Publications

on the conservation of calcium wave speeds.	most long distance calcium signals are believed to take the form of actively propagated calcium waves. in 1991, when this proposal was first advanced, all such waves were thought to belong to one class, for which fertilization waves were the prototype. moreover, the speeds of such waves were found to be conserved at about 10 microns/s for primary fertilization waves and 30 microns/s for waves through fully active systems at 20 degrees c. in 1993, preliminary evidence for a second class of such w ...	1998	9793683
evidence for introduction of a variable g1 phase at the midblastula transition during early development in axolotl.	after fertilization in axolotl, the synchronous cell cleavages are triphasic (s, g2 and m phases). midblastula transition (mbt) begins at the ninth cleavage and is the consequence of lengthening of cell cycles. by spectrofluorometry and incorporation of 3h thymidine into the nuclear dna followed by autoradiography on individual cells, the time at which a g1 phase appears during early development was investigated. the present results show that the g1 phase was introduced for the first time at mbt ...	1998	9783475
three-dimensional reconstruction of live embryos using robotic macroscope images.	to determine the three-dimensional (3-d) shape of a live embryo is a technically challenging task. we show that reconstructions of live embryos can be done by collecting images from different viewing angles using a robotic macroscope, establishing point correspondences between these views by block matching, and using a new 3-d reconstruction algorithm that accommodates camera positioning errors. the algorithm assumes that the images are orthographic projections of the object and that the camera ...	1998	9735567
cloning, sequencing and expression of a novel homeobox gene axnox-1 from the mexican axolotl.	we have cloned and sequenced a cdna containing a homeobox gene, axnox-1, from a stage 18 axolotl embryonic cdna library which shows only moderate levels of similarity to other known homeobox genes. the nucleotide sequence of the cdna has an open reading frame for 335 amino acids and besides the homeodomain, there is an acidic domain and a proline-rich domain present in the protein. the transcripts for this gene are detectable at stage 4 of embryonic development and, hence, there is a good possib ...	1998	9714797
anterior/posterior influences on neural crest-derived pigment cell differentiation.	the neural crest of vertebrate embryos has been used to elucidate steps involved in early embryonic cellular processes such as differentiation and migration. neural crest cells form a ridge along the dorsal midline and subsequently they migrate throughout the embryo and differentiate into a wide variety of cell types. intrinsic factors and environmental cues distributed along the neural tube, along the migratory pathways, and/or at the location of arrest influence the fate of neural crest cells. ...	1998	9711533
expression of hoxd genes in developing and regenerating axolotl limbs.	hox genes play a critical role in the development of the vertebrate axis and limbs, and previous studies have implicated them in the specification of positional identity, the control of growth, and the timing of differentiation. axolotl limbs offer an opportunity to distinguish these alternatives because the sequence of skeletal differentiation is reversed along the anterior-posterior axis relative to that of other tetrapods. we report that during early limb development, expression patterns of h ...	1998	9705229
effect of calcium on development of amiloride-blockable na+ transport in axolotl in vitro.	the axolotl, ambystoma mexicanum, which has no specific calcium-containing sieve layer in the dermis, provides useful material for the study of the effect of ca2+ on the development of amiloride-blockable active na+ transport across the skin of amphibians. we raised axolotls in thyroid hormone or aldosterone or cultured the skin with corticoid plus one of several ca2+ concentrations and found that 1) although the short-circuit current (scc) was increased by both aldosterone and 3,3',5-triiodo-l- ...	1998	9688962
cloning and sequencing of the cdna for an rna-binding protein from the mexican axolotl: binding affinity of the in vitro synthesized protein.	a full length cdna for an rna-binding protein (axolotl rbp) with consensus sequence (rnp-cs) from the mexican axolotl, ambystoma mexicanum, has been cloned from a subtraction library. in vitro translation with synthetic mrna and subsequent hybrid-arrested translation with a specific antisense oligonucleotide confirms that the axolotl rbp cdna encodes an approx. 16 kda polypeptide. computer-assisted analyses revealed amino acid similarities of 58-60% to various rna-binding proteins and a 90 amino ...	1998	9655917
regulation of homeobox-containing genes during lens regeneration.	in this study, the expression of homeobox-containing genes was evaluated after lentectomy in the newt, which is competent for lens regeneration, and in the axolotl which is not. such a comparison was designed to offer insights about possible regulation due to regenerative abilities. six homeobox-containing genes were examined: nvhox a4, nvhox b1, nvhox 7, nvhox x, nvmsx-1 and xbr1. for all genes examined, it was found that soon after lentectomy in the newt there was a general down-regulation in ...	1998	9533863
structure and diversity of the t-cell receptor alpha chain in the mexican axolotl.	polymerase chain reaction was used to isolate cdna clones encoding putative t-cell receptor (tcr) alpha chains in an amphibian, the mexican axolotl (ambystoma mexicanum). five tcralpha-v chain-encoding segments were identified, each belonging to a separate family. the best identity scores for these axolotl tcralpha-v segments were all provided by sequences belonging to the human tcralpha-v1 family and the mouse tcralpha-v3 and tcralpha-v8 families. a total of 14 different tcra-j segments were id ...	1997	9002443
analysis of the three-dimensional distributions of alpha-actinin, ankyrin, and filamin in developing hearts of normal and cardiac mutant axolotls (ambystoma mexicanum).	alpha-actinin is an actin binding protein that assists in the stabilization of the plasma membrane and helps to fix organelles in position in a variety of cell types. in muscle, it is a major component of the z-lines of organized myofibrils. ankyrin binds to various elements of the cytoskeletal system including microtubules, microfilaments, and intermediate filaments and may help to anchor these structures to the cell membrane. filamin is a well-characterized actin-associated protein first isola ...	1997	9045985
evidence for the presence and participation of 85-75 kda extracellular matrix components in cell interactions of bufo arenarum gastrulation.	we studied the presence and distribution of the extracellular materials (ecm), obtained by mild embryonic dissociation through nondenaturing and denaturing page, immunoblotting and immunocytochemical wholemount in the gastrulation of anuran amphibian bufo arenarum. the sds-page, under reducing conditions, revealed the protein profile of the ecm which comprised six bands. the western immunoblotting effected with antibodies against fibronectins (fn) of xenopus laevis, ambystoma mexicanum and bufo ...	1997	9062995
expression pattern of an axolotl floor plate-specific fork head gene reflects early developmental differences between frogs and salamanders.	gastrulation is one of the most important stages of animal development and, as such, tends to be remarkably conserved. therefore it is interesting to see that the two amphibian species, xenopus laevis (frog) and ambystoma mexicanum (axolotl), are different in the arrangement of cell types just before and during gastrulation. in xenopus, the cells that will form dorsal mesoderm are located deep in the dorsal marginal zone, while in the axolotl, these are on the surface of the embryo. in this stud ...	1997	9144925
thyroid hormone receptor genes of neotenic amphibians.	since thyroid hormones play a pivotal role in amphibian metamorphosis we used pcr to amplify dna fragments corresponding to a portion of the ligand-binding domain of the thyroid hormone receptor (tr) genes in several neotenic amphibians: the obligatory neotenic members of the family proteidea the mudpuppy necturus maculosus and proteus anguinus as well as two members of the facultative neotenic ambystoma genus: the axolotl ambystoma mexicanum and the tiger salamander ambystoma tigrinum. in addit ...	1997	9169551
effects of urea on m4-lactate dehydrogenase from elasmobranchs and urea-accumulating australian desert frogs.	we measured the effect of urea on m4-lactate dehydrogenase (m4-ldh) from elasmobranchs and australian desert frogs (urea accumulators) and from two animals that do not accumulate urea, the axolotl and the rabbit. an analysis of the effect of urea on the kd(nadh), v, v/k(m(prr)) and v/k(m(nadh)) shows that in all cases the major effect of urea was on the binding of pyruvate, which fits with data in the literature that show that urea acts as a competitive inhibitor of ldh. the characteristics of t ...	1997	9180022
abbreviated junctional sequences impoverish antibody diversity in urodele amphibians.	of the six complementarity-determining regions (cdr) forming the structure of the ab combining site, cdr3 of heavy chain is the most variable in length and sequence. diversity of this loop is determined by the number of gene segments involved, extent of addition to or deletion from the joining genes, and imprecision of the site of recombination. in neonatal mice and xenopus tadpoles, the last two factors occur less frequently than in adults, which in tadpoles result in low affinity ab responses ...	1997	9317138
molecular cloning from neurulating ambystoma mexicanum embryos of the cdna encoding an orphan nuclear receptor (ador1) closely related to tr2-11.	we have isolated a cdna encoding a novel orphan nuclear receptor, ador1, closely related to testicular receptor-2 (tr2) orphan receptor family members, from neurulating ambystoma mexicanum embryos. the cdna sequence predicts a protein primary sequence of 416 amino acids with a calculated molecular weight of 45.8 kda. while the dna-binding domains of ador1 and htr2-11 share 96% identity, considerable divergence is observed at both extremities of the peptides. at the n-terminus, ador1 is 66% ident ...	1997	9503600
melatonin levels in the gastrointestinal tissues of fish, amphibians, and a reptile.	melatonin was detected by radioimmunoassay in the gastrointestinal tract (git) of several species of fish (sturgeon, rainbow trout, carp), amphibians (axolotl, leopard frog, bullfrog), and one reptile (red-sided garter snake), which were sacrificed during the daytime. the highest levels of melatonin were detected in the snake [means = 1018 pg/g stomach, 328 pg/g proximal gut (pg), 511 distal gut (dg)] and carp (means = 102 pg/g stomach, 146 pg/g pg and 141 pg/g dg). lowest levels were found in t ...	1997	9204376
transferrin is necessary and sufficient for the neural effect on growth in amphibian limb regeneration blastemas.	cell proliferation during the early phase of growth in regenerating amphibian limbs requires a permissive influence of nerves. based on analyses of proliferative activity in denervated blastemas, it was proposed that nerves provide factors important for cells to complete the proliferative cycle rather than for mitogenesis itself. one such factor, the iron-transport protein transferrin (tf), is abundant in regenerating peripheral nerves where it is axonally transported and released at growth cone ...	1997	9493827
hormone-induced rise in cytosolic ca2+ in axolotl hepatocytes: properties of the ca2+ influx channel.	calcium entry in nonexcitable cells occurs through ca(2+)-selective channels activated secondarily to store depletion and/or through receptor- or second messenger-operated channels. in amphibian liver, hormones that stimulate the production of adenosine 3',5'-cyclic monophosphate (camp) also regulate the opening of an ion gate in the plasma membrane, which allows a noncapacitative inflow of ca2+. to characterize this ca2+ channel, we studied the effects of inhibitors of voltage-dependent ca2+ ch ...	1997	9374637
abnormal limb regeneration in the short-toes mutant of the axolotl, ambystoma mexicanum: studies of age, level of amputation, and extracellular matrix.	limb regeneration in the short-toes axolotl is impaired. our goal was to characterize the regeneration process in this mutant by histological and immunocytochemical methods. previous research indicates that age and a defective basement membrane may be instrumental factors in short-toes axolotl regeneration (del rio-tsonis et al. [1992] proc. natl. acad. sci. u.s.a., 89:5502-5506). the present results show that limb regeneration can occur even in older (1-2-year-old) short-toes axolotls. the proc ...	1997	9399429
the role of thyroid hormone in zebrafish and axolotl development.	exogenous thyroid hormone (th) induces premature differentiation of the zebrafish pectoral fins, which are analogous to the forelimbs of tetrapods. it accelerates the growth of the pelvic fins but not precociously. goitrogens, which are chemical inhibitors of th synthesis by the thyroid gland, inhibit the transition from larva to juvenile fish including the formation of scales, and pigment pattern; they stunt the growth of both pectoral and pelvic paired fins. inhibition by goitrogens is rescued ...	1997	9371791
adaptive evolution via a major gene effect: paedomorphosis in the mexican axolotl.	although adaptive evolution is thought to depend primarily on mutations of small effect, major gene effects may underlie many of the important differences observed among species in nature. the mexican axolotl (ambystoma mexicanum) has a derived mode of development that is characterized by metamorphic failure (paedomorphosis), an adaptation for an entirely aquatic life cycle. by using an interspecific crossing design and genetic linkage analysis, a major quantitative trait locus for expression of ...	1997	9391174
taste disks are induced in the lingual epithelium of salamanders during metamorphosis.	morphological changes of oral cavity during metamorphosis with special reference to the taste organ were examined in ezo salamanders (hynobius retardatus) and axolotis (ambystoma mexicanum), and compared with those in bullfrogs (rana catesbeiana). the non-distensible tongue of salamanders changed the structure progressively during metamorphosis: a small area of the rostrum protruded and developed caudally with recession of the flat area of the tongue. the protrusion that developed on the tongue ...	1997	9363353
a primary cell culture model for defective cardiac myofibrillogenesis in mexican axolotl embryos.		1997	9358282
reduced epidermal expression of a pg-m/versican-like proteoglycan in embryos of the white mutant axolotl.	axolotl embryos have previously been used to study neural crest cell migration. in embryos of the normal wild type, neural crest cells migrate subepidermally to form pigment cells. in the trunk of the white mutant embryo, these cells are unable to migrate, possibly due to an inherited delay in the maturation of the local extracellular matrix. the present investigation reveals a reduced incorporation of [35s]sulfate into pg-m/versican-like proteoglycans synthesized in epidermal explants from the ...	1997	9344585
homeobox genes in axolotl lateral line placodes and neuromasts.	gene expression has been studied in considerable detail in the developing vertebrate brain, neural crest, and some placode-derived organs. as a further investigation of vertebrate head morphogenesis, expression patterns of several homeobox-containing genes were examined using whole-mount in situ hybridization in a sensory system primitive for the vertebrate subphylum: the axolotl lateral lines and the placodes from which they develop. axolotl msx-2 and dlx-3 are expressed in all of the lateral l ...	1997	27747426
structure and diversity of the heavy chain vdj junctions in the developing mexican axolotl.	the immune capacity of young and adult axolotls (ambystoma mexicanum) was evaluated by examining the combinatorial and junctional diversity of the vh chain. a large number of vdj rearrangements isolated from 2.5-, 3.5-, 10-, and 24-month-old animals were sequenced. six jh segments were identified with the canonical structure of all known vertebrate jhs, including the conserved trp103-gly104-x-gly106 motif. four core dh-like sequences were used by most (80%) of the vdj junctions. these g-rich seq ...	1997	9271630
hypochord, an enigmatic embryonic structure: study of the axolotl embryo.	the hypochord of the axolotl embryo is first visible at an early tailbud stage, forming a rod-like structure, situated immediately under the notochord. a profusion of extracellular matrix fibrils is attached to the dorsolateral regions of the hypochord, linking it with the somites. a basal lamina develops around the hypochord, indicating an epithelial type of cell differentiation. abundant rough endoplasmic reticula in the hypochord cells suggest lively synthetic activity. prospective endoderm c ...	1997	9068201
differential expression of a novel isoform of alpha-tropomyosin in cardiac and skeletal muscle of the mexican axolotl (ambystoma mexicanum).	alternative mrna splicing is a fundamental process in eukaryotes that contributes to tissue-specific and developmentally regulated patterns of tropomyosin (tm) gene expression. northern blot analyses suggest the presence of multiple transcripts of tropomyosin in skeletal and cardiac muscle of adult mexican axolotls. we have cloned and sequenced two tropomyosin cdnas designated atmc-1 and atmc-2 from axolotl heart tissue and one tm cdna from skeletal muscle, designated atms-1. nucleotide sequence ...	1997	9055812
pg-m/versican-like proteoglycans are components of large disulfide-stabilized complexes in the axolotl embryo.	large disulfide-stabilized proteoglycan complexes were previously shown to be synthesized by the epidermis of axolotl embryos during stages crucial to subepidermal migration of neural crest cells. we now show that the complexes contain pg-m/versican-like monomers in addition to some other component with low buoyant density. metabolically 35s-labeled proteoglycans were extracted from epidermal explants and separated by size exclusion chromatography and density equilibrium gradient centrifugation. ...	1997	9013561
synaptic body movements in the sensory cells of lateral line organs in the urodele amphibian ambystoma mexicanum.	examination of the neuromasts in the tail of the living juvenile axolotl ambystoma mexicanum with interference contrast (nomarski) microscopy shows that their cellular structures can be identified in considerable detail. microscopy was performed with a 40 x water immersion objective or with a 100 x objective in a tail insertion chamber. thus the sensory hair bundles can be seen and their orientation can be determined. large spheres in the basal part of the sensory cells were predicted to be syna ...	1997	9119761
improved preservation of the subepidermal extracellular matrix in axolotl embryos using electron microscopical techniques based on cryoimmobilization.	the purpose of this metholdological survey was to find optimal methods for the fixation and demonstration of glycosaminoglycans, mainly hyaluronan, and proteoglycans, in subepidermal extracellular matrix (ecm) regions of axolotl embryos. we compared living ecm in the laser-scanning microscope (lsm) with chemically fixed or cryoimmobilized extracellular matrix in the transmission (tem) and scanning electron microscope (sem). the gel-like structure of living extracellular matrix in the lsm undoubt ...	1997	9087914
expression of integrins during axolotl limb regeneration.	limb regeneration in urodeles is achieved through the dedifferentiation of tissues at the amputation plane and through the production of the blastema. this tissue breakdown is possible by extensive alterations in molecules of the extracellular matrix. in this respect we describe the regulation of several integrins during such events. it was found that alpha 1 and beta 1 integrins were down-regulated as blastema formation proceeded. in contrast, the expression of alpha 3, alpha 6 and alpha v inte ...	1997	9079030
molecular biology of heart development in the mexican axolotl, ambystoma mexicanum.		1997	9505339
kinematics and efficiency of steady swimming in adult axolotls (ambystoma mexicanum)	the kinematics of steady swimming at a wide range of velocities was analysed using high-speed video recordings (500 frames s-1) of eight individuals of ambystoma mexicanum swimming through a tunnel containing stationary water. animals in the observed size range (0.1350.238 m total body length) prefer to swim at similar absolute speeds, irrespective of their body size. the swimming mechanism is of the anguilliform type. the measured kinematic variables the speed, length, frequency and ...	1997	9319776
glial fibrillary acidic protein and vimentin in radial glia of ambystoma mexicanum and triturus carnifex: an immunocytochemical study.	the molecular characterization of glial lineage cells in two urodele species, ambystoma mexicanum and triturus carnifex, has been investigated immunocytochemically with antibodies directed against intermediate filament proteins, glial fibrillary acidic protein (gfap) and vimentin. ambystoma astroglia shows clear gfap-immunopositivity and vimentin-immunonegativity. the condition in triturus is quite the opposite, showing only a strong vimentin immuno-reaction. in these urodele brain the astroglia ...	1997	9176731
isolation of mhc class i cdnas from the axolotl ambystoma mexicanum.	class i major histocompatibility complex (mhc) cdna clones were isolated from axolotl mrna by polymerase chain reaction (pcr) and by screening a cdna phage library. the nucleotide and predicted amino acid sequences show definite similarities to the mhc class ialpha molecules of higher vertebrates. most of the amino acids in the peptide binding region that dock peptides at their n and c termini in mammals are conserved. several amino acids considered to be important for the interaction of beta2-m ...	1997	9038100
regulation of intracellular ph in salamander retinal rods.	1. we measured intracellular ph (phi) in rods isolated from the retina of the axolotl salamander, ambystoma mexicanum, using the fluorescent indicator 2',7'-bis(carboxyethyl)-5(and -6)-carboxyfluorescein (bcecf). 2. the light exposures associated with data acquisition had no marked effect on phi. there was no sharp change between the value obtained from the first exposure of dark-adapted rods and subsequent readings. increasing the acquisition frequency from 1 to 10 min-1 either had no effect, o ...	1997	9023768
the polytypic species revisited: genetic differentiation and molecular phylogenetics of the tiger salamander ambystoma tigrinum (amphibia: caudata) complex.	we present a phylogenetic analysis of the ambystoma tigrinum complex, based on approximately 840 base pairs of mitochondrial-dna sequence from the rapidly evolving d-loop and an adjacent intron. our samples include populations of the continentally distributed species, a. tigrinum, plus all described species of mexican ambystomatids. sequence divergence is low, ranging from 0-8.5%, and most phylogenetic groupings are weakly supported statistically. we identified eight reasonably well-defined clad ...	1996	28568845
three muscle fibre types in the axial muscle of axolotl (ambystoma mexicanum shaw): a quantitative light- and electron microscopic study.	morphometric analysis by light microscopy of p-phenylene-diamine stained semithin sections of axolotl tail muscle revealed differences in the cross-sectional area of the fibres and in the number of mitochondria and of lipid inclusions per fibre, and indicated the presence of three distinct types of fibres. the tripartition was found to be statistically highly significant. representative fibres from each group established by light microscopic morphometry were subjected to an ultrastructural morph ...	1996	178448
antagonism of glutamate receptors by a chromatographic fraction from the exudate of the sea anemone phyllactis flosculifera.	in the search for new glutamate antagonists it seems promising to characterize the effects of venom from invertebrates that prey mainly on crustaceans. in this work, the exudate of the sea anemone phyllactis flosculifera was used as a source of this type of compound. the action of chromatographic fraction d from p. flosculifera was tested upon microion-tophoretically evoked glutamate responses in intracellular recordings from central neurons of the land snail zachrysia guanensis. bath applicatio ...	1996	8735243
histochemistry and role of nitric oxide synthase in the amphibian (ambystoma tigrinum) inner ear.	nicotinamide adenine dinucleotide phosphate reduced-diaphorase (nadph-d) histochemistry was investigated in the axolotl (ambystoma tigrinum) inner ear. hair cells showed an intense nadph-d reaction; afferent neurones also stained but less intensely than hair cells. effects of ng-nitro-l-arginine (l-noarg) on the basal discharge and mechanical responses of semicircular canal afferent neurones recorded extracellularly were also studied. l-noarg (1 mu m) diminished the basal discharge and the respo ...	1996	8907334
embryo surface morphology during post-gastrula development of the frog, bombina orientalis, as revealed by scanning electron microscopy.	to further study the morphology of the developing amphibian embryo, and to provide a basis for the characterization of abnormal embryogenesis, surface features of the bombina orientalis embryo during post-gastrula development were examined with the scanning electron microscope. ciliated cells similar to those reported for rama pipiens and ambystoma mexicanum were observed in the epidermis. epidermal secretory cells displaying large numbers of exocytotis apertures become prominent at the early ta ...	1996	500492
neural crest cell migration and pigment pattern formation in urodele amphibians.	this review deals with research on the development and differentiation of the neural crest (nc) in amphibians carried out during the past twenty years. first, earlier studies on the migration and differentiation of nc cells in vitro are summarized. these studies include the modes of nc cell migration and their differentiation into chondroblasts, perichondral cells, neurons, schwann cells and pigment cells (melanophores and xanthophores). then a summary is given on the development of cranial sens ...	1996	8735933
nucleotide sequence and expression of ribosomal protein s3 mrna during embryogenesis in the mexican axolotl (ambystoma mexicanum).	we have isolated and sequenced a full-length (0.9 kb) cdna clone of ribosomal protein s3 by subtraction hybridization using a single-stranded cdna library from stage 25-27 (tracer) and the mrna from stage 15-17 (driver) of embryonic mexican axolotl (ambystoma mexicanum). the axolotl is a unique animal model for studying heart development as well as myofibrillogenesis because it carries a mutation in gene c. the deduced amino acid sequence of axolotl s3 protein shows about 93.9% identity with hum ...	1996	8739028
effects of extracellular matrix molecules on subepidermal neural crest cell migration in wild type and white mutant (dd) axolotl embryos.	migration of neural crest (nc) derived pigment cells is restricted in the white mutant (dd) axolotl embryo (ambystoma mexicanum). transplantations between mutant and wild type embryos show that the extracellular matrix (ecm) of the white mutant is unable to support the migration of prospective pigment cells in wild type embryos (löfberg et al., 1989, dev. biol. 131:168-181). in the present study, we test the effects of various purified ecm molecules on nc cell migration in the subepidermal migra ...	1996	8739557
surface contraction and expansion waves correlated with differentiation in axolotl embryos. ii. in contrast to urodeles, the anuran xenopus laevis does not show furrowing surface contraction waves.	we have observed a number of contraction waves traversing the axolotl (ambystoma mexicanum) embryo (a urodelan amphibian) from the midblastula transition up to at least neural tube closure, and wished to learn if similar "differentiation waves" appear on the popular laboratory anuran amphibian, the south african clawed toad, xenopus laevis. time lapse video microscopy showed that no contraction waves are visible on the surface of xenopus from gastrulation through neurulation. it is possible that ...	1996	8877438
morphogenesis of the axolotl pronephric duct: a model system for the study of cell migration in vivo.	pronephric duct (pnd) morphogenesis is a critical early event in the development of the vertebrate excretory system. this structure is the exit channel for both pronephric and mesonephric filtrate, forms the ureteric bud of the metanephros and gives rise to the ductus deferens of the testis. in addition, the pnd and ureteric bud epithelia induce terminal differentiation of the mesonephric and metanephric mesenchyme, respectively. elongation of the pnd in all vertebrates involves active cell migr ...	1996	8877443
lens induction in axolotls: comparison with inductive signaling mechanisms in xenopus laevis.	amphibian lens induction is an embryonic process whose broad outlines are conserved between anurans and urodeles; however, it has been argued that some aspects of this process differ significantly between even closely related species. classical embryologists concluded that in some species direct contact between the optic vesicle and ectoderm was both necessary and sufficient to induce the ectoderm to form a lens, while in other species tissues other than the optic vesicle induce lens formation. ...	1996	8877449
a specific synthetic rna promotes cardiac myofibrillogenesis in the mexican axolotl.	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. however, the defect can be corrected by organ-culturing the mutant heart in the presence of rna from anterior endoderm or rna from endoderm mesoderm-conditioned medium. we constructed a cdna library from total conditioned medium rna in a pcdnaii expression vector. we scre ...	1996	8955002
insights into pigmentary phenomena provided by grafting and chimera formation in the axolotl.	the expression of pigmentation patterns in axolotl pigmentary mutants was observed following three types of experimental manipulations including chimera formation, reciprocal neural crest grafts, of gonadal primordia. three pigmentary genes were utilized including the wild type (d), white (d), and albino (a). in chimeras between white and albino embryos, melanoblasts from the white half crossed the graft interface to differentiate in albino skin. neural crest grafts from white embryos to albinos ...	1996	9125751
cardioventilatory responses to hypoxia and nacn in the neotenous axolotl.	ventilatory and cardiac responses to hypoxia, sodium cyanide (nacn), and intra-arterial injection of atropine, noradrenaline and dl-propranolol were investigated in the neotenous axolotl (ambystoma mexicanum). hypoxia elicited increased gill and lung ventilation and a tachycardia. gill ventilation and air-breathing were stimulated by nacn infused either into the ventilatory water stream or into the bloodstream. cardiac responses to nacn were complex, with an initial bradycardia followed by a tac ...	1996	9017844
nerve dependency of regeneration: the role of distal-less and fgf signaling in amphibian limb regeneration.	dlx-3, a homolog of drosophila dll, has been isolated from an axolotl blastema cdna library, and its expression in developing and regenerating limbs characterized. the normal expression pattern, and the changes that occur during experimental treatments, indicate a correlation between dlx-3 expression and the establishment of the outgrowth-permitting epidermis. dlx-3 is expressed at high levels in a distal-to-proximal gradient in the epidermis of developing limb buds, and is upregulated in the ap ...	1996	8951064
influence of insulin-like growth factors and insulin on the [35s]sulfate uptake by cartilage of the axolotl (ambystoma mexicanum).	the actions of mammalian insulin-like growth factors (igf-i and igf-ii) and insulin on skeletal growth of the axolotl, ambystoma mexicanum, were examined by monitoring the in vitro uptake of [35s]sulfate by cartilage. both growth factors stimulated sulfate uptake significantly at a concentration of 13 nm. the increase after incubation with 130 nm insulin was similar (uptake ca. 160% of control), but the effect was not significant. further, the binding of 125i-igf-i and 125i-igf-ii was studied in ...	1996	8921360
activation by mitogens and superantigens of axolotl lymphocytes: functional characterization and ontogenic study.	urodele amphibians have weak and slow immune responses compared to mammals and anuran amphibians. using new culture conditions, we tested the ability of lymphocytes of a well-studied salamander, the mexican axolotl (ambystoma mexicanum) to proliferate in vitro with diverse mitogenic agents. we demonstrated that the axolotl has a population of b lymphocytes that proliferate specifically and with a high stimulation index to the lipopolysaccharide (lps) known as a b-cell mitogen in mammals. this pr ...	1996	8881761
how to observe surface contraction waves on axolotl embryos.		1996	8877469
treatment of axolotls with retinoids for limb regeneration studies.		1996	8877467
a method for the isolation and culture of embryonic cardiomyocytes from mexican axolotl.		1996	8877466
urodele (e.g., axolotl) embryos in the undergraduate laboratory class: an essay describing a multifaceted learning experience.		1996	8877465
axolotls in the second grade.		1996	8877463
what insights into the developmental traits of urodeles does the study of interspecific hybrids provide?	natural and artificial hybrids represent an important source of material for developmental and evolutionary studies of urodeles. we review the available literature on hybrid salamanders, emphasizing the unique developmental insights that these organisms provide. of particular interest is the application of new molecular tools to identify dna markers for traditional characters in developmental research, and we discuss our own results using bulk segregant analysis to identify rapd markers for the ...	1996	8877462
molecular mechanisms in the control of limb regeneration: the role of homeobox genes.	axolotls are unique among vertebrates in their ability to regenerate lost appendages as adults. they provide the opportunity to study the mechanism of regeneration in vertebrates and are an inspiration to pursue the goal of appendage regeneration in humans. in this article, we review data on the role of homeobox-containing genes in the regulation of limb regeneration. as a group, these genes are important in pattern formation in the primary body axis, developing limbs and regenerating limbs. to ...	1996	8877453
what insights into vertebrate pigmentation has the axolotl model system provided?	amphibians have been judiciously exploited by developmental biologists for many years for studying basic developmental mechanisms in vertebrates. in this review, the contributions that have been made by urodeles, in particular the axolotl (ambystoma mexicanum), to the study of pigment cell biology are elaborated. pigment cell differentiation is described, and the wild-type pigment phenotype is contrasted to pigment mutants such as albino, axanthic, melanoid, and white. methods used for studying ...	1996	8877441
what mechanisms control neoteny and regulate induced metamorphosis in urodeles?	the mexican axolotl, like a number of other urodele species, is an obligatory neotene, completing its full life cycle without metamorphosis. metamorphosis can be induced with thyroid hormone, thyroid stimulating hormone, or stimulation of hypothalamic neurons. thus, neoteny represents a deviation from the standard course of amphibian ontogeny, affecting the thyroid axis at one or more levels. analysis of the thyroid axis at strategic ontogenic stages and after completed neotenic development sugg ...	1996	8877439
embryonic taste buds develop in the absence of innervation.	it has been hypothesized that taste buds are induced by contact with developing cranial nerve fibers late in embryonic development, since descriptive studies indicate that during embryonic development taste cell differentiation occurs concomitantly with or slightly following the advent of innervation. however, experimental evidence delineating the role of innervation in taste bud development is sparse and equivocal. using two complementary experimental approaches, we demonstrate that taste cells ...	1996	8620837
morphogenetic movements during axolotl neural tube formation tracked by digital imaging.	during neurulation in vertebrate embryos, epithelial cells of the neural plate undergo complex morphogenetic movements that culminate in rolling of the plate into a tube. resolution of the determinants of this process requires an understanding of the precise movements of cells within the epithelial sheet. a computer algorithm that allows automated tracking of epithelial cells visible in digitized video images is presented. it is used to quantify the displacement field associated with morphogenet ...	1996	28306034
expression of myosin heavy chain transcripts in normal and cardiac mutant mexican axolotls.	in this study, we have cloned a 1.0 kb myosin heavy chain (mhc) cdna by screening an axolotl heart cdna library with the monoclonal antibody mf20 against a light meromyosin (lmm) region of mhc. the nucleotide sequence analysis shows 85-86% homology at the amino acid and 78-81% homology at the nucleic acid level with mhc from other vertebrates. phylogenetic analyses suggest that axolotl beta-mhc forms a cluster with the myosin ii group of vertebrate striated muscles. within the myosin ii cluster, ...	1996	8932525
differential expression of c-protein isoforms in the developing heart of normal and cardiac lethal mutant axolotls (ambystoma mexicanum).	regulated assembly of contractile proteins into sarcomeric structures, such as a- and i-bands, is still currently being defined. the presence of distinct isoforms of several muscle proteins suggests a possible mechanism by which myocytes regulate assembly during myofibrillogenesis. of several muscle isoforms located within the a-band, myosin binding proteins (mybp) are reported to be involved in the regulation and stabilization of thick filaments during sarcomere assembly. the present confocal s ...	1996	8834470
distribution of keratan sulphate and chondroitin sulphate in wild type and white mutant axolotl embryos during neural crest cell migration.	in embryos of the white mutant axolotl, prospective pigment cells are unable to migrate from the neural crest (nc) due to a deficiency in the subepidermal extracellular matrix (ecm). this raises the question of the molecular nature of this functional defect. some pgs can inhibit cell migration on ecm molecules in vitro, and an excess of this class of molecules in the migratory pathways of neural crest cells might cause the restricted migration of prospective pigment cells seen in the white mutan ...	1996	8739556
regeneration of sensory cells after laser ablation in the lateral line system: hair cell lineage and macrophage behavior revealed by time-lapse video microscopy.	the regeneration of sensory hair cells in lateral line neuromasts of axolotls was investigated via nearly continuous time-lapse microscopic observation after all preexisting hair cells were killed by a laser microbeam. the laser treatments left neuromasts with one resident cell type, which was supporting cells. over the course of 1 week, replacement hair cells arose either directly via differentiation of cells present in the epithelium from the beginning of the time-lapse period or via the devel ...	1996	8551349
effects of the antiepileptic drug valproic acid on the development of the axolotl (ambystoma mexicanum): histological investigations.	in the amphibian ambystoma mexicanum, valproic acid (vpa) causes retarded development and malformations including neural tube defects. some of the observed abnormalities resemble exencephaly. we present the light microscopic characteristics of vpa-induced effects on the developing central nervous system (cns) as well as on other developing tissues of this species. to induce malformations, various concentrations of vpa were applied to embryos from blastula stage on, either as 24-h pulse or as con ...	1996	8983118
the structure, rearrangement, and ontogenic expression of db and jb gene segments of the mexican axolotl t-cell antigen receptor beta chain (tcrb).	we sequenced a total of 189 independent rearrangements in which the vb7.1 element is associated with cb1 (99 clones) or cb2 (90 clones) isotypes of the t-cell receptor (tcr) beta chain in the mexican axolotl. three stages of development were analyzed: 2.5 months, 10 months, and 25 months. three jb1 segments were associated with the vb-cb1 rearrangements and six jb2 segments with vb-cb2. as in other vertebrates, some amino acid positions were conserved in all jbetas (e. g., phe-108, gly-109, gly- ...	1996	8753858
hard tissue of teeth and their calcium and phosphate content in ambystoma mexicanum (urodela: ambystomatidae).	the wall of the pulp cavity, fracture faces and the demineralized surfaces of teeth from larvae and adults of ambystoma mexicanum were investigated by scanning electron microscopy (sem). calcium and phosphate contents were determined by microanalysis. the apical part of the tooth (crown, tooth apex) contains dentin canals. in the larva, these do not reach the enamel-dentin border but end below this border in front of a denser hard substance, possibly enameloid. the pedicel in the adult and the b ...	1996	8717330
expression of pax-6 during urodele eye development and lens regeneration.	regeneration of eye tissues, such as lens, seen in some urodeles involves dedifferentiation of the dorsal pigmented epithelium and subsequent differentiation to lens cells. such spatial regulation implies possible action of genes known to be specific for particular cell lineages and/or axis. hox genes have been the best examples of genes for such actions. we have, therefore, investigated the possibility that such genes are expressed during lens regeneration in the newt. the pax-6 gene (a gene th ...	1995	7761453
the identification and partial cloning by pcr of the gene for tyrosinase-related protein-1 in the mexican axolotl.	the tyrosinase gene family is currently composed of three members, tyrosinase and two tyrosinase-related proteins, trp-1 and trp-2. these three gene products have all been found to act in the synthesis of melanin pigments with the enzyme tyrosinase catalyzing the initial rate-limiting steps. thus far these genes have primarily been analyzed in higher vertebrates. we have used degenerate pcr primers to isolate a large fragment of an axolotl tyrosinase-related protein. sequence analysis of the ent ...	1995	7792254
immunohistochemical analysis of c-protein isoforms in cardiac and skeletal muscle of the axolotl, ambystoma mexicanum.	of the several proteins located within sarcomeric a-bands, c-protein, a myosin binding protein (mybp) is thought to regulate and stabilize thick filaments during assembly. this paper reports the characterization of c-protein isoforms in juvenile and adult axolotls, ambystoma mexicanum, by means of immunofluorescent microscopy and western blot analyses. c-protein and myosin are found specifically within the a-bands, whereas tropomyosin and alpha-actin are detected in the i-bands of axolotl myofib ...	1995	8581934
the epidermis is a source of directional information for the migrating pronephric duct in ambystoma mexicanum embryos.	in the urodele ambystoma mexicanum, the pronephric duct (pnd) is formed from a coherent group of cells that migrate from the pronephros to the cloaca along a pathway immediately ventral to the developing somites. the guidance cues used by the migrating pnd primordium to find the cloaca are a local property of the migration substratum, are temporally regulated, and are both polarized and oriented. since the pronephric duct migrates between two tissues--the underlying lateral mesoderm and the over ...	1995	8612962
identification and expression of a homologue of the murine hoxa5 gene in the mexican axolotl (ambystoma mexicanum).	an excellent model for studying heart development in vertebrates is the cardiac non-function lethal mutant (gene c) mexican axolotl, ambystoma mexicanum. in order to facilitate our analyses of the mutant system, we have undertaken a search for stage-specific molecular markers during embryonic development of the axolotl. we have concentrated on homeobox genes as suitable candidates for monitoring molecular changes during development. a 270-bp probe encoding a portion of the axolotl homeobox gene ...	1995	7557438
a "minimal essential mhc" and an "unrecognized mhc": two extremes in selection for polymorphism.	the high polymorphism of classical mhc molecules found in mammals is not simply the result of strong selection for pathogen resistance in the recent past, since there are virtually no examples of diseases caused by infectious pathogens for which resistance is determined by particular mhc haplotypes, and in the best-studied case, a particular aspect of malaria in humans, the selection is remarkably weak. we discuss three possibilities to explain high polymorphism in mammals: accumulating, merging ...	1995	7558083
regulation of hoxa expression in developing and regenerating axolotl limbs.	homeobox genes are important in the regulation of outgrowth and pattern formation during limb development. it is likely that homeobox genes play an equally important role during limb regeneration. we have isolated and identified 17 different homeobox-containing genes expressed by cells of regenerating axolotl limbs. of these, nearly half of the clones represent genes belonging to the hoxa complex, which are thought to be involved in pattern formation along the proximal-distal limb axis. in this ...	1995	7600989
erratic deposition of agrin during the formation of xenopus neuromuscular junctions in culture.	in order to disclose the mechanism that regulate synapse development we compared the distributions of agrin, acetylcholine receptors (achr) and a basal lamina heparan sulfate proteoglycan (hspg) in sections and cultures prepared from xenopus laevis and ambystoma mexicanum embryos. while agrin, achr and hspg may accumulate almost synchronously at synapses in vivo, agrin deposition usually lagged well behind the other synaptic markers during development in culture, and was not detectable at many d ...	1995	7601300
cloning, sequencing and expression of an isoform of cardiac c-protein from the mexican axolotl (ambystoma mexicanum).	c-protein, a myosin binding protein, is thought to regulate and stabilize thick filaments during assembly of sarcomeric a-bands. multiple isoforms of c-protein have been characterized in avian and mammalian systems. we now report the isolation and the nucleic acid sequence of a partial c-protein cdna clone from an axolotl heart cdna expression library in lambda gt11. the clone was isolated by screening the library with a heterologous monoclonal anti-c-protein antibody (mf1). sequence comparison ...	1995	7639739
expression of the axolotl homologue of mouse chaperonin t-complex protein-1 during early development.	molecular chaperones assist in the folding of proteins, but their role during development is not well understood. here we report the temporal and spatial expression pattern of the axolotl homologue of mouse chaperonin tcp-1 during normal amphibian embryogenesis and in several models of abnormal embryogenesis. a partial axolotl tcp-1 cdna (646 bp; 519 coding bp) isolated by 3' race pcr shows considerable homology to mouse tcp-1. developmental northerns and rt-pcr analyses of whole axolot1 embryos ...	1995	7841192
the third component of xenopus complement: cdna cloning, structural and functional analysis, and evidence for an alternate c3 transcript.	although the third component of complement has been purified from two amphibian species, xenopus laevis and the axolotl, only limited information is available about its primary structure in these species. we now present (a) 95% of the cdna sequence encoding c3 from a xenopus laevis/xenopus gilli (xenopus lg) hybrid (b) an analysis of the c3 convertase and factor i cleavage sites in xenopus c3, and (c) evidence for an alternative form of c3. the xenopus lg sequence has a 57% nucleotide and 52% am ...	1995	7875221
cloning and expression of the axolotl proto-oncogene ski.	in vitro and in vivo overexpression studies have demonstrated that the c-ski proto-oncogene can influence proliferation, morphological transformation and myogenic differentiation. we report the isolation and expression of an axolotl (ambystoma mexicanum) c-ski (aski) gene. sequence analysis revealed a high degree of nucleotide and predicted amino acid (aa) homology with mammalian and anuran c-ski, showing the highest conservation to xenopus laevis c-ski (74% nucleotide and 87% aa). northern anal ...	1995	7999783
evidence for a nuclear factor involved in c-myc rna degradation during axolotl oocyte maturation.	we have previously described an in vivo heterologous system which has allowed us to study the stability of different xenopus c-myc rna constructs injected into axolotl oocytes. in full-grown oocytes, degradation of c-myc rna does not occur. in mature oocytes treated with progesterone, transcripts containing the coding sequence of the gene are degraded, whereas those corresponding to the 3'utr (untranslated region) alone are stable. in order to study the role of nuclear or cytoplasmic components ...	1995	28306080
differential stability of xenopus c-myc rna during oogenesis in axolotl involvement of the 3' untranslated region in vivo.	we have used the axolotl oocyte (ambystoma mexicanum shaw) to study the stability of exogenously injected xenopus rnas. three different cellular developmental stages have been analysed: (1) the growing oocyte (stage iii-iv of vitellogenesis), (2) the full-grown oocyte at the end of vitellogenesis (stage vi) and (3) the progesterone-matured stage vi oocyte. three exogenous rnas have been synthesized in vitro from a c-myc xenopus cdna clone. one transcript is 2.3 kb long (full length), the second ...	1995	28306079
activin a and transforming growth factor-beta stimulate heart formation in axolotls but not rescue cardiac lethal mutants.	in the mexican axolotl (salamander), ambystoma mexicanum, a recessive cardiac lethal mutation causes an incomplete differentiation of the myocardium. mutant hearts lack organized sarcomeric myofibrils and do not contract throughout their lengths. we have previously shown that rna purified from normal anterior endoderm or from juvenile heart tissue is able to rescue mutant embryonic hearts in an in vitro organ culture system. under these conditions as many as 55% of formerly quiescent mutant hear ...	1995	8565053
characterization of an ultraviolet photoreception mechanism in the retina of an amphibian, the axolotl (ambystoma mexicanum).	spectral sensitivity measurements from the retina of the mexican salamander ambystoma mexicanum (the 'axolotl') were used to provide evidence for and to characterize an amphibian ultraviolet-sensitive photoreception mechanism. electroretinograms (transretinal voltage responses) were recorded from open eye cup preparations to analyze the spectral sensitivity of the retina. both dark-adapted and white light-adapted preparations exhibited a peak in sensitivity between 360-370 nm. under selective ch ...	1995	8552288
tissue boundaries and cell behavior during neurulation.	we have analyzed the dynamics of the boundaries between the neural plate and the epidermis and between the neural plate and the notoplate. our experiments confirm that these two boundaries have important roles in neurulation. measurements of the lengths of neural fold (the boundary between epidermis and neural plate) in embryos of axolotls and newts reveal that neural folds abutting the prospective brain decrease in length while neural folds abutting the prospective spinal cord increase in lengt ...	1995	7556911
the relationship between migration and chondrogenic potential of trunk neural crest cells in ambystoma mexicanum.	based on results of transplantation experiments, it has long been believed that trunk neural crest cells are incapable of chondrogenesis. when pigmented trunk neural crest cells of ambystoma mexicanum are transplanted to cranial levels of albino (a/a) embryos, the graft cells ultimately produce ectopic fins, but are incapable of following the chondrogenic cranial neural crest pathways. therefore, heterotopic transplantation does not expose these cells to the same environment experienced by crani ...	1995	28305867
uncoupling histogenesis from morphogenesis in the vertebrate embryo by collapse of the transneural tube potential.	we have shown that unidirectional pumping of na+ out of the neural tube's luminal fluids in amphibian embryos produces a large potential difference (40-90 mv, lumen negative to the abluminal surface). this transneural tube potential (tntp) is analogous to the na+ dependent transepithelial potential (tep) that exists across surface ectoderm. this tep is retained in ectoderm after it is internalized when the neural folds fuse to form the neural tube. the tntp can be markedly reduced for several ho ...	1995	7496037
protein synthesis and release by normal and lesioned axolotl peripheral nerves.	previous studies in urodeles (holder et al., 1982, j. physiol. 326:371; holder et al., 1984, proc. r. soc. lond. b 222:477; aaronson et al., 1995, neuroscience 66:201) have shown that regenerating axons of peripheral nerves tend to grow toward distal nerve stumps, which is consistent with the hypothesis that axonal growth may be stimulated by factors released from degenerating nerves. in the present study we used two-dimensional gel electrophoresis and autoradiography to compare the incorporatio ...	1995	7672042
the role of vertical and planar signals during the early steps of neural induction.	the classical einsteck-test (spemann and mangold, roux arch. dev. biol. 100: 599-638, 1924) and data from total exogastrulae (holtfreter, 1933) suggest that vertical signals are transmitted between the chordamesoderm (organizer) and reacting ectoderm in the early phase of neural induction. in contrast to these results with axoloti (urodeles), several authors observed the expression of neural specific genes in xenopus exogastrulae, isolated dorsal blastopore lip with adjacent ectoderm (open-face ...	1995	7577445
effects of melanocyte-stimulating hormone on wild-type and white axolotl neural crest cells.	the goals of the current research were twofold: to study the effects of melanocyte-stimulating hormone (msh) on undifferentiated axolotl (ambystoma mexicanum) neural crest cells and to determine whether wild-type or white mutant axolotl neural crest cells respond differently to msh or to either of two agonists of the msh signal transduction pathway (cholera toxin or n6,o2-dibutyryl adenosine 3',5'-monophosphate (dbcamp). we found that msh induces melanophore differentiation in axolotl neural cre ...	1995	7755596
development of branchiomeric and lateral line nerves in the axolotl.	the differentiation of neural crest and ectodermal placodes was examined in the axolotl in order to clarify the contribution of these tissues to the formation of the sensory ganglia of the branchiomeric and lateral line cranial nerves in salamanders. the most rostral branchiomeric nerves, the profundal and trigeminal nerves, appear to arise solely from an ectodermal placode and from neural crest, respectively. the sensory ganglia of the more caudal branchiomeric nerves--the facial, glossopharyng ...	1995	7636024
embryonic origin of amphibian taste buds.	despite numerous descriptive studies, the embryonic origin of vertebrate taste buds has never been experimentally determined. a number of different alternatives have been suggested for taste bud origins, including epibranchial placodes, the neural crest, and the local epithelium of the oropharyngeal cavity. the role of a series of epibranchial placodes and the cephalic neural crest, which together give rise to the cranial nerves innervating taste buds, was examined with regard to the development ...	1995	7750643
oriented growth of regenerating axons in axolotl forelimbs is consistent with guidance by diffusible factors from distal nerve stumps.	previous studies have shown that when peripheral nerves in axolotl limbs are cut and surgically misdirected, regenerating axons grow back to the original pathways and innervate their correct muscles. in the present study however, we demonstrate that when given a choice between their correct nerve stump and an incorrect stump (forearm flexor nerve), regenerating extensor cranialis nerve axons grow towards both pathways. this result suggests that the directed growth of regenerating axons in the pe ...	1995	7637870
electroreceptors and mechanosensory lateral line organs arise from single placodes in axolotls.	the lateral line system in salamanders consists of mechanoreceptive neuromasts and pit organs, distributed in lines on the head and trunk, and electroreceptive ampullary organs located adjacent to the cephalic lines of mechanoreceptors. although numerous studies have documented that neuromast and pit organs and the cranial nerves that innervate these receptors arise from a dorsolateral series of placodes, there is no agreement concerning the number of these placodes, the specific groups of recep ...	1995	7729575