Search results for "Ascidia"

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…

Acetylcholinesterase activity in juvenileCiona intestinalis(Ascidiacea, Urochordata) after exposure to tributyltin

2012

The acetylcholinesterase (AChE) activity has been studied in 4-day post-fertilization juveniles of Ciona intestinalis exposed to tributyltin (TBT) at 10-5 M using the histochemical method of Karnovsky and Roots. Relative to vertebrate tissues and organs, the development of adult form of ascidians is interesting, because the analysis of many nuclear genes indicated that the ascidians are the closest living relatives of the vertebrates. Therefore, toxicity research using different approaches could provide data for comparative studies with vertebrates. AChE is over-expressed under chemical stress and in some diseases of vertebrates. Therefore, AChE is considered a biomarker of environmental co…

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…

Il sistema di attivazione della profenolossidasi nell'ascidia Clona intestinalis (L.) durante il processo infiammatorio.

2011

Effects of tributyltin(IV) chloride on fertilization ofStyela plicata(Ascidiacea: Tunicata): II. Scanning and transmission electron microscopy studies

2003

The morphological aspects of Styela plicata fertilization after treatment with tributyltin(IV) chloride are described by means of scanning and transmission electron microscopy investigations. Alterations have been shown both on female and male gametes; spermatozoa, all the egg envelopes and the mitochondria of the egg cortical cytoplasm are modified in relation to incubation time. As a consequence, the damage to gametes blocks sperm–egg interaction and fertilization does not occur. Copyright © 2003 John Wiley & Sons, Ltd.

Onset of DNA synthesis in experimentally activated ascidian eggs

1994

DNA synthesis was studied autoradiographically in unfertilized ascidian eggs (Ascidia malaca and Ciona intestinalis) that had been artificially activated by a K+-free external medium or a Ca-ionophore. Naked eggs of A. malaca were incubated in K+-free seawater that contained [3H]-thymidine for 30 min, and naked eggs of C. intestinalis were incubated in seawater supplemented with a Ca-ionophore and [3H]-thymidine for 15 min. The observations revealed limited activation in eggs treated with K+-free seawater. Activation consisted of surface modifications and the onset of DNA synthesis. Incorporation of [3H]-thymidine was detected in female nuclei of treated eggs which had not ejected their pol…

The Follicle Cells of Styela Plicata (Ascidiacea, Tunicata): A Sem Study

2000

The morphological aspect of the follicle cells of Styela plicata eggs is described by means of scanning electron microscope investigations. The follicular layer is made of spaced, cylindrical box-like cells which are arranged hexagonally. They adhere to the egg through a complex network of membrane extensions making an overall thin layer on the vitelline coat. The walls of the follicle cells are plentifully provided with microvilli, filopodia and lamellipodia, which allow a connection among the cells. At their apical end lies a large vacuole containing a granule, probably involved in secretion. At insemination the majority of spermatozoa is distributed on the apical membrane of the follicle…

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.

Ultrastructural comparative analysis on the adhesive papillae of the swimming larvae of three ascidian species

2009

This paper presents a preliminary report on the papillae of the swimming larvae of three ascidian species: Ascidia malaca, Phallusia mammillata and Ciona intestinalis. The investigations, carried out at ultrastructural level and at confocal laser microscope, have evidenced, in the adhesive papillae of the three studied species, three different cell-types: axial columnar cells, collocytes, sensory cells respectively. The adhesive papillae of A. malaca and P. mammillata show central axial columnar cells with long microvilli emerging from the apical edge and extending throughout the hyaline cap. Collocytes are elongated secreting cells, lying in middle-lateral side. Sensory cells have a cilium…