Publications

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
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
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
[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
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
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
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
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
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
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
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
increase of substance p-like immunoreactivity in the peripheral nerve of the axolotl after injury.	that substance p may be a neurotrophic factor in urodele limb regeneration was investigated in the axolotl (ambystoma mexicanum). two weeks after section of the peripheral nerves to the forelimb, there was a marked increase in substance p-like immunoreactivity (ir) content of the nerves proximal to the lesion. a smaller increase occurred as early as 3 days after section of nerves innervating a regrowing limb bud (blastema), and substance p-ir fibres were observed by immunocytochemistry to innerv ...	1987	2447537
anatomy of axolotl flank integument during limb bud development with special reference to a transcutaneous current predicting limb formation.	we have compared the anatomy of immature axolotl integument from limb-forming regions with adjacent non-limb-forming regions of the flank, concentrating on the earliest stages of limb bud development. we have extended these observations to include prominent buds just prior to their differentiation. at the ultrastructural level, we note striking differences between these two regions of skin, including a complete loss of hemidesmosomes and tonofilaments in the basal cells of the epidermis; a marke ...	1987	3430119
fine structure of taste buds in the tongue, palatal mucosa and gill arch of the axolotl, ambystoma mexicanum.		1987	3431793
use of retinoids to analyze the cellular basis of positional memory in regenerating amphibian limbs.	cells of the amphibian limb regeneration blastema inherit memories of their level of origin (positional memory) along the limb axes. these memories serve as boundaries of what is to be regenerated, thus preventing regeneration of any but the missing structures. because of its importance in determining the boundaries of regenerate pattern, it is essential to understand the cellular and molecular basis of positional memory. one approach to this problem is to look for position-related differences i ...	1987	3325080
hormone action in newt limb regeneration: insulin and endorphins.	although several hormones have been linked to newt limb regeneration, a cohesive hypothesis as to how these hormones control the process is yet to emerge. a critical review of the traditional approaches and a reevaluation of currently operative assumptions and interpretations of results precede the data on insulin and beta-endorphin. results from in vivo and in vitro experiments on insulin are summarized, showing that insulin not only promotes various cellular events but also is essential for th ...	1987	2963650
involvement of the cytoskeleton in early grey crescent formation in axolotl oocytes.	maturing axolotl oocytes which are treated with protein synthesis inhibitors or which are heat-shocked can be induced to reorganize their cytoplasm and to form an early grey crescent. the maturing axolotl oocyte has been used as a model system to study the role of the cytoskeleton in dorsoventral polarization as visualized by grey crescent formation. results presented here provide evidence for the involvement of microtubules in the formation of the early grey crescent. whereas inhibitors of micr ...	1987	28305553
selective reinnervation of transplanted muscles by their original motoneurons in the axolotl.	the motoneurons innervating 3 hindlimb extensor muscles, anterior and posterior iliotibialis and iliofibularis, were studied separately by retrograde labeling with hrp. the motor pools for these 3 muscles overlapped to such an extent that individual motoneurons between ventral roots 16 and 17 could not be assigned unambiguously to one pool or another. thus, conventional retrograde labeling could not identify particular axolotl motoneurons. instead, a double retrograde-labeling technique was empl ...	1987	3598652
neurotransmitter-induced currents in retinal bipolar cells of the axolotl, ambystoma mexicanum.	1. whole-cell patch clamping was used to study the membrane properties of isolated bipolar cells and the currents evoked in them by putative retinal neurotransmitters. 2. isolated bipolar cells show an approximately ohmic response to voltage steps over most of the physiological response range, with an average input resistance of 1.3 g omega and resting potential of -35 mv. these values are underestimates because of the shunting effect of the seal between the patch electrode and the cell membrane ...	1987	2443677
detection of mutagenicity in drinking water using a micronucleus test in newt larvae (pleurodeles waltl).	we have previously described a micronucleus test using erythrocytes from larvae of the urodele amphibians pleurodeles waltl (pleurodele) and ambystoma mexicanum (axolotl). the test is based on a comparison of the levels of micronucleated erythrocytes in blood smears from larvae reared in water containing a clastogen, with the levels from larvae reared in purified water. using larvae from the pleurodele, we have employed this test to evaluate mutagenic activity in drinking water. groups of larvae ...	1987	3325745
the effects of retinoic acid on mitosis during tail and limb regeneration in the axolotl larva, ambystoma mexicanum.	regenerating tails and limbs of axolotl larvae (a. mexicanum) were studied for overall growth and for mitosis after the animals received intraperitoneal injections of all-trans retinoic acid. both processes were depressed to approximately the same extent (60-70%). some mitosis always survived, even when the treatment was in effect during the entire history of the regenerate. the treatment duration was a major variable in the severity of the effect, whereas the post-amputation age of the regenera ...	1987	28305840
the surfactant system of the lung in the mexican axolotl ambystoma mexicanum.	the broncho-alveolar space of axolotl contains numerous osmiophilic structures, which have been classified morphologically into 3 types of inclusions. type i inclusions exhibited lattices of square to rectangular grid patterns with membranous elements 6 nm thick. this lattice was crossed by a 2 nm dense line. type ii inclusions were composed of 7 nm dark lines and 15.5 nm light lines in an alternating repeating pattern. furthermore, the light lines showed an intrapenoid line of 2 nm. type iii in ...	1987	3581181
dorsal root ganglia grafts stimulate regeneration of denervated urodele forelimbs: timing of graft implantation with respect to denervation.	amphibian forelimb regeneration is a nerve-dependent process; nerves presumably release one or more neurotrophic factors that stimulate blastema cell division. to date several candidate molecules/factors have been shown to stimulate macromolecular synthesis and/or mitosis but sustained cell cycle activity and blastema development have not been achieved. because dorsal root ganglia (drg) implants are capable of promoting regeneration of denervated adult newt limbs (kamrin & singer, 1959), we have ...	1987	3652994
induction of myofibrillogenesis in cardiac lethal mutant axolotl hearts rescued by rna derived from normal endoderm.	a strain of axolotl, ambystoma mexicanum, that carries the cardiac lethal or c gene presents an excellent model system in which to study inductive interactions during heart development. embryos homozygous for gene c contain hearts that fail to beat and do not form sarcomeric myofibrils even though muscle proteins are present. although they can survive for approximately three weeks, mutant embryos inevitably die due to lack of circulation. embryonic axolotl hearts can be maintained easily in orga ...	1987	2443338
the eyeless mutant mexican salamander (ambystoma mexicanum): evidence for an imbalanced anteroposterior morphogenetic system.	prospective anterolateral neural fold was grafted from normal axolotls into the posterior neural fold region (statocyst area) of eyeless mutant hosts. these unilateral anteroposterior grafts stimulated bilateral eye formation in the eyeless mutant at a rate of 79%. replacing the statocyst area of mutants with the statocyst area from normals stimulated bilateral eye formation in 49% of the cases. grafting of prospective anterolateral neural fold between normals and mutants or excising the statocy ...	1987	3559793
effects of exogenous guanosine on chromatophore differentiation in the axolotl.	guanosine is shown to dramatically alter the pigment phenotype of axolotls by suppressing melanization and enhancing the biosynthesis and deposition of purine-derived pigments. phenotypic changes caused by guanosine are manifested by altered chromatophore differentiation patterns such that few black pigment cells (melanophores) differentiate (and those that do are punctate and necrotic in appearance), whereas the development of yellow (xanthophore) and reflecting (iridophore) pigment cells is en ...	1987	3507661
is gaba an afferent transmitter in the vestibular system?	this study was undertaken to determine the possible role of gaba as an afferent transmitter in the vestibular system of the axolotl. we studied the effects of gaba, muscimol, bicuculline and picrotoxin on the spontaneous spike discharge of the afferent fibers of the sacculi lagena and anterior semicircular canal. it was found that gaba and muscimol produce a very weak excitatory effect which does not mimic either the temporal course or the amplitude of the response of vestibular afferents to phy ...	1987	3497911
the role of cartilage and fibronectin during respecification of pattern induced in the regenerating amphibian limb by retinoic acid.	when retinoic acid (ra) is applied to the regenerating limb the positional information of blastemal cells is respecified and extra limb segments develop. we are trying to elucidate the molecular basis of the action of ra and report here experiments focused on the role that fibronectin (fn) might play in the process. the fn distribution in stump tissues, regeneration blastemas and ra-treated blastemas was investigated by immunocytochemistry. two effects of ra were observed. firstly, excessive ded ...	1987	3449397
differentiation of cartilage from cranial neural crest in the axolotl (ambystoma mexicanum).	explants of cranial neural crest from neurula-stage ambystoma mexicanum embryos form cartilage nodules in 10-14 days, when cultured with pharyngeal endoderm. the time course of formation of the nodules, and their appearance, correspond closely to that observed for visceral cartilage in vivo. endoderm from any area of the sheet surrounding the pharyngeal cavity can induce cartilage formation, but endoderm from regions posterior to the pharyngeal cavity cannot. no other tissues are required for in ...	1987	3428510
changes in brain gangliosides of the neotene and metamorphic (thyroxine-induced) newt axolotl (ambystoma mexicanum).	qualitative and quantitative changes in the concentration of proteins, sialoglycoproteins and gangliosides and in the composition of gangliosides in the brains of the neotene and the thyroxine-induced metamorphic newt axolotl (ambystoma mexicanum) were investigated. during metamorphosis two polar gangliosides (gt1b and gq1b) decreased by about 5% each. on the contrary gd1a increased to 10%. another developmental trend was a slight increase of two other disialogangliosides (gd1b, gd2). additional ...	1987	3428191
bipolar cell membrane currents and signal processing in the axolotl retina.		1987	2446219
basal lamina is not a barrier to neural crest cell emigration: documentation by tem and by immunofluorescent and immunogold labelling.	one of the factors proposed to control initiation of migration of neural crest (nc) cells is disruption of the basal lamina (bl) that is presumed to exist over the dorsal portion of the neural tube. previously, we discovered that, in the mouse embryo, a continuous bl is not deposited over the dorsal portion of the neural tube until emigration of the nc cells is terminated. here, we show that the pattern of bl deposition in chick embryos is similar, but not identical, to that in the mouse. in par ...	1987	3332260
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
immunocytochemical localization and spatial relation to the adenohypophysis of a somatostatin-like and a corticotropin-releasing factor-like peptide in the brain of four amphibian species.	the distribution of somatostatin (srif) - and corticotropin-releasing factor (crf)-like - immunoreactive material was studied in the brain of four amphibian species (ambystoma mexicanum, pleurodeles waltlii, xenopus laevis, rana ridibunda) by use of immunocytochemistry. a wide network of srif-immunoreactive fibers and numerous perikarya were observed in all amphibians examined, with a dense accumulation of nerve endings in the external layer of the median eminence (elme). in the representatives ...	1987	2880668
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
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
calcium-independent stimulation of glycogenolysis by arginine vasotocin and catecholamines in liver of the axolotl (ambystoma mexicanum) in vitro.	arginine vasotocin (avt) caused a concentration-dependent increase of glycogen phosphorylase alpha activity, breakdown of glycogen and release of glucose, when added to pieces of axolotl liver in organ culture. the concentration causing half-maximal response (ec50) was about 1 nmol/l. these actions of avt were unaffected by the adrenergic antagonists propranolol, yohimbine and prazosin, but were blocked by equimolar amounts of d(ch2)5tyr(me)avt, a synthetic antagonist of vasopressin. arginine va ...	1986	3701246
cyclic amp and cell differentiation in amphibian embryonic explants.	conflicting results have been published concerning the effects of cyclic nucleotides on amphibian cell differentiation. here we report the effects of cyclic adenosine monophosphate (camp) and dibutyryl-cyclic adenosine monophosphate (db-camp) on isolated explants from late blastulae of ambystoma mexicanum and xenopus laevis. both camp and db-camp (10(-4)-10(-9) m) promote 'neuralizing' differentiation in ambystoma explants. xenopus explants treated with the nucleotides (10(-4), 10(-6), 10(-8) m) ...	1986	3011532
behavioral development in the absence of neural activity: effects of chronic immobilization on amphibian embryos.	embryos of xenopus laevis and ambystoma mexicanum were continually immobilized from premotile stages of development to stages at which normally reared embryos were swimming well. immobilization was achieved through exposure to solutions of chloretone, lidocaine, or alpha-bungarotoxin. at a number of stages after recovery from the drugs, spontaneous and stimulated behaviors were extensively quantified. immobilization of ambystoma embryos resulted in temporary defects in musculoskeletal developmen ...	1986	3711983
myelin lipids: a phylogenetic study.	the lipid composition of cns and pns myelin was studied in rat, xenopus, trout and torpedo. the main difference lay in the proportion of cerebrosides, which decreased in the sequence rat greater than xenopus greater than torpedo greater than trout. in addition torpedo cns and pns myelins were extremely rich in sulfatides. in some respects, torpedo appeared closer to tetrapods than trout. otherwise the proportion of the different lipid classes did not reveal any clear evolutionary trends. the pre ...	1986	3785545
axolotl retina and lens development: mutual tissue stimulation and autonomous failure in the eyeless mutant retina.	during eye development in the axolotl (ambystoma mexicanum shaw), morphogenetic movements bring together tissues from head epidermis, neuroectoderm and neural crest. the stages 0 to 14 of axolotl eye development were expanded from rabl's (1898) stages 1 to 10 and correlated with harrison's (1969) stages. at the onset of neurulation (stage 13 of harrison), the head epidermis is already determined to form skin, and the neuroectoderm is committed to form brain, because these tissues develop autonom ...	1986	3805980
the migration of dermal cells during blastema formation in axolotls.	using the diploid/triploid cell marker in the axolotl (ambystoma mexicanum) we have examined the movement of cells from the dermis into the early limb blastema. cells of dermal origin begin to migrate beneath the wound epithelium at about 5 days postamputation, and by 10 days they are widely distributed across the amputation surface. by 15 days, a dense accumulation of blastema cells is present beneath the apical cap, and these cells are preferentially oriented in a circumferential direction. th ...	1986	3792618
the effect of replacing different regions of limb skin with head skin on regeneration in the axolotl.	head skin was used to replace different halves of limb skin from the upper and lower arms of axolotls. replacement of upper arm posterior skin caused the regeneration of a high proportion of single-digit limbs while replacement of dorsal, ventral or anterior skin caused only minor defects to the normal skeletal pattern. when dorsal or ventral skin was replaced, however, regenerates often lacked dorsal or ventral muscle. results from the lower arm were different in that replacement of any half of ...	1986	3309120
pigment cell differentiation: the relationship between pterin content, allopurinol treatment, and the melanoid gene in axolotls.	the effects of allopurinol (an inhibitor of the enzyme xanthine dehydrogenase (xdh] and the melanoid gene on pigment cell differentiation in the axolotl were examined by analyzing pigment components of the xanthophore (pterins). pterin contents of skin extracts (70% ethanol) from wild type, allopurinol-treated and melanoid axolotls were determined by thin layer chromatography (tlc) and fluorometric scanning of tlc plates. heights of peaks produced were used as a quantitative measure for pterin c ...	1986	3791419
dna-ligase activity in axolotl early development: evidence for a multilevel regulation of gene expression.		1986	3625120
retinoic acid-binding protein in the axolotl: distribution in mature tissues and time of appearance during limb regeneration.	analysis of cytoplasmic protein preparations from axolotl tissues revealed the presence of a cytoplasmic retinoic acid-binding protein (crabp), of approximate molecular weight 17k. this protein was found to be present at various concentrations in skin, muscle, and limb tissue preparations, but not in liver and serum preparations. the distribution and molecular weight of this protein agrees with that reported in mammalian studies. the level of crabp in cone stage blastemas was found to be signifi ...	1986	3019799
effects of retinoids on regenerating limbs: comparison of retinoic acid and arotinoid at different amputation levels.	retinoic acid and the synthetic retinoid, arotinoid, were compared for their efficacy in inducing proximodistal (pd) pattern duplication in regenerating axolotl limbs, after amputation through either the distal zeugopodium (lower arm or leg) or distal stylopodium (upper arm or leg). at each level of amputation, the morphology of the duplications produced was the same for both retinoids, and the mean level of proximalization was dose-dependent. blastema formation was delayed by both retinoids and ...	1986	28305407
selective innervation of transplanted limb muscles by regenerating motor axons in the axolotl.	the segmental pattern of motor innervation of hindlimb muscles in the axolotl was studied before and after reinnervation. to ascertain the specificity of reinnervation, the four spinal nerves innervating the hindlimb were severed and allowed to regenerate. the segmental origin of axons reinnervating particular muscles was then determined by intracellular recording from muscle fibers. muscles were reinnervated in a specific manner: from the outset, the axons reinnervating each muscle originated l ...	1986	3746433
identification of a second type of catecholaminergic neuron in the spinal cord of the axolotl salamander.	two distinct groups of catecholaminergic neurons were observed by histofluorescence techniques in the spinal cord of the axolotl salamander, only one of which was detected in normal intact cords. these neurons were located in the ventral ependymal zone. when the spinal cord was transected, a second group of catecholaminergic neurons was observed in the lateral portions of the ventral gray matter of the spinal cord caudal to the transection site. these observations suggest that the amount of cate ...	1986	3732481
cellular contribution from dermis and cartilage to the regenerating limb blastema in axolotls.	using the triploid/diploid cell marker in the axolotl, ambystoma mexicanum, we have analyzed the extent to which cells derived from the dermis and the skeleton contribute to the regenerating limb blastema. we found that dermal cells contribute 43% of the blastemal cell population whereas cells derived from skeletal tissue contribute only 2%. when compared to the availability of cells at the plane of amputation, dermal cells overcontribute by greater than twofold whereas skeletal cells undercontr ...	1986	3732605
a scanning electron microscopy and histological study on the effects of the mutant eyeless (e/e) gene upon the hypothalamus in the mexican axolotl ambystoma mexicanum shaw.	a scanning electron microscopy, histological, and immunochemical investigation examined the effects of the mutant gene (e) upon hypothalamic development in the mexican axolotl. the adult eyeless mutant is sterile. previous studies indicated that this reproductive defect was due to the mutation's effect upon the hypothalamus. the present study demonstrated the pleiotropic effects of the eyeless gene upon development of the hypothalamus. scanning electron microscopy studies looked at the early ont ...	1986	2426993
the regeneration of double dorsal and double ventral limbs in the axolotl.	surgically made double dorsal and double ventral upper arms, comprising double extensor and double flexor muscles respectively, were amputated immediately following operation; both limb types regenerated. in terms of skeletal anatomy, a range of limb types was found. these included four-digit limbs of normal cartilage pattern, and hypomorphic limbs having from one to three digits. all of the double dorsal and the majority of the double ventral limbs were symmetrical in the dorsal-ventral axis. t ...	1986	3760762
effects of retinoic acid on regenerating normal and double half limbs of axolotls : histological studies.	retinoids induce proximodistal (pd) pattern duplication in zeugopodial (lower arm or leg) regenerates of normal limbs and pd pattern duplication plus anteroposterior (ap) pattern completion in double anterior half zeugopodial regenerates. in contrast, retinoids inhibit the regeneration of double posterior half zeugopodia (kim and stocum, 1986). here we describe the developmental histology of regenerating normal, double anterior half and double posterior half zeugopodia in axolotls after intraper ...	1986	28306010
induction of micronuclei in peripheral erythrocytes of axolotl larvae following in vivo exposure to mutagenic agents.	previous work from this laboratory demonstrated the presence of micronuclei in erythrocytes from larvae of the urodele amphibian pleurodeles waltl reared in water containing clastogenic substances. in order to investigate the generality of this finding, larvae from another urodele ambystoma mexicanum (axolotl) were reared in water containing one of the two following compounds: benzo[a]pyrene (bap) or ethylmethane sulphonate (ems). the level of micronucleated erythrocytes on blood smears was comp ...	1986	3331662
expression of dna ligase genes by ram spermatid nuclei and rna in amphibian eggs.	during animal development and gametogenesis two dna ligases are found and successively expressed. in this study the two dna ligases present in the axolotl egg and the two ligases present during ram sperm cell maturation were distinguished by biochemical and immunological methods. the expression of the genes for the heavy and light ram dna ligases has been studied using transplantation of spermatid and sperm nuclei in axolotl eggs. we found that ram dna ligases were expressed in axolotl egg cytop ...	1986	28305254
pattern discontinuity, polarity and directional intercalation in axolotl limbs.	axolotl limb stumps with dorsal-ventral confrontations between digits 2 and 3 but with a normal anterior-posterior pattern were created by grafting between contralateral limbs. graft and host differed in ploidy to permit a determination of the origin of cells in the regenerated limb. after regeneration, limbs were analysed for skeletal and muscle patterns and for the distribution of marked cells in the regenerate. regenerated limbs showed varying degrees of abnormality in their dorsal-ventral or ...	1986	3734687
the pigmentary system of developing axolotls. iii. an analysis of the albino phenotype.	the albino mutant in the mexican axolotl (ambystoma mexicanum) is analysed with respect to the differentiation of pigment cells. pigment cells were observed with the transmission electron microscope in order to determine any unusual structural characteristics and to determine what happens to each of the cell types as development proceeds. chemical analyses of pteridine pigments were also carried out, and the pattern of pteridines in albino animals was found to be more complex than, and quantitat ...	1986	3723064
the precision of pathway selection by developing peripheral axons in the axolotl.	at the time of hindlimb development in the axolotl there is a well-established but still developing trunk innervation. the trunk innervation is primarily composed of the segmental nerves, each of which consists of a dorsal and a ventral ramus and its branches. at a few segmental levels in the region of the hindlimb a large number of additional axons arise to innervate the limb. to reach the limb, they must grow via the ventral rather than the dorsal rami. the precision with which this pathway is ...	1986	3711780
urodele egg jelly and fertilization.	fertilization of urodele amphibians is physiologically polyspermic. these amphibians lack sperm entry blocking mechanisms at the egg surface, such as a cortical reaction or a membrane depolarization. although, egg jelly is necessary for sperm capacitation, a late block to sperm entry does occur about 30 min after fertilization at a precise interface between jelly layers. the jelly is secreted by oviductal cells. in order to investigate its role in fertilization, we studied some biochemical prope ...	1986	3825680
quantitative analysis of lymphocyte migration from the thymus to periphery in the mexican axolotl.		1986	3817254
environmental control in pigment pattern formation of the axolotl larva.		1986	3749176
investigating possible mechanisms of specific nerve regeneration in the axolotl.		1986	3749170
regeneration from discontinuous circumferences in axolotl limbs.		1986	3749160
involvement of the cytoskeleton in early gray crescent formation in axolotl oocyte: relationships with germinal vesicle breakdown.		1986	3749155
biochemical and ultrastructural studies on vitamin a induced proximalization of limb regeneration in axolotl.		1986	3749115
[structural characteristics and innervation of chromaffin tissue in the adrenal gland of the axolotl].	each adrenal gland of the axolotl consists of a strip lying all along the medio-lateral edge on the ventral surface of the kidney. the gland is composed of interrenal cells (ic) and chromaffin cells (cc). the ic contained a great number of pleomorphic lipid droplets, smooth endoplasmic reticulum and elongated mitochondria with tubulo-vesicular cristae. two types of cc, always disposed in clusters and exhibiting long cytoplasmic processes were described according to the electron density, size and ...	1986	3094843
glucagon and insulin regulate in vitro hepatic glycogenolysis in the axolotl ambystoma mexicanum via changes in tissue cyclic amp concentration.	glucagon increases the rate of glycogenolysis in in vitro cultures of hepatic tissue from the axolotl ambystoma mexicanum. the hormone causes an increase in the concentration of cyclic amp in the tissue which is followed by activation of glycogen phosphorylase and subsequent breakdown of glycogen and release of glucose from the tissue. insulin counteracts the glycogenolytic effect of glucagon by inhibiting the increase in tissue cyclic amp concentration brought about by glucagon. this inhibitory ...	1986	2416634