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PubMed1988

Topologic and connectional analysis of the dorsal thalamus of Triturus alpestris (amphibia, urodela, salamandridae).

A morphological and connectional analysis was performed on the dorsal thalamus of the alpine newt, Triturus alpestris. We have used a graphic reconstruction technique for the evaluation of the connectional (HRP) data. On the basis of these reconstructions, we propose a subdivision of the salamandrid dorsal thalamus into subhabenular, anteroventral, and posterodorsal zones. Each of these zones is defined by its telencephalic projections ("ascending thalamofugal systems"). The posterodorsal zone projects to the striatum, the anteroventral zone to the pallium. The subhabenular zone projects to the subpallial telencephalon and to the tegmentum. This zonal subdivision allows a more detailed comparison of the salamandrid dorsal thalamic features with ranid dorsal thalamic structures. We compare our dorsal thalamic zones to the ones proposed by Herrick (J. Comp. Neurol. 62:239-261, '35, The Brain of the Tiger Salamander. Chicago: The University of Chicago Press, '48). Furthermore, using the same reconstructive technique, we undertook an analysis of the spatial relations of various inputs to the salamandrid dorsal thalamus ("thalamopetal systems"). Besides the well-known retinal inputs, we identified the tectum and the tegmentum as sources of inputs to the thalamus. We provide evidence that there is no extensive multi- or unimodal overlap of these thalamopetal systems.

Afferent Pathways↗
PubMed1977

Regeneration of the retina in the adult newt, Triturus cristatus, following surgical division of the eye by a post-limbal incision.

An autoradiographic and histological study of retinal regeneration following a post-limbal ocular incision, in Triturus cristatus, is described. In these cases there is a major contribution to the regenerating retina from both the anterior complex (pars ciliaris retinae: ora serrata) and the retinal pigment epithelium. The tissue derived from the anterior complex can independently differentiate into retinal tissue if the anterior and posterior parts of the regenerate do not join. This contrasts with the situation following a limbal incision to the eye where the regenerative response of the anterior complex is inhibited. The significance of labelling patterns in the regenerating retina, following administration of 3H-thymidine, is discussed.

Animals↗
PubMed2006

Thyroid and hypoxic stress in the newt Triturus carnifex.

When specimens of the newt Triturus carnifex, under anaesthesia by submersion in a 0.2% chlorbutol solution for 25 min, are isolated in a respiratory chamber at 18 degrees C containing water with only 1.3 ppm of oxygen, they consume the oxygen completely in about 3 hr, but they can stay alive for many more hours and wake up with no apparent exterior consequences. Hypoxia induces rapid onset of hepatic steatosis and melanosis, as well as a controlled haemolytic process involving a pool of red blood cells of the same order of size as that held as a reserve in the spleen by animals in an aerial habitat. At the origin of the phenomena is an intense response by the hypophysis, histologically detectable 1 hr from the onset of treatment and confirmed 2 hr later by a highly significant increase in the plasma thyroidstimulating hormone (TSH) concentration compared with the controls (41.5 +/- 13.7 microU/L vs. 15.5 +/- 6.2; P < 0.005). The thyroid follicles react by reabsorbing their colloid, but instead of an increase in the plasma free T3 and T4 concentrations, fT3 falls significantly (1.5 +/- 0.3 pg/mL vs., the 2.4 +/- 0.7; P < 0.05), whereas fT4 remains stationary (4.0 +/- 0.5 pg/mL vs. 4.6 +/- 0.8; N.S.). After 6 hr, the plasmatic TSH concentration is still higher than in the controls (27.0 +/- 3.0 microU/L vs. 15.5 +/- 6.2; P < 0.05), whereas fT3 and fT4 remain stable (1.5 +/- 0.3 and 4.4 +/- 0.5 pg/mL, respectively). If T3 or T4 labelled with 125I is administered prior to hypoxia, after 6 hr of treatment the radioactivity is found to be limited exclusively to the liver and kidney; the thyroid, gall bladder and gut result negative, and this does not agree with hypotheses of hormone inactivation by deiodination, sulphation or glucuronidation. This apparently peculiar endocrine path has not been observed in previous studies on hypoxia in vertebrates, because the experiments were always designed to analyse plasma hormone levels after at least 24 hr of hypoxia or during chronic treatments, losing the most interesting phases of the endocrine response. The possibility that the hypoxic newt possesses alternative or complementary metabolic pathways to anaerobic glycolysis to sustain steatogenesis and melanogenesis and maintain the same cardiac activity as the controls is briefly discussed.

Animals↗
PubMed2004

Effects of adrenaline administration on the interrenal gland of the newt, Triturus carnifex: evidence of intraadrenal paracrine interactions.

The existence of paracrine control of steroidogenic activity by adrenochromaffin cells in Triturus carnifex was investigated by in vivo adrenaline (A) administration. The effects were evaluated by examination of the ultrastructural morphological and morphometrical features of the tissues as well as the serum levels of aldosterone, noradrenaline (NA), and adrenaline. In March and July, adrenaline administration reduced aldosterone release (from 187.23 +/- 2.93 pg/ml to 32.28 +/- 1.85 pg/ml in March; from 314.60 +/- 1.34 pg/ml to 87.51 +/- 2.57 pg/ml in July) from steroidogenic cells. The cells showed clear signs of lowered activity: they appeared full of lipid, forming large droplets. Moreover, adrenaline administration decreased the mean total number of secretory granules in the chromaffin cells in July (from 7.74 +/- 0.74 granules/microm(2) to 5.14 +/- 1.55 granules/microm(2)). In this period T. carnifex chromaffin cells contain almost exclusively NA granules (NA: 7.42 +/- 0.86 granules/microm(2); A: 0.32 +/- 0.13 granules/microm(2)). Adrenaline administration reduced noradrenaline content (4.36 +/- 1.40 granules/microm(2)) in the chromaffin cells, enhancing noradrenaline secretion (from 640.19 +/- 1.65 pg/ml to 1030.16 +/- 3.03 pg/ml). In March, adrenaline administration did not affect the mean total number of secretory vesicles (from 7.24 +/- 0.18 granules/microm(2) to 7.25 +/- 1.97 granules/microm(2)). In this period the chromaffin cells contain both catecholamines, noradrenaline (3.88 +/- 0.13 granules/microm(2)), and adrenaline (3.36 +/- 0.05 granules/microm(2)), in almost equal quantities; adrenaline administration reduced adrenaline content (1.74 +/- 0.84 granules/microm(2)), increasing adrenaline release (from 681.27 +/- 1.83 pg/ml to 951.77 +/- 4.11 pg/ml). The results of this study indicate that adrenaline influences the steroidogenic cells, inhibiting aldosterone release. Adrenaline effects on the chromaffin cells (increase of noradrenaline or adrenaline secretion) vary according to the period of chromaffin cell functional cycle. The existence of intraadrenal paracrine interactions in T. carnifex is discussed.

Aldosterone↗
PubMed1983

The structure of the kidney of Japanese newts, Triturus (Cynops) pyrrhogaster.

The construction of renal lobules in Triturus (Cynops) pyrrhogaster was studied by reconstruction from serial semithin sections, and the structure of nephrons, collecting ducts and ureters was investigated by means of light and electron microscopy. In T. pyrrhogaster the kidney was mesonephros in construction; renal lobules were arranged segmentally and each of them sent one ureter. Male ureters ran caudally and met together before joining the Wolffian duct. In renal lobules, long collecting ducts ran medio-laterally in the dorsal aspect of the kidney and sent several branches ventrally. Each branch duct or short collecting duct received one nephron. Each nephron had five segments; 1) renal corpuscle, 2) ciliated neck segment with or without a naphrostome, 3) proximal tubule, 4) ciliated intermediate segment and 5) distal tubule. Proximal and distal tubules were segregated spacially in renal lobules and occupied the peripheral and central zone respectively. The filtration barrier of the glomerulus consisted of both the basal lamina of podocytes and the subendothelial connective tissue, and was much thicker than the mammalian filtration barrier. Proximal tubule cells had a brush border, apical specialization for reabsorption of organic materials and well-developed smooth endoplasmic reticulum, but few baso-lateral interdigitations. In distal tubule cells, baso-lateral interdigitations and infoldings were well-developed. Collecting duct cells had a sparse cytoplasm. Ureter cells in males contained many secretory granules. On the basis of structural organization of the newt kidney as well as physiological data in literature, we suggest that in land vertebrates proximal tubules were primarily adapted to reabsorption of organic materials and distal tubules to reabsorption of electrolytes and water.

Animals↗
PubMed1992

Distribution of catecholaminergic and serotoninergic systems in forebrain and midbrain of the newt, Triturus alpestris (Urodela).

Mapping of monoaminergic systems in the brain of the newt Triturus alpestris was achieved with antisera against (1) thyrosine hydroxylase (TH), (2) formaldehyde-conjugated dopamine (DA), and (3) formaldehyde-conjugated serotonin (5-HT). In the telencephalon, the striatum was densely innervated by a large number of 5-HT-, DA- and TH-immunoreactive (IR) fibers; IR fibers were more scattered in the amygdala, the medial and lateral forebrain bundles, and the anterior commissure. In the anterior and medial diencephalon, TH-IR perikarya contacting the cerebrospinal fluid (CSF-C perikarya) were located in the preoptic recess organ (PRO), the organum vasculosum laminae terminalis and the suprachiasmatic nucleus. Numerous TH-IR perikarya, not contacting the CSF, were present in the posterior preoptic nucleus and the ventral thalamus. At this level, DA-IR CSF-C neurons were only located in the PRO. In the posterior diencephalon, large populations of 5-HT-IR and DA-IR CSF-C perikarya were found in the paraventricular organ (PVO) and the nucleus infundibularis dorsalis (NID); the dorsal part of the NID additionally presented TH-IR CSF-C perikarya. Most regions of the diencephalon showed an intense monoaminergic innervation. In addition, numerous TH-IR, DA-IR and 5-HT-IR fibers, originating from the anterior and posterior hypothalamic nuclei, extended ventrally and reached the median eminence and the pars intermedia of the pituitary gland. In the midbrain, TH-IR perikarya were located dorsally in the pretectal area. Ventrally, a large group of TH-IR cell bodies and some weakly stained DA-IR and 5-HT-IR neurons were observed in the posterior tuberculum. No dopaminergic system equivalent to the substantia nigra was revealed. The possible significance of the differences in the distribution of TH-IR and DA-IR neurons is discussed, with special reference to the CSF-C neurons.

Animals↗
PubMed1988

Development of retinofugal neuropil areas in the brain of the alpine newt, Triturus alpestris. II. Topographic organization and formation of projections.

The development of retinal projections and the formation of their retinotopic organization were studied by means of anterograde transport of horseradish peroxidase in the newt, Triturus alpestris. All tracts found in the adult on the contralateral brain side are established during embryonic stages. At this stage a few uncrossed fibers are also detectable. Retinal fibers project first to the contralateral optic tectum. These are followed by contralateral projections to the thalamic recipient areas. Beginning at embryonic stages, the projections from the retinal quadrants into the optic tectum are topographically organized. The other terminal areas innervated by the marginal optic tract (MaOT) show a topographic order from midlarval stages. The terminal areas innervated by the medial optic tract (MeOT) show no clear topographic organization at any stage. The contralateral projection of the MeOT originates from the central area of the retina, whereas the uncrossed projection originates from the temporal peripheral retina. Ipsilateral (uncrossed) retinal projections develop during metamorphic climax. The MeOT is more distinct than the MaOT. The latter shows a clear retinotopic organization. The topography of the ipsilateral MaOT and its corresponding terminal areas are mirror-symmetric to the contralateral tract and terminal areas.

Animals↗
PubMed1979

Tissue-specific changes in nuclear RNA content during early development of Triturus vulgaris.

During early development of Triturus vulgaris, as a measure for nuclear activity in neuroectoderm, mesoderm and endoderm, nuclear RNA content was determined by cytochemical methods. In the first stages of gastrulation, that is to say during the early phase of neural induction, the RNA content of the inducing system is considerably higher than in the reacting system. Then, with a phase-shift of about 10 h, the RNA content of the neuroectoderm increases quickly also. In the following stages the nuclear RNA content of both regions is reduced. A second continuous increase in the RNA amount coincides with the formation of the neural tube. In the mesoderm, enhancement of RNA content correlates with cytodifferentiation of the chorda. In all stages the RNA content of the endoderm is higher than in the other tissues and it becomes successively diminished from the early gastrula to the tailbud stage.

Animals↗
PubMed1978

The toxicity of manganese ethylenebisdithiocarbamate to the adult newt, Triturus cristatus.

The toxicity of ethylenebisdithiocarbamate (maneb), a widely used agricultural fungicide, to the adult newt (Triturus cristatus carnifex) was evaluated after percutaneous exposure. Maneb was lethal to all the animals at the 50 ppm level within fifteen days. Male newts seem to be less resistant to the toxicant than females. At concentrations as low as 25 ppm all males died within 25 days, whereas some of the females were still alive after 5 months. Microscopic examination showed that the skin and the kidney were the most severely affected organs. It has been hypothesized that an osmoregulatory breakdown and an impairment of cutaneous respiratory exchanges play a role in the death of the animals. Renal failure must also be taken into account. However, additional mechanisms can not be ruled out at present.

Animals↗
PubMed1977

Changes in the thermal denaturation profiles of DNA from different developmental stages of the newt Triturus vulgaris.

The melting profiles of DNA samples from the early gastrula and early neurula of Triturus vulgaris are essentially the same, whereas DNA from mid to late gastrula possesses higher Tm values and shows a deviation from the regular sigmoidal shape at temperatures above Tm. The plot on normal probability paper indicates a second DNA fraction which melts at higher temperatures and, consequently, it has a higher GC-content than the bulk of DNA. These facts confirm our idea that differential DNA replication occurs during gastrulation.

Animals↗
PubMed1984

The effect of 5 alpha-dihydrotestosterone and 5 beta-dihydrotestosterone on erythropoiesis of the newt, Triturus cristatus carnifex (Laur.).

The erythropoietic effects of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 beta-dihydrotestosterone (5 beta-DHT) were compared in the newt, Triturus cristatus carnifex (Laur.). In normal animals, 5 beta-DHT was more active than 5 alpha-DHT in increasing the number of circulating erythrocytes. In animals rendered completely anemic, only 5 beta-DHT was effective. The biochemical parameters of delta-aminolevulinic acid synthase and delta-aminolevulinic acid dehydratase of new basophilic erythroblasts, and incorporation of labeled glycine into heme and globin of new polychromatic erythroblasts were enhanced by 5 beta-DHT. The results are discussed with reference to a direct erythropoietin-independent action of 5 beta-DHT on erythroid stem cells.

5-Aminolevulinate Synthetase↗
PubMed1992

Mammalian GnRH involvement in prostaglandin F2 alpha and sex steroid hormones testicular release in two amphibian species: the anuran water frog, Rana esculenta, and the urodele crested newt, Triturus carnifex.

The present work was carried out to study the in vitro effects of mammalian gonadotropin-releasing hormone (mGnRH) on Rana esculenta and Triturus carnifex testis production of prostaglandin F2 alpha (PGF2 alpha) and sex steroid hormones during the prereproduction, reproduction, and postreproduction periods. In R. esculenta, testicular PGF2 alpha release was lower during postreproduction, and mGnRH increased PGF2 alpha in prereproduction and reproduction. Androgens were higher during prereproduction, and mGnRH induced an androgens increase in prereproduction and reproduction. In T. carnifex testicular PGF2 alpha release was lower during reproduction, and mGnRH increased PGF2 alpha in prereproduction and reproduction. Androgens were higher in reproduction and lower in postreproduction, and mGnRH induced an androgens increase in reproduction. Estradiol-17 beta release was higher in postreproduction, and mGnRH induced an estradiol decrease in reproduction and an increase in postreproduction. These results seem to indicate the involvement of PGF2 alpha in the testicular reproductive activity, and a similar mGnRH mechanism of action, both in R. esculenta and in T. carnifex. In addition, taken together with previous studies, they seem to suggest that the relationship found between mGnRH and PGF2 alpha or sex steroids could be widespread in amphibians.

Androgens↗
PubMed1986

Two thalamo-telencephalic pathways in a urodele, Triturus alpestris.

Ascending thalamo-telencephalic projection systems have been investigated in an urodele, Triturus alpestris, using the horseradish peroxidase technique. Two separate dorsal thalamic projections onto the telencephalon have been identified; one arises from the posterior dorsal thalamus and terminates in the ipsilateral striatum, the other originates from anterior dorsal thalamic cells and reaches the medial pallium and a part of the dorsal pallium bilaterally. Both systems, which are spatially well segregated, might carry visual information to the telencephalon, as the posterior dorsal thalamus receives tectal, and the anterior dorsal thalamus direct retinal input. The urodele projection scheme as described here shows great similarities to the one described in anurans, although there are remarkable cytoarchitecture differences between the anuran and the urodele thalamus.

Animals↗
PubMed2006

The newt Triturus carnifex as a model for monitoring the ecotoxic impact of the fungicide thiophanate methyl: adverse effects on the adrenal gland.

The aims of this study were to propose a bioindicator organism, the newt Triturus carnifex, for the assessment of toxicological impact of thiophanate methyl in the Campania region (Italy) and the possible adverse activity on the adrenal gland. In the acute toxicity study, experimental groups of T. carnifex were exposed to 2.40, 4.80, 9.60 and 19.20 microg/L tap water of thiophanate methyl for 2 days; the LD50 was found to be 9.60 microg/L. To evaluate the effects on the adrenal gland, newts were exposed to a dose of 25% of the LD50 2 days for 8 days. The ultrastructural features of the tissues as well as the serum levels of aldosterone, corticosterone, norepinephrine (NE) and epinephrine (E) were evaluated. The number of secretory vesicles in the chromaffin cells appeared significantly decreased, whereas NE and E serum levels appeared strongly increased. Moreover, corticosterone and aldosterone serum levels appeared significantly reduced. The results suggest that: 1) T. carnifex has the features of an ideal bioindicator, due to its high sensitivity to thiophanate methyl, 2) thiophanate methyl acts as endocrine disruptor, affecting the adrenal gland at very low doses, 3) thiophanate methyl may be toxic for nontarget organisms, such as newts.

Adrenal Glands↗
PubMed2003

Nuclear markers, mitochondrial DNA and male secondary sexual traits variation in a newt hybrid zone (Triturus vulgaris x T. montandoni).

The smooth and the Montandon's newts (Triturus vulgaris and T. montandoni) are genetically similar sister species with highly divergent male secondary sexual traits involved in complex courtship behaviour. Their parapatric ranges overlap at moderate elevations in the Carpathian Mountains where they hybridize readily. Here we present a detailed study of genetic and morphological variation in populations from the area of sympatry. Analysis of variation at seven nuclear markers, mtDNA and male sexual secondary traits was complemented with an ecological survey of breeding sites characteristics. Extensive hybridization was revealed with back-cross individuals similar to either parental species predominating among hybrids. The hybrid zone exhibited a mosaic pattern: the genetic composition of the populations was correlated only weakly with their geographical position. No association with habitat type was found. Departures from Hardy-Weinberg proportions, significant linkage disequilibria and bimodal distribution of genotypes suggest strongly that assortative mating is an important factor shaping the genetic composition of hybrid populations. The pattern of cytonuclear disequilibria did not indicate much asymmetry in interspecific matings. Changes in the frequency of nuclear markers were highly concordant, whereas mtDNA showed much wider bidirectional introgression with 14% excess of T. montandoni haplotype. We argue that the mosaic structure of the newt hybrid zone results mainly from stochastic processes related to extinction and recolonization. Microgeographical differences in mtDNA introgression are explained by historical range shifts. Since morphologically intermediate males were underrepresented when compared to hybrid males identified by genetic markers, sexual selection acting against the morphological intermediates is implied. We discuss the implications of these findings in the context of reinforcement of prezygotic isolation in newts.

Animals↗
PubMed1969

Development of the neuromuscular junction. I. Cytological and cytochemical studies on the neuromuscular junction of differentiating muscle in the regenerating limb of the newt Triturus.

Development of the neuromuscular junction on differentiating muscle was investigated in the regenerating limb of the newt Triturus. Motor end-plate formation begins when vesicle-filled axon terminations approach differentiating muscle cells that have reached the stage of a multinucleate cell containing myofibrils. Slight ridges or elevations occur on the muscle surface, and there is an increase in density of the cytoplasm immediately beneath the plasma membrane of the elevation. The axon becomes more closely approximated to the muscle cell and comes to lie in a shallow depression or gutter on the surface of the muscle. The surface ridges increase in length and constrict at their bases to form junctional folds. In the axon terminal, focal accumulations of vesicles are found where the axon contour projects slightly opposite the secondary synaptic clefts. Cholinesterase activity in the developing junctions was demonstrated by the thiolacetic acid-lead nitrate method. Enzymatic activity is not found on intercellular nerve fibers or the muscle surface prior to close approximation of axon endings and muscle. Eserine- and DFP-sensitive activity appears concurrently with morphological differentiation. Activity occurs in membranous tubulovesicles in the sarcoplasm subjacent to the neuromuscular junction and in association with the sarcolemma. The largest reaction deposits occur at the tips of the emerging junctional folds. Smaller and less numerous localizations occur on the axon membrane and within the axoplasm. It is concluded from these studies that the nerve endings have an inductive effect on both the morphological and chemical specializations of the neuromuscular junction.

Animals↗
PubMed1966

Electrical characteristics of Triturus egg cells during cleavage.

The membrane potential in the blastomeres of dividing Triturus egg cells increases progressively from the first cleavage to the late morula stages. Both the animal and vegetal poles show the same increasing trend in potential; there is no significant potential difference between them. Upon first cell cleavage, the total resistance of the egg cell surface in contact with the exterior decreases to about one-tenth of its value before cleavage, and then remains rather constant up to the late morula stage. The specific resistance of this membrane surface drops rather abruptly upon first cleavage, and rises progressively during the morula stage. The resistance of the junctional membrane surface of the blastomeres, that is, the membrane formed at the former planes of cleavage, is small in relation to that of the cell surface in contact with the exterior. As a result, the blastomeres are electrically coupled throughout all stages of embryonic development examined.

Animals↗
PubMed2005

Consequences of metamorphosis for the locomotor performance and thermal physiology of the newt Triturus cristatus.

During metamorphosis, most amphibians undergo rapid shifts in their morphology that allow them to move from an aquatic to a more terrestrial existence. Two important challenges associated with this shift in habitat are the necessity to switch from an aquatic to terrestrial mode of locomotion and changes in the thermal environment. In this study, I investigated the consequences of metamorphosis to the burst swimming and running performance of the European newt Triturus cristatus to determine the nature and magnitude of any locomotor trade-offs that occur across life-history stages. In addition, I investigated whether there were any shifts in the thermal dependence of performance between life-history stages of T. cristatus to compensate for changes in their thermal environment during metamorphosis. A trade-off between swimming and running performance was detected across life-history stages, with metamorphosis resulting in a simultaneous decrease in swimming and increase in running performance. Although the terrestrial habitat of postmetamorphic stages of the newt T. cristatus experienced greater daily fluctuations in temperature than the aquatic habitat of the larval stage, no differences in thermal sensitivity of locomotor performance were detected between the larval aquatic and postmetamorphic stages. The absence of variation across life-history stages of T. cristatus may indicate that thermal sensitivity may be a conservative trait across ontogenetic stages in amphibians, but further studies are required to investigate this assertion.

Analysis of Variance↗