The power in new scientific knowledge does not yield practical uses of its own accord; clever ways to use it must be coaxed along.
One of the more clever ways to put genetic engineering to use was shown recently when Scottish researchers transplanted a sheep gene into mice, enabling the female mice to secrete a new chemical in their milk.
Milk carries a potent mix of chemicals and nutrients manufactured by the body, and researchers believe that the body may be coaxed to add several more desirable items to the list.
Milk provides 20 percent to 30 percent of the total protein intake in the developed world, said A. John Clark, lead researcher on the Scottish team. Besides the possibility of making nutritionally enhanced milk, he said, it is conceivable that milk could be made that is better suited chemically to produce other dairy products such as cheese and butter.
Alternately, genetically altered mammary glands could serve as a convenient biological factory in which to produce important chemicals such as ones to aid blood-clotting.
In the Aug. 6 issue of the British journal Nature, the researchers reported that they successfully injected into mouse embryos a gene that causes mammary tissues in sheep to manufacture a substance called beta-lactoglobulin.
The substance apparently helps the body make use of vitamin A. Mice have none of it, and the researchers were attempting to prove that mammary genes can be transferred from one species to another and make the second species produce substantial quantities of useful substances.
About 200 fertilized mouse eggs were injected. The embryos were implanted in pregnant mice, who produced 46 mouse pups.
Of those, 16 took up the foreign gene. They made varying amounts of the substance, sometimes five times more concentrated than in the milk of the donor sheep.
Five mice passed on the foreign gene to their offspring.
Clark, J. Paul Simons and their colleagues at the Institute of Animal Physiology and Genetics Research in Edinburgh also have produced preliminary results suggesting that they have successfully altered sheep to produce a human body chemical in their milk.
The substance is called factor IX, a blood component that hemophiliacs lack and receive in medical treatment.