Robert Ledley`s latest invention looks like a Rube Goldberg device, what with its Geiger counter, plastic trays, robot arm and microwave oven, but in fact it is a technological marvel that is on the cutting edge of human genetics.
What biophysicist Ledley has wrought, in his workshop at Georgetown University Medical Center in Washington, D.C., is nothing less than the world`s first Automatic Genetic Analyzer.
The AGA, as it`s called, fills up half a room. Entirely automated, it can test a patient`s DNA, or genetic material, for the presence of eight inherited diseases at once and do it ten times faster than a laboratory technician.
A diagnosis that would take months manually--such as whether a person is genetically susceptible to any of 100 different hereditary ailments or environmental hazards--can be done by the AGA in little more than a week. The cost would be only a few hundred dollars. The rewards in terms of prevention and peace of mind could be immeasurable.
Diagnostic tools like the AGA--and more sophisticated models to follow
--are just one dividend of the molecular revolution in medicine that is going to transform the delivery of health care in the United States within the next several years.
The revolution, which has been ebulliently described by Arthur Riggs, chairman of the biology division of the City of Hope research hospital in Duarte, Calif., as ``molecular paths to a disease-free society,`` is no figment, nor does it represent a sudden breakthrough.
It is the logical culmination of more than 30 years of dedicated tinkering with particles of nature so minute they resist observation by even the most sophisticated electron microscope, but which are so powerful that they control the destiny of all living things, be they protozoa or prime ministers.
These particles, the genes, are actually long chains of DNA. The key elements in the chain are four chemical subunits of DNA, called nucleotides, which may occur in an endless variety of combinations. Each gene contains a precise order, or sequence, of these nucleotides, which is, in essence, a code telling the cell how to make a particular protein. Proteins are the family of substances needed by the body for health and function.
When the fruit of this gene research is brought soon into general clinical use, the sick will find themselves wandering through a bazaar of exotic techniques and therapies for which they have been poorly prepared.
Perhaps the most dazzling will be gene therapy, the total cure of formerly irreversible genetic diseases by the insertion of new genes. But gene repair is just one of these awesome prospects. Others include:
-- Cancer diagnosis and treatment by means of so-called ``magic bullets,`` tiny laboratory products called monoclonal antibodies that seek and destroy tumors with the single-minded tenacity of a Royal Canadian mountie.
-- Improvement of existing natural enzymes and hormones by ``protein engineering,`` in which substitutions are made in an enzyme`s amino acid building blocks that actually streamline its physiological performance. Similarly, enzymes may one day be invented that do not even exist in nature. The result, for patients whose genes produce deficient proteins, may be cures that actually go nature one better.
-- The increased use of genetic engineering to turn common bacteria into miniature factories cranking out gobs of such scarce drugs as interferon, insulin, growth hormone, and TPA, a substance that dissolves the blood clots that cause heart attacks. The hope is that manufacturing costs can be lowered dramatically. New vaccines will also be mass-produced in this manner.
Among the first of these bold new technologies to confront the average person will be medicine`s advanced capacity to screen people for genetically- based ills.
Machines like Robert Ledley`s will greatly improve doctors` ability to test the unborn for the presence of rare inherited disorders, such as cystic fibrosis, phenylketonuria (PKU), muscular dystrophy and others.
Prenatal tests already exist for some 300 inherited or congenital disorders. The tests make use of samples of fetal cells and enzymes obtained via amniocentesis, in which a needle is inserted into an expectant mother`s uterus, through her abdomen, and amniotic fluid is withdrawn.
The problem with current methods is that amniocentesis cannot be done before the 16th week of pregnancy, when enough amniotic fluid begins to accumulate. To make matters worse, the yield of fetal cells is generally small, hence there is another four-week wait while the cells multiply in culture.
By the time researchers have a large enough cell sample to work with, there are only a few weeks left in which the pregnancy can be terminated safely, should serious abnormalities be found in the fetus. Thus, there is not enough time to screen a fetus for more than a few genetic disorders. Manual DNA testing is labor intensive and quite slow.