Publications
| Title | Abstract | Year(sorted descending) Filter | PMID Filter |
|---|
| the effect of thymectomy at different stages of larval development on the immune response of the clawed toad to sheep erythrocytes. | the role of the thymus during the first three weeks of larval life in the maturation of humoral immunity in the amphibian, xenopus laevis, is examined. thymectomy throughout this period dramatically affects the heterologous red cell response of young adults. sheep erythrocyte (srbc) administration elicited haemolytic antibody production in the blood and in the spleen (measured by the appearance of plaque forming cells) of control animals, but failed to do so in all thymectomized toadlets. moreov ... | 1976 | 944762 |
| cell-free translation of messenger rna from oocytes of xenopus laevis. | 1976 | 945202 | |
| control of 5s rna synthesis in xenopus laevis. | 1976 | 945465 | |
| nuclear swelling and chromatin decondensation can occur without cortical granule explosion in eggs of xenopus laevis. | 1976 | 945774 | |
| subunit homologies of lactate dehydrogenase (ldh) isoenzymes between amphibians (xenopus laevis) and mammals (wistar rat). | 1976 | 947661 | |
| dna-dependent rna polymerase c from xenopus laevis ovaries. ability to transcribe intact double-stranded dna. | dna-dependent rna polymerase c, partially purified from xenopus laevis ovaries, has been resolved by deae-sephadex chromatography in two forms, eluting at 0.2 m and 0.3 m ammonium sulfate, respectively. both are sensitive to high concentrations of alpha-amanitin (200 mug/ml). their ionic strength dependence and divalent cation requirements are indistinguishable. quantitatively, rna polymerase c represents the major form of rna polymerase activity solubilized from the ovaries. both rna polymerase ... | 1976 | 947751 |
| melanoblast-tissue interactions and the development of pigment pattern in xenopus larvae. | the melanophores of larval xenopus laevis are disparately distributed on the hypomere in that the upper region (uht) is densely pigmented, the median region (mht) is moderately pigmented, and the lower region (lht) is unpigmented. the roles of the melanoblasts and their tissue environment in determining the melanophore pattern was investigated by heterotopic transplantation of hypomeric tissues, culture of neural crest explants in vesicles derived from hypomeric tissues and radioactive marking o ... | 1976 | 947992 |
| stage-sensitivity and dose-response curve of u.v. effect on germ cell formation in embryos of xenopus laevis. | ultraviolet light (u.v.) irradiation of the vegetal hemisphere of xenopus laevis eggs resulted in the elimination of primordial germ cells in tadpoles. quantitative studies were performed on this phenomenon. the stage sensitivity to u.v. inactivation of germ cell formation was obtained for the early developmental stages ranging from immediately after fertilization to small-cell blastula. it was found that u.v. irradiation at the stage immediately after fertilization was more injurious than irrad ... | 1976 | 947996 |
| measurement of potassium and chloride ion concentrations in the cupulae of the lateral lines of xenopus laevis. | 1. potential measurements were made with double barrel ion selective electrodes from the cupulae of lateral line organs in the aquatic toad xenopus laevis. 2. a positive endocupular potential (ecp) of 15-50 mv was recorded within the cupula, immediately above the hair cells. 3. increases in the cl- and k+ potentials were recorded when the ion selective electrodes touched the cupula. cupular cl- and k+ varied between 35 and 70 mm and 24 and 100 mm respectively. this variation existed between, rat ... | 1976 | 948058 |
| processes for sodium permeability inactivation in the myelinated nerve fibre of the frog (xenopus laevis). | 1976 | 949010 | |
| direct induction by estradiol on vitellogenin synthesis in organ cultures of male xenopus laevis liver. | organ cultures of liver from untreated male xenopus respond to 17 beta-estradiol in the culture medium by synthesizing and secreting the yolk protein precursor vitellogenin. vitellogenin synthesis, as a primary response, is first detectable on the fourth day of culture, and comprises up to 12% of the protein synthesized on the eighth day. estradiol is required during the lag period of 4 days. tissue from male xenopus injected with 1 mg of estradiol 30 days before the start of culture responds mo ... | 1976 | 949740 |
| vital dye mapping of the gastrula and neurula of xenopus laevis. ii. prospective areas and morphogenetic movements of the deep layer. | 1976 | 950072 | |
| freeze-fracture electron microscopy of preexisting and nascent cell membrane in cleaving eggs of xenopus laevis. | during cell division in the xenopus egg (diameter 1.25 mm) new cell membrane is formed in the furrow region (rate of growth approx 4-10(4) mum2/min). freeze-fracture electron microscopy has produced the following data. preexisting plasma membrane faces show a reversed polarity with respect to particle distribution, i.e. more particles are attached to the e-face (density 1600-2200 particles/mum2) than to the p-face (300 particles/mum2). a frequency histogram of 2331 measured intramembranous parti ... | 1976 | 953012 |
| neurite outgrowth from explanted xenopus retina: an effect of prior optic nerve section. | experimental conditions are described for the in vitro study of explanted eyes from embryos of xenopus laevis and of retinas from older larvae. when eyes are explanted from embryos of stages 25-34, a rapid outgrowth of fibroblast-like and pigment cells is observed, upon which a neuritic outgrowth is eventually superimposed. outgrowth from the retina of later stage tadpoles (50-54) is not seen until about a week following explantation and resembles the mixed cell outgrowth observed in whole eye e ... | 1976 | 953737 |
| application of a multiwire proportional chamber to the detection of axoplasmic transport. | a new technique for the detection of the axoplasmic transport of beta-radioactively labelled materials is described wherein a multiwire proportional chamber is used to measure the distribution of activity along peripheral nerve fibers which are maintained in vitro. the operating principles of the chamber are described and basic construction parameters given. potential radiolabels are discussed. two types of studies were performed at room temperature in vitro using sciatic nerves of the amphibian ... | 1976 | 953854 |
| low molecular weight viral rnas transcribed by rna polymerase iii during adenovirus 2 infection. | nuclei isolated from human cells productively infected with adenovirus 2 have been shown to synthesize four low molecular weight rna species which hybridize efficiently to viral dna. one species corresponds to the 5.5s or va rna (ohe, weissman, and cooke, 1969), and is designated v156. the other three species are novel and have been designated v200, v140, v130, since they are approximately 200, 140, and 130 nucleotides in length, respectively. these viral rnas retain their distinct electrophoret ... | 1976 | 954087 |
| a reinvestigation of 5' leads to 3' polarity in 40s ribosomal rna precursor of xenopus laevis. | the 5' leads to 3' polarity of the 40s precursor rrna molecule relative to the location of the 18s and 28s rna regions in the precursor has been reinvestigated. fragments of rdna derived by the restriction endonuclease ecori and cloned in e. coli were partially digested with the exonuclease induced by bacteriophage lambda and with exonuclease iii from e. coli. the resulting rdna fragments with single-stranded tails were hybridized separately with 18s and 28s rrna, and the formation of the hybri ... | 1976 | 954098 |
| the size of the guanosine triphosphate pool active in the synthesis of stable rna by stage 6 oocytes of xenopus laevis. | 1976 | 954858 | |
| hormone effects on male sex behavior in adult south african clawed frogs, xenopus laevis. | 1976 | 955579 | |
| direct adaptation of cells to temperature: similar changes of ldh isozyme patterns by in vitro and in situ adaptations in xenopus laevis. | 1976 | 963983 | |
| induction of meiosis by injection of heterologous protein kinase and phosphorylase kinase in xenopus laevis oocytes. | meiosis reinitiation has been triggered by injection of beef heart protein kinase or rabbit phosphorylase kinase into xenopus laevis oocytes. successful injections are followed by germinal vesicle breakdown, chromosome condensation, formation of a normal meiotic spindle, and appearance of an amplifiable maturation promoting factor. meiosis reinitiation does not occur when the enzymes are introduced into the oocytes simultaneously with egta or after pretreatment with cycloheximide. antipain, an a ... | 1976 | 965920 |
| electrophoretic introduction of calcium ions into the cortex of xenopus laevis oocytes triggers meiosis neinitiation. | meiosis reinitiation has been triggered via electrophoretic driving of ca++ into the cortex of xenopus laevis oocytes freed from functional follicle cells by collagenase treatment. mg++ could not be substituted for ca++. ca++ induced maturation resembles progesterone induced maturation in so far both are inhibited by cycloheximide, give rise to amplifiable mpf in the cytoplasm of treated oocytes and allow chromosome condensation and the formation of a normal meiotic spindle. | 1976 | 965921 |
| the deleterious effects of fungicides and herbicides on xenopus laevis embryos. | groups of 30 xenopus laevis embryos, at "tail-bud" stage (nieukoop-faber stages 22-24) were exposed to 0.1-2 ppm concentrations of various pesticides for 1 to 10 days. the pesticides used were chloranil and dichlone (both are fungicidal and herbicidal); diquat (herbicide); and nabam (fungicide). the parameters examined were mortality, gross morphology, histology, and behavior. chloranil (1.25 to 1.75 ppm) treated embryos showed abnormalities of the otolith, optic cup, and general pigmentation. t ... | 1976 | 970983 |
| arrangement of length heterogeneity in repeating units of amplified and chromosomal ribosomal dna from xenopus laevis. | 1976 | 972392 | |
| ribosomal genes of xenopus laevis: evidence of nucleosomes in transcriptionally active chromatin. | most of the reiterated ribosomal genes in the somatic cells of larvae of a mutant of xenopus laevis appear to be protected from short-term nuclease digestion by being packaged in the form of chromatin subunits or nucleosomes. since these mutant animals probably require all of their ribosomal genes to be active in order to maintain viability, at least some of the transcriptionally active gene sequences are probably associated with chromatin subunits. thus, association of dna with nucleosomes may ... | 1976 | 973136 |
| the arrangement of 18-s and 28-s ribosomal ribonucleic acids within the 40-s precursor molecule of xenopus laevis. | the arrangement of 18-s rrna and 28-s rrna within their 40-s common precursor molecule (pre-rrna) of xenopus laevis was investigated by electron microscopic analysis of secondary structure of nascent pre-rrna chains of oocytes, and by 5'-end analysis of 18-s rrna and 28-s rrna hybridized to the ecori fragment of rdna cloned as plasmid pcd42. secondary structure mapping of phenol-extracted rna from nucleolar cores revealed complete pre-rrna chains or molecules at various stages of processing and ... | 1976 | 976269 |
| observations on the migration and proliferation of gonocytes in xenopus laevis. | the process of primordial germ cell formation in the normal course of development of xenopus laevis was examined with a light microscope on paraffin and epon sections of embryos or tadpoles, extending over the period from the gastrula to the feeding tadpole stage. positional changes of gonocytes with development were nearly the same as those reported on the same species by blackler (1958) and whitington & dixon (1975). the following points were newly demonstrated. gonocytes which have been locat ... | 1976 | 978127 |
| [transfer of behavior patterns through transplantation of anlagen of neuro-anatomic structures in amphibian larva. 1. xenoplastic exchange of medulla anlagen between xenopus laevis and hymenochirus boettgeri (amphibia, anura)]. | by transplantation of parts of the neural plate (latter medulla oblongata) from xenopus laevis (daud.) to hymenochirus boettgeri (torn.) larval chimaeras were obtained, which showed donorlike rhythmical movements of the mouth and pharyngeal region, movements which the host species lacks. nevertheless, some of these tadpoles were still able to catch small prey in a reaction which is typical for the host and lacking in the donor. | 1976 | 983425 |
| nuclear localization of dna polymerase alpha in xenopus laevis oocytes. | 1976 | 985524 | |
| isolation, physicochemical properties, and the macromolecular composition of the vitelline and fertilization envelopes from xenopus laevis eggs. | as a step toward defining in molecular terms the sperm-triggered block to polyspermy reaction established by the egg at fertilization, vitelline (ve) and fertilization (fe) envelopes were isolated from eggs of the sounth african clawed toad xenopus laevis and some of their physicochemical properties determined. envelopes were isolated after lysis of the fertilized or unfertilized eggs by sieving techniques; isolated envelopes retained their in situ morphology as determined by electron microscopy ... | 1976 | 986165 |
| repeating units of xenopus laevis oocyte-type 5s dna are heterogeneous in length. | the restriction enzymes hind iii and hae iii cleave xenopus laevis 5s dna at one and three sites, respectively, in each repeating unit of approximately 700 base pairs. the cleavage sites for both enzymes have been located within the repeating unit by denaturation mapping of the restriction fragments. the hind iii products and one of the hae iii fragments are variable in length, indicating heterogeneity in the length of the repeating unit in 5s dna. this length heterogeneity is confined to the ma ... | 1976 | 986247 |
| a study of foldback dna. | nuclear dna from eucaryotes contains a significant fraction which forms duplexes very rapidly and also independently of the dna concentration. this fraction can be isolated by adsorption to hydroxylapatite and has been called foldback dna (britten and smith, 1970). here we extend previous studies to show that the foldback fraction is due to the existence of a finite number of foldback foci in each genome equivalent of dna, approximately 10(5) in the case of xenopus laevis. more significantly, we ... | 1976 | 986250 |
| the 5' leads to 3' polarity of the xenopus ribosomal rna precursor molecule. | evidence is presented that in xenopus laevis the 18s rrna sequence is proximal to the 5' end of the rrna precursor molecule and the 28s secquence is proximal to the 3' end. this assignment was made by digesting amplified ribosomal gene transcription complexes with ecori restriction endonuclease and spreading the cleaved transcription complexes for electron microscopy. from the known location of the ecori cutting sites within the transcribed region and the length of nascent chains on the cleaved ... | 1976 | 986254 |
| sequences of 5s ribosomal rna from xenopus mulleri and the evolution of 5s gene-coding sequences. | sequences for 5s rna from somatic cells and oocytes of xenopus mulleri are presented. comparison with sequences previously given for xenopus laevis indicates that the somatic 5s rna genes of each species are more closely related to each other than either is to its own set of oocyte genes, suggesting that somatic and oocyte genes within each species are evolving independently. however, detailed analysis of sequence variants in each species suggests that there is a mechanism which allows occasiona ... | 1976 | 986255 |
| defined nutrient medium for the in vitro maintenance of xenopus laevis oocytes. | a procedure is described for the isolation and culture of large numbers of follicle cell-free xenopus laevis oocytes in all stages of development. the isolation procedure involves the incubation of pieces of ovary in a calcium-free solution or2 containing 0.2% collagenase. a defined nutrient medium for the maintenace of the oocytes in vitro is presented. it is shown that this medium, referred to as dnom, can maintain certain morpological and functional characteristics of oocytes for periods up t ... | 1976 | 986365 |
| initiation of meiotic maturation in xenopus laevis oocytes by lanthanum. | 1976 | 986558 | |
| the synthesis of freezing-point-depressing protein of the winter flounder pseudopleuronectus americanus in xenopus laevis oocytes. | 1976 | 986821 | |
| isolation and some properties of dna coding for trna1met from xenopus laevis. | dna containing the reiterated genes for trna1met has been partially purified from xenopus laevis by centrifugation in actinomycin c1-cscl and ag+-cs2so4 gradients. these gradients separate the trna1met genes from those coding for trna2met and trnaval, thus confirming our earlier suggestion that these genes are not intermingled with each other (clarkson, birnstiel, and purdom, 1973a). the gradients also demonstrate the existence of a minor 5s dna fraction which appears to differ from that previou ... | 1976 | 986875 |
| on the existence of polyadenylated histone mrna in xenopus laevis oocytes. | in a variety of systems, histone mrna has been shown to lack poly(a) (adesnik and darnell, 1972; grunstein et al., 1973). we have found, however, that in xenopus laevis oocytes, poly (a)-containing mrna codes for histones, in a wheat germ cell-free system, based on the following criteria: first, co-migration with authentic x. laevis oocyte histones on polyacrylamide gels; second, no detectable incorporation of tryptophan; third, differential incorporation of lysine and methionine into histone fr ... | 1976 | 987857 |
| morphological changes of the surface of the eggs of xenopus laevis in the course of development. 2. cytokinesis and early cleavage. | 1976 | 988190 | |
| effects of light and dark upon photoreceptor synapses in the retina of xenopus laevis. | photoreceptor synapses in xenopus retina were studied after exposure to day/night cycles and continuous light or dark. in the rods, dense-core vesicles appear alongside the synaptic ribbons in animals exposed to light. in dark-adapted rods, electron-dense material is present in the synaptic clefts, but no dense-core vesicles are found associated with the synaptic ribbons. cone photoreceptors do not show these ultrastructural changes in response to light and dark. prolonged exposure to light (21 ... | 1976 | 991238 |
| reiteration frequency of the histone genes in the genome of the amphibian, xenopus laevis. | radioactive rna was obtained from xenopus laevis gastrula-stage embryos which had been labelled by microinjection of [3h]uridine. a 9-12-s rna fraction was isolated by phenol extraction of whole embryos followed by sucrose gradient centrifugation of the rna and polyacrylamide gel electrophoresis. this rna was identified as histone mrna on the basis of its chemical and physical properties. on polyacrylamide gels the labelled rna could be subfractionated into different components with electrophore ... | 1976 | 991862 |
| studies on the deiodination of thyroid hormones in xenopus laevis tadpoles. | 1976 | 992332 | |
| the relationship of ribosomal rna synthesis to the formation of segregated nucleoli and nucleolus-like bodies. | the relationship of ribosomal rna (rrna) synthesis to nucleolar ultrastructure was studied in partial nucleolar mutants of xenopus laevis. these mutations are the result of a partial deletion of rrna genes and therefore alow studies on nucleolar structure and function without using drugs that inhibit rrna synthesis. ultrastructural studies demonstrated that normal embryos have reticulated nucleoli that are composed of a loose meshwork of granules and fibrils and a typical nucleolonema. in contra ... | 1976 | 993274 |
| photoreceptor thresholds and visual pigment levels in normal and vitamin a-deprived xenopus tadpoles. | 1. measurements of the aspartate-isolated piii component of the electroretinogram (erg) were used to estimate photoreceptor threshold in dark-adapted tadpoles of the clawed toad, xenopus laevis raised on a normal diet. spectral sensitivity functions established that the rod mechanism governed absolute dark thresholds from stage 40 to the end of premetamorphic development. 2. parallel measures of rod outer-segment dimensions and visual pigment levels demonstrated a) that visual pigment concentrat ... | 1976 | 993831 |
| effective stimulus for the xenopus laevis lateral-line hair-cell system. | an in vitro preparation of the lateral-line organ of the african clawed toad xenopus laevis was used to evaluate the properties of the physiological stimuli which are most effective in evoking neural responses in this simple hair-cell system. changes in the mean firing rate and the amount of modulation of the neural activity in the fibers innervating the hair cells were determined during the presentation of well-controlled pressure or water-movement stimuli in a specially designed chamber that p ... | 1976 | 994676 |
| physiological basis of cochlear transduction and sensitivity. | experiments were conducted in the guinea pig cochlea and the xenopus laevis lateral line organ to obtain information about the electrical impedance properties of the cochlea, the sources and characteristics of the cochlear potentials, and to determine if hair cells are electrically excitable. the significance of the resting and evoked cochlear potentials in the transduction process leading to excitation of the acoustic nerve fibers was evaluated by comparing the results of electrophysiological e ... | 1976 | 999136 |
| dna-dependent rna polymerase c from xenopus laevis ovaries: formation of stable heparin-resistant dna-binding complexes. | 1976 | 1001472 | |
| protein labelling patterns in oocytes of xenopus laevis. | soluble and microsomal proteins synthesized at various stages of oogenesis in xenopus laevis were compared by 3h and 14c dual-isotope labelling with subsequent mixing and analysis on sodium dodecyl sulfate (sds)-polyacrylamide gels. the results indicated that the proteins labelled in all the stages of oogenesis studied are remarkably similar. however, the patterns in the small and medium-sized oocytes are more similar to one another than to the patterns characteristic of large oocytes. the great ... | 1976 | 1010160 |
| on the diversity of sperm histones in the vertebrates. i. changes in basic proteins during spermiogenesis in the newt notophthalmus viridescens. | sperm histones display great variability in contrast to the conservation of most classes of somatic histones. to study this paradox, this series of papers examines the variation of histone patterns in the testis and sperm of vertebrates, particularly amphibians and reptiles, and attempts to relate such variation to genetically based sex determination as hypothesized by bloch [genetics supplement 61, 93 (1969)]. in the present study we have investigated spermiogenesis in the newt notophthalmus vi ... | 1976 | 1010162 |
| the response of the brachial ventral horn or xenopus laevis to forelimb amputation during development. | the normal development of the brachial ventral horn of the frog xenopus laevis and the response of the brachial ventral horn to complete forelimb extirpation at five developmental stages were assessed histologically. differentiation of brachial ventral horn neurons occurred in pre-metamorphic tadpoles between stages 52/53 and 57. mean cell number in the brachial ventral horn reached a peak of 2576 (s.e.m. equals +/- 269, n equals 2) per side of the spinal cord at stage 55 and decreased to 1070 ( ... | 1976 | 1010975 |
| scanning electron microscopy of lithium-induced exogastrulae of xenopus laevis. | lithium-induced exogastrulae are abnormal embryos which fail to complete gastrulation and do not form normal neural structures. scanning electron microscopy has been used to compare the surface structure of the ectoderm cells of exogastrulae with that of the ectoderm cells of normal embryos and has shown that the appearance of ciliated cells is delayed in exogastrulae. in addition, the structure of endoderm cells, which remain exposed in these embryos, has been studied. | 1976 | 1010976 |
| injected nuclei in frog oocytes: fate, enlargement, and chromatin dispersal. | a method is described by which nuclei associated with some cytoplasm can be rapidly prepared from a suspension of cells. the method involves the use of lysolecithin and bovine serum albumin. oocytes of xenopus laevis were injected with about 200 nuclei perpared from human hela cells by this method. nuclei were deposited in oocyte cytoplasm, in the oocyte nucleus, or in the dispersed contents of a ruptured oocyte nucleus. injected hela nuclei enlarge up to several hundred times in volume in the c ... | 1976 | 1010977 |
| ultrastructural analysis of some functional aspects of xenopus laevis pancreas during development and metamorphosis. | morphological studies using both light and electron microscope were carried out with the aim of characterizing cells present in the larval and adult pancreas of xenopus laevis. the following cell types have been seen: (1) exocrine cells, with a very well developed r.e.r. (rough endoplasmic reticulum), well defined golgi complexes and numerous large secretory granules (a cells); (2) cells without either r.e.r. or secretory granules but with a large number of well developed mitochondria (b cells); ... | 1976 | 1010987 |
| [histological studies on allografts and xenografts of lymphoid tissue in newts (triturus cristatus laur.) and xenopus (xenopus laevis daud.)]. | 1976 | 1013596 | |
| the distribution of intercellular gap junctions in the developing retina and pigment epithelium of xenopus laevis. | the distribution of gap junctions in the developing retina and pigment epithelium of xenopus has been examined from optic vesicle to photoreceptor outer segment stages. in the retina and pigment epithelium walls of the optic vesicle gap junctions are found between ventricular cells in the apical contact zone and close to the outside wall; a neural tube type of distribution. optic cup formation brings the retina and pigment epithelium into contact and gap junctions form between them. after the st ... | 1976 | 1015633 |
| incorporation of (3h) leucine into the nucleoli of previtellogenic and early vitellogenic oocytes of xenopus laevis: a high resolution autoradiographic study. | 1976 | 1015838 | |
| circus movements and blebbing locomotion in dissociated embryonic cells of an amphibian, xenopus laevis. | circus movements, which involve the circumferential rotation of a hyaline cytoplasmic protrusion, occur in cells obtained by edta dissociation of gastrula-stage xenopus laevis embryos. only a few dissociated blastula-stage cells show circus movements, more early gastrula-stage cells show them, and nearly all late gastrula-stage cells show them. circus movements cease in cells prior to mitosis and begin again in daughter cells after mitosis is completed. in early gastrulae, only 17% of prospectiv ... | 1976 | 1018045 |
| investigation of the mechanisms and consequences of steroid hormone action on vitellogenin synthesis in xenopus laevis. | 1976 | 1020011 | |
| a recessive semi-lethal mutation, "distended lungs" (dl) affecting the tadpoles of xenopus laevis. | 1976 | 1020625 | |
| [comparison of the formation of the mesonephric, medullary, and adrenal blastema of common toad embryos, bufo bufo l., and the clawed toad, xenopus laevis duad. (anuran amphibians)]. | 1976 | 1022319 | |
| [role of bruch's membrane in the process of metaplasia of the ocular pigmented epithelium of xenopus laevis]. | the metaplasia of pigmented epithelium into retina with the formation of nuclear and reticular layers took place in the experiments with wrapping a sheet of pigmented epithelium from tadpoles up in the bruch's membrane of adult frogs x. laevis. the implant with de novo formed retina resembled the inverted eye. in those experiments where the bruch's membrane of tadpoles came into contact with that of adults only depigmentation of the pigmented epithelium cells was observed. the pigmented epitheli ... | 1976 | 1023084 |
| [proliferative potentials of xenopus laevis tadpole and toad optic thalamus nerve tissue cells following injury]. | after the injury of the thalamus right hemisphere in tadpoles and young frogs x. laevis, 3h-thymidine incorporated in the cells of the thalamus ventricular zone, but not in the middle and large neurons of the type of neurons of the trigeminal nerve mesencephalic nucleus and the large ganglion cells of vi and viii layers of the thalamus cortex. the brain trauma in tadpoles resulted in the activation of cell proliferation in the ventricular zone, whereas in young frogs the proliferation of glyocyt ... | 1976 | 1023086 |
| [quantitative limits of the feulgen reaction: analysis of interference caused by dehistonization and denaturation and renaturation treatments]. | the feulgen reaction intensity (measured with a microdensitometer vickers m86 on the nucleus of erytrocytes of xenopus laevis daud.) is increased after dehistonization according to brody (1974) only if the dehistonization is made before the fixation in acetic acid. the denaturation and renaturation treatments which should act specifically on the screws of the dna and therefore should not affect the feulgen reaction, act in a specific manner, probably going away another histonic components. on th ... | 1976 | 1023332 |
| [some cytochemical characteristics of the chromatin in the erythrocytes of xenopus laevis daud]. | the xenopus laevis daud. genome offers a stimulating model of a chromatin (davidson et al., 1975) in which a high ratio of repetitious dna sequences has been recorded (45% of total genome according to davidson et al., 1975). we have studied cytochemically this model "in situ", on the erythrocytes of air-dried smears of peripheral blood. the cells, which are non-dividing and not engaged in dna reduplication, constitute almost hypothetically a homogeneous class constantly in g1 phase of the cellul ... | 1976 | 1023333 |
| [electronmicroscopical, functional morphological, morphometric analysis of anterior pituitary of xenopus leavis (anura)]. | 1976 | 1023590 | |
| [relationships between endocardial cushion development and hemodynamics in embryonic heart. experimental study on xenopus laevis larvae]. | 1976 | 1024374 | |
| demonstration of thymus-independent immune system in xenopus laevis. response to polyvinylpyrrolidone. | larvae of xenopus laevis were thymectomized at stage 45 (4 days old), and raised beyond metamorphosis. thymectomized toads, when injected with polyvinylpyrrolidone (pvp), produced the same titres of antibodies as non-thymectomized animals, providing strong evidence that the thymus-independent immune response is present in this anuran. antibodies were of exclusively high molecular weight, heat-stable, and 2-mercaptoethanol sensitive. after immunization, lymphoid accumulations were evident in the ... | 1976 | 1027717 |
| early changes in the ultrastructure of the pars intermedia of the pituitary of xenopus laevis after change of background color. | stereological analysis of the secretory cells of the pars intermedia of xenopus laevis over a period of 3 days following the transfer of animals from a white to a black background has revealed that significant alterations in the ultrastructural appearance of these cells can be detected 8 h after the transfer. in particular, changes in the secretory granules and the rough endoplasmic reticulum were found to correlate well with previous reports concerning the melanocyte-stimulating hormone (msh) c ... | 1976 | 1028946 |
| functional significance of the variations in the geometrical organization of tight junction networks. | using freeze-fracture techniques, we have examined the morpholog of tight junction networks found along the length of the alimentary tract of xenopus laevis before and after metamorphosis. we have developed the hypothesis, based on these observations, that the geometrical organization of the network determined by the stress-induced shape changes normally experienced by the cells linked by the network. consistent with this theory, tight junctions can be classified into two distinct types of netwo ... | 1976 | 1030707 |
| amino acid uptake in xenopus laevis oocytes. | 1976 | 1033078 | |
| translation and stability of human globin mrna in xenopus oocytes. | human globin messenger rna (mrna) prepared from erythroid cells of patients with sickle cell anemia has been translated in xenopus laevis oocytes. addition of hemin to the injected mrna causes total globin synthesis to increase and the ratio of alpha- to betas-globin synthesis (alpha/betas ratio) to approach unity. to determine the effect of the length of the poly-(a) segment on human globin mrna stability, 10 s globin mrna was fractionated into poly-(a)-poor fractions by oligo (dt)-cellulose co ... | 1976 | 1033208 |
| protein synthesis and germ plasm in cleavage embryos of xenopus laevis. | (3h) leucine was injected into unfertilized eggs, fertilized eggs, and stage 2-12 embryos of x. laevis. incorporation of the leucine into protein by blastomeres containing germ plasm was studied autoradiographically. eggs, both fertilized and unfertilized, actively synthesized protein, ad did embryos from stage 2 onwards. probably all blastomerers containing germ plasm were labelled. in embryos from stages 4-12, the germ plasm itself was also labelled, and this result suggests that the germ plas ... | 1976 | 1033986 |
| uv effect on germ cell determinant and a proposed scheme for germ cell formation process in embryos of xenopus laevis. | 1976 | 1035637 | |
| microinjection of trna into amphibian oocytes. | the microinjection technique affords us the possibility to introduce purified components into living cells and to answer the question of what effects the change introduced has on cellular metabolism. this technique can therefore be used to test the hypothesis that transfer rna plays a regulatory role in cellular protein synthesis. prior to these experiments it is important, however, to test whether transfer rna microinjected into amphibian oocytes is stable and functional inside this cells. thes ... | 1976 | 1036012 |
| evidence that the fertilization envelope blocks sperm entry in eggs of xenopus laevis: interaction of sperm with isolated envelopes. | 1976 | 1036730 | |
| [the development of the vestibular apparatus under conditions of weightlessness]. | the spawn of the aquarium fish brachydanio rerio was developing during 5--6 days under conditions of weightlessness (first on board the spaceship "sojuz-16", then in the space station "salut-4") in special aquariums "emkon", in thermostable installations. electron microscopically the embryos were found to have a well developed labyrinth in early developmental histologically and cytologically differentiated receptory structures of the macula utriculi and macula saccili. in contrast to controls, t ... | 1976 | 1082742 |
| a cytoplasmic factor promoting oocyte maturation: its extraction and preliminary characterization. | cytoplasm of maturing amphibian oocytes possesses a factor that induces germinal vesicle breakdown. this factor was extracted from rana pipiens eggs and assayed by microinjection in xenopus laevis oocytes. the activity of this factor is mg-dependent, ca-sensitive, and associated with heat-labile protein. centrifugation on a sucrose density gradient revealed that the factor exists in three different molecular sizes. | 1976 | 1083070 |
| aluminium localization in amphibian skin with the electron microprobe and ion microanalyzer. | emp and ima studies show the presence of a1 in the epidermis of larvae and young adults of discoglossus pictus and rana esculenta, which disappears during later stages of development. a1 is practically absent in the epidermis of xenopus laevis and pleurodeles waltlii. the localization of a1 with emp and ima supports the biochemical results. the function of a1 in the epidermis is not known at present. | 1976 | 1083571 |
| architecture of the marrow vasculature in three amphibian species and its significance in hematopoietic development. | architecture of the bone marrow vasculature, particularly that of the femur, was analyzed in three amphibian species in relation to the early phylogeny of marrow hematopoiesis. a dye-injection method and histological techniques, including both serial sectioning and reconstruction methods, were used for this purpose. from these observations the following conclusions may be drawn. (1) marrow hematopoiesis is absent from the femur of the urodelan (triturus pyrrhogaster) and appears first in the fem ... | 1976 | 1083670 |
| evidence for corticotropin releasing factor (crf) synthesis in the preoptic nucleus of xenopus laevis tadpoles: a preliminary report based on lesion experiments. | for the study of the hypothalamo-hypophysial system of xenopus laevis tadpoles, hypothalamic lesions were made by means of the electrocoagulation technique. lesioning of the ventral region of the preoptic nucleus resulted in a decrease of the number of acth cells in the pars distalis of the pituitary gland and in a diminution of the pas-positive reaction of these cells. in addition, regeneration of the neurosecretory cells of the ventral region of the preoptic nucleus observed 6 weeks after lesi ... | 1976 | 1084220 |
| species specificity in the response of an in vitro amphibian (xenopus laevis) ovulation assay to mammalian luteinizing hormones. | 1976 | 1085276 | |
| [regeneration of the crystalline lens in anuran amphibia in the postembryonal stage. experimental excision of the crystalline lens in rana esculenta and xenopus laevis larvae]. | 1976 | 1088056 | |
| competition between motor nerves in the establishment of neuromuscular junctions in striated muscles of xenopus laevis. | after sectioning one of the two nerves of the pauci-innervated pectoralis muscle of xenopus laevis, a sprouting of the intact nerve is observed in the denervated zone. on subsequent reinnvervation by the original nerve, dually innervated end-plates are found in which the quantal content of the responses to foreign nerve stimulation does not change significantly while that from the original nerve increases during the course of reinnervation. on the other hand, functional innervation from both the ... | 1976 | 19604861 |
| particulate dna polymerase from the cytoplasm of xenopus laevis oocytes. | a dna polymerase has been partially purified and characterized from xenopus laevis stage 6 oocytes. the enzyme is present only in the cytoplasm and has been shown to be able to copy poly(a) x oligo(dt), to be sensitive to n-ethylmaleimide, and to sediment faster than 4 s in high salt glycerol gradient. the enzyme can be extracted from particulate material which has a density in sucrose gradient ranging from 1.200 to 1.225 g/cc. this particulate material is identified by its ability to use poly(a ... | 1976 | 15625871 |
| inducing activity of fractionated microsomal material from thexenopus laevis gastrula stage. | the postmitochondrial supernatant fromxenopus gastrulae has been fractionated on sucrose gradients. part of the microsomal material was treated with edta, which dissociates most of the polysomal and monosomal material into ribosomal subunits. in addition, a series of pooled fractions from the edta treated gradients has been applied to discontinuous gradients in more concentrated sucrose to separate membranous material from the remaining microsomal components.pooled fractions from all gradients h ... | 1976 | 28305523 |
| tissue typing by skin grafting during metamorphosis of the toad xenopus laevis (daudin). | 1975 | 1089553 | |
| replication of amplifying ribosomal deoxyribonucleic acid in rolling circles in xenopus laevis oocytes. | 1975 | 1095648 | |
| in situ hybridization of ribosomal dna labelled with 125iodine to metaphase and lampbrush chromosomes from newts. | methods are described for in situ hybridization of ribosomal dna from xenopus laevis, labelled in vitro with 125iodine, to mitotic and lampbrush chromosomes from triturus cristatus carnifex. the hybridization reaction was carried out in a mixture containing 50% formamide, 4 x ssc, 0.1 m ki, at 37 degrees c, or in 2 x ssc, 0.1 m ki at 65 degrees c. autoradiographs of mitotic metaphases from 2 males showed labelling over the middle of the short arm of one chromosome ix in each metaphase. in some c ... | 1975 | 1097214 |
| aminoacylation of transfer rna microinjected into xenopus laevis oocytes. | 1975 | 1097945 | |
| types and distribution of lamellar bodies in first cleavage xenopus embryos. | lamellar bodies in first cleavage xenopus laevis embryos have been examined with the electron microscope. based on the arrangement and relative thickness of the lamellae, three types of lamellar bodies have been identified. in the first type, a band of two to ten lamellae (spacing about 3.5 nm) was interwined at random. this type of lamellar body was seen closely associated with the concave or the forming face of the golgi body and may have been derived from this organelle. the frequent associat ... | 1975 | 1102108 |
| replication and expression of constructed plasmid chimeras in transformed escherichia coli--a review. | ecori restriction-endonuclease-generated fragments of bacterial plasmids isolated from staphylococcus aureus or escherichia coli, or of amplified dna coding for the 18s and 28s ribosomal rna of xenopus laevis, have been linked to the psc101 plasmid replicon and introduced into e. coli by transformation. the constructed plasmid chimeras can be cloned as stable replicons in e. coli, where they synthesize rna and/or protein products specified by their component genes. | 1975 | 1103843 |
| distribution of 18+28s ribosomal genes in mammalian genomes. | in situ hybridization with 3h 18s and 28s ribosomal rna from xenopus laevis has been used to study the distribution of dna sequences coding for these rnas (the nucleolus organizing regions) in the genomes of six mammals. several patterns of distribution have been found: 1) a single major site (rat kangaroo, seba's fruit bat), 2) two major sites (indian muntjac), 3) multiple sites in centromeric heterochromatin (field vole), 4) multiple sites in heterochromatic short arms (peromyscus eremicus), 5 ... | 1975 | 1104290 |
| messenger activity of ribonucleic acid form yeast mitochondria. | total yeast mitochondrial rna was shown to possess messenger rna activity when injected into oocytes of the frog xenopus laevis. the specific polypeptides formed were precipitated by mitochondrial antisera. a comparison was made of the molecular weights of the proteins obtained form this system with those made by mitochondria in vivo in the presence of cycloheximide. no rna containing poly(a) sequences was detected in yeast mitochondria. | 1975 | 1106402 |
| readenylation of polyadenylate-free globin messenger rna restores its stability in vivo. | using an atp:rna adenyltransferase from escherichia coli, a polyadenylic sequence was resynthesized onto rabbit globin mrna from which the poly (a) segment had been previously removed. conditions for obtaining a homogenous reconstituted globin mrna preparation containing 30 adenylic residues per message molecule were determined. the reconstituted globin mrna was microinjected into xenopus laevis oocytes. its stability was very similar to that of native mrna. | 1975 | 1107033 |
| ribosomal protein synthesis in xenopus laevis oocytes. | 1975 | 1112442 | |
| synthesis of soluble protein in oocytes of xenopus laevis. | oocytes of five stages of development were isolated from ovaries of xenopus laevis and allowed to take up radioactive amino acids. after six hours of labeling the amount of label incorporated into perchloric acid precipitable material from the soluble oocyte fraction and the specific activity of the label free pool was determined. from these figures an estimate of the rate of protein synthesis was calculated. labeled soluble protein from each oocyte stage was analyzed by electrophoresis on sds p ... | 1975 | 1113071 |
| initiation factor distribution in xenopus laevis eggs. | the distribution of activity similar to that of one of the initiation factors (if2) was determined as a function of developmental stage in xenopus laeviseggs and embryos. in vivo exposure of mature oocytes to hormone increases the total amount of detectable factor activity and facilitates the binding of if2-like factor to ribosomes. the quality of factor bound is not correlated with polysome content. | 1975 | 1113074 |
| control of somite number during morphogenesis of a vertebrate, xenopus laevis. | during xenopus embryogenesis and early growth, somite number stays close to a species-typical value for each morphological stage. this remains true even after operations on blastulae which lead to the development of abnormally small but otherwise complete early embryos, involving reduction in number of cells assigned to each somite. evidence presented suggests that a body-position gradient may be involved, but in rather different ways at different stages, in controlling total somite number. | 1975 | 1113883 |
| biochemical research on oogenesis. comparison between the proteins of the ribosomes and the proteins of the 42 s particles from small oocytes of xenopus laevis. | 1975 | 1116647 |