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PubMed1988

Heterochromatic DNA in Triturus (Amphibia, Urodela) II. A centromeric satellite DNA.

The MspI family of highly repeated sequences is a centromeric satellite DNA representing about 1% of the genome of the Italian smooth newt, Triturus vulgaris meridionalis. We have studied the structure, genomic organization, chromosomal localization and conservation across species of this family. MspI sequences are around 197 bp long, as shown by sequencing of three cloned units. The family is organized in large clusters of tandemly arrayed units, present at almost all the centromeres of T.v. meridionalis, and is well conserved in the T.v. vulgaris subspecies. Conserved MspI sequences are also present in the related species T. helveticus, where they appear to be clustered at the centromeres of only a few chromosomes. MspI sequences are not found in other Triturus species analysed. The correlation of these sequences with the overall distribution pattern of heterochromatin and the extent of their conservation within the genus Triturus, are discussed.

Animals↗
PubMed1991

The connections of the anterior pallium in Pleurodeles waltl and Triturus carnifex: an HRP study.

In order to provide cues about the evolution of the telencephalon in tetrapods, the connections of the anterior pallium were studied in two adult Urodeles, Pleurodeles waltl and Triturus carnifex, by means of the HRP-tracing method. The staining of HRP-immunopositive cell bodies indicates that the pallial regions studied receive afferent projections from the main olfactory bulb and are reciprocally interconnected by intrapallial associative fiber systems. In the ventral hemispheric wall, HRP-immunoreactive perikarya are observed in the pars medialis of the amygdala and in the rostral and caudal striatum. Triturus exhibits a more complex pattern of pallial afferents, including interhemispheric connections and thalamic ascending projections that were not discovered in Pleurodeles. HRP-immunopositive fibers are observed in the dorsal and medial walls of the telencephalon, from the rostral part to the foraminal level. In Triturus, the dorsal fibers extend to the caudal part of the hemisphere. Another group of labelled fibers extends, throughout the lateral and ventral walls, to the most caudal part of the telencephalon, and, through the stria medullaris and the habenular commissure, crosses over to the controlateral hemisphere. These results allow us to specify the basic pattern of the pallial connections in Urodeles and to compare them with data previously obtained in other Amphibians.

Animals↗
PubMed1997

Glial fibrillary acidic protein and vimentin in radial glia of Ambystoma mexicanum and Triturus carnifex: an immunocytochemical study.

The molecular characterization of glial lineage cells in two urodele species, Ambystoma mexicanum and Triturus carnifex, has been investigated immunocytochemically with antibodies directed against intermediate filament proteins, glial fibrillary acidic protein (GFAP) and vimentin. Ambystoma astroglia shows clear GFAP-immunopositivity and vimentin-immunonegativity. The condition in Triturus is quite the opposite, showing only a strong vimentin immuno-reaction. In these urodele brain the astroglia is represented by radial glial cells with their somata lining cerebral ventricles (tanycytes). Each of them originates a thick process which radially crosses the periventricular gray matter and branches within the neuropil. These glial fibers originate endfeet on the subpial surface and on blood vessel wall. Only in the spinal cord cell bodies of immunopositive radial glia are displaced from the ependyma of the central canal which is almost immunonegative except the tanycytes forming the dorsal and ventral septum. No mammalian-like astrocytes appear neither in brain nor in spinal cord. The interspecific difference in the intermediate filament protein expression in radial glial cells could suggest that as regards this character Triturus retains a more immature condition than Ambystoma.

Ambystoma mexicanum↗
PubMed2002

Display lateralisation in the courtship behaviour of the alpine newt (Triturus alpestris).

Among urodelan amphibians, European newts of the genus Triturus have evolved a complex sequence of displays to the effect of stimulating the female to actively pick up the spermatophore deposited by the male. Courtship is varied, with plenty of potential for asymmetric uses of tails and of asymmetric turns. The analysis of the temporal structure of the behavioural sequences showed that both males and females significantly utilise the same side during a single courtship sequence. Moreover, if an individual prefers to exhibit one side during its lateral displays, then the duration of its displays on that side is longer than the duration of its displays on the other side. The only significantly contralateral display is creep-on. Less than 50% of the alpine newts show a significant left- or right-side preference and no lateral bias at population level was found. At the population level, male Triturus vulgaris showed a marked bias towards left turning after spermatophore deposition, in spite of the existence of both "left-turning" and "right-turning" individuals in the population (Green, 1997). The presence of population biases may be adaptive if it can influence the sensory processes and the motor responses involved in social interactions. In fact, Triturus vulgaris is characterised by a more complex courtship sequence than T. alpestris and by complex male-male interference mechanisms, but no selective advantages were shown for either left- or right-turning males (Green, 1997).

Journal Article↗
PubMed1977

The effects of hydrocortisone and bacterial lipopolysaccharide on the anti-erythrocyte response in the spleens of adult Triturus viridescens.

The effects of hydrocortisone (HC) and bacterial lipopolysaccharide (LPS) have been tested separately and in combination, on the antigen-binding response of splenocytes of the newt. Triturus viridescens immunized with horse erythrocytes (HRBC). The timing of the presentation of each was made relative to when challenge with either low (0.0025%) or high (25%) doses of the immunogen (HRBC) was effected. Our results showed inhibition of both low and high dose responses by HC and additionally suggested that the helper-cell population of the newt is HC-sensitive. LPS given four days prior to antigen challenge initiated the generation of antigen-binding cells which enhanced the low, but not the high dose response. The use of LPS in conjunction with HC provided suggestive evidence that those LPS stimulated cells which had enhanced the low immunogen dose antigen-binding cell response were HC-resistant. Thus LPS may stimulate a non-helper cell population in the newt which is HC-resistant. The use of these two immunologic probes has provided supportive evidence on the heterogeneity of the lymphoid population of the newt, Triturus viridescens.

Animals↗
PubMed1995

Androgen synthesis modulation by prostaglandin E2 is differentially mediated via adenylate cyclase and phospholipase C in the testis of the crested newt, Triturus carnifex: in vitro studies.

To study the possible postreceptor mechanisms of prostaglandin E2 in modulating the male newt Triturus carnifex androgen synthesis, during reproduction, testes were in vitro superfused with medium alone, prostaglandin E2, protein kinase C activator (phorbol-12-myristate-13-acetate), prostaglandin E2 plus protein kinase C inhibitor (staurosporine), prostaglandin E2 plus phospholipase C inhibitor (compound 48/80), cAMP analog (dibutyryl cAMP), adenylate cyclase activator (forskolin), prostaglandin E2 plus AC inhibitor (2-0-methyladenosine), prostaglandin E2 plus protein kinase A inhibitor (H-89). In January (reproduction beginning), prostaglandin E2 and phorbol-12-myristate-13-acetate increased androgens, while staurosporine and compound 48/80 counteracted the prostaglandin E2 effect. In March (reproduction ending), prostaglandin E2, dibutyryl cAMP and forskolin decreased androgens, while 2-0-methyladenosine and H-89 counteracted the prostaglandin E2 effect. These data suggest that in Triturus carnifex prostaglandin E2 increases testicular androgens synthesis via phospholipase C at reproduction beginning; on the contrary, this prostaglandin decreases androgens via adenylate cyclase at reproduction ending.

Adenylyl Cyclases↗
PubMed1995

Prostaglandin E2-9-ketoreductase and prostaglandin F2 alpha activate brain aromatase to induce courtship in the male crested newt, Triturus carnifex.

Testosterone, 17 beta-estradiol, prostaglandin E2 (PGE2), and prostaglandin F2 alpha (PGF2alpha) were monitored in plasma and in vitro brain incubations during the main phases of male Triturus carnifex courtship. Plasma and in vitro results were similar: testosterone was highest in inactive males, while 17 beta-estradiol and PGF2 alpha were highest and PGE2 lowest during approach. PGF2 alpha in vitro treatments decreased testosterone and increased 17 beta-estradiol, while 9-ketoreductase inhibitor in vitro treatments increased testosterone and decreased estradiol. In addition, in vitro aromatase and PGE2-9-ketoreductase activities were highest during approach. PGF2 alpha in vitro treatments increased aromatase, while 9-ketoreductase inhibitor decreased aromatase. These results suggest that 9-ketoreductase and PGF2 alpha enhance aromatase activity to trigger male Triturus carnifex courtship.

Animals↗
PubMed1977

Histological, immuno- and enzyme-histochemical investigations on the adenohypophysis of the urodeles, Mertensiella caucasica and Triturus cristatus and the caecilian, Chthonerpeton indistinctum.

The pituitary glands of two urodelan species (Mertensiella caucasica, Triturus cristatus) and one one caecilian species (Chthonerpeton indistinctum) were examined with histological (Alcian blue, Brookes' trichrome stain), enzyme histochemical (acid phosphatase, alpha-naphthylacetate-esterase, acetylcholinesterase) and immunofluorescence techniques (anti-carp GTH, anti-ovine prolactin, anti-synthetic alpha-MSH). In the pituitary gland of Mertensiella and Triturus six chromophilic cell types could be distinguished. A strong fluorescence was observed in the MSH-, GTH- and TSH-cells. In the pituitary gland of Chthonerpeton only five chromophilic cell types could be distinguished: in the rostral part of the pituitary gland the B3-cell; in the basal region of the central area the B2-cell; dorsocaudally the B1-cell. The acidophilic cells were found in the central and caudal part of the pars distalis. The basophils of the pars intermedia could be observed in the dorsocaudal part of the pituitary gland surrounding the neurohypophysis. All acidophilic cells showed a strong immunofluorescence with anti-ovine prolactin (LTH).

Acetylcholinesterase↗
PubMed1986

Heterochromatic DNA in Triturus (Amphibia, Urodela). I. A satellite DNA component of the pericentric C-bands.

We have studied the structure, genome organization, chromosomal location, conservation across species and transcription on lampbrush chromosomes, of an AT-rich satellite DNA component of the newt, Triturus vulgaris meridionalis. The satellite (Sat G), originally isolated by gradient centrifugation, represents about 2% of the vulgaris genome and comprises a highly repetitive sequence family (HindIII family), whose monomers have been cloned. The repeat units are about 330 bp long, as measured on gels, and a cloned unit (pTvm1) is 310 bp long, as shown by sequencing. Abundant clusters of the HindIII family sequences are located within the pericentric heterochromatin (i.e. the C-bands placed at both sides of, and at a certain distance from, the centromeres) in most chromosomes. Both the sequence family and its overall pattern of chromosomal distribution are conserved within the genus Triturus, despite a few species-specific differences. The great majority of the HindIII family sequences are unexpressed on lampbrush chromosomes; they reside within pericentric, condensed segments of the chromosome axis ("loopless bars"). Only a few sequences are transcribed on some loops, suggesting that transcription promotion does not depend on the satellite sequences themselves.

Ambystoma↗
PubMed1980

Chromosome polymorphism in the Italian newt, Triturus italicus.

A chromosomal variation, changing shape and C-banding pattern of chromosome XII of Triturus italicus was detected among the offspring of two F1 hybrid families of T. italicus female x T. vulgaris meridionalis male. In both families a number of individuals appeared to have a metacentric instead of the expected subtelocentric chromosome XII of T. italicus.--Investigations in three well separated localities in the range of the species showed the polymorphism to have a wide distribution and to be part of a complex pattern involving at least two inversions and (presumably) deficiencies of large C-bands. At meiosis, the shape of bivalent XII, and the location and frequency of chiasmata in the bivalent varied with the karyomorph involved. It is suggested that large rearrangements may still play an important role in the karyological evolution of Triturus.

Animals↗
PubMed1980

Cytological evidence of transcription of highly repeated DNA sequences during the lampbrush stage in Triturus cristatus carnifex.

Highly repeated, or satellite, DNA fractions have been isolated from total Triturus cristatus carnifex DNA by renaturation kinetics, caesium salt centrifugation and restriction endonuclease digestion. We have shown by DNA/DNA in situ hybridisation and autoradiography that all of these probes bind to C-band positive regions on mitotic or lampbrush chromosomes of T.c. carnifex. Under conditions of DNA to RNA-transcript in situ hybridisation labelled satellite DNA binds to nascent RNA transcripts that are still associated with the DNA axes of many lampbrush loops. The majority of the loops that label heavily in these experiments are located on the long arms of chromosome I, a region previously shown to be rich in highly repeated DNA and to have many of the properties of heterochromatin. These satellite DNA probes also label many loops on a comparable chromosome region in T. marmoratus, a species closely related to T. cristatus. However, in DNA/RNA-transcript hybrids to other more distantly related species of Triturus, there are no chromosome regions that have the same concentration of labelled loop pairs as the long arms of T.c. carnifex and T. marmoratus, although some loop pairs do label. We have cloned two satellite sequences in pBR322, and have obtained the same results using these pure probes as we obtained using satellite probes isolated by other techniques. These results demonstrate unequivocally that satellite DNA is transcribed on lampbrush chromosomes during oogenesis in crested newts.

Animals↗
PubMed1984

The effects of thyroidectomy on androgen and prolactin receptors in the dorsal skin and caudal fin of Triturus cristatus carnifex.

The interactions between thyroid hormones and receptors for steroid hormones and prolactin in dorsal skin and caudal fin of Triturus cristatus carnifex were studied during the annual cycle. Thyroidectomy induces an increase of prolactin binding in the dorsal skin and caudal fin in the animals captured in March. In these thyrodectomized animals the androgen receptors became undetectable. Results indicate that in Triturus cristatus carnifex the thyroid induces an increase of androgen receptors and a decrease, that is removed by thyroidectomy, of prolactin receptors.

Animals↗
PubMed1992

Plasma testosterone and 17 beta-estradiol concentrations, and aromatase activity, during courtship in male Triturus carnifex.

Plasma testosterone and 17 beta-estradiol were monitored during the main phases of male Triturus carnifex courtship. "Inactive" males showed higher levels of testosterone with respect to those found during the various courtship phases. Estradiol was low in "inactive" males, and it reached the highest values at the beginning of the courtship. In addition aromatase activity was higher in the brain of the newts at the beginning of the courtship. These findings seem to support the "aromatization hypothesis" in Triturus carnifex.

Animals↗
PubMed1992

Relationships among mammalian gonadotropin-releasing hormone, prostaglandins, and sex steroids in the brain of the crested newt, Triturus carnifex.

The present study was carried out to evaluate the in vitro brain release of prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 (PGE2), androgens, and 17 beta-estradiol in male and female crested newt, Triturus carnifex, during three different periods of the annual sexual cycle; in addition, the effects of mammalian gonadotropin-releasing hormone (mGnRH), PGF2 alpha, and PGE2 on prostaglandins and steroids release by the brain were evaluated during the same periods. In brain incubations of both sexes, PGF2 alpha and estradiol were higher during postreproduction, while PGE2 and androgens were higher during reproduction. In both sexes, mGnRH increased PGF2 alpha and estradiol during postreproduction, and PGE2 during reproduction; PGF2 alpha increased estradiol secretion during postreproduction. Only in the male, did both mGnRH and PGE2 increase androgens during reproduction. It could be suggested that in Triturus carnifex, the regulation of the reproductive activity in the central nervous system (CNS) depends on the relationships among mGnRH, prostaglandins and steroids. In particular, PGF2 alpha and PGE2 seem to play different roles in the CNS of the newt: PGF2 alpha is involved in the postreproductive processes, through estradiol secretion, while PGE2 in the reproductive ones (through androgens secretion?).

Androgens↗
PubMed1977

A comparative cytochemical study of the yolk platelets in the growing oocytes of Triturus cristatus and Rana esculenta.

Recent cytochemical techniques for the detection of proteins, neutral and acid mucopolysaccharides, lipids and phospholipids in the yolk platelets of the growing oocytes of Rana esculenta and Triturus vulgaris are employed. Cytochemical analysis showed that the yolk in the form of granules or platelets, in the constituting itself the most prominent cytoplasmic inclusion of amphibian eggs, contains a protein moiety consisting of individual typical amino acids lacking tryptophan in Triturus, a carbohydrate fraction consisting of neutral mucopolysaccharides distributed in the superficial layer of each platelet, and phospholipids, phosphoproteins and lipoproteins which are present only in the main body of the same platelets. The different amino acid composition indicated a protein heterogeneity which could be connected with the tissue incompatibility of the transplantations when these last were effected between the orders Urodela and Anura. The different protein composition of the yolk also can be reflected at the species-specific level. The cytochemical data are further reviewed with the mode of utilization of the yolk platelets.

Amino Acids↗
PubMed2000

Planar signalling is not sufficient to generate a specific anterior/posterior neural pattern in pseudoexogastrula explants from Xenopus and Triturus.

Early observations on the morphology of total exogastrulae from urodeles (Axolotl) had provided evidence for essential vertical signalling mechanisms in the process of neural induction. Conversely, more recent studies with anurans (Xenopus laevis) making use of molecular markers for neural-specific gene expression appear to support the idea of planar signalling as providing sufficient information for neural differentiation along the anterior-posterior axis. In an attempt to resolve this apparent contradiction, we report on the comparative analysis of morphology and gene expression characteristics with explants prepared from both urodeles (Triturus alpestris) and anurans (Xenopus laevis). For this purpose, we have made use of a refined experimental protocol for the preparation of exogastrulae that is intended to combine the advantages of the Holtfreter type exogastrula and the Keller sandwich techniques, and which we refer to as pseudoexogastrula explants. Analysis of histology and expression of several neural and ectodermal marker genes in such explants suggests that neural differentiation is induced in both species, but only within the intermediate zone between ectoderm and endomesoderm. Therefore, experiments with Xenopus and Triturus explants described in this communication argue against planar signalling events as being sufficient to generate a specific anterior/posterior neural pattern.

Animals↗
PubMed2000

Substance P downregulates basal and gonadotropin-releasing hormone-induced gonadotropin in vitro secretion by pituitary gland of crested newt, Triturus carnifex.

The possible role of Substance P (SP) was studied in the modulation of basal and gonadotopin-releasing hormone (GnRH)-induced gonadotropin secretion in the urodele crested newt, Triturus carnifex. During prereproduction, reproduction (noncourtship and courtship), refractory, recovery and aestivation, male and female pituitaries were incubated with medium-alone, GnRH, SP, GnRH receptor antagonist (antide), and SP receptor antagonist (L-703606). Since antisera raised against gonadotropins are not available for this species, we measured these hormones indirectly through their effects on the secretion of testicular androgens and ovarian progesterone from gonads superfused with the preincubated pituitaries. Pituitaries of both sexes preincubated with medium-alone, GnRH, GnRH plus L-703606, and GnRH plus SP plus L-703606 increased steroid secretion during prereproduction, noncourtship, courtship, and recovery; the increase induced by the pituitaries incubated with medium-alone was lower during prereproduction, noncourtship, and recovery. Pituitaries preincubated with SP, GnRH plus SP, GnRH plus SP plus antide, and SP plus antide did not change basal steroid secretion in any of the reproductive phases considered. Antide, L-703606, GnRH plus antide, GnRH plus SP plus antide plus L-703606, SP plus L-703606, and antide plus L-703606 experimental groups showed the same results as those with medium-alone. These results suggest that SP downregulates gonadotropin release in both Triturus carnifex sexes. In addition, an antagonist role, through receptor-independent mechanisms, exists between GnRH (upregulation) and SP (downregulation) in the modulation of pituitary.

Androgens↗