Search results for "Ascidian"
showing 8 items of 48 documents
Early stages of test formation in larva of Ascidia malaca (Tunicata, Ascidiacea): ultrastructural and cytochemical investigations.
2003
Abstract The swimming larvae of ascidians are entirely covered by a hyalin coat called tunic, or test. This covering consists of two cuticular layers, C 1 and C 2 , which surround an inner compartment composed of an amorphous hyalin matrix with numerous fibrils dispersed inside. Data from the literature agree on the key role played by the cells of the larval ectodermic layer in the synthesis and secretion of larval test components. In the present article are reported ultrastructural and cytochemical investigations made during test formation in the swimming larva of Ascidia malaca . Besides confirming the role played by ectodermic cells during the early stages of test formation, the investig…
Cloning and expression of a type IX-like collagen in tissues of the ascidian Ciona intestinalis
2002
Collagens are highly preserved proteins in invertebrates and vertebrates. To identify the collagens in urochordates, the total RNA extracted from the pharynx of the ascidian Ciona intestinalis was hybridized with a heterologous probe specific for the echinoderm Paracentrotus lividus fibrillar type I-like larval collagen. Using this probe, two main bands (i.e. 6 and 2.8 kb mRNA) were observed on Northern blot hybridization. The cDNA library prepared from poly(A)+RNA extracted from pharyngeal tissue was screened and a cDNA that specifies a type IX-like collagen was identified. This molecule presents a conceptual open reading frame for a protein containing 734 amino acids. In particular, we sh…
Indagini ultrastrutturali sugli effetti di un organometallo dello stagno [tributyltin (IV) chloride] sul processo di neurulazione delle Ascidie.
2006
Un’attenzione particolare è stata rivolta, negli anni più recenti, allo studio degli effetti di un organo metallo contenente stagno, il TBT (IV) chloride, sugli stadi iniziali dello sviluppo embrionale di animali marini. Gli effetti di questo potente inquinante sullo sviluppo e sulla sopravvivenza degli embrioni sono stati proposti come parametri utili per il controllo e il monitoraggio delle acque. Nel presente lavoro sono riportati gli effetti tossici del TBT (IV) chloride sulla neurulazione sull’ascidia Ciona intestinalis, stadio molto importante durante il quale avviene la determinazione del sistema nervoso e la formazione del tubo neurale. L’esposizione degli embrioni allo stadio di ne…
Effects of tri-n-butyltin(IV) chloride on neurulation of Ciona intestinalis (Tunicata, Ascidiacea): an ultrastructural study
2005
This paper reports the cytotoxic effects of tri-n-butyltin (IV) chloride, TBTCl, on the neurulation process of the ascidian Ciona intestinalis. Exposure of the embryos at early neurula stage in 10−5 and 10−7M TBT (IV) chloride solutions for 1–2 h provoked the irreversible arrest of their development. Morphological and ultrastructural observations suggested that most probably there are two principal causes determining the neurulation process block. The first is due to the TBT effects of inhibiting the polymerization and/or degradation of microfilaments and microtubules, proteins that constitute the cytoskeleton. The lack of orientation and extension of both microtubules and microfilaments of…
The ascidian prophenoloxidase activating system
2009
Phenoloxidases/tyrosinases initiate melanin synthesis in almost all organisms, and are involved in different biological activities such as the colour change of human hair and the browning or blackening of fruit skin etc. In many invertebrates, defence reactions are linked to phenoloxidase activity and/or melanization. Contacts with foreign molecules are able to trigger the prophenoloxidase (proPO) system that requires serine protease cleavage for activating the zymogen to phenoloxidase (PO). It is generally accepted that the proPO system is fully expressed in arthropods, and, recently, progress in the regulation of crustacean and insect proPO activation steps have been achieved. After cells…
Contribution of microscopy to the study of proliferating blood cells in Ciona intestinalis immune response
2010
Following an inflammatory stimulus such as the injection of erythrocytes into the tunic of Ciona intestinalis, hemocytes respond to events occurring in the tunic within a short time, and infiltrate the inflamed tissue being massively involved in the acute inflammatory response and capsule formation. The proliferative response of circulating hemocytes and pharynx assume particular interest as it is significantly enhanced during these defence reactions. Microscopy clearly may contribute to extend our understanding of the phenomenon showing interesting mitotic figures and hematogenic nodules with proliferative characteristics.
Focusing on Ciona intestinalis (Tunicata) innate immune system. Evolutionary implications
2009
Phylogenetic analyses based on molecular data provide compelling evidence that ascidians are of critical importance for studying chordate immune system evolution. The Ciona intestinalis draft genome sequence allows searches for phylogenetic relationships, gene cloning and expression of immunorelevant molecules. Acidians lack of the pivotal components of the vertebrate recombinatory adaptive immunity, i.e., MHC, TCRs and dimeric immunoglobulins. However, bioinformatic sequence analyses recognized genic elements indicating the essential features of the Ig superfamily and ancestor proto-MHC genes, suggesting a primitive pre-duplication and pre-recombination status. C. intestinalis genes for in…
Characterization and transcription studies of a phytochelatin synthase gene from the solitary tunicate Ciona intestinalis exposed to cadmium.
2014
The major thiol-containing molecules involved in controlling the level of intracellular ROS in eukaryotes, acting as a nonenzymatic detoxification system, are metallothioneins (MTs), glutathione (GSH) and phytochelatins (PCs). Both MTs and GSH are well-known in the animal kingdom. PC was considered a prerogative of the plant kingdom but, in 2001, a phytochelatin synthase (PCS) gene was described in the nematode Caenorhabditis elegans; additional genes encoding this enzyme were later described in the earthworm Eisenia fetida and in the parasitic nematode Schistosoma mansoni but scanty data are available, up to now, for Deuterostomes. Here, we describe the molecular characteristics and transc…