Publications

[cytochemistry of the nucleotides and nucleic acids in axolotl liver cells].		2006	13975042
[effect of x-rays on the postembryonal growth of the telencephalon in ambystoma mexicanum].		2006	5525143
an experimental analysis of regional organization in the regenerating fore limb of the axolotl (ambystoma mexicanum).		2006	13821173
the axolotl (siredon mexicanum). ii. morphology and pathology.		2006	13272307
the origin of spontaneous heteroploids in the progeny of diploid, triploid, and tetraploid axolotl females.		2006	13698113
the axolotl (siredon mexicanum). i. as material for scientific research.		2006	13234311
the development of the hindbrain afferent projections in the axolotl: evidence for timing as a specific mechanism of afferent fiber sorting.	the aim of this study is to reveal the timing and growth pattern of central octavolateral projection development in the mexican axolotl, ambystoma mexicanum. in this amphibian species the development of the inner ear occurs first, followed by mechanosensory lateral line organs, and finally by ampullary electroreceptors. several hypotheses have been proposed about how the development of peripheral organs, including differential projections of the ear, might relate to the development of central pr ...	2005	16351978
histamine (h3) receptors modulate the excitatory amino acid receptor response of the vestibular afferents.	although the effectiveness of histamine-related drugs in the treatment of peripheral and central vestibular disorders may be explained by their action on the vestibular nuclei, it has also been shown that antivertigo effects can take place at the peripheral level. in this work, we examined the actions of h3 histaminergic agonists and antagonists on the afferent neuron electrical discharge in the isolated inner ear of the axolotl. our results indicate that h3 antagonists such as thioperamide, clo ...	2005	16310756
an investigative laboratory exercise examining the cell signaling and regulatory properties of neurons in the regenerating forelimbs of the axolotl ambystoma mexicanum.	many students understand the electrical properties of neurons and can adequately describe the creation and transmission of electrical impulses. however, students often have difficulty when it comes to understanding how neurons have an equally important role in cell signaling. this latter function is crucial in the establishment of proper cell fate during regeneration. i have devised a lab that includes in its goals: 1) an investigation into the cell signaling role of neurons, 2) experience with ...	2005	23493055
axolotl hemoglobin: cdna-derived amino acid sequences of two alpha globins and a beta globin from an adult ambystoma mexicanum.	erythrocytes of the adult axolotl, ambystoma mexicanum, have multiple hemoglobins. we separated and purified two kinds of hemoglobin, termed major hemoglobin (hb m) and minor hemoglobin (hb m), from a five-year-old male by hydrophobic interaction column chromatography on alkyl superose. the hemoglobins have two distinct alpha type globin polypeptides (alpham and alpham) and a common beta globin polypeptide, all of which were purified in fplc on a reversed-phase column after s-pyridylethylation. ...	2005	16143550
automated 3-d reconstruction of the surface of live early-stage amphibian embryos.	although three-dimensional (3-d) reconstructions of the surfaces of live embyos are vital to understanding embryo development, morphogenetic tissue movements and other factors have prevented the automation of this task. here, we report an integrated set of software algorithms that overcome these challenges, making it possible to completely automate the reconstruction of embryo surfaces and other textured surfaces from multiview images. the process involves: 1) building accurate point corresponde ...	2005	16119236
tensile properties of embryonic epithelia measured using a novel instrument.	we present the first measurements of the tensile properties of embryonic epithelia, data that are crucial to understanding the mechanics of morphogenetic movements. fine wires were glued to the surface of an intact, live embryo using cyanoacrylate glue, after which the epithelium between the wires was separated from the remainder of the embryo by microsurgery. the wires were then separated from each other in 0.1 microm steps under computer control in order to elongate the tissue at a constant tr ...	2005	16084209
multiview robotic microscope reveals the in-plane kinematics of amphibian neurulation.	a new robotic microscope system, called the frogatron 3000, was developed to collect time-lapse images from arbitrary viewing angles over the surface of live embryos. embryos are mounted at the center of a horizontal, fluid-filled, cylindrical glass chamber around which a camera with special optics traverses. to hold them at the center of the chamber and revolve them about a vertical axis, the embryos are placed on the end of a small vertical glass tube that is rotated under computer control. to ...	2005	16078621
corticotropin-releasing hormone-mediated metamorphosis in the neotenic axolotl ambystoma mexicanum: synergistic involvement of thyroxine and corticoids on brain type ii deiodinase.	in the present study, morphological changes leading to complete metamorphosis have been induced in the neotenic axolotl ambystoma mexicanum using a submetamorphic dose of t(4) together with an injection of corticotropin-releasing hormone (crh). an injection of crh alone is ineffective in this regard presumably due to a lack of thyrotropic stimulation. using this low hormone profile for induction of metamorphosis, the deiodinating enzymes d2 and d3 known to be present in amphibians were measured ...	2005	15993107
hedgehog signaling controls dorsoventral patterning, blastema cell proliferation and cartilage induction during axolotl tail regeneration.	tail regeneration in urodeles requires the coordinated growth and patterning of the regenerating tissues types, including the spinal cord, cartilage and muscle. the dorsoventral (dv) orientation of the spinal cord at the amputation plane determines the dv patterning of the regenerating spinal cord as well as the patterning of surrounding tissues such as cartilage. we investigated this phenomenon on a molecular level. both the mature and regenerating axolotl spinal cord express molecular markers ...	2005	15983402
expression of heat-shock protein 70 during limb development and regeneration in the axolotl.	urodele amphibians (e.g., axolotls) have the unique ability, among vertebrates, to regenerate perfectly many parts of their body after amputation. the limb has been the most widely studied regenerating structure in these organisms and provides an ideal model in which to understand how vertebrates can regenerate complex tissues. the present study focuses on hsp-70, a member of the stress-related heat-shock protein family. this protein is normally induced after a stress or trauma such as heat-shoc ...	2005	15965983
limb chondrogenesis of the seepage salamander, desmognathus aeneus (amphibia: plethodontidae).	salamanders are infrequently mentioned in analyses of tetrapod limb formation, as their development varies considerably from that of amniotes. however, urodeles provide an opportunity to study how limb ontogeny varies with major differences in life history. here we assess limb development in desmognathus aeneus, a direct-developing salamander, and compare it to patterns seen in salamanders with larval stages (e.g., ambystoma mexicanum). both modes of development result in a limb that is morpholo ...	2005	15880507
anti-sense-mediated inhibition of expression of the novel striated tropomyosin isoform tpm1kappa disrupts myofibril organization in embryonic axolotl hearts.	striated muscle tropomyosin (tm) is described as containing ten exons; 1a, 2b, 3, 4, 5, 6b, 7, 8, and 9a/b. exon 9a/b has critical troponin binding domains and is found in striated muscle isoforms. we have recently discovered a smooth (exon 2a)/striated (exons 9a/b) isoform expressed in amphibian, avian, and mammalian hearts, designated as an isoform of the tpm1 gene (tpm1kappa). tpm1kappa expression was blocked in whole embryonic axolotl heart by transfection of exon-specific anti-sense oligonu ...	2005	15838882
cardiac myofibril formation is not affected by modification of both n- and c-termini of sarcomeric tropomyosin.	although the role of tropomyosin is well-defined in striated muscle, the precise mechanism of how tropomyosin functions is still unclear. it has been shown that extension of either n- or c-terminal ends of sarcomeric tropomyosin do not affect cardiac myofibrillogenesis, but it is not known whether simultaneous extension of both ends affects the process. for studying structural/functional relationships of sarcomeric tropomyosin, we have chosen the ambystoma mexicanum because cardiac mutant hearts ...	2005	15738580
histological analysis of forelimb regeneration in the california newt taricha granulosa.	the regenerative ability of the forelimbs of the california rough-skinned newt, taricha granulosa was determined and compared to the same ability of the adult mexican axolotl, ambystoma mexicanum. forelimbs were amputated distally at the wrist and limbs removed at 1, 2, 3, 4, 5 and 6 weeks post-amputation were examined by histological analysis. since vitamin a and its derivatives cause extreme changes in pattern formation in the regenerating amphibian limb, we decided to study the ability of ret ...	2005	1525332
intracellular recordings of rod responses during dark-adaptation.	1. dark-adaptation of rod photoreceptors has been studied in the isolated axolotl (ambystoma mexicanum) retina by intracellular recordings. rod responsiveness was greatly reduced immediately after a 30 sec partial bleach, but partially recovered with time in the dark. 2. in parallel spectrophotometric measurements using isolated retinas, regeneration of the rod pigment could not be detected after a 30 sec bleach. 3. during rod dark-adaptation, the response of a rod to a given stimulus increased ...	2005	1151778
molecular characterization of major histocompatibility complex class ii alleles in wild tiger salamanders (ambystoma tigrinum).	major histocompatibility complex (mhc) class ii genes are usually among the most polymorphic in vertebrate genomes because of their critical role (antigen presentation) in immune response. prior to this study, the mhc was poorly characterized in tiger salamanders (ambystoma tigrinum), but the congeneric axolotl (ambystoma mexicanum) is thought to have an unusual mhc. most notably, axolotl class ii genes lack allelic variation and possess a splice variant without a full peptide binding region (pb ...	2005	16195876
a comprehensive expressed sequence tag linkage map for tiger salamander and mexican axolotl: enabling gene mapping and comparative genomics in ambystoma.	expressed sequence tag (est) markers were developed for ambystoma tigrinum tigrinum (eastern tiger salamander) and for a. mexicanum (mexican axolotl) to generate the first comprehensive linkage map for these model amphibians. we identified 14 large linkage groups (125.5-836.7 cm) that presumably correspond to the 14 haploid chromosomes in the ambystoma genome. the extent of genome coverage for these linkage groups is apparently high because the total map size (5251 cm) falls within the range of ...	2005	16079226
quantitative evaluation of morpholino-mediated protein knockdown of gfp, msx1, and pax7 during tail regeneration in ambystoma mexicanum.	vertebrate regeneration is a fascinating but poorly understood biological phenomena. urodele amphibians such as ambystoma mexicanum (the axolotl) can functionally regenerate complex body structures such as the limb and tail, including the spinal cord, throughout life. so far, molecular studies on regeneration have been limited due to the paucity of tools for knocking-down gene and protein function. in this article, we quantitatively assessed the ability of morpholinos to specifically down-regula ...	2005	15580632
evidence for emergence of an amphibian iridoviral disease because of human-enhanced spread.	our understanding of origins and spread of emerging infectious diseases has increased dramatically because of recent applications of phylogenetic theory. iridoviruses are emerging pathogens that cause global amphibian epizootics, including tiger salamander (ambystoma tigrinum) die-offs throughout western north america. to explain phylogeographical relationships and potential causes for emergence of western north american salamander iridovirus strains, we sequenced major capsid protein and dna me ...	2005	15643965
diminished myofibril organization in mutant axolotl hearts transfected with site-directed mutants of sarcomeric tropomyosins.	we used a model lacking endogenous sarcomeric tropomyosin, the cardiac mutant of the mexican axolotl, to examine the effect of mutant tropomyosins on sarcomeric myofibril formation. previous studies have introduced wild-type mouse alpha-tropomyosin into mutant hearts in organ culture with subsequent for-mation of organized myofibrils. this study examines the predominant embry-onic axolotl tpm-4 type tropomyosin (tpm4alpha), containing a conservative re- placement of glutamic acid for aspartic ac ...	2005	15738587
haem conformation of amphibian nytrosylhaemoglobins detected by xanes spectroscopy.	we investigated for the first time the haem stereochemistry in the nitrosylated derivative of two amphibian haemoglobins, xenopus laevis and ambystoma mexicanum, by means of x-ray absorption spectroscopy technique with the aim to explain the relationships between the active site structure and physiological function of these proteins, compared to that from humans. our results show that while the fe site local structure of human hbno is modulated by an allosteric effector such as ihp shifting the ...	2005	15744461
proximodistal identity during vertebrate limb regeneration is regulated by meis homeodomain proteins.	the mechanisms by which cells obtain instructions to precisely re-create the missing parts of an organ remain an unresolved question in regenerative biology. urodele limb regeneration is a powerful model in which to study these mechanisms. following limb amputation, blastema cells interpret the proximal-most positional identity in the stump to reproduce missing parts faithfully. classical experiments showed the ability of retinoic acid (ra) to proximalize blastema positional values. meis homeobo ...	2005	16107473
transcriptional and phylogenetic analysis of five complete ambystomatid salamander mitochondrial genomes.	we report on a study that extended mitochondrial transcript information from a recent est project to obtain complete mitochondrial genome sequence for 5 tiger salamander complex species (ambystoma mexicanum, a. t. tigrinum, a. andersoni, a. californiense, and a. dumerilii). we describe, for the first time, aspects of mitochondrial transcription in a representative amphibian, and then use complete mitochondrial sequence data to examine salamander phylogeny at both deep and shallow levels of evolu ...	2005	15780978
identification of angiotensin i in several vertebrate species: its structural and functional evolution.	in order to delineate further the molecular evolution of the renin-angiotensin system in vertebrates, angiotensin i (ang i) has been isolated after incubation of plasma and kidney extracts of emu (dromiceus novaehollandiae), axolotl (ambystoma mexicanum), and sea lamprey (petromyzon marinus). the identified sequences were [asp1, val5, asn9] ang i in emu, [asp1, val5, his9] ang i in axolotl, and [asn1, val5, thr9] ang i in sea lamprey. these results confirmed the previous findings that tetrapods ...	2004	14723880
cloning and analysis of axolotl isl2 and lhx2 lim-homeodomain transcription factors.	we cloned and characterized the isl2 and lhx2 lim-homeodomain transcription factors of the mexican salamander, or axolotl, ambystoma mexicanum. using a degenerate pcr approach, partial cdnas representing five lim-homeodomain genes were cloned, indicating conservation of this class of transcription factors in urodeles. full-length cdnas for isl2 and lhx2 were identified and sequenced. the predicted isl2 and lhx2 proteins are well conserved, especially in the lim and dna-binding domains. the isl2 ...	2004	15048808
patterns of spatial and temporal visceral arch muscle development in the mexican axolotl (ambystoma mexicanum).	vertebrate head development is a classical topic that has received renewed attention during the last decade. most reports use one of a few model organisms (chicken, mouse, zebrafish) and have focused on molecular mechanisms and the role of the neural crest, while cranial muscle development has received less attention. here we describe cranial muscle differentiation and morphogenesis in the mexican axolotl, ambystoma mexicanum. to determine the onset of differentiation we use antibodies against d ...	2004	15216519
expression of a novel cardiac-specific tropomyosin isoform in humans.	tropomyosins are a family of actin binding proteins encoded by a group of highly conserved genes. humans have four tropomyosin-encoding genes: tpm1, tpm2, tpm3, and tpm4, each of which is known to generate multiple isoforms by alternative splicing, promoters, and 3' end processing. tpm1 is the most versatile and encodes a variety of tissue specific isoforms. the tpm1 isoform specific to striated muscle, designated tpm1alpha, consists of 10 exons: 1a, 2b, 3, 4, 5, 6b, 7, 8, and 9a/b. in this stud ...	2004	15249230
cell contact-dependent mechanisms specify taste bud pattern during a critical period early in embryonic development.	after gastrulation, the pharyngeal endoderm is specified to give rise to taste receptor organs without further signaling from other embryonic tissues. we hypothesized that intercellular signaling might be responsible for the specification of taste buds. to test if and when this signaling was occurring, intercellular contacts were transiently disrupted in cultures of pharyngeal endoderm from axolotl embryos, and the number, size, and distribution of taste buds analyzed. disruption of cell contact ...	2004	15254897
the scarless heart and the mrl mouse.	the ability to regenerate tissues and limbs in its most robust form is seen in many non-mammalian species. the serendipitous discovery that the mrl mouse has a profound capacity for regeneration in some ways rivalling the classic newt and axolotl species raises the possibility that humans, too, may have an innate regenerative ability. the adult mrl mouse regrows cartilage, skin, hair follicles and myocardium with near perfect fidelity and without scarring. this is seen in the ability to close th ...	2004	15293806
from biomedicine to natural history research: est resources for ambystomatid salamanders.	establishing genomic resources for closely related species will provide comparative insights that are crucial for understanding diversity and variability at multiple levels of biological organization. we developed ests for mexican axolotl (ambystoma mexicanum) and eastern tiger salamander (a. tigrinum tigrinum), species with deep and diverse research histories.	2004	15310388
gene expression in the axolotl germ line: axdazl, axvh, axoct-4, and axkit.	primordial germ cells (pgcs) in embryos of mammals and urodele amphibians are formed by induction in the absence of germ plasm. we describe expression of four germ cell-related genes through the germ cell cycle of the axolotl. the orthologs of vasa and daz-like are up-regulated in pgcs of tail bud embryos before the gonad forms and are expressed throughout the female germ cell cycle. mammalian oct-4 is a marker of pluripotency in embryonic cells. axolotl oct-4 has higher homology to oct-4 than t ...	2004	15517581
the axolotl (ambystoma mexicanum), a neotenic amphibian, expresses functional thyroid hormone receptors.	neotenic amphibians such as the axolotl (ambystoma mexicanum) are often unable to undergo metamorphosis under natural conditions. it is thought that neoteny represents a deviation from the standard course of amphibian ontogeny, affecting the thyroid axis at different levels from the central nervous system to peripheral organs. thyroid hormone receptors (trs) that bind the thyroid hormone (th) t(3) have been described in axolotl. however, the full sequences of tr were needed to better characteriz ...	2004	14576183
neurotrophin-independent attraction of growing sensory and motor axons towards developing xenopus limb buds in vitro.	the mechanisms for directing axons to their targets in developing limbs remain largely unknown though recent studies in mice have demonstrated the importance of neurotrophins in this process. we now report that in co-cultures of larval xenopus laevis limb buds with spinal cords and dorsal root ganglia of xenopus and axolotl (ambystoma mexicanum) axons grow directly to the limb buds over distances of up to 800 microm and in particular to sheets of epidermal cells which migrate away from the limb ...	2004	14697361
an ambystoma mexicanum est sequencing project: analysis of 17,352 expressed sequence tags from embryonic and regenerating blastema cdna libraries.	the ambystomatid salamander, ambystoma mexicanum (axolotl), is an important model organism in evolutionary and regeneration research but relatively little sequence information has so far been available. this is a major limitation for molecular studies on caudate development, regeneration and evolution. to address this lack of sequence information we have generated an expressed sequence tag (est) database for a. mexicanum.	2004	15345051
isoproterenol-produced damage in amphibian heart could be mediated by adrenergic receptors located in the heart muscle.	in mammals, isoproterenol may produce heart damage in part by binding to adrenergic receptors in the coronary arteries. previously we showed evidence that isoproterenol produces cellular necrosis and interstitial fibrosis in the ventricle of the heart of an amphibian, which has no coronary arteries. the present study examines responses to 3-adrenergic receptor stimulation in the heart of urodele amphibians. the hearts from three amphibians; ambystoma mexicanum, a. tigrinum and a. dumerilii were ...	2004	15633614
developmental origins and evolution of jaws: new interpretation of "maxillary" and "mandibular".	cartilage of the vertebrate jaw is derived from cranial neural crest cells that migrate to the first pharyngeal arch and form a dorsal "maxillary" and a ventral "mandibular" condensation. it has been assumed that the former gives rise to palatoquadrate and the latter to meckel's (mandibular) cartilage. in anamniotes, these condensations were thought to form the framework for the bones of the adult jaw and, in amniotes, appear to prefigure the maxillary and mandibular facial prominences. here, we ...	2004	15531376
an introduction to the mexican axolotl (ambystoma mexicanum).	a number of unusual traits, including a remarkable capacity for wound healing and limb regeneration, make the axolotl an interesting animal model. the author provides an overview of axolotl care and use in biomedical research.	2004	15457201
role of cranial neural crest cells in visceral arch muscle positioning and morphogenesis in the mexican axolotl, ambystoma mexicanum.	the role of cranial neural crest cells in the formation of visceral arch musculature was investigated in the mexican axolotl, ambystoma mexicanum. dii (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine, perchlorate) labeling and green fluorescent protein (gfp) mrna injections combined with unilateral transplantations of neural folds showed that neural crest cells contribute to the connective tissues but not the myofibers of developing visceral arch muscles in the mandibular, hyoid, and bran ...	2004	15366001
a critical role for thrombin in vertebrate lens regeneration.	lens regeneration in urodele amphibians such as the newt proceeds from the dorsal margin of the iris where pigment epithelial cells (pec) re-enter the cell cycle and transdifferentiate into lens. a general problem in regeneration research is to understand how the events of tissue injury or removal are coupled to the activation of plasticity in residual differentiated cells or stem cells. thrombin, a pivotal regulator of the injury response, has been implicated as a regulator of cell cycle re-ent ...	2004	15293804
discrimination of conspecific sex and reproductive condition using chemical cues in axolotls ( ambystoma mexicanum).	chemosensory cues play an important role in the daily lives of salamanders, mediating foraging, conspecific recognition, and territorial advertising. we investigated the behavioral effects of conspecific whole-body odorants in axolotls, ambystoma mexicanum, a salamander species that is fully aquatic. we found that males increased general activity when exposed to female odorants, but that activity levels in females were not affected by conspecific odorants. although males showed no difference in ...	2004	15034733
activation of cdc2 kinase during meiotic maturation of axolotl oocyte.	activity of cdc2, the universal inducer of mitosis, is regulated by phosphorylation and binding to cyclin b. comparative studies using oocytes from several amphibian species have shown that different mechanisms allow cdc2 activation and entry into first meiotic division. in xenopus, immature oocytes stockpile pre-m-phase promoting factor (mpf) composed of cdc2-cyclin b complexes maintained inactive by thr14 and tyr15 phosphorylation of cdc2. activation of mpf relies on the conversion of pre-mpf ...	2004	15013793
retinoic acid repatterns axolotl lateral line receptors.	the effects of all-trans retinoic acid on the development of the lateral line placodes of axolotls was studied. late gastrula and early neurula were exposed to 10(-7) to 10(-5) m retinoic acid for one hour and then reared until they would normally be feeding larvae. as in other vertebrates, the extent of the developmental abnormalities is concentration dependent. those embryos exposed to the highest concentration of retinoic acid failed to form much of the forebrain and midbrain, including the o ...	2004	15005576
coupled amplification and degradation of exogenous rna injected in amphibian oocytes.	the early development of amphibians takes place in the absence of significant transcription and is controlled at the post-transcriptional level. we have reported that in vitro synthesized transcripts injected into axolotl fertilized eggs or oocytes were not continuously degraded as their abundance apparently fluctuated over time, with detected amounts sometimes higher than initial injected amounts. to further characterize this phenomenon, we have co-injected rna chain terminators to prevent rna ...	2004	15161959
low submetamorphic doses of dexamethasone and thyroxine induce complete metamorphosis in the axolotl (ambystoma mexicanum) when injected together.	entanglement of functions between the adrenal (or interrenal) and thyroid axis has been well described for all vertebrates and can be tracked down up to the level of gene expression. both thyroid hormones and corticosteroids may induce morphological changes leading to metamorphosis climax in the neotenic mexican axolotl (ambystoma mexicanum). in a first series of experiments, metamorphosis was induced with an injection of 25 microg t(4) on three alternate days as judged by a decrease in body wei ...	2004	15158126
early expression of two tdt isoforms in the hematopoietic system of the mexican axolotl. implications for the evolutionary origin of the n-nucleotide addition.	nontemplate (n)-nucleotide addition by the terminal dideoxynucleotidyl transferase (tdt) at the junctions of rearranging v( d) j gene segments greatly contribute to antigen-receptor diversity. tdt has been identified in several vertebrate species, where it is highly conserved. we report here the isolation of two forms of tdt mrna in an amphibian, the mexican axolotl. the isoform tdt1 shares all of the conserved structural motifs required for tdt activity and displays an average of 50-58% similar ...	2004	15146297
combined intrinsic and extrinsic influences pattern cranial neural crest migration and pharyngeal arch morphogenesis in axolotl.	cranial neural crest cells migrate in a precisely segmented manner to form cranial ganglia, facial skeleton and other derivatives. here, we investigate the mechanisms underlying this patterning in the axolotl embryo using a combination of tissue culture, molecular markers, scanning electron microscopy and vital dye analysis. in vitro experiments reveal an intrinsic component to segmental migration; neural crest cells from the hindbrain segregate into distinct streams even in the absence of neigh ...	2004	14738875
downregulation of n1 gene expression inhibits the initial heartbeating and heart development in axolotls.	recessive mutant gene c in the axolotl results in a failure of affected embryos to develop contracting hearts. this abnormality can be corrected by treating the mutant heart with rna isolated from normal anterior endoderm or from endoderm conditioned medium. a cdna library was constructed from the total conditioned medium rna using a random priming technique in a pcdnaii vector. we have previously identified a clone (designated as n1) from the constructed axolotl cdna library, which has a unique ...	2004	14729455
endogenous electric fields in embryos during development, regeneration and wound healing.	all embryos that have been investigated drive ionic currents through themselves and these currents will generate internal electric fields. here, those examples in which such fields have been measured directly are discussed. the first such measurements were made in chick embryos and about 20 mv mm(-1) was measured near the posterior intestinal portal in 2-4 day-old embryos. this electric field is important for the development of tail structures because reducing its magnitude results in abnormal t ...	2003	14690282
gustatory neurons derived from epibranchial placodes are attracted to, and trophically supported by, taste bud-bearing endoderm in vitro.	taste buds are multicellular receptor organs innervated by the viith, ixth, and xth cranial nerves. in most vertebrates, taste buds differentiate after nerve fibers have reached the lingual epithelium, suggesting that nerves induce taste buds. however, under experimental conditions, taste buds of amphibians develop independently of innervation. thus, rather than being induced by nerves, the developing taste periphery likely regulates ingrowing nerve fibers. to test this idea, we devised a cultur ...	2003	14651931
axolotl pronephric duct migration requires an epidermally derived, laminin 1-containing extracellular matrix and the integrin receptor alpha6beta1.	the epidermis overlying the migrating axolotl pronephric duct is known to participate in duct guidance. this epidermis deposits an extracellular matrix onto the migrating duct and its pathway that is a potential source of directional guidance cues. the role of this matrix in pronephric duct guidance was assayed by presenting matrix deposited on microcarriers directly to migrating pronephric ducts in situ. we found that reorientation of extracellular-matrix-bearing carriers prior to their present ...	2003	14522870
characterization of glycosaminoglycans during tooth development and mineralization in the axolotl, ambystoma mexicanum.	glycosaminoglycans (gags) involved in the formation of the teeth of ambystoma mexicanum were located and characterized with the cuprolinic blue (cb) staining method and transmission electron microscopy (tem). glycosaminoglycan-cuprolinic blue precipitates (gagcb) were found in different compartments of the mineralizing tissue. various populations of elongated gagcb could be discriminated both according to their size and their preferential distribution in the extracellular matrix (ecm). gagcb pop ...	2003	14517102
tooth development in ambystoma mexicanum: phosphatase activities, calcium accumulation and cell proliferation in the tooth-forming tissues.	prerequisites of tooth formation, cell proliferation in the tooth-forming tissues, calcium accumulation and the enzymatic activities of alkaline (alp) and acid phosphatases (acp) were investigated by immunohistochemical and histochemical methods in various developmental stages of the mexican axolotl, ambystoma mexicanum. during the growth of replacement teeth, the tooth-forming tissues continually recruit cells from the surrounding regions. the basal layer of the oral epithelium, the dental lami ...	2003	12801088
olfactory signal modulation by molluscan cardioexcitatory tetrapeptide (fmrfamide) in axolotls (ambystoma mexicanum).	the terminal nerve, which innervates the nasal epithelia of most jawed vertebrates, is believed to release neuropeptides that modulate activity of sensory receptor neurons. the terminal nerve usually contains gonadotropin-releasing hormone as well as at least one other peptide that has not been characterized, but which bears some structural similarity to molluscan cardioexcitatory tetrapeptide (fmrfamide) and neuropeptide tyrosine (npy). we investigated the effects of fmrfamide on both voltage-g ...	2003	12771020
relationship between cardiac protein tyrosine phosphorylation and myofibrillogenesis during axolotl heart development.	the axolotl, ambystoma mexicanum, is a useful system for studying embryogenesis and cardiogenesis. to understand the role of protein tyrosine phosphorylation during heart development in normal and cardiac mutant axolotl embryonic hearts, we have investigated the state of protein tyrosine residues (phosphotyrosine, p-tyr) and the relationship between p-tyr and the development of organized sarcomeric myofibrils by using confocal microscopy, two-dimensional isoelectric focusing (ief)/sds-polyacryla ...	2003	12747935
selective activation of thrombin is a critical determinant for vertebrate lens regeneration.	the regeneration of structures in adult animals depends on a mechanism for coupling the acute response to tissue injury or removal with the local activation of plasticity in residual differentiated cells or stem cells. many potentially relevant signals are generated after injury, and the nature of this mechanism has not been elucidated for any instance of regeneration. lens regeneration in adult vertebrates always occurs at the pupillary margin of the dorsal iris, where pigmented epithelial cell ...	2003	12747839
a point mutation in bioactive rna results in the failure of mutant heart correction in mexican axolotls.	ambystoma mexicanum is an intriguing animal model for studying heart development because it carries a mutation in gene c. hearts of homozygous recessive (c/c) mutant embryos do not contain organized myofibrils and fail to beat. the defect can be corrected by organ-culturing the mutant heart in the presence of rna from anterior endoderm or endoderm/mesoderm-conditioned medium. by screening a cdna library made of total conditioned medium rna from normal axolotl embryonic endoderm, we isolated a si ...	2003	12721841
neural crest contributions to the lamprey head.	the neural crest is a vertebrate-specific cell population that contributes to the facial skeleton and other derivatives. we have performed focal dii injection into the cranial neural tube of the developing lamprey in order to follow the migratory pathways of discrete groups of cells from origin to destination and to compare neural crest migratory pathways in a basal vertebrate to those of gnathostomes. the results show that the general pathways of cranial neural crest migration are conserved thr ...	2003	12702647
gonadotropin releasing hormone (gnrh) modulates odorant responses in the peripheral olfactory system of axolotls.	peripheral signal modulation plays an important role in sensory processing. activity in the vertebrate olfactory epithelium may be modulated by peptides released from the terminal nerve, such as gonadotropin releasing hormone (gnrh). here, we demonstrate that gnrh modulates odorant responses in aquatic salamanders (axolotls, ambystoma mexicanum). we recorded electrical field potentials (electro-olfactograms, or eogs) in response to stimulation with four different amino acid odorants, l-lysine, l ...	2003	12672784
surface glycoconjugates in the olfactory system of ambystoma mexicanum.	lectin binding histochemistry was performed on the olfactory system of neotenic and metamorphosed ambystoma mexicanum to investigate the distribution and density of defined carbohydrate residues on the cell surface glycoproteins of the olfactory and vomeronasal receptor cells and their terminals in the olfactory bulbs. the lectin binding patterns indicate that the main olfactory system possesses a high density of n-acetyl-galactosamine and n-acetyl-glucosamine residues, while the vomeronasal sys ...	2003	12655612
ontogeny of the vip system in the gastro-intestinal tract of the axolotl, ambystoma mexicanum: successive appearance of co-existing pacap and nos.	evidence for the presence and potential co-existence of vasoactive intestinal polypeptide (vip), pituitary adenylate cyclase-activating polypeptide (pacap) and nitric oxide synthase (nos) in gastro-intestinal endocrine cells and/or nerve fibers is conflicting and very few results exist on development. this immunofluorescence study aims to clarify the appearance and localization of vip, pacap and nos in the gastro-intestinal tract of the axolotl, ambystoma mexicanum, during ontogeny. vip-immunore ...	2003	12649730
extending the table of stages of normal development of the axolotl: limb development.	the existing table of stages of the normal development of the axolotl (ambystoma mexicanum) ends just after hatching. at this time, the forelimbs are small buds. in this study, we extend the staging series through completion of development of the forelimbs and hindlimbs.	2003	12619140
expression of complement 3 and complement 5 in newt limb and lens regeneration.	some urodele amphibians possess the capacity to regenerate their body parts, including the limbs and the lens of the eye. the molecular pathway(s) involved in urodele regeneration are largely unknown. we have previously suggested that complement may participate in limb regeneration in axolotls. to further define its role in the regenerative process, we have examined the pattern of distribution and spatiotemporal expression of two key components, c3 and c5, during limb and lens regeneration in th ...	2003	12594255
electroporation as a tool to study in vivo spinal cord regeneration.	tailed amphibians such as axolotls and newts have the unique ability to fully regenerate a functional spinal cord throughout life. where the cells come from and how they form the new structure is still poorly understood. here, we describe the development of a technique that allows the visualization of cells in the living animal during spinal cord regeneration. a microelectrode needle is inserted into the lumen of the spinal cord and short rapid pulses are applied to transfer the plasmids encodin ...	2003	12557220
ultrastructure of the external gill epithelium of the axolotl, ambystoma mexicanum with reference to ionic transport.	the ultrastructure of the external gill epithelium of the axolotl, ambystoma mexicanum, has been examined using conventional transmission electron microscopy to elucidate its role in ionic transport. four cell types are identified in the gill filament and primary gill bar epithelium. these are granular, ciliated, leydig and basal cells. a fifth cell type, the flat mitochondria-rich cell is only found in the gill bar epithelium. the predominant granular cells display microvilli at their surface a ...	2003	15137686
the epithelia of the protrusible tongue of eurycea longicauda guttolineata (hoolbrook 1838) (urodela: plethodontidae).	in this study the lingual and sublingual glands, the lingual stem and the epithelial surface of the protrusible secondary tongue were investigated by light, scanning and transmission electron microscopy. the quality of the secretions of the epithelia was characterized histochemically. the lingual epithelium is formed by superficial (pavement) and goblet cells and at the margin of the tongue pad are also regions covered by ciliated cells. on the dorsal part of the tongue there are goblet cells of ...	2003	15121544
myoseptal architecture of sarcopterygian fishes and salamanders with special reference to ambystoma mexicanum.	during axial undulatory swimming in fishes and salamanders muscular forces are transmitted to the vertebral axis and to the tail. one of the major components of force transmission is the myoseptal system. the structure of this system is well known in actinopterygian fishes, but has never been addressed in sarcopterygian fishes or salamanders. in this study we describe the spatial arrangement and collagen fiber architecture of myosepta in latimeria, two dipnoans, and three salamanders in order to ...	2003	16351889
opioid receptors mediate a postsynaptic facilitation and a presynaptic inhibition at the afferent synapse of axolotl vestibular hair cells.	this study was designed to determine the effects of opiate drugs on the electrical activity of afferent neurons and on the ionic currents of hair cells from semicircular canals. experiments were done on larval axolotls (ambystoma tigrinum). the multiunit spike activity of afferent neurons was recorded in the isolated inner ear under both resting conditions and mechanical stimulation. ionic currents were recorded using voltage clamp of hair cells isolated from the semicircular canal. in the isola ...	2003	12676139
regulative germ cell specification in axolotl embryos: a primitive trait conserved in the mammalian lineage.	how germ cells are specified in the embryos of animals has been a mystery for decades. unlike most developmental processes, which are highly conserved, embryos specify germ cells in very different ways. curiously, in mouse embryos germ cells are specified by extracellular signals; they are not autonomously specified by maternal germ cell determinants (germ plasm), as are the germ cells in most animal model systems. we have developed the axolotl (ambystoma mexicanum), a salamander, as an experime ...	2003	14511484
injection of exogenous rna in amphibian oocytes leads to rna level fluctuations which are sensitive to cordycepin, an rna chain elongation terminator.	using an in vivo heterologous system to study the stability of xenopus laevis rna injected into axolotl (ambystoma mexicanum) fertilized eggs, we have previously observed unexpected fluctuations in rna level during early development [andéol et al., differentiation 63 (1998) 69-79]. in this study, we further characterize this phenomenon and establish its existence during axolotl and xenopus oogenesis, suggesting a phylogenetically conserved mechanism. the phenomenon can occur with a variety of ex ...	2003	14746268
sheep heart rna stimulates myofibril formation and beating in cardiac mutant axolotl hearts in organ culture.	in the mexican axolotl, ambystoma mexicanum, recessive mutant gene c, when homozygous, results in a failure of the heart to form sarcomeric myofibrils and contract normally. previous studies have shown that purified rna from normal anterior endoderm or from medium conditioned with anterior endoderm/pre-cardiac mesoderm has the capacity to rescue mutant hearts in organ culture. in the present study, rna extracted from adult sheep heart was tested for its capacity to promote differentiation in the ...	2003	12684761
examination of an amphibian-based assay using the larvae of xenopus laevis and ambystoma mexicanum.	semistatic acute toxicity tests of amphibian larvae (xenopus laevis and ambystoma mexicanum) were conducted at different developmental stages and by different methods to establish a simple amphibian-based assay. test substance was pentachlorophenol sodium salt (pcp-na). the endpoint was mortality and the 24-, 48-, 72-, and 96-h lc50 values were calculated by probit analysis. interspecific differences in larval responses were not clear. larval sensitivity tended to increase with larval age. newly ...	2003	12706392
ph modulates the vestibular afferent discharge and its response to excitatory amino acids.	in the isolated inner ear of the axolotl (ambystoma tigrinum) acid ph decreased and basic ph increased the resting and mechanically evoked spike discharge of semicircular canal afferent neurons. variations in ph also modified the afferent neuron response to n-methyl-d-aspartic acid (nmda) acid and to (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (ampa). responses to both excitatory amino acid agonists increased at ph 7.8 (41% and 22%, respectively) and decreased by perfusion of ...	2003	12876466
candidate gene analysis of metamorphic timing in ambystomatid salamanders.	although much is known about the ecological significance of metamorphosis and metamorphic timing, few studies have examined the underlying genetic architecture of these traits, and no study has attempted to associate phenotypic variation to molecular variation in specific genes. here we report on a candidate gene approach (cga) to test specific loci for a statistical contribution to variation in metamorphic timing. three segregating populations (sp1, sp2 and sp3) were constructed utilizing three ...	2003	12694285
responses to amputation of denervated ambystoma limbs containing aneurogenic limb grafts.	the developing neural tubes and associated neural crest cells were removed from stage 30 ambystoma maculatum embryos to obtain larvae with aneurogenic forelimbs. forelimbs were allowed to develop to late 3 digit or early 4 digit stages. limbs amputated through the mid radius-ulna regenerated typically in the aneurogenic condition. experiments were designed to test whether grafts of aneurogenic limb tissues would rescue denervated host limb stumps into a regeneration response. in experiment 1, an ...	2003	12911114
albino axolotls from an albino tiger salamander through hybridization.		2003	6055330
[induction of haploid androgenesis in the axolotl by ultraviolet irradiation and a cytomorphological study of the mechanism of its origin].		2003	5896234
[autoradiographic study of rna synthesis during the restoration of regenerative capacity of the extremities of the axolotl supressed by x-radiation].		2003	5343939
spermatogenesis and 3beta-hsdh activity in the testis of the axolotl.		2003	1012324
identification of cdna clones encoding hmg 2, a major protein of the mexican axolotl hydrocortisone-sensitive thymocytes.	we have identified and analyzed cdna clones encoding a major 26 kda protein of the hmg1-2 family which is abundant in the cytoplasm and nucleus of axolotl hydrocortisone-sensitive thymocytes. the axolotl hmg2 protein is very similar to proteins belonging to the hmg1-2 family, from teleost fish to mammals. all the molecular features of the hmg1-2 proteins are conserved, including the high proportion of basic and aromatic residues, and the characteristic acidic c-terminus tail. the 3'-untranslated ...	2003	8654668
[origin of the cells in the symmetrical forelimbs of the axolotl ambystoma mexicanum].		2003	2740070
radioresistance of regenerating axolotl tissues.		2003	4778512
cortical reaction in axolotl eggs.		2003	5154619
time relationships between the onset of rna synthesis and the manifestation of the morphogenetic function in axolotl nuclei.		2003	4668026
urodeles remove mesoderm from the superficial layer by subduction through a bilateral primitive streak.	urodeles begin gastrulation with much of their presumptive mesoderm in the superficial cell layer, all of which must move into the deep layers during development. we studied the morphogenesis of superficial mesoderm in the urodeles ambystoma maculatum, ambystoma mexicanum, and taricha granulosa. in all three species, somitic, lateral, and ventral mesoderm move into the deep layer during gastrulation, ingressing through a "bilateral primitive streak" just inside the blastopore. the mesodermal epi ...	2002	12167400
cloning and modeling of cd8 beta in the amphibian ambystoma mexicanum. evolutionary conserved structures for interactions with major histocompatibility complex (mhc) class i molecules.	mammalian and avian t-cells exhibit a large number of well characterized surface molecules associated with their maturation degree. very little is known in comparison with t-cell differentiation in ectothermic vertebrates. this is mainly due to the lack of probes to identify t-cell subsets. we cloned and sequenced the first ectothermic cd8 beta dna complementary to rna from an amphibian species, the mexican axolotl. the cd8 beta chain was 30-36% identical with its avian and mammalian homologues. ...	2002	12034498
a novel striated tropomyosin incorporated into organized myofibrils of cardiomyocytes in cell and organ culture.	striated muscle tropomyosin is classically described as consisting of 10 exons, 1a, 2b, 3, 4, 5, 6b, 7, 8, and 9a/b, in both skeletal and cardiac muscle. a novel isoform found in embryonic axolotl heart maintains exon 9a/b of striated muscle but also has a smooth muscle exon 2a instead of exon 2b. translation and subsequent incorporation into organized myofibrils, with both isoforms, was demonstrated with green fluorescent protein fusion protein construct. mutant axolotl hearts lack sufficient t ...	2002	12044866
cell cycle reentry of ventricular and atrial cardiomyocytes and cells within the epicardium following amputation of the ventricular apex in the axolotl, amblystoma mexicanum: confocal microscopic immunofluorescent image analysis of bromodeoxyuridine-labeled nuclei.	to understand how to reinitiate cell division in adult human myocardium, a heart regeneration model was examined in the amphibian axolotl salamander, amblystoma mexicanum. the ventricular apex was surgically amputated and resected for 3 weeks. at 14 days of recovery, the thymidine analog 5-bromo-2'-deoxyuridine (brdu) was injected intraperitoneally to identify cell types undergoing s-phase by indirect immunofluorescence using primary anti-brdu antibodies. this is the first report showing a conce ...	2002	12107494
cyclopamine induces digit loss in regenerating axolotl limbs.	axolotls, with their extensive ability to regenerate as adults, provide a useful model for studying the mechanisms of regeneration in a vertebrate, in hopes of understanding why other vertebrates cannot regenerate. although the expression of many genes has been described in regeneration, techniques for gain and loss of function analyses have been limited. we demonstrated in a previous study that gain of function for secreted proteins was possible in the axolotl using the vaccinia virus to drive ...	2002	12115913
membranes, minerals, and proteins of developing vertebrate enamel.	developing tooth enamel is formed as organized mineral in a specialized protein matrix. in order to analyze patterns of enamel mineralization and enamel protein expression in species representative of the main extant vertebrate lineages, we investigated developing teeth in a chondrichthyan, the horn shark, a teleost, the guppy, a urodele amphibian, the mexican axolotl, an anuran amphibian, the leopard frog, two lepidosauria, a gecko and an iguana, and two mammals, a marsupial, the south american ...	2002	12430167
expression of fibroblast growth factors 4, 8, and 10 in limbs, flanks, and blastemas of ambystoma.	members of the fibroblast growth factor (fgf) family of molecules are critical to limb outgrowth. here, we examine the expression of fgfs in three types of limbs-embryonic (developing), mature (differentiated), and regenerating-as well as in the surrounding non-limb tissues in the mexican axolotl, ambystoma mexicanum. we have previously cloned partial cdnas of fgf4, 8, and 10 from the axolotl (christensen et al., 2001); the complete fgf10 cdna sequence is presented here. axolotl fgf10 showed ded ...	2002	11836784
cranial neural crest emergence and migration in the mexican axolotl (ambystoma mexicanum).	the timing and pattern of cranial neural crest cell emergence and migration in the mexican axolotl, ambystoma mexicanum, are assessed using scanning electron microscopy (sem). cranial neural crest cells emerge and begin to migrate at the time of neural fold closure and soon form three distinct streams. the most anterior (mandibular) stream emerges first, at the level of the mesencephalon. cells in this stream migrate rostroventrally around the optic vesicle. the second (hyoid) and third (branchi ...	2002	16351868
ectoderm to mesoderm lineage switching during axolotl tail regeneration.	foreign environments may induce adult stem cells to switch lineages and populate multiple tissue types, but whether this mechanism is used for tissue repair remains uncertain. urodele amphibians can regenerate fully functional, multitissue structures including the limb and tail. to determine whether lineage switching is an integral feature of this regeneration, we followed individual spinal cord cells live during tail regeneration in the axolotl. spinal cord cells frequently migrate into surroun ...	2002	12471259
amphioxus and lamprey ap-2 genes: implications for neural crest evolution and migration patterns.	the neural crest is a uniquely vertebrate cell type present in the most basal vertebrates, but not in cephalochordates. we have studied differences in regulation of the neural crest marker ap-2 across two evolutionary transitions: invertebrate to vertebrate, and agnathan to gnathostome. isolation and comparison of amphioxus, lamprey and axolotl ap-2 reveals its extensive expansion in the vertebrate dorsal neural tube and pharyngeal arches, implying co-option of ap-2 genes by neural crest cells e ...	2002	12397104
immunocytochemical localization of keratins, associated proteins and uptake of histidine in the epidermis of fish and amphibians.	keratinization and the role of histidine in some species of fish and amphibians have been analyzed by immunocytochemistry and autoradiography. in cartilaginous and bony fishes, staining of acidic (ae1-positive) and basic (ae3-positive) keratins was strong and their distribution patterns were uniform in all epidermal layers. the ae2 antibody (for keratins k1 and k10 that are typical for keratinization) did not produce any positivity. this was also observed in lungfish epidermis but the ae2 antibo ...	2002	12389745