Publications

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fine structure of the epidermal leydig cells in the axolotl ambystoma mexicanum in relation to their function.the fine structure of the leydig cells in the epidermis of the strictly aquatic adult axolotl ambystoma mexicanum resembles that of similar cells in larval salamanders. the major finding of this study is that the mucous secretion of the leydig cells is released into the intercellular spaces from which it is discharged through pores onto the surface of the epidermis where it forms a mucous layer to protect the skin.20092630544
organization of positional information in the axolotl limb.we have used the phenomenon of position-dependent growth stimulation, brought about by the confrontation of cells with dissimilar positional values, to reveal the organization of positional information in the center of the upper and lower arms of axolotls. when either humerus or radius was transplanted into either dorsal or posterior positions, extra growth leading to the formation of supernumerary digits occurred following amputation through the graft. however, transplants of humerus or radius ...20092769199
immunofluorescent, immunogold, and electrophoretic studies for desmin in embryonic hearts of normal and cardiac mutant mexican axolotls, ambystoma mexicanum.recessive mutant gene c for "cardiac nonfunction" in axolotls results in an absence of normal heart contractions in affected embryos due to a failure of myofibril formation. in the present study, the intermediate filament protein, desmin, is compared in developing normal and mutant hearts by means of two-dimensional gel electrophoresis, immunofluorescent microscopy, and immunoelectron microscopy. tissues were fixed in periodate-lysine-paraformaldehyde or paraformaldehyde-glutaraldehyde solutions ...20092681791
microarray and cdna sequence analysis of transcription during nerve-dependent limb regeneration.microarray analysis and 454 cdna sequencing were used to investigate a centuries-old problem in regenerative biology: the basis of nerve-dependent limb regeneration in salamanders. innervated (nr) and denervated (dl) forelimbs of mexican axolotls were amputated and transcripts were sampled after 0, 5, and 14 days of regeneration.200919144100
genic regions of a large salamander genome contain long introns and novel genes.the basis of genome size variation remains an outstanding question because dna sequence data are lacking for organisms with large genomes. sixteen bac clones from the mexican axolotl (ambystoma mexicanum: c-value = 32 x 10(9) bp) were isolated and sequenced to characterize the structure of genic regions.200919144141
evidence for directional selection at a novel major histocompatibility class i marker in wild common frogs (rana temporaria) exposed to a viral pathogen (ranavirus).whilst the major histocompatibility complex (mhc) is well characterized in the anuran xenopus, this region has not previously been studied in another popular model species, the common frog (rana temporaria). nor, to date, have there been any studies of mhc in wild amphibian host-pathogen systems. we characterise an mhc class i locus in the common frog, and present primers to amplify both the whole region, and specifically the antigen binding region. as no more than two expressed haplotypes were ...200919240796
induction of metamorphosis in axolotls (ambystoma mexicanum). 200920147244
axolotl (ambystoma mexicanum) limb and tail amputation. 200920147243
grafting axolotl (ambystoma mexicanum) limb skin and cartilage from gfp+ donors to normal hosts. 200920147242
axolotl (ambystoma mexicanum) embryonic transplantation methods. 200920147241
generation of transgenic axolotls (ambystoma mexicanum). 200920147240
axolotl (ambystoma mexicanum) in vitro fertilization. 200920147239
ambystoma mexicanum, the axolotl: a versatile amphibian model for regeneration, development, and evolution studies. 200920147230
effect of thyroid hormone concentration on the transcriptional response underlying induced metamorphosis in the mexican axolotl (ambystoma).thyroid hormones (th) induce gene expression programs that orchestrate amphibian metamorphosis. in contrast to anurans, many salamanders do not undergo metamorphosis in nature. however, they can be induced to undergo metamorphosis via exposure to thyroxine (t4). we induced metamorphosis in juvenile mexican axolotls (ambystoma mexicanum) using 5 and 50 nm t4, collected epidermal tissue from the head at four time points (days 0, 2, 12, 28), and used microarray analysis to quantify mrna abundances.200818267027
conserved pattern of otp-positive cells in the paraventricular nucleus and other hypothalamic sites of tetrapods.the paraventricular nucleus complex (pa) is a component of central neural circuitry that regulates several homeostatic variables. the paraventricular nucleus is composed of magnocellular neurons that project to the posterior pituitary and parvicellular neurons that project to numerous sites in the central nervous system. according to the revised prosomeric model, the paraventricular nucleus is located caudal to the eye stalk along the rostrocaudal dimension of the dorsal hypothalamic alar plate. ...200818331876
chytridiomycosis survey in wild and captive mexican amphibians.mexico, a rich country in terms of amphibian diversity, hosts about 375 described species. population declines have been documented for several species where it is evident that their habitat is being destroyed or modified. however, other species which inhabit pristine areas are declining as well. it has been suggested that the chytrid fungus batrachochytrium dendrobatidis (b.d.) may be one of the causes of the enigmatic declines in mexico. we surveyed a total of 45 localities, in 12 states acros ...200818648793
oleic acid loading does not add to the nephrotoxic effect of albumin in an amphibian and chronic rat model of kidney injury.under proteinuric conditions, ultrafiltrated albumin can induce an inflammatory and fibrotic response in proximal tubular cells. it is unclear whether albumin per se or compounds bound to albumin are nephrotoxic. some studies have supported the toxicity of albumin-bound fatty acids; however, these compared untreated, fatty acid containing, albumin and delipidated albumin. to prevent confounding by the delipidation procedure, we compared delipidated albumin and oleic acid (oa)-loaded delipidated ...200818653900
expression cloning of tmem16a as a calcium-activated chloride channel subunit.calcium-activated chloride channels (caccs) are major regulators of sensory transduction, epithelial secretion, and smooth muscle contraction. other crucial roles of caccs include action potential generation in characean algae and prevention of polyspermia in frog egg membrane. none of the known molecular candidates share properties characteristic of most caccs in native cells. using axolotl oocytes as an expression system, we have identified tmem16a as the xenopus oocyte cacc. the tmem16 family ...200818805094
chytridiomycosis in an aquarium collection of frogs: diagnosis, treatment, and control.the introduction of a new group of dendrobatid frogs to an established captive amphibian collection was followed by several acute mortalities in both resident and introduced frog populations. chytridiomycosis, caused by batrachochytrium dendrobatidis, was diagnosed by histology in two of the dead frogs. following the diagnosis, all amphibians were moved to a specially made quarantine room with strict handling protocols and treated with itraconazole. frogs, being terrestrial amphibians, were trea ...200818817004
pitx1 expression in developing and regenerating axolotl limbs.the expression of the homeobox transcription factor pitx1 was investigated in the mexican axolotl (ambystoma mexicanum) during limb development and regeneration by whole-mount mrna in situ hybridizations. this clone shares high amino acid identity with pitx1 from other vertebrates (92% xenopus; 87% chick; 75% human and mouse) within the region isolated. in the developing limbs, pitx1 was expressed in hindlimb mesenchyme, as has been reported in other species. the expression pattern in the hindli ...200818833906
transcriptional response of mexican axolotls to ambystoma tigrinum virus (atv) infection.very little is known about the immunological responses of amphibians to pathogens that are causing global population declines. we used a custom microarray gene chip to characterize gene expression responses of axolotls (ambystoma mexicanum) to an emerging viral pathogen, ambystoma tigrinum virus (atv).200818937860
working with oocyte nuclei: cytological preparations of active chromatin and nuclear bodies from amphibian germinal vesicles.the giant nucleus or germinal vesicle (gv) of amphibian oocytes presents a remarkable opportunity to examine nuclear structures in unprecedented levels of detail. by making use of spread preparations of gvs, it is possible to investigate the structure and function of transcription units in active chromatin and a variety of nuclear bodies, all within the limits of resolution of the light microscope. the basic method for producing gv spreads that is described here is based on simple manual dissect ...200818951160
ranavirus-associated mass mortality in imported red tailed knobby newts (tylototriton kweichowensis): a case report.a mass die-off of imported red tailed knobby newts (tylototriton kweichowensis) occurred in 2004 in belgium and the netherlands. in addition to massive infection with rhabdias tokyoensis, ranavirus was isolated from three dead newts examined virologically and the gene coding for the major capsid protein of the virus was sequenced. the isolate showed 99.8% similarity to the published sequence of frog virus 3. upon experimental infection of axolotls (ambystoma mexicanum) with this isolate, no mark ...200817449300
chondrogenesis and ossification of the lissamphibian pectoral girdle.knowledge of amphibian shoulder development is requisite for further understanding of gnathostome pectoral girdle evolution. fish and amniotes share few pectoral girdle elements, but modern amphibians exhibit a unique combination of traits that bridge the morphological gap between these two groups. i analyzed patterns of chondrogenesis, ossification, and bone histology of the pectoral girdles of two anuran species (xenopus laevis and bombina orientalis) and two urodele species (ambystoma mexican ...200817999401
electrogenic glutamate uptake is a major current carrier in the membrane of axolotl retinal glial cells.glutamate is taken up avidly by glial cells in the central nervous system. glutamate uptake may terminate the transmitter action of glutamate released from neurons, and keep extracellular glutamate at concentrations below those which are neurotoxic. we report here that glutamate evokes a large inward current in retinal glial cells which have their membrane potential and intracellular ion concentrations controlled by the whole-cell patch-clamp technique. this current seems to be due to an electro ...20082885752
the appearance of neural and glial cell markers during early development of the nervous system in the amphibian embryo.cell-type-specific antibodies have been used to follow the appearance of neurones and glia in the developing nervous system of the amphibian embryo. differentiated neurones were recognized with antibodies against neurofilament protein while glial cells were identified with antibodies against glial fibrillary acidic protein (gfap). the appearance of neurones containing the neurotransmitters 5-hydroxytryptamine and dopamine has been charted also. in xenopus, neurofilament protein in developing neu ...20082627893
mathematical model of the cupula-endolymph system with morphological parameters for the axolotl (ambystoma tigrinum) semicircular canals.by combining mathematical methods with the morphological analysis of the semicircular canals of the axolotl (ambystoma tigrinum), a system of differential equations describing the mechanical coupling in the semicircular canals was obtained. the coefficients of this system have an explicit physiological meaning that allows for the introduction of morphological and dynamical parameters directly into the differential equations. the cupula of the semicircular canals was modeled both as a piston and ...200819593455
a comparative proteomic analysis during urodele lens regeneration.to examine underlying mechanisms of urodele lens regeneration we have employed a proteomic analysis of 650 proteins involved in several signaling pathways. we compared expression of these proteins between the regeneration-competent dorsal iris and the regeneration-incompetent ventral iris in the newt. after a series of screenings we selected several proteins to evaluate their expression quantitatively on immunoblots. we then used these selected proteins to compare their expression between the do ...200818848527
regeneration in axolotls: a model to aim for!urodele amphibians such as the axolotl are the champions of tissue regeneration amongst vertebrates. these animals have mastered the ability to repair and replace most of their tissues following damage or amputation even well into adulthood. in fact it seems that the ability of these organisms to regenerate perfectly is not affected by their age. in addition to being able to regenerate, these animals display a remarkable resistance to cancer. they therefore represent a unique model organism to s ...200818814845
dual epithelial origin of vertebrate oral teeth.the oral cavity of vertebrates is generally thought to arise as an ectodermal invagination. consistent with this, oral teeth are proposed to arise exclusively from ectoderm, contributing to tooth enamel epithelium, and from neural crest derived mesenchyme, contributing to dentin and pulp. yet in many vertebrate groups, teeth are not restricted only to the oral cavity, but extend posteriorly as pharyngeal teeth that could be derived either directly from the endodermal epithelium, or from the ecto ...200818794902
glucose transporter distribution in the vessels of the central nervous system of the axolotl ambystoma mexicanum (urodela: ambystomatidae).the glut-1 isoform of the glucose transporter is commonly considered a reliable molecular marker of blood-brain barrier endothelia in the neural vasculature organized in a three-dimensional network of single vessels. the central nervous system of the axolotl ambystoma mexicanum is characterized by a vascular architecture that contains both single and paired vessels. the presence and distribution of the glut-1 transporter are studied in this urodele using both immunoperoxidase histochemistry and ...200818727107
identification of differentially expressed genes in 4-day axolotl limb blastema by suppression subtractive hybridization.the goal of our study was the identification of up-regulated genes during axolotl (ambystoma mexicanum) hindlimb regeneration 4 days after amputation using suppression subtractive hybridization (ssh). approximately 400 clones that harbored upregulated genes in regenerating blastema tissue were selected for sequence analysis. a blast homology search against ncbi non-redundant database and an ambystoma est database revealed 102 clones that showed homology to known sequences in genbank with annotat ...200818663994
a novel protein involved in heart development in ambystoma mexicanum is localized in endoplasmic reticulum.the discovery of the naturally occurring cardiac non-function (c) animal strain in ambystoma mexicanum (axolotl) provides a valuable animal model to study cardiomyocyte differentiation. in homozygous mutant animals (c/c), rhythmic contractions of the embryonic heart are absent due to a lack of organized myofibrils. we have previously cloned a partial sequence of a peptide cdna (n1) from an anterior-endoderm-conditioned-medium rna library that had been shown to be able to rescue the mutant phenot ...200818563628
neurotrophic regulation of epidermal dedifferentiation during wound healing and limb regeneration in the axolotl (ambystoma mexicanum).adult urodeles (salamanders) are unique in their ability to regenerate complex organs perfectly. the recently developed accessory limb model (alm) in the axolotl provides an opportunity to identify and characterize the essential signaling events that control the early steps in limb regeneration. the alm demonstrates that limb regeneration progresses in a stepwise fashion that is dependent on signals from the wound epidermis, nerves and dermal fibroblasts from opposite sides of the limb. when all ...200818533144
effects of nitrate on embryos of three amphibian species.embryos of three aquatic breeding amphibian species, ambystoma mexicanum, hyla chrysoscelis, and rana clamitans, were exposed to increasing levels (0, 5, 10, 30, 60, 100, 300, and 500 mg/l) of nitrate-n (no(3)-) in laboratory, static-renewal experiments. lethal effects were recorded from gosner stage 2 (h. chrysoscelis and r. clamitans) or harrison stage 2 (a. mexicanum) to time of hatching. date of hatching and length at hatching were also compared between treatments for a. mexicanum. no signif ...200818496633
multi-scale finite element modeling allows the mechanics of amphibian neurulation to be elucidated.the novel multi-scale computational approach introduced here makes possible a new means for testing hypotheses about the forces that drive specific morphogenetic movements. a 3d model based on this approach is used to investigate neurulation in the axolotl (ambystoma mexicanum), a type of amphibian. the model is based on geometric data from 3d surface reconstructions of live embryos and from serial sections. tissue properties are described by a system of cell-based constitutive equations, and pa ...200818408255
orexin-a immunoreactive cells and fibers in the central nervous system of the axolotl brain and their association with tyrosine hydroxylase and serotonin immunoreactive somata.orexin-a-like immunoreactivity in the axolotl brain was investigated by immunohistochemistry. immunoreactive somata formed a single group in the hypothalamus, but were distributed beyond several nuclei, namely, the ventral aspect of the nucleus preopticus posterior, dorsal aspect of the nucleus suprachiasmaticus and anterior aspect of the pars ventralis hypothalami. immunoreactive fibers were distributed throughout the brain from the olfactory bulb to the spinal cord except the cerebellum. the d ...200818378425
all about axolotls. 200818356918
analysis of the expression and function of wnt-5a and wnt-5b in developing and regenerating axolotl (ambystoma mexicanum) limbs.urodele amphibians are unique adult vertebrates because they are able to regenerate body parts after amputation. studies of urodele limb regeneration, the key model system for vertebrate regeneration, have led to an understanding of the origin of blastema cells and the importance of positional interactions between blastema cells in the control of growth and pattern formation. progress is now being made in the identification of the signaling pathways that regulate dedifferentiation, blastema morp ...200818336582
igx antibodies in the urodele amphibian ambystoma mexicanum.until recently, it was believed that urodele amphibians are able to synthesize only two immunoglobulin isotypes, igm and igy. we reinvestigated this issue in the iberian ribbed newt pleurodeles waltl and reported recently that this urodele expresses at least three isotypes: igm, igp and igy. in this study, we demonstrate that another urodele, ambystoma mexicanum, has also a third isotype whose amino acid sequence presents the highest homology with the amino acid sequence of xenopus igx. this iso ...200818280565
calcium waves.waves through living systems are best characterized by their speeds at 20 degrees c. these speeds vary from those of calcium action potentials to those of ultraslow ones which move at 1-10 and/or 10-20 nm s(-1). all such waves are known or inferred to be calcium waves. the two classes of calcium waves which include ones with important morphogenetic effects are slow waves that move at 0.2-2 microm s(-1) and ultraslow ones. both may be propagated by cycles in which the entry of calcium through the ...200818192175
regulation of dermal fibroblast dedifferentiation and redifferentiation during wound healing and limb regeneration in the axolotl.adult urodeles (salamanders) are unique in their ability to regenerate complex organs perfectly. the accessory limb model (alm) in the axolotl allows for the identification of signals from the wound epidermis, nerves and dermal fibroblasts that interact to regenerate a limb. in the present study, we have used the alm to identity the axolotl (ambystoma mexicanum) orthologue of twist (amtwist), a basic helix-loop-helix transcription factor that is involved in the regeneration of the dermis during ...200819046162
axolotl/newt. 200819030817
bone morphogenetic protein-4 and noggin signaling regulates pigment cell distribution in the axolotl trunk.wild-type (dark) and white mutant axolotl (ambystoma mexicanum) embryos were used to investigate the role of the secreted growth factor bone morphogenetic protein-4 (bmp-4) and its antagonist, noggin, in dorso-lateral trunk neural crest (nc) migration. implantation of a bmp-4-coated microbead caused a melanophore-free zone around the bead, reduction of the dorsal fin above the bead, and disappearance of myotome tissue. we established a novel method that allows controlled induction of protein syn ...200817662068
[changes in the sensitivity of axolotl eggs to the thermal action during maturation, fertilization and early cleavage]. 20085893410
[changes in sensitivity to heat in the embryonic development of axolotls]. 20085754704
the short toes mutation of the axolotl.the axolotl mutant strain, short toes (s/s), can regenerate spinal cord and tail, but not limbs. this makes s/s potentially very useful for limb regeneration studies. this mutant merits a new examination that integrates the original description of the mutant, existing experimental studies, new data and current thinking about stem cells and regeneration. there are still major gaps in information about this mutant; the gene(s) causing the defects has not yet been discovered, and even the histologi ...200717661741
bmp-4 and noggin signaling modulate dorsal fin and somite development in the axolotl trunk.bmp-4, a member of the tgf-beta superfamily of growth factors, is involved in various developmental processes. we investigated the effects of bmp-4 and its antagonist noggin on axolotl trunk development. implantation of bmp-4-coated microbeads caused inhibition of muscle and dorsal fin formation in the vicinity of the microbeads. at some distance, myotomes developed with reduced height but increased width, which was accompanied by increased cell proliferation. these effects could be modulated by ...200717654602
highly restricted diversity of tcr delta chains of the amphibian mexican axolotl (ambystoma mexicanum) in peripheral tissues.gammadelta t cells localize at mammalian epithelial surfaces to exert both protective and regulatory roles in response to infections. we have previously characterized the mexican axolotl (ambystoma mexicanum) t cell receptor delta (trd) chain. in this study, trd repertoires in spleen, liver, intestine and skin from larvae, pre-adult and adult axolotls were examined and compared to the thymic trd repertoire. a trdv transcript without n/d diversity, trdv1s1-trdj1, dominates the trd repertoires unt ...200717523213
a clonal analysis of neural progenitors during axolotl spinal cord regeneration reveals evidence for both spatially restricted and multipotent progenitors.complete regeneration of the spinal cord occurs after tail regeneration in urodele amphibians such as the axolotl. little is known about how neural progenitor cells are recruited from the mature tail, how they populate the regenerating spinal cord, and whether the neural progenitor cells are multipotent. to address these issues we used three types of cell fate mapping. by grafting green fluorescent protein-positive (gfp(+)) spinal cord we show that a 500 microm region adjacent to the amputation ...200717507409
characterization and expression of a maternal axolotl cyclin b1 during oogenesis and early development.the m phase promoting factor (mpf) is a dimer composed of a catalytic cdk1 subunit and a cyclin b regulatory subunit. we have characterized a cdna containing the entire coding sequence of an axolotl cyclin b1 protein that is able to promote mpf activity when added to a fraction from prophase i oocytes that contains monomeric cdk1. the axolotl cyclin b1 gene is expressed as a maternal mrna in oocytes and early embryos. its poly(a) tail length increases in metaphase ii oocytes and then decreases r ...200717428262
modulation of the reaction cycle of the na+:ca2+, k+ exchanger.ca(2+) concentration in retinal photoreceptor rod outer segment (os) strongly affects the generator potential kinetics and the receptor light adaptation. the response to intense light stimuli delivered in the dark produce potential changes exceeding 40 mv: since the ca(2+) extrusion in the os is entirely controlled by the na(+):ca(2+), k(+) exchanger, it is important to assess how the exchanger ion transport rate is affected by the voltage and, in general, by intracellular factors. it is indeed ...200717415556
role of myofibril-inducing rna in cardiac tnt expression in developing mexican axolotl.the mexican axolotl, ambystoma mexicanum, has been a useful animal model to study heart development and cardiac myofibrillogenesis. a naturally-occurring recessive mutant, gene "c", for cardiac non-function in the mexican axolotl causes a failure of myofibrillogenesis due to a lack of tropomyosin expression in homozygous mutant (c/c) embryonic hearts. myofibril-inducing rna (mir) rescues mutant hearts in vitro by promoting tropomyosin expression and myofibril formation thereafter. we have studie ...200717408593
isolation and characterization of axolotl npdc-1 and its effects on retinoic acid receptor signaling.retinoic acid, a key morphogen in early vertebrate development and tissue regeneration, mediates its effects through the binding of receptors that act as ligand-induced transcription factors. these binding events function to recruit an array of transcription co-regulatory proteins to specific gene promoters. one such co-regulatory protein, neuronal proliferation and differentiation control-1 (npdc-1), is broadly expressed during mammalian development and functions as an in vitro repressor of ret ...200717331771
transforming growth factor: beta signaling is essential for limb regeneration in axolotls.axolotls (urodele amphibians) have the unique ability, among vertebrates, to perfectly regenerate many parts of their body including limbs, tail, jaw and spinal cord following injury or amputation. the axolotl limb is the most widely used structure as an experimental model to study tissue regeneration. the process is well characterized, requiring multiple cellular and molecular mechanisms. the preparation phase represents the first part of the regeneration process which includes wound healing, c ...200718043735
a clash of traditions: the history of comparative and experimental embryology in sweden as exemplified by the research of gösta jägersten and sven hörstadius.until the 1940s research traditions were often imported from germany to sweden, and young scientists went to german universities to learn new techniques and get in touch with the latest ideas. in developmental biology, the comparative, phylogenetic embryology advocated most forcefully by ernst haeckel co-existed with the "entwickelungsmechanik" tradition developed by wilhelm his, wilheln roux and others partly as a reaction to haeckel's ideas. i use the zoology department at uppsala university a ...200718008099
evidence for balancing selection at the dab locus in the axolotl, ambystoma mexicanum.the axolotl (ambystoma mexicanum) has been characterized as immunodeficient, and the absence of major histocompatibility complex (mhc) class ii polymorphism has been cited as a possible explanation. here we present evidence for considerable allelic polymorphism at the mhc class ii dab locus for a sample of wild-caught axolotls. evidence that these sequences are the product of balancing selection for disease resistance is discussed.200718001306
a reduction of tropomyosin limits development of sarcomeric structures in cardiac mutant hearts of the mexican axolotl.the cardiac lethal mutation in mexican axolotl (ambystoma mexicanum) results in a lack of contractions in the ventricle of mutant embryos. previous studies have demonstrated that tropomyosin, a component of thin filaments, is greatly reduced in mutant hearts lacking myofibril organization. confocal microscopy was used to examine the structure and comparative amount of tropomyosin at heartbeat initiation and at a later stage. the formation of functional sarcomeres coincided with contractions in n ...200717990128
muscular derivatives of the cranialmost somites revealed by long-term fate mapping in the mexican axolotl (ambystoma mexicanum).the fate of single somites has not been analyzed from a comparative perspective with modern cell-marking methods. most of what we know is based on work using quail-chick chimeras. consequently, to what degree cell fate has been conserved despite the anatomical differences among vertebrates is unknown. we have analyzed the cell fate of the cranialmost somites, with the focus on somite two, in the mexican axolotl (ambystoma mexicanum). somite cells were marked by injection of dextran-fluorescein a ...200717976053
nerve-induced ectopic limb blastemas in the axolotl are equivalent to amputation-induced blastemas.adult urodeles (salamanders) are unique in their ability to regenerate complex organs perfectly. the recently developed accessory limb model (alm) in the axolotl provides an opportunity to identify and characterize the essential signaling events that control the early steps in limb regeneration. the alm demonstrates that limb regeneration progresses in a stepwise fashion that is dependent on signals from the wound epidermis, nerves and dermal fibroblasts from opposite sides of the limb. when all ...200717959163
migratory patterns and developmental potential of trunk neural crest cells in the axolotl embryo.using cell markers and grafting, we examined the timing of migration and developmental potential of trunk neural crest cells in axolotl. no obvious differences in pathway choice were noted for dii-labeling at different lateral or medial positions of the trunk neural folds in neurulae, which contributed not only to neural crest but also to rohon-beard neurons. labeling wild-type dorsal trunks at pre- and early-migratory stages revealed that individual neural crest cells migrate away from the neur ...200717183528
measurement of in vivo stress resultants in neurulation-stage amphibian embryos.in order to obtain the first quantitative measurements of the in vivo stresses in early-stage amphibian embryos, we developed a novel instrument that uses a pair of parallel wires that are glued to the surface of an embryo normal to the direction in which the stress is to be determined. when a slit is made parallel to the wires and between them, tension in the surrounding tissue causes the slit to open. under computer control, one of the wires is moved so as to restore the original wire spacing, ...200717237990
microarray analysis identifies keratin loci as sensitive biomarkers for thyroid hormone disruption in the salamander ambystoma mexicanum.ambystomatid salamanders offer several advantages for endocrine disruption research, including genomic and bioinformatics resources, an accessible laboratory model (ambystoma mexicanum), and natural lineages that are broadly distributed among north american habitats. we used microarray analysis to measure the relative abundance of transcripts isolated from a. mexicanum epidermis (skin) after exogenous application of thyroid hormone (th). only one gene had a >2-fold change in transcript abundance ...200716926121
the axolotl limb: a model for bone development, regeneration and fracture healing.among vertebrates, urodele amphibians (e.g., axolotls) have the unique ability to perfectly regenerate complex body parts after amputation. the limb has been the most widely studied due to the presence of three defined axes and its ease of manipulation. hence, the limb has been chosen as a model to study the process of skeletogenesis during axolotl development, regeneration and to analyze this animal's ability to heal bone fractures. extensive studies have allowed researchers to gain some knowle ...200716920050
molecular and immunohistochemical analyses of cardiac troponin t during cardiac development in the mexican axolotl, ambystoma mexicanum.the mexican axolotl, ambystoma mexicanum, is an excellent animal model for studying heart development because it carries a naturally occurring recessive genetic mutation, designated gene c, for cardiac nonfunction. the double recessive mutants (c/c) fail to form organized myofibrils in the cardiac myoblasts resulting in hearts that fail to beat. tropomyosin expression patterns have been studied in detail and show dramatically decreased expression in the hearts of homozygous mutant embryos. becau ...200716888779
inhibition of sonic hedgehog signaling leads to posterior digit loss in ambystoma mexicanum: parallels to natural digit reduction in urodeles.molecular mechanisms patterning the tetrapod limb, including anterior-posterior axis determination involving sonic hedgehog (shh), have received much attention, particularly in amniotes. anterior-posterior patterning in urodele amphibians differs radically from that of amniotes in that it shows a pronounced anterior-to-posterior sequence of digit development. in contrast, amniotes develop their digits almost simultaneously with a slight posterior-to-anterior polarity. here we use cyclopamine, an ...200717117438
localized co-transcriptional recruitment of the multifunctional rna-binding protein celf1 by lampbrush chromosome transcription units.the highly-extended transcription units of lampbrush chromosomes (lbcs) offer unique opportunities to study the co-transcriptional events occurring on nascent transcripts. using lbcs from amphibian oocytes, i investigated whether celf1, an rna binding protein involved in the regulation of alternative splicing, mrna stability and translation, is localized to active transcription units. antibodies raised against mammalian (cug-bp1) and amphibian (eden-bp) celf1 were used to immunostain lbc spreads ...200718095176
comparative analysis of xenopus vegt, the meso-endodermal determinant, identifies an unusual conserved sequence.the transcription factor, vegt, is the meso-endodermal determinant in xenopus laevis. we examined vegt orthologs from several anuran amphibians and the urodele amphibian, the mexican axolotl. in addition to the conserved t-box, the dna-binding domain, the orthologs share a conserved 57 amino acid domain at the c-terminal. most striking is a 17-nucleotide (nt) sequence near the 3' end of the open reading frame. the 17 nts are absolutely conserved among the anurans, whose last common ancestor live ...200717459091
urodele p53 tolerates amino acid changes found in p53 variants linked to human cancer.urodele amphibians like the axolotl are unique among vertebrates in their ability to regenerate and their resistance to develop cancers. it is unknown whether these traits are linked at the molecular level.200717903248
rna of amvegt, the axolotl orthologue of the xenopus meso-endodermal determinant, is not localized in the oocyte.the transcription factor, vegt, is the meso-endodermal determinant in xenopus laevis, and the localization of vegt rna to the vegetal cortex of the oocyte is an important starting point for embryonic patterning. we have cloned the vegt orthologue from the urodele amphibian, ambystoma mexicanum, the mexican axolotl. axolotl vegt (amvegt) is expressed zygotically in the presumptive mesoderm and rohon-beard neurons as in x. laevis, and its expression persists at the tip of the tail as with zebrafis ...200716920404
early gene expression during natural spinal cord regeneration in the salamander ambystoma mexicanum.in contrast to mammals, salamanders have a remarkable ability to regenerate their spinal cord and recover full movement and function after tail amputation. to identify genes that may be associated with this greater regenerative ability, we designed an oligonucleotide microarray and profiled early gene expression during natural spinal cord regeneration in ambystoma mexicanum. we sampled tissue at five early time points after tail amputation and identified genes that registered significant changes ...200717241119
proteolytic cleavage of acth in corticotropes of sexually mature axolotls (ambystoma mexicanum).immunohistochemical analysis of the pituitary of sexually mature axolotls revealed both acth(1-39)-related and alpha-msh-related immunoreactivity present in corticotropic cells located in the rostral anterior pituitary. gel filtration analysis indicated that the acth(1-39)-sized immunoreactivity and the alpha-msh-sized immunoreactivity detected in acid extracts of the axolotl anterior pituitary were present in a ratio in a range between 1:1 and 1:0.6. reversed-phase hplc analyses indicated that ...20078284252
interaction of cells of wolffian duct and mesothelium during initial growth period of mullerian ducts in the axolotl (ambystoma mexicanum). 20074117072
[the epiphysis of axolotl]. 200714301966
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 ...20079617586
[properties of neurons of the tectal portion of the visual system of the axolotl ambystoma mexicanum].in the tectum opticum of the adult neotenic a. mexicanum, responses of single neuronal units to diffuse illumination and moving visual stimuli have been investigated. of 111 unites investigated, 27 are presented by tectal neurons, their maximum distribution being observed at a depth of 500-600 mu. in superficial layers 9 ipsi-elements were found; their receptive fields are located in the antero-dorsal part of the visual field, at both sides of the body axis. among the units identified as the ter ...20071020556
[model studies of the effect of structural changes in cleaving embryo on electrical parameters of cellular interactions].two models of the embryo developing from one initial cell by cleavage division are considered. equivalent electrical schemes were constructed, changes in electrical coupling coefficient (kec) and input resistance (ri) of the embryos during cleavage were estimated. considerable influence of cleavage-related changes of membrane parameters on kec and ri appears at the first five--ten cleavages and essentially depends on the ratio of contact and incontact membrane resistances. a comparison of the es ...20077317491
developmental and evolutionary origins of the vertebrate dentition: molecular controls for spatio-temporal organisation of tooth sites in osteichthyans.the rainbow trout (oncorhynchus mykiss) as a developmental model surpasses both zebrafish and mouse for a more widespread distribution of teeth in the oro-pharynx as the basis for general vertebrate odontogenesis, one in which replacement is an essential requirement. studies on the rainbow trout have led to the identification of the initial sequential appearance of teeth, through differential gene expression as a changing spatio-temporal pattern, to set in place the primary teeth of the first ge ...200616496402
crystal structure of axolotl (ambystoma mexicanum) liver bile acid-binding protein bound to cholic and oleic acid.the family of the liver bile acid-binding proteins (l-babps), formerly called liver basic fatty acid-binding proteins (lb-fabps) shares fold and sequence similarity with the paralogous liver fatty acid-binding proteins (l-fabps) but has a different stoichiometry and specificity of ligand binding. this article describes the first x-ray structure of a member of the l-babp family, axolotl (ambystoma mexicanum) l-babp, bound to two different ligands: cholic and oleic acid. the protein binds one mole ...200616555310
conjecture: can continuous regeneration lead to immortality? studies in the mrl mouse.a particular mouse strain, the mrl mouse, has been shown to have unique healing properties that show normal replacement of tissue without scarring. the serendipitous discovery that the mrl mouse has a profound capacity for regeneration in some ways rivaling the classic newt and axolotl species raises the possibility that humans, too, may have an innate regenerative ability. we propose this mouse as a model for continuous regeneration with possible life-extending properties. we will use the class ...200616608389
conserved roles for oct4 homologues in maintaining multipotency during early vertebrate development.all vertebrate embryos have multipotent cells until gastrulation but, to date, derivation of embryonic stem (es) cell lines has been achieved only for mouse and primates. es cells are derived from mammalian inner cell mass (icm) tissue that express the class v pou domain (pouv) protein oct4. loss of oct4 in mice results in a failure to maintain icm and consequently an inability to derive es cells. here, we show that oct4 homologues also function in early amphibian development where they act as s ...200616651543
the rise of the boy-genius: psychological neoteny, science and modern life.the mid-20th century saw the rise of the boy-genius, probably because a personality type characterized by prolonged youthfulness is advantageous both in science and modern life generally. this is the evolution of 'psychological neoteny', in which ever-more people retain for ever-longer the characteristic behaviours and attitudes of earlier developmental stages. whereas traditional societies are characterized by initiation ceremonies marking the advent of adulthood, these have now dwindled and di ...200616750307
nitric oxide in the amphibian (ambystoma tigrinum) lateral line.nicotinamide adenine dinucleotide phosphate reduced-diaphorase (nadph-d) histochemistry was investigated in the axolotl (ambystoma tigrinum) lateral line. hair cells of neuromast organs of the head skin and neurons of the postotic ganglia showed a significant nadph-d reaction. multiunit recording of neuromast afferent activity was also performed. nitric oxide synthase inhibitor n omega-nitro-l-arginine methyl ester (l-name) produced an initial slight excitation followed by a significant inhibiti ...200616225991
ontogeny of immunoglobulin expression in the mexican axolotl.the ontogeny of immunoglobulin (ig) synthesis was followed at both cellular and serological levels in the mexican axolotl (ambystoma mexicanum) using polyclonal antibodies recognizing all ig molecules and a set of monoclonal antibodies (mabs) specific for the c mu and cv heavy ig chain isotypes and for the light chain constituents shared by igm and igy molecules. clusters of igm- and of igy-synthesizing lymphocytes, often located in separate sites, are first present in spleen sections of 7-week- ...20062698798
wnt/beta-catenin signaling regulates vertebrate limb regeneration.the cellular and molecular bases allowing tissue regeneration are not well understood. by performing gain- and loss-of-function experiments of specific members of the wnt pathway during appendage regeneration, we demonstrate that this pathway is not only necessary for regeneration to occur, but it is also able to promote regeneration in axolotl, xenopus, and zebrafish. furthermore, we show that changes in the spatiotemporal distribution of beta-catenin in the developing chick embryo elicit apica ...200617114576
terminal nerve-derived neuropeptide y modulates physiological responses in the olfactory epithelium of hungry axolotls (ambystoma mexicanum).the vertebrate brain actively regulates incoming sensory information, effectively filtering input and focusing attention toward environmental stimuli that are most relevant to the animal's behavioral context or physiological state. such centrifugal modulation has been shown to play an important role in processing in the retina and cochlea, but has received relatively little attention in olfaction. the terminal nerve, a cranial nerve that extends underneath the lamina propria surrounding the olfa ...200616855098
differential expression of tropomyosin during segmental heart development in mexican axolotl.the mexican axolotl, ambystoma mexicanum, serves as an intriguing model to investigate myofibril organization and heart development in vertebrates. the axolotl has a homozygous recessive cardiac lethal gene "c" which causes a failure of ventricular myofibril formation and contraction. however, the conus of the heart beats, and has organized myofibrils. tropomyosin (tm), an essential component of the thin filament, has three known striated muscle isoforms (tpm1alpha, tpm1kappa, and tpm4alpha) in ...200616741969
identification of the non-specific cytotoxic cell receptor protein 1 (nccrp1) in regenerating axolotl limbs.the teleost non-specific cytotoxic cells (ncc) are evolutionary precursors of the mammalian natural killer (nk) cells and an important element of innate immunity. the non-specific cytotoxic cell receptor protein (nccrp1) is a characteristic cell surface protein with main functions in target cell recognition and cytotoxicity with sequence information available for many species of fish. we have isolated a cdna encoding the axolotl homologue of fish nccrp1 out of limb regeneration blastema and anal ...200616676190
a germline gfp transgenic axolotl and its use to track cell fate: dual origin of the fin mesenchyme during development and the fate of blood cells during regeneration.the development of transgenesis in axolotls is crucial for studying development and regeneration as it would allow for long-term cell fate tracing as well as gene expression analysis. we demonstrate here that plasmid injection into the one-cell stage axolotl embryo generates mosaic transgenic animals that display germline transmission of the transgene. the inclusion of scei meganuclease in the injections (thermes, v., grabher, c., ristoratore, f., bourrat, f., choulika, a., wittbrodt, j., joly, ...200616387293
[myocardial regeneration in ambystoma mexicanum after surgical injury].ventricular resection of the heart of ambystoma mexicanum was performed and the type of tissue that restored the lesion and if it is by hypertrophy or hyperplasia of myocardium, were evaluated. masson's trichrome stain indicated that 5 days after resection, the gap was occupied with a blood clot surrounded by collagen fibres (83 +/- 6%) and muscle (10 +/- 3%) and the rest of area (7 +/- 2%) free of tissue. a proportion of 50 +/- 4 and 90 +/- 2% was muscular tissue, 10 and 30 days after injury. t ...200616366167
limb regeneration in axolotl: is it superhealing?the ability of axolotls to regenerate their limbs is almost legendary. in fact, urodeles such as the axolotl are the only vertebrates that can regenerate multiple structures like their limbs, jaws, tail, spinal cord, and skin (the list goes on) throughout their lives. it is therefore surprising to realize, although we have known of their regenerative potential for over 200 years, how little we understand the mechanisms behind this achievement of adult tissue morphogenesis. many observations can ...200617205184
tropomodulin expression in developing hearts of normal and cardiac mutant mexican axolotl.in the axolotl, ambystoma mexicanum, a simple, recessive cardiac-lethal mutation in gene "c" results in the hearts of c/c homozygous animals being deficient in sarcomeric tropomyosin (tm) and failing to form mature myofibrils. subsequently, the mutant hearts do not beat. a three-step model of myofibril assembly recently developed in cell culture prompted a reassessment of the myofibril assembly process in mutant hearts using a relatively new late marker for thin filament assembly, tropomodulin ( ...200617303917
[proliferative activity of the pigment epithelium and regenerating retinal cells in ambystoma mexicanum].cellular sources of retinal regeneration and proliferative activity of the cells taking part in retina restoration have been studied in axolotls using 3h-thymidine. the cells of ciliary-terminal zone proved to be the main source of retinal restoration. besides these cells, the pigmented cells of the iris inner and outer layers and pigment epithelium cells can take part in this process. morphological stages of retinal regeneration have been established and regular changes in the level of prolifer ...20066657169
a lethal mutant gene in the mexican axolotl.gene ph was discovered in a wild-type axolotl male received from mexico city. larvae homozygous for this gene become recognizable by their lighter color at hatching or shortly after. the development of their forelimbs is retarded, and all limbs are of subnormal length because of the reduction in length of their long bones. many affected larvae die without feeding, and very few survive beyond their third month. at death, older larvae usually show abnormalities of the renal system, edema, ascites, ...2006608947
[radioautographic study of the cellular proliferation of retinal pigment epithelium in axolotls].the proliferative activity of the pigment epithelium cells in the axolotl eyes was studied using 3h-thymidine in two types experiments: after the removal of lens, iris and retina and upon the cultivation of the pigment epithelium pieces in the cavity of lens-less eye. irrespective of the operation type, the level of proliferation of the pigment epithelium cells changed regularly with respect to the time of observation. in the intact eye, the level of proliferation of the pigment epithelium cells ...20066521975
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 ...200610810037
[nuclear behavior of embryonic cells and growing oocytes from the clawed toad in the cytoplasm of maturing axolotl oocytes].the behaviour of the nuclei of the x. laevis vitellogenic oocytes was studied by their transplantation into the cytoplasm of the axolotl maturing oocytes. after the germinal vesicle breakdown, in the case the transplanted nuclei were located close to each other a common giant spindle united the chromosomes of all transplanted nuclei. a mosaic spindle united sometimes the chromosomes of the two amphibian species. the embryonic nuclei transplanted in the cytoplasm of the maturing oocytes formed, a ...20066504501
matrix metalloproteinase production in regenerating axolotl spinal cord.in urodele amphibian spinal cord regeneration, the ependymal cells lining the central canal remodel the lesion site to favor axonal regrowth. we profiled the production of matrix metalloproteinases by injury-reactive mesenchymal ependymal cells in vivo and in vitro and found that matrix metalloproteinases are involved in this remodeling process in the axolotl (ambystoma mexicanum). the production of cell-associated matrix metalloproteinases in vivo was shown to be identical to that in our cultur ...200611013020
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 ...20069824557
[recovery of acetylcholinesterase activity in the axolotl embryo following inhibition with the organophosphorus inhibitor gd-7].the restoration of acetylcholinesterase (ache) activity in axolotl ambystoma mexicanum embryo after treatment at 38-42 stages with irreversibly ache-inhibiting gd-7 phosphororganic inhibitor in concentrations, significantly decreasing ache activity level, but not interfering with ontogenesis has been studied. the rate of ache activity restoration in gd-7 treated axolotl embryo depends on the level of the enzyme restraint and the stage of the embryo development. the value of maximal restoration o ...20063696676
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