Epizoic and parasitic rotifers

Many rotifer species live in close association with plants or other animals. Most of these associations are of a commensal or synoecious nature, some rotifer species having lost the ability to live independently. Few rotifers are true parasites, actually harming their hosts.The Seisonidae, Monogononta and Bdelloidea include epizoic and parasitic species. The most widely known are probably the parasites of colonial and filamentous algae (e.g. Volvox, Vaucheria). However, rotifers are also found on a wide range of invertebrates: colonial, sessile Protozoa; Porifera; Rotifera; Annelida; Bryozoa; Echinodermata; Mollusca, especially on the shells and egg masses of aquatic gastropods; Crustacea, including the lower forms (e.g. Daphnia, Asellus, Gammarus) and in the gill chambers of Astacus and Chasmagnathus; the aquatic larvae of insects. There appear to be few records of epizoic or parasitic rotifers among vertebrates, apart from Encentrum kozminskii on carp, Limnias ceratophylli on the Amazonian crocodile, Melanosuchus niger, and an unidentified Bdelloid apparently living as a pathogenic rotifer in Man.     

Protoplast production in Chondrus crispus gametophytes (gigartinales,rhodophyta)

Protoplasts were isolated from female gametophytes of Chondrus crispus (Stackh.) using commercial cellulase and various carrageenases prepared from marine bacteria. Depending on the nature of the donor tissue (apices or whole thallus, wild or cultivated strains), yields ranged from 1.0–8.5×10⁸ protoplasts per gram of fresh tissue. Preincubating the tissue with a potassium chelator, Kryptofix 222, enhanced protoplast yields by 30–50 %. Based on staining with fluorescein diacetate most protoplasts were viable. A few protoplasts regenerated a cell wall and divided.     

Isolation and chromosomal localization of the human glutathione peroxidase gene

We have isolated cDNA clones for the gene, termed GPX1, encoding the major human selenoprotein, glutathione peroxidase. Sequence analysis confirmed previous findings that the unusual amino acid seleno-cysteine is encoded by the opal terminator codon UGA. Southern blot analysis of human genomic DNA with the GPX1 cDNA showed that restriction endonucleases without sites in the probe sequence produced three hybridizing bands at standard stringency, diminishing to one strongly and one weakly hybridizing band at high stringency. In situ hybridization localized the human GPX1 gene to a single site on chromosome 3, at region 3q11-13.1. Thus, three genomic sites bear sequence homology to the GPX1 cDNA, and the one most homologous maps to 3q11-13.1.