Karyotype analysis, nucleolar organizer regions(NORs), and C-banding pattern of Dicentrarchus iabrax(L.) and Dicentrarchus punctatus(Block, 1792)(Pisces, Perciformes) with evidence of chromosomal structural polymorphism

Production and characterization of a continuous embryonic cell line from sea bass (Dicentrarchus labrax L.)

Continuous cell lines represent an important tool both for biological studies and for their applications in marine biotechnology. In this article we describe the production and characterization of a continuous adherent cell line, named DLEC, derived from early embryos of the European sea bass Dicentrarchus labrax L. (Actinopterygii, Moronidae). Cells were obtained by disrupting 2- to 12-hour-old embryos and culturing resulting cells at 18 degrees C in RPMI medium containing 5% fetal calf serum (FCS) and 10% supernatant fraction of the embryo homogenate. After 8 weeks culture medium was replaced with Liebovitz's L15 medium containing 10% FCS and DLEC cells started proliferation. Subsequently, they were continuously cultured until the 50th passage without evident changes in their morphology. DLEC cells show a fibroblast-like shape and a modal chromosome number of 48, as do the wild-type cells; conversely the constant presence of six to nine meta-submetacentric elements in the karyotype (vs. zero to two in the wild-type) indicates the occurrence of chromosomal rearrangements during stabilization. DLEC cells are sensitive to substances known to induce differentiation of mammalian cells such as retinoic acid and phorbol esters. They have been transfected using liposomes with a commercial plasmid vector containing a reporter gene, thus suggesting a possible importance as an alternative expression system of recombinant vertebrate proteins in teleost cells.

Ribosomal RNA location in the Antarctic fish Champsocephalus gunnari (Notothenioidei, Channichthyidae) using banding and fluorescence in situ hybridization

A biotinylated 28S rDNA probe was prepared from the genomic DNA of the Antarctic ice-fish Champsocephalus gunnari and hybridized to metaphase chromosomes of the same species by fluorescence in situ hybridization (FISH). The hybridization signal appeared over the whole heterochromatic arm of the submetacentric chromosomes bearing the nucleolar organizer regions. The results of rDNA/FISH are compared with those coming from classical cytogenetic (C, Q, Ag-NOR, chromomycin A3) banding techniques. The in situ detection of a specific DNA sequence offers a new more precise perspective for understanding the evolving process in chromosomes of Antarctic fish and will provide an interesting contribution to comparative cytogenetics of lower vertebrates.