197,900 research outputs found
Calcareous nannofossils biostratigraphy (Upper Bajocian – Lower Bathonian) of the Ravin du Bès section (Bas Auran, Subalpine Basin, SE France), evolutionary trends of Watznaueria barnesiae and new enigmatic morphotypes of genus Rucinolithus
No full textA biostratigraphic and evolutionary study based of calcareous nannofossils was performed on the Ravin du Bès section (Bas Auran area, SE France), proposed as formal candidate of Global Boundary Stratotype Section and Point (GSSP) for the base of the Bathonian stage (Fernàndez-Lòpez et al., 2007). Semiquantitative estimates of total nannofloral abundance and single species abundance were carried out. The following biohorizonts were identified and calibrated to ammonite biostratigraphy: the first occurrence (FO) of Watznaueria aff. W. barnesiae, the FO of Pseudoconus enigma; the FO of Rucinolithus sp.; the last occurrence (LO) of Hexalithus magharensis; the FO of Stephanolithus speciosum octum and the FO of Watznaueria barnesiae. These results, consistent with biostratigraphic scheme previously proposed (Erba 1988, 1990; de Kaenel & Bergen 1993; de Kaenel et al. 1996; Bown & Cooper 1998; Mattioli & Erba 1999) confirm that the calcareous nannofossils are good biostratigraphic markers for the Bajocian/Bathonian boundary interval. Moreover, the finding of P. enigma within of the Sub-Mediterranean province allows a direct calibration between Tethyan and Boreal nannofossil events and biozones.
This study showed an evolutionary trend from Watznaueria communis to Watznaueria barnesiae that seems to support the theory of punctuated equilibria rather than a phyletic gradualism.
We also documented the occurrence of new morphotypes of uncertain polycycloliths. These enigmatic nannoliths are very similar to specimens of the Cretaceous taxon R. terebrodentarius, whose peculiar structure poses doubts on its origin. In fact, as previously speculated (Tremola & Erba 2002; Erba 2004), R. terebrodentarius nannoliths might be CaCO3 precipitates or biocalcification by bacteria under peculiar oceanographic conditions rather than products of coccolithophorid algae.
REFERENCES
Bown, P.R., Cooper, M.K.E, 1998. Jurassic. In: Bown, P.R. (EDS.), Calcareous Nannofossil Biostratigraphy. British Micropaleont. Soc. Publ. Series. Kluwer Academic Publishers, London: 34-85.
De Kaenel, E., Bergen, J.A., 1993. New early and Middle Jurassic coccolith taxa and biostratigraphy from the eastern proto-Atlantic (Morocco, Purtugal and DSDP Site 547B). Eclogae Geol. Helv., 86: 861-907.
De Kaenel, E., Bergen, J.A., von Salis Perch Nielsen, K., 1996. Jurassic calcareous nannofossils biostratigraphy of western Europe. Compilation of recent studies and calibration of bioevents. Bull. Soc. Geol. Fr., 167: 15-28.
Erba, E., 1988. Calcareous nannofossils from the Bas Auran section. In: M., Innocenti, C., Mangold, G., Pavia and H. Torrens, A proposal for the formal ratification of the basal boundary stratotype of the Bathonian stage based on a Bas Auran section (S.E. France). 2nd International Symposium on Jurassic Stratigraphy, 333-346.
Erba, E., 1990. Calcareous nannofossil biostratigraphy of some Bajocian sections from Digne area (SE france). Mem. Descr. Carta geol. Ital.,40: 237-356.
Erba, E. 2004. Calcareous nannofossils and Mesozoic Oceanic Anoxic Events. Marine Micropaleont. 52, 85-106.
Fernando-Lòpez, S.R., Pavia, G., Erba, E., Guiomar, M., Henriques, M.H., Lanza, R., Mangold, Morton, N., C., Olivero, D., Tiraboschi, D., 2007. Formal proposal for the Global Boundary Stratotype Section and Point (GSSP) of the Bathonian Stage, at the base of the Zigzag Zone in the Ravin du Bès Section (Bas-Auran, Sudalpine Basin, SE France). International Subcommission of Jurassic Stratigraphy. Bathonian Working Group Ballot: 1-43.
Mattioli, E., Erba, E., 1999. Synthesis of calcareous nannofossil events in Tethyan Lower and Middle Jurassic successions. Riv. Ital. Paleontol. Stratigr., 105: 373- 376.
Tremolada, F., Erba, E., 2002. Morphometric analyses of Aptian Assipetra infracretacea and Rucinolithus terebrodentarius nannoliths: Implications for taxonomy, biostratigraphy and paleoceanography. Marine Micropaleont., 44: 77-92
Kinetic and thermodynamic analysis of leech-derived tryptase inhibitor interaction with bovine tryptase and bovine trypsin
No full textThe interaction of leech-derived tryptase inhibitor (LDTI) with bovine liver capsule tryptase (BLCT) and bovine trypsin has been studied using both thermodynamic and kinetic approaches. Several differences were detected: (i) the equilibrium affinity of LDTI for BLCT (K-a = 8.9 x 10(5) M-1) is about 600-fold lower than that for bovine trypsin (K-a = 5.1 x 10(8) M-1); (ii) LDTI behaves as a purely non-competitive inhibitor of BLCT, while it is a purely competitive inhibitor of bovine trypsin. These functional data are compared with those previously reported for the LDTI binding to human tryptase, where tight inhibition occurs at two of the four active sites of the tetramer (K-a = 7.1 x 10(8) M-1). Amino acid sequence alignment of BLCT, human beta II-tryptase and bovine trypsin allows us to infer some possible structural basis for the observed functional differences
v-erbA overexpression is required to extinguish c-erbA function in erythroid cell differentiation and regulation of the erbA target gene CAII.
No full textUdgivelsesdato: 1991-NovThe v-erbA oncoprotein represents a retrovirus-transduced oncogenic version of the thyroid hormone (T3/T4) receptor c-erbA (type alpha). It contributes to virus-induced erythroleukemia by efficiently arresting differentiation of red cell progenitors and by suppressing transcription of erythrocyte-specific genes. Here, we show that v-erbA and c-erbA bind directly to sequences within the promoter of the erythrocyte-specific carbonic anhydrase II (CAII), a gene whose transcription is efficiently suppressed by v-erbA. This erbA-binding site confers thyroid hormone responsiveness to a heterologous promoter in transient expression experiments and is a target for efficient down-regulation of CAII transcription by the v-erbA oncoprotein. In stably transformed erythroblasts coexpressing the v-erbA oncoprotein and the c-erbA/T3 receptor at an approximately equimolar ratio, c-erbA activity is dominant over v-erbA. T3 efficiently induced erythroid differentiation in these cells, thus overcoming the v-erbA-mediated differentiation arrest. Likewise, T3 activated CAII transcription as well as transient expression of a T3-responsive reporter gene containing the CAII-specific erbA-binding site. The c-erbA-dependent activation of this CAII reporter construct could only be suppressed by very high amounts of v-erbA. Our results suggest that overexpression of v-erbA is required for its function as an oncoprotein
v-erbA oncogene activation entails the loss of hormone-dependent regulator activity of c-erbA.
No full textUdgivelsesdato: 1990-Jun-15The v-erbA oncogene, one of the two oncogenes of the avian erythroblastosis virus, efficiently blocks erythroid differentiation and suppresses erythrocyte-specific gene transcription. Here we show that the overexpressed thyroid hormone receptor c-erbA effectively modulates erythroid differentiation and erythrocyte-specific gene expression in a T3-dependent fashion, when introduced into erythroid cells via a retrovirus. In contrast, the endogenous thyroid hormone receptor does not detectably affect erythroid differentiation. The analysis of a series of chimeric v-/c-erbA proteins suggests that the v-erbA oncoprotein has lost one type of thyroid hormone receptor function (regulating erythrocyte gene transcription in response to T3), but constitutively displays another function: it represses transcription in the absence of T3. The region responsible for the loss of hormone-dependent regulator activity of v-erbA has been mapped to the very C-terminus of c-erbA, encompassing a cluster of highly conserved amino acid residues with the potential to form an amphipathic alpha-helix
A conserved C-terminal sequence that is deleted in v-erbA is essential for the biological activities of c-erbA (the thyroid hormone receptor)
No full textThe thyroid hormone (T3) receptor type alpha, the c-ErbA alpha proto-oncoprotein, stimulates transcription of T3-dependent promoters, interferes with AP-1 activity, and induces erythroid differentiation in a ligand-dependent manner. The v-ErbA oncoprotein does not bind hormone and has lost all of these activities. Using c-ErbA/v-ErbA chimeras, we found that a deletion of 9 amino acids, conserved among many members of the nuclear receptor superfamily, which are located at the extreme carboxy terminus of c-ErbA alpha is responsible for loss of both transactivation and transcriptional interference activities. Single, double, and triple amino acid substitutions within this region completely abolished T3-dependent transcriptional activation, interference with AP-1 activity, and decreased T3 binding by c-ErbA alpha. However, the lower T3 binding by these mutants does not fully account for the loss of transactivation and transcriptional interference, since a c-ErbA/v-ErbA chimera which was similarly reduced in T3 binding activity has retained both of these functions. Deletion of homologous residues in the retinoic acid receptor alpha (RAR alpha) resulted in a similar loss of transactivation and transcriptional interference activities. The ability of c-ErbA alpha to induce differentiation of transformed erythroblasts is also impaired by all of the mutations introduced into the conserved carboxy-terminal sequence. We conclude that this 9-amino-acid conserved region is essential for normal biological function of c-ErbA alpha and RAR alpha and possibly other T3 and RA receptors
LONG-WAVELENGTH LIMIT OF THE EMHD TEARING MODE
No full textThe frequency spectrum of the modes that lead to fast reconnection of magnetic-field lines in a plasma configuration with sharp current density gradients is obtained and compared to that of the more familiar magnetohydrodynamic tearing modes
Architetture di informazione per l’information management
No full textLa presenza di soluzioni di business intelligence nelle aziende italiane rappresenta oggi un fenomeno consolidato, però le provocazioni poste dal concetto di information management spingono a riflettere su alcune possibili linee di evoluzione. In ogni caso l'obiettivo finale è chiaro: rendere possibile e facile la fruizione di ogni tipologia di dati presenti in azienda, indipendentemente dalla loro origine, natura e format
Recruitment of the Oncoprotein v-ErbA to Aggresomes
No full textAggresome formation, a cellular response to misfolded protein aggregates, is linked to cancer and neurodegenerative disorders. Previously we showed that Gag-v-ErbA (v-ErbA), a retroviral variant of the thyroid hormone receptor (TRα1), accumulates in and sequesters TRα1 into cytoplasmic foci. Here, we show that foci represent v-ErbA targeting to aggresomes. v-ErbA colocalizes with aggresomal markers, proteasomes, hsp70, HDAC6, and mitochondria. Foci have hallmark characteristics of aggresomes: formation is microtubule-dependent, accelerated by proteasome inhibitors, and they disrupt intermediate filaments. Proteasome-mediated degradation is critical for clearance of v-ErbA and T3-dependent TRα1 clearance. Our studies highlight v-ErbA's complex mode of action: the oncoprotein is highly mobile and trafficks between the nucleus, cytoplasm, and aggresome, carrying out distinct activities within each compartment. Dynamic trafficking to aggresomes contributes to the dominant negative activity of v-ErbA and may be enhanced by the viral Gag sequence. These studies provide insight into novel modes of oncogenesis across multiple cellular compartments.Biolog
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