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At least 973 records · Page 54Linked to original sources
PubMed1991

Temperature acclimation of respiratory function in the salamander Taricha granulosa.

The effect of acute and chronic temperature change on oxygen uptake (VO2) and the respiratory properties of blood was determined in the newt, Taricha granulosa. Acclimation to 20-24 degrees C for 4 weeks caused a significant increase in hemoglobin concentration (6.5-9.5 g/dl) and O2 capacity of blood but no change in oxygen affinity compared with animals acclimated to 4-6 degrees C. Cold acclimated animals had a reverse Bohr effect compared with warm acclimated animals (dlogP 50/dpH = +0.13 and -0.12, respectively) but the present data offer no mechanism. There was no difference between the two acclimation groups with respect to temperature sensitivity of O2 binding, cooperativity of binding, buffer capacity, red cell organic phosphate concentration, or red cell dimensions. There was no evidence for thermal acclimation of VO2. Over the seasonal range of water temperature experienced by this species (5-25 degrees C), the major adaptation to the ca. 4 fold increase in VO2 is a 49% increase in blood O2 capacity.

Acclimatization↗
PubMed1981

Spermatophores of the salamander Ambystoma texanum.

Living spermatozoa were observed in freshly deposited spermatophores and in fluid from vasa deferentia. In the distal, but not proximal, vas deferens spermatozoa moved together in whorls with heads and tails in alignment. Around the entire periphery of the spermatophore cap, similar slowly undulating groups of spermatozoa had their heads aligned and directed outward. Over time, some individual spermatozoa left the cap of the spermatophore and moved into the surrounding water (cap deterioration). Microscopical observations were made on spermatophore squashes and paraffin sections of spermatophores and vasa deferentia. Spermatozoa around the periphery of the cap were underlain by a PAS-positive membrane-like material. Cytoplasmic droplets, which were attached to spermatozoan necks in the vas deferens, were accumulated in the center of the spermatophore cap deep to the PAS-positive membrane. Spermatophore stalks were strongly PAS and Alcian blue positive and showed positive reaction for RNA. Tests for lipids and proteins were negative in the whole spermatophore. Electron microscopic observations showed the stalk of the spermatophore to be composed of rounded 'balls' of fibrous material. At the juncture of the stalk and cap a less dense fibrous material impacted the stalk enclosing many sperm tails and some heads and, although no attachment devices were visualized, the sperm were closely apposed to this material as was the spermatophore stalk. This finely filamentous material encircled the cap and was more prominent in some regions than others. The PAS-positive material detected with the light microscope was also observed with the electron microscope. It was circumferentially oriented and was composed of 200 A packed filamentous densities. Sperm heads and tails were found lying external to the membrane, whereas only tails and cytoplasmic droplets occupied the core of the spermatophore. Cytoplasmic droplets were usually free of the sperm tail and contained membranous sacs and two types of nuage material.

Ambystoma↗
PubMed1993

Effects of GABA on horizontal cells in the tiger salamander retina.

Application of gamma-aminobutyric acid (GABA) slows down the horizontal cell response time course (HCRRT) and induces membrane depolarization in horizontal cells (HCs) after synaptic inputs are blocked by Co2+. We present evidence that suggests both effects are probably mediated by GABAA receptors which open chloride channels in the HC membrane. In any given concentration of GABA, ranged from 0 to 100 microM, the HC membrane potential (VHC) in saturating light and in the presence of 100 microM Co2+ are identical. This result suggests that GABA in both light and 100 microM Co2+ opens the same amount of chloride channels (same gCl) so that VHC determined by chloride and leak conductances has the same value. Higher concentrations of Co2+ (> 300 microM) not only blocks synaptic transmission from photoreceptors to HCs, but also acts as an antagonist that suppresses the GABA-mediated depolarization in HCs.

Ambystoma↗
PubMed1994

Changes in the light-sensitive current of salamander rods upon manipulation of putative pH-regulating mechanisms in the inner and outer segment.

The light-sensitive current of dark-adapted rods isolated from the Ambystoma retina was recorded while either the inner or the outer segment (IS or OS) protruding from the suction pipette was exposed to treatments intended to reveal the physiological roles of pH-regulating transport mechanisms. Applied to the IS, both amiloride (presumed to block Na+/H+ exchange, 2 mM) and 4-4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) (presumed to block bicarbonate transport, 0.1 mM) generally abolished light sensitivity completely but reversibly, consistent with acidification of the IS. Yet, the circulating ("dark") current often persisted, implying that the OS was not acidified. Applied to the OS, amiloride depressed but DIDS increased the dark current and photoresponses. Given the fact that the current increases with rising OS-pHi, this suggests alkalinization, which could be due to DIDS inhibiting bicarbonate extrusion by HCO3-/Cl- exchangers in the OS. Consistent with this idea, replacing external Cl- by other anions increased the current as would be expected if HCO3-/Cl- exchange is reversed. We propose that the IS and OS manage their acid balances independently and with different sets of transport mechanisms. Acidosis in either compartment suppresses the photosensitivity of the rod, but by differing mechanisms.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

Miniature excitatory postsynaptic currents in bipolar cells of the tiger salamander retina.

The synapse between photoreceptor and bipolar cell is important for at least three reasons: (1) it is the first synapse in the visual pathway; (2) it is the best-known tonic chemical synapse; and (3) it has perhaps the most complex and highly organized synaptic morphology in the entire brain. Yet little is known about how neurotransmitter is released from this synapse. We present in this report evidence which suggests that the release of photoreceptor neurotransmitter, presumably glutamate, is probably mediated by clusters of synaptic vesicles which give rise to discrete miniature excitatory postsynaptic currents (MEPSCs) in bipolar cells. The MEPSCs are Ca(2+)-, osmotic- and CNQX-sensitive, and they share the same reversal potential (near -3 mV) as the glutamate-induced postsynaptic current. The frequency of MEPSCs increases upon presynaptic depolarization, and the mean peak conductance is about 54 pS. MEPSCs exhibit wide variations of amplitudes and durations, probably resulting from random variations of number of synaptic vesicles and the degree of synchronization in individual release clusters.

Ambystoma↗
PubMed1982

Effect of thyroid hormones on the switch from larval to adult hemoglobin synthesis in the salamander Pleurodeles waltlii.

The evolution of globin chain synthesis was studied in larvae treated either with thyroxine or with an anti-thyroid substance. Thyroxine treatment accelerated the rate of Hb switching; it induced a preferential synthesis of adult globins while the synthesis of larval globins decreased rapidly. Treatment with thiourea did not prevent the Hb transition, which occurred even at concentrations of thyroid hormones that did not permit induction of anatomical metamorphosis.

Animals↗
PubMed1995

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.

Ambystoma↗
PubMed1987

Synaptic connections between neurons in living slices of the larval tiger salamander retina.

Synaptic connections between retinal cells were studied by recording simultaneously from pre- and postsynaptic cells in the retinal slice preparation. The time course and waveform of the pre- and postsynaptic light responses were monitored, and the postsynaptic voltage responses to presynaptic current injection were measured. Results obtained provide direct evidence showing that the rod-HBC and rod-HC synapses are sign-preserving, and the rod-DBC, HC-HBC and amacrine-DBC synapses are sign-inverting. Moreover, the synaptic delays between rods and bipolar cells are shorter than that between rods and horizontal cells. The methodology of making retinal slices and the subsequent recording and stimulation procedures are described. The advantages of the retinal slice preparation and its potential in retinal research are discussed.

Ambystoma↗
PubMed1984

Specific and non-specific immunosuppressive factors in salamander pregnancy serum.

In vitro experiments employing pregnant Salamandra salamandra have previously shown a maternal specific cytotoxic cellular reaction against larval cells and an inhibition of this reaction by maternal serum. Two serum fractions, 19S and 13S, have been implicated in this inhibition. In the present work, the site of action and the identity of the factors responsible for this activity have been determined. Pre-incubation experiments indicate that the 19S fraction from pregnancy serum specifically protects embryonic epithelial cells derived from the same pregnant female. The 13S fraction non-specifically inhibits cytotoxic activity of maternal cells. Both factors implicated in these reactions are respectively an IgM and an alpha 2-macroglobulin. The question of whether the alpha 2M is responsible for immunosuppression is discussed, with particular reference to its vitellogenin analogue and also in view of the fact that the presence of this alpha 2M is not always linked with the immunosuppressive properties (except during pregnancy).

Animals↗
PubMed1994

Polysialic acid expression in the salamander retina is inducible by thyroxine.

Polysialylation of the neural cell adhesion molecule (NCAM) in the retina of Pleurodeles waltl is up-regulated during metamorphosis. Incubation of larvae in thyroxine permanently induced polysialic acid expression in the retina in a concentration-dependent but age-independent manner within 3 days of incubation (3 x 10(-7) M). Retinoic acid had no effect. This suggests direct hormonal regulation of a post-translational modification of NCAM in the amphibian retina.

Aging↗
PubMed1993

Phototaxic behavior and the retinotectal transport of horseradish peroxidase (HRP) in surgically created cyclopean salamander larvae (Ambystoma).

UNLABELLED: Negative phototaxis (NP) was used to evaluate the recovery of vision in albino axolotl larvae with one eye discarded and the other transplanted either to the orbit (orthoclops) or to the top of the head (cyclops). NP was assessed at approximately 1, 2 and 3 months postoperatively, using an automated, infrared monitor. Some 88% of the orthoclopes and 64% of the cyclopes recovered NP. However, among the cyclopes that did recover, the quantitative aspects of NP were virtually the same as those of the orthoclopes. That the cyclopean eye can regenerate retinotectal pathways was established by anterograde tracing of horseradish peroxidase (HRP). But where previously uninjured animals transported HRP to the contralateral tectum, both the cyclopes and the orthoclopes distributed the enzyme to the left and right tectal halves. Heavy deposits of HRP were found in the tecta of some animals that lacked NP. To find out if an optic tectum is actually required for NP, a series of ablation experiments were performed, using Ambystoma punctatum larvae. Tectectomy had the same effect on NP as bilaterally extirpating the eyes or intracranially severing both optic nerves, i.e. removing the tectum abolished NP. THE RESULTS: (1) confirm the efficacy of the ectopic eye in the cyclops preparation; (2) show that the ectopic eye can regenerate retinotectal pathways; (3) indicate that retinotectal contact is a necessary but insufficient condition for NP.

Ambystoma↗