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PubMed1979

Scanning and transmission electron microscopy of intraventricular dendrite terminals of hypothalamic cerebrospinal fluid contacting neurons in Triturus vulgaris.

A scanning (SEM) and transmission electron microscopic (TEM) study of the ventricular wall of the hypothalamus of Triturus vulgaris was performed with special regard to the intraventricular dendrite terminals of the cerebrospinal fluid (CSF) contacting neurons of the preoptic area (magnocellular and parvocellular preoptic nuclei), the infundibular lobe (anterior periventricular nucleus, infundibular nucleus), and the paraventricular organ. In the preoptic area and infundibular lobe, the terminals were knob-like or club-shaped, of various sizes (diameter about 0,5 to 3,0 micrometer) and located immediately above the ependyma. Ultrastructurally, they may contain dense-core vesicles of varying sizes. The CSF contacting dendrite endings of the paraventricular organ built up a supraependymal labyrinthic layer which could be divided into a rostral crest-like part and a caudal flat and broad division. In both parts, three main types of terminals of various size and shape could be distinguished: a) ramifying, b) elongated, and c) bulb-like dendrite endings which also differed by their TEM structure. The bulk-like terminals, first of all the small ones, originated from the distal part of the nucleus of the organ (nucleus organi paraventricularis) while the other two types took their origin from its intra- and subependymal part. In all areas investigated, each intraventricular dendrite ending gave rise to a solitary cilium (type 9 X 2 + 0). It differed from the ependymal kinocilia by both SEM and TEM characteristics. In the paraventricular organ, the neuronal cilia were hidden inside, or below the supraependymal layer of terminals. There were intraventricular axons which formed synapses on CSF contacting dendrite endings of both parts of the paraventricular organ. Free intraventricular neurons, further ependymal areas heavily or scarcely ciliated, were described. The CSF contacting dendrite terminals were predominantly present near ventricular recesses and in regions where the ependyma was scarcely ciliated.

Animals↗
PubMed1983

The form and structure of supernumerary hindlimbs formed following skin grafting and nerve deviation in the newt Triturus cristatus.

The results of a series of skin grafting experiments performed on the hindlimb of the newt Triturus cristatus are described. In an attempt to limit the position of origin and the complexity of supernumerary limb outgrowths four experimental features were varied. These were 1) size of skin grafts; 2) their position of origin; 3) the position to which they were grafted; and 4) the presence or absence of nerves of two different sizes at the graft site. The degree of distal outgrowth and the pattern of the supernumerary structures in the anterior to posterior and dorsal to ventral axes were assessed. The results are discussed in terms of the control of pattern regulation in localized populations of limb blastema cells.

Animals↗
PubMed1978

Digit regeneration in the amphibian--Triturus cristatus.

Digit regeneration has been examined in Triturus cristatus. Because of their size, blastemas that form after digit amputation are relatively a lot more suitable for quantitative studies that involve for example the counting of cells in histological sections. They are also very useful for the study of some basic histological aspects of regeneration particularly cartilage formation. This has been looked at in regenerating digits, as there are only a maximum of three bones to regenerate and these lie in sequence, one after the other. It was seen that the cartilage is laid down as a solid rod by about 17 days post-amputation, and that by about 20 days, it starts to be split up into its three elements. An X-ray study of the growth of digit regeneration together with autoradiography experiments were also carried out as a comparison to studies already undertaken on larger more proximal blastemas. It was shown that in fact the behaviour of digit blastemas is very similar to those of a more proximal origin. This fact, together with the advantages of its size, make the digit a very strong candidate for the further study of regeneration.

Animals↗
PubMed1978

[Transfer of behavior patterns through transplantation of systems of neuroanatomic structures in amphibian larvae. II. Xenoplastic transplantation of hind brain systems between Xenopus laevis (Daud.) as well as Hymenochirus boettgeri (Torn.) and Triturus vulgaris].

By replacing parts of the neural plate (prospective medulla oblongata) of Triturus vulgaris by neural ectoderm of Xenopus laevis larval chimaeras were obtained, which showed donorlike rhythmical movements of distinct parts of the visceral musculature according to the place of implantation. Especially the branchial region with its external gills showed rhythmical movements and is the special object of this investigation.

Amphibians↗
PubMed1983

The structure of supernumerary limbs formed after 180 degrees blastemal rotation in the newt Triturus cristatus.

The structure of supernumerary limbs formed following 180 degrees ipsilateral blastema rotations in the arm of the newt Triturus cristatus is analysed. Both the skeletal pattern and the muscle patterns are examined. As is the case after comparable experiments in the axolotl (see, for example, Maden & Mustafa, 12982) the extra limbs which form show a range of anatomies. Limbs symmetrical about the dorsal-ventral and anterior-posterior axis are reported as well as some limbs which were part symmetrical and part asymmetrical. It is clear that newts and axolotls appear to react in similar ways to this particular experimental procedure.

Animals↗
PubMed1982

Chromosome variation in two populations of the crested newt, Triturus cristatus carnifex, with different melanoma incidence.

Morphometric analysis of the chromosomes of the crested newt, Triturus cristatus carnifex, was carried out for two populations, one from Rosate (Milan) and one from Bagnaia (Perugia), which differed in the prevalence of melanoma (2.9 and 0.8%, respectively). Chromosomes were arranged in pairs both by the cytologist and by a previously developed computer programme. The two populations had significant differences in the relative lengths of chromosomes 9 and 10, and in the arm ratio values of 6 and 11. Though the morphometric parameters of the other elements of the complement appeared to be similar, the Rosate population showed significantly higher chromosomal asymmetry. In the Rosate population, there was greater intra-population and intra-individual variability than in the Bagnaia population. The karyotype variations observed suggest that chromosomal rearrangement may have occurred.

Analysis of Variance↗
PubMed1978

Surface topography of isolated gastrula ectoderm of Triturus vulgaris.

The surface topography of the outer cell layer of the two-layered gastrula ectoderm of Triturus vulgaris resembles that of the other amphibians: the cells are tightly packed and devoid of pseudopodia. The cells of the inner layer are spherical and interconnected with pseudopodia of various lengths. After excision of the ectoderm the peripheral cells of the outer layer elongate perpendicularly to the edge of the explant, while the number of pseudopodia on the inner layer greatly increases. The results show that the curling-up of the explant and formation of a sphere results from locomotor activity of the cells in both layers.

Animals↗
PubMed1980

Ultrastructural and morphometric changes in the lung of newt, Triturus cristatus carnifex Laur. during ontogeny.

Ultrastructural and morphometric studies of the lungs in the newt, Triturus cristatus carnifex Laur, were performed at three stages of its life cycle: during metamorphosis; 2 to 3 weeks after metamorphosis; and in adult individuals. The lungs have the form of simple sacs, devoid of septa and lined with one type of respiratory epithelial cells. Ciliated and goblet cells are localized exclusively along the pulmonary vein. During the period from metamorphosis to sexual maturity (2 to 3 years) the number of respiratory epithelial cells increases, the cells change their shape and become embedded into connective tissue. In their cytoplasm appear lamellar and multivesicular bodies, and the amount of other organelles increases. The ciliated epithelium transforms from simple to pseudostratified type. The capillaries, initially flat and wide, gradually protrude into the lung lumen and the air-blood barrier increases in thickness, as does also the whole lung wall.

Animals↗
PubMed1980

Qualitative changes in DNA indicating differential DNA replication during early embryogenesis of the newt Triturus vulgaris.

During gastrulation of the newt Triturus vulgaris considerable changes in the melting behaviour and in the CsCl density gradient pattern of DNA occur. The melting curves of DNAs from mid to late gastrulae (stages 11b-12c) deviate from the regular shape. Whereas the Tm values are identical in the stages 11a (early gastrula) and 15 (early neurula), and correspond to the standard DNA (stage 36 = tailbud), a significant rise of Tm (0.8-1.2 degrees C) has been recorded in the stages 12a/b (yolk plug). The differences in melting behaviour become visible by the deviation of the curves above Tm. These deviations from the normal sigmoidal shape are caused by the fact that a portion of DNA melts at higher temperatures than usual. Therefore the thermal denaturation of DNA is completed at approximately 3-4 degrees C later than in standard DNA. Both the derivative curves and the plots on normal probability paper demonstrate a heterogeneity of DNA in the stages 11b-12c which indicates the presence of an additional GC-rich satellite fraction. These findings are confirmed by CsCl density gradient studies. Thus, in the stages 12a/b a slight shoulder on the heavy side of the gradients occurs, being absent in the other stages. From these facts we have to conclude that there is a stage-dependent multiplication and elimination of GC-rich sequences.

Animals↗
PubMed1995

Partially purified factor from embryonic chick brain can provoke neuralization of Rana temporaria and Triturus alpestris but not Xenopus laevis early gastrula ectoderm.

A high neuralizing activity has been determined in forebrain of 7.5-day old chick embryos using Rana temporaria early gastrula ectoderm as reacting tissue (Mikhailov and Gorgolyuk, Soviet Scientific Reviews, Section of Physiology and General Biology, Vol. 1: 267-306, 1987). The corresponding protease-sensitive agent was extracted, partially purified by chromatography on DEAE-Toyopearl and Heparin-Ultragel columns, and its neuralizing activity was tested in vitro on ectoderm isolated from early gastrulae of R. temporaria, Triturus alpestris, and Xenopus laevis at different concentrations and for different periods of time (animal cap assay). Induction of neural structures was found in R. temporaria and T. alpestris explants (up to 100 and 60%, respectively), but not in cultures of X. laevis ectoderm. Under our experimental conditions, so-called "autoneuralization" of the ectoderm explants can safely be excluded. The results are discussed in relation to the neural competence of amphibian ectoderm and the mechanisms of neuralizing actions of different factors which might be involved in neural induction and patterning.

Animals↗
PubMed1995

[The symmetrical relation of intestines, the habenular nuclei and the intestinal venous system in dorsal-doral and ventral-ventral grown parabiontic larva of mountain salamanders (Triturus alpestris)].

Embryos of the newt Triturus alpestris were fused in their dorsal regions (DD-parabionts) of their ventral regions (VV-parabionts), while the longitudinal axes were in equal direction. In these parabionts situs and symmetry of the gut, the heart, the habenular nuclei and the vitelline vein were studied. The fusion of the embryos of the DD-parabionts was performed in three developmental stages (after Harrison): phase of neurulation (14-18, N-parabionts), late phase of neurulation (19-22, E-parabionts) and tail bud stage (23-27, S-parabionts). VV-parabionts were only fused in phase of neurulation (14-18). The external development of the parabionts in most cases was normally. DD-parabionts showed a more or less pronounced deformation of their longitudinal axes. In DD-parabionts all organs developed separately in nearly all cases. In VV-parabionts a partial fusion of the heart was sometimes observed, while fusion of large part of gut occurred regularly. In DD-parabionts complete and incomplete inversions of all organs and the vitelline vein are extremely abundant in the N-parabionts, much lower in E-parabionts and nearly absent in S-parabionts. The differences are statistically of high significance. The "pair situs" symmetries of N-parabionts (DD-parabionts) show always a strong dominance of a transindividual organ- and vitellin vein-symmetry. In VV-parabionts (N-parabionts) the tendency for inversion of the asymmetric organs is statistically significant lower as in DD-parabionts. In regard to this observation there is a preference for an asymmetric "pair situs" in the heart, habenular nuclei and vitelline vein system. In "polarisied" DD-parabionts ("left" as well as "right" parabionts) the asymmetric organs as well as the vitelline vein system inversions were more often observed in the "left" parabiont compared with the "right" parabiont in N- and E-parabionts. These right-left differences partial are statistically significant (P < 0.05). The organ situs-correlation as well as the situs-correlation between vitelline vein and gut or heart, respectively, are mostly positive (concordant). The frequency of dominance of "left" organ inversions argues against a morphogenetic "left dominance" of the amphibian embryo. The determination of organ-asymmetries is irreversible only after the end of neurulation in tail-bud-stage. The results suggest the efficiency of a "symmetry-factor", which determines the organ symmetry during neurulaphase. The differences between DD- and VV-parabionts are statistically significant and point to a dorso-ventral polarity of the embryo, with a maximal morphogenetic potency in the dorsal region.

Animals↗
PubMed1993

Persistence of a high degree of structural organization of the telencephalon in brain homotransplants in adult Triturus carnifex (Urodele Amphibians).

Brains of adult Urodele Amphibians (Triturus carnifex Laur.) were homoplastically transplanted in conditions of complete morpho-functional isolation and fixed 100 and 365 days after the operation. Results show that in the post-telencephalic regions structural organization disappear in all cases, while, in some cases the telencephalon retain a fairly complex structural organization even after one year. The heterogeneous nature of the histological patterns observed may be attributed to the different size of the matrix areas, besides the different degree of immune response of the host to the graft. In the telencephalic district, where the matrix areas are particularly well developed, undifferentiated elements of these areas would be capable of opposing the degenerative phenomena in the transplants by neoformation of neurons. However, in post-telencephalic districts, where the matrix areas are less developed or absent, it would not be possible to make up for neuronal degeneration and these regions disappear or are formed only by some undifferentiated elements outside the surviving ependyma portions.

Animals↗
PubMed1977

[Determination of the relative iodine concentration in the lumens of thyroid follicles of normal and neotenic Triturus helveticus, and evaluation of the halogen content of the thyroid colloid. Electron microprobe study (author's transl)].

The stable, bound iodine in the thyroid colloid of Triturus helveticus has been studied with the electron microprobe. Some animals show a normal development. Others are accidentally neotenic due to certain ecological conditions. The values of punctate iodine concentrations (CPI) have been computed and expressed in relative units (counts/s). The mean CPI per lumen is very variable from one follicle to another in the same thyroid section. During normal development, the mean CPI per animal is generally higher in metamorphosing individuals than in larvae. During development with neoteny, the mean CPI per animal attains high values if the larval state is maintained in its totality; the CPI decreases in partially metamorphosed animals, but increases again after metamorphosis. The amount of halogen contained in the thyroid colloid has been computed in relative units (colloid iodine pool). Throughout normal development, the pool remains small if the animals have not attained the adult state. In increases considerably in entirely larval neotenic newts, decreases during metamorphosis but increases afterwards. In totally neotenic newts, the thyroid gland receives only a low hypophyseal stimulation and reacts as the thyroid gland of various hypophysectomized Urodeles. Our results pose the problem as to whether TSH regulates the transepithelial iodine flows, which permit the expansion of the colloid iodine pool, when this hormone is secreted at a very low levels.

Animals↗
PubMed1976

Cytological and microspectrophotometric analysis of mesodermalized explants of Triturus gastrula ectoderm.

Using isolated presumptive ectoderm of the newt (Triturus pyrrhogaster) embryos as a reactor and extract of rat bone marrow as a mesodermal inductor, changes of cell number and mitotic index of the reactor cells were studied. In early stages of cultivation the increase in cell number in the mesodermalized ectodermal piece was slower than in the non-mesodermalized epidermal piece; but after 24 h it showed abrupt increase and reached a cell population equal to that of the control at 48 h of cultivation. In the experimental series, the mitotic index was 0 at 4 h after the application of the inducing stimulus, but increased precipitously in the next 8 h and reached a level of 4-4% at 12 h and thereafter decreased gradually. The cell cycle stopped at the S phase and stayed in it for several hours after the application of inductor. A sudden fall in cell number, observed in the mesodermalized epidermal piece between the 4th and the 8th h after the application of inducing stimulus, seems to be attributable to cell death which was brought about by the inducing stimulus. In the histogenetic process phases of repression on mitosis by an inducing stimulus, cell proliferation and nonproliferation seem to succeed each other.

Animals↗
PubMed2000

Paedogenesis in european newts (Triturus: salamandridae): cranial morphology during ontogeny.

A cross-sectional analysis using different ontogenetic stages (larvae, juveniles, paedotypic, and metamorphic adults) of the smooth newt, Triturus vulgaris, and the alpine newt, T.alpestris, revealed a broad spectrum of perennibranchiation influences on cranial ontogeny in European newts, more pronounced than previously thought. These influences included marked variation in ossification levels, pronounced morphometric variability of many cranial elements, and considerable skull shape changes in the transition from larvae to the adult stage. In comparison with metamorphosed individuals, paedotypic newts had a higher level of variability in both individual cranial traits and cranial shape changes. Sexual size difference of the skull traits was mostly negligible, especially in comparison to the influence of paedogenesis. The main changes in cranial shape of the European newts occurred during metamorphosis. Cranial morphological organization in the majority of examined paedotypes corresponds to cranial organization at late larval stages prior to metamorphosis or at the onset of metamorphosis.

Animals↗
PubMed1975

The ultrastructure of Wallerian degeneration in the severed optic nerve of the newt (Triturus viridescens).

Wallerian degeneration in the severed newt's (Triturus viridescens) optic nerve is complete between the 10-14th post operative day (p.o.d.). Consequently, the newt optic nerve displays one of the most rapid degenerative responses yet reported for the central nervous system of vertebrates. In most cases it also exhibits the speed of degenerative phenomenon in the vertebrate peripheral nervous system. The degeneration of unmyelinated axons is most rapid and is completed by 2-3 p.o.d., compared to myelinated axons, most of which degenerate between 2-10 p.o.d. Myelin ring formation (vesicular transformation) is the principal form of lamellar breakdown and occurs in a highly organized manner which can be clearly staged. The glial cell response to Wallerian degneration is two-fold: cytoplasmic hypertrophy and myelin-lytic. Glial hypertrophy subsides by the 10-14 p.o.d. with the ingrowth of numerous regenerating nerve fibers. The myelin-lytic response accounts for most of the myelin destruction. Leukocyte-like and microglia-like cells also participate in myelin breakdown but to a lesser degree.

Animals↗
PubMed1977

The early stages of Wallerian degeneration in the severed optic nerve of the newt (Triturus viridescens).

The initiation of Wallerian degeneration in the severed optic nerve of the newt (Triturus viridescens) was very rapid and intense. Significant degeneration of nonmyelinated axons was observed as early as six hours after lesion (h.a.l.) and was almost complete by 48 h.a.l. Initial degeneration of non-myelinated axons began in "extracellular digestion chambers" formed between burgeoning ependymoglial processes. The remaining fragments and debris were later phagocytized by surrounding ependymoglial processes. Many axons of myelinated fibers have degenerated as early as 6 h.a.l. However, the overall population of myelinated axons degenerates at a much slower rate than nonmyelinated ones, for many of them appear intact as late as 48 h.a.l. Some myelin sheaths show significant signs of degeneration by 6 h.a.l. Indeed, by this time a number of myelinated fibers have completely degenerated leaving only large vacuolated spaces in the nerve parenchyma. Swelling and vacuolization of the sheath are among the earliest signs of myelin degeneration. The ependymoglial cell response to optic nerve lesion is manyfold and dramatic. By 6 h.a.l. there are signs of burgeoning ependymoglial processes which begin to resemble scar formation (gliosis) by 48 h.a.l. The morphological evidence is consistent with the concept of an important phagocytic role of ependymoglial cells during the early stages of optic nerve degeneration.

Animals↗
PubMed1982

Comparison of lens regeneration in adult newts, Triturus viridescens, between light and dark preadapted and non-preadapted animals.

It is well known that if the original lens is removed from the eyeball in certain Urodeles, a new lens will regenerate from the dorsal iris. Experiments were designed to study the different effects on lens regeneration in the newt, Triturus viridescens, between the light and dark preadapted animals and light and dark non-preadapted animals. The preadapted animals were preadapted to continuous light or dark for 90 days prior to lentectomy. The newts remained in the same controlled environments postlentectomy for 25 days to test the effect of light preadaptation on lens regeneration. The non-preadapted animals were placed in the light controlled environment immediately after lentectomy for a 25-day regeneration period. The results indicated that there was no difference in the rate of regeneration between continuous light preadapted and non preadapted animals. However, the dark non-preadapted animals regenerated new lenses at a much slower rate than the dark preadapted animals. The rate of lens regeneration was similar among the controls with 12 hours of light per 24-hour period, the dark preadapted, the continuous light preadapted, and continuous light non-preadapted groups.

Adaptation, Physiological↗