A 125IUdR technique for measuring the cell loss from subcutaneously growing canine transmissible venereal tumours

A technique for measuring the cell loss from subcutaneous canine transmissible venereal tumours (TVT) has been devised. The tumour-bearing animal is injected with the intranuclear label 125 Iododeoxyuridine (125IUdR). By excising tumours at intervals and measuring their radioactive content per unit weight, an estimate of potential doubling time and so of cell loss can be made. Results using this technique compare well with previous estimates of the cell loss from TVT using the much more laborious labelled mitoses technique. Estimates of the effect of treatment on cell loss can also be made. Radio-therapy, specific passive immunotherapy and intravenous BCG inoculation were also shown to increase TVT cell death. Despite some innate mathematical inaccuracies and assumptions, this technique offers many advantages over conventional methods of estimating cell loss.