| learning about non-predators and safe places: the forgotten elements of risk assessment. | a fundamental prerequisite for prey to avoid being captured is the ability to distinguish dangerous stimuli such as predators and risky habitats from non-dangerous stimuli such as non-predators and safe locations. most research to date has focused on mechanisms allowing prey to learn to recognize risky stimuli. the paradox of learned predator recognition is that its remarkable efficiency leaves room for potentially costly mistakes if prey inadvertently learn to recognize non-predatory species as ... | 2011 | 21203793 |
| scoliosis in a tiger salamander (ambystoma tigrinum) associated with encysted digenetic trematodes of the genus clinostomum. | a group of 202 tiger salamanders (ambystoma tigrinum) was brought into captivity due to habitat destruction. half of these animals died, over two mo, showing generalized hemorrhages compatible with an infectious disease, but an etiologic agent was not determined. encysted metacercarial stages of trematodes within the skeletal musculature, coelomic cavity, and subcutaneous space were additional necropsy findings. one salamander had scoliosis and multiple skin nodules. a radiograph showed no skele ... | 2010 | 20688654 |
| microarray analysis of a salamander hopeful monster reveals transcriptional signatures of paedomorphic brain development. | the mexican axolotl (ambystoma mexicanum) is considered a hopeful monster because it exhibits an adaptive and derived mode of development - paedomorphosis - that has evolved rapidly and independently among tiger salamanders. unlike related tiger salamanders that undergo metamorphosis, axolotls retain larval morphological traits into adulthood and thus present an adult body plan that differs dramatically from the ancestral (metamorphic) form. the basis of paedomorphic development was investigated ... | 2010 | 20584293 |
| light-evoked nmda receptor-mediated currents are reduced by blocking d-serine synthesis in the salamander retina. | experiments were carried out in the retina of the tiger salamander (ambystoma tigrinum) to evaluate the importance of d-serine synthesis on light-evoked n-methyl d-aspartate (nmda) receptor-mediated components of ganglion cells and contributions to the proximal negative field potential. we blocked the synthesis of d-serine through brief exposures of the retina to phenazine ethosulfate and validated the changes in the tissue levels of d-serine using capillary electrophoresis methods to separate a ... | 2010 | 20101193 |
| complexity and context of mhc-correlated mating preferences in wild populations. | there is now substantial and growing evidence for a role of the major histocompatibility complex (mhc) in shaping individual mate preferences. in view of both its codominant expression and its function in immune response, it is often expected that females aim to avoid inbreeding or maximize offspring mhc-heterozygosity by selecting as mates those males which share fewest or no mhc alleles with themselves. however, it is becoming increasingly clear that this view is over-simplistic: not only is m ... | 2009 | 19682244 |
| invasive hybrid tiger salamander genotypes impact native amphibians. | although the ecological consequences of species invasions are well studied, the ecological impacts of genetic introgression through hybridization are less understood. this is particularly true of the impacts of hybridization on "third party" community members not genetically involved in hybridization. we also know little about how direct interactions between hybrid and parental individuals influence fitness. here, we examined the ecological effects of hybridization between the native, threatened ... | 2009 | 19564601 |
| condition-dependent mate choice and a reproductive disadvantage for mhc-divergent male tiger salamanders. | major histocompatibility complex (mhc) alleles likely have adaptive value because of overdominance, in which case mhc heterozygous individuals have increased fitness relative to homozygotes. because of this potential benefit, the evolution of sexual reproduction between mhc-divergent individuals (i.e. negative assortative mating, nam) may be favoured. however, the strongest evidence for mhc-based nam comes from inbred animals, and context-dependent mating preferences have rarely been evaluated a ... | 2009 | 19508451 |
| toxicity and immune system effects of dietary deltamethrin exposure in tiger salamanders (ambystoma tigrinum). | one theory proposed to explain the global declines in amphibian populations involves contaminant-induced immune alteration and subsequent increased susceptibility to infectious disease. the goal of this study was twofold, to (1) study acute oral toxicity of deltamethrin (cyclopropanecarboxylic acid, 3-(2,2-dibromoethenyl)-2,2-dimethyl cyano(3-phenoxyphenyl)methyl ester) in tiger salamanders (ambystoma tigrinum), and (2) evaluate whether the insecticide deltamethrin produces immunosuppression in ... | 2009 | 19267312 |
| amphibian sex determination: segregation and linkage analysis using members of the tiger salamander species complex (ambystoma mexicanum and a. t. tigrinum). | little is known about the genetic basis of sex determination in vertebrates though considerable progress has been made in recent years. in this study, segregation analysis and linkage mapping were performed to localize an amphibian sex-determining locus (ambysex) in the tiger salamander (ambystoma) genome. segregation of sex phenotypes (male and female) among the second generation individuals of interspecific crosses (ambystoma mexicanum x ambystoma tigrinum tigrinum) was consistent with mendeli ... | 2009 | 19259115 |
| microsatellite mutation rates in the eastern tiger salamander (ambystoma tigrinum tigrinum) differ 10-fold across loci. | microsatellites are commonly used for mapping and population genetics because of their high heterozygosities and allelic variability (i.e., polymorphism). microsatellite markers are generally more polymorphic than other types of molecular markers such as allozymes or snps because the insertions/deletions that give rise to microsatellite variability are relatively common compared to nucleotide substitutions. nevertheless, direct evidence of microsatellite mutation rates (mmrs) is lacking in most ... | 2009 | 19107324 |
| amphibian malformations and inbreeding. | inbreeding may lead to morphological malformations in a wide variety of taxa. we used genetic markers to evaluate whether malformed urodeles were more inbred and/or had less genetic diversity than normal salamanders. we captured 687 adult and 1,259 larval tiger salamanders (ambystoma tigrinum tigrinum), assessed each individual for gross malformations, and surveyed genetic variation among malformed and normal individuals using both cytoplasmic and nuclear markers. the most common malformations i ... | 2008 | 18593670 |
| polymorphism of alternative splicing of major histocompatibility complex transcripts in wild tiger salamanders. | alternative splicing (as) of mrna transcripts is increasingly recognized as a source of transcriptome diversity. to date, most as studies have focused either on comparisons across taxa or on intragenomic comparisons across gene families. we generated a novel data set that represents one of the first population genetic comparisons of as across individuals. in ambystomatid salamanders, as of the major histocompatibility complex (mhc) class iibeta gene (amti-dab) produces two transcripts, one full- ... | 2008 | 18543016 |
| inferring population history and demography using microsatellites, mitochondrial dna, and major histocompatibility complex (mhc) genes. | microsatellites and mitochondrial dna (mtdna) have traditionally been used in population genetics because of their variability and presumed neutrality, whereas genes of the major histocompatibility complex (mhc) are increasingly of interest because strong selective pressures shape their standing variation. despite the potential for mhc genes, microsatellites, and mtdna sequences to complement one another in deciphering population history and demography, the three are rarely used in tandem. here ... | 2008 | 18331461 |
| sophisticated temporal pattern recognition in retinal ganglion cells. | pattern recognition is one of the most important tasks of the visual system, and uncovering the neural mechanisms underlying recognition phenomena has been a focus of researchers for decades. surprisingly, at the earliest stages of vision, the retina is capable of highly sophisticated temporal pattern recognition. we stimulated the retina of tiger salamander (ambystoma tigrinum) with periodic dark flash sequences and found that retinal ganglion cells had a wide variety of different responses to ... | 2008 | 18272878 |
| acute toxicity and tissue distributions of malathion in ambystoma tigrinum. | the kinetics of the bioaccumulation of malathion (o,o-dimethyl phosphorodithioate of diethyl mercaptosuccinate) and the biological impact of exposure for tiger salamanders, ambystoma tigrinum, were assessed through exposure to soil surface contaminated with 50 microg/cm(2) or 100 microg/cm(2 )malathion and ingestion of an earthworm exposed to soil contaminated with 200 microg/cm(2) malathion. malathion and malaoxon burdens in salamanders sampled at different times after exposure(s) were measured ... | 2008 | 18227961 |
| hybrid vigor between native and introduced salamanders raises new challenges for conservation. | hybridization between differentiated lineages can have many different consequences depending on fitness variation among hybrid offspring. when introduced organisms hybridize with natives, the ensuing evolutionary dynamics may substantially complicate conservation decisions. understanding the fitness consequences of hybridization is an important first step in predicting its evolutionary outcome and conservation impact. here, we measured natural selection caused by differential viability of hybrid ... | 2007 | 17884982 |
| iteroparity in the variable environment of the salamander ambystoma tigrinum. | simultaneous estimation of survival, reproduction, and movement is essential to understanding how species maximize lifetime reproduction in environments that vary across space and time. we conducted a four-year, capture-recapture study of three populations of eastern tiger salamanders (ambystoma tigrinum tigrinum) and used multistate mark-recapture statistical methods to estimate the manner in which movement, survival, and breeding probabilities vary under different environmental conditions acro ... | 2007 | 17536706 |
| low-voltage activated calcium currents in ganglion cells of the tiger salamander retina: experiment and simulation. | we examined the functional properties of a low-voltage-activated (lva) calcium current in ganglion cells of the neotenous tiger salamander (ambystoma tigrinum) retina. our analysis was based on whole-cell recordings from acutely dissociated ganglion cell bodies identified by retrograde dye injections. using a continuously perfused cell preparation, the lva current was isolated with the use of potassium channel blocking agents added to the bathing medium and the pipette solution, while tetrodotox ... | 2014 | 17430608 |
| amphibian survival, growth and development in response to mineral nitrogen exposure and predator cues in the field: an experimental approach. | mineral nitrogen (n) has been suggested as a potential factor causing declines in amphibian populations, especially in agricultural landscapes; however, there is a question as to whether it remains in the water column long enough to be toxic. we explored the hypothesis that mineral n can cause both lethal and sublethal toxic effects in amphibian embryos and larvae in a manipulative field experiment. we sampled 12 ponds, fertilizing half with ammonium nitrate fertilizer early in the spring, and m ... | 2007 | 17351792 |
| immunolocalisation of nitric oxide synthase isoforms in the epidermis of the tiger salamander, ambystoma tigrinum. | a. tigrinum: immunoreactivity for isoforms of nitric oxidase synthase is found in the flash cells and outer-deep epidermal cell layers of the tiger salamander a. tigrinum. despite the absence of physiological data we assume no may be lumped together as cytocrine regulators in the amphibian epidermis. | 2006 | 16824585 |
| insights into the mating habits of the tiger salamander (ambystoma tigrinum tigrinum) as revealed by genetic parentage analyses. | among urodeles, ambystomatid salamanders are particularly amenable to genetic parentage analyses because they are explosive aggregate breeders that typically have large progeny arrays. such analyses can lead to direct inferences about otherwise cryptic aspects of salamander natural history, including the rate of multiple mating, individual reproductive success, and the spatial distribution of clutches. in 2002, we collected eastern tiger salamander (ambystoma tigrinum tigrinum) egg masses (> 100 ... | 2006 | 16689907 |
| natural images and contrast encoding in bipolar cells in the retina of the land- and aquatic-phase tiger salamander. | intracellular recordings were obtained from 57 cone-driven bipolar cells in the light-adapted retina of the land-phase (adult) tiger salamander (ambystoma tigrinum). responses to flashes of negative and positive contrast for centered spots of optimum spatial dimensions were analyzed as a function of contrast magnitude. on average, the contrast/response curves of depolarizing and hyperpolarizing bipolar cells in the land-phase animals were remarkably similar to those of aquatic-phase animals. thu ... | 2014 | 16597349 |
| form and function of on-off amacrine cells in the amphibian retina. | on-off amacrine cells were studied with whole cell recording techniques and intracellular staining methods using intact retina-eyecup preparations of the tiger salamander (ambystoma tigrinum) and the mudpuppy (necturus maculosus). morphological characterization of these cells included three-dimensional reconstruction methods based on serial optical sections obtained with a confocal microscope. some cells had their detailed morphology digitized with a computer-assisted tracing system and converte ... | 2006 | 16481463 |
| molecular characterization of major histocompatibility complex class ii alleles in wild tiger salamanders (ambystoma tigrinum). | major histocompatibility complex (mhc) class ii genes are usually among the most polymorphic in vertebrate genomes because of their critical role (antigen presentation) in immune response. prior to this study, the mhc was poorly characterized in tiger salamanders (ambystoma tigrinum), but the congeneric axolotl (ambystoma mexicanum) is thought to have an unusual mhc. most notably, axolotl class ii genes lack allelic variation and possess a splice variant without a full peptide binding region (pb ... | 2005 | 16195876 |
| temporal response of the tiger salamander (ambystoma tigrinum) to 3,000 years of climatic variation. | amphibians are sensitive indicators of environmental conditions and show measurable responses, such as changes in phenology, abundance and range limits to local changes in precipitation and temperature regimes. amphibians offer unique opportunities to study the important ecological and evolutionary implications of responses in life history characteristics to climatic change. we analyzed a late-holocene fossil record of the tiger salamander (ambystoma tigrinum) for evidence of population-level ch ... | 2005 | 16159383 |
| ontogenic delays in effects of nitrite exposure on tiger salamanders (ambystoma tigrinum tigrinum) and wood frogs (rana sylvatica). | under certain conditions, nitrite can be present in freshwater systems in quantities that are toxic to the fauna. i exposed wood frog (rana sylvatica) and eastern tiger salamander (ambystoma tigrinum tigrinum) embryos and young tadpoles and larvae to elevated concentrations of nitrite in chronic toxicity tests: 0, 0.3, 0.6, 1.2, 2.1, 4.6, and 6.1 mg/l no2-n, exposing individuals as both embryos and larvae. nitrite caused significant declines in wood frog hatching success (3.4 mg/l no2-n, wood fr ... | 2005 | 16117132 |
| a comprehensive expressed sequence tag linkage map for tiger salamander and mexican axolotl: enabling gene mapping and comparative genomics in ambystoma. | expressed sequence tag (est) markers were developed for ambystoma tigrinum tigrinum (eastern tiger salamander) and for a. mexicanum (mexican axolotl) to generate the first comprehensive linkage map for these model amphibians. we identified 14 large linkage groups (125.5-836.7 cm) that presumably correspond to the 14 haploid chromosomes in the ambystoma genome. the extent of genome coverage for these linkage groups is apparently high because the total map size (5251 cm) falls within the range of ... | 2005 | 16079226 |
| landscape genetics of the blotched tiger salamander (ambystoma tigrinum melanostictum). | the field of landscape genetics has great potential to identify habitat features that influence population genetic structure. to identify landscape correlates of genetic differentiation in a quantitative fashion, we developed a novel approach using geographical information systems analysis. we present data on blotched tiger salamanders (ambystoma tigrinum melanostictum) from 10 sites across the northern range of yellowstone national park in montana and wyoming, usa. we used eight microsatellite ... | 2005 | 15969734 |
| d-serine uptake by isolated retinas is consistent with asct-mediated transport. | uptake of the neuromodulator d-serine by isolated larval tiger salamander (ambystoma tigrinum) retinas was measured using capillary electrophoresis (ce). excised retinas were incubated in ringer's solution in the presence of 5 microm d-serine. the supernatant was removed after 30 min, mixed with 4-fluoro-7-nitrobenz-2-oxa-1,3-diazole (nbd-f) to fluorescently label amines and analyzed using ce. significant d-serine uptake was observed over a period of 1.5h. this is the first observation of d-seri ... | 2005 | 15950382 |
| evaluation of two methods for measuring nonspecific immunity in tiger salamanders (ambystoma tigrinum). | study of amphibian immunotoxicology is a growing area of research, but very little information is available on how environmental contaminants affect disease resistance in urodele amphibians. urodele amphibians lack the more highly evolved aspects of the specific immune system that are present in anurans, birds, and mammals. instead, these animals rely more heavily on innate defense mechanisms than do anurans to provide rapid, nonspecific protection from pathogens. thus, it is prudent that immuno ... | 2005 | 15827225 |
| effects of steroids and dioxin (2,3,7,8-tcdd) on the developing wolffian ducts of the tiger salamander (ambystoma tigrinum). | this study was undertaken to investigate effects of the prototypical dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (tcdd) on steroid-dependent development of the wolffian ducts of an amphibian, the tiger salamander (ambystoma tigrinum). larvae with immature gonads and undeveloped mullerian ducts were injected with the steroid hormones estradiol (e2), dihydrotestosterone (dht), or vehicle alone. additionally, steroid-treated and vehicle-control larvae were immersed in sub-lethal solutions of techni ... | 2005 | 15707598 |
| metacercariae of clinostomum attenuatum in ambystoma tigrinum mavortium, bufo cognatus and spea multiplicata from west texas. | tissues from barred tiger salamanders (ambystoma tigrinum mavortium), great plains toads (bufo cognatus) and new mexico spadefoots (spea multiplicata) collected from 16 playa wetlands in texas during 1999 and 2000 were examined by light microscopy. digenean cysts were primarily distributed subcutaneously throughout the specimens and occasionally coelomic invasion was noted. the parasites within the cysts were 1.5-2 mm in diameter, with a thin (c. 10 microm wide) eosinophilic-staining tegument, t ... | 2004 | 15575998 |
| expression of calcium transporters in the retina of the tiger salamander (ambystoma tigrinum). | changes in intracellular calcium concentration, [ca2+]i, modulate the flow of visual signals across all stages of processing in the retina, yet the identities of ca2+ transporters responsible for these changes are still largely unknown. in the current study, the distribution of plasma membrane and intracellular ca2+ transporters in the retina of tiger salamander, a model system for physiological studies of retinal function, was determined. plasma membrane calcium atpases (pmcas), responsible for ... | 2004 | 15236230 |
| olfactory receptor gene expression in tiger salamander olfactory epithelium. | physiological studies of odor-elicited responses from the olfactory epithelium and bulb in the tiger salamander, ambystoma tigrinum, have elucidated a number of features of olfactory coding that appear to be conserved across several vertebrate species. this animal model has provided an accessible in vivo system for observing individual and ensemble olfactory responses to odorant stimulation using biochemical, neurophysiological, and behavioral assays. in this paper we have complemented these stu ... | 2004 | 15174087 |
| morphology and escape performance of tiger salamander larvae (ambystoma tigrinum mavortium). | the ability of an individual to escape predators is an important component of fitness. several adaptive explanations of body shape variation in amphibians hypothesize relationships between swimming performance and morphology, but these ideas have rarely been tested. here we investigate bivariate and multivariate relationships between natural variation in morphology and performance. we used high-speed video to examine fast-starts associated with escape responses in small tiger salamander larvae ( ... | 2003 | 12945751 |
| contrast encoding in retinal bipolar cells: current vs. voltage. | to investigate the influence of voltage-sensitive conductances in shaping light-evoked responses of retinal bipolar cells, whole-cell recordings were made in the slice preparation of the tiger salamander, ambystoma tigrinum. to study contrast encoding, the retina was stimulated with 0.5-s steps of negative and positive contrasts of variable magnitude. in the main, responses recorded under voltage- and current-clamp modes were remarkably similar. in general agreement with past results in the inta ... | 2016 | 12699080 |
| center-surround organization in bipolar cells: symmetry for opposing contrasts. | intracellular recordings were obtained from 73 cone-driven bipolar cells in the light-adapted retina of the tiger salamander (ambystoma tigrinum). responses to flashes of negative and positive contrast for centered spots and concentric annuli of optimum spatial dimensions were analyzed as a function of contrast magnitude. for both depolarizing and hyperpolarizing bipolar cells, it was found that remarkably similar responses were observed for the center and surround when comparisons were made bet ... | 2014 | 12699078 |
| properties of exocytotic response in vertebrate photoreceptors. | synaptic transmission at the photoreceptor synapse is characterized by continuous release of glutamate in darkness. release is regulated by the intracellular calcium concentration ([ca2+]i). we here examined the physiological properties of exocytosis in tiger salamander (ambystoma tigrinum) retinal rods and cones. patch-clamp capacitance measurements were used to monitor exocytosis elicited by a rapid and uniform increase in [ca2+]i by photolysis of the caged ca2+ compound np-egta. the amplitude ... | 2003 | 12660355 |
| the effect of fiber-type heterogeneity on optimized work and power output of hindlimb muscles of the salamander ambystoma tigrinum. | most vertebrate muscles are composed of a mixture of fiber types. however, studies of muscle mechanics have concentrated on homogeneous bundles of fibers. hindlimb muscles of the tiger salamander, ambystoma tigrinum, present an excellent system to explore the consequences of fiber heterogeneity. isometric twitches and work loops were obtained in vitro from two muscles, the m. iliotibialis pars posterior (heterogeneous, containing types i, iia and iib fibers) and the m. iliofibularis (nearly homo ... | 2002 | 12355237 |
| acceleration of ambystoma tigrinum metamorphosis by corticotropin-releasing hormone. | previous work of others and ours has shown that corticotropin-releasing hormone (crh) is a positive stimulus for thyroid and interrenal hormone secretion in amphibian larvae and that activation of crh neurons may mediate environmental effects on the timing of metamorphosis. these studies have investigated crh actions in anurans (frogs and toads), whereas there is currently no information regarding the actions of crh on metamorphosis of urodeles (salamanders and newts). we tested the hypothesis t ... | 2002 | 12115924 |
| the naris muscles in tiger salamander. ii. innervation as revealed by enzyme histochemistry and immunocytochemistry. | the naris muscles control the aperature of the external naris in tiger salamanders, ambystoma tigrinum, and may contribute to glandular secretion. autonomic neurons of the palatine ganglion and possibly neurons associated with the nervus terminalis innervate these muscles. to elucidate the neural control of the naris muscles, neurotransmitters in nerve fibers supplying the naris muscles and in neurons of the palatine ganglion were examined using acetylcholinesterase enzyme histochemistry and imm ... | 2002 | 12107487 |
| cardiac effects of hypoxia in the neotenous tiger salamander ambystoma tigrinum. | the aquatic form of the tiger salamander ambystoma tigrinum lives in high-altitude ponds and is exposed to a hypoxic environment that may be either chronic or intermittent. in many animal species, exposure to hypoxia stimulates cardiac output and is followed by an increase in cardiac mass. the working hypothesis of the present study was that the hearts of these aquatic salamanders exposed to 10-14 days of 5 % oxygen in a laboratory setting would become larger and would differentially express pro ... | 2002 | 12042331 |
| effects of light adaptation on contrast processing in bipolar cells in the retina. | effects of light adaptation on contrast processing in the outer retina were investigated over nearly four decades of background illumination by analyzing the intracellular responses of 111 bipolar cells, 66 horizontal cells, and 22 cone photoreceptors in the superfused eyecup of the tiger salamander (ambystoma tigrinum). light adaptation had striking and similar effects on the average contrast responses of the hyperpolarizing (bh) and depolarizing (bd) classes of bipolar cells: over the lower tw ... | 2008 | 11829304 |
| twisting and bending: the functional role of salamander lateral hypaxial musculature during locomotion. | the function of the lateral hypaxial muscles during locomotion in tetrapods is controversial. currently, there are two hypotheses of lateral hypaxial muscle function. the first, supported by electromyographic (emg) data from a lizard (iguana iguana) and a salamander (dicamptodon ensatus), suggests that hypaxial muscles function to bend the body during swimming and to resist long-axis torsion during walking. the second, supported by emg data from lizards during relatively high-speed locomotion, s ... | 2001 | 11441039 |
| fate and the biochemical effects of 2,4,6-trinitrotoluene exposure to tiger salamanders (ambystoma tigrinum). | biotransformation, metabolic enzyme profiles, and the glutathione antioxidant system in tiger salamanders (ambystoma tigrinum) from a 14-day exposure to 2,4,6-trinitrotoluene (tnt) in situ were examined. concentrations of parent compound and metabolites were measured in skin, kidney, and liver tissue. in addition, cytochrome p450 (p450) and cytochrome b5 content and their dependent isozyme activities, ethoxyresorufin o-dealkylation, pentoxyresorufin o-dealkylation, and the glutathione antioxidan ... | 2000 | 10831332 |
| effects of 2,4,6-trinitrotoluene in a holistic environmental exposure regime on a terrestrial salamander, ambystoma tigrinum. | 2,4,6-trinitrotoluene (tnt) is a defense-related environmental contaminant present at high concentrations in soil at some military installations. tiger salamanders (ambystoma tigrinum, family ambystomatidae) were exposed to tnt in a soil matrix and fed earthworms that had also been exposed to tnt via contaminated soil. such exposure was previously shown to result in significant accumulation of both tnt and tnt metabolites by salamanders. following 14 days of combined oral and dermal exposures, s ... | 2017 | 10805152 |
| mechanics of lung ventilation in a post-metamorphic salamander, ambystoma tigrinum. | the mechanics of lung ventilation in frogs and aquatic salamanders has been well characterized, whereas lung ventilation in terrestrial-phase (post-metamorphic) salamanders has received little attention. we used electromyography (emg), x-ray videography, standard videography and buccal and body cavity pressure measurements to characterize the ventilation mechanics of adult (post-metamorphic) tiger salamanders (ambystoma tigrinum). three results emerged: (i) under terrestrial conditions or when f ... | 2000 | 10683167 |
| relationships between odor-elicited oscillations in the salamander olfactory epithelium and olfactory bulb. | oscillations in neuronal population activity, or the synchronous neuronal spiking that underlies them, are thought to play a functional role in sensory processing in the cns. in the olfactory system, stimulus-induced oscillations are observed both in central processing areas and in the peripheral receptor epithelium. to examine the relationship between these peripheral and central oscillations, we recorded local field potentials simultaneously from the olfactory epithelium and olfactory bulb in ... | 2000 | 10669491 |
| contrast rectification and distributed encoding by on-off amacrine cells in the retina. | the encoding of luminance contrast by on-off amacrine cells was investigated by intracellular recording in the retina of the tiger salamander (ambystoma tigrinum). contrast flashes of positive and negative polarity were applied at the center of the receptive field while the entire retina was light adapted to a background field of 20 cd/m(2). many amacrine cells showed remarkably high contrast gain: up to 20-35% of the maximum response was evoked by a contrast step of only 1%. in the larger signa ... | 1999 | 10515958 |
| cutaneous mastocytomas in the neotenic caudate amphibians ambystoma mexicanum (axolotl) and ambystoma tigrinum (tiger salamander). | spontaneous mastocytomas studied in 18 axolotls (ambystoma mexicanum) and six tiger salamanders (ambystoma tigrinum) were gray-white, uni- to multilobular cutaneous protrusions from 2 mm to 2 cm in diameter. tumors were moderately cellular unencapsulated masses that usually infiltrated the dermis and hypodermis with the destruction of intervening tissues. some tumors were invading superficial bundles of the underlying skeletal muscle. tumors consisted of mitotically active cells derived from a s ... | 1999 | 10235473 |
| impulse encoding across the dendritic morphologies of retinal ganglion cells. | nerve impulse entrainment and other excitation and passive phenomena are analyzed for a morphologically diverse and exhaustive data set (n = 57) of realistic (3-dimensional computer traced) soma-dendritic tree structures of ganglion cells in the tiger salamander (ambystoma tigrinum) retina. the neurons, including axon and an anatomically specialized thin axonal segment that is observed in every ganglion cell, were supplied with five voltage- or ligand-gated ion channels (plus leakage), which wer ... | 1999 | 10200204 |
| rapid desensitization converts prolonged glutamate release into a transient epsc at ribbon synapses between retinal bipolar and amacrine cells. | the mechanisms underlying the conversion of prolonged glutamate release from ribbon synapses in bipolar cells to sustained and transient excitatory postsynaptic responses in identified retinal amacrine cells were studied in tiger salamander (ambystoma tigrinum) retina. a retina slice preparation with whole cell patch recording techniques under voltage- and current-clamp conditions was used to assay the electrical properties of bipolar and amacrine cells. amacrine cells were categorized into two ... | 1999 | 9987038 |
| mechanics of lung ventilation in a larval salamander ambystoma tigrinum. | the larval stage of the tiger salamander ambystoma tigrinum is entirely aquatic, but the larvae rely on their lungs for a large proportion of their oxygen uptake. x-ray video and pressure measurements from the buccal and body cavities demonstrate that the larvae inspire using a two-stroke buccal pump and exhale actively by contracting the hypaxial musculature to increase body pressure. larvae begin a breath by expanding the buccal cavity to draw in air through the mouth, while simultaneously exh ... | 1998 | 9866876 |
| pathogen transmission as a selective force against cannibalism. | cannibalism is uncommon in most species despite being taxonomically widespread. this rarity is surprising, because cannibalism can confer important nutritional and competitive advantages to the cannibal. a general, but untested, explanation for why cannibalism is rare is that cannibals may be especially likely to acquire pathogens from conspecifics, owing to greater genetic similarity among conspecifics and selection for host specificity and resistance to host immune defences among pathogens. we ... | 1998 | 9632508 |
| habitat-contingent reproductive behaviour in radio-implanted salamanders: a model and test. | all tiger salamanders, ambystoma tigrinum, entering a small pond in new york state were given radio-implants and tracked throughout breeding to determine whether reproductive behaviour in nature differs from that described in laboratory studies. i formed an extended model of adult reproductive behaviour that included male and female strategies and differential use of habitat components in the breeding pond, and then tested four key predictions regarding adult movement using the sequence of posit ... | 1998 | 9632505 |
| effects of the herbicide atrazine on ambystoma tigrinum metamorphosis: duration, larval growth, and hormonal response. | we exposed larval tiger salamanders (ambystoma tigrinum) reared in the laboratory from eggs collected from a prairie wetland in north dakota to three concentrations of atrazine (0, 75, and 250 micrograms/l) in a static renewal test to determine the pesticide's effect on (1) plasma corticosterone and thyroxine concentrations, (2) larval size, and (3) days-to-stage at stages 2 and 4 of metamorphic climax. we found significant effects of atrazine on each of these response variables. plasma thyroxin ... | 2013 | 9798254 |
| contrast enhancement and distributed encoding by bipolar cells in the retina. | responses of bipolar cells, cone photoreceptors, and horizontal cells were recorded intracellularly in superfused eyecup preparations of the tiger salamander (ambystoma tigrinum). contrast flashes of positive and negative polarity were applied at the center of the receptive field while the entire retina was light adapted to a background field of 20 cd/m2. for small contrasts, many bipolar cells showed remarkably high contrast gain: up to 15-20% of the bipolar response was evoked by a contrast st ... | 1998 | 9744922 |
| mechanics of lung ventilation in a larval salamander ambystoma tigrinum. | the larval stage of the tiger salamander ambystoma tigrinum is entirely aquatic, but the larvae rely on their lungs for a large proportion of their oxygen uptake. x-ray video and pressure measurements from the buccal and body cavities demonstrate that the larvae inspire using a two-stroke buccal pump and exhale actively by contracting the hypaxial musculature to increase body pressure. larvae begin a breath by expanding the buccal cavity to draw in air through the mouth, while simultaneously exh ... | 1998 | 9739071 |
| experimental analysis of character coupling across a complex life cycle: pigment pattern metamorphosis in the tiger salamander, ambystoma tigrinum tigrinum. | developmental relationships among characters are expected to bias patterns of morphological variation at the population level. studies of character development thus can provide insights into processes of adaptation and the evolutionary diversification of morphologies. here i use experimental manipulations to test whether larval and adult pigment patterns are coupled across metamorphosis in the tiger salamander, ambystoma tigrinum tigrinum (ambystomatidae). previous investigations showed that the ... | 1998 | 9642792 |
| responses of ganglion cells to contrast steps in the light-adapted retina of the tiger salamander. | the impulse discharge of single ganglion cells was recorded extracellularly in superfused eyecup preparations of the tiger salamander (ambystoma tigrinum). contrast flashes (500 ms) were applied at the center of the receptive field while the retina was light adapted to a background field of 20 cd/m2. the incidence of cell types in a sample of 387 cells was: on cells (4%), off cells (28%), and on/off cells (68%). quantitative contrast/response measurements were obtained for 83 cells. on the basis ... | 2014 | 9605524 |
| actin cytoskeleton regulates ion channel activity in retinal neurons. | the actin cytoskeleton is an important contributor to the integrity of cellular shape and responses in neurons. however, the molecular mechanisms associated with functional interactions between the actin cytoskeleton and neuronal ion channels are largely unknown. whole-cell and single channel recording techniques were thus applied to identified retinal bipolar neurons of the tiger salamander (ambystoma tigrinum) to assess the role of acute changes in actin-based cytoskeleton dynamics in the regu ... | 1998 | 9559935 |
| estimating the contributions of nmda and non-nmda currents to epsps in retinal ganglion cells. | whole-cell recordings were obtained from retinal ganglion cells of the tiger salamander (ambystoma tigrinum) in a superfused slice preparation to evaluate contributions of nmda (n-methyl-d-aspartate) and ka/ampa (kainate/alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid) receptors to excitatory postsynaptic potentials (epsps) of retinal ganglion cells. synaptic activation of retinal ganglion cells was achieved through the use of a brief pressure pulse of hyperosmotic ringer (ringer + suc ... | 2016 | 9447684 |
| interactions of gonadal steroids and pesticides (ddt, dde) on gonaduct growth in larval tiger salamanders, ambystoma tigrinum. | in view of the current worldwide decline in amphibian populations, exploratory studies are needed to assess the potential for environmental contaminants to act as endocrine disrupters of the amphibian reproductive system. the present study investigated the effects of ddt dichlorodiphenyltrichloroethane (ddt) and dichlorodiphenyldichloroethylene (dde) on the development of amphibian gonaducts. larval male and female tiger salamanders (ambystoma tigrinum), with immature gonads, were immersed in a ... | 1998 | 9446727 |
| response sensitivity and voltage gain of the rod- and cone-bipolar cell synapses in dark-adapted tiger salamander retina. | response sensitivity and voltage gain of the rod- and cone-bipolar cell synapses in dark-adapted tiger salamander retina. j. neurophysiol. 78: 2662-2673, 1997. rods, cones, and bipolar cells were recorded in superfused, flat-mounted isolated retinas of the larval tiger salamander, ambystoma tigrinum, under dark-adapted conditions. voltage responses of 24 rods, 15 cones, and 41 bipolar cells in dark-adapted retinas to 500 nm light steps of various intensities were listed and fitted with hyperboli ... | 1997 | 9356416 |
| differential effects of mate competition and mate choice on eastern tiger salamanders | male tiger salamanders, ambystoma tigrinum tigrinumare slightly larger in body size and have considerably higher and longer tails than females. to determine how these dimorphic traits affected reproductive performance and success, we conducted breeding trials using 12 males and six females per trial and monitored male-female and male-male interactions. larger males had an advantage in most aspects of mate competition investigated. males with higher tails had no advantage in either mate competiti ... | 1997 | 9236030 |
| rapid classical conditioning of odor response in a physiological model for olfactory research, the tiger salamander. | in recent years there have been a number of important advances in the understanding of cellular mechanisms related to olfactory function. hypotheses regarding the complex relationships among odorant structure, physiological activity and behavioral outcome generated by these findings, however, remain largely untested due to a paucity of psychophysical data on stimulus discrimination in the same experimental species. comparisons between behavioral and physiological responses are essential for eluc ... | 1997 | 9218140 |
| interactions of androgens and estradiol on sex accessory ducts of larval tiger salamanders, ambystoma tigrinum. | immature tiger salamander larvae were treated with 12.5 or 25 micrograms of estradiol, testosterone, or dihydrotestosterone (dht), or 12.5 micrograms of estradiol combined with 12.5 micrograms of either testosterone or dht. müllerian duct epithelium was more stimulated by combined steroid treatment than by any steroid alone. estradiol antagonized the action of dht in the wolffian duct. both of the androgens and estradiol when administered alone at the higher dose stimulated enlargement of connec ... | 1997 | 9204368 |
| maintenance of the adh polymorphism in ambystoma tigrinum nebulosum (tiger salamanders). i. genotypic differences in time to metamorphosis in extreme oxygen environments. | populations of gilled tiger salamanders (ambystoma tigrinum nebulosum) living in ephemeral ponds were studied in order to determine what evolutionary processes might be affecting genetic variation at the alcohol dehydrogenase (adh) locus. ponds frequently dried in late summer; salamanders that did not metamorphose and leave drying ponds died of desiccation. low levels of water oxygen significantly slowed metamorphosis of tiger salamanders in both natural and laboratory populations. adh- ss frequ ... | 1997 | 16397643 |
| response sensitivity and voltage gain of the rod- and cone-horizontal cell synapses in dark- and light-adapted tiger salamander retina. | 1. rods, cones, and horizontal cells (hcs) were recorded in superfused, flat-mounted isolated retinas of the larval tiger salamander, ambystoma tigrinum, under dark- and light-adapted conditions. 2. under dark-adapted conditions, hc responses to dim 500-nm light stimuli were mediated only by rods. in the linear voltage range (near the dark potentials), the average response to a light step of 0.5 s (500 nm, 0.438 photons per micron2 per s) was 0.41 +/- 0.06 (sd) mv for rods and 1.86 +/- 0.52 mv f ... | 1996 | 8985884 |
| receptive field of the retinal bipolar cell: a pharmacological study in the tiger salamander. | 1. it is widely believed that signals contributing to the receptive field surrounds of retinal bipolar cells pass from horizontal cells to bipolar cells via gabaergic synapses. to test this notion, we applied gamma-aminobutyric acid (gaba) agonists and antagonists to isolated, perfused retinas of the salamander ambystoma tigrinum while recording intracellularly from bipolar cells, horizontal cells, and photoreceptors. 2. as we previously reported, administration of the gaba analogue d-aminovaler ... | 1996 | 8890310 |
| molecular cloning of a rhodopsin gene from salamander rods. | salamander photoreceptor cells have been used widely as models in vision research. however, the salamander opsin genes had not been cloned. the purpose of this study was to clone a salamander rhodopsin and to determine its primary structure and cell type-specific expression. | 1996 | 8759361 |
| nitric oxide synthase in tiger salamander retina. | previous studies have indicated that nitric oxide, a labile freely diffusible biological messenger synthesized by nitric oxide synthase, may modulate light transduction and signal transmission in the retina. in the present work, the large size of retinal cells in tiger salamander (ambystoma tigrinum) allowed the utilization of nicotinamide adenine dinucleotide phosphate (nadph)-diaphorase histochemistry and nitric oxide synthase immunocytochemistry to delineate the cell-specific intracellular lo ... | 1995 | 8550897 |
| ancestry of an isolated subspecies of salamander, ambystoma tigrinum stebbinsi lowe: the evolutionary significance of hybridization. | most phylogenetic systematists assume speciation results in dichotomously branching phylogenies. hybridization that gives rise to a new lineage can produce character homoplasty that might obscure a species' true history. we report the results of a restriction-enzyme analysis of mitochondrial dna (mtdna) variation in three tiger salamander subspecies (ambystoma trigrinum mavortium, ambystoma tigrinum nebulosum, and ambystoma trigrinum stebbinsi) and compare the results to studies of morphological ... | 1995 | 7663764 |
| separating population structure from population history: a cladistic analysis of the geographical distribution of mitochondrial dna haplotypes in the tiger salamander, ambystoma tigrinum. | nonrandom associations of alleles or haplotypes with geographical location can arise from restricted gene flow, historical events (fragmentation, range expansion, colonization), or any mixture of these factors. in this paper, we show how a nested cladistic analysis of geographical distances can be used to test the null hypothesis of no geographical association of haplotypes, test the hypothesis that significant associations are due to restricted gene flow, and identify patterns of significant as ... | 1995 | 7498753 |
| similar effects of carbachol and dopamine on neurons in the distal retina of the tiger salamander. | though there is considerable evidence that dopamine is an important retinal neuromodulator that mediates many of the changes in the properties of retinal neurons that are normally seen during light adaptation, the mechanism by which dopamine release is controlled remains poorly understood. in this paper, we present evidence which indicates that dopamine release in the retina of the tiger salamander, ambystoma tigrinum, is driven excitatorily by a cholinergic input. we compared the effects of app ... | 2015 | 7654602 |
| calcium waves in dissociated retinal glial (müller) cells are evoked by release of calcium from intracellular stores. | calcium imaging techniques were used to study intracellular free calcium ion regulation in isolated müller cells in response to changes in extracellular potassium concentration and to caffeine and ryanodine. müller cells were dissociated from the adult tiger salamander (ambystoma tigrinum) retina and studied using the calcium indicator fura-2 and video imaging microscopy techniques. our results demonstrate that elevation of extracellular potassium in the presence of extracellular calcium evokes ... | 1995 | 7615342 |
| enkephalin immunoreactivity in the paraneurons of the tiger salamander (ambystoma tigrinum) tongue. | immunohistochemical tests have demonstrated the presence of leu-5-enkephalin and other bioactive compounds (serotonin and neuron-specific enolase) in the basal cells of lingual taste buds in ambystoma tigrinum; there was also a weak reaction for met-5-enkephalin. similar reactions were obtained from particular cells dispersed within the lingual epithelium, which are provisionally identified as merkel cells. | 1995 | 7603585 |
| morphology of ganglion cells in the neotenous tiger salamander retina. | the morphology of retinal ganglion cells in the neotenous tiger salamander (ambystoma tigrinum) was analyzed with the aid of morphometric techniques to determine the diversity of cell types and to evaluate the widely held notion that this form of ambystoma has a simple retina, with little variance among its cell morphologies. single-cell staining was achieved through retrograde labeling with horseradish peroxidase injected around the optic nerve sheath followed by a period of several days before ... | 1995 | 7721999 |
| interaction of anionic and cationic currents leads to a voltage dependence in the odor response of olfactory receptor neurons. | 1. we recorded odor-induced currents from isolated olfactory receptor neurons of the land phase tiger salamander (ambystoma tigrinum) with the whole cell patch clamp. 2. in a subset of cells the current-voltage relation for the odor-induced current showed a strong rectification with, in some cells, a negative resistance slope between about -45 and -25 mv. in these cells there was little or no odor-induced current at -55 mv, the average resting potential of olfactory neurons. 3. depolarizing the ... | 1995 | 7760118 |
| cyclic gmp diffusion coefficient in rod photoreceptor outer segments. | cyclic gmp (cgmp) is the intracellular messenger that mediates phototransduction in retinal rods. as photoisomerizations of rhodopsin molecules are local events, the longitudinal diffusion of cgmp in the rod outer segment should be a contributing factor to the response of the cell to light. we have employed the truncated rod outer segment preparation from bullfrog (rana catesbeiana) and tiger salamander (ambystoma tigrinum) to measure the cgmp diffusion coefficient. in this preparation, the dist ... | 1995 | 7536055 |
| individual responses to population size structure: the role of size variation in controlling expression of a trophic polyphenism. | we investigated how size structure affects development of alternative larval phenotypes in arizona tiger salamanders, ambystoma tigrinum nebulosum, by testing the hypothesis that population size structure per se is a significant component of an individual's environment. larvae of this subspecies exhibit one of two feeding phenotypes; typical larvae eat zooplankton and macroinvertebrates and cannibalistic larvae feed primarily on conspecifics. previous laboratory experiments showed that larval de ... | 1994 | 28307011 |
| gating, selectivity and blockage of single channels activated by cyclic gmp in retinal rods of the tiger salamander. | 1. patches in the inside-out configuration were excised from the membrane of outer and inner segments of the larval tiger salamander, ambystoma tigrinum. the current flowing through single channels opened by cyclic gmp was studied with the voltage clamp technique. 2. amplitude histograms of current recordings from patches containing only one flickering channel, excised from the inner segment and in the presence of 100 microm cyclic gmp, could be fitted by a theoretical scheme in which the single ... | 1994 | 7516427 |
| aquatic prey transport and the comparative kinematics of ambystoma tigrinum feeding behaviors | four definable feeding behaviors used during the metamorphic life history of tiger salamanders are terrestrial prey capture and transport (as adults) and aquatic prey capture and transport (as larvae). previous studies have focused primarily on the first three of these behaviors and thus aquatic prey transport is poorly understood. these studies have indicated that terrestrial prey capture has unique kinematic and motor patterns, whereas the other behaviors are quite similar to one another. usin ... | 1994 | 9317549 |
| modulation of transduction gain in light adaptation of retinal rods. | the effect of light adaptation on the period of photocurrent saturation induced by a bright stimulating flash was examined in rod photoreceptors of the larval-stage tiger salamander (ambystoma tigrinum). using suction electrodes, photocurrent responses to brief flashes were recorded from single, isolated rods in the presence and absence of steady background illumination. background light decreased the saturation period (t) measured at fixed flash intensity (fixed if) and in this respect light-ad ... | 2008 | 8011583 |
| the composition and function of the pulmonary surfactant system during metamorphosis in the tiger salamander ambystoma tigrinum. | mammalian lungs secrete a mixture of surface-active lipids (surfactant), which greatly reduces the surface tension of the fluid coating the inner lung surface, thereby reducing the risk of collapse upon deflation and increasing compliance upon inflation. during foetal lung maturation, these lipids become enriched in the primary and active ingredient, a disaturated phospholipid. however, disaturated phospholipids exist in their inactive gel-like form at temperatures below 37 degrees c and thus ar ... | 1994 | 7983248 |
| modulation of transmission gain by protons at the photoreceptor output synapse. | synaptic transmission of the light response from photoreceptors to second-order cells of the retina was studied with the whole-cell patch-clamp technique in tiger salamander (ambystoma tigrinum) retinal slices. synaptic strength is modulated by extracellular ph in a striking manner: light-sensitive postsynaptic currents in horizontal and bipolar cells were found to be exponential functions of ph, exhibiting an e-fold increase per 0.23 ph unit over the ph range from 7 to 8. calcium channel curren ... | 1993 | 7694280 |
| the relation between stimulus and response in olfactory receptor cells of the tiger salamander. | 1. olfactory receptor cells were isolated from the adult tiger salamander ambystoma tigrinum and the current in response to odorant stimuli was measured with the whole-cell voltage-clamp technique while odorants at known concentrations were rapidly applied for controlled exposure times. 2. three odorants, cineole, isoamyl acetate and acetophenone, were first applied at 5 x 10(-4) m. out of forty-nine cells tested, 53% responded to one odorant only, 22% to two odorants and 25% to all three odoran ... | 1993 | 8254501 |
| distribution and morphology of motoneurons innervating different muscle fiber types in an amphibian muscle complex. | the distribution and morphology of motoneurons innervating specific types of muscle fibers in the levator scapulae superior (lss) muscle complex of the bullfrog (rana catesbeiana) and tiger salamander (ambystoma tigrinum) were studied by retrograde labelling with cholera toxin-conjugated horseradish peroxidase (ct-hrp). the lss muscle complex in both of these amphibians has a segregated pattern of muscle-fiber types (tonic; fast oxidative-glycolytic twitch [fog]; fast glycolytic twitch [fg]) alo ... | 1993 | 8315651 |
| divalent cations block the cyclic nucleotide-gated channel of olfactory receptor neurons. | 1. the effects of external divalent cations on odor-dependent, cyclic amp-activated single-channel currents from olfactory receptor neurons of the tiger salamander (ambystoma tigrinum) were studied in inside-out membrane patches taken from dendritic regions of freshly isolated sensory cells. 2. channels were reversibly activated by 100 microm cyclic amp. in the absence of divalent cations, the channel had a linear current-voltage relation giving a conductance of 45 ps. with increasing concentrat ... | 1993 | 7685377 |
| kinship affects morphogenesis in cannibalistic salamanders. | inclusive fitness theory predicts that organisms can often increase their fitness by helping relatives. indeed, many animals modify their behaviour towards kin in a fashion consistent with theory. morphogenesis may also be sensitive to kinship environment, especially in species that facultatively produce distinct morphs that differ in their ability to harm relatives, such as those that produce alternative cannibalistic and non-cannibalistic phenotypes. we tested this hypothesis by examining whet ... | 1993 | 8479520 |
| fine structure of the retinal photoreceptors of the tiger salamander (ambystoma tigrinum). | the retinal photoreceptors of the tiger salamander (ambystoma tigrinum) have been studied by light and electron microscopy in both light- and dark-adaptation. rods and cones are present in this duplex retina in a ratio of about 20:1. as in other urodele species these photoreceptors are very large cells. the rod outer segment is composed of bi-membranous discs of uniform diameter displaying several very deep incisures. the rod inner segment displays an ellipsoid of mitochondria and a myoid region ... | 1993 | 8490253 |
| fine structure of the retinal epithelium of the tiger salamander (ambystoma tigrinum). | the retinal pigment epithelium (rpe) of the tiger salamander (ambystoma tigrinum) consists of a single layer of large squamous-shaped cells. these rpe cells are but minimally infolded basally (sclerally) but show numerous apical (vitreal) processes that interdigitate with the photoreceptor cells. a series of apically-located tight junctions joins the rpe cells to form part of the blood-ocular barrier. internally the rpe nucleus is large, vesicular and flattened. smooth endoplasmic reticulum pred ... | 1993 | 8490252 |
| ultrastructure and immunocytochemistry of the neuroepithelial bodies in the lung of the tiger salamander, ambystoma tigrinum (urodela, amphibia). | light and electron microscopy of the lungs of ambystoma tigrinum (urodela) revealed a relatively complex pattern of the neuroendocrine (ne) cells. in the apical parts of smaller septa single ne cells not associated with nerve fibres were covered and surrounded by pneumocytes. the larger septa possessed small areas of ciliated epithelium, in which the ne cells were grouped in a form of neuroepithelial bodies (neb) consisting of 3-5 cells and covered by goblet cells. ne cells possessed a large nuc ... | 1992 | 1443667 |
| biochemical plasticity in the arizona tiger salamander (ambystoma tigrinum nebulosum). | the arizona tiger salamander, ambystoma tigrinum nebulosum, is a developmentally polymorphic species. some individuals become sexually mature while retaining some larval traits (paedomorphs), while other individuals mature as metamorphosed salamanders. in this study, relative enzyme activities of the products of two duplicate loci in each of three enzyme systems (aconitase, malate dehydrogenase, and isocitrate dehydrogenase) were measured in paedomorphs and in paedomorphs forced to metamorphose ... | 2013 | 1624768 |
| properties of depolarizing bipolar cell responses to central illumination in salamander retinal slices. | the voltage and current responses of depolarizing bipolar cells to central illumination were studied by means of whole-cell recording in retinal slices of the larval tiger salamander, ambystoma tigrinum. to stabilize the responses, it was necessary to limit exchanges between the cytosol and the solution in the patch pipette by reducing the diameter of the pipette tip opening. the current-voltage relationship of the cell membrane in darkness displayed a strong outward rectification, and the inwar ... | 1992 | 1515915 |
| neurofilaments are prominent in bullfrog olfactory axons but are rarely seen in those of the tiger salamander, ambystoma tigrinum. | bullfrog olfactory axons show variable numbers (0-29) of structurally typical neurofilaments (nfs) about 10 nm in diameter. in studies tracking these nfs through serial sections of axons in cross section, they were found to be discontinuous, with a calculated average length of about 118 microns. in contrast to olfactory axons in bullfrogs, those of the tiger salamander ambystoma trigrinum rarely show nfs. to be certain that the absence of nfs is a specific characteristic of olfactory axons, piec ... | 1992 | 1578003 |
| site of action potential initiation in amphibian retinal ganglion cells. | 1. we applied morphological, pharmacological, electrophysiological, and computer simulation techniques to analyze the origin of impulse initiation in amphibian retinal ganglion cells. 2. morphological studies of retinal ganglion cells in the mudpuppy (necturus maculosus) and larval tiger salamander (ambystoma tigrinum) were carried out with the use of either retrograde or intracellular labeling with horseradish peroxidase. these studies identified a characteristic thinning of the axon that begin ... | 1992 | 1569462 |
| effects of 2-amino-4-phosphonobutyric acid on cells in the distal layers of the tiger salamander's retina. | 1. we studied the effects of 2-amino-4-phosphonobutyric acid (apb) on the response properties of rods, horizontal cells and bipolar cells in the isolated, perfused retina of the tiger salamander, ambystoma tigrinum. a concentration of 100 microm was found to be sufficient to elicit maximal effects. 2. rods hyperpolarized slightly upon exposure to 100 microm-apb and their response amplitudes were slightly reduced. the amplitude of the cone-generated component of the rod's response to 700 nm light ... | 1992 | 1501153 |
| reduced calcium and inhibition of protein kinase c mimic the enhancement of ornithine decarboxylase activity of prolactin in ambystoma tigrinum tissues. | we previously reported that prolactin (prl) could increase the activity of ornithine decarboxylase (odc) in liver slices taken from larval tiger salamanders (ambystoma tigrinum). this action of the hormone was inhibited by oxytocin (ot), the calcium ionophore a23187, and diacyglycerol (dg) and was duplicated by 10 microm verapamil (vml), a calcium channel blocker. here, we expand these results to show that 1) a higher dose of vml (50 microm) produces an additive effect with prl; 2) addition of s ... | 1991 | 1940822 |
| pathogens as a factor limiting the spread of cannibalism in tiger salamanders. | intraspecific predation is taxonomically widespread, but few species routinely prey on conspecifics. this is surprising as conspecifics could be a valuable resource for animals limited by food. a potential cost of cannibalism that has been largely unexplored is that it may enhance the risk of acquiring debilitating pathogens or toxins from conspecifics. we examined how pathogens affect variation in the incidence of cannibalism in tiger salamander larvae (ambystoma tigrinum nebulosum), which occu ... | 1991 | 28312127 |