradiol, a steroid antagonist of pregesterone (the natural hormone that provokes meiosis). the xenopus laevis oocytes may serve as a model for the study of the poorly understood effect of insulin on cell division. | 1979 | 472755 |