Publications

variations in differentiation in the regenerating lens of xenopus laevis.		1977	70371
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 ...	1977	70278
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 ...	1977	70260
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 ...	1977	69707
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 ...	1977	69706
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 ...	1977	69676
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 ...	1977	68800
changes in the rate of histone synthesis during oocyte maturation and very early development of xenopus laevis.		1977	67977
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 ...	1976	66091
estimation of rdna content in xenopus laevis eggs during early development [proceedings].		1976	66019
translation products of the alfalfa mosaic virus ribonuclei acids in wheat-germ cell-free system and in oocytes from xenopus laevis.		1976	64215
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 ...	1976	61708
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 ...	1976	57921
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 ...	1975	50397
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 ...	1975	50138
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 ...	1975	48536
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 ...	1975	48453
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 ...	1975	47834
vital dye mapping of the gastrula and neurula of xenopus laevis. i. prospective areas and morphogenetic movements of the superficial layer.		1975	46836
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
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
synaptic organization of the inner plexiform layer of the retina of xenopus laevis.		1978	27791
the occurrence and transmission of a pattern of dna methylation in xenopus laevis ribosomal dna.		1978	26077
calcium dependence of alpha-adrenoreceptor stimulation of myoepithelial cell contraction in the granular glands of xenopus laevis skin proceedings.		1978	25958
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
in vitro studies on the effects on granular gland secretion in xenopus laevis skin of stimulation and blockade of alpha and beta adrenoceptors of myoepithelial cells.	secretion from the granular glands of xenopus laevis skin was stimulated by alpha-adrenergic agonists, an effect which was blocked by alpha-adrenergic antagonists and inhibited by beta-adrenergic agonists, db-camp and diazoxide. the inhibition by isoprenaline and salbutamol, but not that by diazoxide, was blocked by a beta-adrenergic antagonist. it is concluded that the myoepithelial cells surrounding the secretory compartment of the granular glands bear alpha and beta adrenoceptors, and that th ...	1977	24501
lectin-mediated agglutination of amphibian embryonic cells.	dissociated blastula cells of xenopus laevis are agglutinated with wheat germ agglutinin (wga), ricinus communis agglutinin (rca), concanavalin a (con a) and, to a lesser extent with soya bean agglutinin (sba). they are not agglutinated with fucose-binding protein. neuraminidase treatment of cells enhances their agglutinability with rca and sba, but has no effect on con a- and wga-mediated agglutinability. treatment of cells with procaine, or xylocaine, has no effect on the cells' agglutinabilit ...	1977	22553
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 ...	1977	21937
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 ...	1977	18549
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 ...	1977	16285
histochemical and biochemical investigations on the changes of catecholamine content in the adrenal tissue of xenopus laevis--ii. effects of drug applications.		1977	15774
histochemical and biochemical investigations on the changes of catecholamine content in the adrenal tissue of xenopus laevis--i. effect of salt-water stress.		1977	15773
ontogeny of tyrosine aminotransferase in xenopus laevis.		1977	14857
translation of messenger rna specific for tyrosine aminotransferase in oocytes of xenopus laevis.		1976	10910
chemoreceptors of the lateral-line organs in intact, hypophysectomized, and prolactin-treated hypophysectomized xenopus laevis specimens.		1976	9241
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 ...	1976	9200
surface immunoglobulins on xenopus laevis lymphocytes.		1976	3324
visual deprivation and intertectal neuronal connexions in xenopus laevis.		1975	1778