| cloning of cdnas encoding retinoic acid receptors rar gamma 1, rar gamma 2, and a new splicing variant, rar gamma 3, from aambystoma mexicanum and characterization of their expression during early development. | to analyze retinoic acid (ra) receptor (rar) expression during early development in the urodele embryo, we have isolated cdnas for four members of the axolotl (ambystoma mexicanum) rar family, namely rar alpha (nr1b1), arar gamma 1 (nr1b3a), arar gamma 2 (nr1b3b), and a new splicing variant of arar gamma 2, arar gamma 3 (nr1b3c), which contains an insertion of five hydrophobic amino acids in the c-terminal region of the dna binding domain. the temporal expression pattern of the rar gamma isoform ... | 2000 | 11004482 |
| directed axonal growth towards axolotl limb blastemas in vitro. | limb amputation in urodele amphibia is followed by formation of a blastema, which subsequently develops into a complete limb with normal pattern of innervation. in this study, we investigated the effects of axolotl limb blastemas on axonal growth in gels of collagen and extracellular matrix (matrigel). when peripheral nerves with attached dorsal root ganglia were cultured in collagen gels together with blastemas, axonal outgrowth was markedly increased compared with control preparations. blastem ... | 2000 | 10996470 |
| all-trans-retinoic acid and all-trans-retinoyl-beta-d-glucuronide alter the development of axolotl embryos (ambystoma mexicanum) in vitro. | retinoids are involved in several physiological processes and are used in the treatment of various skin disorders. therapy with retinoids during pregnancy may induce severe embryotoxic effects like craniofacial and cardiovascular malformations in the developing embryo. we investigated the effects of all-trans-retinoic acid (atra) and all-trans-retinoyl-beta-d-glucuronide (atrag) in an amphibian embryotoxicity assay with ambystoma mexicanum (axolotl) as an alternative in vitro method. embryos wer ... | 2000 | 10877004 |
| elongation of axolotl tailbud embryos requires gpi-linked proteins and organizer-induced, active, ventral trunk endoderm cell rearrangements. | application of phosphatidylinositol-specific phospholipase c to early tailbud stage axolotl embryos reveals that a specific subset of morphogenetic movements requires glycosylphosphatidylinositol (gpi)-linked cell-surface proteins. these include pronephric duct extension, "gill bulge" formation, and embryonic elongation along the anteroposterior axis. the work of kitchin (1949, j. exp. zool. 112, 393-416) led to the conclusion that extension of the notochord provided the motive force driving ant ... | 2000 | 10864458 |
| analysis of cranial neural crest migratory pathways in axolotl using cell markers and transplantation. | we have examined the ability of normal and heterotopically transplanted neural crest cells to migrate along cranial neural crest pathways in the axolotl using focal dii injections and in situ hybridization with the neural crest marker, ap-2. dii labeling demonstrates that cranial neural crest cells migrate as distinct streams along prescribed pathways to populate the maxillary and mandibular processes of the first branchial arch, the hyoid arch and gill arches 1-4, following migratory pathways s ... | 2000 | 10821772 |
| 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 |
| alteration of cardiac myofibrillogenesis by liposome-mediated delivery of exogenous proteins and nucleic acids into whole embryonic hearts. | a precise organization of contractile proteins is essential for contraction of heart muscle. without a necessary stoichiometry of proteins, beating is not possible. disruption of this organization can be seen in diseases such as familial hypertrophic cardiomyopathy and also in acquired diseases. in addition, isoform diversity may affect contractile properties in such functional adaptations as cardiac hypertrophy. the mexican axolotl provides an uncommon model in which to examine specific protein ... | 2000 | 10794163 |
| apical epithelial cap morphology and fibronectin gene expression in regenerating axolotl limbs. | urodele amphibians (salamanders) are unique among adult vertebrates in their ability to regenerate limbs. the regenerated structure is often indistinguishable from the developmentally produced original. thus, the two processes by which the limb is produced - development and regeneration - are likely to use many conserved biochemical and developmental pathways. some of these limb features are also likely to be conserved across vertebrate families. the apical ectodermal ridge (aer) of the developi ... | 2000 | 10706145 |
| the epithelium of the tongue of ambystoma mexicanum. ultrastructural and histochemical aspects. | the distribution pattern of taste buds and goblet cells and histochemical and ultrastructural aspects of the tongue epithelium of ambystoma mexicanum are here described. this study is also concerned with the developmental stages and origins of the epithelial cells. pavement cells and goblet cells of the stratum superficiale are replaced by basal cells of the stratum germinativum in larvae and neotenous adults. the pavement cells of the larvae are characterized by a marginal layer of mucin grana. ... | 1999 | 10609049 |
| axolotl mhc architecture and polymorphism. | the mhc of the urodele amphibian ambystoma mexicanum consists of multiple polymorphic class i loci linked, so far as yet known, to a single class ii b locus. this architecture is very different from that of the anuran amphibian xenopus. the number of class i loci in the axolotl can vary from 6 to 21 according to the haplotypes as shown by cdna analysis and southern blot studies in families. these loci can be classified into seven sequence groups with features ranging from the class ia to the cla ... | 1999 | 10508264 |
| expression of mmp-9 and related matrix metalloproteinase genes during axolotl limb regeneration. | one of the earliest events in limb regeneration is the extensive remodeling of the extracellular matrix (ecm). matrix metalloproteinases (mmps) are a family of matrix degrading enzymes that have been identified in both normal and disease states. using rt-pcr and cdna library screening, we have isolated sequences homologous to four different mmp genes. the spatial and temporal expression of one of these, mmp-9, has been analyzed during axolotl limb regeneration. northern blot analysis identifies ... | 1999 | 10474160 |
| the axolotl as an animal model for the comparison of 3-d ultrasound with plain film radiography. | we assessed the usefulness of an animal model, the axolotl (ambystoma mexicanum), in comparing 3-d ultrasound (3-d us) and plain film radiographs. hindlimbs were amputated from 5 animals, at either the zeugopodial or stylopodial level, and each regenerating limb was imaged 16 times with 3-d us and 14 times with plain film x ray over 315 days. us images were acquired with a siemens sonoline versa pro and a 10-mhz linear array transducer. for 3-d us images, the probe was translated in a motor-driv ... | 1999 | 10461726 |
| axolotl/newt. | | 1999 | 10443382 |
| the cardiac neural crest in ambystoma mexicanum. | to establish whether a region of the cranial neural crest contributes cells to the developing heart of ambystoma mexicanum (axolotl), as it does in many other vertebrates, we constructed a fate map for the neural crest in late neurula stage (stage 19-20) embryos. the fluorescent vital dye, dil, was used as the lineage label. the various regions of the cranial neural folds were identified in relation to such landmarks as the developing forebrain, midbrain and hindbrain, and the appearance and ext ... | 1999 | 10410907 |
| sonic hedgehog (shh) expression in developing and regenerating axolotl limbs. | sonic hedgehog (shh) expression is detectable in the posterior mesenchyme of many developing vertebrate limbs. we have isolated an rt-pcr fragment from the axolotl, ambystoma mexicanum, that has high identity to other vertebrate shh genes. we describe the localization of this transcript during development and regeneration and in response to tissue grafts and retinoic acid (ra) exposure in the axolotl. even though axolotl digits show a reversed polarity of differentiation (anterior [a] to posteri ... | 1999 | 10404648 |
| genetic analysis of steel and the pg-m/versican-encoding gene axpg as candidates for the white (d) pigmentation mutant in the salamander ambystoma mexicanum. | vertebrate non-retinal pigment cells are derived from neural crest (nc) cells, and several mutations have been identified in the mexican axolotl ambystoma mexicanum (ambystomatidae) that affect the development of these cell lineages. in "white" (d) mutant axolotls, premigratory nc cells differentiate as pigment cells, yet fail to disperse, survive, or both, and this leads to a nearly complete absence of pigment cells in the skin. previous studies revealed that d affects pigment cell development ... | 1999 | 10370116 |
| changes of the lingual epithelium in ambystoma mexicanum. | changes in the lingual epithelium during ontogenesis and after induced metamorphosis in ambystoma mexicanum are described as observed by light microscopy and scanning electron microscopy. the epithelium of the tongue is always multilayered in the larva as well as in the adult. it consists of a stratum germinativum with little differentiated basal cells and a stratum superficiale (superficial layer) with specialized superficial cells and goblet cells. usually, there are more than two layers becau ... | 1998 | 10099954 |
| the role of innervation in the development of taste buds: insights from studies of amphibian embryos. | amphibian embryos have long been model organisms for studies of development because of their hardiness and large size, as well as the ease with which they can be experimentally manipulated. these particular advantages have allowed us recently to test the role of innervation in the development of vertebrate taste buds using embryos of an aquatic salamander, the axolotl. the predominant model of taste bud genesis has been one of neural induction, in which ingrowing sensory neurites induce taste bu ... | 1998 | 9929586 |
| structure of mhc class i and class ii cdnas and possible immunodeficiency linked to class ii expression in the mexican axolotl. | despite the fact that the axolotl (ambystoma spp. a urodele amphibian) displays a large t-cell repertoire and a reasonable b-cell repertoire, its humoral immune response is slow (60 days), non-anamnestic, with a unique igm class. the cytotoxic immune response is slow as well (21 days) with poor mixed lymphocyte reaction stimulation. therefore, this amphibian can be considered as immunodeficient. the reason for this subdued immune response could be an altered antigenic presentation by major histo ... | 1998 | 9914918 |
| expression of the third component of complement, c3, in regenerating limb blastema cells of urodeles. | in this study we have shown that complement component c3 is expressed in the regenerating tissue during urodele limb regeneration. c3 was expressed in the dedifferentiated regeneration blastema and in the redifferentiated limb tissues in the axolotl, amblystoma mexicanum, and in notophthalmus viridescens. this expression was verified by immunofluorescent staining using an ab against axolotl c3 and by in situ hybridization with an axolotl c3 cdna probe. in the early stages of regeneration c3 appe ... | 1998 | 9862713 |
| retinoic acid and thyroid hormone may function through similar and competitive pathways in regenerating axolotls. | the objective of this study was to determine whether thyroid hormone (th) would interfere with retinoic acid (ra), which proximalizes axolotl larvae regenerate limb pattern. ra and th are ligands for members of the steroid hormone thyroid hormone nuclear binding protein superfamily which form functional homodimers, but may also form stable heterodimers with the rxr protein and may recognize identical dna sequences. th alone does not affect limb pattern but induces metamorphosis in regenerating a ... | 1998 | 9846384 |
| expression of msx-2 during development, regeneration, and wound healing in axolotl limbs. | msx genes are transcription factors that are expressed during embryogenesis of developing appendages in regions of epithelial-mesenchymal interactions. various lines of evidence indicate that these genes function to maintain embryonic tissues in an undifferentiated, proliferative state. we have identified the axolotl homolog of msx-2, and investigated its expression during limb development, limb regeneration, and wound healing. as in limb buds of higher vertebrates, axolotl msx-2 is expressed in ... | 1998 | 9846383 |
| 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 |
| 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 |
| 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 |
| structure, diversity, and repertoire of vh families in the mexican axolotl. | the mexican axolotl v(h) segments associated with the igh c mu and c nu isotypes were isolated from anchored pcr libraries prepared from spleen cell cdna. the eight new v(h) segments found bring the number of v(h) families in the axolotl to 11. each v(h) had the canonical structural features of vertebrate v(h) segments, including residues important for the correct folding of the ig domain. the distribution of ser agc/t (agy) and tcn codons in axolotl v(h) genes was biased toward agy in complemen ... | 1998 | 9570539 |
| cellular plasticity among axolotl neural crest-derived pigment cell lineages. | many of the factors and mechanisms guiding the migration/differentiation of neural crest cells that give rise to a number of distinguishable cell types, including all dermal and epidermal pigment cells, remain unknown. the axolotl possesses three pigment cell types that differentiate according to specific developmentally programmed sequences and contribute to pigment pattern in the adult. a single lineage of the crest that becomes restricted to one of three pigment cell types gives us the opport ... | 1998 | 9523334 |
| immunolocalization of aromatic l-amino acid decarboxylase, tyrosine hydroxylase, dopamine, and serotonin in the forebrain of ambystoma mexicanum. | to improve basic knowledge about the neurochemical organization of the urodele brain, and to study discrepancies in the localization of monoaminergic markers, we immunohistochemically charted the distribution of four such markers (tyrosine hydroxylase, aromatic l-amino acid decarboxylase, dopamine, and serotonin) in the axolotl (ambystoma mexicanum) forebrain. catecholaminergic and serotoninergic systems were found in similar locations to those seen in other urodela. as seen in other vertebrates ... | 1998 | 9518271 |
| wide tissue distribution of axolotl class ii molecules occurs independently of thyroxin. | unlike most salamanders, the mexican axolotl (ambystoma mexicanum) fails to produce enough thyroxin to undergo anatomical metamorphosis, although a "cryptic metamorphosis" involving a change from fetal to adult hemoglobins has been described. to understand to what extent the development of the axolotl hemopoietic system is linked to anatomical metamorphosis, we examined the appearance and thyroxin dependence of class ii molecules on thymus, blood, and spleen cells, using both flow cytometry and ... | 1998 | 9510551 |
| 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 |
| 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 |
| 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 |
| identification of cdna clones encoding hmg 2, a major protein of the mexican axolotl hydrocortisone-sensitive thymocytes. | we have identified and analyzed cdna clones encoding a major 26 kda protein of the hmg1-2 family which is abundant in the cytoplasm and nucleus of axolotl hydrocortisone-sensitive thymocytes. the axolotl hmg2 protein is very similar to proteins belonging to the hmg1-2 family, from teleost fish to mammals. all the molecular features of the hmg1-2 proteins are conserved, including the high proportion of basic and aromatic residues, and the characteristic acidic c-terminus tail. the 3'-untranslated ... | 2003 | 8654668 |
| 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 |
| confrontation of developing melanophore bars of dark and white axolotls with endogenous dark-embryo mannose-binding lectin correlates with melanophore bar disruption. | lectins are carbohydrate-binding proteins suggested to be important in embryonic cell adhesion/differentiation. dark and white axolotls contain an endogenous mannose-binding lectin that is especially prevalent during larval melanophore pattern formation (martha et al., 1990). to determine if this lectin can alter melanophore patterning, lectin extracts have been isolated from dark embryos by affinity chromatography. the main protein band is 44k on sds-page. dark and white embryos at the early ch ... | 1995 | 7659679 |
| effect of induced metamorphosis on the immune system of the axolotl, ambystoma mexicanum. | metamorphosis was induced in neotenic axolotls by immersion of the animals in a solution of thyroid hormone. hematology of the axolotls was examined before, during, and after metamorphosis. there was a transient decrease in numbers of certain white blood cells during metamorphic climax and a permanent shift in the pattern of circulating cells. the eosinophilic granulocyte was the dominating leukocyte type in neotenes and in metamorphosing animals up to midclimax. lymphocytes and neutrophilic gra ... | 1995 | 7789746 |
| three-dimensional gradients of voltage during development of the nervous system as invisible coordinates for the establishment of embryonic pattern. | we are interested in the generation of endogenous electric fields associated with ionic currents driven through the vertebrate embryo by the transepithelial potential of its surface ectoderm. using a non-invasive vibrating electrode for the measurement of ionic current, we have provided measurements of currents traversing amphibian embryos, and a preliminary report of the internal, extracellular voltage gradient under the neural plate which polarizes the embryo in the rostral/caudal axis (metcal ... | 1995 | 7734729 |