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At least 217 records · Page 12Linked to original sources
PubMed1998

Impact of guthion on survival and growth of the frog Pseudacris regilla and the salamanders Ambystoma gracile and Ambystoma maculatum.

The effects of the insecticides Guthion (technical grade) and Guthion 2S (commercial formulation) on survival and growth of tadpoles of the Pacific treefrog Pseudacris regilla, and larvae of the Northwestern salamander Ambystoma gracile and the spotted salamander Ambystoma maculatum were determined in continuous-flow exposures in the laboratory. Ninety-six-hour LC50 values were >3.6 mg/L for P. regilla with technical grade Guthion and 1.47 mg/L with the formulation Guthion 2S (measured as active ingredient Guthion). Ten-day LOAEL and NOAEL values based on length and weight for P. regilla with Guthion were 3.60 and 0.98 mg/L. LOAEL and NOAEL values based on length and weight for P. regilla with Guthion 2S were 0.17 and 0.07 mg/L. The 96-h LC50 for Guthion 2S was 1.67 and 1.90 mg/L for A. gracile and A. maculatum, respectively. LOAEL and NOAEL values based on length and weight for A. gracile with Guthion 2S were 0.22 and 0.10 mg/L; they were 0.11 and 0.03 mg/L for A. maculatum based on weight. These species are as similar in sensitivity as some fish species but are more tolerant to Guthion than most invertebrates.

Ambystoma↗
PubMed2006

Up-regulation of P450arom and down-regulation of Dmrt-1 genes in the temperature-dependent sex reversal from genetic males to phenotypic females in a salamander.

When larvae of the salamander Hynobius retardatus were reared at a high temperature (28 degrees C) during their thermosensitive period (TSP=15-30 days after hatching), all larvae developed to phenotypic females irrespective of their genetic sexes. Hynobius P450 aromatase (P450arom) and Dmrt-1 complementary DNAs were isolated and their expression patterns were analyzed by competitive and conventional reverse transcriptase-polymerase chain reaction. While the P450arom gene was expressed predominantly in the ovary, Dmrt-1 was expressed exclusively in the testis. When larvae were reared at the female-producing temperature (28 degrees C) during the TSP, a strong expression of the P450arom gene and a complete suppression of the Dmrt-1 gene were induced in all experimental larvae. Up-regulation of the P450arom gene and down-regulation of the Dmrt-1 gene even in genetic males constitute a part of the molecular biological cascade for the temperature-dependent sex reversal from genetic males to phenotypic females in this salamander.

Amino Acid Motifs↗
PubMed1999

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 single lineage but showing a range of differentiation. Immature cells had nearly smooth to lightly cleft or folded basophilic nuclei bordered by a band of cytoplasm with few cytoplasmic processes and containing a few small uniform eccentric granules. Mature cells had basophilic nuclei with deep clefts or folds and abundant eosinophilic cytoplasm with multiple long intertwining cytoplasmic extensions packed with metachromatic granules. The axolotls were old individuals from an inbred laboratory colony. The tiger salamanders were wild animals from a single polluted pond. They could have been old and inbred. Both groups were neotenic. These are the first mastocytomas discovered in cold-blooded animals.

Ambystoma↗
PubMed2003

Salamanders ( Plethodon cinereus) go for more: rudiments of number in an amphibian.

Techniques traditionally used in developmental research with infants have been widely used with nonhuman primates in the investigation of comparative cognitive abilities. Recently, researchers have shown that human infants and monkeys select the larger of two numerosities in a spontaneous forced-choice discrimination task. Here we adopt the same method to assess in a series of experiments spontaneous choice of the larger of two numerosities in a species of amphibian, red-backed salamanders ( Plethodon cinereus). The findings indicate that salamanders "go for more," just like human babies and monkeys. This rudimentary capacity is a type of numerical discrimination that is spontaneously present in this amphibian.

Animals↗
PubMed1986

Effects of gamma-aminobutyric acid on cones and bipolar cells of the tiger salamander retina.

The gamma-aminobutyric acid (GABA) system in the tiger salamander retina was studied using autoradiographic and electrophysiological techniques. A high-affinity uptake mechanism for GABA has been localized in about 60% of the horizontal cells and about 30% of the amacrine cells. Effects of exogeneously applied GABA on the membrane conductance of cones and hyperpolarizing bipolar cells (HBC) were examined using the two electrode current-clamp technique in the living retinal slices. In both cell types, 1 mM of GABA caused a conductance increase. In perfused eyecups, 2 mM of GABA selectivity abolished the surround response of the HBC and left the center response unchanged. These results are consistent with the notion that a population of horizontal cells and a population of amacrine cells in the salamander retina may use GABA as their neurotransmitter.

Ambystoma↗
PubMed1988

Melatonin enhances horizontal cell sensitivity in salamander retina.

Intracellular electrophysiological recording techniques were utilized to investigate the possible function of retinal melatonin in the larval tiger salamander. Endogenous retinal melatonin was present and appeared to bind a membrane-enriched fraction of the salamander retina, as determined by radioimmunoassay and receptor binding studies. Melatonin added through the perfusion bath to flat-mounted retinas resulted in a horizontal cell (HC) hyperpolarization of 10-20 mV. Additionally, the amplitude of HC responses to short test flashes increased in the presence of melatonin. Voltage-intensity plots revealed that application of 500 microM of melatonin caused an increase of the HC light sensitivity and this effect was reversible. These results suggest that melatonin synthesized and released during the dark period of the diurnal cycle may alter the sensitivity of second-order neurons at a time of day when photopic input is at its lowest level.

Animals↗
PubMed1991

A re-examination of enkephalin's coexistence with gamma-aminobutyric acid in amacrine cells of the larval tiger salamander retina.

Double-label immunocytochemistry was utilized to re-examine the colocalization of enkephalin and gamma-aminobutyric acid (GABA) in amacrine cells of the larval tiger salamander retina. A total of 465 enkephalin-immunoreactive amacrine cells were identified and in all cases these cells were GABA-immunoreactive. This finding corroborates a previous study that showed greater than 96% of enkephalin-amacrine cells in the tiger salamander retina to specifically accumulate [3H]GABA and provides additional evidence for the GABAergic nature of these enkephalin-amacrine cells.

Animals↗
PubMed1993

Double-label analyses of the coexistence of somatostatin with GABA and glycine in amacrine cells of the larval tiger salamander retina.

To investigate the possible GABAergic nature of somatostatin-immunoreactive neurons of the larval tiger salamander retina, somatostatin immunocytochemistry was combined with either gamma-aminobutyric acid (GABA) immunocytochemistry or autoradiography of GABA high-affinity uptake. A total of 1,062 somatostatin cells were visualized in these studies. Double-label immunocytochemistry revealed that 96.3% of somatostatin-immunoreactive cells expressed GABA immunoreactivity. Double-label studies combining somatostatin immunocytochemistry with autoradiography of GABA high-affinity uptake revealed a slightly lower percentage (93%) of colocalization. Double-labelled cells were identified as Type 1, Type 2 and displaced amacrine cells. The small percentage of somatostatin-immunoreactive cells that did not co-label for GABA were identified as Type 1 amacrine cells. An analysis of retinal sections processed for double-label immunocytochemistry revealed that approximately 5% of GABA-immunoreactive cells in the amacrine and ganglion cell layers co-label for somatostatin. Somatostatin immunocytochemistry was combined with autoradiography of glycine high-affinity uptake to examine whether tiger salamander somatostatin-amacrine cells express this glycine marker. A total of 100 somatostatin-immunoreactive amacrine cells were visualized in double-label preparations. None of these cells were observed to exhibit glycine high-affinity uptake.

Animals↗
PubMed1983

Biochemical studies on muscarinic receptors in the salamander olfactory epithelium.

Muscarinic cholinergic receptors in the olfactory epithelium of the salamander, Ambystoma tigrinum, were studied via binding of 3-[3H]quinuclidinyl benzilate. The receptors are present on the olfactory receptor cells in the epithelium to an amount of 0.08 pmol/mg homogenate protein. Both choline acetyltransferase and acetylcholine esterase are present in the salamander olfactory epithelium.

Ambystoma↗
PubMed1988

Interrenal activity during metamorphosis of the tiger salamander, Ambystoma tigrinum.

Plasma corticosterone concentrations were low in premetamorphic tiger salamander larvae (Norman Stage I; M. F. Norman (1985) Anat. Rec. 211, 102-109). Corticosterone levels were significantly elevated at midmetamorphosis (Norman Stage IV) but decreased at the end of metamorphosis (Norman Stage VII). Corticosterone levels remained low 2 weeks after metamorphosis. Interrenal 3 beta-hydroxysteroid dehydrogenase activity was low in premetamorphic larvae (Norman Stage I) but was significantly elevated by midmetamorphosis (Norman Stage IV) and remained elevated at the end of metamorphosis (Norman Stage VII). There were no significant changes in interrenal cell nuclear size during metamorphosis. There was a significant decrease in body weight as well as a significant increase in hematocrit accompanying metamorphosis. The increase in plasma corticosterone concentration seen during metamorphosis of the tiger salamander is accompanied by an increase in interrenal steroidogenesis.

Adrenal Glands↗
PubMed1987

There is an alpha-actin skeletal muscle-specific gene in a salamander (Pleurodeles waltlii).

We cloned, from a cDNA library, an alpha-actin sequence from a salamander (Pleurodeles waltlii), which codes for the 125 COOH-terminal amino acid residues of a skeletal muscle actin (without any difference from the corresponding protein of warm blood vertebrates). An important conservation in the 3' untranslated region between this sequence and skeletal alpha-actin genes of chicken and man was noted. These results demonstrate, contrary to what was thought previously, that there exists in salamander a true skeletal alpha-actin gene. The results suggest that striated muscle actin genes in lower vertebrates could be a mosaic of cardiac and skeletal-specific amino acid residues, and that the divergence between these two types of genes is older than the NH2-terminal analysis of actins suggested previously.

Actins↗
PubMed1990

Two-eyed versus one-eyed salamanders: does binocularity enhance the optically evoked skin blanching reactions of Ambystoma larvae?

A wide variety of visual functions show increases attributable to binocularity, and the question pursued here was whether a second eye enhances the visually stimulated skin blanching reaction of the larval salamander. Dermal melanin spots (produced by the aggregations of melanosomes within dermal melanophores and which contract or expand to lighten or darken the skin) were measured in eyeless (controls), one-eyed and two-eyed Ambystoma punctatum larvae after chronic adaptation of the subjects to a white background (i.e., stimulus conditions for maximum blanching). The eyeless subjects showed no blanching (thus remained dark) in white cups, and they exhibited melanin spots 7 or 8 times the size of those of the other two groups. All one-eyed or two-eyed subjects exhibited blanching reactions; planometric comparison revealed a significantly larger melanin spot area for one-eyed than for two-eyed animals; i.e., the binocular condition permitted greater contraction of the pigment spots than did the monocular condition. Analytical data compared favorably with independently ascertained pigmentation indices. The results indicate that a second eye quantitatively elevates the blanching maximum of a larval salamander.

Ambystoma↗
PubMed1975

Kinetics of inert gas equilibration in an exclusively skin-breathing salamander, Desmognathus fuscus.

Characteristics of cutaneous gas exchange in amphibians were studied by analysis of the equilibration kinetics of an inert test gas in salamanders which have neither lungs nor gills. Specimens of the common dusky salamander (Desmognathus fuscus, Plethodontidae, Urodela), average body mass 6.1 g were equilibrated with 20% chlorodifluoromethane (Freon 22) in oxygen. The time course of subsequent elimination of Freon 22 into atmospheric air was more rapid in living than in dead animals. This difference was attributed to convective transport by blood flow. Several alternative models were proposed, providing a basis for quantitative analysis of the data. All models yielded similar values for convective conductance due to blood flow. In order to calculate blood flow therefrom, a simplified circulation model based on anatomical evidence was used: the cardiac output is in part directed to the skin, subserving gas exchange with the environment, and in part to the internal organs; the blood returning from both skin and internal organs is mixed before reaching the heart. Depending on assumptions regarding the model and the partitioning of blood flow to the skin and to internal organs, the following range of values was calculated from the experimental data: cardiac output, 85-195 mul/(min-g body mass); cutaneous blood flow, 27-63 mul/(min-g body mass). Due to inherent assumptions these values must be considered minimum estimates.

Animals↗
PubMed1983

Mechanisms of underwater hearing in larval and adult tiger salamanders Ambystoma tigrinum.

1. A standing wave tube apparatus was used to determine the biophysical basis of underwater hearing in Ambystoma tigrinum. 2. A. tigrinum responds to the pressure component of underwater sound, and the mouth cavity appears responsible for transduction of sound pressure. 3. Near-field displacements produced by pulsations of the air-filled mouth cavity apparently stimulate the inner ear. 4. Salamander head preparations with no air-filled mouth cavity respond to the particle motion component of underwater sound, but only at sound pressure levels 40 dB or more above levels producing clear pressure sensitivity in intact salamanders or head preparations including an air-filled mouth cavity.

Acoustic Stimulation↗
PubMed1981

Pretectal neurons project to the salamander retina.

Injection of horseradish peroxidase solution into the eye of some european salamander species labeled retrogradely pretectal neurons. These neurons lie near the commissura posterior and extend their dendrites into the visual pretectal neuropil. On the average, each animal contained 28 labeled cells. Their distribution is bilaterally with a slight preference to the contralateral pretectum. As in other vertebrates these retrogradely labeled pretectal cells may be considered as efferents to the salamander retina.

Animals↗
PubMed1990

Quantitative distribution of descending tectal efferent cells in salamanders.

In salamanders of the species Salamandra salamandra, Pleurodeles waltl, and Plethodon jordani, tectal efferent neurons projecting to the bulbar reticular formation show a stereotyped distribution as revealed by the horseradish peroxidase (HRP) method. The density of these cells increases toward caudal tectal levels reaching its maximum at the isthmic region. Neurons with ipsilaterally descending axons constitute 60-87% and are concentrated in the dorsomedial and ventrolateral sector of the tectal hemisphere, with only few neurons in the intermediate part. The contralaterally descending neurons are concentrated in the lateral sector. This pattern is assumed to reflect a motor map in the coordinates of the salamander neck muscle system.

Animals↗
PubMed1983

Density distribution, characterization and comparative aspects of plasma lipoproteins in the salamander, Pleurodeles waltii.

Blood plasma from a Urodele amphibian, Pleurodeles waltii, has been found to contain very-low density, low-density and high-density lipoproteins (VLDL, LDL and HDL, respectively). HDL and LDL predominated (concentration range 72-114 and 51-101 mg/dl) with lesser quantities of VLDL (23-51 mg/dl). Following isolation by density gradient ultracentrifugation, the physicochemical properties (morphology, particle size, hydrated density, electrophoretic mobility, and chemical composition) of the three major classes resembled, but were not identical with, those of the corresponding fractions in normal human plasma. The protein moieties of VLDL and LDL consisted mainly of polypeptides of high molecular weight (Mr greater than 60,000), which in their solubility were akin to human apo-B; smaller amounts of another protein migrated to the position of human apo-C-III in basic polyacrylamide gels. The major HDL apolipoproteins were of Mr 31,000 and 27,000, with minor amounts of 13,000, 61,000 and 76,000 components; in alkaline, urea-containing polyacrylamide gels, these major proteins migrated faster than the major components (apo-AI and apo-AII) of human HDL. Immunochemically, lipoproteins with pre-beta-, beta- and alpha-mobility were detected in the VLDL, LDL and HDL, respectively. Salamander VLDL and LDL were found to share an antigenic site(s) with the LDL of trout, chicken and guinea-pig, suggesting the presence of an apo-B-like protein. The chemical compositions and immunochemical reactions of salamander lipoproteins indicate that their structure and metabolism resemble that of other amphibia, reptiles and fish rather more closely than that of most mammals and birds.

Animals↗
PubMed1984

Distribution of cadmium, copper and zinc in the liver of spot salamander, Ambystoma maculatum and their binding to metallothionein.

Cadmium (Cd) was injected intramuscularly into male spot salamanders, Ambystoma maculatum. Concentrations and contents of Cd, zinc (Zn), copper (Cu), iron, magnesium and calcium in the livers of control and Cd-injected animals were determined simultaneously. A low molecular weight Cd, Cu, Zn-binding protein present in the hepatic supernatant prepared from control and Cd-injected animals was characterized as metallothionein (MT) from several properties characteristic of MT. MT induced and present in the liver supernatants of spot salamanders consisted of a single isoform.

Ambystoma↗