Publications

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
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
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
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
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
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
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
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
developmental and evolutionary origins of the vertebrate dentition: molecular controls for spatio-temporal organisation of tooth sites in osteichthyans.	the rainbow trout (oncorhynchus mykiss) as a developmental model surpasses both zebrafish and mouse for a more widespread distribution of teeth in the oro-pharynx as the basis for general vertebrate odontogenesis, one in which replacement is an essential requirement. studies on the rainbow trout have led to the identification of the initial sequential appearance of teeth, through differential gene expression as a changing spatio-temporal pattern, to set in place the primary teeth of the first ge ...	2006	16496402
crystal structure of axolotl (ambystoma mexicanum) liver bile acid-binding protein bound to cholic and oleic acid.	the family of the liver bile acid-binding proteins (l-babps), formerly called liver basic fatty acid-binding proteins (lb-fabps) shares fold and sequence similarity with the paralogous liver fatty acid-binding proteins (l-fabps) but has a different stoichiometry and specificity of ligand binding. this article describes the first x-ray structure of a member of the l-babp family, axolotl (ambystoma mexicanum) l-babp, bound to two different ligands: cholic and oleic acid. the protein binds one mole ...	2006	16555310
conjecture: can continuous regeneration lead to immortality? studies in the mrl mouse.	a particular mouse strain, the mrl mouse, has been shown to have unique healing properties that show normal replacement of tissue without scarring. the serendipitous discovery that the mrl mouse has a profound capacity for regeneration in some ways rivaling the classic newt and axolotl species raises the possibility that humans, too, may have an innate regenerative ability. we propose this mouse as a model for continuous regeneration with possible life-extending properties. we will use the class ...	2006	16608389
conserved roles for oct4 homologues in maintaining multipotency during early vertebrate development.	all vertebrate embryos have multipotent cells until gastrulation but, to date, derivation of embryonic stem (es) cell lines has been achieved only for mouse and primates. es cells are derived from mammalian inner cell mass (icm) tissue that express the class v pou domain (pouv) protein oct4. loss of oct4 in mice results in a failure to maintain icm and consequently an inability to derive es cells. here, we show that oct4 homologues also function in early amphibian development where they act as s ...	2006	16651543
the rise of the boy-genius: psychological neoteny, science and modern life.	the mid-20th century saw the rise of the boy-genius, probably because a personality type characterized by prolonged youthfulness is advantageous both in science and modern life generally. this is the evolution of 'psychological neoteny', in which ever-more people retain for ever-longer the characteristic behaviours and attitudes of earlier developmental stages. whereas traditional societies are characterized by initiation ceremonies marking the advent of adulthood, these have now dwindled and di ...	2006	16750307
nitric oxide in the amphibian (ambystoma tigrinum) lateral line.	nicotinamide adenine dinucleotide phosphate reduced-diaphorase (nadph-d) histochemistry was investigated in the axolotl (ambystoma tigrinum) lateral line. hair cells of neuromast organs of the head skin and neurons of the postotic ganglia showed a significant nadph-d reaction. multiunit recording of neuromast afferent activity was also performed. nitric oxide synthase inhibitor n omega-nitro-l-arginine methyl ester (l-name) produced an initial slight excitation followed by a significant inhibiti ...	2006	16225991
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
apoptosis in regenerating and denervated, nonregenerating urodele forelimbs.	denervated limbs of larval salamanders fail to regenerate if amputated and, unlike adult limbs, undergo regression. the cellular basis of the tissue loss is poorly understood. we used tunel staining of larval axolotl limbs fixed and sectioned at intervals after bilateral amputation and unilateral denervation to investigate the role of apoptosis during normal limb regeneration and denervated limb regression. in the first week after amputation a small percentage of apoptotic cells was found in bot ...	2006	10810037
matrix metalloproteinase production in regenerating axolotl spinal cord.	in urodele amphibian spinal cord regeneration, the ependymal cells lining the central canal remodel the lesion site to favor axonal regrowth. we profiled the production of matrix metalloproteinases by injury-reactive mesenchymal ependymal cells in vivo and in vitro and found that matrix metalloproteinases are involved in this remodeling process in the axolotl (ambystoma mexicanum). the production of cell-associated matrix metalloproteinases in vivo was shown to be identical to that in our cultur ...	2006	11013020
terminal nerve-derived neuropeptide y modulates physiological responses in the olfactory epithelium of hungry axolotls (ambystoma mexicanum).	the vertebrate brain actively regulates incoming sensory information, effectively filtering input and focusing attention toward environmental stimuli that are most relevant to the animal's behavioral context or physiological state. such centrifugal modulation has been shown to play an important role in processing in the retina and cochlea, but has received relatively little attention in olfaction. the terminal nerve, a cranial nerve that extends underneath the lamina propria surrounding the olfa ...	2006	16855098
differential expression of tropomyosin during segmental heart development in mexican axolotl.	the mexican axolotl, ambystoma mexicanum, serves as an intriguing model to investigate myofibril organization and heart development in vertebrates. the axolotl has a homozygous recessive cardiac lethal gene "c" which causes a failure of ventricular myofibril formation and contraction. however, the conus of the heart beats, and has organized myofibrils. tropomyosin (tm), an essential component of the thin filament, has three known striated muscle isoforms (tpm1alpha, tpm1kappa, and tpm4alpha) in ...	2006	16741969
identification of the non-specific cytotoxic cell receptor protein 1 (nccrp1) in regenerating axolotl limbs.	the teleost non-specific cytotoxic cells (ncc) are evolutionary precursors of the mammalian natural killer (nk) cells and an important element of innate immunity. the non-specific cytotoxic cell receptor protein (nccrp1) is a characteristic cell surface protein with main functions in target cell recognition and cytotoxicity with sequence information available for many species of fish. we have isolated a cdna encoding the axolotl homologue of fish nccrp1 out of limb regeneration blastema and anal ...	2006	16676190
a germline gfp transgenic axolotl and its use to track cell fate: dual origin of the fin mesenchyme during development and the fate of blood cells during regeneration.	the development of transgenesis in axolotls is crucial for studying development and regeneration as it would allow for long-term cell fate tracing as well as gene expression analysis. we demonstrate here that plasmid injection into the one-cell stage axolotl embryo generates mosaic transgenic animals that display germline transmission of the transgene. the inclusion of scei meganuclease in the injections (thermes, v., grabher, c., ristoratore, f., bourrat, f., choulika, a., wittbrodt, j., joly, ...	2006	16387293
[myocardial regeneration in ambystoma mexicanum after surgical injury].	ventricular resection of the heart of ambystoma mexicanum was performed and the type of tissue that restored the lesion and if it is by hypertrophy or hyperplasia of myocardium, were evaluated. masson's trichrome stain indicated that 5 days after resection, the gap was occupied with a blood clot surrounded by collagen fibres (83 +/- 6%) and muscle (10 +/- 3%) and the rest of area (7 +/- 2%) free of tissue. a proportion of 50 +/- 4 and 90 +/- 2% was muscular tissue, 10 and 30 days after injury. t ...	2006	16366167
tropomodulin expression in developing hearts of normal and cardiac mutant mexican axolotl.	in the axolotl, ambystoma mexicanum, a simple, recessive cardiac-lethal mutation in gene "c" results in the hearts of c/c homozygous animals being deficient in sarcomeric tropomyosin (tm) and failing to form mature myofibrils. subsequently, the mutant hearts do not beat. a three-step model of myofibril assembly recently developed in cell culture prompted a reassessment of the myofibril assembly process in mutant hearts using a relatively new late marker for thin filament assembly, tropomodulin ( ...	2006	17303917
limb regeneration in axolotl: is it superhealing?	the ability of axolotls to regenerate their limbs is almost legendary. in fact, urodeles such as the axolotl are the only vertebrates that can regenerate multiple structures like their limbs, jaws, tail, spinal cord, and skin (the list goes on) throughout their lives. it is therefore surprising to realize, although we have known of their regenerative potential for over 200 years, how little we understand the mechanisms behind this achievement of adult tissue morphogenesis. many observations can ...	2006	17205184
wnt/beta-catenin signaling regulates vertebrate limb regeneration.	the cellular and molecular bases allowing tissue regeneration are not well understood. by performing gain- and loss-of-function experiments of specific members of the wnt pathway during appendage regeneration, we demonstrate that this pathway is not only necessary for regeneration to occur, but it is also able to promote regeneration in axolotl, xenopus, and zebrafish. furthermore, we show that changes in the spatiotemporal distribution of beta-catenin in the developing chick embryo elicit apica ...	2006	17114576
effects of peripheral nerve implants on the regeneration of partially and fully innervated urodele forelimbs.	this study addresses the cellular mechanism of the nerve requirement for regeneration of the urodele forelimb. others have suggested that only the schwann cell lineage of the blastema requires nerves for regeneration and that upon limb denervation, schwann cells arrest in the cell cycle and produce a factor that inhibits the cycling of the remaining blastema cells. our objective was to test this schwann cell inhibitor model. first, pieces of peripheral nerve were implanted into partially denerva ...	2006	9824557
[recovery of acetylcholinesterase activity in the axolotl embryo following inhibition with the organophosphorus inhibitor gd-7].	the restoration of acetylcholinesterase (ache) activity in axolotl ambystoma mexicanum embryo after treatment at 38-42 stages with irreversibly ache-inhibiting gd-7 phosphororganic inhibitor in concentrations, significantly decreasing ache activity level, but not interfering with ontogenesis has been studied. the rate of ache activity restoration in gd-7 treated axolotl embryo depends on the level of the enzyme restraint and the stage of the embryo development. the value of maximal restoration o ...	2006	3696676
[nuclear behavior of embryonic cells and growing oocytes from the clawed toad in the cytoplasm of maturing axolotl oocytes].	the behaviour of the nuclei of the x. laevis vitellogenic oocytes was studied by their transplantation into the cytoplasm of the axolotl maturing oocytes. after the germinal vesicle breakdown, in the case the transplanted nuclei were located close to each other a common giant spindle united the chromosomes of all transplanted nuclei. a mosaic spindle united sometimes the chromosomes of the two amphibian species. the embryonic nuclei transplanted in the cytoplasm of the maturing oocytes formed, a ...	2006	6504501
[radioautographic study of the cellular proliferation of retinal pigment epithelium in axolotls].	the proliferative activity of the pigment epithelium cells in the axolotl eyes was studied using 3h-thymidine in two types experiments: after the removal of lens, iris and retina and upon the cultivation of the pigment epithelium pieces in the cavity of lens-less eye. irrespective of the operation type, the level of proliferation of the pigment epithelium cells changed regularly with respect to the time of observation. in the intact eye, the level of proliferation of the pigment epithelium cells ...	2006	6521975
[cytochemistry of the nucleotides and nucleic acids in axolotl liver cells].		2006	13975042
an experimental analysis of regional organization in the regenerating fore limb of the axolotl (ambystoma mexicanum).		2006	13821173
the origin of spontaneous heteroploids in the progeny of diploid, triploid, and tetraploid axolotl females.		2006	13698113
the axolotl (siredon mexicanum). ii. morphology and pathology.		2006	13272307
the axolotl (siredon mexicanum). i. as material for scientific research.		2006	13234311
[effect of x-rays on the postembryonal growth of the telencephalon in ambystoma mexicanum].		2006	5525143
[proliferative activity of the pigment epithelium and regenerating retinal cells in ambystoma mexicanum].	cellular sources of retinal regeneration and proliferative activity of the cells taking part in retina restoration have been studied in axolotls using 3h-thymidine. the cells of ciliary-terminal zone proved to be the main source of retinal restoration. besides these cells, the pigmented cells of the iris inner and outer layers and pigment epithelium cells can take part in this process. morphological stages of retinal regeneration have been established and regular changes in the level of prolifer ...	2006	6657169
a lethal mutant gene in the mexican axolotl.	gene ph was discovered in a wild-type axolotl male received from mexico city. larvae homozygous for this gene become recognizable by their lighter color at hatching or shortly after. the development of their forelimbs is retarded, and all limbs are of subnormal length because of the reduction in length of their long bones. many affected larvae die without feeding, and very few survive beyond their third month. at death, older larvae usually show abnormalities of the renal system, edema, ascites, ...	2006	608947
interaction of cells of wolffian duct and mesothelium during initial growth period of mullerian ducts in the axolotl (ambystoma mexicanum).		2007	4117072
[the epiphysis of axolotl].		2007	14301966
[properties of neurons of the tectal portion of the visual system of the axolotl ambystoma mexicanum].	in the tectum opticum of the adult neotenic a. mexicanum, responses of single neuronal units to diffuse illumination and moving visual stimuli have been investigated. of 111 unites investigated, 27 are presented by tectal neurons, their maximum distribution being observed at a depth of 500-600 mu. in superficial layers 9 ipsi-elements were found; their receptive fields are located in the antero-dorsal part of the visual field, at both sides of the body axis. among the units identified as the ter ...	2007	1020556
[model studies of the effect of structural changes in cleaving embryo on electrical parameters of cellular interactions].	two models of the embryo developing from one initial cell by cleavage division are considered. equivalent electrical schemes were constructed, changes in electrical coupling coefficient (kec) and input resistance (ri) of the embryos during cleavage were estimated. considerable influence of cleavage-related changes of membrane parameters on kec and ri appears at the first five--ten cleavages and essentially depends on the ratio of contact and incontact membrane resistances. a comparison of the es ...	2007	7317491
axolotl (ambystoma mexicanum) lymphocytes produce and are growth-inhibited by transforming growth factor-beta.	recombinant (r)tgf-beta 5, an isoform of tgf-beta thus far identified only in the frog, xenopus' laevis, inhibited phytohemagglutinin (pha)-induced mitogenesis of salamander (axolotl) splenocytes and thymocytes, and t cell growth factor-induced proliferation of splenic lymphoblasts. this inhibition could be reversed by incubating (r)tgf-beta 5 with an anti-tgf-beta 5 antibody, but not with an antibody directed against tgf-beta 2, another xenopus-produced tgf-beta isoform. acid-treated supernatan ...	2007	9617586
microarray analysis identifies keratin loci as sensitive biomarkers for thyroid hormone disruption in the salamander ambystoma mexicanum.	ambystomatid salamanders offer several advantages for endocrine disruption research, including genomic and bioinformatics resources, an accessible laboratory model (ambystoma mexicanum), and natural lineages that are broadly distributed among north american habitats. we used microarray analysis to measure the relative abundance of transcripts isolated from a. mexicanum epidermis (skin) after exogenous application of thyroid hormone (th). only one gene had a >2-fold change in transcript abundance ...	2007	16926121
the axolotl limb: a model for bone development, regeneration and fracture healing.	among vertebrates, urodele amphibians (e.g., axolotls) have the unique ability to perfectly regenerate complex body parts after amputation. the limb has been the most widely studied due to the presence of three defined axes and its ease of manipulation. hence, the limb has been chosen as a model to study the process of skeletogenesis during axolotl development, regeneration and to analyze this animal's ability to heal bone fractures. extensive studies have allowed researchers to gain some knowle ...	2007	16920050
molecular and immunohistochemical analyses of cardiac troponin t during cardiac development in the mexican axolotl, ambystoma mexicanum.	the mexican axolotl, ambystoma mexicanum, is an excellent animal model for studying heart development because it carries a naturally occurring recessive genetic mutation, designated gene c, for cardiac nonfunction. the double recessive mutants (c/c) fail to form organized myofibrils in the cardiac myoblasts resulting in hearts that fail to beat. tropomyosin expression patterns have been studied in detail and show dramatically decreased expression in the hearts of homozygous mutant embryos. becau ...	2007	16888779
migratory patterns and developmental potential of trunk neural crest cells in the axolotl embryo.	using cell markers and grafting, we examined the timing of migration and developmental potential of trunk neural crest cells in axolotl. no obvious differences in pathway choice were noted for dii-labeling at different lateral or medial positions of the trunk neural folds in neurulae, which contributed not only to neural crest but also to rohon-beard neurons. labeling wild-type dorsal trunks at pre- and early-migratory stages revealed that individual neural crest cells migrate away from the neur ...	2007	17183528
inhibition of sonic hedgehog signaling leads to posterior digit loss in ambystoma mexicanum: parallels to natural digit reduction in urodeles.	molecular mechanisms patterning the tetrapod limb, including anterior-posterior axis determination involving sonic hedgehog (shh), have received much attention, particularly in amniotes. anterior-posterior patterning in urodele amphibians differs radically from that of amniotes in that it shows a pronounced anterior-to-posterior sequence of digit development. in contrast, amniotes develop their digits almost simultaneously with a slight posterior-to-anterior polarity. here we use cyclopamine, an ...	2007	17117438
measurement of in vivo stress resultants in neurulation-stage amphibian embryos.	in order to obtain the first quantitative measurements of the in vivo stresses in early-stage amphibian embryos, we developed a novel instrument that uses a pair of parallel wires that are glued to the surface of an embryo normal to the direction in which the stress is to be determined. when a slit is made parallel to the wires and between them, tension in the surrounding tissue causes the slit to open. under computer control, one of the wires is moved so as to restore the original wire spacing, ...	2007	17237990
transforming growth factor: beta signaling is essential for limb regeneration in axolotls.	axolotls (urodele amphibians) have the unique ability, among vertebrates, to perfectly regenerate many parts of their body including limbs, tail, jaw and spinal cord following injury or amputation. the axolotl limb is the most widely used structure as an experimental model to study tissue regeneration. the process is well characterized, requiring multiple cellular and molecular mechanisms. the preparation phase represents the first part of the regeneration process which includes wound healing, c ...	2007	18043735
a clash of traditions: the history of comparative and experimental embryology in sweden as exemplified by the research of gösta jägersten and sven hörstadius.	until the 1940s research traditions were often imported from germany to sweden, and young scientists went to german universities to learn new techniques and get in touch with the latest ideas. in developmental biology, the comparative, phylogenetic embryology advocated most forcefully by ernst haeckel co-existed with the "entwickelungsmechanik" tradition developed by wilhelm his, wilheln roux and others partly as a reaction to haeckel's ideas. i use the zoology department at uppsala university a ...	2007	18008099
evidence for balancing selection at the dab locus in the axolotl, ambystoma mexicanum.	the axolotl (ambystoma mexicanum) has been characterized as immunodeficient, and the absence of major histocompatibility complex (mhc) class ii polymorphism has been cited as a possible explanation. here we present evidence for considerable allelic polymorphism at the mhc class ii dab locus for a sample of wild-caught axolotls. evidence that these sequences are the product of balancing selection for disease resistance is discussed.	2007	18001306
a reduction of tropomyosin limits development of sarcomeric structures in cardiac mutant hearts of the mexican axolotl.	the cardiac lethal mutation in mexican axolotl (ambystoma mexicanum) results in a lack of contractions in the ventricle of mutant embryos. previous studies have demonstrated that tropomyosin, a component of thin filaments, is greatly reduced in mutant hearts lacking myofibril organization. confocal microscopy was used to examine the structure and comparative amount of tropomyosin at heartbeat initiation and at a later stage. the formation of functional sarcomeres coincided with contractions in n ...	2007	17990128
muscular derivatives of the cranialmost somites revealed by long-term fate mapping in the mexican axolotl (ambystoma mexicanum).	the fate of single somites has not been analyzed from a comparative perspective with modern cell-marking methods. most of what we know is based on work using quail-chick chimeras. consequently, to what degree cell fate has been conserved despite the anatomical differences among vertebrates is unknown. we have analyzed the cell fate of the cranialmost somites, with the focus on somite two, in the mexican axolotl (ambystoma mexicanum). somite cells were marked by injection of dextran-fluorescein a ...	2007	17976053
nerve-induced ectopic limb blastemas in the axolotl are equivalent to amputation-induced blastemas.	adult urodeles (salamanders) are unique in their ability to regenerate complex organs perfectly. the recently developed accessory limb model (alm) in the axolotl provides an opportunity to identify and characterize the essential signaling events that control the early steps in limb regeneration. the alm demonstrates that limb regeneration progresses in a stepwise fashion that is dependent on signals from the wound epidermis, nerves and dermal fibroblasts from opposite sides of the limb. when all ...	2007	17959163
the short toes mutation of the axolotl.	the axolotl mutant strain, short toes (s/s), can regenerate spinal cord and tail, but not limbs. this makes s/s potentially very useful for limb regeneration studies. this mutant merits a new examination that integrates the original description of the mutant, existing experimental studies, new data and current thinking about stem cells and regeneration. there are still major gaps in information about this mutant; the gene(s) causing the defects has not yet been discovered, and even the histologi ...	2007	17661741
bmp-4 and noggin signaling modulate dorsal fin and somite development in the axolotl trunk.	bmp-4, a member of the tgf-beta superfamily of growth factors, is involved in various developmental processes. we investigated the effects of bmp-4 and its antagonist noggin on axolotl trunk development. implantation of bmp-4-coated microbeads caused inhibition of muscle and dorsal fin formation in the vicinity of the microbeads. at some distance, myotomes developed with reduced height but increased width, which was accompanied by increased cell proliferation. these effects could be modulated by ...	2007	17654602
highly restricted diversity of tcr delta chains of the amphibian mexican axolotl (ambystoma mexicanum) in peripheral tissues.	gammadelta t cells localize at mammalian epithelial surfaces to exert both protective and regulatory roles in response to infections. we have previously characterized the mexican axolotl (ambystoma mexicanum) t cell receptor delta (trd) chain. in this study, trd repertoires in spleen, liver, intestine and skin from larvae, pre-adult and adult axolotls were examined and compared to the thymic trd repertoire. a trdv transcript without n/d diversity, trdv1s1-trdj1, dominates the trd repertoires unt ...	2007	17523213
a clonal analysis of neural progenitors during axolotl spinal cord regeneration reveals evidence for both spatially restricted and multipotent progenitors.	complete regeneration of the spinal cord occurs after tail regeneration in urodele amphibians such as the axolotl. little is known about how neural progenitor cells are recruited from the mature tail, how they populate the regenerating spinal cord, and whether the neural progenitor cells are multipotent. to address these issues we used three types of cell fate mapping. by grafting green fluorescent protein-positive (gfp(+)) spinal cord we show that a 500 microm region adjacent to the amputation ...	2007	17507409
characterization and expression of a maternal axolotl cyclin b1 during oogenesis and early development.	the m phase promoting factor (mpf) is a dimer composed of a catalytic cdk1 subunit and a cyclin b regulatory subunit. we have characterized a cdna containing the entire coding sequence of an axolotl cyclin b1 protein that is able to promote mpf activity when added to a fraction from prophase i oocytes that contains monomeric cdk1. the axolotl cyclin b1 gene is expressed as a maternal mrna in oocytes and early embryos. its poly(a) tail length increases in metaphase ii oocytes and then decreases r ...	2007	17428262
modulation of the reaction cycle of the na+:ca2+, k+ exchanger.	ca(2+) concentration in retinal photoreceptor rod outer segment (os) strongly affects the generator potential kinetics and the receptor light adaptation. the response to intense light stimuli delivered in the dark produce potential changes exceeding 40 mv: since the ca(2+) extrusion in the os is entirely controlled by the na(+):ca(2+), k(+) exchanger, it is important to assess how the exchanger ion transport rate is affected by the voltage and, in general, by intracellular factors. it is indeed ...	2007	17415556
role of myofibril-inducing rna in cardiac tnt expression in developing mexican axolotl.	the mexican axolotl, ambystoma mexicanum, has been a useful animal model to study heart development and cardiac myofibrillogenesis. a naturally-occurring recessive mutant, gene "c", for cardiac non-function in the mexican axolotl causes a failure of myofibrillogenesis due to a lack of tropomyosin expression in homozygous mutant (c/c) embryonic hearts. myofibril-inducing rna (mir) rescues mutant hearts in vitro by promoting tropomyosin expression and myofibril formation thereafter. we have studie ...	2007	17408593
isolation and characterization of axolotl npdc-1 and its effects on retinoic acid receptor signaling.	retinoic acid, a key morphogen in early vertebrate development and tissue regeneration, mediates its effects through the binding of receptors that act as ligand-induced transcription factors. these binding events function to recruit an array of transcription co-regulatory proteins to specific gene promoters. one such co-regulatory protein, neuronal proliferation and differentiation control-1 (npdc-1), is broadly expressed during mammalian development and functions as an in vitro repressor of ret ...	2007	17331771
comparative analysis of xenopus vegt, the meso-endodermal determinant, identifies an unusual conserved sequence.	the transcription factor, vegt, is the meso-endodermal determinant in xenopus laevis. we examined vegt orthologs from several anuran amphibians and the urodele amphibian, the mexican axolotl. in addition to the conserved t-box, the dna-binding domain, the orthologs share a conserved 57 amino acid domain at the c-terminal. most striking is a 17-nucleotide (nt) sequence near the 3' end of the open reading frame. the 17 nts are absolutely conserved among the anurans, whose last common ancestor live ...	2007	17459091
urodele p53 tolerates amino acid changes found in p53 variants linked to human cancer.	urodele amphibians like the axolotl are unique among vertebrates in their ability to regenerate and their resistance to develop cancers. it is unknown whether these traits are linked at the molecular level.	2007	17903248
localized co-transcriptional recruitment of the multifunctional rna-binding protein celf1 by lampbrush chromosome transcription units.	the highly-extended transcription units of lampbrush chromosomes (lbcs) offer unique opportunities to study the co-transcriptional events occurring on nascent transcripts. using lbcs from amphibian oocytes, i investigated whether celf1, an rna binding protein involved in the regulation of alternative splicing, mrna stability and translation, is localized to active transcription units. antibodies raised against mammalian (cug-bp1) and amphibian (eden-bp) celf1 were used to immunostain lbc spreads ...	2007	18095176
rna of amvegt, the axolotl orthologue of the xenopus meso-endodermal determinant, is not localized in the oocyte.	the transcription factor, vegt, is the meso-endodermal determinant in xenopus laevis, and the localization of vegt rna to the vegetal cortex of the oocyte is an important starting point for embryonic patterning. we have cloned the vegt orthologue from the urodele amphibian, ambystoma mexicanum, the mexican axolotl. axolotl vegt (amvegt) is expressed zygotically in the presumptive mesoderm and rohon-beard neurons as in x. laevis, and its expression persists at the tip of the tail as with zebrafis ...	2007	16920404
early gene expression during natural spinal cord regeneration in the salamander ambystoma mexicanum.	in contrast to mammals, salamanders have a remarkable ability to regenerate their spinal cord and recover full movement and function after tail amputation. to identify genes that may be associated with this greater regenerative ability, we designed an oligonucleotide microarray and profiled early gene expression during natural spinal cord regeneration in ambystoma mexicanum. we sampled tissue at five early time points after tail amputation and identified genes that registered significant changes ...	2007	17241119