Search results for "demos"
showing 10 items of 87 documents
The demos in Herodian
2021
In Herodian’s historical view the demos appears to play an important political role in critical stages of the Roman empire. The political success of an emperor depends on the popular approval in Rome or in the provincial cities, besides the support of the soldiers. The essay aims to evaluate the relationship between demos and armies, between demos and senate from Commodus to Maximinus, and to analyze the differences in this chronological period. The use of the words demos and ochlos, in Herodian’ s historical work, has different values: it reveals that the historian cannot be defined philo-popular, but shows throughout interest in the popular partecipation in civil struggles.
Commento esegetico e filologico alle Epistole di Demostene.
2014
Il lavoro si propone di offrire introduzione, traduzione e commento delle Epistole 1-4 di Demostene. L'introduzione alle singole epistole illustra il motivo della composizione, il momento della stesura, la struttura retorica, mettendo in luce la distinzione tra obiettivi ufficiali e obiettivi nascosti dell'epistola e discutendo i casi in cui tradizione medievale e papiracea siano in disaccordo. La traduzione delle epistole, per le quali si segue l'edizione Oxford curata da Rennie (1931), è corredata da un commento per lemmi, che fornisce informazioni sulle scelte sintattiche, lessicali, retoriche e stilistiche, con accenni all'interessante funzione delle clausole prosodiche. This work conta…
Molecular Mechanism of Spicule Formation in the Demosponge Suberites domuncula: Silicatein-Collagen-Myotrophin
2003
In living organisms four major groups of biominerals exist: (1) iron compounds, which are restricted primarily to Prokaryota; (2) calcium phosphates, found in Metazoa; (3) calcium carbonates, used by Prokaryota, Protozoa, Plantae, Fungi and Metazoa and (4) silica (opal) present in sponges and diatoms (reviewed in: Bengtson 1994; Baeuerlein 2000). It is surprising that the occurrence of silica as a major skeletal element is restricted to some Protozoa and to sponges (Porifera). The element silicon (Si) contributes to 28% of the earth crust and is - after oxygen - the second most abundant element on earth (Windholz 1983).
A cryptochrome-based photosensory system in the siliceous sponge Suberites domuncula (Demospongiae)
2010
Based on the light-reactive behavior of siliceous sponges, their intriguing quartz glass-based spicular system and the existence of a light-generating luciferase [Muller WEG et al. (2009) Cell Mol Life Sci 66, 537–552], a protein potentially involved in light reception has been identified, cloned and recombinantly expressed from the demosponge Suberites domuncula. Its sequence displays two domains characteristic of cryptochrome, the N-terminal photolyase-related region and the C-terminal FAD-binding domain. The expression level of S. domuncula cryptochrome depends on animal’s exposure to light and is highest in tissue regions rich in siliceous spicules; in the dark, no cryptochrome transcri…
Apposition of silica lamellae during growth of spicules in the demosponge Suberites domuncula: Biological/biochemical studies and chemical/biomimetic…
2006
Recently it has been discovered that the formation of the siliceous spicules of Demospongiae proceeds enzymatically (via silicatein) and occurs matrix guided (on galectin strings). In addition, it could be demonstrated that silicatein, if immobilized onto inorganic surfaces, provides the template for the synthesis of biosilica. In order to understand the formation of spicules in the intact organism, detailed studies with primmorphs from Suberites domuncula have been performed. The demosponge spicules are formed from several silica lamellae which are concentrically arranged around the axial canal, harboring the axial filament composed of silicatein. Now we show that the appositional growth o…
Hardening of bio-silica in sponge spicules involves an aging process after its enzymatic polycondensation: evidence for an aquaporin-mediated water a…
2011
Abstract Background Spicules, the siliceous skeletal elements of the siliceous sponges, are synthesized enzymatically via silicatein. The product formed, bio-silica, constitutes their inorganic matrix. It remained unexplored which reactions are involved in molding of the amorphous bio-silica and formation of a solid and rigid biomaterial. Methods Cell and molecular biological techniques have been applied to analyze processes resulting in the hardening of the enzymatically synthesized bio-silica. The demosponge Suberites domuncula has been used for the studies. Results Cell aggregates (primmorphs) from the sponge S . domuncula , grown in the presence of Mn-sulfate, form spicules that compris…
Sponge biosilica formation involves syneresis following polycondensation in vivo.
2011
Syneresis is a process observed during the maturation/aging of silica gels obtained by sol-gel synthesis that results in shrinkage and expulsion of water due to a rearrangement and increase in the number of bridging siloxane bonds. Here we describe how the process of biosilica deposition during spicule ("biosilica" skeleton of the siliceous sponges) formation involves a phase of syneresis that occurs after the enzyme-mediated polycondensation reaction. Primmorphs from the demosponge Suberites domuncula were used to study syneresis and the inhibition of this mechanism. We showed by scanning electron microscopy that spicules added to primmorphs that have been incubated with manganese sulfate …
Selenium affects biosilica formation in the demosponge Suberites domuncula
2005
Selenium is a trace element found in freshwater and the marine environment. We show that it plays a major role in spicule formation in the demosponge Suberites domuncula. If added to primmorphs, an in vitro sponge cell culture system, it stimulates the formation of siliceous spicules. Using differential display of transcripts, we demonstrate that, after a 72-h exposure of primmorphs to selenium, two genes are up-regulated; one codes for selenoprotein M and the other for a novel spicule-associated protein. The deduced protein sequence of selenoprotein M (14 kDa) shows characteristic features of metazoan selenoproteins. The spicule-associated protein (26 kDa) comprises six characteristic repe…
Crystalline nanorods as possible templates for the synthesis of amorphous biosilica during spicule formation in Demospongiae.
2009
In tandem: High-resolution TEM shows that during the initial stages of demosponge spicule formation, a primordial crystalline structure is formed within the axial filament. The recently developed electron diffraction tomography technique (ADT) reveals that the nanorods have a layered structure that matches smectitic phyllosilicates. These intracellular nanorods have been considered as precursors of mature spicules. High-resolution microscopy shows that, during the initial stages of demosponge spicule formation, a primordial crystalline structure is formed within the axial filament. The recently developed electron diffraction tomography technique reveals that the nanorods have a layered stru…
Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellid Monorhaphis chuni.
2008
SUMMARYSilicateins, members of the cathepsin L family, are enzymes that have been shown to be involved in the biosynthesis/condensation of biosilica in spicules from Demospongiae (phylum Porifera), e.g. Tethya aurantium and Suberites domuncula. The class Hexactinellida also forms spicules from this inorganic material. This class of sponges includes species that form the largest biogenic silica structures on earth. The giant basal spicules from the hexactinellids Monorhaphis chuni and Monorhaphis intermedia can reach lengths of up to 3 m and diameters of 10 mm. The giant spicules as well as the tauactines consist of a biosilica shell that surrounds the axial canal, which harbours the axial f…