0000000000204879
AUTHOR
Eleonora Patricolo
Onset of DNA synthesis in experimentally activated ascidian eggs
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 effect of L-thyroxine on the metamorphosis of Ascidia malaca
Larvae of Ascidia malaca, both before and after hatching, were treated with L-thyroxine solutions. The effect of the thyroid hormone was to induce the onset of metamorphosis and then to cause the rate at which body reorganization occurred to increase. In treated larvae the resorption of the tail occurred only few hours after hatching, and a beating heart appeared form 10 to 15 h earlier than in the control larvae. These results are discussed in the context of a probable relationship between the occurrence of a hormonal metamorphic factor and the button cells of the trunk.
Presence of thyroid hormones in ascidian larvae and their involvement in metamorphosis
In this study we investigated the presence and localization of thyroxine in Ciona intestinalis larvae and its involvement in metamorphosis. To date, the mechanisms regulating the metamorphosis of ascidians remain largely unknown. In vivo treatment of swimming larvae with exogenous L-thyroxine and thiourea, and in vitro experiments utilizing high performance liquid chromatography, radioimmunoassay, and immunoperoxidase staining demonstrate the presence of thyroxine at the larval stage. This suggests that this hormone may participate in the control of metamorphosis and thus play a different role from that observed in adults.
Studies on the Fibrous Components of the Test ofCiona intestinalisLinnaeus. I. Cellulose-like Polysaccharide
Chemical, histochemical and electron microscopic studies on the fibrous polysaccharide component of the test of Ciona intestinalis L. were made. The results showed cellulose-like fibres to be present in the cuticle layer and in the ground substance. Bundles of fibres varying in diameter from 80 to 600 nm interweave to form a conspicuous network. The bundle appears to be formed of flat fibres, 10–13 nm in width, while the fibre is composed of fibrils 3.5–5 nm; the rectangular cross section of fibres can be supposed. The probable role of this polysaccharide is discussed.
Fine Structure of the Tunic ofCiona intestinalisL. II. Tunic morphology, cell distribution and their functional importance
Ciona intestinalis L. tunic architecture and cell distribution were investigated with the electron microscope. The observations showed that the ascidian covering is formed by a thin outer cuticle, a subcuticle of variable width and a large single layer of ground substance. “Large granule”, morula, phagocyte and granulocyte are the cellular types encountered; they appear mainly in highly vacuolated states and are distributed throughout the whole tunic. The “large granule” cells, however, are mainly seen in the cuticle layer and the morula cells appear mostly in the outer zone of the ground substance. The role of these cells in tunic construction, repair and regeneration as well as their scav…
Identification of Type I and IX Collagens in the Ascidian Ciona intestinalis
Immunohistochemical methods showed that a type I collagen is a component of the tunic of Ciona intestinalis, involved in the encapsulation process. Since the fibril-forming collagen types are characterized by triple helical domain with a highly preserved Gly-Xaa-Yaa repeated sequence, a probe coding the fibril-forming type I collagen of the echinoderm Paracentrotus lividus was used to identify ascidian cDNA clones. Northern blot hybridization established that P. lividus probe cross-hybridizes with a 6 Kb C. intestinalis mRNA isolated from the pharynx. Using the echinodermal type I collagen cDNA as a probe several positive clones were identified. Analysis of sequence and the deduced amino ac…
Organometallic complexes with biological molecules: XVI. Endocrine disruption effects of tributyltin(IV)chloride on metamorphosis of the ascidian larva
The effects of tributyltin(IV)chloride (TBT) on the metamorphosis of ascidian larvae of Ciona intestinalis, 2 h after hatching, were investigated. Ascidians are protochordates that lack thyroid follicles and possess thyroid hormones (THs) and their precursors, 3-monoiodo-tyrosine (MIT) and 3,5-diiodo-tyrosine (DIT), in their endostyle. According to recent findings, these hormones are also present at larval stages, localize in mesenchymal cells and their function seems to be mainly related to larval transformations. Here, we investigate the effects of TBT on thyroxine (T4) content and localization by exposing larvae of C. intestinalis for different times to TBT concentrations known to block …
The Follicle Cells of Styela Plicata (Ascidiacea, Tunicata): A Sem Study
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…
Follicle Cells of Styela plicata Eggs (Ascidiacea)
Styela plicata eggs are surrounded by large follicle cells that at LM appear as highly vacuolated and columnar in shape; at the apical end of each cell lies a very large and clear vacuole, half of which extends inward. Electron microscope observations show a Single layer of largely spaced box-like follicle cells; the close cell-cell contact at their base is realized by interdigitations. The cell surface shows a peculiar structure, more developed in the latero-basal regions, consisting of a complex of membrane extensions, i.e. microvilli, filopodia and lamellipodia. Filopodia irradiate in all directions towards the adjacent cells and the outermost vitelline coat, thus creating a complex netw…
Blue-green algalike cells associated with the tunic of Ciona intestinalis L.
Certain organisms resembling blue-green algae embedded in the tunic of the solitary ascidian Ciona intestinalis L. are described. Their probable symbiotic role as related to the peculiar habitat of this ascidian is suggested.