Publications

heterogeneity in spinal radial glia demonstrated by intermediate filament expression and hrp labelling.	considerable evidence indicates that radial glial cells play an active role in guiding growing neurites during development of the vertebrate cns. in this paper we describe subpopulations of radial glial in the spinal cord of the axolotl. amphibians maintain radial glia throughout life, and subpopulations are described using anatomical criteria following filling of individual cells with horseradish peroxidase and immunocytochemical staining with a range of intermediate filament antibodies. radial ...	1990	1705577
localization of calmodulin in epidermis and skin glands: a comparative immunohistological investigation in different vertebrate species.	the study deals with the immunolocalization of calmodulin-reactive epithelial cells in different vertebrates (tinca tinca, ambystoma mexicanum, xenopus laevis, rana ridibunda, columba domestica, sus scrofa domestica, homo sapiens sapiens). the immunoperoxidase technique was performed on acetone fixed frozen sections using monoclonal (bf8) and polyclonal (acam) anti-calmodulin antibodies. we were able to differentiate 2 major types of staining patterns: 1. a more superficial epidermal staining in ...	1991	1718122
hydrogen ion currents in rat alveolar epithelial cells.	alveolar epithelial cells isolated from rats and maintained in primary culture were studied using the whole-cell configuration of the "patch-clamp" technique. after other ionic conductances were eliminated by replacing permeant ions with n-methyl-d-glucamine methanesulfonate, large voltage-activated hydrogen-selective currents were observed. like h+ currents in snail neurons and axolotl oocytes, those in alveolar epithelium are activated by depolarization, deactivate upon repolarization, and are ...	1991	1722118
the differential transcriptional activity of two amphibian u1 small-nuclear rna genes correlates with structural differences in the proximal sequence element.	we previously analyzed the transcription of an axolotl u1 small-nuclear rna (snrna) gene (amu1) by microinjection into xenopus laevis oocytes. in such an assay, amu1 showed a low template activity compared to that of an x. laevis u1 snrna gene (xlu1b2). swapping the proximal sequence element (pse) with that of xlu1b2 was required for amu1 to acquire a transcription level equal to that of xlu1b2. in the present work, we examine the functional importance of the nucleotides that are common or diffe ...	1992	1735429
[adaptative differential maturation of neurohypophyseal provasotocin in amphibians: presence of hydrin 2(vasotocinyl-glycine) in anura but not in urodela].	occurrence of hydrin 2 (vasotocinyl-glycine), an intermediate in the provasotocin processing, has been shown in the neurointermediate lobe of the pituitary of semi-aquatic or terrestrial amphibian species belonging to the order anura, namely rana esculenta, r. temporaria, r. pipiens (ranidae), and bufo bufo, b. marinus, b. ictericus (bufonidae). in contrast hydrin 2 appears absent in species belonging to the order urodela, namely the axolotl ambystoma mexicanum (ambystomidae) and the pleurodele ...	1991	1756409
a light and electron microscopic study of the development of the mauthner cell and vestibular nerve in the axolotl.	vestibular axons form synapses on a restricted area of the lateral dendrite of the mauthner cell, a large, identified brainstem neuron found in fish and amphibians. the differentiation of the vestibular nerve, medullary neuropil, and mauthner cell of the axolotl (ambystoma mexicanum) was studied to understand better the means by which this synaptic specificity arises. the mauthner cell first extends a medial process and then a lateral dendrite. the latter initially elongates as a simple process ...	1991	1761753
effect of precocious and delayed afferent arrival on synapse localization on the amphibian mauthner cell.	afferents often form synapses on restricted regions of their target cells. the connections between vestibular axons and the mauthner cell are an example of this sort of specificity. the mauthner cells are a pair of identifiable central neurons in certain fish and amphibians. in the axolotl (ambystoma mexicanum), the large vestibular axons form club endings on only one portion of one dendrite of the mauthner cell. during development, this specific distribution might result from nothing more than ...	1991	1761755
streptomycin blocks the postsynaptic effects of excitatory amino acids on the vestibular system primary afferents.	it has been suggested that streptomycin might be an antagonist of the glutamate receptors, and that it selectively blocks quisqualic acid receptors. we studied whether streptomycin blocks the responses to excitatory amino acid agonists on the vestibular system primary afferents, and if it allows us to differentiate between kainate (ka) and quisqualate (qa) receptor mediated responses. the experiments were performed in the axolotl (ambystoma tigrinum). intra- and extracellular records of the elec ...	1991	1786535
the glossopharyngeal nerve of the axolotl labeled with carbocyanine dye (dii).	fluorescent carbocyanine dye (dii) was used to label the glossopharyngeal (ix) nerve in the fixed preparation of the mexican salamander, axolotl. when the cell bodies were viewed with a confocal laser scanning microscope and nomarski optics, the cytoplasm was brightly fluorescent, but not the cell nucleus. the cell bodies which send peripheral axons in the two branches of the ix nerve were mainly distributed in the rostral part of the combined glossopharyngeal-vagus ganglion, but a few cells wer ...	1989	1791970
measures of phototaxis and movement detection in the larval salamander.	in this investigation, we describe two precise tests of visual function that integrate quasinatural situations with time-lapse video recording and infrared computerized monitoring of activity to assess movement detection and phototaxic tendencies, respectively. four groups of larvae from a. punctatum, a. tigrinum, a. mexicanum, and a mutant albino axolotl were tested in an alley containing light and dark halves and lined with infrared sensors to monitor their phototaxic response. a. punctatum sh ...	1991	1801024
retinoic acid stimulates neurite outgrowth in the amphibian spinal cord.	there is increasing evidence that retinoic acid (ra), a vitamin a metabolite, plays a role in the development of the nervous system. here we specifically test this notion by examining the effect of ra on neurite outgrowth from explanted segments of the axolotl spinal cord. we show that there is a threshold concentration in the region of 0.1-1 nm above which neurite outgrowth is stimulated 4-5 fold. retinol, by contrast, only stimulated the migration of glial cells from the explants. using hplc w ...	1991	1850835
extracellular matrix of the developing heart in normal and cardiac lethal mutant axolotls, ambystoma mexicanum.	as part of an ongoing study of heart development in normal and cardiac lethal mutant axolotls (mexican salamanders) we examined the extracellular matrix (ecm) by microscopical methods. with scanning electron microscopy we are unable to detect ecm on the apical surface of cells of the early cardiogenic mesoderm. during the period of lateral plate migration, which coincides with the period of cardiogenic induction of mesoderm by anterior endoderm, there is little ecm, aside from some microfibrils, ...	1991	1867413
reinvestigation of dna ligase i in axolotl and pleurodeles development.	we have recently shown that the exclusion process causing the replacement of dna ligases ii by dna ligase i in amphibian eggs after fertilization does not occur in the case of xenopus laevis [hardy, s., aoufouchi, s., thiebaud, p., and prigent, c., (1991) nucleic acids res. 19, 701-705]. since this result is in contradiction with the situation reported in axolotl and pleurodeles we decided to reinvestigate such results in both species. three different approaches have been used: (1) the substrate ...	1991	1886765
radial glia give rise to perinodal processes.	nodes of ranvier in the central nervous system in mammals are characterized by the presence of perinodal astrocytic processes. this study examines the association between processes of radial glia and the axolemma at nodes of ranvier in the spinal cord of the mature axolotl, an animal in which radial glia represent a large portion of the total glial population. the radial glial cells have their cell bodies located close to the central canal. those situated dorsal to the canal send long processes ...	1991	1893250
retinoic acid does not induce formation of cilia on the surface of wound epithelial cells in axolotls.	it has been reported that vitamin a palmitate induces the production of cilia on the epidermal cells of the regenerating axolotl limb, and the formation of crevices in the epidermal surface. the aim of the present investigation was to reexamine under well defined conditions the potential of retinoids to evoke the above described metaplastic changes. in order to achieve our purpose we administered axolotls with retinoic acid for 2, 4, 6, 8, and 10 days after limb amputation. the young regenerates ...	1991	1913848
axonal transport and release of transferrin in nerves of regenerating amphibian limbs.	transferrin, a plasma protein required for proliferation of normal and malignant cells, is abundant in peripheral nerves of birds and mammals and becomes more concentrated in this tissue during nerve regeneration. we are testing the hypothesis that this factor is involved in the growth-promoting effect of nerves during the early, avascular phase of amphibian limb regeneration. a sensitive enzyme-linked immunosorbent assay for axolotl transferrin was developed and used to determine whether this p ...	1991	1916015
large disulfide-stabilized proteoglycan complexes are synthesized by the epidermis of axolotl embryos.	proteoglycans (pgs) synthesized by the epidermis during stages crucial to the subepidermal migration of neural crest cells in the trunk of the axolotl (ambystoma mexicanum, urodela, amphibia) embryo were studied. the glycosaminoglycan chains were biosynthetically labeled with [35s]sulfate in vitro during a period corresponding to the onset of migration. after extraction with guanidine hcl, the radiolabeled pgs were separated according to size by molecular-sieve chromatography on sepharose cl-2b ...	1991	1929407
well-defined growth factors promote cardiac development in axolotl mesodermal explants.	the effect of growth factors on the formation of cardiac mesoderm in the urodele, ambystoma mexicanum (axolotl), has been examined using an in vitro explant system. it has previously been shown that cardiac mesoderm is induced by pharyngeal endoderm during neurula stages in urodeles. in this study, explants of prospective cardiac mesoderm from early neurula stage embryos rarely formed beating cardiac tissue in culture. when transforming growth factor beta-1 (tgf-beta 1) or platelet-derived growt ...	1991	1935698
heart development in normal and cardiac-lethal mutant axolotls: a model for the control of vertebrate cardiogenesis.	the mechanisms which regulate myocardial differentiation are poorly understood. the cardiac-lethal (c) mutant of ambystoma mexicanum, in which the heart never begins to beat, provides a valuable model system for studying this process. using an in vitro assay, we examine the nature of the defect in c/c embryos and find (contrary to previous reports) that the inductive endoderm is not affected by the mutation. rather, the pre-cardiac mesoderm is directly affected by the c gene and is incapable of ...	1991	1959711
identification of kainic and quisqualic acid receptors on inner retinal cells of the salamander ambystoma mexicanum.	the presence of kainic (ka) and quisqualic acid (qa) receptors on inner retinal neurones of the axolotl ambystoma mexicanum has been studied using intracellular recording techniques. in the presence of cocl2, which blocks neurotransmitter release, ka and qa depolarized the membrane. the minimum concentration of ka that induced a response was 1 microm and a maximum response was obtained with 10 microm (ec50: 3 microm). the operating range of qa was between 0.5 and 5 microm with an ec50 of 1 micro ...	1990	1976525
expression of the 9g1 antigen in the apical cap of axolotl regenerates requires nerves and mesenchyme.	monoclonal antibody 9g1 (mab 9g1) is reactive to the wound epithelium of axolotl larvae and therefore provided the opportunity to examine the interaction between the wound epithelium, nerves, and blastemal mesenchyme during axolotl limb regeneration. in unamputated limbs, mab 9g1 is reactive to most or all cells of the dermis, skeletal elements, blood vessels, and nerves, to a few unidentified cells in muscle, and to none in epidermis. during regeneration of axolotl limbs, mab 9g1 reacts strongl ...	1991	2005423
continuous growth of the motor system in the axolotl.	during growth of the axolotl, motor neurons, and muscle fibres are added to the motor system. by double labelling neurons with tritiated thymidine and retrogradely transported hrp, we show that some motor neurons are born at postembryonic stages. further analysis of motor neurons with the aid of hrp reveals this population of newly born cells relatively frequently in small (5-7 cm long) axolotls, but only rarely in large (7-13 cm long) axolotls. evidence is presented that suggests that these imm ...	1991	2013645
organization of motor units in the axolotl: a continuously growing animal.	the characteristics of motor units in the iliotibialis posterior muscle of the axolotl hindlimb are described. tension recording and intracellular electrophysiological methods demonstrate that the physiological properties of the population of motor units are continuously distributed rather than grouped into a series of discrete types. overlap between motor units occurs and this is positively correlated with motor unit size but negatively correlated with differences in time to peak tension. immun ...	1991	2013646
dna ligase i from xenopus laevis eggs.	we have purified the major dna ligase from xenopus laevis eggs and raised antibodies against it. estimates from sds page indicate that this dna ligase is a 180 kda protein. this enzyme is similar to the mammalian type i dna ligase which is presumed to be involved in dna replication. we have also analysed dna ligase activity during x. laevis early development. unfertilized eggs contain the highest level of activity reflecting the requirement for a large amount of dna replicative enzymes for the p ...	1991	2017356
nucleotide sequence of a cdna encoding wnt-1 of the mexican axolotl ambystoma mexicanum.		1991	2017393
sequence, organization and transcriptional analysis of a gene encoding a u1 snrna from the axolotl, ambystoma mexicanum.	amu1, a dna fragment containing a u1 small nuclear rna (snrna)-encoding gene, was isolated from the axolotl, ambystoma mexicanum. although this u1 snrna, produced in axolotl oocytes, exhibits the lowest degree of sequence conservation among vertebrates, its secondary structure is maintained by a number of compensatory base changes. the proximal sequence element (pse) is only weakly similar to that of the previously characterized xenopus laevis pse. exchanging either the entire upstream regions w ...	1991	2022330
acidic fibroblast growth factor is present in regenerating limb blastemas of axolotls and binds specifically to blastema tissues.	the growth of regenerating limbs of amphibians depends upon proliferation of the blastema cells that accumulate beneath the epidermal cap. the epidermal cap is known to be mitogenic for the blastema cells. we have extracted a mitogenic activity from both the mesenchymal and epidermal (epidermal cap) components of cone stage blastemas which is retained on heparin-sepharose and elutes with 1.15 m nacl. this fraction stimulates neurite outgrowth of pc12 cells and [3h]thymidine incorporation into cc ...	1991	2040374
localization of smooth-muscle markers in the ovaries of some ectothermic vertebrates.	in the present study, we have localized desmin and alpha-smooth-muscle actin in the ovaries of the zebrafish, the axolotl, and the red-eared turtle, using the unlabelled antibody peroxidase-antiperoxidase technique. in the axolotl ovary both smooth-muscle markers were demonstrated in cord-like structures, extended along ovarian blood vessels, and in some inner ovarian epithelium cells. in the ovaries of the teleost, smooth-muscle-like cells are detected in a suspensory apparatus formed by venous ...	1991	2048748
effects of fetal bovine serum and serum-free conditions on white and dark axolotl neural crest explants.	neural crest cells from both white mutant and dark (wildtype) axolotls (ambystoma mexicanum) were cultured in increasing concentrations of fetal bovine serum (fbs; 2 to 20%). for each explant, the total number of cells that migrated and the percent of differentiated melanophores were recorded. at concentrations of fbs above 2% melanophore differentiation was essentially equivalent (32 to 59%) for both the white and dark neural crest cultures, but subtle differences in cell behavior and different ...	1991	2071543
high levels of hmg1-2 protein expression in the cytoplasm and nucleus of hydrocortisone sensitive amphibian thymocytes.	a major 26 kda protein was identified in the cytoplasmic and nuclear compartments of axolotl thymocytes. a polyclonal antiserum was produced against the denatured form of this protein. high levels of 26 kda were expressed by hydrocortisone-sensitive lymphocytes which represent a major thymocyte subpopulation in young animals. however, no further expression of the 26 kda protein was observed in involuted thymus of adult animals nor in thymus of young artificially metamorphosed axolotls. the 26 kd ...	1990	2097001
structural and compositional divergencies in the extracellular matrix encountered by neural crest cells in the white mutant axolotl embryo.	the skin of the white mutant axolotl larva is pigmented differently from that of the normal dark due to a local inability of the extracellular matrix (ecm) to support subepidermal migration of neural crest-derived pigment cell precursors. in the present study, we have compared the ecm of neural crest migratory pathways of normal dark and white mutant embryos ultrastructurally, immunohistochemically and biochemically to disclose differences in their structure/composition that could be responsible ...	1990	2119290
selective labeling of sensory hair cells and neurons in auditory, vestibular, and lateral line systems by a monoclonal antibody.	this study reports that zn-1, a monoclonal antibody, labels hair cells but not supporting cells in the inner ear and the lateral line of the axolotl salamander, ambystoma mexicanum. zn-1 immunocytochemically labels the cytoplasm and stereocilia of mature hair cells in the sacculus, in the utriculus, and in the mechanoreceptive neuromast organs of the lateral line. lower levels of labeling mark newly formed hair cells in the periphery of the sacculus and in regenerating neuromasts. zn-1 also sele ...	1990	2124588
eliminating afferent impulse activity does not alter the dendritic branching of the amphibian mauthner cell.	in the developing amphibian, the formation of extra vestibular contacts on the mauthner cell (m-cell) enhances dendritic branching, while deprivation reduces it (goodman and model, 1988a). the mechanism underlying the interaction between afferent fibers and developing dendritic branches is not known; neural activity may be an essential component of the stimulating effect. we examined the role of afferent impulse activity in the regulation of m-cell dendritic branching in the axolotl (ambystoma m ...	1990	2155302
the mhc molecules of nonmammalian vertebrates.	there is very little known about the long-term evolution of the mhc and mhc-like molecules. this is because both the theory (the evolutionary questions and models) and the practice (the animals systems, functional assays and reagents to identify and characterize these molecules) have been difficult to develop. there is no molecular evidence yet to decide whether vertebrate immune systems (and particularly the mhc molecules) are evolutionarily related to invertebrate allorecognition systems, and ...	1990	2180813
the origins of neural crest cells in the axolotl.	we address the question of whether neural crest cells originate from the neural plate, from the epidermis, or from both of these tissues. our past studies revealed that a neural fold and neural crest cells could arise at any boundary created between epidermis and neural plate. to examine further the formation of neural crest cells at newly created boundaries in embryos of a urodele (ambystoma mexicanum), we replace a portion of the neural folds of an albino host with either epidermis or neural p ...	1990	2210034
[metamorphosis today].	in conjunction with the 100th anniversary of birth of the czech physiologist v. laufberger who discovered in 1913 the possibility to induce metamorphosis in neotenous larvae of axolotls by feeding them with thyroid gland, the author gives an account on the development of knowledge regarding metamorphosis in amphibia. he analyzes the participation of endocrine glands, in particular thyroid hormones and prolactin. special attention is devoted to mechanisms leading to resorption of the tail in tadp ...	1990	2224961
[v. laufberger on metamorphosis in the axolotl].		1990	2225132
development of the mechanoreceptive lateral-line system in the axolotl: placode specification, guidance of migration, and the origin of neuromast polarity.	the mechanosensory lateral-line system offers a unique opportunity to study a wide variety of developmental phenomena, including cell migration, the origin of polarity, and pattern formation. in this study, we use a series of transplantation experiments to examine some of the factors affecting the origin of the lateral-line placodes, the establishment of sensory organ polarity and placement, and the guidance of cell migration in the mexican axolotl (ambystoma mexicanum). we find that placode-for ...	1990	2244689
nucleotide sequence of a cdna encoding wnt-1 of the mexican axolotl ambystoma mexicanum.		1990	2259633
effects of tributyltin oxide on the skeletal structures of developing and regenerating limbs of the axolotl larvae, ambystoma mexicanum.		1990	2279120
characterization of the yellow pigment in the axanthic mutant of the mexican axolotl, ambystoma mexicanum.	the yellow pigment observed in older axanthic (ax/ax) mutant mexican axolotls (ambystoma mexicanum) was analyzed by thin layer chromatography and by spectrofluorometry of its acetyl derivative. ethanol extracts from the skin of axanthic animals were acetylated and the chloroform-soluble portion of the product mixture was compared with a chloroform solution of an authentic riboflavin tetraacetate standard prepared in the same manner. the pigment in these two solutions behaved identically on thin ...	1990	2290784
epicardial development in the axolotl, ambystoma mexicanum.	recent studies on avian and mammalian embryos have established that the epicardium is derived, not from the early heart tube, but from mesothelial tissue overlying the sinus venosus. we tested the validity of this concept for amphibia by examining normal and cardiac lethal (c/c) mutant axolotl embryos (stages 35-43) by electron microscopy. in axolotl embryos, the myocardial surface of the heart remains exposed to the pericardial fluid through stage 39. at this stage the transverse septum release ...	1990	2301739
developmentally regulated lectin in dark versus white axolotl embryos.	the white mutant of the mexican axolotl, a. mexicanum, involves an ectodermal defect which prevents melanophore colonization. endogenous lectins have been suggested to function in neural crest-derived melanophore adhesion in other animals. to determine if differences in endogenous lectins exist in dark and white axolotls during melanophore colonization, white and dark ectoderm and carcass tissues have been assayed for lectin activity at premigratory, early migratory, and late migratory neural cr ...	1990	2302235
comparative studies on the vascular organization of carotid labyrinths of anurans and caudates.	the three-dimensional structures of the carotid labyrinth in five species of anurans representing four families (rana nigromaculata, rana catesbeiana, bufo japonicus, hyla arborea, and xenopus laevis), and three species of caudates representing three families (cynops pyrrhogaster, hynobius nebulosus, ambystoma mexicanum) were compared using vascular corrosion castings and scanning electron microscopy (sem). anuran carotid labyrinths are spherical in shape and are classified into two groups accor ...	1990	2338718
isolation and characterization of the third complement component of axolotl (ambystoma mexicanum).	1. using a monoclonal anti-human c3 antibody and a polyclonal anti-cobra venom factor antibody as probes, a protein homologous to the mammalian third complement component (c3) was purified from axolotl plasma and found to be axolotl c3. 2. axolotl c3 consists of two polypeptide chains (mr = 110,000 and 73,000) linked by disulfide bonds. an internal thiolester bond in the alpha chain was identified by the incorporation of [14c]methylamine and nh2-terminal sequence from the c3d fragment of c3. 3. ...	1990	2344737
development and application of homologous radioimmunoassay for newt prolactin.	a specific and sensitive homologous radioimmunoassay (ria) for newt (cynops pyrrhogaster) prolactin (prl) was developed. prl isolated from newt pituitary glands was used for generating antiserum in a rabbit, for radioiodination, and for the standard. several dilutions of plasma and pituitary homogenate of newts yielded dose-response curves which were parallel to the standard curve. plasma from hypophysectomized newts showed the least amount of cross-reaction. pituitary homogenates of other speci ...	1990	2354781
polymorphism of hyaluronidase in serum from man, various mouse strains and other vertebrate species revealed by electrophoresis.	polymorphism of hyaluronidase (ec 3.2.1.35) was detected in the serum from 6 out of 20 vertebrate species by electrophoretic analysis. electrophoresis was performed on a hyaluronan-containing polyacrylamide gel, that visualizes hyaluronidase activity upon incubation at acid ph. no hyaluronidase activity was detected in the sera of horse, swine, cattle, goat, sheep, rabbit, chicken, triton alpestris, triton palmatus, triton vulgaris, pleurodeles, axolotl, eel and dog-fish. the 6 positive sera wer ...	1990	2357493
the effect of retinoic acid on positional memory in the dorsoventral axis of regenerating axolotl limbs.	we investigated the effect of retinoic acid (ra) on pattern regulation in the dorsoventral (dv) axis of regenerating axolotl limbs. half and double half dorsal and ventral zeugopodia (lower arms or legs) were amputated through their distal ends, and 4 days later the animals were injected intraperitoneally with 50 (large animals) or 100 (small animals) micrograms ra/g body wt. half and double half dorsal and ventral zeugopodia of uninjected axolotls, and sham-operated zeugopodia of untreated and ...	1990	2358123
the development of the larval pigment patterns in triturus alpestris and ambystoma mexicanum.	1. melanophores and xanthophores are pigment cell derivatives of the nc. in amphibian embryos they migrate from their original position on the neural tube dorsally (into the dorsal fin) as well as laterally (between somites and epidermis) and arrange themselves into typical pigment patterns of the skin. we investigated pigment pattern formation in two species of tailed amphibians, triturus alpestris (alpine newt) and ambystoma mexicanum (mexican axolotl). in larvae of t. alpestris alternating lo ...	1990	2368640
a horseradish peroxidase study of motorneuron pools of the forelimb and hindlimb musculature of the axolotl.	motorneuron pools innervating axolotl limb muscles have been investigated by using the retrograde neuronal tracer horseradish peroxidase. four muscles in the forelimb (biceps, anconeus, flexor digitorum and extensor digitorum) and four functionally equivalent muscles in the hindlimb (puboischiotibialis, iliotibialis, flexor digitorum and extensor digitorum) were studied. motorneuron pools were characterized by using four criteria: position in the rostrocaudal axis; position of the median in the ...	1985	2410930
motorneuron pools innervating muscles in vitamin a-induced proximal-distal duplicate limbs in the axolotl.	serially duplicated limbs containing two sets of proximal muscles were created in axolotls by vitamin a treatment. the innervation of three replicated proximal muscles was studied by using retrograde transport of horseradish peroxidase. these were the forelimb muscles biceps (seven cases) and anconeus (five cases) and the hindlimb muscle puboischiotibialis (five cases). in two cases (both of anconeus) innervation was from a correct motorneuron pool. in the other 15 cases the innervation was from ...	1985	2410931
normal fates and states of specification of different regions in the axolotl gastrula.	a fate map was constructed for four regions of the early gastrula of ambystoma mexicanum using orthotopic grafts from donors labelled with fldx (fluoresceinated-lysinated-dextran). the region around the animal pole gave rise to epidermis only and did not include prospective neural plate. the dorsal marginal zone contributed to cephalic endoderm and to the whole length of the axial mesoderm (notochord and somites), the lateral marginal zone to lateroventral and somitic mesoderm, and the ventral m ...	1985	2411838
embryonic induction and cation concentrations in amphibian embryos.	explanted ectoderm from early gastrulae of triturus alpestris was treated with the na-k ionophore gramicidin (10(-9) to 10(-5) m) and the ca-ionophore a 23187 (10(-7) to 10(-5) m). the ectoderm developed almost exclusively to atypical epidermis as in the control explants. when the ectoderm was treated with ouabain (10(-4) m), intracellular na+ increased about 4.4-fold and k+ was reduced by half. mesenchyme cells in small number differentiated in about 40% of the ouabain-treated explants. the tim ...	1985	2416476
glucagon and insulin regulate in vitro hepatic glycogenolysis in the axolotl ambystoma mexicanum via changes in tissue cyclic amp concentration.	glucagon increases the rate of glycogenolysis in in vitro cultures of hepatic tissue from the axolotl ambystoma mexicanum. the hormone causes an increase in the concentration of cyclic amp in the tissue which is followed by activation of glycogen phosphorylase and subsequent breakdown of glycogen and release of glucose from the tissue. insulin counteracts the glycogenolytic effect of glucagon by inhibiting the increase in tissue cyclic amp concentration brought about by glucagon. this inhibitory ...	1986	2416634
a model of inward and outward membrane currents in cultured embryonic amphibian spinal neurons and reconstruction of the action potential.	a model of the membrane currents in embryonic amphibian neurons has been developed in order to investigate the ionic mechanisms underlying developmental changes in excitability. differentiating amphibian neurons both in situ and in vitro show a gradual change in the ionic sensitivity of their action potential from ca- to na-dependent, with an intermediate period in which the action potential shows a mixed ionic sensitivity. the model developed incorporates quantitative descriptions of na, ca and ...	1985	2422357
a scanning electron microscopy and histological study on the effects of the mutant eyeless (e/e) gene upon the hypothalamus in the mexican axolotl ambystoma mexicanum shaw.	a scanning electron microscopy, histological, and immunochemical investigation examined the effects of the mutant gene (e) upon hypothalamic development in the mexican axolotl. the adult eyeless mutant is sterile. previous studies indicated that this reproductive defect was due to the mutation's effect upon the hypothalamus. the present study demonstrated the pleiotropic effects of the eyeless gene upon development of the hypothalamus. scanning electron microscopy studies looked at the early ont ...	1986	2426993
induction of myofibrillogenesis in cardiac lethal mutant axolotl hearts rescued by rna derived from normal endoderm.	a strain of axolotl, ambystoma mexicanum, that carries the cardiac lethal or c gene presents an excellent model system in which to study inductive interactions during heart development. embryos homozygous for gene c contain hearts that fail to beat and do not form sarcomeric myofibrils even though muscle proteins are present. although they can survive for approximately three weeks, mutant embryos inevitably die due to lack of circulation. embryonic axolotl hearts can be maintained easily in orga ...	1987	2443338
neurotransmitter-induced currents in retinal bipolar cells of the axolotl, ambystoma mexicanum.	1. whole-cell patch clamping was used to study the membrane properties of isolated bipolar cells and the currents evoked in them by putative retinal neurotransmitters. 2. isolated bipolar cells show an approximately ohmic response to voltage steps over most of the physiological response range, with an average input resistance of 1.3 g omega and resting potential of -35 mv. these values are underestimates because of the shunting effect of the seal between the patch electrode and the cell membrane ...	1987	2443677
bipolar cell membrane currents and signal processing in the axolotl retina.		1987	2446219
increase of substance p-like immunoreactivity in the peripheral nerve of the axolotl after injury.	that substance p may be a neurotrophic factor in urodele limb regeneration was investigated in the axolotl (ambystoma mexicanum). two weeks after section of the peripheral nerves to the forelimb, there was a marked increase in substance p-like immunoreactivity (ir) content of the nerves proximal to the lesion. a smaller increase occurred as early as 3 days after section of nerves innervating a regrowing limb bud (blastema), and substance p-ir fibres were observed by immunocytochemistry to innerv ...	1987	2447537
characterization of axolotl heavy and light immunoglobulin chains by monoclonal antibodies.	axolotl specific antibodies to 2,4-dinitrophenyl (dnp) were purified by affinity chromatography from the sera of animals immunized with 2,4,6-trinitrophenylated sheep red blood cells (tnp-srbc). the purified anti-tnp/dnp antibodies, when analyzed by sds-page, were constituted of high molecular weight molecules, which in reducing conditions, were separated into heavy 72-88 kd and light 27-30 kd polypeptides. the axolotl heavy antibody chains strongly bound concanavalin-a and migrate faster in sds ...	1987	2449389
induction of mesodermal tissues by acidic and basic heparin binding growth factors.	the inducing activity of two heparin binding growth factors hbgf-1 (prostate epithelial cell growth factor; acidic pi) and hbgf-2 (fibroblast growth factor; basic pi) from bovine brain has been tested on totipotent ectoderm from early amphibian (xenopus laevis, ambystoma mexicanum) embryos. both factors induced, at high concentrations, mostly compact spheres surrounded by a non-epidermal epithelium. when the concentration or time of incubation was reduced, large muscle inductions frequently orga ...	1988	2451566
diverse supernumerary structures develop after inverting the anteroposterior limb axis of the anuran.	contralateral limb bud graftings were performed on tadpoles of the anuran bufo bufo. the anteroposterior axis was inverted while the larvae were at stage iv or v (e.g., between 22-30 days after fertilization). eighty-four tadpoles were operated on, 10 of which were used as controls. at anterior or posterior location 104 supernumerary structures developed in toto. they were collected and whole-mount examined after being stained with alcian blue. they were further prepared for serial sectioning, m ...	1989	2466718
the distribution of fibronectin and tenascin along migratory pathways of the neural crest in the trunk of amphibian embryos.	it is generally assumed that in amphibian embryos neural crest cells migrate dorsally, where they form the mesenchyme of the dorsal fin, laterally (between somites and epidermis), where they give rise to pigment cells, and ventromedially (between somites and neural tube), where they form the elements of the peripheral nervous system. while there is agreement about the crest migratory routes in the axolotl (ambystoma mexicanum), different opinions exist about the lateral pathway in xenopus. we in ...	1988	2470571
homing behaviour of regenerating axons in the amphibian limb.	following peripheral nerve deviation in the limbs of urodele amphibians axons regrow distally toward their previous target muscles (holder et al. 1984; proc. roy. soc. lond. b 222, 477-489). this study describes analysis of this axon regeneration over time following deviation of the forearm flexor nerve in triturus cristatus and the extensor cranialis nerve in the axolotl. using horseradish peroxidase (hrp) axonal tracing, electrophysiology and electron microscopy, we describe the sequence of ev ...	1989	2485244
[experimental teratomas from xenogenic embryonic implants in the urodele amphibian, pleurodeles waltlii michah].	ambystoma mexicanum embryos in stages 5 to 32 were implanted into the coelomic cavity of larvae or metamorphosing larvae of pleurodeles waltlii. out of 76 experimental animals, 43 presented teratomas a few months later. in another series of experiments, ambystoma embryos together with pleurodeles embryos were implanted in 18 pleurodeles larvae. teratomas developed in 13 cases. considering the two series, tumors evolved slowly and remained benign in 31 animals, whereas in 25 others, the tumor gro ...	1989	2499409
biosynthesis of sulfated proteoglycans in amphibian embryonal cells.	the synthesis of sulfated proteoglycans in small explants from various parts of late blastulae from ambystoma mexicanum or xenopus laevis was investigated by incorporation of radioactive sulfate or glucosamine and galactosamine in media of low, normal or high tonicity. the explants differentiated into ciliated aggregates of fibroblast-like cells, or remained undifferentiated depending upon their origin in the embryo. high tonicity induces the explants to dissociate and prevents morphological dif ...	1989	2504303
immunohistochemical localization of beta-endorphin-like material in the urodele and anuran amphibian tissues.	in the present study, we have localized for the first time beta-endorphin (beta-ep)-like material in the adult and larval urodele and anuran tissues using immunohistochemical techniques. in the adult notophthalmus viridescens and ambystoma mexicanum, strong immunoreactivity to beta-ep antisera was observed in the region of the intermediate lobe, the latter fluorescing as a discrete body. the fluorescence was confined to the periphery of the cells, while the nuclei and the immediately surrounding ...	1989	2530130
the relationship among retinoid structure, affinity for retinoic acid-binding protein, and ability to respecify pattern in the regenerating axolotl limb.	to further our understanding of the action of retinoids on the respecification of pattern in the regenerating axolotl limb we have studied the relative potencies of a range of synthetic and natural retinoids administered locally to the blastema. alterations in the polar end group of the retinoic acid (ra) molecule to produce esters, the alcohol, or the aldehyde abolish the ability of the molecule to respecify pattern. on the other hand, alterations of the ring or side chain to produce the synthe ...	1989	2537244
axolotl pronephric duct cell migration is sensitive to phosphatidylinositol-specific phospholipase c.	on the basis of its distribution pattern in embryos of the axolotl (ambystoma mexicanum), we recently identified alkaline phosphatase as a molecule potentially involved in guiding the migration of the pronephric duct. alkaline phosphatase is a cell surface protein anchored to cell membranes via a covalent linkage to a phosphatidylinositol glycan (pi-g). the enzyme phosphatidylinositol-specific phospholipase c (piplc) specifically releases from cell surfaces molecules anchored by the pi-g linkage ...	1989	2553384
the role of retinoid-binding proteins in the generation of pattern in the developing limb, the regenerating limb and the nervous system.	we summarize existing data and describe new information on the levels and distribution of cellular retinoic acid-binding protein (crabp) and cellular retinol-binding protein (crbp) in the regenerating axolotl limb, the developing chick limb bud and the nervous system of the chick embryo in the light of the known morphogenetic effects of retinoids on these systems. in the regenerating limb, levels of crabp rise 3- to 4-fold during regeneration, peaking at the time when retinoic acid (ra) is most ...	1989	2561479
kinetics of light-sensitive channels in vertebrate photoreceptors.	we have studied the ion channels mediating the light response of vertebrate rod photoreceptors by analysing fluctuations in the current across the rod membrane, using the whole cell patch-clamp technique on rods isolated from the axolotl retina. light decreases the membrane current fluctuations. noise analysis reveals two components to this decrease: a low frequency component due to biochemical noise in the transduction mechanism, and a high frequency component we attribute to the random opening ...	1985	2579400
regulatory peptides (glucagon, somatostatin, substance p, and vip) in the brain and gastrointestinal tract of ambystoma mexicanum.	the concentrations of immunoreactive components of glucagon, somatostatin, substance p, and vasoactive intestinal polypeptide (vip) in the brain, stomach, and gut of the neotenic mexican axolotl (ambystoma mexicanum) were determined by radioimmunoassay using antibodies of defined regional specificity. the molecular forms of the immunoreactive components were analyzed by high-performance liquid chromatography (hplc). the concentrations and molecular forms of somatostatin and vip in axolotl brain ...	1985	2580753
cellular contribution to symmetrical forelimbs from triploid-marked "polarizing region" in the embryo of axolotl, ambystoma mexicanum.	grafts of posterior tissue placed anterior to the limb bud in the salamander embryo exert a polarizing influence. to explain this result, the idea that the anteroposterior axis of the developing forelimb is polarized by a diffusible morphogen has been proposed. an alternative hypothesis, and the working hypothesis of the present study, is that the polarization of the developing salamander forelimb is accomplished by short-range cellular interactions resulting in intercalation rather than by the ...	1989	2600559
evolution of motor patterns: aquatic feeding in salamanders and ray-finned fishes.	patterns of muscle activity (motor patterns) have generally been found to be strongly conserved during the evolution of aquatic feeding behavior within closely related groups of fishes and salamanders. we conducted a test of the generality of motor pattern conservation with a much broader phylogenetic scope than has been done previously. activity patterns of three cranial muscles were quantified from electromyographic (emg) recordings made during suction feeding in a salamander (ambystoma mexica ...	1989	2611639
organization of connective tissue patterns by dermal fibroblasts in the regenerating axolotl limb.	a set of tendons, aponeurotic sheets and retinaculae, which transduce muscle action from proximal limb levels to flexion and extension of the digits, is found in limbs of many vertebrates. this set of structures, here termed the digit tendon complex, is described for the axolotl forelimb. we show that the complex forms autonomously in muscleless axolotl limb regenerates produced from a cuff of unirradiated dermis surrounding an irradiated limb stump, and persists for up to a year after amputatio ...	1989	2612366
the appearance of neural and glial cell markers during early development of the nervous system in the amphibian embryo.	cell-type-specific antibodies have been used to follow the appearance of neurones and glia in the developing nervous system of the amphibian embryo. differentiated neurones were recognized with antibodies against neurofilament protein while glial cells were identified with antibodies against glial fibrillary acidic protein (gfap). the appearance of neurones containing the neurotransmitters 5-hydroxytryptamine and dopamine has been charted also. in xenopus, neurofilament protein in developing neu ...	2008	2627893
fine structure of the epidermal leydig cells in the axolotl ambystoma mexicanum in relation to their function.	the fine structure of the leydig cells in the epidermis of the strictly aquatic adult axolotl ambystoma mexicanum resembles that of similar cells in larval salamanders. the major finding of this study is that the mucous secretion of the leydig cells is released into the intercellular spaces from which it is discharged through pores onto the surface of the epidermis where it forms a mucous layer to protect the skin.	2009	2630544
spatial aspects of neural induction in xenopus laevis.	a monoclonal antibody, 2g9, has been identified and characterised as a marker of neural differentiation in xenopus. the epitope is present throughout the adult central nervous system and in peripheral nerves. staining is first detected in embryos at stage 21 in the thoracic region. by stage 29 it stains the whole central nervous system, except the tail tip. the epitope is present in a 65k mr protein, and includes sialic acid. the antibody also reacts with neural tissue in mice and axolotls and n ...	1989	2632233
amphibian (urodele) myotomes display transitory anterior/posterior and medial/lateral differentiation patterns.	myotome differentiation during mexican axolotl (ambystoma mexicanum) somitogenesis was analyzed by employing anti-actin and anti-myosin monoclonal antibodies as molecular probes. myotome differentiation occurs after segmentation and proceeds in the cranial-to-caudal direction along the somite file. within individual somites myotome differentiation displays distinct polarities. examination of the somite file at the tailbud stage revealed that soon after segmentation, actin/myosin accumulate predo ...	1989	2647546
cellular morphogenesis and the formation of marginal bands in amphibian splenic erythroblasts.	the spleen of ambystoma mexicanum (axolotl) larvae develops as a closed sac containing differentiating nucleated erythrocytes, and is typically isolated from the general circulation for about 10 days post-hatching. beginning 3-4 days posthatching, it can be removed intact for examination of the morphology and cytoskeletal structure of the erythropoietic cells. in the smallest (earliest) spleens, spheroidal cells predominate, while older ones contain a preponderance of cells exhibiting the flatte ...	1989	2653647
immunocytochemical localization and immunochemical characterization of an insulin-related peptide in the pancreas of the urodele amphibian, ambystoma mexicanum.	the pancreas of the axolotl, ambystoma mexicanum, was investigated by immunocytochemical methods for the presence of immunoreactivity to a number of antisera raised against mammalian insulins. all anti-insulin antisera tested revealed substantial amounts of reaction products confined solely to the aldehyde-fuchsinophilic b cells of the endocrine pancreas. the reactive cell population was detected by use of one polyclonal antiserum against bovine insulin and eight different monoclonal antibodies ...	1989	2663173
analysis of actin and tropomyosin in hearts of cardiac mutant axolotls by two-dimensional gel electrophoresis, western blots, and immunofluorescent microscopy.	when homozygous, recessive mutant gene c in ambystoma mexicanum results in a failure of embryonic heart function. this failure is apparently due to abnormal inductive influences from the anterior endoderm resulting in an absence of normal sarcomeric myofibril formation. biochemical and immunofluorescent studies were undertaken to evaluate the contractile proteins actin and tropomyosin in normal and mutant hearts. for the immunofluorescent studies, cardiac tissues were fixed in periodate-lysine-p ...	1989	2664186
immunofluorescent, immunogold, and electrophoretic studies for desmin in embryonic hearts of normal and cardiac mutant mexican axolotls, ambystoma mexicanum.	recessive mutant gene c for "cardiac nonfunction" in axolotls results in an absence of normal heart contractions in affected embryos due to a failure of myofibril formation. in the present study, the intermediate filament protein, desmin, is compared in developing normal and mutant hearts by means of two-dimensional gel electrophoresis, immunofluorescent microscopy, and immunoelectron microscopy. tissues were fixed in periodate-lysine-paraformaldehyde or paraformaldehyde-glutaraldehyde solutions ...	2009	2681791
ontogeny of immunoglobulin expression in the mexican axolotl.	the ontogeny of immunoglobulin (ig) synthesis was followed at both cellular and serological levels in the mexican axolotl (ambystoma mexicanum) using polyclonal antibodies recognizing all ig molecules and a set of monoclonal antibodies (mabs) specific for the c mu and cv heavy ig chain isotypes and for the light chain constituents shared by igm and igy molecules. clusters of igm- and of igy-synthesizing lymphocytes, often located in separate sites, are first present in spleen sections of 7-week- ...	2006	2698798
studies of heart development in normal and cardiac lethal mutant axolotls: a review.	the morphology of developing hearts in axolotls, ambystoma mexicanum, has been studied by scanning electron microscopy in order to provide a chronology of morphogenesis that can be correlated with ongoing biochemical and immunocytochemical studies. in addition to normal embryos we have studied homozygous recessive cardiac lethal mutant axolotls. the mutant myocardium undergoes aberrant sarcomere development and lacks a normal heartbeat. morphogenesis of mutant hearts appears to be nearly normal ...	1989	2699076
neural fold formation at newly created boundaries between neural plate and epidermis in the axolotl.	according to a recent model, the cortical tractor model, neural fold and neural crest formation occurs at the boundary between neural plate and epidermis because random cell movements become organized at this site. if this is correct, then a fold should form at any boundary between epidermis and neural plate. to test that proposition, we created new boundaries in axolotl embryos by juxtaposing pieces of neural plate and epidermis that would not normally participate in fold formation. these bound ...	1989	2707486
lack of proliferative response in denervated, reamputated limb regenerates of larval ambystoma.	this paper describes the response of early four-digit regenerates of axolotls to reamputation and denervation. reamputation of innervated regenerates led to sharp increases in 3h-thymidine labeling index (li) and mitotic index (mi) on days 2-5 post-reamputation. this resembles the response of innervated limbs following initial amputation. regenerates that were denervated at the time of reamputation exhibited no proliferative response through day 5. this is in marked contrast to denervated, origi ...	1989	2708951
analysis of the endocardium and cardiac jelly in truncal development in the cardiac lethal mutant axolotl ambystoma mexicanum.	recessive mutant gene c in axolotls results in a failure of the heart to function because of abnormal embryonic induction processes. the myocardium in this mutant lacks organized sarcomeric myofibrils. the present study was undertaken to determine if developmental abnormalities were evident in other areas of the heart besides the myocardium. a detailed comparative survey of the structure of developing normal and mutant hearts, including the endocardium, its cellular derivatives, and the extracel ...	1989	2724338
[origin of the cells in the symmetrical forelimbs of the axolotl ambystoma mexicanum].		2003	2740070
electrosensory activity in the telencephalon of the axolotl.	electrical shock of the anterior lateral line nerve evokes slow wave potentials in the contralateral corpus striatum and bilaterally in the medial pallium of the telencephalon of axolotls. the onset latency of the evoked response in the medial pallium (70 ms) is considerably longer than that of the corpus striatum (46 ms). quasi-natural stimuli, such as weak uniform electric fields (100 microv/cm) or water drops striking the surface of the water surrounding the axolotls elicited evoked potential ...	1989	2748022
ultrastructural localization of acetylcholinesterase in axolotl brain capillaries.	the ultrastructural distribution of cholinesterases on the brain capillaries of axolotl has been studied. the axolotl brain contains branching, anastomosing capillary network and capillary loops. the presence of acetylcholinesterases is seen on the basal lamina and in the spaces between the endothelial cells and the pericytes of both types of vessels. the role of this enzyme in the blood-brain barrier is discussed.	1989	2756743
the effect of eel calcitonin on calcium influx and plasma ion levels in axolotls, ambystoma mexicanum.	plasma total calcium and calcium influx, measured during 4-h 45ca influx experiments, were lower in control axolotls, ambystoma mexicanum, during august when compared to those in july. a single intraperitoneal injection of 10 micrograms of synthetic eel calcitonin significantly reduced the calcium influx rates during both months but the effect was greater in july (p less than 0.001) than in august (p less than 0.05). plasma levels of calcium, sodium, potassium, and magnesium were not affected. i ...	1989	2767402
organization of positional information in the axolotl limb.	we have used the phenomenon of position-dependent growth stimulation, brought about by the confrontation of cells with dissimilar positional values, to reveal the organization of positional information in the center of the upper and lower arms of axolotls. when either humerus or radius was transplanted into either dorsal or posterior positions, extra growth leading to the formation of supernumerary digits occurred following amputation through the graft. however, transplants of humerus or radius ...	2009	2769199
drug-induced and genetic hypermelanism: effects on pigment cell differentiation.	allopurinol, a drug that inhibits the enzyme xanthine dehydrogenase (xdh), is known to cause hypermelanism in the axolotl. the hypermelanistic condition that results from allopurinol treatment is similar in most respects to the phenotype that results from the action of the melanoid (m) gene in axolotls. on the basis of structural and biochemical studies, it now seems clear that genetic and drug-induced hypermelanism are the same in the following ways. 1) both types of melanism result in the prod ...	2016	2771877
evidence for a change in expression of dna ligase genes in the pleurodeles waltlii germ line during gonadogenesis.	the expression of dna ligase genes was studied using the nuclear transplantation approach in the germ line of pleurodeles waltlii (p. waltlii) just before and during gonadogenesis. germ cell (gc) nuclei were isolated from larvae of p. waltlii and transplanted into unfertilized ambystoma mexicanum eggs. dna ligase activity in these eggs was then analyzed after sucrose gradient fractionation. the activity of dna ligase i (heavy form, 7.5 s) of p. waltlii was present when the transplanted gc nuclei ...	2009	2776966
neuroepithelial endocrine cells in the lung of ambystoma mexicanum.	neuroepithelial endocrine (nee) cells were for the first time identified in the lung of the entirely aquatic urodele, ambystoma mexicanum, by using light and electron microscopy, histochemistry, and immunocytochemistry. in the basal part of the ciliated epithelium and, less often, in the respiratory portion of the lung, nee cells were found to occur both solitarily and in small clusters. no typical neuroepithelial bodies could be found. using the method of fernandez pascual, some nee cells were ...	1989	2817428
cellular retinoic acid binding protein: detection and quantitation in regenerating axolotl limbs.	the concentrations of apo (unoccupied), holo (occupied), and total cellular retinoic acid binding protein (crabp) were measured at various stages of axolotl limb regeneration. the ratio of apo-crabp to holo-crabp declined with advancing regenerate stage until the crabp was all in the holo form. the increase in holo-crabp is correlated with a stage-dependent shift in the effect of exogenous retinoic acid on regenerate pattern, from pattern duplication to inhibition of regeneration. the data sugge ...	2010	2838564
binding of adrenergic ligands to liver plasma membrane preparations from the axolotl, ambystoma mexicanum; the toad, xenopus laevis; and the australian lungfish, neoceratodus forsteri.	the beta-adrenergic ligand iodocyanopindolol (icp) bound specifically to hepatic plasma membrane preparations from the axolotl, ambystoma mexicanum (bmax, 40 fmol/mg protein (p) at free concentration above 140 pm; kd, 42 pm); the toad, xenopus laevis (bmax, 200 fmol/mg p at 1 nm; kd, 300 pm); and the australian lungfish, neoceratodus forsteri (bmax, 100 fmol/mg p at 5 nm). for the lungfish, the scatchard plot was curved showing two classes of binding site with kd's of 20 and 500 pm. neither the ...	1988	2847957
in vitro differentiation of neuronal precursor cells from amphibian late gastrulae; morphological, immunocytochemical studies, biosynthesis, accumulation and uptake of neurotransmitters.	neuronal differentiation has been studied in dissociated cell cultures from early neurulae of pleurodeles waltl and ambystoma mexicanum. cocultures were prepared from the neural primordium and underlying chordamesoderm. np and nf cultures were prepared from isolated neural plate and neural folds, respectively. neuronal precursors in np and nf cultures had distinctive aggregation properties already evident after 1-2 days in culture. after 10-15 days, mature neurones and synapses were observed by ...	1985	2863321