ppl therapeutics, the Scottish firm that last year helped Edinburgh's Roslin Institute clone Dolly the sheep, is developing a chemical technology to alter the plasma (the pale yellow protein-rich liquid in which the cells of the blood are suspended) genes of sheep and cows, replacing them with the human equivalent. When these animals lactate, their milk contains key elements of human blood plasma albumen, clotting factors and antibodies. PPL plans to rear herds of these animals and manufacture plasma from the proteins extracted from their milk. Ron James, the firm's managing director hopes the process will be ready within a few months. Genetically modified animals could produce 10,000 times more plasma a year than a human donor. However, Britain's national blood service has been more cautious. "Using animal-grown human plasma is fine in theory, but until the clinical trails are complete one can not be sure that whether the animals will pass on diseases to man,' said a PPL spokesperson. Surgeons and hospital administrators, facing shortages of blood supplies, have welcomed the breakthrough, saying it could save lives and help prevent the spread of blood-borne viruses.