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PubMed1993

Spinal cord neuron classes in embryos of the smooth newt Triturus vulgaris: a horseradish peroxidase and immunocytochemical study.

Spinal cord neurons were investigated in embryos of Triturus vulgaris, the smooth newt, just prior to hatching. These embryos can swim if freed from their egg membranes. Horseradish peroxidase (HRP) labelling, together with GABA and glycine immunocytochemistry (ICC), revealed nine distinct anatomical classes of neuron. 1. Ventrolateral motoneurons with mainly dorsal dendrites, sometimes a descending central axon and peripheral axon innervating the trunk muscles. 2. Dorsal primary sensory Rohon-Beard neurons innervating skin and with dorsal ascending and descending axons in spinal cord. 3. Commissural interneurons with mid-cord unipolar soma, glycine-like immunoreactivity, dendrites on initial segment of ventral axon which crosses cord to ascend or branch. 4. Dorsolateral commissural interneurons with multipolar soma in dorsolateral position with dorsal dendrites and ventral axon which crosses and ascends or branches. 5. Giant dorsolateral commissural interneurons with large dorsolateral somata widely spaced (130-250 microns spacing) with process projecting dorsally to other side, dorsolateral dendrites and ventral axon which crosses to ascend and branch. 6. Dorsolateral ascending interneurons in dorsolateral position with multipolar soma and ascending axon on same side. 7. Ascending interneurons with unipolar soma, GABA-like immunoreactivity and ascending axon on same side. 8. Descending interneurons with bi- or multi-polar soma, extensive dorsal and ventral dendrites, and descending axon on same side. They may also have ascending axons. 9. Kolmer-Agduhr cerebrospinal fluid contacting neurons with cilia and microvilli in lateral corners of neural canal. GABA-like immunoreactivity, no dendrites and ascending axon. Eight of the nine cells classes were found to bear a marked resemblance to neurons previously described in zebrafish and Xenopus embryos in terms of their anatomy, distribution and immunoreactivity to GABA and glycine. Homologies and possible functions are discussed. Giant dorsolateral commissural neurons, were not found in Xenopus or teleosts but were present in Ambystoma mexicanum and Neoceratodus. The regular, possibly segmental longitudinal distribution pattern of these cells within the cord is unusual among amphibian spinal neurons.

Animals↗
PubMed1994

Immunohistochemical localization of GnRH in the crested newt (Triturus carnifex) brain and terminal nerve: a developmental study.

Localization of GnRH-immunoreactive neuronal system was studied by immunohistochemistry in the nasal-brain area of the crested newt, Triturus carnifex. Besides adults, developmental stages were those from hatchlings up to complete metamorphosis. Neurons containing immunoreactive GnRH were first detected in the nasal area of larvae with yet undifferentiated gonads. Subsequently, in prometamorphic stages, GnRH-immunoreactive cell bodies and fibers were detected in the proximal part of the terminal nerve as well as along the ventromedial surface of the olfactory bulbs. In older larvae with sexually differentiated gonads and up to the metamorphic climax GnRH-neurons were detected, as a rostral to caudal continuum, along the ventromedial surface of the olfactory bulbs and midtelencephalon. This is exactly the route followed by the terminal nerve. In the adult brain, besides the presence of occasional GnRH-neurons and fibers in the terminal nerve proximal to olfactory bulbs, olfactory bulbs and the mid-basal telencephalon, another aggregate of immunoreactive neurons was present in the anterior preoptic area, and a greater number of fibers in the habenular area as well as in the infundibular floor, median eminence and pars nervosa. These data suggest the nasal area to forebrain migration (along the course of the terminal nerve) of GnRH-neurons during development in the crested newt.

Animals↗
PubMed2006

Genetic structure in northeastern populations of the Alpine newt (Triturus alpestris): evidence for post-Pleistocene differentiation.

Genetic variation in 13 populations of the Alpine newt, Triturus alpestris, was assessed at the northeastern margin of its range (southern Poland). Variation at six microsatellite loci was scored in 354 newts, and two mitochondrial DNA fragments (c. 2000 bp) were sequenced in a subset of 27 individuals. Significant differences in allele frequencies and the presence of private alleles determined genetic units corresponding to three separate mountain ranges, i.e. the Carpathian, Sudetes and Holy Cross Mountains. F(ST)'s were three times greater in among than in within mountain range pairwise comparisons. An assignment test and pairwise F(ST)'s suggested relatively high levels of gene flow at the local level, although the Sudetes populations revealed some subtle structuring. Genetic variation was lower in the Carpathians and Holy Cross Mountains. The geographic pattern of mitochondrial DNA variation indicated that these newt populations originated from a single glacial refugium/founder population, and that the colonization of southern Poland took place in an easterly direction. The data show that substantial neutral variation and between group divergence has accumulated relatively quickly in these low-vagility organisms. The Alpine newt case exemplifies species history as a factor determining patterns of genetic diversity in marginal populations.

Alleles↗
PubMed1976

The surface charge of mesodermal and neural cells of Triturus embryos.

The electrical surface charge of disaggregated mesodermal and neural cells of the neurula stage of Triturus vulgaris embryos is estimated by using the apparatus described in Figure 1. The results showed a significant difference between the net charges of these two cell types: the neural cells had a clearly negative charge, whereas the mesodermal cells seemed to be more or less neutral. The difference of the surface charges may partly explain the "sorting-out" phenomenon in the mixed reaggregates of the disaggregated cells.

Animals↗
PubMed1978

The ectomesenchymal-endodermal interaction system of Triturus alpestris in tissue culture: morphological and histochemical characterization of developing neural derivatives.

In the ectomesenchymal-endodermal interaction system (EEIS), a hanging drop culture in which an explant of neural fold from behind the prospective ear region of a Triturus alpestris neurula together with a piece of ventrolateral pharynx endoderm is cultivated, the differentiation of a variety of neural crest-derived cells (nerve cells, pigment cells, cartilage cells, perichondrial cells, Schwann cells) can be followed. While cartilage cells develop only in contact to pharynx endoderm, the differentiation of neural crest-derived neuroblasts, rhombencephalic brain derivatives and epidermis which segregate from the explant of neural fold, does not depend on the presence of pharynx endoderm. The development of neural derivatives was studied with respect to morphology and histochemistry. Outgrowing axons may be observed 2-3 days after the beginning of cultivation. The fibres increase in thickness and length during further development and frequently make contact with other cells. Cytophotometric measurements of Feulgen-stained neural crest cells in the EEIS revealed that 72% of cells had a 2c and 9% a 4c DNA content while 18% were in S phase. Nerve cells had a 2c DNA content and prospective chondroblasts were in S phase. About 60-70% of S phase and 4c cells were observed at the margin of the culture. Neural crest-derived neuroblasts and melanoblasts obviously reacted catecholamine-positive upon formaldehyde-induced fluorescence (FIF), while axons from the brain derivative were catecholamine-negative but acetylcholinesterase (AChE)-positive. Neural crest cells prior to visible differentiation and neural crest-derived neuroblasts were AChE-negative. Catecholamine-positive (= fluorescing) cells can be recognized as either neuro- or melanoblasts prior to displaying phenotypic features. In cultures incubated with 3H-Dopa, freeze-dried, treated with the FIF-procedure, and subjected to autoradiography, only melanoblasts specifically accumulated the label.

Animals↗
PubMed1981

Functional properties of hemoglobins from Triturus cristatus.

The functional properties of hemoglobins from Triturus cristatus carnifex have been characterized both from an equilibrium and a kinetic point of view. A special attention has been given to the effect of organic phosphates in view of their role in the modulation of the hemoglobin function. Under stripped conditions newt hemoglobins display a negative Bohr effect which becomes much less pronounced in the presence of 0.2 M inorganic phosphates. The effect of organic phosphates involves not only a drop in the O2 affinity but also a large change in the shape of the O2 Bohr effect which becomes markedly positive in the presence of myo-inositol hexakis(phosphate). The experimental data reported make it possible to give a complete picture of the functional behaviour of newt hemoglobins, making a contribution to clarifying the dependence of the sign of the Bohr effect on the acclimatization temperature of the animals that has been previously reported [Morpurgo, G., Battaglia, P. A. and Leggio, T. (1970) Nature (Lond.) 225, 76--77].

Adenosine Triphosphate↗
PubMed1989

Kinetics of phototransduction in retinal rods of the newt Triturus cristatus.

1. The kinetics of photoresponses to flashes and steps of light of rods, from the retina of the newt Triturus cristatus, were analysed by recording the membrane current with a suction electrode. 2. In dark-adapted conditions the relation between the normalized amplitude of the photoresponse at a fixed time 1 s after the onset of light and the light intensity could be fitted by an exponential or a polynomial relation. In the presence of a steady bright light the same relation could be fitted by a Michaelis-Menten relation. 3. The kinetics of photoresponses to light stimuli was reconstructed using a model in which: (i) three molecules of guanosine 3'.5'-cyclic monophosphate (cyclic GMP) open a light-sensitive channel; (ii) light activates the enzyme phosphodiesterase, which hydrolyses cyclic GMP, thus closing light-sensitive channels: (iii) Ca2+ ions permeate through light-sensitive channels: and (iv) intracellular Ca2+ inhibits, in a co-operative way, the enzyme cyclase, which synthesizes cyclic GMP. 4. The model reproduces the shortening of the time to peak of brief flash photoresponses from about 1080 ms to about 690 ms with brighter lights. The model also explains the shortening of the time to peak to 350 ms observed in the presence of a steady light and the lack of a further acceleration with brighter flashes of lights. 5. The presence in the model of an intracellular calcium buffer accounts for the partial reactivation of the photocurrent following a step of light, lasting several seconds. The time course of this reactivation is not accelerated by a steady bright light both experimentally and in the model. 6. After the extinction to a long step of light the photocurrent showed a rapid partial reactivation, which was followed by a slow component of the photoresponse which extinguished with a rate constant of about 0.05 s-1. The model explains the origin of this slow component by assuming that the inactivation of excited rhodopsin is partially reversible. 7. The model is also able to explain the particular changes of kinetics when different amounts of exogenous calcium buffers are incorporated into rods (Torre, Matthews & Lamb, 1986).

Animals↗
PubMed1983

Intracellular Cl- activity of the proximal tubule of Triturus kidney: dependence on extracellular ionic composition and transmembrane potential.

Intracellular Cl- activity (aiCl) was measured with double-barreled Cl- -selective microelectrodes in Triturus proximal tubule and the effects of ionic composition of the perfusion solutions and the cell membrane potentials were studied. In the absence of HCO-/3, aiCl averaged 22.4 +/- 0.4 mM, the value being 3.8 times that expected from the Nernst equation. Increases in peritubular HCO -/3 concentration without changing pH resulted in drastic decreases in aiCl. Addition of HCO-/3 to only the luminal fluid had no effect. Elimination of Na+ from the luminal fluid caused no immediate changes in aiCl, but long-lasting perfusions with a Na+-free solution resulted in a gradual decrease in aiCl. Lowering or raising intraluminal pH rapidly increased or decreased aiCl, respectively. Alanine-induced depolarization of the cell membranes exceeding 15-20 mV rapidly increased aiCl, and the increase was proportional to the driving force for Cl-. The results suggest the presence of a Cl-/OH- antiport mechanism in the luminal membrane and a Cl-/HCO-/3 exchange mechanism and voltage-dependent rectifying Cl- pathways in the peritubular membrane.

Alanine↗
PubMed1990

Striatal afferents in the newt Triturus cristatus.

In order to investigate the neuronal populations projecting to the corpus striatum in the brain of a urodele, Triturus cristatus, horseradish peroxidase (HRP) retrograde labeling was used in parallel with anterograde degeneration, glyoxylic acid histofluorescence and behavioral testing. Striatal injections of HRP revealed that the main striatal afferent systems originate within the diencephalon, specifically in the dorsal thalamus and paraventricular organ of the hypothalamus. Several small groups of neurons in other diencephalic areas also participate in striatal innervation: proeminentia ventralis, amygdala, contralateral corpus striatum, preoptic area, posterior tuberal nucleus, locus coeruleus and raphe nuclei. Degeneration experiments after mechanical lesion of the paraventricular organ established the existence of a hypothalamostriatal projection. Degenerating axonal profiles were also found in many of the structures already identified as projecting to the striatum, suggesting that the paraventricular organ might influence the striatum not only directly but also indirectly through these other afferent systems. In the paraventricular organ, glyoxylic acid fluorescence histochemistry showed numerous monoamine neurons that corresponded in distribution and morphology to the retrogradely HRP-labeled neurons. Paraventricular-organ-lesioned males displayed a severe impairment of courtship behavior in the form of decreased tail beating and head stepping by the females. This suggests that the regulation of stereotyped hypermotricity might involve the monoamine component of the hypothalamo-striatal projection.

Afferent Pathways↗
PubMed1992

Heterochromatin characterization of sex chromosomes in Triturus marmoratus (Urodela, Salamandridae).

The sex chromosomes of the Iberian marbled newt, Triturus marmoratus, were studied using various banding techniques, including restriction enzyme/nick translation (RE/NT) procedures. Four types of heterochromatin on the sex chromosomes could be distinguished: (1) distamycin A/DAPI and chromomycin A3/distamycin A positive, EcoRI/NT negative, and HaeIII/NT and HinfI/NT positive; (2) distamycin A/DAPI and chromomycin A3/distamycin A positive, but RE/NT negative; (3) AT rich, but RE/NT negative; and (4) distamycin A/DAPI and chromomycin A3/distamycin A positive, EcoRI/NT and HinfI/NT negative, but HaeIII/NT positive. These data suggest a common origin for the terminal heterochromatic domains of both the X and Y chromosomes in this species.

Animals↗
PubMedDate not supplied

Electrophysiological study of L-lysine transport across Triturus proximal tubule: evidence for Na(+)-independent entry and Na(+)-dependent exit.

Cell membrane depolarization induced by intraluminal injection of lysine was entirely independent of the presence of Na+ in Triturus proximal tubule, confirming our previous observation. The amplitude of the depolarization conformed to Michaelis-Menten kinetics regardless of the presence or absence of Na+ in the perfusion solutions. pH of the intraluminal solution had no effect on the electrical response in its range from 5.5 to 8.5. In a Na(+)-free medium, particularly in a Tris-substituted medium, the depolarization induced by a constant concentration of lysine gradually decreased in its size when injection followed by washout of lysine was repetitively tested. The addition of Na+ to the peritubular side after extinction of the responsiveness resulted in a significant restoration of the voltage response to intraluminal lysine. In addition, influx of Na+ from the peritubular fluid into the cells was significantly greater in lysine-loaded tubules than in nonloaded tubules as indicated by a greater rate of increase in intracellular Na+ activity in the presence of ouabain. The data strongly suggest that lysine enters the cells via an electrogenic uniport mechanism and leaves the cells via Na+:amino acid exchange transport mechanism.

Animals↗
PubMed1991

A spontaneous melanoma-like tumor in the adult newt Triturus cristatus.

We present here a case of a spontaneous melanoma-like tumor in the adult newt Triturus cristatus, lying above the scapula. The melanized cellular mass had infiltrated the subcutaneous connective tissue. The presence of this tumor is discussed with respect to the incidence of tumors in amphibia in relation to the animals' regenerative capacity.

Animals↗
PubMed1994

Allografting of a nontransmissible, spontaneous dermal melanoma in the newt Triturus cristatus.

Regeneration-competent urodele Amphibia are highly resistant to spontaneous development of neoplasms, in comparison with other vertebrates which do not exhibit great regenerative power. This observation implies that at least one growth parameter of urodele cells might be subject to different developmental mechanisms than the cells of animals incapable of epimorphic regeneration. Therefore, keeping records concerning the incidence of tumors in urodeles and investigating those exceptional cases might prove invaluable in understanding the basic biological principles governing organ regeneration and carcinogenesis, and might therefore help in cancer therapy. The present report depicts a case of two spontaneous, dermal, melanoma-like tumors found in an adult newt Triturus cristatus. Both tumors were located in the pelvic region. Histological examinations and tumor transplantations were conducted. It was found that the tumors were melanomata. When allografted within the body cavity, their mass was progressively eliminated.

Animals↗
PubMed1981

Analysis of the changes in the morphology and staining density characteristics of cartilagenous cell nuclei from Triturus cristatus during aging and regeneration.

The modifications in the morphology and staining intensity of cell nuclei reflect their physiologic and functional state. In order to appreciate the variations in the metabolic activity of hind limb chondrocytes from Triturus cristatus during aging and regeneration, we have studied the nuclear size and shape, the DNA concentration, and the distribution and degree of condensation of the chromatin. This study was carried out using scanning cytophotometry on semithin 1 micrometer sections, Feulgen-stained for DNA, which is the major nuclear component. During aging, the nuclei decrease in size, becoming irregular in shape. The concentration of DNA increases and the chromatin distribution becomes more heterogeneous with an increase in condensed chromatin and a subsequent decrease in the diffuse chromatin fraction. During regeneration, however, these modifications are reversed whatever the age of the animal, but even more noticeably when the animal is old. The changes that occur in the chromatin fractions defined according to their state of condensation are discussed from a functional point of view.

Aging↗
PubMed1979

An experimental analysis of bivalent interlocking in spermatocytes of the new Triturus vulgaris.

Interlocked bivalents at 1st meiotic metaphase are relatively uncommon in spermatocytes of the newt Triturus vulgaris, but their frequency of occurrence can be significantly increased by subjecting newts to a 24-h heat shock. Newt spermatocytes are sensitive to a heart shock at any stage between the end of premeiotic S and mid to late pachytene. The heat shock does not cause evidence desynapsis, nor does it significantly affect chiasma frequency; therefore the interlocked condition induced in spermatocytes which were subjected to a heat shock when they were in zygotene or pachytene is unlikely to be a consequence of synaptic trapping. By way of explanation it is suggested that a heat shock may cause telomers to detach from the nuclear membrane, or from the synaptonemal complex where the latter is attached to the membrane, thus allowing non-homologous chromonemata to become interwined before chiasmata have formed. If this explanation is valid, it is then further suggested that the recombination process which results in chiasma formation probably takes place in chromosomal regions lying outside the synaptonemal complex, rather than inside, between its 2 lateral elements.

Animals↗
PubMed2006

Triturus newts defy the running-swimming dilemma.

Conflicts between structural requirements for carrying out different ecologically relevant functions may result in a compromise phenotype that maximizes neither function. Identifying and evaluating functional trade-offs may therefore aid in understanding the evolution of organismal performance. We examined the possibility of an evolutionary trade-off between aquatic and terrestrial locomotion in females of European species of the newt genus Triturus. Biomechanical models suggest a conflict between the requirements for aquatic and terrestrial locomotion. For instance, having an elongate, slender body, a large tail, and reduced limbs should benefit undulatory swimming, but at the cost of reduced running capacity. To test the prediction of an evolutionary trade-off between swimming and running capacity, we investigated relationships between size-corrected morphology and maximum locomotor performance in females of ten species of newts. Phylogenetic comparative analyses revealed that an evolutionary trend of body elongation (increasing axilla-groin distance) is associated with a reduction in head width and forelimb length. Body elongation resulted in reduced maximum running speed, but, surprisingly, also led to a reduction in swimming speed. The evolution of longer tails was associated with an increase in maximal swimming speed. We found no evidence for an evolutionary trade-off between aquatic and terrestrial locomotor performance, probably because of the unexpected negative effect of body elongation on swimming speed. We conclude that the idea of a design conflict between aquatic and terrestrial locomotion, mediated through antagonistic effects of body elongation, does not apply to our model system.

Animals↗
PubMed1983

Lumen-positive chloride transport potential in the early distal tubule of Triturus kidney: its absolute dependence on the presence of Na+ and K+ in the luminal fluid.

Microperfusion experiments with Na+-free and/or K+-free solutions revealed that the generation of Cl- -dependent lumen-positive transtubular potentials of the early distal tubule of Triturus kidney was absolutely dependent on the presence of both Na+ and K+ in the lumen. Increases in luminal Na+ or K+ concentration increased the luminal positivity in a saturable manner, and the half saturation concentration was found to be about 1 mM for both cations. The results strongly suggest that Cl- is cotransported with Na+ and K+ across the luminal membrane.

Animals↗
PubMed1985

Effects of Ba2+ on secretory K+ movement and electrical properties of the early distal tubule of Triturus kidney.

The mechanism of secretory supply of K+ into the diluting segment of nephron was studied in Triturus kidneys by observing Ba2+ effects on electrical phenomena related to K+ movements and other electrical properties of the segment. Ba2+ (1-2 mM) applied into the luminal fluid completely blocked K+ movement into the lumen during the stop-flow of the intraluminal K+-free solution. Also, Ba2+ inhibited transepithelial K+ diffusion potential induced by alterations in the intraluminal K+ concentration and increased transtubular resistance (Rt). A rapidly decaying time course of the K+ diffusion potential and its high peak amplitude (near the maximum expected from an imposed concentration difference) suggest that the diffusion potential was generated across the paracellular pathways. Step-changes in the Na+ concentration induced similar but smaller diffusion potentials, which were also inhibited by Ba2+. Replacement of Cl- with So2-(4) converted the time courses of both K+ and Na+ diffusion potentials to a sustained type. These suggest that the pathway has a specially high permeability to K+ and lower permeabilities to Na+ and Cl-. Triaminopyrimidine and kinetin similarly blocked K+ movement during stop-flow of a K+-free solution. The low Rt, a unique property of the segment, could be ascribed to the leakiness of the paracellular pathway from the comparison of input resistances of cells and cell surface areas between this segment and the proximal tubule. Based on these findings and other reported data, a novel mechanism of K+ supply was proposed which assumed the presence of a local pool of a high K+ concentration in the paracellular pathway and secretory movement of K+ through intercellular junctional complexes.

Animals↗