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PubMed2000

A novel RNA-binding protein from Triturus carnifex identified by RNA-ligand screening with the newt hammerhead ribozyme.

The newt hammerhead ribozyme is transcribed from Satellite 2 DNA, which consists of tandemly repeated units of 330 bp. However, different transcripts are synthesized in different tissues. In all somatic tissues and in testes, dimeric and multimeric RNA transcripts are generated which, to some extent, self-cleave into monomers at the hammerhead domain. In ovaries, primarily a distinct monomeric unit is formed by transcription, which retains an intact hammerhead self-cleavage site. The ovarian monomeric RNA associates to form a 12S complex with proteins that are poorly characterised so far. In this work we identified NORA, a protein that binds the ovarian form of the newt ribozyme. We show that the newt ribozyme binds to the Escherichia coli -expressed protein, as well as to a protein of identical size that is found exclusively in newt ovaries. Also NORA mRNA was detectable only in ovary, but in neither somatic tissues nor testes. The tissue-specific expression of NORA is analogous to the ovary-specific transcription of the newt ribozyme. Although NORA was identified by its ability to bind to the newt ribozyme in the presence of a vast excess of carrier RNA, it was able to interact with certain other RNA probes. This novel RNA-binding protein does not contain any motif characteristic for RNA-binding proteins or any other known protein domain, but it shares a striking similarity with a rat resiniferatoxin-binding protein.

Amino Acid Sequence↗
PubMed1985

Organization of skeletal muscle in the urodele Triturus cristatus: muscle fibre types and motor units.

Four muscle fibre types are described in the biceps and extensor digitorum communis muscles of the newt forelimb. The histological criteria forming the basis for the distinctions include differential staining with p-phenylenediamine and succinate dehydrogenase histochemistry and electron microscopy. In addition, three distinctive motor unit types are described for the biceps muscle. These are fast units, slow units and intermediate units. The structure of muscle fibre and the physiological characteristics of muscle fibres belonging to each motor unit, have been correlated by using iontophoretic passage of Lucifer yellow into muscle fibres belonging to physiologically characterized motor units and their subsequent histological identification by the succinate dehydrogenase reaction. The three motor unit types correspond to slow muscle fibres, intermediate muscle fibres and two classes of fast muscle fibres.

Aminopyridines↗
PubMed1982

The accessory optic system in the newt, Triturus cristatus: unitary response properties from the basal optic neuropil.

Recordings from the basal optic neuropil (BON) demonstrated directional sensitivity. These directional sensitivities were different in different units, however, most of them displayed a strong vertical component. Inhibition in the non-preferred direction did not occur, only a lower activation than in the preferred direction was found. The identified velocity functions correlate well with the velocity dependence of the nystagmus frequency demonstrated in the behavior. The units responded well to moving large-area stimuli and exhibited horizontally elongated receptive fields with diameters up to 120 degrees. Additionally, bimodal recordings were observed in the BON which were probably due to input from the otoliths. As the recordings are likely to be presynaptic, the BON receives types of input which establish its function in the control of visuomotor behavior.

Animals↗
PubMed1975

An electron-microscope study of the lampbrush chromosomes of the newt Triturus cristatus.

The ultrastructure of lampbrush chromosomes has been examined in sections of end-embedded spread preparations, where the nuclear sap was dispersed prior to fixation, and in oocyte nuclei fixed entire, in 60-kV and i-MV electron microscopes. In spread preparations the axial chromomeres are seen to be organized as regularly spaced, unravelled skeins of DNP, each with a skein width of some 30 nm, though in some chromomeres there are regions where the DNP is much more densely packed. In both unravelled and dense regions, the 'ultimate' DNP fibres, wherever they can be identified, appear to be some 5 nm wide and thrown into loose coils. The unravelled state, although it clearly reflects an orderly packaging of the non-transcribing DNP, is an artifact of preparation; in sections of entire nuclei all chromomeres are seen to consist of DNP fibrils in the more densely packed state. The interchromeric fibril is single, and some 10 nm or less wide; it shows no sign of transcriptional activity. In sections of end-embedded preparations the RNPmatrix of most lateral loops, where transcription occurs, is seen to be made up of particles, each uniformly some 30 nm in diameter and strung together in linear array. These RNP particles are equally evident in sections of whole nuclei. In many loops the strings of particles are wound back on themselves to form regularly spaced, dense aggregates, each some 200-300 nm wide or wider; the larger aggregates can be resolved in the light micrpscope. The RNP particles are of the same dimensions throughout the lengths of individual lateral loops, and of substantially the same dimensions in loops of different gross morphologies. It is suggested that as each successive short length of RNA is transcribed from loop axis DNA, a protein associates with this RNA and winds it up to form a 'manageable' package, allowing transcription to proceed.

Animals↗