PRONEPHRIC CARCINOMA - CHROMOSOMES OF CELLS RESCUED FROM APOPTOSIS BYAN ONCOGENIC HERPESVIRUS DETECTED WITH A POLYMERASE CHAIN-REACTION

The amphibian pronephros is fated to die during early development. Pro nephric cells undergo apoptosis and their function is replaced by the mesonephros, which becomes the functional kidney of the adult frog. Ta dpoles of the northern leopard frog, Rana pipiens, were inoculated wit h a Lucke tumour herpesvirus (LTV) preparation. Most of the animals de veloped typical Lucke renal carcinomas at metamorphosis. Fewer develop ed carcinomas of the pronephric cell type. A pronephric carcinoma, res cued from apoptosis by the herpesvirus, was harvested from a post-meta morphic frog. The tumour was judged to be pronephric by its anatomical location (in the anterior part of the body) and because both mesoneph ric kidneys were Intact and tumour-free upon removal of the tumour mas s. A tumour fragment was fixed for histological examination, which con firmed that the tissue was a renal carcinoma. A further fragment was s ubjected to short-term culture in order to produce metaphase cells for cytogenetical analysis. Based upon silver-stained nucleolar organizin g region numbers, 14 of 15 metaphase cells were estimated to have the diploid number (2N=26) of chromosomes and a karyotype was constructed which did not appear to differ from that of normal cells. A single cel l was estimated to be tetraploid (4N=52). This is the first report of chromosomes of a pronephric Lucke carcinoma. LTV replicates only in tu mour tissue maintained in the cold. Because the frog in this study had been maintained in the laboratory at 22 degrees C for about 10 months , no viruses would have been detectable with electron microscopy. Howe ver, the presence of Lucke herpesvirus DNA was detected in tumour homo genates by polymerase chain reaction amplification of a 1.2 kbp Hind I II restriction fragment of the LTV DNA. The presence of LTV DNA provid ed assurance that the rescued pronephric tumour was indeed a Lucke car cinoma. (C) 1995 Academic Press Limited