Publications

regulation by thyroid hormones of terminal differentiation in the skeletal dorsal muscle. ii. urodelan amphibians.	in the urodelan amphibian pleurodeles waltlii, spontaneous anatomical metamorphosis was correlated with an increase in the serum level of thyroxine (t4). it was also accompanied by a change in the myofibrillar atpase profile of the dorsal skeletal muscle; fibers of larval type were gradually replaced by the adult fiber types i, ii a, and ii b. likewise, a myosin isoenzymic transition was observed in dorsal muscle, larval isomyosins were replaced by adult isoforms. in a related species, ambystoma ...	1987	2957262
antibody diversity in amphibians. noninbred axolotls used the same unique heavy chain and a limited number of light chains for their anti-2,4-dinitrophenyl antibody responses.	noninbred axolotls (ambystoma mexicanum, amphibia, urodela) were immunized with trinitrophenylated sheep red blood cells (tnp-srbc) and anti-2,4-dinitrophenyl (dnp)/tnp antibodies were individually purified by affinity chromatography. the isolated igm-like antibodies were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sds-page) and isoelectric focusing (ief) under reducing conditions. the sds-page and ief-separated heavy (h) and light (l) chains were electroblotted onto n ...	1987	3106061
characterization of axolotl heavy and light immunoglobulin chains by monoclonal antibodies.	axolotl specific antibodies to 2,4-dinitrophenyl (dnp) were purified by affinity chromatography from the sera of animals immunized with 2,4,6-trinitrophenylated sheep red blood cells (tnp-srbc). the purified anti-tnp/dnp antibodies, when analyzed by sds-page, were constituted of high molecular weight molecules, which in reducing conditions, were separated into heavy 72-88 kd and light 27-30 kd polypeptides. the axolotl heavy antibody chains strongly bound concanavalin-a and migrate faster in sds ...	1987	2449389
reformation of the pattern of neuromuscular connections in the regenerated axolotl hindlimb.	retrograde neuronal tracing with horseradish peroxidase (hrp) was used to determine the position in the spinal cord of motor neurone pools innervating muscles in the regenerated axolotl hindlimb. this method allows a detailed analysis of the accuracy of reformation of neuromuscular connections. the results show that regenerated distal limb muscles are reinnervated by motor neurones in the same region of the cord as those that innervate normal control distal limb muscles but that proximal muscles ...	1987	3652997
a test of the punctuated-cycling hypothesis in ambystoma forelimb regenerates: the roles of animal size, limb innervation, and the aneurogenic condition.	the punctuated-cycling (pc) hypothesis [39] predicts that the proportion of actively cycling (ac) cells within the blastema influences the rate of limb regeneration in urodele amphibians. to test this, we compared the rate of regeneration and the parameters of the pc hypothesis in small and large ambystoma mexicanum larvae and in aneurogenic limbs of ambystoma maculatum. aneurogenic limbs regenerated more slowly than limbs of small axolotls, but considerably faster than limbs of large axolotls. ...	1987	3428513
regeneration of descending axons in the spinal cord of the axolotl.	horseradish peroxidase was used to describe the positions and approximate numbers of neurones with axons that descend to the lumbar spinal cord in normal axolotls and axolotls whose spinal cord had been transected 3-23 months previously. three to 4 months after the transection approximately 10% of the axons had grown across the cut and returned to the lumbar spinal cord whereas 23 months after the transection the number and distribution of these cells were approaching those of the controls.	1988	3399135
reformation of specific neuromuscular connections during axolotl limb regeneration: evidence that the first contacts are correct.	retrograde neuronal tracing with horseradish peroxidase was used to determine the position in the spinal cord of the motor neurone pools of a proximal (biceps) and a distal (extensor digitorum) limb muscle at various times during axolotl limb regeneration. it was found that from the earliest stages of muscle redifferentiation (as judged by light and electron microscopic analysis) the vast majority of axons innervating the regenerating muscles came from cells within the bounds of the normal motor ...	1988	3224559
connections between the nucleus isthmi and the tectum in larval and post-metamorphic axolotls.	the nucleus isthmi (ni) is the primary relay for the frog's ipsilateral visuotectal projection. using electrophysiological methods, ipsilateral visuotectal activity has been recorded in thyroxine-treated, postmetamorphic axolotls but not in larval axolotls. in order to determine whether changes in isthmotectal projections are responsible for this change in electrophysiological responsiveness, we have investigated the connections between the tectum and the ni using horseradish peroxidase. our res ...	1988	3351504
induction of mesodermal tissues by acidic and basic heparin binding growth factors.	the inducing activity of two heparin binding growth factors hbgf-1 (prostate epithelial cell growth factor; acidic pi) and hbgf-2 (fibroblast growth factor; basic pi) from bovine brain has been tested on totipotent ectoderm from early amphibian (xenopus laevis, ambystoma mexicanum) embryos. both factors induced, at high concentrations, mostly compact spheres surrounded by a non-epidermal epithelium. when the concentration or time of incubation was reduced, large muscle inductions frequently orga ...	1988	2451566
paraboloid of axolotl retinal photoreceptor and bovine pituitary thyrotropin fraction share an antigen.	lenses of newts (genera notophthalmus, triturus, cynops) regenerate from irises in the presence of retinae of larval frogs (rana) or adult salamanders (hynobius, ambystoma), species which are themselves incapable of lens regeneration from the iris. in newts, bovine pituitary thyrotropin preparation nih-tsh-b8 can also stimulate lens regeneration from the iris. an antiserum against nih-tsh-b7 (purified as is nih-tsh-b8), absorbed with bovine lutropin preparation nih-lh-b9, cross-reacts with bovin ...	1988	3121378
thyroxine and triiodothyronine in plasma and thyroids of the neotenic and metamorphosed axolotl ambystoma mexicanum: influence of trh injections.	circulating levels of t3 and t4, as well as t3 and t4 content of the thyroid glands were measured by radioimmunoassay in the neotenic and metamorphosed axolotl ambystoma mexicanum. in the two experiments which were performed plasma t4 concentrations were more elevated in metamorphosed axolotls, especially in the first experiment (2.12 +/- 0.40 ng/ml vs. 369 +/- 30 pg/ml). t3 plasma values which were only estimated in the second experiment were about five times higher in metamorphosed animals (63 ...	1988	3131185
injection of an antibody against a p21 c-ha-ras protein inhibits cleavage in axolotl eggs.	the presence of a ras protein was demonstrated in cleaving axolotl eggs by selective immunoprecipitation with a polyclonal antibody against a peptide encoded by the c-ha-ras oncogene, cellular homolog of the v-ha-ras oncogene of harvey rat sarcoma virus. injection of this antibody into axolotl oocytes subjected to progesterone treatment does not prevent meiotic maturation. injection of the same antibody into a blastomere of axolotl eggs at the 2- or 4-cell stage causes cleavage arrest in the des ...	1988	3277177
[hormonal determination of the differentiation of striated skeletal muscle in urodele amphibians].	in the urodelan amphibian pleurodeles waltlii, spontaneous external metamorphosis was correlated with an increase in the serum level of thyroxine (t4). within the same period, a change occurred in the myofibrillar atpase profile of the dorsal skeletal muscle; fibres of larval type were gradually replaced by transitional fibres (type iic), then by adult fibres of the types i, iia, and iib. likewise, a myosin isoenzymic transition was observed. in larval animals, myosin electrophoresis revealed 3 ...	1988	2973102
luteinizing hormone-releasing hormone induces thyroxine release together with testosterone in the neotenic axolotl ambystoma mexicanum.	in male neotenic axolotls ambystoma mexicanum plasma concentrations of thyroxine (t4) and testosterone were increased following intravenous injection of 10 micrograms luteinizing hormone-releasing hormone. a dose of 50 micrograms influenced only plasma t4 levels. this observation suggests for the first time that a hypothalamic hormone is capable of stimulating the thyroidal axis in the neotenic axolotl.	1988	3056776
differential cytolocalization of prosomes in axolotl during oogenesis and meiotic maturation.	the prosomes, a novel type of small rna-protein complex previously characterized in avian and mammalian cells, were isolated from axolotl (ambystoma mexicanum) oocytes and identified by sedimentation analysis and protein composition. the prosomal nature of these particles was further ascertained by immunoblot analysis with anti-duck prosome monoclonal antibodies. by in vitro [35s]methionine labelling, de novo synthesis of prosomal proteins could be detected neither during oogenesis nor meiotic m ...	1988	3075616
binding of adrenergic ligands to liver plasma membrane preparations from the axolotl, ambystoma mexicanum; the toad, xenopus laevis; and the australian lungfish, neoceratodus forsteri.	the beta-adrenergic ligand iodocyanopindolol (icp) bound specifically to hepatic plasma membrane preparations from the axolotl, ambystoma mexicanum (bmax, 40 fmol/mg protein (p) at free concentration above 140 pm; kd, 42 pm); the toad, xenopus laevis (bmax, 200 fmol/mg p at 1 nm; kd, 300 pm); and the australian lungfish, neoceratodus forsteri (bmax, 100 fmol/mg p at 5 nm). for the lungfish, the scatchard plot was curved showing two classes of binding site with kd's of 20 and 500 pm. neither the ...	1988	2847957
a synapse-specific carbohydrate at the neuromuscular junction: association with both acetylcholinesterase and a glycolipid.	with the aim of investigating the roles of carbohydrates in synapse formation, we have characterized a synapse-specific saccharide at the vertebrate neuromuscular junction. two lectins of similar specificity (dolichos biflorus agglutinin, dba, and vicia villosa-b4 agglutinin, vva-b4) stain synaptic but not extrasynaptic regions of the rat muscle fiber surface and thus define a synapse-specific carbohydrate. using these and other probes, we show that the carbohydrate moiety concentrated at the ne ...	1988	3346730
factors involved in the formation and stabilization of cell aggregates obtained from amphibian embryonic explants.	the effect of factors influencing the formation and stability of animal and vegetal aggregates from xenopus laevis and ambystoma mexicanum was examined in the light and scanning electron microscopes. at extreme values of ph the surface coat covering the vegetal aggregates is dissolved and dissociation may take place. animal aggregates are more resistant. at high tonicities vegetal aggregates may be dissociated, and in the animal aggregates the epidermal differentiation is suppressed. in the abse ...	1988	3370680
ionic mechanism for the generation of horizontal cell potentials in isolated axolotl retina.	the ionic mechanism of horizontal cell potentials was investigated in the isolated retina of the axolotl ambystoma mexicanum. the membrane potentials of both receptors and horizontal cells were recorded intracellularly while the ionic composition of the medium flowing over the receptor side of the retina was changed. the membrane potential of the horizontal cell is highly depender side of the retina was changed. the membrane potential of the horizontal cell is highly dependent on the extracellul ...	1988	202664
myocardial cell relationships during morphogenesis in normal and cardiac lethal mutant axolotls, ambystoma mexicanum.	sarcomere formation has been shown to be deficient in the myocardium of axolotl embryos homozygous for the recessive cardiac lethal gene c. we examined the developing hearts of normal and cardiac mutant embryos from tailbud stage 33 to posthatching stage 43 by scanning electron microscopy in order to determine whether that deficiency has any effect on heart morphogenesis. specifically, we investigated the relationships of myocardial cells during the formation of the heart tube (stage 33), the in ...	1988	3213830
actions of excitatory amino acid acid agonists and antagonists on the primary afferents of the vestibular system of the axolotl (ambystoma mexicanum).	in order to determine the nature of the transmitter in the synapse between hair cells and primary afferent fibers, both resting and evoked spike activity of vestibular system afferents were recorded. excitatory amino acid agonists and antagonists were applied by micro perfusion. excitatory amino acid agonists consistently increased the firing rate of these afferents. the rank order in potencies of the agonists tested was: kainate greater than or equal to quisqualate greater than d-aspartate grea ...	1988	3052698
a quantitative analysis of glial cell coupling in the retina of the axolotl (ambystoma mexicanum).	the strength of gap junctional coupling of radial glial cells (müller cells) in the isolated axolotl retina was assessed by monitoring the spread of dye between cells, and by injecting current into one cell and recording the voltage response in surrounding cells. dye injected into one müller cell spread to surrounding müller cells, and could be detected up to 130 micron away, i.e. over 4 times the mean müller cell spacing of 30 micron. injecting 1 na of current into a müller cell evoked response ...	1988	3224259
the organization of the cardiac ganglion of the axolotl (ambystoma mexicanum).	the heart of the axolotl ambystoma mexicanum was studied with histochemical methods to determine the distribution of neurons containing acetylcholine esterase, catecholamines and 5-hydroxytryptamine. the cardiac ganglion is made up of cholinergic nerve fibers and somata, and of catecholaminergic fibers. small intensely fluorescent cells were found along blood vessels in the pericardial wall at the base of the heart, but not in the heart itself, except, in a few instances, in the region bordering ...	1988	3209798
the location of cues promoting selective reinnervation of axolotl muscles.	the selective reinnervation of muscles suggests that muscles have intrinsic recognition cues that promote selective synaptogenesis. for example, the anterior and posterior heads of the axolotl iliotibialis (ilt) muscle are preferentially reinnervated by their original motoneurons even after surgically exchanging them. the nature and location of cues that promote such selectivity are unknown, although previous work suggests that the muscle fibers themselves might harbor the relevant molecules. to ...	1988	3171683
identification of pigment cells during early amphibian development (triturus alpestris, ambystoma mexicanum).	the purpose of the present investigation was to provide and apply a methodological manual with which the distribution, patterning and relationship of melanophores and xanthophores can be analyzed during early amphibian development. for demonstration of the methods, which include ultrastructural, histochemical and biochemical approaches, triturus alpestris and ambystoma mexicanum (axolotl) embryos are used. these two species differ conspicuously in their larval pigment patterns, showing alternati ...	1988	3141059
regenerating afferent fibers stimulate the recovery of mauthner cell dendritic branching in the axolotl.	in the medulla of the axolotl (ambystoma mexicanum), mauthner cells (m-cells) occur as a pair of large identifiable neurons at the level of entry of the vestibular nerve (nviii). each receives synapses from the ipsilateral nviii; the terminals can be identified as club endings and are restricted to a specific set of m-cell dendritic branches. we have examined these branches for morphologic changes following long-term deafferentation in the presence and absence of nerve regeneration. deafferentat ...	1988	3411367
the distribution of fibronectin and tenascin along migratory pathways of the neural crest in the trunk of amphibian embryos.	it is generally assumed that in amphibian embryos neural crest cells migrate dorsally, where they form the mesenchyme of the dorsal fin, laterally (between somites and epidermis), where they give rise to pigment cells, and ventromedially (between somites and neural tube), where they form the elements of the peripheral nervous system. while there is agreement about the crest migratory routes in the axolotl (ambystoma mexicanum), different opinions exist about the lateral pathway in xenopus. we in ...	1988	2470571
ir-met and ir-leu enkephalin content in the axolotl brain (ambystoma mexicanum).	the peptides met- and leu-enkephalin were identified in the telencephalon, rombencephalon, diencephalon and hypophysis of ambystoma mexicanum brain by radioimmunoassay procedure. the met-enkephalin was the predominant peptide present in the axolotl brain in contrast with leu-enkephalin, except in the hypophysis where the ratio met/leu was 2.2/l. the clear differences in the concentration between enkephalins through a submammalian brain species as ambystoma genus and the possibility that leu-enke ...	1988	3419559
hypersensitivity to light of the iris (sphincter pupillae) of the albino axolotl (ambystoma mexicanum).	as is common for amphibians, the sphincter pupillae of the axolotl contracts in vitro in response to illumination with visible light. 1. in a comparison of photomechanical responses of albino and normally pigmented axolotls, similar time courses and maxima of force development were found. 2. the dependence of isometric active force development on the length of the sphincter pupillae is similar to that of other smooth muscles. 3. the action spectrum of the axolotl is similar to the absorption spe ...	1988	3209975
a molecular marker for cell guidance information in the axolotl embryo.	previous studies from this laboratory suggested that the elongation of the pronephric duct (pnd) in the axolotl ambystoma mexicanum is directed by an adhesion gradient along the migrating cells' substratum. we have also shown that cranial neural crest (cnc) cells are able to follow the pnd guidance information, for which these cells serve as useful probes (s.l. zackson and m.s. steinberg, (1986) dev. biol. 117, 342-353). these experiments allow the construction of a map of the cell guidance info ...	1988	3378673
monoclonal antibodies to axolotl immunoglobulins specific for different heavy chains isotypes expressed by independent lymphocyte subpopulations.	an immunoblotting analysis of purified axolotl immunoglobulins (ig) separated by sds-page reveals two heavy (h) chains isotypes: a 76 kda chain recognized by the monoclonal antibody (mab) 33.45.1 and a 66-68 kda doublet recognized by the mab 33.39.2. the 76 kda chain is associated to high molecular weight (hmw) ig molecules and the 66-68 kda h chains are associated to low molecular weight (lmw) ig of 172 kda. both h chains isotypes are linked to identical light (l) chains, labelled in immunoblot ...	1988	3136082
effect of transferrin on amphibian limb regeneration: a blastema cell culture study.	in order to study mitogenic control during axolotl limb regeneration, we have developed a primary blastema cell culture as a very sensitive bioassay for blastema mitogens. transferrin, an iron-binding glycoprotein which has been shown to be the neurotrophic factor for muscle cells, is the mitogen which has been analysed in the present report. addition of approximately 2 μg human transferrin/ ml of serum-free culture medium enhances blastema cell proliferation 11-fold over control levels and 2-fo ...	1988	28305565
accessory limb production by nerve-induced cell proliferation.	the deviation of large limb nerves to a more proximal skin wound yielded a high proportion of accessory limb responses in different age groups of ambystoma mexicanum (axolotls). in some instances the deviated nerve was positioned on skin previously grafted from an animal of different age and pigmentation from that of the host. grafts were found not to be a necessary prerequisite for accessory limb induction, but the presence of wound epithelium was required. the rule of distal morphogenesis was ...	1988	3291642
superinnervation enhances the dendritic branching pattern of the mauthner cell in the developing axolotl.	mauthner cells (m-cells) occur as a pair of large, uniquely identifiable neurons at ear level in the hindbrain of premetamorphic amphibians. each receives synapses from the ipsilateral vestibular nerve (nviii); these morphologically distinctive terminals, or club endings, are confined to the proximoventral surface and branches of the m-cell lateral dendrite. we have superinnervated this portion of the m-cell to examine the extent to which forming afferent contacts regulate the growth and branchi ...	1988	3346721
progressive patterning precedes somite segmentation in the mexican axolotl (ambystoma mexicanum).	beginning at mid-neurulation, a wave of somite segmentation passes down the axolotl body axis in a cephalocaudal direction. at 20 degrees c a somite forms every 2.57 hr. fate-mapping of the presomitic mesoderm indicates that the primordia for the next few somites occupy nearly the same space that they will after segmentation, but that the remaining somites are densely packed in tip of the tail bud. brief heat shocks at 37 and 38.5 degrees c reveal that within the first of these two zones, there ...	1988	3342928
surface markers of axolotl lymphocytes as defined by monoclonal antibodies.	in an attempt to identify urodele amphibian lymphocyte subpopulations by their surface markers, we prepared hybridomas from balb/c mice spleen immunized with axolotl (ambystoma mexicanum) blood and splenic leucocytes and purified immunoglobulins. sixty-five hybridomas were selected and subsequently subcloned. among numerous monoclonal antibodies (mabs) thus obtained, four mabs were extensively characterized by immunoblotting, single and double fluorescence and immunohistology. mab 34.38.6 recogn ...	1988	3127327
change in the level of free amino acids in the regenerating limb of ambystoma mexicanum.		1988	3412355
effects of forelimb amputation on protein synthesis in spinal cord of the axolotl.		1988	3412354
intercalary limb regeneration after auto- and xenoplastic grafting of mature autopodia at the stylopodial stump in larval salamandra salamandra and ambystoma mexicanum.		1988	3412343
blastema cell proliferation in vitro: effects of limb amputation on the mitogenic activity of spinal cord extracts.	primary cultures of mesenchymal cells of axolotl limb blastemas provide a very sensitive in vitro bioassay for studying nerve dependence of newt regeneration. these cells can be stimulated by crude spinal cord extracts of non-amputated animals in a dose-dependent manner up to 60 micrograms protein/ml of culture medium; at this concentration the mitotic index is increased 4-fold. spinal cord extracts of axolotls 14 days after forelimb amputation (i.e., late bud stage) are more efficient in stimul ...	1988	3390627
membrane currents in retinal bipolar cells of the axolotl.	by whole-cell patch-clamping bipolar cells isolated from enzymatically dissociated retinae, we have studied the nonsynaptic ionic currents that may play a role in shaping the bipolar cell light response and in determining the level of voltage noise in these cells. between -30 and -70 mv, the membrane current of isolated bipolar cells is time independent, and the input resistance is 1-2 g omega. depolarization past -30 mv activates an outward current (in less than 100 ms), which then inactivates ...	1988	3125305
recovery of acetylcholinesterase activity after irreversible inhibition by organophosphorous compounds in embryonic development.	1. recovery of acetylcholinesterase (ache) activity was studied using the embryos of sea urchins strongylocentrotus intermedius and s. nudus, embryos of axolotl ambystoma mexicanum and in the chick embryo muscle culture treated by "irreversible" organophosphorous inhibitors (opi). 2. ache activity was assayed by a modified ellman's procedure. 3. it follows from the data obtained that, unlike the plutei of sea urchins and the monolayer culture of chick embryo muscle cells, the embryos of axolotl ...	1988	2898993
retinoic acid proximalizes level-specific properties responsible for intercalary regeneration in axolotl limbs.	the objective of this study was to determine whether retinoic acid (ra) coordinately proximalizes positional memory and the cellular recognition system that detects pattern discontinuity in regenerating amphibian limbs. the strategy was to test the capacity of ra-treated blastemas to evoke intercalary regeneration when grafted to an amputation level proximal to their level of origin. control wrist and ankle, or elbow and knee blastemas treated with the retinoid solvent, dimethylsulphoxide, evoke ...	1988	3268411
a rapid method for observing the internal morphology of amphibian embryos.	a simple, rapid method for visualizing the internal morphology of amphibian embryos is described. fixed embryos of ambystoma mexicanum are surrounded with commercial embedding material and are frozen. internal structure is revealed by cutting the embryos with a cooled scalpel or razor blade, removing the frozen embedment with an aqueous buffer, and processing the halved embryos for scanning electron microscopy (sem). this technique allows the internal anatomy of the embryo to be viewed but is mu ...	1988	3238382
characterization of an igy-like low molecular weight immunoglobulin class in the mexican axolotl.	the general thinking about the phylogenic distribution of vertebrate ig classes is that fish and urodele amphibians are only able to synthesize polymeric igm-like molecules and that the emergence of a new class of lmw ig occurs for the first time in anouran species. following immunization of the mexican axolotl (ambystoma mexicanum, amphibia, urodela) with tnp-srbc, hmw anti-tnp antibody molecules are only detected. we have previously shown that these polymeric ig are constituted of 76 kda h-cha ...	1988	3237220
lateral-line neuromast development in ambystoma mexicanum and a comparison with rana pipiens.	we have examined the embryonic development of the major neuromast lines of the lateral-line system in the urodele ambystoma mexicanum both in vivo (using microsurgical techniques to transplant placodes) and in preserved embryos using scanning electron microscopy (sem). we have compared this to sem observations of embryos of the anuran rana pipiens. we have determined the approximate locations of the lateral-line placodes in a. mexicanum and the approximate timing of both the migration of the lat ...	1988	29879797
studies of heart development in normal and cardiac lethal mutant axolotls: a review.	the morphology of developing hearts in axolotls, ambystoma mexicanum, has been studied by scanning electron microscopy in order to provide a chronology of morphogenesis that can be correlated with ongoing biochemical and immunocytochemical studies. in addition to normal embryos we have studied homozygous recessive cardiac lethal mutant axolotls. the mutant myocardium undergoes aberrant sarcomere development and lacks a normal heartbeat. morphogenesis of mutant hearts appears to be nearly normal ...	1989	2699076
cellular contribution to symmetrical forelimbs from triploid-marked "polarizing region" in the embryo of axolotl, ambystoma mexicanum.	grafts of posterior tissue placed anterior to the limb bud in the salamander embryo exert a polarizing influence. to explain this result, the idea that the anteroposterior axis of the developing forelimb is polarized by a diffusible morphogen has been proposed. an alternative hypothesis, and the working hypothesis of the present study, is that the polarization of the developing salamander forelimb is accomplished by short-range cellular interactions resulting in intercalation rather than by the ...	1989	2600559
neuroepithelial endocrine cells in the lung of ambystoma mexicanum.	neuroepithelial endocrine (nee) cells were for the first time identified in the lung of the entirely aquatic urodele, ambystoma mexicanum, by using light and electron microscopy, histochemistry, and immunocytochemistry. in the basal part of the ciliated epithelium and, less often, in the respiratory portion of the lung, nee cells were found to occur both solitarily and in small clusters. no typical neuroepithelial bodies could be found. using the method of fernandez pascual, some nee cells were ...	1989	2817428
the effect of eel calcitonin on calcium influx and plasma ion levels in axolotls, ambystoma mexicanum.	plasma total calcium and calcium influx, measured during 4-h 45ca influx experiments, were lower in control axolotls, ambystoma mexicanum, during august when compared to those in july. a single intraperitoneal injection of 10 micrograms of synthetic eel calcitonin significantly reduced the calcium influx rates during both months but the effect was greater in july (p less than 0.001) than in august (p less than 0.05). plasma levels of calcium, sodium, potassium, and magnesium were not affected. i ...	1989	2767402
analysis of the endocardium and cardiac jelly in truncal development in the cardiac lethal mutant axolotl ambystoma mexicanum.	recessive mutant gene c in axolotls results in a failure of the heart to function because of abnormal embryonic induction processes. the myocardium in this mutant lacks organized sarcomeric myofibrils. the present study was undertaken to determine if developmental abnormalities were evident in other areas of the heart besides the myocardium. a detailed comparative survey of the structure of developing normal and mutant hearts, including the endocardium, its cellular derivatives, and the extracel ...	1989	2724338
neural fold formation at newly created boundaries between neural plate and epidermis in the axolotl.	according to a recent model, the cortical tractor model, neural fold and neural crest formation occurs at the boundary between neural plate and epidermis because random cell movements become organized at this site. if this is correct, then a fold should form at any boundary between epidermis and neural plate. to test that proposition, we created new boundaries in axolotl embryos by juxtaposing pieces of neural plate and epidermis that would not normally participate in fold formation. these bound ...	1989	2707486
electrosensory activity in the telencephalon of the axolotl.	electrical shock of the anterior lateral line nerve evokes slow wave potentials in the contralateral corpus striatum and bilaterally in the medial pallium of the telencephalon of axolotls. the onset latency of the evoked response in the medial pallium (70 ms) is considerably longer than that of the corpus striatum (46 ms). quasi-natural stimuli, such as weak uniform electric fields (100 microv/cm) or water drops striking the surface of the water surrounding the axolotls elicited evoked potential ...	1989	2748022
lack of proliferative response in denervated, reamputated limb regenerates of larval ambystoma.	this paper describes the response of early four-digit regenerates of axolotls to reamputation and denervation. reamputation of innervated regenerates led to sharp increases in 3h-thymidine labeling index (li) and mitotic index (mi) on days 2-5 post-reamputation. this resembles the response of innervated limbs following initial amputation. regenerates that were denervated at the time of reamputation exhibited no proliferative response through day 5. this is in marked contrast to denervated, origi ...	1989	2708951
organization of connective tissue patterns by dermal fibroblasts in the regenerating axolotl limb.	a set of tendons, aponeurotic sheets and retinaculae, which transduce muscle action from proximal limb levels to flexion and extension of the digits, is found in limbs of many vertebrates. this set of structures, here termed the digit tendon complex, is described for the axolotl forelimb. we show that the complex forms autonomously in muscleless axolotl limb regenerates produced from a cuff of unirradiated dermis surrounding an irradiated limb stump, and persists for up to a year after amputatio ...	1989	2612366
the relationship among retinoid structure, affinity for retinoic acid-binding protein, and ability to respecify pattern in the regenerating axolotl limb.	to further our understanding of the action of retinoids on the respecification of pattern in the regenerating axolotl limb we have studied the relative potencies of a range of synthetic and natural retinoids administered locally to the blastema. alterations in the polar end group of the retinoic acid (ra) molecule to produce esters, the alcohol, or the aldehyde abolish the ability of the molecule to respecify pattern. on the other hand, alterations of the ring or side chain to produce the synthe ...	1989	2537244
compatible limb patterning mechanisms in urodeles and anurans.	we have experimentally tested the similarity of limb pattern-forming mechanisms in urodeles and anurans. to determine whether the mechanisms of limb outgrowth are equivalent, we compared the results of two kinds of reciprocal limb bud grafts between xenopus and axolotls: contralateral grafts to confront anterior and posterior positions of graft and host, and ipsilateral grafts to align equivalent circumferential positions. axolotl limb buds grafted to xenopus hosts are immunologically rejected a ...	1989	2912797
timing in the regulation of neural crest cell migration: retarded "maturation" of regional extracellular matrix inhibits pigment cell migration in embryos of the white axolotl mutant.	in larvae of the white axolotl mutant (ambystoma mexicanum), contrary to normal dark ones, trunk pigmentation is restricted because the epidermis is unable to support subepidermal migration of pigment cells from the neural crest (nc). this study examines whether the subepidermal extracellular matrix (ecm) is the defective component which prevents pigment cell migration in the white embryo. we transplanted subepidermal ecm, adsorbed in vivo on membrane microcarriers, from and to white and dark em ...	1989	2909402
ultrastructural localization of acetylcholinesterase in axolotl brain capillaries.	the ultrastructural distribution of cholinesterases on the brain capillaries of axolotl has been studied. the axolotl brain contains branching, anastomosing capillary network and capillary loops. the presence of acetylcholinesterases is seen on the basal lamina and in the spaces between the endothelial cells and the pericytes of both types of vessels. the role of this enzyme in the blood-brain barrier is discussed.	1989	2756743
cellular morphogenesis and the formation of marginal bands in amphibian splenic erythroblasts.	the spleen of ambystoma mexicanum (axolotl) larvae develops as a closed sac containing differentiating nucleated erythrocytes, and is typically isolated from the general circulation for about 10 days post-hatching. beginning 3-4 days posthatching, it can be removed intact for examination of the morphology and cytoskeletal structure of the erythropoietic cells. in the smallest (earliest) spleens, spheroidal cells predominate, while older ones contain a preponderance of cells exhibiting the flatte ...	1989	2653647
the role of retinoid-binding proteins in the generation of pattern in the developing limb, the regenerating limb and the nervous system.	we summarize existing data and describe new information on the levels and distribution of cellular retinoic acid-binding protein (crabp) and cellular retinol-binding protein (crbp) in the regenerating axolotl limb, the developing chick limb bud and the nervous system of the chick embryo in the light of the known morphogenetic effects of retinoids on these systems. in the regenerating limb, levels of crabp rise 3- to 4-fold during regeneration, peaking at the time when retinoic acid (ra) is most ...	1989	2561479
axolotl pronephric duct cell migration is sensitive to phosphatidylinositol-specific phospholipase c.	on the basis of its distribution pattern in embryos of the axolotl (ambystoma mexicanum), we recently identified alkaline phosphatase as a molecule potentially involved in guiding the migration of the pronephric duct. alkaline phosphatase is a cell surface protein anchored to cell membranes via a covalent linkage to a phosphatidylinositol glycan (pi-g). the enzyme phosphatidylinositol-specific phospholipase c (piplc) specifically releases from cell surfaces molecules anchored by the pi-g linkage ...	1989	2553384
[experimental teratomas from xenogenic embryonic implants in the urodele amphibian, pleurodeles waltlii michah].	ambystoma mexicanum embryos in stages 5 to 32 were implanted into the coelomic cavity of larvae or metamorphosing larvae of pleurodeles waltlii. out of 76 experimental animals, 43 presented teratomas a few months later. in another series of experiments, ambystoma embryos together with pleurodeles embryos were implanted in 18 pleurodeles larvae. teratomas developed in 13 cases. considering the two series, tumors evolved slowly and remained benign in 31 animals, whereas in 25 others, the tumor gro ...	1989	2499409
the glossopharyngeal nerve of the axolotl labeled with carbocyanine dye (dii).	fluorescent carbocyanine dye (dii) was used to label the glossopharyngeal (ix) nerve in the fixed preparation of the mexican salamander, axolotl. when the cell bodies were viewed with a confocal laser scanning microscope and nomarski optics, the cytoplasm was brightly fluorescent, but not the cell nucleus. the cell bodies which send peripheral axons in the two branches of the ix nerve were mainly distributed in the rostral part of the combined glossopharyngeal-vagus ganglion, but a few cells wer ...	1989	1791970
evolution of motor patterns: aquatic feeding in salamanders and ray-finned fishes.	patterns of muscle activity (motor patterns) have generally been found to be strongly conserved during the evolution of aquatic feeding behavior within closely related groups of fishes and salamanders. we conducted a test of the generality of motor pattern conservation with a much broader phylogenetic scope than has been done previously. activity patterns of three cranial muscles were quantified from electromyographic (emg) recordings made during suction feeding in a salamander (ambystoma mexica ...	1989	2611639
spatial aspects of neural induction in xenopus laevis.	a monoclonal antibody, 2g9, has been identified and characterised as a marker of neural differentiation in xenopus. the epitope is present throughout the adult central nervous system and in peripheral nerves. staining is first detected in embryos at stage 21 in the thoracic region. by stage 29 it stains the whole central nervous system, except the tail tip. the epitope is present in a 65k mr protein, and includes sialic acid. the antibody also reacts with neural tissue in mice and axolotls and n ...	1989	2632233
amphibian (urodele) myotomes display transitory anterior/posterior and medial/lateral differentiation patterns.	myotome differentiation during mexican axolotl (ambystoma mexicanum) somitogenesis was analyzed by employing anti-actin and anti-myosin monoclonal antibodies as molecular probes. myotome differentiation occurs after segmentation and proceeds in the cranial-to-caudal direction along the somite file. within individual somites myotome differentiation displays distinct polarities. examination of the somite file at the tailbud stage revealed that soon after segmentation, actin/myosin accumulate predo ...	1989	2647546
immunocytochemical localization and immunochemical characterization of an insulin-related peptide in the pancreas of the urodele amphibian, ambystoma mexicanum.	the pancreas of the axolotl, ambystoma mexicanum, was investigated by immunocytochemical methods for the presence of immunoreactivity to a number of antisera raised against mammalian insulins. all anti-insulin antisera tested revealed substantial amounts of reaction products confined solely to the aldehyde-fuchsinophilic b cells of the endocrine pancreas. the reactive cell population was detected by use of one polyclonal antiserum against bovine insulin and eight different monoclonal antibodies ...	1989	2663173
analysis of actin and tropomyosin in hearts of cardiac mutant axolotls by two-dimensional gel electrophoresis, western blots, and immunofluorescent microscopy.	when homozygous, recessive mutant gene c in ambystoma mexicanum results in a failure of embryonic heart function. this failure is apparently due to abnormal inductive influences from the anterior endoderm resulting in an absence of normal sarcomeric myofibril formation. biochemical and immunofluorescent studies were undertaken to evaluate the contractile proteins actin and tropomyosin in normal and mutant hearts. for the immunofluorescent studies, cardiac tissues were fixed in periodate-lysine-p ...	1989	2664186
diverse supernumerary structures develop after inverting the anteroposterior limb axis of the anuran.	contralateral limb bud graftings were performed on tadpoles of the anuran bufo bufo. the anteroposterior axis was inverted while the larvae were at stage iv or v (e.g., between 22-30 days after fertilization). eighty-four tadpoles were operated on, 10 of which were used as controls. at anterior or posterior location 104 supernumerary structures developed in toto. they were collected and whole-mount examined after being stained with alcian blue. they were further prepared for serial sectioning, m ...	1989	2466718
biosynthesis of sulfated proteoglycans in amphibian embryonal cells.	the synthesis of sulfated proteoglycans in small explants from various parts of late blastulae from ambystoma mexicanum or xenopus laevis was investigated by incorporation of radioactive sulfate or glucosamine and galactosamine in media of low, normal or high tonicity. the explants differentiated into ciliated aggregates of fibroblast-like cells, or remained undifferentiated depending upon their origin in the embryo. high tonicity induces the explants to dissociate and prevents morphological dif ...	1989	2504303
immunohistochemical localization of beta-endorphin-like material in the urodele and anuran amphibian tissues.	in the present study, we have localized for the first time beta-endorphin (beta-ep)-like material in the adult and larval urodele and anuran tissues using immunohistochemical techniques. in the adult notophthalmus viridescens and ambystoma mexicanum, strong immunoreactivity to beta-ep antisera was observed in the region of the intermediate lobe, the latter fluorescing as a discrete body. the fluorescence was confined to the periphery of the cells, while the nuclei and the immediately surrounding ...	1989	2530130
homing behaviour of regenerating axons in the amphibian limb.	following peripheral nerve deviation in the limbs of urodele amphibians axons regrow distally toward their previous target muscles (holder et al. 1984; proc. roy. soc. lond. b 222, 477-489). this study describes analysis of this axon regeneration over time following deviation of the forearm flexor nerve in triturus cristatus and the extensor cranialis nerve in the axolotl. using horseradish peroxidase (hrp) axonal tracing, electrophysiology and electron microscopy, we describe the sequence of ev ...	1989	2485244
high levels of hmg1-2 protein expression in the cytoplasm and nucleus of hydrocortisone sensitive amphibian thymocytes.	a major 26 kda protein was identified in the cytoplasmic and nuclear compartments of axolotl thymocytes. a polyclonal antiserum was produced against the denatured form of this protein. high levels of 26 kda were expressed by hydrocortisone-sensitive lymphocytes which represent a major thymocyte subpopulation in young animals. however, no further expression of the 26 kda protein was observed in involuted thymus of adult animals nor in thymus of young artificially metamorphosed axolotls. the 26 kd ...	1990	2097001
the mhc molecules of nonmammalian vertebrates.	there is very little known about the long-term evolution of the mhc and mhc-like molecules. this is because both the theory (the evolutionary questions and models) and the practice (the animals systems, functional assays and reagents to identify and characterize these molecules) have been difficult to develop. there is no molecular evidence yet to decide whether vertebrate immune systems (and particularly the mhc molecules) are evolutionarily related to invertebrate allorecognition systems, and ...	1990	2180813
comparative studies on the vascular organization of carotid labyrinths of anurans and caudates.	the three-dimensional structures of the carotid labyrinth in five species of anurans representing four families (rana nigromaculata, rana catesbeiana, bufo japonicus, hyla arborea, and xenopus laevis), and three species of caudates representing three families (cynops pyrrhogaster, hynobius nebulosus, ambystoma mexicanum) were compared using vascular corrosion castings and scanning electron microscopy (sem). anuran carotid labyrinths are spherical in shape and are classified into two groups accor ...	1990	2338718
isolation and characterization of the third complement component of axolotl (ambystoma mexicanum).	1. using a monoclonal anti-human c3 antibody and a polyclonal anti-cobra venom factor antibody as probes, a protein homologous to the mammalian third complement component (c3) was purified from axolotl plasma and found to be axolotl c3. 2. axolotl c3 consists of two polypeptide chains (mr = 110,000 and 73,000) linked by disulfide bonds. an internal thiolester bond in the alpha chain was identified by the incorporation of [14c]methylamine and nh2-terminal sequence from the c3d fragment of c3. 3. ...	1990	2344737
development and application of homologous radioimmunoassay for newt prolactin.	a specific and sensitive homologous radioimmunoassay (ria) for newt (cynops pyrrhogaster) prolactin (prl) was developed. prl isolated from newt pituitary glands was used for generating antiserum in a rabbit, for radioiodination, and for the standard. several dilutions of plasma and pituitary homogenate of newts yielded dose-response curves which were parallel to the standard curve. plasma from hypophysectomized newts showed the least amount of cross-reaction. pituitary homogenates of other speci ...	1990	2354781
polymorphism of hyaluronidase in serum from man, various mouse strains and other vertebrate species revealed by electrophoresis.	polymorphism of hyaluronidase (ec 3.2.1.35) was detected in the serum from 6 out of 20 vertebrate species by electrophoretic analysis. electrophoresis was performed on a hyaluronan-containing polyacrylamide gel, that visualizes hyaluronidase activity upon incubation at acid ph. no hyaluronidase activity was detected in the sera of horse, swine, cattle, goat, sheep, rabbit, chicken, triton alpestris, triton palmatus, triton vulgaris, pleurodeles, axolotl, eel and dog-fish. the 6 positive sera wer ...	1990	2357493
mhc-like molecules in some nonmammalian vertebrates can be detected by some cross-reactive monoclonal antibodies.	mab to human and mouse mhc molecules were tested for binding to blood or spleen cells of various nonmammalian vertebrates by immunofluorescence and flow cytometry. those that bound were used to immunoprecipitate cross-reactive molecules from biosynthetically or cell surface-labeled spleen or blood cells. in addition, mab to human mhc molecules were screened by western blots. as expected from the results with xenoantisera, there were few mab that cross-reacted, and many of these cross-reactions w ...	1990	1690241
isolation and characterization of a developmentally regulated homeobox sequence in the mexican axolotl ambystoma mexicanum.	a homeobox-containing genomic dna fragment was isolated from the mexican axolotl. this clone was obtained from a partial genomic library enriched for sequences that cross-hybridized with the drosophila antp homeobox under low stringency hybridization conditions. dna sequence analysis revealed that this sequence (ahox1) was 66% homologous to the antp homeobox sequence and was most closely related to the mouse hox-1.6 (84% identity) and drosophila lab (79% identity) homeobox sequences. several cro ...	1990	1695851
alkaline phosphatase and dipeptidylpeptidase iv staining of tissue components of skeletal muscle: a comparative study.	a combined alkaline phosphatase (ap) and dipeptidlypeptidase iv (dpp iv) staining reaction has demonstrated enzymatic heterogeneity of the arterial and venous segments of capillaries in rat skeletal muscle. this study compared the staining reactions of skeletal muscles in many commonly used laboratory animals, including the axolotl, chick, quail, monodelphys, rat, mouse, hamster, guinea pig, rabbit, dog, monkey, and human. dpp iv activity was found in the venous ends of the capillaries and in th ...	1990	1701462
heterogeneity in spinal radial glia demonstrated by intermediate filament expression and hrp labelling.	considerable evidence indicates that radial glial cells play an active role in guiding growing neurites during development of the vertebrate cns. in this paper we describe subpopulations of radial glial in the spinal cord of the axolotl. amphibians maintain radial glia throughout life, and subpopulations are described using anatomical criteria following filling of individual cells with horseradish peroxidase and immunocytochemical staining with a range of intermediate filament antibodies. radial ...	1990	1705577
primary culture of axolotl spinal cord ependymal cells.	in order to examine the role of ependymal cells in the spinal cord regeneration of urodele amphibians, procedures were established to identify and culture these cells. cell isolation and culture conditions were determined for ependymal cells from larval and adult axolotls (ambystoma mexicanum). dissociated cells prepared from intact spinal cords were cultured on fibronectin- or laminin-coated dishes. dissociated cells attached more rapidly to fibronectin, but attached and spread on both fibronec ...	1990	18620322
nucleotide sequence of a cdna encoding wnt-1 of the mexican axolotl ambystoma mexicanum.		1990	2259633
morphology and distribution of the glossopharyngeal nerve afferent and efferent neurons in the mexican salamander, axolotl: a cobaltic-lysine study.	cobaltic-lysine complex was used to label the afferent and efferent components of the glossopharyngeal nerve in the ganglion and brainstem of the mexican salamander, axolotl (ambystoma mexicanum). the distribution of afferent cell bodies in the combined glossopharyngeal-vagus ganglion (the ix-x ganglion) was reconstructed from serial sections, and the sizes of the cell bodies were measured. the central projection of afferents and the location of efferent cell bodies were determined by the tracer ...	1990	1702112
selective labeling of sensory hair cells and neurons in auditory, vestibular, and lateral line systems by a monoclonal antibody.	this study reports that zn-1, a monoclonal antibody, labels hair cells but not supporting cells in the inner ear and the lateral line of the axolotl salamander, ambystoma mexicanum. zn-1 immunocytochemically labels the cytoplasm and stereocilia of mature hair cells in the sacculus, in the utriculus, and in the mechanoreceptive neuromast organs of the lateral line. lower levels of labeling mark newly formed hair cells in the periphery of the sacculus and in regenerating neuromasts. zn-1 also sele ...	1990	2124588
effects of tributyltin oxide on the skeletal structures of developing and regenerating limbs of the axolotl larvae, ambystoma mexicanum.		1990	2279120
the origins of neural crest cells in the axolotl.	we address the question of whether neural crest cells originate from the neural plate, from the epidermis, or from both of these tissues. our past studies revealed that a neural fold and neural crest cells could arise at any boundary created between epidermis and neural plate. to examine further the formation of neural crest cells at newly created boundaries in embryos of a urodele (ambystoma mexicanum), we replace a portion of the neural folds of an albino host with either epidermis or neural p ...	1990	2210034
characterization of the yellow pigment in the axanthic mutant of the mexican axolotl, ambystoma mexicanum.	the yellow pigment observed in older axanthic (ax/ax) mutant mexican axolotls (ambystoma mexicanum) was analyzed by thin layer chromatography and by spectrofluorometry of its acetyl derivative. ethanol extracts from the skin of axanthic animals were acetylated and the chloroform-soluble portion of the product mixture was compared with a chloroform solution of an authentic riboflavin tetraacetate standard prepared in the same manner. the pigment in these two solutions behaved identically on thin ...	1990	2290784
[metamorphosis today].	in conjunction with the 100th anniversary of birth of the czech physiologist v. laufberger who discovered in 1913 the possibility to induce metamorphosis in neotenous larvae of axolotls by feeding them with thyroid gland, the author gives an account on the development of knowledge regarding metamorphosis in amphibia. he analyzes the participation of endocrine glands, in particular thyroid hormones and prolactin. special attention is devoted to mechanisms leading to resorption of the tail in tadp ...	1990	2224961
identification of kainic and quisqualic acid receptors on inner retinal cells of the salamander ambystoma mexicanum.	the presence of kainic (ka) and quisqualic acid (qa) receptors on inner retinal neurones of the axolotl ambystoma mexicanum has been studied using intracellular recording techniques. in the presence of cocl2, which blocks neurotransmitter release, ka and qa depolarized the membrane. the minimum concentration of ka that induced a response was 1 microm and a maximum response was obtained with 10 microm (ec50: 3 microm). the operating range of qa was between 0.5 and 5 microm with an ec50 of 1 micro ...	1990	1976525
the effect of retinoic acid on positional memory in the dorsoventral axis of regenerating axolotl limbs.	we investigated the effect of retinoic acid (ra) on pattern regulation in the dorsoventral (dv) axis of regenerating axolotl limbs. half and double half dorsal and ventral zeugopodia (lower arms or legs) were amputated through their distal ends, and 4 days later the animals were injected intraperitoneally with 50 (large animals) or 100 (small animals) micrograms ra/g body wt. half and double half dorsal and ventral zeugopodia of uninjected axolotls, and sham-operated zeugopodia of untreated and ...	1990	2358123
structural and compositional divergencies in the extracellular matrix encountered by neural crest cells in the white mutant axolotl embryo.	the skin of the white mutant axolotl larva is pigmented differently from that of the normal dark due to a local inability of the extracellular matrix (ecm) to support subepidermal migration of neural crest-derived pigment cell precursors. in the present study, we have compared the ecm of neural crest migratory pathways of normal dark and white mutant embryos ultrastructurally, immunohistochemically and biochemically to disclose differences in their structure/composition that could be responsible ...	1990	2119290
in vitro control of blastema cell proliferation by extracts from epidermal cap and mesenchyme of regenerating limbs of axolotls.	the presence of a mitogenic activity in limb blastemas of axolotls was detected in crude extracts of blastemas at the mid-bud stage. the mitogenicity of the extracts was estimated from the mitotic index of blastema cells grown for 6 days in the presence of limb blastema extracts, with colchicine present for the last 2 days. all the extracts tested (whole blastema, blastemal mesenchyme, epidermal cap) significantly enhanced proliferation of blastema cells. the highest stimulation factors we obser ...	1990	28305671
melanin as a natural germ cell marker for intraspecific transplantation experiments in ambystoma mexicanum (urodela, amphibia).	in urodele amphibians, the lack of a reliable germ cell marker restricts the experimental study of the germ lineage. in the present work, we conducted genetic and histological analyses in order to demonstrate that melanin from oocytes constitutes a germ cell marker available for intraspecific experiments in ambystoma mexicanum. then, using this marker, we implanted germ cells from undifferentiated gonads (stage 48) into the blastocoel of host embryos and investigated their fate and determined st ...	1990	28305537
an extracellular matrix molecule of newt and axolotl regenerating limb blastemas and embryonic limb buds: immunological relationship of mt1 antigen with tenascin.	several well-characterized extracellular matrix (ecm) components have been localized to the amphibian limb regenerate, but the identification and characterization of novel ecm molecules have received little attention. here we describe, using mab mt1 and immunocytochemistry, an ecm molecule expressed during limb regeneration and limb development. in limb stumps, mab mt1 reactivity was restricted to tendons, myotendinous junctions, granules in the basal layers of epidermis, periosteum (newts) and ...	1990	1696876
heart induction in wild-type and cardiac mutant axolotls (ambystoma mexicanum).	we have re-examined some of the factors affecting the induction of heart-forming mesoderm in the axolotl. the formation of functional, rhythmically contracting myocardial tissue was used as an assay. we have found that heart-forming mesoderm is fully induced and capable of completing its developmental repertoire by the end of neurulation. as has been previously reported, pharyngeal endoderm appears to be the major inductor of heart mesoderm. unlike previous workers, we have found that the induci ...	1990	1693393
eliminating afferent impulse activity does not alter the dendritic branching of the amphibian mauthner cell.	in the developing amphibian, the formation of extra vestibular contacts on the mauthner cell (m-cell) enhances dendritic branching, while deprivation reduces it (goodman and model, 1988a). the mechanism underlying the interaction between afferent fibers and developing dendritic branches is not known; neural activity may be an essential component of the stimulating effect. we examined the role of afferent impulse activity in the regulation of m-cell dendritic branching in the axolotl (ambystoma m ...	1990	2155302
serially duplicated regenerates from the anterior half of the axolotl limb after retinoic acid treatment.	axolotl (ambystoma mexicanum) forearms were divided, by an incision between the radius and ulna, to produce anterior and posterior halves. these were prevented from fusing together again by a graft of head skin and amputated through the wrist. this procedure enabled independent regeneration from both halves of the stump. anterior half stumps produced a single digit while the posterior halves mainly regenerated three digits, the two halves together making a single hand. treatment with retinoic ac ...	1990	28305663