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PubMed1990

Studies on the bile acids of the gall bladder bile of a mud-puppy, Salamander necturus.

The major bile acids of gall bladder bile of salamander necturus have been reported and shown to be taurine conjugates. The bile acid conjugates were hydrolysed and the free bile acids were separated by thin layer chromatography and identified through gas liquid chromatography and mass spectrometry (GC-MS) as methyl esters and methyl-ester trimethyl silyl ethers. About 56.3% of the total bus acid was present as allocholic acid whereas 3alpha, 7alpha, l2alpha-dihydroxy-5alpha-cholestanoic acid and cholic acid represented 30.4 and 12.3% respectively. Dihydroxy bile acids such as deoxycholic, allodeoxycholic and allochenodeoxycholic were present in less than 0.5% of the total bile acids.

Journal Article↗
PubMed1992

Occurrence of polyhydroxy alcohols in the gall bladder bile of a mud-puppy, Salamander necturus.

Bile obtained from the gall bladder of Salamander necturus was investigated for the presence of bile alcohols by a combined technique of Thin Layer Chromatography (TLC), Gas Liquid Chromatography (GLC) and Gas Chromatography-Mass Spectrometry (GC-MS). Dried bile salts were hydrolysed with 2.5N KOH in an autoclave at 121 degrees C. Unsaponifiable matter was extracted with ethyl acetate, three times, washed with distilled water, dried with anhydrous sodium sulphate,evaporated to dryness and analysed for its bile alcohols. Analytical GLC revealed the presence of at least thirteen bile alcohols in the mixture. Two major bile alcohols, i.e. 5alpha-anhydrocyprinol and 5alpha-cyprinol constituted about 73% of the total unsaponifiable matter. Others were identified as 3alpha, 7alpha, 12alpha,trihdroxy-5beta-delta23-homocholene,3alpha,7alpha,12alpha-trihydroxy-5alpha-delta24-nor-27-cholestene,3alpha,7alpha,12alpha-rihydroxy-5alpha-delta24-cholestene,5alpha-bufol and 5alpha-dermophol.

Journal Article↗
PubMed1990

Localization of classical neurotransmitters in interneurons of the larval tiger salamander retina.

Autoradiography was used to visualize the neurons in the tiger salamander retina that exhibit high-affinity uptake of 3H-dopamine, [3H]-serotonin, [3H]-glycine, and [3H]-GABA. Both [3H]-dopamine and [3H]-serotonin were accumulated by amacrine cells and by displaced amacrine cells. [3H]-glycine was taken up by amacrine cells, displaced amacrine cells, bipolar cells, and displaced bipolar cells. [3H]-GABA was accumulated by amacrine cells and by cells in the ganglion cell layer that may be displaced amacrine or ganglion cells. [3H]-GABA was also taken up by horizontal cells, bipolar cells, and displaced bipolar cells.

Animals↗
PubMed1991

Effects of retinoic acid on the muscle patterns produced during forelimb regeneration in larval salamanders (Ambystoma).

After systemic treatment with retinoic acid (RA), Ambystoma opacum and A. punctatum larvae regenerated forelimbs with a wide variety of skeletal and gross anatomical abnormalities. Yet the musculatures within the RA-treated limb regenerates were normal even in instances where the cartilages were deformed beyond recognition as components of the limb skeleton. RA is known to induce reduplication of limb structures, sometimes entire segments. When the latter condition occurred in the present study, the corresponding replicates exhibited limb musculatures which were perfect down to minute details, yet of opposite bilateral symmetry. The results attest, firstly, to the independence of myogenesis and chondrogenesis during limb regeneration. Secondly, RA treatment unmasked an otherwise hidden potential within postembryonic salamander limb tissue for the morphogenesis of the contralateral musculature.

Abnormalities, Drug-Induced↗
PubMed1990

Central olfactory and vomeronasal pathways in salamanders.

Central olfactory and vomeronasal pathways were studied in salamanders of the families Salamandridae and Plethodontidae by means of the HRP method. HRP was injected into the olfactory and accessory olfactory bulb as well as into the lateral/dorsal pallium, the main termination areas of secondary olfactory projections. Fibers leaving the olfactory bulb constitute two main tracts, the lateral olfactory tract (LOT), which is mostly restricted to the ipsilateral telencephalon, and the anterior olfactory habenular tract (AOHT), which represents the main contralateral connection. Fibers of the LOT project to the lateral pallium, dorsal striatum and the habenula. Efferent connections of the accessory olfactory bulb (AOT) terminate within the amygdala pars lateralis. No interspecific differences concerning the targets of central olfactory and vomeronasal projections were observed, but the number of olfactory tracts and their separation from each other varies.

Animals↗
PubMedDate not supplied

[An atrial hematopoietic locus in the heart of the cave salamander (urodele amphibian)].

Lungless Salamanders of the family Plethodontidae have a reduced interatrial septum. The pulmonary vein is lacking. In these species, the septum as a membranous thin sheet attaches near the dorsal lip of the sino-atrial valve where a connective and muscular column, supporting the valve, extends its branches over the upper wall of the undivided atrial cavity where a sponge-like structure is formed. The meshes of this structure are the site of a erythropoietic activity as shown in the plates. Early stages in active reproduction are found in the external acid layer while in the basic inner layer the red cells undergo differentiation. This locus may be correlated to the particular anatomy of the heart concerning the lacking of the pulmonary vein, the position of the sino-arterial aperture shifted to the left side and the reduced interatrial septum. In the large upper cavity of the atrium a certain degree of blood stagnation could be possible which could allow the settlement of this locus. No ventricular erythropoiesis nor epicardial granulopoiesis have been found. This hemopoietic locus is lacking in the family Salamandridae and Anura.

Animals↗
PubMed1990

Synaptic inputs from rods and cones to horizontal cells in the tiger salamander retina.

Synaptic inputs from rods and cones to horizontal cells (HCs) were studied in the flatmounted isolated retinas of the tiger salamander. Voltage-intensity relations, spectral sensitivities and response waveforms of the rod, the cone, and the HC under dark- and light-adapted conditions were examined. HCs receive mixed inputs from rods and cones in both dark- and light-adapted retinas. The relative rod/cone input in HCs depends on the intensity of stimulus and background illumination, and it varies from HC to HC.

Ambystoma↗
PubMed1988

The effect of cadmium on the light-sensitive current of isolated rods of the tiger salamander.

The effect of cadmium on the light-sensitive current of isolated rods of the tiger salamander was analysed by rapidly changing the ionic medium using the technique of Hodgkin et al. (1985). Addition of millimolar amounts of cadmium to the extracellular medium caused a rapid, but transient, decrease of the photocurrent. The effect of cadmium on the movement of divalent cations, such as Ba2+ and Ca2+, differs according to the experimental protocol: when cadmium is introduced into the bathing medium at the same time as Ca2+ or Ba2+, it blocks the entry of these ions into the rod; and when the rod is exposed to cadmium first for a few seconds the entry of Ca2+ and Ba2+ is enhanced. The effect of cadmium is best explained as a dual effect: firstly, an external effect on the channel, and secondly, by metabolic changes, which are caused by a drop of intracellular Ca2+.

Ambystoma↗
PubMed1989

Effects of background illumination on the horizontal cell responses in the tiger salamander retina.

Synaptic transmission between photoreceptors and horizontal cells (HCs) was studied in the flat-mounted isolated retinas of the tiger salamander. Background illumination expedited the rise time of the HC light response, and the HC response rise time (HCRRT) reached steady state about 2 sec after the onset of the background illumination. The change in HCRRT is probably responsible for the background-induced enhancement of the HC responses to short light stimuli. The amplitude of the HC responses to 100 msec light steps in the presence of background illumination was 2-5 times larger than that measured under dark-adapted conditions. Background illumination exerted little effect on the response rise time in cones and bipolar cells, and thus it caused no significant response enhancement in those cells. The background-induced change in HCRRT correlated closely with the rod voltage but not with the HC voltage. These results suggest that the background-induced change in HCRRT is probably mediated by postsynaptic events in HCs because no significant time course change is observed in photoreceptors and bipolar cells (which share the same synapses with the HCs). A suppressive rod action on the cone inputs in HCs may be responsible for modulating the HCRRT. By shortening the HCRRT, background illumination regulates the frequency response of the photoreceptor-HC synapse and alters the capacity of spatial resolution of retinal bipolar cells.

Ambystoma↗
PubMed1988

Synaptic transmission from rods to horizontal cells in dark-adapted tiger salamander retina.

Synaptic transmission between rods and horizontal cells (HCs) was studied by simultaneously recording from the pre- and postsynaptic cells in the living retinal slices of the larval tiger salamander. Voltage tails after the termination of a flash were observed in dark-adapted rods and HC somata, but not in cones. These simultaneously recorded voltage tails were used to isolate the rod input from the cone input to the HCs. The rod voltage versus the HC voltage in the response tails yielded the input-output relation of the rod-HC synapse. Two factors, a luminance-dependent signal delay between the rod and HC responses and a voltage-dependent depolarizing current in the HCs, complicate the analysis of the rod-HC synapse. A single input-output relation of the rod-HC synapse was obtained after these two factors had been corrected. The rod-HC synapse was approximately linear near the rod dark potential (-40 mV) with a synaptic gain around 12, but it became progressively nonlinear at more hyperpolarized potentials. The synaptic gain at Vrod = -50 mV was about 0.65.

Ambystoma↗
PubMed1988

Ultrastructure and histochemistry of the vas deferens of the salamander Rhyacotriton olympicus: adaptations for sperm storage.

The vas deferens of the salamander Rhyacotriton olympicus is composed of (1) a peritoneal epithelium, (2) connective tissue with fibroblasts, melanophores, circular smooth muscle, capillaries, and unmyelinated nerves within a collagenous matrix, and (3) an inner layer of cuboidal epithelium partially covered by ciliated squamous cells at the lumen. The lumen and apical cytoplasm of both epithelial cell types contain strongly PAS-positive granules. The cuboidal cells contained numerous swollen rough endoplasmic reticulum cisternae, mitochondria, and apical dense granules suggesting a high degree of secretory activity possibly involved in sperm maintenance. Fewer mitochondria, rough endoplasmic reticula, and granules in squamous cells suggest less secretory activity. Squamous cells may protect the cuboidal cells from possible abrasion by sperm masses and/or their cilia may aid in distributing secretory products in the lumen.

Animals↗
PubMed1986

Relation between light responses and dendritic branching in the salamander ganglion cells.

Ganglion cells in larval tiger salamander retina were differentiated into different types according to their light response and morphology. Sustained hyperpolarizing responses were recorded from ganglion cells branching in the sclerad half of the inner plexiform layer (IPL). Sustained depolarizing responses were elicited in cells with dendrites confined in the vitread portion of the IPL. Transient responses were associated with two types of morphological units sharing level of branching, in the middle of the IPL, but differing for soma location (inner plexiform or inner nuclear layer).

Animals↗
PubMed1985

Electrophysiological properties of identified cells in the in vitro olfactory epithelium of the tiger salamander.

An in vitro preparation of the salamander olfactory epithelium has been developed for electrophysiological analysis. Intracellular measurements of membrane properties of the main epithelial cell types have been carried out, combined with Lucifer Yellow injections. The most prevalent type of cell had a high resting membrane potential and relatively low input resistance. This cell never discharged impulses, either spontaneously or to injected current. Lucifer Yellow injections identified this cell type as a supporting cell. A less frequent type had a medium resting potential and a very high input resistance. This type always discharged impulses in response to injected depolarizing current. Lucifer Yellow injections identified this cell type as an olfactory receptor neuron. The least frequent type had a medium resting potential and a high input resistance. It never generated action potentials. This nonspiking type was tentatively identified as an immature receptor neuron in the process of differentiating from basal stem cells in the epithelium. These are the first results to document physiological properties for the main cell types and morphological identification of two of the types in the same preparation of the olfactory epithelium. Our results support previous suggestions regarding the glial-like properties of the supporting cells. The membrane properties of the receptor neurons appear to be well suited for mediating the olfactory sensory response of these cells.

Action Potentials↗
PubMed1985

Changes in the electrical properties of olfactory epithelial cells in the tiger salamander after olfactory nerve transection.

Transection of olfactory nerves causes degeneration of receptor neurons in the olfactory epithelium, followed by generation of new receptor neurons. We have carried out intracellular recordings to document changes in epithelial cell populations during receptor neuron degeneration and regrowth at 1, 2, and 4 weeks following olfactory nerve transection in the salamander. Receptor neurons were greatly reduced in numbers at 1 week, and gradually returned to the normal percentage of intracellular penetrations by 4 weeks. They had a resting membrane potential between -30 and -50 mV and high input resistance, 100 to 600 megohms, characteristically seen in normal epithelium. However, at 1 week, the receptor neurons were able to generate only a single spike in response to injected current, and did not re-acquire their ability to respond repetitively until 4 weeks. Cells with the properties of immature receptor neurons (resting membrane potential between -30 and -50 mV and high input resistance, 100 to 600 megohms, but unable to generate spikes) increased significantly in number in the post-transection period. This correlates with the burst of mitotic activity giving rise to new receptor neurons after nerve transection. Supporting cells changed their properties in the aftermath of transection. One type (A) showed a decrease in resting membrane potential and a small increase in input resistance. A second type (B) showed a very large increase in input resistance. These results imply that the degenerating receptor neurons transmit a signal that leads to changes in the functional properties of the glial-like supporting cells. These may involve changes in the membrane properties or in electrical coupling between cells.

Ambystoma↗
PubMed1985

The fate of larval chondrocytes during the metamorphosis of the epibranchial in the salamander, Eurycea bislineata.

The metamorphosis of the epibranchial cartilage, a skeletal component of the hyobranchial apparatus, in the salamander Eurycea bislineata entails a combination of the reabsorption of a larval cartilaginous element with the simultaneous genesis of an adult cartilage in the same place. In this study we focus on the fate of the larval chondrocytes. Two hypotheses are considered: one, larval cells simply die off during metamorphosis, or, alternatively, they dedifferentiate and participate in the formation of the adult element. Thyroxine treatment and experimental tissue manipulation coupled with measurements of thyroxine levels using radioimmunoassay show that, within 24 h after T4 treatment, larval chondrocytes in the epibranchials exhibit large autophagocytic vacuoles, disruption of the rough endoplasmic reticulum, abnormally shaped mitochondria, abundance of lysosomes and nuclear degeneration, all symptoms of the onset of cell death. In conclusion, evidence from light microscopy, TEM and SEM show that the larval chondrocytes in response to rising levels of thyroid hormones undergo a process of lysosomal autophagocytosis and do not participate in the formation of adult structures.

Animals↗
PubMed1979

An electron microscope study of the respiratory epithelium in the lungs of the fire salamander (Salamandra salamandra).

The respiratory epithelium in the lungs of the common fire salamander (Salamandra salamandra) has been studied by electron microscopy. The entire pulmonary gas-exchange area is covered by a continuous epithelium, the cells of which are all of the same type and are termed 'pneumonocytes'. Typically, each pneumonocyte is squamous and has attenuated sheets of cytoplasm which extend over the pulmonary capillaries. Its free surface bears squat microvilli, and osmiophilic inclusion bodies and other organelles are prominent in the cytoplasm. The lateral cell walls have numerous desmosomes and interdigitating cytoplasmic processes. Many cells send cytoplasmic processes deep into the substance of the lung septa. The morphological evidence suggests that the pneumonocytes are responsible for the secretion of pulmonary surface-active agents and for maintaining the integrity of the gaseous diffusion membrane.

Animals↗
PubMed1984

[Heat resistance level of muscles and muscle models of salamander larvae kept at different temperatures and their thermal selection].

The larvae of salamanders isolated from 19 pregnant females were grown to the middle of pre-metamorphosis. The siblings obtained from each single female were divided into two parts; larvae of one group were kept at 21 degrees C (control group), and those of the other--at 27 degrees C (experimental group). In all, 38 groups of experimental animals were employed. In animals kept at 21 degrees C the heat resistance of the organism, muscles and contractile muscle models were determined, whereas in those kept at 27 degrees C only the thermoresistance of muscles and their models only was registered. The time of loss of excitability in response to the electrical stimulus during heating in the Ringer solution at 36 degrees C served a criterion of heat resistance of muscles. The time of loss of contractility with the addition of ATP at 36 degrees C was a criterion of heat resistance of muscle models. The time of the onset of thermal shock at 34 degrees C being a criterion of heat resistance of the organism. It has been found that siblings showing a lower resistance level of muscles and of their models at 21 degrees C, when kept at 27 degrees C, increased their resistance much more as did siblings with the initially higher resistance. During the thermal selection, individuals of such initially less resistant families displayed selective advantages.

Animals↗
PubMed1983

Optical monitoring of activity from many areas of the in vitro and in vivo salamander olfactory bulb: a new method for studying functional organization in the vertebrate central nervous system.

We have investigated the use of voltage-sensitive dyes to monitor neuronal activity in the intact salamander olfactory bulb. After a 10- to 20-min staining period, a magnified image of an in vitro or an in vivo preparation was formed on a 124-element photodiode array. The array was used to simultaneously record absorption or fluorescence changes from 124 adjacent areas of the bulb. At the magnifications used, each detector received light from 100 to 1000 neurons. Relatively large absorption and fluorescence signals were found in response to olfactory nerve stimulation; all of the results presented were from single trials. Because of the large signal size, measurements on in vivo preparations using epi-illumination also had good signal-to-noise ratios. There were significant differences in signal time course between adjacent detectors which suggested a spatial resolution on the order of 200 microns. Tentative assignments of the cellular origins of some signals could be made from the results of paired volley experiments. The results suggest that optical monitoring of membrane potential could provide a useful method for studying neuronal organization in the intact vertebrate central nervous system.

Ambystoma↗