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PubMed1978

Chromosome location of the ribosomal RNA genes in Triturus vulgaris meridionalis (Amphibia, Urodela).

The mitotic chromosomes of six specimens from Triturus vulgaris meridionalis have been examined by both in situ hybridization with 3H 18S + 28S rRNA and AS-SAT staining method. The results of these two sets of experiments can be summarized as follows: 1) in each specimen the NORs and the additional ribosomal sites, which react positively to in situ hybridization with 3H 18S + 28S rRNA, are also stained by silver; 2) other chromosomal regions, which do not hybridize in situ with 3H 18S + 28S rRNA, are on the other hand stained by the AS-SAT method. These latter AG-positive sites show a species-specific pattern of chromosomal distribution.

Animals↗
PubMed1980

Multiple ribosomal gene sites revealed by in situ hybridization of Xenopus rDNA to Triturus lampbrush chromosomes.

A variety of 3H-labelled ribosomal gene probes were hybridized in situ to the nascent transcripts of lampbrush chromosomes from the crested newt, Triturus cristatus carnifex. The probes were from Xenopus laevis and included rDNA isolated by CsCl gradient centrifugation, recombinant plasmids and purified restriction fragments of rDNA. All the probes gave essentially the same result. About 10-15 loop pairs were distinctly labelled in each preparation, almost all of them located on the heteromorphic arms (HTAs) of chromosome 1. Ribosomal gene probes were also hybridized in situ to the DNA of denatured mitotic chromosomes from some of the individuals used to provide lampbrush preparations. Minor, scattered sites of hybridization were found in the HTAs, but the main clusters of ribosomal genes were found on chromosomes 6 and/or 9, in agreement with previous determinations of nucleolus organizer position in this species. However, the nucleolus organizers were not sites of labelled loops in lampbrush transcript hybridizations.--We have incubated isolated lampbrush-stage nuclei in media containing alpha-amanitin and labelled RNA precursors. Although extrachromosomal nucleolar genes incorporated label, supposedly due to transcription by RNA polymerase I, no lampbrush loops were labelled.--It appears that in T. c. carnifex there are ribosomal gene sequences at the main nucleolus organizers and at a number of sites scattered along the HTAs. The ribosomal genes at the nucleolus organizers are not extended in the form of actively transcribing loops unlike the ribosomal sequences on the HTAs, which are heavily labelled in transcript hybridization. The ribosomal sequences on the HTAs appear not to be transcribed by the same RNA polymerase that transcribes the ribosomal genes of extrachromosomal nucleoli.

Animals↗
PubMed1977

Chromosome location of the ribosomal RNA genes in Triturus vulgaris meridionalis (Amphibia, Urodela). II. Intraspecific variability in number and position of the chromosome loci for 18S + 28S ribosomal RNA.

Ribosomal genes have been localized on mitotic and lampbrush chromosomes of 20 specimens of Triturus vulgaris meridionalis by in situ hybridization with 3H 18S + 28S rRNA. The results may be summarized as follows: 1) each individual shows positive in situ hybridization at the nucleolus organizing region (NOR) on chromosome XI; 2) in addition, many specimens exhibit a positive reaction in chromosomal sites other than the NOR (additional ribosomal sites); 3) the chromosomal distribution of the additional sites appears to be identical in different tissues from the same specimen and to follow a specific individual pattern; 4) the additional ribosomal sites are preferentially found at the telomeric, centromeric or C-band regions of the chromosomes involved.

Animals↗
PubMed1981

Development of retinofugal neuropil areas in the brain of the alpine newt, Triturus alpestris.

The development of the retinofugal projection areas of the brain has been studied in larvae of Triturus alpestris by means of anterograde transported horseradish peroxidase. The optic tract establishes contacts with the optic tectum prior to the onset of robust terminal formation in the diencephalon. The tectum becomes covered by the retinofugal projection in a rostro-caudal direction. The basal optic neuropil develops synchronously with the oculomotor neurons. Their dendrites extend into this neuropil area. A small amount of uncrossed label occurs long before metamorphosis. Around metamorphotic climax this ipsilateral label increases but does not attain the adult pattern even three monts postmetamorphosis. The data are compared with the onset of visual induced behaviour.

Animals↗
PubMed1978

Chromosome location of the ribosomal genes in Triturus vulgaris meridionalis (Amphibia Urodela). III. Inheritance of the chromosomal sites for 18S + 28S ribosomal RNA.

In Triturus vulgaris meridionalis, the 18S + 28S rDNA sequences have been shown to be located in a number of additional chromosomal sites besides the nucleolus organizing region. The additional ribosomal sites have been found to vary as to their number and chromosomal location in different individuals of the species.--The data presented in this study concern the chromosomal distribution of the ribosomal sequences as analyzed by in situ hybridization technique in two individuals as well as in their offspring. The evidence obtained by this analysis indicates quite clearly that all 18S + 28S rRNA sites present in each individual genome are inherited according to simple mendelian principles.

Animals↗
PubMed1985

Centromeric satellite DNA in the newt Triturus cristatus karelinii and related species: its distribution and transcription on lampbrush chromosomes.

Two abundant satellite DNA sequences have been identified in and cloned from the DNA of Triturus cristatus karelinii. The smaller of these with a repeat unit of 33 base pairs (bp) is designated TkS1, the larger with 68 bp is designated TkS2. These satellites are also present in DNA from T.c. cristatus, T.c. carnifex and T. marmoratus but in substantially lower copy number. In situ hybridisations to lampbrush chromosomes of T.c. karelinii and T.c. cristatus have shown that the satellites are concentrated in the heterochromatic centromere bars of T.c. karelinii and in a region around the centromere granule in T.c. cristatus. The satellites also bind specifically to the centromere regions of mitotic metaphase chromosomes. They do not bind to the heteromorphic arms of chromosome 1, which have previously been shown to be rich in highly repeated DNA. DNA/RNA-transcript in situ hybrids to lampbrush chromosomes with TkS1 suggest that this sequence is occasionally transcribed on lampbrush loops near the centromeres.

Animals↗
PubMed1975

The mitotic chromosomes of Notophthalmus (=Triturus) viridescens: localization of C banding regions and DNA sequences complementary to 18S, 28S and 5S ribosomal RNA.

The metaphase chromosomes of Notophthalmus (Triturus) viridescens have been studied by C-banding and in situ hybridization. The chromosomes show the pericentric C-banding seen in many organisms and in addition have interstitial C-bands located a short distance from the pericentric C-bands on each chromosome arm. A few C-bands are seen in telomeric regions. Regions which hybridize in situ with 18S and 28S ribosomal RNA were found on three chromosome pairs. The animals studied fell into three groups with respect to which of the six possible sites showed detectable hybridization with 18S and 28S RNA. Individual animals differed not only in the pattern of in situ hybridization of ribosomal RNA but also in the number of ribosomal RNA cistrons in the genome as measured by saturation hybridization on purified DNA. In situ hybridization showed five pairs of chromosomes which contained DNA complementary to 5S RNA. The four pairs of subtelocentric chromosomes in the N. viridescens karyotype all have 5S DNA in the pericentric regions. The fifth cluster of 5S DNA is in the middle of one arm of the chromosomes in one of the two smallest submetacentric pairs in the genome. The five sites of 5S DNA differ markedly in the level of in situ hybridization with 5S cRNA.

Animals↗
PubMed1975

Identification of the lampbrush chromosome loops which transcribe 5S ribosomal RNA in Notophthalmus (Triturus) viridescens.

The loops which transcribe 5S ribosomal RNA in lampbrush chromosomes of the newt, Notophthalmus (Triturus) viridescens, were identified by hybridizing purified 5S DNA to nascent 5S RNA in situ. The genes which code for 5S RNA were found near the centromeres of chromosomes 1, 2, 6, and 7 by hybridizing iodinated 5S RNA to denatured lampbrush and mitotic chromosomes in situ. These genes and their intervening spacer DNA were isolated from Xenopus laevis using sequential silver-cesium sulfate equilibrium centrifugations. This purified 5S DNA was iodinated and hybridized to non-denatured lampbrush chromosomes in situ, where it bound to nascent 5S RNA on loops at the base of the centromeres of chromosomes 1, 2, 6, and 7. The number of 5S genes present in the haploid chromosome complement of N. viridescens was determined. - The 5S loops were chosen for study, since (1) the synthesis of 5S RNA has been demonstrated during the lampbrush stage, (2) both 5S RNA and 5S DNA could be isolated in pure form, and (3) the localization of the repetitive 5S genes could be verified by conventional in situ hybridization procedures. These methods may be applicable to the identification of other loops, leading to a better understanding of lampbrush chromosome function.

Animals↗
PubMed1979

Expermental hybridization within the genus Triturus (Urodela: Salamandridae). III. Evidence for crossing-over, true chiasmata and chomosomal homologies in the spermatogenesis of F1 species hybrids, T. cristatus carnifex female X T. marmoratus male.

Spermatogenesis in the F1 hybrid (2n=24=12 female + 12 male) between the closely related newt species T. cristatus carnifex and T. marmoratus was apparently normal up to pachytene. Many unpaired chromosomes were present at diplotene and a typical diakinesis was lacking. Primary spermatocytes at meta- and meta-anaphase contained up to 12 regular intergenomal bivalents and a corresponding number of univalents when less then 12 II. Most chiasmata were terminal or subterminal, some intercalary. Chiasmata between corresponding heterospecific chromosomes can be reported as true: real crossing over has taken place, proving the presence of primary chromosomal homologies between the 2 sets of the parental species. Evidence for recombination is based on the segregation of particular markers (i.e., subterminal C-bands and NORs) observed in certain chromosomes at metaphase II. One chromatid of single chromosomes can show the T. cristatus "pheno-type" and the other the T. marmoratus phenotype". A few primary spermatocytes contain a certain number of irregular associations (intragenomal or intrahaploid bivalents, irregular intergenomal bivalents, chromosome multivalents) joined by chiasmata which can be defined as anomalous. Other abnormalities concern the occurrence of interlocked bivalents which occasionally show an anomalous exchange between heterologous chromatids. Cytogenetic criteria useful to evaluate the taxonomic relationships between different species have been discussed as well as some possible trends in chromosome evolution and speciation within the genus Triturus.

Animals↗
PubMed1979

In situ hybridization of highly repetitive DNA to chromosomes of Triturus cristatus.

Highly repetitive DNA of C0t 0--0.2 was purified from whole DNA of Triturus cristatus carnifex, labelled by nick translation, and in situ hybridized to RNA transcripts on the loops of lampbrush chromosomes and to the DNA of mitotic chromosomes from intestinal epithelium from the same species. The labelled DNA bound to 20--30 loops on the long arms of lampbrush bivalent 1, a pair of loops near the centromere on bivalent 10, and a number of other loops most of which were localized in pericentric regions. In mitotic preparations the same labelled DNA bound to the heteromorphic regions of the long arms of both chromosomes 1, and to the centromeric regions of all chromosomes. Centromeric labelling was light on chromosomes 4 and particularly clear on the 3 shortest chromosomes of the set. The heavy labelling of the heteromorphic arms of chromosome 1 is discussed in relation to several other peculiar properties of these arms, including their extraordinary lengths, their Giemsa banding patterns, and the absence of meiotic crossing over. It is suggested that insofar as the results with DNA/DNA hybridization and mitotic chromosomes match those obtained with the DNA/RNA-transcript hybridization and lampbrush chromosomes, confidence in the latter technique may be increased accordingly.

Animals↗
PubMed1982

The electrical profile of the distal tubule in Triturus kidney.

The transepithelial potential difference (VTE) and transepithelial resistance (RTE) were determined along the length of the distal tubule of the amphibian Triturus alpestris. The site of impalements was determined at the end of each experiment by latex injection and microdissection. Two segments, differing by their distribution at the surface of the kidney, by their respective diameters and by their electrical properties could be identified: the early distal tubule (EDT) and the late distal tubule (LDT). VTE was invariably positive in the EDT; it increased from approximately + 5 mV to approximately + 22 mV within the first 30% of this segment and remained roughly constant distally to this site. RTE was estimated at 57 omega X cm2 in the EDT. The LDT exhibited essentially negative VTE figures with the exception of its very initial portion; the peak negativity at the end of the LDT was -35 mV. RTE was assessed from 8 measurements performed in the first 30% of the LDT; the tentative transepithelial resistance was 530 omega X cm2. Provisional evidence suggests that the transepithelial resistance of the terminal portion of the LDT may be substantially larger than the resistance measured in other parts of this segment.

Animals↗
PubMed1976

Cytochemical evidence for stage-specific changes of nuclear RNA and nonhistone protein content during early development of Triturus vulgaris.

During early embryogenesis of Triturus vulgaris, RNA and nonhistone protein contents of neuroectoderm nuclei change with stage specifically. Maximum values were found in the late gastrula after embryonic induction, and in the late neurula with the formation of the neural tube. The stage-specific increases of RNA and nonhistone protein are correlated with a preceding increase of Feulgen-DNA content.

Animals↗
PubMed1980

An electrophoretic polymorphism that mimics a true genetic polymorphism in Triturus cristatus carnifex (Amiphibia, Urodela).

Phosphoglucomutase electrophoretic patterns have been studied in 60 tail homogenates of Triturus cristatus carnifex. Our results show that the same sample produces a different electrophoretic pattern with homogenate ageing; a new band of intermediate mobility appears, together with the one produced by the fresh preparation. The phenomenon can mimic a true genetic polymorphism when differently stored samples are analyzed.

Animals↗
PubMed2002

Classification and molecular organization of satellites elucidated by phylogenetic network analysis - examples from Triturus salamanders and Palorus beetles.

A phylogenetic network of 244 satellite DNA sequences across five species of aquatic salamanders (genus Triturus) revealed four types of satellite DNAs in a 'p'-shaped 1-2*-3-4-2* arrangement. Analysis of dimer and trimer DNA sequences revealed a prevalence of homosequential (e.g. 1-1, 2-2) and particular (1-4 and 2-3) heterosequential repeat motifs. Genetic diversity across types and species phylogeny indicated that type 1 and type 4 are derived from types 2 and 3. Support was also found for alternating motifs in Palorus flour beetle tandem repeats. The results were statistically significant, whether or not the underlying satellite DNA phylogenies were robust under bootstrap analysis.

Animals↗
PubMed1997

Molecular structure of the rDNA intergenic spacer (IGS) in Triturus: implications for the hypervariability of rDNA loci.

Ribosomal DNA (rDNA) variation in the species Triturus vulgaris meridionalis (Amphibia, Urodela) is remarkable because of unusually high intraspecific variability in the number and distribution of ribosomal loci in the karyotype; in addition, portions of the intergenic spacer (IGS) are clustered at chromosomal loci where they are not associated with ribosomal 18S and 28S RNA genes. These clusters are referred to as extraribosomal, and they appear to consist mostly of repetitive BamHI elements. In this paper, we report the complete nucleotide sequence of an IGS of T. v. meridionalis; this structural analysis is aimed to get insight into the molecular mechanism(s) of spreading of the ribosomal cistrons as well as its possible functional significance. We found that the IGS of T. vulgaris has a modular structure: modular repetitive elements contain sequences possibly related to the regulation of transcription of the ribosomal units. In particular, both ribosomal and extraribosomal IGS elements contain presumptive enhancers. Interestingly, the enhancer-containing region is mostly conserved between ribosomal and extraribosomal elements, while mutations accumulate in a region characterized by repetitions of a simple sequence motif, that we consider as a possible recombination hotspot. Our data suggest that extraribosomal elements most probably originated from ribosomal enhancer-containing elements able to move independently from the ribosomal unit at novel chromosomal positions, perhaps with the aid of the simple repetitive motif. We argue that a similar mechanism may lead to the spreading of complete repetition units as well, giving rise to multiple, and variable, ribosomal sites. We propose that hypervariability in the number and distribution of the rDNA loci, as seen in T. vulgaris, is a further mechanism to ensure redundancy, which seems to be an intrinsic property of rDNA biology, the occurrence of IGS elements independently clustered at separate chromosomal loci being a by-product of this mechanism.

Animals↗
PubMed2006

The adrenal gland of newt Triturus carnifex (Amphibia, Urodela) following in vivo betamethasone administration.

The response of the adrenal gland of Triturus carnifex to betamethasone administration was studied; the effects were evaluated by examination of the ultrastructural morphological features of the tissues as well as the serum levels of aldosterone, corticosterone, norepinephrine and epinephrine. In March and June, betamethasone significantly decreased the serum levels of aldosterone and corticosterone and the lipid droplet content in the steroidogenic cells. Moreover, betamethasone influenced the chromaffin tissue, enhancing in March (when the chromaffin cells produce norepinephrine and epinephrine in almost equal quantities) epinephrine serum levels and the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells. In June, (when the chromaffin cells contain almost exclusively norepinephrine granules) betamethasone administration raised norepinephrine serum levels, whereas a decrease in the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells was found. Finally, betamethasone administration did not evoke in June any increase in the mean number of epinephrine granules in the chromaffin cells and/or in epinephrine serum levels, as would be expected if phenyletanolamine-N-methyl transferase (PNMT) enzyme, converting norepinephrine into epinephrine, were activated by corticosteroids. The results of this study showed that betamethasone decreased aldosterone and corticosterone serum levels and enhanced catecholamine serum concentrations. Moreover, the present results suggest that a stimulatory role of glucocorticoids on PNMT enzyme may be ruled out.

Adrenal Glands↗