| new effects of roundup on amphibians: predators reduce herbicide mortality; herbicides induce antipredator morphology. | the use of pesticides is important for growing crops and protecting human health by reducing the prevalence of targeted pest species. however, less attention is given to the potential unintended effects on nontarget species, including taxonomic groups that are of current conservation concern. one issue raised in recent years is the potential for pesticides to become more lethal in the presence of predatory cues, a phenomenon observed thus far only in the laboratory. a second issue is whether pes ... | 2012 | 22611860 |
| parasitism in a community context: trait-mediated interactions with competition and predation. | predation and competition can induce important density- and trait-mediated effects on species, with implications for community stability. however, interactions of these factors with parasitism remain understudied. here we investigate interactions among competition, predation and parasitism by crossing tadpole density (bufo americanus), presence of a caged predator (notophthalmus viridescens), and echinostoma trivolvis trematodes, experimentally partitioning their effects on tadpole exposure and ... | 2010 | 20715608 |
| the toxicity of roundup original max to 13 species of larval amphibians. | with the increased use of glyphosate-based herbicides (marketed under several names, including roundup and vision), there has been a concomitant increased concern about the unintended impacts that particular formulations containing the popular surfactant polyethoxylated tallowamine (poea) might have on amphibians. published studies have examined a relatively small number of anuran species (primarily from australia and eastern north america) and, surprisingly, no species of salamanders. using a p ... | 2009 | 19405783 |
| helminth communities in five species of sympatric amphibians from three adjacent ephemeral ponds in southeastern wisconsin. | representatives of 5 amphibian species (313 individuals), including eastern american toads (bufo americanus), wood frogs (rana sylvatica), spring peepers (pseudacris crucifer), blue-spotted salamanders (ambystoma laterale), and central newts (notophthalmus viridescens louisianensis), were collected from 3 ephemeral ponds during spring 1994, and they were inspected for helminth parasites. the component communities of anurans were more diverse than those of caudates. infracommunities of all host s ... | 2007 | 17918353 |
| the lethal impacts of roundup and predatory stress on six species of north american tadpoles. | the decline in amphibians across the globe has sparked a search for the causes, and recent evidence suggests a connection with pesticides. however, for most pesticides, tests on amphibians are rare and conducted only for short durations (1 to 4 days) and without natural stressors. recent studies have discovered that the stress of predator cues in the water can make insecticides much more lethal to larval amphibians, but it is unknown whether this phenomenon can be generalized to other types of p ... | 2005 | 15886853 |
| amphibians have immunoglobulins similar to ancestral igd and iga from amniotes. | we studied the immunoglobulin genes from either the genomes or rnas of amphibians. in particular, we obtained data from one frog genome (nanorana parkeri) and three transcriptomes of the caudata order (andrias davidianus, notophthalmus viridescens and cynops pyrrhogaster). apart from the immunoglobulins igm and igy previously described, we identified several igd related immunoglobulins. the species n. parkeri, n. viridescens and c. pyrrhogaster have two igd genes, while andrias davidianus has th ... | 2016 | 26675067 |
| herpetofaunal community change in multiple habitats after fifteen years in a southwest florida preserve, usa. | herpetofaunal declines have been documented globally, and southern florida, usa, is an especially vulnerable region because of high impacts from hydrological perturbations and nonindigenous species. to assess the extent of recent change in herpetofauna community composition, we established a baseline inventory during 1995-97 at a managed preserve in a habitat rich area of southwest florida, and repeated our sampling methods fifteen years later (2010-11). nine drift fence arrays were placed in fo ... | 2015 | 26016475 |
| retinal ganglion cells in the eastern newt notophthalmus viridescens: topography, morphology, and diversity. | the topography and morphology of retinal ganglion cells (rgcs) in the eastern newt were studied. cells were retrogradely labeled with tetramethylrhodamine-conjugated dextran amines or horseradish peroxidase and examined in retinal wholemounts. their total number was 18,025 +/- 3,602 (mean +/- sem). the spatial density of rgcs varied from 2,100 cells/mm(2) in the retinal periphery to 4,500 cells/mm(2) in the dorsotemporal retina. no prominent retinal specializations were found. the spatial resolu ... | 2009 | 19673005 |
| light-dependent magnetic compass in iberian green frog tadpoles. | here, we provide evidence for a wavelength-dependent effect of light on magnetic compass orientation in pelophylax perezi (order anura), similar to that observed in rana catesbeiana (order anura) and notophthalmus viridescens (order urodela), and confirm for the first time in an anuran amphibian that a 90° shift in the direction of magnetic compass orientation under long-wavelength light (≥ 500 nm) is due to a direct effect of light on the underlying magnetoreception mechanism. although magnetic ... | 2010 | 20978882 |
| analysis of chromatin-associated fiber arrays. | electron microscopic examination of chromatin from embryonic nuclei of oncopeltus fasciatus and drosophila melanogaster reveals arrays of chromatin associated fibers. the lengths and spacings of these fibers were analyzed to provide a basis for defining and interpreting regions of transcriptionally active chromatin. the results of the analysis are consistent with the interpretation of some fibers as nascent rna with associated protein (rnp). the chromatin segments underlying these fiber arrays w ... | 1976 | 826376 |
| a linkage map for the newt notophthalmus viridescens: insights in vertebrate genome and chromosome evolution. | genetic linkage maps are fundamental resources that enable diverse genetic and genomic approaches, including quantitative trait locus (qtl) analyses and comparative studies of genome evolution. it is straightforward to build linkage maps for species that are amenable to laboratory culture and genetic crossing designs, and that have relatively small genomes and few chromosomes. it is more difficult to generate linkage maps for species that do not meet these criteria. here, we introduce a method t ... | 2016 | 27265323 |
| chryseobacterium angstadtii sp. nov., isolated from a newt tank. | as part of an undergraduate microbiology course, a yellow-orange-pigmented, gram-staining negative, rod-shaped, non-motile bacterial strain was isolated from a glass tank housing several red-spotted newts (notophthalmus viridescens). the sequence of the 16s rrna gene of this strain, designated km(t), was 97.4-98.0 % similar to those of the type strains of chryseobacterium luteum, c. shigense and c. vrystaatense, while the similarity levels for protein-coding genes were less than 94.7 % for rpob, ... | 2013 | 23996834 |
| field evidence for leech-borne transmission of amphibian ichthyophonus sp. | parasites have been implicated in mass mortality events and population declines of amphibians around the world. one pathogen associated with mortality events in north america is an ichthyophonus sp.-like organism that affects red-spotted newts (notophthalmus viridescens) and several frog species, yet little is known about the distribution of this pathogen in wild populations or the mechanism of transmission. in an effort to identify factors influencing the distribution and abundance of this path ... | 2006 | 17304803 |
| a search for immunoreactive substance p and other neural peptides in the limb regenerate of the newt notophthalmus viridescens. | immunochemical studies demonstrate that the undecapeptide substance p (sp) may be detected by radioimmunoassay in newt limb regenerates and that sp is localized in the blastemal epidermis by immunofluorescence and peroxidase-antiperoxidase staining. immunoreactive sp is predominantly distributed at the periphery of epidermal cells, suggesting the presence of sp binding sites on the cell surface; the basal germinative layer of the epidermis and blastemal mesenchyme cells remain unreactive. the pa ... | 1990 | 1693394 |
| plagitura intermedia sp. n. (trematoda: plagiorchiidae) from the common newt, notophthalmus viridescens viridescens. | | 1965 | 5857275 |
| dominance-function relationships in the amphibian skin microbiome. | some amphibian skin bacteria inhibit growth of a fungal amphibian pathogen, batrachochytrium dendrobatidis (bd), but it is unclear how dominant these anti-bd bacteria are in skin communities. using in vitro co-culture challenge assays, we quantified bd inhibition by bacterial isolates collected from the skin of four amphibian species: bullfrogs, eastern newts, spring peepers and american toads. the 16s rrna sequences for each isolate were matched to culture-independent amplicon sequences from th ... | 2017 | 28677171 |
| the influence of breeding phenology on the genetic structure of four pond-breeding salamanders. | understanding metapopulation dynamics requires knowledge about local population dynamics and movement in both space and time. most genetic metapopulation studies use one or two study species across the same landscape to infer population dynamics; however, using multiple co-occurring species allows for testing of hypotheses related to different life history strategies. we used genetic data to study dispersal, as measured by gene flow, in three ambystomatid salamanders (ambystoma annulatum, a. mac ... | 2017 | 28690797 |
| modifications of the genital kidney proximal and distal tubules for sperm transport in notophthalmus viridescens (amphibia, urodela, salamandridae). | male salamanders use nephrons from the genital kidney to transport sperm from the testicular lobules to the wolffian duct. the microstructure of the epithelia of the genital kidney proximal tubule and distal tubule was studied over 1 year in a population of notophthalmus viridescens from crawford and pike counties in central missouri. through ultrastructural analysis, we were able to support the hypothesis that the genital kidney nephrons are modified to aid in the transportation of sperm. a lac ... | 2014 | 24643856 |
| studying newt brain regeneration following subtype specific neuronal ablation. | the realization that neuronal injury does not result in permanent functional or cellular loss in all vertebrates has fascinated regenerative biologists. neuronal regeneration occurs in a subset of species, including lizards, teleost fish, axolotls, and newts. one tool for studying neuronal regeneration in the adult brain is intraventricular injection of selective neuronal toxins, which leads to loss of subpopulations of neurons. to trace cells involved in the regeneration process, plasmids encod ... | 2015 | 25740479 |
| fundamental differences in dedifferentiation and stem cell recruitment during skeletal muscle regeneration in two salamander species. | salamanders regenerate appendages via a progenitor pool called the blastema. the cellular mechanisms underlying regeneration of muscle have been much debated but have remained unclear. here we applied cre-loxp genetic fate mapping to skeletal muscle during limb regeneration in two salamander species, notophthalmus viridescens (newt) and ambystoma mexicanum (axolotl). remarkably, we found that myofiber dedifferentiation is an integral part of limb regeneration in the newt, but not in axolotl. in ... | 2014 | 24268695 |
| expression of complement 3 and complement 5 in newt limb and lens regeneration. | some urodele amphibians possess the capacity to regenerate their body parts, including the limbs and the lens of the eye. the molecular pathway(s) involved in urodele regeneration are largely unknown. we have previously suggested that complement may participate in limb regeneration in axolotls. to further define its role in the regenerative process, we have examined the pattern of distribution and spatiotemporal expression of two key components, c3 and c5, during limb and lens regeneration in th ... | 2003 | 12594255 |
| expression of the third component of complement, c3, in regenerating limb blastema cells of urodeles. | in this study we have shown that complement component c3 is expressed in the regenerating tissue during urodele limb regeneration. c3 was expressed in the dedifferentiated regeneration blastema and in the redifferentiated limb tissues in the axolotl, amblystoma mexicanum, and in notophthalmus viridescens. this expression was verified by immunofluorescent staining using an ab against axolotl c3 and by in situ hybridization with an axolotl c3 cdna probe. in the early stages of regeneration c3 appe ... | 1998 | 9862713 |
| retinoic acid-induced pattern duplication in regenerating urodele limbs. | the effects of varying doses of retinoic acid on forelimb regeneration in larval ambystoma mexicanum amputated through the wrist joint and in adult notophthalmus viridescens amputated through the basal carpals were compared. in both species, the major effect of retinoic acid was to cause the proximodistal duplication, in the regenerate, of stump segments proximal to the amputation plane. transverse axial duplications (anteroposterior and dorsoventral) occurred in a smaller percentage of cases; t ... | 1984 | 6724131 |
| the formation of muscles in regenerating limbs of the newt after denervation of the blastema. | the purpose of this experiment was to examine the relationship, if any, between nerve fibers and the formation of muscle pattern in the regenerating amphibian limb. during embryogenesis, nerve fibers grow into the limb bud at the time when the common muscle blastemas subdivide into individual muscle primordia, whereas in regeneration nerve fibers are always present. in order to learn whether or not the muscle pattern could be laid down in the absence of nerves we amputated 58 limbs of newts (not ... | 1979 | 528874 |
| histological observations on allografts and reciprocal xenografts in newts (notophthalmus viridescens) and axolotis (ambystoma mexicanum). | | 1972 | 4561282 |
| spheroidal and ring nucleoli in amphibian oocytes. patterns of uridine incorporation and fine structural features. | in maturing oocytes of the newt triturus viridescens, the nucleoli undergo a series of morphological changes that are very similar to those described by callan for the axolotl, ambystoma mexicanum. the nucleoli first assume the form of spheroids which then become extended into ring or necklace shapes that are dnase-sensitive; in mature oocytes the nucleoli revert to a spheroidal form. short term in vitro incorporation studies with uridine-(3)h on both species show that rna synthesis occurs in a ... | 1967 | 6055993 |
| comparative and developmental patterns of amphibious auditory function in salamanders. | early amphibious tetrapods may have detected aquatic sound pressure using sound-induced lung vibrations, but their lack of tympanic middle ears would have restricted aerial sensitivity. sharing these characteristics, salamanders could be models for the carryover of auditory function across an aquatic-terrestrial boundary without tympanic middle ears. we measured amphibious auditory evoked potential audiograms in five phylogenetically and ecologically distinct salamanders (amphiuma means, notopht ... | 2016 | 27766381 |
| novel requirements in peripheral structures of the extended satellite 2 hammerhead. | a number of rnas that infect plants self-cleave using a domain called the hammerhead. the consensus plant hammerhead has three base paired stem structures. stems i and iii flank the cleaved phosphodiester and are connected to stem ii by two unpaired and highly conserved sequences. we demonstrated previously that satellite 2 transcripts from the newt, notophthalmus viridescens, use a modified hammerhead structure for self-cleavage. here we show that hammerheads with similar modifications occur in ... | 1996 | 8756412 |
| dna replication in the amphibia. | autoradiographic techniques were used to measure rate of replication and length of the replication unit in cultured cells of scaphiopus couchi, bufo cognatus, rana clamitans, and triturus viridescens, having nuclear dna amounts in the ratio 1:4:7:39 respectively. the autoradiographic experiments were designed to show whether the larger amounts of nuclear dna are correlated with more rapid rates of synthesis and/or with longer replication units. -- the dna replication rate was 2.5 mu/minute (corr ... | 1975 | 125187 |
| keystone predators (eastern newts, notophthalmus viridescens) reduce the impacts of an aquatic invasive species. | predation, competition, and their interaction are known to be important factors that influence the structure of ecological communities. in particular, in those cases where a competitive hierarchy exists among prey species, the presence of certain keystone predators can result in enhanced diversity in the prey community. however, little is known regarding the influence of keystone predator presence on invaded prey communities. given the widespread occurrence of invasive species and substantial co ... | 2006 | 16463174 |
| functional trade-offs in the aquatic feeding performance of salamanders. | during aquatic feeding salamanders use the hyobranchial apparatus to capture prey. the hyobranchial apparatus depresses the floor of the mouth, effectively expanding the oropharyngeal cavity and generating suction. within the family salamandridae, there is a wide range of ecological diversity, with salamanders being terrestrial, semi-aquatic, or aquatic as adults. the purpose of this research was to quantify the diverse morphology and suction feeding performance of aquatically feeding salamandri ... | 2017 | 28893437 |
| tetrodotoxin in asian newts (salamandridae). | tetrodotoxin (ttx) and its analogues occur in a wide range of marine animals but also in terrestrial vertebrates such as frogs, toads and newts. despite numerous studies on ttx in new world newts (notophthalmus viridescens, taricha spp.), few data only exist for asian newts. methanolic extracts of newts from china (cynops orientalis, pachytriton labiatus, paramesotriton chinensis), vietnam (paramesotriton deloustali, p. guangxiensis), and laos (laotriton laoensis) were analyzed by liquid-chromat ... | 2017 | 28528177 |
| [identification of the gene encoding nucleostemin in the eye tissues of pleurodeles waltl]. | nucleotide sequences were identified in the eye tissues (lens, retina, and retinal pigment epithelium) of the adult newt pleurodeles waltl by the polymerase chain reaction with primers for the ns gene. sequencing showed that these nucleotide sequences belong to the ns gene of the newt p. walt, which encodes the nucleolar protein nucleostemin. structural analysis revealed a high homology of ns nucleotide sequences of p. walt! with those of newts. cynops pyrrhogaster and notophthalmus viridescens. ... | 2016 | 26638232 |
| differential avoidance of mimetic salamanders by free-ranging birds. | members of a free-ranging avian community avoided the mimetic morph of the salamander plethodon cinereus significantly more often than a nonmimetic morph when offered with the model eft stage of notophthalmus viridescens and the palatable salamander desmognathus ochrophaeus. this is apparently the first demonstration of the efficacy of mimetic coloration of salamanders to uncaged birds. | 1980 | 17745538 |
| effects of parentage on competitive ability and vulnerability to predation in hyla chrysoscelis tadpoles. | four sibships of hyla chrysoscelis larvae were used to examine the effects of parentage on mass at day 23 of growth and on vulnerability to predation. the h. chrysoscelis larvae were raised alone, in competition with rana clamitans larvae, and in competition with siblings. vulnerability to predation by adult notophthalmus viridescens dorsalis was evaluated for hyla that had been raised in competition with siblings. sibships differed in body mass and vulnerability to predation. competition with r ... | 1986 | 28310127 |
| immunocytochemical localization of fibronectin in limb tissues of the adult newt, notophthalmus viridescens. | this study describes the immunocytochemical localization of fibronectin, a defined connective tissue and plasma glycoprotein, and its relationship to collagen and reticulin in adult newt limb tissues. we have also isolated the plasma form of fibronectin in a related species, the adult mudpuppy. the insoluble form of fibronectin was detected with immunoperoxidase stain in basement membranes and loose connective tissue. the endoneurium and perineurium of nerve bundles and the connective tissue ele ... | 1981 | 7024400 |
| cellular basis of brain maturation and acquisition of complex behaviors in salamanders. | the overall bauplan of the tetrapod brain is highly conserved, yet significant variations exist among species in terms of brain size, structural composition and cellular diversity. understanding processes underlying neural and behavioral development in a wide range of species is important both from an evolutionary developmental perspective as well as for the identification of cell sources with post-developmental neurogenic potential. here, we characterize germinal processes in the brain of notop ... | 0 | 29217751 |
| the association between male-biased sex ratio and indicators of stress in red-spotted newts. | in populations with a male-biased operational sex ratio, coercive mating by males can have fitness consequences for females. one component of reduced fitness for females in populations with a male-biased osr may be greater activation of the stress response, resulting in higher corticosterone release rates (cort; a glucocorticoid stress hormone in amphibians). we test the hypothesis that a male-biased sex ratio affects female activity and release rates of cort and testosterone (t) in male and fem ... | 2017 | 28167148 |
| phylogeography and evolution of the red salamander (pseudotriton ruber). | phylogeographic studies frequently result in the elevation of subspecific taxa to species given monophyly, or the synonymy of subspecies that are not monophyletic. however, given limited or incongruent datasets, retention of subspecies can be useful to describe hypothesized incipient species or to illustrate interesting biological phenomena driving morphological diversity. four subspecific taxa have been used to describe largely allopatric geographic variation within the species pseudotriton rub ... | 2016 | 26872531 |
| ecological character displacement between the sexes. | theory suggests that the evolution of sexual dimorphism in ecologically relevant traits can evolve purely through competition between the sexes for a shared resource. although more parsimonious hypotheses exist for the evolution of ecological sexual dimorphisms, there are some underappreciated reasons to expect that competition may often play some role in the evolution of sexual dimorphism. here, we build on past work to outline a set of sufficient criteria to demonstrate a role for resource com ... | 2015 | 26655977 |
| the mesencephalic locomotor region sends a bilateral glutamatergic drive to hindbrain reticulospinal neurons in a tetrapod. | in vertebrates, stimulation of the mesencephalic locomotor region (mlr) on one side evokes symmetrical locomotor movements on both sides. how this occurs was previously examined in detail in a swimmer using body undulations (lamprey), but in tetrapods the downstream projections from the mlr to brainstem neurons are not fully understood. here we examined the brainstem circuits from the mlr to identified reticulospinal neurons in the salamander notophthalmus viridescens. using neural tracing, we s ... | 2016 | 26470600 |
| is there more than one way to skin a newt? convergent toxin resistance in snakes is not due to a common genetic mechanism. | convergent evolution of tetrodotoxin (ttx) resistance, at both the phenotypic and genetic levels, characterizes coevolutionary arms races between amphibians and their snake predators around the world, and reveals remarkable predictability in the process of adaptation. here we examine the repeatability of the evolution of ttx resistance in an undescribed predator-prey relationship between ttx-bearing eastern newts (notophthalmus viridescens) and eastern hog-nosed snakes (heterodon platirhinos). w ... | 2016 | 26374236 |
| a differential response to newt regeneration extract by c2c12 and primary mammalian muscle cells. | dedifferentiation, a process whereby differentiated cells lose their specialized characteristics and revert to a less differentiated state, plays a key role in the regeneration process in urodele amphibians such as the red spotted newt, notophthalmus viridescens. dedifferentiation of fully mature tissues is generally absent in mammalian cells. previous studies have shown that mouse c2c12 multinucleated myotubes treated with extract derived from regenerating newt forelimbs can re-enter the cell c ... | 2015 | 26090089 |
| high pheromone diversity in the male cheek gland of the red-spotted newt notophthalmus viridescens (salamandridae). | male salamanders (urodela) often make use of pheromones that are produced in sexually dimorphic glands to persuade the female into courtship and mating. the mental gland of lungless salamanders (plethodontidae) and dorsal cloacal glands (or abdominal glands) of newts (salamandridae) have been particularly well studied in that respect. in both families, sodefrin precursor-like factor (spf) proteins have been identified as major components of the courtship pheromone system. however, similar to ple ... | 2015 | 25888438 |
| batesian mimics influence the evolution of conspicuousness in an aposematic salamander. | conspicuousness, or having high contrast relative to the surrounding background, is a common feature of unpalatable species. several hypotheses have been proposed to explain the occurrence of conspicuousness, and while most involve the role of conspicuousness as a direct signal of unpalatability to potential predators, one hypothesis suggests that exaggerated conspicuousness may evolve in unpalatable species to reduce predator confusion with palatable species (potential batesian mimics). this hy ... | 2015 | 25786622 |
| parasitism and the expression of sexual dimorphism. | although a negative covariance between parasite load and sexually selected trait expression is a requirement of few sexual selection models, such a covariance may be a general result of life-history allocation trade-offs. if both allocation to sexually selected traits and to somatic maintenance (immunocompetence) are condition dependent, then in populations where individuals vary in condition, a positive covariance between trait expression and immunocompetence, and thus a negative covariance bet ... | 2015 | 25750721 |
| data mining in newt-omics, the repository for omics data from the newt. | salamanders are an excellent model organism to study regenerative processes due to their unique ability to regenerate lost appendages or organs. straightforward bioinformatics tools to analyze and take advantage of the growing number of "omics" studies performed in salamanders were lacking so far. to overcome this limitation, we have generated a comprehensive data repository for the red-spotted newt notophthalmus viridescens, named newt-omics, merging omics style datasets on the transcriptome an ... | 2015 | 25740498 |
| maintaining eastern newts (notophthalmus viridescens) for regeneration research. | the adult eastern newt, notophthalmus viridescens, has long served as a model for appendage as well as heart muscle regeneration studies. newt tissues include all major cell types known in other vertebrates and mammals, including bone, cartilage, tendon, muscle, nerves, dermis, and epidermis. therefore, these aquatic salamanders make an excellent model for studying the regeneration of complex tissues. regeneration of adult tissues requires the integration of new tissues with preexisting tissues ... | 2015 | 25740474 |
| the thermal plasticity of locomotor performance has diverged between northern and southern populations of the eastern newt (notophthalmus viridescens). | many temperate ectotherms undergo thermal acclimation to remain functional over a wide range of body temperatures, but few studies have investigated whether populations of a single species have evolved differences in the thermal plasticity of locomotor performance. therefore, we asked whether the thermal plasticity of locomotor performance has diverged between northern and southern populations of eastern newts (notophthalmus viridescens). we acclimated eastern newts from florida and maine to col ... | 2015 | 25388211 |
| does the thermal plasticity of metabolic enzymes underlie thermal compensation of locomotor performance in the eastern newt (notophthalmus viridescens)? | eastern newts (notophthalmus viridescens) upregulate the metabolic capacity of skeletal muscle in winter to compensate for thermodynamic effects on metabolism. however, whether this compensation facilitates locomotor performance at low temperature is unknown. therefore, our aim was to determine if thermal acclimation of metabolic enzymes in muscle benefits locomotion. eastern newts from southern ohio were acclimated to cold (5°c, 10:14 l:d) or warm (25°c, 14:10 l:d) conditions for 12 weeks. foll ... | 2015 | 25382581 |
| an acute increase in the stress hormone corticosterone is associated with mating behavior in both male and female red-spotted newts, notophthalmus viridescens. | hormones play key, functional roles in mediating the tradeoff between survival and reproduction. glucocorticoid hormones can inhibit reproduction and improve chances of survival during periods of stress. however, glucocorticoid hormones are, at times, also associated with successfully engaging in energetically costly courtship and mating behaviors. corticosterone (cort), a primary glucocorticoid hormone in amphibians, reptiles and birds, may be important in activating or sustaining energetically ... | 2014 | 25157790 |
| exogenous oct-4 inhibits lens transdifferentiation in the newt notophthalmus viridescens. | from the cocktail of four factors that were able to induce pluripotent stem cells from differentiated cells, oct-4, c-myc, sox-2 and klf4, only oct-4 was not expressed during regeneration in newts. to explore the possible action of this stemness factor we developed an assay where we introduced exogenous oct-4 protein to an in vitro system for lens regeneration in newts. we found that exogenous oct-4 inhibits differentiation of iris pigmented epithelial cells into lens cells and also regulates so ... | 2014 | 25019378 |
| interactive effects of competition and social environment on the expression of sexual dimorphism. | the expression of sexual dimorphism is expected to be influenced by the acquisition of resources available to allocate to trait growth, combined with sex-specific patterns of resource allocation. resource acquisition in the wild may be mediated by a variety of ecological factors, such as the density of interspecific competitors. allocation may in turn depend on social contexts, such as sex ratio, that alter the pay-off for investment in sexual traits. how these factors interact to promote or con ... | 2014 | 24819816 |
| a stable niche assumption-free test of ecological divergence. | understanding the impact of geological events on diversification processes is central to evolutionary ecology. the recent amalgamation between ecological niche models (enms) and phylogenetic analyses has been used to estimate historical ranges of modern lineages by projecting current ecological niches of organisms onto paleoclimatic reconstructions. a critical assumption underlying this approach is that niches are stable over time. using notophthalmus viridescens (eastern newt), in which four ec ... | 2014 | 24632489 |
| predator perception of batesian mimicry and conspicuousness in a salamander. | in batesian mimicry a palatable mimic deceives predators by resembling an unpalatable model. the evolution of batesian mimicry relies on the visual capabilities of the potential predators, as prey detection provides the selective force driving evolutionary change. we compared the visual capabilities of several potential predators to test predictions stemming from the hypothesis of batesian mimicry between two salamanders: the model species notophthalmus viridescens, and polymorphic mimic, pletho ... | 2014 | 24274647 |
| mir-128 regulates non-myocyte hyperplasia, deposition of extracellular matrix and islet1 expression during newt cardiac regeneration. | cardiovascular disease is a global scourge to society, with novel therapeutic approaches required in order to alleviate the suffering caused by sustained cardiac damage. micrornas (mirnas) are being touted as one such approach in the fight against heart disease, acting as possible post-transcriptional molecular triggers responsible for invoking cardiac regeneration. to further ones understanding of mirnas and cardiac regeneration, it is prudent to learn from organisms that can intrinsically rege ... | 2013 | 24055866 |
| a focus on the optical properties of the regenerated newt lens. | lens regeneration studies in the adult newt suggest that molecular aspects of lens regeneration are complete within 5 weeks of lentectomy. however, very little is known about the optical properties of the regenerated lens. in an aquatic environment, the lens accounts for almost all of the refractive power of the eye, and thus, a fully functional lens is critical. we compared the optical properties of 9- and 26-week regenerated lenses in the red spotted newt, notophthalmus viridescens, with the o ... | 2013 | 23990914 |
| intrinsic lens forming potential of mouse lens epithelial versus newt iris pigment epithelial cells in three-dimensional culture. | adult newts (notophthalmus viridescens) are capable of complete lens regeneration that is mediated through dorsal iris pigment epithelial (ipe) cells transdifferentiation. in contrast, higher vertebrates such as mice demonstrate only limited lens regeneration in the presence of an intact lens capsule with remaining lens epithelial cells. to compare the intrinsic lens regeneration potential of newt ipe versus mouse lens epithelial cells (mle), we have established a novel culture method that uses ... | 2014 | 23672748 |
| salamander hox clusters contain repetitive dna and expanded non-coding regions: a typical hox structure for non-mammalian tetrapod vertebrates? | hox genes encode transcription factors that regulate embryonic and post-embryonic developmental processes. the expression of hox genes is regulated in part by the tight, spatial arrangement of conserved coding and non-coding sequences. the potential for evolutionary changes in hox cluster structure is thought to be low among vertebrates; however, recent studies of a few non-mammalian taxa suggest greater variation than originally thought. using next generation sequencing of large genomic fragmen ... | 2013 | 23561734 |
| a reference transcriptome and inferred proteome for the salamander notophthalmus viridescens. | salamanders have a remarkable capacity to regenerate complex tissues, such as limbs and brain, and are therefore an important comparative model system for regenerative medicine. despite these unique properties among adult vertebrates, the genomic information for amphibians in general, and salamanders in particular, is scarce. here, we used massive parallel sequencing to reconstruct a de novo reference transcriptome of the red spotted newt (notophthalmus viridescens) containing 118,893 transcript ... | 2013 | 23454602 |
| a de novo assembly of the newt transcriptome combined with proteomic validation identifies new protein families expressed during tissue regeneration. | notophthalmus viridescens, an urodelian amphibian, represents an excellent model organism to study regenerative processes, but mechanistic insights into molecular processes driving regeneration have been hindered by a paucity and poor annotation of coding nucleotide sequences. the enormous genome size and the lack of a closely related reference genome have so far prevented assembly of the urodelian genome. | 2013 | 23425577 |
| a microarray analysis of gene expression patterns during early phases of newt lens regeneration. | notophthalmus viridescens, the red-spotted newt, possesses tremendous regenerative capabilities. among the tissues and organs newts can regenerate, the lens is regenerated via transdifferentiation of the pigment epithelial cells of the dorsal iris, following complete removal (lentectomy). under normal conditions, the same cells from the ventral iris are not capable of regenerating. this study aims to further understand the initial signals of lens regeneration. | 2013 | 23378727 |
| multi-tissue microarray analysis identifies a molecular signature of regeneration. | the inability to functionally repair tissues that are lost as a consequence of disease or injury remains a significant challenge for regenerative medicine. the molecular and cellular processes involved in complete restoration of tissue architecture and function are expected to be complex and remain largely unknown. unlike humans, certain salamanders can completely regenerate injured tissues and lost appendages without scar formation. a parsimonious hypothesis would predict that all of these rege ... | 2012 | 23300656 |
| behavioral and physiological female responses to male sex ratio bias in a pond-breeding amphibian. | the phenomenon of sexual conflict has been well documented, and in populations with biased operational sex ratios the consequences for the rarer sex can be severe. females are typically a limited resource and males often evolve aggressive mating behaviors, which can improve individual fitness for the male while negatively impacting female condition and fitness. in response, females can adjust their behavior to minimize exposure to aggressive mating tactics or minimize the costs of mating harassm ... | 2012 | 22988835 |
| spiked-in pulsed in vivo labeling identifies a new member of the ccn family in regenerating newt hearts. | the newt notophthalmus viridescens , which belongs to the family of salamanders (urodela), owns remarkable regenerative capacities allowing efficient scar-free repair of various organs including the heart. salamanders can regrow large parts of the myocardium unlike mammals, which cannot replace lost cardiomyocytes efficiently. unfortunately, very little is known about the molecules and the regulatory circuits facilitating efficient heart regeneration in newts or salamanders. to identify proteins ... | 2012 | 22891955 |
| recovery of function following regeneration of the damaged retina in the adult newt, notophthalmus viridescens. | the red-spotted newt, notophthalmus viridescens, is one of few adult vertebrate organisms that has retained the remarkable ability to regenerate a complete retina following injury or removal. the aim of this study was to develop a non-invasive method to monitor recovery of components within the retinal circuitry, in vivo, following surgical removal (retinectomy) of the adult newt retina. a novel and reproducible protocol was established for full-field electroretinography in the intact newt retin ... | 2012 | 22729667 |
| temperature preference during forelimb regeneration in the red-spotted newt notophthalmus viridescens. | red-spotted newts (notophthalmus viridescens) are model organisms for regenerative research. these animals can regenerate limbs, tails, jaws, spinal cords, as well as the lens of the eye. newts are small ectotherms that are aquatic as adults; as ectotherms, they naturally conform to the temperature of their surroundings. environmental temperatures, however, can increase or decrease the red-spotted newt's metabolic processes, including their rate of tissue regeneration; whether an optimal tempera ... | 2012 | 22539209 |
| tetrodotoxin does not protect red-spotted newts, notophthalmus viridescens, from intestinal parasites. | tetrodotoxin (ttx) and its analogue 6-epittx had been detected in the red-spotted newt, notophthalmus viridescens. thirty specimens of a population from pennsylvania, usa were histologically examined for the presence of intestinal parasites. more than 50% were found to be infected with nematodes (trichocephalidae), trematodes or cestodes (pseudophyllidae). the mean values of ttx and 6-epittx in parasitized and in non-parasitized newts were not significantly different. using a monoclonal antibody ... | 2012 | 22480787 |
| biochemical and mechanical environment cooperatively regulate skeletal muscle regeneration. | during forelimb regeneration in the newt notophthalmus viridescens, the dynamic expression of a transitional matrix rich in hyaluronic acid, tenascin-c, and fibronectin controls muscle cell behavior in vivo and in vitro. however, the influence of extracellular matrix (ecm) remodeling on tissue stiffness and the cellular response to mechanical variations during regeneration was unknown. by measuring the transverse stiffness of tissues in situ, we found undifferentiated regenerative blastemas were ... | 2012 | 22415307 |
| variability of tetrodotoxin and of its analogues in the red-spotted newt, notophthalmus viridescens (amphibia: urodela: salamandridae). | efts and adult specimens (n = 142) of the red-spotted newt notophthalmus viridescens from various locations in canada and usa were analyzed for the presence of tetrodotoxin (ttx) and of its analogues 6-epitetrodotoxin and 11-oxotetrodotoxin. considerable individual variations in toxin levels were found within and among populations from new hampshire, new york, pennsylvania, and virginia ranging from non-detectable to 69 μg ttx per g newt. ttx and its analogues were absent in efts and adults from ... | 2012 | 22197660 |
| newt-omics: a comprehensive repository for omics data from the newt notophthalmus viridescens. | notophthalmus viridescens, a member of the salamander family is an excellent model organism to study regenerative processes due to its unique ability to replace lost appendages and to repair internal organs. molecular insights into regenerative events have been severely hampered by the lack of genomic, transcriptomic and proteomic data, as well as an appropriate database to store such novel information. here, we describe 'newt-omics' (http://newt-omics.mpi-bn.mpg.de), a database, which enables r ... | 2012 | 22039101 |
| life history benefits of residency in a partially migrating pond-breeding amphibian. | species with partial migration, where a portion of a population migrates and the other remains residential, provide the opportunity to evaluate conditions for migration and test mechanisms influencing migratory decisions. we conducted a five-year study of two populations of red-spotted newts (notophthalmus viridescens), composed of individuals that either remain as residents in the breeding pond over the winter or migrate to the terrestrial habitat. we used multistate mark-recapture methods to ( ... | 2011 | 21797152 |
| efficient regeneration by activation of neurogenesis in homeostatically quiescent regions of the adult vertebrate brain. | in contrast to mammals, salamanders and teleost fishes can efficiently repair the adult brain. it has been hypothesised that constitutively active neurogenic niches are a prerequisite for extensive neuronal regeneration capacity. here, we show that the highly regenerative salamander, the red spotted newt, displays an unexpectedly similar distribution of active germinal niches with mammals under normal physiological conditions. proliferation zones in the adult newt brain are restricted to the for ... | 2010 | 21068061 |
| endogenous regeneration after collagenase-induced knee joint damage in the adult newt notophthalmus viridescens. | to determine whether adult newts (notophthalmus viridescens) are able to repair experimentally-induced joint damage in order to generate a model system for the study of endogenous joint regeneration. | 2011 | 20810393 |
| toxicity of coal-tar and asphalt sealants to eastern newts, notophthalmus viridescens. | between 1970 and 2000 the concentration of total polycyclic aromatic hydrocarbons (tpah) in several lakes across the country increased whereas those of other persistent organic pollutants (pops) tended to remain stable or declined. urbanized watersheds experienced greater rises in tpah concentration compared to non-urban lakes. sources for urban pahs include industrial wastes, vehicular exhausts and oil leaks and sealants from pavement surfaces. both coal-tar and asphalt sealants are used to pro ... | 2010 | 20696464 |
| phenotypic flexibility and thermoregulatory behavior in the eastern red-spotted newt (notophthalmus viridescens viridescens). | eastern red-spotted newts are ectotherms, aquatic as adults, and active year-round, breeding even during winter under ice. earlier research, with field-captured newts, showed a correlation between seasonal changes in the activity of some muscle metabolic enzymes and in the behavior of the newts in a thermal gradient. this study was undertaken to further characterize acclimatory responses in the newts in a more controlled laboratory environment. newts were obtained during fall, and maintained at ... | 2010 | 20187089 |
| tissue distribution of tetrodotoxin in the red-spotted newt notophthalmus viridescens. | high levels of tetrodotoxin (ttx) and of its analogue 6-epi-tetrodotoxin have been detected in skin and liver extracts of the red-spotted newt notophthalmus viridescens assayed by a post-column fluorescent-hplc system. using a monoclonal antibody-based immunoenzymatic technique, ttx was localized in the granular glands of the epidermis as well as in the muscle layer between the muscle fibres, but also in most organs suggesting that ttx is stored in the whole body of the newt and is secreted by s ... | 2010 | 20167230 |
| advanced identification of proteins in uncharacterized proteomes by pulsed in vivo stable isotope labeling-based mass spectrometry. | despite progress in the characterization of their genomes, proteomes of several model organisms are often only poorly characterized. this problem is aggravated by the presence of large numbers of expressed sequence tag clones that lack homologues in other species, which makes it difficult to identify new proteins irrespective of whether such molecules are involved in species-specific biological processes. we have used a pulsed stable isotope labeling with amino acids in cell culture (silac)-base ... | 2010 | 20139370 |
| a new species of hysterothylacium (nematoda: anisakidae) from the stomach of the red-spotted newt, notophthalmus viridescens, from pennsylvania fishless ponds. | species of hysterothylacium ward & magath, 1917 (nematoda: anisakidae) have previously been reported only from marine and freshwater fishes. here, we describe a new species that infects red-spotted newts (notophthalmus viridescens), a north american amphibian species with fully aquatic adults. aside from the unique characteristic of infecting an amphibian host, the new species differs from congeners by the presence of lateral alae, the length of intestinal cecum (0.54–0.73 mm, 39.67–49.09% of es ... | 2009 | 19473051 |
| comparison of buprenorphine and butorphanol analgesia in the eastern red-spotted newt (notophthalmus viridescens). | the experimental use of amphibian models in biomedical research increases yearly, but there is a paucity of reports concerning analgesic use in many of these species. in this study, buprenorphine given by intracoelomic injection and butorphanol added to the tank water were compared for analgesic effect in the eastern red-spotted newt after bilateral forelimb amputations. newts undergoing anesthesia but not surgery and newts having surgery but not given analgesia postoperatively were used as cont ... | 2009 | 19383214 |
| sex- and context-dependent migration in a pond-breeding amphibian. | partial migration, variation in the percentage of a population that completes a migration, can be influenced by the local environment and condition of an individual. we examined the direct and interacting effects of habitat quality and gender on migration decision by manipulating population density and sex ratio in a factorial field experiment using aquatic enclosures. in partially migrating red-spotted newts (notophthalmus viridescens), we measured the percentage of newts migrating to the terre ... | 2009 | 19323212 |
| life cycle polyphenism as a factor affecting ecological divergence within notophthalmus viridescens. | polyphenism, which allows a single genotype to express multiple discrete phenotypes in response to environmental cues, is an adaptive trait in heterogeneous environments. pond hydroperiod is an important ecological parameter affecting amphibian life history, and variation in local pond hydrology has been hypothesized to play a role in species divergence via changes in polyphenism. the eastern newt (notophthalmus viridescens) expresses life cycle polyphenism. larvae develop along three possible p ... | 2008 | 18709388 |
| parasite age-intensity relationships in red-spotted newts: does immune memory influence salamander disease dynamics? | acquired immune memory in vertebrates influences transmission and persistence of infections, with consequences for parasite dynamics at both the individual and population levels. the potential impact of acquired immunity is of particular interest for salamanders, whose acquired immune systems are thought to be less effective than those of frogs and other tetrapods. one way to examine the importance of acquired immunity to parasite dynamics at the population level is by examining the relationship ... | 2009 | 18708064 |
| newt opportunities for understanding the dedifferentiation process. | urodele amphibians, such as the newt notophthalmus viridescens, have the unique ability to regenerate limbs, spinal cord, eye structures, and many vital organs through a process called epimorphic regeneration. although the cellular basis of regeneration has been studied in detail, we know relatively little about the molecular controls of the process. this review provides an overview of forelimb regeneration in the newt, addressing what we know about cellular and molecular aspects. particular foc ... | 2006 | 17205187 |
| timing the commitment to a wound-healing response of denervated limb stumps in the adult newt, notophthalmus viridescens. | adult newt limbs that are denervated 1 day after amputation undergo a wound-healing response and, although they become reinnervated, will not regenerate unless reinjured. experiments were designed to determine when denervated limb stumps of adult newts become committed to a wound-healing response. in experiment i, limbs were amputated and denervated 1 day after amputation. on days 7, 14, 21, 28, and 35 days after the initial amputation and denervation, stumps were reamputated to remove the dista ... | 2006 | 16939577 |
| correlation of seasonal acclimatization in metabolic enzyme activity with preferred body temperature in the eastern red spotted newt (notophthalmus viridescens viridescens). | eastern red spotted newts, as aquatic adults, are active year round. they are small and easy to handle, and thus lent themselves to a laboratory study of seasonal changes in preferred body temperature and biochemical acclimatization. we collected newts in summer (n=20), late fall (n=10) and winter (n=5). ten each of the summer and late fall newts were subjected to an aquatic thermal gradient. summer newts maintained higher cloacal temperatures than late fall newts (26.8+/-0.5 degrees c and 17.2+ ... | 2006 | 16716618 |
| newt orthologue of growth arrest-specific 6 (nvgas6) is implicated in stress response during newt forelimb regeneration. | red-spotted newts are capable of regenerating various structures and organs through the process of epimorphic regeneration. receptor tyrosine kinases (rtks) and their ligands are important for normal cellular development and physiology but most have not yet been characterised during regeneration. we have isolated a newt orthologue of growth arrest-specific 6 (nvgas6), and examined its expression during forelimb regeneration and within a blastema cell line (b1h1). during limb regeneration, nvgas6 ... | 2006 | 16444701 |
| dryness increases predation risk in efts: support for an amphibian decline hypothesis. | one hypothesis for amphibian declines is that increased dryness attributed to global climate change exposes amphibians to greater biotic threat and, consequently, greater mortality. but, little is known about behavioral responses of terrestrial amphibians to dry conditions alone or in combination with biotic threats. we used field observations and laboratory experiments to test the response of efts (terrestrial juveniles) of the eastern red-spotted newt, notophthalmus viridescens, to separate an ... | 2003 | 16228260 |
| nvbeta-actin and nvgapdh as normalization factors for gene expression analysis in limb regenerates and cultured blastema cells of the adult newt, notophthalmus viridescens. | the red-spotted newt has the ability to fully regenerate complex structures by creating a pool of dedifferentiated cells that arise in response to tissue injury. an understanding of the mechanisms involved in the regenerative ability of the newt is limited by a lack of characterized assays. this deficiency includes the cloning and validation of housekeeping genes for normalizing gene expression data. we describe the cloning, characterization and real-time quantitative pcr evaluation of the norma ... | 2005 | 16172979 |
| limb developmental stages of the newt notophthalmus viridescens. | the current study consists of a detailed description of normal larval forelimb and hindlimb development in the newt, notophthalmus viridescens. this is the first comprehensive record of staging limb development in this urodele amphibian species, augmenting fankhauser's work which was published in fragments 60 years ago. larvae were obtained by natural spawning, without hormone injections and while experimental conditions such as temperature and light cycles were kept constant (20 degrees c and 1 ... | 2005 | 15968583 |
| retinoic acid-dependent attraction of adult spinal cord axons towards regenerating newt limb blastemas in vitro. | adult urodele amphibians possess the unique ability to regenerate amputated limbs and to re-innervate these regenerating structures; however, the factors involved in mediating this re-innervation are largely unknown. here, we investigated the role of retinoic acid (ra) and one of its receptors, rarbeta, in the reciprocal neurotropic interactions between regenerating limb blastemas and spinal cord explants from the adult newt notophthalmus viridescens. first, we showed that retinoic acid induced ... | 2005 | 15848393 |
| hair cell regeneration in sensory epithelia from the inner ear of a urodele amphibian. | the capacity of urodele amphibians to regenerate a variety of body parts is providing insight into mechanisms of tissue regeneration in vertebrates. in this study the ability of the newt, notophthalmus viridescens, to regenerate inner ear hair cells in vitro was examined. intact otic capsules were maintained in organotypic culture. incubation in 2 mm gentamicin for 48 hours resulted in ablation of all hair cells from the saccular maculae. thus, any hair cell recovery was not due to repair of dam ... | 2005 | 15717301 |
| normal newt limb regeneration requires matrix metalloproteinase function. | newts regenerate lost limbs through a complex process involving dedifferentiation, migration, proliferation, and redifferentiation of cells proximal to the amputation plane. to identify the genes controlling these cellular events, we performed a differential display analysis between regenerating and nonregenerating limbs from the newt notophthalmus viridescens. this analysis, coupled with a direct cloning approach, identified a previously unknown notophthalmus collagenase gene (ncol) and three k ... | 2005 | 15708560 |
| growth and apoptosis during larval forelimb development and adult forelimb regeneration in the newt ( notophthalmus viridescens). | many of the genes involved in the initial development of the limb in higher vertebrates are also expressed during regeneration of the limb in urodeles such as notophthalmus viridescens. these similarities have led researchers to conclude that the regeneration process is a recapitulation of development, and that patterning of the regenerate mimics pattern formation in development. however, the developing limb and the regenerating limb do not look similar. in developing urodele forelimbs, digits a ... | 2004 | 15322877 |
| occurrence of 11-oxotetrodotoxin in the red-spotted newt, notophthalmus viridescens, and further studies on the levels of tetrodotoxin and its analogues in the newt's efts. | an analogue of tetrodotoxin (ttx), 11-oxottx, was semi-purified from the red-spotted newt, notophthalmus viridescens, and identified by esi-ms and 1h nmr spectra. the levels of ttx, 11-oxottx and 6-epittx in early stage of development (efts) of this newt were investigated by a post-column fluorescent-hplc system, and compared with those of adult newts. the level of 11-oxottx in both of adults and efts were remarkably high, almost close to those of ttx, while 6-epittx was a minor component in bot ... | 2003 | 12782090 |
| bimodal locomotion elicited by electrical stimulation of the midbrain in the salamander notophthalmus viridescens. | the present experiments were designed to identify the mesencephalic locomotor region (mlr) in the salamander. an in vitro semi-intact preparation from a decerebrate adult salamander (notophthalmus viridescens) was developed in which the locomotor activities were monitored from electromyographic and video recordings. the results show that the two locomotor modes exhibited by salamanders (i.e., stepping and swimming) were evoked by electrical microstimulation (5-15 hz; 0.1-10 microa; 2 msec pulses ... | 2003 | 12657703 |
| amyloid-like fibril formation in an all beta-barrel protein. partially structured intermediate state(s) is a precursor for fibril formation. | acidic fibroblast growth factor from newt (notopthalmus viridescens) is a approximately 15-kda, all beta-sheet protein devoid of disulfide bonds. in the present study, we investigate the effects of 2,2,2-trifluoroethanol (tfe) on the structure of newt acidic fibroblast growth factor (nfgf-1). the protein aggregates maximally in 10% (v/v) tfe. congo red and thioflavin t binding experiments suggest that the aggregates induced by tfe have properties resembling the amyloid fibrils. transmission elec ... | 2003 | 12584201 |
| bone formation during forelimb regeneration: a microtomography (microct) analysis. | in our study of bone regeneration in the forelimbs of mature newts (notophthalmus viridescens), we used noninvasive x-ray microtomography (microct) to image regenerating limbs from 37 to 85 days and matching (contralateral) controls. we compared the patterns of regenerated and existing (nonregenerated) bone, investigating in particular the onset of mineralization of specific bones, the level of mineral present, and the lengths of the different bones. overall, we find that the missing limb skelet ... | 2003 | 12557219 |
| retinoic acid involvement in the reciprocal neurotrophic interactions between newt spinal cord and limb blastemas in vitro. | the purpose of this study was to investigate the reciprocal neurotrophic interaction between regenerating limb blastemas and spinal cord explants from the newt notophthalmus viridescens. axon outgrowth was measured from spinal cord explants in vitro to assess the neurotrophic activity of early to mid-bud stage blastemas after various treatments. when retinoic acid, a vitamin a metabolite, was added to the medium, it increased both the number and length of axons extending from spinal cord explant ... | 2003 | 12524177 |
| mitotic chromosomes are chromatin networks without a mechanically contiguous protein scaffold. | isolated newt (notophthalmus viridescens) chromosomes were studied by using micromechanical force measurement during nuclease digestion. micrococcal nuclease and short-recognition-sequence blunt-cutting restriction enzymes first remove the native elastic response of, and then to go on to completely disintegrate, single metaphase newt chromosomes. these experiments rule out the possibility that the mitotic chromosome is based on a mechanically contiguous internal non-dna (e.g., protein) "scaffold ... | 2002 | 12438695 |