Observations on lesser-known flatworms: temnocephala

Temnocephala novae-zealandie, a flatworm epizoic on crayfish, was examined by light and electron microscopy to investigate the variation within rhabdocoel turbellarians and to provide information on the possible structural modifications in the evolution of parasitism. The sucker is clearly glandular; the tentacular glands are eosinophilic and at the surface store and often release mucus as a coiled thread; the epidermis is clearly not reduced in structure and contains septate junctions in the anterior portion. Light microscope studies documented the presence of ten pair of paranephrocytes (athrocytes). In the laboratory, egg deposition, survival on and apart from the host and another crayfish, and behavior during the host molt were observed.     

Prophage F116: Evidence for Extrachromosomal Location in Pseudomonas aeruginosa Strain PAO

F116 is a temperate-generalized transducing phage of Pseudomonas aeruginosa. Genetic evidence leads to the conclusion that F116 prophage DNA is maintained extrachromosomally as a plasmid. Preliminary physical evidence is presented to support this hypothesis.     

Loss of three major auto phosphorylation sites in the EGF receptor does not block the mitogenic action of EGF

The EGF receptor cDNA has been transfected into receptor-negative Chinese hamster ovary (CHO) cells. A mutant cell line (CHO 11) was isolated that expresses a receptor of lower molecular weight than the EGF receptor from A431 cells (150,000 daltons compared to 170,000 daltons) and which appeared as a doublet on SDS-PAGE. By digestion of the receptor with endoglycosidase F it was shown that an altered pattern of glycosylation could not account for the smaller size of the protein, although it could explain the appearance of the CHO 11 receptor as a doublet protein. A deletion was located to the transfected cDNA and shown to involve the removal of coding sequences for the most C-terminal 20,000 daltons of the EGF receptor, which contains the three major autophosphorylation sites. Despite the loss of these sites the EGF receptor from CHO 11 cells binds EGF, demonstrates protein tyrosine kinase activity in response to EGF, and transduces a mitogenic signal. The CHO 11 receptor protein is still autophosphorylated on alternative tyrosine residues. We conclude that phosphorylation of the three tyrosines (P1, P2, and P3) in the C-terminal domain of the receptor is not required for signal transduction by the EGF receptor in these cells.